• 한국농림기상학회지
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• 제5권2호
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• pp.128-137
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• 2003

순복사는 지표 에너지 수지의 가장 근본적인 요소 중 하나이다. 순복사의 정확한 관측을 위해, 주기적이고 지속적인 순복사계 보정이 요구된다. 플럭스 관측에 널리 사용되는, 두 가지 타입의 대표적인 순복사계 (Q-7.1과 CNR1)의 상호 비교 및 보정 실험이 약 4개월 간격으로 두 차례 시행되었다. Q-7.1과 CNR1 간의 차이는 7.7% 이내였고, 표준 기기와의 보정 후 오차는 3.2%이내였다. 순복사계의 반응 차이와 보정 계수는 대기 상태, 특히 계절 변화에 따른 온도 차이에 따라 다르게 나타났다. 결론적으로, 주기적으로 보정된 Q-7.1은 CNR1을 대체하여 장기 관측에 사용될 수 있고, 보정 주기로는 4-6개월이 권장된다.

• 한국환경과학회지
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• 제16권3호
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• pp.261-267
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• 2007

In this study, the Slab Ocean Model (SOM) is coupled with an Atmospheric General Circulation Model (AGCM) which developed in University of Kangnung based on the land surface model of Biosphere-Atmosphere Transfer Scheme (BATS). The purposes of this study are to understand radiative role of clouds considering of the atmospheric feedback, and to compare the Clouds Radiative Forcing (CRF) come from the analyses using the clear-cloud sky method and CGCM. The new CGCM was integrated by using two sets of the clouds with radiative role (EXP-A) and without radiative role (EXP-B). Clouds in this two cases show the negative effect $-26.0\;Wm^{-2}$ of difference of radiation budget at top of atmosphere (TOA). The annual global means radiation budget of this simulation at TOA is larger than the estimations ($-17.0 Wm^{-2}$) came from Earth Radiation Budget Experiment (ERBE). The work showed the surface negative effect with $-18.6 Wm^{-2}$ in the two different simulations of CRF. Otherwise, sensible heat flux in the simulation shows a great contribution with positive forcing of $+24.4 Wm^{-2}$. It is found that cooling effect to the surface temperature due to radiative role of clouds is about $7.5^{\circ}C$. From this study it could make an accurate of the different CRF estimation considering either feedback of EXP-B or not EXP-A under clear-sky and cloud-sky conditions respectively at TOA. This result clearly shows its difference of CRF $-11.1 Wm^{-2}$.

• 한국토양비료학회지
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• 제21권1호
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• pp.15-19
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• 1988

옥수수 군락형성과정(群落形成過程)에서 순폭사를 구성(構成)하는 열(熱)에너지의 배분(配分)을 보우엔비(比)-에너지수지방법(收支方法)으로 조사(調査)하여 다음과 같은 결론(結論)을 얻었다. 1. 옥수수 전생육기간(全生育期間)동안 군락초관부(群落草冠部)에 도달(到達)된 전천일사량(全天日射量)은 $1,559MJm^{-2}$이었으며 증발잠열(蒸發潛熱)로 쓰여진 열량(熱量)은 $960MJm^{-2}$로 전천일사량(全天日射量)의 61.6%가 군락증발산(群落蒸發散)의 열원(熱源)으로 사용(使用)되었다. 2. 계절별(季節別) 일평균(日平均) 증발산량(蒸發散量)은 2.7mm-5.6mm 범위(範圍)이었다. 3. 증발산(蒸發散)으로 소비(消費)된 물량(量)은 394mm, 전체건물생산량(全體乾物生産量)은 $2,214gm^{-2}$로 전체(全體)옥수수 군락증발산량(群落蒸發散量)에 대(對)한 전건물중(全乾物重)의 비율(比率)인 물이용효율(利用效率)은 $5.6gm^{-2}mm^{-1}$이었다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.799-805
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• 2014

