• Composites Research
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• v.22 no.6
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• pp.39-44
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• 2009

The effect of exposure times on the aging characteristics of carbon fiber/epoxy composite ring specimen was evaluated using an accelerating aging tester. Combined exposure conditions, such as temperature, moisture, and ultraviolet, were applied up to 3000 hours. Tensile properties and flexural properties including the effect of curvature were evaluated on the specimens subject to various exposure times through a material testing system. Their aging surfaces were observed through a scanning electron microscope. According to the results, tensile modulus was little affected by the exposure times. However, tensile strength, at the early stage of the exposure times, increased due to physical aging and curing reaction, but tensile strength slightly decreased due to degradation as the exposure times increased. The flexural modulus and flexural strength increased at the early stage of the exposure times, but slightly decreased as the exposure times increased. Aging surfaces of the specimens examined using the scanning electron microscope revealed a different morphology in various exposure times and provided useful information for identifying the degradation in mechanical properties of the composite subject to various exposure times.

• Design & Manufacturing
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• v.17 no.3
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.1-12
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• 2017

This paper proposes nominal flexural strength considering strain-hardening effect of HSB600 high performance steel for compact composite I-girders in positive bending. Unlike conventional steels, HSB600 undergoes strain-hardening just after yielding without going through yield plateau. However, because the nominal flexural strength specified in domestic and foreign bridge design specifications has been developed for the conventional steel composite girders, the nominal flexural strength does not appropriately consider the strain-hardening of HSB600. Therefore, plastic moment considering a strain-hardening is proposed so as to consider effect of the strain-hardening of HSB600 on flexural strength and then moment-curvature analysis is performed to a wide range of cross-sections. From results of the analysis, a parameter representing the effect of the strain-hardening on the flexural strength of HSB600 composite girders is proposed. Furthermore, by using this parameter, the nominal flexural strength considering the strain-hardening effect for HSB600 composite I-girders in positive bending is proposed and then evaluated by comparing with the current AASHTO LRFD bridge design specifications.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.138-145
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• 2018

This paper studies the bending behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams focused on the effect of variation in major material design parameters such as tensile strength, elastic modulus of UHPFRC, and rebar ratio. Analytical results show that the variation in the range of ${\pm}20%$ in the tensile strength of UHPFRC causes the significant difference in ${\pm}8{\sim}9%$ of bending strength compared to the reference condition. The variation of elastic modulus in UHPFRC rarely causes the effect on the bending strength of the UHPFRC section, whereas causes the difference in the slopes of moment-curvature curves, indicating different bending stiffness of UHPFRC sections. For the rebar with yield strength of 400MPa, the bending strength of SC120f is increased by 30, 67, and 99% when the rebar ratio is 1.0, 1.5, and 20%, respectively, compared to the rebar ratio of 0.5%. Therefore, it is observed that the variation of rebar ratio significantly affects the difference in bending strength of UHPFRC beams. However, as the compressive strength of UHPFRC becomes greater, the effect of rebar ratio on the increase of bending strength is decreased.

• Journal of Acupuncture Research
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• v.23 no.3
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• pp.207-214
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• 2006

Objectives : This study is designed in order to evaluate the therapeutic effect of Scalp Acupuncture and Do-ma Acupuncture related with Governer Vessel(Dok) and Bladder Meridian(Chok-taeyang) on acute low back pain Methods : We investigated 30 patients suffering from acute low back pain were admitted to Dunsan O.M.hospital from March. 1st 2005 to December. 30th 2005. We divided into two groups: one group was treated with Scalp acupunture, another group was treated with common acupuncture. 30 patients, were diagnosed only straightened curvature on lateral view of lumbar spine X -ray. Scalp acupunture related with Governer Vessel(Dok) and Bladder Meridian(Chok-taeyang) and Do-ma acupuncture. To estimate the efficacy of treatment that applied for two groups, we compared the visual analog scale(VAS), Oswestry disabiliby index(ODI) and Straight Leg Raising Test(SLRT) score of two groups statistically. Results : Both Scalp acupuncture related with Governer Vessel(Dok) and Bladder Meridian (Chok-taeyang) and Do-ma acupuncture therapy showed good effect on acute low back pain. It was proved by the difference between VAS, ODI and SLRT score checked before treatment and what checked after treatment on each groups. Conclusion: The therapeutic effect of Scalp Acupuncture and Do-ma Acupuncture on acute low back pain can be recommended as a useful therapy to treat acute low back pain.

