基于几何特征的不平整路面三维建模与分析研究

在对比利时路关键几何特征、特征的分布特点及其约束条件进行分析的基础上,提出了基于几何特征的参数化路面三维建模方法。通过比利时路三维理论模型与生成的三维随机路面融合,得到真实准确的比利时路三维模型;在建立标准化车辆振动模型的基础上,以IRI指数和车身振动加速度均方根值(RMS)作为评价指标,分析了比利时路的关键几何参数对车辆振动的影响。通过实测道路数据与所建立模型对比分析,验证模型的准确性;提出的道路三维建模方法可以扩展至卵石路、鱼鳞坑路、波纹路、搓板路等几乎所有不平整强化试验路面,为全面构建车辆虚拟试验场提供了一种参数可调、真实准确的道路三维建模途径。     

Motion planning and coupling analysis based on 3-RRR(4R) parallel mechanism

This paper presents the kinematics analysis of a 3-RRR(4R) parallel mechanism. A new approach of motion planning based on the planned trajectory is proposed and demonstrated on parallel mechanism 3-RRR(4R). Both forward and inverse kinematics relationships are derived. Based on the structure analysis and inverse kinematics analysis of the parallel mechanism, the movement law of the three input motors can be derived from the equations of the planned trajectory. The approach is verified by simulation results, which are consistent with the planned trajectory. Coupling analysis was performed for the output–input of the parallel mechanism and was significantly simplified by using the simulation software relative to the conventional mathematical method. The project was supported by ZJNSF(Y104351).     

An improved FMEA method based on the linguistic weighted geometric operator and fuzzy priority

Using the group linguistic information aggregation method, this research improved upon conventional failure mode and effect analysis (FMEA), which had the problems of the inevitable subjectivity of expert evaluations, and of the difficulty of determining the weights of experts' evaluations. First, this research treated the three risk factors of FMEA evaluation as linguistic variables and introduced a linguistic weighted geometric (LWG) operator to implement algebraic operations on the results of expert evaluations. This treatment overcame the disadvantage of fuzzy theory-based methods in which decision-making information could be lost due to the twice conversion process. Second, the weights of experts' evaluations were calculated based on the consistency of experts' ranking using a fuzzy priority method. This method placed a lower weight for the experts whose evaluation departed from group consensus, and therefore decreased the impact of the unfairness of experts on evaluation results. Finally, this article demonstrated the effectiveness and applicability of this method by an example of failure-mode analysis on the grinding wheel system of a numerical control machine.     

A review of production planning and control: the applicability of key concepts to the make-to-order industry

The paper reviews ‘classic approaches’ to Production Planning and Control (PPC) such as Kanban, Manufacturing Resource Planning (MRP II) and Theory of Constrains (TOC), and elaborates upon the emergence of techniques such as Workload Control (WLC), Constant Work In Process (CONWIP), Paired cell Overlapping Loops of Cards with Authorization (POLCA) and web- or e-based Supply Chain Management (SCM) solutions. A critical assessment of the approaches from the point of view of various sectors of the Make-To-Order (MTO) Industry is presented. The paper considers factors such as the importance of the customer enquiry stage, company size, degree of customization and shop floor configuration and shows them to play a large role in the applicability of planning and control concepts. The paper heightens the awareness of researchers and practitioners to the PPC options, aids managerial system selection decision-making, and highlights the importance of a clear implementation strategy. WLC emerges as the most effective Job Shop solution; whilst for other configurations there are several alternatives depending on individual company characteristics and objectives. The paper outlines key areas for future research, including the need for empirical research into the use of Workload Control in small and medium sized MTO companies.     

