The evolution of U.S. rail freight pricing in the post-deregulation era: revenues versus marginal costs for five commodity types

There have now been over three decades of experience with rate-making freedom for all modes of intercity freight transport in the United States. Most evidence suggests that regulatory change has been beneficial for the rail industry and its users. Despite evidence of positive impacts of regulatory reform of U.S. freight transport, there is limited evidence related to long-term pricing trends by commodity in the deregulated era. Moreover, U.S. shipper groups have called for increased regulation of U.S. railroads, citing increased rates and profits, and monopoly pricing to “captive shippers.” This study estimates U.S. railroad revenue-marginal cost ratios for seven different commodities between 1986 and 2008. Interestingly, we find no significant increase in revenue-cost margins for commodities thought to be “most captive” (coal and chemicals), while finding large increases for some commodities thought to be “non-captive.” These results may provide insight into the impacts of regulatory reform in other countries, where there are similar concerns of equitable pricing and financial viability. They suggest that a move toward a more market-based pricing system can enhance railroad viability without harming those with fewer transport options.     

法兰连接螺栓疲劳分析方法的探讨

以华电重工在澳大利亚昆士兰州的一个项目中的一台桥式刮板取料机料耙连接为实例,详细讨论法兰连接中螺栓的疲劳计算的各种算法.通过比较澳洲钢结构规范AS4100中对螺栓疲劳等级的界定和我国机械设计手册中对螺栓疲劳的计算,得到清晰的螺栓疲劳计算思路,并了解两种规范中螺栓疲劳计算的差异,以便在实际设计分析中能快速准确地确定相关参数.     

Influence of pilot injection on combustion characteristics and emissions in a DI diesel engine fueled with diesel and DME

This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy.     

Active approach to Electronic Stability Control for front-wheel drive in-wheel motor electric vehicles

Recently, motion control for electric vehicles has gradually gained respect in automotive society due to increased strictness of vehicle safety evaluation over time. Electronic Stability Control (ESC) is the kernel technology, which refers to two-dimensional motion stabilization. Many investigations have demonstrated that Direct Yaw-moment Control (DYC) is an effective and practical way to carry out the ESC of electric vehicles. However, based on the drive train of conventional steering, conventional approaches are using braking to achieve the DYC. This paper proposes a new ESC based on the construction of DYC. The presented approach is based on a core of individual traction control measures for propulsion wheels. This approach not only constrain the longitudinal slip, but also ensure the performance and the effectiveness of two-dimensional motion control. With a proper control, the vehicle can be maintained to a nearly neutral-steering under high speed turning. Hence, the vehicle’s dynamic stability can be enhanced under aggressive driving by yaw-moment control. Evaluation of the entire control system is performed by well-acknowledged software, which demonstrates that the vehicle’s dynamic stability can be enhanced under aggressive driving by the proposed approach.     

Combined power management/design optimization for a fuel cell/battery plug-in hybrid electric vehicle using multi-objective particle swarm optimization

In this paper, the combined power management/design optimization problem is investigated for a fuel cell/Liion battery PHEV. Formulated as a constrained multi-objective optimization problem (MOP), the combined optimization problem simultaneously minimizes the vehicle cost and fuel consumption subject to the vehicle performance requirements. With an emphasis on developing a generic optimization algorithm to find the Pareto front for the synthesized MOP, the Pareto based multi-objective particle swarm optimization (PMOPSO) algorithm is developed, which solely depends on the concept of Pareto dominance. Three approaches are introduced to the PMOPSO method to address the constrained MOP. They are: (i) by incorporating system constraints in the original objective functions, the constrained MOP is transformed to an unconstrained MOP; (ii) to avoid being trapped in local minima, a disturbance operator with a decaying mutation possibility is introduced; (iii) to generate a sparsely distributed Pareto front, the concept of crowding distance is utilized to determine the global guidance for the particles. Finally, under the Matlab/Simulink software environment, simulation results are presented to demonstrate the effectiveness of the PMOPSO in the derivation of the true Pareto front.     

Prediction procedure for wear distribution of transient rolling tire

As a research method, finite element analysis (FEA) with ABAQUS can help researchers to study throughout the whole process of abnormal tire wear. For precise tread wear simulation, this paper introduces a tire finite element model building method. Then, the model is verified by comparing its simulation results with experiment data. Based on the verified model, tire high-speed rolling procedure is presented by combining steady-state transport analysis and dynamic analysis. To predict the wear distribution, micro tread wear calculation method is described. Finally, the wear prediction procedure of tread mesh evolving is introduced and tire polygonal wear pattern is simulated by this procedure.     

Automotive windshield — pedestrian head impact: Energy absorption capability of interlayer material

During accident, the interlayer of windshield plays an important role in the crash safety of automotive and protection of pedestrian or passenger. The understanding of its energy absorption capability is of fundamental importance. Conventional interlayer material of automotive windshield is made by Polyvinyl butyral (PVB). Recently, a new candidate of high-performance nanoporous energy absorption system (NEAS) has been suggested as a candidate for crashworthiness. For the model problem of pedestrian head impact with windshield, we compare the energy absorption capabilities of PVB and NEAS interlayers, in terms of the contact force, acceleration, velocity, head injury criteria, and energy absorption ratio, among which results obtained from PVB interlayers are validated by literature references. The impact speed is obtained from virtual test field in PC-CRASH, and the impact simulations are carried out using explicit finite element simulations. Both the accident speed and interlayer thickness are varied to explore their effects. The explicit relationships established among the energy absorption capabilities, impact speed, and interlayer material/thickness, are useful for safety evaluation as well as automotive design. It is shown that the NEAS interlayer may absorb more energy than PVB interlayer and it may be a competitive candidate for windshield interlayer.     

Optimization of drying performance considering driving conditions

Compressed air can be used as an energy source for brake systems in medium-heavy and heavy-duty commercial vehicles. The moisture in compressed air, which is due to high temperature and humidity, can be eliminated by using an air dryer. In this paper, drying performance data for a cartridge were obtained and used to develop a drying performance program, to predict the moisture and relative humidity in the air tanks of vehicles. The on-load time, off-load time, air flow, duty cycle, humidity and dew point temperature were calculated according to air consumption. The validity of the program was verified, and it was shown to be able to predict humidity changes in the air tank. The air tank capacity was increased from 100 to 130 to reduce the duty cycle. Therefore, the regeneration rate decreased from 18% to 15%, but the dew point depression temperature (ΔT) remained above 30°C. The duty cycle decreased from 50% to 43%, and the total operation time and power consumption of the air compressor were reduced. In conclusion, fuel savings were obtained by changing the parameters to optimize the system.     

Development of a path planning system using mean shift algorithm for driver assistance

The longitudinal and lateral vehicle control techniques have been widely used in several active driver assistance systems. The adaptive cruise control, lane keeping assistant control, vehicle platooning and stop-and-go control are typical examples of the most important applications. In this study, a novel path planning method is proposed considering the driving environment such as road shape, ego vehicle and surrounding vehicles’ movement. The relative distance and velocity between the ego vehicle and surrounding vehicles are identified with respect to the predicted lane shape in front of the ego vehicle. Based on the identified information, the road shape and surrounding vehicles are mapped into the intensity image and the desired vector for the ego vehicle’s movement is determined by the maximum intensity density tracing method. The desired vehicle path is followed by the acceleration/deceleration control and the steering assist control, respectively. In order to evaluate the performance of the proposed system, simulations are conducted and compared with ACC systems.