Models for Structuring Convention Visitors Bureau 城市会议局的设立模式
AEC英国bim标准 v2.0v版
General Naming Conventions Model File Naming Division Naming Library Object Naming Object Property Naming View Naming View List Scheduling Data Organisation Sheet Naming Introduction AEC (UK) Compliant Materials Annotation Text Assignment Line Weights Line Patterns Line Styles Hatching and Filled Regions View Templates Dimensioning Drawing borders and Titleblocks Symbols Copyright Introduction Software BIM Content / Resource Libraries Keynotes Custom metadata Keyboard Shortcuts Model File Naming Codes Project Folder Structure
LS-DYNA混凝土本构模型的性能 Performance of LS-DYNA Concrete Constitutive Models
(1)
where I1 is the 1st invariant of stress tensor, which represents volumetric responses; J 2 and J 3 are the 2nd and 3rd invariants of deviatoric stress tensor and they account for deviatoric responses. In general, the primary difference between various concrete constitutive models is how the deviatoric and volumetric responses are characterized. 2.1. Karagozian & Case Concrete (KCC) Model – MAT072 Intended for analyzing RC structural responses to blast and impact loadings, the KCC model was initially developed in early 1990s in DYNA3D and was ported to LS-DYNA in 2004. This model allows automatic generation of all the parameters by inputting only the unconfined compressive strength and density of the concrete. It has been applied in analyzing many RC structures subjected to quasi-static, blast, and impact loads [5, 9, 10]. A comprehensive model review and validation application is provided in Reference [11]. The KCC model has three independent strength surfaces and they can be formulated in a generalized form as:
达芬奇DAQNavi SDK软件开发包说明书
FeaturesDAQNavi/SDKSoftware Development Package for Advantech DAQ Products IntroductionDAQNavi is a comprehensive software package, for programmers to develop their application programs using Advantech DAQ boards or devices. This integrated software package includes drivers, SDK, tutorial and utility. With the user-friendly design, even the beginner can quickly get familiar with how to utilize DAQ hardware and write programs through the intuitive "Advantech Navigator" utility environment. Many example codes for different development environment dramatically decrease users’ programming time and effort. You can go to /daqnavi for more information about Advantech DAQNavi.Feature DetailsMultiple Operating System SupportDAQNavi supports many popular operating systems (OS) used in automation applications. For different OSs, API functions will be the same, so users can simply install the driver without modifying their program again when migrating between two different OSs. DAQNavi supports latest Windows system up to Windows 10. (both 32-bit and 64-bit). Besides Windows operating system, Linux is famous for its openness and flexibility. DAQNavi software package also supports Linux OS distributions including Ubuntu, Fedora, Debian and, Redhat. For other distributions, please contact Advantech local branch/support for more information..NET SupportDAQNavi offers a series of .NET Component objects, that you can benefit from platform-unified feature with the latest .NET technology. Users can simply drag and drop the .NET Components within .NET programming environment, such as Microsoft Visual C# and VB .NET. An intuitive window (called "DAQNavi Wizard") will pop-up, and user can perform all configurations by sequence. Programmers also can choose writing code manually with the .NET Component, to have a more flexible object calling. With Advantech CSCL technology, engineers can do the similar programming in Native environment such as Visual C++.LabVIEW SupportLabVIEW is one popular graphical development environment used for measurement and automation. For LabVIEW user, DAQNavi offer two options for programming: Express VI and Polymorphic VI. DAQNavi Express VI for LabVIEW helps user quickly complete his LabVIEW without extra wiring. When the user drags the Express VI on LabVIEW Block Diagram, a pop-up intuitive wizard window will appear and user can perform hardware parameter configurations. After that, the programming is done. So it is similar to the .NET control used in Microsoft Visual Studio environment, suitable for programming beginners. As for the Polymorphic VI, users can use several VIs and wiring to build more complex program.C/C++, Qt, ActiveX and Java SupportDAQNavi also offers C++ Class Library (for VC++ and Borland C++ Builder) and ActiveX (for Visual Basic, Delphi and BCB) for Native programming environment with the same calling interface as .NET Class Library. With DAQNavi Java Class Library, user can develop Java program to across different platforms (including Windows and Linux) by means of Java engine.Device SupportDAQNavi supports all Advantech PCI Express, PCI, PC-104, and PCI-104 cards, as well as all USB DAQ devices.Intuitive UtilityDAQNavi delivers one integrated easy-to-use and powerful utility, called Advantech Navigator. Within the Navigator, engineers can quickly start configuration and function testing for all Advantech DAQ devices, without any programming. Related user manuals are also displayed in the same environment. Besides, to help shorten development time, Advantech offers a series of DAQ applications examples (called "scenarios" in the Advantech Navigator). So programmers can refer to its source code and develop their application based on it, as well as the wiring information. Without a DAQ device at hand, engineers can generate a simulated device and use that device for programming and testing. Except for device testing, Navigator also offers complete documentation to describe how to use DAQNavi SDK to program in various development environments. Moreover, video tutorials for how to create applications in different development environments are available.Supports multiple operating systems including Windows (32-bit and 64-bit), LinuxSupports common-used development environment including Visual C/C++, Borland C Builder, Visual Basic .NET, Visual C#, Delphi, Java, VB, LabVIEW Supports Advantech PCI Express, PCI, PC/104, PCI-104, USB DAQ devices Integrated utility environment (Advantech Navigator) for device functionality testing without programmingAble to generate a simulator device in utility to program and run application without real hardware devicePre-defined scenario application examples with source code to shorten programming learning and development timeExpress VI and Polymorphic VIs for both beginner and advanced programming in LabVIEW environmentComprehensive documentations and tutorials for hardware specifications,wiring, example code and SDK programmingAll product specifications are subject to change without st updated: 20-Mar-2020。
商务英语翻译 Unit 9
译文：毫无疑问，我们还必须作出更大的努力来对抗全 球变暖的威胁，这个威胁最能清楚地体现各国的 命运是如何紧紧相连的。
5. This Contract is made by and between the Buyer and the Seller, whereby the Buyer agrees to buy and the Seller agrees to sell the under-mentioned commodity according to the terms and conditions stipulated below. 译文：买卖双方同意按下列条款购买、出售下述商品， 并签订本合同。（reduction)
John… preached the baptism of repentance unto the forgiveness of sins.
John preached the message to the people; John baptized the people; The people repented of their sins; God forgave the people their sins; The people sinned. John preached that the people should repent and be baptized so that god would forgive the evil they had done. John preached, ―Repent and be baptized so that God will forgive the evil you have done.‖
译文：我的母亲简· 兰普顿· 克莱门斯88岁才去世。这对于 一位40岁就身体虚弱、被认为痼疾缠身、注定不久于 世的人来说，是难得的高龄。
SOLID MODELING翻译
SOLID MODELING实体造型6.1 Application of Solid Models实体模型的应用In mechanical engineering, a solid model is used for the following applications:在机械工程中，一个实体模型被用于以下应用：1、Graphics: generating drawings, surface and solid models图形：生成图纸，表面和实体模型2、Design: Mass property calculation, interference analysis, finite element modeling, kinematics and mechanism analysis, animation, etc.设计：质量计算、干涉分析、有限元建模、运动学及机理分析、动画等。
3 、Manufacturing: Tool path generation and verification, process planning, dimension inspection, tolerance and surface finish.制造业：刀具轨迹的生成和验证，工艺设计，尺寸检验，公差及表面处理。
4 、Component Assembly: Application to robotics and flexible manufacturing: Assembly planning, vision algorithm, kinematics and dynamics driven by solid models.组件组装：应用于机器人和柔性制造：装配规划，视觉算法，运动学和动力学模型的驱动。
6.2 Solid Model Representation实体模型表示There are three different forms in which a solid model can be represented in CAD:有三种不同的形式，其中一个实体模型可以表示在计算机辅助设计：·Wireframe Model线架模型·Surface Model曲面模型·Solid Model实体模型Wireframe Models: Joining points and curves creates wireframe models. These models can be ambiguous and unable to provide mass property calculations, hidden surface removal, or generation of shaded images. Wireframe models are mainly used for a quick verification of design ideas.线框模型：连接点和曲线创建线框模型。
Engineering Viscoelasticity(工程粘弹性)
Figure 1: Temperature dependence of rate. Conversely, at temperatures much less than Tg , the rates are so slow as to be negligible. Here the chain uncoiling process is essentially “frozen out,” so the polymer is able to respond only by bond stretching. It now responds in a “glassy” manner, responding instantaneously 2
where E † is an apparent activation energy of the process and R = 8.314J/mol − ◦ K is the Gas Constant. At temperatures much above the “glass transition temperature,” labeled Tg in Fig. 1, the rates are so fast as to be essentially instantaneous, and the polymer acts in a rubbery manner in which it exhibits large, instantaneous, and fully reversible strains in response to an applied stress.
