• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.97-100
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• 2008

Polar and non-polar GaN was grown by the HVPE on various substrates and influence of polarity has been investigated. The $10\;{\mu}m$ thickness GaN were grown by HVPE is along A-plane ($11{\bar{2}}0$), C-plane (0001) and M-Plane ($10{\bar{1}}0$) sapphire substrate respectively. Surface properties were observed by optical microscope and atomic force microscopy. High resolution X-ray diffraction (HR-XRD) confirms the wurtzite structure. The donor band exciton peak located at ${\sim}3.4\;eV$ and also located yellow luminescence peak at 2.2 eV. The polarity of the GaN film has a strong influence on the morphology and the optical properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.259-264
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• 2012

Automatic magnetic abrasive polishing (MAP), which can be applied after machining of a mold on a machine tool without unloading, is very effective for finishing a free-form surface such as a complicated injection mold. This study aimed to improve the efficiency of MAP of a non-ferrous mold surface. The magnetic array table and control of the electromagnet polarity were applied in the MAP of a free-form surface. In this study, first, the magnetic flux density on the mold surface was simulated to determine the optimal conditions for the polarity array. Then, the MAP efficiency for polishing a non-ferrous mold surface was estimated in terms of the change in the radius of curvature and the magnetic flux density. The most improved surface roughness was observed not only in the upward tool path but also in the working area of larger magnetic flux density.

• Polymer(Korea)
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• v.36 no.6
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• pp.699-704
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• 2012

Double-layered polymeric carrier was designed for release control of hydrophilic drug in oral administration. Biopolymeric chitosan and alginate were examined as polar absorbents, poly(D,L-lactide) as a hydrophobic shell, and theophylline and diclofenac sodium as loading drugs. The fabrication of the carriers was prepared in the form of double-layered microsphere for delayed and successively extended release, which consisted of outer shell of poly(D,L-lactide) and inner core of alginate or chitosan with drugs. Morphologies and drug-release behaviors of the carriers were investigated, which were influenced by a combination of polarity between carrier and drug. It was confirmed that the relative polarities of the carriers, the drugs, and the environmental pH affected significantly the drug-release property.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.1
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• pp.109-118
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• 2016

Traffic congestions are rapidly increasing in urban areas. In order to reduce these problems, it needs real-time data and intelligent techniques to quickly identify traffic activities with useful information. This paper proposes a Fuzzy Domain Ontology(FDO)-based opinion mining system to monitor the transportation network in real-time as well to make a city polarity map for travelers. The proposed system retrieves tweets and reviews related to transportation activities and a city. The feature opinions are extracted from these tweets and reviews and then used FDO to identify transportation and city features polarity. This FDO and intelligent prototype are developed using $Prot{\acute{e}}g{\acute{e}}$ OWL (Web Ontology Language) and JAVA, respectively. The experimental result shows satisfactory improvement in tweets and review's analyzing and opinion mining.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.67-73
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• 2009

The magnetic saliency effect in surface-mounted permanent-magnet (SMPM) motors on the torque control at high speeds is first presented and analyzed in this paper. The d- and q- axes impedance are measured by proposed State-Filter. Measurement of the d- and q- axes impedance difference is performed to prove the existence of the magnetic saliency. Then, the saliency effects on the torque control performance in the flux weakening region are discussed. Based on the developed motor modeling with the reluctance torque, the proposed control adjusts the d- and q-axis current toward the operating point to track the commanded torque. The feasibility of the presented idea is verified by experimental results on a commercial 600[W] SMPM motor.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.490-492
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• 2008

