• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.466-471
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• 2004

In gas turbines, excess air for combustion is available and therefore lean premixed combustion is the most promising approach to the significant reduction of thermal NOx emissions. At lean conditions, however, flame stability is inherently worse and hence combustion tends to be incomplete. Efforts have been devoted toward extending the operating range of complete combustion at leaner conditions. One of them is the lean-lean two-stage combustion where lean to ultra-lean secondary mixtures are mixed with the hot burned gas from the primary stage. Conventional flame combustion or flameless reaction are initiated depending on the conditions of the secondary zone. In the first part of the present study, the effects of fuel injection on the emissions and flame stability were investigated for a single tubular flame, In the second part, the emissions and flame stability were studied for a two-stage combustor with secondary mixture injected through the tangential slots on a cylindrical combustor wall. The effects of the ratio of air flow rates to the primary and secondary zones on the emissions and combustion characteristics were investigate.

• 한국자원식물학회지
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• 제11권1호
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• pp.30-39
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• 1998

Carrot seedling emgryos showing variations in cotyledon number were selected and anatomical comparisons of the embryo vascular systems were performed between the variants and normal two cotyledonary (5) embryos from 800 seedings germinated . Externally, all of the four and six cotyledonary embryos had two cotyledonary petioles. Each of the cotyledonary petioles divided into two or three on the upper part fo the petiole which result in four and six cotyledons, respectively. However, the embryos had three different cotyledonary petioles in the three cotyledonary embryos. On the basis of the pattern of vascular system, the four and six cotyledonary embryos had the same basic vascular system as fnormal two cotyledonary embryos, Therefore the cotyledon number abnormality could result from the branching split of the abnormally thickened upper part of the cotyledonary petiole. However, the three cotyledonaryembryos had a different vascular system from the normla two cotyledonary embryos. They could be regarded as different varieties form the two cotyledon embryos. All embryos observed had short cylindrical plumule sheath which formed by the fusion of the cotyledon bases. The presence of plumule sheath strontgly implied that the initiation of the cotyledons was not from the two localized primordia but from the circular proimordiu formed at the blobular stageof embryo, and it is not consistent with current views of cotyledon initiation. On the formation of the primary vascular system of carrot seedlings, it is suggested that the primary vascular system of the plumule was formed independently from that of the root-hypocotyle-cotyledon system.

• 항공우주시스템공학회지
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• 제14권2호
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• pp.44-49
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• 2020

This work is intended to develop a flapping-type vertical wind turbine system that will be applicable to diesel generators and wind turbine generator hybrid systems. In the aerodynamic design of the wind turbine blade, parametric studies were performed to determine an optimum aerodynamic configuration. After the aerodynamic design, the structural design of the blade was performed. The major structural components of the flapping-type wind turbine are the flapping blade, the connecting part, and the stopper. The primary focus of this work is the design and analysis of the connecting part. Structural tests were performed to evaluate the blade design, and the test results were compared with the results of the analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1306-1311
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• 2006

The root cause of abnormal sound from a heat exchanger of condensate water system in a nuclear power plant is investigated by using the impact signal-processing methodology based on the Hertz theory. The predicted results for the location of impact force and the loose part size meet good agreement with the identified materials during the overhaul period in the plant. Nuclear power plants have experienced several loose parts and the frequency of the loose part will be increased along the aging of the plants. So, this analysis methodology for the impact signal will be widely utilized for the primary and secondary side of the nuclear power plant.

• 산업공학
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• 제10권2호
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• pp.1-13
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• 1997

The problem of the formation of machine-part cells in FMS is a very important issue at the planning and operating stages of FMS. This problem is inherently a combinatorial optimization problem, proven to be NP-complete(or, NP-hard). Among the several kinds of approaches which have been applied to solve the combinatorial optimization problems, the Simulated Annealing(SA) algorithm, a technique of random search type with a flexibility in generating alternatives, is a powerful problem solving tool. In this paper, the SA algorithm is used to solve machine cell-part family formation problems. The primary purpose of the study is to find the near-optimal solution of machine cell-part family formation problem, whare the product volume and number of operations are prespecified, that can minimize the total material handling cost caused by exceptional elements and intercell moves as much as possible. The results show that the SA algorithm is able to find a near-optimal solution for practical problems of the machine cell-part family formation.

• 한국통신학회논문지
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• 제29권2C호
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• pp.324-332
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• 2004

최근 영상 전체를 전송ㆍ복원하기보다는 영상의 일부 특정 영역이나 사용자 위주의 관심영역(ROI)에 대한 우선적 처리 요구가 웹 브라우징, 이미지 데이터베이스, 원격진료 등과 같은 응용 분야에서 증가하고 있다. 본 논문에서는 기존의 JPEG2000 Part1에서 사용한 Maxshift 방식을 이용하여 둘 이상의 ROI를 가지는 multiple-ROI 코딩 기법을 제안한다. 제안한 기법은 기존의 방식에서처럼 하나의 ROI 뿐만 아니라, multiple ROI를 가지는 영상 전송이 가능함을 보여준다. 또한 웨이브렛 변환(Wavelet Transform)을 이용한 점진적 전송 방식을 사용하기 때문에 낮은 대역폭에서도 사용자가 원하는 ROI를 non-ROI 보다 좀 더 우수한 품질로 전송ㆍ복원 할 수 있고 효율적인 압축이 가능함을 시뮬레이션을 통하여 확인하였다.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1199-1209
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• 2021

The detection of unexpected loose parts in the primary coolant system in a nuclear power plant remains an extremely important issue. It is essential to develop a methodology for the localization and mass estimation of loose parts owing to the high prediction error of conventional methods. An effective approach is presented for the localization and mass estimation of a loose part using machine-learning and deep-learning algorithms. First, a methodology was developed to estimate both the impact location and the mass of a loose part at the same times in a real structure in which geometric changes exist. Second, an impact database was constructed through a series of impact finite-element analyses (FEAs). Then, impact parameter prediction modes were generated for localization and mass estimation of a simulated metallic loose part using machine-learning algorithms (artificial neural network, Gaussian process, and support vector machine) and a deep-learning algorithm (convolutional neural network). The usefulness of the methodology was validated through blind tests, and the noise effect of the training data was also investigated. The high performance obtained in this study shows that the proposed methodology using an FEA-based database and deep learning is useful for localization and mass estimation of loose parts on site.