1
Introduction
This document is intended to outline an important aspect of the mechanical response of polymers and polymer-matrix composites: the field of linear viscoelasticity. The topics included here are aimed at providing an instructional introduction to this large and elegant subject, and should not be taken as a thorough or comprehensive treatment. The references appearing either as footnotes to the text or listed separately at the end of the notes should be consulted for more thorough coverage. Viscoelastic response is often used as a probe in polymer science, since it is sensitive to the material’s. The concepts and techniques presented here are important for this purpose, but the principal objective of this document is to demonstrate how linear viscoelasticity can be incorporated into the general theory of mechanics of materials, so that structures containing viscoelastic components can be designed and analyzed. While not all polymers are viscoelastic to any important practical extent, and even fewer are linearly viscoelastic1 , this theory provides a usable engineering approximation for many applications in polymer and composites engineering. Even in instances requiring more elaborate treatments, the linear viscoelastic theory is a useful starting point.
abaqus中UMAT子程序编写方法
UMATUser subroutine to define a material's mechanical behavior.Product: Abaqus/StandardWarning: The use of this subroutine generally requires considerable expertise. You are cautioned that the implementation of any realistic constitutive model requires extensive development and testing. Initial testing on a single-element model with prescribed traction loading is strongly recommended.References∙“User-defined mechanical material behavior,” Section 25.7.1 of the Abaqus Analysis User's Manual∙“User-defined thermal material behavior,” Section 25.7.2 of the Abaqus Analysis User's Manual∙*USER MATERIAL∙“SDVINI,” Section 4.1.11 of the Abaqus Verification Manual∙“UMAT and UHYPER,” Section 4.1.21 of the Abaqus Verification Manual OverviewUser subroutine UMAT:∙can be used to define the mechanical constitutive behavior of a material;∙will be called at all material calculation points of elements for which the material definition includes a user-defined materialbehavior;∙can be used with any procedure that includes mechanical behavior;∙can use solution-dependent state variables;∙must update the stresses and solution-dependent state variables to their values at the end of the increment for which it is called;∙must provide the material Jacobian matrix, , for the mechanical constitutive model;∙can be used in conjunction with user subroutine USDFLD to redefine any field variables before they are passed in; andis described further in “User-defined mechanical material behavior,” Section 25.7.1 of the Abaqus Analysis User's Manual. Storage of stress and strain componentsIn the stress and strain arrays and in the matrices DDSDDE, DDSDDT, and DRPLDE, direct components are stored first, followed by shear components. There are NDI direct and NSHR engineering shear components. The order of the components is defined in “Conventions,” Section 1.2.2 of the Abaqus Analysis User's Manual. Since the number of active stress and strain components varies between element types, the routine must be coded to provide for all element types with which it will be used.Defining local orientationsIf a local orientation (“Orientations,” Section 2.2.5 of the Abaqus Analysis User's Manual) is used at the same point as user subroutine UMAT, the stress and strain components will be in the local orientation; and, in the case of finite-strain analysis, the basis system in which stress and strain components are stored rotates with the material.StabilityYou should ensure that the integration scheme coded in this routine is stable—no direct provision is made to include a stability limit in the time stepping scheme based on the calculations in UMAT.Convergence rateDDSDDE and—for coupled temperature-displacement and coupledthermal-electrical-structural analyses—DDSDDT, DRPLDE, and DRPLDT must be defined accurately if rapid convergence of the overall Newton scheme is to be achieved. In most cases the accuracy of this definition is the most important factor governing the convergence rate. Since nonsymmetric equation solution is as much as four times as expensive as the corresponding symmetric system, if the constitutive Jacobian (DDSDDE) is only slightly nonsymmetric (for example, a frictional material with a small frictionangle), it may be less expensive computationally to use a symmetric approximation and accept a slower convergence rate.An incorrect definition of the material Jacobian affects only the convergence rate; the results (if obtained) are unaffected.Special considerations for various element typesThere are several special considerations that need to be noted. Availability of deformation gradientThe deformation gradient is available for solid (continuum) elements, membranes, and finite-strain shells (S3/S3R, S4, S4R, SAXs, and SAXAs). It is not available for beams or small-strain shells. It is stored as a3 × 3 matrix with component equivalence DFGRD0(I,J) . For fully integrated first-order isoparametric elements (4-node quadrilaterals in two dimensions and 8-node hexahedra in three dimensions) the selectively reduced integration technique is used (also known as the technique). Thus, a modified deformation gradientis passed into user subroutine UMAT. For more details, see “Solid isoparametric quadrilaterals and hexahedra,” Section 3.2.4 of the Abaqus Theory Manual.Beams and shells that calculate transverse shear energyIf user subroutine UMAT is used to describe the material of beams or shells that calculate transverse shear energy, you must specify the transverse shear stiffness as part of the beam or shell section definition to define the transverse shear behavior. See “Shell section behavior,” Section 28.6.4 of the Abaqus Analysis User's Manual, and “Choosing a beam element,” Section 28.3.3 of the Abaqus Analysis User's Manual, for information on specifying this stiffness.Open-section beam elementsWhen user subroutine UMAT is used to describe the material response of beams with open sections (for example, an I-section), the torsional stiffness is obtained aswhere J is the torsional constant, A is the section area, k is a shear factor, and is the user-specified transverse shear stiffness (see “Transverse shear stiffness definition” in “Choosing a beam element,” Section 28.3.3 of the Abaqus Analysis User's Manual).Elements with hourglassing modesIf this capability is used to describe the material of elements with hourglassing modes, you must define the hourglass stiffness factor for hourglass control based on the total stiffness approach as part of the element section definition. The hourglass stiffness factor is not required for enhanced hourglass control, but you can define a scaling factor for the stiffness associated with the drill degree of freedom (rotation about the surface normal). See “Section controls,” Section 26.1.4 of the Abaqus Analysis User's Manual, for information on specifying the stiffness factor.Pipe-soil interaction elementsThe constitutive behavior of the pipe-soil interaction elements (see “Pipe-soil interaction elements,” Section 31.12.1 of the Abaqus Analysis User's Manual) is defined by the force per unit length caused by relative displacement between two edges of the element. The relative-displacements are available as “strains” (STRAN and DSTRAN). The corresponding forces per unit length must be defined in the STRESS array. The Jacobian matrix defines the variation of force per unit length with respect to relative displacement.For two-dimensional elements two in-plane components of “stress” and “strain” exist (NTENS=NDI=2, and NSHR=0). For three-dimensional elements three components of “stress” and “strain” exist (NTENS=NDI=3, and NSHR=0).Large volume changes with geometric nonlinearityIf the material model allows large volume changes and geometric nonlinearity is considered, the exact definition of the consistent Jacobian should be used to ensure rapid convergence. These conditions are most commonly encountered when considering either large elastic strains or pressure-dependent plasticity. In the former case, total-form constitutive equations relating the Cauchy stress to the deformation gradient are commonly used; in the latter case, rate-form constitutive laws are generally used.For total-form constitutive laws, the exact consistent Jacobian is defined through the variation in Kirchhoff stress:Here, J is the determinant of the deformation gradient, is the Cauchy stress, is the virtual rate of deformation, and is the virtual spin tensor, defined asandFor rate-form constitutive laws, the exact consistent Jacobian is given byUse with incompressible elastic materialsFor user-defined incompressible elastic materials, user subroutine UHYPER should be used rather than user subroutine UMAT. In UMAT incompressible materials must be modeled via a penalty method; that is, you must ensure that a finite bulk modulus is used. The bulk modulus should be large enough to model incompressibility sufficiently but small enough to avoid loss of precision. As a general guideline, the bulk modulus should be about– times the shear modulus. The tangent bulk modulus can be calculated fromIf a hybrid element is used with user subroutine UMAT, Abaqus/Standard will replace the pressure stress calculated from your definition of STRESS with that derived from the Lagrange multiplier and will modify the Jacobian appropriately.For incompressible pressure-sensitive materials the element choice is particularly important when using user subroutine UMAT. In particular, first-order wedge elements should be avoided. For these elements the technique is not used to alter the deformation gradient that is passed into user subroutine UMAT, which increases the risk of volumetric locking.Increments for which only the Jacobian can be definedAbaqus/Standard passes zero strain increments into user subroutine UMAT to start the first increment of all the steps and all increments of steps for which you have suppressed extrapolation (see “Procedures: overview,” Section 6.1.1 of the Abaqus Analysis User's Manual). In this case you can define only the Jacobian (DDSDDE).Utility routinesSeveral utility routines may help in coding user subroutine UMAT. Their functions include determining stress invariants for a stress tensor and calculating principal values and directions for stress or strain tensors. These utility routines are discussed in detail in “Obtaining stress invariants, principal stress/strain values and directions, and rotating tensors in an Abaqus/Standard analysis,” Section 2.1.11.User