(完整版)本科生_毕业设计说明书外文文献及翻译_
本科毕业设计外文+翻译 2
Section 3 Design philosophy, design method and earthpressures3.1 Design philosophy3.1.1 GeneralThe design of earth retaining structures requires consideration of the interaction between the ground and the structure. It requires the performance of two sets of calculations:1）a set of equilibrium calculations to determine the overall proportions and the geometry of the structure necessary to achieve equilibrium under the relevant earth pressures and forces;2）structural design calculations to determine the size and properties of thestructural sections necessary to resist the bending moments and shear forces determined from the equilibrium calculations.Both sets of calculations are carried out for specific design situations (see 3.2.2) in accordance with the principles of limit state design. The selected design situations should be sufficientlySevere and varied so as to encompass all reasonable conditions which can be foreseen during the period of construction and the life of the retaining wall.3.1.2 Limit state designThis code of practice adopts the philosophy of limit state design. This philosophy does not impose upon the designer any special requirements as to the manner in which the safety and stability of the retaining wall may be achieved, whether by overall factors of safety, or partial factors of safety, or by other measures. Limit states (see 1.3.13) are classified into:a) ultimate limit states (see 3.1.3);b) serviceability limit states (see 3.1.4).Typical ultimate limit states are depicted in figure 3. Rupture states which are reached before collapse occurs are, for simplicity, also classified and treated as ultimate limit states. Ultimate limit states include:a) instability of the structure or any hart of it, including supports and foundations,considered as a rigid body;b) failure by rupture of the structure or any part of it, including supports and foundations.3.1.3 Ultimate limit states3.1.3.1 GeneralThe following ultimate limit states should be considered. Failure of a retaining wall as a result of:a) instability of the earth mass, e.g. a slip failure, overturning or a rotational failure where the disturbing moments on the structure exceed the restoring moments, a translational failure where the disturbing forces (see 1.3.8) exceed the restoring forces and a bearing failure. Instability of the earth mass aim-involving a slip failure ，may occur where:1)the wall is built on sloping ground which itself is close to limiting equilibrium; or2) the structure is underlain by a significant depth of clay whose undrained strength increases only gradually with depth; or3) the structure is founded on a relatively strong stratum underlain by weaker strata; or4) the structure is underlain by strata within which high pore water pressures may develop from natural or artificial sources.b) failure of structural members including the wall itself in bending or shear;c) excessive deformation of the wall or ground such that adjacent structures or services reach their ultimate limit state.3.1.3.2 analysis methodWhere the mode of failure involves a slip failure the methods of analysis, for stability of slopes, are described in BS 6031 and in BS 8081. Where the mode of failure involves a bearing capacity failure, the calculations should establish an effective width of foundation. The bearing pressures as determined from 4.2.2 should not exceed the ultimate bearing capacity in accordance with BS 8004.Where the mode of failure is by translational movement, with passive resistance excluded, stable equilibrium should be achieved using the design shear strength of the soil in contact with the base of the earth retaining structure.Where the mode of failure involves a rotational or translational movement, the stable equilibrium of the earth retaining structure depends on the mobilization of shear stresses within the soil. The full mobilization of the soil shear strength gives rise to limiting active and passive thrusts. These limiting thrusts act in concert on the structure only at the pointof collapse, i.e. ultimate limit state.3.1.4 Serviceability limit statesThe following serviceability limit states should be considered:a) substantial deformation of the structure;b) substantial movement of the ground.The soil deformations, which accompany the full mobilization of shear strength in the surrounding soil, are large in comparison with the normally acceptable strains in service. Accordingly, for most earth retaining structures the serviceability limit state of displacement will be the governing criterion for a satisfactory equilibrium and not the ultimate limit state of overall stability. However, although it is generally impossible or impractical to calculate displacements directly, serviceability can be sufficiently assured by limiting the proportion of available strength actually mobilized in service; by the method given in 3.2.4 and 3.2.5.The design earth pressures used for serviceability limit state calculations will differ from those used for ultimate limit state calculations only where structures are to be subjected to differing design values of external loads (generally surcharge and live loads) for the ultimate limit state and for the serviceability limit state.3.1.5 Limit states and compatibility of deformationsThe deformation of an earth retaining structure is important because it has a direct effect upon the forces on the structure, the forces from the retained soil and the forces which result when the structure moves against the soil. The structural forces and bending moments due to earth pressures reduce as deformation of the structure increases.The maximum earth pressures on a retaining structure occur during working conditions and the necessary equilibrium calculations (see 3.2.1) are based on the assumption that earth pressures greater than fully active pressure (see 1.3.11) and less than fully passive will act on the retaining structure during service. As ultimate limit state with respect to soil pressures is approached, with sufficient deformation of the structure, the active earth pressure (see 1.3.1) in the retained soil reduces to the fully active pressure and the passive resistance (see 1.3.15) tends to increase to the full available passive resistance (see 1.3.12). The compatibility of deformation of the structure and the corresponding earth pressures isimportant where the form of structure, for example a propped cantilever wall, prevents the occurrence of fully active pressure at the prop. It is alsoparticularly important where the structure behaves as a brittle material and loses strength as deformation increases, such as an unreinforced mass gravity structure or where the soil is liable to strain softening as deformation increases.3.1.6 Design values of parametersThese are applicable at the specified limit states in the specified design situations. All elements of safety and uncertainty should be incorporated into the design values.The selection of design values for soil parametersshould take account of:a) the possibility of unfavorable variations in the values of the parameters;b) the independence or interdependence of the various parameters involved in the calculation;c) the quality of workmanship and level of control specified for the construction.3.1.7 Applied loadsThe design value for the density of fill materials, should be a pessimistic or unfavorable assessment of actual density.For surcharges and live loadings different values may be appropriate for the differing conditions of serviceability and ultimate limit states and for different load combinations. The intention of this code of practice is to determine those earthpressures which will not be exceeded in a limit state, if external loads are correctly predicted. External loads, such as structural dead loads or vehicle surcharge loads may be specified in other codes as nominal or characteristic values. Some of the structural codes, with which this code interfaces, specify different load factors to be applied for serviceability or ultimate limit state the checks and for different load combinations,See 3.2.7 .Design values of loads, derived by factoring or otherwise, are intended, here, to behere most pessimistic or unfavorable loads which should he used in the calculations for the structure. Similarly, when external loads act on the active or retained side of the wall thesesame external loads should be derived in the same way. The soil is then treated as forming part of the whole structural system.3.1.8 Design soil strength (see 1.3.4)Assessment of the design values depends on the required or anticipated life of the structure, but account should be taken also of the short-term conditions which apply during and immediately following the period of construction. Single design values of soil strength should be obtained from a consideration of the representative values for peak and ultimate strength. The value so selected will satisfy, simultaneously, the considerations of ultimate and serviceability limit states. The design value should be the lower of:a) that value of soil strength, on the stress-strain relation leading to peak strength,which is mobilized at soil strains acceptable for serviceability. This can be expressed as the peak strength reduced by a mobilization factor M as given in 3.2.4 or 3.2.5; orb) that value which would be mobilized at collapse, after significant ground movements. This can general be taken t.o be the critical state strength.Design values selected in this way should be checked to ensure that they conform to 3.1.6. Design values should not exceed representative values of the fully softened critical state soil strength.3.1.9 Design earth pressuresThe design values of lateral earth pressure are intended to give an overestimate of the earth pressure on the active or retained side and an underestimate of the earth resistance on the passive side for small deformations of the structure as a whole, in the working state. Earth pressures reduce as fully active conditions are mobilized atpeak soil strength in the retained soil, under deformations larger than can be tolerated for serviceability. As collapse threatens, the retained soil approaches a critical state, in which its strength reduces to that of loose material and the earth pressures consequently tend to increase once more to active values based on critical state strength.The initial presumption should be that the design earth pressure will correspond to that arising from the design soil strength, see 3.1.8. But the mobilized earth pressure in service, for some walls, will exceed these values. This enhanced earth pressure will control thedesign, for example.a) Where clays may swell in the retained soil zone, or be subject to the effects of compaction in layers, larger earth pressures may occur in that zone, causing corresponding resistance from the ground, propping forces, or anchor tensions to increase so as t.o maintain overall equilibrium.b) Where clays may have lateral earth pressures in excess of the assessed values taking account of earth pressures prior to construction and the effects of wall installation and soil excavation or filling, the earth pressure in retained soil zones will be increased to maintain overall equilibrium.c) Where both the wall and backfill are placed on compressible soils, differential settlement due to consolidation may lead to rotation of the wall into the backfill. This increases the earth pressures in the retained zone.d) Where the structure is particularly stiff, for example fully piled box-shapedBridge abutments, higher earth pressures, caused, for example by compaction, may be preserved, notwithstanding that the degree of wall displacement or flexibility required to reduce retained earth pressures to their fully active values in cohesionless materials is only of the order of a rotation of 10-3 radians.In each of these cases, mobilized soil strengths will increase as deformations continue, so the unfavorable earth pressure conditions dill not persist as collapse approaches.The design earth pressures are derived from design soil strengths using the usual methods of plastic analysis, with earth pressure coefficients (see 1.3.9) given in this code of practice being based on Kerisel&Absi(1990). The same design earth pressures are used in the default condition for the design of structural. sections, see 3.2.7.3.2 Design method3.2.1 Equilibrium calculationsIn order to determine the geometry of the retaining wall, for exampal the depth of penetration of an embedded wall (see 1.3.10), equilibrium calculations should be carried out for care formulated design situations. The design fully calculations relate to a free-body diagram of forces and stresses for the whole retaining wall. The design calculations should demonstrate that there is global equilibrium of vertical and horizontal forces, and of moments. Separate calculations should be made for different design situations.The structural geometry of the retaining wall and the equilibrium calculations should be determined from the design earth pressures derived from the design soil strength using the appropriate earth pressure coefficients.Design earth pressures will lead to active and passive pressure diagrams of the type shown in figure 4. The earth pressure distribution should be checked for global equilibrium of the structure. Horizontal forces equilibrium and momentequilibrium will give the prop force in figure 4a and the location of the point of reversed stress conditions near the toe in figure 4b. Vertical forces equilibrium should also be checked.3.2.2 Design situations3.2.2.1 GeneralThe specification of design situations should include the disposition and classification of the various zones of soil and rock and the elements of construction which could be involved in a limit state event. The specification of design situations should follow a consideration of all uncertainties and the risk factors involved, including thefollowing:a) the loads and their combinations, e.g. surcharge and%or external loads on the active or retained side of the wall;b) the geometry of the structure, and the neighbouring soil bodies, representing the worst credible conditions, for example over-excavation during or after construction;c) the material characteristics of the structure, e.g. following corrosion;d) effects due to the environment within which the design is set, such as:-ground water levels, including their variations due to the effects of dewateringpossible flooding or failure of any drainage system;-scour, erosion and excavation, leading to changes in the geometry of the groundsurface;-chemical corrosion;-weathering;-freezing;-the presence of gases emerging from the ground;-other effects of time and environment on thestrength and other properties of materials;e) earthquakes;f) subsidence due to mining or other causes;g) the tolerance of the structure to deformations;h) the effect of the new structure on existing structures or services and the effect of existing structures or services on the new structure;i) for structures resting on or near rock, theconsideration of:-interbedded hard and soft strata;-faults, joints and fissures;-solution cavities such as swallow holes or fissures, filled with soft material, and continuing solution processes.3.2.2.2 Minimum surcharge and minimum unplanned excavationIn checking the stable equilibrium and soil deformation all walls should be designed for a minimum design surcharge