• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.86-88
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• 2005

The line-start permanent magnet synchronous motor has a high efficiency and an advantage in constant speed operation regardless of the effect of load variation. However it is difficult to predict the performance of characteristics accurately, because of the unbalanced starting torque with the initial starting position of the rotor and the generation of a break torque. In this paper the dynamic characteristics of the line-start permanent magnet synchronous motor arc described and compared with those of the squirrel-cage induction motor through the simulation to find the characteristics of the permanent magnets and the rotor bars in the line-start permanent magnet synchronous motor.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1460-1465
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• 2012

본 연구에서는 소방배관용 아연도금 강관을 용접하기 위하여 반자동 가스메탈아크용접장치를 개발하고 최적 용접 조건을 확립하고 용접성을 조사하기 위해 보호가스, 전압을 변화시켜 용접시험을 수행하였다. Ar 가스에 $O_2$를 첨가함으로써 미려한 비드외관과 기공률이 감소되었다. 반자동 용접부는 기계적 강도와 용접이음효율이 수동용접부에 비해 약 1.8배 우수하였으며 수압시험에 의해 건전성이 확인되었다. 본 연구에서 개발된 반자동용접장치로 비숙련자도 강관용접이 가능하며 용접결함이 적고 용접생산성을 증대시킬 수 있을 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2185-2189
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• 2010

Closely arranged CdSe and Zn doped CdSe vertical nanorod bundles were grown directly on FTO coated glass by using electrodeposition method. Structural analysis by XRD showed the hexagonal phase without any precipitates related to Zn. FE-SEM image showed end capped vertically aligned nanorods arranged closely. From the UV-vis transmittance spectra, band gap energy was found to vary between 1.94 and 1.98 eV due to the incorporation of Zn. Solar cell parameters were obtained by assembling photoelectrochemical cells using CdSe and CdSe:Zn photoanodes, Pt cathode and polysulfide (1M $Na_2S$ + 1M S + 1M NaOH) electrolyte. The efficiency was found to increase from 0.16 to 0.22 upon Zn doping. Electrochemical impedance spectra (EIS) indicate that the charge-transfer resistance on the FTO/CdSe/polysulfide interface was greater than on FTO/CdSe:Zn/polysulfide. Cyclic voltammetry results also indicate that the FTO/CdSe:Zn/polysulfide showed higher activity towards polysulfide redox reaction than that of FTO/CdSe/polysulfide.

• 대한기계학회논문집
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• 제7권3호
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• pp.263-269
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• 1983

Underwater welding by a gravity arc welding process was investigated by using six types of coated electrodes and SM41A steel plates of 10 mm thickness as base metal and it was ascertained that this process may be put to practical use. Main results obtained are summarized as follows: 1. Angle of electrode affects no influence on bead appearance and the proper range of welding current and diameter of electrode for the high titanium oxide type is relatively wider than that for the ilmenite type. And the lime titania type, high titanium oxide type and ilmenite type of domestic coated arc welding electrodes of .phi.4 mm could attain the soundest underwater welded joints which contain no welding imperfection. 2. According to macro-structure, micro-structure and hardness distribution inspectionson underwater welded joint, the area between the HAZ and the surface of the weld in neighbourhood of the bond has the maximum hardness value. The structure of these parts is martensite and bainite. Other parts contain mocro-ferrite, micro-pearlite structure, which contain soundness of welded joint free from weld imperfection. 3. On consideration of both tensile strength of more than 100% joint efficiency and sufficient impact value, the welding condition which can get optimal welding strength is heat input of 1,400-1,500 J/mm, current of 200-215 ampere (voltage of 32-33 volts) in the case of lime titania type electrode. 4. Underwater welding strength (tensile strength, impact strength) depends on heat input (or current) quantitatively and they have the relationship of parabolic function. Each experimental equation has a high reliability and its percent of mean error is 4.14%. 5. It is suggested that the optimal design of weld strength by welding condition (current, heat input) could be utilized for a quality control of underwater welding.

• Journal of Computational Design and Engineering
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• 제2권4호
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• pp.206-217
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• 2015

This paper presents a complete S-shape feed rate scheduling approach (CSFA) with confined jerk, acceleration and command feed rate for parametric tool path. For a Non-Uniform Rational B-Spline (NURBS) tool path, the critical points of the tool path where the radius of curvature reaches extreme values are found firstly. Then, the NURBS curve is split into several NURBS sub-curves or blocks by the critical points. A bidirectional scanning strategy with the limitations of chord error, normal/tangential acceleration/jerk and command feed rate is employed to make the feed rate at the junctions between different NURBS blocks continuous. To improve the efficiency of the feed rate scheduling, the NURBS block is classified into three types: short block, medium block and long block. The feed rate profile corresponding to each NURBS block is generated according to the start/end feed rates and the arc length of the block and the limitations of tangential acceleration/jerk. In addition, two compensation strategies are proposed to make the feed rate more continuous and the arc increment more precise. Once the feed rate profile is determined, a second-order Taylor's expansion interpolation method is applied to generate the position commands. Finally, experiments with two free-form NURBS curves are conducted to verify the applicability and accuracy of the proposed method.

