• Title/Summary/Keyword: thermodynamic properties

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Development of Chiral Stationary Phases for the Gas Chromatographic Separation of Amino Acid Enantiomers New diamide chiral stationary phase (아미노산 광학이성질체 분리를 위한 가스크로마토그라피용 키랄 고정상의 개발 -새로운 diamide계 키랄 고정상의 응용-)

  • Park, Man-Ki;Yang, Jeong-Sun;Lee, Mi-Yung
    • YAKHAK HOEJI
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    • v.33 no.2
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    • pp.129-139
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    • 1989
  • New diamide chiral stationary phases of four systematically substituted optically active N-(N-benzoyl-L-amino acid)-anilide synthesized from L-valine, L-leucine, L-isoleucine, and L-phenylalanine were described. The behaviors of these diamides as optically active stationary phases for the separation of N-trifluoroacetyl-D,L-amino acids were examined with respect to separation factors(${\alpha}$) and thermodynamic properties of interaction. The separation of twelve N-trifluoroacetyl-D,L-amino acid isopropyl esters were improved by the order of N-(N-benzoyl-L-leucyl)-anilide>N-(N-benzoyl-L-isoleucyl)-anilide>N-(N-benzoyl-L-valyl)-anilide>N-(N-benzoyl-L-phenylalanyl)-anilide. Eight amino acid derivatives with non-polar R-group and threonine, serine, aspartic acid, and glutamic acid enantiomers were separated on N-(N-benzoyl-L-leucyl)-anilide as chiral stationary phase with good separation factor between 1.07-1.25. The separation factors decreased with respect to increasing column temperature. Possible working temperature of diamide phase was between $130-190^{\circ}C$ for N-(N-benzoyl-L-phenylalanyl)-anilide and $130-180^{\circ}C$ for other three diamide phases. The differential Gibb's free energy (${\Delta}{\Delta}G$) of enantiomers was in the range of -100--180 cal/mol for ten amino acids and -40--60 cal/mol for alanine and aspartic acid.

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Optimization of KOGAS DME Process From Demonstration Long-Term Test (KOGAS DME 공정의 실증 시험을 통한 최적화 기술개발)

  • Chung, Jongtae;Cho, Wonjun;Baek, Youngsoon;Lee, Changha
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.5
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    • pp.559-571
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    • 2012
  • Dimethyl ether (DME) is a new clean fuel as an environmentally-benign energy resource. DME can be manufactured from various energy sources including natural gas, coal, and biomass. In addition to its environmentally friendly properties, DME has similar characteristics to those of LPG. The aim of this article is to represent the development of new DME process with KOGAS's own technologies. KOGAS has investigated and developed new innovative DME synthesis process from synthesis gas in gaseous phase fixed bed reactor. DME has been traditionally produced by the dehydration of methanol which is produced from syngas, a product of natural gas reforming. This traditional process is thus called the two-step method of preparing DME. However, DME can also be manufactured directly from syngas (single-step). The single-step method needs only one reactor for the synthesis of DME, instead of two for the two-step process. It can also alleviate the thermodynamic limitations associated with the synthesis of methanol, by converting the produced methanol into DME, thereby potentially enhancing the overall conversion of syngas into DME. KOGAS had launched the 10 ton/day DME demonstration plant project in 2004 at Incheon KOGAS LNG terminal. In the mid of 2008, KOGAS had finished the construction of this plant and has successively finished the demonstration plant operation. And since 2008, we have established the basic design of commercial plant which can produce 3,000 ton/day DME.

Effect of Crystal Form on Bioavailability (결정형이 생체이용률에 미치는 영향)

  • Sohn, Young-Taek
    • Journal of Pharmaceutical Investigation
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    • v.34 no.6
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    • pp.443-452
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    • 2004
  • Habit is the description of the outer appearance of a crystal. If the environment of a growing crystal affects its external shape without changing its internal structure, a different habit results. Crystal habit and the internal structure of a drug can affect bulk and physicochemical properties, which range from flowability to chemical stability. A polymorph is a solid crystalline phase of a given compound resulting from the possibility of at least two different arrangements of the molecules of that compound in the solid state. Chemical stability and solubility changes due to polymorphism can have an impact on a drug's bioavailability and its development program. During crystallization from a solution, crystals separating may consist of a pure component or be a molecular compound. Solvates are molecular complexes that have incorporated the crystallizing solvent molecule in their lattice. When the solvent incorporated in the solvate is water, it is called a hydrate. To distinguish solvates from polymorphs, which are not molecular compounds, the term pseudopolymorph is used. Identification of possible hydrate compounds is important since their aqueous solubilities can be significantly less than their anhydrous forms. Conversion of an anhydrous compound to a hydrate within the dosage form may reduce the dissolution rate and extent of drug absorption. An amorphous solid may be treated as a supercooled liquid in which the arrangement of molecules is random. Amorphous solids lack the three-dimensional long-range order found in crystalline solids. Since amorphous forms are usually of higher thermodynamic energy than corresponding crystalline forms, solubilities as well as dissolution rates are generally greater. A study on crystal form includes characterization of (l)crystal habit, (2)polymorphism, (3)pseudopolymorphism, (4)amorphous solid.

