Reverse time-restricted shortest paths: Application to air traffic management

In this paper, we consider a particular class of network flow problems that seeks a shortest path, if it exists, between a source node s and a destination node d in a connected digraph, such that we arrive at node d at a specified time τ while leaving node s no earlier than a lower-bounding time LB, and where the availability of each network link is time-dependent in the sense that it can be traversed only during specified intervals of time. We refer to this problem as the reverse time-restricted shortest path problem (RTSP), and it arises, for example, in the context of generating flight plans within air traffic management approaches under severe convective weather conditions. We show that this problem is NP-hard in general, but is polynomially solvable under a special regularity condition. A pseudo-polynomial time dynamic programming algorithm is developed to solve Problem RTSP, along with an effective heap implementation strategy. Computational results using real flight generation test cases as well as random simulated problems are presented.     

A dichotomous choice survey for quantifying option and non-use values of bus services in Korea

The total economic value for a transportation service consists of use, option, and non-use value. The use benefit is based on a traveler’s willingness to pay for usual consumption of the service. The optional value, on the other hand, is related to the possible use of the service for trips not yet anticipated or currently accommodated by other travel modes. The non-use value, however, is derived from the intrinsic merit of the service, even though a trip-maker never actually or potentially depends on the mode. A closed-ended contingent valuation method is considered for the quantification of the option and non-use values. A survey of single- and double-bounded dichotomous choices is conducted with a case study of South Korean bus operations. A logistic regression model and a survival analysis for the single- and double-bounded approaches, respectively, are applied. The estimation result is examined according to the statistical property required and the behavioral validity expected. In particular, three issues from the output are discussed. First, the results help to show the preferable framework between single- and double-bounded surveys for addressing an individual’s option and non-use values. Second, the differences in the absolute values of option and non-use values are compared. Thirdly, the relationship between trip-makers’ willingness to pay and the level of service of their primary travel modes are investigated. In conclusion, the summary of research and the possibilities for future studies are given.     

Exploring Public Knowledge,Attitudes, and Perceptions of the Marianas Trench Marine National Monument

With the increase in development of large marine protected areas (LMPAs) worldwide, there have been calls from social scientists to gather better empirical information about the human dimensions of LMPAs. Of the social research done on LMPAs to date, most has focused on the perceptions of stakeholders closely connected to their implementation, and little research has explored the general public's response. This paper presents the results of a phone survey conducted in the US territories of Guam and the Commonwealth of the Northern Mariana Islands to assess residents' knowledge, attitudes, and perceptions of the Marianas Trench Marine National Monument—a LMPA designated offshore in 2009. The survey was administered in 2012 to 500 randomly-selected residents from each territory. Findings suggest: (1) public awareness of the Monument prior to the survey was low; (2) residents generally supported designation of the Monument; (3) most residents did not believe that the Monument would affect them or their community; and (4) knowledge and perceptions of the Monument varied between fishing and non-fishing households. This research illustrates that awareness and views differ between stakeholders and those of the general public, which should be used to inform social research on LMPAs and outreach for LMPA managers.     

Influence of Short Time-Scale Water-Column Temperature Fluctuations on Broadband Signal Angular Beam Spreading

Temporal fluctuations in vertical thermocline structure and depth span (on a time scale of 30 to 40 min) are shown to affect the arrival angle, and focusing of measured broadband (22–28 kHz) non-surface-interacting acoustic signals at a depth of ~100 m. Measurements were taken in the Pacific Missile Range Facility near Kauai island, Hawaii, for a source-receiver range of 1.0 km. The arrival time and angular spread of acoustic beams are obtained for measured signals using a plane wave beamformer with a-prior gaussian weighting. The weighting process reduces ambiguity in angular measurements due to spatial aliasing from a vertical array with element spacing d much greater than half the acoustic wavelength \( \left(\frac{\lambda_{\mathrm{a}}}{2}\right) \) of the highest frequency in the broadband signal. Over two full periods of thermocline oscillation, 2 times of high and 2 times of low isotherm depth are selected to show fluctuations in angular beam spreading, focusing, and the robustness of the weighted beamformer routine. To benchmark the performance of the weighted beamformer, a two-dimensional (2D) Parabolic Equation (PE) model calculates the angular signal spread and focusing using parameters to satisfy spatial sampling requirements for broadband beamforming. In the absence of spatial aliasing, beamforming the output of the 2D PE can be conducted without weighting. Comparison of measured and modeled results shows less than a degree of difference in the angular beam spread of direct, bottom reflected, and refracted paths. It is shown that a vertical array with \( d\gg \left(\frac{\lambda_{\mathrm{a}}}{2}\right) \) and gaussian weighting can resolve changes in angular spread and beam focusing as a function of vertical isotherm displacement.     

