Heteroskedasticity-consistent covariance matrix estimators for spatial autoregressive models

In the presence of heteroskedasticity, conventional test statistics based on the ordinary least squares (OLS) estimator lead to incorrect inference results for the linear regression model. Given that heteroskedasticity is common in cross-sectional data, the test statistics based on various forms of heteroskedasticity-consistent covariance matrices (HCCMs) have been developed in the literature. In contrast to the standard linear regression model, heteroskedasticity is a more serious problem for spatial econometric models, generally causing inconsistent extremum estimators of model coefficients. This paper investigates the finite sample properties of the heteroskedasticity-robust generalized method of moments estimator (RGMME) for a spatial econometric model with an unknown form of heteroskedasticity. In particular, it develops various HCCM-type corrections to improve the finite sample properties of the RGMME and the conventional Wald test. The Monte Carlo results indicate that the HCCM-type corrections can produce more accurate results for inference on model parameters and the impact effects estimates in small samples.     

中国主要贵金属资源利用及关键性评估

贵金属资源同时具备工业属性和金融属性，不仅关系着国民经济的发展，更关系着国家的金融安全和国防安全。中国经济的发展带动了矿产资源需求的增加，对贵金属的需求量也是全球之最。本文参照欧盟的关键性矩阵研究，从经济重要性和供应风险两个维度，对金、银、铂、钯4种贵金属的供应风险开展研究，得到了中国贵金属的关键性矩阵，综合来看，4种贵金属的经济重要性由大到小的顺序为金>银>铂> 钯，供应风险由大到小的顺序为银>钯>铂>金。     

Structuring an effective human error intervention strategy selection model for commercial aviation

Flight safety cannot be compromised. Thus, commercial airlines should constantly develop safety management strategies to mitigate the diverse hazardous factors in flight operations. Given the constraint of organizational resource, a commercial airline may not have sufficient resources to implement all the necessary strategies simultaneously. This study uses a well-structured process to develop a qualitative evaluation model that will enable airlines to identify human errors and select an intervention strategy with the highest success potential. To clarify the decision problem, the Human Factors Intervention Matrix framework is utilized to construct the decision hierarchy. The Analytic Hierarchy Process is then used to attain the priorities of potential alternative strategies for various unsafe acts. Finally, Zero-One Goal Programming models are formulated to select an optimal portfolio based on the specific target and the available organizational resources. An empirical study is presented to illustrate the application of the proposed model. According to the results of the combined model, an optimal portfolio, including the intervention approaches of organizational/administrative, human/crew, and operational/physical environment, can remediate four unsafe acts, namely, decision errors, skill-based errors, perceptual errors, and violations, under resource constraints of the organization.     

Modelling regional policy scenarios in the agri-food sector: a case study of a Spanish region

The agri-food industry has several features of great importance for sustainable economic growth in rural areas. The objective of this work is to evaluate the effects associated with different scenarios of growth, and changes in the regional agri-food industry. These scenarios simulate changes in exports and imports, changes in technology and changes in the level of industrial integration. We develop a computable general equilibrium model calibrated for the region. Our results indicate that policies trying to improve the competitiveness and dynamism of strategic sectors as the agro-industrial complex in this regional economy exert positive effects on its growth and income, having notable impacts on local job markets but also in other sectors and activities linked through the whole production chain.     

Multiple Levels of Corporate Sustainability

According to Dr. Clare Graves, mankind has developed eight core value systems,1 as responses to prevailing circumstances. Given different contexts and value systems, a one-solution-fits-all concept of corporate sustainability is not reasonable. Therefore, this paper presents various definitions and forms of sustainability, each linked to specific (societal) circumstances and related value systems. A sustainability matrix– an essential element of the overall European Corporate Sustainability Framework – is described showing six types of organizations at different developmental stages, with different forms of corporate sustainability, each supported by specific institutional arrangements.     

新形势下券商核心竞争力的战略选择

面对悄然而至的加入WTO的挑战 ,国内券商今后如何应对来自国外大券商的竞争压力 ,如何不断地壮大自身实力 ,对于券商的发展具有十分重要的现实意义。从业务创新、人才和研发实力、企业文化、资本规模与融资能力、风险控制能力等多方面讨论券商核心竞争力的培养 ,并结合券商核心竞争力矩阵 ,设计出核心竞争能力选择坐标图 ,以此来分析券商核心竞争力的战略选择与发展策略。     

Ka频段上变频模块的设计

介绍了Ka频段上变频模块的方案设计与性能测试.该模块采用单一本振源两次变频方案,将L频段500MHz带宽信号上变频至Ka频段.通过整体方案的优化设计和高性能滤波器的使用,在信号带内获得极低的杂散、优良的相噪特性和较为理想的幅频响应特性.经加工、测试,整套模块性能优良,工作状态稳定,满足设计指标的要求.     

质检机构中实验室信息管理系统的设计与研究

论文结合质检机构的实验室信息管理系统的实际运用,研究了主要集C/S三层分布式体系结构在信息系统设计中的特征体现,并根据质检机构检验流程、组织结构职能影响下的LIMS多个模块功能以及仪器连接、报表模板设计等技术要求。     

基于ISM的可达矩阵的简便算法

解释结构模型化技术是最基本、最具特色的系统结构模型化技术,求可达矩阵又是建立递阶结构模型(ISM)中最重要的一步,本文基于ISM有向图,根据布尔代数运算规则,阐述一种更简便的由邻接矩阵求可达矩阵的新算法。本文与Warshall算法作对比,体现出该新算法的简便之处。该算法以后也可以实现计算机化。     

基于熵权与改进的TOPSIS法的蔬菜供应商评估研究

蔬菜供应链的基础上,借助于熵权与相关系数矩阵的TOPSIS法相结合的供应商评价模型。首先构建供应商的评价指标体系,然后采用熵权法得到各指标的权重,再结合实例验证该模型的可行性。结果表明该模型能够更客观地对蔬菜供应商的选择进行有效评估。