• 대한기계학회논문집B
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• 제36권10호
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• pp.1001-1009
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• 2012

본 연구에서는 액체산소와 케로신을 추진제로 사용하는 액체로켓엔진의 연소 가스에 액체질소를 분사하여 연소 가스의 냉각 특성을 알아보고자 하였다. 일반적인 액체로켓엔진의 연소실 후단에 액체질소 분사기와 혼합용 연소실을 추가적으로 장착하였고, 혼합용 연소실 후단에 노즐을 연결하여 전체적인 시스템을 구성하였다. 연소실험은 안전을 고려하여 점화실험부터 순차적으로 수행하였으며, 최종적으로 20초 연소실험을 수행하였다. 그 결과 기존의 액체로켓엔진에 액체질소를 분사함으로써, 연소 가스의 온도를 저하시킬 수 있음을 확인하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제18권7호
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• pp.1003-1010
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• 2005

A study consisting of 3 trials was designed to assess the relative biological efficacy of DL-methionine (DL-Met) in comparison to liquid methionine hydroxy analogue (MHA-FA) in growing pigs. In trial I a basal diet was supplemented with three graded levels of DL-methionine (0.25, 0.50 and 0.75 g/kg) or liquid MHA-FA (0.0285, 0.0570 and 0.0855 g/kg) on equimolar basis. The basal diet contained 18.3% CP, 0.22% Met and 0.51% Met+Cys, which is below the methionine requirement for weaned pigs between 10 and 20 kg BW according to NRC (1998) but adequate in all other essential nutrients and energy. Using an exponential model, the efficacy of the two methionine sources was estimated from nitrogen retention data obtained in 42 piglets with an initial BW between 11.0 kg (Exp. 1) and 11.7 kg (Exp. 2). In trials II and III, with a total of 192 and 96 pigs, and with an initial BW of 10.6 and 21 kg, respectively, growth response criteria were assessed to determine if in agreement with previous studies in pigs and poultry a biological effectiveness of about 65% on average could be confirmed for liquid MHA-FA in comparison to DL-met. Based on N-retention (trial I) the biological efficacy of liquid MHA-FA on a weight-to-weight basis was calculated to be 62% relative to DL-met. Basically, these results were confirmed using growth response criteria as measures; the results of trial II and III revealed no significant differences in growth performance and feed conversion between treatments indicating that 100 parts of liquid MHA-FA can be replaced by 65 parts of DL-met.

• 한국식품과학회지
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• 제16권1호
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• pp.1-6
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• 1984

담금수의 일부를 비율을 달리한 액체국(70%, 50%, 30%의 대체구)으로 대체한 후 곡류원료를 증자만 하여 고추장을 담금하고 고체국을 사용한 고추장과 숙성과정중의 성분을 비교하였다. 수분, 조단백질, 조지방, 염분, 에틸알콜은 각 시험구간에 큰 차이가 없었다. 고추장 숙성과정중의 아미노태질소, 수용성질소, 환원당 함량 및 pH는 대조구, 70%대체구, 50%대체구, 30%대체구의 순으로 높았다. 특히 대조구는 전 숙성기간을 통하여 pH 5.0 이상이었으며 적정산도는 50% 대체구와 30% 대체구에서 높았다.

• Bulletin of the Korean Chemical Society
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• 제16권1호
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• pp.33-36
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• 1995

Macrocyclic ligands have been studied as cation carriers in a supported liquid membrane system. Cd2+ has been transported using nitrogen substituted macrocycles as carriers and several divalent metal ions (M2+=Zn, Co, Ni, Cu, Pb, Mg, Ca, and Sr) have been transported using DBN3O2, DBN2O2and PolyNtnoen as carriers in a supported liquid membrane system. Competitive Cd2+-M2+ transport studies have also been carried out with the same system. Ligand structure, stability constant, membrane solvent and carrier concentration are also important parameters in the transport of metal ions.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.44-47
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• 2015

High voltage superconducting apparatuses have been developed presently around the world under AC and DC sources. In order to improve electrical reliability of superconducting apparatuses with AC and DC networks, a study on the DC as well as the AC electrical breakdown characteristics of cryogenic insulations should be conducted for developing a high voltage superconducting apparatus. Recently, a sub-cooled liquid nitrogen cooling system is known to be promising method for developing a high voltage superconducting apparatus. A sub-cooled liquid nitrogen cooling system uses gaseous nitrogen to control the pressure and enhance the dielectric characteristics. However, the dielectric characteristics of gaseous nitrogen are not enough to satisfy the grade of insulation for a high voltage superconducting apparatus. In this case, the application of solid insulating barriers is regarded as an effective method to reinforce the dielectric characteristics of a high voltage superconducting apparatus. In this paper, it is dealt with a barrier effect on the DC and AC dielectric characteristics of gaseous nitrogen with respect to the position and number of solid insulating barriers. As results, the DC and AC electrical breakdown characteristics by various barrier effects is verified.

