• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.103-111
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• 2002

Steady-state creep analysis of power generation turbine blade is carried out considering thermal loads and centrifugal forces. Creep strains and stresses of the turbine blade are calculated for 3-D finite clement model of the turbine blade. From the numerical results, creep life of the turbine blade is predicted. The results of creep analysis during about 200 hours indicate that creep strains of the turbine blade do not reach the rupture strain of GTD111. Creep stresses of the turbine blade are relaxed as time increases. Maximum creep strain occurs at the tip section of the airfoil pressure surface. The maximum creep strain of the turbine blade is expected close to the rupture strain after 50,000 hours approximately. The turbine blade may not have creep damage for the starting procedure of the turbine.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.632-637
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• 2016

A streetlight control system was developed using information technology and LED lights for efficient management and energy savings. The proposed system can control the power usage of an LED streetlight luminaire using GPS satellite communication and an Arduino with a built-in microprocessor. A control circuit was designed to control the current using GPS, a control unit, transistor, resistor, and constant-current supply circuit. The circuit was validated through experiments with normal operation. Using GPS, the control system extracts accurate time and location information according to the season, and it controls the current supplied to the LED streetlight according to the extracted time. Power consumption was reduced by more than 11%. The control system could reduce accidents caused by conventional lighting systems used to save energy, and it could improve the inefficient management of energy by preserving constant brightness of a streetlight at times and in areas that have less traffic.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.913-921
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• 2012

The current PC-based desktop environment is being converted into server-based virtual desktop environment due to security, mobility, and low upgrade cost. In this paper, a desktop virtualization system is implemented using an open source-based cloud computing platform and hypervisor. The implemented system is applied to the virtualziation of computer in university. In order to reduce the image transfer time, we propose a solution using HDFS. In addition, an image management structure needed for desktop virtualization is designed and implemented, and applied to a real computer lab which accommodates 30 PCs. The performance of the proposed system is evaluated in various aspects including implementation cost, power saving rate, reduction rate of license cost, and management cost. The experimental results showed that the proposed system considerably reduced the image transfer time for desktop service.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.88-96
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• 2017

Purpose: The purpose of this study is to assess the relationship between the time spent designing custom abutments and repeated learning using dental implant computer aided design (CAD) software. Materials and Methods: The design of customized abutments was performed four stages using the 3DS CAD software and the EXO CAD software, and measured repeatedly three times by each stage. Learning effect by repetition was presented with the learning curve, and the significance of the reduction in the total time and the time at each stage spent on designing was evaluated using the Friedman test and the Wilcoxon signed rank test. The difference in the design time between groups was analyzed using the repeated measure two-way ANOVA. Statistical analysis was performed using the SPSS statistics software (P < 0.05). Results: Repeated learning of the customized abutment design displayed a significant difference according to the number of repetition and the stage (P < 0.001). The difference in the time spent designing was found to be significant (P < 0.001), and that between the CAD software programs was also significant (P = 0.006). Conclusion: Repeated learning of CAD software shortened the time spent designing. While less design time on average was spent with the 3DS CAD than with the EXO CAD, the EXO CAD showed better results in terms of learning rate according to learning effect.

• The Korean Journal of Pain
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• v.5 no.2
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• pp.213-220
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• 1992

The sciatic nerves of anesthetized rabbits were exposed and stimulated by a nerve stimulator in order to observe the myoneural response. These rabbits were divided into three groups and respectively injected with morphine (Group 1), meperidine(Group 2) and pentazocine (Group 3). The sciatic nerves were stimulated periodically and gait changes were observed to see the myoneural activity after the injections. When the distal part of the sciatic nerves were stimulated by the nerve stimulator after the respective drug injections, the normal muscle twitch responses were observed in all the progressional stages of Group 1. However, in Group 2 and 3, the muscle twitch responses decreased gradually, finally disappearing after approximately 10 minutes in these two groups. Complete motor paralysis continued for about 60 minutes. The muscle reactions returned to normal approximately 90 minutes after injection. Specimens drug-injected tissues were severed 4 hours, 24 hours and 1 week after injection respectively. These tissue were investigated under light as well as electron microscopy. The tissue revealed rare to moderate vacuolizations scattered in the axons of the myelinated and unmyelinated nerves of some of the specimens; however, there were no significant pathologic lesions. These results provide evidence that neurophysiologically, meperidine and pentazocine have a local anesthetic-like effect such as motor paralysis, but morphine does not. In addition, the results indicated that neurohistologically, the three narcotics have no significant toxic effects on the nerve tissue.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.33-37
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• 2001

