Some Cracks in the Empire of Chance (Flaws in the Foundations of Reliability)

Making quantified statements about the uncertainty associated with the lifelength of an item is one of the most fundamental tasks of reliability assessment. Most practitioners routinely do this using one of the several available statistical techniques. The purpose of this paper is two-fold. The first is to give the user an overview of the key tenets of two of the most commonly used parametric approaches. The second is to point out that these commonly used approaches involve strategies that are either ad hoc, or are in violation of some of the underlying tenets. A method that is devoid of logical flaws can be proposed, but this method is difficult to implement. The user must therefore resign to using that technique against which the fewest objections can be hurled.     

中国宏观经济总量的实时预报与短期预测——基于混频数据预测模型的实证研究

季度GDP的走势与波动不仅会影响政府的财政收支、企业的盈利和财务状况,甚至还会影响家庭和个人的收入与支出,是宏观经济总量预报、预测与分析的重中之重。传统的宏观经济总量预测模型是基于同频数据进行的,高频和超高频数据必需处理为低频数据,这不仅忽略了高频数据信息的变化,还影响了模型预报和预测的及时性,降低了模型的预测精度。本文将混合数据抽样模型(MIDAS)用于中国季度GDP的预报和预测,实证研究表明,出口是造成我国金融危机时期经济增长减速的主要因素,MIDAS模型在中国宏观经济总量的短期预测方面具有精确性的比较优势,在实时预报方面具有显著的可行性和时效性。     

微波带状线低通滤波器的设计制作与性能改善

讨论了带状线低通滤波器因实际制作的导带宽度发生变化引起滤波器性能下降时,如何改善滤波器性能的方法。我们采用惠普公司ＥＥＳＯＦ软件,对滤波器的结构和电气参数和分别作了灵敏度分析,以此为改善滤波器性能的依据。经实验对比,改进后的滤波器性能有了明显改善,且性能稳定。     

跳频信号的归一化多普勒频差最大似然估计

针对双站定位涉及的跳频信号多普勒频差估计问题,提出了归一化的频差最大似然估计算法,利用两个定位站接收到的跳频脉冲串信号,构建一个关于基准跳频频率多普勒频差的似然函数,通过网格搜索得到使似然函数最大的多普勒频差估计,既解决了跳频信号在不同跳频频率上多普勒频差不一致的问题,又充分利用在不同频率的脉冲串信号提高了多普勒频差估计精度。通过仿真对算法的性能进行了评估,结果表明,与基于子空间的算法比较,在脉冲数达到240个时,所提算法执行效率提升30%以上。     

我国高被引作者群体属性研究

高被引作者是国家或地区最具影响力的科研群体,体现了国家或地区知识创新的制高点。利用中国引文数据库,对我国前100名高被引作者群体属性进行统计分析,并得出相应结果。从基本属性看,我国高被引作者平均发文量349篇,平均年龄64岁,集中于苏、浙、沪地区;从教育属性看,博士研究生已成为我国科技研究的主力军,且数量持续扩大,第一学历颁发单位较为分散,最后学历颁发单位较为集中;从研究领域看,自然科学仍占绝对优势;从流动性看,我国高被引作者流动性较好,但同时也存在一定程度的学术近亲繁殖现象;从职业属性看,绝大多数高被引作者集中在高校及科研院所,普遍缺少企业从业经历,且承担着较重的行政职务及较多的社会兼职。     

宽覆盖锁相调频技术

本文侧重分析了自动频偏控制系统的工作原理,推导出环路方程,阐述了几种主要的特性。     

Brexit and its economic consequences

As the formal process of Brexit has already started, there is much uncertainty about Brexit's impacts on Britain's social, political and economic future. This paper examines the economic impact. After briefly discussing some significant EU treaties that serve as the background materials, it presents the key arguments advocated by the leave and remain camps. The economic impact depends critically on the negotiation outcomes. Aside from the debate on the divorce costs, there are numerous issues that must be negotiated, such as immigration, trade in goods, services, agriculture, fisheries and financial regulations. We discuss various scenarios of possible new trade regimes, resulting in different impacts on the UK economy. With each side having its bargaining chips to play, the trade‐offs between “give and take” in the negotiation game are analysed. Considering various strategic options, this paper urges rationality and cooperation, especially weighing both sides’ entwined economic interests, in addition to their mutual security, defence, environmental and world concerns. The potential gains and losses in the event where the UK contemplates new trade arrangements with the non‐EU countries are analysed in the Appendix .     

射频识别技术在商品储运领域的应用

文中介绍了RFID技术在商品储运领域中的优势,然后从危险品跟踪、集装箱跟踪、食品跟踪和仓库管理等方面列举了RFID在商品储运领域的典型应用,最后分析RFID在商品储运领域的应用环节。     

变频技术在数控机床上的应用

介绍了采用数控车床的主轴驱动中变频控制的系统结构与运行模式,并简述了无速度传感器的矢量变频器的基本应用。     

Specification testing for regression models with dependent data

We examine a consistent test for the correct specification of a regression function with dependent data. The test is based on the supremum of the difference between the parametric and nonparametric estimates of the regression model. Rather surprisingly, the behaviour of the test depends on whether the regressors are deterministic or stochastic. In the former situation, the normalization constants necessary to obtain the limiting Gumbel distribution are data dependent and difficult to estimate, so it may be difficult to obtain valid critical values, whereas, in the latter, the asymptotic distribution may not be even known. Because of that, under very mild regularity conditions, we describe a bootstrap analogue for the test, showing its asymptotic validity and finite sample behaviour in a small Monte-Carlo experiment.