• Membrane Journal
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• v.15 no.1
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• pp.52-61
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• 2005

Permeate flux decline in a microfiltration was analyzed by measuring the permeability of bentonite colloidal solution through polyethylene capillary membranes. The flux decline with time was due to the growth of cake layer on the membrane surface and to the pore blocking by particles. As the time approaches to steady state, the permeate flux is almost controlled by the cake filtration model. Faster flux decline at high trans-membrane pressure was attributed to the formation of denser packed cake layer and pore blocking. The ratio of permeate flux to the initial permeate flux, J/J₁, decreased with increasing the trans-membrane pressure, from 45% for 0.5 kg/sub f//㎠ to 38% for 2.0 kg/sub f//㎠. In comparing the ratio of each fouling component to the total fouling for the 0.5 kg/sub f//㎠ TMP condition, complete blocking was 23.4%, standard blocking was about 14.6% and cake filtration was 62.0%, respectively. Permeate flux through the membrane increases with cross flow velocity, and the effect of the variation of velocity is more significant at 1.0 kg/sub f//㎠ rather than at 2.0 kg/sub f//㎠ of the operation pressure. Permeate flux for the membrane having the average pore diameter of 0.34 ㎛ was higher than that for the membrane of 0.24 ㎛ pore size, with the higher flux with the low concentration of feed. On the operation using the membrane of 0.34 ㎛ pore, the pore blocking in the low concentration of 200 ppm is negligible relative to the pore blocking in the 1000 ppm feed.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.531-541
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• 2023

The most important thing in the 4th industry, AI era, and smart construction era is digital data. Basic data in the civil engineering field begins with ground investigation. The Ministry of Land, Infrastructure and Transport operates the Geotechnical Information Database Center to manage ground survey data, including drilling but the focus is on data distribution. This study seeks to devise a plan for long-term use of the results of drilling investigation conducted for the design and construction of various construction projects. For this purpose, a pilot area was set up and a 'geotechnical design parameters digital map' was created using some geotechnical design parameters from the drilling investigation data. Using the developed algorithm, a digital map of friction angle and permeability coefficient for the hard rock stratum in the pilot area was created. Geotechnical design parameters digital map can identify the overall condition of the ground, but reliability needs to be improved due to the lack of initial data input. Through additional research, it will be possible to produce a more complete geotechnical design parameters digital map.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.399-415
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• 1999

From bacteria to mammalian cells, one of the most important mediators of intracellular signal transduction mechanisms which regulate a variety of intracellular processes is free calcium. In salivary acinar cells, elevation of intracellular calcium concentration ($[Ca^{2+}]_i$) is essential for the salivary secretion induced by parasympathetic stimulation. However, in addition to $[Ca^{2+}]_i$, gap junctions which couple individual cells electrically and chemically have also been reported to regulate enzyme secretion in pancreatic acinar cells. Since the plasma membrane of salivary acinar cells has a high density of gap junctions, and these cells are electrically and chemically coupled with each other, gap junctions may modulate the secretory function of salivary glands. In this respect, I planned to investigate the role of gap junctions in the modulation of salivary secretion and $[Ca^{2+}]_i$, using mandibular salivary glands of rats. In order to measure the salivary flow rate, fluid was collected from the cannulated duct of the isolated perfused rat mandibular glands at 2 min intervals. $[Ca^{2+}]_i$, was measured from the cells loaded with fura-2 by spectrofluorometry. The results obtained were as follows: 1. CCh-induced salivary secretion was reversibly inhibited by 1 mM octanol, a gap junction blocker. 2. CCh-induced increase in $[Ca^{2+}]_i$, was also reversed by the application of 1 mM octanol. 3. Octanol did not block the initial increase in $[Ca^{2+}]_i$ caused by CCh, which suggested that the reduction of $[Ca^{2+}]_i$, caused by gap junction blockade was not resulted from the inhibition of $Ca^{2+}$ release from intracellular $Ca^{2+}$ stores. 4. Addition of octanol during stimulation with $1{\mu}M$ thapsigargin, a potent microsomal ATPase inhibitor, reduced $[Ca^{2+}]_i$, to the basal level. This suggested that inhibition of gap junction permeability closed plasma membrane $Ca^{2+}$ channels. 5. 2,5-di-tert-butyl-1,4-benzohydroquinone (TBQ) generated $[Ca^{2+}]_i$ oscillations resulting from periodic influx of $Ca^{2+}$ via plasma membrane. The TBQ-induced $[Ca^{2+}]_i$ oscillations were stopped by the application of 1mM octanol which implicated that gap junctions modulate the permeability of plasma membrane $Ca^{2+}$ channels. 6. Glycyrrhetinic acid, another well known gap junction blocker, also inhibited CCh-induced salivary secretion from rat mandibular glands. These results suggested that gap junctions play an important role in the modulation of fluid secretion from the rat mandibular glands and this was probably due to the inhibition of $Ca^{2+}$ influx through the plasma membrane $Ca^{2+}$ channels.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.596-601
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• 2010

