• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.2
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• pp.209-222
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• 1997

Authors surveyed the ground water near the waste disposed from a fiberglass production factory to confirm the presence of glassfiber in the water and to determine the effect of sampling conditions and storage on the recovery of fibrous materials in the ground water. Sample was collected at every 4 hours for 48 hours consecutively. After finishing the 48 hours sample, water sampling was done from each tap after repeated turning on and off the water for 30 seconds at each time. Sample was collected in the two 1.5 liter polyethylene bottle after vigorously shaking the bottle with the same water several times with the flowing tap water. At each paired sample, one bottle was stored stand still at room temperature, and the other sample was filtered immediately after sampling. Water was filtered on the Mixed Cellulose Ester filter with negative pressure. Each sample was divided into upper and lower layer. The other bottle was stored at room temperature standstill for 7 days and filtered in the same fashion as the other pair of sample did. Each MCE filter was divided into 4 pieces and one piece was treated with acetone to make it transparent. Each prepared sample was observed by two researchers under the light and polarizing microscopy, scanning electron microscopy and energy dispersive X-ra microanalysis. Fibers were classified by the morphology and polarizing pattern under the polarizing microscope, and count was done. 1. There was a significant fluctuation in number of the fibers, but there was no specific demonstrable pattern. 2. Non-polarizing fibers frequently disappeared after 7 days's storage. But cluster of fibers were found at the wall of the same container by scratching technique. 3. Polarizing fibers were usually found in between the filter and the manicure pasted area. Possible explanations for this phenomenon will be that either these fibers are very light or have electronic polarity. Hence, these fibers are not able to be attached on the surface of slide glass. 4. Under the scanning electron microscopic examination, the fibers which are not refractive under the light microscopy were identified as glassfiber. Other fibers which is refractive under the polarizing microscopy were identified as magnesium silicate fibers. It is strongly suggested that development of standardized method of sample collection and measurement of fibrous material in the water is needed.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.615-621
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• 2014

This study suggests the design and assembly drawing of the prefabricated precast concrete arch ammo magazines using the numerical analysis as well as the explosion verification test. The protective capacity of the proposed magazines is identified with the maximum support rotation angles measured by explosion verification tests according to the U.S. Unified Facility Criteria 3-340-02. Using numerical analysis, it is examined that oval-type members are better than the semi-circle ones in terms of protective capacity. Based on this numerical results, the design and assemble drawing for the prefabricated precast concrete arch ammo magazine are developed. It is identified that the structure constructed by invented design and assembly drawing has enough protective capacity against blast pressure caused by 133.75kg TNT explosion. The detonation point cannot be open due to the military security. In sum, it could be concluded that the ammo magazine proposed in this study has reliable protective capacity with enough redundancy. The redundancy means that there are more economic design approach with reducing the curved wall thickness.

• Composites Research
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• v.23 no.2
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• pp.1-9
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• 2010

This study analyzes the apparent fracture toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate apparent fracture toughness. The approach is demonstrated for a cylinder with a TiC/$Al_{2}O_{3}$ FGM coating and some numerical results of apparent fracture toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the apparent fracture toughness are investigated in details. It is found that all of these factors play an important role in controlling the apparent fracture toughness of the cylinder.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.47-67
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• 1996

The purpose of this study was to observe the effect of $Biocoral^R$ graft and bioglass 45S5 graft in combination with ePTFE membrane in periodontal osseous defects for new bone formation. Nine healthy dogs were used. Under general anesthesia, 3-wall defects were created on the mesial and distal surfaces of the maxillary right canines, the mesials of the maxillary right second premolars, the distals of the mandibular right canines and the mesials of the mandibular right third premolars. To induce periodontitis, a silicone rubber, $Provil^R$ light body, was injected under pressure into the defects. Ninety days later, $Provil^R$was removed and followed by thorough root planing. The followings were then applied in the mesial and distal defects of the maxillary right canines, the mesials of the maxillary right second premolars, the distals of the mandibular right canines and the mesials of the mandibular right third premolars by random selections : 1) ePTFE membrane only application, 2) $Biocoral^R$ graft, 3) $Biocoral^R$ graft and ePTFE membrane application, 4)Bioglass 45S5 graft, 5) Bioglass 45S5 graft and ePTFE membrane application. The membranes were removed 1 month later. The dogs were sacrified at 1, 2 and 3 months following the graft, and block sections were made, demineralized, embedded, stained and examined by light microscope and transmission electron microscope. On the sections from teeth treated with ePTFE membrane only, the defect demonstrated extensive connnective tissue and alveolar bone regeneration. The $Biocoral^R$ graft group demonstrated extensive bone regeneration compared with ePTFE membrane only group. In the $Biocoral^R$ graft plus ePTFE membrane group, regeneration of new alveolus and crest occurred within the defect. As the experimental period lengthened, bone regeneration was increased and bone bridge was formed among the graft particles. The but bioglass 45S5 graft group demonstrated extensive bone regeneration but the amount of new bone was less than that of the $Biocoral^R$ graft group. For the bioglass 45S5 graft plus ePTFE membrane group, the amount of new bone was also increased. As the experimental period lengthened, bone regeneration was increased. Multinucleated giant cells, fibroblasts and macrophages were observed. As the bone formation was increased, the number of such cells was decreased. In conclusion, the $Biocoral^R$ was found better than the bioglass 45S5 for new bone formation, and the use of ePTFE membrane alone or with $Biocoral^R$/bioglass 45S5 can be supported as potential methods of promoting bone formation.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.87-92
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• 2014