Functionalization of multi-walled carbon nanotubes and its application in preparing the 3D graphene/carbon nanotubes hybrid architectures

A facile strategy for the preparation of water-dispersible multi-walled carbon nanotubes (MWCNTs) in aqueous solution for the preparation of the three-dimensional (3D) graphene/carbon nanotube (G/CNT) hybrid architectures is proposed, where MWCNTs were functionalized by simultaneous radiation-induced graft polymerization of acrylic acid under the γ-ray (denoted as MWCNT-g-PAA) for improving its dispersibility. The stability of the aqueous solution of MWCNT-g-PAA in water is highly improved. We also use the MWCNT-g-PAA fabricating three-dimensional cylindrical graphene/carbon nanotube (G/CNT) hybrid architectures by a simple one-step hydrothermal process. We found that the as-prepared MWCNTs-g-PAA showed a very good dispersibility in GO solution with different concentration ratio and a promising precursor for preparing the graphene/CNT hybrid materials.     

An integrated multi-criteria Taguchi computer simulation-DEA approach for optimum maintenance policy and planning by incorporating learning effects

Modelling the maintenance activities could be complex and non-linear system which consists of different parameters. In this paper, a new approach for maintenance policy and planning problem is developed. First, maintenance activities are simulated by incorporating learning effects. Production and maintenance functions are estimated using historical data. Then, simulation is carried out for different scenarios which are combinations of periodic maintenance and different policies. Several outputs including machines and operators’ availability, reliability, efficiency and queue length are computed. Since the problem is multi-criteria, data envelopment analysis method is used to select the preferred policy. In order to show the applicability of the proposed approach, the data for a series production line is used and different scenarios with different policies are investigated. Since many scenarios are needed to be simulated, Taguchi orthogonal array design is used to reduce the number of scenarios. The proposed approach of this study would help managers to identify the preferred strategy considering and investigating various parameters and policies. This is the first study that introduces an integrated multi-criteria approach for optimum maintenance policy and planning.     

3D free vibration analysis of elastically supported thick nanocomposite curved panels with finite length and different boundary conditions via 2D GDQ method

Based on the three-dimensional theory of elasticity, free vibration characteristics of nanocomposite panels reinforced by randomly oriented, straight, single-walled carbon nanotubes (SWCNTs) are considered. The volume fractions of randomly oriented agglomerated SWCNTs are assumed to be graded not only in the radial direction but also in the axial direction of the curved panel. This study presents a 2D six-parameter power-law distribution for CNTs volume fraction of 2D continuously graded nanocomposite that gives designers a powerful tool for flexible designing of structures under multi-functional requirements. The material properties are determined in terms of local volume fractions and material properties by the Mori-Tanaka scheme.     

Finite Element Simulation on the Spin-forming of the 3D Non-axisymmetric Thin-Walled Tubes

The roller movement trace for the 3D non-axisymmetric thin-walled tubes is a complex space curve. Besides the roller rotation caused by contact with the blank, the roller rotates around the workpiece together with the main spindle, and also moves simultaneously along the direction of the revolution radius. The method to correctly establish the finite element (FE) models of the metal spinning is based on the MSC. MARC software was introduced. The calculation formulas considering both the revolution and rotation of the roller were obtained by the mathematical deduction. The saving calculation points m should be a multiple of 4 for one revolution of the roller around the workpiece to obtain the maximum forming force for the spinning of the 3D non-axisymmetric thin-walled tubes. The simulation results conform well to the experimental ones for several spinning methods; the maximum error is less than ±15%.     

Integration of occupational health and safety in the facility layout planning,part II: design of the kitchen of a hospital

Facility layout design has an important effect on the performance of manufacturing systems. It intends to determine relative location of departments and machines within a plant. A good layout design must ensure that a set of criteria and objectives are met and optimised, e.g. area requirements, cost, communication and safety. The most common objective used in facility planning methods is to minimise the transportation cost. However, factors such as the plant safety, flexibility for future design changes, noise and aesthetics must be considered as well. In this paper, a case study is carried out to investigate the safety concerns in facility layout design. In this regard, a facility layout planning methodology, integrating occupational health and safety (OHS) is presented. This methodology considers transportation cost as well as safety in the facility design. By this means, OHS issues are considered at the design stage of the facility. In other words, this research demonstrates the improvements in the layout design by integrating safety aspects.     

