• Membrane Journal
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• v.12 no.4
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• pp.226-239
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• 2002

A process simulation model of pervaporation process has been developed as a design tool to analyse and optimize the dehyhration of organic solvents through a commercial scale of pervaporative plate-and-frame modules that contain a stack of membrane sheets. In the simulation model, the mass balance, the heat balance and the concentration balance are integrated in a finite elements-in-succession method to simulate the overall process. In the integration method, a feed channel between membrane sheets in the modules was taken as differential unit element volume to simplify calculation procedure and shorten computing time. Some of permeation parameters used in the simulation model, were quantified directly from the dehydration experiment of ethanol through $AzeoSep^{TM}$-2002 membrane which is a commercial pervaporation membrane. The simulation model was verified by comparing the simulated values with experimental data. Using the model, continuous and batch pervaporation processes were simulated, respectively, to acquire basic data for analysing and optimizing in the dehydration of ethanol through the membrane. Based on the simulation results, a comparison between the continuous and the batch pervaporation processes would be discussed.

• Journal of Korean Public Health Nursing
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• v.26 no.1
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• pp.147-157
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• 2012

Purpose: The purpose of this study was to identify the related factors of change affecting the stages of change for exercise, on the assumption that there are various stages of change in the exercise behavior of women in nursing college. Methods: The subjects were 496 female college students in D city. The research instruments were stages of change for exercise behavior, the process of change, decisional balance, and self-efficacy. The dates were analyzed by descriptive statistics, ANOVA, and stepwise multiple regression using the SPSS 18.0 program. Results: The distribution of the subjects across the stages was: pre-contemplation, 17.7%; contemplation, 58.7%; preparation, 19.0%; action, 2.8%; maintenance, 1.8%. Analysis of variance showed that cognitive process (F=17.26, p<0.01), behavioral process (F=27.05, p<0.01), the pros of decisional-balance (F=7.07, p<0.01), the cons of decision-balance (F=5.82, p<0.01), and self efficacy (F=17.79, p<0.01) were significantly associated with the change of exercise behavior stages. The related factors of change affecting the change of exercise behavior stage were the cons of decision-making, counter conditioning, self re-evaluation, and body mass index, including 28.4% R-square. Conclusion: The transtheoretical model would be applicable to explain the exercise behavior of some women in nursing college. So, this study will be useful information for developing effective exercise behavior programs considering female students' stages of change.

• Journal of the Korean Applied Science and Technology
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• v.36 no.3
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• pp.866-875
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• 2019

In this study, The Chemical Mass Balance (CMB) model was used to identify pollutant sources and their contributions to $PM_{2.5}$. The contribution rankings by emission source in A city were ash dust (30.1%) > biomass burning (21.9%) > secondary pollutants (21.1%) > mobile source (19.3%) > area sources (7.6%), and The emission sources increased from the contribution of the CMB model and the Clean Air Policy Support System (CAPSS) emissions were biomass burning and secondary pollutants, and The emission sources reduced were mobile source, ash dust, and area sources.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.2
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• pp.141-145
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• 2002

Successive ion Exchange Column model was developed with the combination of mass action law and mole balance equation. consuming that ions entering the ion exchange bed pass the resin layer via consecutive ion exchange equilibrium. The application of the model to condensate polishing demineralizer in nuclear power plants indicates that the leakage of $Na^+$ and $Cl^-$ depends upon the degree of resin regeneration and that the ratio of specific ion concentration in Influent to in effluent is subject to the characteristics of resin and solution. The model can account for the local in-equilibrium with the correction of resin concentration and also can be applicable to a competitive ion exchange.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1160-1165
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• 2004

The purpose of this study was to calculate three dimensional angular displacements, moments and joint reaction forces of the ankle joint during the waist pulling, and to assess the ankle joint reaction forces according to different perturbation modes and different levels of perturbation magnitude. Ankle joint model was assumed 3-D ball and socket joint which is capable of three rotational movements. We used 6 cameras, force plate and waist pulling system. Two different waist pulling systems were adopted for forward sway with three magnitudes each. From motion data and ground reaction forces, we could calculate 3-D angular displacements, moments and joint reaction forces during the recovery of postural balance control. From the experiment using falling mass perturbation, joint moments were larger than those from the experiment using air cylinder pulling system with milder perturbation. However, JRF were similar nevertheless the difference in joint moment. From this finding, we could conjecture that the human body employs different strategies to protect joints by decreasing joint reaction forces, like using the joint movement of flexion or extension or compensating joint reaction force with surrounding soft tissues. Therefore, biomechanical analysis of human ankle joint presented in this study is considered useful for understanding balance control and ankle injury mechanism.

• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.7-12
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• 2012

Extrusion is one of the most important operations in the polymer-processing industry. Development of models for extrusion and computer tools offer a route to developing reliable and optimized process designs. The models are based on the analysis of physical phenomena encountered during the process. Balance equations for mass, momentum and energy are fundamental to the problem. A predictive computer model has been developed for the single screw extruders with conventional screws of different geometry. The model takes into account melting zones of the extruder and describes an operation of the extruder system, making it possible to predict mass flow rate of the polymer, pressure and velocity profiles along the extruder screw channel. The simulation parameters are the material and rheological properties of the polymer; the screw pitch, and screw speed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.189-194
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• 2012

The purpose of this study is to predict the performance of a cyclone drying machine and air ejector used in drying applications. This paper deals with optimization of the geometry of the ejector for sludge drying using computational fluid dynamics. To facilitate the design of a jet ejector for air drying machines, a numerical model of simultaneous mass and heat transfers between the liquid(sludge) and gas(air) phases in the jet ejector was developed. The steady-state model was based on unidimensional balance equations of mass, energy and momentum for the liquid and gas phases. It was shown that the optimum condition to minimize pressure and momentum loss of air in the ejector was d=220mm. It was found that sludge particles inside the cyclone was smoothly discharged by the conical wedge installed on the bottom of the cyclone.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1368-1379
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• 2000

A numerical study on swirling pulverized coal combustion in an axisymmetric enclosure is carried out by applying the 2-phase weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard and RNG k-${\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase. The eddy-dissipation model is employed for the reaction rate for gaseous mixture, and the single-step and two-step first-order reaction model for the devolatilization process for coal. Special attention is given to establish the thermal boundary conditions on radiative transfer equation By comparing the numerical results with experimental ones, the radiation model used here is confirmed and found to provide an alternative for simulating the radiative transfer.

• Journal of Ecology and Environment
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• v.35 no.2
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• pp.99-109
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• 2012

Litterfall dynamics in forests are assessed by estimating biomass production and decomposition. However, there have been few studies on how litter dynamics impact the health and management of ecosystems. Here, a new approach to measure and assess ecosystem function is presented based on conventional methods using littertraps, litterbags, and the mass on the forest floor. To assess the status of litter dynamics, the decay rate (k) was estimated from a litterbag experiment, and removal rates ($k_i$) were determined from mass balance on the forest floor at 21 sites on three mountains in South Korea. The $k_3$ (organic mass ratio of $O_i$ and $O_e+O_a$ + A horizons in November) values in an equilibrium state in South Korea were within the range of $k{\pm}0.174$ when considering the annual variation of litterfall production. This study also suggests that sampling sites for these types of studies should be in the middle, not at the ends, of steady slopes on the forest floor.

• Journal of Environmental Science International
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• v.17 no.10
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• pp.1069-1073
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• 2008

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and $NO_2$ generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential N02 deposition constant of 0.94 $hr^{-1}$. Mean generation rate of $NO_2$ was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher $NO_2$ generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.