• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.69-75
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• 2000

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 1호
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• pp.103-108
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• 1999

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about loom underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

• 조명전기설비학회논문지
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• 제25권12호
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• pp.60-66
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• 2011

There are several technological problems have to be resolved for LEDs to be used as a general purpose light source. In addition, there are several differences between existing luminaires and the general planer LED luminaire for the intensity distribution. Therefore, the optical engineer then faces the challenging a problem of designing for a spatially extended and non-uniform light source. In the previous studies on the optical design of luminaires, a lot of studies on reflectors and light source have been conducted but the ones on prisms and lenses are insufficient at present. This study developed the numerical model of planar prism LED luminaire to control luminous intensity distribution of LED luminaires. And this study presents an optical calculation process for the prism optical design of a planar prism LED luminaire and a comparison of the simulation results between the developed numerical model and Photopia 2.0 to verify the accuracy of the numerical model. In addition, this study showed a method for the control of various luminous intensity distribution from the developed numerical model.

• 한국광학회지
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• 제9권3호
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• pp.129-133
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• 1998

광전자 계수법을 이용하여 준열광원에서 방츨되는 빛의 광전자 분포를측정하였다. 준열광원은 선편광된 He-Ne 레이저빔을 9$\mu$m의 거칠기로 표면이 연마된 유리판에 트과시킨 것으로, 연마유리판의 회전속도에 따라 결맞음시간에 따라 회전속도에 따라 결맞음 시간은 31.4$\mu$s로부터 2.48$\mu$s까지 변하는 특징을 갖는다. 준열과원의 결맞음시간보다 측정시간이 매우 길 때 광전자 분포는 Poisson 분포를 나타내었으나측정시간보다 광원의 결맞음시간이 길러질수록 광전자 분포는 Bose-Einstein 통계를 보였다.

• 한국음향학회지
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• 제37권6호
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• pp.437-442
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• 2018

본 논문에서는 환형배열을 이용하여 단일음원이 코히어런트 분산 분포를 가지는 경우 닫힌 형태로 음원의 위치를 추정하는 기법을 제안한다. 음원이 다중경로를 거쳐 센서에 도달하는 경우 분산음원으로 보이며 이때 음원의 위치는 대표 방위, 대표 고각, 대표 방위의 분포, 대표 고각의 분포 네 가지 변수로 표현될 수 있다. 이러한 경우 DSPE(Distributed Source Parameter Estimator) 기법과 같은 탐색 기법으로 네 변수를 찾기 위해서는 매우 많은 탐색과정을 필요로 한다. 본 논문에서는 빠른 위치 추정을 위해 센서간의 상관함수와 최소자승기법을 이용하여 닫힌 형식으로 대표 방위와 고각을 추정하는 기법을 제안한다. 특히 음원이 대표적인 분포 모델인 가우시안 분포를 따를 경우 방위와 고각의 표준편차 또한 닫힌 형식으로 추정한다. 시뮬레이션에서는 DSPE 기법과 비교하여 제안 기법의 타당성을 확인하였다.

• 한국대기환경학회지
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• 제15권6호
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• pp.757-765
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• 1999

Lagrangian particle dispersion model(LPDM) is an effective tool to calculate the dispersion from a point source since it dose not induce numerical diffusion errors in solving the pollutant dispersion equation. Fictitious particles are released to the atmosphere from the emission source and they are then transported by the mean velocity and diffused by the turbulent eddy motion in the LPDM. The concentration distribution from the dispersed particles in the calculation domain are finally estimated by applying a particle count method or a Gaussian kernel method. The two methods for calculating concentration profiles were compared each other and tested against the analytic solution and the tracer experiment to find the strength and weakness of each method and to choose computationally time saving method for the LPDM. The calculated concentrations from the particle count method was heavily dependent on the number of the particles released at the emission source. It requires lots fo particle emission to reach the converged concentration field. And resulting concentrations were also dependent on the size of numerical grid. The concentration field by the Gaussian kernel method, however, converged with a low particle emission rate at the source and was in good agreement with the analytic solution and the tracer experiment. The results showed that Gaussian kernel method was more effective method to calculate the concentrations in the LPDM.

• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1211-1218
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• 2017

Monte Carlo neutron transport codes generally use the method of successive generations to converge the fission source distribution to-and then maintain it at-the fundamental mode. Recently, a phenomenon called "clustering" has been noted, which produces fission distributions that are very far from the fundamental mode. In this study, a mathematical model of clustering in Monte Carlo has been developed. The model draws on previous work for continuous-time birth-death processes, as well as methods from the field of population genetics.

• 한국물환경학회지
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• 제21권3호
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• pp.236-241
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• 2005

The purpose of this study is to find out the source(s) and distribution of boron in Nak-dong River. In the year of 2002, the boron has been adopted as a toxic constituent for Korean drinking water standard. In this study, the analytical samples were collected at 11 stations in March, June, September and December 2002. These samples were analyzed by inductively coupled plasma-mass (ICP-MS) method. The recovery, relative standard deviation and method detection limit of the ICP-MS method for boron was $89{\sim}111.3%$, $2.21{\sim}3.81%$ and $5{\mu}g/L$, respectively. The distribution of boron was ranged $65{\sim}155{\mu}g/L$ in March, $26{\sim}125{\mu}g/L$ in June, $22{\sim}140{\mu}g/L$ in September and $50{\sim}162{\mu}g/L$ in December. The higher levels of boron were found at Kum-ho river nearby the industrial complex, which seemed to be greatly affected by domestic sewages and wastewater from the upper streams. Thus, the concentration of boron and that of other components showed strong statistical correlation in this area. In the Nak-dong River, industrial wastewater and domestic sewages is thought to be the sources of boron.

• 전기학회논문지
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• 제63권9호
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• pp.1206-1211
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• 2014

Most LV customers have been applying three-phase four-wire electric distribution system which supplies 1-phase and 3-phase load concurrently. Due to its structural simplicity, This system is easy to run. But it can also cause many problems from the unbalance, such as reduced output, increased loss etc. Also the unbalance in the load side causes the unbalance in the source side; it may lower the stability of the whole power system. In this paper, we propose the Y-Tz transformer winding method to reduce the current unbalance in the source side. Efficiency of this method was proven through the simulation and verification experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.211-213
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• 1999

This paper describes a new method for source current optimization of the electromagnetic devices. In a conventional method of current distribution optimization using design sensitivity based on a finite element method, position and width of coils are generally optimized under condition that shape of those is given. they cannot find the global minimum because the number of coils is pre-determined. To avoid this local minimum, source current region which is discretized uniformly is considered as design parameter. This discretized regions have zero or one current value during the optimization process. The proposed method is applied to magnetic resonance imaging(MRI) magnet.