• Journal of radiological science and technology
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• v.20 no.2
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• pp.49-55
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• 1997

This study was carried out to investigate radiographical and operating conditions of X-ray units and exposure doses to patients during chest radiography, so that the results could provide basic data used for reducing the exposure dose and for providing the diagnostic information with better quality. The conditions and exposure doses of 100 X-ray units mainly used for chest radiography were examined and also 100 radiological technologists mainly handling those apparatus at 76 medical facilities in Pusan were surveyed using a questionnaire from October 1 to December 31 in 1995. The following results were obtained from the study : 1. It was found that most units were capable of taking a high tube voltage radiography by showing 67% of the units equipped with the maximum tube voltage of 150 kV, 94% with more than 500 mA for the rating capacity and 85% with the full wave type of a signal phase. 2. For actual chest radiographical conditions, however, 80% of the units were operated at $60{\sim}100\;kVp$ and only 14% at 100 kVp and over for the high tube voltage. 3. The average exposure time was less than 0.1 second, and eighty four percent of the units adapted the X-ray tube currents ranging from 200 to 300 mA, 80% the focus-film distances between 180 and 210 cm, and 63% the focus sizes of more than 2.0 mm. 4. Most units(98%) employed additional filters made of aluminum, 75% the thickness of filters less than 2.0 mm, and only 2 units the compound filters. 5. Ortho chromatic system was only adopted in 13% of screen film system for the units, and 73% used the grid ratio at 8 : 1 for the low tube voltage during chest radiography. 6. The average exposure dose of all X-ray units during chest radiography was $371\;{\mu}Sv$ with a difference of about 16 times between the minimum to the maximum, and $386\;{\mu}Sv$ both at hospitals and at health centers, followed by $380\;{\mu}Sv$ at general hospitals and $263\;{\mu}Sv$ at university hospitals without showing any statistically significant differences. In conclusion, since patients during chest radiography at medical facilities in Pusan exposed to high levels of radiation, it is recommended that appropriate added filters and grids necessary for the high tube voltage radiography and high-speed screen systems should be adopted and used as soon as possible in order to reduce exposure dose to the patients.

• Journal of the Korean Geotechnical Society
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• v.36 no.5
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• pp.25-34
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• 2020

Studies on nondestructive evaluation methods using electromagnetic waves have been commonly conducted to evaluate necking defects in bored piles. However, the propagation of electromagnetic waves are affected by water contents of surrounding materials. This study aims to investigate a suitability of electromagnetic waves for evaluating necking defects in bored piles embedded in sandy soils through laboratory experiments. Laboratory experiments are performed with a model pile having a necking defect. The diameter and length of model pile are 600 mm and 1 m, respectively, and the model pile is embedded in sandy soils with different water contents of 10%, 20%, and 30%. For the propagation of electromagnetic waves, a transmission line is configured in reinforcement cage using an electrical wire. The generation and detection of electromagnetic waves are conducted using a time domain reflectometer. Experimental results show that the peak amplitude of electromagnetic waves reflected at the necking defect decreases with an increase in the water content in sandy soils. In addition, the velocity of electromagnetic waves reflected from the toe of the model pile decreases win an increase in the water content. However, estimated locations of the necking defects are almost the same to that of the actual location of the necking defect. This study demonstrates that electromagnetic waves may be an effective method for evaluating necking defects in bored piles embedded in sandy soils

• Journal of Yeungnam Medical Science
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• v.12 no.2
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• pp.246-259
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• 1995