subroutine interfaceSUBROUTINE UMAT(STRESS,STATEV,DDSDDE,SSE,SPD,SCD,1 RPL,DDSDDT,DRPLDE,DRPLDT,2 STRAN,DSTRAN,TIME,DTIME,TEMP,DTEMP,PREDEF,DPRED,CMNAME,3 NDI,NSHR,NTENS,NSTATV,PROPS,NPROPS,COORDS,DROT,PNEWDT,4 CELENT,DFGRD0,DFGRD1,NOEL,NPT,LAYER,KSPT,KSTEP,KINC)CINCLUDE 'ABA_PARAM.INC'CCHARACTER*80 CMNAMEDIMENSION STRESS(NTENS),STATEV(NSTATV),1 DDSDDE(NTENS,NTENS),DDSDDT(NTENS),DRPLDE(NTENS),2 STRAN(NTENS),DSTRAN(NTENS),TIME(2),PREDEF(1),DPRED(1),3 PROPS(NPROPS),COORDS(3),DROT(3,3),DFGRD0(3,3),DFGRD1(3,3)user coding to define DDSDDE, STRESS, STATEV, SSE, SPD, SCDand, if necessary, RPL, DDSDDT, DRPLDE, DRPLDT, PNEWDTRETURNENDVariables to be definedIn all situationsDDSDDE(NTENS,NTENS)Jacobian matrix of the constitutive model, , where are thestress increments and are the strain increments. DDSDDE(I,J) defines the change in the Ith stress component at the end of the time increment caused by an infinitesimal perturbation of the Jth component of the strain increment array. Unless you invoke the unsymmetric equation solution capability for the user-defined material, Abaqus/Standard will use only the symmetric part of DDSDDE. The symmetric part of the matrix is calculated by taking one half the sum of the matrix and its transpose.STRESS(NTENS)This array is passed in as the stress tensor at the beginning of the increment and must be updated in this routine to be the stress tensor at the end of the increment. If you specified initial stresses (“Initial conditions in Abaqus/Standard and Abaqus/Explicit,” Section 32.2.1 of the Abaqus Analysis User's Manual), this array will contain the initial stresses at the start of the analysis. The size of this array depends on the value of NTENS as defined below. In finite-strain problems the stress tensor has already been rotated to account for rigid body motion in theincrement before UMAT is called, so that only the corotational part of the stress integration should be done in UMAT. The measure of stress used is “true” (Cauchy) stress.STATEV(NSTATV)An array containing the solution-dependent state variables. These are passed in as the values at the beginning of the increment unless they are updated in user subroutines USDFLD or UEXPAN, in which case the updated values are passed in. In all cases STATEV must be returned as the values at the end of the increment. The size of the array is defined as described in “Allocating space” in “User subroutines: overview,” Section 17.1.1 of the Abaqus Analysis User's Manual.In finite-strain problems any vector-valued or tensor-valued state variables must be rotated to account for rigid body motion of the material, in addition to any update in the values associated with constitutive behavior. The rotation increment matrix, DROT, is provided for this purpose.SSE, SPD, SCDSpecific elastic strain energy, plastic dissipation, and “creep” dissipation, respectively. These are passed in as the values at the start of the increment and should be updated to the corresponding specific energy values at the end of the increment. They have no effect on the solution, except that they are used for energy output.Only in a fully coupled thermal-stress or a coupledthermal-electrical-structural analysisRPLVolumetric heat generation per unit time at the end of the increment caused by mechanical working of the material.DDSDDT(NTENS)Variation of the stress increments with respect to the temperature.DRPLDE(NTENS)Variation of RPL with respect to the strain increments.DRPLDTVariation of RPL with respect to the temperature.Only in a geostatic stress procedure or a coupled pore fluiddiffusion/stress analysis for pore pressure cohesive elementsRPLRPL is used to indicate whether or not a cohesive element is open to the tangential flow of pore fluid. Set RPL equal to 0 if there is no tangential flow; otherwise, assign a nonzero value to RPL if an element is open. Once opened, a cohesive element will remain open to the fluid flow.Variable that can be updatedPNEWDTRatio of suggested new time increment to the time increment being used (DTIME, see discussion later in this section). This variable allows you to provide input to the automatic time incrementation algorithms in Abaqus/Standard (if automatic time incrementation is chosen). For a quasi-static procedure the automatic time stepping that Abaqus/Standard uses, which is based on techniques for integrating standard creep laws (see “Quasi-static analysis,” Section 6.2.5 of the Abaqus Analysis User's Manual), cannot be controlled from within the UMAT subroutine.PNEWDT is set to a large value before each call to UMAT.If PNEWDT is redefined to be less than 1.0, Abaqus/Standard must abandon the time increment and attempt it again with a smaller time increment. The suggested new time increment provided to the automatic time integration algorithms is PNEWDT × DTIME, where t he PNEWDT used is the minimum value for all calls to user subroutines that allow redefinition of PNEWDT for this iteration.If PNEWDT is given a value that is greater than 1.0 for all calls to user subroutines for this iteration and the increment converges in this iteration, Abaqus/Standard may increase the time increment. The suggested new time increment provided to the automatic time integration algorithms is PNEWDT × DTIME, where the PNEWDT used is the minimum value for all calls to user subroutines for this iteration.If automatic time incrementation is not selected in the analysis procedure, values of PNEWDT that are greater than 1.0 will be ignored and values of PNEWDT that are less than 1.0 will cause the job to terminate.Variables passed in for informationSTRAN(NTENS)An array containing the total strains at the beginning of the increment. If thermal expansion is included in the same material definition, the strains passed into UMAT are the mechanical strains only (that is, the thermal strains computed based upon the thermal expansion coefficient have been subtracted from the total strains). These strains are available for output as the “elastic” strains.In finite-strain problems the strain components have been rotated to account for rigid body motion in the increment before UMAT is called and are approximations to logarithmic strain.DSTRAN(NTENS)Array of strain increments. If thermal expansion is included in the same material definition, these are the mechanical strain increments (the total strain increments minus the thermal strain increments).TIME(1)Value of step time at the beginning of the current increment.TIME(2)Value of total time at the beginning of the current increment.DTIMETime increment.TEMPTemperature at the start of the increment.DTEMPIncrement of temperature.PREDEFArray of interpolated values of predefined field variables at this point at the start of the increment, based on the values read in at the nodes.DPREDArray of increments of predefined field variables.CMNAMEUser-defined material name, left justified. Some internal material models are given names starting with the “ABQ_” character string. To avoid conflict, you should not use “ABQ_” as the leading string for CMNAME.NDINumber of direct stress components at this point.NSHRNumber of engineering shear stress components at this point.NTENSSize of the stress or strain component array (NDI + NSHR).NSTATVNumber of solution-dependent state variables that are associated with this material type (defined as described in “Allocating space” in “User subroutines: overview,” Section 17.1.1 of the Abaqus Analysis User's Manual).PROPS(NPROPS)User-specified array of material constants associated with this user material.NPROPSUser-defined number of material constants associated with this user material.COORDSAn array containing the coordinates of this point. These are the current coordinates if geometric nonlinearity is accounted for during the step (see “Procedures: overview,” Section 6.1.1 of the Abaqus Analysis User's Manual); otherwise, the array contains the original coordinates of the point.DROT(3,3)Rotation increment matrix. This matrix represents the increment of rigid body rotation of the basis system in which the components of stress (STRESS) and strain (STRAN) are stored. It is provided so that vector- ortensor-valued state variables can be rotated appropriately in this subroutine: stress and strain components are already rotated by this amount before UMAT is called. This matrix is passed in as a unit matrix for small-displacement analysis and for large-displacement analysis if the basis system for the material point rotates with the material (as in a shell element or when a local orientation is used).CELENTCharacteristic element length, which is a typical length of a line across an element for a first-order element; it is half of the same typical length for a second-order element. For beams and trusses it is a characteristic length along the element axis. For membranes and shells it is a characteristic length in the reference surface. For axisymmetric elementsit is a characteristic length in the plane only. For cohesive elementsit is equal to the constitutive thickness.DFGRD0(3,3)Array containing the deformation gradient at the beginning of the increment. If a local orientation is defined at the material point, the deformation gradient components are expressed in the local coordinate system defined by the orientation at the beginning of the increment. For a discussion regarding the availability of the deformation gradient for various element types, see “Availability of deformation gradient.”DFGRD1(3,3)Array containing the deformation gradient at the end of the increment. If a local orientation is defined at the material point, the deformation gradient components are expressed in the local coordinate system defined by the orientation. This array is set to the identity matrix if nonlinear geometric effects are not included in the step definition associated withthis increment. For a discussion regarding the availability of the deformation gradient for various element types, see “Availability of deformation gradient.”NOELElement number.NPTIntegration point number.LAYERLayer number (for composite shells and layered solids).KSPTSection point number within the current layer.KSTEPStep number.KINCIncrement number.Example: Using more than one user-defined mechanical material modelTo use more than one user-defined mechanical material model, the variable CMNAME can be tested for different material names inside user subroutine UMAT as illustrated below:IF (CMNAME(1:4) .EQ. 'MAT1') THENCALL UMAT_MAT1(argument_list)ELSE IF(CMNAME(1:4) .EQ. 