• 전기학회논문지
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• 제58권12호
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• pp.2446-2452
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• 2009

A Ceramic Metal-halide lamp is achieved by adding multiple metals to a basic mercury discharge. Because the vapor pressure of most metals is very much lower than mercury itself, metal-halide salts of the desired metals, having higher vapor pressures, are used to introduce the material into the basic discharge. The metal compounds are usually polyatomic iodides, which vaporize and subsequently dissociate as they diffuse into the bulk plasma. Metals with multiple visible transitions are necessary to achieve high photometric efficiency and good color. Compounds of Sc, Dy, Ho, Tm, Ce, Pr, Yb and Nd are commonly used. The maximum visible efficacy of a Ceramic Metal Halide lamp, under the constant of a white light source, is predicted to be about 450lm/W. This is controlled principally by the chemical fill chosen for a particular lamp. Current these lamps achieve 130lm/W and these life time are the maximum 16,000[hr]. So factors of performance lower are necessary to improve lamp performance. In this paper, we analyzed factors of performance lower by accelerated deterioration test. The lamp was operated with short duration turn-on/turn-off procedure to enhance the effect due to electrode sputtering during lamp ignition. The tested lamp that was operated with a longer turn-on/off(20/20 minutes) showed blackening, changed distance between electrodes and lowered color rendering & color temperature by losses of Dy at 421.18nm, I at 511nm, T1 at 535nm and Na at 588nm compared with the new lamp.

• 전력전자학회논문지
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• 제9권2호
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• pp.112-118
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• 2004

본 논문은 선박 추진 장치를 위한 저속 영역에서 최대 토크를 내는 대용량 BLDCM(Brushless DC motor)의 설계에 관한 연구이다. 기존의 추진 장치용 모터는 직류기 및 권선형 유도 전동기 등을 사용함으로 인하여 유지 보수가 필요하였다. 본 논문에서는 유지 보수가 필요 없고 저속에서 큰 토크를 발생 할 수 있는 BLDCM 설계를 하였다. 설계시 출력 리플 및 진동, 소음을 유발하는 코깅 토크 저감을 고려하기 위해 설계변수로 공극길이와 자극 각 등을 취하여 이의 변화에 대한 최저 코깅 토크를 가지는 최적형상을 구하고, 전동기 특성을 FEM과 Maxwell stress tensor법을 이용하여 해석하였다. 최저의 코깅 토크를 가지며 저속영역에서 최대 토크를 발생 할 수 있는 선박 추진 장치용 SPM type의 BLDCM을 설계하였다.

• 한국진공학회지
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• 제17권2호
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• pp.96-101
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• 2008

MgO는 플라즈마 디스플레이 패널 (Plasma Display Panel, PDP)의 보호막으로 널리 쓰이고 있다. 기존의 산소 이온빔 보조 증착(Ion-Beam-Assisted Deposition, IBAD) 방법을 이용하여 MgO 보호막을 형성시킨 경우 이온빔의 충전에 의해 야기되는 아크(Arc) 문제 등이 있었다. 이 문제점을 해결하기 위하여, 산소 중성빔 보조증착(Neutral-Beam-Assisted Deposition, NBAD) 방법을 이용하여 MgO를 증착하였다. 그리고 산소 중성빔의 에너지를 변화시킴에 따라 MgO 보호막의 특성과 PDP 패널 방전 특성에 미치는 영향을 분석하였다. 이에 따른 실험 결과로부터 산소 중성빔 에너지가 300eV일 때, 최소 방전 개시 전압, 최고 발광 휘도 및 최고 발광 효율을 얻을 수 있었다.

• Transactions on Electrical and Electronic Materials
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• 제5권1호
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• pp.1-6
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• 2004

Zinc sulfide is a semiconductor with wide band gap and high refractive index and hence promising material to be used as ARC on commercial silicon solar cells. Uniform deposition of zinc sulfide (ZnS) by using chemical bath deposition (CBD) method over a large area of silicon surface is an emerging field of research because ZnS film can be used as a low cost antireflection coating (ARC). The main problem of the CBD bath process is the huge amount of precipitation that occurs during heterogeneous reaction leading to hamper the rate of deposition as well as uniformity and chemical stoichiometry of deposited film. Molar concentration of thiorea plays an important role in varying the percentage of reflectance and refractive index of as-deposited CBD ZnS film. Desirable rate of film deposition (19.6 ${\AA}$ / min), film uniformity (Std. dev. < 1.8), high value of refractive index (2.35), low reflectance (0.655) have been achieved with proper optimization of ZnS bath. Decrease in refractive index of CBD ZnS film due to high temperature treatment in air ambiance has been pointed out in this paper. Solar cells of conversion efficiency 13.8 ％ have been successfully achieved with a large area (103 mm ${\times}$ 103 mm) mono-crystalline silicon wafers by using CBD ZnS antireflection coating in this modified approach.

• 자원리싸이클링
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• 제26권1호
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• pp.37-42
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• 2017

이산화탄소 저감을 위한 유효한 방법 중의 하나로 칼슘규산염 광물의 간접탄산염화 공정이 보고되고 있다. 이 공정은 염산, 질산 등의 산에 의하여 칼슘규산염으로부터 칼슘성분을 침출하는 단계와 이산화탄소에 의한 침출용액의 탄산염화 단계의 두 과정으로 구성된다. 침출용매로 초산수용액을 사용하는 경우에는 침출용액을 이산화탄소로 탄산염화 하는 과정에서 초산이 재생성 되어 침출단계로 순환되어 침출용매로 재사용될 수 있다. 제철 및 제강슬래그와 같은 산업부산물은 칼슘규산염을 많이 함유하고 있어 간접탄산염화공정의 원료로 사용될 수 있다. 본 연구에서는 초산수용액에 의한 국내 전기로제강슬래그의 침출효율을 조사하기 위하여, 초산수용액 농도, 침출온도 및 침출시간 등의 침출조건 변화에 따른 침출실험을 수행하였다.