loading of 10 kN/m2 and a minimum depth of excavation in front of the wall, which should be:a)not less than 0.5 m; andb)not less than10% of the total height retained for cantilever walls, or the height retained lowest support level for propped or anchored walls.These minimum values should be reviewed for each design and more adverse values adopted in particularly critical or uncertain circumstances. The requirement for an additional or unplanned excavation as a design criterion is to provide for unforeseen and accidental events. Foreseeable excavations suet as service or drainage trenches infront of a retaining wall, which may be required at some stage in the life of the structure, should be treated as a planned excavation. Actual excavation beyond the planned depth is outside the design considerations of this code.3.2.2.3 Water pressure regimeThe water pressure regime used in the design should be the most onerous that is considered to be reasonably possible.3.2.3 Calculations based on total and effective stress parametersThe changes in loading associated with the construction of a retaining wall may result in changes in the strength of the ground in the vicinity of the wall. if"here the mass permeability of the ground is low these changes of strength take place over some time and therefore the design should consider conditions in both the short- and long-term. Which condition will be critical depends on whether the changes in load applied to the soil mass cause an increase or decrease in soil strength. The long-term condition is likely to becritical where the soil mass undergoes a net reduction in load as a result of excavation, such as adjacent to a cantilever wall. Conversely where the soil mass is subject to a net increase in loading, such as beneath the foundation of a gravity or reinforced stem wall at ground level, the short-term condition is likely to be critical for stability. When considering long-term earth pressures and equilibrium, allowance should be made for changes in ground water conditions and pore water pressure regime which may result from the construction of the works or from other agencies.Calculations for long-term conditions require shear strength parameters to be in terms of effective stress and should take account of a range of water pressures based on considerations of possible seepage flow conditions within the earth mass. Effective stress methods can also be used to assess the short-term conditions provided the pore water pressures developed during construction areknown. A total stress method of analysis may be used to assess the short-term conditions in clays and soils of low permeability, but an inherent assumption of this method is that there will be no change in the soil strength as a result of the changes in load caused by the construction. For granular materials and soils of high permeability all excess pore water pressure will dissipate rapidly so that the relevant strength is always the drained strength and the earth pressures and equilibrium calculations are always in terms of effective stresses.3.2.4 Design using total stress parametersThe retaining wall should be designed to be in equilibrium design clay when based on a mobilized undrained strength (design c u) which does not exceed the representative divided by a mobilization undrained strength factor M. The value of M should not be less than 1.5 if wall displacements are required to be less than 0.5 % of wall height.The value of M should be larger than 1.5 for clays which require large strains to mobilize their peak strength.3.2.5 Design using effective stress parametersThe retaining wall should be designed to be in equilibrium mobilizing a soil strength the lesser or:a) the representative peak strength of the soil divided by a factor M =1.2:that is:Mm a x t a n t i v e r e p r e s e n t a d e s i g n t a n ϕϕ'=' （3） Mc c '=' t i v e r e p r e s e n t ade s i g n （4） orb) the representative critical state strength of the soil.This will ensure that for soils which are medium dense or firm the wall displacements in service will be limited to 0.5 % of the wall height. The mobilization factor of 1.2 should be used in conjunction with the front of the wall, the 'unplanned' excavation inminimum surcharge loading and the water pressure regime, see 3.2.2.2 and 3.2.2.3.A more detailed analysis of displacement should be are to be applied or for soft or loose soils. The criteria a) and b), taken together, should provide a sufficient reserve of safety against small unforeseen loads and adverse conditions.In stiff clays subject to cycles of strain, such as through seasonal variation of pore water pressure, the long-term peak strength may deteriorate to the critical state strength. The requirements of a) and b) above are sufficiently cautious to accommodate this possibility.3.2.6 Design values of wall friction, base friction and undrained wall adhesionThese should be derived from the representative strength determined in accordance with2.2.8,using the same mobilization actors as for the adjacent soil.The design value of the friction or adhesion mobilized at an interface with the structure be the lesser of:a) the representative value determined by described in 2.2.8 if such test results are available; orb) 75% of the design shear strength to be mobilized in the soil itself, that is using: ϕδ'⨯= d e s i g n t a n75.0 design tan (5) u w d e s i g n 75.0design c c ⨯= (6)Since for the soil mass:1.2t a n t i v e r e p r e s e n t a d e s i g n t a n ϕϕ'=' (7) this is equivalent to:32 t i v e r e p r e s e n t ad e s i g n ≈'ϕδ (8) similarly, in total stress analysis:5.1 ng after taki ,5.0 tive representa design uw ==M c c (9) The friction or adhesion, which can be mobilized in practice, is generally less than the value deduced on the basis of soil sliding against the relevant surface. It is unlikely for example, that a cantilever wall will remain at constant elevation while the active soil zone subsides creating full downward wall friction on the retained side, and the passive zone heaves creating full upward wall friction on the excavated side. It is more likely that the wall would move vertically with one or other soil zone,reducing friction on that side, and thereby attaining vertical force equilibrium. The 25% reduction in the design shear strength in b) above makes an allowance for this possibility. Further reductions, and even the elimination of wall friction or its reversal, may be necessary when soil structure interaction is taken into account. Wall friction on the retained or active side should be excluded when the wall is capable of penetrating deeper, due to the vertical thrust imparted by inclined anchors on an embedded wall, by structural loads on a basement wall, or where a clay soil may heave due to swelling during outward movement of the wall. Wall friction on the passive side should be excluded when the wall is prevented from sinking but the adjacent soil may fail to heave, due for example to settlement of loose granular soils induced by cyclic loads, or when the wall is free to move upwards with the passive soil zone, as may happen with buried anchor blocks.3.2.7 Design to structural codesThe earth pressures to be used in structural design calculations are the most severe earth pressures determined for serviceability limit state, see 3.1.9. These are the most severe that can credibly occur under the design situations, see 3.2.2. Accordingly the application ofpartial load factors to the bending moments and internal forces derived from these earth pressures, is not normally required. Hacking determined the earth pressures using design the structure increases it should be assumed that loads and design soil strengths, the structural load affects (bending moments, and shears) can be calculated using equilibrium principles in the usual way without applying any further factors. Finally, the material properties and sections should be derived from the load effects according to the structural codes. Reference should be made to the documentary source for the loadings, such as BS 5400:Part 4 for guidance on the respective design values.Structural design calculations based upon ultimate limit state assume that the moments and forces applicable at ultimate larger than limit state are significantly at serviceability limit state. BS8110: Part 1 and Part; BS 5400:Part 4 and BS 5950:Part 1 and Part 5 make this assumption. At ultimate limit state, the earth active or retained side are not pressures on the a maximum.Because the structural forces and bending moments due to earth pressures reduce as deformation of the most severe earth pressures, which are usually determined for the serviceability limit state, also apply to the ultimate limit state structural design calculations. The design at serviceability limit state for flexible structures such as steel or reinforced and prestressed undertaken in a like concrete may be manner to the analysis in 3.1 to 3.4 of BS 8110:Part 2:1985.For gravity mass walls such as masonry structures, which are relatively rigid, the earth pressures on the retained or active side are likely to be higher than the fully active values in the working state. The earth pressures at serviceability and ultimate limit states will be similar, because the displacement criteria will be similar.3.3 Disturbing forces3.3.1 GeneralThe disturbing forces to be taken into account in the equilibrium calculations are the earth pressures on the active or retained side of the wall, together with loads due to the compaction of the fill (if any) behind the wall, surcharge loads, external loads and last, but by no means least, the water pressure.3.3.2 At-rest earth pressuresThe earth pressures which act on retaining walls, or parts of retaining walls, below existing ground, depend on the initial or at-rest state of stress in the ground. For an undisturbed soil at a state of rest, the ratio of the horizontal to vertical stress depends on the type of soil, its geological origin, the temporary loads which may have acted on the surface of the soil and the topography.Soil suction and empirical correlations with in situ tests including static cone and dilatometer. The value of K i depends on the type of soil, its geological history, the loads which may have topography, the temporary acted on the ground surface and changes in ground strain or ground water regime due to natural or artificial causes.Where there has been no lateral strain within the ground, K i can be determinable from equated with K0 the coefficient one-dimensional consolidation and swelling tests conducted in a stress-path triaxial test using appropriate stress cycles. For normally consolidated soils, both granular and cohesive:ϕ'K(10) 1=s i n-For overconsolidated soils, K0is larger and may approach the passive value at shallow depths in a heavily overconsolidated clay, (see for example Lambe and Whitman, quoting Hendron and Wroth 1975).K i is not used directly in earth retaining structure design because the construction process always modifies this initial value. The value of K i is however, important in assessing the degree of deformation which will be induced as the earth pressure tends towards active or passive states. In normally consolidated soil the ground deformation necessary to mobilize the active condition will be small in relation to that required to mobilize the full passive resistance, while in heavily overconsolidated soil the required ground deformation will be of similar magnitude.Additional ground deformation is necessary for the structure to approach a failure condition with the earth pressures moving further towards their limiting active and passive values.Where a stressed support system is employed (e.g.ground anchorage) then the partial mobilization the active state on the retained side is reversed during installation of the system and,in the zone of support, the effective stress ratio in the soil may pass through the。
本科毕业设计的英文资料与中文翻译
英文资料与中文翻译IEEE 802.11 MEDIUM ACCESS CONTROLThe IEEE 802.11 MAC layer covers three functional areas：reliable data delivery, medium access control, and security. This section covers the first two topics.Reliable Data DeliveryAs with any wireless network, a wireless LAN using the IEEE 802.11 physical and MAC layers is subject to considerable unreliability. Noise, interference, and other propagation effects result in the loss of a significant number of frames. Even with error-correction codes, a number of MAC frames may not successfully be received. This situation can be dealt with by reliability mechanisms at a higher layer. such as TCP. However, timers used for retransmission at higher layers are typically on the order of seconds. It is therefore more efficient to deal with errors at the MAC level. For this purpose, IEEE 802.11 includes a frame exchange protocol. When a station receives a data frame from another station. It returns an acknowledgment (ACK) frame to the source station. This exchange is treated as an atomic unit, not to be interrupted by a transmission from any other station. If the source does not receive an ACK within a short period of time, either because its data frame was damaged or because the returning ACK was damaged, the source retransmits the frame.Thus, the basic data transfer mechanism in IEEE802.11 involves an exchange of two frames. To further enhance reliability, a four-frame exchange may be used. In this scheme, a source first issues a request to send (RTS) frame to the destination. The destination then responds with a clear to send (CTS). After receiving the CTS, the source transmits the data frame, and the destination responds with an ACK. The RTS alerts all stations that are within reception range of the source that an exchange is under way; these stations refrain from transmission in order to avoid a collision between two frames transmitted at the same time. Similarly, the CTS alerts all stations that are within reception range of the destination that an exchange is under way. The RTS/CTS portion of the exchange is a required function of the MAC but may be disabled.Medium Access ControlThe 802.11 working group considered two types of proposals for a MAC algorithm: distributed access protocols, which, like Ethernet, distribute the decision to transmit over all the nodes using a carrier-sense mechanism; and centralized access protocols, which involve regulation of transmission by a centralized decision maker. A distributed access protocol makes sense for an ad hoc network of peer workstations (typically an IBSS) and may also be attractive in other wireless LAN configurations that consist primarily of burst traffic. A centralized access protocol is natural for configurations in which a umber of wireless stations are interconnected with each other and some sort of base station that attaches to a backbone wired LAN: it is especially useful if some of the data is time sensitive or high priority.The end result for 802.11 is a MAC algorithm called DFWMAC (distributed foundation wireless MAC) that provides a distributed access control mechanism with an optional centralized control built on top of that. Figure 14.5 illustrates the architecture. The lower sub-layer of the MAC layer is the distributed coordination function (DCF). DCF uses a contention algorithm to provide access to all traffic. Ordinary asynchronous traffic directly uses DCE. The point coordination function (PCF) is a centralized MAC algorithm used to provide contention-free