毕业设计-中英文翻译模板
毕业论文英文翻译模板【范本模板】
湖北汽车工业学院科技学院毕业设计(论文)参考文献译文译文内容无线短消息服务的用户接受:解构感知价值译文出处【作者】Ofir Turela;Alexander Serenkob andNick Bontisa【刊名】Information and Management【出版日期】2007 【卷号】Vol。
44 【期号】NO.1系别：经济管理学院专业：工商管理（汽车市场营销）班级：K1253-3学生姓名：黄登宇学号：20129530310指导教师：李建忠题目Information ＆ Management 44 (2007） 63–73www.elsevier。
com/locate/imUser acceptance of wireless short messagingservices：Deconstructing perceivedvalueOfir Turel a，＊， Alexander Serenko b， Nick Bontis aa DeGroote School of Business, McMaster University， Hamilton, Ontario L8S 4M4， Canadab Faculty of Business Administration， Lakehead University, Thunder Bay， Ontario P7B 5E1, CanadaReceived 22 June 2005; received in revised form 12 April 2006； accepted 26 October 2006Available online 28 November 2006译文原文：译文内容:无线短消息服务的用户接受：解构感知价值无线增值服务，每使用服务，如短消息服务（短信）,近年来吸引了越来越多的关注。
然而，现存的文献提供了一些洞察技术采用无线支付,每使用服务.我们的研究探讨了这一采用相结合的营销和观点的222个年轻的，成人短信用户的实证调查.这是假设知觉价值将是一个关键的多维行为意向的决定因素。
毕业设计中英文翻译【范本模板】
英文The road (highway)The road is one kind of linear construction used for travel。
It is made of the roadbed，the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility。
The roadbed is the base of road surface, road shoulder，side slope, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the base of travel, must guarantee that it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.The road surface is the surface of road. It is single or complex structure built with mixture。
The road surface require being smooth，having enough intensity，good stability and anti—slippery function. The quality of road surface directly affects the safe, comfort and the traffic。
毕业设计英语翻译全文
[1]. These brake systems use compressed air as the energy transmitting medium to actuate the foundation brakes mounted on the axles.The air brake system currently found in commercial vehicles is made up of two subsystems —the pneumatic subsystem and the mechanical subsystem. The pneumatic subsystem includes the compressor, storage reservoirs, treadle valve (or the brake application valve), brake lines, relay valves, quick release valve, brake chambers, etc. The mechanical subsystem starts from the brake chambers and includes push rods, slack adjusters, S-cams, brake pads and brake drums. One of the most important differences between a hydraulic brake system (found in passenger cars) and an air brake system is in their mode of operation. In a hydraulic brake system, the force applied by the driver on the brake pedal is transmitted through the brake fluid to the wheel cylinders mounted on the axles. The driver obtains a sensory feedback in the form of pressure on his/her foot. If there is a leak in the hydraulic brake system, this pressure will decrease and the driver can detect it through the relatively easy motion of the brake pedal. In an air brake system, the application of the brake pedal by the driver meters out compressed air from a supply reservoir to the brake chambers. The force applied by the driver on the brake pedal is utilized in opening certain ports in the treadle valve and is not used to pressurize air in the brake system. This leads to a lack of variation in the sensory feedback to the driver in the case of leaks, worn brake pads and other defects in the brake system.Air brake systems can degrade significantly with use and need periodic inspection and maintenance [2]. As a result, periodic maintenance inspections are performed by fleet owners and roadside enforcement inspections are carried out by state and federal inspection teams. The performance requirements of brakes in newly manufactured and “on-the-road”commercial vehicles in the United States are specified by the Federal Motor V ehicle Safety Standard (FMVSS) 121 [3]and the Federal Motor Carrier Safety Regulation (FMCSR) Part 393 [4], respectively. These regulations specify the stopping distance, deceleration and brake force that should be achieved when the vehicle is braked from an initial speed of 20 mph. Due to the difficulty in carrying out such tests on the road, equivalent methods have been developed to inspect the brake system. A chronology of the development of the various commercial vehicle brake testing procedures used in the United States can be found in [5].Inspection techniques that are currently used to monitor the air brake system can be broadly divided into two categories —“visual inspections”and “performance-based inspections”[6]. Visual inspections include observing the stroke of the push rod, thickness of the brake linings, checking for wear in other components and detecting leaks in the brake system through aural and tactile means. They are subjective, time-consuming and difficult on vehicles with a low ground clearance since an inspector has to go underneath a vehicle to check the brake system. In fact, the average time required for a typical current roadside inspection of a commercial vehicle is 30 min, with approximately half of the time spent on inspecting brakes [7]. Performance-based inspections involve the measurement of the braking force/torque, stopping distance, brake pad temperature, etc. A description of two performance-based brake testers —the roller dynamometer brake tester and the flat plate brake tester —and the associated failure criteria when an air brake system is tested with them can be found in [8]. It is appropriate to point out that, in an appraisal of the future needs of the trucking industry [9], the authors call for the development of improved methods of brake inspections.Also, in recent years, studies have been carried out to develop “Adaptive Cruise Control”(ACC)systems or “Autonomous Intelligent Cruise Control”(AICC) systems. The objective of these systems is to maintain a constant distance between two consecutive vehicles by mainly controlling the engine throttle and the brake system. While most of the research on ACC systems has focused on passenger cars, the benefits of implementing such systems on heavy trucks are significant [10].A typical ACC system for heavy trucks controls the engine throttle, the transmission and the brake system and will be interfaced with existing systems like the Antilock Braking System (ABS), Traction Control System (TCS), etc. A typical truck ABS monitors the speed of the wheels and modulates the brake system pressure in the event of an impending wheel lock-up [11]. The ABS consists of an Electronic Control Unit (ECU) that receives signals from the wheel speed sensors and processes this information to regulate the brake system pressure through modulator valves. It should be noted that ABS does not control the treadle valve to regulate the pressure in the brake system. It reduces the brake system pressure that is “commanded”by the driver when it senses an impending wheel lock-up. It cannot provide a higher pressure than that corresponding to the pedal input from the driver.It is important to note that the ABS modulates the brake system pressure only under conditions when a wheel lock-up is impending. The ABS is disengaged during “normal”braking operations. In fact, it has been pointed out in [12] that ABS is “passive during the vast majority of braking operations”. During such braking operations, the pressure of air in the brake system is the level that is commanded by the driver through the motion of the brake pedal. Hence, in order to implement ACC systems on commercial vehicles it is necessary to develop control schemes that will automatically regulate the brake system pressure during all braking operations.Motivated by the above issues, our overall objective is to develop model-based control and diagnostic systems for air brake systems. Such a model of the air brake system should correlate the pressure transients in all the brake chambers of the air brake system with the treadle valve plunger displacement (i.e., the displacement of the brake pedal) and the supply pressure of air provided from the reservoirs to the treadle and relay valves. We have already developed a model [13], and control and diagnostic schemes [14] and [15]based on this model, for the configuration of the air brake system where the primary circuit of the treadle valve is directly connected to one of the two front brake chambers. This model predicts the pressure transients in a front brake chamber during a given brake application with the input data being the treadle valve plunger displacement and the supply pressure to the treadle valve. In order to extend these control and diagnostic schemes, a model should be developed to predict the response of all the brake chambers in the air brake system. One of the steps involved in obtaining a model for the entire air brake system is to develop a model to predict the response of the relay valve, and this is the focus of this article.We will show in the subsequent sections that a relay valve has three phases (or modes) of operation and the evolution of pressure in each of the modes is different. The transition from one mode to another depends primarily on the pressure in the brake chamber and for this reason, it can be naturally modeled as a hybrid system.This article is organized as follows. In Section 2, we present a brief description of the air brake system and the experimental setup that has been constructed at Texas A&M University. A hybrid dynamical model of the relay valve to predict its pressure response is derived in Section 3. We present the equations governing the motion of the mechanical components in the relay valve and the flow of air in the system. This model is corroborated against experimental data and the resultsare provided in Section 4.2. A brief description of the air brake system and the experimental setupA layout of the air brake system found in a typical tractor is presented in Fig. 1. An engine-driven air compressor is used to compress air and the compressed air is collected in storage reservoirs. The pressure of the compressed air in the reservoirs is regulated by a governor. Compressed air is supplied from these reservoirs to the treadle and relay valves. The driver applies the brake by pressing the brake pedal on the treadle valve. This action meters the compressed air from the supply port of the treadle valve to its delivery port. Then, the compressed air travels from the delivery port of the treadle valve through air hoses to the relay valve (referred to as the service relay valve in Fig. 1) and the quick release valve and finally to the brake chambers mounted on the axles.Fig. 1. A general layout of a truck air brake system.View thumbnail imagesThe S-cam foundation brake, found in more than 85% of the air-braked vehicles in the United States [1], is illustrated in Fig. 2. Compressed air metered from the storage reservoirs enters the brake chamber and acts against the diaphragm, generating a force resulting in the motion of the push rod. The motion of the push rod serves to rotate, through the slack adjuster, a splined shaft on which a cam in the shape of an ‘S’is mounted. The ends of two brake shoes rest on the profile of the S-cam and the rotation of the S-cam pushes the brake shoes outwards so that the brake pads make contact with the rotating drum. This action results in the deceleration of the rotating drum. When the brake pedal is released by the driver, air is exhausted from the brake chamber and the push rod strokes back into the brake chamber thereby rotating the S-cam in the opposite direction. The contact between the brake pads and the drum is now broken and the brake is thus released.Fig. 2. The S-cam foundation brake.View thumbnail imagesA schematic of the experimental setup at Texas A&M University is provided in Fig. 3. Two “Type-20”brake chambers (having an effective cross-sectional area of 20 in2) are mounted on a front axle of a tractor and two “Type-30”brake chambers (having an effective cross-sectional area of 30 in2) are mounted on a fixture designed to simulate the rear axle of a tractor. The air supply to the system is provided by means of two compressors and storage reservoirs. The reservoirs are chosen such that their volume is more than twelve times the volume of the brake chambers that they provide air to, as required by the Federal Motor V ehicle Safety Standard (FMVSS) 121 [3]. Pressure regulators are mounted at the delivery ports of the reservoirs to control the supply pressure to the treadle valve and the relay valve. A cross-sectional view of the treadle valve used in the experiments is illustrated in Fig. 4. The treadle valve consists of two circuits —the primary circuit and the secondary circuit. The delivery port of the primary circuit is connected to the control port of the relay valve and the delivery ports of the relay valve are connected to the two rear brake chambers. The relay valve has a separate port for obtaining compressed air supply from the reservoir. The delivery port of the secondary circuit is connected to the Quick Release V alve (QRV) and the delivery ports of the QRV are connected to the two front brake chambers.Fig. 3. A schematic of the experimental facility.View thumbnail imagesFig. 4. A sectional view of the treadle valve.View thumbnail imagesThe treadle valve is actuated by means of a pneumatic actuator and compressed air is supplied to this actuator from the storage reservoirs through a pressure regulator. The displacement of the treadle valve plunger is measured by means of a displacement transducer. A pressure transducer is mounted at the entrance of each of the four brake chambers by means of a custom designed and fabricated pitot tube fixture. A displacement transducer is mounted on each of the two front brake chamber push rods through appropriately fabricated fixtures in order to measure the push rod stroke. All the transducers are interfaced with a connector block through shielded cables. The connector block is connected to a PCI-MIO-16E-4 Data Acquisition (DAQ) board [16] (mounted on a PCI slot inside a desktop computer) that collects the data during brake application and release. An application program is used to collect and store the data in the computer.3. Modeling the response of the relay valveIn this section, we shall present a description of the model of the relay valve. We adopt a lumped parameter approach in the development of this model. Friction at the sliding surfaces in the treadle and relay valves is neglected since they are well lubricated. The springs present in these valves have been experimentally found to be nearly linear in the range of their operation (except the rubber graduating spring used in the treadle valve, see Fig. 4) and the spring constants have been determined from experimental data. Other parameters such as areas, initial deflections, etc., are measured and used in the model.In this article, our objective is to develop a model for predicting the pressure transients in the rear brake chambers actuated by the relay valve during the brake application process. The relay valve is controlled by means of the compressed air delivered by the primary circuit of the treadle valve during a brake application. We shall consider the configuration of the brake system where the delivery port of the primary circuit of the treadle valve is connected to the control port of the relay valve. Compressed air is provided from the storage reservoirs to the relay valve at its supply port and one of the delivery ports of the relay valve is connected to a rear brake chamber. We shall measure the pressure transients at the primary delivery port of the treadle valve and in the rear brake chamber in our experiments. The pressure measured at the primary delivery port of the treadle valve will be provided as input to the numerical scheme that solves the model equations developed to predict the pressure transients in the rear brake chamber.When the driver presses the brake pedal, the primary piston in the treadle valve (see Fig. 4) first closes the primary exhaust port (by moving a distance equal to xpt) and then opens up the primary inlet port (xpp>xpt, xpp being the displacement of the primary piston from its initial position). This action serves to meter the compressed air from the reservoir to the primary delivery port. We shall refer to this phase as the “apply phase”. When the pressure in the primary circuit increases to a level such that it balances the force applied by the driver, the primary piston closes the primary inlet port with the exhaust port also remaining closed (xpp=xpt). We shall refer to this phase as the “hold phase”. When the driver releases the brake pedal, the primary piston return spring forces the primary piston to its initial position. This action opens the exhaust port (xpp<xpt) and air is exhausted from the primary delivery port to the atmosphere. We shall refer to this phase as the “exhaust phase”. A detailed derivation of the model of the treadle valve can be foundin [13].A schematic of the cross-sectional view of the relay valve used in our experimental setup is presented in Fig. 5. The compressed air from the delivery port of the primary circuit of the treadle valve enters the control port of the relay valve. The resulting force pushes the relay valve piston and the exhaust port of the relay valve is closed when the relay valve piston moves a distance equal to xrpt. Once the pre-loads on the relay valve assembly gasket are overcome, the inlet port of the relay valve is opened (xrpp>xrpt, xrpp being the displacement of the relay valve piston from its initial position). Compressed air is now metered from the supply port of the relay valve to its delivery port and subsequently to the rear brake chambers. This is the apply phase associated with the operation of the relay valve. When the pressure in the delivery port of the relay valve increases to a level such that it balances the forces acting on the relay valve piston due to the compressed air from the treadle valve, the inlet port of the relay valve is closed with its exhaust port also remaining closed (xrpp=xrpt). This is the hold phase associated with the operation of the relay valve. When the brake pedal is released by the driver, air is exhausted from the primary circuit of the treadle valve and consequently from the control port of the relay valve. Due to the presence of compressed air in the delivery port of the relay valve, the relay valve piston is pushed back to its initial position and this opens the exhaust port of the relay valve (xrpp<xrpt). Thus, air is exhausted from the delivery port of the relay valve to the atmosphere. This is the exhaust phase associated with the operation of the relay valve.Fig. 5. A sectional view of the relay valve.View thumbnail imagesThe equation of motion governing the mechanics of the operation of the relay valve piston and the relay valve assembly gasket during the apply and the hold phases is given by(1)where Mrpp and Mrv denote respectively the mass of the relay valve piston and the relay valve assembly gasket, xrpp denotes the displacement of the relay valve piston from its initial position, xrpt is the distance traveled by the relay valve piston before it closes the relay valve exhaust port, Krv is the spring constant of the relay valve assembly return spring, Fkrvi is the pre-load on the same, Arpp is the net area of the relay valve piston exposed to the pressurized air at the control port of the relay valve, Arpp1 is the net area of the relay valve piston exposed to the pressurized air at the delivery port of the relay valve, Arpp2 is the net area of the relay valve piston exposed to the exhaust port of the relay valve, Arv1 is the net cross-sectional area of the relay valve assembly gasket exposed to the pressurized air at the supply port of the relay valve, Arv2 is the net cross-sectional area of the relay valve assembly gasket exposed to the pressurized air at the delivery port of the relay valve, Ppd is the pressure of air at the delivery port of the primary circuit of the treadle valve, Prs is the pressure of air being supplied to the relay valve, Prd is the pressure of air at the delivery port of the relay valve and is the atmospheric pressure.The mass of the relay valve piston is of the order of around 0.1 kg and the magnitude of the spring and pressure forces is found to be of the order of 102 N. Thus, the acceleration required for the inertial forces to be comparable with the spring force and the pressure force terms has to be of theorder of 102–103 m/s2, which is not the case. Hence the inertial forces are neglected and the above equation reduces to(2)The equation of motion of the relay valve piston during the exhaust phase is given by(3)Neglecting inertial forces, the above equation reduces to(4)PpdArpp=Prd(Arpp1+Arpp2).Next, we will consider the flow of air in the portion of the brake system under study. The relay valve opening is modeled as a nozzle. For the flow through a restriction, if the ratio of the cross-sectional area of the upstream section to the cross-sectional area of the restriction is 4.4 or higher, the approach velocity to this restriction can be neglected and the upstream properties (such as pressure, enthalpy, temperature, etc.) can be taken to be the upstream total or stagnation properties [17]. In our case, the minimum ratio of the cross-sectional area of the supply chamber of the relay valve to the cross-sectional area of the relay valve opening (the restriction) is found to be more than this value. Hence, we can consider the valve opening as a nozzle and take the properties in the supply chamber of the valve as the stagnation properties at the inlet section of the nozzle. The flow through the nozzle is assumed to be one-dimensional and isentropic. We also assume that the fluid properties are uniform at all sections in the nozzle. Air is assumed to behave like an ideal gas with constant specific heats. Under the above assumptions, the part of the pneumatic subsystem under consideration can be visualized as illustrated in Fig. 6.Fig. 6. The simplified visualization of the pneumatic subsystem under consideration.View thumbnail imagesThe energy equation for the flow of air through the nozzle under the above assumptions can be written as [18](5)where ho is the specific stagnation enthalpy at the entrance section of the nozzle, h is the specific enthalpy at the exit section of the nozzle and u is the magnitude of the velocity of air at the exit section of the nozzle.For isentropic flow of an ideal gas with constant specific heats, the pressure (P), density (ρ) and temperature (T) are related by(6)where γis the ratio of specific heats.The mass flow rate of air from the relay valve opening at any instant of time (denoted by ) isgiven bywhere Ap is the cross-sectional area of the valve opening. This is the rate at which air is accumulating in the hoses and the brake chamber once the relay valve is actuated. Since we lump the properties of air inside the hose and the brake chamber, the mass of air in the brake chamber at any instant of time is obtained from the ideal gas equation of state as(8)where Vb is the volume of air in the brake chamber and Trd is the temperature of air in the brake chamber at that instant of time.Let us now consider the mechanics of the operation of the brake chamber. A cross-sectional view of the brake chamber is shown in Fig. 7. When the brake is applied, the brake chamber diaphragm starts to move only after a minimum threshold pressure is reached. This pressure is required to overcome the pre-loads on the diaphragm. When this pressure is attained in the brake chamber, the diaphragm moves such that the push rod is pushed out of the brake chamber. Once the brake pads contact the brake drum and steady state is reached, the volume of air in the brake chamber will be the maximum during that particular brake application. Thus, the volume of air in the brake chamber at any instant of time during the brake application process is given by(9)where V o1 is the initial volume of air in the brake chamber before the application of the brake, V o2 is the maximum volume of air in the brake chamber, Ab is the cross-sectional area of the brake chamber, xb is the displacement of the brake chamber diaphragm, i.e., the stroke of the push rod, and xbmax is the maximum stroke of the push rod.Fig. 7. A sectional view of the brake chamber.View thumbnail imagesIn our current experimental setup, the rear brake chambers are mounted on a fixture and the end of the push rod outside the brake chamber is not connected to a slack adjuster. The push rod is brought to rest during a given brake application when it strikes a plate mounted with its face perpendicular to the direction of motion of the push rod. The position of this plate can be adjusted to vary the push rod stroke. Hence, a reasonable model for the brake chamber is given by(10)where Mb is the mass of the brake chamber diaphragm, Kb is the spring constant of the brake chamber return spring and Fkbi is the pre-load on the brake chamber diaphragm return spring. It should be noted that the pressure of air in the rear brake chamber at any instant of time is assumed to be the same as the pressure of air at the delivery port of the relay valve at that instant of time. Neglecting inertial forces when compared to the force due to the pressure and spring forces, the above equation reduces toIn the case of a brake chamber mounted on an actual axle, the relationship between the push rod stroke and the brake chamber pressure has been found to be different than the one given by Eq.(11) due to the presence of additional components such as the slack adjuster, S-cam, brake pads and brake drum [15]. Thus, the model relating the push rod stroke and the brake chamber pressure for a rear brake chamber mounted on an actual rear axle should be developed as described in [15]. Differentiating Eq. (8) with respect to time and comparing the result with Eq. (7), and using Eqs.(5), (6), (9) and (11), we obtain the equation describing the pressure response of the relay valve during the apply and hold phases as(12)where Trs is the temperature of the air being supplied to the relay valve, CD is the discharge coefficient, R is the specific heat of air, γis the ratio of specific heats of air (both R and γare assumed to be constants) and(13)Ap=2πrrv(xrpp−xrpt),with rrv being the external radius of the relay valve inlet section. The discharge coefficient (CD) is used in order to compensate for the losses during the flow. Due to the complexity involved in calibrating the valve to determine the value of the discharge coefficient, we assumed a value of 0.82 for CD as recommended in [17]. The pressure transients in the brake chamber during the apply and hold phases are obtained by solving Eqs. (2) and (12) along with the initial condition that at the start of a given brake application, the brake chamber pressure is equal to the atmospheric pressure.4. Corroboration of the modelIn this section, we corroborate the model for the relay valve by comparing its predictions against experimental data obtained from various test runs carried out over a range of supply pressures. It should be noted that the typical supply pressure in air brake systems is usually between 825.3 kPa (105 psig) and 928.8 kPa (120 psig) and this is the pressure range provided by the compressor used in our experimental setup. Eqs. (2) and (12) are solved numerically to obtain the pressure transients in the rear brake chamber during the apply and hold phases of a given brake application. The pressure measured at the delivery port of the primary circuit of the treadle valveis given as the input data to the numerical scheme. The prediction of the model for a test run is compared with the data collected during that test run and the results from various test runs are presented in Fig. 8, Fig. 9, Fig. 10, Fig. 11 and Fig. 12. In these figures, time (in seconds) and brake chamber pressure (in Pa) have been plotted on the abscissa and the ordinate respectively. The value corresponds to that instant of time at which the computer program for collecting the data is started.Fig. 8. Pressure transients at 653 kPa (80 psig) supply pressure —apply phase.View thumbnail imagesFig. 9. Pressure transients at 722 kPa (90 psig) supply pressure —apply phase.View thumbnail imagesFig. 10. Pressure transients at 584 kPa (70 psig) supply pressure —apply and exhaust phases. View thumbnail imagesFig. 11. Pressure transients at 653 kPa (80 psig) supply pressure —apply and exhaust phases. View thumbnail imagesFig. 12. Pressure transients at 584 kPa (70 psig) supply pressure —repeated application.View thumbnail imagesIt can be observed from these figures that the model is able to predict the beginning and end of each brake application reasonably well. The steady state brake chamber pressure is also predicted well by the model in all the cases. The model has also captured the pressure transients well in the exhaust phase during a complete brake application and release cycle as shown in Fig. 10 and Fig. 11. It has also predicted the pressure transients well in the case of repeated brake applications as can be observed from Fig. 12.5. ConclusionsIn this article, we have developed a hybrid model for predicting the response of the relay valve used in air brake systems of commercial vehicles. The relay valve is actuated by the compressed air from the delivery port of the primary circuit of the treadle valve. We have presented the main governing equations for the pressure transients in a rear brake chamber attached to a delivery port of the relay valve. We have corroborated this model using data obtained from experimental test runs performed over a range of supply pressures. We plan to incorporate this model of the relay valve into an overall model of the air brake system which can be used in control and diagnostic applications.References[1]S.F. Williams, R.R. Knipling, Automatic slack adjusters for heavy vehicle air brake systems, Tech. Rep. DOT HS 807 724, National Highway Traffic Safety Administration, Washington, D. C., February 1991。
