基于GSPN制造系统工作流建模及性能分析

依据制造系统离散性和自组织性的特点,应用广义随机Petri网(GSPN)与马尔可夫链理论相结合的方法,对汽车工业面对订单生产(MTo)工作流模型进行构建和定量分析,得出了制造系统工作流模型中的等待时间、资源的利用率以及吞吐量和系统瓶颈等参数,为制造系统工作流性能的有效评估提供了理论依据.通过实例,验证了该建模与分析方法的实用性和有效性.     

一种新的基于Petri网的分层工作流过程模型

过程模型的描述能力和分析能力难以满足企业的要求,为此,提出了一种新的基于Petri网的分层工作流过程模型。在深入研究各种工作流模型的基础上,通过对基本网进行一定的扩展,给出工作流过程的分层模型。该模型由工作流描述模型和工作流分析模型组成。工作流描述模型直接支持所有工作流模式,特别是多实例、取消、高级同步等高级Petri网无法直接描述的模式。工作流描述模型在Petri网的基础上增加了控制变量,并将变迁划分为变迁入口和变迁体两部分。控制变量与变迁之间构成读写关系。变迁入口函数通过判断控制变量,消解工作流描述模型中的冲突;变迁体函数通过可扩展逻辑描述语句,实现对控制变量的读写操作。工作流分析模型作为工作流描述模型的分析模型,剥离了工作流描述模型个案的语义信息,可以直接利用已有的Petri网分析技术来分析模型。最后,通过几个例子说明了如何使用本文提出的模型对各种复杂流程进行建模和分析。     

基于面向对象赋时Petri网的工作流建模方法

介绍了一般Petri网代数表示的基本定义，分析了赋时Petri网引入时间因素的两种方式。将面向对象建模技术融入到Petri网模型中，形成了面向对象赋时Petri网模型，讨论了建立基于面向对象赋时Petri网的工作流模型的步骤。最后运用面向对象赋时Petri网建立了某制造企业业务流程的工作流模型，并运用可达树分析方法分析了网模型的活性。     

基于层次时间Petri网的工作流模型可达性分析方法

为了有效管理工作流,需要对工作流模型进行合理性分析与验证.为此,提出了一种基于层次时间Petri网的工作流模型,给出了从时间Petri网工作流模型转化成基于层次时间Petri网工作流模型的规则及算法.证明了任何一个能够转化成基于层次时间Petri网的时间Petri网工作流模型在物理上都是可达的.在时间方面,提出了基于层次时间Petri网工作流模型的层次时间树算法,并给出了时间可达性的静态和动态分析与验证方法.通过实例验证了该方法在工作流模型的物理、时间静态和时间动态可达性分析中的有效性.     

基于广义随机Petri网的可重组制造单元建模与分析方法

为揭示可重组制造单元的重组过程并计算重组方式对系统性能的影响,根据可重组制造单元的特征,提出了基于广义随机Petri网的模块化建模及分析方法。该方法将制造单元的不同资源及重组生产过程对应于相应的广义随机Petri网基本模块,并通过过渡变迁合成广义随机Petri网模型。在此基础上,采用马尔可夫理论及相关数学方法,分析可重组制造系统的性能指标,并通过实际应用,验证了该建模与分析方法的有效性。     

工作流模型时间有界性验证与分析研究

对工作流模型分析进行了层次划分后，提出了工程流模型时间有界性的问题，从完成工作流管理联盟给出的工作流图形化模型向工作流网的模型映射之后，利用绝大多数描述业务过程的工作流模型都具有自由选择性的特点，提出了一种将映射得到的自由选择工作流网分解为一组变迁组件网的分解算法，在此基础上，结合工作流模型的资源视图，详细阐述了基于Petri网理论的工作流模型时间有界性分析与验证方法。     

一种新的面向用户的工作流模型

为满足企业用户对工作流模型的描述能力和分析能力的要求,提出了一种新的面向用户的工作流描述模型——工作流描述网。该描述网可直接支持所有的工作流模式,特别是多实例、取消、高级同步等绝大多数工作流模型不直接支持的模式;通过提供多实例任务、取消任务、带传递变迁的任务等高级组件,直接支持工作流模式中几个主要复杂模式,每一个高级组件都对应一定结构的工作流描述网,并具有形式化的语义,在分析时按照一定的规则展开;基于Petri网,通过增加控制变量,及其与变迁间的通信机制来弥补Petri网无法处理复杂数据结构的缺陷。最后,通过实例说明了如何对各种复杂流程进行建模和分析。     

基于Petri网的海关业务流程工作流模型分析

Petri网作为当今最具有前途的建模工具,它的应用几乎涉及到计算机学科的各个领域。这里通过对基于Petri网的海关业务流程工作流模型的实例分析,最终得出优秀的工作流模型可以优化工作流程、提高企业运行效率、增强企业竞争力的结论,而且该建模方式也为设计与开发高可靠性、柔性和适用性的工作流模型提供很好的依据。     

基于矩母函数的工作流网性能分析方法

现有的基于Petri网工作流性能分析方法对模型中活动的时间分布函数有较多限制,求解过程也较为复杂.为此,通过引入矩母函数,并结合Petri网可达图分析方法,将活动服从任意分布的工作流模型同构于可达图,在进一步消减可达图突发状态的基础上,用传递函数替代整个网络的矩母函数.最后,根据矩母函数的特征,结合实例分析了工作流网的系统件能,验证了该方法用于分析工作流模型的时间性能和资源利用率的可行性.     

基于Petri网的轻量级工作流引擎设计与实现

工作流引擎是工作流管理系统的核心。一个可复用、可扩展的工作流引擎将极大的缩短整个系统的开发周期。该文通过将Petri网映射到工作流过程模型,提出一种基于Petri网的轻量级工作流引擎的设计与实现方法。该工作流引擎能方便地嵌入到到各种体系架构中,可以容易地进行扩展,形成完整的工作流管理系统。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.