• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.203-209
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• 2010

In this study, the fatigue characteristics and life of a woven glass fabric/epoxy laminate composite applied to railway vehicles was evaluated. The fatigue test was conducted using a tension-tension load with a stress ratio R of 0.1 and frequency of 5 Hz. Two types of woven glass fabric/epoxy laminate composite was used in the fatigue test: with and without carbon/epoxy ply reinforcement. In addition, the fatigue life of the woven glass fabric/epoxy laminate composite was compared with that of aluminum 6005, which is used in the car body and underframe structures of railway vehicles. The test results showed that the failure strength and life of the woven glass fabric/epoxy laminate composite reinforced with three carbon/epoxy plies had a remarkable improvement compared with that of the bare specimen without reinforcement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.813-820
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• 2010

The vertical roller mill is important for machine grinding and mixing various crude materials in the process of producing Portland cement. A vertical roller mill is subjected to cyclic bending stress because of the roller load. Because of the cyclic bending stress, only $4{\times}10^6-8{\times}10^6$ cycles are achieved instead of $4{\times}10^7$ cycles. The stress also causes fractures at the edge of grinding path of the outer roller. The expenses incurred in repairing the grinding path amounts to 30% of the total maintenance cost. Therefore, it is desirable to redesign the vertical roller mill in order to reduce the expenses incurred in repairing the roller. In this study, artificial neural networks (ANNs) were applied in order to solve the multiobjective optimization problem for vertical roller mills by using the function approximation ability of ANNs. To learn and generalize ANNs, the maximum and minimum stresses were estimated from the results of the finite-element analysis of a vertical roller mill. Thus, ANNs could be applied to solve the multiobjective optimization problem.

• 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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.7-12
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• 2007

Previously study on structural design of the main wing of the twenty-seat class WIG (Wing in Ground Effect) craft. In the final design, three spars construction was selected for safety in the critical flight load, and the Carbon-Epoxy material was selected for lightness and structural stability. In this study, the forced vibration analysis was performed on the composite main wing structure of the twenty-seat class WIG craft with two-stroke pusher type reciprocating engine. The vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the Y-mode (lateral mode), the Z-mode (vertical mode) and the $M_{xyz}$-mode (twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the X-mode (longitudinal mode) with the oscillating propeller thrust which occurs in operation.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.5
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• pp.447-452
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• 2015

A hybrid power system was developed for agricultural machines with a 20kW output capacity, and it was attached to a multi-purpose cultivator to improve the performance of the cultivator. The hybrid system combined heterogeneous sources: an internal-combustion engine and an electric power motor. In addition, a power splitter was developed to simplify the power transmission structure. The cultivator using a hybrid system was designed to have increased fuel efficiency and output power and reduced exhaust gas emissions, while maintaining the functions of existing cultivators. The fuel consumption for driving the cultivator in the hybrid engine vehicle (HEV) mode was 341g/kWh, which was 36% less than the consumption in the engine (ENG) mode for the same load. The maximum power take off output of the hybrid power system was 12.7kW, which was 38% more than the output of the internal-combustion engine. In the HEV mode, harmful exhaust gas emissions were reduced; i.e., CO emissions were reduced by 36~41% and NOx emissions were reduced by 27~51% compared to the corresponding emissions in the ENG mode. The hybrid power system improved the fuel efficiency and reduced exhaust gas emissions in agricultural machinery. The hybrid system's lower exhaust gas emissions have considerable advantages in closed work environments such as crop production facilities. Therefore, agricultural machinery with less exhaust gas emissions should be commercialized.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3475-3481
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• 2014

This paper describes how primary contaminants in ambient air affect the performance of the cathode in fuel cell electric vehicle applications. The effect of four atmospheric pollutants ($SO_2$, $NH_3$, $NO_2$, and CO) on cathode performance was investigated by air impurity injection and recovery test under load. Electrochemical analysis via polarization and electrochemical impedance spectroscopy was performed for various concentrations of contaminants during the impurity test in order to determine the origins of performance decay. The variation in cell voltage derived empirically in this study and data reported in the literature were normalized and juxtaposed to elucidate the relationship between impurity concentration and performance. Mechanisms of cathode degradation by air impurities were discussed in light of the findings.

