• Journal of the Korean Chemical Society
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• v.50 no.2
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• pp.141-152
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• 2006

In this study computer assisted instruction materials for the ‘Solution' chapter in high school chemistry II textbook were developed based on a view of particle and analyze the effect of the materials on 10th and 11th high school students. The contents of developed materials are dissolution, vapor pressure, the change of boiling point and freezing point, osmosis, and so on which are the major contents of Solution chapter in high school chemistry II textbook. Materials were developed with using animation and simulation for students understanding of the phenomena with a particle view point. Many phenomena in a solution were not simplified by colligative property of solution, but tried to explain by the concept of attraction between solute and solvent molecules. This computer assisted learning materials were developed using Flash 5.0 and Flash 6.0 Action Script. Educational effects of the materials on 10th and 11th grade students represented statistically meaningful increase of concept understanding. Especially the materials were effective to the transition stage or formal stage students in 10th grade and formal stage or the natural science major students in 11th grade.

• Membrane Journal
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• v.4 no.4
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• pp.221-231
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• 1994

The GR51PP(MWCO 50,000) and GR40PP(MWCO 100,000) membranes manufactured by DDS were used in ultrafiltration of dextran(Mw. : 500,000) solution in flat plate ultrafiltration cell filled with various types of turbulence promoters. The flux improvement by using turbulence promoter was higher in laminar flow region than in turbulent flow region. The maximum improvements of permeate flux were foud as 112% and 50% I laminar flow region and turbulent flow region, respectively. Also, the solute rejection of the ultrafiltration membrane was improved by turbulence promoters and its effect was significant in the high transmembrane pressure and laminar flow region. The smaller the spacer mesh size was used, the higher the flux improved, but the pressure drop in ultrafiltration cell also increased. In laminar flow region, pressure drop by the spacer was negligible, but in turbulent flow region it changed significantly depending upon the mesh size of the spacer and therefore, its mesh size must be baken into account in the design of the process. The predicted results of the modified mass transfer correlation had better agreement with experimental results than those of unmodified one, The modified mass transfer correlations for laminar and turbulent flow region are shown as follow. $N_{sh}=0.151(N_{Re})^{0.199}(N_{Sc})^{0.22}(N_{Scm})^{0.197}\;(625 $N_{sh}=0.0165(N_{Re})^{0.428}(N_{Sc})^{0.33}(N_{Scm})^{0.223}\;(5015

• Korean Journal of Materials Research
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• v.3 no.2
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• pp.111-120
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• 1993

Abstract In this study, the Mo-Hf-O ingots containing 0.31-1.14at % Hf and 0.08-1.00at % 0 were prepared by plasma arc melting. The change of microstructure depending on the condition of heat treatmen~ was analysed by optical microscophy, auger electron microscophy, and transmission electron microscophy. Molybdenum powder with the oxygen content of 830ppm was compacted, and then melted. The oxygen content of molybdenum ingots was detected to be 40 -130ppm. As the contents of Hf and 0 increased, the grain size of ingots decreased. When molybdenum igot containing l.14at % Hf and 1.00at % C was heat treated, p-molybdenum carbide in grains was transformed into ${\alpha}$-molybdenum carbide at 130$0^{\circ}C$. Between 140$0^{\circ}C$ and 150$0^{\circ}C$, the precipitation of hafnium carbide was due to the reaction of solute Hf and C, and the hafnium carbide was saturated at grain boundaries at 150$0^{\circ}C$. When the sample was heat treated from 150$0^{\circ}C$ to 170$0^{\circ}C$, Hafnium oxide more stable thermodynamically precipitated both at grain boundaries and in grains after hafnium carbide had been dissolved at grain boundaries.

• The Korean Journal of Ecology
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• v.27 no.6 s.122
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• pp.355-361
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• 2004

In order to elucidate the ecophysiological characteristics of coastal plants, we collected them on salt marsh and sand dune, and analyzed inorganic ($Na^+,\;K^+,\;Mg^{2+},\;Ca^{2+}$) and organic solutes (soluble carbohydrate, glycine betaine). Chenopodiaceous plant species (Atriplex gmelini, Salicornia europaea, Salsola collina, Suaeda glauca, Suaeda japonica) showed a tendency to accumulate inorganic ions such as $Na^+\;and\;Cl^-$ instead of $K^+$. However, Chenopodium serotinum which lives in ruderal habitat contained more $K^+$ and less $Na^+$ than the other Chenopodiaceous plants. Most Chenopodiaceous plant species maintained very low level of soluble $Ca^{2+}$ and relatively low concentration of carbohydrates and showed high concentration of glycine betaine which is among the most effective known compatible solutes in the leaves of plant under drought and saline conditions. On the other hand, plant species which belong to Gramineae (Ishaemum anthephoroides, Phragmites communis, Zoysia sinica) and Cyperaceae (Carex kobomugi, Carex pumila) absorbed $K^+$ selectively and excluded $Na^+\;and\;Cl^-$ effectively regardless of habitat conditions, and they accumulated more soluble carbohydrate as osmoticum than Chenopodiaceous plants. These results suggested that physiological characteristics such as high storage capacity for inorganic ions (especially alkali cations, chloride) and the accumulation of glycine betaine in chenopodiaceous plants and $K^+$-preponderance, an efficient regulation of ionic uptake (exclusion of $Na^+\;and\;Cl^-$) and the accumulation of soluble carbohydrate in monocotyledonous plants enable them to grow dry and saline habitats.

