• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.66-73
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• 2018

A computational fluid dynamics simulation of pyrotechnic material combustion inside a cylindrical closed vessel was carried out using the Eulerian-Lagrangian method. The 5th order upwind WENO scheme and the improved delayed detached eddy turbulence model were implemented to capture shock waves. The flow structure was analyzed inside the cylindrical vessel with a pressure sensor installed at the side wall center. The analysis revealed that the pressure oscillated because of the shock wave vibration. Additionally, the simulation results with four different sensor tab depths implied that, inside the sensor tab, eddies were generated by the excessively large gap between the sensor diaphragm and the side wall. These eddies caused irregularity to the measured time-pressure curve, which is an undesirable characteristic.

• Acute and Critical Care
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• v.33 no.4
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• pp.222-229
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• 2018

Background: The diagnosis of pediatric acute respiratory distress syndrome (PARDS) is a pragmatic decision based on the degree of hypoxia at the time of onset. We aimed to determine whether reclassification using oxygenation metrics 24 hours after diagnosis could provide prognostic ability for outcomes in PARDS. Methods: Two hundred and eighty-eight pediatric patients admitted between January 1, 2010 and January 30, 2017, who met the inclusion criteria for PARDS were retrospectively analyzed. Reclassification based on data measured 24 hours after diagnosis was compared with the initial classification, and changes in pressure parameters and oxygenation were investigated for their prognostic value with respect to mortality. Results: PARDS severity varied widely in the first 24 hours; 52.4% of patients showed an improvement, 35.4% showed no change, and 12.2% either showed progression of PARDS or died. Multivariate analysis revealed that mortality risk significantly increased for the severe group, based on classification using metrics collected 24 hours after diagnosis (adjusted odds ratio, 26.84; 95% confidence interval [CI], 3.43 to 209.89; P=0.002). Compared to changes in pressure variables (peak inspiratory pressure and driving pressure), changes in oxygenation (arterial partial pressure of oxygen to fraction of inspired oxygen) over the first 24 hours showed statistically better discriminative power for mortality (area under the receiver operating characteristic curve, 0.701; 95% CI, 0.636 to 0.766; P<0.001). Conclusions: Implementation of reclassification based on oxygenation metrics 24 hours after diagnosis effectively stratified outcomes in PARDS. Progress within the first 24 hours was significantly associated with outcomes in PARDS, and oxygenation response was the most discernable surrogate metric for mortality.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.206-210
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• 2004

This paper proposes a new training system for equilibrium sense using unstable platform. This training system for equilibrium sense consists of an unstable platform, a computer interface circuit and software program. Postural instability changes the weighting of different types of sensory information and the state of the equilibrium maintenance system. In order to improve the equilibrium sense, we developed software program such as a block game, sine curve training (SCT) and pingpong game using Visual C++. Using this system and training programs, we performed an experiment to train the equilibrium sense of a subject. To evaluate the effects of balance training, the time maintained on the target and the moving time to the target are measured. As a result, the moving time to the target and time to maintain cursor on the target improved through repeating equilibrium sense training. It was concluded that this system was reliable in the evaluation of equilibrium sense. We expect that this system might be applied to clinical use as an effective balance training system.

• The Korean Journal of Financial Management
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• v.26 no.1
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• pp.65-94
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• 2009

The event of change in KOSPI 200 Index composition is one of the main subjects for the test of EMH. According to EMH, when a certain event is not related with firm's fundamental value, stock price should not change after the announcement of news. This hypothesis leads us to the conclusion of horizontal demand curve of stock. This logic was questioned by Shleifer(1986) and argued that downward sloping demand curve hypothesis was supported. But Harris and Gruel(1986) found a different empirical evidence that price reversal occurs in the long run, which is called price pressure hypothesis. They argued that short term price effect by large block trading (price pressure) is offset in the long run because these event is unrelated to fundamental value. Therefor, they argued that EMH can not be rejected in the long run. Until now, there are two empirical studies with Korean market data in this area. Using a data with same time period of $1996{\sim}1999$, Kweon and Park(2000) and Ahn and Park(2005) showed that stock price or beta is not significantly affected by change in index composition. This study retested this event expanding sample period from 1996 to 2006, and analyzed why this event was considered an uninformative events in the preceding studies. We analyzed a market impact by separating samples according to firm size and market condition. In case of newly enlisted firm, we found the evidence supporting price pressure hypothesis on average. However, we found the long run price effect in the sample of large firms under bearish markets. At the same time, we know that the number of samples under the category of large firms under bearish markets is relatively small, which drives the same result of supporting the hypothesis that change in index composition is a non-informative event on average. Also, the long run price effect of large size firms under bearish markets was supported by the analyses using trading volumes. On the other hand, in case of delisting from the index, we found the long run price effect but that was not supported by trading volume analyses.

