A Rework Reduction Mechanism in Complex Projects Using Design Structure Matrix Clustering Methods

To reduce the uncertainty and reworks in complex projects,a novel mechanism is systematically developed in this paper based on two classical design structure matrix(DSM)clustering methods:Loop searching method(LSM)and function searching method(FSM).Specifically,the optimal working areas for the two clustering methods are first obtained quantitatively in terms of non-zero fraction(NZF)and singular value modularity index(SMI),in which the whole working area is divided into six sub-zones.Then,a judgement procedure is proposed for conveniently choosing the optimal DSM clustering method,which makes it easy to determine which DSM clustering method performs better for a given case.Subsequently,a conceptual model is constructed to assist project managers in effectively analyzing the network of projects and greatly reducing reworks in complex projects by defining preventive actions.Finally,the aircraft design process is presented to show how the proposed judgement mechanism can be utilized to reduce the reworks in actual projects.

Schedule Model for Project Portfolio Based on Design Structure Matrix

To improve the enterprise resource utilization and shorten the cycle of the whole project portfolio, a scheduling model based on Design Structure Matrix （DSM） is built. By setting the project activity weight index system and calculating the activity weight for the project portfolio, the constraint relationship between project portfolio information and resource utilization, as the two dimensions of the DSM, are fully reflected in the sched- ule model to determine the order of these activities of project portfolio. A project portfolio example is given to il- lustrate the applicability and effectiveness of the schedule model.

An improved pseudo-static method for seismic resistant design of underground structures

This paper describes a commonly used pseudo-static method in seismic resistant design of the cross section of underground structures. Based on dynamic theory and the vibration characteristics of underground structures, the sources of errors when using this method are analyzed. The traditional seismic motion loading approach is replaced by a method in which a one-dimensional soil layer response stress is differentiated and then converted into seismic live loads. To validate the improved method, a comparison of analytical results is conducted for internal forces under earthquake shaking of a typical shallow embedded box-shaped subway station structure using four methods： the response displacement method, finite element response acceleration method, the finite element dynamic analysis method and the improved pseudo-static calculation method. It is shown that the improved finite element pseudo-static method proposed in this paper provides an effective tool for the seismic design of underground structures. The evaluation yields results close to those obtained by the finite element dynamic analysis method, and shows that the improved finite element pseudo-static method provides a higher degree of precision.

Structural Design Strategies of Polymer Matrix Composites for Electromagnetic Interference Shielding:A Review

With the widespread application of electronic communication technology,the resulting electromagnetic radiation pollution has been significantly increased.Metal matrix electromagnetic interference(EMI)shielding materials have disadvantages such as high density,easy corrosion,difficult processing and high price,etc.Polymer matrix EMI shielding composites possess light weight,corrosion resistance and easy processing.However,the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding performance.This review firstly discusses the key concept,loss mechanism and test method of EMI shielding.Then the current development status of EMI shielding materials is summarized,and the research progress of polymer matrix EMI shielding composites with different structures is illustrated,especially for their preparation methods and evaluation.Finally,the corresponding key scientific and technical problems are proposed,and their development trend is also prospected.

MATRIX PERTURBATION METHOD FOR THE VIBRATION PROBLEM OF STRUCTURES WITH INTERVAL PARAMETERS

When the parameters of structures are uncertain, the structural natural frequencies become uncertain. The interval parameters description, i.e. the unknown-but bounded parameters description is one of the methods to study the uncertainty. In this paper, the vibration problem of structure with interval parameters was studied, and the eigenvalue problem of the structures with interval parameters was transferred into two different eigenvalue problems. The perturbation method was applied to the vibration problem of the structures with interval parameters. The numerical results show that the proposed method is sufficiently accurate and needs less computational efforts.

Biomimetic Lightweight Design of Legged Robot Hydraulic Drive Unit Shell Inspired by Geometric Shape of Fish Bone Rib Structure

The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.

Probabilistic estimate of rock mass static and dynamic demands for underground excavation stabilisation

Excavation damage under high in situ stress depends largely upon the potential block size associated with any violent ejection.The size and shape of the dynamic instability are largely controlled by the location,orientation and extent of the pre-existing geological discontinuities.A new methodology is presented in which the rock mass demand can be expressed in terms of the mass in tonnes of unstable rock that is ejected per unit area of the excavation surface where failure occurs.A probabilistic approach has been implemented to estimate the potential rock mass instabilities and their associated static and dynamic demands.The new methodology considers that the strain energy released by the rock mass during violent stress-driven failure is largely converted into kinetic energy of ejection for blocks.The estimated dynamic demand has been favourably compared with observations of rock mass damage in a number of underground excavations.

