• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.2
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• pp.197-203
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• 2014

In this paper, the effect of unsteady radiation on the horizontal fin of an external fuel tank by flame of a flying flare was analysed to see the temperature increase of the fin and the thermal impact on the fin. Radiation between two surfaces was calculated using the concept of radiation resistance of surface and space including radiation, irradiation and shape factor for two flying trajectories of a flare, maximum temperature of 2200 K, emissivity of 0.95, flying velocity of 30 m/s, and thermal surface area of $0.01m^2$. The result shows that the temperature increase of the fin is 0.236 K, and the thermal effect on the fin is ignorable. And it was found that temperature is increased a little because small amount of heat energy can be radiated due to the short exposure time to the heat source.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.1-6
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• 2010

River crossing pipelines have been being operated with buried depth of 1.2~4m underneath river bottom to prevent buoyance and external impact. River crossing pipelines have to show resistance to soil load and hydrostatic pressure. In this study, structural integrity of the river crossing pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. Hoop stress increased with increasing buried depth under identical water height in case of without concrete encasement, however, hoop stress decreased with increasing water height under identical buried depth.

• Journal of the Korean Wood Science and Technology
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• v.41 no.2
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• pp.123-133
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• 2013

This paper presents experimental and numerical tests on a recently developed timber column concealed base joint. This joint was designed to replace the wood-wood connection found in the post-and-beam structure of Hanok, the traditional Korean timber house. The use of metallic connectors provides an increased ductility and energy dissipation for a better performance under reversed loading, especially seismic. In this study, we investigate the performance of the joint under pseudo-static reversed cyclic moment loading through the study of its ductility and energy dissipation. We first perform experimental tests. Results show that the failure occurs in the metallic connector itself because of stress concentrations, while no brittle fracture of wood occur. Subsequent numerical simulations using a refined finite element model confirm these conclusions. Then, using a practical modification of the joint configuration with limited visual impact, we improve the ductility and energy dissipation of the joint while retaining a same level of rotational strength as the originally designed configuration. We conclude that the joint has a satisfying behavior under reversed moment loading for use in earthquake resistant timber structure in low to moderate seismicity areas like Korea.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.275-278
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it finds use in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. In order to design optimal structural parts made of INCONEL 718, accurate understanding of material's mechanical properties, dynamic behavior and fracture characteristic as a function of strain rates are required. This paper concerned with the dynamic material properties of the INCONEL 718 for the various strain rates. The dynamic response of the INCONEL 718 at intermediate strain rate is obtained from the high speed tensile test machine test and at the high strain rate is from the split Hopkinson pressure bar test. Based on the experimental results, the effects of strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure are evaluated. Experimental results from both quasi-static and high strain rate up to the 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of INCONEL 718.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.399-406
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• 2005

Alloy 625 is used widely in industrial applications such as aeronautical aerospace, chemical, petrochemical and marine applications. Because of a good combination of yield strength. tensile strength, creep strength, excellent fabricability, weldability and good resistance to high temperature corrosion on prolonged exposure to aggressive environments. High qualify weldments for this material are readily produced by commonly used processes. But all of processes are not applicable to this material by reason of unavailability of matching, position or suitable welding filler metals and fluxes may limit the choice of welding processes. Recently, the flux cored wire is developed and applied for the better productivity in several welding position including the vortical position. In this study. the weldability and weldment characteristics of Alloy 625 are evaluated in FCAW weld associated with the several shielding gases($80\%Ar+20\%\;CO_2,\;50\%Ar+50\%\;CO_2.\;100\%\;CO_2$) in viewpoint of welding productivity. The results of the experimental study on corrosive characteristics of Alloy 625 are as follows; There is no remarkable difference among shielding gases. however they has a striking difference among corrosive solutions by results of distinguished density and time of corrosive solution. Generally, the shielding gases($80\%Ar+20\%\;CO_2$) was superior to the other gases on high temperature tensile and a low temperature impact. but all of the shield gases were making satisfactory results on corrosion test.