Vaporization of Hydrocarbon Fuel Droplet in Supercritical Environments (아임계 및 초임계 탄화수소 연료 액적의 기화 특성 연구)

  • Lee,Gyeong-Jae;Lee,Bong-Su;Kim,Jong-Hyeon;Gu,Ja-Ye
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.7
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    • pp.85-93
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    • 2003
  • Droplet vaporization at various ambient pressures is studied numerically by formulating one dimensional evaporation model in the mixture of hydrocarbon fuel and air. The ambient pressure ranged from atmospheric conditions to the supercritical conditions. The modified Soave-Redlich-Kwong state equation is used to account for the real gas effects in the high pressure condition. Non-ideal thermodynamic and transport properties at near critical and supercritical conditions are considered. Some computational results are compared with Sato's experimental data for the validation of calculations. The comparison between predictions and experiments showed quite a good agreement. The droplet lifetime increases with increasing pressure at temperature lower than the critical temperature, however, it decreases with increasing pressure at temperature higher than the critical temperature. The solubility of nitrogen can not be neglected in the high pressure and it becomes higher as the temperature and the pressure go up.

Modelling the wide temperature range of steam table using the neural networks (신경회로망을 사용한 넓은 온도 범위의 증기표 모델링)

  • Lee, Tae-Hwan
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.11
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    • pp.2008-2013
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    • 2006
  • In numerical analysis on evaluating the thermal performance of the thermal equipment, numerical values of thermodynamic properties such as temperature, pressure, specific volume, enthalpy and entropy are required. But the steam table itself cannot be used without modelling. In this study applicability of neural networks in modelling the wide temperature range of wet saturated vapor region was examined. the multi-layer neural network consists of a input layer with 1 node, two hidden layers with 10 and 20 nodes respectively and a output layer with 6 nodes. Quadratic and cubic spline interpoations methods were also applied for comparison. Neural network model revealed similar percentage error to spline interpolation. From these results, it is confirmed that the neural networks could be powerful method in modelling the wide range of the steam table.

An Analysis of Thermal Conductivity of Ceramic Fibrous Insulator by Modeling & Simulation Method I (모델링/시뮬레이션 기법을 이용한 세라믹 섬유 단열재의 열전도도 해석 I)

  • Kang, Hyung;Baek, Yong-Kee
    • Journal of the Korea Institute of Military Science and Technology
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    • v.5 no.1
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    • pp.83-95
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    • 2002
  • Thermal conductivity of ceramic fibrous insulator was analysed and predicted by using the modeling/simulation technique. Ceramic fibrous insulators are widely used as high temperature insulator on account of their lightweight mass and heat resisting properties. Especially it is suitable to protect the high speed aircraft and missiles from severe aero-thermodynamic heating. Thermal conductivity of ceramic fibrous insulator could be determined from the conductive heat transfer and the radiative heat transfer through the insulator. In order to estimate conductive thermal conductivity, homogenization technique was applied, while radiative thermal conductivity was computed by means of random number and radiation probability. Particularly radiation probability can make it possible to estimate the conductivity of fibrous insulator without any experimental constant. The calculated conductivity predicted in the present study have a reasonable accuracy with an average error of 7 percent to experimental data.