毕业设计中英文翻译
Programmable logic controllerA programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.1.HistoryThe PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay.In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner.One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM,when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance.The automotive industry is still one of the largest users of PLCs.2.DevelopmentEarly PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver.Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Logic, a very high-level programming language designed to program PLCs based on state transition diagrams.Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, for the aforementioned reasons. Newer formats such as State Logic and Function Block (which is similar to the way logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic.A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats.2.1ProgrammingEarly PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory.More recently, PLCs are programmed using application software on personal computers. The computer is connected to the PLC through Ethernet, RS-232, RS-485 or RS-422 cabling. The programming software allows entry and editing of theladder-style logic. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC though a programming board which writes the program into a removable chip such as an EEPROM or EPROM.3.FunctionalityThe functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.4.PLC TopicsFeaturesThe main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.System scaleA small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O. Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants.User interfacePLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control.A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface.CommunicationsPLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BACnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols.Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.ProgrammingPLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.IEC 61131-3 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST(Structured text, similar to the Pascal programming language), IL (Instruction list, similar to assembly language) and SFC (Sequential function chart). These techniques emphasize logical organization of operations.While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible.DDER LOGIC FUNCTIONSTopics:• Functions for data handling, mathematics, conversions, array operations, statistics,comparison and Boolean operations.• Design examplesObjectives:• To understand basic functions that allow calculations and comparisons• To understand array f unctions using memory files5.1INTRODUCTIONLadder logic input contacts and output coils allow simple logical decisions. Functionsextend basic ladder logic to allow other types of control. For example, the addition oftimers and counters allowed event based control. A longer list of functions is shown inFigure 5.1. Combinatorial Logic and Event functions have already been covered. Thischapter will discuss Data Handling and Numerical Logic. The next chapter will coverLists and Program Control and some of the Input and Output functions. Remaining functionswill be discussed in later chapters.Combinatorial Logic- relay contacts and coilsEvents- timer instructions- counter instructionsData Handling- moves- mathematics- conversionsNumerical Logic- boolean operations- comparisonsLists- shift registers/stacks- sequencersProgram Control- branching/looping- immediate inputs/outputs- fault/interrupt detectionInput and Output- PID- communications- high speed counters- ASCII string functionsFigure 5.1 Basic PLC Function CategoriesMost of the functions will use PLC memory locations to get values, store values and track function status. Most function will normally become active when the input is true. But, some functions, such as TOF timers, can remain active when the input is off. Other functions will only operate when the input goes from false to true, this is known as positive edge triggered. Consider a counter that only counts when the input goes from false to true, the length of time the input is true does not change the function behavior. A negative edge triggered function would be triggered when the input goes from true to false. Most functions are not edge triggered: unless stated assume functions are not edge triggered.NOTE: I do not draw functions exactly as they appear in manualsandprogramming software.This helps save space and makes the instructionssomewhat easier to read. All of the necessary information is given.5.2 DATA HANDLING5.2.1 Move FunctionsThere are two basic types of move functions;MOV(value,destination) - moves a value to a memory locationMVM(value,mask,destination) - moves a value to a memory location, but with a mask to select specific bits.The simple MOV will take a value from one location in memory and place it inanother memory location. Examples of the basic MOV are given in Figure 5.2. When A is true the MOV function moves a floating point number from the source tothe destination address. The data in the source address is left unchanged. When B is true the floating point number in the source will be converted to an integer and storedin the destination address in integer memory. The floating point number will be rounded up or down to the nearest integer. When C is true the integer value of 123will be placed in the integer file N7:23.NOTE: when a function changes a value, except for inputs and outputs, the value is changed immediately. Consider Figure 15.2, if A, B and C are all true, then the value in F8:23 will change before the next instruction starts. This is different than the input and output scans that only happen before and after the logic scan.Figure 5.2 Examples of the MOV FunctionA more complex example of move functions is given in Figure 5.3. When Abecomes true the first move statement will move the value of 130 into N7:0. And, the second move statement will move the value of -9385 from N7:1 to N7:2. (Note: The number is shown as negative because we are using 2s compliment.) For the simple MOVs the binary values are not needed, but for the MVM statement the binary values are essential. The statement moves the binary bits from N7:3 to N7:5, but only those bits that are also on in the mask N7:4, other bits in the destination will be left untouched. Notice that the first bit N7:5/0 is true in the destination address before and after, but it is not true in the mask. The MVM function is very useful for applications where individual binary bits are to be manipulated, but they are less useful when dealing with actual number values.5.2.2 Mathematical FunctionsMathematical functions will retrieve one or more values, perform an operation andstore the result in memory. Figure 15.4 shows an ADD function that will retrieve values from N7:4 and F8:35, convert them both to the type of the destination address, add the floating point numbers, and store the result in F8:36. The function has two sources labelled source A and source B. In the case of ADD functions the sequence can change, but this is not true for other operations such as subtraction and division. A list of other simple arithmetic function follows. Some of the functions, such as the negative function are unary, so there is only one source.Figure 5.4 Arithmetic FunctionsAn application of the arithmetic function is shown in Figure 5.5. Most of theoperations provide the results we would expect. The second ADD function retrieves avalue from N7:3, adds 1 and overwrites the source - this is normally known as an increment operation. The first DIV statement divides the integer 25 by 10, the result is rounded to the nearest integer, in this case 3, and the result is stored in N7:6. The NEG instruction takes the new value of -10, not the original value of 0, from N7:4 inverts the sign and stores it in N7:7.Figure 5.5 Arithmetic Function ExampleA list of more advanced functions are given in Figure 15.6. This list includes basictrigonometry functions, exponents, logarithms and a square root function. Thelast function CPT will accept an expression and perform a complex calculation.Figure 5.6 Advanced Mathematical FunctionsFigure 5.7 shows an example where an equation has been converted to ladderlogic. The first step in the conversion is to convert the variables in the equation to unused memory locations in the PLC. The equation can then be converted using the most nested calculations in the equation, such as the LN function. In this case the results of the LN function are stored in another memory location, to be recalled later. The other operations are implemented in a similar manner. (Note: This equation could have been implemented in other forms, using fewer memory locations.)Figure 5.7 An Equation in Ladder LogicThe same equation in Figure 5.7 could have been implemented with a CPT function as shown in Figure 5.8. The equation uses the same memory locations chosen in Figure 5.7. The expression is typed directly into the PLC programmingsoftware.Figure 5.8 Calculations with a Compute FunctionMath functions can result in status flags such as overflow, carry, etc. care mustbetaken to avoid problems such as overflows. These problems are less commonwhen using floating point numbers. Integers are more prone to these problemsbecause they are limited to the range from -32768 to 32767.5.2.3 ConversionsLadder logic conversion functions are listed in Figure 5.9. The example function will retrieve a BCD number from the D type (BCD) memory and convert it to a floating point number that will be stored in F8:2. The other function will convert from 2s compliment binary to BCD, and between radians and degrees.Figure 5.9 Conversion FunctionsExamples of the conversion functions are given in Figure 5.10. The functionsload in a source value, do the conversion, and store the results. The TOD conversion to BCD could result in an overflow error.Figure 5.10 Conversion Example5.2.4 Array Data FunctionsArrays allow us to store multiple data values. In a PLC this will be a sequential series of numbers in integer, floating point, or other memory. For example, assume we are measuring and storing the weight of a bag of chips in floating point memory starting at #F8:20 (Note the ’#’ for a data file). We could read a weight value every 10 minutes, and once every hour find the average of the six weights. This section will focus on techniques that manipulate groups of data organized in arrays, also called blocks in the manuals.5.2.4.1 - StatisticsFunctions are available that allow statistical calculations. These functions arelisted in Figure 5.11. When A becomes true the average (AVE) conversion will start at memory location F8:0 and average a total of 4 values. The control word R6:1 is used to keep track of the progress of the operation, and to determine when the operation is complete. This operation, and the others, are edge triggered. The operation may require multiple scans to be completed. When the operation is done the average will be stored in F8:4 and the R6:1/DN bit will be turned on.Figure 5.11 Statistic FunctionsExamples of the statistical functions are given in Figure 5.12 for an array of data that starts at F8:0 and is 4 values long. When done the average will be stored in F8:4, and the standard deviation will be stored in F8:5. The set of values will also be sorted in ascending order from F8:0 to F8:3. Each of the function should have their own control memory to prevent overlap. It is not a good idea to activate the sort and the other calculations at the same time, as the sort may move values during the calculation, resulting in incorrect calculations.5.2.4.2 - Block OperationsA basic block function is shown in Figure 5.13. This COP (copy) function will copy an array of 10 values starting at N7:50 to N7:40. The FAL function will perform mathematical operations using an expression string, and the FSC function will allow two arrays to be compared using an expression. The FLL function will fill ablock of memory with a single value.Figure 5.13 Block Operation FunctionsFigure 5.14 shows an example of the FAL function with different addressingmodes. The first FAL function will do the following calculations N7:5=N7:0+5, N7:6=N7:1+5, N7:7=N7:2+5, N8:7=N7:3+5, N7:9=N7:4+5. The second FAL statement does not have a file ’#’ sign in front of the expression value, so the calculations will be N7:5=N7:0+5, N7:6=N7:0+5, N7:7=N7:0+5, N8:7=N7:0+5,N7:9=N7:0+5. With a mode of 2 the instruction will do two of the calculations for every scan where B is true. The result of the last FAL statement will be N7:5=N7:0+5, N7:5=N7:1+5,N7:5=N7:2+5, N7:5=N7:3+5, N7:5=N7:4+5. The last operation would seem to be useless, but notice that the mode is incremental. This mode will do one calculation for each positive transition of C. The all mode will perform all five calculations in a single scan. It is also possible to put in a number that will indicate the number of calculations per scan. The calculation time can be long for large arrays and trying to do all of the calculations in one scan may lead to a watchdog time-out fault.5.3 LOGICAL FUNCTIONS5.3.1 Comparison of ValuesComparison functions are shown in Figure 15.15. Previous function blocks were outputs, these replace input contacts. The example shows an EQU (equal) function that compares two floating point numbers. If the numbers are equal, the output bit B3:5/1 is true, otherwise it is false. Other types of equality functions are also listed.Figure 5.15 Comparison FunctionsThe example in Figure 15.16 shows the six basic comparison functions. To the right of the figure are examples of the comparison operations.Figure 5.16 Comparison Function ExamplesThe ladder logic in Figure 5.16 is recreated in Figure 5.17 with the CMP function that allows text expressions.Figure 5.17 Equivalent Statements Using CMP StatementsExpressions can also be used to do more complex comparisons, as shown in Figure 5.18. The expression will determine if F8:1 is between F8:0 and F8:2.Figure 5.18 A More Complex Comparison ExpressionThe LIM and MEQ functions are shown in Figure 5.19. The first three functions will compare a test value to high and low limits. If the high limit is above the low limit and the test value is between or equal to one limit, then it will be true. If the low limit is above the high limit then the function is only true for test values outside the range. The masked equal will compare the bits of two numbers, but only those bits that are true in the mask.Figure 5.19 Complex Comparison FunctionsFigure 5.20 shows a numberline that helps determine when the LIM function willbe true.Figure 5.20 A Number Line for the LIM FunctionFile to file comparisons are also permitted using the FSC instruction shown in Figure 5.21. The instruction uses the control word R6:0. It will interpret the expression 10 times, doing two comparisons per logic scan (the Mode is 2). The comparisons will be F8:10<F8:0, F8:11<F8:0 then F8:12<F8:0, F8:13<F8:0 then F8:14<F8:0,F8:15<F8:0 then F8:16<F8:0, F8:17<F8:0 then F8:18<F8:0,F8:19<F8:0. The function will continue until a false statement is found, or the comparison completes. If the comparison completes with no false statements the output A will then be true. The mode could have also been All to execute all the comparisons in one scan, or Increment to update when the input to the function is true - in this case the input is a plain wire, so it will always be true.Figure 5.21 File Comparison Using Expressions5.3.2 Boolean FunctionsFigure 5.22 shows Boolean algebra functions. The function shown will obtain data words from bit memory, perform an and operation, and store the results in a new location in bit memory. These functions are all oriented to word level operations. The ability to perform Boolean operations allows logical operations on more than a single bit.Figure 5.22 Boolean FunctionsThe use of the Boolean functions is shown in Figure 15.23. The first three functions require two arguments, while the last function only requires one. The AND function will only turn on bits in the result that are true in both of the source words. The OR function will turn on a bit in the result word if either of the source word bits is on. The XOR function will only turn on a bit in the result word if the bit is on in only one of the source words. The NOT function reverses all of the bits in the source word.6.PLC compared with other control systemsPLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands or millions of units.For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.。
毕业设计外文翻译模板
本科生毕业设计（论文）外文翻译毕业设计（论文）题目：组合钻床动力滑台液压系统及电控系统设计外文题目： Drilling machine译文题目：组合钻床学生姓名：马莉莉专业：机械设计制造及其自动化0701班指导教师姓名：王洁评阅日期：正文内容小四号字，宋体，行距1.5倍行距。
The drilling machine is a machine for making holes with removal of chips and it is used to create or enlarge holes. There are many different types of drilling machine for different jobs, but they can be basically broken down into two categories.The bench drill is used for drilling holes through raw materials such as wood, plastic and metal and gets its name because it is bolted to bench for stability so that larger pieces of work can be drilled safely. The pillar drill is a larger version that stands upright on the floor. It can do exactly the same work as the bench drill, but because of its size it can be used to drill larger pieces of materials and produce bigger holes. Most modern drilling machines are digitally automated using the latest computer numerical control (CNC) technology.Because they can be programmed to produce precise results, over and over again, CNC drilling machines are particularly useful for pattern hole drilling, small hole drilling and angled holes.If you need your drilling machine to work at high volume, a multi spindle drill head will allow you to drill many holes at the same time. These are also sometimes referred to as gang drills.Twist drills are suitable for wood, metal and plastics and can be used for both hand and machine drilling, with a drill set typically including sizes from 1mm to 14mm. A type of drill machine known as the turret stores tools in the turret and positions them in the order needed for work.Drilling machines, which can also be referred to as bench mounted drills or floor standing drills are fixed style of drills that may be mounted on a stand or bolted to the floor or workbench. A drilling machine consists of a base, column, table, spindle), and drill head, usually driven by an induction motor.The head typically has a set of three which radiate from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion. Some older models do however rely on the operator to lift and re clamp the table in position. The table may also be offset from the spindles axis and in some cases rotated to a position perpendicular to the column.The size of a drill press is typically measured in terms of swing which can be is defined as twice the throat distance, which is the distance from the centre of the spindle to the closest edge of the pillar. Speed change on these drilling machines is achieved by manually moving a belt across a stepped pulley arrangement.Some drills add a third stepped pulley to increase the speed range. Moderndrilling machines can, however, use a variable-speed motor in conjunction with the stepped-pulley system. Some machine shop drilling machines are equipped with a continuously variable transmission, giving a wide speed range, as well as the ability to change speed while the machine is running.Machine drilling has a number of advantages over a hand-held drill. Firstly, it requires much less to apply the drill to the work piece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.The use of a table also allows a vice or clamp to be used to position and restrain the work. This makes the operation much more secure. In addition to this, the angle of the spindle is fixed relative to the table, allowing holes to be drilled accurately and repetitively.Most modern drilling machines are digitally automated using the latest computer numerical control (CNC) technology. Because they can be programmed to produce precise results, over and over again, CNC drilling machines are particularly useful for pattern hole drilling, small hole drilling and angled holes.Drilling machines are often used for miscellaneous workshop tasks such as sanding, honing or polishing, by mounting sanding drums, honing wheels and various other rotating accessories in the chuck. To add your products click on the traders account link above.You can click on the links below to browse for new, used or to hire a drilling machine.Drilling machines are used for drilling, boring, countersinking, reaming, and tapping. Several types are used in metalworking: vertical drilling machines, horizontal drilling machines, center-drilling machines, gang drilling machines, multiple-spindle drilling machines, and special-purpose drilling machines.Vertical drilling machines are the most widely used in metalworking. They are used to make holes in relatively small work-pieces in individual and small-lot production; they are also used in maintenance shops. The tool, such as a drill, countersink, or reamer, is fastened on a vertical spindle, and the work-piece is secured on the table of the machine. The axes of the tool and the hole to be drilled are aligned by moving the workpiece. Programmed control is also used to orient the workpiece and to automate the operation. Bench-mounted machines, usually of the single-spindle type, are used to make holes up to 12 mm in diameter, for instance, in instrument-making.Heavy and large workpieces and workpieces with holes located along a curved edge are worked on radial drilling machines. Here the axes of the tool and the hole to be drilled are aligned by moving the spindle relative to the stationary work-piece.Horizontal drilling machines are usually used to make deep holes, for instance, in axles, shafts, and gun barrels for firearms and artillery pieces.Center-drilling machines are used to drill centers in the ends of blanks. They are sometimes equipped with supports that can cut off the blank before centering, and in such cases they are called center-drilling machines. Gang drilling machines with more than one drill head are used to produce several holes at one time. Multiple-spindle drilling machines feature automation of the work process. Such machines can be assembled from several standardized, self-contained heads with electric motors and reduction gears that rotate the spindle and feed the head. There are one-, two-, and three-sidedmultiple-spindle drilling machines with vertical, horizontal, and inclined spindles for drilling and tapping. Several dozen such spindles may be mounted on a single machine. Special-purpose drilling machines, on which a limited range of operations is performed, are equipped with various automated devices.Multiple operations on workpieces are performed by various combination machines. These include one- and two-sided jig boring machines,drilling-tapping machines (usually gang drilling machines with reversible thread-cutting spindles), milling-type drilling machines and drilling-mortising machines used mainly for woodworking, and automatic drilling machines.In woodworking much use is made of single- and multiple-spindle vertical drilling machines, one- and two-sided, horizontal drilling machines (usually with multiple spindles), and machines equipped with a swivel spindle that can be positioned vertically and horizontally. In addition to drilling holes, woodworking machines may be used to make grooves, recesses, and mortises and to remove knots.英文翻译指导教师评阅意见。
毕业设计中英文翻译
本科生毕业设计（论文）外文翻译毕业设计（论文）题目：电力系统检测与计算外文题目：The development of the single chipmicrocomputer译文题目：单片机技术的发展与应用学生姓名： XXX专业： XXX指导教师姓名： XXX评阅日期：单片机技术的发展与应用从无线电世界到单片机世界现代计算机技术的产业革命，将世界经济从资本经济带入到知识经济时代。
在电子世界领域，从 20 世纪中的无线电时代也进入到 21 世纪以计算机技术为中心的智能化现代电子系统时代。
现代电子系统的基本核心是嵌入式计算机系统(简称嵌入式系统)，而单片机是最典型、最广泛、最普及的嵌入式系统。
一、无线电世界造就了几代英才。
在 20 世纪五六十年代，最具代表的先进的电子技术就是无线电技术，包括无线电广播，收音，无线通信(电报)，业余无线电台，无线电定位，导航等遥测、遥控、遥信技术。
早期就是这些电子技术带领着许多青少年步入了奇妙的电子世界，无线电技术展示了当时科技生活美妙的前景。
电子科学开始形成了一门新兴学科。
无线电电子学，无线通信开始了电子世界的历程。
无线电技术不仅成为了当时先进科学技术的代表，而且从普及到专业的科学领域，吸引了广大青少年，并使他们从中找到了无穷的乐趣。
从床头的矿石收音机到超外差收音机；从无线电发报到业余无线电台；从电话，电铃到无线电操纵模型。
无线电技术成为当时青少年科普、科技教育最普及，最广泛的内容。
至今，许多老一辈的工程师、专家、教授当年都是无线电爱好者。
无线电技术的无穷乐趣，无线电技术的全面训练，从电子学基本原理，电子元器件基础到无线电遥控、遥测、遥信电子系统制作，培养出了几代科技英才。
二、从无线电时代到电子技术普及时代。
早期的无线电技术推动了电子技术的发展，其中最主要的是真空管电子技术向半导体电子技术的发展。
半导体电子技术使有源器件实现了微小型化和低成本，使无线电技术有了更大普及和创新，并大大地开阔了许多非无线电的控制领域。
毕业设计中英文翻译
