Risk factors and theory building: a study to improve passenger vessel safety

Given the inherent complexity of the maritime transportation system, developing effective policy can be challenging. Using risk factors identified by an elicitation and aggregation of expert judgment, a relative-risk rating scheme was developed in the theory-building tradition of the social sciences. The model was empirically evaluated using 18 months of data from the US small passenger vessel sector. The model identified that the top 10% of relatively highest risk vessels accounted for 50% of all marine casualties during the period of examination. A policy for deploying the model nationally is proposed.     

Dispatching control at transfer stations in multi‐hub transit networks

Among dispatching control approaches, the holding option has attracted the most attention in bus control. However, holding a vehicle at a transfer station may exacerbate the delays because more passengers might accumulate at downstream stations and may also affect other connecting routes at other transfer stations. Our problem is to minimize the total costs of dispatching ready vehicles at each transfer station along coordinated routes in a multi‐hub transit network. The total costs include the waiting cost for on‐board passengers, the missed connection costs for late arrival passengers at the subject transfer station and possible transfer costs at downstream transfer stations. We develop a heuristic algorithm to optimize the holding times based on real time information about late vehicles. The results show that ready vehicles should be held longer when the arrival variances of late vehicles are small or when many late connecting passengers are expected.     

An examination of factors affecting propensities to use bicycle and pedestrian facilities in suburban locations

The US federal Congestion Mitigation and Air Quality program was created to fund transportation projects that have the potential to contribute to the attainment or maintenance of the National Ambient Air Quality Standards. This study evaluates a random sample of eight suburban bicycle and pedestrian facilities funded by the Congestion Mitigation and Air Quality Program in the Chicago metro area. Users of these facilities were randomly sampled using a “time-based” user sampling approach and surveyed in intercept mode to implement a recall-based evaluation design. A random intercept logit model was used to explain variations in the propensity to switch from single occupant vehicle use to bicycling or walking, using attributes of users and sites. The analysis shows relatively low usage levels but that substitution of motorized modes have resulted, potentially leading to improved air quality outcomes.     

Modelling port choice in an uncertain environment

Port choice is an important issue to be investigated to ensure the effective integration of container supply chains and the sustainable development of regional economy. The selection of appropriate ports to facilitate shipping activities and international trade is crucial for many stakeholders, including shipping lines, port administrators, cargo shippers and national governments. The task is essentially a process of multiple criterion decision-making (MCDM) under uncertainty, requiring analysts to derive rational decisions from uncertain and incomplete data related to different quantitative and qualitative determinants. This paper aims at proposing a new conceptual port choice method by explaining the role fuzzy logic in evidential reasoning in a complementary way, in which various forms of raw data (either objective or subjective) collected to evaluate port performance can first be converted into and presented as fuzzy grades defined using linguistics terms with degrees of belief (DoBs) and second be combined using evidential reasoning to produce a port choice preference score. The method is applied to analyse the selection of major Northeast Asian (NEA) container ports from a shipping line’s perspective. The outcome, a port choice preference score, is calculated using evidential reasoning to directly synthesize the true estimation of the port with respect to each criterion and therefore, unlike a relative ranking index, keeps the ‘goodness’ of port evaluation, capable of benchmarking a specific port’s performance and monitoring the increase of its competitiveness in a longitude study with respect to an individual criterion or all the criteria as a whole.     

Upstream pollution sources and coastal water quality protection in North Carolina

Abstract

A watershed‐based approach to water quality management is necessary for protecting coastal water quality, but the relative importance of inland pollution sources on estuaries is often overestimated. This can lead to a misallocation of coastal water protection resources and ignorance of coastal zone pollution sources. This overestimation of upstream contributions is attributable to a failure to recognize that many estuaries have little or no inland drainage area, the confusion of basinwide pollutant loading with pollutant delivery to estuaries, the low delivery ratios for many pollutants within drainage basins, and disproportionately high pollutant delivery for sources within the coastal zone. Examples are given from North Carolina. As a general rule, resources expended on pollution control within or near the coastal zone will result in more coastal water quality improvement per unit effort than resources expended upstream.     

共用车公司的新点子

共用车汽车租赁已经吸引了数以万计的城市青年加入拼车一族.如今,这场运动正在成为当下汽车消费的主流--就连赫兹租车和福特汽车也想参与其中.     

Perspectives on the commercial development of landing gear health monitoring systems

The development of health monitoring technologies for aerospace systems creates a number of challenges for the community of engineers and technical specialists as they seek to integrate the technology into well defined working practices. These challenges do not just extend to the technical, but require a number of commercial questions to be addressed. It is of vital importance, that there is a clearly identified need for aerospace health monitoring, both from a technological and commercial viewpoint. If these needs cannot be identified, then any attempt for marketing health monitoring as a necessary future technological requirement is doomed for failure. Health monitoring technology will need to either deliver significant cost saving benefits to the aircraft operator or demonstrated increases in aircraft safety. The objective of the paper is to provide an assessment of the commercial benefits and development of aircraft landing gear health monitoring. The commercial need and challenges for health monitoring systems are explored in this paper within the context of a changing aerospace maintenance industry and the role in which new systems technology will play. The key findings of the research study are that within the aerospace industry there is a desired paradigm shift within aircraft maintenance towards offering maintenance systems with predictive capabilities. This maintenance revolution will not just incorporate new technologies, but will result in aircraft maintenance packages tailored towards individual customer requirements. The study illustrates the state-of-the-art in health monitoring currently restricts aerospace integration and a number of key technical and commercial issues need to be addressed. Predictive health monitoring offers a variety of commercial benefits for maintenance providers, aircraft operators and manufacturers. However, in order for these benefits to be realised increased transparency in maintenance related information is required between these key players.     

Spectral signature of wave breaking in surface wave components of intermediate-length scale

This paper investigates the length scale of ocean surface breaking waves in the spectral range of intermediate wavelength components a few centimeters to a few meters long. The spectral properties of wave breaking are examined first with the dissipation function of the wave action density conservation equation. The analysis reveals a strong breaking signature in wave components between 0.15 and 1.5 m long in the form of a quasi-singular behavior of the dissipation function using the present formulation of the wind-generation and breaking dissipation functions. Independent studies of more-direct breaking observations of radar tracking of sea spikes in the past have shown close correlation between sea spikes and scatterers traveling at the speed of surface waves a few meters long and much shorter than the dominant wavelength. This feature of sea-spike properties is consistent with the breaking signature of the dissipation function in similar wavelengths. The intermediate-scale waves are the primary contributor of the ocean surface mean-square slope. The close correlation between the gas transfer rate and the mean-square slope has been demonstrated repeatedly. A better understanding of the wave dynamics of intermediate-scale waves is important for clarification of various gas transfer mechanisms.