• 대한화학회지
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• 제24권6호
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• pp.444-451
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• 1980

극성용매에서 전자의 용매화과정을 구체적으로 고찰하여 보기 위하여 테트라히드로퓨란(THF)-물 이성분계의 메디움효과를 측정하였다. 이 메디움효과는 Pt|$H_2Q$, Q, HCI, THF, $H_2O$|KC1 | $Hg_2Cl_2$|Hg(Pt) 셀로 수용액과 다른 용액(TGF-$H_2O$)에서 결정된 $H^+$ 이온에 대한 자유에너지 변화의 차(${\Delta}{\Delta}G_0$)를 이용하여 연구하였다. 여기서 $H_2Q$와 Q는 히드로퀴논과 퀴논을 각각 나타낸다. 자유에너지 변화의 차와 용매화된 전자의 최대흡수 에너지에 대한 용매의 유전상수 영향을 고찰하기 위하여 THF에서 $H_2O$의 회합정도를 관찰하였다. $H_2O$의 회합정도는 $H_2O$의 근적외선 스펙트럼을 이용하여 분석하였다. 이들 실험결과로부터 이성분 혼합용매에서 전자나 다른 이온의 용매화는 용매의 특정성분과 선택적으로 진행된다는 것을 알았다.

• 대한기계학회논문집
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• 제15권6호
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• pp.2189-2205
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• 1991

본 연구에서는 혼합냉매의 열역학적 물성치를 정확하게 예측하기 위하여 척력 과 인력항으로 된 간단한 형태의 상태방정식을 택하고 이를 이용하여 순수성분에 대한 열역학적 물성치 자료와 혼합냉매에 대한 기액평형상태 자료를 이용하여 혼합물에 대 한 열역학적 물성치를 보다 더욱 정확하게 예측 할 수 있는 방법에 관해 연구하고자 한다.혼합냉매에 대한 상태방정식과 이상기체 상태의 비열자료를 기초로 열역학적 관계식을 이용하여, 압력-엔탈피, 온도-엔트로피 관계를 공식화하며, 혼합냉매에 대한 열펌프 및 냉동사이클 해석에 필요한 자료를 제시한다.

• Journal of Microbiology and Biotechnology
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• 제12권6호
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• pp.909-915
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• 2002

The biodegradation of BTEX components (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) individually and in mixtures was investigated using the o-xylene-degrading thermo-tolerant bacterium Ralsronia sp. strain PHS1 , which utilizes benzene, toluene, ethylbenzene, or o-xylene as its sole carbon source. The results showed that as a single substrate for growth, benzene was superior to both toluene and ethylbenzene. While growth inhibition was severe at higher o-xylene concentrations, no inhibition was observed (up to 100 mg $l^-1$) with ethylbenzene. In mixtures of BTEX compounds, the PHS1 culture was shown to degrade all six BTEX components and the degradation rates were in the order of benzene, toluene, o-xylene, ethylbenzene, and m- and p-xylene. m-Xylene and p-xylene were found to be co-metabolized by this microorganism in the presence of the growth-supporting BTEX compounds. In binary mixtures containing the growth substrates (benzene, toluene, ethylbenzene. and o-xylene), PHS1 degraded each BTEX compound faster when it was alone than when it was a component of a BTEX mixture, although the degree of inhibition varied according to the substrates in the mixtures. p-Xylene was shown to be the most potent inhibitor of BTEX biodegradation in binary mixtures. On the other hand, the degradation rates of the non-growth substrates (m-xylene and p-xylene) were significantly enhanced by the addition of growth substrates. The substrate utilization patterns between PHS1 and other microorganisms were also examined.

