The effects of federal transit subsidy policy on investment decisions: The case of San Francisco's Geary Corridor

In the United States, federal funding for public transit often accounts for a large proportion of a local agency's budget, especially for capital investments. For this reason, local governments can be expected to plan a portfolio of projects that maximize federal contributions. This study examines the financial effects of federal transit subsidy policy on local transit investment decisions. Data from a System Planning Study for the Geary Corridor in San Francisco are used as an illustration. It is found that federal transit subsidy policy provides financial incentives for local decision-makers to select capital-intensive investment options that may not be efficient or effective. While federal financial incentives are not the only factor influencing local investment decisions, some reform of the current subsidy policy may be necessary to reduce the incentive for ineffective use of public resources.     

Optimal bus fleet management strategy for emissions reduction

Transportation is a major cause for environmental degradation via exhaust emissions. For many transit-oriented metropolitan areas, bus trips often constitute a sizeable mode share. Managing the bus fleet, in particular updating buses to comply with the newer emissions standards, therefore, can have a substantial impact on transportation-induced air quality. This paper presents the approach of remaining life additional benefit–cost (RLABC) analysis for maximising the total net benefit by either early-retiring or retrofitting the current bus fleet within their lifespans. By referring to the net benefits for different bus types estimated by RLABC analysis, the most beneficial management scheme for the current bus fleet can be identified. Optimal bus fleet management (BFM) models based on the RLABC analysis for the operator and the government are developed. Then a government subsidy plan is produced to achieve win–win solutions, which will offer efficient and flexible management schemes. To illustrate the approach, the largest bus company in Hong Kong, which carries more than 23% of the total trips in Hong Kong, is taken as a case study example. Instead of adopting a fixed retirement plan, such as replacing buses at the age of 17 as is currently practised, the proposed method develops an optimal BFM scheme that progressively phases out buses or retrofits them. This study produces promising results to demonstrate the large benefit of this approach for optimal bus fleet management.     

航海院校学生资助体系运行效用的研究

本文以问卷调查法研究航海院校学生资助体系运行效用，结果表明的师生的满意度较高，该体系较好地实现了奖优助困教育公平的目的．但是，还要加强贫困生的鉴定工作和后续的监督管理．     

Promoting public bike-sharing: A lesson from the unsuccessful Pronto system

In 2014, Seattle implemented its own bike-sharing system, Pronto. However, the system ultimately ceased operation three years later on March 17th, 2017. To learn from this failure, this paper seeks to understand factors that encourage, or discourage, bike-sharing trip generation and attraction at the station level. This paper investigates the effects of land use, roadway design, elevation, bus trips, weather, and temporal factors on three-hour long bike pickups and returns at each docking station. To address temporal autocorrelations and the nonlinear seasonality, the paper implements a generalized additive mixed model (GAMM) that incorporates the joint effects of a time metric and time-varying variables. The paper estimates models on total counts of pickups and returns, as well as pickups categorized by user types and by location. The results clarify that effects of hilly terrain and the rainy weather, two commonly perceived contributors to the failure. Additionally, results suggest that users in the University District, presumably mostly university students, tend to use shared bikes in neighborhoods with a higher household density and a higher percentage of residential land use, and make bike-sharing trips regardless workdays or non-workdays. The paper also contributes to the discussion on the relationship between public transportation service and bike-sharing. In general, users tend to use bike-sharing more at stations that have more scheduled bus trips nearby. However, some bike-sharing users may shift to bus services during peak hours and rainy weather. Several strategies are proposed accordingly to increase bike ridership in the future.     

The generators of paratransit trips by persons with disabilities

Identifying the generators of paratransit trips by persons with disabilities is important to comprehend the current demand patterns and forecast future demand. Only a handful of studies have been conducted so far to identify the generators of paratransit trips and most focused on the home end of the trips. Given some of the inconsistencies in past studies and the scarcity of studies on the generators of trips away from home, this study attempts to identify the generators of paratransit trips beginning and ending at clients’ homes and away from home. It uses an extremely large dataset consisting of 1.91 million trips made by NJ TRANSIT’s Access Link clients, socioeconomic data from the American Community Survey, employment data from the Longitudinal Employer-Household Dynamics, and establishment data from Dun and Bradstreet. The analytical methods include an ordinary least squares model (OLS) and several spatial generalized linear mixed models (GLMM) to identify the characteristics of census block groups associated with Access Link trip generation at home and away from home, Geographic Information System (GIS) analysis to identify the types of establishments located in the immediate vicinity of drop-offs, and a multinomial logit model (MNL) to examine the relationship between the characteristics of the establishments in the vicinity of drop-offs and the characteristics of the dropped-off clients. Together, the various analyses provide useful insights about paratransit trip generators at the macro and micro levels. Some implications of the findings are discussed.     