基于空间仿射对应点列的双曲抛物面三维构建及分析

利用计算机3D软件构建基于空间仿射对应点列的双曲抛物面。对双曲抛物面进行不同方向的投射,可以准确得到双曲抛物面不同方位和角度的投影图。从这些投影图中,可以更直观、清楚的了解双曲抛物面的投影特点。使用多个不同位置的平面对双曲抛物面进行截切,并通过分析、观察截交线的变化趋势,得出几点规律性的结论。     

Mechanical behaviour and 3D stress analysis of multi-layered wooden beams made with welded-through wood dowels

This paper presents experimental and numerical investigations on multi-layered timber beams using welded-through wood dowels in place of traditional poly(vinyl acetate) (PVAc)-adhesives (or metallic nails). Four-layer beams were constructed with varying numbers of dowels, in each, and then loaded using four-points bending tests to evaluate the mechanical performance of these beams. The practical difficulties encountered in constructing deeper multi-layer beams are discussed and possible solutions which have been employed for the purpose of this work, and proved successful are presented. In order to investigate thoroughly the full potential of multi-layered beams with a very limited number of experimental studies, a 3D FE model has been presented, validated against experimental results and then used to study some influential parameters. The results showed that a reasonable bending stiffness of multi-layered beams is achievable with a good combination of material and geometric parameters.     

基于超导磁储能(SMES)应用的低温热管冷凝段建模与分析

针对超导磁储能系统(SMES)磁体直接冷却G-M制冷机冷头与磁体之传导路径较长造成超导磁体轴向温差的问题,提出了采用低温热管进行均温的方案,以对流换热系数为目标函数建立了相应的热管冷凝数学模型,较之于传统的模型所建模型考虑了二相流界面间的摩擦切应力,所建模型适用于SMES冷却系统降温和失超阶段传递热流量较大工况的传热分析.     

A numerical investigation of the connection between state of dispersion and percolation and its effect on the elastic properties of 2D random microstructures

The present work is dedicated to a numerical investigation of the connection between state of dispersion and percolation and its effect on the elastic properties of 2D random microstructures. The main objective consists in checking out the link between percolation and mechanical response in the context of a heterogeneous medium the reinforcements of which are not homogeneously dispersed. Besides, the influence of the stiffness of inclusions is also investigated since this could impact on the percolation effects. For these purposes, large samples of volume elements are generated according to the Monte Carlo method. We consider the low cost framework of 2D random grids which enables large and in-depth investigations. Besides, the spatial distribution of heterogeneities is simulated with the help of the 2-scale Boolean scheme of disks which is a powerful tool for modelling and studying several states of dispersion. The numerical results highlight beneficial mechanical reinforcements for a heterogeneous dispersion when the percolation phenomenon is enhanced. This improvement is highly sensitive to the stiffness of heterogeneities.     

A study on construction of a kaizen case-base and its utilisation: a case of visual management in fabrication and assembly shop-floors

In this paper, focusing on visual management (VM) as one of the kaizen technologies, a procedure for its new case development is discussed. This procedure consists of two portions. The first portion is construction of kaizen case-base, namely: (1) correction and analysis of kaizen cases; (2) establishment of drivers and instances of investigated kaizen case; and (3) analysis of proximity relationship among kaizen cases. The second portion is utilisation of kaizen case-base, namely: (4) selection of kaizen case from kaizen case-base; (5) consideration of the other related kaizen cases; and (6) new kaizen case design. A case study is performed to assure the relevance of the proposed procedure by focusing on ‘dispatching board’, a typical VM technology. Through collaboration with a factory eager to implement VM, the proposed procedure is qualified by experts as a useful method for kaizen knowledge transfer.     

FMEA下的超市食品HACCP计划制定与实现

结合故障模式与影响分析(FMEA)以及危害分析和关键控制点(HACCP)方法,可以分析超市食品供应中的潜在故障模式和决定给予风险优先级的关键控制点,从而可以产生一个HACCP计划.这一方法在一个超市产生猪肉的供应计划中成功地得到应用.     

