• Journal of the Korean Chemical Society
• /
• v.30 no.2
• /
• pp.159-165
• /
• 1986

The effects of substituents, pressure and temperature on the dissociation constants of alkylpyrines(2, 3 and 4-methyl and ethyl) were studied by measuring the dissociation constants of pyridines by conductance method at various temperatures and pressures in aqueous solution. The constants were increased as the temperature increase but decreased as pressure increase. From the constants various thermodynamic properties were calculated and discussed the dissociation reactions. It was estimated that alkylpyridines have exceptional dissociation reactions.

• Journal of the Korean Chemical Society
• /
• v.31 no.5
• /
• pp.395-399
• /
• 1987

The two dissociation constants of leucine were measured in the temperature range from 15 to 40$^{\circ}$C and pressure up to 2,500 bar by conductometric method. Both constants were increased as the temperature increased but pressure effect was not same as temperature effect. The first constants were increased as pressure increase but the second constants were decreased as pressure increase in the law temperature range but increased in some higher temperature range. These phenomena were discussed from the thermodynamic properties of the dissociation reactions.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.47.1-47.1
• /
• 2010

Mg합금은 모든 구조용 재료 중에서 비강도가 크며 가공성이 가장 우수하여 재료의 실제 적용시에 2차 가공비 측면에서 다른 경량재료에 비해 유리하다. 그래서 경량화를 필요로 하는 최근 산업체의 요구를 충족시킬 수 있는 재료이다. 그러나 마그네슘 합금의 적용이 매우 제한되는 이유는 결정구조가 hcp로서 냉간가공이 어렵고, 강화기구가 석출경화 및 고용강화로 제한되기 때문에 기계적 성질, 즉 강도와 연성이 모두 낮다. 특히 고온에서 기계적 성질이 급격히 저하되기 때문에 구조용 재료로써는 사용이 어렵다. 따라서, 본 연구에서는 고온에서 안정한 MgZn상과 항복강도를 향상시키는 Mg4Ag상의 석출을 보이는 Mg-Zn-Mn-Ag합금의 시효거동 및 미세조직 변화에 대해 검토하고자 하였다. 본 합금의 석출거동, 미세조직 및 경도 변화에 미치는 시효처리의 영향에 관한 연구를 수행하기 위해 Pandat Program을 이용해 열역학적 계산을 통한 상태도 해석 및 석출상을 예측 하였다. 계산된 결과는 DSC실험을 통해 비교 분석함으로써 신뢰성을 확보하였고 미세조직 및 석출상 분석을 위해 OM, SEM 그리고 XRD로 관찰하였다. 또한, 시효처리에 따른 기계적 특성을 분석하기 위해 상온 및 고온 인장시험을 하였고, 인장시험 후 파단면 분석을 통하여 재료의 파괴거동을 분석하였다.

• Analytical Science and Technology
• /
• v.22 no.2
• /
• pp.159-165
• /
• 2009

The thermochromism of fluoran has been examined. The DCF exists as a colorless lactone in aprotic solvents. However, the DCF exists in the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the DCF exists an equilibrium mixture as a colorless lactone and a colored cation even in aprotic solvents. In order to understand the interaction between the DCF and the solvent, absorption spectra of the DCF in various solvents were measured. The thermodynamic parameters of the DCF have also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes ${\Delta}H^0$ of the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change ${\Delta}H^0$ is approximately -2.0 kJ/mol in protic solvents. In acidic solution, the standard enthalpy change is measured to be to zero in protic solvents within the experimental error. When the carboxylic group is protonated in acidic solution, a poor interaction between the dye and the solvent is expected.

• Korean Journal of Materials Research
• /
• v.7 no.4
• /
• pp.303-309
• /
• 1997

기존의 전자 기판에서 땜납으로 사용되고 있는 Sn-Pb계 합금을 대체하기 위한 새로운 합금을 개발하기 위하여 열역학을 이용한 상평형계산을 통해 얻은 다원계 상태도를 바탕으로 적정한 녹는점과 용융구간을 가지는 Sn-Bi-In-Zn계 솔더합금을 설계하였다. 설계된 합금을 제작하여 XRD, DSC및 EDX로 분석하여 상의 확인,조성분석 및 고상점과 액상점 등의 녹음 거동을 확인하였다. 또한 열처리에 따른 미세구조의 변화를 관찰하였고, 이러한 조직변화가 기계적 성질에 미치는 영향을 경도실험과 인장실험을 통해 연구하였다.

• Journal of the Korean Society for information Management
• /
• v.11 no.1
• /
• pp.103-124
• /
• 1994

In an age of fierce global trade-war, the importance of sdenbfic and technologd advancement is clearly rmgruzed and, as a result., the flow of information from develaped countries is get- more restricted. Thus, the e s t a b h e n t of systematic data bdd-up is needed to improve the international com~tivenes of Korean prcducts when the trend of weapnizlng hl-tech know-how's is intensified. This paper demonstrates k c requirements for database bdd-up through analysis of evaluation cnteria, difficulties in management, data clasiKcalion. Structure and procedure of database of thermodynarmc property of new rnatmak is described.

• Journal of Pharmaceutical Investigation
• /
• v.1 no.1
• /
• pp.22-29
• /
• 1971

Barbituric acid 및 thiobarbituric acid 유도체와 beta-cyclodextrin과의 상호반응(相互反應)을 수용액(水溶液)과 유기용매중(有機溶媒中)에서 각(各) 약물(藥物)을 용해도(溶解度), 분자용(分子容), 열역학적(熱力學的)인 면(面)에서 분석(分析) 검계(檢計)하였다. 본실험(本實驗)에 사용한 약물(藥物)이 모두 용액(溶液)에서는 beta-cyclodextrin과 반응(反應)하여 용해도(溶解度)가 증가(增加)하였으며 고형(固型)의 침전을 형성(形成)하지는 않았으나 비교적(比較的) 안정(安定)한 회합(會合)이 이루어졌다. 본반응(本反應)의 기전(機轉)은 주(主)로 beta-cyclodextrin의 주요(主要)한 성질(性質)의 하나인 inclusion능(能)에 의(依)하여 이루어 졌음을 보고(報告)한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.323-326
• /
• 2005

In this study, experimental studies were performed the combustion characteristics of end- burning hybrid propulsion system. PMMA, PE were used as fuel and gas oxygen as oxidizer. The regression rate depend on oxidizer flow rate also on thermodynamic properties of fuel. as result, empirical formula for regression rate was deduces with oxidizer flow rate and mass transfer coefficient B number.

• Journal of the Korean Chemical Society
• /
• v.15 no.6
• /
• pp.285-293
• /
• 1971

The statistical thermodynamical properties of heavy water are calculated according to the transient state theory of significant liquid structure. The calculated values are shown to be in good agreement with the observed ones. The grand canonical ensemble partition function for the adsorbed phase of heavy water on graphite surface is derived using the theory. The adsorption isotherm, the surface pressure, the molar entropy and the molar internal energy for the adsorbed phase and then the molar heat of adsorption are calculated according to the derived partition function. The thermodynamic properties of the adsorbed water are also calculated and the results are compared with those of heavy water and discussed in view of the experimentally observed phenomena.

• Journal of the Korean Chemical Society
• /
• v.12 no.4
• /
• pp.190-193
• /
• 1968

액체구조의 천이상태 이론을 용융염에 확장시켜 액체없이 상태합을 유도하였다. 이 상태함을 액체할로겐화알칼리들에 적용시켜 증기압, 몰부피, 엔트로피등의 열역학적 성질을 계산한 결과 측정치와의 좋은 일치를 보여주었다.