• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.193.1-193.1
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• 2010

Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong dam. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems.

• 한국농공학회지
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• 제17권2호
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• pp.3763-3771
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• 1975

This study was attempted to investigate the changes of specific fuel consumption, compression pressure and power output, consequently to obtain basic data on farm kerosene engine. The samples which are used in this study are a 4 cycle water cooled korosene engine for the use of K6-CT83 power tiller and a 4 cycle air-cooled kerosene engine for the use of G5L-3A water pump. The Korean Industrial Standards (K.S)KS-B 6002 "Test code of small internal combustion engine" was referred in carrying out this study, and its results are as follows. 1. According to load increasing, the speific fuel consumption of the engines generally decreases, however, in case of 10% over-loading it increases. 2. As a result of full load consecutive operation, according to passing of operating time, the amount of wear generally increases, consequently the speific fuel consumption also increases, and inversly the compression pressure decreases. 3. The changes of specific fuel consumption and compression pressure were closely related with time of piston ring exchange, and periodically about 100 hours the engines show the increase of specific fuel consumption and the decrease of compression pressure. 4. After about 300 hours, although the engine had new piston rings, the specific fuel consumption increase, consequently the engine needs boring. In actual use, it is impossible to operate consecutively on full load, therefore the boring time of engine is expected to come later.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.235-240
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• 2011

Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong darn. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems.

• Transactions on Electrical and Electronic Materials
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• 제10권6호
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• pp.193-195
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• 2009

This paper aims to develop a low gate source voltage ($V_{gs}$) N-LDMOS element that is fully operational at a CMOS Logic Gate voltage (3.3 or 5 V) realized using the 0.35 μm BCDMOS process. The basic structure of the N-LDMOS element presented here has a Low $V_{gs}$ LDMOS structure to which the thickness of a logic gate oxide is applied. Additional modification has been carried out in order to obtain features of an improved breakdown voltage and a specific on resistance ($R_{sp}$). A N-LDMOS element can be developed with improved features of breakdown voltage and specific on resistance, which is an important criterion for power elements by means of using a proper structure and appropriate process modification. In this paper, the structure has been made to withstand the excessive electrical field on the drain side by applying the double gate oxide structure to the channel area, to improve the specific on resistance in addition to providing a sufficient breakdown voltage margin. It is shown that the resulting modified N-LDMOS structure with the feature of the specific on resistance is improved by 31%, and so it is expected that optimized power efficiencies and the size-effectiveness can be obtained.

• 설비공학논문집
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• 제19권5호
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• pp.394-402
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• 2007

To estimate the cooling load for the following day, outdoor temperature and humidity are needed in hourly base. But the meteorological administration forecasts only maximum and minimum temperature. New methodology is proposed for predicting hourly outdoor temperature and humidity by using the forecasted maximum and minimum temperature. The correlations for normalized outdoor temperature and specific humidity has been derived from the weather data for five years from 2001 to 2005 at Seoul, Daejeon and Pusan. The correlations for normalized temperature are independent of date, while the correlations for specific humidity are linearly dependent on date. The predicted results show fairly good agreement with the measured data. The prediction program is also developed for hourly outdoor dry bulb temperature, specific humidity, dew point, relative humidity, enthalpy and specific volume.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.592-597
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• 2005

Biogas is widely accepted as one of renewable energy. Raw biogas can be used in internal combustion engines either spark ignition or diesel engines. Since the gas has relatively low calorific values, engine power also is lower than rated power values. Modified engines or biogas-specific engines have been utilized in order to increase efficiency. Recently, gas engine/generators are provided for various purposes. They are mostly for LPG or natural gas. When biogas is fueled to the gas engines, de-rating is inevitable due to its lower calorific values. Meanwhile, massively produced commercial gas engines are more competitive in terms of initial investment for engines, compared to biogas-specific engines. Then, the characteristics of the commercial engine and power generation should be understood for better operation. A 5kW gas engine/generator(natural gas) was tested for determining an allowable maximum concentration of $CO_2$ in synthetic biogas, with respect to engine stating, power generation. Experimental results indicated that about 65% of methane concentration is required to start the gas engine. At this condition, the power generated was about 3 kW. It is about 60% of the nominal power, which is similar to the ratio of calorific values.

