• 한국해양공학회지
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• 제24권2호
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• pp.34-40
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• 2010

When a large ship is advancing in waves, it undergoes hydroelastic response, which affects the structural stability and the fatigue destruction of the ship. Therefore, to predict an accurate hydroelastic response, it is necessary to conduct a thorough analysis of hydroelastic response, including fluid-structure interactions. In this research, the ship is divided into many hull elements, to calculate the fluid forces and wave exciting forces on each element. Using the three-dimensional source distribution method, the calculated fluid forces and wave exciting forces are assigned to nodes of the hull elements. The neighbor nodes are connected with elastic beam elements. We analyzed hydroelastic responses, using the finite elements method.

• 한국전자파학회논문지
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• 제10권2호
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• pp.291-301
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• 1999

원하는 역산란 패턴을 만족시키는 일차원 비선형 분포함수를 합성하는 방법을 제안하였다. 이 방법은 일차 원 역산란 문제로부터 유도된 Riccati 방정식의 해의 역변환에 기본을 두고 있다. 그 해는 collinear 배열 안테 나에서의 배열인자 혹은 정규화된 공간인자와 유사한 형태를 가지므로 연관된 비선형 분포함수를 구하기 위 해 line-source 법에 입각한 패턴 합성법을 사용하였다. 이 과정들은 최적화 기법에 의해 수행되며, 분산특성 을 갖는 매질내에서 임의의 전송선로를 특정 주파수 대역내에서 합성하는 예와 저항성 스트립의 산란패턴 제어 등의 예로부터 제안한 방법의 타당성을 수치적으로 입증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.1100-1102
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• 2015

본 논문에서는 스테레오 기반 감마선원 탐지장치를 통해 감마선원을 포함하는 공간을 래스터 스캔방식으로 스캔하여 가시광영상과 감마선영상을 획득하고, 스테레오 감마선 탐지장치로부터 선원까지의 거리와 방향에 대한 3차원 정보 획득 및 가시화를 수행하였다. 탐지장치의 구성은 감마선원 탐지를 위한 방사선 검출부, 선원탐지를 위해 래스터스캔방식의 스캔을 위한 팬틸트 그리고 가시광영상을 위한 CCD 카메라로 이루어진다. 선원에 대한 공간분포를 측정하기 위해 스테레오 구조의 장치를 구현하였으며 스테레오 영상획득을 위해 CCD 카메라와 감마선 탐지장치는 각각 2대로 구성하였다. 탐지선원에 대한 분포를 나타내기 위해 감마선 탐지 장치와 가시광 카메라에 대한 보정을 수행하였고, 각각의 카메라에 대한 스테레오 보정을 수행한 후 가시광영상과 감마선영상 중첩을 통해 감마선원에 대한 분포를 나타내었다. 좌, 우 분포영상에 대한 정류화처리 후 스테레오 영상에 대한 가시화결과를 도출하였다.

• 한국진공학회지
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• 제18권3호
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• pp.176-185
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• 2009

ICP source의 성능과 구현 가능성은 impedance와 전기장, 자기장의 공간 분포에 큰 영향을 받는다. ICP source의 impedance는 ICP 안테나와 플라즈마의 impedance에 의해 결정된다. 안테나 설계에 있어서 안테나에 형성되는 고전압을 방지하고 공정 중 급격한 impedance 변화를 방지하기 위해서는 ICP source의 허수 impedance가 $-100\;ohm{\sim}+100\;ohm$의 영역에 존재하는 것이 유리하다. 플라즈마 균일도는 안테나에 흐르는 전류와 전압에 의해 형성되는 전기장 세기와 자기장 세기에 영향을 받는다. 원형 안테나와 대칭성이 개선된 안테나에 대해 전자기 simulation과 플라즈마 밀도의 공간분포를 측정하였으며 안테나 형태에 따른 전자기장과 플라즈마 밀도 분포의 개선을 확인하였다. 반경 방향 균일도를 조절하기 위해서는 일반적으로 지름이 다른 복수개의 안테나를 동심원 상에 배치하는 방법을 사용한다. 각 안테나들을 병렬로 연결한 경우 각각의 안테나의 임피던스에 따른 전류 분배 비율이 상이하며, 분배 비율을 조절하기 위해 코일 또는 capacitor를 연결할 경우 나타나는 현상을 계산하였다.

