• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.1001-1009
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• 2012

In this study, the cooling characteristics of combustion gas were investigated by injecting liquid nitrogen ($LN_2$) into a liquid rocket combustion chamber, which uses liquid oxygen (Lox) and kerosene as propellants. $LN_2$ injectors and an extended chamber for mixing were installed at the end of the ordinary LRE combustion chamber, and a nozzle was installed after the chamber for mixing. First, an ignition test of the liquid rocket engine was conducted to verify the stable combustion process. Next, a hot firing test was performed step-by-step for safety. Finally, the test was performed for 20 s. The results showed that the combustion gas of the LRE could be successfully cooled by using $LN_2$.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.7
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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.

• Korean Journal of Food Science and Technology
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• v.16 no.1
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• pp.1-6
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• 1984

The three kinds of Kochujang were prepared with liquid koji equivalent to 30%, 50%, and 70% of brewing water. The qualities of the Kochujangs during aging at $25^{\circ}C$ for 4 months were compared with those of the control group which was made from solid koji. There were no significant differences in the contents of moisture, crude protein, crude fat, NaCl and ethyl alcohol between test groups. The contents of amino nitrogen, soluble nitrogen, reducing sugar and pH of each test group during Kochujang aging were high in the order of control group. 70% liquid koji group, 50% liquid koji group and 30% liquid koji group. The pH of control group was over 5.0 during aging period. The titratable acidity of Kochujang was high in the 50% liquid koji group and the 30% liquid koji group.

• Bulletin of the Korean Chemical Society
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• v.16 no.1
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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.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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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.

• Journal of Sensor Science and Technology
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• v.22 no.6
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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.

• Korean Journal of Organic Agriculture
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• v.26 no.4
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• pp.731-743
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• 2018

This study was conducted to evaluate the effects of green manures and complemental fertilization with oil cake or liquid fertilizer on growth and nitrogen use efficiency of Chinese cabbage cultivated in organi systems. Field experiments were carried out at the National Institute of Agricultural Science in Suwon, South Korea from 2012 to 2014. Two green manure crops, Crotalaria and Hairy vetch, was cultivated in summer and in winter, respectively. The application methods of the green manure consisted of three tillage systems (overall tillage, partial tillage and no tillage). Oil cake and liquid fertilizer were used as complemental fertilizer. The results showed that when used as covering material in the upland soil without tillage, green manure fertilization was more effective in increasing growth and yield of Chinese cabbage than when incorporated into soil. It was possible to grow and harvest Chinese cabbage in the spring season by the application of hairy vetch as winter green manure. The higher yield of Chinese cabbage with green manure application was caused by the lower incidence rate of soft rot and tip-burn. The yield of the Chines cabbage that received green manure applications over two consecutive seasons followed by the supplemental fertilization with oil cake was similar to that of the conventional chemical fertilization. Following a single season green manure application in summer, however, the yield of cabbage was only about 70% of the conventional treatment. Green manure cultivation with additional liquid fertilization produced a yield similar to the conventional fertilization treatment, soil inorganic nitrogen concentration remained stable and the nitrogen use efficiency increased in the green manure applied soil. In conclusion, the organic cultivation of Chinese cabbage in the autumn season could be outperformed in the upland soil receiving two seasons (winter and summer) of green manure fertilization followed by the supplemental fertilization with liquid fertilizer.

• Korean Journal of Materials Research
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• v.24 no.2
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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.

• Journal of ILASS-Korea
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• v.15 no.4
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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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• v.28 no.4
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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.