X频段信标机的设计与实现

为满足船载X频段测控设备信道相位修正和伺服性能检查的需要,设计并研制了一款X频段信标机。首先,选用HMC765LP6CE芯片,利用频率合成技术设计了信源并通过通用串行总线（USB）实现了发射频率用户自定义;其次,针对安装平台面积小的限制,基于高频结构仿真器(HFSS)设计了高次模微带天线并完成了仿真分析和指标优化;最后,完成了X频段信标机的工程实现并给出了硬件电路结构和软件程序设计方法。经测试,该信标机锁相效果良好,控制简便,性能可靠,满足用户使用要求。     

多层介质频率选择表面的等效电路分析方法

基于数值仿真计算和微波网络理论,提出了一种多层介质中频率选择表面（FSS）等效电路的分析方法。该方法物理过程直观,计算量小,适用于二维任意形状FSS等效电路的精确求解。以方形贴片型FSS为例验证了等效电路模型的准确性,并分析了多层介质对其等效电路参数的影响规律。最后,基于滤波器理论与FSS等效电路模型设计了双层带通型FSS,计算结果表明全波仿真结果与理论计算结果基本一致,为多层FSS的综合设计提供了一种精确设计方法。     

中国农产品内生技术性贸易措施：地位与效应

WTO框架下具有合理性的技术性贸易措施是中国农产品贸易领域实施管理的有效手段。文章利用频数比率对其进行量化研究,认为技术性贸易措施在我国农产品进口管理体系中已替代关税居于主要地位,但相应于地位的变化,其建设尚显滞后,限制效应较差。对此,文章从完善进口安全监管体制,加强标准认证和风险评估,建立进口环节技术性贸易措施分析系统及预警机制等几个方面提出相应建议。     

高等师范院校古代汉语教学语料库字频研究

对基于高等师范学校古代汉语教学的语料库相关数据结果做了定量分析,阐述了语料库的用字概况,提出了字区划分的标准,研制了分区字频表。     

Term frequency – function of document frequency: a new term weighting scheme for enterprise information retrieval

In today's business environment, enterprises are increasingly under pressure to process the vast amount of data produced everyday within enterprises. One method is to focus on the business intelligence (BI) applications and increasing the commercial added-value through such business analytics activities. Term weighting scheme, which has been used to convert the documents as vectors in the term space, is a vital task in enterprise Information Retrieval (IR), text categorisation, text analytics, etc. When determining term weight in a document, the traditional TF-IDF scheme sets weight value for the term considering only its occurrence frequency within the document and in the entire set of documents, which leads to some meaningful terms that cannot get the appropriate weight. In this article, we propose a new term weighting scheme called Term Frequency – Function of Document Frequency (TF-FDF) to address this issue. Instead of using monotonically decreasing function such as Inverse Document Frequency, FDF presents a convex function that dynamically adjusts weights according to the significance of the words in a document set. This function can be manually tuned based on the distribution of the most meaningful words which semantically represent the document set. Our experiments show that the TF-FDF can achieve higher value of Normalised Discounted Cumulative Gain in IR than that of TF-IDF and its variants, and improving the accuracy of relevance ranking of the IR results.     

能源自动检测系统的设计

本文介绍一种高精度、多功能、智能化能源检测系统,可对各种液体、蒸汽的温度、压力、流量以及电力负荷等参数进行巡检,越限报警和自动打印(共118个测试点)。该系统适合于在大、中型企业中推广应用。     

Re-examining online customer experience to include purchase frequency and perceived risk

This research examines the important emerging area of online customer experience (OCE) using data collected from an online survey of frequent and infrequent online shoppers. The study examines a model of antecedents for cognitive and affective experiential states and their influence on outcomes, such as online shopping satisfaction and repurchase intentions. The model also examines the relationships between perceived risk, trust, satisfaction and repurchase intentions. Theoretically, the study provides a broader understanding of OCE, through insights into two shopper segments identified as being important in e-retailing. For managers, the study highlights areas of OCE and their implications for ongoing management of the online channel.     

高炮随动系统自动测试中正弦机发送频率的确定

在某型高炮随动系统测试中,正弦机的发送频率直接影响着输出信号的平滑度,从而会影响测试的精度。为了避免在正弦机运行过程中,计算耗用过多机时,在正弦机发送之前,先计算出每个位置信号、前馈信号的数值,存放于内存中。本文根据该正弦机信号的特点,分析了几种正弦机角位置信号发送频率方式的优缺点,确定了正弦机发送频率的方式。     

Causality effects in return volatility measures with random times

We provide a structural approach to identify instantaneous causality effects between durations and stock price volatility. So far, in the literature, instantaneous causality effects have either been excluded or cannot be identified separately from Granger type causality effects. By giving explicit moment conditions for observed returns over (random) duration intervals, we are able to identify an instantaneous causality effect. The documented causality effect has significant impact on inference for tick-by-tick data. We find that instantaneous volatility forecasts for, e.g., IBM stock returns must be decreased by as much as 40% when not having seen the next quote change before its (conditionally) median time. Also, instantaneous volatilities are found to be much higher than indicated by standard volatility assessment procedures using tick-by-tick data. For IBM, a naive assessment of spot volatility based on observed returns between quote changes would only account for 60% of the actual volatility. For less liquidly traded stocks at NYSE this effect is even stronger.     

利用矢量网络分析仪测量时延特性的方法

解释了无线射频系统时延指标测量的意义及重要性,介绍了使用矢量网络分析仪进行时延指标测量的基本原理,归纳了网络分析仪进行线性器件、变频器件时延测量的测量方法,重点分析了变频器件时延测量的三种方法的原理、步骤和准确度.