• 한국전기전자재료학회논문지
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• 제22권12호
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• pp.1084-1088
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• 2009

The measurement of dynamic stagger in electric railways is one of the key test parameters to increase speed and maintain safety in electric railways. This paper is introduces a non-contact optical-based measuring instrument of a catenary system in electric railways. The instrument is implemented by utilizing a CCD (Charge Coupled Device) camera installed on the roof of a vehicle for vision acquisition and image processing techniques including the Canny edge detector and the Hough transform to detect contact wires and calculate dynamic stagger. To check the validity of our approach for the intended application, we measured stagger of a overhead wire of a Korea Tilting Train (TTX). The non-contact optical-based measurement system proposed in this paper performs real-time stagger measurement of an activated high-voltage contact wire. By results of this paper, the instrument should be applied to assess performance and reliability of newly developed electric railway vehicles.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.87-94
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• 2001

Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are useful for a variety of applications, including anti-reflecting coatings in solar cells, passivation layers, dielectric layers in metal/insulator structures, and diffusion masks. PECVD systems are controlled by many operating variables, including RF power, pressure, gas flow rate, reactant composition, and substrate temperature. The wide variety of processing conditions, as well as the complex nature of particle dynamics within a plasma, makes tailoring SiN film properties very challenging, since it is difficult to determine the exact relationship between desired film properties and controllable deposition conditions. In this study, SiN PECVD modeling using optimized neural networks has been investigated. The deposition of SiN was characterized via a central composite experimental design, and data from this experiment was used to train and optimize feed-forward neural networks using the back-propagation algorithm. From these neural process models, the effect of deposition conditions on film properties has been studied. A recipe synthesis (optimization) procedure was then performed using the optimized neural network models to generate the necessary deposition conditions to obtain several novel film qualities including high charge density and long lifetime. This optimization procedure utilized genetic algorithms, hybrid combinations of genetic algorithm and Powells algorithm, and hybrid combinations of genetic algorithm and simplex algorithm. Recipes predicted by these techniques were verified by experiment, and the performance of each optimization method are compared. It was found that the hybrid combinations of genetic algorithm and simplex algorithm generated recipes produced films of superior quality.

• 대한기계학회논문집A
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• 제33권4호
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• pp.388-395
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• 2009

An accelerated fatigue test is essentially required to maintain the reliability of the actual structures of KTX under operation conditions. However, actual fatigue life cannot be obtained because the conventional fatigue tests are not adequate to the real load conditions. Moreover foreign component makers have not provided data of the loading stresses (S) versus cycles at the failure (N). In this study, we suggested a deduction method of the S-N curve for establishing an accelerating test under various load levels. Load history was acquired from the field tests. A Rainflow method was used on the cycle counting of the field load data. After that, an S-N curve was obtained through the iteration process under the condition that the damage index satisfies to 1 in the Miner's rule. The deduced S-N curve was applied to the performance evaluation of Korean-made sealed knuckles compared with imports.

• 한국정밀공학회지
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• 제28권3호
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• pp.357-362
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• 2011

Air springs are prevalently used as suspension in train. However, air springs are seldom used in automobiles where they improve stability and comfort by enhancing the impact-relief, breaking, and cornering performance. Thus, this study proposed a new method to analyze air springs and obtained some reliable design parameter which can be utilized in vehicle suspension system in contrast to conventional method. Among air spring types of suspension, this study focused on sleeve type of air spring as an analysis model since it has potential for ameliorating the quality of automobiles, specifically in its stability and comfort improvement by decreasing the shock through rubber sleeve. As a methodology, this study used MARC, as a nonlinear finite element analysis program, in order to find out maximum stress and maximum strain depending on reinforcement cord's angle variation in sleeves. The properties were found through uniaxial tension and pure shear test, and they were developed using Ogden Foam which is an input program of MARC. As a result, the internal maximum stresses and deformation according to the changes of cord angle are obtained. Also, the results showed that the Young's modulus becomes smaller, then maximum stresses decrease. It is believed that these studies can be contributed in automobile suspension system.