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.355-363
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• 2003

Purpose: Regional contractility can be calculated using the regional volume change of left ventricle measured by gated myocardial SPECT image and curve of central artery pressure obtained from radial artery pressure data. In this study, a program to obtain the regional contractility was developed, and reproducibility of regional contractility measurement was assessed. Materials and Methods: Seven patients(male:female=5:2, $58{\pm}11.9$ years) with coronary artery diseases underwent gated Tc-99m MIBI myocardial SPECT twice without delay between two scans. Regional volume change of left ventricle was estimated using CSA (Cardiac SPECT Analyzer) software developed in this study. Regional contractility was iteratively estimated from the time-elastance curve obtained using the time-pressure curve and regional time-volume curve. Reproducibility of regional contractility measurement assessed by comparing the contractility values measured twice from the same SPECT data and by comparing those measured from the pair of SPECT data obtained from a same patient. Results: Measured regional contractility was $3.36{\pm}3.38{mm}Hg/mL$ using 15-segment model, $3.16{\pm}2.25{mm}Hg/mL$ using 7-segment model, and $3.11{\pm}2.57{mm}Hg/mL$ using 5-segment model. The harmonic average of regional contractility value was almost identical to the global contractility. Correlation coefficient of regional contractility values measured twice from the same data was greater than 0.97 for all models, and two standard deviations of contractility difference on Bland Altman plot were 1.5%, 1.0%, and 0.9% for 15-, 7-, and 5-segment models, respectively. Correlation coefficient of regional contractility values measured from the pair of SPECT data obtained from a same patient was greater than 0.95 for all models, and two standard deviations on Bland Altman plot were 2.2%, 1.0%, and 1.2%. Conclusion: Regional contractility of left ventricle measured using developed software in this study was reproducible. Regional contractility of left ventricle will be a new useful index for myocardial function after analysis of the clinical data.

• Geomechanics and Engineering
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• v.27 no.5
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• pp.527-535
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• 2021

The creep characteristics of rock is of great significance for the study of long-term stability of engineering, so it is necessary to carry out indoor creep test and creep model of rock. First of all, in different water-bearing state and different positive pressure conditions, the granite is graded loaded to conduct indoor shear creep test. Through the test, the shear creep characteristics of granite are obtained. According to the test results, the stress-strain isochronous curve is obtained, and then the long-term strength of granite under different conditions is determined. Then, the fractional-order calculus software element is introduced, and it is connected in series with the spring element and the nonlinear viscoplastic body considering the creep acceleration start time to form a nonlinear viscoplastic creep model with fewer elements and fewer parameters. Finally, based on the shear creep test data of granite, using the nonlinear curve fitting of Origin software and Levenberg-Marquardt optimization algorithm, the parameter fitting and comparative analysis of the nonlinear creep model are carried out. The results show that the test data and the model curve have a high degree of fitting, which further explains the rationality and applicability of the established nonlinear visco-elastoplastic creep model. The research in this paper can provide certain reference significance and reference value for the study of nonlinear creep model of rock in the future.

• Earthquakes and Structures
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• v.22 no.5
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• pp.461-473
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• 2022

