• 한국수산과학회지
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• 제49권1호
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• pp.61-73
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• 2016

Water mass distribution and currents were investigated off the east coast of Korea near the Hupo Bank using the CTD and ADCP data from June to August 2010. The typical water masses were: (1) Tsushima Surface Water (TSW) from the East Korean Warm Current (EKWC) in the surface layer, (2) a shallow thermocline at 20-30 m depth, (3) Tsushima Middle Water (TMW) of high salinity (>34.2) below the pycnocline, (4) North Korean Cold Water (NKCW) of low salinity (<34.05) and low temperature (<4°C) in the lower layer. In June, a double eddy was observed in which a cold filament intruded cyclonically from the south around a pre-existing cold-core eddy. A burst of strong southward current was recorded in mid-August due to a warm filament from the meandering EKWC. Current in the N-S direction was predominant due to topographic effects, and the direction of the northward EKWC was frequently reversed in its direction due to the eddy-filament activity, whereas the influence of the wind was not noticeable. The vertical structure of the current was of a two-layer system, with the northward EKWC in the upper layer and weak southward flows corresponding to the North Korean Cold Current (NKCC) in the deeper layer.

• 한국전자파학회논문지
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• 제15권11호
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• pp.1062-1068
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• 2004

정자표면파가 전파되는 주파수 영역에서 페라이트 위에 놓여진 선로의 모서리 특이성을 Meixner가 제시한 방법을 이용하여 계산하였다. 구해진 모서리 특이성으로부터 정자표면파가 진행하는 방향의 모서리 부근에서의 전류 변화가 반대쪽 모서리에 비하여 급격함을 알 수 있었다. 또한 주파수 변화에 따라 모서리 조건도 변화하였다. 이 결과들은 이전의 수치해석 결과와 일치한다.

• Nuclear Engineering and Technology
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• 제21권3호
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• pp.193-204
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• 1989

본 논문에서는 정보 이론의 maximum entropy Principle을 이용하여 중성자속 분포를 재생하는 새로운 방법을 시도하였다. 어떤 대상에 대한 부분적인 정보가 있을 때, 이 정보의 한도 내에서 entropy를 최대화시키는 확률 분포는 가장 객관적인 것이 된다. Nodal method계산결과인 평균 중성자속과 current의 값을 prior information으로 삼고, 핵 연료 집합체의 경계에서의 중성자속 분포를 확률의 형태로 변환해서 확률로써 다룬다. Prior information의 한도 내에서 entropy를 최대화시키는 경계에서의 확률 분포를 구하면 핵연료 집합체의 경계에서의 중성자속 분포가 구해지는데, 이것을 경계조건으로 heterogeneous assembly calculation을 행하여 세부적인 중성자속 분포를 구한다. 이 새로운 방법을 몇 개의 benchmark problem assembly에 응용해 본 결과, 노심의 안쪽 부분에서는 이 방법이 form function method에 의한 것과 비슷한 정확도를 보였고 바깥 부분에서는 다소 큰 오차를 보였다. 본 논문에서는 surface-averaged neutron current를 prior in-formation에 포함시키지 못했는데, 이것을 포함시키면 결과가 훨씬 개선 될 것으로 보인다.

• 전기학회논문지
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• 제61권8호
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• pp.1115-1122
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• 2012

This paper analyzes eddy-current loss induced in magnets of surface-mounted permanent magnet (SPM) machines by using an analytical method such as a space harmonic method. First, on the basis of a two-dimensional (2D) polar coordinate system and a magnetic vector potential, the analytical solutions for the flux density produced by armature winding current are obtained. By using derived field solutions, the analytical solutions for eddy current density distribution are also obtained. Finally, analytical solutions for eddy current loss induced in rotor magnets are derived by using equivalent electrical resistance calculated from magnet volume and analytical solutions for eddy-current density distribution. In particular, the influence of time harmonics in armature current on the eddy current loss is fully investigated and discussed. All analytical results are validated extensively by finite element analysis (FEA).

• 한국표면공학회지
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• 제27권5호
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• pp.285-291
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• 1994

The effects of pulse current parameters on the composition and the microstructure of Pd-Ni alloy electrodeposits were studied. The cathode current efficiency of p.c. electrolysis conditions decreased with increasing both mean and peak current density and was lower than those under D.C. electrolysis condition. Palladium content of Pd-Ni alloy increased with increasing both peak current density and on-time, while it decreased with increasing mean current density and duty cycle. The preferred orientation of Pd-Ni alloys changed with increasing mean current density in the sequence of (111)+(110).(100) or (110)longrightarrow(111)longrightarrow(100) or random distribution of crystal structure. The surface morphology of Pd-Ni alloy changed mainly according to the mean current density and was related to the preferred orientation.

