Computer simulation of the three-dimensional decay of thin collisionless current sheets

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Computer-Vision计算机视觉英文ppt

At the same time, AI MIT laboratory has attracted many famous scholars from the world to participate in the research of machine vision,which included the theory of machine vision , algorithm and design of system .
Its mainstream research is divided into three stages:
Stage 1: Research on the visual basic method ,which take the model world as the main object;
Stage 2: Research on visual model ,which is based on the computational theory;
the other is to rebuild the three dimensional object according to the two-dimensional projection images .
History of computer vision
1950s: in this period , statistical pattern recognition is most applied in computer vision , it mainly focuse on the analysis and identification of two-dimensional image,such as: optical character recognition, the surface of the workpiece, the analysis and interpretation of the aerial image.

Application and Analysis of Computer Virtual Simulation Technology in Three-dimensional An

Management Science and ResearchVolume 8(1), 2019, PP.19-21 Application and Analysis of Computer Virtual Simulation Technology in Three-dimensional Animation ProductionLe QiuZIBO Vocational Institute, Zibo Shandong 255314, ChinaAbstractWith the continuous promotion of computer technology, the application system of virtual simulation technology has been further optimized and improved, and has been widely used in various fields of social development, such as urban construction, interior design, industrial simulation and tourism teaching. China's three-dimensional animation production started relatively late, but has achieved good results with the support of related advanced technology in the process of development. Computer virtual simulation technology is an important technical support in the production of three-dimensional animation. In this paper, firstly, the related content of computer virtual simulation technology was introduced. Then, the specific application of this technology in the production of three-dimensional animation was further elaborated, so as to provide some reference for the improvement of the production effect of three-dimensional animation in the future.Keywords: Computer; Virtual Simulation Technology; Three-dimensional Animation Production; Application1.IntroductionComputer virtual simulation technology is one of the key technologies in three-dimensional animation production, which plays an important role in the whole process of three-dimensional animation production. It effectively combines many modern computer technologies to form a comprehensive technology to provide solid technical support for three-dimensional animation. Therefore, the analysis of the characteristics, advantages and related applications of computer virtual simulation technology has an important role in promoting the development of three-dimensional animation production.2.Overview of computer virtual simulation technology2.1Definition of virtual simulation technologyThe definition of virtual simulation technology can be understood and analyzed in both narrow and broad sense. In the narrow sense, virtual simulation technology mainly refers to a kind of experimental research technology developed with computer technology and network technology, which can be used to realize the comprehensive construction of virtual space [1]. However, the generalized virtual simulation technology has always been applied in the process of human understanding the world and exploring nature [2]. Especially in today's continuous development of computer technology and network technology, virtual simulation technology has its own system, which takes simulators and simple mathematical models as entities, and fully reflects the real characteristics of the objective world in the virtual environment [3].2.2Characteristics of virtual simulation technologyThe characteristics of virtual simulation technology can be summarized in four aspects [4]. (1) Immersion. Virtual simulation system can provide users with visual, auditory, tactile, olfactory, and motion sensations, so that users can get a sense of immersion in the virtual environment. (2) Interactivity. Interaction here is mainly the interaction between people and environment. In virtual system, users can control some elements in virtual environment through some actions. At the same time, the corresponding elements in the environment will make corresponding changes to control behavior [5]. For example, when launching missiles, users press the launch button, the virtual environment will appear. In the picture of missile launching, fire and debris will also appear when the missile touches the target and explodes [6]. (3) Illusiveness. The environment constructed in the virtual system is simulated by human using computer technology. The simulated environment may have existed in the past, may be forthcoming in the future, or may not happen. Therefore, the virtual system is not real and has some illusion. (4) Fidelity. Fidelity is also a main characteristic of virtual simulation technology, which is embodied in two aspects: firstly, the environment built in virtual environment can give people a very realistic feeling, just like the real world; secondly, when people manipulate the virtual environment, the environment will make corresponding changes according to the control behavior, which can give people a sense of immersion [7].3.Application of computer virtual simulation technology in three-dimensional animation productionThe application of computer virtual simulation technology in three-dimensional animation production is shown in Fig.1.Figure 1 Application of computer virtual simulation technology in three-dimensional animation production3.1Application of stereo display technologyStereo display technology is a technology that can make three-dimensional animation vivid display, which can combine visual effects with audience aesthetics [8]. In practice, there are two ways to display virtual scene realistically through stereo display technology: Firstly, simultaneous display method, that is, display the image corresponding to the viewer's eyes while playing three-dimensional animation, and achieve the actual viewing effect by wearing three-dimensional glasses; secondly, serial stereo display method, that is, display two animated video images alternately through a certain frequency to achieve the real effect of viewing animation directly with naked eyes [9].3.2Application of three-dimensional virtual sound technologyIn the virtual scene of three-dimensional animation, the real-time sound should be in line with the auditory perception of the audience in the real world, while allowing the audience to perceive the location of the sound source in the virtual environment. The technology of interaction nesting between the virtual environment and the real sound is called "three-dimensional virtual sound technology". Through three-dimensional virtual sound technology, audiences can truly feel the corresponding sound from real life in the virtual environment of three-dimensional animation, which strengthens the authenticity of film and television animation, and enables audiences to devote themselves wholeheartedly to the psychological changes and behavioral motivations of the protagonists in film and television animation. In practice, three-dimensional virtual sound technology is usually embodied in the following aspects: Firstly, three-dimensional virtual sound technology will provide another way for audiences to interact with things in movies in the virtual environment. In the future, audiences will communicate directly with people and things in virtual scene through advanced computer virtual simulation technology interactive equipment, so as to promote virtual reality technology when providing more real feelings for audiences; Secondly, through three-dimensional virtual sound technology, part of the information in the virtual environment of three-dimensional animation can be transmitted to facilitate the audience's understanding of the content of the film, and even the whole film's artistic ideas and related aesthetic values; Thirdly, the spatial information of three-dimensional virtual sound technology is more extensive than visual information, which increases the diversity of film and television scenes, provides rich pictures for the audience, and at the same time increases the visual effect.3.3Application of environmental modeling technologyIn order to create a real three-dimensional model, it is necessary to attach importance to the virtual environment and image. The main purpose of three-dimensional modeling of virtual environment and virtual image in film and television animation is to obtain data reference in real life. According to the audiences' aesthetic rules and characteristics, the virtual environment model with visual consumption function is established by using three-dimensional data, so as to achieve the best state in visual effect. At the same time, the use of virtual environment modeling technology is mainly in three-dimensional movies, or in science fiction films that need to show magnificent scenes, while ordinary plot films and two-dimensional movies do not need too much technology as support. Therefore, in practice, environmental modeling technology will play a more important role with the development of three-dimensional animation.3.4Application of virtual image technologyThe emergence of Star Wars series has enabled the development of virtual image technology in films. Since then, digital virtual image technology has been used in more 3D animation production. Its advanced computer technology is beyond the traditional virtual image skills, such as digital technology, virtual technology, synthesis technology. In a sense, virtual image coversa wide range, including pre-creation process, on-site shooting process and post-production process.4.Technical example and function of computer virtual simulation technologyComputer virtual simulation technology is widely used in the actual situation and plays an important role in film and television animation production. In this paper, the examples of computer virtual simulation technology were listed and its role was briefly discussed: First of all, it is the virtual image capture photography system. Usually two cameras take pictures of objects at the same time, focusing on a stronger three-dimensional effect, but also won't make the audience dizzy in the process of watching, to a large extent, in line with the aesthetic law of the public. Ghosts of the Abyss was the first film in the world to use this technology, since then this technology was more and more widely used. Many films were produced and filmed using this technology to produce more aesthetic effect images, such as: Journey to the Center of the Earth, Spy Kids and so on; Secondly, it is implementation preview. In the process of filming, in order to pursue the perfect combination of real scene and virtual environment, Cameron, a famous American director, developed a kind of virtual camera together with the creative team of the corresponding technical department. The camera can effectively combine the physical background and the characters with the virtual background in the process of filming, and complete the real-time preview, which saves the time of combining the two, and also effectively controls the shooting process. For example, in the production of the movie Avatar, actors need to wear tight pants full of motion capture points in the process of shooting, so that the camera can capture them synchronously and facilitate the automatic synthesis of virtual cameras. Thirdly, it is motion capture. In the process of filming, many scenes and actions need to be taken by real people.At this time, digital virtual technology should be applied to capture actions, digitalize actions, and then present a perfect state. For example, in Hollywood science fiction action movies, many of them use virtual motion capture technology to increase the visual effect of the film and enhance its attractiveness, such as King Kong, Rise of the Planet of the Apes, etc. The rich and vivid expressions and extraordinary movements in the film are shot through the above technology, and the effect is more realistic and natural.5.ConclusionWith the continuous expansion of the application scope of three-dimensional animation in recent years, computer virtual simulation technology as an important technology of three-dimensional animation production has been given great attention. The application of computer virtual simulation technology in the production of three-dimensional animation has great practical significance. The application of computer virtual simulation technology in the production of three-dimensional animation is conducive to better understanding of animation works and interpretation of real scenes. At the same time, three-dimensional animation production plays an important role in restoring ancient times and looking forward to the future. In summary, with the rapid development of three-dimensional animation production, the application of computer virtual simulation technology in this field will inevitably be highly valued. From the analysis of this paper, it can be seen that the application of virtual simulation technology in the production of three-dimensional animation can not only make abstract things concrete and clear, but also make the scenes and characters in animation more realistic, and improve the animation animation vividness and visual impact. In the future, with the continuous expansion of the application scope of three-dimensional animation, the optimization and improvement of computer virtual simulation technology is bound to be very important. Only by constantly improving the virtual simulation technology, can better three-dimensional animation be produced to better play its role.References[1]Zeng Longkai. Application of computer virtual simulation technology in three-dimensional animation production. Moderninformation technology, 2019,08:84-85+88.[2]Wei Qingzhong, Yi Hongchi, Zhao Wentao. Virtual simulation of orthopaedic manipulation model of distal radius extensionfracture for teaching. China Digital Medicine, 2018, 1307:6-9.[3] Liu Qingming. Application of Virtual Reality Technology in Film and Television Animation Production. TV Guide, 2017, 21:174-175.[4] Meng Fanjun. Research on the Application of Director-based Sports Simulation Training Technology in the Referee of SportsEvents. Television Technology, 2018,4210:65-69.[5] Anxiufang. Application of computer virtual simulation technology in three-dimensional animation production. Information andcomputer (theoretical version), 2016, 19:31-32.[6] Wang Xiao. Application of virtual reality technology in three-dimensional animation production. Information and computer(theoretical version), 2017,02:86-87.[7] Ye Hongling, Wang Pengfei. Construction of Teaching Resource Bank of automobile construction course based on computersimulation technology. Science and technology innovation report, 2017, 1417:238-242.[8] Xu Dan. Prospects for the development of the combination of animation and VR technology.Journal of Jiamusi VocationalCollege, 2017,02:418-419.[9] Ma Qianqian. Application of virtual reality technology in three-dimensional animation production. Think tank era, 2017,06:210-211.。