Energy-saving block and invisible multiribbed frame composite wall (EBIMFCW) is an important shear wall, which is composed of energy-saving blocks, steel bars and concrete. This paper conducted seismic performance tests on six 1/2-scale EBIMFCW specimens, analyzed their failure process under horizontal reciprocating load, and studied the effect of axial compression ratio on the wall's hysteresis curve and skeleton curve, ductility, energy dissipation capacity, stiffness degradation, bearing capacity degradation. A formula for calculating the peak bearing capacity of such walls was proposed. Results showed that the EBIMFCW had experienced a long time deformation from cracking to failure and exhibited signs of failure. The three seismic fortification lines of the energy-saving block, internal multiribbed frame, and outer multiribbed frame sequentially played important roles. With the increase in axial compression ratio, the peak bearing capacity and ductility of the wall increased, whereas the initial stiffness decreased. The change in axial compression ratio had a small effect on the energy dissipation capacity of the wall. In the early stage of loading, the influence of axial compression ratio on wall stiffness and strength degradation was unremarkable. In the later stage of loading, the stiffness and strength degradation of walls with high axial compression ratio were low. The displacement ductility coefficients of the wall under vertical pressure were more than 3.0 indicating that this wall type has good deformation ability. The limit values of elastic displacement angle under weak earthquake and elastic-plastic displacement angle under strong earthquake of the EBIMFCW were1/800 and 1/80, respectively.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.1-5
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• 2013

Liquefied Natural Gas is liquefied at the condition of atmosphere pressure and cryogenic temperature. LNG is exposed very long time under the cryogenic temperature and high pressure, and it is very important to retain the structural safety in this envelopment. Until now, the material which are composing the storage tank of LNG ship has experimented at room temperature, so it is not enough to apply for the design at the cryogenic temperature. The purposes of this study are investigated mechanical properties for aluminum alloy. To evaluate tensile and fatigue test for aluminum alloy, it was considering static and fatigue conditions at room and cryogenic temperature. S-N curves were designed at both temperature respectively. Also, P-S-N curve was performed statistical method by JSME-S002.

• YAKHAK HOEJI
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• v.44 no.3
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• pp.245-250
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• 2000

Because nonsteroidal anti-inflammatory drugs are reported to cause fluid retention and hypertension by inhibition of prostaglandin synthesis, the effects of piroxicam on pharmacodynamics and pharmacokinetics of nifedipine were studied in male spontaneously hypertensive rats. They received nifedipine (0.5 mg/kg) alone or combined with piroxicam (5 mg/kg) intravenously. Plasma levels norepinephrine, an index of sympathetic stimulation, were measured prior to each treatment and 5 min after drug administration. Changes in blood pressure were examined serially and blood samples for analysis of nifedipine were also taken for 6 hr following drug administration. Plasma nifedipine concentration were assayed by HPLC and pharmacokinetic parameters were calculated. Blood pressure was reduced (p<0.01), but plasma norepinephrine level was increased (p<0.05) by nifedipine administration. Anti-hypertensive effect of nifedipine was potentiated (p<0.05) by piroxicam coadministration, but effect of nifedipine on plasma norepinephrine level was not affected. In case of rats received nifedipine and piroxicam, plasma nifedipine concentrations were higher (p<0.05) than those from rats received nifedipine alone at 2,3,4,5 and 6 hours following drug administration. The area under the plasma concentration vs. time curve was increased (p<0.05), while the elimination rate constant was decreased (p<0.01) by piroxicam coadministration. No significant differences were observed in the plasma clearance, apparent volume of distribution and elimination half-life. Thus, piroxicam not only potentiated antihypertensive effect of nifedipine, but also altered nifedipine pharmacokinetics in the rats. It is concluded that the potentiation of nifedipine antihypertensive effect might correlate with the increment of its plasma concentration by piroxicam coadministration.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.4
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• pp.214-220
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• 2018

Light sources induced by gas discharge using rare gases have been widely used in the thin film deposition, the surface modification and the polymer etching. A dielectric barrier discharge (DBD) has been developed in order to consistently emit light and control the wavelength of the emission light. However, much research on the characteristics of the movement of discharge particles is required to improve the efficiency of the light lamp and the life-time of the light apparatus in detail. In this paper, we developed a He DBD discharge simulation tool and investigated the characteristics of discharge particles which were electrons, two positive ions ($He^+$, $He_2^+$) and 5 excited particles ($He^*(1S)$, $He^*(3S)$, $He^*$, $He^{**}$, $He^{***}$). The discharge currents showed the transition from pulse mode to continuous mode with the increase of power. With the accumulated charges on the barrier walls, the discharge current was rapidly increased and caused oscillation of the discharge voltage. As the gas pressure increased, $He_2^+$ and $He^*(3S)$ became the dominant activated particles. The input power was mostly consumed by electrons and $He_2^+$ ion. And the change curve showed that power consumption by electrons increased more with gas pressure than with source voltage or frequency.