离散事件仿真及其应用的某些新进展

简述系统仿真技术的作用,分析离散事件仿真技术的新进展,包括可视化及动画仿真,图形建模,模块重用、并行离散事件仿真以及仿真系统与其他应用系统如数据库、电子表、ＣＡＤ、计划系统等集成技术,例示仿真技术在澳大利亚、加拿大、南非、美国等硬岩矿山、煤矿、露天矿,地下矿,冶金过程,物料处理系统中应用的现状,讨论仿真技术在矿业中的应用与发展前景,包括分层次建模,基于万维网（ＷＷＷ）的可视化仿真,仿真系统与地质建     

On-line reschedule optimization for passenger railways in case of emergencies

This paper deals with a special case of the Vehicle Re-Scheduling Problem (VRSP) for passenger railways in case of emergencies. These emergencies arise when a service line is disturbed due to a huge and unexpected demand which exceeds the service line capacity. In order to provide a proper response to this type of emergency, an on-line optimization model based on a discrete-event simulation model is proposed to provide and support decisions about reassigning vehicles from other lines of the transport system to the disturbed line. The simulation model is based on a dynamic network loading model, a dynamic demand generation model, and a schedule-based service network. The on-line optimization model has been solved using two greedy heuristics which automatically generate near-optimal decisions about vehicle reassignments considering the total time in system for passengers as the minimization criterion. An experimental study, based on a synthetic network and the Madrid Regional Railway network, shows that the second proposed heuristic provides near-optimal reassignment decisions with short computation times compatible with real-time use.     

TIME WINDOWS: AUTOMATED ABSTRACTION OF CONTINUOUS-TIME MODELS INTO DISCRETE-EVENT MODELS IN HIGH AUTONOMY SYSTEMS∗

This paper describes the automated generation of time windows from continuous system simulation models. Time windows can be used to automatically generate equivalent discrete-event models at a coarser granularity level and they are instrumental to the design of event-based control systems. The generation of time windows represents one facility in the knowledge-based multifacetted modeling and simulation environment. DEVS-Schemc. In this environment, continuous-time and discrete-event models can coexist and they can be amalgamated with AI techniques. The usefulness of these concepts will be demonstrated by means of a model of a robot controlled fluid handling laboratory for Space Station Freedom to be used for research in Life Sciences, Microgravity Sciences, and Space Medicine.     

Multi-commodity flow dynamic resource assignment and matrix-based job dispatching for multi-relay transfer in complex material handling systems (MHS)

Mass management and production of customized products requires material handling systems (MHS) which are flexible and responsive enough to accommodate dynamic and real-time changes in material handling tasks. Towards this goal, we develop a novel control framework to improve the flexibility and responsiveness of material handling systems. Flexibility is achieved by using multi-commodity flow network optimization to find the most optimized job sequence in terms of minimum transfer steps. Responsiveness is achieved by the use of a matrix-based discrete event (DE) supervisory controller to dispatch equipment control commands in real-time based on real-time sensor information, according to the optimized sequence. By modeling the MHS network as multi-commodity flow network to define job routes, and using the matrix-based DE controller to implement the job routes in real-time, the users achieve a seamlessly integrated solution to control the execution of transfer jobs that covers the supervisory planning stage through the real-time actual dispatching decisions. The proposed control framework is evaluated on an industrial case study of airfreight terminal material handling and simulation results show its effectiveness.     

From verified model to executable program: the PAT approach

CSP# is a formal modeling language that emphasizes the design of communication in concurrent systems. PAT framework provides a model checking environment for the simulation and verification of CSP# models. Although the desired properties can be formally verified at the design level, it is not always straightforward to ensure the correctness of the system’s implementation conforms to the behaviors of the formal design model. To avoid human error and enhance productivity, it would be beneficial to have a tool support to automatically generate the executable programs from their corresponding formal models. In this paper, we propose such a solution for translating verified CSP# models into C# programs in the PAT framework. We encoded the CSP# operators in a C# library-“PAT.Runtime”, where the event synchronization is based on the “Monitor” class in C#. The precondition and choice layers are built on top of the CSP event synchronization to support language-specific features. We further developed a code generation tool to automatically transform CSP# models into multi-threaded C# programs. We proved that the generated C# program and original CSP# model are equivalent on the trace semantics. This equivalence guarantees that the verified properties of the CSP# models are preserved in the generated C# programs. Furthermore, based on the existing implementation of choice operator, we improved the synchronization mechanism by pruning the unnecessary communications among the choice operators. The experiment results showed that the improved mechanism notably outperforms the standard JCSP library.     

