• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.37-47
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• 2014

Unsaturated hydraulic conductivity (HC) is integrated theoretically from soil water retention curves (SWRC) by Mualem capillary model, but the prediction of HC is extremely sensitive to small variation of matric suction near saturation. Near saturation, the Mualem HC based on smooth SWRC decreases abruptly and has problems in the reliability of hydraulic behavior and the stability of numerical solutions. To improve van Genuchten-Mualem (VGM) HC, the van Genuchten SWRC model is modified within range of low matric suction (arbitrary air entry pressure). At an arbitrary air entry pressure, the VG SWRC is linearized in log scale until full saturation. The modified VG SWRC does not affect the fit of actual retention behavior and either the parameters of original VG SWRC fit. Using the modified VG SWRC, the VGM HC is modified to integrate for each interval decomposed by arbitrary air entry pressure. An analytical solution on modified VGM HC is proposed each interval, to protect the rapid change in HC near saturation. For silty soils, VGM models of HC function underestimate the unsaturated permeability characteristics and especially show rapid reduction near saturation. The modified VGM model predicts more accurate HC functions for Korean weathered soils. Furthermore, near saturation, the saturated HC is conserved by the modified VGM model. After 2-D infiltration analysis of an actual slope, the hydraulic behaviors are compared for VGM and the modified models. The prediction by the proposed model conserved the convergence of solutions on various rainfall conditions. However, the solution by VGM model did not converge since the conductivity near saturation reduced abruptly for heavy rainfall condition. Using VGM model, the factor of safety is overestimated in both initial and final stage during heavy rainfall. Stability analysis based on infiltration analysis could simulate the actual slope failure by the proposed model on HC.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.683-690
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• 2015

For demolition of offshore facilities, traditional methods such as jackhammer and explosive methods have been often used in construction industry. However, prohibitions for use of those methods are becoming more rigorous especially in environmentally and historically sensitive areas. It was also reported that the explosive demolition method on maritime bedrock can cause a disturbance of ecosystem. For those reasons, use of soundless chemical demolition agent(SCDA) is getting the spotlight. However, researches regarding the mechanical point of SCDA have seldom performed. There is no industrial standard for use of SCDA yet. In this study, a pilot experimental study in order to measure the required expansive pressure that could be generated from SCDA was conducted. Numerical models were developed in order to estimate the required expansive pressures of SCDA for initiating cracks depending on selected key parameters. Obtained results indicate that the required pressure does not decrease linearly as increasing the hole diameter, the number of holes, and the ratio of hole-distance to hole-diameter.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.19-31
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• 1994

The objective of this study is to conduct a thermal-hydraulic analysis on the spent fuel pool and to evaluate a parametric effect for the thermal-hydraulic analysis of spent fuel pool. The selected parameters are the Reynolds Number and the gap flow through the oater gap between fuel cell and fuel bundle. The simplified flow network for a path of fuel cells is used to analyze the natural circulation phenomenon. In the flow network analysis, the pressure drop for each assembly from the entrance of the fuel rack to the exit of the fuel assembly is balanced by the driving head due to the density difference between the pool fluid and the average fluid in each spent fuel assembly. The governing equations ore developed using this relation. But, since the parameters(flow rate, pressure loss coefficient, decay heat, density)are coupled each other, iteration method is used to obtain the solution. For the analysis of the YGN 3&4 spent fuel rack, 12 channels are considered and the inputs such as decay heat and pressure loss coefficient are determined conservatively. The results show the thermal-hydraulic characteristics(void fraction, density, boiling height)of the YGN 3&4 spent fuel rack. There occurs small amount of boiling in the cells. Fuel cladding temperature is lower than 343.3$^{\circ}C$. The evaluation of parametric effect indicates that flow resistances by geometric effect are very sensitive to Reynolds number in the transition region and the gap flow is negligible because of the larger flow resistance in the gap flow path than in the fuel bundle.

• Journal of Trauma and Injury
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• v.30 no.4
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• pp.140-144
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• 2017

Purpose: The optic nerve sheath diameter (ONSD) measured by ultrasonography is among the indicators of intracranial pressure (ICP) elevation. However, whether ONSD measurement is useful for initial treatment remains controversial. Thus, this study aimed to investigate the relationship between ONSD measured by computed tomography (CT) and ICP in patients with traumatic brain injury (TBI). Methods: A total of 246 patients with severe trauma from January 1, 2015 until December 31, 2015 were included in the study. A total of 179 patients with brain damage with potential for ICP elevation were included in the TBI group. The remaining 67 patients comprised the non-TBI group. A comparison was made between the two groups. Receiver operating characteristic (ROC) curve analysis was performed to determine the accuracy of ONSD when used as a screening test for the TBI group including those with TBI with midline shift (with elevated ICP). Results: The mean injury severity score (ISS) and glasgow coma scale (GCS) of all patients were $24.2{\pm}6.1$ and $5.4{\pm}0.8$, respectively. The mean ONSD of the TBI group ($5.5{\pm}1.0mm$) was higher than that of the non-TBI group ($4.7{\pm}0.6mm$). Some significant differences in age ($55.3{\pm}18.1$ vs. $49.0{\pm}14.8$, p<0.001), GCS ($11.7{\pm}4.1$ versus $13.3{\pm}3.0$, p<0.001), and ONSD ($5.5{\pm}1.0$ vs. $4.7{\pm}0.6$, p<0.001) were observed between the TBI and the non-TBI group. An ROC analysis was used to assess the correlation between TBI and ONSD. Results showed an area under the ROC curve (AUC) value of 0.752. The same analysis was used in the TBI with midline shift group, which showed an AUC of 0.912. Conclusions: An ONSD of >5.5 mm, measured on CT, is a good indicator of ICP elevation. However, since an ONSD is not sensitive enough to detect an increased ICP, it should only be used as one of the parameters in detecting ICP along with other screening tests.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.150.1-150.1
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• 2014