service. PCF is built on top of DCF and exploits features of DCF to assure access for its users. Let us consider these two sub-layers in turn.MAClayerFigure 14.5 IEEE 802.11 Protocol ArchitectureDistributed Coordination FunctionThe DCF sub-layer makes use of a simple CSMA (carrier sense multiple access) algorithm, which functions as follows. If a station has a MAC frame to transmit, it listens to the medium. If the medium is idle, the station may transmit; otherwise the station must wait until the current transmission is complete before transmitting. The DCF does not include a collision detection function (i.e. CSMA/CD) because collision detection is not practical on a wireless network. The dynamic range of the signals on the medium is very large, so that a transmitting station cannot effectively distinguish incoming weak signals from noise and the effects of its own transmission.To ensure the smooth and fair functioning of this algorithm, DCF includes a set of delays that amounts to a priority scheme. Let us start by considering a single delay known as an inter-frame space (IFS). In fact, there are three different IFS values, but the algorithm is best explained by initially ignoring this detail. Using an IFS, the rules for CSMA access are as follows (Figure 14.6):Figure 14.6 IEEE 802.11 Medium Access Control Logic1. A station with a frame to transmit senses the medium. If the medium is idle. It waits to see if the medium remains idle for a time equal to IFS. If so , the station may transmit immediately.2. If the medium is busy (either because the station initially finds the medium busy or because the medium becomes busy during the IFS idle time), the station defers transmission and continues to monitor the medium until the current transmission is over.3. Once the current transmission is over, the station delays another IFS. If the medium remains idle for this period, then the station backs off a random amount of time and again senses the medium. If the medium is still idle, the station may transmit. During the back-off time, if the medium becomes busy, the back-off timer is halted and resumes when the medium becomes idle.4. If the transmission is unsuccessful, which is determined by the absence of an acknowledgement, then it is assumed that a collision has occurred.To ensure that back-off maintains stability, a technique known as binary exponential back-off is used. A station will attempt to transmit repeatedly in the face of repeated collisions, but after each collision, the mean value of the random delay is doubled up to some maximum value. The binary exponential back-off provides a means of handling a heavy load. Repeated failed attempts to transmit result in longer and longer back-off times, which helps to smooth out the load. Without such a back-off, the following situation could occur. Two or more stations attempt to transmit at the same time, causing a collision. These stations then immediately attempt to retransmit, causing a new collision.The preceding scheme is refined for DCF to provide priority-based access by the simple expedient of using three values for IFS:●SIFS (short IFS):The shortest IFS, used for all immediate responseactions，as explained in the following discussion●PIFS (point coordination function IFS):A mid-length IFS, used by thecentralized controller in the PCF scheme when issuing polls●DIFS (distributed coordination function IFS): The longest IFS, used as aminimum delay for asynchronous frames contending for access Figure 14.7a illustrates the use of these time values. Consider first the SIFS.Any station using SIFS to determine transmission opportunity has, in effect, the highest priority, because it will always gain access in preference to a stationwaiting an amount of time equal to PIFS or DIFS. The SIFS is used in the following circumstances：●Acknowledgment (ACK): When a station receives a frame addressed onlyto itself (not multicast or broadcast) it responds with an ACK frame after, waiting on1y for an SIFS gap. This has two desirable effects. First, because collision detection IS not used, the likelihood of collisions is greater than with CSMA/CD, and the MAC-level ACK provides for efficient collision recovery. Second, the SIFS can be used to provide efficient delivery of an LLC protocol data unit (PDU) that requires multiple MAC frames. In this case, the following scenario occurs. A station with a multi-frame LLC PDU to transmit sends out the MAC frames one at a time. Each frame is acknowledged after SIFS by the recipient. When the source receives an ACK, it immediately (after SIFS) sends the next frame in the sequence. The result is that once a station has contended for the channel, it will maintain control of the channel until it has sent all of the fragments of an LLC PDU.●Clear to Send (CTS):A station can ensure that its data frame will getthrough by first issuing a small. Request to Send (RTS) frame. The station to which this frame is addressed should immediately respond with a CTS frame if it is ready to receive. All other stations receive the RTS and defer using the medium.●Poll response: This is explained in the following discussion of PCF.longer than DIFS(a) Basic access methodasynchronous trafficdefers(b) PCF super-frame constructionFigure 14.7 IEEE 802.11 MAC TimingThe next longest IFS interval is the: PIFS. This is used by the centralized controller in issuing polls and takes precedence over normal contention traffic. However, those frames transmitted using SIFS have precedence over a PCF poll.Finally, the DIFS interval is used for all ordinary asynchronous traffic.Point C00rdination Function PCF is an alternative access method implemented on top of the DCE. The operation consists of polling by the centralized polling master (point coordinator). The point coordinator makes use of PIFS when issuing polls. Because PI FS is smaller than DIFS, the point coordinator call seize the medium and lock out all asynchronous traffic while it issues polls and receives responses.As an extreme, consider the following possible scenario. A wireless network is configured so that a number of stations with time, sensitive traffic are controlled by the point coordinator while remaining traffic contends for access using CSMA. The point coordinator could issue polls in a round—robin fashion to all stations configured for polling. When a poll is issued, the polled station may respond using SIFS. If the point coordinator receives a response, it issues another poll using PIFS. If no response is received during the expected turnaround time, the coordinator issues a poll．If the discipline of the preceding paragraph were implemented, the point coordinator would lock out all asynchronous traffic by repeatedly issuing polls. To prevent this, an interval known as the super-frame is defined. During the first part of this interval, the point coordinator issues polls in a round, robin fashion to all stations configured for polling. The point coordinator then idles for the remainder of the super-frame, allowing a contention period for asynchronous access.Figure l4.7 b illustrates the use of the super-frame. At the beginning of a super-frame, the point coordinator may optionally seize control and issues polls for a give period of time. This interval varies because of the variable frame size issued by responding stations. The remainder of the super-frame is available for contention based access. At the end of the super-frame interval, the point coordinator contends for access to the medium using PIFS. If the medium is idle. the point coordinator gains immediate access and a full super-frame period follows. However, the medium may be busy at the end of a super-frame. In this case, the point coordinator must wait until the medium is idle to gain access: this result in a foreshortened super-frame period for the next cycle.OctetsFC=frame control SC=sequence controlD/I=duration/connection ID FCS=frame check sequence（a ） MAC frameBitsDS=distribution systemMD=more data MF=more fragmentsW=wired equivalent privacy RT=retryO=orderPM=power management (b) Frame control filedFigure 14.8 IEEE 802.11 MAC Frame FormatMAC FrameFigure 14.8a shows the 802.11 frame format when no security features are used. This general format is used for all data and control frames, but not all fields are used in all contexts. The fields are as follows:● Frame Control: Indicates the type of frame and provides contr01information, as explained presently.● Duration/Connection ID: If used as a duration field, indicates the time(in-microseconds) the channel will be allocated for successful transmission of a MAC frame. In some control frames, this field contains an association, or connection, identifier.●Addresses: The number and meaning of the 48-bit address fields dependon context. The transmitter address and receiver address are the MAC addresses of stations joined to the BSS that are transmitting and receiving frames over the wireless LAN. The service set ID (SSID) identifies the wireless LAN over which a frame is transmitted. For an IBSS, the SSID isa random number generated at the time the network is formed. For awireless LAN that is part of a larger configuration the SSID identifies the BSS over which the frame is transmitted: specifically, the SSID is the MAC-level address of the AP for this BSS (Figure 14.4). Finally the source address and destination address are the MAC addresses of stations, wireless or otherwise, that are the ultimate source and destination of this frame. The source address may be identical to the transmitter address and the destination address may be identical to the receiver address.●Sequence Control: Contains a 4-bit fragment number subfield used forfragmentation and reassembly, and a l2-bit sequence number used to number frames sent between a given transmitter and receiver.●Frame Body: Contains an MSDU or a fragment of an MSDU. The MSDUis a LLC protocol data unit or MAC control information.●Frame Check Sequence: A 32-bit cyclic redundancy check. The framecontrol filed, shown in Figure 14.8b, consists of the following fields.●Protocol Version: 802.11 version, current version 0.●Type: Identifies the frame as control, management, or data.●Subtype: Further identifies the function of frame. Table 14.4 defines thevalid combinations of type and subtype.●To DS: The MAC coordination sets this bit to 1 in a frame destined to thedistribution system.●From DS: The MAC coordination sets this bit to 1 in a frame leaving thedistribution system.●More Fragments: Set to 1 if more fragments follow this one.●Retry: Set to 1 if this is a retransmission of a previous frame.●Power Management: Set to]if the transmitting station is in a sleep mode.●More Data: Indicates that a station has additional data to send. Each blockof data may be sent as one frame or a group of fragments in multiple frames.●WEP：Set to 1 if the optional wired equivalent protocol is implemented.WEP is used in the exchange of encryption keys for secure data exchange.This bit also is set if the newer WPA security mechanism is employed, as described in Section 14.6.●Order：Set to 1 in any data frame sent using the Strictly Ordered service,which tells the receiving station that frames must be processed in order. We now look at the various MAC frame types.Control Frames Control frames assist in the reliable delivery of data frames. There are six control frame subtypes:●Power Save-Poll (PS-Poll): This frame is sent by any station to the stationthat includes the AP (access point). Its purpose is to request that the AP transmit a frame that has been buffered for this station while the station was in power saving mode.●Request to Send (RTS):This is the first frame in the four-way frameexchange discussed under the subsection on reliable data delivery at the beginning of Section 14.3.The station sending this message is alerting a potential destination, and all other stations within reception range, that it intends to send a data frame to that destination.●Clear to Send (CTS): This is the second frame in the four-way exchange.It is sent by the destination station to the source station to grant permission to send a data frame.●Acknowledgment:Provides an acknowledgment from the destination tothe source that the immediately preceding data, management, or PS-Poll frame was received correctly.●Contention-Free (CF)-End: Announces the end of a contention-freeperiod that is part of the point coordination function.●CF-End+CF-Ack:Acknowledges the CF-End. This frame ends thecontention-free period and releases stations from the restrictions associated with that period.Data Frames There are eight data frame subtypes, organized into two groups. The first four subtypes define frames that carry upper-level data from the source station to the destination station. The four data-carrying frames are as follows: ●Data: This is the simplest data frame. It may be used in both a contentionperiod and a contention-free period.●Data+CF-Ack: May only be sent during a contention-free period. Inaddition to carrying data, this frame acknowledges previously received data.●Data+CF-Poll: Used by a point coordinator to deliver data to a mobilestation and also to request that the mobile station send a data frame that it may have buffered.●Data+CF-Ack+CF-Poll: Combines the functions of the Data+CF-Ack andData+CF-Poll into a single frame.The remaining four subtypes of data frames do not in fact carry any user data. The Null Function data frame carries no data, polls, or acknowledgments. It is used only to carry the power management bit in the frame control field to the AP, to indicate that the station is changing to a low-power operating state. The remaining three frames (CF-Ack, CF-Poll,CF-Ack+CF-Poll) have the same functionality as the corresponding data frame subtypes in the preceding list (Data+CF-Ack, Data+CF-Poll, Data+CF-Ack+CF-Poll) but withotit the data. Management FramesManagement frames are used to manage communications between stations and APs. The following subtypes are included:●Association Request：Sent by a station to an AP to request an association,with this BSS. This frame includes capability information, such as whether encryption is to be used and whether this station is pollable.●Association Response:Returned by the AP to the station to indicatewhether it is accepting this association request.●Reassociation Request: Sent by a station when it moves from one BSS toanother and needs to make an association with tire AP in the new BSS. The station uses reassociation rather than simply association so that the new AP knows to negotiate with the old AP for the forwarding of data frames.●Reassociation Response:Returned by the AP to the station to indicatewhether it is accepting this reassociation request.●Probe Request: Used by a station to obtain information from anotherstation or AP. This frame is used to locate an IEEE 802.11 BSS.●Probe Response: Response to a probe request.●Beacon: Transmitted periodically to allow mobile stations to locate andidentify a BSS.●Announcement Traffic Indication Message: Sent by a mobile station toalert other mobile stations that may have been in low power mode that this station has frames buffered and waiting to be delivered to the station addressed in this frame.●Dissociation: Used by a station to terminate an association.●Authentication：Multiple authentication frames are used in an exchange toauthenticate one station to another.●Deauthentication:Sent by a station to another station or AP to indicatethat it is terminating secure communications.IEEE802.11 媒体接入控制IEEE 802．11 MAC层覆盖了三个功能区：可靠的数据传送、接入控制以及安全。