• 센서학회지
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• 제22권6호
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• pp.404-409
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• 2013

We devised calibration procedure for industrial thermometers by a comparison method at the boiling point of nitrogen (${\sim}-196^{\circ}C$). The uncertainty of the calibration was 4 mK (k = 2). As experimentally demonstrated in this work, the effect of the atmospheric pressure on the boiling point of nitrogen can be easily detected by the thermometer. Therefore, when the boiling point of nitrogen is used for calibration of thermometer by comparison, either a reference thermometer must be used to provide the reference temperature or the effect of atmospheric pressure should be carefully considered. The use of a copper block with a large thermal mass soaked into the liquid nitrogen was proven to be more reliable, and the stability of the temperature immersed into the copper block was 1.4 mK. The temperatures at the thermometer wells, evaluated by the crossed-measurement method to compensate for the inaccuracy of the thermometers and the linear drift of the temperature of the copper block, were equivalent within 0.23 mK of standard uncertainty.

• 한국유기농업학회지
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• 제26권4호
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• pp.731-743
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• 2018

배추 유기재배 시 녹비작물과 추비방법이 배추의 생육과 질소이용에 미치는 영향을 구명하기 위하여 2012년부터 2014년까지 수원에 있는 국립농업과학원 포장에서 시험을 수행하였다. 녹비작물은 여름철 크로타라리아와 겨울철 헤어리베치를 이용하였다. 녹비처리 방법은 전면경운 토양혼입방법과 부분경운 토양혼입방법, 그리고 무경운 예취피복처리를 비교하였다. 추비방법은 녹비만 처리한 것과 녹비 처리 후 유박과 액비로 추비한 처리를 비교 하였다. 시험결과 녹비 처리 방법은 예취 후에 경운하여 토양혼입 하는 것보다 무경운 피복처리 하는 것이 좋았다. 봄배추재배 시 동계 녹비작물 헤어리베치 재배로 정상적인 생육과 수량이 가능하였고 관행의 화학비료 처리구에 비하여 무름병과 Tip-burn 발생이 적어 수량성도 높았다. 가을재배에서는 녹비 연속재배와 유박 추비로 관행의 화학비료처리구와 비슷한 수량을 보였다. 하지만 하계 단기성 녹비작물 재배 시에는 관행 수량의 70% 내외에 그쳤다. 녹비재배에 이은 액비 활용 양분관리로 관행과 비슷한 수량이 가능하였고 토양중 무기태 질소가 안정적으로 유지되고 질소이용효율도 향상되었다. 결론적으로 배추 유기재배를 위해서는 겨울과 여름 녹비작물을 재배하고 가을 작기를 선택하여 액비로 추비하는 것이 권장된다.

• 한국재료학회지
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• 제24권2호
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• pp.81-86
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• 2014

The nitrogen solubility and nitride capacity of $CaO-SiO_2-Al_2O_3-MgO-CaF_2$ slag systems were measured by using gas-liquid equilibration at 1773K. The nitrogen solubility of this slag system decreased with increasing CO partial pressure, with the linear relationship between nitrogen contents and oxygen partial pressure being -3/4. This system was expected to show two types of nitride solution behavior. First, the nitrogen solubility decreased to a minimum value and then increased with the increase of CaO contents. These mechanisms were explained by considering that nitrogen can dissolve into slags as "free nitride" at high basicities and as "incorporated nitride" within the network at low basicities. Also, the basicity of slag and nitride capacity were explained by using optical basicity. The nitrogen contents exhibited temperature dependence, showing an increase in nitrogen contents with increasing temperature.

• 한국분무공학회지
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• 제15권4호
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• pp.189-194
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• 2010

This study has been mainly motivated to numerically model the transcritical mixing and reacting flow processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended k-$\varepsilon$ turbulence model. To account for the real fluid effects, the propellant mixture properties are calculated by using SRK (Souve-Redlich-Kwong) equation of state model. In order to realistically represent the turbulence-chemistry interaction in the turbulent non-premixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the real fluid effects and the precise structure of the transcritical cryogenic liquid nitrogen jet and gaseous hydrogen/liquid oxygen coaxial jet flame.

• Tribology and Lubricants
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• 제28권4호
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• pp.167-172
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• 2012

The turbo pump of a liquid rocket engine is composed of three main parts: the oxidizer pump, fuel pump, and turbine. Liquid oxygen ($LO_X$) is the working fluid in the cryogenic environment in the oxidizer pump, but tests are usually performed using liquid nitrogen ($LN_2$), which has a boiling point similar to that of $LO_X$ but is comparatively safer and easier to use for the test. In this study, a bearing test rig is developed and its performance is evaluated using a cryogenic ball bearing with $LN_2$ as the working fluid. Verifying the performance of the bearing test rig is crucial for ensuring correct working of the turbo pump unit in the liquid rocket engine. A stable test rig for the bearing in a cryogenic environment makes the bearing technology enhance its reliability. The test results show that the system operates stably and the requirement of performance time of 500 s is met. The test results of temperature, motor speed, and torque are discussed. The developed cryogenic bearing test rig is expected to help in widening knowledge and expanding research on ball bearings in the future.