Showerhead is used as a main part in the semiconductor equipment. The face plate flatness should remain constant and the cleaning performance must be gained to keep the uniformity level of etching or deposition in chemical vapor deposition process. High operating temperature or long period of thermal loading could lead the showerhead to be deformed thermally. In some case, the thermal deformation appears very sensitive to showerhead performance. This paper describes the methods for robust design using computational fluid dynamics. To reveal the influence of the post distribution on flow pattern in the showerhead cavity, numerical simulation was performed for several post distributions. The flow structure appears similar to an impinging flow near a centered baffle in showerhead cavity. We took the structure as an index to estimate diffusion path. A robust design to reduce the thermal deformation of showerhead can be achieved using post number increase without ill effect on flow. To prevent the showerhead deformation by heat loading, its face plate thickness was determined additionally using numerical simulation. The face plate has thousands of impinging holes. The design key is to keep pressure drop distribution on the showerhead face plate with the holes. This study reads the methodology to apply to a showerhead hole design. A Hagen-Poiseuille equation gives the pressure drop in a fluid flowing through such hole. The assumptions of the equation are the fluid is viscous-incompressible and the flow is laminar fully developed in a through hole. An equation can be expressed with radius R and length L related to the volume flow rate Q from the Hagen-Poiseuille equation, $Q={\pi}R4{\Delta}p/8{\mu}L$, where ${\mu}$ is the viscosity and ${\Delta}p$ is the pressure drop. In present case, each hole has steps at both the inlet and the outlet, and the fluid appears compressible. So we simplify the equation as $Q=C(R,L){\Delta}p$. A series of performance curves for a through hole with geometric parameters were obtained using two-dimensional numerical simulation. We obtained a relation between the hole diameter and hole length from the test cases to determine hole diameter at fixed hole length. A numerical simulation has been performed as a tool for enhancing showerhead robust design from flow structure. Geometric parameters for the design were post distribution and face plate thickness. The reinforced showerhead has been installed and its effective deposition profile is being shown in factory.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.90-103
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• 2018

This paper presents the development of two ANN models which can predict an optimum production rate by controlling choke size in oil well, and gas injection rate in gas-lift well. The input data was solution gas-oil ratio, water cut, reservoir pressure, and choke size or gas injection rate. The output data was wellhead pressure and production rate. Firstly, a range of each parameters was decided by conducting sensitive analysis of input data for onshore oil well. In addition, 1,715 sets training data for choke size decision model and 1,225 sets for gas injection rate decision model were generated by nodal analysis. From the results of comparing between the nodal analysis and the ANN on the same reservoir system showed that the correlation factors were very high(>0.99). Mean absolute error of wellhead pressure and oil production rate was 0.55%, 1.05% with the choke size model, respectively. And the gas injection rate model showed the errors of 1.23%, 2.67%. It was found that the developed models had been highly accurate.

• Composites Research
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• v.35 no.3
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• pp.147-152
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• 2022

Low-temperature characteristics according to internal temperature conditions during rotational molding of Type 4 pressure vessel liners were studied in this paper. Since rotational molding has a sensitive effect on the formability of the liner depending on the temperature conditions, the temperature conditions for the polyamide used should be accurately set. The structural changes of polyamide as the liner material was analyzed the surface by atomic force microscope (AFM), and the crystallinity measured with a differential scanning calorimeter (DSC) is used to evaluate the change of the mechanical strength value at low temperature. In addition, the formability of the liner was confirmed by observation of the yellow index inside the liner. As a result, as the melting range of the internal temperature becomes wider, the yellow index shows a lower value, and the elongation and impact characteristics at low temperatures are improved. It was also confirmed that the structure of the polyamide was uniform and the crystallinity was high by AFM and DSC. These experimental results contribute to the improvement of characteristics at low temperatures due to changes in temperature conditions during rotational molding.

