On Minimally-supported <Emphasis Type="Italic">D</Emphasis>-optimal Designs for Polynomial Regression with Log-concave Weight Function

This paper studies minimally-supported D-optimal designs for polynomial regression model with logarithmically concave (log-concave) weight functions. Many commonly used weight functions in the design literature are log-concave. For example, and exp(−x ²) in Theorem 2.3.2 of Fedorov (Theory of optimal experiments, 1972) are all log-concave. We show that the determinant of information matrix of minimally-supported design is a log-concave function of ordered support points and the D-optimal design is unique. Therefore, the numerically D-optimal designs can be constructed efficiently by cyclic exchange algorithm.     

Can Federal Grants Mitigate Social Competition?

The European economic integration leads to increasing mobilityof factors, thereby threatening the stability of social transferprograms. This article investigates the possibility to achieveby means of voluntary matching grants both the optimal allocationof factors and the optimal level of redistribution in the presenceof factor mobility. We use a fiscal competition model a la Wildasin(1991) in which states differ in their technologies and preferencesfor redistribution. We first investigate a simple process inwhich the federal authority progressively raises the matchinggrants to the district choosing the lowest transfer and alldistricts respond optimally to the resulting change in transfersall around. This process is shown to increase efficiency ofboth production and redistribution. However, it does not guaranteethat all districts gain, nor that an efficient level of redistributionis attained. Assuming complete information among districts,we derive the willingness of each district to match the contributionof other districts and we show that the aggregate willingnessto pay for matching rates converges to zero when both the efficientlevel of redistribution and the efficient allocation of factorsare achieved. We then describe an adjustment process for thematching rates that will lead districts to the efficient outcomeand guarantee that everyone will gain. (JEL Classification:H23, H70)     

Do German Welfare‐to‐Work Programmes Reduce Welfare Dependency and Increase Employment?

Abstract. During the last decade, many Western economies reformed their welfare systems with the aim of activating welfare recipients by increasing welfare‐to‐work programmes (WTWP) and job‐search enforcement. We evaluate the short‐term effects of three important German WTWP implemented after a major reform in January 2005 (‘Hartz IV’), namely short training, further training with a planned duration of up to three months and public workfare programmes (‘One‐Euro‐Jobs’). Our analysis is based on a combination of a large‐scale survey and administrative data that is rich with respect to individual, household, agency level and regional information. We use this richness of the data to base the econometric evaluation on a selection‐on‐observables approach. We find that short‐term training programmes, on average, increase their participants' employment perspectives. There is also considerable effect heterogeneity across different subgroups of participants that could be exploited to improve the allocation of welfare recipients to the specific programmes and thus increase overall programme effectiveness.     

机构侵害中小投资者违规监管博弈仿真

本文主要对股票市场中机构投资者侵害中小投资者利益这种违规行为的监管进行了博弈分析,并使用基于主体建模的动态仿真方法在Swarm仿真平台上建立了仿真模型,同时进行了仿真实验。研究指出,严厉的事前监管、完善的上市公司管理制度以及更高的监管者素质可以有效地杜绝机构投资者侵害违规行为的出现。本文通过运用经济仿真方法对股票市场具体违规行为监管问题进行研究,将股票市场监管、博弈论与经济仿真这三个研究领域结合在一起,拓展了对股票市场监管的研究手段,在经济学研究中做出了一定有益的探索。 更多还原     

一种基于遗传算法的战场频率分配方法

分析了遗传算法的原理及其在频率分配领域中的应用,提出了一种启发式战场频率 分配方法。该方法通过改进传统遗传算法的选择、交叉、变异过程来实现频率分配的特殊 用途,并借助代价函数对生成的频率分配方案进行质量评估。仿真结果表明,该方法能够在 一 定程度上提高频谱资源的使用效率,可为从事频谱管理等相关行业的技术人员提供参考。     

改进的动态反馈负载均衡算法

本文提出了一种改进的动态反馈负载均衡算法,在负载均衡过程中既考虑后台服务器的当前负载,又考虑后台服务器的处理能力,根据每台服务器当前负载比例值的大小合理分配用户请求,进而调整服务器间处理请求的比例,避免服务器超载时依然收到大量的请求,使平均应答时延和吞吐量等获得较好的性能,集群的整体性能得到提高。     

一种改进的松弛迭代图像配准算法

本文展示了一种改进的松弛迭代图像配准算法,此算法首先使用归一化自相关运算求得图像的粗匹配对,接着使用改进的松弛迭代匹配算法进行精匹配。本文通过优化筛选第一轮迭代结果,使得后续迭代时间明显减少。实验证明此算法效率比原始算法有了很大的提高。     

一种分层A~*路径搜索算法及性能

基于层次道路网提出了一种分层A*路径搜索算法,其特点是在同一层路网中采用A*算法,而在层次切换时采用一种启发式定向搜索入口节点的方法。既顾及了道路等级性和朝着目标行进等驾驶员的心理因素,又可以获得比传统算法更快的求解速度。实验表明,该算法是可行的、高效的。     

一种基于LSB的改进信息隐藏算法及实现

传统的LSB算法是将私密信息以二进制的形式嵌入到载体像素值的最低有效位,这样对图像的质量负面影响可以降到最小。本文提出了一种将过滤技术与LSB算法相结合的信息隐藏算法。利用过滤技术增强图片质量,利用LSB算法进行私密信息的嵌入。改进型的LSB算法比原算法具有更高信息存储量以及更高信息安全性等优点。     

The impact of production offshoring on the skill composition of manufacturing firms: evidence from Italy

In this work we explore how the international outsourcing of production impacts the skill composition of employment within Italian manufacturing firms. In particular, our aim is to assess whether the choice to offshore production activities to cheap‐labour countries implies a bias in the employment of skilled workers relative to unskilled ones.

Using a balanced panel of firms covering the period 1995–2003, we set up a counterfactual analysis in which, by using a difference‐in‐differences propensity score matching estimator, we compare the dynamics of skill demand for treated and control firms while addressing the possible problem of selection bias.

Our results identify a ‘potential’ skill bias effect of production offshoring. In particular, we find that treated firms tend to show an upward shift in the skill ratio with respect to the counterfactual sample, but coefficients are not significantly different from zero. When we look at the elements of the skill ratio separately, we find that the skill bias is driven by a fall in the employment of production workers (blue collars), rather than by the increase in the employment of non‐production workers (white collars), thus providing further evidence on the unskilled labour‐saving nature of international outsourcing.