고압 전원 장치(High Voltage Power Supply)는 근래에 와서 산업전반에 응용이 매우 광범위하게 확산되고 있고 고전압 장치가 필수적으로 이용 되어야 하는 분야가 점차 확산되고 있다. 응용분야로는 신소재 개발과 플라즈마 응용을 위한 공업용과 민생용, 의료기기용, 군사용, 또한 프린터에 이르기까지 다양하게 있다. 가정이나 사무실에서 쉽게 접할 수 있는 IT장비인 프린터인 경우에도 전원 공급 장치의 측면에서는 화상형성에 있어 가장 필수적인 안정적이고 다기능을 가지는 고압 전원장치를 적용하고 있고, 수요 또한 증가하고 있다. 본 논문은 낮은 입력 DC전압에서 높은 음의 DC전압을 출력하는 높은 전환 비의 극성 반전 형 DC/DC 전력 변환 회로에 관한 것으로써, 하나의 스위치, 하나의 인덕터, 그리고 다수개의 캐패시터와 다이오드로 구성된다. 기존의 극성 반전 형 DC/DC 컨버터 회로와 비교하여, 고압 변환 트랜스포머 대신에 인덕터를 사용할 수 있어, 자기 소자의 부피 및 크기는 물론 원가저감이 가능하다. 또한 반도체 소자의 Voltage Stress가 감소된다. 제안된 회로의 원리를 분석하고, 종래의 고압 전원장치와 비교함으로써 장점을 알아본 후, 동작원리에 대한 타당성을 Simulation 및 실험을 통하여 검증한다.

• Polymer(Korea)
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• v.25 no.6
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• pp.803-810
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• 2001

A nonlinear optical hyperbranched polyester (PE-Azo/Hyper) was synthesized from 4-[N,N-bis(hydroxyethyl)amino-4'-formyl] azobenzene and cyanoacetic acid by a Knoevenagel polycondensation using 4-(dimethylamino) pyridine as a base. The resulting polymer was soluble in polar aprotic solvents such as N,N-dimethylformamide and 1-methyl-2-pyrrolidinone and could be processed into optical quality films by spin coating. The molecular weight was determined to be $M_w$=61,800 ($M_W/M_n{=1.86}$) by gel permeation chromatography using polystyrene as a standard. No melting point was detected by differential scanning Calorimeter, indicating that this polymer presents an amorphous state. It shows a glass transition temperature of $121^{\circ}C$. The second-order nonlinear optical coefficient $d_{33}$ of the poled polymer determined by the second harmonic generation at 1064 nm was 25.4 pm/V.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.594-599
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• 2017

In this thesis, the development and the verification of the test-aid are described, providing various attitude errors through the electric stimulus to the Sun sensor. This test-aid for 2-axis analogue Sun sensor is used for polarity test in the assembly stage for GK2 satellite. The test-aid used for GK2 satellite is for COMS satellite and, due to the failure risk, manufactured by domestic company. The characteristics of the COMS test-aid used for GK2 satellite and the manufactured test-aid are showed with similar through the several tests. In this thesis, there are conformed the capability for replacing of test-aid because the characteristics of the manufactured test-aid is acquired same as that of the COMS test-aid using the controller tuning functions.

• Korean Journal of Plant Tissue Culture
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• v.27 no.1
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• pp.19-23
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• 2000

The experiment was carried out to investigate the influence of light condition and polarity of explant on adventitious shoot formation from cotyledon of apple in vitro The treatment of light culture after 10days dark treatment showed effective result than other treatments on the rate of adventitious shoot formation on light intensity treatments and also the treatment of blue light treatment after 4days dark treatment showed more effective result than other treatments in light quality treatments. The polarity of explant influence on adventitious shoot formation. Adventitious multiple shoot formation occured at the proximal end of an excised cotyledon. In other words. shoot organogenesis occured at the proximal cut surfaces of both proximal and distal explants rather than at the distal cut surface of proximal explants.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.476-482
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• 2013

In this work, the effects of electrochemical oxidation of carbon fiber surfaces on mechanical interfacial properties of carbon fibers-reinforced polarized-polypropylene matrix composites were studied with various current densities during the treatments. Surface properties of the fibers before and after treatments were observed by SEM, AFM, XPS, and contact angle measurements. Mechanical interfacial properties of the composites were measured in terms of critical stress intensity factor ($K_{IC}$). From the results it was found that $O_{1s}$ peaks of the fiber surfaces were strengthened after electrochemical oxidation which led to the enhancement of surface free energy of the fiber, resulting in good mechanical performance of the composites. It can be concluded that electrochemical oxidation of the carbon fiber surfaces can control the interfacial adhesion between the carbon fibers and polarized-polypropylene in this composites system.