The Ground anchor is reinforcement to resist pull-out through ground that is used supports structure. The pull-out resistance of anchor is constructed by skin friction resistance from compression borehole wall in expanded wings and bearing pressure from the ground. Especially, underreamed ground anchor is reinforcement that adopts active reinforcement to prevent deformation of ground using bearing resistance generated reaming anchorage. This study is conducted to calculate bearing resistance of underreamed ground anchor. Realistic model tests were fulfilled to determine bearing resistance of anchor, and correlate results of tests to Uniaxial Compressive Strengths (UCS) of ground models that assumed weathered rock condition in 8 case. In a comprehensive series of the tests, the bearing resistances were measured by pull-out tests. The bearing resistances derived from tests have a linear correlation with UCS. We also suggest empirical equation between bearing resistance and UCS of rocks by single linear regression analyses. In test results of this study, the bearing resistances were evaluated approximately 13 times higher than UCS of the grounds, and it is qualitatively similar to numerical values of pull-out force derived from theory.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.443-447
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• 2016

The microalgae have cellulose as a main structural component of their cell wall and the lignin content in microalgae is much lower than other lignocellulosic biomass. Therefore, fermentable sugar production from microalgae (Tetraselmis KCTC 12236BP) can be carried out under pretreatment without high temperature and high pressure. It was investigated that the effect of hot-water pretreatment using sulfuric acid for lipid extracted algae which is expected to be a next generation biomass. The effects of three major variables including extraction temperature, acid concentration and time on the enzymatic hydrolysis were investigated. Among the tested variables, temperature and acid concentration showed significant effects and optimum pretreatment conditions for the economic operation criteria were obtained as follows: reaction temperature of $120^{\circ}C$, sulfuric acid concentration of 2 mol and pretreatment time of 40 min. Under the optimum conditions of acidic hot water pretreatment, experimentally obtained hydrolysis yield were 95.9% which showed about 2.1 fold higher compared with enzymatic hydrolysis process. Therefore, acid pretreatment under mild condition was proven to be an effective method for fermentable sugar production from lipid extracted microalgae.

• Archives of Plastic Surgery
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• v.32 no.1
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• pp.5-11
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• 2005

Prostaglandin $E_1$($PGE_1$) is known to have various physiological action such as vasodilatation, decrease of blood pressure, angiogenesis, inhibition of platelet aggregation and so forth. $PGE_1$ has been developed in many different formulations in order to overcome its chemical instability and deactivation in the lungs when administered parenterally. Lipo-AS013 is a potent drug with higher chemical stability and greater vascular wall targeting than others. The study was done on $3{\times}10cm$ model flap of dorsal skin of Sprague-Dawley rats and the flap perfusion survival were observed and documented. The flap treated with Lipo-AS013 beforehand was given intravenously Sodium fluorescein 10 minutes later, and then Percent Dye Fluorescence Index(% DFI) was calculated. The results were compared to a control group and the group administered locally epinephrine.. In the control group, the % DFI and flap survival rate increased from $54.1{\pm}6.7$ to $65.0{\pm}2.6$(p<0.01) while in Lipo-AS013 group from $55.3{\pm}2.2$ to $67.4{\pm}1.9$(p<0.01), respectively. In the epinephrine group, the % DFI(p<0.05) and flap survival rate(p<0.001) decreased. In the both epinephrine and Lipo-AS013 group Percent DFI and flap survival rate are comparable with the control group.The result indicates that the potent Lipo-AS013 enhances the blood flow and flap survival. This highly potent Lipo-AS013 may have targeting ability and accumulate $PGE_1$ onto the vascular walls. A quantitative analysis of fluorescence on the skin surface is a reliable tool to measure the blood perfusion into an ischemic flap and its viability. Further comparative study with conventional $PGE_1$ and Lipo-$PGE_1$ is needed in order to clarify the action and efficiency of Lipo-AS013.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.51-62
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• 2015

