• The Journal of Korean Physical Therapy
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• v.22 no.5
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• pp.39-47
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• 2010

Purpose: The purpose of this study was to characterize changes in back muscles in patients with chronic back pain. Accordingly, we studied 154 patients with chronic low back pain with regard to area, aspect and triggering position of the pain. We also determined muscle atrophy in painful areas. Methods: Subjects were questioned about pain and a pain provoking test was done. On Magnetic Resonance Imaging (MRI), we measured cross sections of the multifidus, erector spinae, iliopsoas and quadratus lumborum muscles at each spinal level. Results: Muscles in painful regions (multifidus and erector spinae muscles) decreased in area significantly more than nonpainful regions, and showed a significant difference (p<0.05) at levels L3, L4, and L5. Painful regions of the iliopsoas and quadratus lumborum did not change significantly more than non-painful regionsexcept at L5 (p<0.05). The group that had unilateral low back pain showed a significant decrease in cross section compared to the group that had central or bilateral pain (p<0.05). Conclusion: Chronic low back pain causes variable decreases in cross-sectional areas of some but not all back muscles, and at some but not all spinal levels.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.61-64
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• 2008

The present study of these experiments are close examination of spray characteristics that are continuous liquid jet and modulated pressure pulse liquid jet. The experiments were conducted using water, over a range of cross-flow velocities from 42${\sim}$136 m/s, with injection frequencies of 35.7${\sim}$166.2 Hz. Between continuous cross-flow jet and pressure pulsed cross-flow jet for characteristics of penetration, breakup point, spray angle and macro spray shape are investigated experimentally. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than pressure pulse frequency. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of pressure pulsation frequency, an inclination of SMD for the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various frequency of pressure pulse was same distribution. And volume flux was decreased when the frequency of pressure pulse increase.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.484-489
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• 2003

The mass flow rate of gas flow through critical nozzle depends on the nozzle supply conditions and the cross-sectional area at the nozzle throat. In order that the critical nozzle can be operated at a wide range of supply conditions, the nozzle throat diameter should be controlled to change the flow passage area. This can be achieved by means of a variable critical nozzle. In the present study, both experimental and computational works are performed to develop variable critical nozzle. A cone-cylinder with a diameter of d is inserted into conventional critical nozzle. It can move both upstream and downstream, thereby changing the cross-sectional area of the nozzle throat. Computational work using the axisymmetric, compressible Navier-Stokes equations is carried out to simulate the variable critical nozzle flow. An experiment is performed to measure the mass flow rate through variable critical nozzle. The present computational results are in close agreement with measured ones. The boundary layer displacement and momentum thickness are given as a function of Reynolds number. An empirical equation is obtained to predict the discharge coefficient of variable critical nozzle.

• Journal of ILASS-Korea
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• v.14 no.2
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• pp.59-64
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• 2009

These experiments are close examination of spray characteristics that are continuous liquid jet and modulated liquid jet. The experiments were conducted using water, over a range of crossflow velocities from $42{\sim}l36\;m/s$, with modulation frequencies of $35.7{\sim}166.2\;Hz$. Between continuous crossflow jet and modulated cross-flow jet of penetration, breakup point, spray angle and macro spray shape are experimentally investigated with image analysis. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than modulation effect. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of modulation frequency, SMD inclination of the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various modulation frequency was same distribution. And volume flux was decreased when the modulation frequency increase.

• Journal of Preventive Medicine and Public Health
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• v.27 no.2 s.46
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• pp.313-325
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• 1994

A cross-sectional study was conducted in an effort to investigate the effect of air pollution on respiratory symptoms. Two groups of female aged more than 20 living in the unpolluted rural area of Taebul (n=159) and urban area of Taegu (n=140) were selected. The ATS-DLD-78 questionnaire was translated into Korean and administered with minor modification. The proportion of smoker was less than 1% in both area. Exposure to smoking and higher educational level were more frequent in Taegu. Age-adjusted prevalence rates of 'chronic cough', 'chronic sputum', 'wheezing', and 'dyspnea' were higher in Taegu than in Taebul. In particular, the prevalence rate of 'chronic sputum' in Taegu was found to be higher, which was statistically significant. Exposure to smoking and education level were not concerned with all respiratory symptom prevalence rates. In conclusion, this study Indicates that an urban factor is related to the rates of respiratory symptoms in Korea.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.269-283
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• 2022

In this paper, a particular type of all-steel HSS brace members with a locally reduced cross-sectional area was experimentally and numerically investigated. The brace member was strengthened against local buckling with inner and outer boxes in the reduced area. Four single-span braced frames were tested under cyclic lateral loadings. Specimens included a simple steel frame with a conventional box-shaped brace and three other all-steel reduced section buckling-restrained braces. After conducting the experimental program, numerical models of the proposed brace were developed and verified with experimental results. Then the length of the proposed fuse was increased and its effect on the cyclic behavior of the brace was investigated numerically. Eventually, the brace was detailed with a fuse-to-brace length of 30%, as well as the cross-sectional area of the fuse-to-brace of 30%, and the cyclic behavior of the system was studied numerically. The study showed that the proposed brace is stable up to a 2% drift ratio, and the plastic cumulative deformation requirement of AISC (2016) is easily achieved. The proposed brace has sufficient ductility and stability and is lighter, as well as easier to be fabricated, compared to the conventional mortar-filled BRB and all-steel BRB.

