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181.
J. K. Park Y. S. Kim O. S. Seo M. G. Lee H. Y. Kim 《International Journal of Automotive Technology》2013,14(5):717-722
There are two types of hot-stamping processes, direct and indirect, depending on the sequence of the heating, forming, and quenching steps and the method used for each step. In this study, an indirect hot-stamping process consisting of forming at room temperature, heating, and water quenching was applied to develop a coupled torsion beam axle. The analysis results indicated that the application of the heat convection coefficient is critical in the simulations and must take into account the temperature and specific location in the model to ensure the accuracy of the heating and quenching analysis. The heat convection coefficients used in the analysis were directly measured at various positions of the tube (e.g., outside, inside, and bending region) using thermocouples, and the final values were determined through correlation between the actual tests and numerical analysis. The experimental and simulated final deformed shape and temperature distribution were in good agreement. 相似文献
182.
Sejoon Kim 《Coastal management》2018,46(3):222-234
The release of captive dolphins (Tursiops aduncus) from South Korean marine parks, which occurred in 2013, 2015, and 2017, is described and evaluated for its usefulness for conservation of coastal ecosystems. The campaign to free the dolphins created a flagship species, uniting the efforts of national government agencies, local government, and NGOs. However, the Korean management agencies framed the release as a species-specific conservation intervention, while the NGOs brought forward welfare-based demands for the curtailment of cetacean captivity. We argue that the release of the Korean dolphins changed the policy climate, to facilitate two major policy changes: revision of anti-whaling regulations to prohibit capture of cetaceans for exhibit, and improvement of regulations for rescue, rehabilitation, and release of stranded marine animals. Tradeoffs between welfare and conservation concerns are described in terms of risk for the management agency, welfare for the animals, and feasibility of a continued commitment to maintain the viability of the dolphin stock in the wild. The release of captive animals to their native range relies on a single-species conservation focus which poses little risk for management agencies but does not guarantee their continued commitment. 相似文献
183.
Sung-Pil Hong Yun-Hong Min Myoung-Ju Park Kyung Min Kim Suk Mun Oh 《Transportation》2016,43(5):749-769
The aim of this study is to estimate both the physical and schedule-based connections of metro passengers from their entry and exit times at the gates and the stations, a data set available from Smart Card transactions in a majority of train networks. By examining the Smart Card data, we will observe a set of transit behaviors of metro passengers, which is manifested by the time intervals that identifies the boarding, transferring, or alighting train at a station. The authenticity of the time intervals is ensured by separating a set of passengers whose trip has a unique connection that is predominantly better by all respects than any alternative connection. Since the connections of such passengers, known as reference passengers, can be readily determined and hence their gate times and stations can be used to derive reliable time intervals. To detect an unknown path of a passenger, the proposed method checks, for each alternative connection, if it admits a sequence of boarding, middle train(s), and alighting trains, whose time intervals are all consistent with the gate times and stations of the passenger, a necessary condition of a true connection. Tested on weekly 32 million trips, the proposed method detected unique connections satisfying the necessary condition, which are, therefore, most likely true physical and schedule-based connections in 92.6 and 83.4 %, respectively, of the cases. 相似文献
184.
In 1994, Townend proposed a method to calculate the relative changes in various wave characteristics and structure-related parameters due to sea level rise for regular waves. The method was extended to irregular waves by Cheon and Suh in 2016. In this study, this method is further extended to include the effect of future change in offshore wave height and the sea level rise. The relative changes in wavelength, refraction coefficient, shoaling coefficient, and wave height in nearshore area are presented as functions of the relative changes in water depth and offshore wave height. The calculated relative changes in wave characteristics are then used to estimate the effect of sea level rise and offshore wave height change on coastal structures by calculating the relative changes in wave run-up height, overtopping discharge, crest freeboard, and armor weight of the structures. The relative changes in wave characteristics and structure-related parameters are all expressed as a function of the relative water depth for various combinations of the relative changes in water depth and offshore wave height. 相似文献
185.
