T_H1 AND T_H2 CELL ANTIGEN RECEPTORS IN EXPERIMENTAL LEISHMANIASIS

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Vehicle Energy Dissipation Due to Road Roughness

Road roughness and surface texture are known to affect tire rolling resistance; however, little emphasis has been placed on the consequent changes in total vehicle energy dissipation due to road roughness. Thus, tire rolling resistance, in isolation from vehicle contributed losses such as dissipation in the suspension, appears to be a weakness in present evaluation procedures as they relate to fuel economy and pollution level testing: Recent work by Funfsinn and Korst has shown that substantial and measurable increases in energy losses occur for vehicles traveling on rough roads. The present investigation uses vehicle axle accelerations as a means of examining various road surfaces. Correlation with computer simulations has allowed the development of a deterministic road roughness model which permits the prediction of energy dissipation in both the tire and suspension as functions of road roughness, tire pressure, and vehicle speed. Comparison to the experiments of Korst and Funfsinn results in good agreement and shows that total rolling loss increases of up to 20 percent compared to ideal smooth roads are possible. The aerodynamic drag coefficient is also found to increase while driving on rough roads.     

Protecting Rhode Island's coastal salt ponds: An economic assessment of downzoning

Abstract

In southern Rhode Island, there is growing concern that housing and recreational demands will soon overwhelm the capacity of the coastal salt ponds to absorb wastes, produce seafood, and maintain scenic qualities. As a result, coastal towns have been studying the feasibility of using land controls such as downzoning to protect these coastal amenities. The paper presents an economic analysis of the downzoning program proposed in the town of South Kingstown. Hedonic price and contingent valuation methods are used to value coastal amenities. The estimated net present value of “swimmable” water is shown to be $3.1 million.     

Trip generation of vulnerable populations in three Canadian cities: a spatial ordered probit approach

This paper provides an analysis of trip generation of three vulnerable groups: single-parent families, low income households, and the elderly. It compares the mobility of these groups to that of the general population in three Canadian urban areas of Hamilton, Montreal and Toronto, based on data from large-sample metropolitan transport surveys. An ordered probit model with spatially expanded coefficients is used for the analysis. Spatial expansion shows that there are spatial mobility trends for elderly populations and low-income populations even after socio-economic attributes are accounted for. Such spatial differences are not generally found for single parent families. This novel spatial analysis provides clues as to where vulnerable populations may experience greater degrees of social exclusion. It provides information to help prioritize transportation infrastructure projects or other social programs to take into account the needs of vulnerable populations with the lowest levels of mobility.     

Intermodal Transit System Coordination

In urban areas where transit demand is widely spread, passengers may be served by an intermodal transit system, consisting of a rail transit line (or a bus rapid transit route) and a number of feeder routes connecting at different transfer stations. In such a system, passengers may need one or more transfers to complete their journey. Therefore, scheduling vehicles operating in the system with special attention to reduce transfer time can contribute significantly to service quality improvements. Schedule synchronization may significantly reduce transfer delays at transfer stations where various routes interconnect. Since vehicle arrivals are stochastic, slack time allowances in vehicle schedules may be desirable to reduce the probability of missed connections. An objective total cost function, including supplier and user costs, is formulated for optimizing the coordination of a general intermodal transit network. A four-stage procedure is developed for determining the optimal coordination status among routes at every transfer station. Considering stochastic feeder vehicle arrivals at transfer stations, the slack times of coordinated routes are optimized, by balancing the savings from transfer delays and additional cost from slack delays and operating costs. The model thus developed is used to optimize the coordination of an intermodal transit network, while the impact of a range of factors on coordination (e.g., demand, standard deviation of vehicle arrival times, etc) is examined.     

Using on-board logging devices to study the longer-term impact of an eco-driving course

In this paper the long-term impact of an eco-driving training course is evaluated by monitoring driving behavior and fuel consumption for several months before and after the course. Cars were equipped with an on-board logging device that records the position and speed of the vehicle using GPS tracking as well as real time as electronic engine data extracted from the controller area network. The data includes mileage, number of revolutions per minute, position of the accelerator pedal, and instantaneous fuel consumption. It was gathered over a period of 10 months for 10 drivers during real-life conditions thus enabling an individual drive style analysis. The average fuel consumption four months after the course fell by 5.8%. Most drivers showed an immediate improvement in fuel consumption that was stable over time, but some tended to fall back into their original driving habits.     

Optimal stop spacing and headway of congested transit system considering realistic wait times

Abstract

This paper revisits the classical transit scheduling problem and investigates the relationship between stop spacing and headway, considering realistic wait time and operable transit capacity. Headway and stop spacing are important determinants for planning a transit system, which influence the service level as well as the cost of operation. A mathematical model is developed, and the objective function is user travel time which is minimized by the optimized stop spacing and headway, subject to the constraints of operable fleet size and route capacity. Optimal stop spacing and headway solutions are obtained in a numerical example. Sensitivity analysis is conducted, and the effect of model parameters on user travel time is explored.     

Optimization of Fare Structure and Service Frequency for Maximum Profitability of Transit Systems

Abstract

Providing efficient public transportation has been recognized as a potential way of alleviating congestion, improving mobility, mitigating air pollution, and reducing energy consumption. Many people use public transportation systems for their daily commute, while others use different transportation modes (e.g. cars, taxis, carpools, etc.). Inexpensive fares with good transit service encourages ridership, and the resulting revenue may be used to provide better service. Optimization of transit service frequency and its associated fare structure is desirable in order to increase revenue at reasonable transit operating expenditure. The objective of the study reported here is to maximize profit subject to service capacity constraint, while elastic demand is considered. The solution methodology is developed and applied to solve the profit maximization problem in a case study based on Newark, NJ, USA. Numerical results, including optimal solutions and sensitivity analyses, are presented. It is found that an optimal temporal headway and differential fare structure that maximizes total profit for the studied subway system can be efficiently solved.     

不同规模城市居民出行方式影响因素分析

明确影响不同规模城市中居民出行方式选择的关键因素及其影响路径,有助于采取针对性策略调节城市居民出行结构,进而提高城市交通系统效率,缓解交通拥堵、空气污染等"城市病".现有研究较少关注中、小城市的居民出行方式选择,较缺少同省份居民出行方式选择的跨城市规模对比分析,不利于策略制定者运用出行方式关键影响因素调节居民出行行为....     

Airline industry deregulation and changes in systematic risk

Deregulation of U.S. Airline Industry may have lowered systematic risk because pricing freedom and route flexibility improved airline management reaction to various economic conditions. Reduced systematic risk offers lower cost of equity capital for the industry as a whole as well as for individual carriers. Previous research has had mixed results in identifying a relationship between deregulation and airline industry cost of capital. This study plots airline industry Beta coefficients across the years 1963 to 1987 and clears up previously conflicting research findings. Beta coefficients had been falling since the fuel crisis of 1974 and continued to fall through 1980. Fluctuations since deregulation have been relatively minor and systematic risk has leveled off at a significantly lower value than before deregulation. Studies which concentrate on the fluctuation in Beta since 1978 are dependent on the exact time period of analysis, and their conclusions that deregulation raised or lowered systematic risk are likewise suspect. A broader view of systematic risk changes in the deregulatory era shows airline Betas peaking from 1971 to 1973 and a gradual decrease as deregulation was being discussed, implemented, and legally mandated. This gradual decline from 1974 to 1980 may be attributed to such factors as fuel prices, interest rates, general inflation as well as deregulation. In any case systematic risk of the U.S. Airline industry has been lower since deregulation than in decades before.