Coverage path planning for UAVs based on enhanced exact cellular decomposition method

In this paper, an enhanced exact cellular decomposition method to plan the coverage path of UAVs in a polygon area is proposed. To be more specific, the contributions of the paper are: firstly, the turning motion of UAVs is shown to be less efficient from the viewpoints of route length, duration and energy. Secondly, the problem of coverage Path Planning (CPP) in a convex polygon area is transformed to width calculation of the convex polygon, and a novel algorithm to calculate the widths of convex polygons with time complexity of O(n) is developed. The path of the least number of turns for an UAV based on the widths of convex polygons is devised. Thirdly, a convex decomposition algorithm for minimum width sum based on the greedy recursive method which revolves around decomposing the concave area into convex subregions is developed. It is proved that the algorithm is a polynomial time algorithm. To avoid unnecessary back and forth motion, some entirely adjacent subregions are combined. Finally, comparing different weights of two joint-points, a subregion connection algorithm based on minimum traversal of weighted undirected graph is proposed to connect the coverage paths of the subregions. Simulation results show that the proposed method is feasible and effective.     

Towards seamless mobility on pervasive hardware

Preserving one’s uniquely customized computing environment as one moves to different locations is an enduring challenge in mobile computing. We examine why this capability is valued so highly, and what makes it so difficult to achieve for personal computing applications. We describe a new mechanism called Internet Suspend/Resume (ISR) that overcomes many of the limitations of previous approaches to realizing this capability. ISR enables a hands-free approach to mobile computing that appears well suited to future pervasive computing environments in which commodity hardware may be widely deployed for transient use. We show that ISR can be implemented by layering virtual machine technology on distributed file system technology. We also report on measurements from a prototype that confirm that ISR is already usable today for some common usage scenarios.     

周期轧管机的自动压下控制

本文介绍了由压下电动机、变频器、PLC和绝对值编码器构成的周期轧管机的压下自动控制系统。作者简介了压下工艺和设备；着重描述了该压下控制系统的硬件配置和应用程序设计。生产实践表明，该控制系统实现了对周期轧管机压下装置高效、准确的控制。     

一种CMOS混合电源供给管理方案

针对目前便携式设备对多电源供电的要求提出了一种CMOS工艺下的片内电源管理方案。该方案可实现3种输入电源即：交流适配器(AC)、USB电源、以及电池电源之间的选择，并设置供电电源优选顺序为：交流电源、USB、电池。另外本文设计了相应的欠压保护电路，使得该电源管理方案更加完整。     

Rapid transit network design for optimal cost and origin–destination demand capture

This paper proposes a tractable model for the design of a rapid transit system. Travel cost is minimized and traffic capture is maximized. The problem is modeled on an undirected graph and cast as an integer linear program. The idea is to build segments within broad corridors to connect some vertex sets. These segments can then be assembled into lines, at a later stage. The model is solved by branch-and-cut within the CPLEX framework. Tests conducted on data from Concepción, Chile, confirm the effectiveness of the proposed methodology.     

无缝钢管内折缺陷的研究

钢管内折缺陷一直是影响无缝厂400轧制作业区生产的主要原因。为了探索内折缺陷成因，从连铸坯、轧卡样、内折缺陷成品试样等进行现场试验并进行性能、低倍组织分析，总结产生钢管内折缺陷的原因。     

磷脱氧铜无缝管断裂原因分析

用ＳＥＭ等方法对电冰箱压缩机用磷脱氧无缝铜管异常断裂进行了分析。结果表明，夹杂物局部偏聚是铜管断裂的内在原因，焊接时产生的热应力及弯曲变形是铜管断裂的外部诱发因素。有效的改进措施是严格控制杂质含量、将高温焊接工艺改为低温焊接工艺。     

Vertical handoff in integrated CDMA and WLAN systems

Future wireless networks are expected to consist of different types of wireless networks such as code division multiple access (CDMA) networks and public wireless local area networks (WLANs). The integrated network will require vertical handoffs between different networks. In this letter, we propose vertical hard- and soft-handoff algorithms and evaluate their performance in commercial wireless networks.     

WLAN Mesh技术城域覆盖探讨

介绍了无线Mesh网络技术发展概况及技术特征,基于实际工程经验,对WLAN Mesh技术的工程应用进行了探讨,以期望助力于国内"无线城市"工程建设。