• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.109-118
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• 1995

The permeability of concrete is closely related to the durability and the latter may be expressed by measuring permeability of concrete. According to the results, the permeability of fly ash concrete was lower than that of OPC(PC1) concrete and decreased with increasing fly ash levels(l5%, 30% and 45%). The permeability values of concrete cured in water is significantly lower than those of concrete cured in air, but the differences were reduced with increasing fly ash level. In comparison with OPC(PC1) concrete and high fly ash concrete containing enhanced early strength cements, the latter also had a lower permeability than the former. The permeability of concrete cured in water was decreased with curing time(28 and 180 days) irrespectwe of cement types. However, the trend of results cured in air was opposite to that cured in water due to the rnicrocrackinp: of concrete. It was found that the properties of strength and permeability of concrete were related each other. However, the permeability of concrete was more dependant upon the type of binder used in concrete.

• Journal of Pharmaceutical Investigation
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• v.36 no.1
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• pp.39-44
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• 2006

Tamsulosin or a salt thereof such as its hydrochloride salt has been known to have an adrenaline ${\alpha}$ receptor blocking action for urethra and prostate areas. It has been widely used as a drug which lowers the prostate pressure and improves urinary disturbance accompanied by prostate-grand enlargement, thus for the treatment of prostatic hyperplasia. To avoid dose-dependent side effects of tamsulosin upon oral administration, the development of sustained-release delivery system is essentially required, that can maintain therapeutic drug levels for a longer period of time. The aim of this study was therefore to formulate sustained-release tamsulosin granules and assess their formulation variables. We designed entric coated sustained-release tamsulosin granules for this purpose. Nano-pores in the outer controlled release membrane were needed in order to obtain initial tamsulosin release even in an acidic environment such as gastric region. In our sustained release osmotic granule system, hydroxypropylmethylcellulose in a drug-containing layer was used as a rate controller. The drug-containing granules were coated with hydroxypropylmethylcellulose phthalate (HPMCP) and Eudragit, along with glycerol triacetate as an aqueous nano-pore former. The release of tamsulosin depended heavily on the type of Eudragit such as RS, RL, NE 30D, used in the formulation of controlled release layer. These results obtained clearly suggest that the sustained-release oral delivery system for tamsulosin could be designed with satisfying drug release profile approved by the Korean Food and Drug Administration.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.521-530
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• 2017

Improving the microstructure of NiO/YSZ is one of several approaches used to enhance the electrical and mechanical properties of an anode support in Solid Oxide Fuel Cells (SOFCs). The aim of the work reported in this paper was to predict the relationship between these microstructural changes and the resulting properties. To this end, modification of the anode microstructure was carried out using different sizes of Poly (Methyl Methacrylate) (PMMA) beads as a pore former. The electrical conductivity and mechanical strength of these samples were measured using four-probe DC, and three-point bend-test methods, respectively. Thermal etching followed by high resolution SEM imaging was performed for sintered samples to distinguish between the three phases (NiO, YSZ, and pores). Recently developed image analysis techniques were modified and used to calculate the porosity and the contiguity of different phases of the anode support. Image analysis results were verified by comparison with the porosity values determined from mercury porosimetry measurements. Contiguity of the three phases was then compared with data from electrical and mechanical measurements. A linear relationship was obtained between the contiguity data determined from image analysis, and the electrical and mechanical properties found experimentally. Based upon these relationships we can predict the electrical and mechanical properties of SOFC support from the SEM images.

• Korean Journal of Human Ecology
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• v.5 no.1
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• pp.48-61
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• 2002

