• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.563-568
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• 2010

Turbopump-gas generator open-loop coupled tests are performed during the development of a 30tonf-LOx/Kerosene rocket engine. In the turbopump-gas generator open-loop tests, the propellants to gas generator are supplied from the outlets of turbopump, while the gas exhausted from the gas generator is vented out to the atmosphere, instead of being used to turbine driving. This paper presents the objectives, procedure, and results of the open-loop coupled test, in addition to a schematic representation of the test apparatus and the operating conditions for the test facility system and control system. The results of turbopump-gas generator open-loop coupled test confirm chill-down procedure, startup characteristics, nominal operability and smooth shutdown of the open-loop coupled Test Plant in test conditions simulating engine system operation environment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.125-128
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• 2008

As a interstage of the 30tonf level LOx/kerosene liquid rocket engine development, turbopump-gas generator open-loop coupled tests are performed. Test schematic and test results of open-loop coupled tests are presented. In engine system operation environment simulating combustion chamber by flow control orifice, chill-down procedure, startup characteristics, nominal operability of turbopump+gas generator open-loop coupled Test Plant are confirmed The results of open-loop coupled test were used for the preparation on turbopump+gas generator closed-loop test.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.15-18
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• 2008

This study fulfilled analysis of startup characteristics of Turbo pump unit-Gas generator open loop test from the viewpoint of simulation. The test results were investigated and the calculated results were compared to test results. The curve for RPM developing predicted by simulation agreed well with test result. The slope of transient combustion pressure of gas generator correspond with test result.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.3
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• pp.80-86
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• 2000

Eddy covariance method is widely used in measuring vertical fluxes of mass and energy between the atmosphere and the biosphere. In this method, scalar concentration is measured with either open-path or closed-path sensors. For the latter, fluctuations of scalar concentration are attenuated as the sample travels through a long tube, resulting in flux loss. To quantify this tube attenuation, water vapor concentrations measured with both closed-path and open-path sensors were analyzed. Our statistical analysis showed that the power spectral density obtained from the closed-path sensor was different from that from the open-path sensor in the frequency range of > 0.5 Hz. The loss of water vapor flux due to tube attenuation was < 5% during midday. At nighttime, however, the flux loss increased significantly because of the low wind speeds and the weak turbulence sources. Theoretical calculation for the tube attenuation showed a small bias in high frequency range probably because of the interaction of sticky water vapor with a tube wall.

• 산림경영
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• s.189
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• pp.20-21
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• 2008

국립수목원(원장 박종서) 보전 복원 연구팀은 그 동안 금강산에서만 분포하는 것으로 알려진 버들개회나무(물푸레나무 과(科))의 자생지를 강원도 남부지방에서 발견하였다고 밝혔다. 국립수목원은 현재 버들개회나무의 생태학적 및 유전적 도태 가능성에 대비하여 현지내 외 보존을 위한 대책 마련을 추진중에 있다.

• 한국전기화학회:학술대회논문집
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• 1999.10a
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• pp.50-50
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• 1999

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.3
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• pp.135-145
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• 2019

Analysis of a long cycle or a trend of time series data based on a long-term observation would require comparability between data observed in the past and the present. In the present study, we proposed an approach to ensure the compatibility among the instruments used for the long-term observation, which would allow to secure continuity of the data. An open-path gas analyzer (Model LI-7500, LI-COR, Inc., USA) has been used for eddy covariance flux measurement in the Gwangneung deciduous forest for more than 10 years. The open-path gas analyzer was replaced by an enclosed-path gas analyzer (Model EC155, Campbell Scientific, Inc., USA) in July 2015. Before completely replacing the gas analyzer, the carbon dioxide ($CO_2$) and latent heat fluxes were collected using both gas analyzers simultaneously during a five-month period from August to December in 2015. It was found that the $CO_2$ fluxes were not significantly different between the gas analyzers under the condition that the daily mean temperature was higher than $0^{\circ}C$. However, the $CO_2$ flux measured by the open-path gas analyzer was negatively biased (from positive sign, i.e., carbon source, to 0 or negative sign, i.e., carbon neutral or sink) due to the instrument surface heating under the condition that the daily mean temperature was lower than $0^{\circ}C$. Despite applying the frequency response correction associated with tube attenuation of water vapor, the latent heat flux measured by the enclosed-path gas analyzer was on average 9% smaller than that measured by the open-path gas analyzer, which resulted in >20% difference of the sums over the study period. These results indicated that application of the additional air density correction would be needed due to the instrument heat and analysis of the long-term observational flux data would be facilitated by understanding the underestimation tendency of latent heat flux measurements by an enclosed-path gas analyzer.

• The Science & Technology
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• v.35 no.8 s.399
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• pp.90-93
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• 2002

2002 세계한민족과학기술자종합학술대회 개회/최신 연구논문 3백50여편 발표/개회식에 과학기술계인사 다수 참석/해외 과학인력 유치 상담도/세계한민족과학기술자공동협의회 총회 개최/제1회 Young Generation Forum 개최/과학기술계 현안에 대한 정책질의-한나라당, 민주당 대통령 후보에

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.426-430
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• 1997

A signal processor is implemented to verify the possibility of a closed-loop signal processing for the open-loop fiber-optic gyroscope (FOG). As an all-digital implementation of phase tracking scheme, it does analog-to digital conversion of the detector output and signal processing all-digitally thereafter for a noise-immune FOG signal processor. It has a potential of 36-bits resolution in the $2\pi$ range which is best in the number and sets no limit in the magnitude of the phase shift. The new signal processor was tested on an all-fiber gyroscope and turned out to have a resolution of $3\mu$rad(corresponds to 0.74 deg/hr), which is good enough to measure the Earth's rotation rate.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.377-383
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• 2002

An all-digital closed-loop (ADCL) signal processor for an open-loop FOG was developed to replace the analog circuitry of a Digital Phase Tracking (DPT) signal processor with new digital circuitry. When the ADCL signal processor without a stabilizer for fiber phase modulator (FPM) was attached to the FOG, temperature drift of FOG was about 0.26$\mu$rad/$^{\circ}C$, which makes the FOG unusable in medium or higher-grade applications. This drift was due to variations of phase modulation amplitude and phase delay of the FPM. The stabilizer controls its phase modulation amplitude and phase delay by regulating the ratio of harmonics of the FOG output. Thus, the stabilizer reduces the drift of the FOG to negligible.