'MAT2') THENCALL UMAT_MAT2(argument_list)END IFUMAT_MAT1 and UMAT_MAT2 are the actual user material subroutines containing the constitutive material models for each material MAT1 and MAT2, respectively. Subroutine UMAT merely acts as a directory here. The argument list may be the same as that used in subroutine UMAT.Example: Simple linear viscoelastic materialAs a simple example of the coding of user subroutine UMAT, consider the linear, viscoelastic model shown in Figure 1.1.40–1. Although this is not a very useful model for real materials, it serves to illustrate how to code the routine.Figure 1.1.40–1 Simple linear viscoelastic model.The behavior of the one-dimensional model shown in the figure iswhere and are the time rates of change of stress and strain. This can be generalized for small straining of an isotropic solid asandwhereand , , , , and are material constants ( and are the Lamé constants).A simple, stable integration operator for this equation is the central difference operator:where f is some function, is its value at the beginning of the increment,is the change in the function over the increment, and is the timeincrement.Applying this to the rate constitutive equations above givesandso that the Jacobian matrix has the termsandThe total change in specific energy in an increment for this material iswhile the change in specific elastic strain energy iswhere D is the elasticity matrix:No state variables are needed for this material, so the allocation of space for them is not necessary. In a more realistic case a set of parallel models of this type might be used, and the stress components in each model might be stored as state variables.For our simple case a user material definition can be used to read in the five constants in the order , , , , and so thatThe routine can then be coded as follows:SUBROUTINE UMAT(STRESS,STATEV,DDSDDE,SSE,SPD,SCD,1 RPL,DDSDDT,DRPLDE,DRPLDT,2 STRAN,DSTRAN,TIME,DTIME,TEMP,DTEMP,PREDEF,DPRED,CMNAME,3 NDI,NSHR,NTENS,NSTATV,PROPS,NPROPS,COORDS,DROT,PNEWDT,4 CELENT,DFGRD0,DFGRD1,NOEL,NPT,LAYER,KSPT,KSTEP,KINC)CINCLUDE 'ABA_PARAM.INC'CCHARACTER*80 CMNAMEDIMENSION STRESS(NTENS),STATEV(NSTATV),1 DDSDDE(NTENS,NTENS),2 DDSDDT(NTENS),DRPLDE(NTENS),3 STRAN(NTENS),DSTRAN(NTENS),TIME(2),PREDEF(1),DPRED(1),4 PROPS(NPROPS),COORDS(3),DROT(3,3),DFGRD0(3,3),DFGRD1(3,3) DIMENSION DSTRES(6),D(3,3)CC EVALUATE NEW STRESS TENSORCEV = 0.DEV = 0.DO K1=1,NDIEV = EV + STRAN(K1)DEV = DEV + DSTRAN(K1)END DOCTERM1 = .5*DTIME + PROPS(5)TERM1I = 1./TERM1TERM2 = (.5*DTIME*PROPS(1)+PROPS(3))*TERM1I*DEVTERM3 = (DTIME*PROPS(2)+2.*PROPS(4))*TERM1ICDO K1=1,NDIDSTRES(K1) = TERM2+TERM3*DSTRAN(K1)1 +DTIME*TERM1I*(PROPS(1)*EV2 +2.*PROPS(2)*STRAN(K1)-STRESS(K1))STRESS(K1) = STRESS(K1) + DSTRES(K1)END DOCTERM2 = (.5*DTIME*PROPS(2) + PROPS(4))*TERM1II1 = NDIDO K1=1,NSHRI1 = I1+1DSTRES(I1) = TERM2*DSTRAN(I1)+1 DTIME*TERM1I*(PROPS(2)*STRAN(I1)-STRESS(I1))STRESS(I1) = STRESS(I1)+DSTRES(I1)END DOCC CREATE NEW JACOBIANCTERM2 = (DTIME*(.5*PROPS(1)+PROPS(2))+PROPS(3)+1 2.*PROPS(4))*TERM1ITERM3 = (.5*DTIME*PROPS(1)+PROPS(3))*TERM1IDO K1=1,NTENSDO K2=1,NTENSDDSDDE(K2,K1) = 0.END DOEND DOCDO K1=1,NDIDDSDDE(K1,K1) = TERM2END DOCDO K1=2,NDIN2 = K1–1DO K2=1,N2DDSDDE(K2,K1) = TERM3DDSDDE(K1,K2) = TERM3END DOEND DOTERM2 = (.5*DTIME*PROPS(2)+PROPS(4))*TERM1II1 = NDIDO K1=1,NSHRI1 = I1+1DDSDDE(I1,I1) = TERM2END DOCC TOTAL CHANGE IN SPECIFIC ENERGYCTDE = 0.DO K1=1,NTENSTDE = TDE + (STRESS(K1)-.5*DSTRES(K1))*DSTRAN(K1) END DOCC CHANGE IN SPECIFIC ELASTIC STRAIN ENERGYCTERM1 = PROPS(1) + 2.*PROPS(2)DO K1=1,NDID(K1,K1) = TERM1END DODO K1=2,NDIN2 = K1-1DO K2=1,N2D(K1,K2) = PROPS(1)D(K2,K1) = PROPS(1)END DOEND DODEE = 0.DO K1=1,NDITERM1 = 0.TERM2 = 0.DO K2=1,NDITERM1 = TERM1 + D(K1,K2)*STRAN(K2)TERM2 = TERM2 + D(K1,K2)*DSTRAN(K2)END DODEE = DEE + (TERM1+.5*TERM2)*DSTRAN(K1)END DOI1 = NDIDO K1=1,NSHRI1 = I1+1DEE = DEE + PROPS(2)*(STRAN(I1)+.5*DSTRAN(I1))*DSTRAN(I1) END DOSSE = SSE + DEESCD = SCD + TDE – DEERETURNEND。
模型收敛 英语
模型收敛英语Convergence of ModelsThe concept of model convergence is a fundamental aspect of various fields, ranging from machine learning and data analysis to scientific research and engineering. In this essay, we will explore the significance of model convergence, its underlying principles, and its practical applications across different domains.At the core of model convergence is the idea that a mathematical or computational model should converge to a stable and consistent solution as the input data or parameters are refined or the algorithm is iterated. This convergence is essential for ensuring the reliability and accuracy of the model's predictions or outputs. Without convergence, the model may produce inconsistent or unpredictable results, rendering it unreliable for decision-making or further analysis.One of the primary reasons for the importance of model convergence is the inherent uncertainty and complexity present in real-world systems. These systems often involve a multitude of variables, interactions, and interdependencies that can be challenging to capture accurately in a model. By achievingconvergence, researchers and practitioners can have confidence that their models are accurately representing the underlying phenomena and can be used to make informed decisions or draw meaningful conclusions.In the field of machine learning, model convergence is crucial for the development of effective and reliable algorithms. During the training process, machine learning models iteratively adjust their parameters to minimize the difference between the predicted outputs and the true outputs (known as the loss function). Convergence in this context means that the model has reached a point where the loss function is minimized, and the model's performance on unseen data is optimized. This convergence is essential for ensuring the generalization of the model to new data, which is a fundamental requirement for real-world applications.Similarly, in scientific research, the convergence of computational models is vital for validating the accuracy and reliability of simulations and experiments. Researchers often use mathematical models to represent complex physical, chemical, or biological phenomena, and the convergence of these models is necessary to ensure that the simulations accurately capture the underlying processes. This convergence can be achieved through techniques such as grid refinement, adaptive mesh generation, and iterative solution methods.In engineering, model convergence is crucial for the design and optimization of complex systems. Engineers often use computational models to simulate the behavior of structures, fluid flows, or energy systems, and the convergence of these models is essential for ensuring the reliability and safety of the final product. For example,in the design of aircraft or automobiles, engineers rely on computational fluid dynamics (CFD) models to predict the aerodynamic performance of the vehicle. The convergence of these models is crucial for accurately predicting the drag, lift, and other important parameters that affect the vehicle's performance and efficiency.Beyond these specific applications, model convergence is also relevant in fields such as finance, economics, and social sciences, where mathematical and statistical models are used to analyze and predict complex phenomena. In these domains, the convergence of the models is essential for making informed decisions, assessing risks, and developing effective policies.In conclusion, the concept of model convergence is a fundamental aspect of various fields, from machine learning to scientific research and engineering. By achieving convergence, researchers and practitioners can ensure the reliability and accuracy of their models, leading to more informed decision-making and a betterunderstanding of the underlying systems. As the complexity of real-world problems continues to increase, the importance of model convergence will only grow, making it a crucial area of study and application across a wide range of disciplines.。
Versus a Model for a Web Repository
Versus:a Model for a Web RepositoryJo˜a o P.Campos M´a rio J.SilvaXLDB Research GroupDepartamento de Inform´a ticaFaculdade de Ciˆe ncias da Universidade de LisboaCampo Grande,1749-016Lisboa,Portugal[jcampos,mjs]@di.fc.ul.ptAbstractWeb data warehouses can prove useful to applications that process large amounts of Web data.Versus is a model for a Repository for Web data management applications,supporting ob-ject versioning and distributed operation.Versus applications control the distribution,and the integration of data.This paper presents the design of Versus and our prototype implementation.Keywords:Web data repository,versioning,distributed database.1IntroductionThe Web is a great personal enhancement tool,but the amount of data available is so vast that its true potential can only be harnessed with tools specialized in aiding usersfind,sort,filter, summarize and mine this data.To handle large amounts of information,applications need bandwidth.With today’s limi-tations,applications wouldn’t be able to solve user queries in due time,because it would take them too long to download the data.Pre-fetching the information(anticipating user interaction)and storing it would be a rea-sonable solution:getting a copy of all the needed information is very expensive(both on time and bandwidth usage),but saved data can then be reused by several applications and users.A Web robot can be used to seek,download and store large portions of Web contents. However available Web robots are either expensive and proprietary[1,8],outdated[9],or both [16].Solutions for storing collected Web data are tightly coupled with the robots used,and, being proprietary,are not readily available for usage by other applications.In addition,to efficiently implement Web applications that deal with Web data,we may need scalable storage,capable of holding large amounts of data,with a high throughput.The motivation for this work is that we couldn’tfind a storage offering high performance meta-data management(like serverlessfilesystems[2]do for data)with an interface to manage web meta-data.Our goal is to provide support for automatically perform the following functions: Retrieval of large quantities of data from the Web.This may represent a huge compu-tational effort,requiring advanced techniques to address scale problems.Applications retrieving and saving data are usually built tightly coupled with the storage system used.Hence,the storage framework for Web data should be highly scalable,allowing the distri-bution of the loading processes among a network of processors.Manage meta-data about Web resources.Most applications built on Web data require both the documents retrieved from the Web and the meta-data available about these documents,such as the URL where the document was retrieved,its last modification date,or MIME-type.The storage system must provide methods for storing and retrieving these meta-data elements along with the documents.Save historic data.History may be relevant.While