최근 대기오염 방지를 위한 각종 규정들이 강화되고, 연료유 가격의 상승으로 인해 LNG(Liquefied Natural Gas)를 선박의 추진연료로 사용하는 Gas Fuelled Ship의 등장은 필연적이게 되었다. 본 연구에서는 Gas Fuelled Ship에서 연료로 사용되는 LNG를 DF(Dual-Fuel)엔진에 공급하기 전 기화 시켜주기 위해 Eglycol water(Ethylene glycol water)를 가열매체로 사용한 재기화 시스템을 구성하고, Eglycol과 물의 혼합비율에 따른 시스템 특성을 분석하여 다음과 같은 결과를 얻었다. DF엔진으로 공급되는 천연가스의 압력과 온도 그리고 유량이 일정하게 유지될 때 Eglycol의 혼합비율이 증가할수록 Eglycol water의 혼합비열이 낮아지게 되면서 물만을 사용했을 때와 대비하여 1.65배 많은 cycle 유량과 1.54배의 펌프 소요 동력이 요구됨을 확인하였고, vaporizer의 크기를 고정한 후 Eglycol의 혼합비에 따른 DF엔진으로 공급되는 천연가스의 온도 및 vaporizer 출구측 Eglycol water의 온도를 산정하였다.

• 한국토양비료학회지
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• 제28권2호
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• pp.183-190
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• 1995

논포장에서 배출되는 메탄가스를 측정하기 위하여 간이폐쇄정태 chamber법을 이용하여 대표적인 시료를 채취할 수 있도록 chamber내 시료채취 높이, 시료채취시 시간간격, 하루중 시료 채취시간을 검토하였다. 1. 대표적인 시료채취를 위한 chamber내 높이는 65cm이었고 chamber 하반부에서 시료가 균일하게 섞이도록 DC fan을 추가로 설치할 필요성이 인정되었다. 2. 시간경과에 따른 chamber내 메탄농도의 변화 및 기온의 변화에서 보면 시료채취를 개시하여 30분이내에 시료를 채취하는 것이 바람직하였다. DC fan으로 chamber내부의 공기가 섞이도록 하는 것은 대표적인 시료를 얻기 위한 것 뿐 아니라 chamber내열평형을 이루어 시료(試料) 채취기간중(採取期間中) 식물(植物)의 생리적(生理的) 활성(活性)에 최소한(最小限)의 변화를 주는 방법으로 판단되었다. 3. 하루중 대표적인 메탄 배출량을 나타내는 오전 9시~12시에 시료를 채취하여 분석하되 부득이한 경우에는 또 하나의 평균적인 배출량을 나타내는 오후 6시~8시의 시료를 채취하여 분석하여도 가능할 것으로 판단되었다. 4. 수도주간(水稻株間)진 토양(土壤)에서 메탄 배출을 측정하는데 사용하는 소형의 chamber는 토양을 교란할 수 있으므로 설치한 후 최소한 6시간이 경과되어야 chamber내 메탄농도가 주위의 메탄 농도로 회복되었다.

• 천문학회지
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• 제37권5호
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• pp.517-525
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• 2004

We present an update on our proposal that during the 'quasar era' (1.5 $\le$ z $\le$ 3), powerful radio galaxies could have played a major role in the enhanced global star-formation, and in the widespread magnetization and metal pollution of the universe. A key ingredient of this proposal is our estimate that the true cosmological evolution of the radio galaxy population is likely to be even steeper than what has been inferred from flux-limited samples of radio sources with redshift data, when an allowance is made for the inverse Compton losses on the cosmic microwave background which were much greater at higher redshifts. We thus estimate that a large fraction of the clumps of proto-galactic material within the cosmic web of filaments was probably impacted by the expanding lobes of radio galaxies during the quasar era. Some recently published observational evidence and simulations which provide support for this picture are pointed out. We also show that the inverse Compton x-ray emission from the population of radio galaxies during the quasar era, which we inferred to be largely missing from the derived radio luminosity function, is still only a small fraction of the observed soft x-ray background (XRB) and hence the limit imposed on this scenario by the XRB is not violated.

