Orientation angle workspaces of planar serial three-link manipulators

This paper presents a classification on the workspaces of planar serial three-link manipulators, that is, position workspace and orientation angle workspace. Position workspace indicates the region reached by the reference point on the end-effector. Orientation angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for every point in the reachable position workspace. By introducing a virtual equivalent mechanism, reachable position workspace can be divided into several Grashof intervals and non-Grashof intervals. The calculation equations of orientation angle workspace are deduced in three situations according to the relationships among four link lengths in the virtual four-bar chain. Three examples are given for three kinds of relationship of link lengths. The orientation angle workspace of extended groups, that is, two of the three link lengths equal, and the orientation angle workspace when the reference point on the end-effector moves along a non-radial direction are also discussed. A program is developed to calculate orientation angle workspaces and output variation curves of orientation angle workspace and key data within the position workspace. The approach and program in this paper can be used for fast calculation and identification of the variation rule of the orientation angle workspace of any given planar serial three-link manipulator on the basis of its link parameters, and for the design of a highly dexterous serial manipulator with proposed link relations. Supported by the Natural Science Foundation of Shanxi Province (Grant No. 20041070)     

基于虚拟现实技术的煤矿安全培训系统

针对传统煤矿安全培训手段单一、效果不理想的问题,提出了基于虚拟现实技术的煤矿安全培训系统。该系统应用虚拟现实开发软件3DS MAX和Virtools DEV来完成设备建模、场景构建和交互式系统的开发,实现了煤矿风险预控、事故案例再现和事故应急救援的仿真。应用结果表明,该系统通过三维仿真和交互形式可有效提高煤矿安全培训的针对性和实施效果,达到提高安全意识、减少安全事故的目的。     

一种嵌入式串口共享服务器的设计

针对目前大多数串口服务器仅支持主副机而不支持多主机、不支持Modbus TCP转Modbus RTU等问题,设计了一种嵌入式串口共享服务器。该串口共享服务器采用Cortex-M3内核的LM3S9B92芯片设计,实现了单芯片以太网到3个串口的转换功能。测试结果表明,该串口共享服务器收发数据准确,通信速率高,且具有Modbus TCP转Modbus RTU功能。     

Investigation of conductivity characteristics of nitrile butadiene rubber vulcanizates filled with semiconducting carbide ceramic

SiC‐ and B₄C‐filled NBR rubber composites were prepared with various volume fractions of filler by a conventional roll‐mill method. The morphological structures of the NBR–SiC and NBR–B₄C composites were analyzed by scanning electron microscopy. The dependence of room‐temperature volume resistivity (ρ_v) on the concentration of filler in the two systems was studied. In addition, variation in the number of current carriers (n), mobility carriers (μ), dielectric constant (ε), and dielectric loss factor (tan δ) on filler concentration in the two systems were investigated in detail. The applicability of composites as negative temperature coefficient (NTCR) linear thermistors was studied by the dependence of volume resistivity on temperature. The resistivity showed negative temperature dependence and changed linearly with temperature parallel. The conduction mechanism of the conductivity of the two composites was analyzed in terms of the computed activation energy and hopping energy. Change in volume resistivity as a function of frequency for the two systems was also investigated. Finally, the dependence of volume resistivity on applied pressure and possible real applications of these composites as transducers in pressure sensors were also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2158–2165, 2007     

快速虚顶点光子映射的焦散绘制

目的 模拟绘制焦散效果是真实感图形绘制的重要组成部分。利用可编程GPU硬件,基于图像的光子映射方法绘制速度快,但由于使用了近似采样和计算,会产生失真。为了克服这一现象,针对理想的镜面反射、折射体,提出一种快速绘制焦散效果的方法（VOBPBT）。方法 该方法首次定义了光子路径映射图的概念,并提出通过基于虚顶点光子映射的光子束跟踪来准确构建光子路径映射图的方法;此外,方法也创新性地提出利用光子路径映射图来查找焦散三角形,创建焦散映射图的方法。结果 实验结果表明,本文绘制结果真实,可以处理多次递归反射、折射,能够绘制连贯的高频焦散效果,同时可以达到交互的绘制性能。结论 本文VOBPBT方法在可交互计算机仿真、计算机游戏、虚拟漫游等应用领域具有一定的实用价值。     

Research on technology of desktop virtualization based on SPICE protocol and its improvement solutions