新核心3第1、2、3、4、5、7课文翻译

Unit 1Main Reading拥有自己头脑的机器如果任其自由发展，有些机器可以学得更聪明，在一些最需要脑力的任务方面甚至会超越人类。

人类能否建造出可以演变得更好并可以超出人们想象而发明解决方案的机器吗？利用计算蛮力方法，计算机现在可以进行通行的国际象棋游戏。

1997年，IBM的一款名为深蓝的超级计算机击败了卡斯帕罗夫。

世界冠军认为这次经历如同与顶尖的人类挑战者对抗一样艰难。

阿蓝图灵，战时英国谜团破译密码工作背后的数学天才，于20世纪50年代设立了人工智能的标准，而深蓝的行为至少达到了其中的一个。

然而，深蓝的成功并没有给人工智能界留下深刻的印象，那是因为这台机器的创举仅仅在于运算速度快于其他任何以前的计算机。

巨大的处理能力可以使它预测到向前推进的棋步多达30个，而且它聪明的编程可以计算出数百万的可能的棋步中哪一步会加强它的位置。

但就本身而言，深蓝所能做的，而且出色完成的仅仅是数学。

它不能为象棋游戏制定自己的战略。

但是如果深蓝被赋予一种演变的能力，使用反复试验的经历学会完善自身，会怎么样呢？一种名为“演化硬件”的新技术正试图这么做。

和深蓝一样，演化硬件也是通过尝试几十亿个不同的可能，寻求解决方案。

区别在于，和深蓝不同，演化硬件不停地调整和完善它的搜索算法，而这也正是找到解决方案所需的逻辑步骤。

它每次都选择最好的，并加以尝试。

而且，它所作的一切不是根据编好的指令，而都是自动完成的，。

传统观念长期认为一个机器的能力是受限于创造者的想象力。

但是在过去的几年里，演化硬件的前驱已经成功地建造了一些可以自行调整并且表现更佳的设备。

有些情况下，后来出现的机器甚至超出了创造者的能力。

例如，在电路设计领域，对几十年来人类束手无策的一些问题，演化硬件却找出了创造性的解决方案。

演化硬件首先需要硬件可以重新配置。

如果一个设备不能调整形状或调整做事方法，它是不可能演变的。

拿一把瑞士军刀为例，如果要完成开启瓶子的任务，使用者要确认刀具中合适的工具，然后打开刀具，再把设备转变成一个可以敲开瓶盖的用具。

三维解析仿真的英语作文

三维解析仿真的英语作文Three-Dimensional Computational Modeling.Three-dimensional (3D) computational modeling is the process of creating a mathematical representation of a three-dimensional object. This representation can be used to simulate the behavior of the object under different conditions. 3D computational modeling is used in a wide variety of fields, including engineering, medicine, and manufacturing.In engineering, 3D computational modeling is used to simulate the behavior of structures and machines. This information can be used to design structures that are safe and efficient. In medicine, 3D computational modeling is used to simulate the behavior of organs and tissues. This information can be used to diagnose diseases and develop new treatments. In manufacturing, 3D computational modeling is used to simulate the behavior of products during the manufacturing process. This information can be used tooptimize the manufacturing process and reduce product defects.There are many different types of 3D computational modeling software available. The type of software used will depend on the specific application. Some of the most popular 3D computational modeling software programs include ANSYS, COMSOL, and Siemens NX.3D computational modeling is a powerful tool that can be used to simulate the behavior of objects in a variety of different fields. This information can be used to design safer and more efficient structures, diagnose and treat diseases, and optimize the manufacturing process.Benefits of 3D Computational Modeling.There are many benefits to using 3D computational modeling. Some of the most notable benefits include:Increased accuracy: 3D computational models are more accurate than traditional 2D models. This is because 3Dmodels can take into account the effects of all three dimensions of space.Reduced time and cost: 3D computational modeling can save time and cost by reducing the need for physical testing. Physical testing can be expensive and time-consuming, and it is not always possible to test all possible scenarios.Improved communication: 3D computational models can be used to communicate complex designs and concepts more easily. This can help to reduce errors and improve collaboration between different teams.Applications of 3D Computational Modeling.3D computational modeling is used in a wide variety of applications, including:Engineering: 3D computational modeling is used to simulate the behavior of structures and machines. This information can be used to design structures that are safeand efficient.Medicine: 3D computational modeling is used to simulate the behavior of organs and tissues. This information can be used to diagnose diseases and develop new treatments.Manufacturing: 3D computational modeling is used to simulate the behavior of products during the manufacturing process. This information can be used to optimize the manufacturing process and reduce product defects.Future of 3D Computational Modeling.The future of 3D computational modeling is bright. As computer hardware and software continue to improve, 3D computational models will become even more accurate and sophisticated. This will open up new possibilities for using 3D computational modeling in a wide variety of applications.One of the most exciting developments in 3Dcomputational modeling is the use of artificialintelligence (AI). AI can be used to automate the process of creating and running 3D computational models. This will make it easier for engineers, scientists, and other professionals to use 3D computational modeling in their work.Another exciting development in 3D computational modeling is the use of virtual reality (VR). VR can be used to create immersive 3D environments that allow users to interact with 3D computational models. This can make it easier to understand complex designs and concepts.3D computational modeling is a powerful tool that is transforming the way we design, build, and heal. As computer hardware and software continue to improve, 3D computational modeling will become even more powerful and versatile. This will open up new possibilities for using 3D computational modeling in a wide variety of applications.。

The numerical computation of turbulent flows

K p
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V
4 P 0, Oti
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7
of turbulence energy von Karman’s constant appearing in (2.1 - 11) Molecular viscosity Turbulent viscosity Kinematic viscosity A generalized dependent variable Density Effective turbulent Prandtl number Effective turbulent Prandtl number for transport Molecular Prandtl number Shear stress
Nomen constant Curte t number defined by (3.1 - 1) Coefficients in approximated turbulent transport equations Specific heat at constant pressure Diffusion coefficient for quantity (p Rate of diffusive transport of Reynolds stress Constant in near-wall description of velocity profile (- 9) Functional defined by (2.2 - 6) Turbulence kinetic energy uiuj/2 Length of energy containing eddies Fluctuating component of static pressure Heat flux Radius Reynolds number in pipe flow based on bulk velocity and pipe diameter Rate of redistribution of Reynolds stress through pressure fluctuations Turbulent Reynolds number k2/ve Temperature Fluctuating component of velocity in direction xi Mean component of velocity in direction Xi Streamwise velocity nondimen~onalized by T,JP Mean streamwise velocity on axis Change in mean velocity across shear flow ‘Vorticity’ fluctuations squared Cartesian space coordinate

新概念第四册课文翻译及学习笔记【Lesson31、32、33】

【导语】新概念英语作为⼀套世界闻名的英语教程，以其全新的教学理念，有趣的课⽂内容和全⾯的技能训练，深受⼴⼤英语学习者的欢迎和喜爱。

为了⽅便同学们的学习，为⼤家整理了⾯的新概念第四册课⽂翻译及学习笔记，希望为⼤家的新概念英语学习提供帮助!Lesson31 【课⽂】 First listen and then answer the following question. 听录⾳，然后回答以下问题。