• Journal of Life Science
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• v.17 no.7 s.87
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• pp.990-995
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• 2007

We tested the effect of sodium tungstate, which disturbs the molybdenum cofactor formation, on the activities of aldehyde oxidase(AO) and the growth of maize(Zea mays) primary roots. As reported in other plants, sodium tungstate inhibited AO also in the maize root concentration-dependently. The inhibitory effect of sodium tungstate was observed only when the inhibitor was applied to the living plants. Application of tungstate to the extracted protein did not show any effect. Western analysis revealed slightly decreased level of AO protein in the presence of tungstate, indicating a positive feedback of gene regulation by the product. We also tested the effects of tungstate on the root growth. The elongation of primary root and the development of lateral roots, which are sensitive to the absolute level of auxin, were decreased in the presence of sodium tungstate. However, the gravitropic curvature of the primary root, which is dependent on the relative amount of auxin at both sides, was unaffected. These data suggested the decrease of auxin biosynthesis by the application of tungstate. However, the level of free IAA was unaffected by tungstate application. We discuss the possible explanations for the observed results.

• Journal of Korean Medicine Rehabilitation
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• v.19 no.1
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• pp.113-124
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• 2009

Objectives : The aim of this study was to observe the effect of Bong Chuna manual therapy(BCMT) and acupuncture on the Turtle Neck Syndrome(TNS) by the changes of radiological findings and symptoms. Methods : Total twenty-eight patients diagnosed as TNS were evaluated. Twenty patients in experimental group were treated by the combination of BCMT and acupuncture, eight patients in control group were treated by acupuncture only. We measured VAS(Visual analogue scale) as pain intensity and Neck Pain and Disability Scale(NDI) at pre- and post-treatment. Also the four line Cobb's method and Jochumsen method were assessed for evaluating the radiographical changes, additionally we used 'two line method'. Results : VAS score showed statistically significant reduction in pain intensity in both experimental group and control group after 8 weeks treatment, $-44.05{\pm}14.91$ vs $-23.75{\pm}14.08$ respectively. Also NDI score presented $-11.40{\pm}8.63$ reduction in experimental group, and it was significant statistically, however not in control group, $-8.63{\pm}9.84$ reduction after 8weeks treatment. In radiological findings, the four line Cobb's method, Jochumsen method and two line method were reduced after 8weeks treatment, $-9.30{\pm}10.33$, $-0.65{\pm}1.72$ and $-14.35{\pm}5.68$ in experimental group respectively, $-0.75{\pm}1.91$, $-0.25{\pm}0.71$ and $0.38{\pm}2.20$ in control group respectively. However they were statistical significance only in the four line Cobb's method and two line method in both group. Conclusions : Combination treatment of CMT and acupuncture showed better effect on pain reduction, VAS score and the correction of neck anteversion than acupuncture only in TNS. Two line method seems valuable for evaluating the improvement of radiographical changes in TNS.