some applications won’t care about old unavailable documents,some others might be interested in looking at how a portion of the Web was some time ago.The storage must provide access methods enabling user applications to specify what they want to see in respect to time.This paper presents an implementable model for a Web data repository satisfying these functional and architectural requirements and the implementation of a working prototype that serves as its proof of concept.Versus is the name used for the model developed for storing and managing Web data.In the text,we also designate the developed prototype system as Versus.The paper is organized as follows:next section presents some work related with Versus; section3presents the Versus model for a distributed repository;section4details our prototype implementation and section5presents the conclusions and future work.2Related WorkVersion models are a powerful means of representing evolution of objects over time.The empha-sis on versioning systems research was on supporting Computer Aided Design(CAD)systems. The design process is slow:complex objects are developed by teams of designers,each of whom designs independent parts.Parts are integrated to form the whole.Eventually some parts are redrawn and some parts are reused from previous projects.Web data collection is similar to CAD engineering design:data is collected at different times (due to bandwidth constraints)and may be related(through the link structure)or integrated with other data to form complex objects,like pages or sites.Some parts(pages)of the collected Web may be revised,recollected and related with old(already stored)parts.The Web grows everyday,revealing new pages to integrate in the global picture.Version models provide semantic extensions to support the organization of engineering data [14],including unified concepts for managing and structuring information changing over time. Versus uses some of the defined concepts,such as workspaces,versions and check-out/check-in operations.Web-based Distributed Authoring and Versioning(WebDAV)is a set of extensions to the HTTP protocol that enable users to collaboratively edit and managefiles on remote Web servers [18,13].WebDAV implements long lasting locks,preventing two users from writing the same resource without merging changes.WebDAV servers are not designed for holding the amount of data we aim to hold with Versus.A WebDAV interface could,in principle,be developed for Versus.Web repositories are data stores designed to hold Web data.Most were developed to sup-port search engines,storing the data needed to build indexes or compute rankings.Some implementations hold large portions of the Web,and their architecture is designed to hold the entire visible Web.WebBase[10]is a repository of web pages designed for maintaining a large shared repository of data downloaded from the Web.The main focus of WebBase is optimizing data access,storing all the meta-data in a separate database management system.From our experiments we found that meta-data management can be a bottleneck to the system perfor-mance.We couldn’tfind details about how WebBase manages meta-data other than it is saved on a relational database(is it centralized or distributed?)WebBase is specifically tailored for supporting a Web crawler.AIDE[7,3]is a difference engine that allows users to track changes on Internet pages; WebGUIDE[6]is a system for exploring the changes storage system,offering a navigational tool to analyze the differences in Web pages over time.The difference engine is supported by a centralized versioning repository that stores versions of documents so that they are available for comparison in the future.Data is saved in this repository in Revision Control System(RCS) [17]format.Meta-data is saved in a relational database.The Internet Archive[12,4,15]goal is to build an Internet library for offering access to collections in digital format.The main focus is on long term preservation of selected contents and offering access to collected items.We have presented other research on topics related to Versus.A comparison between Versus and the systems presented is out of the scope of this paper and is of little practical interest as they all have a small overlap with Versus with respect to functionality.3Versus ModelProcessing large quantities of information in a Web data-warehouse involves integration of data from multiple sources,indexing,summarizing and mining Web data.The key for scaling up these heavy data processing operations lies in distributing the load among several processors, parallelizing the tasks to perform.However,this distribution must be supported by a storage system that can cope with the new complexities introduced,such as partitioning the work into units,physical distribution of data and scheduling work units among the processors,provisioning of methods for accessing distributed data and,finally,the fusion of the independently processed parts to form coherent views.Our approach is based in a versions and workspaces model for data,enabling paralleliza-tion of applications processing large collections of Web pages.Versus follows this approach, supporting concurrent updates,versioning and distribution.3.1A Typical Usage ScenarioOne example of an application with high data interaction is a distributed Web crawler.In a typical implementation,each thread,running on a separate processor,is responsible for collect-ing documents from certain parts of the Web;in the end,the crawler delivers an integrated archive with the collected documents.The running context of such an application is depicted in Figure1.Each thread,when initializing,would get from the storage server the roots of the crawl(the pages where to start looking for links).Crawling the Web consists of iteratively downloading pages,extracting the links referencing other pages,downloading these pages and so on.During the crawl,threads would exchange data through the repository’s storage server to ensure that each document is not processed more than once.When each of the threadsfinishes, it uploads the documents obtained to the repository’s storage server,making them available to other applications.3.2RequirementsWe identified the following main requirements for a web data repository:•Support partitioning of the work into disjoint units that can be processed concurrently;•Support concurrent updates to disjoint subsets of the data;•Support integration of results from processed units;•Enabling threads working on separate units to exchange information so that applications can avoid duplicate processing;HighBandwidthStorageServerProcessingNodesFigure 1:Running context of applications using Versus.The storage server holdsdata to be shared by the several transactions of the running application.Eachtransaction runs in a processing node and has an associated storage,where dataprocessed locally is kept.The time lost in data transfer between the processingnodes and the storage server is compensated by parallel data processing.•Support storage of large amounts of data,ultimately archiving a very large portion of theentire Web;•Enable reading of stored information while other transactions process updates;•Support periodic partial updates to stored information,refreshing stale data items whilemaintaining their relationships to other items;•Reuse storage when new documents are equal to a previously collected version;•Enable views over past states of data,providing the time dimension in stored data.3.3AssumptionsThe design of Versus is based on the following assumptions:rmation spaces can be partitioned into disjoint subsets that can be processed with ahigh degree of independence;2.The performance overhead introduced by intra-thread communication for synchronizationof the non independent part of the computation is largely compensated by the parallel execution of the threads.3.Applications provide the repository with a function to partition the data into processingunits and a function to reconcile conflicting data generated within different units.Independence among working units is application specific.Assumption 2implicitly states that Versus is most suited for applications that can profit from parallel processing.3.4ConceptsWe now present the main concepts of the Versus model.Archive WorkspaceThreadDataThreadDataCheck out Check inGroupWorkspacePrivateWorkspacesDataApplication451Figure2:Versus supports three classes of workspaces:archive,group and pri-vate workspaces.Thefigure depicts an archive workspace holding a data set partitioned in several subsets.Applications check-out to the group workspace only the data sets they will use.Threads concurrently check-out subsets of the data,process them,and check them back in.3.4.1WorkspacesWorkspaces are well bounded and independent environments where application threads can apply transactions to subsets of the data to be processed,minimizing interaction with other data subsets being processed by other clients.We define three kinds of workspaces:private,group and archive.Private workspace:provides storage to application threads.Private workspaces are inde-pendent of one another,and may reside in different processors.Each parallel thread that accesses the repository and generates results for an application should instantiate a private workspace of its own.Group workspace:integrates partial results generated by clients on private workspaces.Each application(possibly with several threads of execution)processing archived data should instantiate a group workspace.Conflicts may arise when consolidating data from several private workspaces into a group workspace.Versus handles the conflicts using the methods provided by the application that generated them.Archive workspace:stores data permanently.It keeps version history for the data and is able to reconstruct earlier views of data.The archive workspace is an append only storage: data stored in the archive workspace can’t be updated or deleted.Data is passed from one workspace to another via check-out and check-in operations through the following steps(seefigure2):1.When an application is started,it instantiates a new group workspace,checking-out datait will need from the archive workspace;2.The application forks n parallel threads;3.Each of the parallel threads starts its own private workspace and checks out one of thedata subsets;4.Whenfinished with one subset,the thread checks in the results into the group workspaceand restarts with another data subset;5.When the applicationfinishes,the results in the group workspace are checked-in into thearchive workspace.3.4.2LayersVersus sees its data as a collection of objects that can be versioned,organizing them in layers.A layer is a storage unit capable of holding one single version of each