• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.189-196
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• 2011

Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.137-142
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• 2017

Recently, the reduction of vehicle weight has been increasingly studied, in order to enhance the fuel efficiency of passenger cars. In particular, the seat frame is being studied actively, owing to considerations of driver safety from external impact damage. Therefore, this study focuses on high strength steel sheet (SPFC980)/polymer heterojunction hybrid materials, and their performance in regards to impact energy absorption. The ratio of impact energy absorption was observed to be relatively higher in the SPFC980/polymer hybrid materials under the impact load. This was found by calculating the equivalent flexural rigidity, which is the bending effect, according to the Castigliano theorem. An efficient wire-web structure was investigated through the simulation of different wire-web designs such as triangular, rectangular, octagonal, and hexagonal structures. The hexagonal wire-web structure was shown to have the least impact damage, according to the simulations. This study can be utilized for seat frame design for passengers' safety, owing to efficient impact absorption.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.2
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• pp.39-47
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• 2012

In this paper, we have developed the system of emergency vehicle preemption signal control based on UTIS(Urban Traffic Information System) which have been deployed and operated in the national capital area. It considered the turning direction(through or left turn) of emergency vehicle at the signalized intersection in order to provide the consecutive progression of emergency vehicle and minimize the control delay of passenger cars. we adopted several EVP control modes such as phase insertion and phase adjustment mode. Also, we evaluated the possibility of field implementation via simulation analysis using CORSIM RTE(Run Time Extension) based HILS(Hardware In the Loop Simulation). We expect that the result of this research contribute to providing the right-of-way to emergency vehicle in this country.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.131-138
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• 2012

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.785-791
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• 2000

GDI (Gasoline Direct Injection) engines are considered as one of the candidates for next generation engines of passenger cars, which reduce exhaust emissions and fuel consumption. In GOI engines, a high-pressure gasoline supply system is required to directly inject the fuel to combustion chambers. Because of low lubricity of gasoline fuel, the clearance between a plunger and a barrel in GDI fuel pumps is too wide to achieve smooth hydrodynamic lubrication. Thus, it is difficult to generate high-pressure condition in GDI fuel pump since large amount of leakage flow occurs between the plunger and the barrel In this study, an optimum plunger design is presented to minimize leakage in the aspect of flow control. This paper analyzes leakage flow characteristics in the clearance to improve pumping performance of GDI fuel pumps. Effects of groove in the plunger are studied according to variations of depth and width. Evaluations of pumping performance are determined by the amount of pressure drop in the leakage path assuming a constant leakage flows. Both of turbulence and incompressible models are introduced in CFD (Computational Fluid Dynamics) analysis. Design parameters have been introduced to minimize leakage in limited space, and a methodological study on geometrical optimization has been conducted. As results of CFD analysis in various geometrical cases, optimum groove depths have been found to generate maximum sealing effects on gasoline fuel between the plunger and the barrel. This procedure offers a methodological way of an enhancement of plunger design for high-pressure GDI fuel pumps.

• Journal of Korean Society of Transportation
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• v.32 no.6
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• pp.694-702
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• 2014

Since Greenhouse Gas Inventory & Research Center (GIR) of Korea was founded in 2010, the annual greenhouse gas inventory reports, one of the collections of GIR's major affairs, have been published from 2012. In the reports many items related to greenhouse gas emission quantities are included, but among them uncertainty values are replaced to basic values which IPCC guideline suggests. Even though IPCC guideline suggests the equations of each Tier level in details, the guideline recommends developing nation's own methodology on uncertainty which is closely related to statistical problems such as the estimation of a probability density function or Monte carlo methods. In the road transportation sector the emissions have been calculated by Tier 1 but the uncertainties have not been reported. This study introduce a bootstrap technique and Monte carlo method to estimates annual emission quantity and uncertainty, given activity data and emission factors such as annual traveled distances, fuel efficiencies and emission coefficients.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.195-207
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• 2007

The urban railways connecting between the inner city and suburb of Seoul metropolitan area, has lost the competitiveness against cars because too many stops deteriorated operating speed and passenger's level of service. This paper suggests that an express train should be introduced into the urban railway system in order to sort out such a complication. There are two considerations in the present study. Firstly, train schedule problem should be taken into account. In this regard, a new model for urban railway system was developed by revising the existing models dealing with single line freight railway. Approximate branch and bound algorithm based on conflict group rather than a single conflict was adopted. Consequently, it was found that the time saving in calculating the optimal schedule is the most meaningful contribution of the algorithm. The second consideration is associated with the application of the model. A case study was carried out using the actual operation data from Ansan line. In conclusion, the operation speed of the line can increase considerably with minimal number of new sidings.

• Journal of Environmental Impact Assessment
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• v.15 no.1
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• pp.23-33
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• 2006

The factor of air pollution in a large industrial city is not only manufactories but also, activities related to trucks. Sihwa National Industrial Complex is located in Siheung City; due to the industries, more diverse activities related to trucks occur in Siheung City than other cities. In particular, the new residential area in Siheung City is close to the industrial complex; so, the damage of this residential area is expected that it would be more serious and vulnerable than other areas. The aim of this study is to analyze influence of the air pollution by a truck in Siheung City. ISCST3 Model and Arc View program were used for this study and Siheung City was divided into 1,000 meter by 1,000 meter grid to analyze. Furthermore, this study suggested two reduction controls of air pollution in Siheung City, and analyzed the results from these reduction managements. The results of the present condition showed that residences located in north of Sihwa Industrial Complex are influenced by air pollution material. Furthermore, air pollution by trucks has affected on the residents which is near the road in Siheung City. Therefore, this study suggested two reduction controls by the Traffic System Management. The first alternative plan is setting the truck traffic limitation zone in the road that is located in south of resident areas and many trucks traffic. Next, the second alternative plan is setting freight truck way on the most traffic road to enter the industrial complex. The reduction effect of the first alternative is good on the residential area. And, the second alternate about freight truck way is divided passenger cars into trucks. Therefore, there are increase of average speed and decrease of average concentration, and spatial reduction effects found in wide areas.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.349-355
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• 2010

The purpose of this paper is to provide basic information on how to make better policies that improves efficiencies and to derive policy directions using DEA (data envelopment analysis) model. Through this paper, we can identify whether or not the railroad service has an excellent performance, if there are any structural problems, in which sector it is experiencing a degree of inefficiency, and, therefore, how to set up a realistic target to improve efficiency of railroad transportation. According to the result, we need to introduce a better resource efficient economic strategy to reduce the rail line extension and the number of passenger cars for better efficiency from a public interest perspective, while to widen headways and/or reduce the rail line extension from an economic point of view.

• Archives of design research
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• v.17 no.3
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• pp.449-460
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• 2004

Various types of the sports utility vehicles become more popular in these days. This phenomenon says the increasing demand of performance oriented vehicles for the various life style It is changing now the rather the simple needs of passenger cars of the past. This popularity is due to not only for the increased leisure time which resulted from the five day working labor policy, but also the development of automotive technology. In addition to a large variety of vehicle and enhanced performance is another reason either. There have been many kind of multi-functional vehicles from the early days of the automotive history, and most of them have been evolved from the $\ulcorner$Jeep$\lrcorner$ which were developed by American makers. And various type of orthodox and crossover vehicles that is combined to many functional aspects for a transportation has been revealed so far. Usually the ambi-tendency has been revealed, in which the crossover vehicle has been become compact, on the other hand the orthodox type of 4-wheel drive vehicles has been become larger for being heavy duty vehicles. And this would be expand widely to more vehicles and brands in the future.