A risk model for the operation of container vessels

Commercial shipping of containerized goods involves certain risks for human safety and environment. In order to actively manage these risks, they must be identified, analyzed, modeled, and quantified. This requires a systematical analysis of design and operation of container vessels. Within the EU-funded research project SAFEDOR, a Formal Safety Assessment has been applied to establish the current safety level of generic container ships and to identify potential cost-effective risk control options. This paper describes a structured approach to develop the underlying high-level risk model. It is structured as risk contribution tree consisting of a series of fault trees and event trees for the major accident categories. Statistical analysis of casualty data is used to estimate the probability of occurrence. Finally, the summation overall individual risk contributions yields the current risk pro file for the operation of container vessels is presented as FN-curve.     

传感器推动汽车环保变革

汽车业未来将走向何方?混合动力还是乙醇燃料?天然气还是氢气?或者是以上全部?人们对此争论不休.但有一点毋庸置疑,就是随着电子技术的发展,未来的汽车将日益与高科技接轨.     

Optimal slack time for timed transfers at a transit terminal

At transit terminals where two routes interchange passengers, total system costs may be reduced by allowing some “slack” time in the vehicle schedules to decrease the probability of missed connections. Transfer cost functions are formulated and used to determine optimal slack time for simple systems with transfers between one bus route and one rail line. Some analytic results are derived for empirical discrete and Gumbel distributions of bus arrival times. Relations between the optimal slack times and headways, transfer volumes, passenger time values, bus operating costs, and standard deviations of bus and train arrivals are also developed numerically using normally distributed arrivals. However, the proposed numerical approach can optimize slack times for any observed arrival distributions. The results provide some guidelines on desirable slack times and show that schedule coordination between the two routes is not worth attempting when standard deviations of arrivals exceed certain levels. Possible extensions of this work are suggested in the last section.     

An algorithm for the combined distribution and assignment problem

Much interest has recently been shown in the combination of the distribution and assignment models. In this paper we adopt a generalized Benders' decomposition to solve this combined problem for a system optimized assignment with linear link costs and explicit capacity constraints on link flows. The master problem which is generated is used to show that the combined problem can be viewed as a modified distribution problem, of gravity form, with a minimax instead of a linear objective function. An algorithm for solving the master problem is discussed, and some computational results presented.     

Marine Shoreline Management—A 35-Year Evaluation of Outcomes in San Juan County,Washington, US

In 1976, Washington became the first state to implement the federal Coastal Zone Management Act (CZMA) primarily through the 1971 WA Shoreline Management Act (SMA). However, there has been little effort in Washington to evaluate outcomes of shoreline protection programs post SMA. In 2006–2008, we characterized shoreline conditions in San Juan County over three time periods spanning pre and post SMA and engaged community members to improve effectiveness of shoreline protection. We found modest improvements in forest retention on marine shorelines between pre and post 1977, but few other improvements through time. While we could not measure shoreline construction rates, construction practices for shore armor and overwater structures (docks) have changed very little, despite the increased regulatory standards. The vast majority of shore armor constructed post SMA occurred without mandatory county or state permits likely due to: widespread perception that permits were unnecessary and that permit standards were arbitrary and inconsistently applied; poor understanding of shoreline ecology by community members; lack of county or state enforcement authority and shoreline monitoring programs; and poor permit tracking systems.     

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.     

Measuring inefficiency in the Norwegian bus industry using multi-directional efficiency analysis

This paper deals with methods of measuring and analyzing efficiency in the transport industry. The aim of the paper is to introduce and demonstrate the advantages of Multi-directional Efficiency Analysis (MEA) in the case of cost data with limited substitution possibilities. For this purpose we reconsider the Norwegian bus data that has previously been analyzed using econometric models and Data Envelopment Analysis; Jørgensenet al. (1995, 1997) and Odeck and Alkadi (2001). It is shown how, using MEA, it becomes possible to disaggregate inefficiency into different components corresponding to different types of cost generating variables and thereby providing both managers of the bus companies and policy makers with more detailed information on possible improvements in performance.     

应用碟片激光器和光学扫描仪进行遥控焊接

采用YAG激光器进行固体焊接,已成为汽车制造过程中一项成熟可靠的工艺。该项工艺现广泛用于车身和车架制造、传动系统制造、车座制造和其它领域。     

Nutrient Assimilation Services for Water Quality Credit Trading Programs: A Comparative Analysis with Nonpoint Source Credits

Water quality trading programs allow regulated point sources to meet some nutrient control requirements by buying nutrient reduction credits from other pollutant sources. Reduction credits can be created when agricultural land managers implement best management practices and regulators predict that those practices will result in water quality conditions equivalent to controlling discharges at the regulated source. However, natural variability in runoff combines with model and data limitations to make predictions of water quality equivalence uncertain. Nutrient assimilation credits can be created by increasing the capacity of the ecosystem to assimilate nutrients through investments in aquatic plant biomass creation and harvest, shellfish aquaculture, stream restoration, and wetlands restoration and creation. Nutrient assimilation credits and agricultural nonpoint source reduction credits are evaluated based on a number of water quality criteria including service quantification certainty, temporal matching, additionality, and leakage. Nutrient assimilation credits can provide greater certainty than agricultural best management practices in producing equivalent water quality outcomes and should be an option in trading programs.     

Road pricing with complications

The rationale for congestion charges is that by internalising the marginal external congestion cost, they restore efficiency in the transport market. In the canonical model underlying this view, congestion is a static phenomenon, users are taken to be homogenous, there is no travel time risk, and a highly stylised model of congestion is used. The simple analysis also ignores that real pricing schemes are only rough approximations to ideal systems and that inefficiencies in related markets potentially affect the case for congestion charges. The canonical model tends to understate the marginal external congestion cost because it ignores user heterogeneity and trip timing inefficiencies. With respect to the relevance of interactions between congestion and congestion charges and tax distortions and distributional concerns, recent insights point out that there is no general case for modifying charges for such interactions. Therefore the simple Pigouvian rule remains a good first approximation for the design of road charging systems.