• Proceedings of the Korean Vacuum Society Conference
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• 2004.02a
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• pp.87-87
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• 2004

• Proceedings of the Korean Magnestics Society Conference
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• 2014.11a
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• pp.174-174
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• 2014

• Publications of The Korean Astronomical Society
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• v.23 no.2
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• pp.37-45
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• 2008

We present the results of image simulations of 43.1 GHz SiO maser emission toward a Mira variable using the KVN (Korean VLBI Network) and other facilities which can make joint VLBI experiments with the KVN. To test the imaging capability of the KVN we used the image of SiO masers in the simulation obtained by the VLBA, which is considered to be the optimum VLBI facility at present to study SiO masers toward evolved stars. The simulated images of SiO maser emission confirm that coordinate VLBI expriments of KVN with several more stations in Japan or in the neighborhood of Korean Peninsula are necessary to exert the functional benefit of the KVN as the first mm VLBI facility which can perform simultaneous observations at four different frequency bands.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.654-660
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• 1991

Natural convection heat transfer in a horizontal annulus from an inner tube with two vertical fins has been studied for the effects of dimensionless fin length and Rayleigh number. The maximum local Nusselt number of inner tube was obtained at .theta. = 145.deg. and that of outer cylinder at .theta. = 0.deg. for the case of $l_{F}$=0.3 Local Nusselt number distributions for the lower fins show higher values than that of the upper fins. The mean Nusselt number of inner tube was increased with the values of dimensionless fin length. The mean Nusselt number can be represented in an exponential function of Grashof number at various fin lengths. As compared with experimental and numerical results, isotherms and local Nusselt number show good agreement.t.

• Solar Energy
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• v.12 no.1
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• pp.25-33
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• 1992

Laminar natural convection heat transfer from a hot body in a square enclosure has been stooled for various inclination angles at $Gr=1.5{\times}10^5$, Pr= 0.71 and $k_s/k_f=14710$. The area of a hot body is 1/25 of the enclosure and the aspect ratio is 1.0. The total mean Nusselt number decreases as the inclination angle increases and in case of ${\theta}=90^{\circ}$ is 14% lower than that of ${\theta}=0^{\circ}$.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.482-484
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• 2006

This paper describes fast-hopping frequency synthesizers for multi-band OFDM(MB-OFDM) ultra-wide band(UWB) systems. Three different structures in generating 3 center frequencies(3432MHz, 3960MHz, 4488MHz) are designed and compared. The first structure generates 3 center frequencies using only one PLL operating at 4224MHz. The second uses three PLLs operating at corresponding center frequencies. The third employes two PLLs operating at 3960MHz and 528MHz. Simulation results using a 0.18um RF CMOS process parameters show that the third structure exhibit the best characteristics. The band switching time of the proposed synthesizer is less than 1.3ns and the spur is less than -36dBc. The synthesizer consumes 22mA from a 1.8V supply.

• YAKHAK HOEJI
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• v.12 no.1_2
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• pp.32-34
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• 1968

Aconitum Uchiyamai NAKAI "geu-neul-dol-che-gi"(Ranunculaceae), is geographically distributed only in Korea. An aconite collected at Mt. Dukwoo, Kangwon-Do flowers with white color in October. The aconite is different from Aconitum Uchiyamai NAKAI from the point of anatomical and morphological views in transplanted and collected aconites. Being a new variety of Aconitum Uchiyamai NAKAI, this aconite is anounced under the name of Aconitum Uchiyamai NAKAI var. albiflorum CHUNG et RIM, "Hin-geu-neul-dol-che-gi" called in Korea. Aconitum Uchiyamai NAKAI var. albiflorum CHUNG et RIM Differt a planta Aconitum Uchiyamai NAKAI per colorem album.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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• pp.99-104
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• 1990

A Study has been conducted experimentally on heat transfer characteristics of louvered fin heat exchangers with various louvered positions in air. The experimental results are as follows; 1. Mean heat transfer coefficient is increased with increasing air velocity and decreasing temperature difference. The maximum value of heat transfer coefficient shows at 10㎜ backward louvered fins. 2. Pressure drop is increased with increasing air velocity and apparently depended on the louvered positions at V>10m/sec. 3. $\bar{h}/{\Delta}P$ is decreased with increasing air velocity and its maximum value shows at 10mm forward louvered fins and its minimum value shows at plate fins.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.43.2-43.2
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• 2010

Following the success of detecting fringes on KVN (Korean VLBI Network), a phase referencing observation is currently planned in order to achieve a better sensitivity in mm-VLBI. The high frequency observation ($\geq$ 22 GHz), wide bandwidths (~512 MHz) and high speed data recording (~1 Gbps, Mark5B) will result in resolution and sensitivity improvement on KVN. In particular, two powerful techniques of VLBI phase correction by fast-antenna switching and multi-frequency phase referencing are also introduced in KVN, hoping to resolve the problem of atmospheric delay errors which degrade the coherence significantly. In this study, we have compared the expected performance of phase referencing between fast antenna switching and multi-frequency phase referencing and discussed the essential condition and postulates of phase referencing for KVN.

• 한국벤처창업학회:학술대회논문집
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• 2017.11a
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• pp.133-137
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• 2017

벤처캐피탈의 공동투자전략은 투자 위험의 분산과 투자 자원의 효율적 관리, 투자사에 관련된 정보비대칭 완화 관점에서 단독투자전략보다 장점이 있다. 공동투자는 다른 한편으로는 투자정보 공유 네트워크와 투자기회 확보를 위한 경쟁을 드러내 보이기도 한다. 본 연구는 2014년부터 2016년까지 3년간 공개된 한국 벤처캐피탈의 한국 스타트업에 대한 투자 정보를 수집 및 분석하여 벤처캐피탈의 투자 전략 및 네트워크에 대한 실증 분석을 수행한다. 네트워크 분석, 로지스틱 회귀분석 등을 포함한 통계적 검정을 수행한 결과 벤처캐피탈의 분야별 전문성(투자집중도), 내적역량(업력 및 전문 인력의 수), 투자 네트워크, 피투자 스타트업의 업력 모두 공동투자여부에 영향을 끼친다는 증거를 발견할 수 없었다. 본 연구의 분석 결과 한국의 벤처캐피탈이 공동투자를 결정짓는 요인은 피투자기업의 사업 분야를 제외하면 투자금액의 크기와 보유 펀드의 규모 등 자금요인이 유일했다. 이 결과가 시사하는 바는, 한국의 벤처캐피탈 대다수가 투자형태의 결정에 있어 자사의 전문성이나 피투자기업의 본연적 사업 리스크를 고려한다거나 투자 기회 정보의 공유를 통해 투자형태를 전략적으로 결정하기 보다는 단순 자금운용 측면에 경도되어 있지 않은가 하는 점이다.