Implementation of trailer steering control on a multi-unit vehicle at high speeds

A high-speed path-following controller for long combination vehicles (LCVs) was designed and implemented on a test vehicle consisting of a rigid truck towing a dolly and a semitrailer. The vehicle was driven through a 3.5 m wide lane change maneuver at 80 km/h. The axles of the dolly and trailer were steered actively by electrically-controlled hydraulic actuators. Substantial performance benefits were recorded compared with the unsteered vehicle. For the best controller weightings, performance improvements relative to unsteered case were: lateral tracking error 75% reduction, rearward amplification (RA) of lateral acceleration 18% reduction, and RA of yaw rate 37% reduction. This represents a substantial improvement in stability margins. The system was found to work well in conjunction with the braking-based stability control system of the towing vehicle with no negative interaction effects being observed. In all cases, the stability control system and the steering system improved the yaw stability of the combination. © 2014 by ASME.

A power-saving scheme for IEEE 802.11 Ad hoc networks

In the Wireless Local Area Networks (WLANs), the terminals are often powered by battery, so the power-saving performance of the wireless network card is a very important issue. For IEEE 802.11 Ad hoc networks, a power-saving scheme is presented in Medium Access Control (MAC) layer to reduce the power consumption by allowing the nodes enter into the sleep mode, but the scheme is based on Time-Drive Scheme (TDS) whose power-saving efficiency becomes lower and lower with the network load increasing. This paper presented a novel energy-saving mechanism, called as Hybrid-Drive Scheme (HDS), which introduces into a Message.-Drive Scheme (MDS) and combines MDS with the conventional TDS. The MDS, could obtain high efficiency when the load is heavy; meanwhile the TDS has high efficiency when the network load is small. The analysis shows that the proposed HDS could obtain high energy-efficiency whether the network load is light or heavy and have higher energy-saving efficiency than conventional scheme in the IEEE 802.11 standard.

基于策略的域间访问控制和信息流控制框架

随着互联网及其相关技术的发展，多域环境下的资源共享越来越普遍。域间的资源共享给域间合作带来了便利的同时也带来了安全问题。其中两个关键安全问题是跨域访问控制和跨域信息流控制。本文针对典型的跨域资源共享系统的安全需求，提出了基于策略的跨域访问控制与信息流控制框架。框架包括了授权和访问控制体系结构、授权策略模型、用于生成和维护授权策略的协议和算法、 用于表示和分析跨域信息流的信息流图和用于控制跨域信息流的机制。主要贡献具体体现在以下几个方面： 1）框架的提出使得安全互操作可以以一种无策略协调器的方式进行。在对资源共享进行控制的现有方案中， 其安全互操作都是以基于中心协调器的方式进行，存在如下问题：中心协调器会成为仲裁域间资源共享的瓶颈；有时很难找到一个可信的第三方来持有中心协调器。框架通过以一种无策略协调器的方式使得这些问题得到解决。首先，框架给出一个分布式跨域授权策略模型；根据此模型，跨域策略被分布到每个域，而每个域所保留的策略对于安全违反检测以及资源的访问判定来说是可靠的和完备的。其次，框架给出了协议和算法以在域初始建立合作时生成这样的跨域授权策略，并给出了跨域策略变更的协议和算法。其中，跨域授权策略初始建立与变更过程中的安全违反检测可以在单个域本地进行 — 也就是说, 每个域检查是否有对其自身的安全违反并引导协商以去除违反；对一个域的资源的访问判定由此域自身来确定（根据其保留的策略）。 2）框架给出了一个渐进的策略变更方案。此方案只涉及与策略变更相关的域，并且只涉及到与策略变更相关的策略。在多种情况下，变更不会带来任何安全违反或者只会带来某种类型的安全违反。如果存在任何安全违反，此安全违反也是被限定在相关策略范围内。此方案适合策略变更频繁的动态环境。 3）框架给出了一种面向多域资源共享的信息流控制方案。该方案面向采用了基于角色访问控制（RBAC）策略和单向角色映射的多域环境。方案给出了如何用信息流图来表示和分析跨域信息流的方法。根据与信息扩散相关的需求，给出域内信息安全和域间信息安全的概念。域可以定义域内和域间信息安全需求以控制信息扩散。而且给出了角色划分、角色激活上的限制、角色映射激活上的限制等措施来满足由域定义的需求。

基于量化权限的门限访问控制方案

研究了在引入量化权限观点后从访问控制角度实现秘密保护的问题.元权限是从哲学上"质"和"量"的角度认识传统意义上的权限所探究出的新概念,较以往访问控制中认识和使用权限而言,它全面而深入地反映了权限这一概念的本质.进一步结合门限思想和基于角色的访问控制机制所提出的基于量化权限的门限访问控制方案,从访问控制的角度研究了秘密保护问题.在秘密保护方面,基于量化权限的门限访问控制方案具有一些独特的优点,比如分发给参与者的秘密分片和要保护的秘密无知识上的联系、可以反映出参与者信任度的差异以及运算量低.

