• 한국전자파학회논문지
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• 제21권9호
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• pp.1013-1022
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• 2010

원격으로 지표면 온도를 측정하는 C-대역 라디오미터를 설계하고, 아스팔트를 대상으로 실시한 측정 결과를 제시하였다. 높은 감도와 낮은 전력 소모를 위해 전전력(total power)형 라디오미터 형태를 선택하였고, 안정적으로 높은 이득을 확보하기 위해 슈퍼헤테로다인(super-heterodyne) 방식으로 설계하였다. 중심 주파수 5.1 GHz에서 110 MHz의 대역폭을 가지도록 설계된 라디오미터는 59 dB의 이득과 2.7 dB의 잡음 지수를 가지며, 0.45 K의 수신 감도를 가진다. 제작된 시스템과 온도계를 사용해 아스팔트의 지표면 온도를 측정하였다. 그리고 각각의 측정 결과를 분석하여 설계된 라디오미터가 온도 변화에 대해 6 $mV/^{\circ}C$의 전압 변화율을 가지고 선형적으로 동작함을 보였다. 이를 통해 설계된 C-대역 라디오미터의 지표면 원격 온도 측정 센서로의 적용 가능성을 검증하였다.

• 천문학회보
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• 제44권1호
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• pp.84.3-84.3
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• 2019

We investigate 3D radiation-hydrodynamics (RHD) for surface convection of the solar-type low-mass stars (M = 0.8, 0.9, and 1.0 Msun). The outer convection zone (CZ) of low-mass stars is an extremely turbulent region composed of partly ionized compressible gases at high temperature. Particularly, the super-adiabatic layer (SAL), the top of the CZ is the transition region where the transport of energy changes drastically from convection to radiation. In order to accurately describe physical processes, a realistic treatment of radiation should be considered as well as convection. As a starting model, the initial stratification in the outer envelope calculated using the solar calibrations in the context of the standard stellar theory. When the numerical fluid becomes thermally relaxed, the thermodynamic structure of the steady-state turbulent flow was explicitly collected. In this presentation, we compared thermodynamic properties of turbulent convection of the solar-type low-mass stars.

• 암석학회지
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• 제5권2호
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• pp.129-134
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• 1996

피스톤 실린더와 DAC 및 방사광을 이용하여 비정질의 탄질물에서 흑연으로, 흑연에서 다이아몬드로의 상변이의 가능성이 연구되었다. 속성작용이나 낮은 변성도의 흑연생성과정을 피스톤 실린더를 사용하여 0.7 Gpa와 250-$360^{\circ}C$의 환경하에서 실시되었으며 초고압 실험은 Mao-Bell형의 DAC와 EDXRD 및 방사광 가속기를사용하여 상온에서 최고압력 39.6Gpa까지 실시되었다. $Li_2CO_3$를 촉매로 사용한 피스톤 실린더 실험에서는 온도변화에 따라 TGD가 9에서 53으로 누진적으로 변화하는 무질서흑연을 얻었으며 이로부터 0.7Gpa에서 흑연화 온도는 $270^{\circ}C$와 $300^{\circ}C$사이임을 알수 있다. 흑연의 초고압 실험에서는 여러개의 새로운 XRD피크가 관찰되며 이들중에는 육방 다이아몬드의 것으로 보이는 것들로 있으리라 사료되나 이를 단정하기에는 보다 구체적인 실험연구가 필요하다. 또한 다른 종류의 고압 실험기기나 특수한 X선을 이용하여 여러 종료의 흑연시료를 대상으로한 연구가 요구된다.

