• Macromolecular Research
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• 제14권2호
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• pp.220-229
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• 2006

Several equations of state for hard-sphere chains with various perturbation terms are reviewed. For each model, three characteristic parameters are required to represent phase equilibria of normal fluids and obtained from thermodynamic properties of pure saturated liquids. The models are then compared with computer simulation data to show the effect of attractive contribution forms employed. Calculated values of vapor-liquid equilibria (VLE) of hydrocarbons that can be reproduced for each model are also compared with experimental results. An additional parameter, ${\zeta}_{KB}$, is required to represent the VLE of pure water, which is ascertained to have a strong influence on the theoretical coexistence curve.

• Coupled systems mechanics
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• 제7권1호
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• pp.5-25
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• 2018

A fully-coupled thermodynamic-based transient finite element formulation is proposed in this article for electric, magnetic, thermal and mechanic fields interactions limited to the linear case. The governing equations are obtained from conservation principles for both electric and magnetic flux, momentum and energy. A full-interaction among different fields is defined through Helmholtz free-energy potential, which provides that the constitutive equations for corresponding dual variables can be derived consistently. Although the behavior of the material is linear, the coupled interactions with the other fields are not considered limited to the linear case. The implementation is carried out in a research version of the research computer code FEAP by using 8-node isoparametric 3D solid elements. A range of numerical examples are run with the proposed element, from the relatively simple cases of piezoelectric, piezomagnetic, thermoelastic to more complicated combined coupled cases such as piezo-pyro-electric, or piezo-electro-magnetic. In this paper, some of those interactions are illustrated and discussed for a simple geometry.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.255.2-255.2
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• 2014

Electrode erosion is indispensable for atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from arc plasmas to contacts, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. Our investigation is concerned with argon free-burning arcs with anode erosion at atmospheric pressure by computational fluid dynamics (CFD) analysis. We are also interested in the energy flux and temperature transferring to the anode with a simplified unified model of arcs and their electrodes. In order to determine two thermodynamic quantities such as temperature and pressure and flow characteristics we have modified Navier-Stokes equations to take into account radiation transport, electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. From the simplified self-consistent solution the energy flux to the anode can be derived.

• 한국분말재료학회지
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• 제6권1호
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• pp.18-35
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• 1999

Phase equilibria in the system Si3N4-TiC-TiCxN1-x-C-N were determined by thermodynamic calculations (CALPHAD-method). The reaction peaction paths for Si3N4-TiC and SiC-TiC composites in the Ti-Si-C-n system were simulated at I bar N2-pressure and varying terpreatures. At a temperature of 1923 K two tie-triangles (TiC0.34N0.66+SiC+C and TiC0.13N0.87+SiC+Si3N4) and two 2-phase fieds (TiCxN1-x+SiC; 0.13

• 설비공학논문집
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• 제7권1호
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• pp.98-111
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• 1995

The objective of this work is to investigate the form of equations of state for specific refrigerants. In particular, equations of the extended van der Waals form have been studied. As a result, a new equation of state has been developed and tested over ranges of pressure and density up to 5 and 1.5 times critical, respectively. The equation of state separates the compressibility factor into two parts. One is the repulsive compressibility factor and the other is attractive. The former is in the same form of Carnahan-Starling's repulsive term with constant hard-sphere volume. The latter is based on a combination of two different functions linear to density. The equation of state developed here has 12 adjustable parameters and correlates PVT data successfully. All properties are in reduced forms.

• 폴리머
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• 제25권4호
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• pp.536-544
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• 2001

실험적 사실에 근거하여 고분자 유체의 점탄성 구성방정식에 빈번히 적용되어온 time-strain separability 가설의 타당성을 수학적 안정성 관점에서 분석한다. 안정성 조건으로는 방정식의 빠른 응답과 관련된 Hadamard 안정성과 소산 성질에 의하여 결정되는 소산 안정성이 있으며, asymptotic 분석을 이용한 결과 가설을 따르는 구성방정식은 Hadamard 또는 소산 불안정함이 증명되었다. 응력완화 실험에서 이미 관찰된 짧은 시간영역에서 time-strain separability의 가설이 적용되지 않는다는 사실은 본 결과와 일치한다. 따라서 separability를 구성방정식에 적용하는 것은 수학적 불안정뿐 아니라 열역학적 모순점을 나타내게 되며, 또한 실험에서도 그 타당성의 한계에 주의할 필요가 있다. 더욱이 damping 함수 역시 실제와는 무관한 가상적 값을 제공하므로 damping 함수의 사용은 긴 시간영역에서 응력완화 거동을 기술하기 위한 curve fitting 이상의 의미는 없다 하겠다.

