• 전자공학회논문지S
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• 제36S권8호
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• pp.113-122
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• 1999

본 논문에서는 스위칭 손실을 저감시키고, 높은 주파수 동작에 적합한 새로운 Watkins - Johnson 공진형 컨버터를 제안하였다. 정상상태 해석에서는 제안 된 공진형 컨버터의 전압이득은 스위칭 주파수에 의존하게 된다는 것을 밝혔다. 따라서 컨버터의 출력전압을 안정시키기 위해서는 부하 전류 변화에 따라 스위칭 주파수도 함께 변화시켜야한다. 또한 해석결과를 토대로, 스위치의 전압 스트레스를 최소화시키고, 영전압 스위칭되는 조건하에서 컨버터의 공진소자 값을 결정할 수 있는 최적의 설계방식을 제시하였다. 끝으로 Watkins-Johnson 공진형 컨버터의 실험회로를 구성하여 최적 설계방식의 타당성을 입증하였다.

• 한국세라믹학회지
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• 제42권2호
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• pp.140-144
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• 2005

The microstructures and mechanical properties of Tetragonal Zirconia Polycrystals (TZP) sintered bodies, which made by pressureless and spark plasma sintering techniques, were investigated using XRD, SEM, and TEM techniques. In the spark plasma sintered samples, the TZP grains were equiaxed type including many sub-grain boundaries regardless of sintering conditions. The biaxial strength of TZP having an average of 80 nm grains in diameter was high in value with 1025 MPa, but fracture toughness showed a low value due to the absence of a fracture toughening mechanism such as transformation toughening. In the Pressureless Sintered (PLSed) samples, the grain size of TZP was strongly dependent on the sintering temperature; i.e., it gradually increased as the sintering temperature increased. The value of fracture toughness increased as the grain size increased by the stress-induced phase transformation and Borne crack deflection.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.527-533
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• 2011

CNFs had been well addressed due to numerous promising applications in science and technology. Besides the same physicochemical properties of ordinary carbon materials such as active carbons and carbon black, they exhibit specific, e.g., tubular or fibrous structures, a large surface area, high electrical conductivity stability, as well as extremely high mechanical strengh and modulus, which make them a superior material for electrochemical capacitors. In this study, CNFs were pretreated by mechanical milling with different time in mortar and pestle. The milled CNFs were used as active material of electrode whose electrochemical property was tested to find physicochemical characterization variation. CNF electrode milled for 5 min has the highest electric capacitance. XPS spectrum were employed to explore changes in functional group induced from mechanical milling. Crystal size was calculated to analyze change of peak from different milling time by XRD. The CNF milled for 5 min has the largest crystal size and the highest electric capacitance.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.290-293
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• 2012

This article introduces the characterization of spin coated ZnO transparent conducting oxide on the flexible substrates. As a II-IV compound semiconductor, ZnO has a wide band gap of 3.37 eV with transparent properties. Due to this transparent properties, ZnO materials can be also employed as the transparent conducting electrode materials. Therefore, strong demands have been required for the transparent electrodes with low temperature processing and cheap cost. So, We will investigate the electrical property and optical transmittance of ZnO transparent conducting oxide through the 4-point probe resistivity meter, and ultraviolet-vis spectrometer Lamda 35, respectively.

• Ocean and Polar Research
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• 제31권4호
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• pp.401-414
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• 2009

Yellow Sea Buoy (YSB) was moored in the center of the Yellow Sea at 35$^{\circ}$51'36"N, 124$^{\circ}$34'42"E, on 12 September 2007. YSB is a large buoy of 10 m diameter, and as such is more durable against collision by ships and less likely to be lost or removed by fishing nets compared to small ordinary buoys of 2.3 m diameter. YSB is equipped with 12 kinds of oceanic and meteorologic instruments, and transfers its realtime observation data to KORDI through ORBCOMM system every 1 hour. Data on ocean winds, air temperature, air pressure, and sea temperature appear to be accurate, while water property sensors (AAQ1183), which are sensitive to fouling, are producing errors. YSB (2007), Ieodo ocean research station (2003), and Gageocho ocean research station, which was completed in October 2009, will establish the 2 degrees interval by latitude in the Yellow Sea, and they will contribute though the 'Operational Oceanography System' as the important realtime observation network.