Know means no: Incorporating knowledge into discrete-event controlsystems

Modal logic is introduced into the modeling of discrete-event systems. Analysis within this framework includes formal reasoning about what supervisors know or do not know about a given system. This model can be used to develop control strategies that solve decentralized discrete-event control problems. When a problem cannot be solved using fully decentralized supervisors, reasoning about knowledge may provide guidelines for incorporating communication and pooled information into the model     

A computational model of time for stiff hybrid systems applied to control synthesis

Computation has quickly become of paramount importance in the design of engineered systems, both to support their features as well as their design. Tool support for high-level modeling formalisms has endowed design specifications with executable semantics. Such specifications typically include not only discrete-time and discrete-event behavior, but also continuous-time behavior that is stiff from a numerical integration perspective. The resulting stiff hybrid dynamic systems necessitate variable-step solvers to simulate the continuous-time behavior as well as solver algorithms for the simulation of discrete-time and discrete-event behavior. The combined solvers rely on complex computer code which makes it difficult to directly solve design tasks with the executable specifications. To further leverage the executable specifications in design, this work aims to formalize the semantics of stiff hybrid dynamic systems at a declarative level by removing implementation detail and only retaining ‘what’ the computer code does and not ‘how’ it does it. A stream-based approach is adopted to formalize variable-step solver semantics and to establish a computational model of time that supports discrete-time and discrete-event behavior. The corresponding declarative formalization is amenable to computational methods and it is shown how model checking can automatically generate, or synthesize, a feedforward control strategy for a stiff hybrid dynamic system. Specifically, a stamper in a surface mount device is controlled to maintain a low acceleration of the stamped component for a prescribed minimum duration of time.     

基于通信协议的接口测试用例自动生成框架

为了实现对软件配置项和软件系统的接口测试的测试用例自动生成,建立了基于通信协议的接口测试用例自动生成框架,对该生成框架的输入模型和算法集合进行研究。提出了基于通信协议的接口测试用例生成框架的输入模型,并在输入模型中建立数据帧之间的一级关联矩阵和数据帧内字段间的二级关联矩阵。以输入模型为基础,说明发送端和接收端的接口测试用例自动生成算法。结合实际项目中的通信协议,介绍了如何将通信协议信息转换至输入模型,如何通过算法集合自动生成测试用例集。实验结果表明：基于通信协议的接口测试用例自动生成框架生成的接口测试用例可以替代人工生成的接口测试用例,极大地提高了软件接口测试工作的效率。     

基于遗传算法的网络安全配置自动生成框架

合理配置网络安全设备以对信息系统实施必要的访问控制,是网络安全管理的一项重要任务。随着网络规模的不断扩大,各种用户权限之间会形成复杂的依赖关系,传统基于人工的方式配置网络访问控制策略,主要是依据业务系统的实际需求,按照最小权限的原则进行分配,这种分配方式忽略了权限之间的依赖关系,容易产生过授权的现象,从而为网络带来安全隐患。为解决该问题,提出了一个基于遗传算法的安全配置自动生成框架。首先,以网络规划信息和配置信息为基础,确定用户可能的权限,提取网络基础语义,构建相应的网络安全风险评估模型,实现不同安全配置的安全评估;然后,对网络中所有可能的安全配置进行合理编码,确定遗传算子和算法参数,生成初始种群;最后,通过遗传算法,自动选取较优个体来生成子代个体。该框架能够通过自动比较不同的安全配置下的网络安全风险,以及在可能的配置空间内自动搜索安全配置的最优解,来实现网络安全设备访问控制策略的自动生成。构造一个拥有20个设备、30个服务的模拟网络环境对该框架进行验证,在该模拟环境下,该框架能够在种群样本数目为150的条件下,不超过10次迭代即可找到较优的安全配置。实验结果充分表明,该框架能够根据网络的安全需求,自动生成合理的网络安全配置。     

基于Petri网的流程供应链过程建模分析

煤炭供应链是一个涉及原煤开采、分选加工、煤炭销售及其煤炭运输过程的一个物流、信息流、资金流的综合过程。论文应用供应链思想对煤炭供应链进行研究时应用Petri网对供应链物流及供应流运行过程进行建模,然后运用子过程分析煤炭供应链存在的问题,最后结合煤炭供应链过程模型运用VB方法完成供应链决策过程的可视化仿真,找出煤炭供应链运营瓶颈。     