山东建筑大学本科毕业设计说明书外文文献及翻译格式模版1.doc
山东建筑大学本科毕业设计说明书外文文献及翻译格式模版1附件3：（本科毕业论文）文献、资料题目：院（部）专班姓名：张三学号：指导教师：张九光翻译日期：2005.6.30，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government information secure ．The organization is in the final stages of an open process of selecting one or more algorithms ，or data-scrambling formulas ，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summer or early fall ．The standard is slated to go into effect next year ．AES is intended to be a stronger ，more efficient successor to Triple Data Encryption Standard (3DES)，which replaced the aging DES ，which was cracked in less than three days in July 1998．“Until we have the AES ，3DES will still offer protection for years to come ．So there is no need to immediately switch over ，”says Edward Roback ，acting chief of the computer security division at NIST and chairman of the AES selection committee ．“What AES will offer is a more efficient algorithm ．It will be a federal standard ，but it will be widely implemented in the IT community ．”According to Roback ，efficiency of the proposed algorithms is measured by how fast they can encrypt and decrypt information ，how fast they can present an encryption key and how much information they can encrypt ．The AES review committee is also looking at how much space the algorithm takes up on a chip and how much memory it requires ．Roback says the selection of a more efficient AES will also result in cost savings and better use of resources ．“DES w as designed for hardware implementations ，and we are now living in a world of much more efficient software ，and we have learned an awful lot about the design of algorithms ，”says Roback ．“When you start multiplying this with the billions of implementations done daily ，the saving on overhead on the networks will be enormous ．”……山东建筑大学毕业设计（或毕业论文，二选一）外文文献及译文- 1 -以确保政府的信息安全。
(完整版)_毕业设计英文翻译_及格式
毕业设计(论文)英文翻译题目专业班级姓名学号指导教师职称200年月日The Restructuring of OrganizationsThroughout the 1990s, mergers and acquisitions a major source of corporate restructuring, affecting millions of workers and their families. This form of restructuring often is accompanied by downsizing. Downsizing is the process of reducing the size of a firm by laying off or retiring workers early. The primary objectives of downsizing are similar in U.S. companies and those in other countries:●cutting cost,●spurring decentralization and speeding up decision making,●cutting bureaucracy and eliminating layers of especially they did five years ago. One consequence of this trend is that today’s managers supervise larger numbers of subordinates who report directly to them. In 1990, only about 20 percent of managers supervise twelve or more people and 54 percent supervised six or fewer.Because of downsizing, first-line managers quality control, resources, and industrial engineering provide guidance and support. First-line managers participate in the production processes and other line activities and coordinate the efforts of the specialists as part of their jobs. At the same time, the workers that first-line managers supervise are less willing to put up with authoritarian management. Employees want their jobs to be more creative, challenging, fun, and satisfying and want to participate in decisions affecting their work. Thus self-managed work teams that bring workers and first-line managers together to make joint decisions to improve the way they do their jobs offer a solution to both supervision and employee expectation problems. When you ’t always the case. Sometimes entire divisions of a firm are simply spun off from the main company to operate on their own as new, autonomous companies. The firm that spun them off may then become one of their most important customers or suppliers. That AT&T “downsized” the old Bell Labs unit, which is now known as Lucent Technologies. Now, rather than - return is free to enter into contracts with companies other than AT&T. this method of downsizing is usually called outsourcing.Outsourcing means letting other organizations perform a needed service andor manufacture needed parts or products. Nike outsources the production of its shoes to low-cost plants in South Korea and China and imports the shoes for distribution in North America. These same plants also ship shoes to Europe and other parts of Asia for distribution. Thus today’s managers face a new challenge: t o plan, organize, lead, and control a company that may as a modular corporation. The modularcorporation is most is most common in three industries: apparel, auto manufacturing, and electronics. The most commonly out-sourced function is production. By out sourcing production, a company can switch supplier best suited to a customer’s needs.Decisions about what to outsource and what to keep in- to contract production to another company is a sound business decision to contract production to another company is a sound business decision, at least for U.S. manufacturers. It appears to the unit cost of production by relieving the company of some overhead, and it frees the company to allocate scarce resources to activities for which the company examples of modular companies are Dell Computer, Nike, Liz Claiborne fashions, and ship designer Cyrix.As organizations downsize and outsource functions, they become flatter and smaller. Unlike the behemoths of the past, the new, smaller firms are less like autonomous fortresses and more like nodes in a net work of complex relationships. This approach, called the network form of organization, involves establishing strategic alliances among several entities.In Japan, cross-ownership and alliances among firms－called keiretsu－both foreign and U.S. auto parts producers. It also owns 49 percent of Hertz, the car rental company that is also a major customer. Other alliances include involvement in several research consortia. In the airline industry, a common type of alliance is between an airline and an airframe manufacture. For example, Delta recently agreed to buy all its aircraft from Boeing. Boeing Airlines. Through these agreements, Boeing guarantees that it will be able to sell specified models of its aircraft and begin to adapt their operations to the models they will be flying in the future. Thus both sides expect to reap benefits from these arrangements for many years.Networks forms of organizations are prevalent in access to the universities and in small, creative organizations. For example, the U.S. biotechnology industry is characterized by network of relationships between new biotechnology firms dedicated to research and new products development and established firms in industries that can use these new products, such as pharmaceuticals. In return for sharing technical information with the larger firms, the smaller firms gain access to their partners’ resources for product testing, marketing, and distribution. Big pharmaceutical firms such as Merk or Eli Lily gain from such partnerships because the smaller firms typically development cycle in the larger firms.Being competitive increasingly requires establishing and managing strategic alliances with other firms. In a strategic alliance, two or more firms agree to cooperate in a venture that is expected to benefit both firms.企业重组整个20世纪90年代中，合并和收购一直是企业重组的主要起源，影响着千百万的工人和他们的家庭。
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。
本科毕业设计外文文献翻译
（Sheaｒ waｌl ｓt ｒuctural desigｎ ofh ｉgh-ｌev ｅl fr ａmeworkＷｕ Jiche ｎgＡbstract ： In t ｈis pape ｒ the basic c ｏｎcepts of ｍａn ｐow ｅr ｆｒom th ｅ ｆra ｍｅ sh ｅａr w ａｌl str ｕc ｔｕｒｅ, analy ｓis of the ｓtruct ｕr ａｌ des ｉgn ｏf th ｅ c ｏnt ｅnt ｏｆ t ｈe fr ａme she ａr wall, in ｃｌudi ｎg the ｓeism ｉc wa ｌl she ａr spa本科毕业设计外文文献翻译学校代码： 10128学 号：题 目：Shear wall structural design of high-level framework 学生姓名： 学 院：土木工程学院 系 别：建筑工程系 专 业：土木工程专业（建筑工程方向） 班 级：土木08-（5）班 指导教师： (副教授)ｎratiｏdesign, ａnd a concrｅtｅｓtruｃtuｒe in thｅmｏst co ｍmonｌy useｄframe shear walｌstｒｕcturｅtｈｅdesign of p ｏiｎｔs to note.Keyworｄs: cｏncrｅｔｅ; fｒaｍｅshｅａｒwall sｔｒucｔｕre；hiｇh－risｅbuildｉｎｇsThe wall is aｍoｄern high－rｉｓe buiｌdiｎgs is an iｍpo ｒｔant buiｌdinｇconｔｅnt, the ｓize of thｅfraｍe sheａr wall must comｐly with buildｉng reguｌａtｉons. The pｒｉnｃipｌe is ｔhat the largeｒsｉzｅbｕt the thｉｃknessｍuｓt ｂｅsmaller gｅoｍetric featｕrｅｓshoｕlｄｂe ｐｒeｓented ｔo the pｌatｅ,ｔｈe forｃe is close to cylｉndrｉcal.Ｔhe waｌl sｈｅar wa ｌl strｕｃｔure ｉs a flaｔcomｐonent. Itｓeｘposure to tｈe force aｌoｎg ｔhe ｐlane leｖｅl of theｒole ofｓｈear and momｅｎt, must also take ｉｎtｏａccounｔthe veｒｔical preｓsure.Opeｒate unｄer thｅcomｂiｎed actｉｏn oｆbenｄing momeｎts and axial force aｎｄsheａr forcｅbｙthe caｎtilｅｖｅr deep beａm uｎder ｔｈe acｔion of the force leveｌｔo lｏo ｋinto ｔｈe bottom mouｎted on ｔhe basｉs of. Sheaｒｗaｌl ｉｓdiｖidｅｄinｔo a whole walｌand ｔheａssoｃiated ｓｈeａr wall in thｅactual project,a wholｅwａlｌfor ｅxａmpl ｅ, suｃh as ｇenｅraｌhｏusiｎｇｃonstｒuction in tｈe gablｅｏr fish bｏne strｕcture ｆｉlｍwａｌls ａnd small opｅningｓwall.Cｏupled Sｈeａr ｗalls are ｃonnｅcted bｙｔhｅcｏupｌing ｂeam shｅａr wall.Buｔｂecause tｈeｇｅnerａlｃｏupling beaｍstｉｆfness is less thaｎｔhe wall stiｆfnｅsｓof the lｉmbs，ｓｏ. Wａlｌliｍb aｌonｅis obviｏus.The ｃｅntral beam of tｈeｉnflｅｃtion pｏｉnｔtｏpay aｔtenｔiｏｎto tｈeｗaｌl pressｕre thａn the limiｔs of the lｉmb axis. Will forｍa shortｗiｄe beａms，widｅcolｕmn wａll liｍｂｓhear wａll ｏpｅnings toｏlarge ｃomｐonｅnt aｔbothｅn ｄs ｗith jｕst the domain of vａｒiabｌe crosｓ－ｓecｔｉon ro ｄin ｔhe intｅrｎａｌforcｅｓｕnder tｈｅaｃtioｎof maｎy Ｗalｌlｉmb iｎflｅcｔion point Ｔhｅｒeｆoｒe, ｔhe cａｌcula ｔions ａｎd consｔruction sｈouldAccordinｇtｏappｒoxiｍａｔe tｈe framｅstｒucｔure to ｃonsideｒ.Tｈe desｉｇｎof ｓhｅａr walls ｓhoulｄbe based on the cｈａractｅrisｔics ｏf ａvａｒｉｅty oｆwall itseｌｆ,ａnd dｉfferｅnｔmeｃhanical ch ａrａcteｒisｔｉcｓand requireｍents,wall oｆthｅinternａｌforceｄistrｉbutｉon and failurｅmoｄｅs ｏf sｐecific and cｏmprehensive ｃonｓideration of the design rｅinｆorcemｅnt aｎd stｒuctural measｕres. Ｆrame sｈear wall ｓｔrｕctuｒe deｓiｇn is to cｏｎsider the ｓtructｕre of the oｖerall ａnａｌysis for ｂoｔh dｉrecｔｉｏｎsｏｆthｅhｏrｉzontal and vｅrtiｃalｅfｆects. Oｂtain thｅinternal force ｉs reｑuirｅd in ａccｏrdancｅｗｉｔｈtｈe bias or paｒtｉal ｐull normal sｅcｔｉon forｃｅｃaｌculatiｏn.The waｌl strｕcture oｆtheｆｒame sｈear ｗall ｓｔructural dｅsign of ｔhe coｎtent frame hｉgh-rise buildings, in ｔhe actual ｐrｏjeｃｔiｎｔhｅuse of thｅｍoｓt seisｍic ｗａlls have suffiｃient quantitｉeｓto meｅt ｔheｌｉmitsｏf the lａyer displacement, the loｃation iｓｒelａtiｖely flexiblｅ. Seiｓmic wａll for cｏntinuous layout，ｆulｌ-length ｔhroｕgh．Should bｅdesigned to avoid the waｌl mutaｔioｎs ｉn limb ｌｅｎgth and alignment is noｔuｐａnd down the ｈolｅ. The samｅtｉme．Tｈe inｓide of ｔhe hole marginｓcｏlｕｍｎshｏｕld not ｂｅｌｅssｔhan３00mm ｉｎordｅｒtｏguaraｎteｅtheｌengtｈof the colｕｍn ａs the edgｅof tｈe coｍponent and constｒａiｎt eｄgｅcｏｍponeｎts．Thｅbi-direc ｔiｏnal laｔerａl forｃe ｒesiｓting strucｔurａl fｏrm of verticａl aｎｄhorｉzontaｌwalｌcoｎnected.Eａｃh ｏｔhｅr as ｔhe ａffiｎiｔｙof the shｅar wall. Ｆor ｏnｅ, two seismic frａme sｈe ａr ｗalｌｓ,ｅｖen beam highｒatio ｓhould noｔgreateｒthan 5 aｎd a height of nｏt less thaｎ400mm.Midline colｕmnａnd beａmｓ,wall ｍｉdline shouｌdｎoｔbe greaｔer tha ｎthe ｃoｌｕmｎwidｔｈof1/4，ｉn ordｅr ｔｏreｄuce thｅtoｒsional eｆfect of the sｅiｓmｉｃacｔion ｏnｔｈｅｃolｕmn．Oｔhｅrwｉsｅcan be taken tｏstrengthｅn theｓtirruprａｔｉo iｎｔhe cｏlｕmn tｏmake ｕp.If thｅshear wａｌl sheａｒsｐａn ｔhａnｔhe ｂig twｏ. Ｅveｎthe beａｍcro ｓs-heｉｇht ratiｏgreateｒthan 2.5, ｔhen tｈe design presｓｕｒe ｏf thｅｃｕt shoulｄnoｔmａkｅａｂig 0.2. Howevｅｒ, ｉf the sheａｒwallｓheａr sｐａｎｒatiｏof ｌess than two couｐlinｇｂeａms sｐan of ｌeｓs than ２．5, then the shear coｍｐres ｓiｏn rａｔiｏis noｔgreaｔer thａn 0.15. Thｅｏther haｎｄ，ｔhe bｏttom oｆthe fraｍe ｓhｅar walｌstructure ｔo enhａnce tｈｅdｅsign sｈould ｎoｔbe leｓs thaｎ２０0mmａnd noｔlesｓthaｎstorey 1/１6，othｅｒｐaｒtｓｓhｏulｄnot be lｅss than 160mm ａnd ｎｏt ｌｅss thaｎｓtoｒey １/20. Arounｄthe wall of the frame ｓhｅar ｗall strucｔure sｈｏulｄbe set ｔo the beａm or dark bｅamａnd the sｉｄe columｎｔｏform a borｄｅr. Ｈoｒizｏntａl ｄｉｓtrｉbuｔioｎoｆsｈear waｌls cａn from the sheａr effect，tｈｉs design wｈen ｂuilｄｉng higｈｅr longeｒor fｒaｍｅｓtructｕre reinfoｒcｅment shｏuld be aｐprｏpｒiatelｙincｒeａｓed, ｅspｅcｉａlｌy in the sｅnｓitivｅｐarts of the beam pｏsition ｏr teｍperaｔuｒe, stiffnｅsｓchａnge is besｔappｒopriatｅly increased, ｔｈeｎcｏnsidｅration sｈoulｄbe ｇｉveｎｔo the wａlｌvertｉcaｌreiｎforｃemeｎt,becaｕse ｉt is mａinly fｒom the bｅnding efｆecｔ, aｎｄtake in ｓome ｍｕlti-ｓtorｅｙshｅａｒｗａll structuｒereinforcｅｄreｉnｆorceｍent rate -likｅlｅsｓconｓtｒained edgｅｏｆｔhｅcomｐonent or components reinforｃemeｎt of thｅedge ｃomｐｏnent.Referｅnces: [1 sad Hａyaｓhi,He Yaming. Ｏn the shorｔshｅar ｗall ｈigh-riｓe bｕilｄinｇｄesign ［J]．Kｅｙｕaｎ, 2008, (O2).高层框架剪力墙结构设计吴继成摘要: 本文从框架剪力墙结构设计的基本概念人手, 分析了框架剪力墙的构造设计内容, 包括抗震墙、剪跨比等的设计, 并出混凝土结构中最常用的框架剪力墙结构设计的注意要点。
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。
(完整版)本科_毕业设计(论文)外文翻译_格式
本科毕业设计（论文）外文翻译译文
学生姓名：李浩
院（系）：机械工程学院
专业班级：装备1001
指导教师：李晓红
完成日期： 2014 年 3 月 10日
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毕业设计外文文献翻译【范本模板】
毕业设计（论文)外文资料翻译系别：专业：班级:姓名：学号:外文出处:附件： 1. 原文; 2。
译文2013年03月附件一：A Rapidly Deployable Manipulator SystemChristiaan J。
J。
Paredis, H. Benjamin Brown，Pradeep K. KhoslaAbstract:A rapidly deployable manipulator system combines the flexibility of reconfigurable modular hardware with modular programming tools，allowing the user to rapidly create a manipulator which is custom-tailored for a given task. This article describes two main aspects of such a system，namely，the Reconfigurable Modular Manipulator System （RMMS)hardware and the corresponding control software。
1 IntroductionRobot manipulators can be easily reprogrammed to perform different tasks, yet the range of tasks that can be performed by a manipulator is limited by mechanicalstructure。
Forexample，a manipulator well-suited for precise movement across the top of a table would probably no be capable of lifting heavy objects in the vertical direction. Therefore，to perform a given task,one needs to choose a manipulator with an appropriate mechanical structure.We propose the concept of a rapidly deployable manipulator system to address the above mentioned shortcomings of fixed configuration manipulators。
(完整版)_毕业设计(论文) 外文文献翻译_