Integrated circuitAn integrated circuit or monolithic integrated circuit (also referred to as IC, chip, or microchip) is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material. Additional materials are deposited and patterned to form interconnections between semiconductor devices.Integrated circuits are used in virtually all electronic equipment today and have revolutionized the world of electronics. Computers, mobile phones, and other digital appliances are now inextricable parts of the structure of modern societies, made possible by the low cost of production of integrated circuits.IntroductionICs were made possible by experimental discoveries showing that semiconductor devices could perform the functions of vacuum tubes and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach tocircuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC than to construct a discrete circuit. Performance is high because the components switch quickly and consume little power (compared to their discrete counterparts) as a result of the small size and close proximity of the components. As of 2006, typical chip areas range from a few square millimeters to around 350 mm2, with up to 1 million transistors per mm2.TerminologyIntegrated circuit originally referred to a miniaturized electronic circuit consisting of semiconductor devices, as well as passive components bonded to a substrate or circuit board.[1] This configuration is now commonly referred to as a hybrid integrated circuit. Integrated circuit has since come to refer to the single-piece circuit construction originally known as a monolithic integrated circuit.[2]InventionEarly developments of the integrated circuit go back to 1949, when the German engineer Werner Jacobi (Siemens AG) filed a patent for an integrated-circuit-like semiconductor amplifying device showing five transistors on a common substrate arranged in a 2-stage amplifier arrangement. Jacobi disclosed small and cheap hearing aids as typical industrial applications of his patent. A commercial use of his patent has not been reported.The idea of the integrated circuit was conceived by a radar scientist working for the Royal Radar Establishment of the British Ministry of Defence, Geoffrey W.A. Dummer (1909–2002). Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington, D.C. on May 7, 1952.[4] He gave many sympodia publicly to propagate his ideas, and unsuccessfully attempted to build such a circuit in 1956.A precursor idea to the IC was to create small ceramic squares (wafers), each one containing a single miniaturized component. Components could then be integrated and wired into a tridimensional or tridimensional compact grid. This idea, which looked very promising in 1957, was proposed to the US Army by Jack Kilby, and led to the short-lived Micro module Program. However, as the project was gaining momentum, Jack Kilby came up with a new, revolutionary design: the IC.Newly employed by Texas Instruments, Jack Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on September 12, 1958.In his patent application of February 6, 1959, Jack Kilby described his new device as ―a body of semiconductor material ... wherein all the components of the electronic circuit are completely integrated.‖Jack Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit.Jack Kilby's work was named an IEEE Milestone in 2009.Noyce also came up with his own idea of an integrated circuit half a year later than Jack Kilby. His chip solved many practical problems that Jack Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon, whereas Jack Kilby chip was made of germanium. GenerationsIn the early days of integrated circuits, only a few transistors could be placed on a chip, as the scale used was large because of the contemporary technology, and manufacturing yields were low by today's standards. As the degree of integration was small, the design was done easily. Over time, millions, and today billions of transistors could be placed on one chip, and to make a good design became a task to be planned thoroughly. This gave rise to new design methods.SSI, MSI and LSIThe first integrated circuits contained only a few transistors. Called "small-scale integration" (SSI), digital circuits containing transistors numbering in the tens for example, while early linear ICs such as the Plessey SL201 or the Philips TAA320 had as few as two transistors. The term Large Scale Integration was first used by IBM scientist Rolf Landauer when describing the theoretical concept, from there came the terms for SSI, MSI, VLSI, and ULSI.SSI circuits were crucial to early aerospace projects, and aerospace projects helped inspire development of the technology. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertial guidance systems; the Apollo guidance computer led and motivated the integrated-circuit technology,while the Minuteman missile forced it into mass-production. The Minuteman missile program and various other Navy programs accounted for the total $4 million integrated circuit market in 1962, and by 1968, U.S. Government space and defense spending still accounted for 37% of the $312 million total production. The demand by the U.S. Government supported the nascent integrated circuit market until costs fell enough to allow firms to penetrate the industrial and eventually the consumer markets. The average price per integrated circuit dropped from $50.00 in1962 to $2.33 in 1968.[13] Integrated circuits began to appear in consumer products by the turn of the decade, a typical application being FMinter-carrier sound processing in television receivers.The next step in the development of integrated circuits, taken in the late 1960s, introduced devices which contained hundreds of transistors on each chip, called "medium-scale integration" (MSI).They were attractive economically because while they cost little more to produce than SSI devices, they allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other advantages.Further development, driven by the same economic factors, led to "large-scale integration" (LSI) in the mid 1970s, with tens of thousands of transistors per chip.Integrated circuits such as 1K-bit RAMs, calculator chips, and the first microprocessors, that began to be manufactured in moderate quantities in the early 1970s, had under 4000 transistors. True LSI circuits, approaching 10,000 transistors, began to be produced around 1974, for computer main memories and second-generation microprocessors.VLSIThe final step in the development process, starting in the 1980s and continuing through the present, was "very large-scale integration" (VLSI). The development started with hundreds of thousands of transistors in the early 1980s, and continues beyond several billion transistors as of 2009. Multiple developments were required to achieve this increased density. Manufacturers moved to smaller design rules and cleaner fabrication facilities, so that they could make chips with more transistors and maintain adequate yield. The path of process improvements was summarized by the International Technology Roadmap for Semiconductors (ITRS). Design tools improved enough to make it practical to finish these designs in a reasonable time. The more energy efficient CMOS replaced NMOS and PMOS, avoiding a prohibitive increase in power consumption. Better texts such as the landmark textbook by Mead and Conway helped schools educate more designers, among other factors.In 1986 the first one megabit RAM chips were introduced, which contained more than one million transistors. Microprocessor chips passed the million transistor mark in 1989 and the billion transistor mark in 2005.[14] The trend continues largely unabated, with chips introduced in 2007 containing tens of billions of memory transistors.[15]ULSI, WSI, SOC and 3D-ICTo reflect further growth of the complexity, the term ULSI that stands for "ultra-large-scale integration" was proposed for chips of complexityof more than 1 million transistors.Wafer-scale integration (WSI) is a system of building very-large integrated circuits that uses an entire silicon wafer to produce a single "super-chip". Through a combination of large size and reduced packaging, WSI could lead to dramatically reduced costs for some systems, notably massively parallel supercomputers. The name is taken from the term Very-Large-Scale Integration, the current state of the art when WSI was being developed.A system-on-a-chip (SoC or SOC) is an integrated circuit in which all the components needed for a computer or other system are included on a single chip. The design of such a device can be complex and costly, and building disparate components on a single piece of silicon may compromise the efficiency of some elements. However, these drawbacks are offset by lower manufacturing and assembly costs and by a greatly reduced power budget: because signals among the components are kept on-die, much less power is required (see Packaging).A three-dimensional integrated circuit (3D-IC) has two or more layers of active electronic components that are integrated both vertically and horizontally into a single circuit. Communication between layers useson-die signaling, so power consumption is much lower than in equivalent separate circuits. Judicious use of short vertical wires can substantially reduce overall wire length for faster operation.Advances in integrated circuitsAmong the most advanced integrated circuits are the microprocessors or "cores", which control everything from computers and cellular phones to digital microwave ovens. Digital memory chips and ASICs are examples of other families of integrated circuits that are important to the modern information society. While the cost of designing and developing a complex integrated circuit is quite high, when spread across typically millions of production units the individual IC cost is minimized. The performance of ICs is high because the small size allows short traces which in turn allows low power logic (such as CMOS) to be used at fast switching speeds.ICs have consistently migrated to smaller feature sizes over the years, allowing more circuitry to be packed on each chip. This increased capacity per unit area can be used to decrease cost and/or increase functionality—see Moore's law which, in its modern interpretation, states that the number of transistors in an integrated circuit doubles every two years. In general, as the feature size shrinks, almost everything improves—the cost per unit and the switching power consumption godown, and the speed goes up. However, ICs with nanometer-scale devices are not without their problems, principal among which is leakage current (see subthreshold leakage for a discussion of this), although these problems are not insurmountable and will likely be solved or at least ameliorated by the introduction of high-k dielectrics. Since these speed and power consumption gains are apparent to the end user, there is fierce competition among the manufacturers to use finer geometries. This process, and the expected progress over the next few years, is well described by the International Technology Roadmap for Semiconductors (ITRS).In current research projects, integrated circuits are also developed for sensoric applications in medical implants or other bioelectronic devices. Particular sealing strategies have to be taken in such biogenic environments to avoid corrosion or biodegradation of the exposed semiconductor materials.[16] As one of the few materials well established in CMOS technology, titanium nitride (TiN) turned out as exceptionally stable and well suited for electrode applications in medical implants.[17][18] ClassificationIntegrated circuits can be classified into analog, digital and mixed signal (both analog and digital on the same chip).Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. These digital ICs, typically microprocessors, DSPs, and micro controllers, work using binary mathematics to process "one" and "zero" signals.Analog ICs, such as sensors, power management circuits, and operational amplifiers, work by processing continuous signals. They perform functions like amplification, active filtering, demodulation, and mixing. Analog ICs ease the burden on circuit designers by having expertly designed analog circuits available instead of designing a difficult analog circuit from scratch.ICs can also combine analog and digital circuits on a single chip to create functions such as A/D converters and D/A converters. Such circuits offer smaller size and lower cost, but must carefully account for signal interference.ManufacturingFabricationRendering of a small standard cell with three metal layers (dielectric has been removed). The sand-colored structures are metal interconnect, with the vertical pillars being contacts, typically plugs of tungsten. The reddish structures are poly-silicon gates, and the solid at the bottom is the crystalline silicon bulk.Schematic structure of a CMOS chip, as built in the early 2000s. The graphic shows LDD-Misfit's on an SOI substrate with five materialization layers and solder bump for flip-chip bonding. It also shows the section for FEOL (front-end of line), BEOL (back-end of line) and first parts of back-end process.The semiconductors of the periodic table of the chemical elements were identified as the most likely materials for a solid-state vacuum tube. Starting with copper oxide, proceeding to germanium, then silicon, the materials were systematically studied in the 1940s and 1950s. Today, silicon monocrystals are the main substrate used for ICs although someIII-V compounds of the periodic table such as gallium arsenide are used for specialized applications like LEDs, lasers, solar cells and the highest-speed integrated circuits. It took decades to perfect methods of creating crystals without defects in the crystalline structure of the semiconducting material.Semiconductor ICs are fabricated in a layer process which includes these key process steps:∙Imaging∙Deposition∙EtchingThe main process steps are supplemented by doping and cleaning.∙Integrated circuits are composed of many overlapping layers, each defined by photolithography, and normally shown in different colors.Some layers mark where various dopants are diffused into thesubstrate (called diffusion layers), some define where additional ions are implanted (implant layers), some define the conductors(poly-silicon or metal layers), and some define the connectionsbetween the conducting layers (via or contact layers). All components are constructed from a specific combination of these layers.∙In a self-aligned CMOS process, a transistor is formed wherever the gate layer (poly-silicon or metal) crosses a diffusion layer.∙Capacitive structures, in form very much like the parallel conducting plates of a traditional electrical capacitor, are formedaccording to the area of the "plates", with insulating material between the plates. Capacitors of a wide range of sizes are common on ICs.∙Meandering stripes of varying lengths are sometimes used to form on-chip resistors, though most logic circuits do not need any resistors.The ratio of the length of the resistive structure to its width, combined with its sheet resistivity, determines the resistance.∙More rarely, inductive structures can be built as tiny on-chip coils, or simulated by gyrators.Since a CMOS device only draws current on the transition between logic states, CMOS devices consume much less current than bipolar devices.A random access memory is the most regular type of integrated circuit; the highest density devices are thus memories; but even a microprocessor will have memory on the chip. (See the regular array structure at the bottom of the first image.) Although the structures are intricate – with widths which have been shrinking for decades – the layers remain much thinner than the device widths. The layers of material are fabricated much like a photographic process, although light waves in the visible spectrum cannot be used to "expose" a layer of material, as they would be too large for the features. Thus photons of higher frequencies (typically ultraviolet) are used to create the patterns for each layer. Because each feature is so small, electron microscopes are essential tools for a process engineer who might be debugging a fabrication process.Each device is tested before packaging using automated test equipment (ATE), in a process known as wafer testing, or wafer probing. The wafer is then cut into rectangular blocks, each of which is called a die. Each good die (plural dice, dies, or die) is then connected into a package using aluminum (or gold) bond wires which are welded and/or thermosonic bonded to pads, usually found around the edge of the die. After packaging, the devices go through final testing on the same or similar ATE used during wafer probing. Industrial CT scanning can also be used. Test cost can account for over 25% of the cost of fabrication on lower cost products, but can be negligible on low yielding, larger, and/or higher cost devices.As of 2005, a fabrication facility (commonly known as a semiconductor fab) costs over $1 billion to construct,[19] because much of the operation is automated. Today, the most advanced processes employ the following techniques:∙The wafers are up to 300 mm in diameter (wider than a common dinner plate).∙Use of 32 nanometer or smaller chip manufacturing process. Intel, IBM, NEC, and AMD are using ~32 nanometers for their CPU chips.IBM and AMD introduced immersion lithography for their 45 nmprocesses[20]∙Copper interconnects where copper wiring replaces aluminium for interconnects.∙Low-K dielectric insulators.∙Silicon on insulator (SOI)∙Strained silicon in a process used by IBM known as strained silicon directly on insulator (SSDOI)∙Multigate devices such as trin-gate transistors being manufactured by Intel from 2011 in their 22 nim process.PackagingIn the late 1990s, plastic quad flat pack (PQFP) and thin small-outline package (TSOP) packages became the most common for high pin count devices, though PGA packages are still often used for high-end microprocessors. Intel and AMD are currently transitioning from PGA packages on high-end microprocessors to land grid array (LGA) packages.Ball grid array (BGA) packages have existed since the 1970s. Flip-chip Ball Grid Array packages, which allow for much higher pin count than other package types, were developed in the 1990s. In an FCBGA package the die is mounted upside-down (flipped) and connects to the packageballs via a package substrate that is similar to a printed-circuit board rather than by wires. FCBGA packages allow an array of input-output signals (called Area-I/O) to be distributed over the entire die rather than being confined to the die periphery.Traces out of the die, through the package, and into the printed circuit board have very different electrical properties, compared to on-chip signals. They require special design techniques and need much more electric power than signals confined to the chip itself.When multiple dies are put in one package, it is called SiP, for System In Package. When multiple dies are combined on a small substrate, often ceramic, it's called an MCM, or Multi-Chip Module. The boundary between a big MCM and a small printed circuit board is sometimes fuzzy. Chip labeling and manufacture dateMost integrated circuits large enough to include identifying information include four common sections: the manufacturer's name or logo, the part number, a part production batch number and/or serial number, and a four-digit code that identifies when the chip was manufactured. Extremely small surface mount technology parts often bear only a number used in a manufacturer's lookup table to find the chip characteristics.The manufacturing date is commonly represented as a two-digit year followed by a two-digit week code, such that a part bearing the code 8341 was manufactured in week 41 of 1983, or approximately in October 1983. Legal protection of semiconductor chip layoutsLike most of the other forms of intellectual property, IC layout designs are creations of the human mind. They are usually the result of an enormous investment, both in terms of the time of highly qualified experts, and financially. There is a continuing need for the creation of new layout-designs which reduce the dimensions of existing integrated circuits and simultaneously increase their functions. The smaller an integrated circuit, the less the material needed for its manufacture, and the smaller the space needed to accommodate it. Integrated circuits are utilized in a large range of products, including articles of everyday use, such as watches, television sets, washing machines, automobiles, etc., as well as sophisticated data processing equipment.The possibility of copying by photographing each layer of an integrated circuit and preparing photomasks for its production on the basis of the photographs obtained is the main reason for the introduction of legislation for the protection of layout-designs.A diplomatic conference was held at Washington, D.C., in 1989, which adopted a Treaty on Intellectual Property in Respect of Integrated Circuits (IPIC Treaty). The Treaty on Intellectual Property in respect of Integrated Circuits, also called Washington Treaty or IPIC Treaty (signed at Washington on May 26, 1989) is currently not in force, but was partially integrated into the TRIPs agreement.National laws protecting IC layout designs have been adopted in a number of countries.Other developmentsIn the 1980s, programmable logic devices were developed. These devices contain circuits whose logical function and connectivity can be programmed by the user, rather than being fixed by the integrated circuit manufacturer. This allows a single chip to be programmed to implement different LSI-type functions such as logic gates, adders and registers. Current devices called field-programmable gate arrays can now implement tens of thousands of LSI circuits in parallel and operate up to 1.5 GHz (Anachronism holding the speed record).The techniques perfected by the integrated circuits industry over the last three decades have been used to create very small mechanical devices driven by electricity using a technology known asmicroelectromechanical systems. These devices are used in a variety of commercial and military applications. Example commercial applications include DLP projectors, inkjet printers, and accelerometers used to deploy automobile airbags.In the past, radios could not be fabricated in the same low-cost processes as microprocessors. But since 1998, a large number of radio chips have been developed using CMOS processes. Examples include Intel's DECT cordless phone, or Atheros's 802.11 card.Future developments seem to follow the multi-coremulti-microprocessor paradigm, already used by the Intel and AMD dual-core processors. Intel recently unveiled a prototype, "not for commercial sale" chip that bears 80 microprocessors. Each core is capable of handling its own task independently of the others. This is in response to the heat-versus-speed limit that is about to be reached using existing transistor technology. This design provides a new challenge to chip programming. Parallel programming languages such as theopen-source X10 programming language are designed to assist with this task.集成电路集成电路或单片集成电子电路（也称为IC、集成电路片或微型集成电路片）是一种电子电路制作的图案扩散微量元素分析在基体表面形成一层薄的半导体材料。
毕业设计中英文翻译
Bridge Waterway OpeningsIn a majority of cases the height and length of a bridge depend solely upon the amount of clear waterway opening that must be provided to accommodate the floodwaters of the stream. Actually, the problem goes beyond that of merely accommodating the floodwaters and requires prediction of the various magnitudes of floods for given time intervals. It would be impossible to state that some given magnitude is the maximum that will ever occur, and it is therefore impossible to design for the maximum, since it cannot be ascertained. It seems more logical to design for a predicted flood of some selected interval ---a flood magnitude that could reasonably be expected to occur once within a given number of years. For example, a bridge may be designed for a 50-year flood interval; that is, for a flood which is expected (according to the laws of probability) to occur on the average of one time in 50 years. Once this design flood frequency, or interval of expected occurrence, has been decided, the analysis to determine a magnitude is made. Whenever possible, this analysis is based upon gauged stream records. In areas and for streams where flood frequency and magnitude records are not available, an analysis can still be made. With data from gauged streams in the vicinity, regional flood frequencies can be worked out; with a correlation between the computed discharge for the ungauged stream and the regional flood frequency, a flood frequency curve can be computed for the stream in question. Highway CulvertsAny closed conduit used to conduct surface runoff from one side of a roadway to the other is referred to as a culvert. Culverts vary in size from large multiple installations used in lieu of a bridge to small circular or elliptical pipe, and their design varies in significance. Accepted practice treats conduits under the roadway as culverts. Although the unit cost of culverts is much less than that of bridges, they are far more numerous, normally averaging about eight to the mile, and represent a greater cost in highway. Statistics show that about 15 cents of the highway construction dollar goes to culverts, as compared with 10 cents for bridge. Culvert design then is equally as important as that of bridges or other phases of highway and should be treated accordingly.Municipal Storm DrainageIn urban and suburban areas, runoff waters are handled through a system of drainage structures referred to as storm sewers and their appurtenances. The drainage problem is increased in these areas primarily for two reasons: the impervious nature of the area creates a very high runoff; and there is little room for natural water courses. It is often necessary to collect the entire storm water into a system of pipes and transmit it over considerable distances before it can be loosed again as surface runoff. This collection and transmission further increase the problem, since all of the water must be collected with virtually no ponding, thus eliminating any natural storage; and though increased velocity the peak runoffs are reached more quickly. Also, the shorter times of peaks cause the system to be more sensitive to short-duration, high-intensity rainfall. Storm sewers, like culverts and bridges, are designed for storms of various intensity –return-period relationship, depending upon the economy and amount of ponding that can be tolerated.Airport DrainageThe problem of providing proper drainage facilities for airports is similar in many ways to that of highways and streets. However, because of the large and relatively flat surface involved the varying soil conditions, the absence of natural water courses and possible side ditches, and the greater concentration of discharge at the terminus of the construction area, some phases of the problem are more complex. For the average airport the overall area to be drained is relatively large and an extensive drainage system is required. The magnitude of such a system makes it even more imperative that sound engineeringprinciples based on all of the best available data be used to ensure the most economical design. Overdesign of facilities results in excessive money investment with no return, and underdesign can result in conditions hazardous to the air traffic using the airport.In other to ensure surfaces that are smooth, firm, stable, and reasonably free from flooding, it is necessary to provide a system which will do several things. It must collect and remove the surface water from the airport surface; intercept and remove surface water flowing toward the airport from adjacent areas; collect and remove any excessive subsurface water beneath the surface of the airport facilities and in many cases lower the ground-water table; and provide protection against erosion of the sloping areas. Ditches and Cut-slope DrainageA highway cross section normally includes one and often two ditches paralleling the roadway. Generally referred to as side ditches these serve to intercept the drainage from slopes and to conduct it to where it can be carried under the roadway or away from the highway section, depending upon the natural drainage. To a limited extent they also serve to conduct subsurface drainage from beneath the roadway to points where it can be carried away from the highway section.A second type of ditch, generally referred to as a crown ditch, is often used for the erosion protection of cut slopes. This ditch along the top of the cut slope serves to intercept surface runoff from the slopes above and conduct it to natural water courses on milder slopes, thus preventing the erosion that would be caused by permitting the runoff to spill down the cut faces.12 Construction techniquesThe decision of how a bridge should be built depends mainly on local conditions. These include cost of materials, available equipment, allowable construction time and environmental restriction. Since all these vary with location and time, the best construction technique for a given structure may also vary. Incremental launching or Push-out MethodIn this form of construction the deck is pushed across the span with hydraulic rams or winches. Decks of prestressed post-tensioned precast segments, steel or girders have been erected. Usually spans are limited to 50～60 m to avoid excessive deflection and cantilever stresses , although greater distances have been bridged by installing temporary support towers . Typically the method is most appropriate for long, multi-span bridges in the range 300 ~ 600 m ,but ,much shorter and longer bridges have been constructed . Unfortunately, this very economical mode of construction can only be applied when both the horizontal and vertical alignments of the deck are perfectly straight, or alternatively of constant radius. Where pushing involves a small downward grade (4% ~ 5%) then a braking system should be installed to prevent the deck slipping away uncontrolled and heavy bracing is then needed at the restraining piers.Bridge launching demands very careful surveying and setting out with continuous and precise checks made of deck deflections. A light aluminum or steel-launching nose forms the head of the deck to provide guidance over the pier. Special teflon or chrome-nickel steel plate bearings are used to reduce sliding friction to about 5% of the weight, thus slender piers would normally be supplemented with braced columns to avoid cracking and other damage. These columns would generally also support the temporary friction bearings and help steer the nose.In the case of precast construction, ideally