Concurrent design of machined products: a multivariate decisionapproach

In the traditional process of product design, a sequential approach treats each of the design steps individually without considering requirements of manufacturing, assembly and other downstream activities in the product life cycle. The lack of systematic and simultaneous consideration on the impact of design decisions on manufacturing and assembly leads to repeated and excessive changes in design and processes. To resolve this problem, the concurrent engineering approach to product design foresees and avoids potential design flaws by incorporating design requirements from downstream activities of the product development life cycle early in the design stage. This research develops a methodological framework for product life cycle design in concurrent engineering. Through a cohesive organization of semantics of high-level design features and relationships, this representation provides a means to evaluate the impact of design on subsequent activities in the product life cycle, including design for manufacture (DFM), design for assembly (DFA), and design for productivity (DFP). In the first stage of a two-level design, selection of design candidates is made based on multiple design criteria using utility theory taking into account imprecision of design information and user preference. The second stage of design further fine-tunes attribute values of the selected design by a genetic algorithm based parametric optimization procedure. An illustrative example of two alternative designs of a milling fixture demonstrates the effectiveness of the framework and its implementation methodology     

A scheduling approach for design activities in concurrentengineering

This paper presents an optimization scheduling approach for concurrent design projects, in which activities may be executed in more than one operating mode and renewable as well as nonrenewable resources exist. Research on the development of a scheduling approach for concurrent scheduling is expected to shorten development lead time, minimize cost, and eliminate unnecessary redesign periods. In this paper, an integrated criterion function is proposed to ensure optimal concurrent scheduling and effective utilization of resources along with fluent delivery of information. In the criterion function, some key factors such as time order, resources, lead time and overlapping time of activities, which can make concurrent activities execute successfully, are taken into account adequately. Besides, two cruxes in concurrent engineering-role allocation, prerelease, and feedback revision process are discussed in detail. The example is part of a certain product development process, and the scheduling results demonstrate that the proposed algorithm is feasible     

The influence of process concurrency on project outcomes in productdevelopment: an empirical study of cross-functional teams

This study examines the practice of concurrent engineering (CE) in terms of process concurrency, and the impact of concurrency on success of product development projects. The study is based on 50 cross-national projects from companies in Australia, Canada, Denmark, Finland, United Kingdom, and the United States in the aerospace, automobile, chemical, computer, electronics, shipbuilding, and telecommunications industries. Four dimensions of process and behaviors of engineering/R&D and manufacturing members of cross-functional product development teams were reliably operationalized: (1) two-way communication, (2) overlapping problem solving, (3) readiness to make decisions on the basis of uncertain and ambiguous information, and (4) readiness to release uncertain and ambiguous information. These dimensions of process concurrency were found to be reliable predictors of development projects' success, as measured by product cost and quality, project schedule and budget performance, and project team satisfaction. The paper offers implications for theory and practice and models of CE management for future research     

一种基于QoS的事务工作流并发调度算法

并发冲突引起的连锁夭折会降低系统性能,提出了一种基于QoS的事务工作流调度算法,该算法适应异构环境需求,支持基于QoS的延迟调度优化策略和SAFE集合扩充优化策略,可根据QoS参数调整相应的调度决策,在保证分布异构环境中复杂事务工作流并发正确性的同时减少连锁夭折.证明了算法不会引起循环等待和饿死现象,可保证调度的可串行性和可恢复性,性能模拟表明该算法适用于长期运行的事务工作流的并发调度,可有效减少连锁夭折,从而减少由此带来的性能损失.     

公平的多方并发签名方案

Tonien等在ISC2006上首次提出了多方并发签名体制,但Xie和谭指出Tonien等的方案并不满足公平性,进而分别重新构造了多方并发签名方案。分别对Xie和谭的多方并发签名方案进行了分析,指出他们的方案也不满足公平性,进而正式定义了公平多方并发签名的安全模型,并基于双线性对及多方密钥协商技术重新构造了一个多方并发签名方案。分析表明,在随机预言模型下,假设CDH问题是难解的,新方案同时满足正确性、不可伪造性、模糊性、并发性和公平性,并且与同类方案相比,新方案在签名长度、计算量、通信代价方面效率较高。     

A decision analytic framework for evaluating concurrent engineering

This paper quantifies key issues with regard to concurrent engineering through the use of risk and decision analysis techniques that enable us to better understand, structure, and manage the design process. In concurrent engineering, the information structure of a design process does not usually imply the execution patterns of the corresponding design tasks. On the contrary, this gap between the information structure and execution patterns is the essence of concurrent engineering and its basic advantage over traditional sequential design. In this paper, we relate the structure of information flow in a design process to three different execution strategies: sequential, partial overlapping, and concurrent. The risks of excessive task iterations or redesigns associated with each execution pattern are probabilistically modeled. Risk and decision analysis methodology is used to determine the best execution strategy and the optimal overlapping policy for a set of activities given their information structure. Applying this theoretical framework to a real-world design application of an automotive cylinder block suggested a potential 18% reduction in development cycle time     