基于扩展XACML的策略管理

在XACML（extensible access control markup language）和其管理性策略草案的基础上，针对目前XACML访问控制框架的特点，提出将XACML策略管理权限判定归结为利用委托策略对一个委托判定请求的判定，使用XML（extensible markup language）模式定义了此委托判定请求语法，描述了将策略管理请求规约为一个委托判定请求的过程，以及根据委托策略进行委托判定请求的判定过程，通过这种方法可以利用委托策略，对策略管理请求是否有效进行判断，从而实现基于扩展XACML的策略管理。

基于可信平台的一种访问控制策略框架——TXACML

根据可信平台访问控制需求,提出一个可信平台属性分类规则,定义属性评估函数,可以实现可信平台数据安全分发和访问.同时针对XACML现有的策略合成算法不能有效满足可信平台自动方策略复合需求,设计了一个基于平台可信度的策略合成算法,该算法可以使策略的优先级和可信度保持一致,实现自动方策略复合.在此基础上,进一步对XACML实施扩展,形成可信平台策略语言框架TXACML(XACML based on trusted platform).采取TXACML对一个实例给出了策略描述和策略合成过程,验证了TXACML的有效性.

基于静态分析的强制访问控制框架的正确性验证

现阶段对操作系统的强制访问控制框架的正确性验证的研究主要集中于对授权钩子放置的验证.文中基于TrustedBSD MAC框架对强制访问控制框架的正确性验证问题进行了研究,在授权钩子放置验证的基础上,提出了安全标记的完全初始化验证和完全销毁验证.为了实现上述验证,文中提出了一个路径敏感的、基于用户自定义检查规则的静态分析方法.该方法通过对集成于编译器的静态分析工具mygcc进行扩展来验证强制访问控制框架的钩子放置的准确性和完备性.该方法具有完全的路径覆盖性,且具有低的误报率和时间开销.

基于访问控制空间的多策略安全体系结构

为解决LSM在策略重用和策略共存方面存在的问题，提出了一个新的安全体系结构ELSM，它引入一个模型组合器作为主模块实施模块堆栈管理和模块决策管理，其中模块决策的实施采用了访问控制空间的策略规范方法，可支持通用性，ELSM的设计及其在安胜OS安全操作系统中的实例分析表明其有效性。

一种基于访问控制的安全Web服务发现机制

当前的Web服务发现机制大多依赖集中式的统一描述、发现和集成注册中心,但组织机构出于安全和地域的考虑,倾向于构建私有的分布式注册中心,只有注册且可信的请求者才能浏览到他们有权限访问的服务信息。该文给出Web服务发现阶段基于角色的访问控制模型RBAC4WSD,发现代理依照服务提供者指定的安全策略对请求者实施访问控制,并以跨国公司内部的文档服务为例介绍原型系统的实现。

基于ARM Linux的门禁系统的设计与实现

门禁系统主要负责对出入通道进行管制，是社区楼宇安全监控系统的一部分。传统的门禁系统通常采用密码识别、卡片识别的方式进行验证，由于密码、卡片容易被盗用、丢失，系统安全性不高。在通信方式上传统门禁系统通常采用RS485或者RS232连接，传输距离、速度和连接终端数均受限制。本文提出的人像识别门禁系统解决方案采用ARM-Linux系统平台，依靠社区宽带综合业务网的传输和存储能力，结合密码、RFID和人像识别三种识别方式，利用网络技术和生物识别技术达到识别率高、响应速度快、扩展能力强的要求，并能够与驻地网的其它业务集成，提供业务级的联动服务。此外，该门禁系统还支持用户使用电话开门，由服务器完成对用户来电的识别和防伪验证。本文工作的主要贡献是：参与了ARM-Linux系统的裁剪、移植和声卡驱动的修改；建立了ARM-Linux交叉编译环境；完成了门禁前端软件系统的整体设计和实现；完成了服务器软件电话呼叫响应子系统的设计。