• The Journal of Internal Korean Medicine
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• v.37 no.4
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• pp.579-590
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• 2016

Objectives: This study aimed to investigate the impact of Ephedra sinica pharmacopuncture on the weight and lipid metabolism of obese mice.Methods: Obesity was induced in male C57BL/6 mice by a 60% fat diet. The animals were divided into three groups (n=5) fed a normal diet, high-fat diet, and high-fat diet with Ephedra sinica pharmacopuncture. After 13 wk, fasting blood sugar levels were measured in each group, and oral glucose tolerance tests were conducted. After 15 wk, body weight, epididymal fat pad weight, subcutaneous fat pad weight, and serum lipid and gene expression of hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL), monoacylglycerol lipase (MGL), perilipin, and peroxisome proliferator-activated receptor (PPAR)-γ were measured in each group.Results: In the Ephedra group, body weight, fasting blood sugar, and oral glucose tolerance were significantly decreased. In addition, in the Ephedra group, the gene expression of HSL was significantly increased, whereas that of perilipin was significantly decreased.Conclusions: These results provide evidence that E. sinicapharmacopuncture affects obesity and obesity-induced metabolic syndrome, including insulin resistance and dyslipidemia, by activating lipolysis via the HSL pathway in adipose tissue.

• Journal of muscle and joint health
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• v.15 no.1
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• pp.5-23
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• 2008

Purpose: This study aims to conduct a systematic review of the physical, psychosocial and physiological effects of Tai Chi exercise in elderly. Method: 37 articles from Medline search of foreign journals (1966-2006) were surveyed by the key words 'Tai Chi', 'Tai-chi program' and 'Tai-chi and elderly' limiting the range to age 65 or older, choosing clinical trial and randomized controlled trial research in English articles. Four articles were excluded due to methodological study, pilot study and review. The research was analyzed according to health status of the subjects, styles and forms of Tai Chi exercises, factors for physical, psychosocial and physiological measures. Result: A short forming Yang style was commonly used in chronic diseases and health for elderly. Variable outcome measures were used in Tai Chi studies relating to balance, muscle strength, walking and mobility, flexibility and cardiorespiratory function in physical measure, quality of life, depression, self-efficacy, health status, cognition and impact questionnaire in psychosocial measure, lipids, insulin resistance and hormone in physiological measure. Conclusion: Tai Chi exercise appears to have physical and psychosocial benefits and also appears to be safe for elderly and chronic diseases. It is suggested that future studies analyze statistical part of systematic reviews through meta analysis.

• Journal of Surface Science and Engineering
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• v.49 no.4
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• pp.389-394
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• 2016

The operation method of nuclear power plants is currently changing to high burn-up and long period that can enhance economics and efficiency of the plant. Since nuclear plant operation environment has been becoming severe, the amount of absorbed hydrogen also has increased. Absorbed hydrogen can be fatal securing safety of nuclear fuel cladding in case of Loss of Coolant Accidents(LOCA). In order to examine the impact of hydride on high-temperature oxidation, high-temperature oxidation experiment was performed on normal Zry-4 cladding and on Zry-4 cladding where hydrogen is charged in air pressure steam atmosphere under the $950^{\circ}C$ and $1000^{\circ}C$. According to the results, while oxidation acceleration due to charged hydrogen was not observed prior to breakaway oxidation creation, oxidation began to accelerate in cladding where hydrogens charged as soon as the breakaway oxidation started. If so much hydrogen are charged in the cladding, equiaxial monoclinic phase to unstable of stress is formed and it is presumed that oxidation is accelerated because nearby stress caused a crack in equiaxial phase, and that makes corrosion resistance decline sharply.

• Journal of International Academy of Physical Therapy Research
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• v.10 no.2
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• pp.1785-1790
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• 2019

Background: Lumbar disc herniation (LDH) causes neurological symptoms by compression of the dura mater and nerve roots. Due to the changed in proprioception inputs that can result in abnormal postural pattern, delayed reaction time, and changed in deep tendon reflex. Objective: To investigate the effects of lumbar stabilization exercises on motor neuron excitability and neurological symptoms in patients with LDH. Design: Randomized Controlled Trial (single blind) Methods: Thirty patients with LDH were recruited; they were randomly divided into the balance center stabilization resistance exercise group (n=15) and the Nordic walking group (n=15). Each group underwent their corresponding 20-minute intervention once a day, four times a week, for four weeks. Participants' motor neuron excitability and low back pain were assessed before and after the four-week intervention. Results: There were significant differences in all variables within each group (p<.05). There were significant differences between the experimental and control groups in the changes of upper motor neuron excitability and pain (p<.05), but not in the changes of lower motor neuron excitability and Korean Oswestry Disability Index. Conclusion: Lumbar stabilization exercises utilizing concurrent contraction of deep and superficial muscles improved low back function in patients with LDH by lowering upper motor neuron excitability than compared to exercises actively moving the limbs. Lumbar stabilization exercises without pain have a positive impact on improving motor neuron excitability.