基于硬化泥膜的填舱换刀技术研究

为了解决砂土地层盾构刀盘换刀作业面易涌水、涌砂进而导致作业面失稳坍塌问题,采用水泥砂浆和膨润土浆液组成的混合浆液在土舱压力作用下,通过刀盘开口向砂土地层渗透,经固化后在原有稳定泥膜的基础上形成新型混合泥膜,在利用风镐清除土舱内硬化混合浆液的同时,保留刀盘前段形成的混合泥膜,即可进行盾构刀盘换刀作业。通过在广州某地铁盾构施工项目中的应用,表明本施工技术能为砂土地层盾构换刀提供高效且安全的解决方案。     

A data model applied to the knowledge-based ICAS

Image-guided computer aided surgery system (ICAS) contributes to safeness and success of surgery operations by means of displaying anatomical structures and showing correlative information to surgeons in the process of operation. Based on analysis of requirements for ICAS, a new concept of clinical knowledge-based ICAS was proposed. Designing a reasonable data structure model is essential for realizing this new concept. The traditional data structure is limited in expressing and reusing the clinical knowledge such as locating an anatomical object, topological relations of anatomical objects and correlative clinical attributes. A data structure model called mixed adjacency lists by octree-path-chain (MALOC) was outlined, which can combine patient's images with clinical knowledge, as well as efficiently locate the instrument and search the objects' information. The efficiency of data structures was analyzed and experimental results were given in comparison to other traditional data structures. The result of the nasal surgery experiment proves that MALOC is a proper model for clinical knowledge-based ICAS that has advantages in not only locating the operative instrument precisely but also proving surgeons with real-time operation-correlative information. It is shown that the clinical knowledge-based ICAS with MALOC model has advantages in terms of safety and success of surgical operations, and help in accurately locating the operative instrument and providing operation-correlative knowledge and information to surgeons in the process of operations.     

“船舶—堆场—列车”混堆堆场箱位分配模型

集装箱海铁联运港口堆场作业箱型复杂,为了提高港口作业能力和效率,基于进口、出口箱的混合堆存方式,对"船舶-堆场-列车"作业堆场箱位分配问题进行研究."船舶-堆场-列车"作业堆场负责堆存通过船舶、列车及外集卡进出港口的集装箱.本文在待分配箱的作业时间及箱区已知的前提下,以集装箱堆存产生的压箱数最小为目标,建立"船舶-堆场-列车"作业混堆堆场箱位分配模型,根据模型特点设计了启发式算法进行求解,并进行算例分析.结果表明,所建模型和求解算法能够有效减少堆场的压箱数,满足箱型堆存要求,提高港口作业效率.     

船用低速柴油机曲轴轴向振动研究

以船用大功率低速柴油机柔性体曲轴为对象,在考虑气体力、运动部件惯性力、扭纵耦合效应等因素的情况下,建立曲轴、连杆、活塞的刚柔混合动力学模型。通过数值仿真,分别对连杆推力、连杆法向力和切向力对曲轴轴向振动的影响进行分析。分析结果表明：法向力是曲轴轴向振动的直接激励源,切向力是曲轴轴向振动的间接激励源-切向力引起曲轴扭振,进而引起曲轴纵振;同时法向力和切向力对曲轴轴向振动的影响非常相近;而连杆推力(法向力和切向力合力)引起的曲轴轴向振动是扭纵耦合振动的结果,并非两种分力作用结果的简单叠加。     

型钢水泥土搅拌桩在上海邯郸路地道工程中的应用

简述型钢水泥土搅拌桩的基本原理和特点,结合上海市中环线邯郸路地道工程实际,着重介绍型钢水泥土搅拌桩的设计技术参数及搅拌桩的钻孔、注浆、水泥土搅拌与型钢的插放、拔除等施工关键技术,对同类工程有借鉴意义。