基于三层交换的VLAN间DHCP配置与实现

介绍了DHCP、VLAN和三层交换的基本概念和工作原理,并详细分析了在Cisco路由器2621和Cisco交换机3550上实现基于三层交换的VLAN问DHCP的配置过程。     

Cultural Traditions and the Scandinavian Social Policy Model

This article assesses the extent to which cultural interpretation may be useful in understanding social policy models. By surveying cultural traditions, the study explores the context in which the Scandinavian social policy model was developed. The study investigates the institutional legacies of Scandinavian agrarian societies and identifies certain cultural traits, making observations as to their implications for the social policy model. The study does not intend to establish any “causal relation” between specific historical phenomena and the modern welfare states, but regards cultural traditions as forming the “contextual basis” for the operation of a welfare state system. Hence this is not merely a case study of Scandinavia, but a methodological undertaking that could play a significant role in broadening the scope of the study of social policy.     

Ad-hoc MPLS协议体系及其性能分析

基于无线MPLS协议体系,结合无线移动Ad-hoc网特点,提出了一种采用扩展CR-LDP信令建立标记交换路径的Ad-hoc网QoS路由协议-AMPLS。通过构建Ad-hoc网络仿真模型,仿真分析了AMPLS路由协议的性能,并验证了协议的差别服务、流量工程等网络特性,为实现具有某种程度QoS服务的Ad-hoc组网提供了一种方法。     

‘Who was the best?’: Power,knowledge and rationality in bilingual girls’ code choices1

This paper examines how pre‐adolescent bilingual girls employ linguistic choices to construct relations of dominance and subordination in a competitive exchange of knowledge and expertise in a pretend‐school activity. Quantitative and qualitative analyses demonstrate that code choices used by the girls to constitute and exploit different sources of power are systematically related to the construction of currently salient identities, prevailing structural constraints, and individual goals and desires. It is argued that even young children act as rational, social actors who actively make strategic and meaningful linguistic choices with the overall aim to achieve optimal outcomes in a given interaction.     

Bayesian analysis for mixtures of discrete distributions with a non-parametric component

Bayesian finite mixture modelling is a flexible parametric modelling approach for classification and density fitting. Many areas of application require distinguishing a signal from a noise component. In practice, it is often difficult to justify a specific distribution for the signal component; therefore, the signal distribution is usually further modelled via a mixture of distributions. However, modelling the signal as a mixture of distributions is computationally non-trivial due to the difficulties in justifying the exact number of components to be used and due to the label switching problem. This paper proposes the use of a non-parametric distribution to model the signal component. We consider the case of discrete data and show how this new methodology leads to more accurate parameter estimation and smaller false non-discovery rate. Moreover, it does not incur the label switching problem. We show an application of the method to data generated by ChIP-sequencing experiments.     

基于马尔科夫状态转移模型的股指收益率研究

金融资产收益率的分布是金融资产投资和风险管理等应用中的重要决定因素。针对经济和金融的潜在状态改变可能引起金融资产收益率分布结构性变化的现实情况,提出考虑收益率分布的时变性,将马尔科夫状态转移结构应用于中国股票指数对数收益率分布的建模,并提出使用混合正态分布模型刻画股指收益率在各状态的分布,建立隐马尔科夫状态转移-混合正态分布(HMS-MND)模型,使用期望最大化算法(E-M算法)和Baum-Welch算法给出模型的参数估计,采用2002年7月1日至2010年10月29日沪深两市11种主要股票指数的对数日、周收益率作为实证数据。模型参数估计和似然比检验结果表明,大部分股票指数收益率的分布中都存在显著的马尔科夫状态转移结构,且HMS-MND模型可以较好地刻画对数收益率分布的高阶矩统计特征。因此,引入马尔科夫状态转移结构对股指收益率的相关研究具有重要意义。     

两寡头序贯进入下的B2B电子商务网站IT投资决策

在竞争性的B2B电子商务网站这一市场中,用户转移成本及网络外部性的存在会阻碍用户转向市场后入者,从而给市场先入者带来用户规模优势,而IT成本下降可以给后入者带来成本优势,在这些因素交互影响的市场环境下,先入者和后入者应采取何种IT投资策略以保持竞争优势是一重要问题。针对上述问题,通过综合考虑IT成本下降、用户转移成本及网络外部性等因素,构建了一个序贯进入的、两寡头垄断的B2B电子商务网站的IT投资决策模型,探讨了IT成本下降、用户转移成本及网络外部性等参数变化对B2B电子商务网站IT投资决策的影响。研究结果表明,随着IT成本下降,当用户具有高转移成本时,先入者可采取进攻性的、增加投资的策略;反之,当用户具有低转移成本时,后入者则可采取进攻性的、增加投资的策略,并且能够提供更高质量的网站,获得相对于先入者更高的市场份额;当网络外部性增强时,先入者则可采取进攻性的、增加投资的策略,而后入者只能采取防守性的、减少投资的策略。     

我国经济增长“软扩张”过程中的“反弹效应”度量及其检验

我国经济实现"软着陆"以后,经济增长一直在平稳运行中酝酿着积极"反弹"的势头。2003年我国经济增长速度快速攀升到9 1%,意味着我国经济增长过程中一轮具有"软扩张"性质的经济周期波动已经开始。为此,我们利用推广的马尔可夫区制转移模型(Markovs witching model)来描述我国经济增长过程的动态性质。通过模型估计和检验,发现我国经济增长过程中存在显著的"反弹效应",并且导致了经济周期波动的非对称性。在当前经济周期态势下,经济政策仍然应该保持稳定的操作方向,以保证"反弹效应"充分体现出来,并促使我国经济增长"软扩张"过程的巩固、持续和完成。     

Testing for Regime Switching

We analyze use of a quasi‐likelihood ratio statistic for a mixture model to test the null hypothesis of one regime versus the alternative of two regimes in a Markov regime‐switching context. This test exploits mixture properties implied by the regime‐switching process, but ignores certain implied serial correlation properties. When formulated in the natural way, the setting is nonstandard, involving nuisance parameters on the boundary of the parameter space, nuisance parameters identified only under the alternative, or approximations using derivatives higher than second order. We exploit recent advances by Andrews (2001) and contribute to the literature by extending the scope of mixture models, obtaining asymptotic null distributions different from those in the literature. We further provide critical values for popular models or bounds for tail probabilities that are useful in constructing conservative critical values for regime‐switching tests. We compare the size and power of our statistics to other useful tests for regime switching via Monte Carlo methods and find relatively good performance. We apply our methods to reexamine the classic cartel study of Porter (1983) and reaffirm Porter's findings.     

死锁恢复的多维交换结构容错路由算法

在高性能路由器中采用多维交换结构是解决可扩展性的一种方法。在实现这种交换结构时,随着节点数目的增多,交换结构出现故障的概率也随之增加。该文在mesh/torus结构上提出了一种基于死锁恢复策略的容错路由算法MMAR。基于各非故障节点周围链路的状态,MMAR能容错任意形状的故障模型且所需虚拟通道数少。通过在凹形区域表面节点中设置该凹形区域内节点位置信息表,该算法能避免消息进入与其目的节点无关的凹形区域以使绕道路径最短。该文给出了在256个节点的二维torus中的仿真结果,验证了算法的有效性。