object stored in a workspace. Each workspace may contain objects from several layers.Each workspace has an active layer.All objects that are added to the workspace are as-sociated to the active layer.Workspaces can’t save objects in layers other then the active layer.A Versus repository may be set to increment the active layer number automatically or manually.If set to automatically increase the layer number,the current layer is incremented whenever a new version of an object that already exists in the current layer is added;then the new version is added to the new layer.If the repository is set to manually increment the current layer number,then any addition of an object that already exists in that layer is denied and an error is raised.Layers are represented by integers monotonically incremented in a repository,they store the time dimension of data,showing the partial order of object manipulation operations within the repository;for example,in a manually incremented repository,one application knows that any two objects stored in the same layer are contemporary,meaning that they were both inserted into the repository when that layer was the active layer.3.4.3VersionsVersion models allow the storage of several instances of the same objects as saved in different instants over time.This is very useful for storing the evolution of the state of objects,enabling applications to see views of the represented world at different points in time.As the Web can’t (and shouldn’t)be represented at once,saved representations of it can’t be easily refreshed. The application of the version model to Web data is very useful because it allows the refreshing of parts of the represented data known to be stale,maintaining coherence between fresh and non fresh data.Furthermore,applications can choose to work with different views over data: for instance,a search engine built on top of the repository may use the latest available version of each document,while a web difference engine can choose to read all versions of a document to track how it was changed.Versus assumes that if any two versions have the same id,then they both are versions of the same object.As all versions have an associated layer number,which is unique for every version of any given object,two versions of one object have distinct layer numbers,and the order of the layer numbers can be used to derive which of these is the oldest version.3.4.4Objects and AssociationsVersus is designed to process webs of objects that can be viewed as labeled graphs,where nodes are object instances and edges are associations between them.Edge labels denote association types.Objects saved in a Versus repository are modeled as having an associated name,a property set and a stream of data.Streams of data are to be saved in afilesystem,and their management is external to Versus.An object o is represented in Versus as a tuple o(name,{properties},stream). The object name is the identifier of an object and can’t be changed.Objects may be related to each other by oriented,typed associations,modeling the rich associations that exist in the real world between objects.A relationship R of type t from objecta to objectb is represented as a tuple R(a,b,t),where a is the anchor of the relation,b its target and t is the association type.3.4.5Partition and Data UnitsA partition of a workspace is defined as the division of the workspace into disjoint subsets.We call each of the subsets forming the partition a strict data unit,or simply a strict unit.3.4.6PredicatesWhen checking out data from one workspace to another,applications specify the disjoint subset of the data(objects and versions)to be checked out.If applications had to enumerate the objects to check-out one by one,they would have to know in advance the objects’identifiers.This may turn out impossible to some applications. In Versus,applications specify sets of objects to check-out using predicates.A predicate is a function P red A that,given an object o returns true when o belongs to A.P red A is not a belongs-to operation.The application of a predicate to all objects in the workspace defines the unit.On check-out,the repository tests the supplied predicate against candidate objects and returns those that satisfy the predicate.For instance,if one thread wants to perform a transaction on all objects whose identifier starts with letter d,it provides a function to the repository that returns true if an object starts with d and false otherwise.The repository then evaluates that function on all objects of the workspace tofind out which are to be checked-out.Predicates must be defined by Versus applications because only applications have the knowl-edge of how their data can be processed in independent subsets.Predicates defined over one workspace must obey to two invariant conditions:1.No object in a workspace can satisfy two different predicates simultaneously.2.Every object in a workspace will satisfy a predicate for the lifetime of all applications thatoperate on the workspace.Invariant2implies that predicates can’t depend on object attributes that are updated by the application and should be functions of object properties that are invariant(such as the name).3.4.7Strict Data UnitsA strict data unit represents a set of data that can be checked out by a transaction.Partitions vary according to the predicates given.As predicates are application defined,the size of the data units is application dependent.The minimum check-out granularity is ultimately a single object.Invariant1implies that data units defined by a partition are disjoint.The union of all strict data units in a workspace always represents a set of objects contained in the workspace.3.4.8Working unitsA working unit is a container used to check-out a strict data unit from one workspace to another and checking the results of the operations executed on the objects of the working unit back in.A valid working unit definition would consist in creating a data unit for each letter and making all objects whosefirst letter of their identifier match the working unit letter part of the corresponding data unit.This definition would always generate26working units(one for each letter),independently of being applied to an empty workspace or to a workspace with thousands of objects to partition.This working unit definition complies with both repository invariants:tt t t tiii)check-out of the working unit containing the circles data unit;iii)private workspace objects are updated and three new objects(a circle,a cross and a square)are inserted;iv)data is checked back in the original group workspace.an object with a given identifier will only match one starting letter;and as the identifier will always have the samefirst letter,it will always belong to the same data unit and will be always checked out to the same working unit.3.4.9Loose Data UnitsA loose data unit is a strict data unit plus all objects for which there is a relationship between versions belonging to the strict data unit and other versions added to the working unit.Objects can only be added to a working unit if they satisfy the predicate defining the strict data unit that originated it,or if they are directly related with objects in the strict data unit.Figure3represents the relationship between working units and workspaces.At check-out, a working unit is identical to the strict working unit:all the checked out objects satisfy the predicate originating the unit.At check-in,there might be objects(like the new square in the example of Figure3)that don’t satisfy the predicate(“is a circle?”in the example).Loose data units are the data units in this condition.3.5OperationsSo far we have seen that,to update an object,an application checks out the working unit that contains the object into a private workspace,modifies the object and then checks the working unit back in.The intuition behind this mode of operation is that if we have a massive processing on a large collection of objects,we can make it concurrently by copying the objects into separate data stores,have them manipulated while isolated from the collection,and then reconcile them with the collection.We now present the semantics of these operations on workspaces.3.5.1Operations on data and conflict generationAddition of new objects to a working unit while isolated would be very restricted if this were possible only with objects within the strict data unit checked out.For example,consider a crawler collecting pages from the Web,working on a private workspace that checked out a working unit for all objects of a given site;if,when downloading one of the Web pages itfinds a link to some page on another site,how would it save that reference?Not within the partition, because it doesn’t satisfy the predicate.It would not be able to check-out the proper working unit either,because it can’t handle two working units at a time.To mitigate this problem,we allow for data that doesn’t belong to the current strict data unit(the one previously checked out)to be conditionally inserted within the working unit, enlarging it into a loose data unit.Insertion is allowed for objects that,albeit not belonging to the strict working unit,are directly associated with objects that are within the strict working unit.On the other hand,insertion is always allowed for objects belonging to the strict working unit.Inserting or updating object belonging to the working unit does not generate conflicts as objects in data units are checked out to one workspace at a time,no two parallel threads concur to use the same objects.However,conditional insertion of objects that don’t belong to the strict working unit may generate conflicts,because two parallel processes might insert the same object while isolated.When reconciling the data,conflicts must be automatically resolved by an application-supplied code.3.5.2Check-outTransactions check-out a data unit from one workspace,called the source workspace,into an-other,called the target workspace.They determine what to check-out by applying the predicate associated with the working unit to the source workspace.The check-out operation for a given unit defined by a predicate takes one argument,the source workspace to check-out,and generates two workspaces:the source workspace after the check-out and the target workspace.The check-out operation is defined only if the unit to check-out is not already in use.The only modification to the source workspace is that the unit is added to the set of units currently in use.The target workspace will contain all the objects of the source workspace that satisfy the predicate,plus all the relationships from the source workspace where both the anchor and target objects are checked out.Check-out doesn’t copy relationships from objects that belong to