An range-free localization scheme for large scale underwater wireless sensor networks

In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS.     

Effects of denial of service attack in mobile ad hoc networks

Mobile ad hoc networks are often deployed in environments where the nodes of the networks are unattended and have little or no physical protection against tampering. The nodes of mobile ad hoc networks are thus susceptible to compromise. The networks are particularly vulnerable to denial of service (DoS) attacks launched through compromised nodes or intruders. In this paper, we investigated the effects of flooding attacks in network simulation 2 (NS-2) and measured the packet delivery ratio and packet delay under different flooding frequencies and different numbers of attack nodes. Simulation results show that with the increase the flooding frequencies and the numbers of attack nodes, network performance drops. But when the frequency of flooding attacks is greater than a value, the performance decrease gets smooth. Meanwhile the packet delay firstly increases and then declines to a value of stability at the end.     

植筋技术在桥梁拼接施工中的应用

植筋技术用于桥梁拼接施工时,具有对原结构的破损小、工艺简单、锚固后结构整体性好等特点。本文结合合宁扩建高速公路扩建工程新、老桥梁的拼接,较详细地介绍植筋技术的施工工艺及施工中的注意事项。     

软土地基高填方路堤综合施工技术

结合沪蓉国道高速公路一段软土地基高填方路堤的施工,总结了类似地质条件的高填方路堤施工技术,针对软土基础采用的振动沉管碎石挤密桩结合土工格栅和砂砾垫层综合处治措施,详细介绍了振动沉管碎石桩的施工组织和工艺。     

中国港口拥挤的原因及对策

港口作为国家最重要的交通基础设施,对中国的经济发展特别是外贸业的发展起到非常重要的作用,但是随着货运量的增加和其他原因,中国很多港口出现了拥挤现象,在一定程度制约了港口行业和区域经济的发展,本文分析了中国港口拥挤的原因,对缓解港口拥挤现象提出了一些建议．     

语篇在翻译中的具体运用

把语篇运用于翻译,有着重要的实践意义。不但能使上下文联系紧密,凸显句式在文章中的功能,而且能更好地处理社会文化现象,有效地完成翻译的目的。     

快速测量法在隧道施工中的应用

测量工作伴随隧道开挖的整个过程,因洞内条件的限制,洞内开挖断面的测量放样工作占用的时间不少,直接影响着隧道的施工安全、进度。文中通过对待测断面坐标系中的坐标与隧道三维坐标的关系,编制简易的程序,利用简易普及的全站仪进行数据输入、分析,能快速地给出待测断面的坐标,通过几尾隧道的施工放样实践,收到了较好的效果。     

轮对跑合试验台计算机测控系统的研究与研发

针对中国铁路的不断提速,为了提高我国机车和客车走行部的测控手段,研制一种轮对跑合试验台计算机测控系统.通过控制不同的加裁力和跑合速度,测量其振动和温升情况,对轮对的修造质量和安装质量进行有效的综合评判.     

综合爆破技术在路基施工中的应用

基于爆破理论和山区高等级公路石方路基工程的特点,探讨综合爆破技术在山区高等级公路建设石方路基施工中应用的可行性和关键技术问题。实践表明,在山区高等级公路路基施工中,由于实际施工条件的限制及施工进度、质量的要求,多种爆破技术的综合应用是加快施工进度和保证施工质量的有效措施。     

滑模式摊铺机用于水泥混凝土路面摊铺的施工技术

该文通过对滑模式混凝土摊铺机的发展过程和应用的简要说明,结合HW-165B型混凝土滑模机在菲律宾薄荷岛的施工经历,主要阐述滑模式水泥混凝土摊铺机在公路路面工程施工中的应用与管理情况。从水泥混凝土摊铺机的摊铺技术要求、准备工作及摊铺过程中应注意的问题以及管理等几个方面,根据工艺要求进行介绍,以达到预期使用设备的目的。