• KSBB Journal
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• 제14권3호
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• pp.371-376
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• 1999

제조용 액체 크로마토그래피를 전산모사하는 것은 최적의 분리와 조건을 위해 필수적이다. 제조용 액체 크로마토그래피에서의 단일 성분과 2성분 용출 피크의 거동을 설명하는 수학적 모델을 equilibrium-dispersive model을 이용해 계산을 수행하였다. 모델의 전산모사를 통해 주입되는 시료부피, 시료속의 용질의 농도, 유속, 컬럼길이가 용출되는 피크에 미치는 영향을 확인해 보았다. Equilibrium-dispersive model로 전산모사된 data를 이용하여 단일 성분 시료 주입에 대해 주입 농도와 유속에 대한 영향을 알아본 결과 주입 농도를 증가시킬수록 용출이 일어나는 시점이 앞당겨져 평균 체류 시간이 감소하고 날카로운 피크를 얻을 수 있다. 유속을 증가시키면 시료의 용출 시점이 앞당겨지고, 고정상과의 충분한 상호 작용을 일으키기 전에 용출되기 때문에 피크가 날카로와 진다. 2성분 시료 주입에 대해 분리도값들을 계산한 결과 두번째로 용출되는 시료의 농도를 증가시킬수록 이 시료성분이 더 빨리 용출되므로 분리도값이 감소함을 알 수 있다. 칼럼길이가 분리도에 미치는 영향을 보면 칼럼길이를 길게 할수록 시료성분이 고정상과의 완전한 상호작용으로 분리가 잘되고, 시료의 주입량을 증가시키면 두 성분간의 용출 피크의 간격이 좁아져 분리도 값이 감소함을 알 수 있다. 이 내용을 바탕으로 다성분 분리에 대한 simulation 연구로 확장할 수 있다.

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.520-529
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• 2017

Viscosity data were measured at 298.15 K and 308.15 K for formamide + 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol or 2-methyl-2-propanol mixtures. For an equimolar mixture, deviation in viscosity follows the sequence: 2-methyl-2-propanol >2-methyl-1-propanol>1-butanol>2-propanol>1-propanol. The viscosity data were further analyzed in terms of graph theory. Free energy of activation was also calculated from experimental viscosity data along with previously reported excess volume data. The deviation in viscosity and free energy of activation were fitted to Redlich-Kister polynomial equation. The viscosity data were also correlated by correlations like Grunberg-Nissan, Tamura-Kurata, HindMcLaughlin-Ubbelohde, and Katti-Chaudhari relation. Various adjustable parameters, $G_{12}$, $T_{12}$, $H_{12}$, and $W_{vis}/RT$, of various correlations were used to predict viscosity deviation of binary mixtures. Positive value of $G_{12}$ indicates strong interaction in the studied systems. Grunberg-Nissan relation has lowest deviation among the four correlations for formamide + 1-propanol or 2-propanol mixtures; and for mixtures of formamide with 1-butanol or 2-methyl-1-propanol, TamuraKurata has lowest deviation. Grunberg-Nissan gives lowest deviation for formamide + 2-methyl-2-propanol mixtures.

• Corrosion Science and Technology
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• 제2권3호
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• pp.141-147
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• 2003

Sputter-deposited Nb-Al-Cr alloys. $3-5{\mu}m$ thick, have been prepared on quartz substrates as oxidation-and sulfidation-resistant materials at high temperatures. The oxidation or the alloys in the $Ar-O_2$ atmosphere of an oxygen partial pressure of 20 kPa follows approximately the parabolic rate law, thus being diffusion controlled. Their oxidation rates are almost the same as or even lower than those ofthc typical chromia-forming alloys. The multi-lavered oxide scales are formed on the ternary alloys. The outermost layer is composed of $Cr_2O_3$, which is"mainly responsible for the high oxidation'resistance of these alloys. In contrast to sputter-deposited Cr-Nb binary alloys reported previously, the inner layer is not porous. TEM observation as well as EDX analysis indicates that the innermost layer is a mixture of $Al_2O_3$ and niobium oxide. The dispersion of $Al_2O_3$ in niobium oxide may be attributable to the prevention of the formation of the porous oxide layer. The sulfidation rates of the present ternary alloys arc higher than those of the sputter-deposited Nb-AI binary alloys, but still several orders of magnitude lower than those of conventional high temperature alloys. Two-layered sulfide scales are formed, consisting of an outer $Al_2S_3$ layer containing chromium and an inner layer composed of $NbS_2$ and a small amount of $Cr_2S_3$. The presence of $Cr_2S_3$ in the inner protective $NbS_2$ layer may be attributed to the increase in the sulfidation rates.