J. Kim 《International Journal of Automotive Technology》2010,11(3):331-337
A methodology is presented for estimating vehicle handling dynamics, which are important to control system design and safety
measures. The methodology, which is based on an extended Kalman filter (EKF), makes it possible to estimate lateral vehicle
states and tire forces on the basis of the results obtained from sinusoidal steering stroke tests that are widely used in
the evaluation of vehicle and tire handling performances. This paper investigates the effect of vehicle-road system models
on the estimation of lateral vehicle dynamics in the EKF. Various vehicle-road system models are considered in this study:
vehicle models (2-DOF, 3-DOF, 4-DOF), tire models (linear, non-linear) and relaxation lengths. Handling tests are performed
with a vehicle equipped with sensors that are widely used by vehicle and tire manufacturers for handling maneuvers. The test
data are then used in the estimation of the EKF and identification of lateral tire model coefficients. The accuracy of the
identified values is validated by comparing the RMS error between experimentally measured states and regenerated states simulated
using the identified coefficients. The results show that the relaxation length of the tire model has a notable impact on the
estimation of lateral vehicle dynamics. 相似文献
186.
Kwang Hyo Jung Kyung Chun Kim Sang Youl Yoon Seong Hun Kwon Ho Hwan Chun Moon Chan Kim 《Journal of Marine Science and Technology》2006,11(4):270-278
Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main
wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure
distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios.
Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow
into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular
to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was
observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex
pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot
proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least
three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of
CFD simulations applied to the waterjet system. 相似文献
187.
J. Kim 《International Journal of Automotive Technology》2016,17(2):319-326
In this paper, the optimal power distribution of the front and rear motors for minimizing energy consumption of a 4WD EV is investigated. An optimal power distribution control is developed based on the mathematical energy consumption model of an EV. The objective function is defined while ignoring time. And, the time effect is applied by considering the objective function for every single driving point which consists of the vehicle driving force and velocity. From the optimization problem, the optimal torque distribution maps of the front and rear motors can be obtained for all vehicle driving force and velocity ranges. These maps can be expressed using a 3-dimensional map. If the vehicle driving force and velocity are determined, the optimal front and rear motor torques can be determined using these maps. These maps can distribute the front and rear motor torques for the entire velocity range. Thus, these maps can perform the optimal power (torque times speed) distribution of the front and rear motors for minimizing the energy consumption of the 4WD EV. The performance of the optimal power distribution is evaluated by comparing the energy consumption to that of simple power distribution control. For obtaining the energy consumption, a vehicle driving simulation is performed. For the simulation, the driving cycle is required, and the NEDC (New European Driving Cycle) is used. From the simulation results, it is found that the energy consumption of simple power distribution is 4.8 % larger than the optimal one. Thus, the optimal power distribution can minimize the 4WD EV energy consumption as the optimization objective function. 相似文献
188.
J. Kim 《International Journal of Automotive Technology》2016,17(6):977-982
This paper describes the design and shifting dynamics of a novel and small-sized transmission which composed of three epicyclic gear modules and a hub shaft in conjunction with several clutches. The proposed epicyclic gear train can be used in a personal mobility vehicle such as an electric utility vehicle and small car, etc. And it is distinguished from others for its small size, light weight, high efficiency, and wide speed range up to 18 gear steps. In this paper, its dynamic behavior is dealt with in order to ensure the automatic and robust shifts according to the shift commands, focused on the shift mechanism design. First the overall structure and operating principles of the transmission are described in detail. Based on the CAD data of whole components, a detailed multibody dynamic model is built using ADAMS software which can analyze the dynamic behavior of a mechanical system. Then numerical simulations are performed during the shift and whole operating period. From the simulation and experiment results, the overall performance and operating principles of the 18 speed epicyclic transmission are discussed and the design of shift device is optimized to ensure the robust shift finally. 相似文献
189.
Transportation - Electric vehicles (EVs) are considered as a driving force behind the automotive industry’s transformation based on eco-friendliness and high energy efficiency. Unlike... 相似文献
190.