Detailed thermal modelling of a tubular linear machine for marine renewable generation

A detailed lumped-parameter thermal model is presented for a tubular linear machine that has been designed for use in a marine environment. The model has been developed for a static machine, the worst-case thermal scenario, and is used to establish a rating for the machine. The model has been validated against a large range of experimental tests and shows good correlation to both steady-state and transient experimental results. The model was constructed from a mostly theoretical basis with very little calibration, suggesting that the techniques used are applicable in a more general sense. © 2013 IEEE.

Experimental evaluation of layout designs for 3 × 3 MIMO-enabled radio-over-fiber distributed antenna systems

This paper experimentally demonstrates that, for two representative indoor distributed antenna system (DAS) scenarios, existing radio-over-fiber (RoF) DAS installations can enhance the capacity advantages of broadband 3 × 3 multiple-input-multiple-output (MIMO) radio services without requiring additional fibers or multiplexing schemes. This is true for both single-and multiple-user cases with a single base station and multiple base stations. First, a theoretical example is used to illustrate that there is a negligible improvement in signal-to-noise ratio (SNR) when using a MIMO DAS with all N spatial streams replicated at N RAUs, compared with a MIMO DAS with only one of the N streams replicated at each RAU for N ≤ 4. It is then experimentally confirmed that a 3 × 3 MIMO DAS offers improved capacity and throughput compared with a 3 × 3 MIMO collocated antenna system (CAS) for the single-user case in two typical indoor DAS scenarios, i.e., one with significant line-of-sight (LOS) propagation and the other with entirely non-line-of-sight (NLOS) propagation. The improvement in capacity is 3.2% and 4.1%, respectively. Then, experimental channel measurements confirm that there is a negligible capacity increase in the 3 × 3 configuration with three spatial streams per antenna unit over the 3 × 3 configuration with a single spatial stream per antenna unit. The former layout is observed to provide an increase of ∼1% in the median channel capacity in both the single-and multiple-user scenarios. With 20 users and three base stations, a MIMO DAS using the latter layout offers median aggregate capacities of 259 and 233 bit/s/Hz for the LOS and NLOS scenarios, respectively. It is concluded that DAS installations can further enhance the capacity offered to multiple users by multiple 3 × 3 MIMO-enabled base stations. Further, designing future DAS systems to support broadband 3 × 3 MIMO systems may not require significant upgrades to existing installations for small numbers of spatial streams. © 2013 IEEE.

AI in the 21st century - With historical reflections

The discipline of Artificial Intelligence (AI) was born in the summer of 1956 at Dartmouth College in Hanover, New Hampshire. Half of a century has passed, and AI has turned into an important field whose influence on our daily lives can hardly be overestimated. The original view of intelligence as a computer program - a set of algorithms to process symbols - has led to many useful applications now found in internet search engines, voice recognition software, cars, home appliances, and consumer electronics, but it has not yet contributed significantly to our understanding of natural forms of intelligence. Since the 1980s, AI has expanded into a broader study of the interaction between the body, brain, and environment, and how intelligence emerges from such interaction. This advent of embodiment has provided an entirely new way of thinking that goes well beyond artificial intelligence proper, to include the study of intelligent action in agents other than organisms or robots. For example, it supplies powerful metaphors for viewing corporations, groups of agents, and networked embedded devices as intelligent and adaptive systems acting in highly uncertain and unpredictable environments. In addition to giving us a novel outlook on information technology in general, this broader view of AI also offers unexpected perspectives into how to think about ourselves and the world around us. In this chapter, we briefly review the turbulent history of AI research, point to some of its current trends, and to challenges that the AI of the 21st century will have to face. © Springer-Verlag Berlin Heidelberg 2007.

Characterization of stress induced in SOS and Si/gamma-Al2O3/Si heteroepitaxial thin films by Raman spectroscopy

Raman spectroscopy technique has been performed to investigate the stress induced in as-grown silicon-on-sapphire (SOS), solid-phase-epitaxy (SPE) re-grown SOS, and Si/gamma-Al2O3/Si double-heteroepitaxial thin films. It was demonstrated that the residual stress in SOS film, arising from mismatch and difference of thermal expansion coefficient between silicon and sapphire, was reduced efficiently by SPE process, and that the stress in Si/gamma-Al2O3/Si thin film is much smaller than that of as-grown SOS and SPE upgraded SOS films. The stress decrease for double heteroepitaxial film Si/gamma-Al2O3/Si mainly arises from the smaller lattice mismatching of 2.4% between silicon top layer and the gamma-Al2O3/Si epitaxiial composite substrate, comparing with the large lattice mismatch of 13% for SOS films. It indicated that gamma-Al2O3/Si as a silicon-based epitaxial substrate benefits for reducing the residual stress for further growth of silicon layer, compared with on bulk sapphire substrate. (c) 2005 Elsevier B.V. All rights reserved.