segments should be cast on beds near the abutments and transferred by rail to the post-tensioning bed, the actual transport distance obviously being kept to the minimum. Usually a segment is cast against the face of the previously concerted unit to ensure a good fit when finally glued in place with an epoxy resin. If this procedure is not adopted , gaps of approximately 500mm shold be left between segments with the reinforcements running through andstressed together to form a complete unit , but when access or space on the embankment is at a premium it may be necessary to launch the deck intermittently to allow sections to be added progressively .The correponding prestressing arrangements , both for the temporary and permanent conditions would be more complicated and careful calculations needed at all positions .The pricipal advantage of the bridge-launching technique is the saving in falsework, especially for high decks. Segments can also be fabricated or precast in a protected environment using highly productive equipment. For concrete segment, typically two segment are laid each week (usually 10 ~ 30 m in length and perhaps 300 to 400 tonnes in weight) and after posttensioning incrementally launched at about 20 m per day depending upon the winching/jacking equipment.Balanced Cantiulever ConstructionDevelopment in box section and prestressed concrete led to short segment being assembled or cast in place on falsework to form a beam of full roadway width. Subsequently the method was refined virtually to eliminate the falsework by using a previously constructed section of the beam to provide the fixing for a subsequently cantilevered section. The principle is demonsrated step-by-step in the example shown in Fig.1.In the simple case illustrated, the bridge consists of three spans in the ratio 1:1:2. First the abutments and piers are constructed independently from the bridge superstructure. The segment immediately above each pier is then either cast in situ or placed as a precast unit .The deck is subsequently formed by adding sections symmetrically either side.Ideally sections either side should be placed simultaneously but this is usually impracticable and some inbalance will result from the extra segment weight, wind forces, construction plant and material. When the cantilever has reached both the abutment and centre span,work can begin from the other pier , and the remainder of the deck completed in a similar manner . Finally the two individual cantilevers are linked at the centre by a key segment to form a single span. The key is normally cast in situ.The procedure initially requires the first sections above the column and perhaps one or two each side to be erected conventionally either in situ concrete or precast and temporarily supported while steel tendons are threaded and post-tensioned . Subsequent pairs of section are added and held in place by post-tensioning followed by grouting of the ducts. During this phase only the cantilever tendons in the upper flange and webs are tensioned. Continuity tendons are stressed after the key section has been cast in place. The final gap left between the two half spans should be wide enough to enable the jacking equipment to be inserted. When the individual cantilevers are completed and the key section inserted the continuity tendons are anchored symmetrically about the centre of the span and serve to resist superimposed loads, live loads, redistribution of dead loads and cantilever prestressing forces.The earlier bridges were designed on the free cantilever principle with an expansion joint incorporated at the center .Unfortunately，settlements , deformations , concrete creep and prestress relaxation tended to produce deflection in each half span , disfiguring the general appearance of the bridge and causing discomfort to drivers .These effects coupled with the difficulties in designing a suitable joint led designers to choose a continuous connection, resulting in a more uniform distribution of the loads and reduced deflection. The natural movements were provided for at the bridge abutments using sliding bearings or in the case of long multi-span bridges, joints at about 500 m centres.Special Requirements in Advanced Construction TechniquesThere are three important areas that the engineering and construction team has to consider:(1) Stress analysis during construction: Because the loadings and support conditions of the bridge are different from the finished bridge, stresses in each construction stage must be calculated to ensurethe safety of the structure .For this purpose, realistic construction loads must be used and site personnel must be informed on all the loading limitations. Wind and temperature are usually significant for construction stage.(2) Camber: In order to obtain a bridge with the right elevation, the required camber of the bridge at each construction stage must be calculated. It is required that due consideration be given to creep and shrinkage of the concrete. This kind of the concrete. This kind of calculation, although cumbersome, has been simplified by the use of the compiters.(3) Quality control: This is important for any method construction, but it is more so for the complicated construction techniques. Curing of concrete, post-tensioning, joint preparation, etc. are detrimental to a successful structure. The site personnel must be made aware of the minimum concrete strengths required for post-tensioning, form removal, falsework removal, launching and other steps of operations.Generally speaking, these advanced construction techniques require more engineering work than the conventional falsework type construction, but the saving could be significant.大桥涵洞在大多数情况中桥梁的高度和跨度完全取决于河流的流量，桥梁的高度和跨度必须能够容纳最大洪水量.事实上，这不仅仅是洪水最大流量的问题,还需要在不同时间间隔预测不同程度的水灾。
毕业设计(论文)外文翻译【范本模板】
华南理工大学广州学院本科生毕业设计(论文）翻译英文原文名Review of Vibration Analysis Methods for Gearbox Diagnostics and Prognostics中文译名对变速箱振动分析的诊断和预测方法综述学院汽车工程学院专业班级车辆工程七班学生姓名刘嘉先学生学号201130085184指导教师李利平填写日期2015年3月15日英文原文版出处：Proceedings of the 54th Meeting of the Society for Machinery Failure Prevention Technology, Virginia Beach，V A, May 1-4，2000，p. 623-634译文成绩：指导教师(导师组长）签名：译文：简介特征提取技术在文献中有描述;然而，大多数人似乎掩盖所需的特定的预处理功能。
一些文件没有提供足够的细节重现他们的结果，并没有一个全面的比较传统的功能过渡齿轮箱数据。
常用术语,如“残差信号”,是指在不同的文件不同的技术.试图定义了状态维修社区中的常用术语和建立所需的特定的预处理加工特性。
本文的重点是对所使用的齿轮故障检测功能。
功能分为五个不同的组基于预处理的需要。
论文的第一部分将提供预处理流程的概述和其中每个特性计算的处理方案。
在下一节中，为特征提取技术描述，将更详细地讨论每一个功能。
最后一节将简要概述的宾夕法尼亚州立大学陆军研究实验室的CBM工具箱用于齿轮故障诊断。
特征提取概述许多类型的缺陷或损伤会增加机械振动水平。
这些振动水平，然后由加速度转换为电信号进行数据测量。
原则上,关于受监视的计算机的健康的信息被包含在这个振动签名。
因此，新的或当前振动签名可以与以前的签名进行比较,以确定该元件是否正常行为或显示故障的迹象。
在实践中，这种比较是不能奏效的。
由于大的变型中,签名的直接比较是困难的。
相反,一个涉及从所述振动署名数据特征提取更多有用的技术也可以使用。
毕业设计英文翻译原文
桂林航天工业学院英文翻译专业：姓名：学号：指导教师：宋美杰2013年6月10日The Application Of Modern Information Technology1 IntroductionModern information technology in the modern education thought, under the guidance of the theory of education, in the teaching field, is widely used in education, teaching, to bring new atmosphere and new pattern.In twenty-first Century, the comprehensive national strength and international competitiveness will more and more depend on the development of education, science and technology and the knowledge innovation level.To realize the socialism modernization, science and technology is a key, education is a foundation.This approach shows that education in China in the future development of the strategic position, as well as modern information technology innovation and development direction.Modern information technology is an important part of this strategic position.It not only affects the innovation education strategy implementation, also matter to the modernization of education.On our existing education mode, management mode, mode of thinking, including the concept of education, education method, education mode to will produce far-reaching effect.This is an opportunity, but also achallenge.2 The modern information technology in the school teaching management application possibility1）The modern information technology in school teaching and management in the application of inevitability and necessity Promoting educational modernization with informatization of education, the use of information technology to change the traditional education mode, it is the inevitable trend of educational development.In recent years, the education of our country informatization development is very rapid, China Education and research network, the construction of the modern distance education project, information technology education in the schools and "School-to-School" project, educational administration informatization project has started, the campus network, education metropolitan area network, provincial network construction promote education informatization of our country construction process.China is the world's most populous country in the world, taking the world's largest educational, financial, material resources are under great pressure.At the same time, the development of education in China are still at a low level,education structure and system, educational concepts and methods can not meet the need of modernization.Therefore, it is necessary to school management innovation, establish effective and economic way of modern information technology to participate in school management mode.In the informatization of education management in the construction process, widespread heavy hardware, software and application of light phenomena, makes a lot of system become "furnishings", can play a role in.Due to hardware equipment depreciation rate is very rapid, investment is larger, often because of the establishment of the management information system can not get timely and effective application and waste of money.Therefore must establish a set of campus network system using the approach, the school management to keep pace with the times.2）The characteristics of modern information technology①Overall Modern information technology capacity and transmission of information is in the form of many types of.The paper includes (Text), map (Graphics), sound (Sound), as (Images), program (Program), video (Video) (Animation), animation and other media information, covering the various elements of the teaching system of information and socialinformation, is comprehensive, accord with the society for Education requirements②Multidirectional The modern information technology provides the various disciplines, each job, each link, all kinds of personnel, various elements of connections between information channel, and this connection is multidirectional, very patient, is advantageous to the education information resources development, design, management and comprehensive utilization, is advantageous to the teaching process in the development, design, and management.③High efficiency Modern information technology based on high bandwidth, high speed network, is typical of the information superhighway, ensure rapid, comprehensive, accurate contact.Is in favor of educational information resources retrieval, processing and transmission.④Entirety Multimedia computer network as the representative of modern information technology has formed the whole structure of the system, a full range of elements and high efficiency, has formed the whole system.Is in favor of educational information resources management, promote the media technology to realize school management system technical transformation, process optimization.⑤Flexibility Modern information technology has other traditional teaching technique incomparable characteristics, can be in the school, also in the home through the Internet management; if he is at home with no internet access, to the point of teaching on internet.⑥Expansion The modern teaching in information technology strong extendibility, without geographical restrictions, not subject to restrictions on the number of classes, teachers and students, according to actual needs to be configured.⑦Sharing Modern information technology to achieve the resource the most widely shared, participation in the management of the department or the teacher not only confined to a school, an area, a country, through Internet network brings together the nation and even the world's best management approach to management.⑧Timeliness Internet is the mankind to overcome the limit of time and space, with the fastest speed of the best means of transmitting information, can provide the latest management requirements, teaching content and method, the latest information resources.⑨Interactivity Modern information technology tomeet the students and students, students and teachers, students and parents, between parents and teachers, convenient communication and contact, students of various kinds of problems as soon as possible to get the answers to the same question, explore different solution, to the students more challenging, more conducive to the cultivation of innovative ability.3 The modern information technology in the school teaching management applied research1)On information technology in school teaching and management of knowledge①The information technology and the discipline teaching conformity, to consider the information age to the practical requirement of the development of students.Course in the subject especially the integrated practice activity is not a simple learning or manual labor, but also different from the simple interest.To consider the information age to the practical requirement of the development of students, to integrate the information technology into the content and implementation of comprehensive practice activity course.②Cultivating students' information literacy inintegrated practice activity as well as the subject in the whole course of teaching.The field of information technology is the important research content of comprehensive practice activity, to achieve information technology and content of comprehensive practice activity to other content organic integration.To take information technology not only as a comprehensive practical activities as a means of, and should take the cultivation of students' information literacy in integrated practice activity, permeate the whole process, should focus on developing students' the ability of collecting and processing information.As my school teacher He Yan comprehensive practice class "man": this lesson shows "sources of information and the processing mode" (see Figure 1), our students by using modern educational technology to search data, questionnaires and comprehensive practical activity, in the process of fully trained students to collect information processing and analysis of information, communication, information ability, achieves the expected goal and a very good effect.③In the information technology and the discipline curriculum integration research of the implementation process, we should actively use network technology and other means, to expand the research scope, improve research level of implementation.As a modern schools should seek to establish the open system of campus network, and through the campus network and wide area network for students in cross country, cross a region, cross school, cross class of cooperative open up space, but also forteachers to cross a state, cross a region, cross, cross school class as guidance to provide conditions.Guide the students to actively use modern information resources, promote a variety of learning methods.As my school teacher Zhou Yang composition class "composition modification -- botanical description"(see Figure 2) , teachers to guide students in preliminary composition based on the use of our network collaborative learning system, or enjoy excellent essay, or exchange students excellent writing, or into the special subject learning website rich knowledge, deepen the understanding of plant, then on their first draft of the revised even to love classmate re-creation become more perfect, more satisfied with the work, finally will work again provided to conduct online and exchange.This process fully reflects the networked collaborative learning advantage and effect.Figure2④The design and application of information technology means to be committed to the students to create a reflective, independent cooperative learning situation and problem situation, prevent to be immersed in pure skill training.Using information technology to create independent, cooperation, explore learning scenarios and situations, there are many examples, with He Yan teacher's comprehensive practical course of "man" as an example, through modern media presentation disabled reality created "how to take care of the disabled" problem situation, thereby triggering the students include understanding disabilities knowledge, and disabledpeople, care for people with Party put forward suggestions of independent, collaborative learning behaviors.⑤We should try to create wealth, health, multi-source "green" school information environment, as the important guarantee of the implementation of.My school to create a green campus information environment, the school is a must as far as possible to provide rich, health information, the two is to pay attention to students' network morality and the cultivation of students' information analysis ability, so that students in a health information environment the health growth.2) Information technology in school management in some formOur school in the study of the subject and the process of thinking that, to realize the information technology and the course of comprehensive practice and discipline integration courses, teachers' classroom application, green information environment is the main factor, but the key problem is a must for students to create a healthy, lively, sea of green environment information, especially to for school education and teaching of modern media and network construction of a contents providing teaching resources database (see Figure 3).Figure 3: student information environment mapWe think, teaching resources are all available teaching resources collections, this one characteristic to the teaching resources database construction must follow the network, systematic, open principle.The network of teaching resource library must be based on the network platform, the advantages of Internet to realize resource exchange, sharing of teaching resources database; system should be scientific and systematic planning, classification, management, to maximize its effectiveness; open the teaching resource library is able to update all rivers run into sea, open system, through a number of technology allows the resource library information can beunlimited growth.My school repeatedly during the study process, the construction of teaching resource base as the focal point of the construction of software system.The initial construction of a campus network based teaching resources database, by local resources, teaching resources retrieval link system, resource and resource information automatic login system three modules to integrate into, its role is the:①Local resources,in the school campus network server for teachers to provide high speed local resources, including a variety of commodities, making courseware, courseware webpage material, classroom observation, teaching materials and so on;②Teaching resources retrieval link system, any employer or school resources more limited, Wan has vast space and resources available for our use, one for the teacher to provide search and link function can make the teachers use these resources become how easily;③Resource and resource information automatic login system, the school owned resources or can find online resources information after all, few, which requires all the teachers to find their own resources or information in the self-help mode do not stop to enrich school local repository or retrievallibrary, so that teachers can make use of information and resources are inexhaustible, continuous growth.The three modules in the "local resources" is the subject, and the other two systems complement each other, with the continuous improvement and constantly enrich we believe will provide our teachers use all kinds of teaching resources to provide strong support for the implementation of electronic lesson preparation.From the teaching resource library operation system, the system for teachers and teaching resources to establish a two-way communication channel, the teacher through the "resource retrieval link system" access to local resources and a wide area network resources or resource information; at the same time, the teacher can also take their own resources or information resources through "self-service information login system" to the local resources and "link system" which is ceaseless and rich, and the other teachers to share this information.(see Figure 4)4 Information technology in school management system1）Campus information management system information distributionCampus management information system will be the school's basic information, the main office room operations of the computer aided management, improve the management and service quality, level, accelerate information feedback, information safety sharing.According to the division of system functions, the main functional modules include the following:Information management of librarySet the Internet, School of information, social information, including school introduction, various departments of basic situation, characteristics of school education, class, teacher, student personal webpage;Management of school librarySet the school organization; management of the basicinformation of teachers, administrative duties, political affiliation, title, year assessment, award winning; teacher salaries, bonuses; provides a variety of teachers' information statistics chart; management of students information; on the school are unified; the management of student achievement, social practice and other information; establishment of middle school directory management school production, storage, receiving, allocation, loss, and can conveniently carry out sector assets collection and use of assets classification; and school information publishing system based on the net, school staff submitted application for repair, repair department received an application to repair.Education ManagementSchool of management subject test scores; School of management science and technology, archives information; the future will further improve the "school teachers management system", "school management system", "school management of the general logistics system" and "archives management system".Teaching management databaseManagement of teachers' daily work of teaching and scientific research, training of teachers, open class, thesis, twinning, student competition, grading standards.2) School of information system and managementTo realize modern educational resources integration and sharing of the height, the key is how to improve the school construction, acquisition, use of modern education resources, and resources into the school to promote quality education, improve the level of education and teachingabilities.Therefore, need to take campus network construction to become a professional network, many schools network through network technology connected, forming a collaborative work platform, in order to achieve maximal share of resources and the best configuration, make the teaching resources of the school management and communication, to realize the optimization of information environment.In order to strengthen the school management and campus network system, the establishment of the school named "XXX" school information release system:现代信息技术的应用(译文)1 引言现代信息技术在现代教育思想、理论的指导下，在教育、教学领域中广泛应用，给教育、教学带来了新的气象和新的格局。
毕业设计英文翻译原文
英文原文1. General description of the SIEMAG disc brake unitThis brake unit is the electro-hydraulic control system of a gearless disc brake for winders. The brake unit operates on the exhaust principle, i.e. the braking force is generated by sets of disc springs and released by hydraulic pressure.The braking force generators with the brake shoes directly act axially on the brake disc. The braking force is generated by sets of disc springs and transmitted onto the brake shoes. The number of brake elements determines the respective braking force required.As soon as the brakes are being released, the brake shoes are lifted form the brake disc with the aid of pressure oil. During the braking, the oil flows back into the tank and the brake shoes are being pressed against the brake disc.The braking force generators type BSFG 408 are s series product supplied by the Swedish firm ASEA-Hagglunds. They have a maximum press-down force of2X7906 kN.For reasons of better system availability, the hydraulic pressure is generated by two regulating pumps that are each driven by an electric motor. Both pumps are started when the system is being switched on. Any failure of a pump will be signaled.The oil filtration is undertaken by a pressure filter‘6.2’provided in front of the braking force generators. Furthermore, two gear pumps that are directly coupled with the regulating pumps, maintain a permanent oil cooling and filtering circuit during system operation (filter‘6.1’and cooler ‘14’). Both filters have an electrical contamination control. The mesh size of the filters is specified by the supplier to be 10μm (see TAS No.3.9.6.4). The equipment includes a controlled electrical tank heating. The fluid level in the tank is monitored as well.The service braking is done with the aid of two electrically controlled proportional pressure relief valves‘43.1’and‘43.2’that are hydraulically connected in series.The safety braking is done with the aid of position-controlled 4/2-way electro valves‘53.1’、‘53.2’、‘39.1’、‘39.2’、‘58.1’、‘58.2’、‘66.1’，and‘66.2’which are electrically actuated in closed-circuit connection.In the event of a safety braking, the directional control valves‘39.1’and‘39.2’are switched off, separating thus the pump pressure from the remaining brake releasing system(hydraulic shunt).During the safety braking, the directional control valves‘6.1’and‘66.2’are acting as pilot valves for the 2/2-way valves‘65.1’and ‘65.2’which again release the pressure relief valves‘64.1’and‘64.2’.The electro valves‘53.1’and‘53.2’operate as outlet valves according to TAS No.3.9.5.9.The mechanically controlled pressure relief valves‘60.1’and‘60.2’are arranged in the outlet line of these valves. They determine the residual pressures in the course of safety braking. These residual pressures (pressure stages 1 and 2) are maintained by bladder-type accumulators.The gas pressure of the respective accumulator used is monitored.The march of pressure is adjusted with the aid of mechanical skids which are adapted to the braking process desired.A hand-operated pump‘48’is provided for assembly purposes, when the controlled main stop cocks‘46.1’and‘46.2’in the outlet line of the brake elements are locked.The position-controlled 4/2-way valves‘63’and the pressure relief valves ‘25.1’and‘25.2’(residual pressure accumulator) are fed by a back-up power supply in open-circuit connection. The valves get open when the solenoids are energized.With the command‘RELEASE BRAKE’，the two residual pressure accumulators are filled through the check valves‘87.1’and‘87.2’.The residual pressure accumulator‘24.1’(pressure stage 1) is connected through the 4/2-way valve‘86’. The residual pressure accumulator‘24.2’(pressure stage 2) is automatically connected by a change-over of the 4/2-way valve‘86’, when the hoisting load changes accordingly.2. Functional description of the electro-hydraulic control system corresponding to the hydraulic drawing No.0905216/12.1 Method of operation of the brake unitThe braking force is the sum of pressing forces per brake shoe, reduced by the forces being generated by the oil pressure in the cylinders of the brake element.The force required for the service braking is achieved by controlling the oil pressure. Two pressure regulating valves‘43.1’and‘43.2’, each being fitted with separate control electronics and function control, are connected in series, permitting thus a stepless adjustment of the valves between a minimum and a maximum pressure. In the case of failure of one brake is applied when the spring forces press the brake shoes against the brake disc without counterpressure. The brake is released when the pressure oil in the cylinders of the brake elements reduces the spring forces to zero and the brake shoes are lifted the brake disc.The brake releasing pressure is