• Journal of the Korean Society of Groundwater Environment
• /
• v.2 no.1
• /
• pp.14-21
• /
• 1995

Colloids such as exogenous biocolloids in a bioremediation operation can enhance the transport of contaminant in ground water by reducing retardation effects. Because of their colloidal size and favorable surface conditions in addition to their low density, bacteria can act as efficient contaminant carriers. When mobile bacteria are present in a subsurface environment, the system can be treated as consisting of three phases: water phase, bacterial phase, and the stationary solid matrix phase. In this work, a mathematical model based on mass balances is developed to describe the facilitated transport and fate of a contaminant in a porous medium. Bacterial partition between the bulk solution and the stationary solid matrix, and the contaminant partition among the three phases are represented by the equilibrium relationships. Solutions were obtained to provide estimates of contaminant and bacterial concentrations. A dimensionless analysis of the transport model was utilized to estimate model parameters from the experimental data. The model results matched with experimental data of Jenkins and Lion (1993). The presence of mobile bacteria enhances the contaminant transport. However, bacterial consumption of the contaminant which serves as a bacterial nutrient, can attenuate the contaminant concentration.

• Korean Chemical Engineering Research
• /
• v.48 no.6
• /
• pp.763-767
• /
• 2010

High-pressure phase behavior for the binary mixture of 1-propanol with supercritical $CO_2$ has been measured by means of a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The equilibrium loci of the pressure - composition and pressure - temperature were obtained for the binary mixture of 1-propanol + $CO_2$ system at 305.15 K, 313.15 K, 323.15 K and 333.15 K, and from 2 MPa to 11 MPa. The critical temperature of the mixture increased with the temperature. The pressure-composition line for the binary mixture of $CO_2$-1-propanol system showed a typical type-II phase behavior. The experimental P-x envelopes were correlated by using the Peng-Robinson equation of state in a satisfactory manner to obtain the parameters with $k_{ij}=0.116$ and ${\eta}_{ij}=-0.065$.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.1 s.34
• /
• pp.73-83
• /
• 1998

Considering dynamic behaviors according to initial tension forces, geometric nonlinearity and the effect of higher eigen modes to participate in dynamic behaviors increase as initial tension forces decrease, and from phase portrait we can realize that period attractors are produced in many area with complexity. If initial tension forxes increase, difference between linear and nonlinear solutions will decrease and the first eigen mode dominate the dynamic behaviors and observing phase portrait, period attractors appear in certain area regularly. These results may offer meaningful informations to nonlinear dynamic analysis using modal reduction methods such as Lanczos modal analysis. And actually nonlinear dynamic analysis needs very large computational efforts. So, if we determine the number of eigen modes to take part in modal analysis corresponding to initial tension forces we will get more accurate data close to exact nonlinear dynamic solutions.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.150.1-150.1
• /
• 2010

가스 하이드레이트는 물분자와 저분자량의 가스분자가 고압과 저온에서 수소결합을 이루며 형성되는 결정성 화합물을 말한다. 최근 가스 하이드레이트의 물리적 특성과 형성 원리를 이용하여 다양한 분야로의 적용 연구가 수행되고 있는데 이의 효과적 달성을 위해서는 가스 하이드레이트의 상평형 연구가 필수적이다. 기존에 수행되는 상평형 실험 방법은 온도의 변화에 따라 하이드레이트를 해리시키고 압력의 변곡점을 찾는 것으로 최소 24시간이 소요되지만, 본 연구진이 제안하는 QCM을 이용한 방법은 1 ng의 무게에 1 Hz의 변화를 나타내는 수정진동자의 민감성을 이용한 것으로 약 2~3시간 내에 상평형 실험을 수행할 수 있고, 하이드레이트의 기억효과(Memory Effect)를 이용하여 연속적인 상평형 실험도 가능하다. 본 연구에서는 QCM 반응기의 원리 및 실험 방법에 대하여 설명하고 열역학적 촉진제를 첨가한 상평형 실험결과를 제시함으로써 상대적으로 저렴한 가격으로 다양한 촉진제와 억제제 첨가 시 나타나는 상평형 효과를 빠른 시간 내에 선별할 수 있는 방법으로 QCM을 이용한 방법을 제안하고자 한다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.12 no.2
• /
• pp.101-109
• /
• 2002

A complex chemical equilibrium analysis was performed to study the hot-wall CVD process of the SiC/C functionally gradient materials (FGM). Thermochemical calculations of the Si-C-H-Cl system were carried out, and the effects of process variables(deposition temperature, reactor pressure, C/[Si+C] and H/[Si+C] ratios in the source gas) on the composition of deposited layers and the deposition yield were investigated. The CVD phase diagrams of the SiC/C FGM deposition were obtained, and the optimum process windows were estimated from the results.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.4
• /
• pp.7-11
• /
• 2011