基于门控化上下文感知网络的词语释义生成方法

传统的词典编纂工作主要采用人工编纂的方式,效率较低且耗费大量的资源。为减少人工编纂的时间和经济成本,该文提出一种基于门控化上下文感知网络的词语释义生成方法,利用门控循环神经网络(GRU)对词语释义生成过程进行建模,自动为目标词生成词语释义。该模型基于编码器—解码器架构。编码器首先利用双向GRU对目标词的上下文进行编码,并采用不同的匹配策略进行目标词与上下文的交互,结合注意力机制分别从粗粒度和细粒度两个层次将上下文信息融合到目标词的向量表示中,最终获得目标词在特定语境中的编码向量。解码器则同时基于目标词的语境与语义信息为目标词生成上下文相关的词语释义。此外,通过向模型提供目标词字符级特征信息,进一步提高了生成释义的质量。在英文牛津词典数据集上进行的实验表明,该文提出的方法能够生成易于阅读和理解的词语释义,在释义建模的困惑度和生成释义的BLEU值上分别超出此前模型4.45和2.19,性能有显著提升。     

Automated generation of multiphysics simulation models to support multidisciplinary design optimization

To ensure a consistent design representation for serving multidisciplinary analysis, this research study proposes an intelligent modeling system to automatically generate multiphysics simulation models to support multidisciplinary design optimization processes by using a knowledge based engineering approach. A key element of this system is a multiphysics information model (MIM), which integrates the design and simulation knowledge from multiple engineering domains. The intelligent modeling system defines classes with attributes to represent various aspects of physical entities. Moreover, it uses functions to capture the non-physical information, such as control architecture, simulation test maneuvers and simulation procedures. The challenge of system coupling and the interactions among the disciplines are taken into account during the process of knowledge acquisition. Depending on the domain requirements, the intelligent modeling system extracts the required knowledge from the MIM and uses this first to instantiate submodels and second to construct the multiphysics simulation model by combining all submodels. The objective of this research is to reduce the time and effort for modeling complex systems and to provide a consistent and concurrent design environment to support multidisciplinary design optimization. The development of an unstable and unmanned aerial vehicle, a multirotor UAV, is selected as test case. The intelligent modeling system is demonstrated by modeling thirty-thousand multirotor UAV designs with different topologies and by ensuring the automatic development of a consistent control system dedicated for each individual design. Moreover, the resulting multiphysics simulation model of the multirotor UAV is validated by comparing with the flight data of an actual quadrotor UAV. The results show that the multiphysics simulation model matches test data well and indicate that high fidelity models can be generated with the automatic model generation process.     

数据驱动的汽车总装线建模与仿真技术研究

现代制造业的生产模式向柔性制造和客户化定制方向发展,为了提高制造系统的快速响应能力,实现快速仿真分析,提出基于数据驱动的建模与仿真方法,其具有建模周期短、模型可读性、可重用性较高的特点.利用IDEFIX建模方法建立模型的底层数据结构,基于Arena构建仿真模型生成器,利用已建好的数据模型提供的属性信息,自动生成目标系统...     

Automated generation of simulation models for control code tests

The correct configuration of the control code is a critical part of every process control system engineering project. To ensure the conformity of the implemented control functions with the customer’s specifications, test activities, e.g., the factory acceptance test (FAT), are conducted in every control engineering project. For the past several years, control code tests have increasingly been carried out on simulation models to increase test coverage and timeliness. Despite the advantages that simulation methods offer, the manual effort for generating an applicable simulation model is still high. To reduce this effort, an automated model generation is proposed in this paper. The models automatically generated by this approach provide a modeling level of detail that matches the requirements for the tests of the control code on the base automation level. Therefore, these models do not need to be as detailed as the high-fidelity models which are used for, e.g., model predictive control (MPC) applications. Within this paper, the authors describe an approach to automatically generate simulation models for control code tests based on given computer aided engineering (CAE) planning documents.     

A model framework-based domain-specific composable modeling method for combat system effectiveness simulation

Combat system effectiveness simulation (CoSES) plays an irreplaceable role in the effectiveness measurement of combat systems. According to decades of research and practice, composable modeling and multi-domain modeling are recognized as two major modeling requirements in CoSES. Current effectiveness simulation researches attempt to cope with the structural and behavioral complexity of CoSES based on a unified technological space, and they are limited to their existing modeling paradigms and fail to meet these two requirements. In this work, we propose a model framework-based domain-specific composable modeling method to solve this problem. This method builds a common model framework using application invariant knowledge for CoSES, and designs domain-specific modeling infrastructures for subdomains as corresponding extension points of the framework to support the modeling of application variant knowledge. Therefore, this method supports domain-specific modeling in multiple subdomains and the composition of subsystem models across different subdomains based on the model framework. The case study shows that this method raises the modeling abstraction level, supports generative modeling, and promotes model reuse and composability.     