A Study on the Additives of mixed Gas charged in Thermostatic Bulb for Expansion Valve (팽창밸브 개폐용 감온통 혼합가스의 첨가제 연구)

  • Kim, Si-Young;Ju, Chang-Sik;Koo, Su-Jin
    • Journal of Power System Engineering
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    • v.18 no.6
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    • pp.126-132
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    • 2014
  • The P-T characteristics of mixed refrigerant in thermostatic expansion valve sensing bulb were studied using R-134a and R-410A refrigerant. The characteristics of mixed refrigerant were investigated according to pressure variation and the variation of composition ratio of R-134A and R-410A in the temperature range of $-15^{\circ}C{\sim}15^{\circ}C$. The Thermodynamic characteristic values of the mixed refrigerants were identified using the characteristic value analysis program of mixed refrigerant(Refrop v9.0, NIST). The P-T characteristics in the case of the mixing ratio of 90:10 for R-410A and R-134A were the same result as R-22. And the physical properties showed similar results with R-22. The Maximum operating pressure(MOP) of mixed refrigerant showed a tendency to decrease with decreasing the mixing ratio of additive gases($N_2$ or He) gases. The characteristics in the case of the mixing ratio of 80:1 for mixed refrigerant and additive gases were the similar result as Reference refrigerant.(R-22 MOP, Sporlan company) In addition $N_2$ and He, both showed the same results. It was able to confirm that a MOP on the thermostatic expansion valve sensing bulb can be maintained by adjusting the mixing ratio of mixed refrigerant gases and additive gases.

Comparison of the neural networks with spline interpolation in modelling superheated water (물의 과열증기 모델링에 대한 신경회로망과 스플라인 보간법 비교)

  • Lee, Tae-Hwan;Park, Jin-Hyun;Kim, Bong-Hwan
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.4
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    • pp.685-690
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    • 2008
  • In numerically evaluating the thermal performance of the heat exchanger, numerical values of thermodynamic properties such as temperature, pressure, specific volume, enthalpy and entropy are required. But the steam table or diagram itself cannot be directly used without modelling. In this study the applicability of neural networks in modelling superheated water vapor was examined. The multi-layer neural networks consist of an input layer with 2 nodes, two hidden layers with 15 and 25 nodes respectively and an output layer with 3 nodes. Quadratic spline interpolation was also applied for comparison. Neural networks model revealed smaller percentage error compared with spline interpolation. From this result, it is confirmed that the neural networks could be a powerful method in modelling the superheated water vapor.

Establishment of Hygrothermal Aging Mechanism via Thermal Analysis and Extraction of Reaction Kinetics of Ti Metal-based Pyrotechnic Materials (티타늄 금속 기반의 파이로테크닉 물질에 대한 열분석 및 반응특성 추출을 통한 열·수분 노화 메커니즘 구축)

  • Oh, Juyoung;Yoh, Jai-ick
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.9
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    • pp.759-769
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    • 2021
  • For aerospace propulsion systems, Titanium Hydride Potassium Perchlorate (THPP) is a material commonly used as a pyrotechnic initiator that generates gas when energy is supplied or as a supplement charge for NASA standard initiator (NSI). However, when the energetic materials are stored for a long time, it faces the problem of 'aging'. In this study, changes in thermodynamic properties of THPP aged under various humidity environments were identified through thermal analysis and surface analysis. First, a considerable amount of cracks on the surface of the oxidant was found in the aged THPPs. Particularly, when the humidity level increased, the number and length of the cracks rapidly increased. Also, the deterioration of Viton was found only in the thermally aged sample whereas the oxidation of the fuel was more pronounced in the hygrothermally aged samples. The extracted kinetic parameters of THPP on the reaction progress vary greatly by the humidity level, indicating that moisture significantly changes the performance and combustion reaction of THPP, which may eventually result in a reduced lifespan.

Theoretical Study on the Selective Reduction of Chiral [2-(diphenyl hydroxy-methyl)pyrrolidine]-AlH Derivatives and Aromatic Ketone ([2-(diphenyl hydroxy-methyl)pyrrolidine]-AlH 유도체와 방향족 케톤의 선택적 환원에 대한 이론적 연구)

  • Lee, Chul Jae;Kim, Jong-Mi
    • The Journal of the Convergence on Culture Technology
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    • v.7 no.2
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    • pp.389-394
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    • 2021
  • In this work, we study the properties of molecular structure and boundary orbital functions of the DPHMP-AlH and propiophenone and butyrophenone, which are forms of alkoxy-amine-aluminum derivatives. Furthermore, we investigate the effect on the selective reduction of the final products (R), (S)-phenylpropanol and (R), (S)-phenylbutanol by calculating the stereoscopic and thermodynamic parameters of the transition state. Considering the three-dimensional molecular structural stability, the transition status of (S) types DPHMP-AlH and alkylphenone was found to be more stable, resulting in the selective reductions of DPHM-AlH and alkylphenone from this result: (S)-(1)-phenylpropanol and (S)-(1)-phenylbutanol was confirmed that the formation was advantageous.