A Network Perspective on Spatially Clustered Territorial Use Rights for Fishers (TURFs) in Vietnam

Co-managed territorial use rights for fishers (TURFs) have shown promise for small-scale fisheries management. The territorial use rights help clarify access and ownership rights, while co-management arrangements create formal relationships between fishers and government. However, there is limited research into the governance processes that influence the interactions and complementarities of TURF zones that are clustered together. In a network of 16 co-managed TURFs in the Cau Hai lagoon, Vietnam, we analyzed management decentralization and the relationship between spatial and networked (social) proximity. Our findings draw attention to several broad lessons for co-managed TURFs: (1) TURFs may operate as isolated silos if co-management agreements do not address relationships among TURF leaders; (2) spatial proximity does not automatically translate to social proximity; and (3) leaders of individuals TURFs need capacity for communication and coordination with other local fisheries leaders. These findings highlight the importance of consideration to the ways that TURF design and implementation influences the relationships and collaboration between fishers, government officials, and other actors.     

The use of recovery time in timetables: rail passengers’ preferences and valuation relative to travel time and delays

Transportation - Recovery time in the rail industry is the additional time that is included in train timetables over and above the minimum journey time necessary often with the explicit aim of...     

The impacts of connected vehicle technology on network-wide traffic operation and fuel consumption under various incident scenarios

ABSTRACT

Incidents are a major source of traffic congestion and can lead to long and unpredictable delays, deteriorating traffic operations and adverse environmental impacts. The emergence of connected vehicles and communication technologies has enabled travelers to use real-time traffic information. The ability to exchange traffic information among vehicles has tremendous potential impacts on network performance especially in the case of non-recurrent congestion. To this end, this paper utilizes a microscopic simulation model of traffic in El Paso, Texas to investigate the impacts of incidents on traffic operation and fuel consumption at different market penetration rates (MPR) of connected vehicles. Several scenarios are implemented and tested to determine the impacts of incidents on network performance in an urban area. The scenarios are defined by changing the duration of incidents and the number of lanes closed. This study also shows how communication technology affects network performance in response to congestion. The results of the study demonstrate the potential effectiveness of connected vehicle technology in improving network performance. For an incident with a duration of 900?s and MPR of 80%, total fuel consumption and total travel time decreased by approximately 20%; 26% was observed in network-wide travel time and fuel consumption at 100% MPR.     

Lightweight Occupancy Estimation on Freeways Using Extended Floating Car Data

Advanced traffic management systems rely heavily on technology to perform accurate estimations of the current state of the traffic as well as its short-term evolution. The objectives are improving traffic flow and enhancing road safety. Their success is based on accurate monitoring of two key variables, specifically speed and occupancy. The latter of the two has, to date, received significantly less attention from the scientific community. In this work we present a lightweight method to perform “on-line” occupancy estimation. We first propose three occupancy measurements calculated from data collected by a floating car: vehicle count, percentage of stop time, and headway. We then extend these discrete values to a continuous estimation of occupancy in space and time. The proposed estimators are based on a pairwise linear regression of each of the previously calculated measurements over certain references obtained from other floating cars or magnetic loop detectors. The method has been calibrated and validated under real traffic conditions and data. Despite the ease of implementation, the method is able to reproduce the occupancy values generated by the actual loop detectors, achieving promising results, with estimation errors down to 6.52%, even before multivehicle systems are considered.     

Travel time reliability: a review of late time valuations,elasticities and demand impacts in the passenger rail market in Great Britain

This paper provides an extensive review and reconciliation of British and European evidence relating to the value of, and demand responses to, rail reliability. In particular, we compare the elasticities implied by stated preference valuations of late time with directly estimated lateness elasticities. We find that the implied lateness elasticities are substantially greater than those directly estimated. A possible explanation for this is that lateness has been over-valued, but more sobering explanations would be to suggest that, whilst rail travellers dislike unreliability, they may be unwilling or unable to reduce their rail travel in response to experiences of poor performance, or else conventional economic approaches to deducing elasticities are not appropriate. The findings have been used to update the recommendations of the UK rail industry’s Passenger Demand Forecasting Handbook.     

A competitive, charter air-service planning model for student athlete travel

This paper presents a model for planning an air charter service for pre-scheduled group travel. This model is used to investigate the competitiveness of such an enterprise for student athlete travel in conference sports. The relevant demand subset to be served by a limited charter fleet is identified through a comparison with existing scheduled travel options. Further, the routing and scheduling of the charter aircraft is performed within the same framework. Through this modeling a method for formulating and accommodating continuous time windows and competitive market dynamics in strategic planning for a charter service is developed. Computational improvements to the basic model are also presented and tested. The model is applied to the Big Sky Conference for the 2006-2007 season, quantifying the benefits to the students from such a service and the change in expenditure associated with such a benefit for various assumptions about operations and value of time. The findings indicate the lack of spatial or sport based patterns for maximizing benefit, indicating the absence of simplistic “rules of thumb” for operating such a service, and validating the need for the model.     