• Journal of Ecology and Environment
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• v.30 no.2
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• pp.187-193
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• 2007

Higher plants can be categorized as C3, C4 or CAM according to their photosynthetic pathways, and some succulent plants are known to shift their patterns of photosynthesis from C3 to CAM in response to environmental stresses such as salt treatment or water deficiency. To investigate fundamental photosynthetic patterns and the induction of pattern shifts (C3, CAM, C3-CAM etc.) as a result of environmental stresses, we measured the water content, diurnal changes in pH, net $CO_2$ exchange, transpiration rate, total ionic contents, and osmolality of Kalancoe daigremontiana, Sedum kamschaticum and Sedum sarmentosum which belong to Crassulaceae known as representative CAM plant, after 10 days of drought treatment. S. kamschaticum and S. sarmentosum did not show a significant difference in diurnal pH variation in the treatment and control conditions. However, the pH of drought-treated Kalancoe was low at night and high in the daytime, with a pH value between 4 and 5. Typical CAM plants display a net $CO_2$ exchange that increases at night and decreases in the daytime. Kalancoe displayed the predicted pattern. However, S. kamschaticum and S. sarmentosum showed a photosynthetic pattern more typical of C3 plants, and did not show changes in photosynthetic pattern under drought stress. Kalancoe also showed a transpiration rate typical for CAM pho-tosynthesis, whereas the transpiration rates of S. kamschaticum and S. sarmentosum were in the typical range for C3 photosynthesis. Kalancoe had high total ionic contents during the night, which decreased somewhat during the daytime, whereas S. kamschaticum and S. sarmentosum displayed the opposite pattern. This result is similar to the diurnal patterns of changes in pH in the three plant species, which suggests a relationship between pH and ionic contents. S. sarmentosum showed lower osmolality under drought stress than in the control condition, whereas the osmolality of Kalancoe and S. kamschaticum did not differ between conditions. S. sarmentosum may have maintained internal water content by lowering its osmolality and raising its total ionic contents. In conclusion, Kalancoe displayed the characteristic responses of a typical CAM plant, whereas S. kamschaticum and S. sarmentosum displayed aspects of the C3 photosynthetic pattern under drought conditions. These results suggest that S. kamschaticum and S. sarmentosum (Crassulacea) in Korea overcome drought stress by increasing solute and ionic contents internally rather than changing their photosynthetic pattern from C3 to CAM under drought stress.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.3
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• pp.111-119
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• 1999

The purpose of this study is the simulation of discontinuous rockmass and identification of characteristics of discontinuity network as a branch of the study on characteristics of groundwater system in discontinuous rockmass for evaluation of safety on disposal site of radioactive waste. In this study the site for LPG underground storage was selected for the similarities of the conditions which were required for disposal site of radioactive waste. Through the identification of hydraulic properties. characteristics of discontinuities and selection of discontinuity model around LPG underground storage facility. the applications of discrete fracture network model were evaluated for the analysis of pathway. The orientation and spatial density of discontinuities are primarily important elements for the simulation of groundwater and solute transportation in discrete fracture network model. In this study three fracture sets identified and the spatial intensity (P$_{32}$) of discontinuities is revealed as 0.85 $m^2$/㎥. The conductive fracture intensity (P$_{32c}$) estimated for the simulation area around propane cavern (200${\times}$200${\times}$200) is 0.536 $m^2$/㎥. Truncated conductive fracture intensity (T-P$_{32c}$) is calculated as 0.26 $m^2$/㎥ by eliminating the fracture with the iowest transmissivity and based on this value the pathway from the water curtain to PC 2. PC 3 analyzed.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.104-114
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• 2001

To investigate the effects of the addition of Nb and Sn on the recrystallization of Zr- Sn-Nb alloys, both Vickers micro-hardness test and TEP measurement were carried out on cold-worked specimens annealed at various temperatures from $300^{\circ}C$ to 75$0^{\circ}C$. The microstructures of heat treated specimens were analyzed by optical microscope, SEM, and TEM. The study of microhardness and microstructures showed that both recrystallization process and grain growth were retarded as the activation energy was increased by the addition of Nb and Sn. Especially, the addition of Sn was more effective on retarding recrystallization. Precipitates were formed more easily when Nb was added because the solubility of Nb into Zr is lower than that of Sn. However, the recrystallization process was affected more by Sn than Nb because the strain field formed by substitutional Sn repressed the dislocation movement. TEP was increased due to the decrease of electron scattering as recovery and recrystallization were proceeded and saturated when the recrystallization completed. However, when precipitates formed, TEP was increased because the decrease of solute concentration near the precipitates caused the decrease of electron scattering.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.274-280
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• 2014