the checked out unit to objects that don’t belong to the corresponding unit at the target workspace.Hence,threads working on the target workspace don’t have access to these relationships.Applications that require access to these relationships should define a partition that generates units big enough to contain them.Transactions can only check-out data from one working unit at a time.As check-out doesn’t copy relationships involving objects outside the strict data unit to the more private workspace, applications operating on the private workspace will only see relationships among objects in the workspace.3.5.3Conflict resolutionImplementation of a conflict resolution policy in the repository would force all the applications to use it,even if it is not appropriate to their needs.To satisfy the specific needs of Web applications the model defines a conflict manager interface that applications must implement to solve the conflicts while saving conflicting data.Figure4:Class model for the data handled by the repository.Versus applications must implement a conflict management function,that,given two can-didate objects,decide which should be saved in the repository.The result may be one third object generated by merging the two candidates.The decision is application driven.3.5.4Check-inApplying an operation to the data in one workspace is equivalent to partitioning the workspace, checking out each of the data units,applying the operation to each of the working units and then checking them in.As this is true for operations that don’t need to see relations between objects in different partitions,the repository is suited for serving applications for loading large amounts of data,allowing the parallelization of the process.The reintegration of working units’data previously checked out from a workspace has to consider the existence of new data that might conflict with the already existing data.Check-in is a function that takes two workspaces W and W x and returns a third workspace, resulting from checking W x into W .Its effects are:1.The resulting set of objects consists of those objects created before the check-out plus:•Objects created before check-out that belong to the strict unit,but were updatedduring isolated operations;•Objects identified by the resolution of conflicts between new objects and those thatexisted before and don’t belong to the unit;•The remaining objects,those created after check-out,that satisfy the predicate.2.The resulting relationships are all the relationships that existed before the check-out,minus relationships from updated versions,plus new relationships.3.The lock created when the unit was checked out is released.3.6Data ModelFigure4shows the UML class model of the data handled in a Versus repository.We have the following main classes:。
ABAQUS建模规范化方法总结Modified
400
0
540
0.075
极限应力（540）对应的应变，按照《混凝土规范》规定的最大力下的总伸
长率限值 7.5%取用。超出该限值，则取为平直段。
另外，如何设置本构的终止点，还有待研究。 从《ABAQUS 有限元分析实例详解》第六章弹塑性分析实例可以看出，ABAQUS 默认*PLASTIC 的塑性数据在超过最大应力时，材料变为理想塑性。同时该书还建 议，在设定关键词为*PLASTIC 的塑性数据时，应保证其中最大的真实应力和塑性 应变大于模型中可能出现的应力应变值。
*************************************************************** 定义参数：
扩散角： Dilation Angle=38°； 偏心率： Eccentricity=0.1；（默认值） 双轴压缩屈服应力与单轴压缩屈服应力的比值： fb0/fc0=1.16；（默认值） 拉伸子午面与压缩子午线的第二应力不变量之比： K（Kc）=2/3; 粘度系数： Viscosity Parameter=默认的参数为 0.0s，选取值为 0.00001s 一般而言，粘性系数取值越小，分析越不容易收敛。这是经验问题。至 于是什么原因，这里还需要进一步的讨论。
1.1. 密度/Density
Mass Density=2.5e-9 tone/mm³（=2500kg/m³）
1.2. 弹性/Elastic
Machanical/Elasticity/Elastic
定义参数： 杨氏模量： Young’s Modulus=34500 N/mm²； 泊松比：
Poisson’s Ratio=0.2
0.313124
0.00087237
地下水模拟软件GMS中文使用手册
2.1.1 纲要....................................................................................................................................... 17
2.2 开始.............................................................................................................................................. 18 2.3 属性对象...................................................................................................................................... 18
1.12.1 创建概念模型..................................................................................................................... 13 1.12.2 根据 GIS 数据作图............................................................................................................. 13
2.4 结论.............................................................................................................................................. 24 25 3 MODFLOW—概念模型法................................................................................................................ ................................................................................................................25 3.1 简介.............................................................................................................................................. 26
open cascade occ 几何模型创建与删除操作 -回复
open cascade occ 几何模型创建与删除操作-回复Open Cascade Technology (abbreviated as OCC) is an open-source library that offers a wide range of functionalities for 3D geometric modeling. In this article, we will explore how to create and delete geometric models using OCC. We will provide a step-by-step guide to help you understand the process thoroughly.1. Introduction to Open Cascade Technology (OCC)Before diving into creating and deleting geometric models, let us have a brief overview of OCC. OCC is a powerful framework that provides tools for 3D modeling, visualization, and simulation. It is widely used in various industries like mechanical engineering, architecture, and computer graphics.2. Installing Open Cascade TechnologyTo get started with OCC, you need to install it on your system. OCC is available for Windows, Linux, and macOS. You can download the latest version from the official OCC website. Follow the installation instructions provided there to set up OCC on your machine.3. Setting up an OCC projectAfter the installation, let us begin by setting up a new OCC project. Create a new directory on your system and open your preferred Integrated Development Environment (IDE). We will assume you are using C++ for this article, but OCC also supports other programming languages like Java and C#.In your IDE, create a new project and configure it to include the OCC header files and link against the OCC library. Refer to the OCC documentation for detailed instructions on setting up the project in your specific IDE.4. Creating a geometric modelNow that we have a project set up, we can start creating geometric models. OCC provides a wide range of classes and functions to define and manipulate various geometric entities like points, lines, curves, and surfaces. Let's take a simple example of creating a 3D box.a. Include the necessary OCC header files in your source code: cpp#include <TopoDS_Shape.hxx>#include <BRepPrimAPI_MakeBox.hxx>#include <TopoDS.hxx>b. Write the code to create a box:cppTopoDS_Shape box = BRepPrimAPI_MakeBox(10.0, 20.0,30.0).Shape();In this code, we first declare a variable `box` of type`TopoDS_Shape`, which represents a generic shape in OCC. We then use the `BRepPrimAPI_MakeBox` class to create a box with dimensions 10.0 units in the X direction, 20.0 units in the Y direction, and 30.0 units in the Z direction. Calling the `Shape()` function on the `BRepPrimAPI_MakeBox` object returns the actual OCC shape.5. Modifying the geometric modelOnce we have created a geometric model, OCC allows us to modify it by adding, removing, or changing its components. Let's continue with the previous example of the box and demonstratesome modifications.a. Extend the code from step 4:cpp#include <BRepBuilderAPI_Transform.hxx>#include <gp_Trsf.hxx>...Create a transformation to move the box 5 units in the X directiongp_Trsf translation;translation.SetTranslation(gp_Vec(5.0, 0.0, 0.0));Apply the transformation to the boxBRepBuilderAPI_Transform transform(box, translation); TopoDS_Shape modifiedBox = transform.Shape();In this code, we include additional header files for transforming the shape. We create a `gp_Trsf` object `translation` that represents a translation transformation with a 5.0 unitdisplacement in the X direction. We then use the`BRepBuilderAPI_Transform` class to apply the translation to the `box` shape. Finally, calling the `Shape()` function on the transformed object returns the modified shape `modifiedBox`.6. Deleting a geometric modelTo delete or destroy a geometric model in OCC, we can simply release its memory by calling the appropriate OCC functions. Let's extend the previous example and demonstrate how to delete the shapes.a. Extend the code from step 5:cpp#include <TopExp.hxx>#include <ShapeFix_Shape.hxx>...Delete the modifiedBoxShapeFix_Shape::Disconnect(modifiedBox);Alternatively, delete all the components of modifiedBox explicitlyTopExp_Explorer explorer(modifiedBox, TopAbs_FACE); Change TopAbs_FACE to the desired component typefor (; explorer.More(); explorer.Next()) {const TopoDS_Shape& component = explorer.Current();ShapeFix_Shape::Disconnect(component);}In this code, we include additional header files for exploring and disconnecting the components of the shape. We use the`ShapeFix_Shape` class to disconnect the components of the`modifiedBox` shape. This frees the memory associated with the shape and removes it from the geometric model.7. ConclusionIn this article, we have explored how to create and delete geometric models using Open Cascade Technology (OCC). OCC provides a powerful framework for 3D modeling and manipulation. By following the step-by-step guide provided, you should now have a good understanding of how to use OCC to create, modify, and delete geometric models. Practice theseconcepts with other types of entities and explore the vast capabilities of OCC to enhance your 3D modeling projects.。
Software_Engineering_9_Solutions_Manual
The essential difference is that in generic software product development, the specification is owned by the product developer. For custom product development, the specification is owned and controlled by the customer. The implications of this are significant – the developer can quickly decide to change the specification in response to some external change (e.g. a competing product) but, when the customer owns the specification, changes have to be negotiated between the customer and the developer and may have contractual implications. For users of generic products, this means they have no control over the software specification so cannot control the evolution of the product. The developer may decide to include/exclude features and change the user interface. This could have implications for the user’s business processes and add extra training costs when new versions of the system are installed. It also may limit the customer’s flexibility to change their own business processes.
