• Journal of The Korean Association For Science Education
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• v.27 no.2
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• pp.144-152
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• 2007

In this study, high school science teachers' and students' various conceptions related to osmosis phenomena were compared with and analyzed in relation to the content of science textbooks used in high school science classrooms and college science courses. The questionnaires developed by the researchers were administered to science teachers and students. Differences can be found between the explanations of science textbooks on osmotic pressure and semi-permeable membranes. Many science teachers and students thought of osmotic pressure as 'membrane pressure occurred by the movement of a solvent'. Moreover, the types of teachers of semi-permeable membranes were similar regardless of their academic majors. Many of the teachers thought of a semi-permeable membrane as a membrane that 'passes small-size particles'; however, many students thought of this type of membrane as being 'selectively permeable'. Also, the salt-pickling cabbage phenomenon seemed to cause significant confusion to science teachers and students. These study results show that teachers and students possess various conceptions related to the osmosis phenomena. These different conceptions related to osmosis phenomena might cause confusion and diverse conceptions including misconceptions among teachers and students.

• Membrane Journal
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• v.27 no.4
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• pp.291-312
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• 2017

Seawater desalination is currently considered to be one of the primary technologies to resolve the global water scarcity problem. A basic understanding of membrane filtration phenomena is significant not only for further technological development but also for integrated design, optimal control, and long-term maintenance. In this vein, the present work reviews the major transport and filtration models, specifically related to reverse osmosis phenomena, provides theoretical insights based on statistical mechanics, and discusses model-based physical meanings as related to their practical implications.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.2
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• pp.123-140
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• 2009

The effect of a solute concentration difference on the osmotic transport of water through the semi-permeable membrane of a simple cell model is investigated. So far, most studies on osmotic phenomena are described by simple diffusion-type equations ignoring all fluid motion or described by Stokes flow. In our work, as the governing equations, we consider the coupled full Navier-Stokes equations which describe the fluid motion and the full transport equation that takes into account of convection and diffusion effects. A two dimensional finite difference model has been developed to simulate the velocity field, concentration field, and semi-permeable membrane movement. It is shown that the cell swells to regions of lower solute concentration due to the uneven water flux through the semi-permeable membrane. The simulation is applied on a red blood cell geometry and the relevant results are presented.

• Journal of The Korean Association For Science Education
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• v.14 no.3
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• pp.293-303
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• 1994

The purpose of this study was to find the effect of molecular movement model based instruction on high school students' conceptions of diffusion and osmosis. The study was composed of two groups, the traditional instruction group in which the so-called traditional instruction was performed, and the other group in which interventions by researchers were made. The subjects of the traditional instruction group consisted of a total of 242 high school students from Seoul, Gwangju and Mokpo. The subjects of the model based instruction group consisted of 177 first-year high school students in Mokpo. The study was focused on the use of the term of 'molecular movement' in their explanation of diffusion and osmosis in the correct contexts. In general, students who got the molecular movement model based instruction showed more frequent use of the terms of 'molecular movement' in the correct contexts than the control group students did. It was found that misconceptions including teleological explanations changed into scientific explanations by the intervention. It seemed that the molecular movement model led students to make scientific explanations on natural phenomena. A further research is recommended to assess the improvement of teleological explanation and scientific attitude by the molecular movement model.

• Membrane Journal
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• v.32 no.2
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• pp.126-132
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• 2022

Water purifiers have a quite different characteristic in comparison with general membrane water treatment processes in which the running and resting are repeated dozens of times a day. In the case of water purifiers using reverse osmosis membranes, this characteristic makes a phenomenon that the total dissolved solids (TDS) of permeate in water purifiers at the beginning of running shows a higher value than a normal value (TDS reduction is lower than a normal value). It is called "TDS creep". The effects of resting times and feed concentrations on the TDS creep were investigated. The feed flushing, the volume increase in permeate side and the flushing with purified water were applied to reduce TDS creep and the effectiveness were observed. Among these trials, the minimization of concentration between feed and permeate side of reverse osmosis membrane like the flushing with purified water can be an ultimate solution to reduce the TDS creep.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.11-14
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• 1998