Purpose : The water exchange rate between bulk water and bound water is an important parameter in deciding the efficiency of paramagnetic contrast agents. In this study, we evaluated the water exchange rates of various Gd-chelates using oxygen-17 NMR technique. Material and Methods : The samples (Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA) were prepared by mixing 5% $^{17}O-enriched$ water (Isotech, USA). The pH of the samples was adjusted to physiological value [pH=7.0] by buffer solution. The variable temperature $^{17}O-NMR$ measurements were performed using Bruker-600 (14.1 T, 81.3 MHz) spectrometer. Bruker VT-1000 temperature control units were used to stabilize the temperature. The $^{17}O$ spin-spin relaxation times (T2) were measured using Carr-Purcell-Meiboom-Gill (CPMG)I pulse sequence with 24 echo trains. The variable temperature T2 relaxation data were then fitted into Solomon-Bloembergen equations using least square fit algorithm to estimate the water exchange times. Results : From the measured $^{17}O-NMR$ relaxation rates, the determined water exchange rates at 300K are $0.42{\;}{\mu}s$ for Gd-DTPA, $1.99{\;}{\mu}s$ for Gd-DTPA-BMA, $0.27{\;}{\mu}s$ for Gd-DOTA, and $0.11{\;}{\mu}s$ for Gd-EOB-DTPA. The Gd-DTPA-BMA showed slowest exchange whereas Gd-EOB-DTPA had fastest water exchange rate. In addition, it was found that the water exchange rates (${\tau}_m$) of all samples had exponential temperature dependence with different decay constant. Conclusion : $^{17}O-NMR$ relaxation rate measurements, when combined with variable temperature technique, provide a solid tool for studying water exchange rate, which is very important in investigating the detailed mechanism of relaxation enhancement effect of the paramagnetic contrast agents.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.133-149
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• 2021

This study aims to report the behavioral mechanism of steel pipe reinforcement grouting, which is being actively used to ensure the stability of the excavation surface during tunnel excavation, based on measurements taken at the actual site. After using a 12 m steel pipe attached with a shape displacement meter and a strain gauge to reinforce the actual tunnel surface, behavioral characteristics were identified by analyzing the measured deformation and stress of the steel pipe. Taking into account that the steel pipes were overlapped every 6 m, the measured data up to 7 m of excavation were used. In addition, the behavioral characteristics of the steel pipe reinforcement according to the difference in strength were also examined by applying steel pipes with different allowable stresses (SGT275 and SGT550). As a result of analyzing the behavior of steel pipes for 7 hours after the first excavation for 1 m and before proceeding with the next excavation, the stress redistribution due to the arching effect caused by the excavation relaxation load was observed. As excavation proceeded by 1 m, the excavated section exhibited the greatest deformation during excavation of 4 to 6 m due to the stress distribution of the three-dimensional relaxation load, and deformation and stress were generated in the steel pipe installed in the ground ahead of the tunnel face. As a result of comparing the behavior of SGT275 steel pipe (yield strength 275 MPa) and SGT550 steel pipe (yield strength 550 MPa), the difference in the amount of deformation was up to 18 times and the stress was up to 12 times; the stronger the steel pipe, the better it was at responding to the relaxation load. In this study, the behavior mechanism of steel pipe reinforcement grouting in response to the arching effect due to the relaxation load was identified based on the measured data during the actual tunnel excavation, and the results were reported.

