• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.11
• /
• pp.281-285
• /
• 1996

Pulsatile swelling behaviors and their application to drug delivery system were studied by using interpenetrating polymer networks(IPN) hydrogels constructed with poly(vinyl alcohol) and poly(acrylic acid). The PVA/PAAc IPNs hydrogels were symthesized by UV irradiation tallowed by repetitive freezing and thawing method. These hydrogels showed pH and temperature sensitive swelling behaviors. From the release experiment, the release amount of model drug incorporated into these hydrogels showed pulsatile patterns. Permeability coefficients obtained by various solutes differed in response to changes of permeation conditions.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.3
• /
• pp.128-131
• /
• 1985

A series of copolymer membranes of 2-hydroxyethylmethacrylate (HEMA) with selected hydrophobic monomers were prepared without crosslinking agents. The equilibrium water content, the partition coefficient, and the permeability of the solutes such as urea, methylurea, 1,3-di-methylurea, and acetamide via these membranes were measured. The partition coefficient data show that as the hydrophobicity of solutes increased, the partition of solutes were dictated by hydrophobic interaction between solute and polymer matrix. Diffusion coefficients obtained in these experiments decrease as the water content of polymer membrane decreases. This decrease is blunt as the excess heat capacities, ${\phi}C^0_p$ (excess) in aqueous solution at infinite dilution of solute increases. To investigate the relationship between water content and diffusion coefficient, the results of the diffusion experiments were examined in light of a free-volume model of diffusive transport. The remarkable increase of urea mobility in the polymer network containing relatively larger bulk water can be considered as water structure breaking effect.

• Journal of Industrial Technology
• /
• v.20 no.A
• /
• pp.101-111
• /
• 2000

This research is results of experimental and numerical works on characteristic of strength increase and bearing capacity in dredged and reclaimed soil due to desiccation shrinkage. For a soil sampled from southern coastal area in Korea, basic soil property tests and standard consolidation test with falling head permeability tests were carried out to obtain consolidational characteristics of soil. Double cone penetration test, laboratory vane test and unconfined compression test were also performed to investigate the change of shear strength with degree of desiccation. Model tests were performed in 1G environment and 30G level artificially accelerated condition by using the centrifuge model test facilities to investigate the bearing capacity of desiccated ground. Test results were analyzed by using the theoretical and load-settlement characteristics method proposed by Meyehof & Hanna(1978). On the other hands, the numerical technique, using the finite strain consolidation theory considering the effect of desiccation was used to estimate the appropriate time of using heavy construction equipments in field with respect to strength increase due to desiccation.

• Journal of Industrial Technology
• /
• v.28 no.A
• /
• pp.11-17
• /
• 2008

Applicability of hyperbolic settlement prediction method to consolidation settlement in the dredged and reclaimed ground was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio - effective stress - permeability and typical self-weight consolidation curves with time were obtained by analyzing centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve obtained by using Terzaghi's consolidation theory was compared with results predicted by the hyperbolic method. It was found to have its own inherent error to predict final consolidation settlement. From results of analyzing thc self-weight consolidation with time by using this method, it predicted relatively well in error range of 0.04~18% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. However, it overestimated the final settlement with large errors if those relation curves were nonlinear.

• Geomechanics and Engineering
• /
• v.7 no.5
• /
• pp.553-567
• /
• 2014

Borehole instability during drilling process occurs frequently when drilling through shale formation. When a borehole is drilled in shale formation, the low permeability leads to an undrained loading condition. The pore pressure in the compressed area near the borehole may be higher than the initial pore pressure. However, the excess pore pressure caused by stress concentration was not considered in traditional borehole stability models. In this study, the calculation model of excess pore pressure induced by drilling was obtained with the introduction of Henkel's excess pore pressure theory. Combined with Mohr-Coulumb strength criterion, the calculation model of collapse pressure of shale in undrained condition is obtained. Furthermore, the variation of excess pore pressure and effective stress on the borehole wall is analyzed, and the influence of Skempton's pore pressure parameter on collapse pressure is also analyzed. The excess pore pressure decreases with the increasing of drilling fluid density; the excess pore pressure and collapse pressure both increase with the increasing of Skempton's pore pressure parameter. The study results provide a reference for determining drilling fluid density when drilling in shale formation.