1. Introduction : Research progresses in Chemistry and Chemical Engineering have been made during the last decades with important contributions to the industrial development and to the quality of our life. An interesting case is related to the membrane science and technology continuous impact to innovative processes and products, particularly appropriate for a sustainable industrial growth. Membrane operations have been familiar for many years to biologists and chemists working in their laboratorier or studying biological phenomena. Only recently engineers started to operate in' this area. The preparation of asymmetric CA membranes at University of California, Los Angeles in the early 60s is generally recognized as a crucial moment for membranology (1). Loeb and Sourirajan with their discovery of how to increase significantly the permeability of polymeric membranes without significant changes in their selectivity, made realistic the possibility of their use in large scale operations for desalting brackish and sea water by reverse osmosis and for various other molecular separations in different industrial areas. Reverse osmosis is today a well recognized basic unit operations, togheter with ultrafiltration, crossflow microfiltration,. nanofiltration, all pressure driven membrane processes. Already in 1992 more than 4 milIions m$^3$/day were the total capacity of RO desalination plants and in 1995 more than 180.000 m$^2$ of ultrafiltration membranes were installed for the treatment of wheys and milk (2) (3).

• Membrane and Water Treatment
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• v.8 no.2
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• pp.125-136
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• 2017

Reverse osmosis technology is being used on large scale for treatment of ground water, brackish water, wastewater and sea water. The most challenging issue in RO process is carbonate scaling which is directly linked with the efficiency and economy. Considering the natural phenomena of carbonate scaling different adaptations have been made to control scaling on the surface of RO membrane including acid dosage and antiscalant addition. As carbonate scaling is directly related with pH level of feed water, present study describes an experimental approach to reduce scaling on RO membrane by lowering the feed water pH by purging $CO_2$. In this comparative study four different conditions including control process (without any scale inhibitor), with dosage of antiscalant, with purging of $CO_2$ and with co addition of antiscalant and $CO_2$ in a feed stream line; it was established that $CO_2$ is a better appliance to reduce carbonate scaling on the membrane surface by reduce pH of feed stream. It was also observed that $CO_2$ and antiscalant mutually function better for scale control.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.133-138
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• 2015

Pressure retarded osmosis (PRO) process is one of membrane processes for harvesting renewable energy by using salinity difference between feed and draw solutions. Power is generated by permeation flux multiplied by hydraulic pressure in draw side. Membrane fouling phenomena in PRO process is presumed to be less sever, but it is inevitable. Membrane fouling in PRO process decreases water permeation through membrane, resulting in significant power production decline. This study intended to investigate the effect of hydraulic pressure in PRO process on alginate induced organic fouling as high and low hydraulic pressures (6.5 bar and 12 bar) were applied for 24 h under the same initial water flux. In addition, organic fouling in draw side from the presence of foulant (sodium alginate) in draw solution was examined. As major results, hydraulic pressure was found to be not a significant factor affecting in PRO organic fouling as long as the same initial water flux is maintained, inidicating that operating PRO process with high hydraulic pressure for efficient energy harvesting will not cause severe organic fouling. In addition, flux decline was negligible from the presence of organic foulant in draw side.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.679-686
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• 2018

Reverse osmosis (RO) concentration of sodium chloride, sodium acetate, and sodium citrate solutions has been performed by polyamide RO membrane. Concentration polarization phenomena was also studied by changing pressure, solute kinds, and initial solution concentration. Pressure effect on permeation flux was that the increase of flux was accompanied by the increase of pressure. Flux increase was observed by the decrease of initial solution concentration. Surface concentration on the RO membrane increases and so flux declines due to the concentration polarization. In the later phase of concentration, concentration polarization effect was decreased by the back diffusion of solute from the polariztion layer. In case of sodium citrate, its large ion size and charge density resulted in the discrepancy between theory and experimental data of concentration polarization. It may be due to electric repulsion on the membrane surface.

• Journal of The Korean Association For Science Education
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• v.40 no.1
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• pp.77-87
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• 2020

Scientific inquiry has emphasized its importance in various aspects of science learning and has been performed according to various methods and purposes. Among the various aspects of science learning, it is emphasized to develop core competencies with science, such as scientific thinking. Therefore, it is necessary to support students to be able to formulate scientific reasoning properly. This study attempts to explore problem-finding and scientific reasoning in the process of performing scientific inquiry. This study also aims to reveal what factors influence this complex process. For this purpose, this study analyzed the inquiry process and results performed by two groups of college students who conducted the inquiry related to osmosis. To analyze, research plans, presentations, and group interviews were used. As a result, it was found that participants used various scientific reasoning, such as deductive, inductive, and abductive reasoning, in the process of problem finding for their inquiry about osmosis. In the process of inquiry and reasoning complexly, anomalous data, which appear regularly, and the characteristics of experimental instruments influenced their reasoning. Various reasons were produced for the purpose of constructing the best explanation about the phenomena observed by participants themselves. Finally, based on the results of this study, several implications for the development context of programs using scientific inquiry are discussed.