• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1108-1111
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• 1999

The Peltier heat absorbed or evolved at the solidiliquid interface in the unidirectional solidification process could contribute to the increase of temperature gradient in liquid and growth velocity, and the enhancement of crystal orientation. In this study, in order to measure the Peltier heat generated at the solidiliquid interface as a way of application to crystal growth, the thermoelectric effects were investigated on the temperature changes at the solid- and liquid-phase of the same material and its interface. Through the theoretical consideration, it was possible to separate sole Peltier. Thomson or Joule heat from the temperature changes due to current density, polarity, and temperature gradient. Thomson coefficient of solid- and liquid-phase as well as Peltier coefficient at the solid/liquid interface could be obtained.

• Proceedings of the KIEE Conference
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• summer
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• pp.851-853
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• 2004

This paper deals with current distribution analysis of the windings of a superconducting transformer with BSCCO-2223 High Tc Superconducting (HTS) tapes. Current distribution of HTS windings wound in parallel is analyzed by electromagnetic field analysis of finite element method and verified by experiments. For the sake of uniform current distribution, windings must be transposed so to make the impedances of each strands same. The parallel HTS tapes were transposed between the pancakes via non-superconducting joints because it is hard to make transpositions inside the pancake windings. In order to measure current distribution, test windings are fabricated and experimented for both transposed and non-transposed windings. We compared test results with calculated ones.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.535-538
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• 2004

Superconducting transmission power cable is one of interesting parts in power application using high temperature superconducting wire. One of important parameters in high-temperature superconduting (HTSC) cable design is transport current distribution because it is related with current transmission capacity and AC loss. In this paper, the transport current distribution at conducting layers was investigated through the analysis of the equivalent circuit for HTSC power cable with shield layer and compared with the case of without shield layer. The transport current distribution due to the pitch lenght was improved in the case of HTSC power cable with shield layer from the analysis.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.552-555
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• 2019

디지털 트윈이란 현실 세계의 물리적인 사물을 컴퓨터 상에 동일하게 가상화 시키는 기술을 의미하는 것으로, 물리적 사물이나 시스템을 모델링하거나 IoT 기술에 접목되어 활용되고 있는 기술이다. 디지털 트윈 기술은 가상의 모델을 무한정 시뮬레이션을 통해 동작을 튜닝하고 환경변화에 대한 대응을 미리 실험하여 리스크를 최소화할 수 있는 장점을 지닌다. 최근 인공지능이나 기계학습에 관련된 기술들이 주목받기 시작하면서, 이와 같은 물리적인 사물의 모델링 작업을 데이터 기반으로 수행하려는 시도가 증가하고 있다. 특히, 산업현장에서 많이 활용되는 인더스트리 4.0 공장 자동화의 핵심인 협력 로봇의 디지털 트윈을 구축하기 위해서는 로봇의 동작을 인지하는 과정이 필수적으로 요구된다. 그러나 현재 협력 로봇의 동작을 인지하기 위한 시도는 미비하며, 센서 데이터를 기반으로 동작을 역으로 예측하는 기술은 더욱 그렇다. 따라서 본 논문에서는 로봇의 동작을 인지하기 위해 가정용 협력 로봇에서 전류 및 관성 데이터를 수집하기 위한 실험 환경을 구축하고, 수집한 센서 데이터를 기반으로 한 동작 예측 모델을 제안하고자 한다. 제안하는 방식은 로봇의 동작 명령어를 조인트 위치 기반으로 분류하고 전류와 위치 센서 값을 사용하여 학습을 통해 예측하는 방식이다. SVM 을 이용하여 학습한 결과, 모델의 성능은 평균적으로 정확도, 정밀도, 및 재현율이 모두 96%로 평가되었다.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1112-1116
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• 1999

Thermoelectric effects on the temperature changes at the solid- and liquid-phase and its interface were studied by using the unidirectional solidification of $\textrm{Bi}_{2}\textrm{Te}_{3}$. Cooling or heating effects measured with current density. polarity and current passing time were quite different. By separating sole Peltier, Thomson and Joule heat theoretically and experimentally, the Peltier coefficient at the solid/liquid interface of $\textrm{Bi}_{2}\textrm{Te}_{3}$ was -1.10$\times\textrm{10}^{-1}$V, and the Thomson coefficients of solid- and liquid-phase were 7.31\times\textrm{10}^{-4}V/K, 5.77\times\textrm{10}^{-5}V/K, respectively. When D.C. passed from solid-phase to liquid-phase during the crystal growth of $\textrm{Bi}_{2}\textrm{Te}_{3}$ the crystal with more directionality was obtained owing to increase of the temperature gradient in liquid by the Peltier cooling. But in reverse current direction, the crystallinity was not changed significantly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2137-2142
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• 2016