Conceptual Design Process for LEO Satellite Constellations Based on System Engineering Disciplines

Satellite design process is an interdisciplinary subject in which the need for collaboration among various science and engineering disciplines is evident.Meanwhile,finding an optimal process for conceptual design of a satellite,which can optimize time and cost,is still an important issue.In this paper,based on system engineering approach,an optimal design process is proposed for LEO satellite constellations.In the proposed method,design process,design sequences,and data flow are established.In this regard,the conceptual design process is divided into two levels of mission(or constellation)and system(or satellite)as well as 15 main activities based on the mission profile,previous experiences of the authors,and existing literature.Then,the relationships between these activities have been determined by considering the importance of relationships according to their priority.Finally,these relations are optimized based on design structure matrix(DSM).By utilizing this approach,system design process of a telecommunication satellite constellation in LEO is formulated in conceptual design phase.Performance and capability of the proposed approach in optimal design process of the satellite constellation are investigated by comparing the outcome with existing results in the literature.

A New Approach to Analyzing Behavioral Change Propagation in Redesigning of Drone Camera Stabilizer

Redesigning of complex products is not an easy task. Engineering change requirements can be extracted at any stage of the product redesign process, and it makes the management of engineering change become a challenging mission. The motivation for this study is to find the shortest path of behavioral change propagation (BCP), minimize the BCP, access to the special behavioral elements in order to better managing the BCP and classifying the behavioral attribute of the elements in terms of their relationship to change by betweenness centrality coefficient (BNCC), clustering coefficient (CLC), reachability coefficient (RC) and change propagation index (CPI). In this article, the procedure of managerial decision-making is proposed by combining system restrictions in behavioral clustering design structure matrix (BCDSM) with optimization algorithms. The practicality of suggested method is verified in redesign procedure of a phantom drone camera stabilizer as a case study. The results, indicate that the absorption of change by behavioral elements is dominant in the mechanical (63.9%), electrical (61.1%) and thermal (38.9%) behaviors of the drone camera stabilizer system in redesign process. These elements are best candidates for reducing the cost and time of behavioral changes in the system redesign and are desirable for the designer.

生物医用支架仿生设计及在组织工程中的应用

背景:基于解剖学对生物组织功能与结构的认识,对于具有恢复、维持或改善组织功能的生物活性材料仿生设计是目前再生医学领域研究的热点。目的:从生物医用支架的机械性能、三维空间结构和生化活性对细胞行为的影响进行讨论,并综述生物医用支架在组织工程领域的应用。方法:应用计算机检索中国知网、万方、Web of Science、PubMed数据库2003年1月至2023年4月发表的文献,中文检索词为“细胞外基质,组织工程,支架,生物材料,仿生结构,机械性能,三维结构,腱骨界面,骨软骨,神经导管,人造血管”;英文检索词为“extracellular matrix,tissue engineering,scaffolds,biomimetic structures,biomaterials,tendon bone interfaces,osteochondral,neural conduits,artificial blood vessels”。结果与结论:细胞处在一个复杂且动态变化的三维环境中,因此细胞外基质是生物材料模拟的最终目标,在设计生物医用支架的仿生结构时需要与其所处真实的微环境相似,让细胞可以正常地贴壁、生长和迁移,并保持其多样的生理功能。生物医用支架在机械性能、三维空间结构以及生物化学性质方面对细胞外基质的仿生设计可以对组织修复过程中的细胞起到决定性作用,从而影响组织修复最后的结果。进行仿生设计的生物医用支架在腱骨界面、骨软骨界面、神经、血管再生等领域已有广泛的应用,在临床上提供了一个有前途的新思路。

国产6.5 kV/400 A SiC MOSFET模块研制及电气特性研究

为满足当前新型电力系统中电能变换装备对器件高压、大容量、工作频率高、开关损耗低的需求,文中自主研制一款国内最高功率等级的6.5 kV/400 A碳化硅金属-氧化物-半导体场效应晶体管(metal-oxide-semiconductor field effect transistor,MOSFET)模块,并对其电气特性开展研究。首先,对模块的电路与封装结构进行设计,通过热仿真和阻抗测量手段,对所研制模块的热特性以及回路寄生参数进行分析;其次,对所研制的模块开展常温(25℃)及高温(150℃)下的静态、动态特性测量。测量结果表明,在常温、高温条件下,模块的阻断漏电流与栅源极漏电流微小,且开关损耗维持一致,具备较好的耐高温特性。同时,相较于同电压电流规格的硅绝缘栅双极型晶体管器件,模块开关损耗可降低72%以上。最后,搭建碳化硅器件连续运行工况实验平台,模拟器件在换流装备中的实际运行工况,对模块进行半桥正弦脉宽调制逆变连续运行实验。连续运行实验结果表明,该模块在电压3600 V、器件电流峰值280 A条件下连续运行1h无异常,初步验证模块具备工程应用能力。研究可为高压碳化硅MOSFET的研制及工程应用提供一定支撑。

基于聚类算法的自动变速箱装配模块划分研究

自动变速箱可实现换挡变速功能,是车辆系统中传递动力的关键部件。由于其结构狭窄紧凑、零件数量繁多,导致装配复杂度大大增加。模块划分是产品模块化设计的关键步骤,可以将系统整体拆分形成若干个高内聚低耦合的模块,从而达到降低产品装配难度的目的。模糊C-均值聚类算法(FCM)是实现模块划分的传统方法,然而其对初值敏感,容易收敛到局部极值点。FCM与优化算法的结合有利于避免陷入局部最优解的情况,因此提出使用基于遗传模拟退火算法的FCM方法进行装配模块划分以获取自动变速箱模块的最佳划分方案。以重庆铁马变速箱有限公司的自动变速箱为例,使用所提方法对其进行装配模块划分,将所得模块划分结果与实际方案进行对比,证明了方法的准确性和有效性。