Express guideway transit: A case for further development in transit automation

Safe and reliable coupling and decoupling of cars from a moving train is feasible with further developments in linear motor propulsion and control of transit vehicles. This allows the last car of a train to decouple and stop at a station for a relative long dwell time, before it accelerates and is coupled to a following train. Controlled doors in front and rear of the transit vehicle permit passengers to walk through the train to the car which stops at their destination. A proposed transit system using these features is described and compared to Bombardier's Advanced Rapid Transit. Potential advantages are high schedule speed, uncrowded trains, smaller and more stations, low energy requirements and a smaller vehicle fleet.     

Measuring the safety impact of road infrastructure systems on driver behavior: Vehicle instrumentation and real world driving experiment

Featured in this pilot experimental study is the construction and design of an instrumented vehicle that is able to capture vehicle trajectory data with an extremely high level of accuracy and time resolution. Once constructed and properly instrumented, the various data collection systems were integrated with one another and a driving experiment was conducted on northern Virginia roadways with 18 participants taking part in the study. Trajectory data were collected for each of the drivers as they traversed a predefined loop of four roadway segments with varying numbers of lanes and varying shoulder widths. Data collected from the experiment were then used to calibrate the parameters of the prospect theory car-following model through a genetic algorithm calibration procedure. Once all model parameters were successfully calibrated, significance testing was carried out to determine the impacts that the varying roadway infrastructure had on driving behavior. Results indicated that there were significant changes in behavior when comparing one lane roadways to their two lane counterparts—specifically in cases where the roadway featured a wide shoulder. Additional testing was conducted to ensure that there was no variation based on gender, as nine study participants were female and nine were male. The successfulness of this first study conducted with the newly constructed instrumented vehicle creates the opportunity for a variety of additional studies to be conducted in the future.     

大都会游侠——斯堪尼亚香港双层巴士

由斯堪尼亚和香港的巴士运营商九龙巴士联合开发的两辆斯堪尼亚新款三轴双层巴士已抵达香港,以满足香港这座国际大都会的的特殊交通状况。斯堪尼亚的模块化生产系统,及EGR废气再循环技术的使用,能在不进行后处理或采用催化剂的前提下改进废气排放控制。     

An analysis of elevator operation in moderate height buildings—II: Multiple elevators

Deterministic approximations for elevator trip times are applied to a system of m elevators. Comparisons of in-system time of passengers are made for elevators which are (a) physically separated, (b) ideally controlled, (c) zoned, or (d) uncontrolled. A more detailed study is then made of in-system passenger time for a pair of elevators subject to a minimum headway control at the lobby. Comparisons are made between rather primitive analytic estimates and simulation results.The main conclusion is that control of headways so as to prevent pairing is of doubtful value. At low traffic it is usually better to use no control; for higher traffic it is better to zone the building and have each elevator serve separate floors.     

Assessing the Utility of Beach Ecolabels for Use by Local Management

Ecolabels for beaches have been around since 1985 and have grown rapidly over the past decade. However, effects from ecolabels on beach ecology and local coastal cultures are unknown. This study reviews the literature on tourism ecolabels and environmental certification for beaches, analyzes the criteria of the most prominent beach ecolabel, and identifies considerations and proposes recommendations for local management that address sandy beach ecology and local cultures. The Blue Flag ecolabel is evaluated for how well the program criteria balance tourism, the processes of sandy beach ecology, and accommodate for local cultural values. This Blue Flag's criteria leave out protecting sandy beach ecology and fail to incorporate local community values in program design. The results of the study include three areas that beach managers need to consider for better understanding the utility of beach ecolabel programs: opportunity costs of participation and consequences of losing certification; evaluate investment in multiple certifications; and identify potential changes from the implementation of ecolabels.     

关于中国游艇制造

“事实最具说服力但统计数字与事实有一定出入．”举一个匿名作者说过的一句话。目前中国的游艇业不存在统计数字的短缺，中国已跻身80英尺以上游艇建造国家前10名。2006年休闲游艇出口额为1—8亿美元．国内游艇市场价值为3000万美元．比2005年增长了40％（资料来源：Marine Dragon咨询公司）。这些数字显示．中国已经确立了作为海外游艇建造商的一个低成本生产基地的地位。