A disaggregate stochastic freight transport model for Sweden

Transportation - This paper presents estimation results for models of transport chain and shipment size choice, as well as an implementation of the estimated disaggregate models (for two commodity...     

Analyzing the dispersion of cargo vapors around a ship’s superstructure by means of wind tunnel experiments

In a previous study, it was found that cargo tank operations like cleaning and venting, lead to higher cargo vapor concentrations around the ship’s superstructure. Can wind tunnel experiments confirm these findings? Is there an improvement when using higher outlets at high velocities compared to lower outlets with a low outlet velocity? Is there a relation between relative wind speed and measured concentration? These questions were investigated in the Peutz wind tunnel. By using a tracer gas for the wind tunnel experiments, concentration coefficients have been calculated for various settings. The study shows that using high-velocity outlets is an efficient way to keep concentrations as low as possible. The only exception is for relative wind directions from the bow. In this last case using a manhole as ventilation outlet leads to lower concentrations. With increasing wind speeds the building downwash effect resulted in higher concentration coefficients near the main deck. This study confirms our on-board measurements and suggests the lowering of the ventilation inlet of the accommodation, so that the high-velocity outlet can be used safely at all times.     

Welfare effects of road pricing and traffic information under alternative ownership regimes

This paper models strategic interactions between a road supplier, a provider of traffic information, and road users, with stochastic travel times. Using a game-theoretical analysis of suppliers’ pricing strategies, we assess the social welfare effects of traffic information under various ownership regimes. The results show that the distortive welfare effect of monopolistic information pricing appears relatively small. Collusion of the road operator and information provider yields higher social welfare than independent pricing by two firms. The intuition behind this result resembles that behind the welfare effects of double marginalization, but is not exactly the same, as traffic information is not strictly complementary to road use.     

Identification and quantification of link vulnerability in multi-level public transport networks: a passenger perspective

Robust public transport networks are important, since disruptions decrease the public transport accessibility of areas. Despite this importance, the full passenger impacts of public transport network vulnerability have not yet been considered in science and practice. We have developed a methodology to identify the most vulnerable links in the total, multi-level public transport network and to quantify the societal costs of link vulnerability for these identified links. Contrary to traditional single-level network approaches, we consider the integrated, total multi-level PT network in the identification and quantification of link vulnerability, including PT services on other network levels which remain available once a disturbance occurs. We also incorporate both exposure to large, non-recurrent disturbances and the impacts of these disturbances explicitly when identifying and quantifying link vulnerability. This results in complete and realistic insights into the negative accessibility impacts of disturbances. Our methodology is applied to a case study in the Netherlands, using a dataset containing 2.5 years of disturbance information. Our results show that especially crowded links of the light rail/metro network are vulnerable, due to the combination of relatively high disruption exposure and relatively high passenger flows. The proposed methodology allows quantification of robustness benefits of measures, in addition to the costs of these measures. Showing the value of robustness, our work can support and rationalize the decision-making process of public transport operators and authorities regarding the implementation of robustness measures.     

热管--一种高效实用的散热方法

任何电子器件冷却的热电路都是由3个最基本的热阻组成的:结-壳热阻Rj-c;壳-散热器热阻Rc-s和散热器至周围介质的热阻Rs-a.为降低这些热阻的临界值,许多工程师费尽心血.文章讨论采用热管有助于降低热阻Rs-a至最小值.散热器至周围介质的热阻是由传导、对流/辐射和被加热的冷却介质形成的3个热阻组成的.典型的风冷散热器中,空气温升的热阻是通风量的直接函数,对流热阻是散热表面积的函数,传导热阻是散热器材料的热导率和几何尺寸的函数.热管能把传导损耗降至最小值,它允许加大散热表面,而且使给定风速下的流量最大,从而有效降低散热器的3个主热阻.文章讨论了能降低风冷散热器热阻的热管.     

On Control Laws for Vehicle Suspensions Accounting for Input Correlations

Input correlations involving time delays are common in active vehicle suspension system problems. One approach to control law derivation fur such systems is to restrict attention to slate feedback laws in the interests of practicality and it is then of interest to determine the law which is, in some sense, the best. Under assumptions which are common in this area. relating to input, system and cost Function forms, a new derivation of the expression for the cost, accounting for time delays, is given. The use of the expression in numerical procedures for determining effective control gains is discussed and an example for a half car planar vehicle model is described. By comparing results with existing ones which are truly optimal, an estimate is made of the loss of performance which results from the restriction of the control law form in this case. Some generalisation of the results is attempted and they are placed in a contemporary context at the conclusion.     

直流车辆用蓄能器

直流车辆用文中所述的蓄能器能在显著降低功率消耗的同时,又在节能方面迈出了重要一步,而且车辆可在局部无接触导线区运行.样车试验证实了这些设想.     

Georgia Ports Authority： Faster to Market, Better for Business

The Port of Savannah is the fourth largest container port of the ＂five＇global U.S. ports.     

Design analysis and comparison between standard and rotary porting systems for IC engine

Many porting systems for internal combustion engines have been tried and tested over the years, however the basic spring actuated poppet valve system has prevailed over the last century. In the goal to lower engine output parasitic losses, a simple rotary valve porting system design is proposed and analyzed. The proposed design concept takes into consideration and combines all the prominent advantages of many ealier mutlitiple design variations over the past century. The inherent primary advantage of such a rotary porting system is the elimination of reciprocating components, thus lowering vibration, and removal of highly stiff springs which contribute to considerable system power loss. Comparable sized 3-D representations of both systems are constructed in CAD (Computer Aided Design) software in order to run mechanical and fluid simulations to validate the efficiency advantage of a rotary valve porting system. Using Pro/Engineer Mechanism Dynamics module, the minimum torque required to actuate both systems at 2000 rpm and 3000 rpm is determined. Fluid simulations are performed using a commercial software CFDesign V10. Volumetric flow rates are compared during the intake stroke as well as turbulence intensity factors which characterizes a systems ability to properly mix the Air/Fuel mixture and the combustion efficiency. Some possible improvement on the rotary geometry is suggested.     

Dynamic modeling of the electro-mechanical configuration of the Toyota Hybrid System series/parallel power train

The hybridization of the conventional thermal vehicles nowadays constitutes a paramount importance for car manufacturers, facing the challenge of minimizing the consumption of the road transport. Although hybrid power train technologies did not converge towards a single solution, series/parallel power trains with power-split electromechanical transmissions prove to be the most promising hybrid technology. In fact, these power trains show maximum power train overall efficiency and maximum fuel reduction in almost all driving conditions compared to the conventional and other hybrid power trains. This paper addresses the model and design of the electro-mechanical configuration of one of the most effective HEV power trains: case study of the 2nd generation Prius. It presents the simulation work of the overall operation of the Toyota Hybrid System (THS-II) of the Prius, and explores not only its power-split eCVT innovative transmission system but also its overall supervision controller for energy management. The kinematic and dynamic behaviors of the THS-II power train are explained based on the power-split aspect of its transmission through a planetary gear train. Then, the possible regular driving functionalities that result from its eCVT operation and the energy flow within its power train are outlined. A feed-forward dynamic model of the studied power train is next proposed, supervised by a rule-based engineering intuition controller. The energy consumption of the THS-II proposed model has been validated by comparing simulation results to published results on European, American and Japanese regulatory driving cycles.