基于毫米波大规模MIMO系统的混合预编码设计

大规模多输入多输出（MIMO）被认为是未来5G的关键技术之一。毫米波因其足够大的频谱带宽近来备受关注。针对部分连接结构、单用户下行链路毫米波大规模MIMO系统,提出了一种新型的混合预编码设计。利用分层设计思想,首先设计模拟预编码器,提出一种模拟预编码器算法;然后通过注水算法获得最佳数字预编码器;最后,将起始最优化问题转化为在每根天线功率分配约束下单个RF链路连接天线子阵列最优化问题,再根据迭代方法获得最佳混合预编码器。仿真结果表明,最佳混合预编码器性能接近纯数字预编码器的性能。     

Unlocking the potential of unoccupied spectrum in developing countries: Southern African Development Community – case study

The lack of adequate telecommunications infrastructure in developing regions makes wireless systems the most feasible solution for providing Internet connectivity. With the global migration of television (TV) systems from analogue to digital, the TV spectrum is expected to be shared between broadcasting and broadband services. However, the absence of suitable regulatory policies for TV band sharing and low average revenue per user experienced by wireless network operators makes it difficult to deploy broadband networks in developing regions, especially in rural areas. This article presents a co-evolution analysis of three key domains of change (policy, technology and business) in providing broadband connectivity focusing on the Southern African Development Community region. Furthermore, the article proposes public–private partnership and public–private–people partnership models for deploying wireless broadband networks in developing regions. This article is useful to various stakeholders, including policy-makers, governments, the wireless communications industry and academia, by addressing the digital divide in developing regions.     

A theory of hyperfinite processes: the complete removal of individual uncertainty via exact LLN

The aim of this paper is to provide a viable measure–theoretic framework for the study of random phenomena involving a large number of economic entities. The work is based on the fact that processes which are measurable with respect to hyperfinite Loeb product spaces capture the limiting behaviors of triangular arrays of random variables and thus constitute the `right' class for general stochastic modeling. The primary concern of the paper is to characterize those hyperfinite processes satisfying the exact law of large numbers by using the basic notions of conditional expectation, orthogonality, uncorrelatedness and independence together with some unifying multiplicative properties of random variables. The general structure of the processes is also analyzed via a biorthogonal expansion of the Karhunen–Loéve type and via the representation in terms of the simpler hyperfinite Loeb counting spaces. A universality property for atomless Loeb product spaces is formulated to show the abundance of processes satisfying the law. Generalizations to a hyperfinite number of continuous (or discrete) parameter stochastic processes are considered. The various necessary and sufficient conditions for the validity of the law provide a rather complete understanding about the cancelation of individual risks or uncertainty in general settings. Some explicit asymptotic interpretations are also given.     

混合遗传算法在运输路径问题中的应用

建立物流运输优化的数学模型,来构造求解该问题的遗传算法。通过分析和比较几种混合遗传算法,提高运输车辆路径优化问题的求解效率并可优化解的质量。     

混合系统随机库存决策研究评述

混合系统包含了制造与翻新两种产品供应模式、可翻新品库存与服务性产品库存两类产品库存,加上混合系统中旧产品数量、质量和返回时机等不确定性的影响,这些使得混合系统的库存决策比传统生产系统的复杂和困难.由于旧产品翻新能够实现原料、能量附加值和劳动附加值的循环利用,降低生产成本.因此,对混合系统进行研究具有重要的现实意叉.本文首先给出了混合系统的定义、库存决策分类的依据,然后分别对确定最优策略结构和最优策略的混合系统随机库存决策模型的相关研究进行评述,最后针对当前研究的不足,将降低混合系统库存决策不确定性、拓展现有的随机库存决策模型、开发新的确定控制参数启发式算法等作为混合系统随机库存决策未来的研究方向.     

基于混合储能的直流微网母线电压控制策略

为了平抑风力发电接入直流微电网的功率波动问题,满足负荷持续高质量供电需求,对由锂电池和超级电容器组成的混合储能系统进行了研究。以超级电容电压和锂电池荷电状态为约束条件,将储能系统平衡所需的功率差分为低频与高频部分;锂电池用于吸收和释放低频部分,超级电容用于吸收和释放高频部分,使风机整流器工作在恒压状态,采用电压外环、电流内环双闭环控制,以直流母线的电压稳定为目标,维持系统功率平衡。仿真结果表明,所提混合储能系统控制策略具有较快的动态响应速度和较好的控制性能,可很好地满足负载功率需求,稳定直流母线电压。研究结果可为分析规模化新能源接入直流微网系统的稳定问题提供参考。     

基于K-means-LSTM模型的证券股价预测

鉴于股票数据具有非平稳、非线性等特征,传统的统计模型无法精准预测股票价格的未来趋势。针对这个问题,构建一种混合深度学习方法来提高股票预测性能。首先,通过将距离算法修改为DTW（动态时间归整）,令K-means聚类算法拓展为更适用于时间序列数据的K-means-DTW,聚类出价格趋势相似的证券;然后,通过聚类数据来训练LSTM（长短时记忆网络）模型,以实现对单支股票价格的预测。实验结果表明,混合模型K-means-LSTM表现出更好的预测性能,其预测精度和稳定性均优于单一LSTM模型。     

EXPLORING THE AMBIGUITY OF HYBRID ORGANISATIONS: A STAKEHOLDER APPROACH

This paper focuses on hybrid organisations, which have both public and private sector elements. Therefore, stakeholders of hybrid organisations have different views regarding what to expect from the organisation and the role of stakeholders tend to be multifaceted. This creates ambiguity that imposes demands on the management of hybrid organisations. In this paper a stakeholder approach is used in order to explore the ambiguity of hybrid organisations and the demands this imposes on managers.     

我国燃煤发电技术进步的节能减排效果分析

依据我国燃煤发电工业所面临的环境保护要求提高和温室气体减排压力等一些现实问题,把燃煤发电的工程子模型与能源CGE模型进行衔接而建立了混合CGE模型,通过对我国能源、经济和环境的复杂系统的仿真计算,对严格的节能减排政策下我国2030年以前的电力需求以及我国发展先进燃煤发电技术的节能量、大气污染物排放和温室气体排放进行了预测。结果表明,我国SO2排放问题在2030年以前将可以达到完全符合环保要求的标准,我国燃煤发电行业近期应该重点开发和推广高效脱硝技术。从可持续发展的观点来看,我国燃煤发电行业在中长期应该引入碳捕集与封存技术。     

An empirical investigation of public choices for green spaces

While the social demand for green spaces is growing, the understanding of local public policies remains scant. The provision of green spaces is subject to market failures, hence they are publicly provided. Yet, the optimal level may not be reached due to government failures. This article highlights potential government failures incurred by the public provision of green spaces. We investigate the median voter hypothesis in a sample of 161 French municipalities. We shall assess various specifications for the provision of green spaces by differentiating operating expenditures and their surfaces. Finally, in order to compare alternative specifications of income and tax price used in the median voter model, we implement tests for non-nested models. The median voter model is weak to explain expenditure levels but is appropriate to explain the ratio of green spaces in the municipalities of the sample.