Serious problems in reclaimed land for agriculture are high soil salinity and very poor vertical drainage. However, desalinization in these soils is very difficult. To identify the change of soil permeability by the gypsum incorporation in soils we observed elution patterns and salt distribution of the soil using soil columns packed with reclaimed saline soil with various rates of gypsum amendment. Saturated hydraulic conductivity ($K_{sat}$) of the top soil of reclaimed saline soils without gypsum incorporation was close 0 cm $hr^{-1}$ while $K_{sat}$ increased up to 0.3 cm $hr^{-1}$ with increasing amount of gypsum for 0.4% or more gypsum. Also $K_{sat}$ of the reclaimed saline soils for top soil was drastically increased to 1.0 cm $hr^{-1}$ or slightly greater after 141 hour's elution experiment. The cumulative amount of cation recovered in the effluent also increased in the order of gypsum incorporation rate 0.8% > 0.6% > 0.4 > 0.2%. Soil EC in soil columns decreased from initial 33.9 dS $m^{-1}$ to less than 0.4 dS $m^{-1}$ and exchangeable Ca 2+ increased by 32~140% according to gypsum incorporation rate.

• Korean Journal of Food Science and Technology
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• v.32 no.4
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• pp.834-842
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• 2000

In order to investigate the characteristics of various sweet potato starches, gelatinization temperatures, solution viscosity of starch separated from two cultivars of the dry type sweet potatoes(Yulmi and Gunmi), one cultivar of moist type sweet potato(Jinmi), and one cultivar of purple colored variety(Jami) were compared, and properties of the edible films prepared with the starches were determined. Under a differential scanning colorimetry(DSC), initial temperatures for starch gelatinization of the dry type sweet potatoes (Yulmi and Gunmi) were higher than that of the moist type sweet potato (Jinmi), and that of Jami was close to those of the dry type ones. The sweet potato starch solutions tested by a cone and plate viscometer, showed peudoplastic characteristics. The moist type sweet potato was the most viscous followed by Jami, Yulmi, and Gunmi among the tested starch solutions. Total color difference of the edible films prepared with different cultivars of sweet potatoes showed appreciable differences between cultivars, caused by differences in Hunterb values. Water Vapor Permeability (WVP) of sweet potato starch films also showed significant differences between cultivars. Films prepared with the dry type sweet potato, Gunmi, showed the lowest WVP value of $0.83{\times}10^{-9}\;g\;{\cdot}\;m/m^{2}\;{\cdot}\;s\;{\cdot}\;Pa$, followed by Jami, Yulmi, and Jinmi. Water solubility of the films did not show any significant differences between cultivars. Tensile strength of the dry type sweet potato and Jami, which ranged 14.18-18.75 MPa, were higher than that of the moist type sweet potato, which was 4.66 MPa. Elongation values of the films, which were 5-6%, indicated that sweet potato starch films were not so elastic.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.515-522
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• 2007

In this study we have attempted to evaluate the technical feasibility of "BB-HY", which is depleted gas reservoir as a gas storage field, using the commercial compositional simulator "ECLIPSE 300". The "BB-HY" reservoir has an initial gas in place of 143 BCF which is relatively small, and its porosity and permeability are 19.5% and 50 md, respectively. For "BB-HY" gas reservoir, we have performed a feasibility analysis by investigating the cushion gas (or working gas), converting time to gas storage field, operation cycle, number of wells and the possible application of horizontal borehole as well. From the simulation results, it was found that the amount of cushion gas in "BB-HY" reservoir is required at least 50% of IGIP in order to operate stably as gas storage field. When one produces gas for longer time and hence the remaining gas in reservoir is less than optimal cushion gas, no technical problem was occurred as long as additional cushion gas is injected up to the optimal cushion gas. In the case of changing the operation cycle into producing gas for three months during winter season from producing five months, the result shows that either the cushion gas should be greater than 60% or the more number of wells should be drilled. Meanwhile, from the results of sensitivity analysis for the number of wells, in cases of operating six or eight vertical wells, the stable reproduction of the injected gas can not be possible in "BB-HY" gas reservoir since the remaining gas in reservoir is increased. Therefore, in "BB-HY" reservoir, at least ten vertical wells should be drilled for the stable operation of gas. This time, when three horizontal wells are additionally drilled including the existing two vertical wells, it was found that the operation of injection and reproduction of gas is relatively stable in "BB-HY" gas reservoir.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.1
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• pp.52-72
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• 1984