Modeling impacts of process architecture on cost and schedule risk in product development

To gain competitive leverage, firms that design and develop complex products seek to increase the efficiency and predictability of their development processes. Process improvement is facilitated by the development and use of models that account for and illuminate important characteristics of the process. Iteration is a fundamental but often unaddressed feature of product development (PD) processes. Its impact is mediated by the architecture of a process, i.e., its constituent activities and their interactions. This paper integrates several important characteristics of PD processes into a single model, highlighting the effects of varying process architecture. The PD process is modeled as a network of activities that exchange deliverables. Each activity has an uncertain duration and cost, an improvement curve, and risks of rework based on changes in its inputs. A work policy governs the timing of activity execution and deliverable exchange (and thus the amount of activity concurrency). The model is analyzed via simulation, which outputs sample cost and schedule outcome distributions. Varying the process architecture input varies the output distributions. Each distribution is used with a target and an impact function to determine a risk factor. Alternative process architectures are compared, revealing opportunities to trade cost and schedule risk. Example results and applications are shown for an industrial process, the preliminary design of an uninhabited combat aerial vehicle. The model yields and reinforces several managerial insights, including: how rework cascades through a PD process, trading off cost and schedule risk, interface criticality, and occasions for iterative overlapping.     

基于随机几何理论的多天线密集异构网络性能分析与优化

无线网络的异构化、密集化部署极大地提高了系统容量,可满足用户日益增长的数据流量需求,但是复杂的网络结构、近乎随机的基站分布不利于系统的性能评估和参数设计。针对这一问题,该文提出一种适用于多天线密集异构网络的性能分析框架。首先,利用随机几何模型推导了覆盖率的闭合表达式并给出了优化方案。为了直观地观察关键系统参数对覆盖率的影响,还给出了一种渐近表达式。其次,推导了区域频谱效率(ASE)的积分表达式,为了减小计算复杂度,给出了一种ASE的上界。最后,还提出了一种有效的算法来设计最优的基站(BSs)部署密度,以在满足覆盖率需求的前提下最大化ASE。仿真结果验证了理论分析的正确性和所提优化算法的有效性。该文的研究成果不但可以为复杂网络的性能分析提供理论依据,还可为系统的优化与设计提供可行性方案。     

基于量子自由粒子模型的优化算法框架

基于量子系统下的自由粒子模型，提出了多尺度自由粒子优化算法（Multi-scale Free Particle Optimization Algorithm，MFPOA），并在物理模型的基础之上研究了该算法的内部机制.通过类比量子系统和优化系统，将优化问题的求解过程转化成粒子在微观系统下的运动过程.通过在MATLAB仿真平台上对自由粒子优化算法的参数设置进行了研究，并分析了与同类搜索机制的算法的区别.最后通过实验得出，MFPOA更适合求解单模简单函数，求解复杂多模函数需要更多的迭代次数.     

The design of weighted minimax quadrature mirror filters

A technique for converting the constrained nonlinear optimization problem encountered in the design of weighted minimax quadrature mirror filters into an iterative unconstrained nonlinear optimization problem is presented. This renders the design of weighted minimax quadrature mirror filters possible. The technique is very efficient, typically taking about seven iterations to converge. A rapidly converging iterative procedure for solving the above nonlinear unconstrained optimization problem is also presented. This procedure typically requires less than five iterations to converge     

Matching 3-D prone and supine CT colonography scans using graphs

In this paper, we propose a new registration method for prone and supine computed tomographic colonography scans using graph matching. We formulate 3-D colon registration as a graph matching problem and propose a new graph matching algorithm based on mean field theory. In the proposed algorithm, we solve the matching problem in an iterative way. In each step, we use mean field theory to find the matched pair of nodes with highest probability. During iterative optimization, one-to-one matching constraints are added to the system in a step-by-step approach. Prominent matching pairs found in previous iterations are used to guide subsequent mean field calculations. The proposed method was found to have the best performance with smallest standard deviation compared with two other baseline algorithms called the normalized distance along the colon centerline (NDACC) ( p = 0.17) with manual colon centerline correction and spectral matching ( p < 1e-5). A major advantage of the proposed method is that it is fully automatic and does not require defining a colon centerline for registration. For the latter NDACC method, user interaction is almost always needed for identifying the colon centerlines.     