• The korean journal of orthodontics
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• v.30 no.2 s.79
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• pp.197-204
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• 2000

[$K^+$]-selective ion channels were studied in excised inside-out membrane patches from human osteoblast-like cells (G292). Three classes of $K^+$channels were present and could be distinguished on the basis of conductance. Conductances were $270\pm27\;pS,\;113\pm12\;pS,\;48\pm8\;pS$ according to their approximate conductances in symmetrical 140 mM KCl saline at holding potential of -80 mV It was found that the small conductance (48 pS) $K^+$channel activation was dependent on membrane voltage. In current-voltage relationship, small conductance $K^+$channel showed outward rectification, and it was activated by the positive potential inside the membrane. In recordings, single channel currents were activayed by a negative pressure outside the membrane. The membrane pressure increased $P_{open}$ of the $K^+$ channel in a pressure-dependent manner. In the excised-patch clamp recordings, G292 osteoblast-like cells have been shown to contain three types of $K^+$ channels. Only the small conductance (48 pS) $K^+$channel is sensitive to the membrane stretch. These findings suggest that a hyperpolarizing current, mediated in part by this channel, may be associated with early events during the mechanical loading of the osteoblast. In G292 osteoblast-like cells, $K^+$channel is sensitive to membrane tension, and may represent a unique adaptation of the bone cell membrane to mechanical stress.

• Journal of Nutrition and Health
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• v.50 no.1
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• pp.32-40
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• 2017

Purpose: Obesogenic environments in children, in particular excessive intake of sodium, generate hypertension, which is a major risk factor for chronic diseases. Methods: In all, 725 children, 379 boys and 373 girls, aged 8~9 years were recruited from seven elementary schools in Kuro-ku, Seoul. To evaluate whether or not obesity risk was modulated by salt-sensitive genes, Solute Carrier Familiy 12 member 3 (SLC12A3) was used as the target. After children were assigned into obese (BMI > 85 percentile) or non-obese groups, anthropometry, blood biochemistry, and dietary intakes were measured according to the genotypes GG (wild) or GA+AA (hetero+mutant). Results: Without gender differences, high TG and low HDLc were detected in the obese group compared to the non-obese group. Regardless of obesity, weight gain and blood pressure (BP) increased in the SLC12A3 GA+AA genotype rather than in the GG type. HDLc was associated with obesity risk without genotype difference. Odd ratios for risk of obesity were 15.57 (95% CI 2.192~110.654), 22.84 (95% CI 1.565~333.469), and 9.32 (95%CI 1.262~68.817) in boys and girls with GA+AA genotypes as sodium intake increased above 4,000 mg/day. Dietary calcium, sodium, folate, and vit C were associated with obesity risk according to gender or genotype differences. Since high folate intake reduced obesity risk in only boys with GG type. Risk for overweight and obesity increased in boys with GA+AA genotypes and dietary habits with high sodium and cholesterol and low folate. Conclusion: The A allele of SLC12A3 rs11643718 was sensitive to development of obesity in children as sodium intake increased.

• Journal of Yeungnam Medical Science
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• v.15 no.1
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• pp.97-113
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• 1998

The sympathoadrenal system plays an important role in homeostasis in widely varing external environments. Conflicting findings, however, have been reported on its response to hypoxia. We investigated the effect of hypoxia on the sympathoadrenal system in dogs under halothane anesthesia by measuring levels of circulating catecholamines in response to graded hypoxia. Ten healthy mongreal dogs were mechanically ventilated with different hypoxic gas mixtures. Graded hypoxia and reoxygenation were induced by progressively decreasing the oxygen fraction in the inhalation gas mixture from 21%(control) to 15%, 10% and 5% at every 5 minutes, and then reoxygenated with 60% oxygen. Mean arterial pressure, central venous pressure and mean pulmonary arterial pressure were measured directly using pressure transducers. Cardiac output was measured by the thermodilutional method. For analysis of blood gas, saturation and content, arterial and mixed venous blood were sampled via the femoral and pulmonary artery at the end of each hypoxic condition. The concentration of plasma catecholamines was determined by radioenzymatic assay. According to the exposure of graded hypoxia, not only did arterial and mixed venous oxygen tension decreased markedly at 10% and 5% oxygen, but also arterial and mixed venous oxygen saturation decreased significantly. An increased trend of the oxygen extraction ratio was seen during graded hypoxia. Cardiac output, mean arterial pressure and systemic vascular resistance were unchanged or increased slightly. Pulmonary arterial pressure(PAP) and pulmonary vascular resistance(PVR) were increased by 55%, 76% in 10% oxygen and by 82%, 95% in 5% oxygen, respectively(p<0.01). The concentrations of plasma norepinephrine, epinephrine and dopamine increased by 75%, 29%, 24% in 15% oxygen and by 382%, 350%, 49% in 5% oxygen. These data suggest that the sympathetic nervous system was activated to maintain homeostasis by modifying blood flow distribution to improve oxygen delivery to tissues by hypoxia, but hemodynamic changes might be blunted by high concentration of nitrous oxide except PAP and PVR. It would be suggested that hemodynamic changes might not be sensitive index during hypoxia induced by high concentration of nitrous oxide exposure.