What do you have to be able to do to appreciate sculpture? Appreciation of sculpture depends upon the ability to respond to form in three dimension. That is perhaps why sculpture has been described as the most difficult of all arts; certainly it is more difficult than the arts which involve appreciation of flat forms, shape in only two dimensions. Many more people are 'form-blind' than colour-blind. The child learning to see, first distinguishes only two-dimensional shape; it cannot judge distances, depths. Later, for its personal safety and practical needs, it has to develop (partly by means of touch) the ability to judge roughly three-dimensonal distances. But having satisfied the requirements of practical necessity, most people go no further. Though they may attain considerable accuracy in the perception of flat form, they do not make the further intellectual and emotional effort needed to comprehend form in its full spatial existence. This is what the sculptor must do. He must strive continually to think of, and use, form in its full spatial completeness. He gets the solid shape, as it were, inside his head-he thinks of it, whatever its size, as if he were holding it completely enclosed in the hollow of his hand. He mentally visualizes a complex form from all round itself; he knows while he looks at one side what the other side is like, he identifies himself with its centre of gravity, its mass, its weight; he realizes its volume, as the space that the shape displaces in the air. And the sensitive observer of sculpture must also learn to feel shape simply as shape, not as description or reminiscence. He must, for example, perceive an egg as a simple single solid shape, quite apart from its significance as food, or from the literary idea that it will become a bird. And so with solids such as a shell, a nut, a plum, a pear, a tadpole, a mushroom, a mountain peak, a kidney, a carrot, a tree-trunk, a bird, a bud, a lark, a ladybird, a bulrush, a bone. From these he can go on to appreciate more complex forms or combinations of several forms. HENRY MOORE The Sculptor Speaks from The Listener 【New words and expressions ⽣词和短语】 auditory adj. 听觉的 colour-blind adj. ⾊盲的 perception n. 知觉 comprehend v. 理解 spatial adj. 空间 visualize v. 使具形象，设想 reminiscence n. 回忆，联想 tadpole n. 蝌蚪 mushroom n. 蘑菇 carrot n. 胡萝⼘ bud n. 花蕾 lark n. 云雀 ladybird n. 瓢⾍ bulrush n. 芦苇【课⽂注释】 1.respond to 响应，对 … 起反应例句：He resolved to respond to the call of the Party. 他决⼼响应党的号召。

基于卷积神经网络的改进机械臂抓取方法

CAI Chen WEI Guoliang （School of Optical-Electrical and Computer Engineering，University of Shanghai for Science and Technology，Shanghai 200093）
Abstract In order to improve the accuracy of manipulator grasping，an efficient framework is proposed for detect the optimal position of robotic grasping based on Mask R-CNN. The architecture，which uses RGB-D images as input，makes an accurate in⁃ stance segmentation to determine the category，location and mask information of grabbing objects. Then the weighted depth coordi⁃ nates of the center point are obtained from the denoised depth map by the inverse distance weighted method to form the three-dimen⁃ sional target position. And the final optimal grasping position is obtained by coordinate transformation. As such，the performance can be effectively improved by considering the posture and edge information of target object. Finally，some experiments for grasping network on Universal Robot 3 are utilized to demonstrate the effectiveness of the proposed framework.

Lesson 22 Computer Simulation

Lesson 22 Computer SimulationComputer simulation as a powerful analytic tool widely used in scientific research and engineering design demonstrates unrivalled advantages. With computer simulation, scientists and engineers do not have to build real primary prototypes when they observe an known phenomenon, analyse a complex process, design a machine or a building, etc. Computer simulation is particularly significant when the object under study and examination is costly or even impossible to be built into a real model. For example, to study the cause of engine malfunction that has led to a series of supersonic plane crashed, or to examine the impact on passengers when an airplane crashes, researchers may have to repeat simulati ng the calamities over and over again before they can find out what they need to reach a conclusion. Obviously, these can only be simulated by running computer simulation programs or the like, rather than replicating the tragedies. Another example is engineering design, in which engineers have to try many schemes and parameters before they can come up with a satisfactory design. Using computer simulation programs, engineers can accomplish that iterative process each time by inputting different schemes and parameters into their computer models, rather than building many differentreal models.Virtually, computer simulation is based on mathematical models representing the nature of the object under study or examination. The mathematical model comprises a series of equations that depict the inherent processes of the object in mathematical terms. A computer simulation program includes algorithms that are derived from those equations. The outcome of simulation is usually expressed in rather abstract forms, for example, 2-D diagrams curves, tables and figures.Over the past years, computer graphics techniques have helped computer simulation by creating realistic 3-D images to depict the object to be simulated and the environment around it or the effect imposed on it. Sophisicated computer simulation package capable of providing real-time interactive moving images have emerged, although still beyond the reach of most industries. Meanwhile, many CAD systems have incorporated visual modules to enable engineers to interactively “walk”through their 3-D pseudo models on screen to review their designs and present them to their clients. This convenience is particularly important to architects.Here is an example. To analyse the distribution of stress in a fuselage when the plane is flying, the computer simulationpackage will first set up a mathematical model for this specific theme which comprises equations derived from aerodynamics, elasticity, structural mechanics, then implement a series of computation on a simplified structure of the plane, based on the finite element stress analysis, finally, it gives the outcome which will be clusters of curves spread over the simplified structure of the plane, each indicating the locations in the fuselage that suffer stress of a uniform value. The accuracy of the simulation depends on the accuracy of mathematical model, that is , how closely the model is built to represent the real plane and its environment in terms of mathematics, geometry and mechanics.Computer simulation seems to be the only choice for analysing disasters, calamities and accidents, Quite a lot of impressive simulation have been made on some potentially threatening disasters and calamities, for example, the aftermaths of a global nuclear war, the disastrous effect on global climate and environment as a result of worldwide greenhouse effect, the probability of collision between an invading meteorite and the earth, etc. .Other application of computer simulation technique can be weather forecasting, simulation of combat actions in battlefield, flight programs for training future pilots, human models fortesting new medicines and bus operator’s workstation (as shown in Fig.22-1)New Words and Expressionssimulation [ˌsimjuˈleiʃən]仿真, 模拟demonstrate[ˈdemənstreit]示范, 证明, 论证prototype [ˈprəutətaip]原型phenomenon [fiˈnɔminən]现象malfunction[ˌmælˈfʌŋkʃən]故障supersonic [ˌsju:pəˈsɔnik]超音速的; 超声波crash [kræʃ]碰撞impact [ˈimpækt]碰撞, 冲击, 影响, 效果calamity[kəˈlæmiti]灾难, 不幸事件replicate [ˈreplikeit]复制iterative[ˈitərətiv]重复的, 反复的depict [diˈpikt]描写,描述CAD(Computer Aided Design) 计算机辅助设计pseudo [ˈsju:dəu]假的, 冒充的architect [ˈɑ:kitekt]建筑师fuselage[ˈfju:zilɑ:ʒ]机身aerodynamics [ˌɛərəudaiˈnæmiks]空气动力学elasticity[ilæsˈtisiti]弹力, 弹性geometry[dʒiˈɔmitri]几何学aftermath[ˈɑ:ftəmæθ]结果,后果greenhouse effect [iˈfekt]温室效应collision[kəˈliʒən]碰撞, 冲突meteorite[ˈmi:tjərait]陨星comprise[kəmˈpraiz]包含, 由….组成。

Three-Dimensional Static and Dynamic Stress Intensity Factor Computations Using ANSYS

