认知型飞蜂窝网络中的子信道分配与功率控制

为了解决宏蜂窝与飞蜂窝构成的两层异构网络上行干扰与资源分配问题,提出了一种在认知型飞蜂窝的双层异构网中结合子信道分配和功率控制进行资源分配的框架。通过对异构网中跨层干扰问题进行分析与建模,将求解最优子信道分配矩阵和用户发射功率矩阵作为干扰管理问题的解决方法。模型中认知型飞蜂窝网络子信道和飞蜂窝网络用户构成非合作博弈,双方利用效用函数最优值进行匹配,构成初始信道分配矩阵;再由接入控制器根据接入条件从初始信道分配矩阵中筛选用户,并优化接入用户的发射功率矩阵,得到最优子信道分配矩阵和功率矩阵。仿真结果表明,优化框架提高了双层异构网络中飞蜂窝网络用户的吞吐量和接入率,降低了异构网中跨层干扰。     

Can an Unemployment Insurance System Generate Multiple Natural Rates?

This article studies some macroeconomic consequences of the financing of an unemployment insurance scheme. Under a balanced-budget rule, when both taxes and unemployment benefits are proportional to wages, the existence of multiple natural rates of unemployment is a generic property of the matching model. Government can lead the economy to a high equilibrium by fixing the rate of tax on wages and then setting the replacement ratio so that its expenditure matches its receipts.     

浅谈物理量的方向性

物理量按方向性可分为矢量和标量,本文通过实例运用平行四边形法则和正交分解法求矢量的大小和方向。进一步明确矢量方向性的物理意义。     

球类竞赛的排各式积分编排方法研究

在球类竞赛中，采用“分组循环＋淘汰赛”的竞赛办法，虽然可以解决赛程适中的问题，但不能解决分组的问题。而棋类积分编排赛制虽然可以避免分组，但由于受到职业等级分排序的局限，使得其它项目的竞赛编排无法参照。通过研究，借鉴棋类积分编排方法理论，我们总结出“排名式积分编排方法”理论。目的是把棋类积分编排方法运用到其他体育项目上。虽然该理论目前还没有在积分编排软件上得到运用，但可以为研究人员提供参考。     

From quality to innovation: Evidence from two French Employer Surveys

In this article we investigate the impact of quality systems on innovation performance using the method of propensity matching. We use two French microeconomic surveys, the “Organizational Changes and Computerization” (COI 1997) and the “Community Innovation Survey” (CIS3 1998–2000). The first hypothesis indicating that quality (ISO 9000 certification) impacts positively on innovation is supported for certain areas of innovation performance. Furthermore, the second hypothesis states that different levels of quality differentially improve innovation performance. Results indicate that the innovation performance of firms with Top Quality Level is higher than that of firms with Medium Quality Level which is also higher than that of firms with Low Quality Level for certain areas of innovation. However, we found that the difference in innovation performance between firms with Medium and Low Quality Levels is not of a great magnitude. This study implies that in order to achieve a significant innovation performance improvement via quality systems, a very well-established quality system is needed within a firm.     

Corrigendum to “On randomized matching mechanisms” [Economic Theory 8(1996)377–381]

Ma (in Econ. Theory 8, 377–381, 1996) studied the random order mechanism, a matching mechanism suggested by Roth and Vande Vate (Econometrica 58, 1475–1480, 1990) for marriage markets. By means of an example he showed that the random order mechanism does not always reach all stable matchings. Although Ma's (1996) result is true, we show that the probability distribution he presented – and therefore the proof of his Claim 2 – is not correct. The mistake in the calculations by Ma (1996) is due to the fact that even though the example looks very symmetric, some of the calculations are not as “symmetric.” We thank two anonymous referees for their helpful comments. B. Klaus’s and F. Klijn’s research was supported by Ramón y Cajal contracts of the Spanish Ministerio de Ciencia y Tecnología. The work of the authors was also partially supported through the Spanish Plan Nacional I+D+I (BEC2002-02130 and SEJ2005-01690) and the Generalitat de Catalunya (SGR2005-00626 and the Barcelona Economics Program of CREA).     

Is There Persistence in the Impact of Emergency Food Aid? Evidence on Consumption, Food Security, and Assets in Rural Ethiopia

We identify the impact of emergency food aid programs after the 2002 drought in rural Ethiopia on future welfare. Based on a difference-in-differences matching estimator, participation in food-for-work increases growth in total consumption and food consumption eighteen months after the drought. Separately, receiving free food raises growth in food consumption, but, surprisingly, negatively impacts food security. Food-for-work benefited households in the middle and upper tail of the consumption distribution, while the better-targeted free food program benefited the poorest. Evidence suggests these impacts demonstrate accumulated and persistent effects of food aid received in the first twelve months after the drought.     

土地流转对农户贫困脆弱性的影响研究

研究目的:探究土地流转对农户贫困脆弱性的影响,为防范农户陷入贫困和解决农村贫困提供理论和实证依据。研究方法:本文借助2016年湖北省1682个农户实地调查数据,基于倾向得分匹配法(PSM)和回归方程的Shapley值分解法,分别考察国定贫困线、1.9美元贫困线和3.1美元贫困线下不同类型土地有无转出和转出面积对农户贫困脆弱性的影响。研究结果:土地转出能够显著降低农户的贫困脆弱性,且农户贫困脆弱性随着转出土地面积的增加而降低;从土地转出的异质性来看,水田转出对缓解农户贫困脆弱性的效果更为明显,旱地转出的效果次之。研究结论:应进一步加快农村土地流转,释放农村剩余劳动力,不断增加农户收入,从而降低农户贫困脆弱性。     

投影寻踪模型在区域海水养殖产业竞争力综合评价中的应用

本文尝试利用投影寻踪模型对我国沿海省份的海水养殖产业竞争力进行综合评价。首先,从海水养殖概况入手,简要介绍了我国海水养殖的基本现状;其次,介绍了投影寻踪模型,该模型应用一般要经过五个步骤;最后,阐述了投影寻踪模型在区域海水养殖产业竞争力综合评价中的应用,并结合评价结果进行了分析。