• 한국가스학회지
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• 제21권4호
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• pp.92-102
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• 2017

피셔-트롭쉬 합성반응은 CO와 H2의 혼합가스로 이루어진 합성가스를 부가가치가 높은 탄화수소 제품으로 변환시킨다. 본 논문에서는 저온 피셔-트롭쉬 합성반응과 단일, 다중 마이크로채널 반응기에 패킹시킨 촉매를 기반으로 강화된 반응조건의 열전달을 고려하여 전산유체역학 기반의 시뮬레이션을 진행하고 분석하였다. 단일채널모델을 통하여 CO 전환률이 ~65% 이상, $C_{5+}$ 선택도가 ~74% 이상을 달성하면서도 Co 기반의 super-active 촉매를 통해 GHSV를 $30000hr^{-1}$을 달성할 수 있음을 보였다. 다중 마이크로채널 반응기모델에서는 열전달 시뮬레이션을 동시에 해석하여, 3가지의 다른 반응기구조에 대해서, 직교류 wall boiling 냉매를 사용시 ${\Delta}T_{max}$가 23 K였으며 평행유동 subcooled 냉매와 평행유동 wall boiling 냉매의 경우 각각 15 K와 13 K의 ${\Delta}T_{max}$를 보였다. 반응기 전체적으로 498 - 521 K에서 온도제어가 가능했으며 계산된 사슬성장 가능성은 저온 피셔-트롭쉬 합성에 적합한 것으로 보인다.

• 한국자기학회지
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• 제5권5호
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• pp.380-382
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• 1995

The pressure dependence of the Curie temperature was determined in 2-dimensional like ferromagnet, MnAlGe up to a maximum pressure of 7.5 Gpa through measurements of electric resistance vs temperature curves. The pressure coefficient was positive with a considerably high rate of 9 K/GPa in the low pressure ragion, while it decreased gradually down to one order of magnitude smaller value at the maximum pressure. It was concluded that ther is an upper limit of about 550 K in the super-exchange type ferromagnetic interaction between Mn layers.

• Smart Structures and Systems
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• 제6권8호
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• pp.939-951
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• 2010

A low-cost wireless sensor network (WSN) solution with highly expandable super and simple nodes was developed. The super node was designed as a sensing unit as well as a receiving terminal with low energy consumption. The simple node was designed to serve as a cheaper alternative for large-scale deployment. A 12-bit ADC inputs and DAC outputs were reserved for sensor boards to ease the sensing integration. Vibration and thermal field tests of the Chi-Lu Bridge were conducted to evaluate the WSN's performance. Integral acceleration, temperature and tilt sensing modules were constructed to simplify the task of long-term environmental monitoring on this bridge, while a star topology was used to avoid collisions and reduce power consumption. We showed that, given sufficient power and additional power amplifier, the WSN can successfully be active for more than 7 days and satisfy the half bridge 120-meter transmission requirement. The time and frequency responses of cables shocked by external force and temperature variations around cables in one day were recorded and analyzed. Finally, guidelines on power characterization of the WSN platform and selection of acceleration sensors for structural health monitoring applications were given.

• 한국표면공학회지
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• 제45권1호
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• pp.43-52
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• 2012

Recently, it has been developed for Eco-environment, Super light, Multi-functional nano materials. As needed mobile parts in Smart phone or TV, computer, information communication for high pass signal, multi-function, Magnetic thin film materials have been developed. As last, magnetic powder, sintered and sputtering parts were thick and low purity than electroplating layer, low pass signal and noise were resulted, vibrated TV screen. Because chemical complex temperature was high and ununiform surface layer, it has been very difficult for data pass in High Frequency (GHz) area. Large capacity data pass is used to GHz. Above GHz, signal pass velocity is dependent on Skin Effect of surface layer. If surface layer is thick or ununiform, attachment is poor, low pass signal and cross talk, noise are produced and leaked. It has been reported technical trend of Electrochemically plating and Surface treatment of Metal, Polymer, Ceramic etc. by dispersion/complex for Multi functional nano-magnetic material in this paper.