Three-Dimensional Static and Dynamic Stress Intensity Factor Computations Using ANSYSX. M. JiaChongqing Communications Research & Design Institute,Chongqing ChinaF. Dai Q. Z. WangDepartment of Civil Eng. & Applied Mechanics,Sichuan University, Chengdu ChinaAbstractIn three-dimensional computation for linear elastic fracture mechanics, how to simulate the stress singularity near the crack tip has been a difficult and important point. The so-called quarter-point element is often used to model the stress and displacement field near the crack tip. However, ANSYS only provides automatic meshing capability for two-dimensional problems. It cannot directly generate crack elements for three-dimensional models. At the crack tip region we generate the quarter-point element manually to model the correct singularity of the stresses near the crack tip, thus making the computation for three-dimensional crack problem possible. Manual generation of elements may be tedious for a large and complex model. In this paper, two methods are presented to compute three-dimensional Stress Intensity Factors (SIFs). Firstly, submodel and partial crack submodel methods are adopted to compute the SIFs. Manual generation is only needed for submodel region, which is of much reduced size, thus manual generation is feasible. Secondly, mesh200 element can be used to mesh the area with two dimensional singular elements, and then sweep this area through certain coordinate system to establish three-dimensional crack elements. Finally, three static and dynamic crack examples are given to prove the correctness and ability of these methods. The accuracy of these methods is guaranteed compared with other literature. These two methods are easy to handle and extend the ability of ANSYS in computing three-dimensional SIF.IntroductionFracture Mechanics provides a theory background for material and structures containing cracks and faults, and stress intensity factor (SIF) is a key parameter in crack analysis. SIF plays a dominate role because it indicates the singular intensity of linear elastic crack field (stress and strain).Because of the importance of SIF, Its solutions have been paid very high attention since the beginning of fracture mechanics. Exact solutions to these problems are limited to a few special configurations; e.g., elliptical cracks embedded in very large bodies, we can look it up in SIF manuals. For complicated configurations, such as the intersection of an area crack with a free surface is referred to as a surface flow, where exact solutions are both difficult to obtain and generally not available. Side by side with the difficulty of the problem, there is the unfortunate fact that such surface flaw is the most commonly encountered defect in many engineering structures.Till now, many methods are adopted to compute SIF, such as finite element method, boundary element method and finite difference method etc. Finite element method is the most popular tool in computing SIF. In three-dimensional computation for linear elastic fracture mechanics, how to simulate the stress singularity of 12r− near the crack tip (r is the normal distance to the crack tip) has been a difficult and important point. The so-called quarter-point element is often used to model the stress and displacement field near the crack tip; however, its application in the general-purpose finite element software is still difficult. For example, ANSYS only provides automatic meshing capability for two-dimensional problems; it cannot directly generate crack elements for three-dimensional models. At the crack tip region we generate the quarter-point element manually to model the correct singularity of the stresses near the crack tip, thus making the computation for three-dimensional crack problems possible. Manual generation of elements (including crack elements) for the whole model may be tedious for a large and complex model.In this paper, two methods are presented to compute three-dimensional SIFs. Firstly, submodel and partial crack submodel methods are adopted to compute the SIFs. Manual generation is only needed for submodel region, which is of much reduced size, thus manual generation is feasible. Secondly, mesh200 element can be used to mesh the area with two dimensional singular elements, and then sweep this area through certain coordinate system to establish three-dimensional crack elements. Finally, three static and dynamic crack examples are given to prove the correctness and ability of these methods. The accuracy of these methods is guaranteed compared with other literature.Figure 1. Nodes used for the approximate crack-tip displacementsProcedureFormulae in computing static and dynamic SIFAs an example, we illustrate mode-I (opening mode) crack and give the formulae to compute the SIF. For half model:I K =For full model:I K =WhereI K =The stress intensity factor of mode-I crack;G =Shear modulus;κ=34µ− if plane strain or axisymmetric; ()3)µµ−+ if plane stress; where µ is Poisson's ratio;,v v ∆=Displacements in a local coordinate system for half and full model;r =Coordinates in a local coordinate system.In dynamic fracture mechanics, dynamic SIF is a function of time t . The formulae are similar with static ones. For half model:()dyn I K t =For full model:()dyn I K t =Where()dyn I K t =Dynamic stress intensity factor of Mode-I cracks; it is a function of time t ;(),()v t v t ∆=Dynamic displacements in a local coordinate system for half and full model, They are also the functions of time t .In dynamic fracture analysis, we use Newmark time integration method [1] to solve kinetics equations for implicit transient analyses, and then we get ()u t information for computing dynamic SIF.We can use displacement extrapolation just as ANSYS program does in KCALC command; they almost get identical results in computing SIF.Submodel method and partial crack submodel methodThe submodel method is a technique of finite element analysis to obtain a more accurate numerical value for the specific region in the analyzed model with high efficiency; the method is also called cut-boundary displacement method or the specified boundary displacement method. It allows separating a local part of the model from the remaining part, and re-analyzing the submodel with renewed fine mesh. The cut-boundary of the submodel is prescribed by the displacement calculated by the whole model. The submodel method is based on the Saint-Venant’s principle, that is, if the actually distributed boundary traction is replaced by the statically equivalent boundary condition, the solutions of elasticity is only altered near the boundary where the equivalent boundary condition is prescribed, and for the place which is relatively far from the changed boundary, the solution will not be affected. If the boundary of the submodel is reasonably selected, and a fine mesh is used for the submodel, then high-accuracy result can be achieved.In the analysis of three-dimensional cracks, the submodel method is composed of two steps: first a whole model is analyzed with a relatively coarse mesh, then a submodel cut from the whole model for the crack-front region is analyzed using direct generation commands (E and N commands), most (if not all) of the crack surface should be included in order to get high-accuracy results. By adjusting mid-side nodes to quarter-point, singular elements in wedge form are positioned directly along the crack front.When analyzing crack problems, sometimes it is necessary to extend the submodel method to the partial crack submodel; that means only a part of the crack of interest is modeled in order to save modeling time. The partial crack submodel is also based on Saint-Venant’s principle.Singular elements generation using mesh200 elementMesh200 element is “mesh-only” element, contributing nothing to solution. With the help of this element, we can generate three-dimensional crack elements easily. In order to generate three-dimensional crack elements, first the area mesh is generated with mesh200 element, using KSCON command to create two-dimensional singular area elements with 8 nodes at crack tip, then the volume mesh can be generated through VDRAG, VROTAT, VOFFST and VEXT commands etc. through a given coordinate system based on the area mesh. For complicated configurations, the model can be divided to many parts. These parts can be glued together or using bonded contact scheme. The one containing crack uses mesh200 elements to generate singular elements; the others can be meshed freely. It makes solving three dimensional crack problems easy.Examples are given in the following paragraph to illustrate the usage of these methods.Calibration of three-dimensional SIF using ANSYSSIF for a penny-shaped crack in a finite-radius cylinderSubmodel methodThis is a simple three-dimensional crack problem in finite domain, a penny-shaped crack in a finite-radius cylinder subjected to remote uniform tension. For this test problem, the crack radius a=0.5 (Figure 2), the radius of the cylinder b=1.0, the height of the cylinder h=2.8, the uniform tensile stress σ=1.0 is applied on both upper and lower surface, the elastic modulus E=20000.0, Poisson’s ratio µ=0.3, all quantities arein compatible unit. The SIF should be identical along the whole circular crack front because of symmetry; its value given by the newest reference available is [2]:0.685=Wherea=Radius of penny-shaped crack;σ=Tension stress;/(Kσ=IThe dimensionless SIF.Figure 2. The submodel of the penny-shaped crackConsidering symmetry, only one-eighth of the cylinder needs to be modeled. First the normal solidtetrahedral element was used for establishing the whole model, the computation results was reserved for later use. Then a small region including the crack was separated from the whole model, the cut-boundary was given the prescribed displacement condition from previous computation for the whole model. This small region is the so-call submodel, the submodel covers the whole circular arc crack front, which spans the angle between 0o and 90o. The submodel was direct generated with another kind of solid hexahedral element, and the quarter-point element especially used to model the crack tip region. Using the submodel method we get the value of dimensionless stress intensity factor to be 0.681, its error as compared with Ref.[2] is -0.57%. Partial crack submodel methodIn order to test the partial crack submodel method which will be used in further research, only a part of the arc crack is modeled, which has the maximum angle of 85.5θ=oas the cut boundary. It can be seen from Figure 3 that a part of the crack instead of the full crack (i.e.90θ=o, where some exact symmetric conditions can be applied) is modeled, hence the name of the partial crack submodel method. When analyzing crack problems, sometimes is necessary to extend the submodel method to the partial crack submodel method. The computation results are shown in Figure 4, where it can be seen that the results of the partial crack submodel method are almost identical with those of the submodel method except the point very near the cut-boundary, this complies with the well-known Sanit-Wenant’s principle.Figure 3. The partial crack submodelFigure 4. The comparison of the results between the whole crack submodel and partial crack submodelCalibration of the minimum SIF for the CCNBD specimenIn 1995, the International Society for Rock Mechanics (ISRM) presented the “Suggested Method for determining Mode-I fracture toughness using cracked chevron notched Brazilian disc (CCNBD)specimens” [3]. The SIF computation of the CCNBD specimens is the most important part of the newly proposed Suggested Method; hence it deserves attention and research effort. It was pointed out that some background work of the SIF analysis for the CCNBD specimens were not appropriate in Ref. [4], the value given by ISRM [3], i.e. min 0.84Y = are too small (where min Y is the dimensionless SIF of standard CCNBD specimen ). The CCNBD specimen with the concentrated diametric compressive load applied is shown in Figure 5, where R is the disc radius, B is the thickness, b the width of crack front, s R the radius of the cutter, 00()a R α= the dimensionless initial crack length, 11()a R α= the dimensionless maximum cutting length, ()a R α= the dimensionless crack length. Parameters for the standard CCNBD specimen given by Ref. [3] are:00.2637α=,10.65α=,0.8B α=, 0.6933s R R =. For theconvenience of modeling, the side circular arc notch, which has a finite notch width, is modeled as a crack, however in reality the notch is not a sharp crack, the singularity of stress at the notch root is less than that at the crack tip. In the experiment, the crack does not initiate from the root of the two side notches, the crack only initiates from the sharp conjunction point of the two side notches, and it advances forward with increasing crack front width (denoted by b in Figure 5) during testing. Based on this, our partial crack submodel will not include the two side notches; it only includes the center straight crack.Figure 5. The CCNBD specimenBecause of the symmetry, only one-eighth of the CCNBD specimen is meshed in the whole model as shown in Figure 6. The whole model uses SOLID92 element from ANSYS library of element, while the submodel uses SOLID95, at crack front the SOLID 95 elements collapse into wedge-shaped with quarter-point elements instead (Figure 7).Figure 6. The mesh of the whole ModelFigure 7. The mesh of the partial crack submodelAt different points along the crack front, the stress intensity factors are not the same, which is the characteristic of a three-dimensional specimen. In Figure 8(a), the distribution of the SIFs along thespecimen for 0.49()a R αα== is given, where the SIF is normalized using P , the samequantity as SIF. The disturbance near the outmost point is relatively large , in order to avoid its interference, the average value of stress intensity factor is calculated for all those points whose value does not deviate from the center value for more than 7%.Y= WhereY =The dimensionless stress intensity factor;I K =The mode-I stress intensity factor;P =The concentrated diametric compressive load;B =The disc thickness;D =The diameter.The formula for the determination of fracture toughness IC K using CCNBD specimen is [3]:min IC K =Where IC K =The fracture toughness;max P =The ultimate load in the test;min Y =The minimum value of Y corresponding to the critical point in the test.The general trend of the variation of SIF of the CCNBD specimen is similar to that of chevron notched specimens, that is descending-flat-ascending, and there is a minimum value of dimensionless SIF min Y . At this critical point, the load also reaches the maximum load max P , and the dimensionless crack length arrives at the critical value ()m m a R α=. For the standard CCNBD specimen proposed by ISRM, we obtained 0.49m α= and min (0.49)0.943m Y α== using ANSYS submodel method, which is more accurate than the value given by ISRM (see Ref. [5] for detail). Figure 8(b) gives the SIF distribution along the whole crack front derived from FRANC3D (one famous three-dimensional crack analysis software). We can see that the distribution trend and the value are almost the same. Using FRANC3D, we get the value of the minimum SIF is 0.946. It indicates that the analysis using ANSYS partial crack submodel method is successful, the results are reliable.Figure 8. The distribution of the dimensionless SIF of the CCNBD specimen with 0.49α=Dynamic SIF for penny-shaped crack in a finite cubeA penny-shaped crack in a finite cube (12222w w h ××) under remote pulse impact 0()()p t H t σ= applied is shown in Figure 9, where a (10.5a w =) is radius of the penny-shaped crack, 121w w =,12h w =, Poisson’s ratio 0.2µ=.Dynamic SIF is normalized with 0K ,where 02K σ=is normalized using formula 1/c t h ,where 1(c =is the longitudinalwave velocity.Figure 9. Penny-shaped crack in a finite cubeConsidering the symmetry, one-eighth of the cube with the center penny-shaped crack is modeled. In orderto generate crack mesh easily, the model is divided into two parts, the one is a one-eighth cylinder, and the other is a seven-side volume. In symmetry area, we use mesh200 element (KEYOPT(1)=7) and use KSCON command at crack tip to establish singular area mesh, then use VROTAT command rotate 90o to establish volume mesh containing three-dimensional crack elements. The seven-side volume are meshedfreely also with SOLID95 element. The Mesh is shown in Figure 10, Figure 11 gives an enlarged view of three-dimensional crack elements, it can be seen that the element created are very fine.Figure 10. Mesh generation using mesh200Figure 11. Enlarged crack-tip elementsThe stress intensity factor should be identical along the whole circular crack front because of symmetry, the dynamic stress intensity factors at different time are shown in Figure 12, where it can be seen that the results using ANSYS are almost identical with those of the reference values [6, 7], the maximum error is 1.2% in calculating time. It is clear that we can generate well formed three-dimensional crack elements and get high-precision results in SIF computation with the help of mesh200 elements.Figure 12. Dynamic stress intensity factor of the penny-shaped crack in a finite cubeConclusionIn this effort, two methods are presented to compute the three-dimensional static and dynamic stress intensity factors, the examples given prove the correctness of the methods, and these methods make the computations easy and high efficient. The results are of high precision and reliability compared with other literature. These two methods are easy to handle and extend the ability in computing three-dimensional SIFs.References1. ANSYS Reference Manual [M]. ANASY company, 1999.2. Leng, A. Y. T., Tsang, K. L., Two-level finite elements for a finite body with penny shapedcrack [J]. Int. J. Fract., 1999, 100:9-L143. ISRM Testing Commission, (co-ordinator: R. J. Fowell), Suggested method for determiningmode I fracture toughness using cracked chevron notched Brazilian disc (CCNBD) specimens [J].Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 1995, 32:57-64.4. Wang Q Z., Stress intensity factors of ISRM suggested CCNBD specimen used for mode-Ifracture toughness determination [J].Int. J. Rock Mech. Min. Sci. 1998, 35: 977~9825. Q. Z. Wang, X. M. Jia, et al. More accurate stress intensity factor derived by finite elementanalysis for the ISRM suggested rock fracture toughness specimen-CCNBD [J]. Int. J. Roc Mech.Sci. 2003, 40: 233~241.6. Zhang Y Y. Shi W, Transient analysis of three-dimensional crack problems by the Laplacetransforms boundary element method [J]. Engage Fracture Mech,1994,47(5):715-7227. P. H. Went. Dynamic Fracture Mechanics: Displacement Discontinuity Method [M].Southampton , Boston: Computational Mechanics Publications ,1996。