generated through the pressure-controlled pumps‘1.1’and‘1.2’which are driven by electric motors‘3.1’and‘3.2’. The pressure regulating valves of the pumps are adjusted in such a way that, as soon as the brake releasing pressure has been reached, the pumps reduce the flow rate from the maximum value to the quantity required for maintaining the releasing the pressure. This means in other words that the pumps only deliver the quantity of oil that is demanded to replace any oil losses from leakage and to maintain the pressure adjusted on the pressure regulating valves‘43.1’and‘43.2’.When starting the safety braking, the circuit of the electro-hydraulic brake control system (including pump motors) is cut off. The 4/2-way valves ‘53.1’，‘53.2’,‘39.1’and‘39.2’are thus de-energized and the pump circuit is separated form the brake elements and the pressure accumulators‘24’. The service brake valves‘43.1’and‘43.2’remain energized through a back-up current supply. The residual pressure is as high as to ensure the winder retardation being below the rope slip limit.The hand-operated pump‘48’is only connected for the start-up operation and stored separately.2.2 Operating states2.2.1 Starting the systemThe winder is at standstill and the brake applied. The control voltage and the voltage for the pump motors‘3.1’and‘3.2’is available. The electrical monitoring system signals the system to be trouble-free and all preconditions for starting the pumps‘1.1’and‘1.2’fulfilled (please see also item 2.3.1), which means that the safety circuit is closed as well.The 4/2-way valves‘39.1’and‘39.2’are energized by starting the pump motors‘3.1’and‘3.2’,thus opening the cross section between pumps and brake elements. The safety brake valves ‘53.1’、‘53.2’、‘58.1’、‘58.2’、‘66.1’and‘66.2’close.The pumps‘1.1’and‘1.2’are now connected through the pressure regulating valves‘43.1’and‘43.2’with the brake elements. The coils of these valves are de-energized, i.e. the valves are open, permitting the oil to return without pressure form the pumps‘1.1’and‘1.2’through the pressure regulating valves into the tank.2.2.2 Releasing the service brakeWith the command‘RELEASE BRAKE’, the coils of the pressure regulating valves‘43.1’and‘43.2’are fed with the maximum valve of regulable current, and the valves retain the maximum releasing pressure adjusted. The pumps‘1.1’and‘1.2’thus feed the oil through the valves‘39.1’and‘39.2’to the brake element. The accumulators for the residual pressure‘24.1’and‘24.2’are also filled through the operating pumps. The brake elements are released as soon as the maximum releasing pressure has been reached. The pressure-controlled pumps then reduce the flow rate to the quantity required for compensating all oil loses form leakage. The releasing pressure is maintained by the pressure regulating valves‘43.1’and‘43.2’.The pressure switches‘34.1’/‘34.2’monitor the filling of the bladder-type accumulators for residual pressure‘24.1’/‘24.2’.With this operating state, the valves‘53.1’and‘53.2’are closed and the outlets of the hydraulic safety circuit thus locked.2.2.3 Service brakingDuring the service braking, the pressure regulating valves‘43.1’and‘43.2’are steplessly controlled. This reduces the releasing pressure in conformity with the position of the brake lever. The oil displaced form the brake elements as well as the excess oil form the pumps‘1.1’and‘1.2’flows back through the pressure regulating valves‘43.1’and‘43.2’into the tank.These proportional pressure regulating valves comprise a pilot control valve and a main valve. They are operated by parallel control of the pilot control valves with the main valves connected in series.This means in other words that both proportional pressure regulating valves are always active in the pilot control circuit. However, the main pressure regulating function is always fulfilled by that valve which is nearer to the pressure source. Only in the event of a failure this function is performed by the subsequent valve.The power supply to the control electronics of each regulating valve is additionally backed up by a battery ensuring, in the event of a total power failure or wire brakeage, that at least one regulating valve remains operative.The buffered voltage supplies are monitored for a failure of the buffering in the electrical and electronical circuits of the brake control system.2.2.4 Safety brakingAs soon as the safety circuit is actuated, the pump motors‘3.1’and‘3.2’and the entire electrical control system, except the control of the service brake regulating valves, are de-energized.The oil draining pressure is released through the pressure relief valves ‘64.1’and‘64.2’by de-energizing the solenoid valves‘66.1’and‘66.2’. The releasing pressure in the brake elementsand in the conduits is thus rapidly reduced to that value at which the brake shoes touch the brake discs without pressing force.The de-energized valves‘39.1’and‘39.2’(hydraulic shunt) isolate the pumps‘1.1’and‘1.2’form the brake elements and, at the same time, connect the brake elements with the residual pressure accumulator ‘24.1’and‘24.2’.The hydraulic pressure is further reduced the residual pressure lever through the directional control valves‘53.1’and‘53.2’, the throttling valves ‘56.1’and‘56.2’as well as the cam-controlled pressure relief valves‘60.1’and‘60.2’connected in parallel.The opening time of the above valves determines the threshold time, it can be adjusted through the throttling valves‘59.1’and‘59.2’in a range of 0.2 and 1.0 s. The minimum pressure valve of the open valves‘60.1’and‘60.2’is equivalent to the residual pressure valve and is limited by the final position of the mechanical cam plate.The residual pressure valve is reached after a prolon-gated threshold time of approx.0.1s.For a fine adjustment of the threshold curve and as an additional safety measure ,two throttling valves‘57’are provided for the respective residual pressure value. These components permit the pressure reduction characteristic (braking curve) to be variably adjusted (depending on requirements) and reproduced at any time.The capacity of the residual pressure accumulator is adapted to the maximum braking time of the winder, under consideration of the opening cross sections of the valves ‘57’and of the leakage rate of all valves. The time of maintaining residual pressure is abt.50% longer than the maximum braking time.When the winder comes to a standstill, a time element is started. After abt.2s, the valve‘63’is opened by a starting pulse and the residual pressure reduced to zero. At the same time, the residual pressure accumulator not needed is discharged through the pressure relief valve‘25.1’or‘25.2’(the valve is energized for a short moment).The possibility of adjusting and reproducing the braking curve between application pressure and residual pressure is of particular importance since, within this period, rope vibrations may occur which, with Koepe winders, may cause a slipping of ropes.The valves‘58’，‘65’，and‘66’as well as‘53’and‘39’are monitored for their position and, prior to the start of the winder releasing the safety brake checked for conformity.Furthermore, the starting and end positions of all curves are checked for conformity and thus also for correct functioning.During the safety braking, the pressure relief valves‘43.1’and‘43.2’remain operative.2.2.5 Releasing the safety brakeSince the control system including the pump motors is de-energized as soon as safety braking is started, the brake control system is in a resting state. The system is depressurized and the brake applied.The power required for the pump motors‘3.1’and‘3.2’and the control system is available.The system can be started when1. the electrical monitoring system does not signal any failure.2.all prerequisites for starting the pumps‘1.1’and‘1.2’are fulfilled.3.conformity of the valves‘39’、‘53’、‘58’、65‘、65’、‘66’and‘89’is given.The system is started and the brake released as described under items 2.2.1and 2.2.2.。
毕业设计翻译定稿 英汉对照(绝版)
A Comparison of AASHTO Bridge Load Rating Methods Authors:Cristopher D. Moen, Ph.D., P.E., Virginia Tech, Blacksburg, VA, cmoen@Leo Fernandez, P.E., TranSystems, New York, NY, lafernandez@INTRODUCTIONThe capacity of an existing highway bridge is traditionally quantified with a load rating factor. This factor, when multiplied by the design live load magnitude, describes the total live load a bridge can safely carry. The load rating factor, RF, is related to the capacity of the controlling structural component in the bridge, C, and the dead load D and live load L applied to that component with the equation:L DC RF -=（1）Visual bridge inspections provide engineers with information to quantify the degradation in structural integrity of a bridge (i.e., the reduction in C). The trends in RF over time can be employed by bridge owners to make decisions regarding bridge maintenance and replacement. For example, when a bridge is first constructed, RF=1.3 means that a bridge can safely carry 1.3 times the weight of its design live load (i.e., that C-D, the existing capacity after accounting for dead load, is 1.3 times the design live load L). If the RF decreases to 0.8 after 20 years of service, deterioration of the primary structural components has most likely occurred and rehabilitation or replacement should be considered.Equation (1) is a simple idea, but C, D, and L can be highly variable and difficult to characterize depending upon the bridge location, bridge type, daily traffic flow, structural system (e.g., simple or continuous span) and choice of constructionmaterials (e.g. steel, reinforced or prestressed concrete, composite construction). The American Association of State Highway and Transportation Officials (AASHTO) Manual for Condition Evaluation of Bridges (MCEB) provides a formal load rating procedure to assist engineers in the evaluation of existing bridges [AASHTO 1994 with interims through 2003]. The MCEB provides two load rating methods, one based on an allowable stress approach (ASR) and another based on a load factor approach (LFR). Both the ASR and LFR methods are consistent with the design loading and capacity calculations outlined in the AASHTO Standard Specification for the Design of Highway Bridges [AASHTO 2002]. Recently momentum has shifted towards a probabilistic-based bridge design approach with the publication of the AASHTO LRFD Bridge Design Specifications [AASHTO 2007]. Bridges designed with this code have a uniform probability of failure (i.e., a uniform reliability). The AASHTO Manual for Condition Evaluation and Load and Resistance Factor Rating (LRFR) of Highway Bridges [AASHTO 2003] extends this idea of uniform reliability from LRFD to the load rating of existing bridges and is currently the recommended load rating method (over the ASR and LFR methods) by the Federal Highway Administration (FHWA).The transition from ASR and LFR to LRFR bridge load rating methodology represents a positive shift towards a more accurate and rational bridge evaluation strategy. Bridge owners are optimistic that the LRFR load rating methodology will improve bridge safety and economy, but they are also currently dealing with the tough questions related to its implementation. Why do ASR, LFR, and LRFR methods produce different load rating factors for the same bridge? Should we change the posting limit on a bridge if the LRFR rating is lower than the MCEB ratings? What are the major philosophical differences between the three methods? It is the goal of this paper to answer some of these questions (and at the same time dispel common myths) with a succinct summary of the history of the three methods. A comparison of the LFR and LRFR methods for a typical highway bridge will also bepresented, with special focus on the benefits inherent in the rational, probabilistic approach of the LRFR load rating method. This paper is also written to serve as an introduction to load rating methodologies for students and engineers new to the bridge evaluation field.S UMMARY OF EXISTING LITERATURESeveral reports have been published which summarize the development of AASHTO design and load rating methodologies. FHWA NHI Report 07-019 is an excellent historical reference describing the evolution of AASHTO live loadings (including the HS20-44 truck) and load factor design [Kulicki 2007b]. NCHRP Report 368 describes the development of the AASHTO LRFD design approach[Nowak 1999], and is supplemented by the NCHRP Project No. 20-7/186 report[Kulicki 2007a] with additional load factor calibration research. NCHRP Report 454 documents the calibration of the AASHTO LRFR load factors [Moses 2000], and NCHRP Web Document 28 describes the implementation of the LRFR load rating method [NCHRP 2001]. The NCHRP Project 20-7/Task 122 report supplements Web Document 28 with a detailed comparison of the LRFR and LFD load rating approaches [Mertz 2005].AASHTO A LLOWABLE STRESS RATING METHODThe Allowable Stress Rating (ASR) method is the most traditional of the three load rating methods, primarily because the performance of a bridge is evaluated under service conditions in the load rating equation [AASHTO 1994]:)1(21l L A D A C RF +-= （2） C is calculated with a “working stress” approach where the capacity of the primary structural members is limited to a proportion of the assumed failure stress (e.g., 0.55F y for structural steel in tension and 0.3f’c for concrete in compression.) Consistent with the service level approach, the demand dead load D and live load Lare unfactored, i.e. A 1=1.0 and A 2=1.0.The uncertainty in the strength of the bridge is accounted for in the ASR approach by limiting the applied stresses, but the variability in the demand loads is neglected. For example, dead load on a bridge has a relatively low variability because the dimensional tolerances of the primary structural members (e.g., a hot-rolled steel girder) are small [Nowak 2000]. Vehicular traffic loads on a bridge have a higher uncertainty because of varying traffic volume (annual average daily truck traffic or ADTT) and varying types of vehicular traffic (e.g., primarily trucks on an interstate or primarily cars on a parkway). The ASR method also does not consider redundancy of a bridge (e.g., continuous or simple spans, hammerhead piers or multiple column bents) or the amplified uncertainty in the capacity of aging structural members versus newly constructed members. The ASR method’s treatment of capacity and demand results in load rating factors lacking a uniform level of reliability (i.e., a uniform probability of failure) across all types of highway bridges. For example, with the ASR method, two bridges can have RF=2 even though one bridge carries a high ADTT with a non-redundant superstructure (higher probability of failure) while the other bridge carries a low AADT with a redundant superstructure (lower probability of failure).AASHTO L OAD F ACTOR R ATING METHODIn contrast to the ASR method’s service load approach to load rating, the AASHTO Load Factor Rating (LFR) method evaluates the capacity of a bridge at its ultimate limit state . The LFR load rating factor equation is:12(1)nR A D RF A L I φ-=+ （3） where the capacity C of the bridge in (2) has been replaced with φ R n , the predicted strength of the controlling structural component in the bridge. R n is the nominal capacity of the structural component and φ is a strength reduction factor which accounts for the uncertainty associated with the material properties,workmanship, and failure mechanisms (e.g., shear, flexure, or compression). For example, φ is 0.90 for the flexural strength of a concrete beam and 0.70 for a concrete column with transverse ties [AASHTO 2002]. The lower φ for the concrete column means that there is more uncertainty inherent in the structural behavior and strength prediction for a concrete column than for a concrete beam. The dead load factor A 1 is 1.3 to account for unanticipated permanent load and A 2 is either 1.3 or2.17, defining a live load envelope ranging from an expected design level (Inventory) to an extreme short term loading (Operating) [AASHTO 1994].The LFR method is different from the ASR method because it calculates the load rating factor RF by quantifying the potential for failure of a bridge (and associated loss of life and property) instead of quantifying the behavior of a bridge in service . The LFR method is similar to the ASR method in that it does not account for the influence of redundancy on the reliability of a bridge. Also, the load factors A 1 and A 2 are defined without a formal reliability analysis (i.e., they are not derived by considering probability distributions of capacity and demand) and therefore do not produce rating factors consistent with a uniform probability of failure.AASHTO L OAD AND R ESISTANCE F ACTOR R ATING METHODThe AASHTO Load and Resistance Factor Rating (LRFR) method evaluates the existing capacity of a bridge using structural reliability theory [Melchers 1999; Nowak 2000]. The LRFR rating factor equation is similar in form to (2) and (3):(1)c s n DC DW L R DC DW RF LL IM ϕϕϕγγγ--=+ （4） where ϕc is a strength reduction factor that accounts for the increased variability in the member strength of existing bridges when compared to new bridges [Moses 1987]. The factor ϕs addresses the failure of structural systems and penalizes older non-redundant structures with lower load ratings [Ghosn 1998]. The dead load factors γDC and γDW have been separated in LRFR to account for a lower variability indead load for primary structural components DC (e.g., columns and beams) and a higher variability for bridge deck wearing surfaces DW.Another important difference between the LRFR method and the ASR and LFR methods is the use of the HL93 notional design live load, which is a modern update to the HS20-44 notional load first implemented in 1944 [Kulicki 2007b] (notional in this case means that the design live load is not meant to represent actual truck traffic but instead is a simplified approximation intended to conservatively simulate the influence of live load across many types of bridge spans). The HL93 loading produces live load demands which are more consistent with modern truck traffic than the HS20-44 live load. The HL93 design loading combines the HS20-44 truck with a uniform load and also considers the load case of a tandem trailer with closely spaced axles and relatively high axle loads (in combination with a uniform load) [AASHTO 2007]. The design tandem load increases the shear demand on shorter bridges and produces, in combination with the design lane load, a live load effect greater than or equal to the AASHTO legal live load Type 3, Type 3S2, and Type 3-3 vehicles [AASHTO 1994].AASHTO LFR VS. LRFR LOAD RATING COMPARISONA parameter study is conducted in this section to explore the differences between the AASHTO LFR and LRFD load rating methods. The ASR method is not included in the study because it evaluates the live load capacity of a bridge at service levels, which makes it difficult to compare against the ultimate limit state LFR and LRFR methods (also note that the ASR method employs less modern “working stress” methods for calculating member capacities than LFR and LRFR). A simple span multi-girder bridge with steel girders and a composite concrete bridge deck is considered. The flexural capacity of an interior girder is assumed to control the load rating. AASHTO legal loads are employed in the study to provide a consistent live loading between the rating methods (although the impact factor and live loaddistribution factor for the controlling girder will be different for LFR and LRFR methods).The LFR load rating equation in (3) is rewritten as:u 12LFR LFD LFD M A D RF A B I L-= （5） where M u is the LFD flexural capacity of the composite girder (φ is implicit in the calculation of M u ), B LFD is the live load distribution factor for an interior girder[AASHTO 1994]:5.5LFD S B = （6） and the live load impact factor I LFD is [AASHTO 1994]:501125LFD I =++ （7） The span length of the bridge is denoted as . A 1 and A 2 are chosen as 1.3 in this study to compare the LFR Operating rating with the LRFR rating method (the intent of the LRFR legal load rating is to provide a single rating level consistent with the LFD Operating level [AASHTO 2003]).The LRFR equation in (4) is rewritten to be consistent with (5):u2c s DC D LFR L LRFD LRFD M M RF B I Lϕϕγγ-= （8） Where B LRFD is the live load distribution factor for moment in an interior girder[AASHTO 2007]0.60.230.075()()()9.512g LRFD sK S S B t =+ （9） and I LRFD , the live load impact factor, is 1.33 [AASHTO 2007]. M D is the dead load moment assuming that the dead load effects from a wearing surface and utilities are zero (i.e., DW is zero) and γDC is 1.25. M u is assumed equivalent in (5) and (8) because the LFD and LRFD prediction methods for the flexural capacity of composite girders are founded on a common structural basis [Tonias 2007]. The term K g /12 t s 3 in (9) is assumed equal to 1 as suggested by the LRFD specification forpreliminary design [AASHTO 2007] (this approximation reduces the number of variables in the parameter study). The term LL in (4), i.e. the LRFD lane loading, is approximated by 2L in (8). This conversion from lane loading to wheel line loading allows for the cancellation of L (i.e., the live load variable) when (8) and (5) are formulated as a ratio:(10)Rearranging the term M u in (10) leads to:（11）The relationship between the LRFR and LFR load rating equations, as described in (11), is explored in Figure 1 to Figure 4. M D/M u is assumed as 0.30 for the bridge span lengths considered in this study. Equation (11) varies only slightly (a maximum of 5%) when M D/M u ranges between 0.10 to 0.50 because the LFR and LRFR dead load factors are similar, i.e. γDC=1.25 and A1=1.3. Figure 1 demonstrates that the LRFR legal load rating is less than the LFD Operating rating for both short and long single span bridges (the span range is 20 ft. to 200 ft. in this study). This is consistent with the findings of NCHRP Web Document 28, which demonstrates that the LRFR legal load rating is lower than the LFD Operating rating but higher than the LFD Inventory rating [NCHRP 2001]. RF LRFR increases for longer span lengths because the live load distribution factor B LRFD in (9) decreases with increasing . RF LRFR also increases as the girder spacing, S, increases (S ranges from 3 ft. to 7 ft. in Figure 1) because the LRFD live load distribution factor B LRFD decreases relative to the LFD live load distribution factor B LFD for larger girder spacings.FIGURE 1-COMPARISON OF LRFR AND LFR (OPERATING) LEGAL LOAD RATING FACTORS FOR FLEXURE IN AN INTERIOR GIRDER OF A SIMPLE SPAN MULTI-GIRDER COMPOSITE BRIDGEThe volume of traffic is directly accounted for in the LRFR load rating method by considering the Average Daily Truck Traffic (ADTT) (this is an improvement over the LFR method which does not account for frequency of bridge usage when calculating RF). Figure 2 highlights the variability of the LRFR legal load rating with ADTT. RF LRFR is approximately 30% greater for a lightly traveled bridge (ADTT≤100) when compared to a heavily traveled bridge (ADTT≥5000), and the LRFR load rating trends toward the LFD Operating load rating for lightly traveled bridges.FIGURE 2 - INFLUENCE OF ANNUAL DAILY TRUCK TRAFFIC ON THE LRFR LEGAL LOAD RATING FACTOR (S=4 FT.)The factors ϕs and ϕc account for system redundancy and the increased uncertainty from bridge deterioration in the LRFR load rating method respectively (this is an important update to the LFR rating method which assumes one level of uncertainty for all bridge types and bridge conditions). Figure 3 demonstrates that RF LRFR decreases by approximately 30% as the bridge condition deteriorates from good to poor. Bridges with a small number of girders (e.g., 3 or 4 girders) are considered to be more susceptible to catastrophic collapse, which is reflected in the lower RF LRFR load rating factors in Figure 4.FIGURE 3 –INFLUENCE OF CONDITION FACTOR ϕs ON THE LRFR LOAD RATING FACTOR (S=4 FT.)FIGURE 4 - INFLUENCE OF SYSTEM FACTOR ϕc ON LRFR LOAD RATING FACTOR (S=4 FT.)D ISCUSSIONThe LRFR load rating method represents an important step in the evolution of bridge evaluation strategies. The method is calibrated to produce a uniform level of reliability across all existing highway bridges (i.e., a uniform probability of failure) and is an improvement over the ASR and LFR methods because it allows bridge owners to account for traffic volume, system redundancy, and the increased uncertainty in the predicted strength of deteriorating bridge components. The LRFR load rating method can be used as a foundation for the development of more accurate performance-based bridge evaluation strategies in the future, where bridge owners directly calculate the existing capacity (or reliability) with in service data from a structural health monitoring network and make maintenance decisions based on relationships between corrosion, structural capacity, and repair or replacement costs.Reliability-based cost models have been proposed, for example [Nowak 2000]: T I F F C C C P =+ (12)Where CT is the total cost of the bridge over its lifetime, CI is the initial cost, CF is the failure cost of the bridge (which could include rehabilitation costs), and PF is the failure probability of the bridge. As PF increases (i.e., as the bridge deteriorates over time), the total cost CT increases, which ties the reliability of the bridge to economy and provides a metric from which to optimize maintenance decisions and minimum rehabilitation costs in a highway system. The continued evolution of bridge evaluation strategies depends on improved methods for evaluating the structural capacity of bridges and defining correlation between corrosion in bridges, strength loss, and failure rates [ASCE 2009].The AASHTO LRFR load rating method is a step forward in bridge evaluation strategy when compared to the ASR and LFR methods because it is calibrated to produce a uniform reliability across all existing highway bridges. The LRFR method provides factors which account for the volume of traffic on the bridge, the redundancy of the superstructure, and the increased uncertainty in structural capacity associated with a deteriorating structure. The flexural LRFR load rating factor for an interior steel composite girder in a multi-girder bridge is up to 40% lower than the LFR Operating load rating over a span range of 20 ft. to 200 ft. and for girder spacings between 3 ft. and 7 ft. The LRFR flexural load rating factor increases for longer span lengths and larger girder spacings, influenced primarily by the LRFD live load distribution factor.A CKNOWLEDGEMENTSThe authors are grateful for the guidance provided by Bala Sivakumar in the organization of this paper. The authors also wish to thank Kelley Rehm and Bob Cullen at AASHTO for their help identifying historical references pertaining to AASHTO live load vehicles and design procedures.R EFERENCESAASHTO, Manual for Condition Evaluation of Bridges, Second Edition, with 1995, 1996, 1998, 2000, 2001, and 2003 Revisions, AASHTO, Washington, D.C., 1994.AASHTO, Standard Specifications for Highway Bridges, 17th Edition, AASHTO, Washington, D.C., 2002.AASHTO, Manual for Condition Evaluation and Load and Resistance Factor Rating (LRFR) of Highway Bridges, AASHTO, Washington, D.C., 2003.AASHTO, LRFD Bridge Design Specifications, 4th Edition, AASHTO, Washington, D.C., 2007.ASCE, "ASCE/SEI-AASHTO Ad-Hoc Group on Bridge Inspection, Rehabilitation, and Replacement White Paper on Bridge Inspection and Rating", ASCE Journal of Bridge Engineering, 14(1), 2009, 1-5.Ghosn, M., Moses, F., NCHRP Report 406: Redundancy in Highway Bridge Superstructures, TRB, National Research Council, Washington, D.C., 1998.Kulicki, J.M., Prucz, Zolan, Clancy, Chad M., Mertz, Dennis R., Updating the Calibration Report for AASHTO LRFD Code (Project No. NCHRP 20-7/186), AASHTO, Washington, DC, 2007a.Kulicki, J.M., Stuffle, Timothy J., Development of AASHTO Vehicular Loads (FWHA NHI 07-019), Federal Highway Administration, National Highway Institute (NHNI-10), 2007b.Melchers, R.E., Structural Reliability Analysis and Prediction, John Wiley and Sons, New York, 1999.Mertz, D.R., Load Rating by Load and Resistance Factor Evaluation Method (NCHRP Project 20-07/Task 122), TRB, National Research Council, Washington DC, 2005.Moses, F., NCHRP Report 454: Calibration of Load Factors for LRFR BridgeEvaluation, TRB, National Research Council, Washington, D.C., 2000.Moses, F., Verma, D., NCHRP Report 301: Load Capacity Evaluation of Existing Bridges, TRB, National Research Council, Washington, D.C., 1987.NCHRP, Manual for Condition Evaluation and Load Rating of Highway Bridges Using Load and Resistance Factor Philosophy (NCHRP Web Document 28), TRB, National Research Council, Washington DC, 2001.Nowak, A.S., NCHRP Report 368: Calibration of LRFD Bridge Design Code, TRB, National Research Council, Washington D.C., 1999.Nowak, A.S., Collins, Kevin R., Reliability of Structures, McGraw Hill, New York, 2000.Tonias, D.E., Zhao, J.J., Bridge Engineering: Design, Rehabilitation, and Maintentance of Modern Highway Bridges, McGraw-Hill, New York, 2007.AASHTO关于桥梁荷载等级评定方法的比较作者:Cristopher D. Moen，Ph.D.，P.E.，Virginia Tech，Blacksburg，VA，cmoen@Leo Fernandez，P.E.，TranSystems，New York，NY，lafernandez@绪论：现有的高速公路桥梁的承载能力是用传统单一荷载等级因数定量化的。
