Singularity robust algorithm in serial manipulators

Singularity is a fundamental problem with robotic manipulators. Various methods of singularity handling have been published in the past. In this paper, a singularity robust method is presented and its implementation issues discussed. It focuses on the discontinuity problem inherent in the singularity robust techniques with removal of degenerate components. Sources of the discontinuity are discussed and the null motion is proposed as the means of providing a continuous control of the end-effector over the boundary of the singular region. The presentation of this paper covers a complete treatment of singularities, starting from identifications of the singular configurations and the associated singular directions, the handling algorithm and the discontinuity issues. The algorithm was implemented on PUMA 560. The experimental results are presented and discussed.     

Reliable regulation in centralized control systems

This paper addresses the design of a reliable control system for a linear, asymptotically stable plant. Specifically, the considered problem consists in finding a regulator which guarantees asymptotic stability, signal tracking and disturbance rejection when all the instrumentation is operational, and ensures that these properties are preserved, to the maximum possible extent, when an arbitrary number of sensors and/or actuators faults occur, that is, some of the feedback loops open. With reference to a centralized control structure and exogenous signals with multiple poles on the imaginary axis, the paper supplies a necessary and sufficient condition for the problem to admit a solution, and a possible least order regulator.     

面向虚拟桌面内外部数据流的安全控制机制研究

桌面虚拟化需要借助虚拟桌面协议来实现内部应用数据和外部操作平台的数据交互。然而该类协议中的数据流控制机制并不完善,存在数据非法交互的安全隐患。为解决该问题,基于网关模式提出了一种面向虚拟桌面内外部数据流的安全控制机制SCIED。它不仅能对协议中的虚拟通道进行全面管控,避免修改协议和大量的终端,还具有较高的兼容性、拓展性。将它部署于网关并用于防护边界攻击,能显著减少服务器端的负载和安全隐患。实验表明,该SCIED能够有效保证数据流的安全交互,并且对现有桌面会话的性能影响较小。     

An internal model principle is necessary and sufficient for linear output synchronization

Output synchronization of a network of heterogeneous linear state–space models under time-varying and directed interconnection structures is investigated. It is shown that, assuming stabilizability and detectability of the individual systems and imposing very mild connectedness assumptions on the interconnection structure, an internal model requirement is necessary and sufficient for synchronizability of the network to polynomially bounded trajectories. The resulting dynamic feedback couplings can be interpreted as a generalization of existing methods for identical linear systems.     

Firms’ involvement in Open Source projects: A trade-off between software structural quality and popularity

Open Source (OS) was born as a pragmatic alternative to the ideology of Free Software and it is now increasingly seen by companies as a new approach to developing and making business upon software. Whereas the role of firms is clear for commercial OS projects, it still needs investigation for projects based on communities. This paper analyses the impact of firms’ participation on popularity and internal software design quality for 643 SourceForge.net projects. Results show that firms’ involvement improves the ranking of OS projects, but, on the other hand, puts corporate constraints to OS developing practices, thus leading to lower structural software design quality.     

Developing a framework for analyzing IS sourcing

This paper develops a framework for the consideration of internal markets as an alternative to information systems (IS) outsourcing. It is based on an assessment of the pros and cons of both outsourcing and of insourcing based on the internal markets approach. It is formulated in terms of the operational, tactical, and strategic impacts of the choice among the alternatives. The framework, and the propositions that are developed from it, should be useful both for researchers, who can use it for developing testable research hypotheses, and for practitioners, who may use it as a basis for developing a comprehensive set of criteria for the evaluation of these sourcing options.     

Optimization of transport passage with dragline system in thick overburden open pit mine

According to the characteristics of opencast coal resources and dragline technology system application in China, the structure and shifting step of transport passage are optimized in this paper. Typical coal transport passage is analyzed in aspects such as the internal dump occupation, dragline operation efficiency, coal transport distance, upper stripping distance and shifting quantities. The middle passage should be given priority in thick overburden open pit mine because the dragline system is only responsible for part stripping task. According to characteristics of middle passage, the transport passage is divided into parallel climbing, vertical climbing and horizontal transport. In addition, the transport passage structure optimization model and shifting distance optimization model are established in this paper. The case study in Heidaigou open pit mine shows that, the parallel climbing height is accounted for about 60% of the total height, and reasonable shifting distances of the first mining area and the second mining area are 240 and 320 m. Sensitivity analysis shows that, the total passage height has important influence on the shifting step, so it is with the stripping height and passage construction cost to the passage structure.     

Evidence for internal phosphorus loading,hypoxia and effects on phytoplankton in partially polymictic Lake Simcoe,Ontario

Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments, is hard to determine in a large, relatively shallow and partially unstratified lake such as Lake Simcoe. Of the lake's three major basins, only Kempenfelt Bay stratifies long enough to develop hypoxia in the stagnant summer hypolimnion. The following indications of sediment P release are available from historic data: 1) hypolimnetic hypoxia still occurs in Kempenfelt Bay although the hypoxic factor (number of days that an area equal to the bay's surface area is overlain by water of ≤ 2 mg/L dissolved oxygen, DO) has decreased substantially and significantly from 15.8 d/yr (1980–1994) to 4.0 d/yr (1995–2011); 2) hypoxic factors for other lake sections and at different DO levels also indicate widespread hypoxia; 3) concentrations of redox dependent metals, Fe and Mn, increase with depth; and 4) euphotic zone P and chlorophyll concentrations increase and water clarity decreases during fall turnover. Cyanobacterial blooms appear to occur in response to internal load as supported by occasional cyanobacteria counts. These indicators provide evidence that internal loading is likely occurring and affecting the water quality in Lake Simcoe. We expect that further monitoring, specific for internal load, will corroborate these results.     

内压支撑下薄壁管弯曲变形力学分析

管件内压弯曲又称为管件充液弯曲,具有减小截面畸变,延缓薄壁管内侧失稳起皱,提高弯曲成形极限等优点。支撑内压在其中起到了关键性的作用,对于环向和轴向的应力应变分量具有重要影响。采用塑性理论,对内压和弯矩共同作用下的薄壁管弯曲变形进行理论分析。考虑内压对微元平衡方程的影响,建立一个新的理论分析模型,通过求解非线性方程组,得到薄壁管应力应变的分布规律,定量分析内压对薄壁管应力应变的影响趋势。同时通过将有限元分析得到的应力应变分量的信息,与理论解进行对比发现,理论预测和模拟结果相符合,验证所建立的理论分析模型的可靠性。结果表明,轴向和环向应力随内压升高均大大提高,环向应变随内压升高线性递增,而厚向应变线性减小。     

论企业内部会计控制

企业内部会计控制的目标是保障企业会计信息的真实性和准确性;保证企业财产物资的安全完整和合理、有效使用;改善经营管理活动,促使经济效益不断提高;确保有关财经法规和内部规章制度的贯彻实施,有效防范企业的经营风险。要搞好企业内部会计控制,必须以人和关键控制点作为内部会计控制的重点和突破点;必须以资金和成本控制作为内部会计控制的主要控制线;必须以点连线、由线成面、点线面齐力推进,全面落实内部控制目标。