产品差异化对市场结构的影响分析——基于演化经济学的观点

以双占垄断为例,产品差异化对市场结构的影响具有以下几个方面:(1)完全垄断可能是同质产品竞争的结果;(2)尽管产品差异化不能排除完全垄断的存在,但是从长期看,它极大增加了厂商共存的可能性;(3)产品差异化程度越大,双占寡头的结构越稳定。     

The servant leadership advantage: When perceiving low differentiation in leader-member relationship quality influences team cohesion,team task performance and service OCB

How does servant leaders' unique ability to place each follower's needs above their own influence relationships between followers and impact their collective performance? In a study that integrates principles of servant leadership with the social comparison theoretical framework, we tested a group-level model to examine how servant leadership induces low perceived differentiation in leader-member relationship quality (perceived LMX differentiation) within a group, which strengthens team cohesion and in turn positively influences team task performance and service-oriented organizational citizenship behaviors (service OCB). Our sample comprised 229 employees nested in 67 work teams. Structural equation modeling results indicate that servant leadership significantly predicts low perceived LMX differentiation; perceived LMX differentiation is strongly related to team cohesion such that the lower the perceived differentiation, the stronger the team's cohesiveness. And, team cohesion is also strongly related to both the team's task performance and service OCB. Perceived LMX differentiation and team cohesion mediate the effect of servant leadership on both team task performance and service OCB.     

Trauma and Bowen Family Systems Theory: Working with Adults Who were Abused as Children

Working with survivors of trauma is mostly challenging, exhausting, long‐term and often ‘messy’, when interventions that ‘should’ work, don't, or the unexpected arises. Nevertheless, explanations that speak to recovery from trauma more and more rely on neurobiological concepts to account for any positive change. Combining the family systems approach of Murray Bowen and recent research on the brain and trauma, post trauma symptoms are viewed as part of the ‘family emotional process’ even when traumatic events have emanated from outside the family system itself. Variations in responses to trauma, including dissociation and self‐harm are discussed in relation to chronic anxiety and ‘differentiation of self’.     

Two-queue polling systems with switching policy based on the queue that is not being served

We study a system of two non-identical and separate M/M/1/? queues with capacities (buffers) C₁ < ∞ and C₂ = ∞, respectively, served by a single server that alternates between the queues. The server’s switching policy is threshold-based, and, in contrast to other threshold models, is determined by the state of the queue that is not being served. That is, when neither queue is empty while the server attends Q_i (i = 1, 2), the server switches to the other queue as soon as the latter reaches its threshold. When a served queue becomes empty we consider two switching scenarios: (i) Work-Conserving, and (ii) Non-Work-Conserving. We analyze the two scenarios using Matrix Geometric methods and obtain explicitly the rate matrix R, where its entries are given in terms of the roots of the determinants of two underlying matrices. Numerical examples are presented and extreme cases are investigated.     

A counterexample to Beder's conjectures about Hadamard matrices

In this note we provide a counterexample which resolves conjectures about Hadamard matrices made in this journal. Beder [1998. Conjectures about Hadamard matrices. Journal of Statistical Planning and Inference 72, 7–14] conjectured that if H$\mathit{H}$ is a maximal m×n$m\times n$ row-Hadamard matrix then m is a multiple of 4; and that if n   is a power of 2 then every row-Hadamard matrix can be extended to a Hadamard matrix. Using binary integer programming we obtain a maximal 13×32$13\times 32$ row-Hadamard matrix, which disproves both conjectures. Additionally for n being a multiple of 4 up to 64, we tabulate values of m   for which we have found a maximal row-Hadamard matrix. Based on the tabulated results we conjecture that a m×n$m\times n$ row-Hadamard matrix with m?n-7$m?n-7$ can be extended to a Hadamard matrix.     

建筑物区分所有权及专有权的概念辨析

建筑物区分所有权制度是近现代社会发展起来的一项新型不动产所有权制度。专有所有权是业主对其建筑物专有部分享有的专有、使用、收益和处分的权利,其性质为对空间的所有权。     

A Comparison of Correlation Structure Selection Penalties for Generalized Estimating Equations

Correlated data are commonly analyzed using models constructed using population-averaged generalized estimating equations (GEEs). The specification of a population-averaged GEE model includes selection of a structure describing the correlation of repeated measures. Accurate specification of this structure can improve efficiency, whereas the finite-sample estimation of nuisance correlation parameters can inflate the variances of regression parameter estimates. Therefore, correlation structure selection criteria should penalize, or account for, correlation parameter estimation. In this article, we compare recently proposed penalties in terms of their impacts on correlation structure selection and regression parameter estimation, and give practical considerations for data analysts. Supplementary materials for this article are available online.     

Continuity of f-projections and applications to the iterative proportional fitting procedure*

This paper proves continuity of f-projections and the continuous dependence of the limit matrix of the iterative proportional fitting procedure (IPF procedure) on the given matrix as well as the given marginals under certain regularity constraints. For finite spaces, the concept of f-projections of finite measures on a compact and convex set is introduced and continuity of f-projections is proven. This result is applied to the IPF procedure. Given a nonnegative matrix as well as row and column marginals the IPF procedure generates a sequence of matrices, called the IPF sequence, by alternately fitting rows and columns to match their respective marginals. The procedure is equivalent to cyclic f-projections. If the IPF sequence converges, the application of the continuity of f-projections yields the continuous dependence of the limit matrix on the given matrix. By generalized convex programming and under some constraints, it is shown that the limit matrix of the IPF sequence continuously depends not only on the given matrix but also on the marginals.     

Joint GEEs for multivariate correlated data with incomplete binary outcomes

This study considers a fully-parametric but uncongenial multiple imputation (MI) inference to jointly analyze incomplete binary response variables observed in a correlated data settings. Multiple imputation model is specified as a fully-parametric model based on a multivariate extension of mixed-effects models. Dichotomized imputed datasets are then analyzed using joint GEE models where covariates are associated with the marginal mean of responses with response-specific regression coefficients and a Kronecker product is accommodated for cluster-specific correlation structure for a given response variable and correlation structure between multiple response variables. The validity of the proposed MI-based JGEE (MI-JGEE) approach is assessed through a Monte Carlo simulation study under different scenarios. The simulation results, which are evaluated in terms of bias, mean-squared error, and coverage rate, show that MI-JGEE has promising inferential properties even when the underlying multiple imputation is misspecified. Finally, Adolescent Alcohol Prevention Trial data are used for illustration.     

Combined asymmetric spatial weights matrix with application to housing prices

In this study, a combined asymmetric spatial weights matrix is proposed for capturing the unequal spatial dependence of housing prices, where the advantage of this matrix was demonstrated by a non-nested hypothesis test. To explore the heterogeneous spatial impacts of urban essential characteristics on housing prices over the eastern, central, and western regions of China, after the Lagrange multiplier and likelihood ratio tests, the spatial Durbin model using the proposed weights matrix was applied to each region. The estimation results showed that the direct impacts of college and new employment were significantly negative in the eastern region, but not significant in the central and western regions. By contrast, the direct impacts of hospitals and scenic spots were significantly positive in eastern China, but not significant in central and western China. In addition, the indirect impacts of the four variables were not significant in the three regions. These results suggest that in eastern China, the government may increase the requirements for using medical resources and close tourist attractions in a single city to cool down the skyrocketing housing prices in this area.