Sequential estimate for linear regression models with uncertain number of effective variables

As a result of novel data collection technologies, it is now common to encounter data in which the number of explanatory variables collected is large, while the number of variables that actually contribute to the model remains small. Thus, a method that can identify those variables with impact on the model without inferring other noneffective ones will make analysis much more efficient. Many methods are proposed to resolve the model selection problems under such circumstances, however, it is still unknown how large a sample size is sufficient to identify those “effective” variables. In this paper, we apply sequential sampling method so that the effective variables can be identified efficiently, and the sampling is stopped as soon as the “effective” variables are identified and their corresponding regression coefficients are estimated with satisfactory accuracy, which is new to sequential estimation. Both fixed and adaptive designs are considered. The asymptotic properties of estimates of the number of effective variables and their coefficients are established, and the proposed sequential estimation procedure is shown to be asymptotically optimal. Simulation studies are conducted to illustrate the performance of the proposed estimation method, and a diabetes data set is used as an example.     

基于科学理论指导的邮政"双定"工作探讨

做好邮政"双定"工作不仅是邮政企业当前的重要工作,也是推动邮政又好又快发展的关键举措.文章旨在探讨运用马克思主义哲学的基本原理解决邮政"双定"工作实践中的有关问题,以期推动邮政"双定"工作的开展.     

Incorporating sustainability criteria into credit risk management

Does a commercial debtor's economic, environmental and social performance in terms of sustainability affect its credit risk rating? Does adding criteria aimed at assessing a lender's environmental, social or sustainability practices provide added value to traditional financial rating criteria? Many analyses have reported that a correlation exists between companies' environmental and their financial performance. We checked out the assertion that it ‘pays to be sustainable’ by analyzing the role that criteria pertaining to sustainability and environmental orientation play in the commercial credit risk management process. Our results show that sustainability criteria can be used to predict the financial performance of a debtor and improve the predictive validity of the credit rating process. We conclude that the sustainability a firm demonstrates influences its creditworthiness as part of its financial performance. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.     

Scarcity Message Effects on Consumption Behavior: Limited Edition Product Considerations

Recently, many luxury brands have begun to launch limited edition (LE) products. When this happens, advertisers implement two typical types of scarcity messages for LE products: limited‐time scarcity (LTS) versus limited‐quantity scarcity (LQS) messages (Cialdini, 2008). Prior research offered empirical evidence that these scarcity messages make consumers feel that LE products are more special, unique, and valuable, and thus, positively influence their evaluation of the product (Aggarwal, Jun, & Huh, 2011). The current study examined the differential effects of LTS and LQS messages on different types of LE products by focusing on consumers’ need for uniqueness.     

Mobility effects of b2c and c2c e-commerce in the Netherlands: a quantitative assessment

For more than a decade researchers have been interested in the implications of e-commerce for personal travel and freight transport. So far it is mostly the mobility effects of business-to-consumer (b2c) e-commerce that have been studied. However, consumer-to-consumer (c2c) e-commerce is becoming popular and may have important implications for mobility as well. Moreover, most studies conducted thus far have looked at the consequences of b2c e-commerce for either personal or freight travel, but not for both.This paper takes a more comprehensive approach. Using a nationwide sample of 3000 Dutch e-shoppers we calculated the potential impacts of both types of e-commerce on personal and freight travel. The results indicated that personal travel in the Netherlands has only marginally decreased as a result of e-shopping, while freight transport has slightly increased. The outcomes showed a net mobility effect, as the reduction in personal travel was not fully compensated by the increase in freight transport. However, this mobility reduction was fully attributed to b2c e-commerce, as c2c e-commerce led to an increase in both personal travel and freight transport.     

新时期国民生活水平和生活质量变迁论略——兼谈存在的问题及主要对策

新时期以来,我国国民的生活水平有了很大的提高,主要表现在GDP的持续增长和人均可支配收入的增加。生活质量也有了很大的提升,主要表现为衣食的多样化和精致化、居住环境的宽敞化和人文化、生活用品高档化、人口素质不断提高和休闲生存状态方面等。但是,从总体上说,我国人民的生活水平和生活质量还存在着很多问题。彻底打破城乡二元结构,对国家的产业结构进一步调整和完善社会保障制度是当前应该采取的主要对策。     

Context sensitive multimodal road planning: a case study in Cape Town, South Africa

Road planning practice relies almost exclusively on parameters related to traffic factors, such as private vehicle speeds and volumes. In many developing countries the requirements for public transport and non-motorised transport are not explicitly integrated into the planning process, despite the fact that these form the primary mode of transport for the majority of the population. This affects the mobility opportunities for these sectors of the population and contributes to poor road safety, especially with regards to pedestrians. The research outlined in the paper posits that, in order to assess the usage and needs of the road holistically, other factors related to the adjacent land uses, socio-economic characteristics of the population the road serves, and the environmental context within which the road is located, factors heavily in how the road is used and should, therefore, be considered within the planning process. The paper describes a methodology to include these factors in the planning of roads. The method attempts to prioritise amongst the five primary road based modes (public transport, car, freight, walking and cycling) based upon a combination of traffic and non-traffic factors. The method employed uses a geographic information system (GIS) based spatial multiple criteria evaluation (SMCE) model with inputs from widely available data sources such as census, household travel surveys, land use and environmental data to arrive at solutions for modal priorities. A case study is conducted along an arterial route in Cape Town, South Africa, providing infrastructure planning recommendations and audit possibilities for the future. Since weighting is an important driver in the SMCE process, a sensitivity analysis is conducted to investigate the effect of alternative weighting schemes on the outputs from the method.