This study was carried out to investigate the effects of four kinds of leavening agents on Jeung-Pyun fermantation. Milk-wine(M), fresh yeast(F), dry yeast(D), instant yeast(I) were used in Jeung-Pyun ingredients. The physicochemical properties, sensory evaluation were examined. The results of this study are summarized as follows: 1. Basic recipes for Jeung-Pyun by preliminary test were developed. 2. Specific volumes and expansion ratio of Jeung-Pyun was higher in the fresh yeast-added sample. 3. The pH of Jeung-Pyun was decreased significantly as the fermentation progressed 4. In the result comparing Jeung-Pyun extracting after 1st fermentation with Jeung-Pyun extracting 2nd fermentation by SEM, the former was widely distributed in stability of bubble and pore than the latter. 5. Standard recipe by Q.D.A. test added four kinds of leavening agents were as follows: (1)Jeung-Pyun added milk wine was 240min for 1st fermentation time, 60min for 2nd fermentation time, 35$^{\circ}C$ for fermentation temperature, 80% for fermentation humidity respectively. (2) Jeung-Pyun added fresh yeast was 90min for 1st fermentation time, 40min for 2nd fermentation time, 35$^{\circ}C$ for fermentation temperature, 80% for fermentation humidity respectively. (3)Jeung-Pyun added dry yeast was 90min for 1st fermentation time, 60min for 2nd fermentation time, 35$^{\circ}C$ for fermentation temperature, 60% for fermentation humidity respectively. (4)Jeung-Pyun added instant yeast was 90min for 1st fermentation time, 40min for 2nd fermentation time, 30$^{\circ}C$ for fermentation temperature, 60% for fermentation humidity respectively. 6.Based on sensory evaluation, Jeung-Pyun added fresh yeast was significantry higher than others in color, sweetness, moistness, softness, and overall quality. There was negative significance between milk wine flavor and astrigentness, and yeast flavor.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.768-774
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• 2006

The microstructure of Ni-YSZ cermets was controlled with fine and coarse starting powders (NiO and YSZ) to obtain a optimum strong and conductive tubular anode support for SOFCs. Three types of cermets with different microstructures, i.e., coarse Ni-fine YSZ, fine Ni-coarse YSZ, and fine Ni-fine YSZ, were fabricated to investigate their electrical and mechanical properties. The cermets from fine NiO powder showed high electrical conductivity due to the enhanced percolation of Ni particles. The cermet by foe Ni and coarse YSZ showed excellent electrical conductivity (>1000 S/cm) despite its high porosity $(\sim40%)$ but it showed poor mechanical strength due to the lack of percolation by YSZ particles and due to large pores. Thus fine NiO and YSZ powders were used to make strong and conductive Ni-YSZ support tube by extrusion. The microstructure of the anode tube was modified by the amount of polymeric additives and carbon black, a pore former. Ni-YSZ tube (porosity $\sim34%$) with the finer microstructure showed better performance both in electrical conductivity (>1000 S/cm) and fracture strength $(\sim140\;MPa)$. Either flat or circular NiO-YSZ tubes with the length from 20 to 40cm were successfully fabricated with the optimized composition of materials and polymeric additives.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.214-219
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• 2010

In this study, we fabricated tubular ceramic support for segmented-in-series solid oxide fuel cell (SOFC) by using CSZ(CaO-stabilized $ZrO_2$) as main material and activated carbon as pore former. Thermal expansion properties of ceramic support with different amounts of activated carbon were analyzed by using dilatometer to decide a suitable sintering temperature. The tubular ceramic supports with different amounts of activated carbon (5, 10, 15wt.%) were fabricated by the extrusion technique. After sintering at $1100^{\circ}C$ and $1400^{\circ}C$ for 5h., cross section and surface morphology of tubular ceramic support were analyzed by using SEM image. Also, the porosity, mechanical property, gas permeability of tubular ceramic supports was measured. Based on these results, we established the suitable fabrication technique of tubular ceramic support for segmented-in-series SOFC.

• Geomechanics and Engineering
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• v.24 no.6
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• pp.519-529
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• 2021

