• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.209-214
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• 2017

Most of the present potential transformers of train vehicles are of the oil-type filled with insulating oil and are susceptible to problems such as explosion due to the increase in the internal pressure during train operation and poor reliability near the end of their life cycle. As a solution to this problem, it is necessary to develop a molded dry-type potential transformer with excellent pressure-resistance performance using insulating resin. In order to localize the product, the Korea Railroad Research Institute has been developing a molded dry-type potential transformer. As part of this research, it is necessary to analyze the vibration characteristics of the developed product and to check the transformer performance in a vibration environment. In this study, a resonance test and simulated long-term life test of the developed product were conducted according to the KS R 9144 and IEC 61373 standards, respectively, which are vibration test methods for railway vehicle parts. Their natural frequencies were analyzed by comparing the results of the numerical modal analysis and resonance test, in order to confirm their adherence to the standards. Also, the performance test after the simulated long-term life test confirmed that the operation of the developed transformer was not problematic even in a long-time vibration environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1307-1313
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• 2011

The mechanical limited slip differential (LSD) in vehicles is being replaced by the electromagnetic LSD because of its fast response and better active control characteristics. The coil housing made of STS 304 is one of the most important parts in the solenoid assembly of the electromagnetic LSD. High geometrical accuracy is a prerequisite for the manufacture of such coil housings, but precision machining is difficult because of the use of STS 304 thin plate and the variance in machining variables. The aim of this study is to optimize the mean and variance of the shape accuracy in the coil housing by finding a robust solution for the machining process conditions. The mean and standard deviation of the jaw contact pressure, cutting speed, and feed rate are considered to be the major parameters for minimizing the geometrical mean and variance. The response surface model based on the second-order Taylor series is combined together to minimize the mean and variance of the shape accuracy of the coil housing.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.2
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• pp.95-108
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• 1996

In ultrasonic testing, flaw signal from which quantitative information on flaws is determined is influenced by 3 factors : (1) the incident wavefield.produced by the transducer, (2) the scattered waves produced by flaws, and (3) the reception of the scattered waves back at the transducer. So even small changes in transducer performance due to aging or unexpected damages can produce the changes in the characteristics of flaw signal and finally the changes in the quantitative information on flaws. Thus a reliable calibration method of transducer performance is desired. Recently, theoretical models for ultrasonic testing have been employed as reference standards for the calibration of transducers which are considered as circular planar piston sources in the most of cases. But this simplification cannot be applied to partially damaged transducer which has lost their symmetry in performance, even not in appearance. Unfortunately there has been no reliable practical model which can be used for the calibration of partially damaged transducers. Here a pulse-echo testing model for partially damaged ultrasonic transducers was developed with experimental verification. The experimental responses agree very well with the theoretical prediction. So we expect that this model can be served as a theoretical reference standards for transducer calibration.

• Wind and Structures
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• v.19 no.2
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• pp.145-167
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• 2014

Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.12-19
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• 2008

Detection of a number plate consists of three stages; division of a number plate, extraction of each character from the plate, recognition of the characters. Among of these three states, division stage of a number plate is the most important part and also the most time-consuming state. This paper suggests an effective region extraction method of a number plate for various images obtained from unmanned inspection systems of illegal parking violation, especially when we have to consider the diverse surrounding environments of roads. Our approaching method detects each region by investigating the characteristics in changes of brightness and intensity between the background part and character part, and the characteristics on character parts such as the sizes, heights, widths, and distance in between two characters. The method also divides a number plate into different types of the plate. This research can solve the number plate region detection failure problems caused by plate edge damages not only for Korean domestic number plates but also for new European style number plates. The method also reduces the time consumption by processing the detection in real-time, therefore, it can be used as a practical solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.237-246
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• 2019

The Electro-Mechanical Brake (EMB) is the next generation braking system for automobiles and railway vehicles. Current brake systems for high-speed trains generate a braking force using a pneumatic cylinder, but EMB systems produce that force through a combination of an electric motor and a gear. In this study, an EMB operation mechanism capable of generating a high braking force was proposed, and structural and vibration analyses of the gears and shafts, which are the core parts of the mechanisms, were performed. Dynamic structural analysis confirmed that the maximum stress in the analysis model was within the yield strength of the material. In addition, the design that maximizes the diameter of the motor shaft was found to be advantageous in strength, and large shear stress could be generated in the bolt fixing the gear and eccentric shaft. In addition, a test apparatus that can reproduce the mechanism of the analytical model was fabricated to measure the strain of the fixed bolt part, which is the most vulnerable part. The strain measurement results showed that the error between the analysis and measurement was within 10%, which could verify the accuracy of the analytical model.

