How the Beast really moves: Cayley analysis of mechanism realization spaces using CayMos

For a common class of 2D mechanisms called 1-dof tree decomposable linkages, the following fundamental problems have remained open: (a) How to canonically represent (and visualize) the connected components in the Euclidean realization space. (b) How to efficiently find two realizations representing the shortest “distance” between two connected components. (c) How to classify and efficiently find all the connected components, and the path(s) of continuous motion between two realizations in the same connected component, with or without restricting the realization type (sometimes called orientation type).For a subclass of 1-dof tree-decomposable linkages that includes many commonly studied 1-dof linkages, we solve these problems by representing a connected component of the Euclidean realization space as a curve in a carefully chosen Cayley (non-edge distance) parameter space; and proving that the representation is bijective. We also show that the above set of Cayley parameters is canonical for all generic linkages with the same underlying graph, and can be found efficiently. We add an implementation of these theoretical and algorithmic results into the new software CayMos, and give (to the best of our knowledge) the first complete analysis, visualization and new observations about the realization spaces of many commonly studied 1-dof linkages such as the amusing and well-known Strandbeest, Cardioid, Limacon and other linkages.     

浅析IPv6邻居发现协议中无状态地址自动配置机制

在IPv6中,地址自动配置分为有状态地址自动配置和无状态地址自动配置。当站点不特别关注主机使用的确切地址,只要求该地址是惟一的并且能通过适当方式被寻路时,则适合使用无状态地址自动配置。本文针对IPv6中无状态地址自动配置机制进行简要的学习和分析。     

Spiral column configuration for protein separation by high-speed countercurrent chromatography

Retention of the stationary phase of aqueous–aqueous polymer phase systems is improved by a spiral column configuration which utilizes the radially acting centrifugal force along the spiral pitch to retain the heavier phase in the outer portion and the lighter phase in the inner portion of the spiral channel. For the separation of proteins which has low mass transfer rates, the system needs further modification of the separation channel to interrupt the laminar flow and enhance mixing of the two phases.     

Local Image Features Resulting from 3-Dimensional Geometric Features,Illumination, and Movement: I

We study images of smooth or piecewise smooth objects illuminated by a single light source, with only background illumination from other sources. The objects may have geometric features (F), namely surface markings, boundary edges, creases and corners; and shade features (S), namely shade curves and cast shadow curves. We determine the local stable interactions between these and apparent contours (C) for the various configurations of F, S, C, and we concisely summarize them using an “alphabet” of local curve configurations. We further determine the generic transitions for the configurations resulting from viewer movement. These classifications are obtained using the methods of singularity theory, which allows us to ensure that our lists are complete, in some cases correcting earlier attempts at similar classifications. Authors were partially supported by Insight 2+ grant from the European Commission. J. Damon was partially supported by the National Science Foundation grants DMS-0405947 and DMS-0706941.     

无尾损装置控制系统速度监测单元简介

主要介绍了冶钢集团公司170无缝钢管厂阿塞尔轧管机无尾损装置控制系统速度监测单元的构成、工作原理和整走过程。实践表明，该控制系统采用软、硬件补偿速度监测单元估算值误差的方法，保证了系统整体控制精度。     

中国联通HSPA＋时代下的选择

在分析中国联通HSPA＋业务承载需求及技术选择的基础上，从PTN综合承载方案承载HSPA＋业务、融合多业务的统一承载平台、网络规划配置方案等方面介绍了中国联通的HSPA＋业务。     

Barriers to effective configuration management application in a project context: An empirical investigation

Configuration management (CM) is not a new set of ideas, what it does represent is an effective way for project managers to use a formalized methodology in order that they can manage status and changes to it throughout the lifecycle. This research sets out to identify and prioritize the obstacles in the effective implementation of the CM practices, categorize these obstacles into more manageable groups of factors, and analyse the effects of multiple factors on the identification and rating of these barriers. Nineteen barriers are finalized and prioritized on the basis of their criticality and as a result three groups (managerial and organizational barriers, implementation barriers, and planning and process barriers) are extracted with the help of factor analysis. This study will help both configuration management and project management professionals to plan better and avoid the impacts of these key obstacles from much earlier in the definition phase.     

Technical and institutional factors in the emergence of project management

This paper explores the fundamental question of why the practice and discipline of project management emerged during the 1940s through the 1960s in the United States. Although projects have been around for millennia, not until the middle of the 20th century in the U.S. military–industrial–academic complex did project management become formalized in institutional processes and as an academic discipline. The paper argues that technical complexity and novelty were the primary factors driving project management and its engineering counterpart systems engineering, as a new organizational form. Institutional factors such as the need for legal separation between government and industry created important secondary effects that drove the particular forms in which project management evolved. This paper uses examples from large scale, complex projects of the 1940s through 1960s in the aerospace and computing industries to tease out the fundamental technical and institutional factors that led to the emergence of project management in these two key American industries during this period.     

一种FPGA动态配置的实现方法

随着嵌入式系统设计的复杂化和功能的多样化,FPGA在其中的作用日渐突出,如何实现FPGA的动态配置便成为一个需要研究的问题。本文介绍了通过DSP的GPIO功能配置FPGA的过程及相关技术,同时介绍FPGA动态配置接口电路的设计。