This study was performed to obtain the basic data which can be applied to the use of epoxy resin mortars. The data was based on the properties of epoxy resin mortars depending upon various mixing ratios to compare those of cement mortar. The resin which was used at this experiment was Epi-Bis type epoxy resin which is extensively being used as concrete structures. In the case of epoxy resin mortar, mixing ratios of resin to fine aggregate were 1: 2, 1: 4, 1: 6, 1: 8, 1:10, 1 :12 and 1:14, but the ratio of cement to fine aggregate in cement mortar was 1 : 2.5. The results obtained are summarized as follows; 1.When the mixing ratio was 1: 6, the highest density was 2.01 g/cm$^3$, being lower than 2.13 g/cm$^3$ of that of cement mortar. 2.According to the water absorption and water permeability test, the watertightness was shown very high at the mixing ratios of 1: 2, 1: 4 and 1: 6. But then the mixing ratio was less than 1 : 6, the watertightness considerably decreased. By this result, it was regarded that optimum mixing ratio of epoxy resin mortar for watertight structures should be richer mixing ratio than 1: 6. 3.The hardening shrinkage was large as the mixing ratio became leaner, but the values were remarkably small as compared with cement mortar. And the influence of dryness and moisture was exerted little at richer mixing ratio than 1: 6, but its effect was obvious at the lean mixing ratio, 1: 8, 1:10,1:12 and 1:14. It was confirmed that the optimum mixing ratio for concrete structures which would be influenced by the repeated dryness and moisture should be rich mixing ratio higher than 1: 6. 4.The compressive, bending and splitting tensile strenghs were observed very high, even the value at the mixing ratio of 1:14 was higher than that of cement mortar. It showed that epoxy resin mortar especially was to have high strength in bending and splitting tensile strength. Also, the initial strength within 24 hours gave rise to high value. Thus it was clear that epoxy resin was rapid hardening material. The multiple regression equations of strength were computed depending on a function of mixing ratios and curing times. 5.The elastic moduli derived from the compressive stress-strain curve were slightly smaller than the value of cement mortar, and the toughness of epoxy resin mortar was larger than that of cement mortar. 6.The impact resistance was strong compared with cement mortar at all mixing ratios. Especially, bending impact strength by the square pillar specimens was higher than the impact resistance of flat specimens or cylinderic specimens. 7.The Brinell hardness was relatively larger than that of cement mortar, but it gradually decreased with the decline of mixing ratio, and Brinell hardness at mixing ratio of 1 :14 was much the same as cement mortar. 8.The abrasion rate of epoxy resin mortar at all mixing ratio, when Losangeles abation testing machine revolved 500 times, was very low. Even mixing ratio of 1 :14 was no more than 31.41%, which was less than critical abrasion rate 40% of coarse aggregate for cement concrete. Consequently, the abrasion rate of epoxy resin mortar was superior to cement mortar, and the relation between abrasion rate and Brinell hardness was highly significant as exponential curve. 9.The highest bond strength of epoxy resin mortar was 12.9 kg/cm$^2$ at the mixing ratio of 1:2. The failure of bonded flat steel specimens occurred on the part of epoxy resin mortar at the mixing ratio of 1: 2 and 1: 4, and that of bonded cement concrete specimens was fond on the part of combained concrete at the mixing ratio of 1 : 2 ,1: 4 and 1: 6. It was confirmed that the optimum mixing ratio for bonding of steel plate, and of cement concrete should be rich mixing ratio above 1 : 4 and 1 : 6 respectively. 10.The variations of color tone by heating began to take place at about 60˚C, and the ultimate change occurred at 120˚C. The compressive, bending and splitting tensile strengths increased with rising temperature up to 80˚ C, but these rapidly decreased when temperature was above 800 C. Accordingly, it was evident that the resistance temperature of epoxy resin mortar was about 80˚C which was generally considered lower than that of the other concrete materials. But it is likely that there is no problem in epoxy resin mortar when used for unnecessary materials of high temperature resistance. The multiple regression equations of strength were computed depending on a function of mixing ratios and heating temperatures. 11.The susceptibility to chemical attack of cement mortar was easily affected by inorganic and organic acid. and that of epoxy resin mortar with mixing ratio of 1: 4 was of great resistance. On the other hand, when mixing ratio was lower than 1 : 8 epoxy resin mortar had very poor resistance, especially being poor resistant to organicacid. Therefore, for the structures requiring chemical resistance optimum mixing of epoxy resin mortar should be rich mixing ratio higher than 1: 4.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.269-274
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• 1995