毕业设计（论文）外文文献翻译题目：金融银行信用风险管理与知识管理教学院：经济与管理学院专业名称：工商管理学号：学生姓名：谭勤辉指导教师：刘显铭2013 年05 月28 日Managing Credit Risks with Knowledge ManagementforFinancial BanksPan JinDepartment of EconomicsEconomics and Management School of Wuhan UniversityWuhan,Hubei ProvinceChinaAbstract-Nowadays,financial banks are operating in a knowledge society and there are more and more credit risks breaking out in banks.So,this paper first discusses the implications of knowledge and knowledge management, and then analyzes credit risks of financial banks with knowledge management. Finally, the paper studies ways for banks to manage credit risks with knowledge management. With the application of knowledge management in financial banks, customers will acquire better service and banks will acquire more rewards.Index Terms–knowledge management; credit risk; risk management; incentive mechanism; financial banksI.INTRODUCTIONNowadays,banks are operating in a“knowledge society”.So, what is knowledge? Davenport(1996)[1]thinks knowledge is professional intellect,such as know-what, know- be shared and communicated. The awareness of the importance of knowledge results in the critical issue of “knowledge management”.So, what is knowledge management? According to Malhothra(2001)[2], knowledge management(KM)caters to the critical issues of organizational adaptation, survival and competence in face of increasingly discontinuous environmental change. Essentially it embodies organizational processes that seek synergistic combination of data and information processing capacity of information technologies and the creative and innovative capacity of beings. Through the processes of creating,sustaining, applying, sharing and renewing knowledge, we can enhance organizational performance and create value.Many dissertations some special fields. Aybübe Aurum(2004)[3] analyzes knowledge management in software engineering and D.J.Harvey ＆R.Holdsworth(2005)[4]study knowledge management in the aerospace industry. Li Yang(2007)[5] studies knowledge management in information-based education and Jayasundara＆Chaminda Chiran(2008)[6] review the prevailing literature on knowledge management in banking industries. Liang ping and Wu Kebao(2010)[7]study the incentive mechanism of knowledge management inBanking.There are also many papers about risks analysis and risks management. Before the 1980s, the dominant mathematical theory of risks analysis was to describe a pair of random vectors.But,the simplificationassumptions and methods used by classical competing risks analysis caused controversy and criticism.Starting around the 1980s, an alternative formulation of risk analysis was developed,with the identifiability. The new formulation is univariate risk analysis.According to Crowder(2001)[8], David＆Moeschberger(1978)[9]and Hougaard(2000)[10],univariate survival risk analysis dominantly, which is based on the i.i.d assumptions(independent and identically distributed) or, at least, based on the independent failure assumption.Distribution-free regression modeling allows one to investigate the influences of multiple covariates on the failure, and it relaxes the assumption of identical failure distribution and to some extent, it also relaxes the single failure risk restriction. However, the independent failures as well as single failure events are still assumed in the univariate survival analysis. Of course,these deficiencies do not invalidate univariate analysis, and indeed, in many applications, those assumptions are realistically valid.Based on the above mentioned studies, Ma and Krings(2008a, 2008b)[11]discuss the relationship and difference of univariate and multivariate analysis in calculating risks.As for the papers on managing the risks in banks, Lawrence J.White(2008)[12]studies the risks of financial innovations and takes out some countermeasures to regulate financial innovations. Shao Baiquan(2010)[13]studies the ways to manage the risks in banks.From the above papers, we can see that few scholars Ⅰis introduction. SectionⅡanalyzes credit risks in banks with knowledge management. SectionⅢstudies ways for banks to manage credit risks with knowledgemanagement. SectionⅣconcludes.II.ANALYZING CREDIT RISKS IN BANKS WITHKNOWLEDGE MANAGEMENTA.Implication of Credit RiskCredit risk is the risk of loss due to a debtor’s non-payment of a loan or other line of credit, which may be the principal or interest or both.Because there are many types of loans and counterparties-from individuals to sovereign governments-and many different types of obligations-from auto loans to derivatives transactions-credit risk may take many forms.Credit risk is common in our daily life and we can not cover it completely,for example,the American subprime lending crisis is caused by credit risk,which is that the poor lenders do not pay principal and interest back to the banks and the banks do not pay the investors who buy the securities based on the loans.From the example,we can find that there are still credit risks,though banks banks includes tacit knowledge and explicit knowledge,which is scattered in different fields.For example, the information about the customers’income, asset and credit is controlled by different departments and different staffs and the information can’t be communicated with others. So it is necessary for banks to set up a whole system to communicate and share the information and knowledge to manage the risks.C.Setting up Incentive Mechanism and Encouraging Knowledge InnovationThe warning mechanism of credit risks depends on the incentive mechanism in banks,so, banks should take out incentive mechanism to urge staffs to learn more knowledge and work creatively to manage credit risks.We can show the incentive mechanism as Fig.1:Fig.1 The model of incentive mechanism with knowledge management From Fig.1,we can see there are both stimulative and punitive measures in the incentive model of knowledge management for financial banks.With the incentive mechanism of knowledge management in financial banks,the staffs will work managing credit risks with knowledge management.We can show them in Fig.2:Fig.2 The blocks of managing credit risksA.Distinguishing Credit RiskDistinguishing credit risks is the basis of risk management.If we can’t recognize the risks,we are unable to find appropriate solutions to manage risks.For example,the United States subprime crisis in 2007 was partly caused by that the financial institutions and regulators didn’t recognize the mortgage securitization risks timely.With knowledge management,we can make out some rules to distinguish credit risks,which are establishing one personal credit rating system for customers and setting up the data warehouse.We can use the system to analyze customers’credit index, customers’credit the changes of customers’property and income to recognize potential risks.B.Assessing and Calculating Credit RiskAfter distinguishing the credit risks,we should assess the riskexposure,risk factors and potential losses and risks, and we should make out the clear links.The knowledgeable staffs in banking should use statistical methods and model and the regulators should establish credit assessment system and then set up one national credit assessment system.With the system and the model of risk assessment,the managers can evaluate the existing and emerging risk factors,such as they prepare credit ratings for internal use.Other firms,including Standard ＆Poor’s,Moody’s and Fitch,are in the business of developing credit rating for use by investors or other third parties.TableⅠshows the credit ratings of Standard＆Poor’s.TABLE ISTANDARD＆POOR’S CREDITT RATINGSCredit ratings ImplicationsAAA Best credit quality,extremely reliableAA Very good credit quality,very reliableA More susceptible to economic conditionsBBB Lowest rating in investment gradeBB Caution is necessaryB Vulnerable to changes in economicCCC Currently vulnerable to nonpaymentCC Highly vulnerable to payment defaultC Close to bankruptD Payment default has actually occurredAfter assessing credit risks,we can use Standardized Approach andInternal Rating-Based Approach to calculate the risks.And in this article,we will analyze uncovered loan.To calculate credit risk of an uncovered loan,firstly,we will acquire the bo rrower’s Probability of Default(PD),Loss Given Default(LGD),Exposure at Default(EAD)and Remaining Maturity(M).Secondly,we calculate the simple risk(SR)of the uncovered loan,using the formula as following: SR=Min{BSR(PD)*[1+b(PD)*(M-3)]*LGD50,LGD*12.5} (1)Where BSR is the basic risk weight and b(PD)is the adjusting factor for remaining maturity(M).Finally,we can calculate the weighted risk(WR)of the uncovered loan,using the following formula:WR=SR*EAD (2)From(1)and(2),we can acquire the simple and weighted credit risk of an uncovered loan,and then we can take some measures to ’t repay the loans,banks can get the compensation from the insurance company.(3)Loans Securitization. Banks can change the loans into security portfolio,according to the different interest rate and term of the loans,and then banks can sell the security portfolio to the special organizations or trust companies.D.Managing Credit Risk and Feeding backA customer may acquire the customer’s credit information,credit the data the banks get.By assessing and calculating the risks of the customer,banks can expect the future behavior of the customers and provides different service for different customers. Banks can provide morevalue-added service to the customers who remedial after the risks broke out.In order to set up the warning and feeding back mechanism,banks should score credit of the customers comprehensively and then test the effectiveness and suitability of the measures,which banks use to mitigate risks.Finally, banks should update the data of the customers timely and keep the credit risk management system operating smoothly.IV.CONCLUSIONIn this paper,we first discuss the implications of knowledge and knowledge management.Then we analyze the credit risks of financial banks with knowledge management. Finally,we put forward ways for banks to manage credit risks with knowledge management.We think banks should set up data warehouse of customers’credit to assess and calculate the credit risks,and at the same time,banks should train knowledgeable staffs to construct a whole system to reduce risks and feed back.With knowledge management,banks can take out systemic measures to manage customers’credit risks and gain sustainable profits.ACKNOWLEDGMENTIt is financed by the of China(NO.06JC790032).REFERENCES[1]Davenport,T.H.et al,“Improving knowledge work processes,”Sloan Management Review,MIT,USA,1996,Vol.38,pp.53-65.[2]Malhothra,“Knowledge management for the new world of business,”New York BRINT Institute,2001, software engineering education,”Proceedings of the IEEE International Conference onAdvanced Learning Technologies,2004,pp..[4]D.J.Harvey＆R.Holdsworth,“Knowledge management in the aerospace industry,”Proceedings of the IEEE International Professional Communication Conference,2005,pp..[5]Li Yang,“Thinking about knowledge management applications in information-based education,”IEEE International Conference on Advanced Learning Technologies,2007,pp.27-33.[6]Jayasundara＆Chaminda Chiran,“Knowledge managemen t in banking industries:uses and opportunities,”Journal of the University Librarians Association of Sri Lanka,2008,Vol.12,pp.68-84.[7]Liang Ping,Wu Kebao,“Knowledge management in banking,”The Conference on Engineering and Business Management,2010, pp..[8]Crowder,M.J.Classical Competing Risks,British:Chapman&Hall, 2001,pp.200.[9]David,H.A.&M.L.Moeschberger,The Theory of Competing Risks, Scotland,Macmillan Publishing,1978,pp.103.金融银行信用风险管理与知识管理摘要：目前，金融银行经营在一个知识型社会中，而且越来越多的信用风险在在银行中爆发。
_毕业设计外文文献及翻译_
_毕业设计外文文献及翻译_Graduation Thesis Foreign Literature Review and Chinese Translation1. Title: "The Impact of Artificial Intelligence on Society"Abstract:人工智能对社会的影响摘要：人工智能技术的快速发展引发了关于其对社会影响的讨论。
本文探讨了人工智能正在重塑不同行业（包括医疗保健、交通运输和教育）的各种方式。
还讨论了AI实施的潜在益处和挑战，以及伦理考量。
总体而言，本文旨在提供对人工智能对社会影响的全面概述。
2. Title: "The Future of Work: Automation and Job Displacement"Abstract:With the rise of automation technologies, there is growing concern about the potential displacement of workers in various industries. This paper examines the trends in automation and its impact on jobs, as well as the implications for workforce development and retraining programs. The ethical and social implications of automation are also discussed, along with potential strategies for mitigating job displacement effects.工作的未来：自动化和失业摘要：随着自动化技术的兴起，人们越来越担心各行业工人可能被替代的问题。
本科毕业设计(论文)外文翻译
附5
本科毕业设计（论文）外文翻译
，TFT θ末端之间的温差。
min TFT ter θθ=的取得的方法是，测量末端温度利用附加的铬镍3. 设备制造
TFT 传感器用于测量切削温度必须遵循以下要求：（1）保护传感器的硬质涂层和下面接触层之间具有足够的附和力，以在加工过程中表现良好的耐磨性和耐久度。
在尺寸和质量上都足够的小，以便实现高灵敏度；同时（3）传感器的构造和安装不会影
的一些制造过程。
TFT的基片是一层氧化铝的嵌入工具，这层嵌入已经被研磨至表面粗糙度Ra至少0.2mm，所以完全的清洁并且脱脂。
第一步，利用直流磁控溅镀将一层
厚的Ni被放置在到面的右半侧和一部分重叠位置，就是热接点产生的地方。
这个过程一直重复到的Ni-Cr（80:20质量%）目标在刀具左半部分表面和重叠位置。
秒。
超过固相线温度加热时间点是只有一小部分时间T e，因此它是太短造成相变。
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11。
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。
(完整版)_毕业设计(论文)外文翻译_(原文)
毕业设计（论文）——外文翻译（原文）NEW APPLICATION OF DATABASERelational databases in use for over two decades. A large portion of the applications of relational databases in the commercial world, supporting such tasks as transaction processing for banks and stock exchanges, sales and reservations for a variety of businesses, and inventory and payroll for almost of all companies. We study several new applications, which recent years.First. Decision-support systemAs the online availability of data , businesses to exploit the available data to make better decisions about increase sales. We can extract much information for decision support by using simple SQL queries. Recently support based on data analysis and data mining, or knowledge discovery, using data from a variety of sources.Database applications can be broadly classified into transaction processing and decision support. Transaction-processing systems are widely used today, and companies generated by these systems.The term data mining refers loosely to finding relevant information, or “discovering knowledge,” from a large volume of data. Like knowledge discovery in artificial intelligence, data mining attempts to discover statistical rules and patterns automatically from data. However, data mining differs from machine learning in that it deals with large volumes of data, stored primarily on disk.Knowledge discovered from a database can be represented by a set of rules. We can discover rules from database using one of two models:In the first model, the user is involved directly in the process of knowledge discovery.In the second model, the system is responsible for automatically discovering knowledgefrom the database, by detecting patterns and correlations in the data.Work on automatic discovery of rules influenced strongly by work in the artificial-intelligence community on machine learning. The main differences lie in the volume of data databases, and in the need to access disk. Specialized data-mining algorithms developed to which rules are discovered depends on the class of data-mining application. We illustrate rule discovery using two application classes: classification and associations.Second. Spatial and Geographic DatabasesSpatial databases store information related to spatial locations, and provide support for efficient querying and indexing based on spatial locations. Two types of spatial databases are particularly important:Design databases, or computer-aided-design (CAD) databases, are spatial databases used to store design information about databases are integrated-circuit and electronic-device layouts.Geographic databases are spatial databases used to store geographic information, such as maps. Geographic databases are often called geographic information systems.Geographic data are spatial in nature, but differ from design data in certain ways. Maps and satellite images are typical examples of geographic data. Maps may provide not only location information -such as boundaries, rivers and roads---but also much more detailed information associated with locations, such as elevation, soil type, land usage, and annual rainfall.Geographic data can be categorized into two types: raster data (such data consist a bit maps or pixel maps, in two or more dimensions.), vector data (vector data are constructed from basic geographic objects). Map data are often represented in vector format.Third. Multimedia DatabasesRecently, there much interest in databases that store multimedia data, such as images, audio, and video. Today multimedia data typically are stored outside the database, in files systems. When the number of multimedia objects is relatively small, features provided by databases are usually not important. Database functionality becomes important when the number of multimedia objects stored is large. Issues such as transactional updates, querying facilities, and indexing then become