• Laser Solutions
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• v.4 no.2
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• pp.1-12
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• 2001

This study has been performed to evaluate basic characteristics of CW-CO$_2$ laser welding process of A5083 and A7N01 Al alloy. The effect of welding parameters, such as shielding gas, gas flow rate, laser power and welding speed on the bead shape and porosity from bead on plate welding tests have been investigated. Welds shielded by He gas had deeper penetration and better bead shape than those shielded by Ar. The penetration depth was augmented with the increase of laser Power and the decrease of welding speed. Welds of A7N01 alloy had deeper penetration than those of A5083 alloy In beads of A5083 alloy which has deeper penetration, the volume fraction of porosities was high due to the number of its was few, but size of its was larger. The case of deeper penetration beads of A7N01 alloy, the porosity reduced under relatively higher power The Volume fraction of porosities in weld of A5083 alloy was significantly higher than that in weld of A7N01 alloy.

• Proceedings of the Korean Society of Laser Processing Conference
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• 1998.11a
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• pp.24-28
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• 1998

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.97-105
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• 2022

The purpose of this study was to analyze the effects of flossing band exercise on the range of motion and vertical jump for taekwondo demonstration athletes with ankle functional instability. The subjects of this study were 21 male Taekwondo Demonstration Team athletes enrolled at D University. They were divided into functional ankle instability group(FAIG, n=7), mild ankle instability group(MAIG, n=7), and ankle stability group(ASG, n=7). All groups performed a acute flossing band exercise program. The results of this study are as follows; dorsi flexion(p<.01), inversion(p<.01), eversion(p<.05) and vertical jump(p<.01) were significantly increased in the FAIG. Flossing band exercise of Taekwondo demonstration team with FAI increased joint range of motion and vertical jump. Therefore, it was confirmed that it could be an intervention that can improve performance and reduce the risk of ankle injury.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2000.11a
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• pp.42-45
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• 2000

• Proceedings of the KWS Conference
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• 1999.10a
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• pp.181-184
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• 1999

• Journal of Welding and Joining
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• v.19 no.4
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• pp.429-436
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• 2001

The effect of welding condition on the microstructures of the weld metal in A7N01 welded by $CO_2$ laser was investigated. The number of ripples was increased with decreasing power and increasing welding speed. In the bead without ripple lines, the subgrain microstructures distribution from the fusion line toward the center of the bead were in the order of cellular, dendritic and equiaxed dendrite. However, in the bead with ripple lines, cellular and dendritic were formed between the fusion boundary and the ripple line. Inaddition, those structures were also observed between the ripple line. Equiaxed dendrites were formed only at the center line region. Cellular and dendritics formed near the ripple line were larger than those formed near the fusion boundary. The cooling rates estimated by the dendrite arm spacing were in the range of 200 to 1150oC/s. Cooling rate was increased with decreasing the power and increasing the welding speed. Mg and Zn segregated at the boundaries of cellulars and dendritics, Mg was segregated more than Zn. The segregation of Mg and Zn decreased with increasing cooling rate. Hardness of the weld metal was lower than that of the base metal in all welding conditions and increased as the cooling rate increased.

• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.1-8
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• 2001

From August 2000 to August 2001, 9 variables of physicochemical factors and phytase activity were investigated at 4 sites in the River Yungpyung and the influences of Physicochemical factors to Phytase activity were analyzed. Phytase activities of Site 1, Site 2, Site 3, and Site 4 varied between N.D ∼566 nmol/ ι /hr, N.D \" 434 nmol/ ι /hr, N.D ∼557 nmol/ ι /hr, and N.D ∼723 nmol/ ι /hr, respectively. The activities of summer season were higher than those of other season. But the activities were not detected on the winter season. The phytase activity and temperature showed high correlation. The correlation coefficients of Site 1, Site 2, Site 3, and Site 4 were 0.82(p<0.01).0.92(p<0.01),0.87(p<0.01), and 0.88(p<0.01), respectively. The phytase activity and NOI₃/sup -/ ion showed negative relation(r=-0.59, p<0.05) at Site 1. And the phytase activity had relation with Zn/sup 2+/at Site 2(r=().57, p<0.05) and Site 3(r=0.7E, p<7.07).