• Macromolecular Research
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• 제12권1호
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• pp.78-84
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• 2004

Advanced epoxy molding compounds (EMCs) should be considered to alleviate the thermal stress problems caused by low thermal conductivity and high elastic modulus of an EMC and by the mismatch of the coefficient of thermal expansion (CTE) between an EMC and the Si-wafer. Though A1N has some advantages, such as high thermal conductivity and mechanical strength, an A1N-filled EMC could not be applied to commercial products because of its low fluidity and high modules. To solve this problem, we used 2-$\mu\textrm{m}$ fused silica, which has low porosity and spherical shape, as a small size filler in the binary mixture of fillers. When the composition of the silica in the binary filler system reached 0.3, the fluidity of EMC was improved more than twofold and the mechanical strength was improved 1.5 times, relative to the 23-$\mu\textrm{m}$ A1N-filled EMC. In addition, the values of the elastic modules and the dielectric constant were reduced to 90％, although the thermal conductivity of EMC was reduced from 4.3 to 2.5 W/m-K, when compared with the 23-$\mu\textrm{m}$ A1N-filled EMC. Thus, the A1N/silica (7/3)-filled EMC effectively meets the requirements of an advanced electronic packaging material for commercial products, such as high thermal conductivity (more than 2 W/m-K), high fluidity, low elastic modules, low dielectric constant, and low CTE.

• 한국연소학회지
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• 제18권2호
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• pp.32-41
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• 2013

This study presents both experimental and numerical investigation of ignition delay time of n-heptane and n-butanol binary fuel. The $O_2$ concentration in the mixture was set to 9-10% to make high exhaust gas recirculation( EGR) rate condition which leads low NOx and soot emission. Experiments were performed using a rapid compression machine(RCM) at compressed pressure 20bar, several compressed temperature and three equivalence ratios(0.4, 1.0, 1.5). In addition, a numerical study on the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species in the combustion process. The results showed that the ignition delay time increased with increasing the n-butanol fraction due to a decrease of oxidation of n-heptane at the low temperature. Moreover, all of the binary fuel mixtures showed the combustion characteristics of n-heptane such as cool flame mode at low temperature and negative-temperature-coefficient(NTC) behavior. Due to the effect of high EGR rate condition, the operating region is reduced at lean condition and the ignition delay time sharply increased compared with no EGR condition.

• 대한기계학회논문집B
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• 제38권11호
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• pp.899-905
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• 2014

본 연구는 고효율 청정 조리용기 개발을 위한 기초 연구로서 기-액 상변화를 이용하여 조리용기의 등온성을 향상시키고자 $100-200^{\circ}C$의 작동온도 범위에 적합한 작동유체를 선정하고 이들 작동유체의 열전달 특성실험을 수행하였다. 이를 위하여 2 상 밀폐 열사이폰을 제작하고 두 가지 작동유체에 대한 비등 및 응축 열전달 특성과 시동특성에 대한 실험하였으며, 실험 결과로부터 2 가지 유체를 혼합한 2 성분 유체 열사이폰의 시동 및 열전달 성능의 상호 보완 가능성을 분석하였다.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.109-116
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• 2014

An electrical resistance tomography (ERT) technique combining the particle swarm optimization (PSO) algorithm with the Gauss-Newton method is applied to the visualization of two-phase flows. In the ERT, the electrical conductivity distribution, namely the conductivity values of pixels (numerical meshes) comprising the domain in the context of a numerical image reconstruction algorithm, is estimated with the known injected currents through the electrodes attached on the domain boundary and the measured potentials on those electrodes. In spite of many favorable characteristics of ERT such as no radiation, low cost, and high temporal resolution compared to other tomography techniques, one of the major drawbacks of ERT is low spatial resolution due to the inherent ill-posedness of conventional image reconstruction algorithms. In fact, the number of known data is much less than that of the unknowns (meshes). Recalling that binary mixtures like two-phase flows consist of only two substances with distinct electrical conductivities, this work adopts the PSO algorithm for mesh grouping to reduce the number of unknowns. In order to verify the enhanced performance of the proposed method, several numerical tests are performed. The comparison between the proposed algorithm and conventional Gauss-Newton method shows significant improvements in the quality of reconstructed images.