• 자원리싸이클링
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• 제27권2호
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• pp.32-37
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• 2018

본 연구는 금속 팔라듐 및 산화 팔라듐의 재활용을 위한 전 단계 연구로 수행되었다. 본 연구에서는 산화 팔라듐(PdO)의 형성을 위한 열역학적 수식들을 확립하였다. 또한 고상의 염화 팔라듐($PdCl_2$)을 염산 용액에 용해시킨 염화 팔라듐 용액을 원료용액으로 사용하였다. 이 원료 용액으로부터 분무열분해 공정에 의하여 평균입도 30 nm 이하의 산화 팔라듐 분체를 제조하였다. XRD 분석 결과 생성된 분체는 오직 PdO 상이었으며 TEM 분석결과 형성된 나노 PdO 입자들은 단결정 상임을 확인하였다. 또한 생성된 PdO 분말의 비표면적은 약 $32m^2/g$이었다.

• 대한조선학회논문집
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• 제47권5호
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• pp.733-742
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• 2010

In this study, optimization was performed to improve the conventional liquefaction process of offshore plants, such as a LNG-FPSO(Liquefied Natural Gas-Floating, Production, Storage, and Offloading unit) by maximizing the energy efficiency of the process. The major equipments of the liquefaction process are compressors, expanders, and heat exchangers. These are connected by stream which has some thermodynamic properties, such as the temperature, pressure, enthalpy or specific volume, and entropy. For this, a process design problem for the liquefaction process of offshore plants was mathematically formulated as an optimization problem. The minimization of the total energy requirement of the liquefaction process was used as an objective function. Governing equations and other equations derived from thermodynamic laws acted as constraints. To solve this problem, the sequential quadratic programming(SQP) method was used. To evaluate the proposed method in this study, it was applied to the natural gas liquefaction process of the LNG-FPSO. The result showed that the proposed method could present the improved liquefaction process minimizing the total energy requirement as compared to conventional process.

• 한국화재소방학회논문지
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• 제17권2호
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• pp.43-49
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• 2003

대체 소화제로 사용되는 불활성 기체 중 Ar, $N_2$, $CO_2$에 대한 혼합물에서의 물성(포화압력, 밀도, 점도)에 관한 실험식을 구하였다. Mixing rule에 의해 계산한 값을 이용하여 다항식 등의 회귀분석에 의해서 실험식을 얻었다. 포화압력은 온도에 대하여 1차 실험식으로 표시하였다. 압축인자와 포화압력을 이용하여 온도에 대한 밀도에 관한 실험식을 제시하였다. 점도는 온도에 대한 지수함수로 표시하였다. Ar, $N_2$, $CO_2$혼합물의 조성이 40/50/10(mol. %)에서 열역학적 실험식을 구하였다.

• 한국화재소방학회논문지
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• 제16권3호
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• pp.16-25
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• 2002

소화제인 Freon-23과 몬트리올 의정서에 의해서 규제받는 CFC의 대체 물질인 HFC-227ea의 물성(포화압력, 밀도, 점도, 엔탈피, 표면장력)에 관한 실험식을 구하였다. 문헌에서 얻은 실험값을 이용하여 다항식등의 회귀분석에 의해서 실험식을 얻었다. 포화압력은 온도에 대하여 각각 3차와 2차의 실험식으로 표시하였다. 압축인자와 포화압력을 이용하여 온도에 대한 밀도에 관한 실험식을 제시하였다. 점도는 온도에 대한 지수함수로 표시하였고, 엔탈피는 열용량과 마찬가지로 온도에 대한 2차 함수로 정의하여 나타내었다. 표면장력에 대해서는 간단한 1차 온도에 대한 선형적인 관계가 있었다.