• Annals of Clinical Neurophysiology
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• v.12 no.2
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• pp.55-60
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• 2010

Background: The aim of this study is to identify the correlation between ultrasonographic findings of median nerve and clinical scale and electrophysiologic data in carpal tunnel syndrome. Methods: Forty three patients (79 hands) with electrophysiologically confirmed carpal tunnel syndrome were evaluated. Clinical symptoms were examined by Historical-Objective (Hi-Ob) scale. Electrophysiologic data and Padua scale were used for severity of electrophysiology. In ultrasonographic study, cross sectional area and flattening ratio of median nerve were measured at distal wrist crease level (DWC), 1cm proximal to distal wrist crease level, and 1cm distal to distal wrist crease level. The correlation between Hi-Ob scale, electrophysiologic data and ultrasonography was measured with Spearman rank test. Results: The mean Hi-Ob scale was 2.4. Mean Padua scale was 4.0. In ultrasnonographic study, cross sectional area and flattening ratio were $0.112\;cm^2{\pm}0.025$ and $3.0{\pm}0.6$ at 1cm proximal to DWC level, $0.118{\pm}0.026\;cm^2$ and $2.9{\pm}0.4$ at DWC level, and $0.107{\pm}0.032\;cm^2$ and $3.0{\pm}0.4$ at 1 cm distal to DWC level. Hi-Ob scale was not correlated with cross sectional area and flattening ratio of median nerve. Hi-Ob scale was correlated with Padua scale positively (r=0.44) and correlated with amplitudes of CMAP and SNAP, negatively (r=-0.33; r=-0.30). Cross sectional area of median nerve was significantly correlated with Padua scale, amplitudes and latencies of CMAP and amplitudes of SNAP. Conclusions: Ultrasonographic findings of median nerve and electrodiagnostic data had statistically significant correlation. Consequently, ultrasonography could be an adjunctive method in diagnosis of carpal tunnel syndrome.

• Restorative Dentistry and Endodontics
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• v.31 no.2
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• pp.96-102
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• 2006

There are various factors affecting the fracture of NiTi rotary files. This study was performed to evaluate the effect of cross sectional area, pecking motion and pecking distance on the cyclic fatigue fracture of different NiTi files. Five different NiTi $files-Profile^{(R)}$ (Maillefer, Ballaigue, Switzerland), $ProTaper^{TM}$(Maillefer, Ballaigue, Switzerland), $K3^{(R)}$ (SybronEndo. Orange, CA) , Hero $642^{(R)}$ (Micro-mega, Besancon, France), Hero $Shaper^{(R)}$ (Micro-mega, Besancon, France)-were used. Each file was embedded in temporary resin, sectioned horizontally and observed with scanning electron microscope. The ratio of cross-sectional area to the circumscribed circle was calculated. Special device was fabricated to simulate the cyclic fatigue fracture of NiTi file in the curved canal,. On this device, NiTi files were rotated (300rpm) with different pecking distances (3 mm or 6 mm) and with different motions (static motion or dynamic pecking motion) . Time until fracture occurs was measured. The results demonstrated that cross-sectional area didn't have any effect on the time of file fracture. Among the files, $Profile^{(R)}$ took the longest time to be fractured. Between the pecking motions, dynamic motion took the longer time to be fractured than static motion. There was no significant difference between the pecking distances with dynamic motion, however with static motion, the longer time was taken at 3mm distance. In this study, we could suggest that dynamic pecking motion would lengthen the time for NiTi file to be fractured from cyclic fatigue.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.4
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• pp.186-192
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• 2005

We investigated the deposition characteristics and mass transport flux estimation of the Nakdong estuary, Korea. To understand the effects of the tidal current circulation that influences estuary terrain changes, we used a 2D numerical model to map seawater circulation under three different situations, with the level of river flow being set as none or flood. The net-water flux of the cross-sectional area between sandbars (known as dung) was estimated. From our review of previous research, we know that the development of local sandbars shifted from the west to the east side of the estuary after the construction of the Nakdong River dike. Current development is occurring mostly at the Bakhap-dung near Tadea. The seawater circulation pattern over this large-scale area of tidal na is brings changes related to the quantity of the outflow from the Nakdong River. Based on the calculated results for the net-water flux of the cross-sectional area, we see very strong accumulation in local waters around Jangjiado, Bakhapdung, and Tadae under flood river flow conditions, but accumulation in local waters around Jinudo under the other states of flow. Consequently, in the Nakdong estuary, the main sensitive regions that are affected by changes in the flow of river discharge are the local waters around Jangiado, Bakhapdung, Tadae, and Jinudo.

• Journal of Convergence for Information Technology
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• v.11 no.10
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• pp.223-229
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• 2021

This study analyzed the effects of an exercise program that combined lumbar stabilization exercise and muscle strengthening exercise and an exercise program that applied only lumbar muscle strengthening exercise on multifidus muscle cross-sectional area, static posture control ability, and low back pain in patients with CLBP. For the study method, 28 patients with CLBP were divided into two exercise propram groups and exercised three times a week for 8-weeks. The data analysis of this study used the t-test to compare before and after group exercise program application, and between each group (p<.05). As a result of the study, significant results were found before and after application of the exercise program within each group, such as multifidus muscle cross-sectional area, static posture control ability, and low back pain (p<.05). Between each group, the exercise program that combined lumbar stabilization exercise and muscle strengthening exercise was found to be more effective (p<.05). In conclusion, it was found that the exercise program with additional lumbar stabilization exercise improved the structure and function of various lumbar vertebrae and reduced lumbar pain.