Hub location with flow economies of scale

A characteristic feature of hub and spoke networks is the bundling of flows on the interhub links. This agglomeration of flows leads to reduced travel costs across the interhub links. Current models of hub location do not adequately model the scale economies of flow that accrue due to the agglomeration of flows. This paper shows that current hub location models, by assuming flow-independent costs, not only miscalculate total network cost, but may also erroneously select optimal hub locations and allocations. The model presented in this paper more explicitly models the scale economies that are generated on the interhub links and in doing so provides a more reliable model representation of the reality of hub and spoke networks.     

柴油机曲轴有限元计算与台架试验数据对比分析

目前，国内柴油机行业普遍使用的曲轴弯曲疲劳强度试验台架，均采用音叉共振板结构。该试验台架对于大多数常规结构曲轴的连杆轴颈圆角疲劳强度的测定是比较准确的，但对于有些特殊结构曲轴的试验，却未能取得理想结果。以某曲轴台架试验、台架仿真模型及有限元计算模型数据为基础，分析对比了不同模型数据的差异及产生原因。     

Fuzzy-logic applied to yaw moment control for vehicle stability

In this paper, we propose a new yaw moment control based on fuzzy logic to improve vehicle handling and stability. The advantages of fuzzy methods are their simplicity and their good performance in controlling non-linear systems. The developed controller generates the suitable yaw moment which is obtained from the difference of the brake forces between the front wheels so that the vehicle follows the target values of the yaw rate and the sideslip angle. The simulation results show the effectiveness of the proposed control method when the vehicle is subjected to different cornering steering manoeuvres such as change line and J-turn under different driving conditions (dry road and snow-covered).     

Target priority determination methods by interval-valued intuitionistic fuzzy sets with unknown attribute weights

The paper aims at the problem of multi-targets threat degree being hard to be evaluated accurately in complex air defense battlefield environments. Combined with multi-sensors information fusion and interval-valued intuitionistic fuzzy sets (IVIFS) theories, the target priority determination is studied. The score and accuracy functions of IVIFS are improved with thinking about the hesitating information in order to increase the rationality. Then, the influence factors of target priority and the nonlinear relationship between the influence factors and target priority are analyzed. Next, the algorithms for calculating the factor weights and sensor weights are given. Based on the theory of IVIFS and technique for order preference by similarity to an ideal solution (TOPSIS), two methods of target priority determination based on the IVIFS and TOPSIS are proposed. At last, an application example verifies the effectiveness and flexibility of the proposed algorithms.     

Effect of interference fits on the fatigue lives of bolted composite joints

The effect of interference fits on the fatigue lives of bolted composite joints is investigated by conducting mechanical tests. Static and fatigue tests are carried out on specimens made of carbon-bismaleimide composites joined together as double-lap single-bolt joints. The bolts having interference fits ranging of 0 (neat fit), 0.5%, 0.75% and 1% are performed. The results demonstrate the relationship between fatigue life and different values of interference fits. After the fatigue tests, non-destructive evaluation (NDE) and scanning electron microscope (SEM) are used to observe the damage of the surrender and surface of the hole. The test results show that the interference fitted specimens have improved fatigue life compared to the neat fitted specimen. The NDE and SEM results reveal that the damage degree of interference fitted specimen is weaker than that for the neat fitted one.     

可持续交通——各方观点和长期挑战

从交通研究者和实践者的角度出发,以可持续交通这一概念为中心展开讨论。可持续交通宽泛地反映了可持续发展在交通领域的原则。随着可持续性这一概念的外延逐渐扩大,在它的定义、应用和价值取向上出现了不同观点。着重讨论可持续交通,以及如何理解和运用可持续交通,包括:1)将可持续性或者可持续发展作为一个整体的概念,包括关于可持续性的不同方法和定义之间的冲突;2)对可持续交通以及交通领域对其理解的探索;3)使用指标来实现可持续性的应用。然后识别了通往可持续交通之路的若干挑战,包括缺乏清晰定义、可持续性的固有冲突、可持续发展的跨领域本质、各种工作框架和指标体系、可持续发展的政治因素和交通领域实践中的不同观点。基于在该课题上的研究积累,总结解决这些问题的工作框架,提出因地制宜、注重结果、整体的方法来解决可持续交通中的挑战。     

Influence of vehicle driving parameters on the noise caused by passenger cars in urban traffic

In this work, a sample of vehicles has been instrumented to measure of variables that influence vehicle noise emissions in Madrid. A circuit reproducing a normal travel pattern in large city is traveled by a fleet of vehicle models representing the fleets of cars in a European city. A sample of drivers covers the test track under different traffic conditions. Driving parameters and noise emitted have been recorded in each test and average values have been extracted. These data have been analyzed to define the noise emissions produced by a vehicle in real driving conditions and to identify the noisiest driving behaviors.     

New potential for multimodal connection: exploring the relationship between taxi and transit in New York City (NYC)

Transportation - Taxi trips have been somewhat neglected in transportation mobility and multimodal connection studies. The socio-demographic characteristics of taxi riders are often not fully...     

The Teachable Moments on Marine Mammal Tours: Watching versus Swim-With Tours

With the continuing growth of the tourism industry over recent decades, has come a change in tourist behavior from the traditional stereotypical 3-S tourist (sun, sand, sex) to an increasingly sophisticated and demanding tourist. These “new” tourists like to learn about history, nature, and wildlife, and they expect an educational component on wildlife tours. This study investigated swim-with-dolphin tours in Kaikoura, New Zealand with regard to the educational content and the overall anatomy of these tours, using data from observations on a total of 32 tours during December 2011. The resulting data were then compared with the data from Hrycik and Forestell's study, which investigated the content of questions asked by passengers on whale-watching tours in Stellwagen Bank National Marine Sanctuary. Results of the on-tour observations indicate that the surveyed tours display a structured approach to interpretation, which is customized to the specific tour anatomy of a “swim-with” tour, and varies in some parts significantly from “watch-only” tour interpretation.     

Reliability Modeling and Maintenance Policy Optimization for Deteriorating System Under Random Shock

Performance degradation and random shock are commonly regarded as two dependent competing risks for system failures. One method based on effective service age is proposed to jointly model the cumulative effect of random shock and system degradation, and the reliability model of degradation system under Nonhomogeneous Poisson processes (NHPP) shocks is derived. Under the assumption that preventive maintenance (PM) is imperfective and the corrective maintenance (CM) is minimal repair, one maintenance policy which combines PM and CM is presented. Moreover, the two decision variables, PM interval and the number of PMs before replacement, are determined by a multi-objective maintenance optimization method which simultaneously maximizes the system availability and minimizes the system long-run expect cost rate. Finally, the performance of the proposed maintenance optimization policy is demonstrated via a numerical example.