The electrical current generated by heart creates not only electric potential but also a magnetic field. In this study, the signals obtained magnetocardiogram(MCG) using 61 channel superconducting quantum interference device(SQUID) system, and the clinical significance of various feature parameters has been developed MCG. Neural network algorithm was used to perform the classification of ischemic heart disease. The MCG signal was obtained to facilitate the extraction of parameters through a process of pre-processing. The data used to research the normal group 10 and ischemic heart disease group 10 with visible signs of stable angina patients. The available clinical indicators were extracted by characteristic point, characteristic interval parameter, and amplitude ratio parameter. The extracted parameters are determined to analysis the significance and clinical parameters were defined. It is possible to classify ischemic heart disease using the MCG feature parameters as a neural network input.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.7
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• pp.878-882
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• 2004

In this paper, we propose a hierarchical hybrid neural network for detecting faults of induction motor. Implementing the classifier based on the input and output data, we apply appropriate transform and classification method at each step. In the proposed method, after obtaining the current of state of motor for each period, we transform it by Principle Component Analysis(PCA) to reduce its dimension. Before the training process, we use the conditional Fuzzy C-means(FCM) for obtaining the initial parameters of neural network for more effective learning procedure. From the various simulations, we find that the proposed method shows better performance to detect and diagnosis of induction motor and compare than other methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.394-399
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• 2012

In recent years, MEMS sensors show huge attraction in machine condition monitoring, which have advantages in power, size, cost, mobility and flexibility. They can integrate with smart sensors and MEMS sensors are batch product. So the prices are cheap. And the suitability of it for condition monitoring is researched by experimental study. This paper presents a comparative study and performance test of classification of MEMS sensors in target machine fault classification by 3 intelligent classifiers. We attempt to signal validation of MEMS sensor accuracy and reliability and performance comparisons of classifiers are conducted. MEMS accelerometer and MEMS current sensors are employed for experiment test. In addition, a simple feature extraction and cross validation methods were applied to make sure MEMS sensors availabilities. The result of application is good for using fault classification.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1085-1092
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• 2001

The high efficient AC powder EL devices classified by low cost and low power consumption type fabricated using screen printing method with film thickness and organic binder. Brightness and current density were measured at frequency range of 400Hz∼1kHz and voltage range of 50∼300V$\_$rms/ to estimate optoelectrical properties of AC powder EL devices, respectively. Frequency generator was used as system producing frequency and voltage of a sine wave. Also brightness and current density were measured by luminometer and multimeter. In the case of low cost type AC powder EL device, brightness and current density were about 43 cd/m$^2$and 20$\mu$A/cm$^2$when the thickness of phosphor and dielectric layer was 45∼50$\mu$m under no addition of plasticizer respectively. In the case of low power consumption type AC powder EL device, brightness and current density were about 74 cd/m$^2$and 30∼40$\mu$A/cm$^2$when the thickness of phosphor and dielectric layer was 45∼50$\mu$m and 15∼20$\mu$m under addition of 15wt% plasticizer respectively. Also, AC powder EL device fabricated in this study showed absolutely excellent characteristics as the lifetime was longer than products of other company.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.133-134
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• 2011

본 논문은 배전시스템 내의 공통 접속점에 연결된 부하를 2단계로 분석하여 추정된 부하의 구성비를 왜곡전력 품질지수에 적용하는 방안에 관한 연구이다. 제안된 2단계 분석법은 기존의 배전시스템 내 전기부하의 구성비를 한꺼번에 추정하는 방법과 달리, 부하의 전류 파형을 고려해 전기부하를 분류하여 각 단계별로 부하구성비를 칼만 필터를 이용하여 추정한다. 제안된 부하구성비 추정법의 유효성은 분산전원이 포함된 모의배전시스템을 구성하여 검증한다. 또한, 모의 배전시스템 내에서 추정된 부하구성비를 왜곡전력 품질지수에 적용하여 부하들의 전력품질을 진단한다.