• Membrane and Water Treatment
• /
• v.11 no.3
• /
• pp.223-229
• /
• 2020

Here magnetic iron oxide particles (MIOPs) were synthesized under atmospheric air and which size was controlled by regulating the flow rate of alkali addition and used for efficient removal of bovine serum albumin (BSA) from water. The MIOPs were characterized using field-emission scanning electron microscopy (FE-SEM), Fourier transformation-Infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The results revealed a successful preparation of the MIOPs. The removal efficiency for BSA using MIOPs was found to be about 100% at lower concentrations (≥ 10 mg/L). The maximum adsorption of 64.7 mg/g for BSA was achieved as per the Langmuir adsorption model. In addition, microfiltration membrane for removal of BSA as model protein organic foulant is also studied. The effect of various MIOPs adsorbent sizes of 210, 680 and 1130 nm on the absorption capacity of BSA was investigated. Water permeability of the BSA integrated with the smallest size MIOPs membrane was increased by approximately 22% compared by the neat BSA membrane during dead-end filtration. Furthermore, the presence of small size MIOPs were also effective in increasing the permeate flux.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.47 no.4
• /
• pp.53-61
• /
• 2005

A series of laboratory tests was carried out fur analyzing of seepage characteristics of two-layers embankment model which consists of gravel and earth fill layers. Gravel layers were built under the earth fill for a half and one-third width of earth fill of the model. Permeability of earth fill was ranged between $5.00\times10^{-5}\~3.00\times10^{-4}\;m/s$.. The tests were performed with hydraulic gradients(i), $0.10\~0.55$. From the test results, hydraulic head of earth fill with gravel layer was 1.6 times higher than that of earth fill without gravel layer. Seepage rate was increased up to $4\~22$ times and safety factor for piping was decreased to $13\~43\;\%$ comparing the earth fill with gravel layer to that without gravel layer. The gravel layer under the earth fill could, in general, give some serious seepage problems to seadike embankment.

• Korean Chemical Engineering Research
• /
• v.53 no.1
• /
• pp.22-30
• /
• 2015

So far, most of research activities on modeling of membrane separation processes have been focused on binary feed mixture. But, in actual separation operations, binary feed is hard to find and most separation processes involve multicomponent feed mixture. In this work models for membrane separation processes treating multicomponent feed mixture are developed. Various model types are investigated and validity of proposed models are analysed based on experimental data obtained using hollowfiber membranes. The proposed separation models show quick convergence and exhibit good tracking performance.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 2006.04a
• /
• pp.123-135
• /
• 2006

Alzheimer's disease (AD) is the most common form of dementia in the aging population and is clinically characterized by a progressive loss of cognitive abilities. Pathologically, it is defined by the appearance of senile plaques - extracellular insoluble, congophilic protein aggregates composed of amyloid $\beta$ (A$\beta$) and neurofibrillary tangles (NFTs) - inyracellular lesions consisting of paired helical filaments from hyperphosphorylated cytoskeletal tau protein as described by Alois Alzheimer a century ago. These hallmarks still serve as the major criteria for a definite diagnosis of the disease. Consequently, one of the key strategy for drug development in this disease area focuses on reducing the concentration of cerebral A$\beta$ plaque by using substances that inhibit A$\beta$ fibril formation. We focused on developing inhibitors by synthesizing several kinds of aromatic molecules. The synthetic compounds were initially screened to evaluate the effective compound by tioflavin T fluorescence assay. The selected effective compounds were tested cytotoxicity and protective effect from A$\beta$-induced neuronal toxicity by cell based MTT assay with HT22 hippocampal neurons. The BBB permeability on effectors was also tested in in vitro co-culture model(HUVEC/C6 cell line). The behavior test wea carried out in mutant APP/PS1 transgenic mouse model of Alzheimer's disease. And inhibition of A$\beta$ fibril formation by the effective compound was monitored with transmitted electron microscopic images.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.31 no.1
• /
• pp.58-70
• /
• 1989

The paper compared the Bishop methed to the Fellenius method in the analysis of slope stability. Laboratory model test was carried out in the case of seepage flow considered. The results obtained from this study were summarized as follows; 1. The slice pieces of 10 were enough to analysis the slope stability. 2. The safety factor. by the Fellenius method was lower than the Bishop method by the 96 to 97% in the case of no seepage flow and by the 95 to 96% in the case of seepage flow considered. 3. Besides the parameter of soil and slope, the safety factor of slope was influenced by the height of slope. This phenomena was distinct in the height of height less than 10 meters. 4. In the case of clay, there was no difference in the safety factor of slope between Fellenius and Bishop rnethod. The safety factors of slope with the seepage flow considered were lower than those with no see-page flow. 5. The influence of cohesion on the safety factor was more significant in the Bishop method than in the Fellenius method. 6. The slope failure of model test of A and B soil samples with high permeability coefficient was taken place slightly in vicinity of toe by the concentration of stress and gradually increased 7. Under condition of same slope height, the shapper the slope, the shorter the radius and the center of critical circle appered downward and finally failure of slope occured inside the slope.