中国农业类上市企业运行效率的DEA分析

本文运用数据包络分析方法对我国12家农业类上市企业的运行效率进行评价,测算了各个农业企业的综合技术效率、纯技术效率和规模效率状况。研究表明：我国农业类上市企业总体效率偏低,两级分化严重,纯技术效率基本有效,规模效率较低,投入不足。     

Induced travel demand: Evidence from a pseudo panel data based structural equations model

Induced traffic, defined as additional demand generated by improvements in travel conditions, has been a topic of research for many years. While previous studies have focused on specific and localised changes, the research described in this paper deals with the aggregate effects of changed generalised costs of travel on traffic generation: the propensity of participating in out-of-home activities on a given day, the number of trips and journeys conducted, and the resulting total times out-of-home and distances travelled. The generalised cost and accessibility elasticities estimated with a structural equations model for a pseudo panel constructed with the Swiss National Travel surveys since 1974 are surprisingly substantial even after correcting for age, cohort and other socio-demographic effects.     

浅谈采用P.O42.5R水泥浇筑C50混凝土箱梁的工艺质量控制

阐述了采用P.O42.5R早强水泥浇筑C50混凝土的工艺质量控制。     

开展科技档案编研工作加快汽车产品开发速度

随着汽车企业竞争的日益激烈，如何加快汽车产品开发速度成为人们十分关注的问题。文章介绍了开展科技档案编研工作对加快汽车产品开发速度的重要性及现存科技档案编研成果的5种基本形式，阐述了开展科技档案编研的基本要求，指出科技档案编研工作要以企业需求为己任，同时要不断总结和探索科技档案编研工作途径和方法，让科技档案为汽车工业的发展发挥更大的作用和潜能。     

PVTxSTUDYOFBINARYSYSTEMR22／R152aWITHBURNETTMETHOD

ＰＶＴｘＳＴＵＤＹＯＦＢＩＮＡＲＹＳＹＳＴＥＭＲ２２／Ｒ１５２ａＷＩＴＨＢＵＲＮＥＴＴＭＥＴＨＯＤＳｕＺｈｉｊｕｎＪｉａｎｇＢａｏｃｈｅｎｇＹａｎＪｉａｌｕ（ＳｈａｎｇｈａｉＪｉａｏｔｏｎｇＵｎｉｖｅｒｓｉｔｙ）（ＨａｒｂｉｎＩｎｓｔｉｔｕｔｅｏｆＴ...     

基于地铁的成都市停车换乘P&R站场规模预测

利用对成都市小汽车出行者进行选择行为分析时所取得的调查数据及优化选址结果,采用非集计分析法,基于“效用”最大化理论运用多项式Logit模型对成都市三环路沿线及外围组团P&R设施高峰时段站场规模进行预测,并对成都市停车换乘P&R设施的建设提出建议.     

Analyzing aviation safety: Problems,challenges, opportunities

This paper reviews the economic literature relating to aviation safety; analyzes the safety record of commercial passenger aviation in the United States and abroad; examines aviation security as a growing dimension of aviation safety; and identifies emerging issues in airline safety and challenges for aviation safety research. Commercial airline safety has improved dramatically since the industry's birth over a century ago. Fatal accident rates for large scheduled jet airlines have fallen to the level where (along many dimensions) aviation is now the safest mode of commercial transportation. However, safety performance has not been evenly distributed across all segments of commercial aviation, nor among all countries and regions of the world. The finding that developing countries have much poorer safety records has been a persistent conclusion in aviation safety research and continues to be the case. Unfortunately, operations data are not available for many of the airlines that experience fatal accidents, so it is not possible to calculate reliable fatality rates for many segments of the worldwide aviation industry. Without more complete information, it will likely be difficult to make substantial improvements in the safety of these operations. Challenges to improving aviation security include: how much to focus on identifying the terrorists as opposed to identifying the tools they might use; determining how to respond to terrorist threats; and determining the public versus private roles in providing aviation security. The next generation of safety challenges now require development and understanding of new forms of data to improve safety in other segments of commercial aviation, and moving from a reactive, incident-based approach toward a more proactive, predictive and systems-based approach.     

Paradoxes of rationality in road safety policy

Rationality is an ideal for transport safety policy. As developed within normative welfare economics, rationality denotes the efficient use of safety measures based on cost–benefit analyses that include all relevant impacts of the measures. Efficiency in the technical sense of the term provides a perfectly clear and precise guideline for policy priorities. Nevertheless, some choices that are guided by cost–benefit analysis may strike us as paradoxical or counterintuitive. A paradox of rationality refers to any situation in which conflicting choices can both be defended as rational. This paper discusses a number of choices that may seem paradoxical. The first involves the choice between options that have identical impacts on safety, but in which these impacts are valued differently. The second deals with the tendency for preference reversals to occur when preferences for the provision of safety are aggregated. The third discusses the inability of conventional measures of willingness-to-pay to reflect the intensity of preferences. The fourth concerns the tendency for policy choice to favour the rich at the expense of the poor when willingness-to-pay is not adjusted for the marginal utility of money. A fifth situation refers to the fact that a policy option that looks attractive ex ante may fail an ex post compensation test because utility functions depend on health state. There is a potential conflict between individual and collective rationality with respect to the costs and benefits of some road safety measures. When developing a road safety programme, a set of road safety measures whose benefits exceed the costs when considered as stand-alone measures could have benefits smaller than cost when combined in a programme consisting of all the measures. Finally, there is a potential conflict between efficiency and negotiated consensus as mechanisms of resource allocation in the public sector. The sources of the paradoxes and ways of avoiding them are discussed. Some of the paradoxes can be avoided if changes in risk are valued in terms of a fixed price per unit of risk rather than according to a non-linear demand function.     

Comparing the fatality risks in United States transportation across modes and over time

This paper analyzes the transportation fatality risk in the United States. The analysis is in two parts. The first part compares the relative risks of the different modes based on data for the decade from 2000 to 2009. The second part is a time-series analysis for each mode using annual data from 1975 to 2010. By almost any measure, transportation is considerably safer now than it was in the mid 1970s. The improvement is especially noticeable for commercial modes such as aviation, railroads and maritime. Even the risks from private highway driving have halved during the past thirty-five years.     

Modeling yard crane operators as reinforcement learning agents

Due to the importance of drayage operations, operators at marine container terminals are increasingly looking to reduce the time a truck spends at the terminal to complete a transaction. This study introduces an agent-based approach to model yard cranes for the analysis of truck turn time. The objective of the model is to solve the yard crane scheduling problem (i.e. determining the sequence of drayage trucks to serve to minimize their waiting time). It is accomplished by modeling the yard crane operators as agents that employ reinforcement learning; specifically, q-learning. The proposed agent-based, q-learning model is developed using Netlogo. Experimental results show that the q-learning model is very effective in assisting the yard crane operator to select the next best move. Thus, the proposed q-learning model could potentially be integrated into existing yard management systems to automate the truck selection process and thereby improve yard operations.