广义空间调制系统的正则化OMP检测算法

在广义空间调制（GSM）系统中，最大似然（ML）检测可以取得最优的检测性能，然而其计算复杂度随激活天线数的增加急剧增长。针对这一问题，提出了一种基于稀疏重构理论的低复杂度检测算法——正则化正交匹配追踪（ROMP）算法。该算法首先根据信道矩阵和当前残差的内积选取多个候选激活天线索引，接着对候选天线索引按正则化标准进行可靠性验证，剔除错误索引，缩小信号的搜索空间，最后通过求解最小二乘问题估计信号。仿真结果表明，与经典的正交匹配追踪（OMP）算法相比，所提算法以少许复杂度的增加为代价极大提升了检测性能，能够在检测性能与复杂度之间取得更好的折中。     

COVID19: Holiday intentions during a pandemic

The travel, tourism and hospitality industries have been the worst affected of the world's major economic sectors during the COVID19 pandemic, which has had a devastating effect on both destinations and organisations. Drawing from a sample (N = 385) of adult permanent residents of Athens, Greece, the study examines the impact of COVID19 upon holiday intention. The chaordic systems are evaluated through the use of fuzzy-set Qualitative Comparative Analysis, whilst the study also used Necessary Condition Analysis for the calculation of the size effects of the examined conditions. The findings reveal two sufficient complex configurations leading to holiday intention: (i) holiday risks, and (ii) impact of COVID19. Based on the results, the article also offers a set of managerial implications. The contribution of the study is to both theoretical and methodological tourism domains.     

高速铁路线路条件对列车追踪间隔时间的影响分析

线路条件是列车追踪间隔时间的主要影响因素之一。为探究线路条件对列车追踪间隔时间的影响机制,在阐述列车追踪间隔时间的计算方法与影响因素的基础上,分析得到线路附加阻力和因线路条件导致的限速运行是线路条件影响列车追踪间隔时间的2个方面,通过探讨线路附加阻力对追踪间隔时间的影响,推导出限速运行下的列车追踪过程与追踪间隔时间的计算方法,最后结合不同线路附加阻力与限速运行下的各类列车追踪间隔时间的检算结果,得到线路条件对列车追踪间隔时间的影响规律,为列车追踪间隔时间的优化以及线路的设计提供参考。     

我国蛋鸡养殖环境全要素生产率测度及省域比较分析

［目的］蛋鸡养殖场规模化养殖与生态环境保护协调发展问题是蛋鸡养殖业可持续发展过程中面临的关键性问题，测度我国大、中、小3种规模下不同省份蛋鸡养殖场的环境全要素生产率，并从时间、地区两个维度对蛋鸡养殖场的环境全要素生产率进行比较。［方法］利用2004—2016年不同养殖规模蛋鸡养殖场的投入和产出数据，文章基于SBM函数的Malmquist Luengerber（ML）指数方法，对蛋鸡养殖场环境全要素生产率进行分解，将其分解为技术进步指数、效率改进指数。［结果］（1）蛋鸡养殖场环境全要素生产率整体呈现下降趋势，同时与蛋鸡养殖规模呈反比，蛋鸡养殖场规模越大，蛋鸡养殖环境生产率越小。（2）蛋鸡养殖场效率存在效率改善，但养殖技术进步率相对较低，尤其是对小规模养殖场而言，改善空间更明显； （3）蛋鸡养殖环境全要素生产率区域差异较为明显，整体来看，蛋鸡养殖主产区环境全要素生产率高于非主产区。［结论］加强蛋鸡产业科技创新水平以及公共服务设施的投入，提高养殖户的废弃物无害化处理能力，推行蛋鸡养殖的规模化和标准化发展，进一步改善养殖效率，以促进蛋鸡养殖规模化和生态环境保护协调发展。     

什么样的数字创新生态系统能提高区域创新绩效——基于NCA与QCA的研究

什么样的数字创新生态系统有助于提高区域创新绩效是亟待解决的热点问题。采用必要条件分析（NCA）和模糊集定性比较分析（fsQCA）两种方法,对我国内地31个省（区、市）进行实证分析。研究发现：①数字企业、政府、高校及科研机构、数字创新基础设施、数字人才和金融服务是数字创新生态系统的关键构成,但单个要素并不是提高区域创新绩效的必要条件;②4种数字创新生态系统要素组态有助于提高区域创新绩效,构成的数字创新生态系统分别是政府引导的智力聚集型、企业开拓的环境支撑型、主体多元的综合发展型和企业主导的资本驱动型;③各地应因地制宜,选择合适的数字创新生态系统,培育区域创新新动能,助推“数字中国”新发展。     

The M4 Competition: Results,findings, conclusion and way forward

The M4 competition is the continuation of three previous competitions started more than 45 years ago whose purpose was to learn how to improve forecasting accuracy, and how such learning can be applied to advance the theory and practice of forecasting. The purpose of M4 was to replicate the results of the previous ones and extend them into three directions: First significantly increase the number of series, second include Machine Learning (ML) forecasting methods, and third evaluate both point forecasts and prediction intervals. The five major findings of the M4 Competitions are: 1. Out Of the 17 most accurate methods, 12 were “combinations” of mostly statistical approaches. 2. The biggest surprise was a “hybrid” approach that utilized both statistical and ML features. This method’s average sMAPE was close to 10% more accurate than the combination benchmark used to compare the submitted methods. 3. The second most accurate method was a combination of seven statistical methods and one ML one, with the weights for the averaging being calculated by a ML algorithm that was trained to minimize the forecasting. 4. The two most accurate methods also achieved an amazing success in specifying the 95% prediction intervals correctly. 5. The six pure ML methods performed poorly, with none of them being more accurate than the combination benchmark and only one being more accurate than Naïve2. This paper presents some initial results of M4, its major findings and a logical conclusion. Finally, it outlines what the authors consider to be the way forward for the field of forecasting.     

人民币名义汇率变动对中美贸易收支影响的研究——基于毕肯戴克—罗宾逊—梅茨勒条件视角的实证分析

从毕肯戴克—罗宾逊—梅茨勒条件的视角,同时考虑需求与供给两方面因素对中美贸易差额的影响,采用SPSS线性回归后退法分析中美贸易差额与人民币名义汇率、两国价格水平、国民收入、劳动力成本及储蓄率差额的相关关系,结果表明,中美双边货物贸易中美国的巨额逆差自有其深刻的经济政治原因,人民币升值无助于消除美国的逆差。     

基于金融形势指数的货币政策操作风险研究

在货币政策操作过程中,中央银行对宏观经济形势的认识偏差,货币政策工具及政策调控时机的选择不当,以及政策信息的披露不及时等,都有可能误导公众预期和增加市场不确定性,从而引致货币政策操作风险。通过建立金融形势指数并考察其实际值与均衡值之间的离差状况,结果表明金融形势指数及其偏差可用于间接测度政策操作风险的大小,所得到的风险指数可作为宏观调控中的参考指标。     

外商直接投资状况分析

随着经济全球化程度的加深和中国改革开放的深化,外商直接投资进入中国的步伐显著加快。外商直接投资状况如何,值得研究和探讨。     

Wisdom and Wealth Go First in a Harmonious Society——The Announcement of "2007 China Top Ten Wealthy and Intelligent People"

In order to implement the strategy "strengthening country on talent", and to form an good environment of respecting knowledge,talent, and fortune, in 2007 December, Bejing Cultural Development Research Institute, China National Condition Research Association, Fortune Times Press, China Election website,and some other institutes jointly elect 2007 China Top Ten Wealthy and Intelligent People, on the principle of"Contribution, creation, and power".