空间信息传输中的多天线技术综述

近年来,空间信息传输中的多天线技术得到了广泛关注和大量研究。首先介绍了多天线技术的信息论基础和演进过程;然后综述了多天线通信和雷达技术的研究进展,包括多输入多输出(Multiple-Input Multiple-Output,MIMO)卫星通信技术、深空天线组阵技术、空间多维协同传输理论与技术、MIMO雷达技术和分布式孔径相参合成雷达技术,分析了其中的关键技术及未来可研究的方向;最后,总结了多天线技术在航天测控领域应用的优势,展望了基于多天线的测控技术。     

民营企业现金持有量影响因素研究

民营企业相对国企较少获得国家支持,其现金持有决策符合市场决策规则。将现金持有量的影响因素定位为内部财务和外部行业特征,通过回归分析,发现现金替代物、企业的银行负债、财务杠杆、企业规模与现金持有量呈负相关关系,企业的增长机会、现金流量、现金股利、激烈的行业竞争与现金持有量呈正相关关系。     

国土空间开发适宜性评价的反思

研究目的：厘清国土空间开发适宜性的概念内涵,揭示国土空间规划语境下适宜性评价的核心需求和现实挑战,反思与改进评价的逻辑思路。研究方法：文献资料法和归纳演绎法。研究结果：（1）国土空间开发适宜性概念经历了从土地利用到国土空间开发保护的嬗变,具有空间协调性、时序统筹性、效益综合性三重内涵;（2）国土空间规划对适宜性评价提出了安全、效率、品质等需求;（3）现行适宜性评价思路忽视了人类活动与国土空间长期交互的“适应性”状态、对地域功能的空间联系缺乏足够重视、对多元人本需求关注不足;（4）国土空间开发适宜性评价需尊重国土空间“适应性”状态、满足人类多层次需求、凸显适宜性空间结构,建立适宜性评价、适应性修正、结构性优化“三位一体”的思路。研究结论：科学辨识国土空间开发适宜性内涵,应对国土空间规划体系下适宜性评价的需求和挑战,改进国土空间开发适宜性评价逻辑和思路,赋能国土空间增值。     

A multiproduct Symmetric Generalized McFadden cost function

This paper introduces a flexible multiproduct cost function that permits zero values of one or more of the outputs and can impose restrictions quite easily, if not automatically satisfied, to ensure global concavity property. It satisfies linear homogeneity (in prices) property and is flexible in the output space. Thus the function is ideal for estimating, for example, economies of scope, cost complementarity, product-specific returns to scale, etc., without worrying about zero values of output(s) and extrapolations to points far from the point of approximation. As an empirical application, we use panel data (1978–1985) on 12 Finnish foundry plants to estimate technical progress, overall returns to scale, product-specific returns to scale and economies of scope.     

金融危机正在改变世界

当前金融危机是经济周期的必然结果,其直接原因是以美元为核心的单体国际货币体系和保护主义日益严重导致的全球经济的长期失衡,要通过这场金融危机来平衡全球金融体系和经济的关系。因此,建立多元的国际货币体系,是这次金融危机之后最重大的金融制度的变革。目前金融还是现代经济的核心和心脏,不能因为金融危机而停止中国金融的市场化改革的步伐;同时,金融危机给中国带来了两个难得的机遇,即人民币的国际化和全球金融中心的构建。     

浅谈一题多解在学生高等数学创造性思维的培养

高等数学是理工科院校一门十分重要的公共基础课,教学不只是吸收前人的知识成果,还需创新和应用,数学思维是培养学生创造性思维的一种重要方式。本文通过对一个具体不等式的一题多解的示范性,来说明在高等数学教学中如何拓宽思路和培养学生的创新思维能力。     

煤矿地震数据动态解释软件设计与开发

为了提高煤田地震勘探的精度,提出了煤矿地震数据动态解释的思路,并通过Qt编程开发了地震资料动态解释软件系统.该系统包括矿井多元数据综合管理、三维地震资料解释、解释成果编辑、三维可视化分析与地震地质成果输出等功能.工程应用表明该软件能够把煤矿三维地震勘探获得的静态勘探成果与矿井生产过程中所获得的各类地质信息相互融合,实现地震资料动态解释,实时更新地震资料解释成果,为煤矿安全高效开采提供了地质保障.     

Measuring Farm and Market Level Economic Impacts of Improved Maize Production Technologies in Ethiopia: Evidence from Panel Data

While it is often recognised that agricultural technology adoption decisions are intertwined and best characterised by multivariate models, typical approaches to examining adoption and impacts of agricultural technology have focused on single technology adoption choice and ignored interdependence among technologies. We examine farm‐ and market‐level impacts of multiple technology adoption choices using comprehensive household survey data collected in 2010/11 and 2012/13 in Ethiopia. Economic surplus analysis combined with panel data switching endogenous regression models are used to compute the supply shift parameter (K‐shift parameter), while at the same time controlling for the endogeneity inherent in agricultural technology adoption among farmers. We find that our improved technology set choices have significant impacts on farm‐level maize yield and maize production costs, where the greatest effect appears to be generated when various technologies are combined. The change in maize yield and production costs results in an average 26.4% cost reduction per kilogram of maize output (the K‐shift parameter). This increases the producer and consumer surpluses by US$ 140 and US$ 105 million per annum, respectively. These changes in economic surplus help to reduce the number of poor people by an estimated 788 thousand per year. We conclude that deliberate extension efforts and other policies that encourage integration of technologies are important for maize technologies to yield their full potential at both farm and market levels.     

Purchasing Power Parity under Regime Shifts: An Application to Asian Countries*

This paper re‐examines the long‐run purchasing power parity (PPP) relationship for nine Asian countries relative to the USA and Japan during a period containing significant structural breaks. The relevance of considering structural breaks in PPP tests is demonstrated by utilizing the Johansen et al. (2000) procedure that allows for up to two pre‐determined structural breaks. Using conventional tests without considering breaks, one is able to reject the null of no cointegration for only four countries. The Johansen et al. procedure clearly demonstrates the importance of allowing for structural breaks and provides strong support for long‐run PPP for all the countries, regardless of the base country, except in the case of the Philippines vis‐à‐vis Japan. The Hansen–Johansen parameter constancy test indicates stability for all the countries except the Philippines relative to the USA and Malaysia relative to Japan.     

What's in a broken promissory obligation? Developing and testing a multiple component form measure of psychological contract breach

While the literature has suggested the possibility of breach being composed of multiple facets, no previous study has investigated this possibility empirically. This study examined the factor structure of typical component forms in order to develop a multiple component form measure of breach. Two studies were conducted. In study 1 (N = 420) multi-item measures based on causal indicators representing promissory obligations were developed for the five potential component forms (delay, magnitude, type/form, inequity and reciprocal imbalance). Exploratory factor analysis showed that the five components loaded onto one higher order factor, namely psychological contract breach suggesting that breach is composed of different aspects rather than types of breach. Confirmatory factor analysis provided further evidence for the proposed model. In addition, the model achieved high construct reliability and showed good construct, convergent, discriminant and predictive validity. Study 2 data (N = 189), used to validate study 1 results, compared the multiple-component measure with an established multiple item measure of breach (rather than a single item as in study 1) and also tested for discriminant validity with an established multiple item measure of violation. Findings replicated those in study 1. The findings have important implications for considering alternative, more comprehensive and elaborate ways of assessing breach.