• Journal of Applied Reliability
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• v.8 no.3
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• pp.135-144
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• 2008

The economic life for three types of military wheeled vehicles with load capacities of 1/4, $1{\cdot}1/4$, and $2{\cdot}1/2$ tones has been evaluated on the basis of the equivalent acquisition and operating costs. The economic life of wheeled vehicles were calculated from 12 to 18 years by using the annual equivalent cost method. The equivalent cost was decided at the lowest point of the total amount of equivalent acquisition cost and operating cost. The operating cost were collected from the field data. The evaluated economic life can be very useful for deciding the total life cycle of these three types of military vehicles. The annual equivalent cost method may be also applied to other military equipments such as communication electronics, weapon systems, and other type of vehicles.

• International Journal of Highway Engineering
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• v.17 no.1
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• pp.91-98
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• 2015

PURPOSES : Although signalized intersections have been considered the best way to control traffic volume in urban areas for several decades, roundabouts are currently being discussed as an alternative way to control traffic volume, especially when traffic is light. Because a roundabout's efficiency depends on the load geometry as well as the traffic volume, design guidelines for roundabouts are recommended only if the incoming traffic volume is very low. It is rare to substitute a roundabout for an existing signalized intersection in urban areas. This study aims to estimate the benefits from the transformation of an existing signalized intersection into a roundabout in an urban area. When there is a more moderate volume of traffic, roundabouts can be effectively used by optimizing signals located at an approaching roadway. METHODS : The methodologies of this paper are as follows: First, a signalized intersection was analyzed to determine the traffic characteristics. Second, the signalized intersection was transformed into a roundabout using VISSIM microscopic traffic simulation. Then, we estimated and analyzed the effects and the performance of the roundabout. In addition, we adjusted a method to improve the benefits of the transformation via the optimization of signals located at an approaching road to control the incoming traffic volume. RESULTS : The results of this research are as follows: The signal-optimized roundabout improved delays compared with the signalized intersection during the morning peak hour, non-peak hour, and evening peak hour by 1.78%, 12.45%, and 12.72%, respectively. CONCLUSIONS : According to the simulation results of each scenarios, the signal-optimized roundabout had less delay time than the signalized intersection. If optimized signal control algorithms are installed in roundabouts in the future, this will lead to more efficient traffic management.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.255-262
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• 2016

There has been intense research on self-diagnosis systems in railway applications, since stability and reliability have become more and more significant issues. Wired sensors have been widely used in the railway vehicles, but because of the difficulty in their maintenance and accessibility, they ar not considered for self-diagnosis systems. To have a self-monitoring system, wireless data transmission and self-powered sensors are required. For this purpose, a thermoelectric energy harvesting module that can generate electricity from temperature gradient between the bogie axle box and ambient environment was introduced in this work. The temperature gradient was measured under actual operation conditions, and the behavior of the thermoelectric module with an external load resistance and booster circuits was studied. The proposed energy harvesting system can be applied for wireless sensor nodes in railroad vehicles with optimization of thermal management.

• Journal of Wetlands Research
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• v.9 no.2
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• pp.9-20
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• 2007

The nonpoint pollutants are originated from various land uses. Of the landuses, the development means the changes of the soil cover and the increases of imperviousness rate, which will increase the nonpoint pollutant emissions during a storm. Therefore, the Ministry of Environment in Korea has programed TPLMS(Total Pollution Load Management System) for four major large rivers to improve the water quality in rivers by controling the total pollutant loadings from the watershed area. The study area was forest landuse before resort development, however it is now changing to the resort. Some of the forest areas will be changed to parking lots, roads and buildings, which can be the major pollutant sources in the future. The paved areas are highly polluted landuses because of high pollutant accumulation rate by vehicle activities during dry periods. Therefore, this research is achieved to determine the changes of pollutant loading rate by development plan and to provide the best management practices for controlling nonpoint pollutants. Finally this research will provide the environment-kindly development technology for protecting the water quality.