important. Multimedia objects often they were created, who created them, and to what category they belong. One approach to building a database for such multimedia objects is to use database for storing the descriptive attributes, and for keeping track of the files in which the multimedia objects are stored.However, storing multimedia outside the database makes it the basis of actual multimedia data content. It can also lead to inconsistencies, such a file that is noted in the database, but whose contents are missing, or vice versa. It is therefore desirable to store the data themselves in the database.Forth. Mobility and Personal DatabasesLarge-scale commercial databases stored in central computing facilities. In the case of distributed database applications, there strong central database and network administration. Two technology trends which this assumption of central control and administration is not entirely correct:1.The increasingly widespread use of personal computers, and, more important, of laptop or “notebook” computers.2.The development of a relatively low-cost wireless digital communication infrastructure, base on wireless local-area networks, cellular digital packet networks, and other technologies.Wireless computing creates a situation where machines no longer at which to materialize the result of a query. In some cases, the location of the user is a parameter of the query. A example is a traveler’s information system that provides data on the current route must be processed based on knowledge of the user’s location, direction of motion, and speed.Energy (battery power) is a scarce resource for mobile computers. This limitation influences many aspects of system design. Among the more interesting consequences of the need for energy efficiency is the use of scheduled data broadcasts to reduce the need for mobile system to transmit queries. Increasingly amounts of data may reside on machines administered by users, rather than by database administrators. Furthermore, these machines may, at times, be disconnected from the network.SummaryDecision-support systems are gaining importance, as companies realize the value of the on-line data collected by their on-line transaction-processing systems. Proposed extensions to SQL, such as the cube operation, of summary data. Data mining seeks to discover knowledge automatically, in the form of statistical rules and patterns from large databases. Data visualization systems data as well as geographic data. Design data are stored primarily as vector data; geographic data consist of a combination of vector and raster data.Multimedia databases are growing in importance. Issues such as similarity-based retrieval and delivery of data at guaranteed rates are topics of current research.Mobile computing systems , leading to interest in database systems that can run on such systems. Query processing in such systems may involve lookups on server database.毕业设计（论文）——外文翻译（译文）数据库的新应用我们使用关系数据库已经有20多年了，关系数据库应用中有很大一部分都用于商业领域支持诸如银行和证券交易所的事务处理、各种业务的销售和预约，以及几乎所有公司都需要的财产目录和工资单管理。
毕业设计外文原文加译文
Basic Concepts PrimerTOPIC P.1: Bridge MechanicsBasic Equations of Bridge Mechanicswhere: A =area; cross-sectional areaA w = areaof web c = distance from neutral axisto extreme fiber (or surface) of beamE = modulus of elasticityF = force; axial force f a= axial stress f b= bending stress f v = shear stress I = moment of inertia L = original length M = applied moment S = stressV = vertical shear force due toexternal loadsD L = change in length e = strainBasic Concepts Primer Topic P.1 Bridge MechanicsP.1.1Introduction Mechanics is the branch of physical science that deals with energy and forces andtheir relation to the equilibrium, deformation, or motion of bodies. The bridgeinspector will primarily be concerned with statics, or the branch of mechanicsdealing with solid bodies at rest and with forces in equilibrium.The two most important reasons for a bridge inspector to study bridge mechanicsare:Ø To understand how bridge members functionØ To recognize the impact a defect may have on the load-carrying capacityof a bridge component or elementWhile this section presents the basic principles of bridge mechanics, the referenceslisted in the bibliography should be referred to for a more complete presentation ofthis subject.P.1.2Bridge Design Loadings Bridge design loadings are loads that a bridge is designed to carry or resist and which determine the size and configuration of its members. Bridge members are designed to withstand the loads acting on them in a safe and economical manner. Loads may be concentrated or distributed depending on the way in which they are applied to the structure.A concentrated load, or point load, is applied at a single location or over a very small area. Vehicle loads are considered concentrated loads.A distributed load is applied to all or part of the member, and the amount of load per unit of length is generally constant. The weight of superstructures, bridge decks, wearing surfaces, and bridge parapets produce distributed loads. Secondary loads, such as wind, stream flow, earth cover and ice, are also usually distributed loads.Highway bridge design loads are established by the American Association of State Highway and Transportation Officials (AASHTO). For many decades, the primary bridge design code in the United States was the AASHTO Standard Specifications for Highway Bridges (Specifications), as supplemented by agency criteria as applicable.During the 1990’s AASHTO developed and approved a new bridge design code, entitled AASHTO LRFD Bridge Design Specifications. It is based upon the principles of Load and Resistance Factor Design (LRFD), as described in Topic P.1.7.P.1.1SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.2Bridge design loadings can be divided into three principal categories:Ø Dead loadsØ Primary live loads Ø Secondary loadsDead LoadsDead loads do not change as a function of time and are considered full-time, permanent loads acting on the structure. They consist of the weight of the materials used to build the bridge (see Figure P.1.1). Dead load includes both the self-weight of structural members and other permanent external loads. They can be broken down into two groups, initial and superimposed.Initial dead loads are loads which are applied before the concrete deck is hardened, including the beam itself and the concrete deck. Initial deck loads must be resisted by the non-composite action of the beam alone. Superimposed dead loads are loads which are applied after the concrete deck has hardened (on a composite bridge), including parapets and any anticipated future deck pavement. Superimposed dead loads are resisted by the beam and the concrete deck acting compositely. Non-composite and composite action are described in Topic P.1.10.Dead load includes both the self-weight of the structural members and other permanent external loads.Example of self-weight: A 6.1 m (20-foot) long beam weighs 0.73 kN per m (50 pounds per linear foot). The total weight of the beam is 4.45 kN (1000 pounds). This weight is called the self-weight of the beam.Example of an external dead load: If a utility such as a water line is permanently attached to the beam in the previous example, then the weight of the water line is an external dead load. The weight of the water line plus the self weight of the beam comprises the total dead load.Total dead load on a structure may change during the life of the bridge due to additions such as deck overlays, parapets, utility lines, and inspection catwalks.Figure P.1.1 Dead Load on a BridgePrimary Live LoadsLive loads are considered part-time or temporary loads, mostly of short-term duration, acting on the structure. In bridge applications, the primary live loads are moving vehicular loads (see Figure P.1.2).To account for the affects of speed, vibration, and momentum, highway live loads are typically increased for impact. Impact is expressed as a fraction of the liveSECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.3load, and its value is a function of the span length.Standard vehicle live loads have been established by AASHTO for use in bridge design and rating. It is important to note that these standard vehicles do not represent actual vehicles. Rather, they were developed to allow a relatively simple method of analysis based on an approximation of the actual live load.Figure P.1.2 Vehicle Live Load on a BridgeAASHTO Truck LoadingsThere are two basic types of standard truck loadings described in the current AASHTO Specifications . The first type is a single unit vehicle with two axles spaced at 14 feet (4.3 m) and designated as a highway truck or "H" truck (see Figure P.1.3). The weight of the front axle is 20% of the gross vehicle weight, while the weight of the rear axle is 80% of the gross vehicle weight. The "H" designation is followed by the gross tonnage of the particular design vehicle.Example of an H truck loading: H20-35 indicates a 20 ton vehicle with a front axle weighing 4 tons, a rear axle weighing 16 tons, and the two axles spaced 14 feet apart. This standard truck loading was first published in 1935.The second type of standard truck loading is a two unit, three axle vehicle comprised of a highway tractor with a semi-trailer. It is designated as a highway semi-trailer truck or "HS" truck (see Figure P.1.4).The tractor weight and wheel spacing is identical to the H truck loading. The semi-trailer axle weight is equal to the weight of the rear tractor axle, and its spacing from the rear tractor axle can vary from 4.3 to 9.1 m (14 to 30 feet). The "HS" designation is followed by a number indicating the gross weight in tons of the tractor only.SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.414’-0”(4.3 m)8,000 lbs (35 kN) 32,000 lbs (145 kN)(3.0 m)10’-0”CLEARANCE AND LOAD LANE WIDTH6’-0” (1.8 m)2’-0” (0.6 m)Figure P.1.3 AASHTO H20 Truck14’-0”(4.3 m)8,000 lbs (35 kN) 32,000 lbs (145 kN)(3.0 m)10’-0”CLEARANCE AND LOAD LANE WIDTH6’-0”(1.8 m)2’-0” (0.6 m)32,000 lbs (145 kN)VFigure P.1.4 AASHTO HS20 TruckExample of an HS truck loading: HS20-44 indicates a vehicle with a front tractor axle weighing 4 tons, a rear tractor axle weighing 16 tons, and a semi-trailer axle weighing 16 tons. The tractor portion alone weighs 20 tons, but the gross vehicle weight is 36 tons. This standard truck loading was first published in 1944.In specifications prior to 1944, a standard loading of H15 was used. In 1944, theSECTION P: Basic Concepts Primer Topic P.1: Bridge MechanicsP.1.5H20-44 Loading HS20-44 Loadingpolicy of affixing the publication year of design loadings was adopted. In specifications prior to 1965, the HS20-44 loading was designated as H20-S16-44, with the S16 identifying the gross axle weight of the semi-trailer in tons.The H and HS vehicles do not represent actual vehicles, but can be considered as "umbrella" loads. The wheel spacings, weight distributions, and clearance of the Standard Design Vehicles were developed to give a simpler method of analysis, based on a good approximation of actual live loads.The H and HS vehicle loads are the most common loadings for design, analysis, and rating, but other loading types are used in special cases.AASHTO Lane LoadingsIn addition to the standard truck loadings, a system of equivalent lane loadings was developed in order to provide a simple method of calculating bridge response to a series, or “train”, of trucks. Lane loading consists of a uniform load per linear foot of traffic lane combined with a concentrated load located on the span to produce the most critical situation (see Figure P.1.5).For design and load capacity rating analysis, an investigation of both a truck loading and a lane loading must be made to determine which produces the greatest stress for each particular member. Lane loading will generally govern over truck loading for longer spans. Both the H and HS loadings have corresponding lane loads.* Use two concentrated loads for negative moment in continuous spans (Refer to AASHTO Page 23)Figure P.1.5 AASHTO Lane Loadings.Alternate Military LoadingThe Alternate Military Loading is a single unit vehicle with two axles spaced at 1.2 m (4 feet) and weighing 110 kN (12 tons)each. It has been part of the AASHTO Specifications since 1977. Bridges on interstate highways or other highways which are potential defense routes are designed for either an HS20 loading or an Alternate Military Loading (see Figure P.1.6).SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.6110 kN (24 k)110 kN (24 k)Figure P.1.6 Alternate Military LoadingLRFD Live LoadsThe AASHTO LRFD design vehicular live load, designated HL-93, is a modified version of the HS-20 highway loadings from the AASHTO StandardSpecifications. Under HS-20 loading as described earlier, the truck or lane load is applied to each loaded lane. Under HL-93 loading, the design truck or tandem, in combination with the lane load, is applied to each loaded lane.The LRFD design truck is exactly the same as the AASHTO HS-20 design truck. The LRFD design tandem, on the other hand, consists of a pair of 110 kN axials spread at 1.2 m (25 kip axles spaced 4 feet) apart. The transverse wheel spacing of all of the trucks is 6 feet.The magnitude of the HL-93 lane load is equal to that of the HS-20 lane load. The lane load is 9 kN per meter (0.64 kips per linear foot) longitudinally and it is distributed uniformly over a 3 m (10 foot) width in the transverse direction. The difference between the HL-93 lane load and the HS-20 lane load is that the HL-93 lane load does not include a point load.Finally, for LRFD live loading, the dynamic load allowance, or impact, is applied to the design truck or tandem but is not applied to the design lane load. It is typically 33 percent of the design vehicle.Permit VehiclesPermit vehicles are overweight vehicles which, in order to travel a state’s highways, must apply for a permit from that state. They are usually heavy trucks (e.g., combination trucks, construction vehicles,or cranes) that have varying axle spacings depending upon the design of the individual truck. To ensure that these vehicles can safely operate on existing highways and bridges, most states require that bridges be designed for a permit vehicle or that the bridge be checked to determine if it can carry a specific type of vehicle. For safe and legal operation, agencies issue permits upon request that identify the required gross weight, number of axles, axle spacing, and maximum axle weights for a designated route (see Figure P.1.7).SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.7Figure P.1.7 910 kN (204 kip) Permit Vehicle (for Pennsylvania)Secondary LoadsIn addition to dead loads and primary live loads, bridge components are designed to resist secondary loads, which include the following:Ø Earth pressure - a horizontal force acting on earth-retaining substructureunits, such as abutments and retaining wallsØ Buoyancy -the force created due to the tendency of an object to rise whensubmerged in waterØ Wind load on structure - wind pressure on the exposed area of a bridge Ø Wind load on live load -wind effects transferred through the live loadvehicles crossing the bridgeØ Longitudinal force -a force in the direction of the bridge caused bybraking and accelerating of live load vehiclesØ Centrifugal force -an outward force that a live load vehicle exerts on acurved bridgeØ Rib shortening -a force in arches and frames created by a change in thegeometrical configuration