Shear behavior obtained by direct shear tests is dependent on shear box and boundary condition. The objective of this study is to analyze problems of conventional direct shear test (type-A) and provide the reliable results by developing type-C direct shear apparatus. Experimental tests are carried out for Ulleung sand by using type-A and -C direct shear devices. The soil specimens, which are prepared at the relative density of 60%, and are applied to vertical confining stresses of 50, 100, 200, 300, and 400 kPa, are sheared at a constant shear strain rate of 0.5 mm/min. By comparing the results obtained by type-A and -C direct shear apparatus under constant normal load (CNL) condition, the performance of new one is verified. In addition, two constrained conditions including constant normal load (CNL) and constant pressure (CP) are applied to type-C one. Experimental results show that type-A direct shear apparatus has some problems such as rotating of loading plate and upper shear box, and the frictional forces between soil and inner wall of upper shear box. Thus, the shear strengths obtained by type-A device are overestimated or underestimated depending on shear box and boundary condition. On the other hand, type-C device produces clear and consistent test results regardless of constrained conditions. This study represents that type-C direct shear apparatus not only can solve the problems of type-A direct shear apparatus but provide the reliable results.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.225-231
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• 2000

The crystallographic and magnetic properties of the sample F $e_{0.8}$ $Co_{0.18}$(BN)$_{0.02}$ synthesized by microwave arc-melting with the maximum power of 3.5 kW have been studied by the methods of an X-ray diffraction and the measurement of the magnetic hysteresis using the vibrating sample magnetometer at room temperature. The samples were prepared in a form of pellet pressed under the pressure of 9,000 N/c $m^2$, rolled coldly, and treated with the different temperatures. The X-ray diffraction pattern of pelleted sample shows that the crystal structure of the sample is bcc as same as that of Fe with a good uniformity. The X-ray diffraction pattern shows that a residual stress, which exists in the sample, is eliminated by final 90$0^{\circ}C$ annealing. As rolling rate and heat treatment temperature increases, the saturation magnetization and the remanence of the samples increase whereas the coercivity of the samples shows decrease. Also the saturation magnetization and the remanence of the samples were affected by rolling rate and rolling direction than heat treatment temperature, but the coercivity of the samples was affected by rolling rate and direction as well as heat treatment temperature. This means that a domain wall motion is easy due to elimination of a residual stress and an inclusion which exists in the sample by rolling and heat treatment and a local induced-magnetization easy axis was also formed to parallel to the rolling direction due to creation of the like-atom pairs across the slip plane by rolling......

• Sleep Medicine and Psychophysiology
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• v.4 no.2
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• pp.129-139
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• 1997

The data collected to date indicate that sleep-related breathing disorders, including sleep-disordered breathing(sleep apnea) and underlying respiratory system diseases, are one of the important risk factors for cardiovascular dysfunction. Sleep-disordered breathing(sleep apnea) is now recognized as one of the leading causes of systemic hypertension, cardiac arrhythmias, coronary heart disease, pulmonary hypertension, right heart failure, and stroke. Sleep may exert a profound effect on breathing in patients with underlying respiratory system disease including bronchopumonary diseases, chest wall abnormalities, central alveolar hypoventilation syndromes or respiratory neuromuscular disorders. Chronic hypoxia and hypercapnia in these patients may accelerate the development of long term cardiovascular complications such as cardiac arrhythmias, pulmonary hypertension, and right heart failure(cor pulmonale). Several recent studies reported that sleep-related breathing disorders are associated with long-term cardiovascular morbidity and mortality. Careful assessment of respiratory and cardiovascular function in these patients is critical. Aggressive and highly effective treatment of sleep-related breathing disorders using tracheostomy, mechanical ventilation, nasal continuous positive airway pressure therapy(nCPAP), intercurrent oxygen therapy or other interventions can reduce the prevalence of cardiovascular dysfunction and the long-term mortality.