• 설비공학논문집
• /
• 제15권4호
• /
• pp.329-335
• /
• 2003

This study is on a experiment which shows to defrost automatically on the optimum time regardless of defrosting method. The result shows that the more defrost layers increase in fin tubes of evaporation, the less the section of the circulating air reduce. Thickness of the frost formation increases, so a pressure difference of ventilation increase, as a result automatic defrosting system sets the time COP drops suddenly up optimum time. Automatical defrosting system can find out the initial related current of evaporator fan motor and the value of load current in the optimum time. And it sets defrosting time, evaporating temperature, and temperature in refrigerator up system requiring value. Consequence of this experiment is that energy consumption with defrost load gets effect of reduction of eleven percent per 25.4 hours compared with common defrosting.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
• /
• pp.249-256
• /
• 2009

The cooling technology of power conversion semiconductors in the propulsion system for the HEMU(High Electrical Multi Unit) are applied in water cooling method and phase change method such as the immersed type and the heat pipe type. This research designs and manufactures the water cooling system that could cool about heat load Q=2kW and performance tests to apply it by an electric power conversion semiconductors(IGBT) cooling technology. Experimental condition made change of a flow rate, an air velocity and a heat load to confirm operation characteristics of water cooling device, and when is heat load 2kW, air velocity 20 m/s, and water flow rate 7kg/s, it is about $80^{\circ}C$ to temperature of cooling plate.

• 에너지공학
• /
• 제15권1호
• /
• pp.14-22
• /
• 2006

원자력발전과 신재생에너지발전에 대하여 과학적, 객관적 검토없이 다양한 정책과 주장이 제기되고 있다. 본 연구에서는 국가별 에너지정책을 조사 분석하고 총 34개의 가능한 전원구성 시나리오를 도출하였다. 이들 시나리오가 우리나라 전력정책에 도입될 경우를 가정하여 전력단가를 계산하였다. 전력단가 계산방법은 현재 우리나라 전력시장에서 사용하는 한계가격결정 방법을 사용하였고 발전원별로 표준건설비 및 운영비를 적용함으로써 계산을 단순화하였다. 계산결과 송배전 비용과 사업자의 이윤을 제외한 현행 전원 구성에 대한 전력단가는 평균 22.18원/kWh이고 전원구성비에 따라 19.74에서 164.07원/kWh까지 분포하였다. 원자력발전비율이 증가할수록 전력단가는 낮아졌고 신재생에너지 발전비율이 증가할수록 전력단가는 높아졌다. 주목할 만한 것은 신재생에너지 발전비율이 20%를 넘어서게 되면 값싼 기저발전을 활용할 수 없게 되어 전력수요가 적은 시간대에 전력단가가 오히려 상승하였다.

• 대한기계학회논문집B
• /
• 제37권11호
• /
• pp.1047-1051
• /
• 2013

최신의 전투장갑차들은 통합형 공조장치를 선호하는 경향이 있음에도 불구하고 분리형 공조장치에 대한 필요성이 제기되고 있다. 본 연구에서는 특수목적용 장갑차량 및 군용규격이 요구되는 장갑차량의 냉방, 난방장치에 대한 연구로 상용 Fluent 를 이용한 유동해석을 통해 덕트 및 최적화 배치를 구현하였으며 실차을 통한 시험 수행으로 해석결과를 검증하고, 선정된 냉방 및 난방기의 유효성을 확인하였다. 기존 차량의 변경 모델이나 계열차량의 경우, 현재 선정된 모델의 부분 변경으로 가능하며, 차륜형 장갑차용으로 선정된 현재 모델의 유효성을 본 연구를 통해서 입증되었다.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 2007년도 추계학술대회 및 정기총회
• /
• pp.477-481
• /
• 2007

The purpose of this study is to provide the ideal forecasting model of cadastral survey work load through the Economeatric Analysis of Time Series, Granger Causality and VAR Model Analysis, it suggested the forecasting reference materials for the total amount of cadastral survey general work load. The main result is that the derive of the environment variables which affect cadastral survey general work load and the outcome of VAR(vector auto regression) analysis materials(impulse response function and forecast error variance decomposition analysis materials), which explain the change of general work load depending on altering the environment variables. And also, For confirming the stability of time series data, we took a unit root test, ADF(Augmented Dickey-Fuller) analysis and the time series model analysis derives the best cadastral forecasting model regarding on general cadastral survey work load. And also, it showed up the various standards that are applied the statistical method of econometric analysis so it enhanced the prior aggregate system of cadastral survey work load forecasting.