This study aimed to investigate the mechanism of action of baclofen on the detrusor muscle isolated from rat. Rats (Sprague-Dawley) were sacrificed by decapitation and exsanguination. Horizontal muscle strips of $2mm{\times}15mm$ were prepared for isometric myography in isolated muscle chamber bubbled with 95% / 5%-$O_2$ / $CO_2$ at $37^{\circ}C$, and the pH was maintained at 7.4. Detrusor strips contracted responding to the electrical field stimulation (EFS) by 2 Hz, 20 msec, monophasic square wave of 60 VDC. The initial peak of EFS-Induced contraction was tended to be suppresed by ${\alpha},{\beta}$-methylene-adenosine 5'-triphosphate (mATP), a partial agonist of purinergic receptor, and baclofen, a $GABA_B$ receptor agonist (statistically nonsignificant). The late sustained contraction by EFS was suppressed significantly (p < 0.05) by additions of atropione, a cholinergic muscarinic receptor antagonist and baclofen. The adenosine 5'-triphosphate-induced contraction was completely abolished by mA TP but not by baclofen. In the presence of atropine, the subsequent addition of acetylcholine could not contract the muscle strips: but the addition of acetylcholine in the presence of baclofen evoked a contraction to a remarkable extent. These results suggest that in the condition of present study, the cholinergic innervation may play a more important role than the purinergic one, and baclofen suppresses the contractility of rat detrusor by the stimulation of the $GABA_B$ receptors to inhibit the release of neurotransmitter from the cholinergic nerve ending.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• Journal of Veterinary Clinics
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• v.30 no.6
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• pp.456-458
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• 2013

The aim of this study is to evaluate the reference value for electrocardiogram in healthy captive raccoon dogs. Forty-one free-ranging adult raccoon dogs rescued from Wildlife rescue centre, Kangwon National University were enrolled in this study. The 6-lead electrocardiogram was obtained in all raccoon dogs without any chemical restraints. The mean heart rate was $146.10{\pm}43.31$ beats/min (95% confidence interval 132.84~159.36 beats/min). The mean respiration rate was $35.73{\pm}11.56$ breaths/min (95% confidence interval 32.19~39.27 breaths/min). The mean systolic blood pressure was $136{\pm}29.26$ mmHg (95% confidence interval 127.99~145.91 mmHg). Electrocardiographical features were also evaluated in all raccoon dogs. The mean duration and amplitude of P-wave were $38.2{\pm}4.0$ ms (range 28-40 ms) and $0.128{\pm}0.039$ mV (range 0.09~0.20). The mean duration and amplitude of QRS complexes were $48.5{\pm}7.2ms$ (range 36-60 ms) and $1.330{\pm}0.650$ mV (range 0.15~2.30). The range of the mean electrical (QRS) axis was $-91^{\circ}{\sim}+96^{\circ}$ ($10^{\circ}{\sim}60^{\circ}$; 95% of confidence interval). The mean corrected QT (QTc) interval was $273.7{\pm}32.7ms$ (range 212-333 ms), while the mean PR interval was $76.1{\pm}10.0ms$ (range 50-82 ms). To the authors' knowledge, this is the first study to provide references in electrocardiogram (ECG) in healthy captive raccoon dogs.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.378-389
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• 2006

The purpose of this study was to compare the sealing ability of root canal obturation with or without the treatment of smear layer. Eighty extracted human teeth with one canal were selected Instrumentation was performed with crown-down technique. After instrumentation, root canals of the NaOCl group and NaOCl-6 group were irrigated with 3% NaOCl. EDTA group and EDTA-6 group were irrigated with 17% EDTA. Then all teeth were obturated using continuous wane obturation technique NaOCl group and EDTA group were immersed in methylene blue solution for 84hours. NaOCl-6 group and EDTA-6 group were immersed in methylene blue solution for 6months. The teeth were sectioned at 1.5 mn (Level 1), 3.0 mm (Level 2) and 4.5 mm (Level 3) from the root apex. The length of dye-penetrated inter-face and the circumferential length of canal at each level were measured using Sigma-Scan Pro 5.0. 1. The mean leakage ratio was decreased cervically. 2. NaOCl group showed higher mean leakage ratio than EDTA group at each level. But there was significant difference at level 1 only (p < 0.05). 3. NaOCl-6 group showed higher mean leakage ratio than EDTA-6 group at each level. But there was significant difference at level 1 only (p < 0.05). 4. NaOCl-6 group showed higher mean leakage ratio than NaOCl group at each level. But there was significant difference at level 1 only (p < 0.05). 5. EDTA-6 group showed higher mean leakage ratio than EDTA group at each level. But there was no significant difference. 6. In NaOCl group and NaOCl-6 group, scanning electron micrographs of tooth sections generally covered with smear layer. In EDTA group and EDTA-6 group, tooth sections showing the penetration of sealers to opened dentinal tubules. The results suggest that removal of smear layer was effective to reduce the apical microleakage of the root canal.

• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1028-1034
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• 2001

The 2.5 vol% TiNi/6061Al composites were fabricated by permanent mold casting. The microstructures and tensile test for the cold rolled composites with maximum 50% reduction ratio were investigated. In the case of TiNi fiber with 2mm interval in preform, the interface bonding of fabricated composites were good, interface diffusion layer of this composites was made by the mutual diffusion. Transverse section of TiNi fiber was decreased with increasing reduction ratio and longitudinal section of TiNi fiber showed multiple wave phenomenon. And the tensile strength of composites at 38% reduction ratio was the most high. In the case of over 38% reduction ratio, the decrease of the tensile strength was due to TiNi fiber rupture by excess working. The fracture mode was appeared brittle fracture with increasing reduction ratio.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.9 s.351
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• pp.64-68
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• 2006

Novel system-on-package (SOP) - D technology to improve the mechanical and thermal properties of a MCM-D substrate was suggested. Based on this investigation, the two types of band pass filters for the V-band application with unique structure were designed and implemented using 2-metals, 3-BCB layers. The first type using distributed resonator had the insertion loss below 2.6 dB at 55 GHz and group delay was below 0.06 ns. For the second type with edge coupled structure, the insertion loss and group delay were 3 dB and 0.1 ns, respectively. Suggested MCM-D substrate with band pass filter can be used to evaluate mm-Wave system including flip-chip bonded MMIC.

• Journal of electromagnetic engineering and science
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• v.17 no.3
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• pp.153-158
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• 2017

This work reports on the effect of plasma area on the frequency characteristics of the monostatic radar cross section (RCS) of a square metallic plate. A dielectric barrier discharge (DBD) plasma actuator consisting of 10 rings is proposed. The actuator is fabricated in three different configurations such that only three inner rings, seven inner rings, and all rings can be biased. By applying an 18-kV bias at 1 kHz, the three types of DBD actuators generate plasma with a total area of 16.96, 36.74, and $53.69cm^2$, respectively, in a ring or circular form. The experimental results reveal that when the DBD actuator is placed in front of a $20mm{\times}20cm$ conducting plate, the monostatic RCS is reduced by as much as 18.5 dB in the range of 9.41-11.65 GHz. Furthermore, by generating the plasma and changing the area, the frequency of maximum reduction in the monostatic RCS of the plate can be controlled. The frequency is reduced by nearly 20% in the X band when all rings are biased. Finally, an electromagnetic model of the plasma is obtained by comparing the experimental and full-wave simulated results.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.11-17
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• 2017

In this paper, an 8-direction switched beamforming antenna system at 28GHz frequency band is described for 5th generation wireless communication. This system is composed of an $8{\times}8$ Butler matrix and an 8-element patch array antenna. The antenna system switches beams in 8-direction in the wide range of ${\pm}40^{\circ}$. The antenna spacing is $0.65{\lambda}$ to achieve ${\pm}40^{\circ}$ steering range. Designed results show that the 8-direction beams are placed at ${\pm}6^{\circ}$, ${\pm}17^{\circ}$, ${\pm}28^{\circ}$, ${\pm}40^{\circ}$ offset from the center. Parasitic radiation effect from the large dimension Butler matrix need to be suppressed by employing a stripline structure.