Low Temperature Deposited Nano-structured Vanadium Oxide Thin Films for Uncooled Infrared Detectors

A novel process of room temperature ion beam sputtering deposition of vanadium oxide films and low temperature post annealing for uncooled infrared detectors was proposed in this work. VOx thin films with relatively low square resistance (70 K Omega / square) and large temperature coefficient of resistance (more than 3%/K) at room temperature were fabricated using this low temperature process which was very compatible with the process of uncooled infrared detectors based on micromachined technology. Furthermore, chemical composition and film surface have been characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results showed that the main composition of the processed thin films was V2O5 and the thin films were in the process of crystallization.

后向无关联性的本地验证撤销群签名研究

数字签名，是密码理论的一个重要分支，在身份认证等方面举足轻重。但随着电子商务、电子政务等业务的不断展开，在多用户参与的应用环境中显得捉襟见肘。群数字签名应运而生，主要特点是保护了签名者的匿名性。 群签名撤销研究的两个主要方向：设计算量小的撤销成员算法，以及保证成员被撤销之前签名的匿名性和无关联性。目前主要有基于撤销列表（RL）和证据的撤销算法是两类主流算法，前者更适用于移动环境中。因此，在网络化、信化的今天，基于撤销列表的群签名的研究显得弥足重要。 本地验证撤销（VLR），是目前效率最高的一种基于撤销列表的方法。后向无关联性（BU），是指当成员即使在某个时段被撤销，以前的签名仍然保持匿名性。本论文主要工作，是对有群签名方案的分析和BU-VLR方案的设计，主要有以下几个方面： 1. 2007年IEEE Transactions on Vehicular Technology上的一个方案，建立在2004年Boneh等在 CRYPTO的群签名方案。本论文指出，方案使得同一成员的签名具有关联性，导致在VLR安全模型下方案不具有匿名性。 2. 分析的另外两个群签名方案，都是方案设计者在设计签名算法时由于设计不当，使得同一成员的签名具有关联性，从而导致方案在相应的安全模型下不具有匿名性。 3. 对一种基于身份的群签名方案，有文献曾对该签名方案做过分析，在本论文将给出另外一种方法来证明方案不具有匿名性。 4. 分析指出了一种新型群签名方案，其本身是建立在一个错误的签名方案之上，因而该方案不过是空中楼阁。此外，方案还存在其他缺陷。 5.构造了一个BU-VLR群签名方案，具有较短的签名长度和较低的运算量。利用k叉树扩展了方案以减少RL的数据量。最后，对2007年IEICE中一个BU-VLR方案加以改进，签名长度为原来的77.8%，运算量不变。 6.设计的第二个方案，针对现有BU-VLR方案中存在的缺陷，使得到的方案公钥长度不再与成员个数相关；撤销上的数据不再随着时间段的更新而更新，而只是在列表需要更新的时间段更新。 7.在q-SDH假设和困难性假设较强的XDH假设下，构造了一个BU-VLR群签名方案，性能上优于目前最高效的VLR方案，即BS04方案。

基于机群架构的并行数据库实现技术研究

在总结了现有并行数据库实现模型的基础上,基于"半重写变换"模型[1]实现了一个并行数据库系统的原型。通过对数据划分/重划分、并行选择、并行排序、并行连接等关键操作的实验分析,指出了"半重写变换"模型存在的缺陷,并提出了一种混合式的改进模型。从理论上说,在机群架构下实现并行数据库系统,这种混合模型较单一模型更有优势。

基于网格技术的密码学计算平台的设计

结合现有的网格技术、思想和密码计算的特点,分析了利用网格技术实现密码学计算的可行性,并结合J2EE开发方式的优势实现系统支持,最后提出了一种有效的、可行的密码计算网格平台构架.

基于可信计算的度量验证关键技术研究

分布式应用的飞速发展让结点平台的可信保障成为信息安全的研究热点。传统计算机平台的信息安全技术很难满足分布式计算环境的安全需求。可信计算技术通过引入可信硬件作为“信任根”，为保障结点平台的可信性提供了新的机制。基于可信计算的度量验证技术是保障平台可信性的核心机制，目前的相关研究在可信性、隐私性、易用性等方面还存在问题。 本文总结度量验证的基本概念和实施模型；分析现有度量验证机制在平台隐私保护、运行时完整性保障上存在的问题，提出相应具体解决方案；并基于度量验证机制提出一种新的对等网络声誉系统，具体创新成果如下： 1. 分析可信与完整性的本质，提出动态系统完整性的概念，并基于Clark-Wilson完整性模型给出具体实施规则，用于指导运行时完整性保障机制的设计与实现。 2. 针对经典度量验证体系架构存在的平台隐私保护不力、验证效率低下、验证方式单一等不足，提出基于Merkle哈希树的度量验证机制RAMT，并阐述其体系架构和具体实现。 3. 分析载入时完整性保障的缺陷，提出运行时完整性保障机制，通过对关键系统构件的运行时完整性进行监控提高其可信性；给出一种基于动态完整性度量模块DIMM的具体实现方案，分析该方案的可靠性和有效性，并阐述其在虚拟机环境下的实际应用vTPM-DIMM。 4. 为解决现有声誉系统的负载平衡、冷启动以及协同作弊问题，基于度量验证机制提出一种多级别的可信声誉系统MRS；通过CCEA实施全局的访问控制规则，MRS还可作为激励机制使用。

scenario-focused development method for a pen-based user interface: model and applications

