• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1694-1700
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• 2004

In this paper, we propose the AWLS/MFT (Adaptive Weighed Least Squares/ Modulation Function Technique) devised by A. E. Pearson et al. for the transfer function estimation of a modal system and investigate the performance of several algorithms, the Gram matrix method, a Luenberger Observer (LO), Least Squares (LS), and Recursive Least Squares (RLS), for the estimation of initial conditions. With the benefit of the Modulation Function Technique (MFT), we can separate the estimation problem into two phases: the transfer function parameters are estimated in the first phase, and the initial conditions are estimated in the second phase. The LO method produces excellent IC estimates in the noise free case, but the other three methods show better performance in the noisy case. Finally, we compared our result with the Prony based method. In the noisy case, the AWLS and one of the three methods - Gram matrix, LS, and RLS- show better performance in the output Signal to Error Ratio (SER) aspect than the Prony based method under the same simulation conditions.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.172-180
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• 2012

In multi-static sonar for detecting an underwater target, received signals contain the target echo, reverberation and clutter. Clutter and reverberation are main causes of increasing the false alarm rate. MRAL classifies received signals according to the spatial similarity, and it regards classified signal as reflected signals from a reflector. MRAL reduces the false alarm rate this way. However, the results of MRAL can have localization errors. In this paper, an MRAL post processing algorithm is proposed to reduce the localization errors with the least square (LS) method.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.82-88
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• 2017

This study proposes a new topology for the performance test of a valve consisting of a modular multilevel converter (MMC)-based static synchronous compensator (STATCOM). The conventional valve performance test equipment requires high-voltage AC source of several kV rating because the number of submodules to be tested in a valve should be at least six or eight. However, the power source of the proposed scheme is DC and not AC source. The DC power source voltage range of the proposed test circuit is from several volts to several tens of volts. Therefore, the size and cost for the performance test equipment can be reduced considerably compared with the conventional method. The proposed scheme satisfies the requirements of the IEC 62927 standard. Simulations are conducted for a valve of 50[MVA] MMC-based STATCOM. Experimental results with a scale-downed setup show the validity of the proposed performance test topology.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.89-90
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• 2016

인버터에 사용되는 전력용 반도체 소자의 정션 온도는 모듈의 보호 및 수명 예측에 중요한 영향을 미친다. 온도를 추정하기 위해 제조사에서 제공되는 데이터 시트로부터 피라미터를 찾아 입력하게 되는데, 온도, 전류 및 $R_g$ 저항 등의 요인에 의해 이 파라미터가 변경된다. 본 논문은 온도 추정 과정에서 사용되는 파라미터에 온도에 따라 변동되는 성분을 선형화하여 추가하여 현재 온도에 맞는 파라미터를 계산해 낼 수 있는 방법에 관한 것으로 데이터 시트로부터 미리 계산된 계수 값을 이용하여 수식적으로 온도 의존성을 반영할 수 있다.이를 이용하여 부하 전류, 스위칭 주파수, DC Link 전압 등의 변동에 따라 정션 온도를 실시간으로 추정하였으며, iGBT 의 상단에 온도 센서를 부착하여 추정결과를 검증하였다. 본 방법을 통해 파라미터의 온도 의존성을 수식적으로 반영할 수 있으므로 파라미터를 저장하는 인버터의 데이터 저장 공간을 최소화 할 수 있다.

• Journal of the Korean Data and Information Science Society
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• v.21 no.5
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• pp.831-839
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• 2010

Least squares support vector machine (LS-SVM) is a kernel trick gaining a lot of popularities in the regression and classification problems. We use LS-SVM to propose a iterative algorithm for a nonlinear generalized autoregressive conditional heteroscedasticity model in the mean (GARCH-M) model to estimate the mean and the conditional volatility of stock market returns. The proposed method combines a weighted LS-SVM for the mean and unweighted LS-SVM for the conditional volatility. In this paper, we show that nonlinear GARCH-M models have a higher performance than the linear GARCH model and the linear GARCH-M model via real data estimations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.295-295
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• 2008