• Journal of the military operations research society of Korea
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• v.35 no.2
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• pp.33-49
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• 2009

The objective of this study is as follows. First, the hazard function on the failure probability density function of the K-1 tracked vehicles can be occurred in the form of the bathtub curve. Second, the failure mode may be different under two different operational situations. The research result shows that the bathtub curve can be fitted in the Weibull distribution, that assumes different shapes according to the specific stage of the system's life cycle. The K-1 tracked vehicle has a relatively high hazard(failure) rate at the time of its first service. The failure rate starts decreasing for a time immediately after it goes into service. After the break-in period, the surviving components have a fairly constant hazard rate. As the K-1 system ages, deterioration of its various parts takes place and the hazard rate starts Increasing. Second, the result shows the failure rate in the harsh operational environment is higher than that in the mild operational environment. In conclusion, the bathtub curve can be logically appropriate in establishing the depot overhaul cycle. Moreover, it is necessary for determining the right time of the depot overhaul to consider not only the age of defense equipment but also the different operational environment.

• Environmental and Resource Economics Review
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• v.18 no.4
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• pp.653-693
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• 2009

Using the Korean environmental input output analysis, this paper provides the emission intensities of the chemicals, especially, the toxic and carcinogenic substances, by linking the structure of demand, and the policy mix to abate these substances emissions. Acording to the results, Industries with the highest total emission intensities(TEI) of toxic substances are ranked : Printing and reproduction of recorded media(21), Other transportation equipment(26), Pulp and paper(11), Leather and fur products(9), Fiber yarn and fabrics(7). And the highest TEI of carcinogenic substances are Wood and wooden products(10), Motor vehicles and parts(25), Plastic and rubber products(15), Audio, video and communications equipment(23), etc.. The economic factors of changing these emissions are emission intensities and final demands. The effective combinations of policy instruments to abate these emissions are varied by the industries and substances. For example, Government need to execute the effective TEI management in the Fiber yarn and fabrics(7) sector, and, in furniture(27) sector, the reduction of final demand is more effective.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.538-548
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• 2016

The purpose of this study is to identify the possibility of effective tuning works, understand the characteristics of tuning engine, and analyse the basic data of engine tuning inspection corresponding to the safe operation and environment of a driving gasoline car. The effects of tuning on the characteristics of performance and exhaust emissions under a wide range of engine speeds are experimentally investigated by the actual driving car with a four-cycle, four-cylinder DOHC, turbo-intercooler, water-cooled gasoline engine operating at four types of non-tuning, tuning 1, 2 and 3. The tuning parts in the gasoline engine are the intake manifold, intake pipe and air filter. In the experiment, the output, torque and air-fuel ratio of the five-speed automatic transmission vehicles were measured at the chassis dynamometer(Dynojet 224xLC) with one person on board. The exhaust emissions of $NO_X$, THC, CO, $O_2$ and $CO_2$, and excess air ratio(${\lambda}$) at the other chassis dynamometer(DASAN-MD-ASM-97-KR-HD) were also measured by the idle/constant-speed mode(ASM2525 mode) test method. It is found that the actual air-fuel ratios of non-tuning and tuning engines were shown to be lower than the stoichiometric air-fuel ratio with increasing engine speed, and the actual air-fuel ratio of non-tuning engine was slightly higher than those of tuning engines when the engine speed is more than 4000 rpm. The output was significantly increased by the tuning whereby the maximum output of tuning engine was more increased to approximately 117.64% than that of non-tuning engine. In addition, CO, THC and $NO_X$ emissions of non-tuning and tuning engines measured by the constant-speed test mode were all satisfied with the inspection standards. CO emission was increased, while THC and $NO_X$ emissions were reduced by tuning.

• Resources Recycling
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• v.22 no.3
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• pp.73-80
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• 2013

Metal prices are rapidly rising due to increasing demand of metals and limited available resources according to the industrial requirement. As a result, securing a stable supply of these metal resources has been recognized as a core element of national competitiveness and sustained economic growth. In the case of magnesium and its alloys which are entirely depending on import, low-grade magnesium scraps from end-of-life vehicles and 3C(Camera, Computer, Communication) parts and magnesium wastes such as sludge and dross generated during melting process are hardly recycled. Accordingly, the development and commercialization of recycling technology of low-grade magnesium scrap is desperately needed to improve efficiency of resource circulation and to establish the required proprietary of resource metal supply and demand. In this study, papers and patents on recycling technologies of waste magnesium were analyzed. The range of search was limited in the open patents of USA (US), European Union (EP), Japan (JP), Korea (KR) and SCI journals from 1974 to 2012. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals was analyzed by the years, countries, companies, and technologies.