due to dead loadØ Shrinkage - applied primarily to concrete structures, this is a multi-directional force due to dimensional changes resulting from the curing processØ Temperature -since materials expand as temperature increases andcontract as temperature decreases, the force caused by these dimensional changes must be consideredØ Earthquake -bridge structures must be built so that motion during anearthquake will not cause a collapseØ Stream flow pressure -a horizontal force acting on bridge componentsconstructed in flowing waterØ Ice pressure - a horizontal force created by static or floating ice jammedagainst bridge componentsØ Impact loading - the dynamic effect of suddenly receiving a live load;this additional force can be up to 30% of the applied primary live load forceØ Sidewalk loading - sidewalk floors and their immediate supports aredesigned for a pedestrian live load not exceeding 4.1 kN per square meter (85 pounds per square foot)Ø Curb loading -curbs are designed to resist a lateral force of not less than7.3 kN per linear meter (500 pounds per linear foot)Ø Railing loading -railings are provided along the edges of structures forprotection of traffic and pedestrians; the maximum transverse load appliedto any one element need not exceed 44.5 kN (10 kips)SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.8A bridge may be subjected to several of these loads simultaneously. The AASHTO Specifications have established a table of loading groups. For each group, a set of loads is considered with a coefficient to be applied for each particular load. The coefficients used were developed based on the probability of various loads acting simultaneously.P.1.3Material Response to LoadingsEach member of a bridge has a unique purpose and function, which directly affects the selection of material, shape, and size for that member. Certain terms are used to describe the response of a bridge material to loads. A working knowledge of these terms is essential for the bridge inspector.ForceA force is the action that one body exerts on another body. Force has two components: magnitude and direction (see Figure P.1.8). The basic English unit of force is called pound (abbreviated as lb.). The basic metric unit of force is called Newton (N). A common unit of force used among engineers is a kip (K), which is 1000 pounds. In the metric system, the kilonewton (kN), which is 1000 Newtons, is used. Note: 1 kip = 4.4 kilonewton.FyFigure P.1.8 Basic Force ComponentsStressStress is a basic unit of measure used to denote the intensity of an internal force. When a force is applied to a material, an internal stress is developed. Stress is defined as a force per unit of cross-sectional area.The basic English unit of stress is pounds per square inch (abbreviated as psi). However, stress can also be expressed in kips per square inch (ksi) or in any other units of force per unit area. The basic metric unit of stress is Newton per square meter, or Pascal (Pa). An allowable unit stress is generally established for a given material. Note: 1 ksi = 6.9 Pa.)A (Area )F (Force )S (Stress =毕业设计外文译文桥梁力学基本概论《美国桥梁检测手册》译文：桥梁结构的基础方程S=F/A(见1.8节)fa=P/A(见1.14节)ε=△L/L(见1.9节)fb=Mc/I(见1.16节)E=S/ε(见1.11节)fv=V/Aw（见1.18节）桥梁额定承载率=（允许荷载–固定荷载）*车辆总重量/车辆活荷载冲击力式中：A=面积；横截面面积Aw=腹板面积c=中性轴与横梁边缘纤维或外表面之间的距离E=弹性模量F=轴心力；轴向力fa=轴向应力fb=弯曲应力fv=剪切应力I=惯性距L=原长M=作用力距S=应力V=由外荷载引起的垂直剪应力△L=长度变量ε=应变1桥梁主要的基本概论第一章桥梁力学1.1引言结构力学是研究物体的能量、力、能量和力的平衡关系、变形及运动的物理科学的分支。
本科毕业设计外文文献及译文1
本科毕业设计外文文献及译文文献、资料题目：Transit Route Network Design Problem:Review文献、资料来源：网络文献、资料发表（出版）日期：2007.1院（部）：xxx专业：xxx班级：xxx姓名：xxx学号：xxx指导教师：xxx翻译日期：xxx外文文献：Transit Route Network Design Problem:Review Abstract:Efficient design of public transportation networks has attracted much interest in the transport literature and practice,with manymodels and approaches for formulating the associated transit route network design problem _TRNDP_having been developed.The presentpaper systematically presents and reviews research on the TRNDP based on the three distinctive parts of the TRNDP setup:designobjectives,operating environment parameters and solution approach.IntroductionPublic transportation is largely considered as a viable option for sustainable transportation in urban areas,offering advantages such as mobility enhancement,traffic congestion and air pollution reduction,and energy conservation while still preserving social equity considerations. Nevertheless,in the past decades,factors such as socioeconomic growth,the need for personalized mobility,the increase in private vehicle ownership and urban sprawl have led to a shift towards private vehicles and a decrease in public transportation’s share in daily commuting (Sinha2003;TRB2001;EMTA2004;ECMT2002;Pucher et al.2007).Efforts for encouraging public transportation use focuses on improving provided services such as line capacity,service frequency,coverage,reliability,comfort and service quality which are among the most important parameters for an efficient public transportation system(Sinha2003;Vuchic2004.) In this context,planning and designing a cost and service efficientpublic transportation network is necessary for improving its competitiveness and market share. The problem that formally describes the design of such a public transportation network is referred to as the transit route network design problem(TRNDP);it focuses on the optimization of a number of objectives representing the efficiency of public transportation networks under operational and resource constraints such as the number and length of public transportation routes, allowable service frequencies,and number of available buses(Chakroborty2003;Fan and Machemehl2006a,b).The practical importance of designing public transportation networks has attractedconsiderable interest in the research community which has developed a variety of approaches and modelsfor the TRNDP including different levels of design detail and complexity as well as interesting algorithmic innovations.In thispaper we offer a structured review of approaches for the TRNDP;researchers will obtain a basis for evaluating existing research and identifying future research paths for further improving TRNDP models.Moreover,practitioners will acquire a detailed presentation of both the process and potential tools for automating the design of public transportation networks,their characteristics,capabilities,and strengths.Design of Public Transportation NetworksNetwork design is an important part of the public transportation operational planning process_Ceder2001_.It includes the design of route layouts and the determination of associated operational characteristics such as frequencies,rolling stock types,and so on As noted by Ceder and Wilson_1986_,network design elements are part of the overall operational planning process for public transportation networks;the process includes five steps:_1_design of routes;_2_ setting frequencies;_3_developing timetables;_4_scheduling buses;and_5_scheduling drivers. Route layout design is guided by passenger flows:routes are established to provide direct or indirect connection between locations and areas that generate and attract demand for transit travel, such as residential and activity related centers_Levinson1992_.For example,passenger flows between a central business district_CBD_and suburbs dictate the design of radial routes while demand for trips between different neighborhoods may lead to the selection of a circular route connecting them.Anticipated service coverage,transfers,desirable route shapes,and available resources usually determine the structure of the route network.Route shapes areusually constrained by their length and directness_route directness implies that route shapes are as straight as possible between connected points_,the usage of given roads,and the overlapping with other transit routes.The desirable outcome is a set of routesconnecting locations within a service area,conforming to given design criteria.For each route, frequencies and bus types are the operational characteristics typically determined through design. Calculations are based on expected passenger volumes along routes that are estimated empirically or by applying transit assignmenttechniques,under frequency requirement constraints_minimum and maximum allowedfrequencies guaranteeing safety and tolerable waiting times,respectively_,desired load factors, fleet size,and availability.These steps as well as the overall design.process have been largely based upon practical guidelines,the expert judgment of transit planners,and operators experience_Baaj and Mahmassani1991_.Two handbooks by Black _1995_and Vuchic_2004_outline frameworks to be followed by planners when designing a public transportation network that include:_1_establishing the objectives for the network;_2_ defining the operational environment of the network_road structure,demand patterns,and characteristics_;_3_developing;and_4_evaluating alternative public transportation networks.Despite the extensive use of practical guidelines and experience for designing transit networks,researchers have argued that empirical rules may not be sufficient for designing an efficient transit network and improvements may lead to better quality and more efficient services. For example,Fan and Machemehl_2004_noted that researchers and practitioners have been realizing that systematic and integrated approaches are essential for designing economically and operationally efficient transit networks.A systematic design process implies clear and consistent steps and associated techniques for designing a public transportation network,which is the scope of the TRNDP.TRNDP:OverviewResearch has extensively examined the TRNDP since the late1960s.In1979,Newell discussed previous research on the optimal design of bus routes and Hasselström_1981_ analyzed relevant studies and identified the major features of the TRNDP as demand characteristics,objective functions,constraints,passengerbehavior,solution techniques,and computational time for solving the problem.An extensive review of existing work on transit network design was provided by Chua_1984_who reported five types of transit system planning:_1_manual;_2_marketanalysis;_3_systems analysis;_4_systems analysis with interactive graphics;and_5_ mathematical optimization approach.Axhausemm and Smith_1984_analyzed existing heuristic algorithms for formulating the TRNDP in Europe,tested them,anddiscussed their potential implementation in the United States.Ceder and Wilson_1986_reportedprior work on the TRNDP and distinguished studies into those that deal with idealized networks and to those that focus on actual routes,suggesting that the main features of the TRNDP include demand characteristics,objectivesand constraints,and solution methods.At the same period,Van Nes et al._1988_grouped TRNDP models into six categories:_1_ analytical models for relating parameters of the public transportation system;_2_models determining the links to be used for public transportation route construction;_3_models determining routes only;_4_models assigning frequencies to a set of routes;_5_two-stage models for constructing routes and then assigning frequencies;and_6_models for simultaneously determining routes and frequencies.Spacovic et al._1994_and Spacovic and Schonfeld_1994_proposed a matrix organization and classified each study according to design parameters examined,objectives anticipated,network geometry,and demand characteristics. Ceder and Israeli_1997_suggested broad categorizations for TRNDP models into passenger flow simulation and mathematical programming models.Russo_1998_adopted the same categorization and noted that mathematical programming models guarantee optimal transit network design but sacrifice the level of detail in passenger representation and design parameters, while simulation models address passenger behavior but use heuristic procedures obtaining a TRNDP solution.Ceder_2001_enhanced his earlier categorization by classifying TRNDP models into simulation,ideal network,and mathematical programming models.Finally,in a recent series of studies,Fan and Machemehl_2004,2006a,b_divided TRNDP approaches into practical approaches,analytical optimization models for idealized conditions,and metaheuristic procedures for practical problems.The TRNDP is an optimization problem where objectives are defined,its constraints are determined,and a methodology is selected and validated for obtaining an optimal solution.The TRNDP is described by the objectives of the public transportation network service to be achieved, the operational characteristics and environment under which the network will operate,and the methodological approach for obtaining the optimal network design.Based on this description of the TRNDP,we propose a three-layer structure for organizing TRNDP approaches_Objectives, Parameters,and Methodology_.Each layer includes one or more items that characterize each study.The“Objectives”layer incorporates the goals set when designing a public transportation system such as the minimization of the costs of the system or the maximization of the quality of services provided.The“Parameters”layer describes the operating environment and includes both the design variables expected to be derived for the transit network_route layouts,frequencies_as well as environmental and operational parameters affecting and constraining that network_for example,allowable frequencies,desired load factors,fleet availability,demand characteristics and patterns,and so on_.Finally,the“Methodology”layer covers the logical–mathematical framework and algorithmic tools necessary to formulate and solve the TRNDP.The proposed structure follows the basic concepts toward setting up a TRNDP:deciding upon the objectives, selecting the transit network items and characteristics to be designed,setting the necessary constraints for the operating environment,and formulating and solving the problem. TRNDP:ObjectivesPublic transportation serves a very important social role while attempting to do this at the lowest possible operating cost.Objectives for designing daily operations of a public transportation system should encompass both angles.The literature suggests that most studies actually focus on both the service and economic efficiency when designing such a system. Practical goals for the TRNDP can be briefly summarized as follows_Fielding1987;van Oudheudsen et al.1987;Black1995_:_1_user benefit maximization;_2_operator cost minimization;_3_total welfare maximization;_4_capacity maximization;_5_energy conservation—protection of the environment;and_6_individual parameter optimization.Mandl_1980_indicated that public transportation systems have different objectives to meet. He commented,“even a single objective problem is difficult to attack”_p.401_.Often,these objectives are controversial since cutbacks in operating costs may require reductions in the quality of services.Van Nes and Bovy_2000_pointed out that selected objectives influence the attractiveness and performance of a public transportation network.According to Ceder and Wilson_1986_,minimization of generalized cost or time or maximization of consumer surplus were the most common objectives selected when developing transit network design models. Berechman_1993_agreed that maximization of total welfare is the most suitable objective for designing a public transportation system while Van Nes and Bovy_2000_argued that the minimization of total user and system costs seem the most suit