Structural Static Models.ppt
Pr[dij|d/ij,β,xij,zj]
Define Aij(dij|d/ij,β,xij,zj) = { ε: Uij(dij,d/ij;β,xij,zj,ε)> Uij(d,d/ij;β,xij,zj,ε) d≠ dij}
➢ Partial information: Ωij= εij → each member maximizes EUij(dij,d/ij;β,xij,zj,εij) over the joint density of the other errors where d/ij becomes a random vector
with conditional expected value ΣiPr[εij Aij(dijk| d/ij,β,xij,zj)]
➢
➢ Minimize quadratic form in deviations between Djk and its conditional moment
Moments Estimation
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Model Specification
➢ Hausman: hik=βyik+αwik+Ziγ+ui
Modelica语言介绍
23
受限类使用场景
类型 class model connector record block type function package 名称 类 模型 连接器 记录 框图 类型 函数 包 作用 通用类 陈述式模型 组件之间的连接接口 数据结构 兼容基于框图的因果建模 类型别名 通过算法实现过程式建模 消除名字冲突和组织模型层次
11
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数值型变量默认0 布尔型变量默认false 字符串型变量默认空串 局部变量和函数返回值默认未定义 仿真初始值： Real x(start=1) "Descriptive string for x"; Real y(start=1,fixed=true);
5
认识Modelica
例子：HelloWorld 例子：Pendulum 例子：DAEExample 例子：VanDerPol 基本的Modelica元素： 变量（Variable） 方程（Equation） 常量（Constant） 变量初值（start） 注释（Comment）
18
类（Class）
Modelica类/模型的结构： 变量：或称为实例、组件，对于时变变量，变量值记录 求解过程中当前时刻的结果。 方程：表示模型行为，与其他存在数据交互的模型方程 一起决定求解过程（LE/NLE/ODE/DAE/DE/PDE）。 模型可以是其他类的嵌套类（递归定义）。
ShirtSize eSize = ShirtSize.Small;
10
常量（Constant）
用途： 作为助记符增强可读性。 易于维护。 命名常量（Named Constant） constant Real PI=3.141592653589793; constant String RedColor="Red"; constant Integer one=1; 参数常量（Parameter Constant） 参数常量在仿真过程中是不变的。 parameter Real mass=20;
【材料成型原理——锻压】第五章 屈服准则
用单向拉伸屈服时的应力状态 ( s ,0,0)
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• 。在 1 2坐 3标系中，屈服准则都是空间曲面，叫做屈服表
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torchvision.models 推理使用 -回复
torchvision.models 推理使用-回复如何使用torchvision.models进行推理。
一、介绍torchvision.models是PyTorch深度学习库中的一个模块，提供了一系列已经预训练好的深度学习模型，用于计算机视觉任务，例如图像分类、目标检测和语义分割等。
这些模型基于流行的深度学习架构（如ResNet、VGG和AlexNet）构建而成，并且在著名的图像数据集（如ImageNet）上进行了训练和验证。
因此，可以直接使用这些预训练模型进行推理，而不必自己从头开始训练模型。
本文将详细介绍如何使用torchvision.models进行推理，并提供一步一步的指导。
二、安装和导入首先，确保你已经安装了PyTorch和torchvision库。
可以使用以下命令进行安装：pip install torch torchvision安装完成后，使用以下代码导入torchvision.models和其他必要的库：pythonimport torchimport torchvisionfrom torchvision import models, transforms三、加载和预处理图像在进行推理之前，需要加载待处理的图像，并对其进行预处理。
torchvision 提供了一系列常用的图像预处理方法，例如缩放、裁剪和归一化等。
通过使用transforms库，可以很方便地将这些预处理操作应用于输入图像。
以下是一个加载和预处理图像的示例代码：pythonimage_path = 'path/to/your/image.jpg'image = Image.open(image_path)preprocess = pose([transforms.Resize(256),transforms.CenterCrop(224),transforms.ToTensor(),transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])])input_tensor = preprocess(image)input_batch = input_tensor.unsqueeze(0)在上面的代码中，首先使用PIL库加载了图像。
IEEE 1471-2000
What is an “Architecture”?
♦ Architecture: the fundamental organization of a system
embodied in its components, their relationships to each other and to the environment and the principles guiding its design and evolution. where: – fundamental organization means essential, unifying concepts and principles – system includes application, system, platform, systemof-systems, enterprise, product line, ... – environment is developmental, operational, programmatic, … context of the system
common terminology exists ♦ To provide a means to talk about Architectural Descriptions in the Context of – System Stakeholders – Life Cycle – Uses of Architectural Description
anadaddressesallstakeholdersconcernssometypicalstakeholderssometypicalstakeholders?client?acquirer?owner?user?operator?architect?systemengineer?developer?designer?builder?maintainer?serviceprovider?vendor?subcontractor?plannerieee1471requirements
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Twitter: #ICCA12
Private Sector Funding Support
• Since the end of 2003, the City ceased to provide financial grants to Tourism Toronto • Early 2003 - Due to the SARS pandemic that spread from HK to 37 countries, Toronto’s business & tourism industry badly affected with massive layoffs in hotel sector • Tourism Toronto and the GTHA rallied support of the hotel community – agreed to establish the DMF – destination marketing fee (3% room levy) collected by the GTHA
Internatintion Association
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Twitter: #ICCA12
Disaster Management
• By end of 2004, TT had a staff of 70 focusing on business development from all markets and hoped to recover from the damage to the convention and tourism industry • Much effort put into marketing and media relations to manage desired outcome of an enhanced public perspective of our multicultural city
International Congress and Convention Association
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Twitter: #ICCA12
Return to Public / Private Funding
• In July 2010, the Provincial Government amalgamated the tax system to Harmonized Sales Tax (HST 13%) • DMF ceased to exist as the Province took ownership of the DMF and controlled the funding to TT • TT’s funding returned to (Public/Private) Government (92% - $28.5M out of a budget of $31M) / Industry (8% or $2.5M)
International Congress and Convention Association
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Twitter: #ICCA12
History and Funding
• 1926 – Toronto Convention & Tourist Bureau was formed as a not-for-profit co-operative marketing/sales & visitor services organization by the Hotel Association of Toronto and the Toronto Board of Trade • Initial Funding Model – Public/Private • City provided grants to TT for destination marketing services ($600,000) • TT staff of (3)
International Congress and Convention Association
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Twitter: #ICCA12
Former Governance
• Report to 42 member Board of Directors, including 7 members of City Council / Mayor served as Honorary Chair • Performance measures determine funding commitments each year • Annual Marketing & Business Plan submission to City Council • Semi-annual briefing by TT’s President to Council on the state of tourism industry • Annual audited statement by chartered accountant to City’s standards & practices
International Congress and Convention Association
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Twitter: #ICCA12
Tourism Toronto’s Current Structure
• Staff of 80 reports to a 22 member Board of Directors drawn from broad spectrum of Greater Toronto’s tourism industry, Municipal & Provincial Government • Focus on driving business tourism, conventions, special events and leisure trade sales • Extensive consumer marketing campaigns and media relations program in key cities to drive visitors to our urban escape
International Congress and Convention Association
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Twitter: #ICCA12
Public/Private Sector Partnership
• Tourism Toronto has a membership of over 1200 members from the hospitality & tourism-related organizations • HQ’d in Toronto with offices in Mississauga, Ottawa, Chicago & Washington DC • TT’s Partners include the Greater Toronto Hotel Association, City of Toronto, Ontario Ministry of Tourism & Culture, Canadian Tourism Commission, City of Mississauga, City of Brampton, Air Canada & Via Rail
International Congress and Convention Association
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Twitter: #ICCA12
TORONTO, ONTARIO, CANADA
Located on the shores of Lake Ontario Major air travel hub to Canada & the US Population: 5.5 million in Greater Toronto Region Annual visitors: 26 million Economic Impact: $4.4 Billion
51st ICCA Congress
Models for Structuring City Convention Bureaux and Other Marketing Organizations
Tuesday 23 Oct 11:00
International Congress and Convention Association
International Congress and Convention Association
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Twitter: #ICCA12
History and Funding
• 1986 – TT incorporated as a non-profit association as the Metro Toronto Convention & Visitors Association (known as Tourism Toronto) representing 750 member organizations • 1988 - City of Toronto grant reached a high of $10M
International Congress and Convention Association
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Twitter: #ICCA12
Structure & Role of Tourism Toronto
• 1995-1998, grant level diminished from $6.17M to $4.31M • January, 2000 – City’s Economic Development & Parks Committee recommended grant increase to $4.5M Tourism Toronto reconfirmed our mandate: • Destination Marketing Services • Advertising, promotion & media service • Visitor information • Market Research