• Journal of Digital Contents Society
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• v.18 no.7
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• pp.1387-1391
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• 2017

Cutting power estimation can be used to select appropriate actuators in the design process of machine tools. Therefore, accurate estimation of cutting power is an important part of the design process. In this study, pipe cutting power is first calculated theoretically using the slotting cutting power equation and then verified experimentally. In this case, a pipe cutting machine is used to cut two pipes made of different materials. Power consumptions in the motor during pipe cutting are measured by using the embedded software, Labview, and NI hardware. The slotting cutting power equation can thus be confirmed easily comparing theoretically calculated cutting powers with experimentally measured cutting powers. The pipe materials used in this study are SUS304 and AL6N01. The specific cutting power of AL6N01 material is proposed through our cutting experiment. As a result, this cutting power can be used to design machining tools for AL6N01 material.

• Journal of Korean society of Dental Hygiene
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• v.14 no.4
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• pp.601-608
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• 2014

Objectives : The purpose of the study is to examine the apoptotic effects of Pseudomonas aeruginosa exotoxin A(PEA) in squamous cell carcinoma(SCC) 25 cells. Methods : Cell growth reduction and apoptosis induced by PEA were confirmed by WST-1 assay, Hoechst 33258 staining, flow cytometry analysis, and Western blot assay. Results : The PEA treatment decreased the cell viability in a dose and time dependent manner: control; $100{\pm}0^e$(p<0.01), 0.1875 nM; $87{\pm}4.36^d$(p<0.01), 0.375 nM; $82{\pm}0.58^d$(p<0.01), 0.75 nM; $72{\pm}1.67^c$(p<0.01), 1.5 nM; $51{\pm}1.53^{bc}$(p<0.01), 7.5 nM; $31{\pm}1.20^{ab}$(p<0.01), 15 nM; $26{\pm}0.67^a$(p<0.01), control; $100{\pm}0^a$(p<0.05), 24 h; $51{\pm}1.53^b$(p<0.05), 48 h; $16{\pm}0.5^c$(p<0.05), 72 h; $12{\pm}1.67^d$%(p<0.05). The PEA was observed on SCC 25 cells with the half maximal inhibitory concentration(IC50) value of 1.5 nM at 24 hours. The PEA treated SCC 25 cells demonstrated several types of apoptotic indications, such as nuclear condensation, the increase of sub G1, and the cleavage of PARP-1 and DFF 45. Conclusions : PEA showed anti-cancer activity against SCC 25 cells via apoptosis. PEA may potentially contribute to human oral cancer treatment.

• Sleep Medicine and Psychophysiology
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• v.15 no.2
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• pp.82-86
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• 2008

Objectives: Obstructive sleep apnea syndrome (OSAS) not only causes respiratory disturbances during sleep but also decreases the quality of nocturnal sleep through sleep fragmentation and sleep structure change. We aimed at comparing the changes in sleep fragmentation and structure between baseline (diagnostic) nocturnal polysomnography (NPSG) and nCPAP (nasal continuous positive airway pressure) titration trial. Methods: One hundred and three patients with a baseline night of respiratory disturbance index (RDI) of 5 or greater and reduced RDI score during nCPAP titration night were retrospectively selected for the study. Sleep fragementation and sleep structure between baseline NPSG and the NPSG during nCPAP titration were compared. Sleep fragmentation index (SFI) was defined as the total number of awakenings and shifts to stage 1 sleep divided by the total sleep time in hour. SFI and other polysomnographic parameters were statistically compared between the two nights. Results: SFI during baseline NPSG and nCPAP titration nights were $29.0{\pm}13.8$ and $15.2{\pm}8.8$, respectively, indicating a significant SFI decrease during nCPAP titration (t=9.7, p<0.01). SFI showed significant negative correlations with sleep efficiency (r=-0.60, p<0.01) and total sleep time (r=-0.45, p<0.01) and a positive correlation with RDI (r=0.28, p<0.01). Conclusion: Use of nCPAP, even during the titration, significantly decreases sleep fragmentation and improves sleep structure in OSAS patients. We suggest that SFI may be utilized as a measure of assessing OSAS severity and nCPAP efficacy.