J型线夹用带电接引流线装置的设计与仿真

目前10kV配电线路的带电接引流线作业为人员采用辅助工具进行操作,劳动强度大、危险系数高。为提高配电线路引流线辅助夹具系统的自动化程度,提出一种J型线夹用带电接引流线装置。根据接引流线的流程,对线夹夹紧进行受力分析,当线夹夹紧力为100N时,电机只需151.404N·mm的力矩就可夹紧导线;运用ANSYS Workbench软件对关键受力部件进行静力学分析,结果表明,翻盖的结构强度满足设计要求;运用ADAMS软件对紧固机构进行动力学分析,在螺母承受350N·mm的力矩条件下,线夹的夹紧力为503N,导线的夹紧力为1345N。根据设计方案,搭建试验样机进行现场试验,预期动作都可实现。该装置实现了带电接引流线的自动化与智能化,适用性强,安全可靠。

复杂装备数字孪生跨域高效协同建模平台与应用

随着装备朝着复杂化、集成化、智能化方向发展,如何快速准确构建高保真数字孪生模型是复杂装备智能运维的基础性工作与最大技术障碍。提出依靠设计结构矩阵(DSM矩阵)进行任务耦合度优化与智能分发的策略,实现复杂装备数字孪生多点建模全方位动态监管;基于DSM矩阵特点提出一种改进遗传算法,改进优化流程并提高任务处理速度;最后,开发基于Web的分布式协同建模平台,实现了丝杠试验台数字孪生实体模型的协同构建。试验结果表明:该试验台协同建模效率得到了显著提升,为复杂装备数字孪生模型快速构建提供了工程案例,为复杂装备智能运维提供了技术支撑。

如通苏湖城际铁路主跨240m斜拉桥设计

新建如通苏湖城际铁路长兴特大桥主桥采用(51+94+240+94+51)m双塔双索面斜拉桥,主梁采用预应力混凝土箱形截面,桥塔采用倒Y形混凝土索塔,空间双索面,半漂浮体系,斜拉索的索塔锚固端采用钢锚箱,斜拉索的主梁锚固端采用混凝土锚槽。结合工程实际,本文介绍了技术标准、主桥总体布置、主要结构设计,并对主桥的静力性能及抗风、抗震、车桥耦合等动力性能进行了计算分析。结果表明:该桥结构受力合理,在合适的成桥索力作用下,主桥静动力计算结果均满足规范要求,主梁后期收缩徐变变形值较小,斜拉桥桥型适用于城际铁路大跨度桥梁结构。

Managing Dynamics in Corporate Networks

A crucial issue in collaborating in manufacturing corporate networks between different companies is to identify to what extent different strategic and operational decisions need to be coordinated between the involved companies. In this paper, we elaborate on the issue of synchronization and coordination of information flow based on interconnectivities between companies in order to coordinate a corporate network by the means of DSM, Dependence Structure Matrix. The results show that DSM can be used to identify interconnectivities, dependencies on information flow among actors in a network and to identify which information needs to be shared between companies in the network.

基于响应面并行子空间设计的载人潜水器优化

为提高载人潜水器的设计效率和综合性能,确定了一型载人潜水器的设计参数,分析了学科与学科、学科与系统之间的关系,完成了基于多学科设计优化思想的载人潜水器学科分解,建立了载人潜水器结构设计矩阵。利用响应面模型建立了艇型与推进、结构等学科的学科分析模型,利用公式建立了其他学科及系统层分析模型。以艇重为目标函数,分别建立了基于响应面并行子空间设计和基于并行子空间优化的载人潜水器优化框架,可实现优化过程中的近似模型更新,以提高求解效率及精度。利用上述2个框架进行了优化求解,结果表明:相比初始方案,并行子空间设计并行子空间设计减重为7.822%、并行子空间优化减重为7.311%,但并行子空间设计在计算精度、求解效率和最优解获取的概率等方面更具有优势。

考虑项目间依赖关系的项目风险应对策略选择模型

文章针对项目组合多项目间风险的相互依赖关系开展风险应对策略选择问题的研究。首先,文章在考虑项目组合结构动态性和复杂性的基础上,分析了项目间依赖关系对项目风险的影响,并利用设计结构矩阵方法进行度量。然后,文章采用心理账户理论和球形模糊集构建了以决策者效用最大化为目标的项目风险应对策略选择优化模型。最后,文章通过算例分析证明了所提方法的可行性和有效性,并分析了不同程度的项目间依赖作用以及心理账户对项目风险应对策略选择的影响。结果表明:1)项目间依赖关系对项目风险应对策略选择有重要影响;2)在达到最优应对预算之前应选择能应对更多风险的应对策略集;3)在达到最优应对预算之后项目间依赖作用不影响策略选择,但影响决策者的效用值;4)考虑心理账户能够提高应对预算的利用效果。