• 오토저널
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• 제3권2호
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• pp.18-26
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• 1981

The purpose of this paper is to study the possibility of practical use of gasoline-methanol mixed fuel as an alternative fuel of gasoline engines in the light of engine performances and harmful exhaust emissions as well as mixings and separations of the mixed fuels. When the methanol of 99.8% purity is mixed with super or regular gasoline available on the market today, the experimental results obtained without modifying carburetor in this study are as follows; 1.The separation ratio depends upon the gasoline-methanol mixing ratio only, regardless of fuel temperature and fuel additives for preventing separation of phase. 2.The critical absorption ratio is affected by the gasoline-methanol mixing ratio, its temperature and the quantity of fuel additives. 3.Concerning the distillation temperature, the initial point of all sorts of fuels is almost same,but 10% point and 35-60% point of mixed fuels are lower than those of gasoline only. 4.In case of throttle valve opening set, engine output using the mixed fuels is decreased compared to gasoline, but thermal efficiency is increased as a consequence of decreasing specific energy consumption. 5.In case of fixed load test, thermal efficiency is increased at low engine speed even under low part-load as well as under comparatively high part-load including full load. 6.CO and NOx emissions are reduced remarkably with the mixed fuels.

• 한국태양에너지학회 논문집
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• 제33권2호
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• pp.70-77
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• 2013

Recently the radiant panel heating and cooling system has been regarded as an alternative of low temperature heating and high temperature cooling by applying the renewable energy sources to the heating and cooling of buildings. Especially this system can be used as HVAC system alternatives in super high-rise buildings for energy saving and thermal comfort. Also it can be possible to reduce the plenum space because the minimum ventilation air will be supplied into the space. This study focused on the evaluation the basic characteristics of thermal output in prefabricated steel wall panel system for radiant heating and cooling. In order to evaluate the thermal output according to both various supply water temperatures and supply water flow rates, three-dimensional dynamic heat transfer analysis was performed. As results, for the heating mode, thermal output increased by 26% with the supply temperature increasing by $5^{\circ}C$. The surface temperature of panels range within $1{\sim}3^{\circ}C$. For the cooling mode, thermal output decreased by 18.2% with the supply temperature increasing by $2^{\circ}C$. The surface temperature of panels range within $0.5{\sim}1^{\circ}C$ and it was shown the even temperature distribution.

• 한국작물학회지
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• 제51권5호
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• pp.432-439
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• 2006

단옥수수와 초당옥수수 종자의 활력을 높일 수 있는 저장 방법을 알기 위하여 단옥수수(Early Sunglow ${\times}$ Golden Cross Bantam 70)와 초당옥수수(Xtrasweet 82 ${\times}$ Fortune) 종자를 온도(5 및 $15^{\circ}C$)와 상대습도(70 및 85%)가 다른 조건에서 10개월간 저장한 후 종자 특성의 변화를 보면 다음과 같다. 1. 종자활력은 초당옥수수가 단옥수수보다 더 빨리 저하되었으며, 초당옥수수가 단옥수수보다 더 낮은 저장온도와 상대습도가 요구되었다. 2. 단옥수수는 저장조건과 저장기간에 따른 cold test에서 출아율이 $25^{\circ}C$에서 발아율보다 약간 낮았으나 경향은 같았고, 초당옥수수는 cold test에서 출아율이 $25^{\circ}C$에서 발아율보다 현저히 낮았다. 3. 단옥수수와 초당옥수수 모두 발아율과 저온처리 후 출아율과는 정의 상관이 있었으나 초당옥수수는 관계가 적었다. 그래서 초당옥수수의 포장 출아율을 추정하기 위하여 반드시 저온처리 후 출아율 검정이 필요하였다. 4. 단옥수수는 모든 저장조건에서 5개월간은 종자활력이 저하되지 않았으나, 초당옥수수는 $5^{\circ}C$, RH 70%에서 활력이 유지되었다. 5. 단옥수수에서는 종자활력과 침종시 종자의 당 누출, 전해질 누출 및 ${\alpha}-amylase$ 활성과는 상관이 없었다. 반면 초당옥수수에서는 종자활력과 ${\alpha}-amylase$ 활성과는 정의 상관이, 침종 시 종자의 전해질 누출과는 부의 상관이 있었으나 당 누출과는 상관이 없었다.