三维地质构造的三角形格架式网格生成方法

三维油气运聚模拟计算方法需要在构造模型的约束下生成三维地质格架式网格。针对这一需求对现有网格生成方法进行了分析对比,并在此基础上提出一套三角形格架式网格生成方法。该方法采用了限定Delaunay三角剖分技术生成基础的地质层面模型,同时提出协同剖分算法来解决地层面网格在公共交线处的几何拓扑一致性问题,并表明了算法的正确性,最后给出地质层面的剖分实例。实验结果表明了该方法在工程实践中的有效性。     

Agent and data mining based decision support system and its adaptation to a new customer-centric electronic commerce

Recently, as the Internet has become more widely used, Electronic Commerce (EC) has emerged and has developed a high-level business environment. The customer-centric EC model is important for the success of EC and this study presents a new customer-centric EC model in make-to-order (MTO) semiconductor manufacturing environment. In this study we proposed the EC model providing the process transparency of process sampling method that can provide online semiconductor customers with the performance information of available process sampling methods which can be used at all manufacturing process steps for their own products in MTO manufacturing environment, and then the capability to select a desirable one among them based on their purchase situations on EC web site. In the proposed EC model the customer can select a process sampling method that is most suitable to him/her according to the customer's purchase situation. In this model the use of intelligent decision support system called customized sampling decision support system (CSDSS) that can autonomously generate available customized sampling methods and provide the performance information of those methods to EC system is requisite. We implemented an Internet-based prototype of CSDSS which had an architecture based on intelligent agent technology and also the successful integration of data mining process for the generation of optimal sampling method into DSS framework by means of applying that technology.     

POEMS: end-to-end performance design of large parallel adaptive computational systems

The POEMS project is creating an environment for end-to-end performance modeling of complex parallel and distributed systems, spanning the domains of application software, runtime and operating system software, and hardware architecture. Toward this end, the POEMS framework supports composition of component models from these different domains into an end-to-end system model. This composition can be specified using a generalized graph model of a parallel system, together with interface specifications that carry information about component behaviors and evaluation methods. The POEMS Specification Language compiler will generate an end-to-end system model automatically from such a specification. The components of the target system may be modeled using different modeling paradigms and at various levels of detail. Therefore, evaluation of a POEMS end-to-end system model may require a variety of evaluation tools including specialized equation solvers, queuing network solvers, and discrete event simulators. A single application representation based on static and dynamic task graphs serves as a common workload representation for all these modeling approaches. Sophisticated parallelizing compiler techniques allow this representation to be generated automatically for a given parallel program. POEMS includes a library of predefined analytical and simulation component models of the different domains and a knowledge base that describes performance properties of widely used algorithms. The paper provides an overview of the POEMS methodology and illustrates several of its key components. The modeling capabilities are demonstrated by predicting the performance of alternative configurations of Sweep3D, a benchmark for evaluating wavefront application technologies and high-performance, parallel architectures.     

基于形式语法的建筑设计细胞衍生法研究

目前可用的计算机辅助设计工具,为设计开发过程后期阶段提供了相当有效地支 持,但对于设计初始阶段,即设计思路成熟、但设计的结构和形状还未确定之时,需要一种新 的CAD 解决方案来支持设计者思维方式并激发创作灵感。因此,提出一种基于空间形式语法的 建筑设计生成方法,描述复杂空间形体如何自动派生--通过限定的规则产生初始体块,在规 则内生成与初始体块相似体块,再而改变局部可变规则生成多样复杂的系统,同时允许设计者 积极参与整个生成过程。以CFS 墙体原型建模为例,验证该参数化建模方法的有效性和可行性。     

Automatic generation of fabrication drawings for façade mullions and transoms through BIM models

Fabrication drawings are essential for manufacturing, design evaluation and inspection of building components, especially for building façade structural components. In order to clearly represent the physical characteristics of the façade structural components, a large number of section views need to be produced, which is very time-consuming and labor intensive. Therefore, automatic generation of fabrication drawings for building façade components (such as mullions and transoms) is of paramount importance. In this paper, attempts have been made to develop an efficient framework in order to automatically generate fabrication drawings for building façade structural components, including mullions and transoms. To represent the complex physical characteristics (such as holes and notches) on mullions and transoms using minimum number of drawing views, a computational algorithm based on graph theory is developed to eliminate duplicated section views. Another methodology regarding the generation of breaks for top views is also proposed to further improve the quality of drawing layouts. The obtained drawing views are then automatically arranged using a developed approach. In addition, primary dimensions of the drawing views focusing on the physical features are also generated. Furthermore, in order to maintain the consistency of drawing formats across multiple drawings, a methodology is proposed to determine the scaling factors of the drawings by using clustering technique. In an illustrative example, the proposed framework is used to generate the fabrication drawings for a typical BIM model containing façade structural components, and saving in time is observed.