• Journal of Nutrition and Health
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• 제32권1호
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• pp.40-49
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• 1999

This study was conducted with 20 female gymnasts and 23 age-matched controls to examine pattern, weight control behavior and nutritional status. Most gymnasts(95.0%) reported that they used weight-control methods, while relatively few age-matched controls employed these methods. These methods included sauna(95.0%), food restriction(90.0%), excess exercise (70.0%), laxative abuse(10%) and use of diet pills(10%). Gymnasts had significantly (p<0.05) lower scores for statements related to 'sneaking food', 'vomiting after overeating', showing more negative eating behavior than age-matched controls. Energy intake of gymnasts was 968.9$\pm$421.4kcal while energy expenditure was 2,091$\pm$361kcal, showing negative evergy balance(-1,1225$\pm$534.6kcal). Female gymnasts consumed less than 70% of the RDA for protein, calcium, iron, vitamin A, thiamin, riboflavin and niacin, which reflects their low energy intake. The average intakes of calcium, iron, vitamin A, thiamin, riboflavin and niacin did not meet the recommended dietary allowances for their age groups. Adolescent athletes who train vigorously and consume a low-energy diet may be exposed to an increase in potential health risks. Therefore, individuals who advise athletic adolescents regarding training and dietary habits need to emphasize the importance of consuming an appropriate energy intake to support performance as well as growth and development. The sports nutritionist is in a position to convey such information to coaches, physicians, parents and to the athletes themselves.

• 전력전자학회논문지
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• 제9권2호
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• pp.158-162
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• 2004

자기부유기는 전자력을 이용해서 자성재료를 공중에 떠있게 할 수 있는 장치로 고속회전기에 사용되는 자기 베어링과 자기 부상 열차의 부상원리 등에 응용될 수 있다. 하지만 자기 부유기는 근본적으로 비선형이며 불안정한 시스템으로서 제어에는 많은 어려움이 따른다. 본 논문에서는 비선형 시스템인 자기부유기를 국부적으로 선형화해서 모델링하고, 가변 위치 제어를 수행할 수 있도록 비례미분 위치제어기를 설계하였다. 또한 PWM 컨버터와 DSP기반 제어보드를 이용한 자기 부유기를 제작하고, 시뮬레이션과 실험을 통하여 위치제어 응답성능을 검증하였다.

• 한국정밀공학회지
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• 제28권5호
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• pp.572-577
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• 2011

Curve squealing of inter-city railway vehicle is a noise with high acoustic pressure and rather narrow frequency spectra. This noise turns out to be very annoying for the people living in the neighborhood of locations and the passenger in railway vehicle where this phenomenon occurs. Squealing is caused by a self-exited stick-slip oscillation in the wheel-rail contact. Curve squeal noise of railway vehicles that passed by a factor of the speed limit, so to overcome in order to improve running performance is one of the largest technology. In the present paper, characteristic of squeal noise behavior at the Hanvit-200 tilting train test-site. Curve squealing of railway wheels/rail contact occurs in R400~ R800 curves with a frequency range of about 4~11 kHz. If the curve is less than the radius of wheel frail contact due to |left-right| noise level difference (dBA) shows a significant effect of squeal noise were more likely.

• 한국자동차공학회논문집
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• 제13권1호
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• pp.90-98
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• 2005

HMT is a type of continuously variable transmission which has split power flow path characteristics with gear train and hydro static unit. The benefit of improved fuel economy and high power capacity enables it to be a promising application fur large vehicles. This paper presents the analysis results including velocity, static torque, transmission efficiency and dynamic model of the HMT that is developed for city buses. The speeds or gear shafts, the static clutch torque and split power ratio for each mode are detailed here. From the analysis of HMT transmission efficiency considering the power loss in meshed gear and hydraulic unit, we can conclude that minimization of hydraulic power is necessary for improved fuel economy design. Also, the dynamic simulation result for mode shift characteristics shows that little shift shock is observed because of the synchronized rotation speed in clutch.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3873-3887
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• 2018

In this paper, we propose a novel method to recover images corrupted by impulse noise. The proposed method uses two stages: noise detection and filtering. In the first stage, we use pixel values, rank-ordered logarithmic difference values, and median values to train a neural-network-based impulse noise detector. After training, we apply the network to detect noisy pixels in images. In the next stage, we use group-based weighted couple sparse representation to filter the noisy pixels. During this second stage, conventional methods generally use only clean pixels to recover corrupted pixels, which can yield unsuccessful dictionary learning if the noise density is high and the number of useful clean pixels is inadequate. Therefore, we use reconstructed pixels to balance the deficiency. Experimental results show that the proposed noise detector has better performance than the conventional noise detectors. Also, with the information of noisy pixel location, the proposed impulse-noise removal method performs better than the conventional methods, through the recovered images resulting in better quality.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집
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• pp.175-179
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• 2005

The main objective of this paper is to module design and pressure relief test a new type of polymer gapless surge arrester for power distribution line. Metal oxide surge arrester for most electric power system applications, power distribution line and electric train are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of gapless elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion.