• 대한기계학회논문집B
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• 제24권8호
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• pp.1029-1037
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• 2000

The present study investigates the local heat/mass transfer characteristics on a rotating disk which is the top disk covered with a shroud in HDD. The naphthalene sublimation technique is employed to determine the local heat/mass transfer coefficients on the rotating disk. Flow field measurements using Laser Doppler Anemometry (LDA) and numerical calculations are performed to analyze the flow patterns induced by the disk rotation. HDD has been developed for compactness and speedy data access, thus the rotating velocity of the disk is increased and the height of a hub is decreased. The experiments are conducted for the various hub heights of 5, 10 and 15 mm, for the rotating Reynolds numbers of $5.5{\times}10^4$ to $1.1{\times}10^5$ and for the effects of the presence of a read/write head arm. The results show that the heat transfer on the rotating disk is enhanced considerably for the decrease of the hub height and for the increase of the rotating Reynolds number. The head arm inserted in the cavity decreases the heat transfer despite the enhancement of tangential RMS velocity because of the deficit of the momentum in the flow field.

• 국제지역연구
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• 제21권2호
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• pp.171-196
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• 2017

본 연구에서는 베트남 일반은행들의 경쟁력제고를 의사결정의 목적으로 삼고 AHP 계층분석기법을 적용하여 이 문제의 해결을 돕기 위한 모형을 제시하고 있다. 은행 분야 전문가들을 대상으로 항목간 쌍방비교방식으로 이루어진 설문지를 배포하고 회수된 의사결정요소들의 상대적 가중치를 분석한 결과 다음의 세 가지의 주요 결과를 도출하였다. 첫째, 은행의 안전성이 베트남 일반은행들의 경쟁력확보에 있어 가장 중요한 평가기준이며 운용의 효율성, 무형가치의 보유정도 및 영업규모가 그 뒤를 뒤따른다. 둘째, 베트남 일반은행들의 경쟁력제고를 위한 대안으로 건전한 재무상태의 확보가 가장 우선시되어야 한다. 효과적인 경영관리시스템, 전략적 인적자원계획 및 고품질의 제품과 서비스 또한 높은 상대적 가중치를 보인다. 셋째, 건전한 재정확보를 위해서 악성부채 해결이 절대 필요한 것으로 나타났다. 또한, 효과적인 경영관리시스템을 구축하고 고품질의 제품과 서비스를 제공하기 위해서는 신기술의 도입이 매우 중요하다. 아울러 전략적 인적자원계획의 달성을 위해서는 임직원의 자질향상이 절대적으로 필요하다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1326-1329
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• 1995

An influences of gap clearance, pressure and applied voltage shape on breakdown characteristics are investigated by using a rod-to-plane electrode in $SF_6$ gas. In case of D.C and A.C, a corona stabilization effect increases the breakdown voltage remarkably for lower pressure than 0.2MPa, whereas incase of negative D.C this effect exists independently of gas pressure. This suggests that an insulation optimization in a pratical apparatus is needed to prevent a corona appearance through the removal of local field enhancement.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.325-328
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• 2000

The control of the data retention time is a main issue for realizing future high density dynamic random access memory. In this paper, we propose the new implantation scheme by gate-related ion beam shadowing effect and buffer-enhanced $\Delta$ Rp increase using buffered N- implantation with tilt and 4X-rotation that is designed on the basis of the local-field-enhancement model of the tail component. We report an excellent tail improvement of the retention time distribution attributed to the reduction of electric field across the cell junction due to the redistribution of N- concentration which is intentionally caused by Ion Beam Shadowing and Buffering Effect using tilt implantation with 4X-rotation.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.38-42
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• 1999

Using the LOCOS process, we have fabricated the lateral type polysilicon field emission triodes with poly-Si/oxide/Si structure and investigated their current-voltage characteristics for three biasing modes of operation. The fabricated devices exhibit excellent electrical performances such as a relatively low turn-on anode voltage of 14 V at VGC = 0V, a stable and high emission current of 92${\mu}$A/triode over 90 hours, a small gate leakage current of 0.23 ${\mu}$A/triode and an outstanding transconductance of 57${\mu}$S/5triodes at VGC = 5V and VAC = 26V. these superior electrical operation is believed to be due to a large field enhancement effect, which is related to the sharp cathode tips produced by the LOCOS process as well as the high aspect ratio (height /radius ) of the cathode tip end.

• 한국주거학회논문집
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• 제28권2호
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• pp.35-45
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• 2017

This study aimed to explore housing welfare service situation in City of Cheongju, Chungbuk, and assess demands for the service improvement through interviews of public and private field specialists in order to seek practical implications for enhancement of housing welfare policy and system in Cheongju. In December 2016, a series of personal and focus group interviews using semi-structured questionnaires were conducted to total 10 specialists who were currently providing and housing services. Major findings and implications are as follow. (1) City's own housing survey and database construction are in need for development and implementation of housing welfare service programs serving local needs effectively and efficiently. (2) The field specialists perceived importance of realignment of service system and to establishment of the Cheongju housing welfare center as a control tower of the services. (3) It is required to provide various opportunities to strengthen the specialists' competence through education, training and networking and to arrange persons in charge of housing programs in every community-level self-government. (4) The specialists showed their strong interests in introduction of diverse housing welfare services and programs.

• 지적과 국토정보
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• 제45권1호
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• pp.17-30
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• 2015

공간정보는 정보의 공유 및 개방, 융 복합 활용 등에 있어서 상위정책과의 연계성을 높일 뿐만 아니라 시민의 능동적 참여와 빅데이터를 연계한 창조적 활용에 기여할 수 있다는 점에서 지방자치단체 공간정보정책의 중요성은 크다. 하지만 수치지형도를 포함한 기본공간정보의 갱신, 공간정보 서비스 발굴, 공간정보 공유 및 협력 등 지방자치단체 공간정보 정책 수립은 미흡한 실정이다. 본 연구에서는 지방자치단체의 공간정보정책 개선방안을 도출하기 위해 중앙정부와 지방자치단체의 공간정보정책 및 시스템을 비교하고 지방자치단체 공간정보정책 시행계획과 서울시 32개 공간정보시스템 활용설문을 분석하였다. 연구결과 지방자치단체의 공간정보정책 개선을 위해 업무 부서와 연계하여 준공도면 등을 이용한 기본도의 수시 갱신, 국가공간정보통합체계를 통한 최신 공공부문 공간정보의 확보, 공간정보 플랫폼을 통한 정보의 공유, 공간정보 기반 정책 참여 관련 성공 사례의 벤치마킹 등이 제시되었다.

• International Journal of Fluid Machinery and Systems
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• 제7권3호
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• pp.86-93
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• 2014

This paper describes performance enhancement of a regenerative blower used for a 20 kW fuel cell system. Two design variables, bending angle of an impeller and blade thickness of an impeller tip, which are used to define an impeller shape, are introduced to enhance the blower performance. Internal flow of the regenerative blower has been analyzed with three-dimensional Navier-Stokes equations to obtain the blower performance. General analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the thickness of impeller tip is effective to increase the blower efficiency in the present blower. Pressure is successfully increased up to 2.8% compared to the reference blower at the design flow condition. And efficiency is also enhanced up to 2.98 % compared to the reference one. It is noted that low velocity region disturbs to make strong recirculation flow inside the blade passages, thus increases local pressure loss. Detailed flow field inside the regenerative blower is also analyzed and compared.

• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.439-449
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• 2002

Experimental investigations of the flow structure and heat transfer enhancement in a channel with a built-in circular cylinder and a wing-let type vortex generator are presented. Without any vortex generators, relatively low heat transfer takes place in the downstream of the circular cylinder where is a recirculation region with low velocity fluid is formed. However with a wing-let type longitudinal vortex generator in the wake region behind the cylinder, heat transfer in the region can be enhanced. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from $20^{circ} to 45^{\circ}$, but spacings between the vortex generations are fixed to be 5 mm. The 3-dimensional mean velocity field downstream of the vortex generator is measured by a five-hole pressure probe, and the hue-capturing method using thermochromatic liquid crystals has been used to provide the local distribution of the heat transfer coefficient. The vorticity field and streamwise velocity contour are obtained from the velocity field. Streamwise distributions of averaged Stanton number on the measurement planes show very similar trends for all the experimental cases($\beta=20^{circ}, 30^{circ} and 45^{\circ}$). Circulation strength and heat transfer coefficient have the maximum values when the angle of attack($\beta$) is $30^{\circ}$.

• Journal of Astronomy and Space Sciences
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• 제25권4호
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• pp.375-382
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• 2008

On August 31, 2001, ${\sim}$ 1705 - 1718 UT, Cluster was located near the midnight magnetotail, GSE (x, y, z) ${\sim}$ (-19, - 2,2) RE, and observed fast earthward flow bursts in the vicinity of the neutral sheet. They occurred while the tail magnetic field suddenly increased. Using simultaneous measurements in the solar wind, at geosynchronous orbit, and on the ground, it is confirmed that tail magnetic field enhancement is due to an increased solar wind pressure. In the neutral sheet region, strongly enhanced earthward flow bursts perpendicular to the local magnetic field $(V_{{\perp}x})$ were observed. Auroral brightenings localized in the pre-midnight sector (${\sim}$ 2200 - 2400 MLT) occurred during the interval of the $V_{{\perp}x}$ enhancements. The $V_{{\perp}x}$ bursts started ${\sim}$ 2 minutes before the onset of auroral brightenings. Our observations suggest that the earthward flow bursts are associated with tail reconnection directly driven by a solar wind pressure impulse and that $V_{{\perp}x}$ caused localized auroral brightenings.