西江流域环境河水地球化学研究

River is a major component of the global surface water and CO2 cycles. The chemistry of river waters reveals the nature of weathering on a basin-wide scale and helps us understand the exogenic cycles of elements in the continent-river-ocean system. In particular, geochemical investigation of large river gives important information on the biogeochemical cycles of the elements, chemical weathering rates, physical erosion rates and CO2 consumption during the weathering of the rocks within the drainage basin. Its importance has led to a number of detailed geochemical studies on some of the world's large and medium-size river systems. Flowing in the south of China, the Xijiang River is the second largest river in the China with respect to its discharge, after the Yangtze River. Its headwaters drain the YunGui Plateau, where altitude is approximately 2000 meters. Geologically, the carbonate rocks are widely spread in the river drainage basin, which covers an area of about 0.17xl06 km2, i.e., 39% of the whole drainage basin. This study focuses on the chemistry of the Xijiang river system and constitutes the first geochemical investigation into major and trace elements concentrations for both suspended and dissolved loads of this river and its main tributaries, and Sr isotopic composition of the dissolved load is also investigated, in order to determine both chemical weathering and mechanical erosion rates. As compared with the other large rivers of the world, the Xijiang River is characterized by higher major element concentration. The dissolved major cations average 1.17, 0.33, 0.15, and 0.04 mmol I"1 for Ca, Mg, Na, and K, respectively. The total cation concentrations (TZ+) in these rivers vary between 2.2 and 4.4 meq I'1. The high concentration of Ca and Mg, high (Ca+Mg)/(Na+K) ratio (7.9), enormous alkalinity and low dissolved SiO2/HCO3 ratio (0.05) in river waters reveal the importance of carbonate weathering and relatively weak silicate weathering over the river drainage basin. The major elements in river water, such as the alkalis and alkaline-earths, are of different origins: from rain water, silicate weathering, carbonate and evaporite weathering. A mixing model based on mass budget equation is used in this study, which allows the proportions of each element derived from the different source to be calculated. The carbonate weathering is the main source of these elements in the Xijiang drainage basin. The contribution of rainwater, especially for Na, reaches to approximately 50% in some tributaries. Dissolved elemental concentration of the river waters are corrected for rain inputs (mainly oceanic salts), the elemental concentrations derived from the different rock weathering are calculated. As a consequence, silicate, carbonate and total rock weathering rates, together with the consumption rates of atmospheric CO2 by weathering of each of these lithologies have been estimated. They provide specific chemical erosion rates varying between 5.1~17.8 t/km2/yr for silicate, 95.5~157.2 t/km2/yr for carbonate, and 100.6-169.1 t/km2/yr for total rock, respectively. CO2 consumptions by silicate and carbonate weathering approach 13><109and 270.5x10 mol/yr. Mechanical denudation rates deduced from the multi-year average of suspended load concentrations range from 92-874 t/km2/yr. The high denudation rates are mainly attributable to high relief and heavy rainfall, and acid rain is very frequent in the drainage basin, may exceed 50% and the pH value of rainwater may be <4.0, result from SO2 pollution in the atmosphere, results in the dissolution of carbonates and aluminosilicates and hence accelerates the chemical erosion rate. The compositions of minerals and elements of suspended particulate matter are also investigated. The most soluble elements (e.g. Ca, Na, Sr, Mg) are strongly depleted in the suspended phase with respect to upper continent crust, which reflects the high intensity of rock weathering in the drainage basin. Some elements (e.g. Pb, Cu, Co, Cr) show positive anomalies, Pb/Th ratios in suspended matter approach 7 times (Liu Jiang) to 10 times (Nanpan Jiang) the crustal value. The enrichment of these elements in suspended matter reflects the intensity both of anthropogenic pollution and adsorption processes onto particles. The contents of the soluble fraction of rare earth elements (REE) in the river are low, and REE mainly reside in particulate phase. In dissolved phase, the PAAS-normalized distribution patterns show significant HREE enrichment with (La/Yb) SN=0.26~0.94 and Ce depletion with (Ce/Ce*) SN=0.31-0.98, and the most pronounced negative Ce anomalies occur in rivers of high pH. In the suspended phase, the rivers have LREE-enriched patterns relative to PAAS, with (La/Yb) SN=1 -00-1 .40. The results suggest that pH is a major factor controlling both the absolute abundances of REE in solution and the fractionation of REE of dissolved phase. Ce depletion in river waters with high pH values results probably from both preferential removal of Ce onto Fe-Mn oxide coating of particles and CeC^ sedimentation. This process is known to occur in the marine environment and may also occur in high pH rivers. Positive correlations are also observed between La/Yb ratio and DOC, HCO3", PO4", suggesting that colloids and (or) adsorption processes play an important role in the control of these elements.

Qualitative evaluation of KA24 (Knowledge Access 24)

Durbin, J. & Urquhart, C. (2003). Qualitative evaluation of KA24 (Knowledge Access 24). Aberystwyth: Department of Information Studies, University of Wales Aberystwyth. Sponsorship: Knowledge Access 24 (NHS)

TCP-friendly SIMD Congestion Control and Its Convergence Behavior

The increased diversity of Internet application requirements has spurred recent interests in flexible congestion control mechanisms. Window-based congestion control schemes use increase rules to probe available bandwidth, and decrease rules to back off when congestion is detected. The parameterization of these control rules is done so as to ensure that the resulting protocol is TCP-friendly in terms of the relationship between throughput and packet loss rate. In this paper, we propose a novel window-based congestion control algorithm called SIMD (Square-Increase/Multiplicative-Decrease). Contrary to previous memory-less controls, SIMD utilizes history information in its control rules. It uses multiplicative decrease but the increase in window size is in proportion to the square of the time elapsed since the detection of the last loss event. Thus, SIMD can efficiently probe available bandwidth. Nevertheless, SIMD is TCP-friendly as well as TCP-compatible under RED, and it has much better convergence behavior than TCP-friendly AIMD and binomial algorithms proposed recently.