• 통상정보연구
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• 제7권3호
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• pp.3-25
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• 2005

It is high time to prepare the online publication system of academic research paper. Online publications like digital research paper, e-Book, etc. are increased day by day as the information technology(IT) is developing continually. But, the legal aspect of publication system of academic research paper in Korea is not prepared yet. The purposes of this study are to examine the problems on the publication system of academic research paper in the context of digital goods and to frame a policy of legal proceedings in relation to the social science. The methodology used in this paper is theoretical analysis which is examining the case of academic research system and scientific journal in Korea. As a result of this study, following measures are suggested: (1) Legal provisions on the online publication system, that is, "Research Promotion Law of Korea" controlled by KRF(Korea Research Foundation) and MOE(Ministry of Education) should be revised. (2) Solution like software program and DB system proceeding the data on academic research paper should be prepared newly. (3) From the viewpoint of digital goods, both protecting the intellectual property right and settling the reliance upon online publication system should also be considered simultaneously.

• Preventive Nutrition and Food Science
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• 제9권1호
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• pp.65-70
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• 2004

Side-stream cigarette smoke (SSCS) is a major component of environmental tobacco smoke. The purpose of this study was to investigate the development of lung injury and lipid peroxidation in the lung and liver of immunodeficient (Nude) mice exposed to acute SSCS (a total 5 hours of exposure). The effects of French maritime bark extract (Pycnogeno $l^{ⓡ}$) supplementation of the mice were also determined. SSCS increased pulmonary resistance and lipid peroxidation in these mice. Pycnogeno $l^{ⓡ}$ supplementation increased vitamin E levels in lung and liver. In addition, Pycnogeno $l^{ⓡ}$ attenuated SSCS-mediated lung injury and lipid peroxidation. It appears that the enhanced resistance against SSCS-induced lung injury and lipid peroxidation may be primarily due to the antioxidant property of Pycnogeno $l^{ⓡ}$ in supplemented mice.

• 한국수학사학회지
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• 제17권4호
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• pp.45-64
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• 2004

${\lambda}$-연산은 ‘다시쓰기 규칙’으로 정의되는 계산을 위해 함수들이 형성되고, 결합되고, 활용되는 수학적 형식 체계이다. 컴퓨터과학의 발전과 더불어 많은 프로그래밍 언어들이 ${\lambda}$-연산을 원리로 삼고 있다. 나아가서, ‘커리-하워드 대응’ 덕분에 미제 연역에 의해 수행된 증명과 컴퓨터 프로그래밍 사이에 대응 관계를 설정할 수 있게 되었다. 이 글의 목적은 교육적인 차원에서 아직은 잘 알려져 있지 않은 주제를 대중화시키는 데에 있다. 논리학과 컴퓨터 과학에서 L-연산의 영향은 차후의 연구과제로 남아 있다.

• 한국표면공학회지
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• 제30권4호
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• pp.262-271
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• 1997

Nickel-matal hydride(Ni-MH) batteries are receiving attention as non-pollunting. high performance rehargeable energy stoage system. The performance of Ni-Mh is significantly influenced by the hydrogen storage alloy materiels used as an anode material. Recently, having discharge capacities higher than the $AB_5$-type hydrogen storage alloys, the Zr-based $AB_2$-Type hydrogen storage alloys has remaining problems regarding cycle life and self-dischareg. These problems need to be solved by improvements in the alloy design and/or surface treatment. This work investiggates the effects the effects of surface property by fluorination on $Zr_{0.7}Ti_{0.3}V_{0.4}Mn_{0.4}Ni{1.2}$ composittion $AB_2$-Type hydrogen storage alloys. EPMA, SEM and AES techniques were used for surface analysis, and the crystal structure was characterized by constant current cycling test and potential sweep methods. Fluorination was found to be effective when La-was incorporated into the alloy, and has unique morphology, higher reactivity, and at the same time formed a protective film. Through, fluorination, the cycle life of an electrode was found to increase significantly, charge/discharge characteristics of the electrode the potential difference between the charge/discharge plateau, i.e polarization(overpotential)were improved.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권8호
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• pp.325-329
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• 2003

Effects of thermal treatment on the structural properties of diamond-like carbon (DU) films were examined. The DLC films were deposited by using a modified filtered cathodic vacuum arc (FCVA) deposition system and by varying the negative substrate bias voltage, deposition time, and nitrogen flow rate. Thermal treatment on DLC films was performed using a rapid thermal annealing (RTA) process at $600^{\circ}C$ for 2min. Raman spectroscopy, x-ray photoemission spectroscopy (XPS), atomic force microscope (AFM), and surface profiler were used to characterize the I$_{D}$I$_{G}$ intensity ratio, sp$^3$ hybrid carbon fraction, internal stress, and surface roughness. It was found for all the deposited DLC films that the RTA-treatment results in the release of internal compressive stress, while at the same time it leds to the decrease of sp$^3$ fraction and the increase of I$_{D}$I$_{G}$ intensity ratio. It was also suggested that the thermal treatment effect on the structural property of DLC films strongly depends on the diamond-like nature (i.e., sp$^3$ fraction) of as-deposited film.ed film.