Pen-based user interface (PUI) has drawn significant interest, owing to its intuitiveness and convenience. While much of the research focuses on the technology, the usability of a PUI has been relatively low since human factors have not been considered sufficiently. Scenario-centric designs are ideal ways to improve usability. However, such designs possess some problems in practical use. To cope with these design issues, the concept of “interface scenarios” is proposed in to facilitate the interface design, and to help users understand the interaction process in such designs. The proposed scenario-focused development method for PUI is coupled with a practical application to show its effectiveness and usability.

GSMBE外延生长SGOI材料的退火行为

在SIMOX SOI超薄硅衬底上外延生长了高质量SiGe合金薄膜来制备SGOI(SiGe on insulator)样品，并研究了其在1050℃氧化气氛中的高温退火行为．用Raman，DCXRD，RBS和光学显微镜等分析手段对SGOI样品在退火前后的性能进行了表征．分析结果表明

高安全等级数据库系统及测评关键技术研究

作为信息存储和处理的核心环节，数据库管理系统的安全性在整个信息安全体系结构中起着至关重要的作用。高安全等级数据库管理系统的设计与测评既是当前发展的客观需求，同时也是一个极大的挑战。针对这一挑战，本文以高安全等级数据库系统及其测评关键技术为中心展开了一系列工作，并取得了以下重要成果： （1）针对高安全等级数据库系统安全功能开发过程中的问题，本文提出基于通用标准的数据库安全功能开发方法，采用自顶而下的安全需求定义方法，依次对系统运行环境分析、安全目标定义直到可用性表示等开发中的问题进行了分析。依此方法开发的安全产品可以完备地应对安全环境中的所有威胁。 （2）提出了入侵容忍的数据库恶意事务处理方法。该方法利用在事务管理器层次扩展的事务恢复日志分析和查找恶意事务的后继，通过数据回滚使受损数据在线的恢复至攻击前的状态。本文证明了该方法的完备性和正确性，与现有技术相比，该方法可以获得更高的运行效率。 （3）针对信息安全产品测评无法量化的问题，本文提出了一种基于三角模糊数的安全保证量化评估方法。量化评估方法包括：如何构造保证评估框架；如何使用模糊数标识评估员对组件的评价和对权重的分配；如何使用底线折中法形成量化的安全评价值。应用该方法进行测评，可使产品安全性以指标值的形式呈现，方便采购方和决策者规避安全风险。 （4）提出了高等级数据库系统测评平台的实现方法。给出兼容GB17859和GB18336等不同标准体系、高度集成、扩展性良好，并具有保护轮廓评估、安全目标评估、测试用例生成、测试案例管理、安全保证评估和模型形式化验证等功能的测评平台实现方法。为测评人员进行高安全等级数据库产品的测试和评估提供了一个全面的操作平台，提高了测评工作的自动化程度。 总的来说，本文的研究成果推动了高安全等级数据库管理系统及其测评关键技术研究的发展，并为实现我国高等级数据库管理系统及其测评打下了坚实的基础。

含油浮渣处理技术研究

含油浮渣是含油污水处理的末端废弃物，产生于处理工艺中的气浮单元，属于含油固体废弃物。目前国内尚无有效的处理工艺，大部分采用堆储方式处理。本文以辽河油田含油浮渣为研究对象，通过对含油浮渣理化性质的研究提出了以反絮凝为技术核心的处理工艺，并在此基础上进行的浮渣的减量化和无害化处理的技术研究。结果表明：通过反絮凝可完全破坏浮化絮凝团的结构，从根本上改变浮渣的流动性，浮渣的脱水性能也得到了显著改善。含油浮渣减量化小试试验根据传统的压滤工艺，采用反絮凝技术作为前处理工艺，浓缩脱水率达50％～60％，压滤脱水率明显提高，压滤后浮渣体积减量90％以上。研究还通过减量化中试试验完善了工艺流程与参数，实验结果显示，样品压滤后含水率从97.4％降低至60.7％，浮渣体积减量94.4％。含油浮渣无害化小试试验，对含油浮渣进行了反絮凝一水基清洗无害化处理，油总的去除率在50％～60％之间，含油浮渣最终的含水率在94％-95％，含油率在0.8％～1.2％。