In coal mining activities, the abutment stress of the coal has to undergo cyclic loading and unloading, affecting the strength and seepage characteristics of coal; additionally, it can cause dynamic disasters, posing a major challenge for the safety of coal mine production. To improve the understanding of the dynamic disaster mechanism of gas outburst and rock burst coupling, triaxial devices are applied to axial pressure cyclic loading-unloading tests under different axial stress peaks and different pore pressures. The existing empirical formula is use to perform a non-linear regression fitting on the relationship between stress and permeability, and the damage rate of permeability is introduced to analyze the change in permeability. The results show that the permeability curve obtained had "memory", and the peak stress was lower than the conventional loading path. The permeability curve and the volume strain curve show a clear symmetrical relationship, being the former in the form of a negative power function. Owing to the influence of irreversible deformation, the permeability difference and the damage of permeability mainly occur in the initial stage of loading-unloading, and both decrease as the number of cycles of loading-unloading increase. At the end of the first cycle and the second cycle, the permeability decreased in the range of 5.777 - 8.421 % and 4.311-8.713 %, respectively. The permeability decreases with an increase in the axial stress peak, and the damage rate shows the opposite trend. Under the same conditions, the permeability of methane is always lower than that of helium, and it shows a V-shape change trend with increasing methane pressures, and the permeability of the specimen was 3 MPa > 1 MPa > 2 MPa.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.135-142
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• 1989

Methyl tert-butyl ether(MTBE) was synthesized from vapor phase reaction of methanol with iso-butylene over HZSM-5 catalysts, and effects of SiO$_2/Al_2O_3$ ratio in the HZSM-5 catalysts and reaction conditions on products distribution have been examined. Acid strength and acid type of each catalyst with different SiO$_2/Al_2O_3$ ratio were measured using pyridine adsorption followed by temperature programmed desorption(TPD) and IR analysis. Reactants and products adsorption characteristics on different acid sites have also been examined. As the SiO$_2/Al_2O_3$ ratio of HZSM-5 catalyst was increased, selectivity to MTBE was improved as a result of decrease in dimethylether(DME) formation at the strong acid sites. Conversion and selectivity to MTBE were also greatly enhanced as $i-C_4H_8/CH_3OH$ reactant ratio was increased, and overall about 80$^{\circ}$C was adequate for the MTBE synthesis. The properties of deposited coke on spent catalysts were examined by TG, DTA and IR spectrum analysis, indicating the amount of the coke deposit in the order of HY > H-Mordenite > HZSM-5. Even if the coke deposited on H-Mordenite was little more in amount than to that on HZSM-5, the former deactivated quickly due to its non-interconnected channel structure. For HY, owing to its lange pore size, significant $i-C_4H_8$ polymerization was occured, and rapid deactivation and severe coke formation has resulted within few hours.

• Membrane Journal
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• v.15 no.4
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• pp.272-280
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• 2005

In this study, asymmetric polysulfone membranes were prepared by the phase inversion method and the casting solutions were containing N-methyl-2-pyrrolidone (NMP) as a solvent. Deionized water and various alcohols(methanol, ethanol, and propanol) were used as a coagulation medium in preparing asymmetric polysulfone membranes. This study investigates the effect of alcohol coagulants having different solubility parameters as a pore-former on the construction of porous structures and their pure water permeation properties. Asymmetric polysulfone membranes immersed in the pure alcohol coagulation bath solution showed the typical sponge-like structures and the reduced water permeability as compared with those of polysulfone membranes precipitated in the pure water coagulation bath solution. In the water/alcohol mixtures, asymmetric polysulfone membranes showed the finger-like structures with the sponge-like structures. Therefore, the sponge-like structure of polysulfone membrane was formed under the delayed demixing systems while the porosity of membrane was decreased significantly. The water permeability of polysulfone membrane precipitated in the pure water coagulant showed 164 [$L/m^2hr$] at 14.7 psi. In case of polysulfone membranes prepared in the pure methanol and ethanol coagulant, they showed the water permeability of 56 and 30 [$L/m^2hr$], respectively.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.118-125
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• 2002

Hydration is the main reason for the growth of the material properties. An exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development of all material properties and the formation of microstructure should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of W/C ratio on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The tatter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration. In this study, the effects of chemical composition of cement, W/C ratio, temperature, and moisture conditions on the degree of hydration are considered. Parameters that can be used to indicate or approximate the real degree of hydration are liberated heat of hydration, amount of chemically bound water, and chemical shrinkage, etc. Thus, the degree of heat liberation and adiabatic temperature rise could be determined by prediction of degree of hydration.