Effects of stack array orientation on fuel cell efficiency for auxiliary power unit applications

The commercial fuel cell products currently appearing on the market are self-contained fuel cell engines. These engines can be used for many applications that are presently dominated by internal combustion engines or batteries. Vehicle mounted fuel cell auxiliary power units have been attracting attention lately. Additionally, there is a market based incentive to use multiple small fuel cell arrays in place of a single large fuel cell for some applications. Typically, fuel cells are designed to operate as stand-alone units. This paper investigates the ability of small commercial stacks to operate in common array arrangements. Although an individual Nexa is able to produce 1500 W, Dual Nexas do not maintain that capability while in array configurations. With an overall load share ratio of 1.02:1 the series array reliably produced 2900 W of power, while with an overall load share ratio of 1.09:1 the parallel array reliably produced only 2800 W of power. This study shows that array orientation affects both system stack net efficiency and individual stack net efficiency. The information gained from this study may be helpful for fuel cell design and integration.     

Analysis of bus rollover protection under legislated standards using LS-DYNA software simulation techniques

A bus rollover is one of the worst vehicle accidents that can occur. Because of the large numbers of passengers, the casualties in a bus rollover are often high and severe. The compliance with rollover safety standards for buses and coaches is mandated by law. This paper presents a comparative analysis of the physical meanings of regulation number 66 of the Economic Commission for Europe (ECE R66) and standard number 220 of the American Federal Motor Vehicle Safety Standards (FMVSS 220). This comparison was carried out using a LS-DYNA finite-element analysis. After performing a comparative analysis following ECE R66 and FMVSS 220 assessments, the investigation further demonstrated the distortion configuration of the vehicle superstructure through the absorbed energy and its distribution over the vehicle and in sections of vehicle superstructure as well as the violation of the passenger compartment under the rollover testing conditions of both ECE R66 and FMVSS 220. Great differences were found between ECE R66 and FMVSS 220 in distortion configuration, reflecting differences in capability and rollover testing conditions. These findings provide a means of evaluating bus superstructure strength and provide guidelines useful in the assessment of regulations applied to the evaluation of bus rollover strength.     

Low cost design of parallel parking assist system based on an ultrasonic sensor

This paper presents a low cost design and implementation of a parallel parking assist system (PPAS) based on ultrasonic sensors. Generally, a PPAS requires several types of sensors, such as an ultrasonic sensor, camera sensor, radar sensor and laser sensor for parking space detection. However, our proposed PPAS only requires two ultrasonic sensors on the front and lateral sides for parking space detection. Moreover, a steering angle sensor and wheel speed sensor installed in the vehicle are used to obtain vehicle position information for localization in ultrasonic range data. The hardware architecture of the PPAS based on an electronic control unit (ECU) module, sensor modules and a human machine interface (HMI) module was proposed. Moreover, the software architecture of the PPAS is based on system initialization, scheduling, recognition and a control algorithm. In particular, a novel sensor algorithm was proposed to minimize the vehicle corner error of the ultrasonic sensor. A prototype of the PPAS based on the proposed architecture was constructed. The experimental results demonstrate that the implemented prototype is robust and successfully performs parking space detection and automatic steering control. Finally, the low cost design and implementation of the PPAS was possible due to the cheap ultrasonic sensors, simple hardware design and low computational complexity of the proposed algorithm.     

Estimation of the adhesion force for a disc brake in a skid control condition

The performance of brakes has become important due to increased train speeds. The brake system of a train must possess a large brake force to stop the train safely within a limited stopping distance. However, an excessive brake force deteriorates the ride comfort and causes the train to skid. Therefore, it is necessary to control the brake force within the adhesion force limit. This paper presents an analytical method to estimate the relationship between the brake and adhesion forces of a disc brake system. This method has been applied to the actual disc braking control system of the Korea High-Speed Train (HSR350x), and the adhesion force is estimated in an actual skid condition.     

Model-based control of an electropneumatic brake system for commercial vehicles

A properly functioning brake system is critical for ensuring the safe operation of any vehicle on roadways. Commercial vehicles such as trucks, tractors-trailers and buses are equipped with an air brake system that uses compressed air as the energy transmitting medium. This paper presents a model-based control scheme for an electropneumatic brake system for use in commercial vehicles. A mathematical model for an electropneumatic brake system was developed and corroborated with experimental data. A control scheme was developed based on this model and was used to regulate the pressure of air inside the brake chamber according to a desired pressure trajectory. This control scheme was implemented on an experimental test bench, and its performance was studied for various values of the controller parameter. The control scheme was tested for various desired pressure trajectories reflecting actual brake operation.     

Inviting travelers to the smorgasbord of sustainable urban transport: evidence from a MaaS field trial

A Mobility-as-a-Service (MaaS) concept, UbiGo, was implemented in Gothenburg, Sweden, and used for a 6-month period by 195 individuals in 83 households. Four participant subgroups were identified: Car shedders, Car accessors, Simplifiers, and Economizers. A qualitative analysis revealed that the subgroups had different reasons to join the service and different expectations of the change that would occur on the basis of the altered preconditions offered by the service. Previous car users reduced their use of private car and increased their use of public transport and active modes. Participants who did not have access to a privately-owned car but thought they needed one discovered that they managed well without. Other participants were reinforced in their existing behaviors but in ways they did not envisage, depending on which goals they had at the outset of the trial. Overall, the participants were also satisfied with the service, as well as with stated changes and non-changes, even if this in some cases meant more planning. Based on the empirical findings it could be argued that a service approach, such as UbiGo, has the potential to reduce the need for private car ownership, and enable people to change their mode choices and travel patterns. The potential relies however on a number of specific features of the service of which flexibility and a need- rather than a mode-based approach are key features.     