Identification and application of requirements and their impact on the design process: a protocol study

Establishing requirements is critical in designing, and therefore a central issue of design research. This article reports an empirical study, based on real-time protocol data about the design processes of four, experienced, individual designers, of how requirements get identified, clarified, and used in the design process, and how these influence the quality of its outcome - the emergent design. This is done by first identifying the activities and methods used by designers to identify and apply requirements during designing, and then investigating how these activities and methods relate to the success or failure of the eventual designs in terms of their degree of fulfilment of the requirements. The results indicate that the quality of the activities and methods used has a strong impact on the quality of the emergent design in terms of its degree of fulfilment of requirements, forming a basis for development of guidelines for effective requirement identification and application.

Preparation of the diphenylcarbazone-functionalized silica gel and its application to on-line selective solid-phase extraction and determination of mercury by flow-injection spectrophotometry

A new solid-phase extractor, diphenylcarbazone-functionalized silica gel has been synthesized and confirmed by IR and Raman spectrometry. The new solid-phase extractor is found to be stable in 1-6 mol L(-1) HCl or H(2)SO(4), and also in common organic solvents. It can be used to separate and enrich Hg(II) selectively from eight metal ions with similar characteristics such as Cd(II), Ni(II), Co(II), Mn(II), Pb(II), Zn(II), Cu(II) and Fe(III). The pre-concentration factor is as high as 500. The results show that this new solid extractor has a good stability and can be reused for many times without decreasing its extraction percentage. The micro-column packed with diphenylcarbazone-functionalized silica gel was used for on-line solid-phase extraction and determination of mercury in real samples by flow-injection spectrophotometry. At the optimal conditions, the linear range and the detection limit for the determination of Hg(II) is found to be 1-1500 and 0.90 ng mL(-1), respectively. The relative standard deviation of 11 replicate measurements is less than 3%. The proposed method was demonstrated to be simple, fast, selective, low cost and less pollution.     

Finite element simulation and experimental study on mechanical behavior of 3D woven glass fiber composite sandwich panels

The results of finite element simulation followed by an experimental study are presented in order to investigate the mechanical behavior of three-dimensional woven glass-fiber sandwich composites using FE method. Experimental load–displacement curves were obtained for flatwise compressive, edgewise compressive, shear, three-point bending and four-point bending loads on the specimens with three different core thicknesses in two principal directions of the sandwich panels, called warp and weft. A 3D finite element model is employed consisting of glass fabric and surrounding epoxy resin matrix in order to predict the mechanical behavior of such complex structures. Comparison between the finite element predictions and experimental data showed good agreement which implies that the FE simulation can be used instead of time-consuming experimental procedures to study the effect of different parameters on mechanical properties of the 3D woven sandwich composites.     

先驱体浸渍裂解结合化学气相渗透工艺下二维半和三维织构SiC/SiC复合材料的结构与性能

通过先驱体浸渍裂解工艺结合化学气相渗透工艺(PIP+CVI)制备了二维半(2.5D)和三维(3D)编织结构的碳化硅纤维增强碳化硅基(SiC/SiC)复合材料,对两者的密度、热导率、力学性能以及微观结构等进行了测试分析。结果表明,PIP+CVI工艺制备的SiC/SiC复合材料具有较低的密度(1.98~2.43g·cm-3)和热导率(0.85~2.08 W·m~(-1)·K~(-1)),初期CVI纤维涂层能够提高纤维-基体界面剪切强度(~141.0 MPa),从而提高SiC/SiC复合材料的力学性能,后期CVI整体涂层明显提高了2.5DSiC/SiC复合材料的密度、热导率和力学性能,对3DSiC/SiC复合材料性能的影响不明显。     

改进的超波束形成算法探讨及性能研究

为进一步提高超波束形成(Hyper Beam Forming,HBF)算法的性能,在传统的HBF基础上提出一种改进的HBF(Improved Hyper Beam Forming,Im-HBF)算法。将基于半阵指向性函数高阶运算修正到基于全阵指向性函数的高阶运算。仿真结果表明,Im-HBF算法具有更窄的主瓣,并且对端射来波信号栅瓣抑制能力更强,进一步提高了对目标的检测能力。同时,Im-HBF算法对指数n具有更为广泛的适用性,当指数n2时也能获得优于常规波束形成(Conventional Beam forming,CBF)的波束性能。