Water tree experiments were done for several types of cross-linked polyethylenes. Test method is followed by ASTM D6097. Polyethylene is divided for four subgroup. First One is chemically cross-linked general XLPE, and second one is chemically cross-linked tree-retardant XLPE, and the third one is silane cross-linked polyethylene made by monosil process, and the last one is silane cross-linked polythylene made by copolymer. Tree retardant XLPE shows the shortest water tree length. Cahemcally cross-linked general XLPE shows the longest water tree length. Silane cross-linked polyethylene by copolymer is similar to tree retardant XLPE and similar breakdown strength. So silane cross-linked XLPE by copolymer could be used for the the medium voltage cable which should have tree retardant characteristics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1401-1407
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• 2002

This paper represents an investigation of the vehicle-to-vehicle distance control system using Hardware-in-the-Loop Simulation(HiLS). Control logic is primarily developed and tested with a specially equipped test vehicle. Establishment of an efficient and low cost development tool is a very important issue, and test vehicle approach is costly and time consuming. HiLS method is useful in the investigation of driver assistance and active safety systems. The HiLS system consists of a stepper motor for throttle control, a hydraulic brake system with an electronic vacuum booster, an electronic controller unit, a data logging computer which are used to save vehicle states and signals of actuator through a CAN and a simulation computer using mathematical vehicle model. Adaptation of a CAN instead of RS-232 Serial Interface for communication is a trend in the automotive industry. Since this environment is the same as a test vehicle, a control logic verified in laboratory can be easily transferred to a test vehicle.

• International Journal of Highway Engineering
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• v.19 no.1
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• pp.21-28
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• 2017

PURPOSES : This paper presents a finite element model to accurately represent the soil-post interaction of single guardrail posts in sloping ground. In this study, the maximum lateral resistance of a guardrail post has been investigated under static and dynamic loadings, with respect given to several parameters including post shape, embedment depth, ground inclination, and embedment location of the steel post. METHODS : Because current analytical methods applied to horizontal ground, including Winkler's elastic spring model and the p-y curve method, cannot be directly applied to sloping ground, it is necessary to seek an alternative 3-D finite element model. For this purpose, a 3D FHWA soil model for road-base soils, as constructed using LS-DYNA, has been adopted to estimate the dynamic behavior of single guardrail posts using the pendulum drop test. RESULTS : For a laterally loaded guardrail post near slopes under static and dynamic loadings, the maximum lateral resistance of a guardrail post has been found to be reduced by approximately 12% and 13% relative to the static analysis and pendulum testing, respectively, due to the effects of ground inclination. CONCLUSIONS : It is expected that the proposed soil material model can be applied to guardrail systems installed near slopes.

• Korean Journal of Adult Nursing
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• v.14 no.4
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• pp.501-509
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• 2002

Purpose: This study was performed to identify the illness intrusiveness, quality of life, and their relationships in patients with chronic liver disease. Method: Data was collected using scales of illness intrusiveness developed by Devins et al and Korean health related quality of life (KoQoLS) developed by Shim et al to measure the illness intrusiveness and quality of life from 141 chronic liver disease patients. Result: The total mean score of illness intrusiveness was $38.85{\pm}18.45$. The domain of illness intrusiveness which showed the highest mean score was health ($4.60{\pm}2.02$), and the lowest mean score domain was relationship with spouse ($20.4{\pm}1.69$). The subcategory of KoQoLS which showed the highest mean score was bodily pain ($6.96{\pm}2.98$), and the lowest mean score subcategory was vitality ($2.75{\pm}1.20$). There were negative relationships between illness intrusiveness and KoQoLS in all subcategories. Abovel all, Illness intrusiveness had the strongest negative relationship with role limitation (r=-0.641) among the KoQoLS subcategories. Conclusion: Because the illness intrusiveness had negative influence on the quality of life in patients with chronic liver disease, further research will need to specify detailed illness intrusiveness and to explore influencing factors on quality of life in them.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.363-368
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• 2015

This paper deals with an improved current source using full-bridge converter type for thyristor valve test of HVDC system. The conventional high-current and low-voltage source of synthetic test circuit requires additional auxiliary power supply to provide the reverse voltage for the auxiliary thyristor valve during turn-off process. The proposed circuit diagram to provide the reverse voltage is extremely simple because no additional component is required. The reverse voltage can be obtained from the input DC voltage of the high-current and low-voltage power supply. The operation principle and design method of the proposed system are described. Simulation and experimental results in scaled down STC of 200 V, 30 A demonstrate the validity of the proposed scheme.