• Journal of Biosystems Engineering
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• 제9권1호
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• pp.22-33
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• 1984

Husk separator is an indispensable equipment in rice milling plants. However, any basic research on the designing and operating criteria of the husk separator have rarely been conducted in Korea. According to the survey results reported recently, grain loss occurs in the process of rice husk separation at custom rice milling plants in Korea and the performance of husk separator has also not been identified. With this regard this study was conducted with a typical commercial husk separator to investigate the effect of the operational factors such as feed rate, blower speed and opening ratio on the velocity distribution in the air duct and the performance of the separator. The results are summerized as follows: 1. The average wind velocity in the primary air duct increased linearly with the blower rpm and the size of air inlet port in both cases of double type and single type operations. 2. The coefficient of variation in the horizontal wind velocities in the primary air duct was the minimum when the opening ratio was 0.22 ($0.052m^2$ of air inlet port) in both cases of single type and double type operations regardless of the blower speeds used in this test. The average wind velocity at the upper part of air duct was greater by 2-5 m/s than the velocity at the bottom part in double type operation. In case of single type operation, however, the average velocity in the middle part was greater than the upper or bottom part when the opening ratio was greater than 0.74. 3. The relationship between the overall effectiveness of separation(Ed for double type and Es for single type) and the average wind velocity (Va) in the primary air duct was expressed in the following quadratic functions. $$Ed=-190.84+106.18Va-10.052Va^2$$ ($r^2$ = 0.97782) $$Es=-223.76+106.23Va-9.1935Va^2$$ ($r^2$ = 0.97029) The average wind velocity required to obtain the overall effectiveness of separation more than 80% ranged from 4.04 m/sec to 5.84 m/sec in case of double type operation, and from 4.70 m/sec to 6.20 m/sec in case of single type. 4. An optimum wind velocity can be obtained with an increase in the blower speed or the size of air inlet port as presented in Figure 8. There was a tendency that the faster the blower speed, the narrower the control range of the air inlet port. 5. The feed rates (1850kg/hr and 2100kg/hr) adopted in this experiment did not bring about a significant difference in both the overall effectiveness of separation and the power consumption. 6. The energy consumption increased cubically with the blower speed but linearly with the size of the air inlet port. On the basis of the results described in items 1, 3, and 6, it would be more economic to adjust the size of the air inlet port larger with a relatively low blower speed than to adjust the size smaller with a relatively high speed.

• KIEAE Journal
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• 제15권2호
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• pp.103-107
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• 2015

Purpose: Since September 1st, 2013, subjects of the evaluation have been expanded, and the evaluation standard has been detailed to enable Building energy rating system for all buildings. Accordingly, the new evaluation program (ECO2) has been developed, and therefore, apartment applied after September 1st, 2013 were evaluated with the new evaluation program. Therefore, this research suggests the improvement plan to figure out reasons for the evaluation result calculation and to calculate the evaluation results close to the actual energy usage by analyzing and comparing primary energy consumption as a result of the new evaluation program (ECO2) and actual heating energy usage on the same building. Method: When comparing evaluation results of the new evaluation program (ECO2) and actual heating energy usage, the tendency was similar but different. Also when comparing seasonally, the tendency was similar, but the different between actual heating energy usage and primary energy consumption during winter is greater than during spring or fall, and when comparing seasonal electric usage, heating alternatives were used through increased electrical usage during winter compared to during spring or fall. Result: Therefore, when evaluating apartment with the new program (ECO2) in the future, evaluation items relevant to the use of heating alternatives should be added, and the modification factor should be added according to the region. Based on the evaluation results of the research and actual energy usage, the Modification factors of the central part and the southern part were calculated respectively as 0.5 and 0.8.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2013년도 추계학술대회
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• pp.163-164
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• 2013

양방향차도선(CAR-FERRY)은 육지와 도서, 도서와 도서 간을 연결하는 교통수단 기능과 지속적인 해양관광객의 수요증가에 따른 해양관광 연계 연안여객 운송수단 역할을 하고 있다. 이에 따른 양방향 차도선은 이용의 편리성이 증대 되고 접안으로 인한 해양 사고를 줄일 수 있다. 양방향차도선은 등흘수(even) 상태로 프로펠러가 양쪽에 있기 때문에 프로펠러가 소직경 저회전으로 인하여 전진 운항 시에 반력에 의한 축계 및 프로펠러 파손 등이 발생할 수 있다. 이에 따른 엔진 출력, 선형, 비틀림 진동 등에 따른 감속기, 탄성커플링 선정, 횡진동 및 축계정렬(Shaft alignment)을 고려한 축계설계(베어링 수량, 폭, 간격)를 하여 선체의 추진축 1차 지지부의 구조에 대한 건전성을 평가하였다.