• 한국해양학회지
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• 제29권3호
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• pp.269-277
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• 1994

득량만의 20여개 지점에 대한 표층퇴적물 입도분포와 부유물총량을 해수에 의한 부유물이동 및 침전작용으로 해석하였다. 득량만의 표층퇴적물은 대부분 비대칭 단일 모드 입도분포를 보이며 거문고 욕지도간의 내대륙붕에 분포하는 뻘구역의 입도분포와 매우 유사하다. 입도분포자료의 분석에 의하면 득량만의 표층쾨적물은 황애쪽에서 동 진하는 부유이동 세립질퇴적물이 만으로 유입되어 퇴적된 것으로 보인다. 조립질퇴적 물의 함량과 계산에 의해 얻어진 조류의 유속(Lee, 1994)이 서로 유사한 공간적인 분 포를 나타내는 것으로 볼 때, 득량만내의 표층퇴적물은 강한 조류와 얕은 수심으로 인 하여 부유이동 및 침전작용을 거듭하는 것으로 판단된다. 이러한 작용이 퇴적물로 하 여 금 특징적인 비대칭 단일모드 입도분포를 가지게끔 하는 것으로 보인다. 또 이러한 작용은 부유물총량의 분포에도 큰 영향을 미치는 듯하다. 득량만에서 의 평균 부유물 농도는 표저층간의 차이는 하계가 동계에 비해 2배 정도크다. 이것은 득량만에서 하계 에는 수괴의 성층현상이 발달하는데 반해 동계에는 균질한 수괴가 발달하는데 원인이 있는 것으로 판단된다. 부유물질의 양적인 분포와 계절적인 변동특성을 종합해서 볼 때 득량만내의 부유물 총량을 크게 좌우하는 요인은 유속 및 성층변동과 같은 수괴의 물리적인 특성, 수심과 같은 지형적 특성 그리고 부분적으로 육지로부터 의 부유물질 의 공급등이다.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.401-405
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• 2012

Current research about voltage leakage involves investigation of the effects of leaked voltage and current on humans through simulated environments and dummies. Electrocution results from leaked current when electricity flows through the body as a result of potential difference. Research that analyzes actual electrocution is insufficient because of the danger from leaked voltage present in the leakage area. This thesis analyzes magnetic flux density from current around a leak to investigate the distribution of current. The authors used a simulated environment to investigate electrocution accidents that frequently occur during floods through leakage along metal surfaces, and evaluated the distribution of leaked magnetic flux.

• Journal of Power Electronics
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• 제13권2호
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• pp.250-255
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• 2013

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

• 대한기계학회논문집
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• 제17권12호
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• pp.2962-2969
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• 1993

Recently, a study on the mirror-like surface grinding of brittle materials is active and as branch of these study, new dressing method for superabrasive wheel, electrolytic inprocess dressing(Elid) was developed. Using Elid, the mirror-like surface of brittle material can be generated without polishing or lapping process. In the future, Elid grinding will take important place in industry. But so far the analysis on Elid grinding was not quantitative but qualitative. In this study, The purpose is the quantitative analysis on Elid grinding by computer simulation, For computer simulation, the mean and the variance of the abrasive distribution were measured by tracing of the grinding wheel with stylus in transverse direction in the case of respective dressing current condition. This measurement result in a density distribution of abrasive by mathematical formulation using statistical method. The prediction of the surface roughness in Elid grinding was based on this density distribution.

• 한국재료학회지
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• 제22권9호
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• pp.482-488
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• 2012

To fabricate a precise micro metal mold, the electrochemical etching process has been researched. We investigated the electrochemical etching process numerically and experimentally to determine the etching tendency of the process, focusing on the current density, which is a major parameter of the process. The finite element method, a kind of numerical analysis, was used to determine the current density distribution on the workpiece. Stainless steel(SS304) substrate with various sized square and circular array patterns as an anode and copper(Cu) plate as a cathode were used for the electrochemical experiments. A mixture of $H_2SO_4$, $H_3PO_4$, and DIW was used as an electrolyte. In this paper, comparison of the results from the experiment and the numerical simulation is presented, including the current density distribution and line profile from the simulation, and the etching profile and surface morphology from the experiment. Etching profile and surface morphology were characterized using a 3D-profiler and FE-SEM measurement. From a comparison of the data, it was confirmed that the current density distribution and the line profile of the simulation were similar to the surface morphology and the etching profile of the experiment, respectively. The current density is more concentrated at the vertex of the square pattern and circumference of the circular pattern. And, the depth of the etched area is proportional to the current density.