• 설비공학논문집
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• 제22권8호
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• pp.562-566
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• 2010

Wind energy is one of the most general natural resources in the world. However, as of today, generating electricity out of wind energy is only available from big wind generator, Furthermore, an axial-flow turbine is the only way to produce electricity in the big wind generator. This paper is for the guidance of drawing impact fact about power turbine using cross-flow type transferring wind energy to electricity energy. It will find the ideal value which enables to make cross-flow power turbine(CPT) using computational fluid dynamics(CFD) code. This study tries to analyze the "Solidity" characteristics. We can find out turbine-blade number through CFD. CFD is using "Fluent_ver 6.3.16", and the data from its result will judge fan-blade performance through specific torque and specific power from each "Solidity" model. Based upon the above, we will make cross-flow power turbine of multi-blade centrifugal fan instead of axial-flow type.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2812-2820
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• 2020

House load operation (HLO) occurs when the generator supplies power to the house load without triggering reactor trips during grid disturbances. In Korea, the HLO capability of optimized power reactor 1000 (OPR1000) plants has prevented several reactor trips. Operational experiences demonstrate the difference in the reactor trip incidence due to grid disturbances between OPR1000 plants and Westinghouse plants in Korea, attributable to the availability of the HLO capability. However, probabilistic safety assessments (PSAs) for OPR1000 plants have not considered their specific design features in the initiating event analyses. In an at-power PSA, the HLO capability can affect the initiating event frequencies of general transients (GTRN) and loss of offsite power (LOOP), resulting from transients within the grid system. The initiating event frequencies of GTRN and LOOP for an OPR1000 plant are reduced by 17.7% and 78.7%, respectively, compared to the Korean industry-average initiating event frequencies, and its core damage frequency from internal events is reduced by 15.2%. The explicit consideration of the HLO capability in initiating event analyses makes significant changes in the risk contributions of the initiating events. Consequently, for more realistic at-power PSAs in Korea, we recommend incorporating plant-specific HLO-related design features when estimating initiating event frequencies.

• 전자공학회논문지
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• 제50권7호
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• pp.159-166
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• 2013

본 논문은 움직임 추정 전용 프로세서를 위한 효율적인 루프 가속기를 제안한다. 실제로 움직임 추정 알고리즘은 복잡하고 다양한 순환 명령어들을 포함하고 있다. 본 논문에서는 효율적인 하드웨어 루프 명령어들을 지원하기 위해서, 네 개의 루프 명령어와 그에 따른 하드웨어 구조를 소개한다. 검증 결과 제안된 루프 가속기가 early-termination을 이용한 움직임 추정 시 비교명령어와 조건부 점프명령어를 갖고 있는 전형적인 구현 방법과 비교했을 때 평균 명령어 사이클 수를 약 29% 줄일 수 있다는 것을 보여준다. 제안된 움직임 추정 전용 프로세서 루프 가속기는 프로그램 메모리의 접근 빈도를 상당히 줄일 수 있고, 전력 소모를 많이 절약할 수 있다. 따라서, 제안된 루프 가속기는 전력 소모가 적고, 유연한 움직임 추정에 적합하다.

• 에너지공학
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• 제25권2호
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• pp.29-36
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• 2016

도시지역에서는 발전용 디젤엔진의 운영비를 절약하기 위해 천연가스와 디젤을 섞어서 쓰려는 노력을 하고 있다. 본 연구에서는 디젤 연료의 일부를 천연가스로 대체 하였을 때 엔진특성과 천연가스로 대체되는 양에 따라 최적의 밸브 타이밍을 찾아보았다. 1-D 엔진 해석프로그램을 사용하여 19.7리터 발전용 디젤 엔진을 대상으로 모델링하여 연구를 진행하였다. 연구 결과 엔진연료에서 천연가스 비율이 증가할수록 연료소비율(Brake Specific Fuel Consumption, BSFC)는 증가하였고 질소산화물(Brake Specific NOx)는 감소하였다. 추가적으로 흡기밸브 타이밍을 조절할 경우 BSFC가 최대 1%감소하였고 BSNOx의 경우 최대 36%감소하는 효과가 있었다.