• Journal of the Korean GEO-environmental Society
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• v.16 no.9
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• pp.43-51
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• 2015

In this paper, a 3D shell-spring model that can perform time history analysis of buried pipelines is used to evaluate the effect of the incident direction of the earthquake motion. When applying harmonic motions, it is shown that the period of vibration has pronounced influence on the response of buried pipelines. With decrease in the period, the curvature of the pipeline and corresponding response are shown to increase. To evaluate the effect of the incident angle, the motions are applied in the direction of the pipleline, horizontal, and vertical planes. When the motion is applied parallel to the direction of the pipeline, it only induces bending strains and therefore, the response is the lowest. Under motions subjected in horizontal and vertical planes at an angle of $45^{\circ}$ from the longitudinal axis of the buried pipeline, the axial deformation is shown to contribute greatly to the response of the pipelines. When imposing two-components simultaneously, the calculated response is similar to the case where only single-component is imposed. It is because one component only induces bending strain, resulting in very small increase in the response. The trend of the response is shown to be quite similar for recorded motions. Therefore, it is concluded that use of a single-component is sufficient for estimation of the longitudinal response of buried pipelines.

• Journal of Acupuncture Research
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• v.18 no.6
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• pp.1-13
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• 2001

Objective : To broaden understanding about relationship between Meridian Tendino-musculature and muscles in a lumbar area and to evaluate the effect of Meridian Tendino-musculature acupuncture and release therapy on acute lumbar sprain. Materials and Methods : From Oct. 1st, 2000 to Mar. 31th, 2001, 692 outpatient's chart of Kyung Won University Hospital were reviewed. Out of them, 39 outpatients were selected. they had low back pain, were diagnosed with acute lumbar sprain, showed only straightened curvature on lateral view of lumbar spine X-ray and get the Tendino-musculature acupuncture and release therapy. Results : 1. On patients' first visit, 72% had GrIII and Gr.IV predominantly. 2. Major muscles related with low back pain were divided into two groups. One was Quadratus lumborum group and the other was Rectus abdominis group. In the correlation with Meridian Tendino-musculature, the former was mainly related with Chok-taeyang(B) and slightly related with Chok-soyang(G), Chok-taeum(SP), the latter was mainly related with Chok-taeyum(SP), Chok-yangmyong(S) and slightly related with Chok-taeyang(B), Chok-soyang(G). 3. In the evaluation of treatment effect, Exellent was 27(69%), Good was 10(6%), Fair was 2(5%) and Bad was 0(0%). Fair rate reached 100% eventually. 4. Most of Gr.Ⅲ, Gr.Ⅳ patients who had severe conditions that almost every R.O.M. was limited and Milgram test positive was shown on the physical examination, were fully recovered and lived normal daily life without admission by Meridian Tendino-musculature acupuncture and release therapy within 3 to 5, 4 to 7 days, respectively, since they had started to get their outpatient treatment. 5. Two patients was troubled with pain induced, by twitching response and acupuncure stimuli, which lasted around acupunctured muscle for about a day after treatment, so they coudn't endure the pain and quitted treatment in spite of Fair condition. conclusion : Meridian Tendino-musculature acupuncture and release therapy was found to be helpful to patients who wish to recover from their back pain induced by acute lumbar sprain as soon as possible, but the treatment actually had some problems to be overcome such as pain during or after the treatment. therefor, in order to make this treatment method more available, we should pay more attention to improving treatment appliance and acupuncture technique.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.103-110
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• 2022

The purpose of this study is to experimentally evaluate the stiffness and strength reduction according to the reinforcing bar details of the vertically divided reinforced concrete shear walls. To confirm the effect of reducing strength and stiffness according to vertical division, four real-scale specimens were fabricated and repeated lateral loading tests were performed. As a result of the experiment, it was confirmed that the strength and stiffness were decreased according to the vertical division. In particular, as the stiffness reduction rate is greater than the strength reduction rate, it is expected that safety against extreme strength can be secured when the load is redistributed according to vertical division. As a result of checking the crack pattern, a diagonal crack occurred in the wall subjected to compression control among the divided walls. It was confirmed that two neutral axes occurred after division, and the reversed strain distribution appeared in the upper part, showing the double curvature pattern. In future studies, it is necessary to evaluate the stiffness reduction rate considering the effective height of the wall, to evaluate additional variables such as wall aspect ratio, and to conduct analytical studies on various walls using finite element analysis.