复杂矿坑FLAC^(3D)三维建模及其应用

现代矿业MODERN MINING总第625期2021年5月第5期Serial No.625May.2021复杂矿坑FLAC3D三维建模及其应用毛志远段蔚平杨强胜邱宇(中钢集团马鞍山矿山研究总院股份有限公司)摘要随着工程建设的发展以及科学技术的进步，对工程的研究由传统的二维逐渐转向三维，计算机技术的成熟为复杂地质体的三维研究提供了可能性。

通过建模软件建立矿坑三维模型，将模型导入FLAC3d可以对模型进行三维应力和变形分析。

基于CAD—3Dmine—Rhino—FLAC3d的建模思路建立复杂矿坑的三维模型，避开了FLAC3d前处理功能弱的缺点。

预计在矿坑内部充填110m高尾砂，在模拟尾砂分级加载的条件下，对矿坑进行三维应力和位移分析。

关键词FLAC3d软件三维建模应力一位移分析D0I：10.3969/j.issn.1674-6082.2021.05.026FLAC3D Three-dimensional Modeling of Complex Mine and its ApplicationMAO Zhiyuan DUAN Weiping YANG Qiangsheng QIU Yu1(Sinosteel Maanshan General Institute of Mining Research Co.，Ltd.)Abstract With the development of engineering construction and the progress of science and technol-ogy，the research on engineering has gradually shifted from the traditional two-dimensional to three-dimensional.The maturity of computer technology provides the possibility for the three-dimensional research of complex geological bodies.The three-dimensional model of the mine pit is established through modeling software,and the model can be imported into FLAC3D to analyze the three-dimensional stress and deformation of the model.Based on the modeling idea of CAD-3Dmine-Rhino-FLAC3D,the three-dimensional model of complex mines is established，which avoids the weak pre-processing function of FLAC3D.It is expected to fill110m high tailings in the pit，and carry out three-dimensional stress and displacement analysis of the pit under the condition of simulated tailings grading loading.Keywords FLAC3D software，three-dimensional modeling，stress-displacement analysis随着工程建设的发展以及科学技术的进步，对工程的研究由传统的二维研究逐渐向三维研究过渡°FLAC(Fast Langrangian of Continua)1］是由Itasca 提出的连续介质力学分析软件。

求解三维装箱问题的混合模拟退火算法

万方数据
１１期
张德富等：求解三维装箱问题的混合模拟退火算法
２１４９
为了能容纳不同种类的箱子，复合块可以包含少量不影响装载的空隙．复合块的引入使得每次装载可选择的块数目增多，也使每次装载的块的箱子体积和增大，加快了装载的速度，也极大提升了算法的效率．
（２）启发式装载算法．该算法接受一个装载序列作为输入，用以指导装载过程中的块选择．装载序列是一个向量，它的每一个元素对应装载阶段的一个选择．具体地说，基础启发式算法在每个装载阶段按照当前剩余空间计算出按箱子体积降序排列的可行块列表，然后按照装载序列来选择采用的装载块，然后将未填充空间重新切割以便下一步装载．通过这种方式，我们可以建立装载序列和放置方案之间的映射，进而使用模拟退火算法进行放置方案的优化．２．１数据结构
导师。主要研究领域为计算智能以及组合优化．１垂丕垂Ｉ，男，１９３６年生，博七生导师。中国丁程院院上，主要研究领域为人丁智能．
万方数据
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１引言
装箱问题在切割加工业和运输业中有许多应用．高利用率的切割和装载可以节约相当大的成本．一个好的装箱问题求解算法在减少损耗，节约天然资源方面起到重要的作用．实际应用中的装箱问题有不同的优化目标和装载约束，这导致了不同种类的装箱问题．Ｄｙｃｋｈｏｆｆ和ＦｉｎｋｅＬ１ｏ概述了不同类型的装箱问题及相关的切割问题．本文所处理的三维装箱问题属于装箱问题中的一类，可以形式化定义如下：
给定一个容器（其体积为Ｖ）和一系列待装载的箱子，容器和箱子的形状都是长方体．问题的目标是要确定一个可行的箱子放置方案使得在满足给定装载约束的情况下，容器中包含的箱子总体积Ｓ尽可能的大，即填充率尽可能的大，这里填充率指的是Ｓ／Ｖ＊１００％．可行放置方案要求放置满足如下３个条件：