大学本科毕业设计--英文原文+中文翻译
Library of C the CNC industrialdeveloped tens of thousands and educational field, he hasNUMERICAL CONTROLNumerical Control technology as it is known today, emerged in the mid 20th century. It can be traced to the year of 1952, the U.S. Air Force, and the names of John Parsons and the Massachusetts Institute of Technology in Cam-bridge, MA, USA. It was not applied in production manu-facturing until the early 1960's. The real boom came in the form of CNC, around the year of 1972, and a decade later with the introduction of affordable micro computers. The history and development of this fascinating technology has been well documented in many publications.In the manufacturing field, and particularly in the area of metal working, Numerical Control technology has caused something of a revolution. Even in the days before comput-ers became standard fixtures in every company and in many homes, the2machine tools equipped with Numerical Control system found their special place in the machine shops. The recent evolution of micro electronics and the never ceasing computer development, including its impact on Numerical Control, has brought significant changes to the manufacturing sector in general and metalworking in-dustry in particular.DEFINITION OF NUMERICAL CONTROLIn various publications and articles, many descriptions have been used during the years, to define what Numerical Control is. It would be pointless to try to find yet another definition, just for the purpose of this handbook. Many of these definitions share the same idea, same basic concept, just use different wording.The majority of all the known definitions can be summed up into a relatively simple statement:Numerical Control can be defined as an operation of machine tools by the means of specifically coded instructions to the machine control systemThe instructions are combinations of the letters of alpha-bet, digits and selected symbols, for example, a decimal point, the percent sign or the parenthesis symbols. All in-structions are written in a logical order and a predetermined form. The collectionNUMERICAL CONTROLof all instructions necessary to ma-chine a part is called an NC Program, CNC Program, or a Part Program. Such a program can be stored for a future use and used repeatedly to achieve identical machining re-sults at any time.♦ NC and CNC TechnologyIn strict adherence to the terminology, there is a differ-ence in the meaning of the abbreviations NC and CNC. The NC stands for the older and original Numerical Control technology, whereby the abbreviation CNC stands for the newer Computerized Numerical Control technology, a modem spin-off of its older relative. However, in practice, CNC is the preferred abbreviation. To clarify the proper us-age of each term, look at the major differences between the NC and the CNC systems.Both systems perform the same tasks, namely manipula-tion of data for the purpose of machining a part. In both cases, the internal design of the control system contains the logical instructions that process the data. At this point the similarity ends. The NC system (as opposed to the CNC system) uses a fixed logical functions, those that are built-in and perma-nently wired within the control unit. These functions can-not be changed by the programmer or the machine opera-tor. Because of the fixed4wiring of the control logic, the NC control system is synonymous with the term 'hardwired'. The system can interpret a part program, but it does not al-low any changes to the program, using the control features. All required changes must be made away from the control, typically in an office environment. Also, the NC system re-quires the compulsory use of punched tapes for input of the program information.The modem CNC system, but not the old NC system, uses an internal micro processor (i.e., a computer). This computer contains memory registers storing a variety of routines that are capable of manipulating logical functions. That means the part programmer or the machine operator can change the program on the control itself (at the ma-chine), with instantaneous results. This flexibility is the greatest advantage of the CNC systems and probably the key element that contributed to such a wide use of the tech-nology in modern manufacturing. The CNC programs and the logical functions are stored on special computer chips, as software instructions, rather than used by the hardware connections, such as wires, that control the logical func-tions. In contrast to the NC system, the CNC system is syn-onymous with the term 'softwired'.NUMERICAL CONTROLWhen describing a particular subject that relates to the numerical control technology, it is customary to use either the term NC or CNC. Keep in mind that NC can also mean CNC in everyday talk, but CNC can never refer to the older technology, described in this handbook under the abbrevia-tion ofNC. The letter 'C 'stands for Computerized, and it is not applicable to the hardwired system. All control systems manufactured today are of the CNC design. Abbreviations such as C&C or C'n 'C are not correct and reflect poorly on anybody that uses them.CONVENTIONAL AMD CNC MACHININGWhat makes the CNC machining superior to the conven-tional methods? Is it superior at all? Where are the main benefits? If the CNC and the conventional machining pro-cesses are compared, a common general approach to ma-chining a part will emerge: Obtain and study the drawingSelect the most suitable machining methodDecide on the setup method (work holding)Select the cutting toolsEstablish speeds and feedsMachine the part6This basic approach is the same for both types of machin-ing. The major difference is in the way how various data are input. A feedrate of 10 inches per minute (10 in/min) is the same in manual or CNC applications, but the method of applying it is not. The same can be said about a coolant - it can be activated by turning a knob, pushing a switch or programming a special code. All these actions will result in a coolant rushing out of a nozzle. In both kinds of machin-ing, a certain amount of knowledge on the part of the user is required. After all, metal working, particularly metal cut-ting, is mainly a skill, but it is also, to a great degree, an art and a profession of large number of people. So is theappli-cation of Computerized Numerical Control. Like any skill or art or profession, mastering it to the last detail is neces-sary to be successful. It takes more than technical knowl-edge to be a CNC machinist or a CNC programmer. Work experience and intuition, and what is sometimes called a 'gut-feel', is a much needed supplement to any skill.In a conventional machining, the machine operator sets up the machine and moves each cutting tool, using one or both hands, to produce the required part. The design of a manual machine tool offers many features that help the process of machining a part -NUMERICAL CONTROLlevers, handles, gears and di-als, to name just a few. The same body motions are re-peated by the operator for every part in the batch. However, the word 'same 'in this context really means'similar 'rather than 'identical'. Humans are not capable to repeat every process exactly the same at all times - that is the job ofma-chines. People cannot work at the same performance level all the time, without a rest. All of us have some good andsome bad moments. The results of these moments, when*applied to machining a part, are difficult to predict. There will be some differences and inconsistencies within each batch of parts. The parts will not always be exactly the same. Maintaining dimensional tolerances and surface fin-ish quality are the most typical problems in conventional machining. Individual machinists may have their own time 'proven' methods, different from those of their fellow col-leagues. Combination of these and other factors create a great amount of mconsistency.The machining under numerical control does away with the majority of inconsistencies. It does not require the same physical involvement as manual machining. Numerically controlled machining does not need any levers or dials or handles, at least8not in the same sense as conventional ma-chining does. Once the part program has been proven, it can be used any number of times over, always returning consistent results. That does not mean there are no limiting factors. The cutting tools do wear out, the material blank in one batch is not identical to the material blank in another batch, the setups may vary, etc. These factors should be considered and compensated for, whenever necessary.The emergence of the numerical control technology does not mean an instant, or even a long term, demise of all man-ual machines. There are times when a traditional machin-ing method is preferable to a computerized method. For ex-ample, a simple one time job may be done more efficiently on a manual machine than a CNC machine. Certain types of machining jobs will benefit from manual or semiauto-matic machining, rather than numerically controlled ma-chining. The CNC machine tools are not meant to replace every manual machine, only to supplement them.In many instances, the decision whether certain machin-ing will be done on a CNC machine or not is based on the number of required parts and nothing else. Although the volume of partsNUMERICAL CONTROLmachined as a batch is always an important criteria, it should never be the only factor. Consideration should also be given to the part complexity, its tolerances, the required quality of surface finish, etc. Often, a single complex part will benefit from CNC machining, while fifty relatively simple parts will not.Keep in mind that numerical control has never machined a single part by itself. Numerical control is only a process or a method that enables a machine tool to be used in a pro-ductive, accurate and consistent way.NUMERICAL CONTROL ADVANTAGESWhat are the main advantages of numerical control?It is important to know which areas of machining will benefit from it and which are better done the conventional way. It is absurd to think that a two horse power CNC mill will win over jobs that are currently done on a twenty times more powerful manual mill. Equally unreasonable are ex-pectations of great improvements in cutting speeds and feedrates over a conventional machine. If the machining and tooling conditions are the same, the cutting time will be very close in both cases.Some of the major areas where the CNC user can and should expect improvement:10Setup time reductionLead time reductionAccuracy and repeatabilityContouring of complex shapesSimplified tooling and work holdingConsistent cutting timeGeneral productivity increaseEach area offers only a potential improvement. Individ-ual users will experience different levels of actual improve-ment, depending on the product manufactured on-site, the CNC machine used, the setup methods, complexity of fixturing, quality of cutting tools, management philosophy and engineering design, experience level of the workforce, individual attitudes, etc.Setup Time ReductionIn many cases, the setup time for a CNC machine can be reduced, sometimes quite dramatically. It is important to realize that setup is a manual operation, greatly dependent on the performance of CNC operator, the type of fixturing and general practices of the machine shop. Setup time is unproductive, but necessary - it is a part of the overhead costs of doing business. To keep the setupNUMERICAL CONTROLtime to a mini-mum should be one of the primary considerations of any machine shop supervisor, programmer and operator. Because of the design of CNC machines, the setup time should not be a major problem. Modular fixturing, standard tooling, fixed locators, automatic tool changing, pallets and other advanced features, make the setup time more efficient than a comparable setup of a conventional machine. With a good knowledge of modern manufacturing, productivity can be increased significantly.The number of parts machined under one setup is also important, in order to assess the cost of a setup time. If a great number of parts is machined in one setup, the setup cost per part can be very insignificant. A very similar re-duction can be achieved by grouping several different oper-ations into a single setup. Even if the setup time is longer, it may be justified when compared to the time required to setup several conventional machines.Lead Time ReductionOnce a part program is written and proven, it is ready to be Bsed again in the future, even at a short notice. Although the lead time for the first run is usually longer, it is virtually nil for any subsequent run. Even if an engineering change of the part design12requires the program to be modi tied, it can be done usually quickly, reducing the lead time.Long lead time, required to design and manufacture sev-eral special fixtures for conventional machines, can often be reduced by preparing a part program and the use of sim-plified fixturing. Accuracy and RepeatabilityThe high degree of accuracy and repeatability of modern CNC machines has been the single major benefit to many users. Whether the part program is stored on a disk or in the computer memory, or even on a tape (the original method), it always remains the same. Any program can be changed at will, but once proven, no changes are usually required any more. A given program can be reused as many times as needed, without losing a single bit of data it contains. True, program has to allow for such changeable factors as tool wear and operating temperatures, it has to be stored safely, but generally very little interference from the CNC pro-grammer or operator will be required. The high accuracy of CNC machines and their repeatability allows high quality parts to be produced consistently time after time. Contouring of Complex ShapesNUMERICAL CONTROLCNC lathes and machining centers are capable of con-touring a variety of shapes. Many CNC users acquired their machines only to be able to handle complex parts. A good examples are CNC applications in the aircraft and automo-tive industries. The use of some form of computerized pro-gramming is virtually mandatory for any three dimensional tool path generation.Complex shapes, such as molds, can be manufactured without the additional expense of making a model for trac-ing. Mirrored parts can be achieved literally at the switch of a button. Storage of programs is a lot simpler than storage of patterns, templates, wooden models, and other pattern making tools.Simplified Tooling and Work HoldingNonstandard and 'homemade' tooling that clutters the benches and drawers around a conventional machine can be eliminated by using standard tooling, specially designed for numerical control applications. Multi-step tools such as pilot drills, step drills, combination tools, counter borers and others are replaced with several individual standard tools. These tools are often cheaper and easier to replace than special and nonstandard tools.Cost-cutting measures have forced many tool suppliers to keep a low or even a nonexistent inventory, increasing the delivery lime14to the customer. Standard, off-the-shelf tooling can usually beob-tained faster then nonstandard tooling.Fixturing and work holding for CNC machines have only one major purpose - to hold the part rigidly and in the same position for all parts within a batch. Fixtures designed for CNC work do not normally require jigs, pilot holes and other hole locating aids.♦ Cutting Time and Productivity IncreaseThe cutting time on the CNC machine is commonly known as the cycle time - and is always consistent. Unlike a conventional machining, where the operator's skill, experi-ence and personal fatigue are subject to changes, the CNC machining is under the control of a computer. The small amount of manual work is restricted to the setup andload-ing and unloading the part. For large batch runs, the high cost of the unproductive time is spread among many parts, making it less significant. The main benefit of a consistent cutting time is for repetitive jobs, where the production scheduling and work allocation to individual machine tools can be done very accurately.The main reason companies often purchase CNCma-chines is strictly economic - it is a serious investment. Also, having a competitive edge is always on the mind of every plant manager. The numerical control teclmology offers excellent means to achieve a significant improvement in the manufacturing productivity and increasing the overall quality of the manufactured parts. Like any means, it has to be used wisely and knowledgeably. When more and more companies use the CNCtechnology, just having a CNC machine does not offer the extra edge anymore. Thecom-panies that get forward are those who know how to use the technology efficiently and practice it to be competitive in the global economy.To reach the goal of a major increase in productivity, it is essential that users understand the fundamental principles on which CNC technology is based. These principles take many forms, for example, understanding the electronic cir-cuitry, complex ladder diagrams, computer logic, metrol-ogy, machine design, machining principles and practices and many others. Each one has to be studied and mastered by the person in charge. In this handbook, the emphasis is on the topics that relate directly to the CNC programming and understanding the most common CNC machine tools, the Machining Centers and the lathes (sometimes also called the Turning Centers). The part quality consideration should be very important to every programmer and ma-chine tool operator and this goal is also reflected in the handbook approach as well as in the numerous examples.TYPES OF CNC MACHINE TOOLSDifferent kinds of CNCmachines cover an extremelylarge variety. Their numbersare rapidly increasing, as thetechnology developmentadvances. It is impossible toiden-tify all the applications,they would make a long list.Here is a brief list of some ofthe groups CNC machines canbe part of: *Mills and Machining centersLathes and Turning CentersDrilling machines CNC machining centers andlathes dominate the number ofinstallations in industry. Thesetwo groups share the marketjust about equally. Someindustries may have a higherneed for one group ofmachines, depending on their □ Boring mills and Profilers □ EDM machines □ Punch presses and Shears □ Flame cutting machines □ Routers □ Water jet and Laser profilers □ Cylindrical grinders □ Welding machines □ Benders, Winding and Spinning machines, etc.needs. One must remember that there are many different kinds of ladies and equally many different kinds ofma-chining centers. However, the programming process for a vertical machine is similar to the one for a horizontalma-chine or a simple CNC mill. Even between differentma-chine groups, there is a great amount of general applica-tions and the programming process is generally the same. For example, a contour milled with an end mill has a lot in common with a contour cut with a wire.♦ Mills and Machining Centers Standard number of axes on a milling machine is three - the X, Y and Z axes. The part set on a milling system is al-ways stationary, mounted on a moving machine table. The cutting tool rotates, it can move up and down (or in and out), but it does not physically follow the tool path.CNC mills - sometimes called CNC milling machines - are usually small, simple machines, without a tool changer or other automatic features. Their power rating is often quite low. In industry, they are used for toolroom work, maintenance purposes, or small part production. They are usuallydesigned for contouring, unlike CNC drills.CNC machining centers are far more popular and effi-cient than drills and mills, mainly for their flexibility. The main benefit the user gets out of a CNC machining center is the ability to group several diverse operations into a single setup. For example, drilling, boring, counter boring, tap-ping, spot facing and contour milling can be incorporated into a single CNC program. In addition, the flexibility is enhanced by automatic tool changing, using pallets to minimize idle time, indexing to a different side of the part, using a rotary movement of additional axes, and a number of other features. CNC machining centers can be equipped with special software that controls the speeds and feeds, the life of the cutting tool, automatic in-process gauging and offset adjustment and other production enhancing and time saving devices.There are two basic designs of a typical CNC machining center. They are the vertical and the horizontal machining centers. The major difference between the two types is the nature of work that can be done on them efficiently. For a vertical CNC machining center, the most suitable type of work are flat parts, either mounted to the fixture on the ta-ble, or held in a vise or a chuck. The work that requires ma-chining on two or more faces m a single setup is more de-sirable to be done on a CNC horizontal machining center. An good example is a pump housing and other cubic-like shapes. Some multi-face machining of small parts can also be done on a CNC vertical machining center equipped with a rotary table.The programming process is the same for both designs, but an additional axis (usually a B axis) is added to the hori-zontal design. This axis is either a simple positioning axis (indexing axis) for the table, or a fully rotary axis for simul-taneous contouring. This handbook concentrates on the CNC vertical ma-chining centers applications, with a special section dealing with the horizontal setup and machining. The program-ming methods are also applicable to the small CNC mills or drilling and/or tapping machines, but the programmer has to consider their restrictions.♦ Lathes and Turning CentersA CNC lathe is usually a machine tool with two axes, the vertical X axis and the horizontal Z axis. The main feature of a lathe that distinguishes it from a mill is that the part is rotating about the machine center line. In addition, the cut-ting tool is normally stationary, mounted in a sliding turret. The cutting tool follows the contour of the programmed tool path. For the CNC lathes with a milling attachment, so called live tooling, the milling tool has its own motor and rotates while the spindle is stationary.The modem lathe design can be horizontal or vertical. Horizontal type is far more common than the vertical type, but both designs have their purpose in manufacturing. Sev-eral different designs exist for either group. For example, a typical CNC lathe of the horizontal group can be designed with a flat bed or a slant bed, as a bar type, chucker type or a universal type. Added to these combinations are many ac-cessories that make a CNC lathe an extremely flexible ma-chine tool. Typically, accessories such as a tailstock, steady rests or follow-up rests, part catchers,pullout-fingers and even a third axis milling attachment are popular compo-nents of the CNC lathe. ?CNC lathe can be veiy versatile - so versatile in fact, that it is often called a CNC TurningCenter. All text and program examples in this handbook use the more traditional term CNC lathe, yet still recogniz-ing all its modern functions.中文翻译：数控正如我们现在所知，数控技术出现于20世纪中叶。
毕 业 设 计(英文翻译)
附录G：英文翻译参考（要求学生完成与论文有关的外文资料中文字数5000字左右的英译汉，旨在培养学生利用外文资料开展研究工作的能力，为所选课题提供前沿参考资料。
）毕业设计（英文翻译）题目系别：专业：班级：学生姓名：学号：指导教师：一位从事质量管理的人约瑟夫·朱兰出生于圣诞夜,1904 在罗马尼亚的喀尔巴阡山脉山中。
他青年时期的村庄中贫穷、迷信和反犹太主义甚是猖獗。
1912年朱兰家搬到了明尼阿波尼斯州，虽然充满了危险，但是它却让一个男孩充满信心和希望。
从如此多了一个在质量观念的世界最好改革者之一。
在他90年的生活中，朱兰一直是一个精力充沛的思想者倡导者，推动着传统的质量思想向前走。
因为九岁就被雇用,朱兰表示在他的生活工作上永不停止。
记者:技术方面如何讲质量?朱兰:技术有不同方面:一、当然是精密。
物的对精密的需求像电子学、化学…我们看来它们似乎需要放大来说,和重要的原子尘的有关于质量。
要做到高精密具有相当大的挑战，而且我们已经遇见非常大的挑战。
另外的一个方面是可信度－没有失败。
当我们举例来说建立一个系统，同类空中交通管制的时候,我们不想要它失败。
我们必须把可信度建入系统。
因为我们投入很大的资金并依赖这些系统，系统非常复杂，这是逐渐增加的。
除此之外,有对公司的失败费用。
如果事物在领域中意外失败,可以说，它影响民众。
但是如果他们失败在内部,然后它影响公司的费用,而且已经试着发现这些费用在哪里和该如何免除他们。
因此那些是相当大的因素:精密、可信度和费用。
还有其它的,当然，但是我认为这些是主要的一些。
记者:据说是质量有在美国变成一种产业的可能?朱兰:资讯科技当然有。
已经有大的变化。
在世纪中初期当质量的一个想法到一个检验部门的时候，这有了分开的工作，东西被做坏之后。
检验是相当易错的程序,实际上。
而且无论如何，资讯科技在那天中相当花时间，直到某事已经被认为是否资讯科技是正确的。
应该强调计划，如此它不被错误首先订定。
毕业设计论文翻译（译文+原文）
