时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性，为有效评估系统的误码性能，给出了符合车载时变信道的一阶自回归（AR1）模型，提出了一种基于AR1模型的自适应解码转发（ADF）协作误码率分析方法。该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发，提升了智能交通系统的可靠性。此外，利用矩生成函数（MGF）推导出ADF协作下多进制正交幅度调制（M-QAM）信号误码率封闭表达式，并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响。数值仿真结果表明，车载系统能通过增加CSI估计精度，有效地减少车载快速移动引起的误码平顶值。该方法相对于放大转发（AF）协作通信方式，平均误码性能提高约8.7 dB。     

省域研发投入溢出效应的实证分析

基于我国2005—2014年的31个省际面板数据，将研发投入作为变量引入到区域经济增长的回归模型中，并结合空间计量的方法研究分析了本省的研发投入对经济的增长和邻近省份的研发投入的溢出效应。全样本和分区域结果都表明自主研发投入对经济的增长均有明显的促进作用；自主研发投入的经济增长效应存在差异，东部最强，中部次之，西部最弱，邻近省份的研发投入溢出效应显著，东中西部呈梯度下降趋势。     

Continuum modeling approach to the spatial analysis of air quality and housing location choice

Today, air pollution is a great issue, and the transport sector is an important emission source. In this study, we present an integrated land use, transport, and environment model in which transport-related pollutants are assumed to influence people's housing location choices, and a continuum modeling approach is applied. The pollutants generated by the transport sector are dispersed by the wind and they affect air quality. The air quality changes people's housing choices, which in turn changes their travel behavior. We assume that the road users are continuously distributed over the city, that the road network is relatively dense, and that this network can be approximated as a continuum. The total demand is categorized into several classes, and the modeled region contains several subdistricts. People who live in different subdistricts or who belong to different classes of commuters are assumed to have different perceptions of travel time, air quality, and the housing provision–demand relationship. The finite element method and the Newton–Raphson algorithm are adopted to solve this problem, and a numerical valuation is given to illustrate the effectiveness and efficiency of the proposed model.     

The spatial agglomeration of museums,a case study in London

Museums play a significant role in urban revival and the tourism development of cities. As part of the cultural industry, the spatial agglomeration of museums becomes important. However, it is an under-researched area. This research uses a combined method of Herfindahl index and Gini Coefficient to analyze the influence of four categories of factors (demand factors, traffic factors, labor cost factors and facilities factors) on the spatial distribution of museums. It uses London as a case study, discussing the spatial distribution and agglomeration of the museums in Greater London. The results prove that a museum agglomeration in Greater London does exist, which is in a distribution of a circular pattern with the city center at the core, meanwhile influenced by the Thames River. It also shows a certain degree of linear distribution of the agglomeration. The results suggest that among the four categories of influencing factors, the demand factors are the robust elements that affect museums’ spatial distribution, which is different from manufacturing and productive services industries. Implications for practice are drawn out.     

Impacts of transportation infrastructure on single-family property values

New or long-standing public infrastructure such as highways, airports, and ports of entry (POE) can increase adjacent property values generating a value premium for private developers and adjacent property owners. States and local governments aim to determine the geographic footprint and anticipate the economic value created by transportation infrastructure proximity and accessibility since it represents an opportunity to capture some infrastructure costs. Hence, it is desirable to understand the degree of correlation between transportation infrastructure proximity and changes in real property values in a spatial context particularly when defining economic development zones where transportation investments are planned and where governments expect to recover some of the infrastructure cost from increases in real property values. This research applies geographically weighted regression (GWR) analysis to determine the geographic footprint and quantify the impacts of transportation infrastructure proximity and accessibility on real property values in El Paso, Texas using a 2013 cross-sectional data set. The presence of spatial nonstationarity and heterogeneity confirms that transportation infrastructure proximity and accessibility might generate premiums on real property values, but that such premiums are not always positive and are occasionally negative. GWR shows that benefits from a transportation facility can be capitalized by non-adjacent parcels. Finally, GWR maps can help better policy development by estimating how much value is added by infrastructure proximity and accessibility throughout particular locations.     

A two-step approach to account for unobserved spatial heterogeneity

A two-step approach to account for unobserved spatial heterogeneity. Spatial Economic Analysis. Empirical analysis in economics often faces the difficulty that the data are correlated and heterogeneous in some unknown form. Spatial econometric models have been widely used to account for dependence structures, but the problem of directly dealing with unobserved spatial heterogeneity has been largely unexplored. The problem can be serious particularly if we have no prior information justified by economic theory. In this paper we propose a two-step procedure to identify endogenously spatial regimes in the first step and to account for spatial dependence in the second step. This procedure is applied to hedonic house price analysis.     

Claiming Rights To Mobility Through The Right To Inhabitance: Discursive Articulations from Civic Actors in Montreal

How do claims for rights to mobility intersect with grievances pertaining to spatial justice in the city? This article addresses the issue by studying the concrete connections made by activists promoting car alternatives in Montreal. The activists' discursive categories point to the centrality of their conditions of inhabitance in their claims for certain rights to mobility. The discourses are analysed in the context of demands for safe spaces to walk and cycle in Montreal, and in the context of opposition to the rebuilding of the Turcot highway interchange. The article discusses internal dynamics of collective action, as well as the external influences and controls on activists contesting automobility to various degrees and with different spatially grounded priorities. The claims for rights to mobility rely on locally articulated priorities for better conditions of inhabitance, yet with a transversal reliance on a shared sense of threat and vulnerability, and on the representations of a community (whether local or multi‐scalar), enabling changes in the physical framing of mobility.     

La Ley de Okun y la flexibilidad laboral en México: un análisis de cointegración, 1997Q3-2014Q1

Because the labor flexibility has become an increasing condition in labor markets, we estimated the effect of labor flexibility on the unemployment rate in Mexico for 1997Q3-2014Q1. For this fact, we estimated a VECM(4) inspired on the Okun's Law which includes a labor flexibility index, measured by the ratio of the temporary contracts to the total employees in the formal labor market. As expected by the Okun's Law (1962), we found a negative relationship between GDP and the unemployment rate. However, the most interesting result is that the labor flexibility index exhibits an increasing effect on the unemployment rate with an elasticity of 1.28.     

Generalized least squares cross‐validation in kernel density estimation

The kernel density estimation is a popular method in density estimation. The main issue is bandwidth selection, which is a well‐known topic and is still frustrating statisticians. A robust least squares cross‐validation bandwidth is proposed, which significantly improves the classical least squares cross‐validation bandwidth for its variability and undersmoothing, adapts to different kinds of densities, and outperforms the existing bandwidths in statistical literature and software.