The installation phase for a topside module suggested can be divided into 9 stages, which include start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the topside module from a transport barge to a crane vessel takes place in the first three stages, from start to lifting, while the transfer of the module onto a floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with significant wave height (1.52m), with suggested force equilibrium diagrams. The effects of the hydrodynamic interactions between the crane vessel and barge during the lifting stage have been considered. The internal forces caused by the load transfer and ballasting are derived for the lifting phases. The results of these internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the lifting phases, the internal force induced pitch motion is too small to show its influence. However, the effect of the internal force on the wave-induced heave responses in the lifting phases is noticeable in the irregular sea condition because the transfer mass-induced draught changes in the floating structure are observed to have higher amplitudes than the external force induced responses.

• Journal of Institute of Convergence Technology
• /
• v.5 no.1
• /
• pp.1-5
• /
• 2015

SI thermochemical hydrogen production process achieves water splitting into hydrogen and oxygen through three chemical reactions. The process is comprised of three sections and one of them is HI decomposition into $H_2$ and $I_2$ called as Section III. The production of $H_2$ included processes involving EED for concentrating a product stream from Section I. Additionally an $I_2$ crystallization would be considered to reduce burden on EED by removing certain amount of $I_2$ out of a process stream prior to EED. In this study, the current thermodynamic model of SI process was briefly described and the calculation results of the applied Electrolytes NRTL model for phase equilibrium calculations was illustrated for ternary systems of Section III. We calculated temperature and heat duty of an $I_2$ crystallizer and heat duty of heaters using UVa model and heat balance equation of simulation tool. The results were expected to be used as operation information in optimizing HI decomposition process and setting up material balance throughout SI process.

• Nuclear Engineering and Technology
• /
• v.31 no.6
• /
• pp.572-585
• /
• 1999

The characteristics of two-phase flow instability in a vertical boiling channel connecting with an unheated riser are investigated through the linear stability analysis model. Various two-phase flow models, including thermal non-equilibrium effects, are taken into account for establishing a physical model in the time domain. A classical approach to the frequency response method is adopted for the stability analysis by employing the D-partition method. The adequacy of the linear model is verified by evaluating experimental data at high quality conditions. It reveals that the flow-pattern-dependent drift velocity model enhances the prediction accuracy while the homogeneous equilibrium model shows the most conservative predictions. The characteristics of density wave oscillations under low-power and low-quality conditions are investigated by devising a simple model which accounts for the gravitational and frictional pressure losses along the channel. The necessary conditions for the occurrences of type-I instability and flow excursion are deduced from the one-dimensional D-partition analysis. The parametric effects of some design variables on low quality oscillations are also investigated.

• Journal of Korean Society on Water Environment
• /
• v.18 no.4
• /
• pp.421-433
• /
• 2002

This study was conducted to develope a simple, rapid and solvent-free solid-phase microextraction(SPME) procedure for extracting three organochlorine, one triazine and nine organophosphorus pesticides from water. The optimal conditions of SPME for analyses of organochlorine pesticides were obtained at $250^{\circ}C$ of desorption temperature, 45 minutes of equilibrium time, pH 6 and NaCl 0% addition using $100{\mu}m$ polydimethylsiloxane fiber and those of triazine and organophosphorus pesticides were obtained at $270^{\circ}C$ of desorption temperature, 60 minutes of equilibrium time, pH 6 and NaCl 0% addition using $100{\mu}m$ polydimethylsiloxane fiber. This method showed good lineality for organochlorine pesticides between 0.0001 and $10{\mu}g/L$ with regression coefficients ranging 0.9986~0.9992 and for triazine and organophosphorus pesticides between 0.01 and $10{\mu}g/L$ with regression coefficients ranging 0.9867~0.9998.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.9
• /
• pp.1273-1281
• /
• 2003

The present study is mainly motivated to investigate the vaporization, auto-ignition, and combustion of liquid fuel spray injected into high pressure environment. The unsteady, multi-dimensional models were used for realistic simulation of spray as well as prediction of accurate ignition delay time. The Separated Flow (SF) model which considers the finite rate of transport between liquid and gas phases was employed to represent the interactions between spray and gas field. Among the SF models, the Discrete Droplet Model (DDM) which simulates the spray using finite number of representative samples of discrete droplets was adopted. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. In order to predict an evaporation rate of droplet in high pressure environment, the high pressure vaporization model was applied using thermodynamic equilibrium and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. In case of vaporization, an interaction between droplets was studied through the simulation of spray. The interaction is shown up differently whether the ambient gas field is at normal pressure or high pressure. Also, the characteristics of spray behavior in high pressure environment were investigated through the comparison with normal ambient pressure case. In both cases, the spray behaviors are simulated through the distributions of temperature and reaction rate in gas field.