Hacking tricks toward security on network environments Tzer-Shyong Chen1, Fuh-Gwo Jeng 2, and Yu-Chia Liu 11 Department of Information Management, Tunghai University, Taiwan2 Department of Applied Mathematics, National Chiayi University, TaiwanE-Mail:****************.edu.twAbstractMounting popularity of the Internet has led to the birth of Instant Messaging, an up-and-coming form of Internet communication. Instant Messaging is very popular with businesses and individuals since it has instant communication ability. As a result, Internet security has become a pressing and important topic for discussion. Therefore, in recent years, a lot of attention has been drawn towards Internet security and the various attacks carried out by hackers over the Internet. People today often handle affairs via the Internet. For instance, instead of the conventional letter, they communicate with others by e-mails; they chat with friends through an instant messenger; find information by browsing websites instead of going to the library; perform e-commerce transactions through the Internet, etc. Although the convenience of the Internet makes our life easier, it is also a threat to Internet security. For instance, a business email intercepted during its transmission may let slip business confidentiality; file transfers via instant messengers may also be intercepted, and then implanted with backdoor malwares; conversations via instant messengers could be eavesdropped. Furthermore, ID and password theft may lose us money when using Internet bank service. Attackers on the Internet use hacking tricks to damage systems while users are connected to the Internet. These threats along with possible careless disclosure of business information make Instant Messaging a very unsafe method of communication for businesses. The paper divides hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing or fraud via e-mails. (3) Fake Websites. Keywords:Hacking tricks, Trojan programs, Phishing, Firewall, Intrusion detection system.1. IntroductionIncreasingly more people are using instant messengers such as MSN Messenger, Yahoo! Messenger, ICQ, etc as the media of communication. These instant messengers transmit alphanumeric message as well as permit file sharing. During transfer, a file may be intercepted by a hacker and implanted with backdoor malware. Moreover, the e-mails users receive every day may include Spam, advertisements, and fraudulent mail intended to trick uninformed users. Fake websites too are prevalent. Websites which we often visit could be counterfeited by imitating the interface and the URL of the original, tricking users. The paper classifies hacking tricks into three categories which are explained in the following sections.2. Hacking TricksThe paper divides hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing (3) Fake Websites.2.1 Trojan programs that share files via instant messengerInstant messaging allows file-sharing on a computer [9]. All present popular instant messengers have file sharing abilities, or allow users to have the above functionality by installing patches or plug-ins; this is also a major threat to present information security. These communication softwares also makeit difficult for existing hack prevention methods to prevent and control information security. Therefore, we shall discuss how to control the flow of instant messages and how to identify dangerous user behavior.Hackers use instant communication capability to plant Trojan program into an unsuspected program; the planted program is a kind of remotely controlled hacking tool that can conceal itself and is unauthorized. The Trojan program is unknowingly executed, controlling the infected computer; it can read, delete, move and execute any file on the computer. The advantages of a hacker replacing remotely installed backdoor Trojan programs [1] with instant messengers to access files are:When the victim gets online, the hacker will be informed. Thus, a hacker can track and access the infected computer, and incessantly steal user information.A hacker need not open a new port to perform transmissions; he can perform his operations through the already opened instant messenger port.Even if a computer uses dynamic IP addresses, its screen name doesn’t change.Certain Trojan programs are designed especially for instant messengers. These Trojans can change group settings and share all files on the hard disk of the infected computer. They can also destroy or modify data, causing data disarray. This kind of program allows a hacker access to all files on an infected computer, and thus poses a great threat to users. The Trojan program takes up a large amount of the resources of the computer causing it to become very slow and often crashes without a reason.Trojan programs that access a user computer through an instant messenger are probably harder to detect than classic Trojan horse programs. Although classic Trojan intrudes a computer by opening a listening or outgoing port which is used to connect toa remote computer, a desktop firewall can effectively block such Trojans. Alternatively, since it is very difficult for the server’s firewall to spot intrusion by controlling an instant messenger’s flow, it is extremely susceptible to intrusion.Present Trojan programs have already successfully implemented instant messengers. Some Trojan programs are Backdoor Trojan, AIMVision, and Backdoor. Sparta.C. Backdoor Trojans use ICQ pager to send messages to its writer. AIMVision steals AIM related information stored in the Windows registry, enabling a hacker to setup an AIM user id. Backdoor. Sparta.C uses ICQ to communicate with its writer and opens a port on an infected host and send its IP Address to the hacker, and at the same time attempts to terminate the antivirus program or firewall of the host.2.1.1 Hijacking and ImpersonationThere are various ways through which a hacker can impersonate other users [7]. The most commonly used method is eavesdropping on unsuspecting users to retrieve user accounts, passwords and other user related information.The theft of user account number and related information is a very serious problem in any instant messenger. For instance, a hacker after stealing a user’s information impersonate the user; the user’s contacts not knowing that the user’s account has been hacked believe that the person they’re talking to is the user, and are persuaded to execute certain programs or reveal confidential information. Hence, theft of user identity not only endangers a user but also surrounding users. Guarding against Internet security problems is presently the focus of future research; because without good protection, a computer can be easily attacked, causing major losses.Hackers wishing to obtain user accounts may do so with the help of Trojans designed to steal passwords. If an instant messenger client stores his/her password on his/her computer, then a hacker can send a Trojan program to the unsuspecting user. When the user executes the program, the program shall search for the user’s password and send it to the hacker. There are several ways through which a Trojan program can send messages back to the hacker. The methods include instant messenger, IRC, e-mails, etc.Current four most popular instant messengers are AIM, Yahoo! Messenger, ICQ, and MSN Messenger, none of which encrypts its flow. Therefore, a hackercan use a man-in-the-middle attack to hijack a connection, then impersonate the hijacked user and participate in a chat-session. Although difficult, a hacker can use the man-in-the-middle attack to hijack the connection entirely. For example, a user may receive an offline message that resembles that sent by the server, but this message could have been sent by the hacker. All at once, the user could also get disconnected to the server. Furthermore, hackers may also use a Denial of Service (DoS) tool or other unrelated exploits to break the user’s connection. However, the server keeps the connection open, and does not know that the user has been disconnected; thus allowing the hacker to impersonate the user. Moreover, since the data flow is unencrypted and unauthenticated, a hacker can use man-in-the-middle attacks that are similar to that of ARP fraud to achieve its purpose.2.1.2 Denial of Service (DoS)There are many ways through which a hacker can launch a denial of service (DoS) attack [2] on an instant messenger user. A Partial DoS attack will cause a user end to hang, or use up a large portion of CPU resources causing the system to become unstable.Another commonly seen attack is the flooding of messages to a particular user. Most instant messengers allow the blocking of a particular user to prevent flood attacks. However, a hacker can use tools that allow him to log in using several different identities at the same time, or automatically create a large number of new user ids, thus enabling a flood attack. Once a flood attack begins, even if the user realizes that his/her computer has been infected, the computer will not be able to respond. Thus, the problem cannot be solved by putting a hacker’s user id on the ignore list of your instant messenger.A DoS attack on an instant messenger client is only a common hacking tool. The difficulty of taking precautions against it could turn this hacking tool into dangerous DoS type attacks. Moreover, some hacking tools do not just cause an instant messenger client to hang, but also cause the user end to consume large amount of CPU time, causing the computer to crash.2.1.3 Information DisclosureRetrieving system information through instant messenger users is currently the most commonly used hacking tool [4]. It can effortlessly collect user network information like, current IP, port, etc. IP address retriever is an example. IP address retrievers can be used to many purposes; for instance, a Trojan when integrated with an IP address retriever allows a hacker to receive all information related to the infected computer’s IP address as soon as the infected computer connects to the internet. Therefore, even if the user uses a dynamic IP address, hackers can still retrieve the IP address.IP address retrievers and other similar tools can also be used by hackers to send data and Trojans to unsuspecting users. Hackers may also persuade unsuspecting users to execute files through social engineering or other unrelated exploits. These files when executed search for information on the user’s computer and sends them back to the hacker through the instant messenger network.Different Trojan programs were designed for different instant messaging clients. For example, with a user accounts and password stealing Trojans a hacker can have full control of the account once the user logs out. The hacker can thus perform various tasks like changing the password and sending the Trojan program to all of the user’s contacts.Moreover, Trojans is not the only way through which a hacker can cause information disclosure. Since data sent through instant messengers are unencrypted, hackers can sniff and monitor entire instant messaging transmissions. Suppose an employee of an enterprise sends confidential information of the enterprise through the instant messenger; a hacker monitoring the instant messaging session can retrieve the data sent by the enterprise employee. Thus, we must face up to the severity of the problem.2.2 PhishingThe word “Phishing” first appeared in 1996. It is a variant of ‘fishing’, and formed by replacing the ‘f’ in ‘fishing’ with ‘ph’ from phone. It means tricking users of their money through e-mails.Based on the statistics of the Internet Crime Complaint Center, loss due to internet scam was as high as $1.256 million USD in 2004. The Internet Crime Complaint Center has listed the above Nigerian internet scam as one of the ten major internet scams.Based on the latest report of Anti-Phishing Working Group (APWG) [8], there has been a 28% growth of Phishing scams in the past 4 months, mostly in the US and in Asia. Through social engineering and Trojans, it is very difficult for a common user to detect the infection.To avoid exploitation of your compassion, the following should be noted:(1)When you need to enter confidentialinformation, first make sure that theinformation is entered via an entirely secureand official webpage. There are two ways todetermine the security of the webpage:a.The address displayed on the browserbegins with https://, and not http://. Payattention to if the letter ‘s’ exists.b.There is a security lock sign on the lowerright corner of the webpage, and whenyour mouse points to the sign, a securitycertification sign shall appear.(2)Consider installing a browser security softwarelike SpoofStick which can detect fake websites.(3)If you suspect the received e-mail is a Phishinge-mail, do not open attachments attached to theemail. Opening an unknown attachment couldinstall malicious programs onto your computer.(4)Do not click on links attached to your emails. Itis always safer to visit the website through theofficial link or to first confirm the authenticityof the link. Never follow or click on suspiciouslinks in an e-mail. It is advisable to enter theURL at the address bar of the web browser,and not follow the given link.Generally speaking, Phishing [3] [5] is a method that exploits people’s sympathy in the form of aid-seeking e-mails; the e-mail act as bait. These e-mails usually request their readers to visit a link that seemingly links to some charitable organization’s website; but in truth links the readers to a website that will install a Trojan program into the reader’s computer. Therefore, users should not forward unauthenticated charity mails, or click on unfamiliar links in an e-mail. Sometimes, the link could be a very familiar link or an often frequented website, but still, it would be safer if you’d type in the address yourself so as to avoid being linked to a fraudulent website. Phisher deludes people by using similar e-mails mailed by well-known enterprises or banks; these e-mails often asks users to provide personal information, or result in losing their personal rights; they usually contain a counterfeit URL which links to a website where the users can fillin the required information. People are often trapped by phishing due to inattentionBesides, you must also be careful when using a search engine to search for donations and charitable organizations.2.3 Fake WebsitesFake bank websites stealing account numbers and passwords have become increasingly common with the growth of online financial transactions. Hence, when using online banking, we should take precautions like using a secure encrypted customer’s certificate, surf the net following the correct procedure, etc.There are countless kinds of phishing baits, for instance, messages that say data expired, data invalid, please update data, or identity verification intended to steal account ID and matching password. This typeof online scam is difficult for users to identify. As scam methods become finer, e-mails and forged websites created by the impostor resemble their original, and tremendous losses arise from the illegal transactions.The following are methods commonly used by fake websites. First, the scammers create a similar website homepage; then they send out e-mails withenticing messages to attract visitors. They may also use fake links to link internet surfers to their website. Next, the fake website tricks the visitors into entering their personal information, credit card information or online banking account number and passwords. After obtaining a user’s information, the scammers can use the information to drain the bank accounts, shop online or create fake credit cards and other similar crimes. Usually, there will be a quick search option on these fake websites, luring users to enter their account number and password. When a user enters their account number and password, the website will respond with a message stating that the server is under maintenance. Hence, we must observe the following when using online banking:(1)Observe the correct procedure for entering abanking website. Do not use links resultingfrom searches or links on other websites.(2)Online banking certifications are currently themost effective security safeguard measure. (3)Do not easily trust e-mails, phone calls, andshort messages, etc. that asks for your accountnumber and passwords.Phishers often impost a well-known enterprise while sending their e-mails, by changing the sender’s e-mail address to that of the well known enterprise, in order to gain people’s trust. The ‘From’ column of an e-mail is set by the mail software and can be easily changed by the web administrator. Then, the Phisher creates a fake information input website, and send out e-mails containing a link to this fake website to lure e-mail recipients into visiting his fake website.Most Phishers create imitations of well known enterprises websites to lure users into using their fake websites. Even so, a user can easily notice that the URL of the website they’re entering has no relation to the intended enterprise. Hence, Phishers may use different methods to impersonate enterprises and other people. A commonly used method is hiding the URL. This can easily be done with the help of JavaScript.Another way is to exploit the loopholes in an internet browser, for instance, displaying a fake URL in the browser’s address bar. The security loophole causing the address bar of a browser to display a fake URL is a commonly used trick and has often been used in the past. For example, an e-mail in HTML format may hold the URL of a website of a well-known enterprise, but in reality, the link connects to a fake website.The key to successfully use a URL similar to that of the intended website is to trick the visual senses. For example, the sender’s address could be disguised as that of Nikkei BP, and the link set to http://www.nikeibp.co.jp/ which has one k less than the correct URL which is http://www.nikkeibp.co.jp/. The two URLs look very similar, and the difference barely noticeable. Hence people are easily tricked into clicking the link.Besides the above, there are many more scams that exploit the trickery of visual senses. Therefore, you should not easily trust the given sender’s name and a website’s appearance. Never click on unfamiliar and suspicious URLs on a webpage. Also, never enter personal information into a website without careful scrutiny.3. ConclusionsBusiness strategy is the most effective form of defense and also the easiest to carry out. Therefore, they should be the first line of defense, and not last. First, determine if instant messaging is essential in the business; then weigh its pros and cons. Rules and norms must be set on user ends if it is decided that the business cannot do without instant messaging functionality. The end server should be able to support functions like centralized logging and encryption. If not, then strict rules must be drawn, and carried out by the users. Especially, business discussions must not be done over an instant messenger.The paper categorized hacking tricks into three categories: (1) Trojan programs that share files via instant messenger. (2) Phishing (3) Fake Websites. Hacking tricks when successfully carried out could cause considerable loss and damage to users. The first category of hacking tricks can be divided into three types: (1) Hijacking and Impersonation; (2) Denial of Service; (3) Information Disclosure.Acknowledgement:This work was supported by the National Science Council, Taiwan, under contract No. NSC 95-2221-E-029-024.References[1] B. Schneier, “The trojan horse race,”Communications of ACM, Vol. 42, 1999, pp.128.[2] C. L. Schuba, “Analysis of a denial of serviceattack on TCP,” IEEE Security and PrivacyConference, 1997, pp. 208-223.[3] E. Schultz, “Phishing is becoming moresophisticated,” Computer and Security, Vol.24(3), 2005, pp. 184-185.[4]G. Miklau, D. Suciu, “A formal analysis ofinformation disclosure in data exchange,”International Conference on Management ofData, 2004, pp. 575-586.[5]J. Hoyle, “'Phishing' for trouble,” Journal ofthe American Detal Association, Vol. 134(9),2003, pp. 1182-1182.[6]J. Scambray, S. McClure, G. Kurtz, Hackingexposed: network security secrets and solutions,McGraw-Hill, 2001.[7]T. Tsuji and A. Shimizu, “An impersonationattack on one-time password authenticationprotocol OSPA,” to appear in IEICE Trans.Commun, Vol. E86-B, No.7, 2003.[8]Anti-Phishing Working Group,.[9]/region/tw/enterprise/article/icq_threat.html.有关网络环境安全的黑客技术摘要：现在人们往往通过互联网处理事务。
毕业设计外文翻译例文
大连科技学院毕业设计(论文)外文翻译学生姓名专业班级指导教师职称所在单位教研室主任完成日期 2016年4月15日Translation EquivalenceDespite the fact that the world is becoming a global village, translation remains a major way for languages and cultures to interact and influence each other. And name translation, especially government name translation, occupies a quite significant place in international exchange.Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. While interpreting—the facilitating of oral or sign-language communication between users of different languages—antedates writing, translation began only after the appearance of written literature. There exist partial translations of the Sumerian Epic of Gilgamesh (ca. 2000 BCE) into Southwest Asian languages of the second millennium BCE. Translators always risk inappropriate spill-over of source-language idiom and usage into the target-language translation. On the other hand, spill-overs have imported useful source-language calques and loanwords that have enriched the target languages. Indeed, translators have helped substantially to shape the languages into which they have translated. Due to the demands of business documentation consequent to the Industrial Revolution that began in the mid-18th century, some translation specialties have become formalized, with dedicated schools and professional associations. Because of the laboriousness of translation, since the 1940s engineers have sought to automate translation (machine translation) or to mechanically aid the human translator (computer-assisted translation). The rise of the Internet has fostered a world-wide market for translation services and has facilitated language localizationIt is generally accepted that translation, not as a separate entity, blooms into flower under such circumstances like culture, societal functions, politics and power relations. Nowadays, the field of translation studies is immersed with abundantly diversified translation standards, with no exception that some of them are presented by renowned figures and are rather authoritative. In the translation practice, however, how should we select the so-called translation standards to serve as our guidelines in the translation process and how should we adopt the translation standards to evaluate a translation product?In the macro - context of flourish of linguistic theories, theorists in the translation circle, keep to the golden law of the principle of equivalence. The theory of Translation Equivalence is the central issue in western translation theories. And the presentation of this theory gives great impetus to the development and improvement of translation theory. It‟s not diffi cult for us to discover that it is the theory of Translation Equivalence that serves as guidelines in government name translation in China. Name translation, as defined, is the replacement of thename in the source language by an equivalent name or other words in the target language. Translating Chinese government names into English, similarly, is replacing the Chinese government name with an equivalent in English.Metaphorically speaking, translation is often described as a moving trajectory going from A to B along a path or a container to carry something across from A to B. This view is commonly held by both translation practitioners and theorists in the West. In this view, they do not expect that this trajectory or something will change its identity as it moves or as it is carried. In China, to translate is also understood by many people normally as “to translate the whole text sentence by sentence and paragraph by paragraph, without any omission, addition, or other changes. In both views, the source text and the target text must be “the same”. This helps explain the etymological source for the term “translation equivalence”. It is in essence a word which describes the relationship between the ST and the TT.Equivalence means the state or fact or property of being equivalent. It is widely used in several scientific fields such as chemistry and mathematics. Therefore, it comes to have a strong scientific meaning that is rather absolute and concise. Influenced by this, translation equivalence also comes to have an absolute denotation though it was first applied in translation study as a general word. From a linguistic point of view, it can be divided into three sub-types, i.e., formal equivalence, semantic equivalence, and pragmatic equivalence. In actual translation, it frequently happens that they cannot be obtained at the same time, thus forming a kind of relative translation equivalence in terms of quality. In terms of quantity, sometimes the ST and TT are not equivalent too. Absolute translation equivalence both in quality and quantity, even though obtainable, is limited to a few cases.The following is a brief discussion of translation equivalence study conducted by three influential western scholars, Eugene Nida, Andrew Chesterman and Peter Newmark. It‟s expected that their studies can instruct GNT study in China and provide translators with insightful methods.Nida‟s definition of translation is: “Translation consists in reproducing in the receptor language the closest natural equivalent of the source language message, first in terms of meaning and secondly in terms of style.” It i s a replacement of textual material in one language〔SL〕by equivalent textual material in another language（TL）. The translator must strive for equivalence rather than identity. In a sense, this is just another way of emphasizing the reproducing of the message rather than the conservation of the form of the utterance. The message in the receptor language should match as closely as possible the different elements in the source language to reproduce as literally and meaningfully as possible the form and content of the original. Translation equivalence is an empirical phenomenon discovered bycomparing SL and TL texts and it‟s a useful operational concept like the term “unit of translati on”.Nida argues that there are two different types of equivalence, namely formal equivalence and dynamic equivalence. Formal correspondence focuses attention on the message itself, in both form and content, whereas dynamic equivalence is based upon “the principle of equivalent effect”.Formal correspondence consists of a TL item which represents the closest equivalent of a ST word or phrase. Nida and Taber make it clear that there are not always formal equivalents between language pairs. Therefore, formal equivalents should be used wherever possible if the translation aims at achieving formal rather than dynamic equivalence. The use of formal equivalents might at times have serious implications in the TT since the translation will not be easily understood by the target readership. According to Nida and Taber, formal correspondence distorts the grammatical and stylistic patterns of the receptor language, and hence distorts the message, so as to cause the receptor to misunderstand or to labor unduly hard.Dyn amic equivalence is based on what Nida calls “the principle of equivalent effect” where the relationship between receptor and message should be substantially the same as that which existed between the original receptors and the message. The message has to be modified to the receptor‟s linguistic needs and cultural expectation and aims at complete naturalness of expression. Naturalness is a key requirement for Nida. He defines the goal of dynamic equivalence as seeking the closest natural equivalent to the SL message. This receptor-oriented approach considers adaptations of grammar, of lexicon and of cultural references to be essential in order to achieve naturalness; the TL should not show interference from the SL, and the …foreignness …of the ST setting is minimized.Nida is in favor of the application of dynamic equivalence, as a more effective translation procedure. Thus, the product of the translation process, that is the text in the TL, must have the same impact on the different readers it was addressing. Only in Nida and Taber's edition is it clearly stated that dynamic equivalence in translation is far more than mere correct communication of information.As Andrew Chesterman points out in his recent book Memes of Translation, equivalence is one of the five element of translation theory, standing shoulder to shoulder with source-target, untranslatability, free-vs-literal, All-writing-is-translating in importance. Pragmatically speaking, observed Chesterman, “the only true examples of equivalence (i.e., absolute equivalence) are those in which an ST item X is invariably translated into a given TL as Y, and vice versa. Typical examples would be words denoting numbers (with the exceptionof contexts in which they have culture-bound connotations, such as “magic” or “unlucky”), certain technical terms (oxygen, molecule) and the like. From this point of view, the only true test of equivalence would be invariable back-translation. This, of course, is unlikely to occur except in the case of a small set of lexical items, or perhaps simple isolated syntactic structure”.Peter Newmark. Departing from Nida‟s receptor-oriented line, Newmark argues that the success of equivalent effect is “illusory “and that the conflict of loyalties and the gap between emphasis on source and target language will always remain as the overriding problem in translation theory and practice. He suggests narrowing the gap by replacing the old terms with those of semantic and communicative translation. The former attempts to render, as closely as the semantic and syntactic structures of the second language allow, the exact contextual meaning of the original, while the latter “attempts to produce on its readers an effect as close as possible to that obtained on the readers of the original.” Newmark‟s description of communicative translation resembles Nida‟s dynamic equivalence in the effect it is trying to create on the TT reader, while semantic translation has similarities to Nida‟s formal equivalence.Meanwhile, Newmark points out that only by combining both semantic and communicative translation can we achieve the goal of keeping the …spirit‟ of the original. Semantic translation requires the translator retain the aesthetic value of the original, trying his best to keep the linguistic feature and characteristic style of the author. According to semantic translation, the translator should always retain the semantic and syntactic structures of the original. Deletion and abridgement lead to distortion of the author‟s intention and his writing style.翻译对等尽管全世界正在渐渐成为一个地球村，但翻译仍然是语言和和文化之间的交流互动和相互影响的主要方式之一。
毕业设计英文翻译中英文对照版
Feasibility assessment of a leading-edge-flutter wind power generator前缘颤振风力发电机的可行性评估Luca Caracoglia卢卡卡拉克格里亚Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering Center, 360 Huntington A venue, Boston, MA 02115, USA美国东北大学土木与环境工程斯内尔工程中心400，亨廷顿大道360，波士顿02115This study addresses the preliminary technical feasibility assessment of a mechanical apparatus for conversion of wind energy. 这项研究涉及的是风能转换的机械设备的初步技术可行性评估。
The proposed device, designated as ‘‘leading-edge-fl utter wind power generator’’, employs aeroelastic dynamic instability of a blade airfoil, torsionally rotating about its leading edge. 这种被推荐的定义为“前缘颤振风力发电机”的设备，采用的气动弹性动态不稳定叶片翼型，通过尖端旋转产生扭矩。
