A new hybrid algorithm for analog ICs optimization based on the shrinking circles technique

This paper presents a novel technique named the Shrinking Circles to enhance the performance of optimization algorithms embedded in automated sizing tools of analog ICs. This technique creates a balance between the exploration and exploitation capabilities when the optimization algorithm is converging to a possible optimum point. With the help of the shrinking circles concept, we upgrade a hybridization version of Gravitational Search Algorithm with Particle Swarm Optimization (Advanced GSA_PSO). Accordingly, a developed tool for the automation of analog ICs sizing is proposed. The performance of this tool is evaluated by two cases: minimizing the power consumption of a two-stage CMOS op-amp and simultaneous minimizing the circuit area and power consumption of a folded-cascode op-amp. In this paper, the corners analysis is also incorporated into the proposed circuit sizing tool based on a straightforward procedure by which this tool not only can obtain the solutions being robust against process, voltage, and temperature (PVT) variations, but also it alleviates the computational burden. Comparisons with available methods show that the proposed tool performs much better in terms of efficiency.     

多孔同轴度检测系统的研制

提出了一个多孔同轴度检测系统,它以无衍射激光束作为检测基准。介绍了检测原理和检测系统特别是检测靶的结构。用640pixel×480pixel的摄像机(光靶分辨率为0.0504mm/pixel),在5、15和24m进行同轴度检测,获得的标准差在x方向上分别为0.0193、0.0262和0.0428mm,在y方向上分别为0.0147、0.0181和0.0250mm。     

Vicious and virtuous circles of offshoring attitudes and relational behaviours. A configurational study of German IT developers

Prior research has shown that the success of offshoring is affected by relational behaviours of the employees involved in an offshoring collaboration. However, hardly anything is known about the attitudes that onshore colleagues hold towards offshoring, and how such offshoring attitudes affect relational behaviours towards offshore colleagues. We therefore present an interpretivist, qualitative case study that explores the offshoring attitudes of German information technology developers. We found that offshoring attitudes affected relational behaviours towards Indian offshore colleagues, in terms of (1) treating Indian colleagues as fellow team members as opposed to suppliers; (2) spending more or less effort in communication and knowledge transfer; and (3) supporting vs. avoiding the task transfer. These relational behaviours fed back into participants' offshoring attitudes, leading to vicious and virtuous circles. The circles created two contrasting configurations of offshoring attitudes and relational behaviours, driven by opposing forces within the departmental context. Our findings highlight the value of taking a configurational perspective for understanding offshoring success and for identifying drivers that need to be managed in order to achieve favourable configurations. We suggest that future research should further expand the typology of attitude‐behaviour configurations and could apply theories of efficacy, self‐reinforcing spirals and planned behaviour.     

Semidefinite programming for Chebyshev fitting of spatial straight line with applications to cutter location planning and tolerance evaluation

This paper presents a novel model for fitting of spatial straight line based on Chebyshev norm. The problem is firstly formulated as a minimax problem, and then reformulated as a semidefinite programming (SDP) problem, which could be solved by many interior-point algorithms. The application of the proposed approach to two problems arising from manufacturing engineering, i.e. planning of the initial location of cylindrical cutter for flank milling and evaluation of the spatial straightness error, is discussed. Examples and numerical simulations illustrate the efficiency of the novel model.     

应用光纤技术在线检测刀具的磨损

以光纤传导理论为基础，提出了一种新的非接触式刀具磨损检测方法——光纤反射位移检测法．该法以激光为光源，以光纤传感器为检测手段，以刀杆振动位移为检测对象来实现对刀具状态的跟踪检测．大量的切削实验表明了这种方法的适用性和可靠性     

成形法加工齿轮技术的探讨

阐述了齿轮刀具的主要类型和工作原理,探讨了指形齿轮铣刀的设计方法,并指出通过采 用计算机程序计算成形齿轮刀具的渐开线齿形坐标,可保证齿轮加工精度达到8级。     

径向剃齿刀在机修磨原理解析计算

径向剃齿是一种高效的齿轮精加工方法,但径向剃齿刀的修磨比较困难。径向剃齿刀在机修磨法是一种新的修形方法,其原理为:用一个与所剃齿轮几何参数完全一致,制造精度较高,齿面镀有金刚石磨粒层的修磨轮,装在径向剃齿机上,取代工序加工中的工件齿轮,与径向剃齿刀啮合,达到修形的目的。运用啮合理论,建立了剃齿刀修形解析模型,推导出了修形时的啮合方程及修形后剃齿刀的齿面方程,并进行了实例分析和计算机运算。试验证明,剃齿刀在机修磨法是一种实用的剃齿刀修形方法。     

Selection of master cutter paths in sculptured surface machining by employing curvature principle

In the Isoscallop strategy of sculptured surface machining, one of the surface edges is generally chosen as the Master Cutter Path (MCP)—from which other cutter paths are derived such that the roughness produced is uniform. In this paper, the MCPs have been chosen from the maximum or minimum curvature loci of the surface. Those loci that divide the surface into distinct zones of similar curvature are adopted as MCPs. Secondary cutter path generation is carried out employing standard isoscallop formulation and problems associated with multiple MCPs have been identified and addressed. MCPs along the locus of maximum convex curvature lead to a considerable reduction in machining time while those for minimum curvature (maximum flatness) yield a reduction in CL data file size.     

TBM分体式刀座系统设计方法及力学性能分析

硬岩隧道掘进机(TBM)通过刀盘上的滚刀破碎剥离岩石开挖,刀座系统是连接滚刀与刀盘之间的桥梁,其联接可靠性和承载能力性能好坏直接关系到设备开挖效率及施工维护成本,刀座系统设计理论及标准的缺乏已无法满足TBM安全、高效发展需求。总结刀座系统的结构设计基本原则,基于系统受载特性分析及轴式滚刀基本结构尺寸,建立了分体式刀座和整体式刀座的结构参数化设计方法。通过对轴式滚刀-刀座系统进行静力学建模,分析额定负载工况、不同螺栓预紧力下、不同工作载荷下的静力学特性,找出了各类刀座的应力分布特性、危险区域,揭示了工程中刀座部分区域开裂、压溃现象的力学原因。此研究可为工程中刀座优化设计提供参考。     

数字刀具测量系统的研究

刀具的几何参数是影响数控机床加工精度和生产效率的重要因素。研究了基于计算机视觉检测技术的高精度刀具测量系统,分析了运行原理和功能模块,并对关键技术做了论述。系统实现了对刀具的刀尖切削特征点、圆弧半径和切削角参数的自动精确测量,并将数值反馈到数控机床刀具数据库,具有较高的效率、精度和自动化程度。实验结果证明,系统测量重复性精度可达3μm。