• 대한안전경영과학회지
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• 제11권3호
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• pp.121-129
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• 2009

Today, many companies will be isolated in competition if they do not have competitive power to overcome quick change and big crisis of market. Nowadays, globally high-grade companies have done their best for increasing their competitive power through a many kinds of methods in keen competition for making of pacesetting position. This study focuses on distribution with the domains like capacity, layout, amount of location, assignment of product, operation procedure and operation rule in order to improve these domains, we make a further application of eight analysis ways based on DMAIC method for improving operation of processes of distribution center as the third profit source. The purpose of this study is to seek an approach that can easily adopt of Lean Six Sigma in operational management of distribution center by a kind of data, analysis method and template.

• 대한전기학회논문지:전력기술부문A
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• 제50권3호
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• pp.146-152
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• 2001

This paper describes an accurate fault location algorithm based on sequence current distribution factors for a double-circuit transmission system. The proposed method uses the voltage and current collected at only the local end of a single-circuit. This method is virtually independent of the fault resistance and the mutual coupling effect caused by the zero-sequence current of the adjacent parallel circuit and insensitive to the variation of source impedance. The fault distance is determined by solving the forth-order KVL(Kirchhoff's Voltage Law) based distance equation. The zero-sequence current of adjacent circuit is estimated by using a zero-sequence current distribution factor and the zero-sequence current of the self-circuit. Thousands of fault simulation by EMTP have proved the accuracy and effectiveness of the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.137-144
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• 2006

This paper proposes novel protection schemes for grid-connected distributed generation (DG) units using the fault location algorithm. The grid-connected DG would be influenced by abnormal distribution line conditions. Identification of the fault location for the distribution lines at the relaying point of DG helps solve the problems of the protection relays for DG. The proposed scheme first identifies fault locations using currents and voltages measured at DG and source impedance of distribution networks. Then the actual faulted feeder is identified, applying time-current characteristic curves (TCC) of overcurrent relay (OCR). The method considering the fault location and TCC of OCR might improve the performance of the conventional relays for DG. Test results show that the method prevents the superfluous operations of protection devices by discriminating the faulted feeder, whether it is a distribution line where DG is integrated or out of the line emanated from the substation to which the DGs are connected.

• 한국안전학회지
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• 제19권2호
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• pp.34-40
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• 2004

This paper presents an analysis of SAR(Specific Absorption Rate) distribution characteristics in a head model using FDTD(Finite Difference Time Domain). In this study human head was modelled in four elements-layered structure, consisting of skin, fat, skull and brain. To calculate the electromagnetic fields wihtin the head model, FDTD method was used. In the FDTD method, the electromagnetic wave is analyzed by solving a Maxwell's equations repeatedly. For the calculation, distance between power source and head model increased by 10[m]. Power density and incident electric field intensity were calculated. Based on the incident electric field, the program which calaculated internal electric fields intensity and SAR calculation of the head model were developed. The results of developed program using FDTD were compared with those of a commericial programs, which showed the availability and usefulness of the suggested scheme in this paper.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제24권1호
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• pp.93-102
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• 2020

The concept of temperature distribution in inhomogeneous semi-infinite solids is examined by making use of direct integration method. The analysis is done on the solution of the in-plane steady state heat conduction problem under certain boundary conditions. The method of direct integration has been employed, which is then reduced to Volterra integral equation of second kind, produces the explicit form analytical solution. Using resolvent- kernel algorithm, the governing equation is solved to get present solution. The temperature distribution obtained and calculated numerically and the relation with distribution of heat flux generated by internal heat source is shown graphically.

• 한국정밀공학회지
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• 제32권12호
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• pp.1023-1029
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• 2015

Laser-assisted machining (LAM) is one of the most effective methods for enhancing the machinability of difficult-to-cut materials, such as titanium alloys and various ceramics, and has been studied by many researchers. LAM is a method that facilitates machining by softening a workpiece using a laser heat source. The advantages of the LAM process are decreases in tool wear, cutting force, and surface roughness. However, when the material is over-heated, melting or burning can occur. This study analyzed the heat source distribution with regard to overlapping of preheating on the laser heating path with an acute angle, a right angle and obtuse angles. Then, a power reduction method was proposed to reduce the melting and burning of the workpiece.