基于Visual Basic 开发机床主传动非常规变速系统的设计--重复转速的传动系统(实例之二)

本文介绍利用Visual Basic工具开发金属切削机床主传动非常规变速系统的设计总体结构，功能和方法，以重复转速的传动系统为例，重点介绍转速图的拟定过程，本系统具有界面美观，操作方便，易于理解的特点。     

基于逐层剪枝的中文高频重复模式快速提取算法

为了从大规模语料中快速提取高频重复模式,以递增n-gram模型为基础,使用散列数据结构提取重复串,并提出了一种基于低频字符和层次剪枝的逐层剪枝算法,用于过滤低频垃圾字串,减少I/O读写次数。在此基础上,应用改进的字串排序算法,使字符串排序可在O(n)时间内完成,从而有效提高重复模式的提取效率。实验表明,该算法是一种有效的重复模式提取算法,其I/O读写次数同语料规模呈线性关系,远小于使用首字符进行语料划分的方法,能快速有效地从规模远大于内存容量的文本语料中提取重复模式,特别适合于大规模语料的高频重复模式提取,对以重复模式为基础的新词识别、术语抽取等具有重要的支撑作用。     

接地降阻剂机理及用量研究

本文介绍我们对降阻剂降低接地电阻的机理所作的试验研究结果。这个问题目前尚有争议,有人认为存在着很大的所谓浸润层,亦有人持怀疑态度。我们的试验表明,在埋设降阻剂时确实存在着降阻剂导电溶液向土壤中渗透的一定区间。经过理论分析计算,确定了渗透层的厚度和渗透层的平均土壤电阻率。渗透层并不大,约几公分到十几公分,它可使降阻率提高约20～30％,并有良好的均压作用。仅少数的试验结果已可看出,降阻率的提高对降咀剂用量的关系具有饱和特性。     

编码协作系统准循环重复累积码的联合设计与性能分析

重复累积(RA)码是一种特殊结构的低密度奇偶校验(LDPC)码,不仅具有LDPC码的优点,还能实现差分编码。针对LDPC编码协作系统编码复杂度高、时延长的问题,该文引入准循环RA(QC-RA)码,推导出信源节点和中继节点采用的QC-RA码对应的联合校验矩阵,基于公差构造方法设计该联合校验矩阵,并证明该方法设计的联合校验矩阵不存在围长为girth-4, girth-6的短环。理论分析和仿真结果表明,同等条件下该系统比相应点对点系统具有更优异的误码率性能。仿真结果同时表明,与采用一般构造QC-RA码或基于Z型构造QC-RA码相比,采用基于公差构造的联合设计QC-RA码的多信源多中继协作均可获得更高的编码增益。     

Tactical combat movements: inter-individual variation in performance due to the effects of load carriage

An examination into the effects of carried military equipment on the performance of two tactical combat movement simulations was conducted. Nineteen Airfield Defence Guards performed a break contact (five 30-m sprints) and a fire and movement simulation (16 6-m bounds) in five load conditions (10–30 kg). Heavier loads significantly increased movement duration on the break contact (0.8%/kg load) and fire and movement (1.1%/kg). Performance deterioration was observed from the beginning to the end of the series of movements (bounds or sprints) with deterioration becoming significantly greater in heavier load conditions. Inter-individual variation between slower and faster participants showed a range in load effects; 0.6, 0.8%/kg for fast and 1.0, 1.4%/kg for slow (break contact, fire and movement, respectively). Velocity profiles revealed that the initial acceleration and peak velocity were the primary determinants of performance. As the duration of these tactical combat movements reflects periods of heightened vulnerability, these findings highlight important implications for commanders.

Practitioner Summary: Increasing amounts of carried military equipment impairs the performance of tactical combat movements. Examination of inter-individual variation in velocity profiles identified that the initial acceleration and the peak velocity achieved during sprints and bounds are key determinants of overall performance.     

Computing maximal-exponent factors in an overlap-free word

The exponent of a word is the quotient of its length over its smallest period. The exponent and the period of a word can be computed in time proportional to the word length. We design an algorithm to compute the maximal exponent of all factors of an overlap-free word. Our algorithm runs in linear-time on a fixed-size alphabet, while a naive solution of the question would run in cubic time. The solution for non-overlap-free words derives from algorithms to compute all maximal repetitions, also called runs, occurring in the word.We also show there is a linear number of occurrences of maximal-exponent factors in an overlap-free word. Their maximal number lies between 0.66n and 2.25n in a word of length n. The algorithm can additionally locate all of them in linear time.     

Discovery of stop regions for understanding repeat travel behaviors of moving objects

GPS trajectory dataset with high sampling-rates is usually in large volume that challenges the processing efficiency. Most of the data points on trajectories are useless. This paper summarizes trajectories using stop points. We define a new concept of stay stability (i.e., time dividing distance or reciprocal of speed) between any two GPS points to detect stop points on individual trajectories. We propose a novel Mining Repeat Travel Behaviors Using Stop Regions (MRTBUSR) method. In MRTBUSR, a stop region is a popular region containing a certain number of close stop points that can be grouped into a cluster. We then retrieve common sequences of stop regions to denote repeat route patterns and further analyze the stop durations on a stop region to find repeat travel behaviors. The experiments on 20 labeled trajectories selected from GeoLife demonstrated the semantic effect, accuracy and near linear efficiency of our proposed method.     

Impact of network effects and diffusion channels on home computer adoption

Researchers have identified network effects as one of the major drivers for the adoption and diffusion of household technologies. However, the mechanisms and social contexts through which network effects induce technology adoption are unclear. In this paper, we investigate the adoption of household computers using the dataset from the 1989-2003 Computer and Internet Supplement to the Current Population Surveys (CPS). We argue that social influence and learning play a dominant role in inducing the adoption of home computers, and workplaces and schools are important channels through which network effects take place. We find that recent adopters have a stronger impact than distant adopters on future computer adoptions. When the adoption rate is low, channels play a more important role, but their effects diminish as the adoption rate grows. We also find that diffusion channels are more effective for first-time adoption than for repeat purchases. Overall, our study provides important theoretical, policy, and managerial implications.     

带避雷线的500kV变电站接地阻抗现场测试

针对目前500kV变电站接地装置接地阻抗测量过程中无法打开避雷线的问题,提出一种在局部停电条件下变电站接地阻抗测量方法．研制测量避雷线分流电流的无线远程测量专用电流传感器,基于GPS定位装置确定各辅助接地极,实现带避雷线的500kV变电站接地阻抗现场测试．该测量方法已通过现场测试验证,满足工程要求．     

青藏铁路110kV输变电工程五道梁和沱沱河变电所所址的土壤结构模型分析

为青藏铁路供电的110kV沱沱河和五道梁变电站地处高寒永冻地区,如何分析得到变电站的土壤模型是设计接地系统的前提.根据土壤电阻率的现场实测结果采用土壤分层的反演理论分析得到了沱沱河和五道梁两变电站的土壤模型;通过统计分析两变电站地温的季节变化来确定冬季地表土壤的电阻率,以反映季节因素对土壤模型的影响;最后通过现场接地装置接地电阻的实测结果验证了土壤分层模型的合理性.不同季节土壤模型的建立为沱沱河和五道梁两变电站接地系统的设计奠定了基础.