Although the exploitation of aeroelastic phenomena has been proposed by the research community for energy harvesting, this apparatus is compact, simple and marginally susceptible to turbulence and wake effects.虽然气动弹性现象的开发已经有研究界提出可以通过能量采集。
毕业设计中英文翻译
Key to the development of four-rotors micro air vehicletechnologyTo date, micro d experimental study on the basic theory of rotary wing aircraft and have made more progress, but to really mature and practical, also faces a number of key technical challenges.1. Optimal designOverall design of rotary-wing aircraft when small, need to be guided by the following principles: light weight, small size, high speed, low power consumption and costs. But these principles there are constraints and conflicting with each other, such as: vehicle weights are the same, is inversely proportional to its size and speed, low energy consumption. Therefore, when the overall design of miniature four-rotor aircraft, first select the appropriate body material based on performance and price, as much as possible to reduce the weight of aircraft; second, the need to take into account factors such as weight, size, speed and energy consumption, ensuring the realization of design optimization.2. The power and energyPower unit includes: rotor, micro DC motor, gear reducer, photoelectric encoder and motor drive module, the energy provided by onboard batteries. Four-rotors micro air vehicle's weight is a major factor affecting their size and weight of the power and energy devices accounted for a large share of the weight of the entire body. For the OS4 II, the proportion is as high as 75%. Therefore, development of lighter, more efficient power and energy devices is further miniaturized four key to rotary wing aircraft.The other hand, the lifting occurs with a power unit, most airborne energy consumption. For example, OS4 II power 91% power consumption. To increase the efficiency of aircraft, the key is to improve the efficiency of the power plant. In addition to maximize transmission efficiency, you must alsoselect the motor and reduction ratios, taking into account the maximum efficiency and maximum power output under the premise of two indicators, electric operating point within the recommended run area.3. The establishment of mathematical modelIn order to achieve effective control of four-rotors micro air vehicles, must be established accurately under various flight model. But during the flight, it not only accompanied by a variety of physical effects (aerodynamic, gravity, gyroscopic effect and rotor moment of inertia, also is vulnerable to disturbances in the external environment, such as air. Therefore, it is difficult to establish an effective, reliable dynamic model. In addition, the use of rotary wing, small size, light weight, easy to shape, it is difficult to obtain accurate aerodynamic performance parameters, and also directly affects the accuracy of the model.Establishment of mathematical model of four-rotor MAV, must also be studied and resolved problems rotor under low Reynolds number aerodynamics. Aerodynamics of micro air vehicle with conventional aircraft is very different, many aerodynamic theory and analysis tools are not currently applied, requires the development of new theories and research techniques.4. Flight controlFour-rotors micro air vehicle is a six degrees of freedom (location and attitude) and 4 control input (rotor speed) of underactuated system (Underactuated System), have more than one variable, linear, strongly coupled and interfere with sensitive features, makes it very difficult to design of flight control system. In addition, the controller model accuracy and precision of the sensor performance will also be affected.Attitude control is the key to the entire flight control, because four-rotors micro air vehicle's attitude and position a direct coupling (roll pitch p directly causes the body to move around before and after p), if you can precisely control the spacecraft attitude, then the control law is sufficient to achieve itsposition and velocity PID control. International study to focus on with attitude control design and validation, results show that although the simulation for nonlinear control law to obtain good results, but has a strong dependence on model accuracy, its actual effect rather than PID control. Therefore, developed to control the spacecraft attitude, also has strong anti-jamming and environment-Adaptive attitude control of a tiny four-rotary wing aircraft flight control system of priorities.5. Positioning, navigation and communicationMiniature four-rotor aircraft is primarily intended for near-surface environments, such as urban areas, forests, and interior of the tunnel. However, there are also aspects of positioning, navigation and communication. One hand, in near-surface environments, GPS does not work often requires integrated inertial navigation, optics, acoustics, radar and terrain-matching technology, development of a reliable and accurate positioning and navigation technology, on the other, near-surface environment, terrain, sources of interference and current communication technology reliability, security and robustness of application still cannot meet the actual demand. Therefore, development of small volume, light weight, low power consumption, reliability and anti-jamming communication chain in four-rotors micro air vehicle technology (in particular the multi-aircraft coordination control technology) development, are crucial.微小型四旋翼飞行器发展的关键技术迄今为止，微小型四旋翼飞行器基础理论与实验研究已取得较大进展，但要真正走向成熟与实用，还面临着诸多关键技术的挑战。
毕业设计英文 翻译(原文)
编号：毕业设计(论文)外文翻译（原文）院（系）：桂林电子科技大学专业：电子信息工程学生姓名： xx学号： xxxxxxxxxxxxx 指导教师单位：桂林电子科技大学姓名： xxxx职称： xx2014年x月xx日Timing on and off power supplyusesThe switching power supply products are widely used in industrial automation and control, military equipment, scientific equipment, LED lighting, industrial equipment,communications equipment,electrical equipment,instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD monitor, LED lighting, communications equipment, audio-visual products, security, computer chassis, digital products and equipment and other fields.IntroductionWith the rapid development of power electronics technology, power electronics equipment and people's work, the relationship of life become increasingly close, and electronic equipment without reliable power, into the 1980s, computer power and the full realization of the switching power supply, the first to complete the computer Power new generation to enter the switching power supply in the 1990s have entered into a variety of electronic, electrical devices, program-controlled switchboards, communications, electronic testing equipment power control equipment, power supply, etc. have been widely used in switching power supply, but also to promote the rapid development of the switching power supply technology .Switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off to maintain a stable output voltage power supply, switching power supply is generally controlled by pulse width modulation (PWM) ICs and switching devices (MOSFET, BJT) composition. Switching power supply and linear power compared to both the cost and growth with the increase of output power, but the two different growth rates. A power point, linear power supply costs, but higher than the switching power supply. With the development of power electronics technology and innovation, making the switching power supply technology to continue to innovate, the turning points of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development.The direction of its development is the high-frequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in high-tech fields, and promote the miniaturization of high-tech products, light of. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.classificationModern switching power supply, there are two: one is the DC switching power supply; the other is the AC switching power supply. Introduces only DC switching power supply and its function is poor power quality of the original eco-power (coarse) - such as mains power or battery power, converted to meet the equipment requirements of high-quality DC voltage (Varitronix) . The core of the DC switching power supply DC / DC converter. DC switching power supply classification is dependent on the classification of DC / DC converter. In other words, the classification of the classification of the DC switching power supply and DC/DC converter is the classification of essentially the same, the DC / DC converter is basically a classification of the DC switching power supply.DC /DC converter between the input and output electrical isolation can be divided into two categories: one is isolated called isolated DC/DC converter; the other is not isolated as non-isolated DC / DC converter.Isolated DC / DC converter can also be classified by the number of active power devices. The single tube of DC / DC converter Forward (Forward), Feedback (Feedback) two. The double-barreled double-barreled DC/ DC converter Forward (Double Transistor Forward Converter), twin-tube feedback (Double Transistor Feedback Converter), Push-Pull (Push the Pull Converter) and half-bridge (Half-Bridge Converter) four. Four DC / DC converter is the full-bridge DC / DC converter (Full-Bridge Converter).Non-isolated DC / DC converter, according to the number of active power devices can be divided into single-tube, double pipe, and four three categories. Single tube to a total of six of the DC / DC converter, step-down (Buck) DC / DC converter, step-up (Boost) DC / DC converters, DC / DC converter, boost buck (Buck Boost) device of Cuk the DC / DC converter, the Zeta DC / DC converter and SEPIC, the DC / DC converter. DC / DC converters, the Buck and Boost type DC / DC converter is the basic buck-boost of Cuk, Zeta, SEPIC, type DC / DC converter is derived from a single tube in this six. The twin-tube cascaded double-barreled boost (buck-boost) DC / DC converter DC / DC converter. Four DC / DC converter is used, the full-bridge DC / DC converter (Full-Bridge Converter).Isolated DC / DC converter input and output electrical isolation is usually transformer to achieve the function of the transformer has a transformer, so conducive to the expansion of the converter output range of applications, but also easy to achieve different voltage output , or a variety of the same voltage output.Power switch voltage and current rating, the converter's output power is usually proportional to the number of switch. The more the number of switch, the greater the output power of the DC / DC converter, four type than the two output power is twice as large,single-tube output power of only four 1/4.A combination of non-isolated converters and isolated converters can be a single converter does not have their own characteristics. Energy transmission points, one-way transmission and two-way transmission of two DC / DC converter. DC / DC converter with bi-directional transmission function, either side of the transmission power from the power of lateral load power from the load-lateral side of the transmission power.DC / DC converter can be divided into self-excited and separately controlled. With the positive feedback signal converter to switch to self-sustaining periodic switching converter, called self-excited converter, such as the the Luo Yeer (Royer,) converter is a typical push-pull self-oscillating converter. Controlled DC / DC converter switching device control signal is generated by specialized external control circuit.the switching power supply.People in the field of switching power supply technology side of the development of power electronic devices, while the development of the switching inverter technology, the two promote each other to promote the switching power supply annual growth rate of more than two digits toward the light, small, thin, low-noise, high reliability, the direction of development of anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, AC / AC DC / AC, such as inverters, DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardization, and has been recognized by the user, but AC / DC modular, its own characteristics make the modular process, encounter more complex technology and manufacturing process. Hereinafter to illustrate the structure and characteristics of the two types of switching power supply.Self-excited: no external signal source can be self-oscillation, completely self-excited to see it as feedback oscillation circuit of a transformer.Separate excitation: entirely dependent on external sustain oscillations, excited used widely in practical applications. According to the excitation signal structure classification; can be divided into pulse-width-modulated and pulse amplitude modulated two pulse width modulated control the width of the signal is frequency, pulse amplitude modulation control signal amplitude between the same effect are the oscillation frequency to maintain within a certain range to achieve the effect of voltage stability. The winding of the transformer can generally be divided into three types, one group is involved in the oscillation of the primary winding, a group of sustained oscillations in the feedback winding, there is a group of load winding. Such as Shanghai is used in household appliances art technological production of switching power supply, 220V AC bridge rectifier, changing to about 300V DC filter added tothe collector of the switch into the transformer for high frequency oscillation, the feedback winding feedback to the base to maintain the circuit oscillating load winding induction signal, the DC voltage by the rectifier, filter, regulator to provide power to the load. Load winding to provide power at the same time, take up the ability to voltage stability, the principle is the voltage output circuit connected to a voltage sampling device to monitor the output voltage changes, and timely feedback to the oscillator circuit to adjust the oscillation frequency, so as to achieve stable voltage purposes, in order to avoid the interference of the circuit, the feedback voltage back to the oscillator circuit with optocoupler isolation.technology developmentsThe high-frequency switching power supply is the direction of its development, high-frequency switching power supply miniaturization, and switching power supply into the broader field of application, especially in high-tech fields, and promote the development and advancement of the switching power supply, an annual more than two-digit growth rate toward the light, small, thin, low noise, high reliability, the direction of the anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, the DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardized, and has been recognized by the user, but modular AC / DC, because of its own characteristics makes the modular process, encounter more complex technology and manufacturing process. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.The switching power supply applications in power electronic devices as diodes, IGBT and MOSFET.SCR switching power supply input rectifier circuit and soft start circuit, a small amount of applications, the GTR drive difficult, low switching frequency, gradually replace the IGBT and MOSFET.Direction of development of the switching power supply is a high-frequency, high reliability, low power, low noise, jamming and modular. Small, thin, and the key technology is the high frequency switching power supply light, so foreign major switching power supply manufacturers have committed to synchronize the development of new intelligent components, in particular, is to improve the secondary rectifier loss, and the power of iron Oxygen materials to increase scientific and technological innovation in order to improve the magnetic properties of high frequency and large magnetic flux density (Bs), and capacitor miniaturization is a key technology. SMT technology allows the switching power supply has made considerable progress, the arrangement of the components in the circuit board on bothsides, to ensure that the light of the switching power supply, a small, thin. High-frequency switching power supply is bound to the traditional PWM switching technology innovation, realization of ZVS, ZCS soft-switching technology has become the mainstream technology of the switching power supply, and a substantial increase in the efficiency of the switching power supply. Indicators for high reliability, switching power supply manufacturers in the United States by reducing the operating current, reducing the junction temperature and other measures to reduce the stress of the device, greatly improve the reliability of products.Modularity is the overall trend of switching power supply, distributed power systems can be composed of modular power supply, can be designed to N +1 redundant power system, and the parallel capacity expansion. For this shortcoming of the switching power supply running noise, separate the pursuit of high frequency noise will also increase, while the use of part of the resonant converter circuit technology to achieve high frequency, in theory, but also reduce noise, but some The practical application of the resonant converter technology, there are still technical problems, it is still a lot of work in this field, so that the technology to be practical.Power electronics technology innovation, switching power supply industry has broad prospects for development. To accelerate the pace of development of the switching power supply industry in China, it must take the road of technological innovation, out of joint production and research development path with Chinese characteristics and contribute to the rapid development of China's national economy.Developments and trends of the switching power supply1955 U.S. Royer (Roger) invented the self-oscillating push-pull transistor single-transformer DC-DC converter is the beginning of the high-frequency conversion control circuit 1957 check race Jen, Sen, invented a self-oscillating push-pull dual transformers, 1964, U.S. scientists canceled frequency transformer in series the idea of switching power supply, the power supply to the size and weight of the decline in a fundamental way. 1969 increased due to the pressure of the high-power silicon transistor, diode reverse recovery time shortened and other components to improve, and finally made a 25-kHz switching power supply.At present, the switching power supply to the small, lightweight and high efficiency characteristics are widely used in a variety of computer-oriented terminal equipment, communications equipment, etc. Almost all electronic equipment is indispensable for a rapid development of today's electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOS-FET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. Toimprove the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for high-speed switch components. However, the switching speed will be affected by the distribution of the charge stored in the inductance and capacitance, or diode circuit to produce a surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Which, in order to prevent the switching Kai - closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magnetic buffer . However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching losses, but also to control the occurrence of surges. This switch is called the resonant switch. Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching losses reduced to zero, and the noise is expected to become one of the high-frequency switching power supply The main ways. At present, many countries in the world are committed to several trillion Hz converter utility.the principle of IntroductionThe switching power supply of the process is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor V - security product is very small (conduction, low voltage, large current; shutdown, voltage, current) V oltammetric product / power device is power semiconductor devices on the loss.Compared with the linear power supply, the PWM switching power supply more efficient process is achieved by "chopping", that is cut into the amplitude of the input DC voltage equal to the input voltage amplitude of the pulse voltage. The pulse duty cycle is adjusted by the switching power supply controller. Once the input voltage is cut into the AC square wave, its amplitude through the transformer to raise or lower. Number of groups of output voltage can be increased by increasing the number of primary and secondary windings of the transformer. After the last AC waveform after the rectifier filter the DC output voltage.The main purpose of the controller is to maintain the stability of the output voltage, the course of their work is very similar to the linear form of the controller. That is the function blocks of the controller, the voltage reference and error amplifier can be designed the same as the linear regulator. Their difference lies in the error amplifier output (error voltage) in the drive before the power tube to go through a voltage / pulse-width conversion unit.Switching power supply There are two main ways of working: Forward transformand boost transformation. Although they are all part of the layout difference is small, but the course of their work vary greatly, have advantages in specific applications.the circuit schematicThe so-called switching power supply, as the name implies, is a door, a door power through a closed power to stop by, then what is the door, the switching power supply using SCR, some switch, these two component performance is similar, are relying on the base switch control pole (SCR), coupled with the pulse signal to complete the on and off, the pulse signal is half attentive to control the pole voltage increases, the switch or transistor conduction, the filter output voltage of 300V, 220V rectifier conduction, transmitted through the switching transformer secondary through the transformer to the voltage increase or decrease for each circuit work. Oscillation pulse of negative semi-attentive to the power regulator, base, or SCR control voltage lower than the original set voltage power regulator cut-off, 300V power is off, switch the transformer secondary no voltage, then each circuit The required operating voltage, depends on this secondary road rectifier filter capacitor discharge to maintain. Repeat the process until the next pulse cycle is a half weeks when the signal arrival. This switch transformer is called the high-frequency transformer, because the operating frequency is higher than the 50HZ low frequency. Then promote the pulse of the switch or SCR, which requires the oscillator circuit, we know, the transistor has a characteristic, is the base-emitter voltage is 0.65-0.7V is the zoom state, 0.7V These are the saturated hydraulic conductivity state-0.1V-0.3V in the oscillatory state, then the operating point after a good tune, to rely on the deep negative feedback to generate a negative pressure, so that the oscillating tube onset, the frequency of the oscillating tube capacitor charging and discharging of the length of time from the base to determine the oscillation frequency of the output pulse amplitude, and vice versa on the small, which determines the size of the output voltage of the power regulator. Transformer secondary output voltage regulator, usually switching transformer, single around a set of coils, the voltage at its upper end, as the reference voltage after the rectifier filter, then through the optocoupler, this benchmark voltage return to the base of the oscillating tube pole to adjust the level of the oscillation frequency, if the transformer secondary voltage is increased, the sampling coil output voltage increases, the positive feedback voltage obtained through the optocoupler is also increased, this voltage is applied oscillating tube base, so that oscillation frequency is reduced, played a stable secondary output voltage stability, too small do not have to go into detail, nor it is necessary to understand the fine, such a high-power voltage transformer by switching transmission, separated and after the class returned by sampling the voltage from the opto-coupler pass separated after class, so before the mains voltage, and after the classseparation, which is called cold plate, it is safe, transformers before power is independent, which is called switching power supply.the DC / DC conversionDC / DC converter is a fixed DC voltage transformation into a variable DC voltage, also known as the DC chopper. There are two ways of working chopper, one Ts constant pulse width modulation mode, change the ton (General), the second is the frequency modulation, the same ton to change the Ts, (easy to produce interference). Circuit by the following categories:Buck circuit - the step-down chopper, the average output voltage U0 is less than the input voltage Ui, the same polarity.Boost Circuit - step-up chopper, the average output voltage switching power supply schematic U0 is greater than the input voltage Ui, the same polarity.Buck-Boost circuit - buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, the inductance transmission.Cuk circuit - a buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, capacitance transmission.The above-mentioned non-isolated circuit, the isolation circuit forward circuits, feedback circuit, the half-bridge circuit, the full bridge circuit, push-pull circuit. Today's soft-switching technology makes a qualitative leap in the DC / DC the U.S. VICOR company design and manufacture a variety of ECI soft-switching DC / DC converter, the maximum output power 300W, 600W, 800W, etc., the corresponding power density (6.2 , 10,17) W/cm3 efficiency (80-90)%. A the Japanese Nemic Lambda latest using soft-switching technology, high frequency switching power supply module RM Series, its switching frequency (200 to 300) kHz, power density has reached 27W/cm3 with synchronous rectifier (MOSFETs instead of Schottky diodes ), so that the whole circuit efficiency by up to 90%.AC / DC conversionAC / DC conversion will transform AC to DC, the power flow can be bi-directional power flow by the power flow to load known as the "rectification", referred to as "active inverter power flow returned by the load power. AC / DC converter input 50/60Hz AC due must be rectified, filtered, so the volume is relatively large filter capacitor is essential, while experiencing safety standards (such as UL, CCEE, etc.) and EMC Directive restrictions (such as IEC, FCC, CSA) in the AC input side must be added to the EMC filter and use meets the safety standards of the components, thus limiting the miniaturization of the volume of AC / DC power, In addition, due to internal frequency, high voltage, current switching, making the problem difficult to solve EMC also high demands on the internal high-density mountingcircuit design, for the same reason, the high voltage, high current switch makes power supply loss increases, limiting the AC / DC converter modular process, and therefore must be used to power system optimal design method to make it work efficiency to reach a certain level of satisfaction.AC / DC conversion circuit wiring can be divided into half-wave circuit, full-wave circuit. Press the power phase can be divided into single-phase three-phase, multiphase. Can be divided into a quadrant, two quadrant, three quadrants, four-quadrant circuit work quadrant.he selection of the switching power supplySwitching power supply input on the anti-jamming performance, compared to its circuit structure characteristics (multi-level series), the input disturbances, such as surge voltage is difficult to pass on the stability of the output voltage of the technical indicators and linear power have greater advantages, the output voltage stability up to (0.5)%. Switching power supply module as an integrated power electronic devices should be selected。
本科毕业设计(论文)英文翻译模板
本科毕业设计（论文）英文翻译论文标题(中文)学院******姓名***专业*******班级**********大气探测2班学号*************** 大气探测、信处、两个专业填写电子信息工程。
生物医学工程、电子信息科学与技术、雷电防护科学与技术As its name implies, region growing is a procedure that groups pixels or subregions into larger regions based on predefined criteria. The basic approach is to start with a set of “seed ” points and from these grow regions by appending to each seed those gray level or color).be used to assignpixels to regions during the centroid of these clusters can be used as seeds.… … …左右手共面波导的建模与带通滤波器设计速发展之势，而它的出现却是源于上世纪本研究提出了一种新型混合左右手（CPW ）的独特功能。
目前这种有效电长度为0°的新型混合左右手共面波导（CRLH CPW ）谐振器正在兴起，这种谐振器工作在5GHz 时的体积比常规结构的谐振器缩减小49.1%。
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