The basic composition of Mn-Zn ferrite was $Mn_{0.631}Zn_{0.316}Fe_{2.053}O_{4}$(specimen A), $Mn_{0.584}Zn_{0.312}Fe_{2.104}O_{4}$(specimen B) and $Mn_{0.538}Zn_{0.308}Fe_{2.154}O_{4}$(specimen C) with additional 0.1 mol % $CaCo_{3}$ and 0.04 mol % $V_{2}O_{5}$. For high per¬meability and acceleration of grain growth, $CaCo_{3}$ and $V_{2}O_{5}$. was added. The mixture of the law materials was calcinated at $950^{\circ}C$ for 3 hours and then milled. The compacts of toroidal type were sintered at different temperature($1250^{\circ}C$, $1300^{\circ}C$, $1350^{\circ}C$) for 2 hours in $N_2$ atmosphere. The effects of the various raw material composition and sintered temperature on the physical properties of Mn-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from SEM was from $18\;\mu\textrm{m}\;to\;23\;\mu\textrm{m}$. As the sintering temperature was increased from $1250^{\circ}C$ to $1350^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen Their values were about 0.45 Oe and $200^{\circ}C$. The frequency of specimen will used in the range from 200 kHz to 2 MHz. The basic composition of $Mn_{0.584}Zn_{0.312}Fe_{2.104}O_{4}$(specimen B) sintered at $1300^{\circ}C$ shows the best results at magnetic induction (Br & Bm).

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.119-129
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• 2009

Building construction trends have been changed dramatically in terms of size and mass. With the need to maximize land usage, there has been an increase in the construction of high-rise buildings. This affects not only the entire construction duration and cost, but also subsequent construction activities, such as work to increase underground facilities and in reclamation land area construction. These types of site conditions require soft ground reinforcement and the proper uplift water pressure treatment. In general, two kinds of methods have been used for uplift water pressure treatment systems. However, there have been some problems arising as the result of a lack of research and analysis on underground construction techniques, and a reliance on experiments over actual survey and analysis of site conditions. This paper focused on the problems of conventional selection procedure, by analyzing drawings and proposing a kind of modeling for a reasonable procedure. The results were applied to OO project as a sample construction case to be verified in this research. The initial plan in the case project was the Rock Anchor System. However, as there were terrible miscalculations of basic site conditions that had an extraordinary influence on the underground water level, such as the site's proximity to the Han-river, it was necessary to change the plan to include apermanent drainage system. This achieved a direct construction cost reduction \ 406,702,000 and a maximum sayings of 4% of operational cost, based on the 50-year building Life Cycle Cost.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.85-103
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• 2023

The in-situ remediation of a solidified stratum containing a large amount of fine-texture material like clay or organic matter in contaminated soil faces limitations such as increased remediation cost resulting from decreased purification efficiency. Even if the soil conditions are good, remediation generally requires a long time to complete because of non-uniform soil properties and low permeability. This study assessed the remediation effect and evaluated the field applicability of a methodology that combines pneumatic fracturing, vacuum extraction, and plasma blasting (the PPV method) to improve the limitations facing existing underground remediation methods. For comparison, underground remediation was performed over 80 days using the experimental PPV method and chemical oxidation (the control method). The control group showed no decrease in the degree of contamination due to the poor delivery of the soil remediation agent, whereas the PPV method clearly reduced the degree of contamination during the remediation period. Remediation effect, as assessed by the reduction of the highest TPH (Total Petroleum Hydrocarbons) concentration by distance from the injection well, was uncleared in the control group, whereas the PPV method showed a remediation effect of 62.6% within a 1 m radius of the injection well radius, 90.1% within 1.1~2.0 m, and 92.1% within 2.1~3.0 m. When evaluating the remediation efficiency by considering the average rate of TPH concentration reduction by distance from the injection well, the control group was not clear; in contrast, the PPV method showed 53.6% remediation effect within 1 m of the injection well, 82.4% within 1.1~2.0 m, and 68.7% within 2.1~3.0 m. Both ways of considering purification efficiency (based on changes in TPH maximum and average contamination concentration) found the PPV method to increase the remediation effect by 149.0~184.8% compared with the control group; its average increase in remediation effect was ~167%. The time taken to reduce contamination by 80% of the initial concentration was evaluated by deriving a correlation equation through analysis of the TPH concentration: the PPV method could reduce the purification time by 184.4% compared with chemical oxidation. However, the present evaluation of a single site cannot be equally applied to all strata, so additional research is necessary to explore more clearly the proposed method's effect.