• Journal of Electrical Engineering and Technology
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• 제2권4호
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• pp.478-484
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• 2007

This paper deals with the high efficient vector control for the reduction of copper losses of the doubly fed motor. Firstly, the feedback linearization control based on Lyapunov approach is employed to design the underlying controller achieving the double fluxes orientation. The fluxes# controllers are designed independently of the speed. The speed controller is designed using the Lyapunov method especially employed to the unknown load torques. The global asymptotic stability of the overall system is theoretically proven. Secondly, a new Torque Copper Losses Factor is proposed to deal with the problem of the machine copper losses. Its main function is to optimize the torque in keeping the machine saturation at an acceptable level. This leads to a reduction in machine currents and therefore their accompanied copper losses guaranteeing improved machine efficiency. The simulation and experimental results in comparative presentation confirm largely the effectiveness of the proposed DFIM control with a very interesting energy saving contribution.

• Ocean and Polar Research
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• 제23권4호
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• pp.401-410
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• 2001

Global climate change will alter many such properties of the Southern Ocean as temperature, circulation, stratification, and sea-ice extent. Such changes are likely to influence the species composition and activity of Antarctic marine microorganisms (protists and bacteria) which playa major role in deter-mining the concentration of atmospheric $CO_2$ and producing precursors of cloud condensation nuclei. Direct impacts of climate change on Antarctic marine microorganisms have been determined for very few species. Increasing water temperature would be expected to result in a southward spread of pelagic cyanobacteria, coccolithophorids and others. Growth rates of many species would be expected to increase slightly but nutrient limitation, especially micronutrients, is likely to result in a negligible increase in biomass. The extent of habitats would be reduced for those organisms presently living close to the upper limit of their thermal tolerance. Increased UVB irradiance is likely to favour the growth of those organisms tolerant of UVB and may change the trophic structure of marine communities. Indirect effects, especially those as a consequence of a diminution of the amount of sea-ice and increased upper ocean stratification, are predicted to lead to a change in species composition and impacts on both trophodynamics and vertical carbon flux.

• Journal of Astronomy and Space Sciences
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• 제30권2호
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• pp.101-106
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• 2013

The length of solar cycle 23 has been prolonged up to about 13 years. Many studies have speculated that the solar cycle 23/24 minimum will indicate the onset of a grand minimum of solar activity, such as the Maunder Minimum. We check the trends of solar (sunspot number, solar magnetic fields, total solar irradiance, solar radio flux, and frequency of solar X-ray flare), interplanetary (interplanetary magnetic field, solar wind and galactic cosmic ray intensity), and geomagnetic (Ap index) parameters (SIG parameters) during solar cycles 21-24. Most SIG parameters during the period of the solar cycle 23/24 minimum have remarkably low values. Since the 1970s, the space environment has been monitored by ground observatories and satellites. Such prevalently low values of SIG parameters have never been seen. We suggest that these unprecedented conditions of SIG parameters originate from the weakened solar magnetic fields. Meanwhile, the deep 23/24 solar cycle minimum might be the portent of a grand minimum in which the global mean temperature of the lower atmosphere is as low as in the period of Dalton or Maunder minimum.

• Journal of Astronomy and Space Sciences
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• 제34권2호
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• pp.119-125
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• 2017

We retrieved rotational temperatures from emission lines of the OH airglow (8-3) band in the sky spectra of the Sloan digital sky survey (SDSS) for the period 2000-2014, as part of the astronomical observation project conducted at the Apache Point observatory ($32^{\circ}N$, $105^{\circ}W$). The SDSS temperatures show a typical seasonal variation of mesospheric temperature: low in summer and high in winter. We find that the temperatures respond to solar activity by as much as $1.2K{\pm}0.8K$ per 100 solar flux units, which is consistent with other studies in mid-latitude regions. After the seasonal variation and solar response were subtracted, the SDSS temperature is fairly constant over the 15 year period, unlike cooling trends suggested by some studies. This temperature analysis using SDSS spectra is a unique contribution to the global monitoring of climate change because the SDSS project was established for astronomical purposes and is independent from climate studies. The SDSS temperatures are also compared with mesospheric temperatures measured by the microwave limb sounder (MLS) instrument on board the Aura satellite and the differences are discussed.