• 한국해양공학회지
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• 제35권1호
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• pp.82-90
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• 2021

Owing to the advantages of assuring the best views and seawater exchange, submerged breakwaters have been widely installed along the eastern coast of Korea in recent years. It significantly contributes to promoting the advancement of shorelines by partially inhibiting incident wave energy. Observations were carried out by a pressure-type wave gauge in the Bongpo Beach to evaluate the coefficients of wave transmission via a submerged breakwater, and the results obtained were compared with those of existing conventional equations on the transmission coefficient derived from hydraulic experiments. After reviewing the existing equations, we proposed a transmission coefficient equation in terms of an error function. Although it exhibited robust relationships with the crest height and breaking coefficient, deviations from the observed data were evident and considered to be triggered by the difference in the incident wave climate. Therefore, in this study, we conducted a numerical experiment to verify the influence of wave period on the coefficients of wave transmission, in which we adopted a parabolic-type mild-slope equation model. Consequently, the deviation from calculated results appears to practically cover all deviation range in the observed data. The wave period and direction of the incident wave increased, the transmission coefficient decreased, and the wave direction was determined to demonstrate a relatively significant influence on the transmission coefficient. It was inferred that this numerical study is expected to be used practically in evaluating the design achievement of the submerged breakwater, which is adopted as a countermeasure to coastal beach erosion.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제16회 학술발표회 논문개요집
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• pp.182-182
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• 1999

• 수산해양기술연구
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• 제27권3호
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• pp.217-223
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• 1991

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.297-305
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• 2005

A high-speed spindle can be very sensitive to rotating mass unbalance which has harmful effect on many machine tools. Therefore, the balancing procedure to reducevibration in rotating system is certainly needed for all high-speed spindles. An active balancing program using influence coefficient method and an active balancing device of an electro-magnetic type have been applied to the developed high-speed spindle system in this study. A reliable gain-scheduling control using influence coefficients of the reference model although system characteristics are changed is applied. The stability of reference influence coefficients is verified by frequency response functions. The active balancing experiment for the developed high-speed spindle during operation is well performed with an active balancing program and device. As a result, controlled unbalance responses are below the vibration limit at all rotating speed ranges with critical speed.

• 대한전자공학회논문지SD
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• 제38권9호
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• pp.624-633
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• 2001

회절격자 반주기 길이의 랜덤 변이가 QWS-DFB 레이저의 특성을 나타내는 척도인 xL 값에 미치는 영향을 알아보았다. QWS-DFB 레이저의 양 거울면은 무반사면으로 하였고, 회절격자 랜덤 변이는 평균이 0이고 분산이 1인 상관되어 있는 두 Gaussian 랜덤 변수로 나타내었다. 회절격자 반주기의 랜덤 변이가 있으면 동일 위상성분의 되먹임이 적어져 유효 xL 값이 감소하고 모드 간격이 줄어든다. 그런데, 회절격자 주기의 랜덤 변이가 있을 때 곁모드 간격에서 구한 결합계수 xL/sub SM/값과 주모드 거울면 손실에서 구한 xL/sub SM/는 일치하지 않으며, 랜덤 변이가 없을 때의 xL값보다 작다. 이 결과는 곁모드 간격 또는 spontaneous emission spectrum을 사용하여 측정한 xL/sub SM/ 값을 실제로 되먹임되는 정도를 나타내는 xL/sub eff/로 해석하여서는 안된다는 사실을 보여준다.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4096-4101
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• 2023

Radon is a radioactive gas produced from the uranium-238 series. Radon gas affects public health and is the second cause of lung cancer. The study samples were collected from one area of the city of Jazan, southwest of the Kingdom of Saudi Arabia. The influence of engineering and physical parameters on the emanation coefficient of gas and other gas parameters was studied. Parameters for radon were measured using a CR-39 Solid-State Nuclear Track Detector (SSNTD) through a sealed emission container. The results showed that the emanation coefficient was affected directly by the change in the grain size of the soil. All parameters of measured radon gas have the same behavior as the emanation coefficient. The relationship between particle size and emanation coefficient showed a good correlation. The values of the emanation coefficient were inversely affected by the mass of the sample, and the rest of the parameters showed an inverse behavior. The results showed that increasing the volume of the container increases the accumulation of radon sons on the wall of the container, which increases the emission factor. The rest of the parameters of radon gas showed an inverse behavior with increasing container size. The results concluded that changing the engineering and physical parameters has a significant impact on both the emanation coefficient and all radon parameters. The emanation coefficient affects the values of the radiation dose of an alpha particle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.701-705
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• 2008

Design analysis and computer experiments (DACE) model is widely used to express efficiently the nonlinear responses in the field of engineering design. Kriging model, a DACE model, can approximately replace a simulation model that is very expensive or highly nonlinear. The kriging model is composed of the summation of a global model and a local model representing deviation from global model. The local model is determined by correlation coefficient of the pre-sampled points, where determination of the correct correlation coefficient has an effect on accuracy and robustness of the kriging model. Therefore, robustness of the correlation coefficient is explored with respect to degrees of the global model. Then we propose the range of correlation coefficient to make correct and robust kriging model and the influence of the correlation coefficients on the degrees of global model with respect to the nonlinearity of the pre-sampled responses.

• 대한전기학회논문지:전력기술부문A
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• 제50권12호
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• pp.568-574
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• 2001

The variations of real time electric power price in competitive electricity markets have influence on electric power demands of the consumers. The effects of the consumers for electric power price can be expressed the price elasticity coefficient of the power demand as a measurement. Residential, commercial, and industrial consumers with different characteristics cause the different price elasticity of the power demand due to changing the pattern of consumption. It is necessary that the effects of electric power demands as a function of elasticity coefficient for each loads should be analyzed in Korea which is processing deregulated electric market. Therefore, this paper calculate the elasticity coefficient of each loads and analysis the effects of electric power demands as a function of elasticity coefficient of inflexible and flexible consumers in competitive electricity market.

• Journal of Advanced Marine Engineering and Technology
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• 제24권3호
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• pp.113-120
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• 2000

On the absorber of absorption chiller/heater, LiBr solution at high concentration is sprinkled on a bundle of horizontal tube cooled by cooling water. In this case, the conditions of LiBr solution and cooling water have an influence on heat/mass transfer coefficient in this system. Therefor it is important to find optimal operation conditions of absorption chiller/heater to save energy. Heat and mass transfer coefficient increased with the increase of solution flow rate, and also heat and mass transfer rate increased but overall heat and mass transfer coefficient decreased by increasing the solution concentration within the experimental range. The superheating of the solution resulted in superior heat transfer character to a state of equilibrium from the point of heat flux and overall heat transfer coefficient.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.160.1-160.1
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• 2011

In this study, the influence of methodology of assessing water levels on the discharge coefficient of sluice for tidal power generation was investigated. A physical experiment was performed in a planar open channel by installing 1/70 scale model of the sluice caisson in the planar open channel. In front of and behind the sluice model, sloping bathymetry was made to reproduce corresponding field condition. By analyzing the experimental results, it was found that the location of measuring water levels significantly affects the estimates of the discharge coefficient, due to the variability of the parameter according to the head difference between the measuring locations. Therefore, it is necessary to be careful in estimating and utilizing the discharge coefficient in the relevant study of a tidal power generation.