Behavior of taxi customers in hailing vacant taxis: a nested logit model for policy analysis

This study models and examines the taxi customers' preferences for hailing vacant taxis on streets. A stated preference survey was conducted to randomly select and interview 1242 taxi customers at taxi stands and pedestrians on streets, who had experiences of taking taxis recently, about their choices under different given hypothetical scenarios. In total, 4968 observations were collected and used for developing the discrete choice models for the analysis. To account for the potential correlations among alternatives, two nested logit models are developed, calibrated, and compared with a standard multinomial logit model in the investigation. The results of likelihood ratio test demonstrate that one of the developed nested logit models is better than the standard multinomial logit model to describe the search behavior of taxi customers. The model results also show that the walking time to and the waiting time at the location for hailing taxis, the extra travel time to the destination because of local circulation for finding a way from the pickup location heading to a passenger's destination, as well as the taxi customers' perceptions for walking to and waiting at taxi stands were found as significant factors to influence their decisions. In addition, the results of market segmentation analysis illustrate the variations in taxi‐search strategies of taxi customers in different districts and regions. Some policy implications on introducing more taxi stands and improving the utilization rates of taxi stands are also discussed. We believe that the proposed models, findings, and discussion are useful for developing micro‐simulation models to evaluate the performance of road traffic networks with taxi services and developing simulation‐based optimization models to answer policy questions related to taxi services. Copyright © 2015 John Wiley & Sons, Ltd.     

Study of Controlling Measures for Existing Railway Deformation Caused by Metro Shield Tunnel Under-passing Construction北大核心CSCD

Based on the background of the first phase project of the R3 line of Jinan Rail Transit, and in view of the metro shield tunnel passing under the existing railway bridge and subgrade, this paper uses Abaqus to establish a numerical model to simulate the deformation of the existing bridge and subgrade of the Jiaoji railway line under the two conditions of non-active reinforcement and reinforcement. The results show that under the condition of no reinforcement, the maximum settlement of the top bridge on the pier is -5.88 mm, and the maximum settlement difference is 5.16 mm, which exceed the deformation control requirements of the 5 mm regarding the bridge pier of the railway with ballast track. The maximum lateral displacement and longitudinal displacement of the pier are 0.28 mm and -3.01 mm, respectively. After the reinforcement measures of the bored piles are adopted, the maximum settlement of the top bridge on the pier is -1.71 mm, and the maximum settlement difference is 1.16 mm, which fully meet the bridge pier deformation control standard. The maximum lateral displacement and longitudinal maximum displacement are -0.245 mm and -2.83 mm, respectively, which meet the requirements of the control standard. The vertical settlement of the railway subgrade is relatively small. The maximum settlement values under the two working conditions are -12.31 mm and -11.97 mm, respectively, which meet the subgrade settlement control requirement of 20 mm. It is proved that the reinforcement effect of the bored pile is good, and the reinforcement scheme is safe and feasible. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Across the waves: a bibliometric analysis of container shipping research since the 1960s

The paper investigates collaborative and semantic patterns that emerged between 1967 and 2013 about the theme of container shipping based on a corpus of 294 articles published in scholarly journals within the fields of transportation, supply chain, economics, geography, regional planning and development, and operations research. An analysis based on the co-occurrence of title words allows identifying dominant sub-themes and their evolution. Main results point to the gradual diversification of container shipping research, from the dominance of economics towards a more trans-disciplinary set of approaches which integrate port-related activities and multimodal networks. Yet, disciplinary specialization remains strong up to nowadays so that container shipping research remains rather fragmented. While co-authorships have increased over time, they remain polarized by few, weakly connected research battalions. Our study suggests that research on container shipping would benefit from more frequent contacts between such communities to foster in-depth cross-disciplinary studies and fundamental cooperation.     

Effective Public Participation is Fundamental for Marine Conservation—Lessons from a Large-Scale MPA

The Representative Areas Program (RAP) was, at the time, the most comprehensive process of community involvement and participatory planning for any environmental issue in Australia. The RAP was a key component of the widely acclaimed rezoning of the Great Barrier Reef Marine Park, and although completed in 2003, many lessons learned are still relevant today. This paper provides an analysis of the comprehensive public participation program that significantly influenced the final planning outcome. It provides insights into a fundamental component of effective marine planning, assessing what worked well and what did not in terms of public engagement. Some aspects of the public participation program were innovative, and some were more effective than others. The outcome was one-third of the Marine Park was declared as highly protected no-take zones in 2004, with the remainder of the park also zoned to provide lower levels of protection. The methods used to engage the public and the 25 lessons discussed in this paper should be of interest for practitioners, policy makers and academics elsewhere aiming for “good practice” approaches to achieve environmental conservation.