• Clinical and Experimental Pediatrics
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• v.52 no.3
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• pp.339-345
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• 2009

Purpose : This study aimed to determine the variation in parameters according to cardiac cycle length (CL; time interval between the QRS peaks on ECG) in children by using the conventional pulsed Doppler and tissue Doppler imaging echocardiography. Methods : Eighteen children with an anatomically normal heart were enrolled for the study. All children were examined by conventional and pulsed Doppler echocardiography at Gangneung Asan hospital between July 2006 and June 2007. We measured the CLs, mitral inflow velocities (E,A) and tissue Doppler imaging (TDI) parameters (s', e', a') from apical 4-chamber view. The TDI parameters were measured at the lateral (Lat) and septal (Sep) part of the mitral valve. All parameters were measured at 6 to 18 consecutive beats from each child. We then evaluated the linear correlation between CL and each parameter. Results : The mean age was $3.6{\pm}0.5$ years (M:F=8:10). There were significantly negative linear correlations between CL and A, Lat s', Lat a', Sep s', Sep e', Sep a' (P<0.01). There were significantly positive linear correlations between CL and E/A, Lat e'/a', Sep e'/a' (P<0.01). However, the E and Lat e' were not correlated with CL (P=0.229 and 0.221, respectively). Conclusion : This study showed that the values of the left ventricular functional parameters were changed according to CL. From our results, it is imperative to carefully examine beat-to-beat variations in children.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.6
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• pp.1035-1042
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• 2002

This study was conducted to investigate the effect of sodium intake on serum lipids and glucose. 20 young adult women were fed the diets containing 290.5 mEq (high-Na diet) and 51.3 mEq (low-Na diets) Na for 6 days, respectively. Serum lipids, glucose, and other parameters after high-Na diet and low-Na diet were compared. The results would be summarized as follows. The mean age, body weight, height, and blood pressure of the subjects were 22.9$\pm$2.5 years,54.7+6.6 kg, 160.0$\pm$4.8 cm, 110.3$\pm$7.7/67.5$\pm$19.7 mmHg, respectively. Body weight, BMI, and diastolic blood pressure were significantly higher at the end of high-Na diet than of low-Na diet (p<0.001 p<0.001, p<0.05). However, there were not significantly different in height and systolic blood pressure between high- and low-Na diet. Serum cholesterol, LDL-cholesterol, and HDL-cholesterol were not significantly different with Na intakes. Serum triglyceride was significantly higher at the end of high-Na diet than of low- Na diet (p<0.05) Serum apo A-I was significantly decreased in low-Na diet, while apo B was increased (p<0.001, p<0.001). Thrombin time and prothrombin time, blood aggregation time were significantly faster following low-Na diet (p<0.001, p<0.05). There was not significantly different in serum glucose between high- and low-Na diet. However, serum insulin was significantly higher following low-Na diet (p<0.01). It is concluded that diastolic blood pressure, serum triglyceride, serum apo A-I, blood aggregation time were decreased in low-Na diet, while serum apo B and serum insulin were increased. These results suggest that Na-restricted diet affects not only blood Pressure but other biochemical parameters in blood. Therefore, for the patients who need restricted Na diet, it would be suggested that various biochemical changes should be carefully considered along with dietary Na manipulation.

• Journal of Life Science
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• v.17 no.2 s.82
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• pp.218-222
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• 2007

The purpose of this study is to evaluate the relationship between high sensitive C-reactive protein (hsCRP) and pulse transit time (PPT). Apparently healthy 233 subjects had been enrolled in the health promotion center of the Pusan National University Hospital from Jan. 29 to Feb. 26, 2004. They had no previous history of diabetes, hypertension and hyperlipidemia. Subjects were categorized according to tertiles of hsCRP level [Group 1: first tertile $(0.01\;{\sim}\;0.02\;mg/dl)$, Group 2: second tertile $(0.03\;{\sim}\;0.05\;mg/dl)$, Group 3: third tertile $(0.06\;{\sim}\;0.12\;mg/dl)$, and Group 4: Fourth tertile $(0.13\;{\sim}\;16.8\;mg/dl)$]. PTT body mass index (BMI), total cholesterol (T-C), LDL-cholesterol(LDL-C), blood sugar (BS), systolic blood pressure (sBP) and diastolic blood pressure (dBP) were significantly different among hsCRP groups (p<0.05). HsCRP is positively related with BMI, tryglyceride (TG), LDL, sBP and dBP (p<0.05), and negatively related with PTT and HDL-cholesterol (HDL-C) (p<0.05). PTT is significantly negatively related with hsCRP, T-C, TG, LDL-C, BS, dBP and sBP (p<0.05). The hsCRP and PTT were related before controlling BMI, T-C, LDL-C, sBP, and dBP, but not related after conkolling. The relationship between hsCRP and PTT depends on cardiovascular disease risk factors.