Increasingly mature cloud computing technology promotes virtual desktop technology, which can solve many problems existing in traditional computing models. However, virtual desktop solutions introduce the thorny problem of how to deliver a real desktop experience to users, as if they are using it locally, especially when playing video. The SPICE （simple protocol for independent computing environments） virtual desktop solution provides several image compression algorithms to address this problem with the purpose of making virtual desktops as real as possible. Although different compression algorithms can contribute their own abilities to different images to a large extent, switching between them is a big problem that consumes a large amount of resources to detect the different type of image and also causes jitter of the virtual desktop. This paper proposes a new solution, called SPICEx, using the JPEG2000 compression algorithm with dynamic compression ratios to solve the problem and finally validates that the performance is better than that of SPICE. With better quality of user experience and also reducing bandwidth consumption, SPICEx solution is meaningful in virtual desktop fields and can be widely used.     

VMware服务器虚拟架构解决数据安全问题

中心机房的传统架构模式已不满足现代计算机的应用和需求,且数据安全得不到保证,数据恢复代价高、恢复困难。本文提出了用VMware虚拟架构解决网络机房的数据安全问题,简化服务器的部署、管理和维护工作,提高了数据中心的安全性和容错能力。     

On‐line determination of the conversion in a styrene bulk polymerization batch reactor using near‐infrared spectroscopy

A fast on‐line method for measuring the monomer conversion of a styrene batch polymerization reaction with near‐infrared spectroscopy (NIR) has been developed. Multivariate calibration was performed, using polymer samples having temperatures around the set point of the batch reactor (75–85°C) and monomer conversions up to 35%. The calibration model was built in such a way that the effect of the temperature on the predicted conversion of the sample was minimized. The method was validated in a number of batch runs. In these runs, the batch temperature and molar mass distributions of the polymer were varied. At‐line size‐exclusion chromatography was used as a reference method for measuring the monomer conversion. Results show that on‐line conversion monitoring with NIR offered overall an excellent accuracy (～ 0.32% conversion). For high and low monomer conversions a small bias in the predicted conversion is present. The method proved to be insensitive to both relative large changes (10°C) of the batch temperature and to considerable changes of the molar mass distribution of the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 90–98, 2002; DOI 10.1002/app.10241     

云环境下基于动态滑动窗口多通道Bi-LSTM的虚拟机故障预测模型

针对点值预测方法预测虚拟机故障,未充分利用虚拟机历史周期特征和上下文信息、预测准确率不高的问题,提出了一种动态滑动窗口多通道Bi-LSTM的虚拟机故障预测模型。该模型首先利用动态滑动窗口动态捕获虚拟机故障发生过程的上下文特征;然后构建多通道机制的Bi-LSTM以同时学习不同指标类之间的相关性特征,预测虚拟机下一周期的故障;最后根据OCSVM和区间偏移度方法对预测结果进行判断,得出具体的故障类型。实验表明,该模型在预测准确率、召回率、F值三个指标上均优于基线模型,验证了模型对虚拟机故障预测的有效性。     

面向智能驾驶的平行视觉感知：基本概念、框架与应用

目的 视觉感知技术是智能车系统中的一项关键技术,但是在复杂挑战下如何有效提高视觉性能已经成为智能驾驶领域的重要研究内容。本文将人工社会（artificial societies）、计算实验（computational experiments）和平行执行（parallel execution）构成的ACP方法引入智能驾驶的视觉感知领域,提出了面向智能驾驶的平行视觉感知,解决了视觉模型合理训练和评估问题,有助于智能驾驶进一步走向实际应用。方法 平行视觉感知通过人工子系统组合来模拟实际驾驶场景,构建人工驾驶场景使之成为智能车视觉感知的“计算实验室”;借助计算实验两种操作模式完成视觉模型训练与评估;最后采用平行执行动态优化视觉模型,保障智能驾驶对复杂挑战的感知与理解长期有效。结果 实验表明,目标检测的训练阶段虚实混合数据最高精度可达60.9%,比单纯用KPC（包括：KITTI（Karlsruhe Institute of Technology and Toyota Technological Institute）,PASCAL VOC（pattern analysis,statistical modelling and computational learning visual object classes）和MS COCO（Microsoft common objects in context））数据和虚拟数据分别高出17.9%和5.3%;在评估阶段相较于基准数据,常规任务（-30°且垂直移动）平均精度下降11.3%,环境任务（雾天）平均精度下降21.0%,困难任务（所有挑战）平均精度下降33.7%。结论 本文为智能驾驶设计和实施了在实际驾驶场景难以甚至无法进行的视觉计算实验,对复杂视觉挑战进行分析和评估,具备加强智能车在行驶过程中感知和理解周围场景的意义。