Polysulfone (PSf) hollow fiber membranes were prepared via the nonsolvent induced phase separation technique. The cosolvent of ${\gamma}$-butyrolactone (GBL) was added to the polymer solution containing a mixture of PSf and N,N-dimethylacetamide (DMAc). Water was utilized as a precipitation nonsolvent. The morphology of prepared membranes was investigated using a field emission scanning electron microscopy. The fabricated membrane showed a typical asymmetric structure such as the dense layer on the porous support layer by the addition of GBL to the polymer solution. As the concentration of GBL increased, the asymmetric porous structure was shown to be more intensified. It was thought that the added GBL played a role of enhancing the liquid-liquid phase separation of the polymer solution, since the cosolvent of GBL might change the thermodynamic solubility parameter of the doping solution. Permeation properties through the prepared hollow fiber membranes were characterized by measuring the pure water flux and the solute rejection using $0.05{\mu}m$ polystyrene latex (PSL) beads. Experimental results revealed that the use of PEG as the internal coagulant enhanced the pure water flux up to 130 times compared to the use of EG while the rejection of the PSL beads decreased only 5%.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.87-94
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• 1992

The elution behavior of polystyrenes(PS), polymethylmethacrylates (PMMA), polybutadienes(PB), PS-PMMA(SM) block copolymers and PS-PB star shaped copolymers on the cross-linked polystyrene gels was studied. An interpretation was proposed for the plots of log hydrodynamic volume versus retention volume of solutes in the mobile phases such as tetrahydrofuran, toluene, chloroform, methylene chloride and tetrahydrofuran-cyclohexane mixture. In order to predict the retention of solutes from their physical properties, multiple stepwise regression analysis was applied to obtain the correlation. The distribution coefficients($K_p$) of solute-gel interactions in GPC for homopolymers and PS copolymers were also obtained in terms of network-limited separation mechanism. In the cases of PS and PB, $K_p$ values approach unity, while $K_p$ values for PMMA decrease as MW increase in the good solvent, but in poor solvent, $K_p$ values increase as MW increase. $K_p$ values of PS copolymers are dependent on their MW and composition, therefore, morohology of SM block copolymer is predicted to be random phase. A single universal plot of log[η]M vs. $(V_r-V_o)/K_p$

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.14-14
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• 2011

Groundwater in the Waikatoregion is a valuable resource for agriculture, water supply, forestry and industries. The 434,000 ha study area comprises the upper Waikato River catchment from the outflow of Lake Taupo (New Zealand's largest lake) through to Lake Karapiro (a man-made hydro lake with high recreational value) (Figure 1). Water quality in the area is naturally high. However, there are indications that this quality is deteriorating as a result of land use intensification and deforestation. Compounding this concern for decision makers is the lag time between land use changes and the realisation of effects on groundwater and surface water quality. It is expected that the effects of land use changes have not yet fully manifested, and additional intensification may take decadesto fully develop, further compounding the deterioration. Consequently, Environment Waikato (EW) have proposed a programme of work to develop a groundwater model to assist managing water quality and appropriate policy development within the catchment. One of the most important and critical decisions of any modelling exercise is the choice of the modelling platform to be used. It must not inhibit future decision making and scenario exploration and needs to allow as accurate representation of reality as feasible. With this in mind, EW requested that two modelling platforms, MODFLOW/MT3DMS and FEFLOW, be assessed for their ability to deliver the long-term modelling objectives for this project. The two platforms were compared alongside various selection criteria including complexity of model set-up and development, computational burden, ease and accuracy of representing surface water-groundwater interactions, precision in predictive scenarios and ease with which the model input and output files could be interrogated. This latter criteria is essential for the thorough assessment of predictive uncertainty with third-party software, such as PEST. This paper will focus on the attributes of each modelling platform and the comparison of the two approaches against the key criteria in the selection process. Primarily due to the ease of handling and developing input files and interrogating output files, MODFLOW/MT3DMS was selected as the preferred platform. Other advantages and disadvantages of the two modelling platforms were somewhat balanced. A preliminary regional groundwater numerical model of the study area was subsequently constructed. The model simulates steady state groundwater and surface water flows using MODFLOW and transient contaminant transport with MT3DMS, focussing on nitrate nitrogen (as a conservative solute). Geological information for this project was provided by GNS Science. Professional peer review was completed by Dr. Vince Bidwell (of Lincoln Environmental).