• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1210-1216
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• 2014

This paper deals with an application of Teager Energy Operator (TEO) and Energy Separation Algorithm(ESA) to detect and determine various voltage waveform distortions like harmonics, inter-harmonics and frequency variation. Because the TEO and DESA algorithm was initially proposed for speech or communication analysis, its applications are limited to some types of waveform in the power quality analysis area. For example, an undistorted voltage signal is similar with a pure sinusoid. A voltage fluctuation is very similar with an amplitude-modulated signal, from the viewpoint of signal theory. And a continuous frequency variation is similar with a frequency-modulated signal, which is also known as a chirp signal. This paper is written to show that the TEO and DESA algorithm can be used for detecting occurrences of the representative waveform distortions and determining their instantaneous information of amplitude and frequency.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1255-1260
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• 2008

This study is simulation of high elevated liquid line of a modular heat pump system to observe longitudinal subcooling variation. In a high elevated tube, subcooled refrigerant(R410A) through a condenser changes its states by heat transfer with surrounding air and by pressure drop from elevation. In this study, the liquid line was simulated through correlations of heat transfer and pressure drop for the variation from single-phase into two-phase flow. Pressure drop, heat transfer rate and vapor quality were calculated as key parameters. Two-phase turning heights and variations of the key parameters were confirmed from the simulation. As a result, high elevation of liquid line has great influence on upward flow, which requires additional equipment to compensate the variation.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.67-75
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• 2007

This study intends to the adequacy inspection of the room temperature variation rate that is available in the building heat performance evaluation index, so we performed the sensitivity analysis about the room temperature variation rate and the energy consumption in the room. For these purpose, we supposed the models which are composed of the various window area, insulation thickness and ventilation rate. Then we analyzed the simulation using the ESP-r and Seoul weather data. In this research, the pattern of the increasing & decreasing rate of annual load according to the change of the various design factors is similar to the pattern of increasing & decreasing rate of not the K-values but the room temperature variation rate. Also we derive the optimum value of the various design factors and the room temperature variation rate in this analysis model. Further study is to be required the development of convenient tool to use in the real design.

• 에너지공학
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• 제24권2호
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• pp.1-8
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• 2015

석유의 생산 과정에서 발생하는 왁스(wax)와 같은 고형물의 생성 및 집적은 유동안정성 확보(flow assurance) 문제를 발생시켜 안정적인 석유 생산을 방해할 수 있으며, 현장에서는 이를 해결하는데 많은 시간 소모와 경제적 손실이 발생할 수 있다. 왁스집적 문제는 왁스가 생성되기 시작하는 온도인 왁스생성온도 이하의 조건에서만 발생하므로 왁스집적 문제를 예측하고 제어하기 위해서는 오일의 왁스생성온도를 사전에 필수적으로 파악해야한다. 컨덴세이트와 같은 투명 오일의 왁스생성온도는 광학적 기술인 표준측정법이 적용되는 반면 대부분의 현장에서 생산되는 불투명 오일에는 적용이 어려운 한계점이 있다. 이 연구에서는 3가지의 투명 오일시료에 열유량 변화 분석, 점도 변화 분석, 밀도 변화 분석 기법을 적용하여 파악한 왁스생성온도와 표준기법으로 측정한 값과 비교하여 밀도 변화 분석 기법이 가장 신뢰도가 높은 것을 확인하였고 이 기법을 2종류의 불투명 오일시료에 적용하여 왁스생성온도를 결정하였다.

• 에너지공학
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• 제21권3호
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• pp.211-220
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• 2012

본 연구에서는 창문을 통한 건물의 에너지손실을 알아보기 위해서 창호시스템의 구조체를 모델링하여 구조체 재질에 따른 열적 손실부분을 분석하였고, 건물에서 창문을 통한 난방부하변화량을 알아보기 위해서 시뮬레이션을 통하여 건물을 모델링하여 창문의 종류와 구조체의 재질에 따른 건물의 에너지 변화량과 온도 변화를 분석하였다.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.1-8
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• 2013

Wind resource data of short-term period has to be corrected a long-term period by using MCP method that Is a statistical method to predict the long-term wind resource at target site data with a reference site data. Because the field measurement for wind assessment is limited to a short period by various constraints. In this study, 2 different MCP methods such as Linear regression and Matrix method were chosen to compare the predictive accuracy between the methods. Finally long-term wind speed, wind power density and capacity factor at the target site for 20 years were estimated for the variability of wind and wind energy. As a result, for 20 years annual average wind speed, Yellow sea off shore wind farm was estimated to have 4.29% for coefficient of variation, CV, and -9.57%~9.53% for range of variation, RV. It was predicted that the annual wind speed at Yellow sea offshore wind farm varied within ${\pm}10%$.

• 대한전기학회논문지
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• 제39권5호
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• pp.516-518
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• 1990

We have derived the equation which involves the variation of electron energy with time in a lowly ionized plasma when a low alternating electric field is applied. We consider only elastic collisions between electrons and neutral atoms. This equation is solved using the 4th-order Runge-Kutta method, and applied to argon gas discharge which is driven by source frequency of 100, 1K, 10K, 100K, and 1M (Hz). The results show that the variation of electron energy becomes flat with higher frequencies.

• Kyungpook Mathematical Journal
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• 제55권3호
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• pp.715-730
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• 2015

In this note, we extend the definition of harmonic and biharmonic maps via the variation of energy and bienergy between two Riemannian manifolds. In particular we present some new properties for the generalized stress energy tensor and the divergence of the generalized stress bienergy.

• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.45-52
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• 2008

In order to clarify characteristics of variation in wind energy over a long-term period, an investigation was carried out at Seoguang site on Jeju island. The wind data for 10 years from Automatic Weather System (AWS) were analyzed for each year. The variation in the annual energy production (AEP) for the 2 MW wind turbine was estimated through statistical work. The result shows that the range of the yearly average wind speed at 15 m above ground level for 10 years was from -22.6% to +13.7%, which is wider range than that in Japan. The coefficient of variation for the AEP was 22.7%, which is about twice of that for the yearly average wind speed. Therefore, for estimating the wind energy potential accurately at a given site, the wind data should be analyzed over a long-term period based on the data from the meteorological station.

• 연구논문집
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• 통권32호
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• pp.45-53
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• 2002

Hydraulic breaker attached excavator generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and etc. The developed breaker are determined their own destructive force and number of impact by the input hydraulic flow rate and pressure than the operating conditions, In this study, the characteristics of pressure variation in closed vessel is invested for testing the impact energy of hydraulic breaker. To test the impact energy, the test system is designed as a mechanism consisted with a hydraulic cylinder, main base, pressure sensor, LVDT, data acquisition system and etc.. The developed test system is applied to measure the impact energy for hydraulic breaker. The proposed testing method could be applied for conventional impact test and the control system evaluation for hydraulic breakers.