Design research of gravity retaining wall based on limit state design methodEI北大核心

Research purposes: Gravity retaining wall limit state design research is based on the design research of retaining structure limit state of open-cut foundation with the lateral earth pressure supported by wall body weight. This paper sums up the research thought of gravity retaining wall and analyzed their main calculation results, which provides reference for the open-cut foundation retaining structure design research of cantilever retaining wall, counterfort retaining wall, groove type retaining wall and so on. Research conclusions: (1) The steps for design research of the gravity retaining wall limit state are to establish a limit state equation, to calculate reliability index and determine the target reliability index, calculate partial coefficient and set up the design expression. (2) The most critical factor influencing gravity retaining wall limit state is comprehensive internal friction angle. (3) There are different function calculations and different design conditions for the gravity retaining wall in the current specification, their underlying reliability index is different, the corresponding partial coefficient should also be different. (4) The research conclusion can be used to guide the design of gravity retaining wall, which provides the reference to the design research of other open-cut foundation retaining structure.     

A network equilibrium approach for modelling activity-travel pattern scheduling problems in multi-modal transit networks with uncertainty

An understanding of the interaction between individuals’ activities and travel choice behaviour plays an important role in long-term transit service planning. In this paper, an activity-based network equilibrium model for scheduling daily activity-travel patterns (DATPs) in multi-modal transit networks under uncertainty is presented. In the proposed model, the DATP choice problem is transformed into a static traffic assignment problem by constructing a new super-network platform. With the use of the new super-network platform, individuals’ activity and travel choices such as time and space coordination, activity location, activity sequence and duration, and route/mode choices, can be simultaneously considered. In order to capture the stochastic characteristics of different activities, activity utilities are assumed in this study to be time-dependent and stochastic in relation to the activity types. A concept of DATP budget utility is proposed for modelling the uncertainty of activity utility. An efficient solution algorithm without prior enumeration of DATPs is developed for solving the DATP scheduling problem in multi-modal transit networks. Numerical examples are used to illustrate the application of the proposed model and the solution algorithm.     

Dynamic system‐optimal traffic assignment for a city using the continuum modeling approach

This paper presents a continuum dynamic traffic assignment model for a city in which the total cost of the traffic system is minimized: the travelers in the system are organized to choose the route to their destinations that minimizes the total cost of the system. Combined with the objective function, which defines the total cost and constraints such as certain physical and boundary conditions, a continuum model can be formulated as an optimization scheme with a feasible region in the function space. To obtain an admissible locally optimal solution to this problem, we first reformulate the optimization in discrete form and then introduce a heuristic method to solve it. This method converges rapidly with attractive computational cost. Numerical examples are used to demonstrate the effectiveness of the method. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal anaysis of an electric water pump for internal combustion engine vehicles

An electric water pump for engine cooling system has an advantage which particularly in the cold start, the use of the electric water pump saves fuel and leads to a corresponding reduction in emissions. However, the electric water pump for internal combustion engine generates much more heat loss than that for hybrid electric vehicle or electric vehicle since it is operated by electric power of high current and low voltage. In this study, the fluid flow and thermal characteristics of the canned type electric water pump with an inverter integrated has been investigated under the effects of heat generation. The analysis conditions such as outdoor air temperature of 125°C, water pump speed of 6000 rpm, coolant temperature of 106°C and coolant flow rate of 120 L/min were used as a standard condition. Therefore, the thermal performance of the canned type electric water pump’s motor and inverter was evaluated by comparison with that of mechanical seal type. In the motor, the temperature reduced by over 10°C, and in the inverter, the amount of temperature decrease equaled to the maximum temperature difference, about 18.7°C. Also, canned type electric water pumps of variable materials were compared for the evaluation of thermal transfer performance for variable thermal conductivity of a can. The motor and inverter were cooled lower to 42°C at motor and about 40°C at inverter for reasonable selection of can’s thermal conductivity.     

Fatigue life estimation of injection mold core using simulation-based approach

The purpose of this study is to present a simulation-based approach capable of predicting the fatigue life of a mold core with the help of CAE technology based on injection molding simulation, core stress analysis and fatigue life prediction. Injection molding simulation is performed in order to obtain the non-uniform pressure acting on a mold core due to the polymer melt flow during injection molding process. Subsequently, the melt pressure profile is used as loading condition for core stress analysis via one-way coupling technique. The lifetime of a mold core is then predicted by fatigue analysis with stress-life approach. For verification of simulation-based approach to the fatigue life prediction, tests were also performed.     

Impact of SME blended fuel combustion on soot morphological characteristics in a diesel engine

The soot morphological study and NOx emissions of soybean oil methyl ester (SME) in a passenger diesel vehicle were investigated experimentally. The soot morphological characteristics were conducted at various injection pressures, engine speeds and engine loads. Soot sampling and image processing analysis with a scanning electron microscope (SEM) were used to investigate the influence on particulate morphologies. The dimensions of average primary particles and the size of the radius of gyration were gradually decreased as injection pressures increased at all operating engine conditions. The average radius of gyration was increased with increasing engine load, while the average primary particle size decreased. NOx emissions were gradually increased with the increasing injection pressure at all operating engine conditions.     

Highly reliable driving workload analysis using driver electroencephalogram (EEG) activities during driving

Traffic accidents are caused by various factors, which can be classified into human factors, vehicle factors and environmental factors. Recently, human factors have been drawing particular attention as efforts are being made to enhance the safety performance of vehicles and improve road conditions. Driving distraction caused by an increased driving workload is a representative human factor. Various studies in the past have attempted to quantify the driving workload by using EEG activities. However, they have failed to consider vibration properties generated from vehicle engines. A number of noise signals were included in brainwave signal processing, which resulted in a failure to obtain reliable outcomes. Thus, this study suggests driver EEG activities free of vehicle engine secondary vibration in order to develop a method that analyzes the driving workload with high statistical reliability. By using the analytical method developed in this study, standard values of driving workload for straight and left-turn driving that has statistical significance could be calculated. The analytical method for driving workload created by this study can be applied to HVI and road design.     

Indicators for Evaluating the Impact of Artificial Islands on the Barcelona Coast

Artificial islands have been constructed next to large cities due to the need for extra space in highly populated areas. These emerged structures have been used by many countries as platforms for developing infrastructure (airports, harbors, highways, etc.), rebuilding ecological areas, and creating new spaces for tourism or residential areas. In this study, two state-of-the-art numerical models for wave propagation and nearshore circulation are used to simulate the effects of an emerged artificial island on the Barcelona coast. Several sea indicators (wave height, intensity and direction of currents, and mean water level) are analyzed to assess the changes likely to be induced by an artificial island. Three different situations are studied and the indicators are compared across the different tests to obtain information that can be used in the planning process of these structures. In two-meter wave conditions, the tests show that wave height is generally reduced in the sheltered area, which leads to improved safety for beach users (bathing is prohibited when wave height exceeds the two-meter threshold). However, the numerical models also reveal that velocities in the sheltered area usually decrease, which must be controlled to prevent stagnation in the bathing area.