• 조명전기설비학회논문지
• /
• 제26권12호
• /
• pp.93-98
• /
• 2012

Economics of available alternatives in the transmission planning are evaluated by the investment cost, loss cost and congestion cost. Congestion/loss cost is calculated in many years and many load levels by unit commitment of generators, optimal dispatch, load flow, judgement about transmission congestion and re-dispatch to reduce the congestion. The greatest difficulties to introduce variable optimization techniques on the transmission planning is the convergence of load flow. In this paper, economics in the transmission planning are evaluated using DC load flow, and case study is conducted on the Korea power system by proposed congestion/loss calculation methods.

• 대한전기학회논문지
• /
• 제37권6호
• /
• pp.331-338
• /
• 1988

A simple algorithm is presented for solving the thermal unit commitment problem which is one of very important areas in economic operation of power systems. This algorithm is based on simple priority ordering by the unit operation cost and it is shown that the operation cost of chosen sets of generators is the minimum. The proposed method differs from the conventional priority-based formulations in that the unit operation are calculated in every load level. Further the poerating reserve requiements are satisfied by the newly derived analytical security function or the expectation of reserve. The proposed method is proven to be very simple, accurate and efficient in a sample system.

• Computers and Concrete
• /
• 제12권6호
• /
• pp.775-783
• /
• 2013

A novel reliability-based work model of k/n (G) system has been developed. Unit failure probability is given based on the load and strength distributions and according to the stress-strength interference theory. Then a dynamic reliability prediction model of repairable k/n (G) system is established using probabilistic differential equations. The resulting differential equations are solved and the value of k can be determined precisely. The number of work unit k in repairable k/n (G) system is obtained precisely. The reliability of whole life cycle of repairable k/n (G) system can be predicted and guaranteed in the design period. Finally, it is illustrated that the proposed model is feasible and gives reasonable prediction.

• 환경영향평가
• /
• 제18권5호
• /
• pp.281-291
• /
• 2009

In Total Water Pollutant Load Management System of Korea, unit load approach based on land register data is currently used for the estimation of non-point pollutant load. However, a problem raised that land register data could not always reflect the actual land surface coverages which determine runoff characteristics of non-point pollution sources. As a way to overcome this, we tried to establish quantitative relationships between the aerial images (0.4m resolution) which reflect actual land surface coverages and the land registration maps according to the 19 major designated land-use categories in Kyeongan watershed. Analyses showed different relationships according to the land-use categories. Only a few land-use categories including forestry, road and river showed essentially identical and some categories such as orchard, parking lot and sport utility site showed no relationships at all between image data and land register data. Except for the two cases, all the other categories showed statistically significant linear relationships between image data and land register data. The analyses indicate that using high resolution aerial maps is a better way to estimate non-point pollutant load. If the aerial maps are not available, application of the linear relationships as conversion factors of land register data to image data could be an possible option to estimate non-point pollutant loads for the specific land-use categories in Kyeongan watershed.

• 상하수도학회지
• /
• 제8권2호
• /
• pp.1-11
• /
• 1994

This study was conducted to develop a new RBC process available for the effective removal of organic matters and nitrogen in sewage. The RBC process for the oxidation organic compounds and nitrification was designed to occur at the 1st-stage and next-stage RBC respectively. Then nitrified water was recycled to the denitrifying RBC located at the lower part of the 1st-stage RBC. Some results were summarized as follows. 1. The loading limitation was represented as $60g{\cdot}COD/gm^2/day$ in experiment of simultaneous removal of organic matter and nitrogen. The maxmum COD % removal was 85% at the load $35g{\cdot}COD/m^2/day$. 2. The $NO_3-N$ % removal was approximately 80% at the load $60g{\cdot}COD/m^2/day$ and the maximum $NO_3-N$ remaval rate was $3.9g{\cdot}COD/m^2/day$ and the overall C/N ratio of 11.0 as required to achive 80% of $NO_3-N$% removal. 3.$NO_3-N$ removal rate was rapidly decreased above the load $7g{\cdot}NH_4{^+}-N/m^2/day$ and the maximum $NO_3-N$ removal rate was $3.7g{\cdot}NO_3-N/m^2/day$. 4. Irrespective of the recycle ratio, the COD % removal at the system of 2-stage RBC unit was nearly constant as 89% while the maximum one in the 1st-stage unit was 77% in the case of 50% recycle. 5. The maximum COD % removal in the 3-stage RBC system was 93% while 1st-stage one being 80%, under the $NH_4{^+}-N$ load of $7.4g/m^2{\cdot}d$. Also maximum percentage of nitrification and denitrification was 69% and 41% respectively, under the same $NH_4{^+}-N$ load.