Computer simulation

Computer simulationA computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system. Computer simulations have become a useful part of mathematical modeling of many natural systems in physics (computational physics), astrophysics, chemistry and biology, human systems in economics, psychology, social science, and engineering. Simulations can be used to explore and gain new insights into new technology, and to estimate the performance of systems too complex for analytical solutions.Computer simulations vary from computer programs that run a few minutes, to network-based groups of computers running for hours, to ongoing simulations that run for days. The scale of events being simulated by computer simulations has far exceeded anything possible (or perhaps even imaginable) using the traditional paper-and-pencil mathematical modeling. Over 10 years ago, a desert-battle simulation, of one force invading another, involved the modeling of 66,239 tanks, trucks and other vehicles on simulated terrain around Kuwait, using multiple supercomputers in the DoD High Performance Computer Modernization Program;a 1-billion-atom model of material deformation (2002); a 2.64-million-atom model of the complex maker of protein in all organisms, a ribosome, in 2005;[3] and the Blue Brain project at EPFL (Switzerland), began in May 2005, to create the first computer simulation of the entire human brain, right down to the molecular level.[Simulation versus modelingTraditionally, forming large models of systems has been via a mathematical model, which attempts to find analytical solutions to problems and thereby enable the prediction of the behavior of the system from a set of parameters and initial conditions.While computer simulations might use some algorithms from purely mathematical models, computers can combine simulations with reality or actual events, such as generating input responses, to simulate test subjects who are no longer present.Whereas the missing test subjects are being modeled/simulated, the system they use could be the actual equipment, revealing performance limits or defects in long-term use by these simulated users.Note that the term computer simulation is broader than computer modeling, which implies that all aspects are being modeled in the computer representation. However, computer simulation also includes generating inputs from simulated users to run actual computer software or equipment, with only part of the system being modeled: an example would be flight simulators which can run machines as well as actual flight software.Computer simulations are used in many fields, including science, technology, entertainment, health care, and business planning and puter simulation was developed hand-in-hand with the rapid growth of the computer, following its first large-scale deployment during the Manhattan Project in World War II to model the process of nuclear detonation. It was a simulation of 12 hard spheres using a Monte Carlo algorithm. Computer simulation is often used as an adjunct to, or substitution for, modeling systems for which simple closed form analytic solutions are not possible. There are many different types of computer simulations; the common feature they all share is the attempt to generate a sample of representative scenarios for a model in which a complete enumeration of all possible states of the model would be prohibitive or impossible. Computer models were initially used as a supplement for other arguments, but their use later became rather widespread.Computer simulation in scienceComputer simulation of the process of osmosisGeneric examples of types of computer simulations in science, which are derived from an underlying mathematical description:a numerical simulation of differential equations which cannot be solved analytically, theories which involve continuous systems such as phenomena in physical cosmology, fluid dynamics (e.g. climate models, roadway noise models, roadway air dispersion models), continuummechanics and chemical kinetics fall into this category.a stochastic simulation, typically used for discrete systems where events occur probabilistically, and which cannot be described directly with differential equations (this is a discrete simulation in the above sense). Phenomena in this category include genetic drift, biochemical or gene regulatory networks with small numbers of molecules. (see also: Monte Carlo method).Specific examples of computer simulations follow:statistical simulations based upon an agglomeration of a large number of input profiles, such as the forecasting of equilibrium temperature of receiving waters, allowing the gamut of meteorological data to be input for a specific locale. This technique was developed for thermal pollution forecasting .agent based simulation has been used effectively in ecology, where it is often called individual based modeling and has been used in situations for which individual variability in the agents cannot be neglected, such as population dynamics of salmon and trout (most purely mathematical models assume all trout behave identically).time stepped dynamic model. In hydrology there are several such hydrology transport models such as the SWMM and DSSAM Models developed by the U.S. Environmental Protection Agency for river water quality puter simulations have also been used to formally model theories of human cognition and performance, e.g. ACT-Rcomputer simulation using molecular modeling for drug puter simulation for studying the selective sensitivity of bonds by mechanochemistry during grinding of organic molecules.]Computational fluid dynamics simulations are used to simulate the behaviour of flowing air, water and other fluids. There are one-, two- and three- dimensional models used. A one dimensional model might simulate the effects of water hammer in a pipe. A two-dimensional model might be used to simulate the drag forces on the cross-section of an aeroplane wing. A three-dimensional simulation might estimate the heating and cooling requirements of a large building.An understanding of statistical thermodynamic molecular theory is fundamental to the appreciation of molecular solutions. Development of the Potential Distribution Theorem (PDT) allows one to simplify this complex subject to down-to-earth presentations of molecular theory.Notable, and sometimes controversial, computer simulations used in scienceinclude: Donella Meadows' World3 used in the Limits to Growth, James Lovelock's Daisyworld and Thomas Ray's puter simulation in practical contexts.Smog around Karl Marx Stadt (Chemnitz), Germany: computer simulation in 1990Computer simulations are used in a wide variety of practical contexts, such as:analysis of air pollutant dispersion using atmospheric dispersion modelingdesign of complex systems such as aircraft and also logistics systems.design of Noise barriers to effect roadway noise mitigation.flight simulators to train pilots.weather forecasting.Simulation of other computers is emulation..forecasting of prices on financial markets (for example Adaptive Modeler).behavior of structures (such as buildings and industrial parts) under stress and other conditions.design of industrial processes, such as chemical processing plants.Strategic Management and Organizational Studies.Reservoir simulation for the petroleum engineering to model the subsurface reservoir.Process Engineering Simulation tools.Robot simulators for the design of robots and robot control algorithms.Urban Simulation Models that simulate dynamic patterns of urban development and responses to urban land use and transportation policies. See a more detailed article on Urban Environment Simulation.Traffic engineering to plan or redesign parts of the street network from single junctions over cities to a national highway network, for transportation system planning, design and operations. See a more detailed article on Simulation in Transportation.modeling car crashes to test safety mechanisms in new vehicle modelsThe reliability and the trust people put in computer simulations depends on the validity of the simulation model, therefore verification and validation are of crucial importance in the development of computer simulations. Another important aspect of computer simulations is that of reproducibility of the results, meaning that a simulation model should not provide a different answer for each execution. Although this might seem obvious, this is a special point of attention in stochastic simulations, where random numbers should actually be semi-random numbers. An exception to reproducibility are human in the loop simulations such as flight simulations and computer games. Here a human is part of the simulation and thus influences the outcome in a way that is hard if not impossible to reproduce exactly.Vehicle manufacturers make use of computer simulation to test safety features in new designs. By building a copy of the car in a physics simulation environment, they can save the hundreds of thousands of dollars that would otherwise be required to build a unique prototype and test it. Engineers can step through the simulation milliseconds at a time to determine the exact stresses being put upon each section of the prototype.[7]Computer graphics can be used to display the results of a computer simulation. Animations can be used to experience a simulation in real-time e.g. in training simulations. In some cases animations may also be useful in faster than real-time or even slower than real-time modes. For example, faster than real-time animations can be useful in visualizing the buildup of queues in the simulation of humans evacuating a building. Furthermore, simulation results are often aggregated into static images using various ways of scientific visualization.In debugging, simulating a program execution under test (rather than executing natively) can detect far more errors than the hardware itself can detect and, at the same time, log useful debugging information such as instruction trace, memory alterations and instruction counts. This technique can also detect buffer overflow and similar "hard to detect" errors as well as produce performance information and tuning data.。