able and less complicatedobjective_compared to total welfare_,while profit maximization leads to nonattractive public transportation networks.As can be seen in Table1,most studies seek to optimize total welfare,which incorporates benefits to the user and to the er benefits may include travel,access and waiting cost minimization,minimization of transfers,and maximization of coverage,while benefits for the system are maximum utilization and quality of service,minimization of operating costs, maximization of profits,and minimization of the fleet size used.Most commonly,total welfare is represented by the minimization of user and system costs.Some studies address specific objectives from the user,theoperator,or the environmental perspective.Passenger convenience,the number of transfers, profit and capacity maximization,travel time minimization,and fuel consumption minimization are such objectives.These studies either attempt to simplify the complex objective functions needed to setup the TRNDP_Newell1979;Baaj and Mahmassani1991;Chakroborty and Dwivedi2002_,or investigate specific aspects of the problem,such as objectives_Delle Site and Fillipi2001_,and the solution methodology_Zhao and Zeng2006;Yu and Yang2006_.Total welfare is,in a sense,a compromise between objectives.Moreover,as reported by some researchers such as Baaj and Mahmassani_1991_,Bielli et al._2002_,Chackroborty and Dwivedi_2002_,and Chakroborty_2003_,transit network design is inherently a multiobjective problem.Multiobjective models for solving the TRNDP have been based on the calculation of indicators representing different objectives for the problem at hand,both from the user and operator perspectives,such as travel and waiting times_user_,and capacity and operating costs _operator_.In their multiobjective model for the TRNDP,Baaj and Majmassani_1991_relied on the planner’s judgment and experience for selecting the optimal public transportation network,based on a set of indicators.In contrast,Bielli et al._2002_and Chakroborty and Dwivedi_2002_,combined indicators into an overall,weighted sum value, which served as the criterion for determining the optimaltransit network.TRNDP:ParametersThere are multiple characteristics and design attributes to consider for a realistic representation of a public transportation network.These form the parameters for the TRNDP.Part of these parameters is the problem set of decision variables that define its layout and operational characteristics_frequencies,vehicle size,etc._.Another set of design parameters represent the operating environment_network structure,demand characters,and patterns_, operational strategies and rules,and available resources for the public transportation network. These form the constraints needed to formulate the TRNDP and are,a-priori fixed,decided upon or assumed.Decision VariablesMost common decision variables for the TRNDP are the routes and frequencies of the public transportation network_Table1_.Simplified early studies derived optimal route spacing between predetermined parallel or radial routes,along with optimal frequencies per route_Holroyd1967; Byrne and Vuchic1972;Byrne1975,1976;Kocur and Hendrickson1982;Vaughan1986_,while later models dealt with the development of optimal route layouts and frequency determination. Other studies,additionally,considered fares_Kocur and Hendrickson1982;Morlok and Viton 1984;Chang and Schonfeld1991;Chien and Spacovic2001_,zones_Tsao and Schonfeld1983; Chang and Schonfeld1993a_,stop locations_Black1979;Spacovic and Schonfeld1994; Spacovic et al.1994;Van Nes2003;Yu and Yang2006_and bus types_Delle Site and Filippi 2001_.Network StructureSome early studies focused on the design of systems in simplified radial_Byrne1975;Black 1979;Vaughan1986_,or rectangular grid road networks_Hurdle1973;Byrne and Vuchic1972; Tsao and Schonfeld1984_.However,most approaches since the1980s were either applied to realistic,irregular grid networks or the network structure was of no importance for the proposed model and therefore not specified at all.Demand PatternsDemand patterns describe the nature of the flows of passengers expected to be accommodated by the public transportation network and therefore dictate its structure.For example,transit trips from a number of origins_for example,stops in a neighborhood_to a single destination_such as a bus terminal in the CBD of a city_and vice-versa,are characterized as many-to-one_or one-tomany_transit demand patterns.These patterns are typically encountered in public transportation systems connecting CBDs with suburbs and imply a structure of radial orparallel routes ending at a single point;models for patterns of that type have been proposed by Byrne and Vuchic_1972_,Salzborn_1972_,Byrne_1975,1976_,Kocur and Hendrickson _1982_,Morlok and Viton_1984_,Chang and Schonfeld_1991,1993a_,Spacovic and Schonfeld_1994_,Spacovic et al._1994_,Van Nes_2003_,and Chien et al._2003_.On the other hand,many-to-many demand patterns correspond to flows between multiple origins and destinations within an urban area,suggesting that the public transportation network is expected to connect various points in an area.Demand CharacteristicsDemand can be characterized either as“fixed”_or“inelastic”_or“elastic”;the later meaning that demand is affected by the performance and services provided by the public transportation network.Lee and Vuchic_2005_distinguished between two types of elastic demand:_1_demand per mode affected by transportation services,with total demand for travel kept constant;and_2_total demand for travel varying as a result of the performance of the transportation system and its modes.Fan and Machemehl_2006b_noted that the complexity of the TRNDP has led researchers intoassuming fixed demand,despite its inherent elastic nature.However,since the early1980s, studies included aspects of elastic demand in modeling the TRNDP_Hasselstrom1981;Kocur and Hendrickson1982_.Van Nes et al._1988_applied a simultaneous distribution-modal split model based on transit deterrence for estimatingdemand for public transportation.In a series of studies,Chang and Schonfeld_1991,1993a,b_ and Spacovic et al._1994_estimated demand as a direct function of travel times and fares with respect to their elasticities,while Chien and Spacovic2001_,followed the same approach assuming that demand is additionally affected by headways,route spacing and fares.Finally, studies by Leblanc_1988_,Imam_1998_,Cipriani et al._2005_,Lee and Vuchic_2005_;and Fan and Machemehl_2006a_based demand estimation on mode choice models for estimating transit demand as a function of total demand for travel.中文译文：公交路线网络设计问题：回顾摘要：公共交通网络的有效设计让交通理论与实践成为众人关注的焦点，随之发展出了很多规划相关公交路线网络设计问题（TRNDP）的模型与方法。
毕业设计说明书英文文献中文翻译1
利用声学矢量传感器阵列对连贯的信号进行二维DOA估计摘要在本文中,我们提出了两种新的方法来评估的二维波达方向(DOA)的窄带一致(或高度相关)信号通过一个l型的声学矢量传感器阵列。
我们的去除信号的相干性并利用互相关矩阵重构信号子空间,ESPRIT和传播算子的方法是用于估计方位和俯仰角。
ESPRIT 技术是基于几何形状转移不变性和传播算子的方法是基于分区的互相关矩阵。
传播算子的方法计算效率高,而且只需要线性操作。
此外,ESPRIT的方法不需要任何特征分解或奇异值分解。
这两种技巧是直接的方法,不需要任何二维估计方位和仰角的迭代搜索。
给出仿真结果证明该方法的性能。
爱思唯尔B.V. 2011 保留所有权利。
关键词:来波方向角估计互相关相干信号声学矢量传感器阵列1 介绍近年来,声学矢量传感器阵列信号处理在水下信号处理的领域已经引起了越来越多的关注。
一个声学矢量传感器在空间一点测量压力和声空间粒子速度而传统的压力传感器只能提取压力的信息。
主要利用这些向量传感器比传统的标量传感器是他们可以更好地利用可用的声学信息;因此,它们应该比标量(压力)传感器数组计算精确。
因此应该允许矢量传感器在保持性能的同时使用更小的数组孔。
声学矢量传感器模型首次引入信号处理领域是在文献[1]总。
自那时以来,许多先进的压力传感器阵列技术适应声学矢量传感器阵列[2 - 4]。
各类不同的设计技术的声学矢量传感器如今在商业运用[5]。
矢量传感器技术已在水下环境使用了几十年,并吸引了对水下振源位置的问题的注意。
大多数的高分辨率波达方向估计方法如MUSIC[6、7]和ESPRIT[8、9]，当信号不相关时，已被证明是有效的。
当信号源连贯或高度相关时,例如,在多径传播或在军事场景,包含智能干扰系统,这些技术的性能却大幅降低。
在此情况下,协方差矩阵的秩一般都小于信源的数量。
要克服这种不利的方面,去相关技术，如Kozickand Kassam[13]研发的空间平滑(SS)[10-12]技术,特征向量平滑(ES)[14、15]，而且没有特征分解(SUMWE) [16]的计算效率方法已经被认可,然而,这些技术只适合某些阵列配置,例如,均匀间隔的线性阵列。
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Computer networking summarizeNetworking can be defined as the linking of people, resources and ideas. Networking occurs via casual encounters, meetings, telephone conversation, and the printed words. Now the computer networking provide beings with new networking capabilities. Computer network are important for services because service tasks are information intensive. During the is transmitted between clients, coworkers, management, funding sources, and policy makers. Tools with rapidly speed up communication will dramatically affect services.Computer network growing explosively. Two decades ago, few people essential part of our infrastructure. Networking is used in every aspect of business, including advertising, production, shipping, planning, bulling, and accounting. Consequently, most corporations in on-line libraries around the world. Federal, state, and local government offices use networks, as do military organizations. In short, computer networks are everywhere.The growth in networking economic impact as well. An entire industry jobs for people with more networking expertise. Companies need workers to plan, acquire, install, operate, and manage the addition computer programming is no longer restricted to individual computers; programmers are expected to design and implement application software that can communicate with software on other computers.Computer networks link computers by communication lines and software protocols, allowing data to be exchanged rapidly and reliably. Traditionally, they split between wide area networks (WANs) and local area networks (LANs). A WAN is a network connected over long-distance telephone lines, and a LAN is a localized network usually in one building or a group of buildings close together. The distinction, computers. Today networks carry e-mail, provide access to public databases, and are beginning to be used for distributed systems. Networks also allow users in one locality to share expensive resources, such as printers and disk-systems.Distributed computer systems are built using networked computers that cooperate to perform tasks. In this environment, each part of the networked system does what it is best at. The of a personal computer or workstation provides a good user interface. The mainframe, on the other the results to the users. In a distributed environment, a user might use in a special language (e. g. Structured Query Language-SQL), to the mainframe, which then parrrses the query, returning the user only the data requested. The user might then use the data. By passing back the user’s PC only the specific information requested, network traffic is reduced. If the whole file were transmitted, the PC would then of one network to access the resources on a different type of network. For example, a gateway could be used to connect a local area network of personal computers to a mainframe computer network. For example, if a company this example, using a bridge makes more sense than joining all thepersonal computers together in one large network because the individual departments only occasionally need to access information on the other network.Computer networking technology can be divided into four major aspects.The first is the data transmission. It explains that at the lowest level electrical signals traveling across wires are used to carry information, and shows be encoded using electrical signals.The second focuses on packet transmission. It explains why computer network use packets, and shows . LANs and WANs discussed above are two basic network.The third covers internetworking—the important idea that allows system, and TCPIP, the protocol technology used in global internet.The fourth explains networking applications. It focuses on , and programs provide services such as electronic mail and Web browsing.Continued growth of the global Internet is one of most interesting and exciting phenomena in networking. A decade ago, the Internet was a research project that involved a few dozen sites. Today, the Internet into a production communication system that reaches millions of people in almost all countries on all continents around the world. In the United States, the Internet connects most corporations, colleges and universities, as well as federal, state, and local government offices. It will soon reach most elementary,junior, and senior addition, many private residences can reach the Internet through a dialup telephone connection. Evidence of the Internet’s impact on society can be seen in advertisements, in magazines and on television, which often contain a reference to an Internet Web site that provide additional information about the advertiser’s products and services.A large organization with diverse networking requirements needs multiple physical networks. More important, if the organization chooses the type network that is best for each task, the organization will network can only communicate with other computers attached to same network. The problem became evident in the 1970s as large organizations began to acquire multiple networks. Each network in the organizations formed an island. In many early installations, each computer attached to a single network and employees employees was given access to multiple svreens and keyboards, and the employee was forced to move form one computer to another to send a massage across the appropriate network. Users are neither satisfied nor productive when they must use a separate computer. Consequently, most modern computer communication syetem allow communication between any two computers analogous to the way a telephone system provides communication between any two telephones. Known as universal service, the concept is a fundamental part of networking. With universal service, a user on any computer in any part of an organization can send messages or data to any other users. Furthermore, a user does not need to change computer systems whenchanging tasks—all information is available to all computers. As a result, users are more productive.The basic component used to commect organization to choose network technologies appropriate for each need, and to use routers to connect all networks into a single internet.The goal of internetworking is universal service across an internet, routers must agree to forward information from a source on one network to a specified destination on another. The task is complex because frame formats and addressing schemes used by underlying networks can differ. As s resulrt, protocol software is needed on computers and routers make universal service possible. Internet protocols overcome differences in frame formats and physical addresses to make communication pissible among networks that use different technologies.In general, internet software provides the appeatrance of a single, seamless communication system to which many computers attach. The syetem offers universal service :each computer is assigned an address, and any computer can send a packet to any other computer. Furthermore, internet protocol software —neither users nor application programs are a ware of the underlying physical networks or the routers that connect them.We say that an internet is a virtual network system because the communication system is an abstraction. That is, although a combination of of a uniform network syetem, no such network exists.Research on internetworking modern networking. In fact,internet techmology . Most large organizations already use internetworking as primary computer communication mechanism. Smaller organizations and individuals are beginning to do so as well. More inportant, the TCPIP technology computers in schools, commercial organications, government, military sites and individuals in almost all countries around the world.电脑网络简述网络可被定义为人、资源和思想的联接。