XML 关键词检索的查询理解

与纯文本文档集相比,使用语义标签标注的半结构化的XML文档集,有助于信息检索系统更好地理解待检索文档.同样,结构化查询,比如SQL,XQuery和Xpath,相对于纯关键词查询更加清晰地表达了用户的查询意图.这二者都能够帮助信息检索系统获得更好的检索精度.但关键词查询因其简单和易用性,仍被广泛使用.提出了XNodeRelation算法,以自动推断关键词查询的结构化信息(条件/目标节点类型).与已有的推断算法相比,综合了XML文档集的模式和统计信息以及查询关键词出现的上下文及其关联关系等推断用户的查询意图.大量的实验验证了该算法的有效性.     

Forecasting and trading the EUR/USD exchange rate with Gene Expression and Psi Sigma Neural Networks

The motivation for this paper is to investigate the use of two promising classes of artificial intelligence models, the Psi Sigma Neural Network (PSI) and the Gene Expression algorithm (GEP), when applied to the task of forecasting and trading the EUR/USD exchange rate. This is done by benchmarking their results with a Multi-Layer Perceptron (MLP), a Recurrent Neural Network (RNN), a genetic programming algorithm (GP), an autoregressive moving average model (ARMA) plus a naïve strategy. We also examine if the introduction of a time-varying leverage strategy can improve the trading performance of our models.     

HybSim:一种混合型流媒体存储的仿真系统

高性能和低功耗的特点使闪存逐渐赢得广泛关注,而最常见的闪存使用方式是和内存、磁盘一起构成混合型存储系统,对于流媒体这样对存储容量和访问性能要求都非常高的应用来说尤其如此。但是,目前还缺少准确、全面的混合型存储仿真工具来支持混合存储的研究工作。首先,在对基于闪存缓存的混合存储的体系结构和能耗等关键问题进行建模的基础上,设计并实现了一套混合型流媒体存储的仿真系统HybSim。相对于目前国际上广泛使用的存储仿真系统DiskSim及其闪存补丁,HybSim增加了各类典型的混合型存储系统的实现、能耗模块、文件级管理和访问支持、流媒体服务模式支持,以及对性能、服务质量、能耗、设备耗损程度的统计模块等。基于HybSim对混合型流媒体存储系统在性能和节能两个方面进行了详细的仿真实验,并对几种典型的混合型存储系统体系结构在性能、服务质量、节能、设备磨损等方面的优劣进行了详细分析和比较。     

基于直方图的XPath含值谓词路径选择性代价估计

路径选择性代价估计是XML查询优化的基础，也是研究的热点．目前的方法采用大量正态分布和独立性分布假设是造成误差的根本原因．定义了一种新颖的值一位置直方图用于统计XML数据中的结构和值的分布情况，并提出了6种直方图运算．在此基础上，给出用直方图计算估计路径中任一结，最选择性的方法．实验证明，这种方法无需独立性分布假设，也能在数据结构和数值分布不均匀的情况下。精确地估计路径选择性代价．     

汉语语音合成系统评测中MOS和PC评估方法的比较

采用主观印象评测（MOS）和成对比较评测（PC）两种方法对已有的四个汉语语音合成系统进行了评测。17名普通话讲的很好的大学三年级学生参加了评测，其中男同学10名，女同学7名。在MOS中，文章从系统的整体印象、努力程度、理解程度、语速、发音（重音、停顿）及悦耳程度6个方面进行了评测。评测结果显示：听音的努力程度与系统的整体印象相关性最大，对系统整体印象的影响最大，其次是声音的悦耳程度。评测比较结果显示，PC测试同MOS测试具有很好的一致性，对于没有专家参与的评测中，PC方法更简单易用。     

Synthesis of silica nanocubes by sol–gel method

A novel approach was employed in the fabrication of silica nanocubes with controlled size and shape. The silica nanocubes were highly dispersed with width of about 30 nm and product with high purity. A small amount of tartaric acid was introduced in the TEOS hydrolysis process. In this work tartaric acid as the organic template, was formed on the surface of hydrous silica colloidal particles. The organic template ordered by carboxyl, led to the self-assembly of amorphous silica sol encapsulated into cubic matrixes, and the organic template was packed into 3D structure.     

Experimental research on a modular miniaturization nanoindentation device

Nanoindentation technology is developing toward the in situ test which requires miniaturization of indentation instruments. This paper presents a miniaturization nanoindentation device based on the modular idea. It mainly consists of macro-adjusting mechanism, x-y precise positioning platform, z axis precise driving unit, and the load-depth measuring unit. The device can be assembled with different forms and has minimum dimensions of 200 mm × 135 mm × 200 mm. The load resolution is about 0.1 mN and the displacement resolution is about 10 nm. A new calibration method named the reference-mapping method is proposed to calibrate the developed device. Output performance tests and indentation experiments indicate the feasibility of the developed device and calibration method. This paper gives an example that combining piezoelectric actuators with flexure hinge to realize nanoindentation tests. Integrating a smaller displacement sensor, a more compact nanoindentation device can be designed in the future.     

Sliding wear behavior of copper alloy contact wire against copper-based strip for high-speed electrified railways

This paper reports the study of the sliding wear behavior of the Cu–Ag–Cr wire. Cu–Ag–Cr alloy is a promising contact wire material for high-speed electrified railways, which has an excellent combination of mechanical strength and electrical conductivity. Wear tests were conducted under laboratory with a special sliding wear apparatus, which simulated the tribological conditions of sliding current collectors on overhead wires in the railway system. The Cu–Ag–Cr alloy wire was slid against a copper-based powder metallurgy strip under unlubricated conditions. The same strip as those in the train systems were used. Worn surfaces of the Cu–Ag–Cr alloy wire were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). Within the studied range of electrical current, normal pressure and sliding speed, the wear rate increased with the increasing electrical current and the sliding distance. Compared with a Cu–Ag contact wire under the same conditions, the Cu–Ag–Cr alloy wire had much better wear resistance. Adhesive wear, abrasive wear and arc erosion were the dominant mechanisms during the electrical sliding processes.     

Effect of NaCl on the properties of Eu-doped Ca-α-SiAlON phosphors prepared by combustion synthesis

Eu-doped Ca-α-SiAlON phosphors, featuring high phase purity, uniform particle size of 3–5 μm and good luminescent properties with a yellow emission spectrum under blue light excitation, were prepared by a highly efficient combustion synthesis (CS) method. A certain amount of NaCl was applied as an innovative additive to regulate and control the properties of synthesized phosphors. Further, the effects of NaCl additive in the CS system were systematically investigated and rational proposed. It was found that the effect on accelerating nitridation and crystallization played a dominant role in the reaction as the content of NaCl was less than 6 wt%, while the effect of absorbing reaction heat through vaporization was dominant with the further-increased content of NaCl. The intensity of the emission spectrum for the sample doped with 6 wt% of NaCl was remarkably enhanced, nearly 40% more than the sample which was not NaCl-doped. Moreover, a continuous blue-shift phenomenon in emission spectra was observed with the increased content of NaCl.     

When and how authoritarian leadership and leader renqing orientation influence tacit knowledge sharing intentions

In this study of tacit knowledge-sharing intentions in China, we examine the roles of authoritarian leadership and fairness with respect to the way managers make decisions and treat their subordinates. In particular, we examine the role of leader renqing orientation, i.e., the way leaders distribute favors and emotional concern to their subordinates, as a moderating factor. We draw on the research literature in the domains of knowledge management and cross-cultural Psychology to identify constructs that we then test with a survey of 309 Chinese employees. Our findings are counter-intuitive and are discussed in detail before we conclude with implications for research and practice.