职业女装有三种基本类型

职业女装有‎三种基本类‎型职业女装包‎括西服套裙‎、夹克衫或不‎成型的上衣‎，以及连衣裙‎或两件套裙‎。

在这三种类‎型中，每一种都要‎考虑其颜色‎和面料。

而西服套裙‎是女性的标‎准职业着装‎，可塑造出强‎有力的形象‎。

单排扣上衣‎可以不系扣‎，双排扣的则‎应一直系着‎（包括内侧的‎纽扣）。

穿单色的套‎裙能使身材‎显得瘦高一‎些。

套裙分两种‎：配套的，其上衣和裙‎子同色同料‎；不配套的，其上衣与裙‎子存在差异‎。

颜色的选择‎：职业套裙的‎最佳颜色是‎黑色、藏青色、灰褐色、灰色和暗红‎色。

精致的方格‎、印花和条纹‎也可以接受‎。

买红色、黄色或淡紫‎色的两件套‎裙要小心，因为它们的‎颜色过于抢‎眼。

Profe‎s sion‎a l women‎'s suit jacke‎t, inclu‎d ing a dress‎or not formi‎n g coat, and dress‎or two dress‎.In these‎three‎types‎, each of which‎type shoul‎d consi‎d er its color‎and fabri‎c s.And the women‎dress‎suit is stand‎a rd busin‎e ss dress‎i ng, which‎can creat‎e a power‎f ul image‎.Butto‎n s can not coat butto‎n s, doubl‎e-breas‎t ed shoul‎d be has been tied with a (inclu‎d ing the insid‎e of the butto‎n).Weari‎n g monoc‎h rome‎dress‎can make you look like talle‎r than befor‎e.Dress‎incul‎e d two tyoes‎:the form a compl‎e te set, the same color‎skirt‎and blous‎e with mater‎i al; Don't match‎, the jacke‎t and dress‎in diffe‎r ent ways.The choic‎e of the color‎of: the best profe‎s sion‎a l dress‎color‎is black‎, navy, beige‎, gray and dark red.Delic‎a te box, print‎i ng and strip‎e s are also accep‎t able‎.Buyin‎g red, yello‎w or light‎purpl‎e two dress‎to be caref‎u l, becau‎s e they color‎too grab an eye.女士职业装‎面料与款式‎介绍我们公司的‎女装面料选‎用进口毛涤‎高支纱工作‎服面料和进‎口羊毛高支‎纱面料为主‎，下面，就由我跟大‎家介绍女士‎职业装面料‎与款式介绍‎：进口毛涤高‎支纱工作服‎面料在后整‎理工序中的‎梳理工艺处‎理得很先进‎，所以面料手‎感柔软，但成衣挺括‎，是目前高价‎位职业装的‎理想面料。

CAD软件在工程地质三维建模中的应用

Journal of Engineering Geology工程地质学报1004-9665/2007/15（02）-0279-05CAD软件在工程地质三维建模中的应用!徐文杰!胡瑞林!李厚恩!李新华"李壮举#（!中国科学院工程地质力学重点实验室北京100029）（"浙江省工程勘察院宁波315012）（#北京双圆工程咨询监理有限公司北京100022）摘要如何快速、准确地建立地质体的三维模型一直是众多岩土工程数值模拟工作者所面临的难题。

虽然三维地学模拟软件具有很好的三维地质建模能力，但是由于数据结构的差异，采用他们现行三维地学模拟软件建立的地质模型难以导入数值模拟分析软件中，以为相应工程问题的数值模拟服务。

目前，随着各种CAD、CAM软件行业的的飞速发展，涌现出了许多优秀的三维建模软件，而且这些软件大都与现行数值分析软件有着良好的数据接口功能。

据此，本文提出了采用现行CAD软件来建立工程地质体的三维模型，使得建立的模型达到既"可视"又"可算"的目的。

将其应用于云南某高速公路边坡的三维建模中，证明了该法具有方便、快捷和合理等优点。

关键词三维建模数值模拟工程地质CAD软件中图分类号：P642 文献标识码：AAPPLICATION OF CAD SOFTWARE IN3D MODELING OF ENGINEERING GEOLOGYXU Wenjie!HU Ruiiin!LI Houen!LI Xinhua"LI Zhuangju#（!Key Laboratory of Engineering Geo-mechanics，Chinese Academy of Sciences，Beijing100029）（"Zhejiang Engineering Prospecting Institute，Ningbo315012）（#Beijing Shuang Yuan Engineering Consultation and surueillance CO.Ltd，Beijing100022）Abstract How to buiid the three dimensionai modei of the geoiogic body guicliy and truiy is a difficuit probiem which iies in the front of the numericai simuiation operators.Aithough the three-dimensionai（3D）geoscience simuiation software has good3D geoiogicai modeiiing abiiity，it can be difficuit to join the corresponding geoiogicai modei estabiished by3D study simuiation software with numericai simuiation software because of the difference in data structures.A majority of CAD software have good data connection with the present numericai anaiysis software. This paper presents a study on how to use CAD software to estabiish3D geoiogicai modei for3D visuaiization and numericai simuiation purposes.The3D modeiing of some highway siopes in Yunnan is used an exampies to iiius-trate this approach is convenient，accurate and reasonabie.Key words3D modeiing，Numericai simuiation，Engineering geoiogy，CAD software!收稿日期：2006-02-24；收到修改稿日期：2006-05-12.基金项目：国家重点基础研究发展规划项目973（NO.2002CB412702）；中国科学院知识创新工程项目（NO.KZCX3-SW-134）.第一作者简介：徐文杰（1978-），男，博士，地质工程专业.Emaii：xwjwy@l引言工程地质体的稳定性分析及其灾害过程研究问题通常是一个非常复杂的地质力学问题。

液态金属超弹纤维应变传感器的制备及其性能研究

液态金属超弹纤维传感器的传感机理主要运用了纤维在变形的过程中，液态金属通道形状随之产
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现代丝綢蚪学与技术
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纤维与液态金属间良好的机械匹配性。此外我们对纤维进行了 1 〇〇〇次〇 %〜2 5 0 % 应变变形的拉伸回复循环，记录其电阻变化 .以展示传感器的耐用性，结果如图 7 所示。可见纤维在 1 0 0 0 次循环中，比电阻变化均保持在一个非常稳定的范围之内，显示了液态金属超弹纤维作为应变传感器出色的稳定性和可靠性。
图 3 为本文制备的超弹纤维的机械性能表征, 其中 a 曲线为实心纤维的应力-应变曲线，b 曲线为
(a)
(b)
图 2 —卷液态金属超弹纤维的数码照片及其截面 S E M 图像
带有液态金属通道纤相同的直径。由图可见，该超弹纤维具有极
图 6 显示的是传感器的电阻与纤维拉伸应变的测试结果 .在 5 个循环内，电阻对拉伸应变表现出良好的依赖性和及时性。可见该液态金属超弹纤维传感器拥有十分优秀的快速响应特性，同时也显示了
本文通过 “预制件 -热拉伸 ”法以液态金属和 S E B S 橡胶为原料，制备了一种液态金属超弹纤维，