The undrained bearing capacity of a spudcan foundation under combined loading in soft clay

Mobile jack-up drilling rigs are typically supported by individual, large diameter spudcan foundations. Before deployment, the suitability of a jack-up to a location must be shown in a site-specific assessment under loads associated with a 50-year return period storm, which ultimately need to be resisted by the foundations. The capacity of the spudcans under combined vertical, horizontal and moment loading is therefore integral to the overall site-specific assessment of the jack-up.In soft clays, spudcans can penetrate deeply into the seabed, sometimes up to several footing diameters, with soil flowing around the downward penetrating footing, sealing the cavity. Although this is generally believed to provide some additional bearing capacity to the footing, no detailed study or formal guidance is available to date. This study, therefore, investigates the influence of soil back-flow on the failure mechanisms and quantifies the effect on the capacity of a spudcan under general loading through finite element analyses. A closed-form analytical expression is developed that describes the capacity envelope under combined loading, applicable to embedment depths ranging from shallow to deep.     

风雨摩纳哥：马克的2008

赛季之前的时候大家都有一个疑问，没有牵引力控制系统的比赛会是怎么样的？来到摩纳哥的时候阴云密布，我当时就在想答案就要在这个周末揭晓了。在街道赛进行雨战，不能不说是老天的良好创意。而周日的雨战很好地回答了这个问题，而且比赛场面的精彩和不可预知性使得比赛充满悬念，非常吸引人。     

Scheduling considerations for a branching transit route

This paper addresses the impacts of different scheduling alternatives for a branching transit route. It examines different schedule alternatives that might be used to optimize the route performance in terms of the passenger traveling time distributed among branch passengers and trunk‐line passengers. The schedule alternatives considered include transit vehicle allocation to different branches, offset shifting across vehicles on different branches, and vehicle holding (slack time) in the transit vehicle schedule. With these variables, several vehicle schedules are devised and examined based on a wide variety of possible passenger boarding scenarios using deterministic service models. Test outcomes provide general conclusions about the performance of the strategies. Vehicle assignment leading to even headways among branches is generally preferred for the case of low passenger demand. However, when passenger demand is high, or the differences between the passenger demands on branches are significant, unequal vehicle assignment will be helpful to improve the overall route performance. Holding, as a proactive strategy in scheduling, has the potential to be embedded into the schedule as a type of slack time, but needs further evidence and study to determine the full set of conditions where it may be beneficial. Offset shifting does not show sufficient evidence to be an efficient strategy to improve route performance in the case of low or high passenger demand.     

Siliceous plankton dominate primary and new productivity during the onset of El Niño conditions in the Santa Barbara Basin, California

The potential for carbon export and the role of siliceous plankton in the cycling of C and N was assessed in natural plankton assemblages in the Santa Barbara Basin, California, by examining uptake rates of inorganic carbon, nitrate and silicic acid. In April–August 1997, the concentrations of chlorophyll a, particulate organic carbon, particulate organic nitrogen and biogenic silica were measured twice monthly, and results revealed the occurrence of at least three blooms, the largest in June. Particulate elemental ratios of C, N and Si were similar to ratios of nutrient-replete diatoms, suggesting that they dominated this bloom. Mean integrated rates of carbon, nitrate and silicon uptake during the 4-month study period are similar to other productive coastal and upwelling regions (103, 8.3 and 13 mmol m⁻² day⁻¹, respectively). New production rates were twice as high as previously reported in this region and indicate that high rates of new production along eastern boundary currents are not confined to the major coastal upwelling regions. C/NO₃⁻, Si/NO₃⁻ and Si/C uptake ratios varied widely, and mean integrated ratios were 14±5.4, 1.6±1.0 and 0.12±0.07 (S.D.), respectively. That mean C/NO₃⁻ uptake ratio corresponds to an f-ratio of about 0.5 indicating a large potential for particulate export. Based on the average Si/NO₃⁻ and Si/C uptake ratios, diatoms could perform all of the primary production and nitrate uptake that occurred during the study; these rates also suggest that export is controlled by diatoms in this system. The mean Si/C biomass ratio was lower than the mean Si/C uptake ratio, consistent with the preferential export of Si relative to C observed in sediment traps in the basin. The study took place during a period of surface-water warming, with nitrate and silicic acid concentrations decreasing throughout the onset of the 1997–1998 El Niño conditions. Although diatoms contributed less to particulate biomass during the low nutrient conditions, high f-ratios (0.33–0.66) were maintained.