基于DDPG的综合化航电系统多分区任务分配优化方法

综合化航电系统（Integrated Modular Avionics,IMA）通过时空分区机制实现共享资源平台下的多航电功能集成,分区间的任务分配方法的优劣决定着航电系统的整体效能。针对航电任务集合在多分区内的分配调度问题,提出了一种基于深度强化学习的优化方法。构建了航电系统模型与任务模型,以系统资源限制与任务实时性需求为约束,以提高系统资源利用率为优化目标,将任务分配过程描述为序贯决策问题。引入马尔科夫决策模型,建立基于深度确定性策略梯度（Deep Deterministic Policy Gradient,DDPG）法的IMA任务分配模型并提出通用分配架构;引入状态归一化、行为噪声等策略训练技巧,提高DDPG算法的学习性能和训练能力。仿真结果表明,提出的优化算法迭代次数达到500次时开始收敛,分析800次之后多分区内驻留任务方案在能满足约束要求的同时,最低处理效率提升20.55%。相较于传统分配方案和AC(Actor-Critic)算法,提出的DDPG算法在收敛能力、优化性能以及稳定性上均有显著优势。     

基于硬件CAS原语的高效多字无锁同步算法

共享内存体系结构下,为解决锁同步导致的并发性能瓶颈,本文提出了一种基于硬件CAS（比较交换）原语的无锁同步算法.该算法利用底层处理器提供的比较交换指令,实现了在多核多线程环境下对共享变量的非阻塞同步操作,通过采用全局标记值的方式,避免了传统设计中由于使用内存字标记导致的性能开销,同时确保数据在并发访问中的一致性.实验结果表明,本文算法可以高效地支持任意多字的CAS同步,提高了对共享数据的并发访问性能,具有较好的可扩展性.     

A simulation-based process model for managing complex design projects

This paper presents a process modeling and analysis technique for managing complex design projects using advanced simulation. The model computes the probability distribution of lead time in a stochastic, resource-constrained project network where iterations take place among sequential, parallel, and overlapped tasks. The model uses the design structure matrix representation to capture the information flows between tasks. We use a simulation-based analysis to account for many realistic aspects of design process behavior which were not possible in previous analytical models. We propose a heuristic for the stochastic, resource-constrained project scheduling problem in an iterative project network. The model can be used for better project planning and control by identifying leverage points for process improvements, and for evaluating alternative planning and execution strategies. An industrial example is provided to illustrate the utility of the model.     

基于Petri网的耳机部件自动装配设备PLC控制系统研究

为解决在具有并发、竞争控制的PLC控制系统中传统的PLC程序设计方法存在不适用,而且易导致程序出错并且难以检查错误等问题,利用Petri网具有图形描述、模拟特点以及分析具有并发和冲突环节等复杂事件的能力,结合Petri网的建模方法与ExSpect模型仿真技术对耳机部件自动装配设备控制系统进行建模与仿真分析,然后利用仿真结果再结合工艺流程,直观地指导构建PLC 控制系统的程序。仿真与调试结果表明：该方法可避免设备运行时相关部件的冲撞等实际问题,缩短调试时间,保证了PLC控制系统可行、可靠性。     

An Object-Oriented Multi-Thread Dialog Model

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Concurrent software engineering: prospects and pitfalls

Software development remains largely a sequential, time-consuming process. Concurrent engineering (CE) principles have been more widely adopted and with greater success in hardware development. In this paper, a methodology for marrying CE principles to software engineering, or concurrent software engineering (CSE), is proposed. CSE is defined as a management technique to reduce the time-to-market in product development through simultaneous performance of activities and processing of information. A hierarchy of concurrent software development activity is defined, ranging from the simplest (within stage) to the most complex (across products and platforms). The information support activities to support this activity hierarchy are also defined, along with two key linking concepts-synchronicity and architectural modularity. Principles of CSE are developed for each level in the activity hierarchy. Research findings that establish limitations to implementing CE are also discussed     

基于激光扫描反射式三维视觉的室内场景CAD模型研究

针对常规模型在配准过程中所需迭代次数过多的问题,提出基于激光扫描反射式三维视觉的室内场景CAD模型研究。获取原始图像空间分布情况,分析场景特征,利用金字塔分层结构,建立高斯差分尺度空间,得到匹配数据,利用池化层提取语义信息,完成基于激光扫描反射式三维视觉的室内场景CAD模型的建立。设计实验,将所建立模型与三种常规模型对比,对比结果证实,所构建模型在配准过程中所需的迭代次数更少,能够有效缩短迭代时长,提高效率。     

From DSM-Based Planning to Design Process Simulation: A Review of Process Scheme Logic Verification Issues

Planning product development processes (PDP), and particularly new product development (NPD) processes, is complex and challenging. The plan should reflect the product-related knowledge, including the influences of performing changes in one product component on the need to rework the design of other components. Given the complexity, dynamics, and uncertainties of design processes (DPs), the plan evaluation requires simulation tools. The design structure matrix (DSM) is a known method for DP planning. However, the DSM itself does not express all the relevant information required for defining process logic. Many logic interpretations are applicable in different business cases; yet, a consistent method of transforming a DSM-based plan to a logically correct concurrent process model in the case of iterative activities is lacking. A gap was identified between the literature concerning activities sequencing based on DSM and the process modeling literature concerning process verification. This survey systematically classifies the approaches used in DSM-based process planning, and discusses their strengths and limitations with problems related to process modeling logic verification of iterative processes. Demonstration of the logic differences emphasizes the need for simulation-based decision making according to the specific process attributes.