三相交流电路模拟分析与应用 - Multisim 10 软件说明书

Simulation Analysis and Application of Three-Phase Alternating Circuits byMultisim 10 SoftwareFang LeiSchool of Electrical Engineering and InformationChangchun Institute of Technology Changchun, China , 130012 Zheng Wen , Zhang JianhongSchool of Electrical Engineering and InformationChangchun Institute of Technology Changchun, China , 130012Abstract —The paper introduces simulation analysis and application of three-phase alternating current circuit by Multisim 10 software. As a well-known software in circuit simulation analysis, Multisim shows many advantages, such as friendly user interface, powerful functions and easily to operate. The paper takes several examples using Multisim software on application of three phase alternating circuit, and its visualization provides very good practical effects.Keywords- Simulation analysis; Three-Phase alternating circuits; Multisim10 softwareI. I NTRODUCTIONMultisim 10 offers many visual components to utilize simulation to produce the data for the analysis we want to perform. These analyses can range from quite basic to extremely sophisticated, and can often require one analysis to be performed (automatically) as part of another. II.S IMULATION A NALYSES OF T HREE -P HASE C IRCUITSF EATUREA. Creation of three-phase A.C. sourcesThree-phase circuits must involve three-phase A.C. sources. We can only consider a balanced three-phase source, which consists of three sinusoidal voltages that have identical amplitudes and frequencies but are out of phase with each other by exactly 120. [1]We can use three single-phase A.C. sources to combine a balanced three-phase source by Multisim 10 software as shown in Fig.1. This is also replaced by three-phase voltage source as shown inFig.2.Figure 1.Combined three-phase A.C. sourceFigure 2. Three-phase A.C. sourceB. Determination of phase sequenceIn some cases it is necessary to identify phase sequence for three-phase A.C. source. Only two possible phase relationships can exist between the a-phase and b-phase and c-voltages. One possible phase sequence is for the b-phase voltage to lag the a-phase voltage by 120, in which case c-phase voltage must lead the a-phase voltage by 120. This phase relationship is known as the abc or positive phase sequence. Adversely, b-phase voltage leads the a-phase voltage by 120, in which case the c-phase voltage must lagthe a-phase voltage by 120.This phase relationship is known as the acb or negative phase sequence.[2] To determine an unknown phase sequence of three- phase source, a capacitor with set value is connected to the a-phase with two sets of bulbs connected to b-phase and c-phase. Compared with their luminance of the two sets of bulbs, we judge which phase is b- or c-phase.Using Simulink 10 software, create a model to simulate the circuit as shown in Fig.3.Figure 3. Determination of phase sequence for three-phase sourceThe simulate result shows the phase with more brilliant light is b-phase and the rest phase is c-phase.C. Analysis of three-phase A. C. circuit features on load There are two ways of interconnecting three-phase load which is either a wye(Y) or a delta (Δ). Fig.4 shows simulation circuit of three-phase balanced loads with each phase two lamps series connection in a wye configuration with neutral conductor. The simulation circuit of three-phase balanced or unbalanced loads (Δconnected) with two or more lamps series connection is shown in Figure5.Figure 4. Simulation circuit of three-phase balanced loads in a wyeconfiguration with neutral conductorFigure 5. Simulation circuit of three-phase balanced loads in a deltaconfiguration with neutral conductorThe simulation results of three-phase balanced or unbalanced loads (Y-connected) with two or more lamps series connection in the case of connection and disconnection of neutral conductor show as follows below in Table.1(see page 3). According to these simulation data, we derive that in these cases each line-to-line voltage is balanced with neutral conductor or without neutral conductor , line-to-neutral voltage and current are balanced with neutral conductor, the magnitude of the line-to-line voltage is √3 times the magnitude of the line-to-neutral voltage and neutral node without neutral conductor is offset in the case of unbalanced loads.The simulation results of three-phase balanced or unbalanced loads (Δ-connected) with three or more lamps series connection is shown in Table.2. (see page 3). From simulation result, we derive that line voltage, line current and phase current are balanced when loads are balanced, and the magnitude of line current is √3 times the magnitude of the phase current, and line current and phase current are unbalanced in the case of unbalanced loads.Thus, there are many three-phase AC circuits models built by multisim 10 in order to perform the result same as the real experiment.D. Measurement of three-phase powerWe measure total three-phase power by three power meters means which is shown in Fig6. After assuming motor parameter R1,R2 and R3 as 200, the sum of three power meter shown is 726.111, which is 3 times the show data of single power meter. Two- meters method can be used in some cases. We select three-phase motor as load shown in Fig.7. When the simulation switch button closes, the analysis is run and we read the data from power meter. The sum of data two meter shown is 726.09W, which is the total power consumed by three-phase motor and power factor of three-phase motor is 0.867 [3].Above two methods both adapt for measuring the total power of three-phase circuits. The three-phase motor can be replaced by other loads.Figure 6. Three-meters method for measurement of three-phase powerFigure 7. Two-meters method for measurement of three-phase powerIII.S UMMARIESMultisim 10 simulation software on computer can provide the all kinds of design models to achieve test data and test images for principle experiments and expanded experiments. In addition to get the correct results，it can also be used for development and study of the experiment. The simulation results can determine whether the circuit design to achieve the desired goal to improve the students the analysis and solving problem skills. Meanwhile, Multisim 10 simulation software using computer as an experiment platform for different types of experiments, the laboratory can decrease the costs for construction and consumed raw materials and increase the operating efficiency because the components and apparatus used in the experiments are not limited..TABLE I. S IMULATION DATA FOR THREE-PHASE LOADS(Y- CONNECTED)With neutral conduct-or Lamps connectionmodeU AB(V)U BC(V)U CA(V)U A(V)U B(V)U C(V)I A(A)I B(A)I C(A)I N(A)U NN′(V) Each phase with twolamps seriesconnection381 381 381 220 220 220 0.764 0.764 0.764 0 \Phases with two-three-two seriesconnection381 381 381 220 220 220 0.764 0.509 0.764 0.255 \A-phase is brokenunder abovecondition381 381 381 220 220 220 0 0.509 0.764 0.674 \With no neutral conduct-or Each phase with twolamps seriesconnection381 381 381 220 220 220 0.764 0.764 0.764 \ 0Phases with two-three-four seriesconnection381 381 381 178.3 232.6 255.5 0.619 0.538 0.444 \ 0.019A-phase is brokenunder abovecondition381 381 381 331.1 163.3 217.7 0 0.378 0.378 \ 113.3A-phase is short(same as abovecondition)381 381 381 0 381 381 1.341 0.882 0.662 \ 220TABLE II. S IMULATION DATA FOR THREE-PHASE LOADS(Δ-CONNECTED)Lamps connection mode U AB(V)U BC(V)U CA(V)I A(V)I B(V)I C(V)I AB(A)I BC(A)I CA(A)Each phasewith threelamps seriesconnection380.998 380.998 380.995 1.528 1.528 1.528 0.882 0.882 0.882Phases withthree-four-three seriesconnection381.031 380.989 380.992 1.528 1.341 1.341 0.882 0.661 0.882Phases withfour-three-four seriesconnection381.031 381.020 381.024 1.146 1.341 1.341 0.662 0.882 0.662R EFERENCES[1]James W. Nilsson; Susan A. Riedel. Introductory Circuits forElectrical and Computer Engineering, Publishing of Electronics Industry [M], 2002, PP:310-312[2]NI Dian; HUANG Pei-gong. Application of Multisim 10 in theDesign of Electronic Circuit ,Publishing of Electronics Industry[M], 2007. PP259-261. [3]National Instruments Corporation. Multisim 10 User Guide [M]2007.01, PP461-463。

数字化外科在正颌外科术前设计中的应用

数字化外科在正颌外科术前设计中的应用刘显文;艾伟健【摘要】正颌外科手术的成功不仅取决于术者的手术技巧，而且依赖于科学、正确的手术设计与计划。

数字化外科的应用极大地改变了正颌外科术前计划的模式。

与传统方法相比，数字化外科辅助的正颌外科术前设计与计划存在诸多不同，它免除了术前石膏模型外科并具有更高的板设计精确度的优势。

本文着重对应用数字化虚拟工具进行正颌外科术前设计的工作流程作一述评，以向临床上需要将数字化外科纳入正颌外科术前设计的外科医生提供虚拟手术操作流程参考。

【期刊名称】《口腔疾病防治》【年(卷),期】2018(026)011【总页数】7页(P1-7)【关键词】正颌外科;数字化外科;术前计划;虚拟骨切开;板设计【作者】刘显文;艾伟健【作者单位】南方医科大学口腔医院口腔颌面外科,广东广州510280;南方医科大学口腔医院口腔颌面外科,广东广州510280;【正文语种】中文【中图分类】R数字化外科学（digital surgery）是一门融合了外科学、图形图像处理、三维重建、计算机辅助设计、计算机辅助制造、快速成形技术、反求技术、外科导航技术等多种先进技术的交叉学科，其可以为临床医师提供三维实物模型，术前进行可视化手术设计和模拟，协助制作复杂手术方案，术中导航精确实现术前设计，术后量化评估手术效果［1］。

近年来数字化外科技术在国内外得到了迅速的发展和应用，本文针对其在口腔颌面外科的分支学科—正颌外科中的发展与应用作一述评。

1 数字化外科在正颌外科中的发展应用近30年以来，正颌外科已经发展成为治疗牙颌面畸形的一项成熟而安全的外科技术［2⁃4］。

传统的正颌外科通过临床体检、头影测量分析、石膏模型外科等步骤制作板用作术中导航，其缺点主要是由于头影测量分析是二维图像，因此，基于对头影描迹图的裁剪、移动、和拼对难以模拟颌骨在三维空间的移动；另外，模型外科技术需要先用面弓转移关系到架上，继而对牙颌模型进行移动、切割和拼对，步骤繁琐，易于产生误差［5］。

计算机网络(第4版)习题答桉(中文版)

ANDREW S. TANENBAUM COMPUTER NETWORKSFOURTH EDITIONPROBLEM SOLUTIONS第 1 章概述1. 答：狗能携带21千兆字节或者168千兆位的数据。

18 公里/小时的速度等于0.005 公里/秒，走过x公里的时间为x / 0.005 = 200x秒，产生的数据传输速度为168/200x Gbps或者840 /x Mbps。

因此，与通信线路相比较，若x<5.6 公里，狗有更高的速度。

2. 使用局域网模型可以容易地增加节点。

如果局域网只是一条长的电缆，且不会因个别的失效而崩溃( 例如采用镜像服务器)的情况下，使用局域网模型会更便宜。

使用局域网可提供更多的计算能力和更好交互式接口。

3. 答：横贯大陆的光纤连接可以有很多千兆位/秒带宽，但是由于光速度传送要越过数千公里，时延将也高。

相反，使用56 kbps调制解调器呼叫在同一大楼内的计算机则有低带宽和较低的时延。

4. 声音的传输需要相应的固定时间，因此网络时隙数量是很重要的。

传输时间可以用标准偏差方式表示。

实际上，短延迟但是大变化性比更长的延迟和低变化性更糟。

5. 答：不，传送.速度为200,000 公里/秒或200米/ 微秒。

信号在10微秒中传送了2千米，每个交换机相当于增加额外的2 公里电缆。

如果客户和服务器之间的距离为5000 公里，平均通过50个交换机给那些总道路只增加100 公里，只是2%。

因此，交换延迟不是这些情形中的主要因素。

6. 答：由于请求和应答都必须通过卫星，因此传输总路径长度为160,000千米。

在空气和真空中的光速为300，000 公里/秒，因此最佳的传播延迟为160,000/300，000秒，约533 msec。

7. 显而易见，在这里没有正确的独立的答案。

但下列问题好像相关：目前的系统有它的很多惯性(检测和平衡)。

当新的团体掌握权力的时候，这惯性可保持法律、经济和社会制度的稳定。