• Journal of The Korean Society of Integrative Medicine
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• v.8 no.4
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• pp.133-142
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• 2020

Purpose : The purpose of this study was to investigate the effective recovery method of exercise-induced fatigue and muscle pain by comparing the effect of the use of illite hot mat product and general hot mat product on the recovery of muscle pain induced by high intensity exercise. Methods : To measure and analyze the changes in lactic acid, CRP, and ACR according to the high-intensity circuit training program, this study was conducted for the healthy adult men and women, who exercise st the K-region sports center. A total of 45 subjects were studied in 15 groups of 15 patients who received an illite hot-water mat recovery group (A group), 15 general hot-water mat recovery group (B group), and 15 control group (C group). The circuit training exercise program was conducted as a one-time exercise, and each exercise time consisted of 30 minutes of warm-up exercise, 5 minutes of main exercise, 20 minutes of clean-up exercise, and 5 minutes of strength exercise. The intensity setting was high intensity of subjective exercise intensity It carried out by setting to (14-16RPE). Results : Changes in Lactic Acid Concentration There was a significant difference in the lactic acid concentrations between the groups after the high intensity circuit training program (p <.05). The illite rest group (A) decreased 7.71 mmol / L and the control group decreased 4.03 mmol / L. Significantly decreased (p <.05). Changes in ACR Concentration. There was a significant difference in the ACR concentrations Significant differences were found in CRP and ACR during the recovery period after exercise. (p <.05), the elite rest group (A) decreased 2.47 mg / mmol, and the control group increased 1.63 mg / mmol. There was a significant difference (p <.05). Conclusion: The static rest on a heated mat after high-intensity exercise has an effect on changes in blood lactate and ACR levels.

• Composites Research
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• v.34 no.6
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• pp.380-386
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• 2021

This paper aims to improve the critical speed of power-take-off (PTO) shafts by using carbon fiber reinforced plastics (CFRPs). The PTO shaft was designed with titanium-CFRPs hybrid structure in order to compensate the low shear strength of CFRPs. Based on the requirements for PTO shafts, the dimensions of PTO shafts were determined through a parametric study. To evaluate the performance of the PTO shaft, a vibration test, a static torsion test, and a torsion durability test were performed. In the vibration test, the critical speed of PTO shafts was 20570 rpm, which was 7.5% higher than that of titanium shafts. Additionally, it was confirmed that the maximum allowable torque of the PTO shaft was 2300 N·m. Finally, under repeated load in the range of 11.3 to 113 N·m, the fatigue failure in the PTO shaft did not occur up to 10⁶ cycles.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.262-269
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• 2023

Purpose: In this study,fire-resistance test were executed to evaluate the effectiveness of the fireproof panel attached to the PSC slab in tunnel. Method: For the fire resistance test, the RWS curve was applied and the furnace of the KICT was used. Result: As a result of the experiment, the maximum temperature measured on the concrete surface of the PSC slab with the fireproof panel was 321.8℃, which was lower than the damage limit temperature of 380℃ for concrete. Also, at the t=25mm, the maximum temperature was 35.2℃, which was lower than the damage temperature of steel, 250℃. The use of precast fire resistance panel(t=30mm) improves fire resistance of PSC structures. Conclusion: As a result of the test, a reinforcement method for attached a fireproof panel in case of fire in a tunnel or an underground roadway is provided to protect a structure from fire. In the future, it is necessary to perform the static performance test of the slab to which the fireproof panel is attached, and to confirm the adhesion performance of the fireproof panel by performing the pull-off test and the fatigue test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.399-405
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• 2008

Development of the paved track is required as a low-maintenance of conventional line. The paved tracks are one of the types of the ballast reinforced tracks those are manufactured by adopting the prepacked concrete technique. The main elements of this tracks are large sleeper, low elastic pad, fastener, cement mortar, geotextile and recycled ballast. Low elastic pad is the most effective element of such tracks on the basis of stress-displacement characteristics, dynamic response and fatigue characteristics. The stiffness of the pad determine the stiffness of the track. Consequently, it is more important in case of concrete track structure such as paved track because application of low elastic pad seriously effect the durability and stability of the track. The main objective of this study is to confirm the reduction of train load, which transfer to roadbed through various pad effects. To achieve this task static, numerical analysis and real scale repeated loading test was performed while load reduction effect of low elastic pad was analyzed by using displacement, stress and strain ratio characteristics of the paved track.

• Composites Research
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• v.30 no.2
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• pp.138-144
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• 2017

Damage sensing of polymer composite films consisting of poly(dicyclopentadiene) p-DCPD and carbon nanotube (CNT) was studied experimentally. Only up to 1st ring-opening polymerization occurred with the addition of CNT, which made the modified film electrically conductive, while interfering with polymerization. The interfacial adhesion of composite films with varying CNT concentration was evaluated by measuring the wettability using the static contact angle method. 0.5 wt% CNT/p-DCPD was determined to be the optimal condition via electrical dispersion method and tensile test. Dynamic fatigue test was conducted to evaluate the durability of the films by measuring the change in electrical resistance. For the initial three cycles, the change in electrical resistance pattern was similar to the tensile stress-strain curve. The CNT/p-DCPD film was attached to an epoxy matrix to demonstrate its utilization as a sensor for fracture behavior. At the onset of epoxy fracture, electrical resistance showed a drastic increase, which indicated adhesive fracture between sensor and matrix. It leads to prediction of crack and fracture of matrix.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.87-95
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• 1988

In the arctic offshore regions, massive offshore gravity platforms are recommended to be construced because of severe environments. In such structures which is so large that its characteristic length is of the order of the wave length, wave-structure interaction problem has been solved using linear diffraction theory. Structural analysis of the large scale offshore structures requires wave force distribution along depth and wave pressure distribution on the body surface. In this study, existing computer program which calculates the total wave force acting on axisymmetric bodies has been modified to calculate wave force distribution along depth and wave pressure distribution on the body surface. Numerical results of pressure distribution for a fixed vertical cylinder obtained from this analysis has been compared with the results of an analytic solution of MacCamy-Fuchs, and good agreements has been obtained. It is desirable to use 6 in the case of analytic solution, and 5 in the case of numerical solution as the Fourier Mode of Green function. The results in this study are expected to be utilized for structural analysis such as pseudo-static analysis, dynamic analysis and fatigue analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.702-709
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• 2018

A quick-hardened concrete track was developed to improve the aged ballasted track to a concrete track, and applied to earthworks and tunnels of main and urban railways. Rebars for reinforcement are not generally applied to prestressed concrete sleepers. On the other hand, many cracked sleepers have been observed in railroad sites. A wide sleeper, which is one of the main components of quick-hardened concrete track, should be structurally safe and crack-resistant in a ballasted and concrete track to avoid this problem. In particular, a wide sleeper manufactured by a post-tension method must have reinforcing bars applied to the rail-seat section. In this paper, static tests, dynamic tests, and fatigue tests were carried out to compare the flexural strength and crack resistance performance of a wide sleeper with and without reinforcing bars for a quick-hardened concrete track. As a result of the test, if some reinforcing bars are applied appropriately to the rail-seat section of a wide sleeper, it will be possible to prevent the occurrence of cracks, delay the expansion of the crack width, and the flexural fracture.

• Composites Research
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• v.24 no.1
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• pp.45-50
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• 2011

Transparent and conductive carbon nanotube on polyethylene terephthalate (PET) were prepared by dip-coating method for self-sensing multi-functional nanocomposites. The changes in the electrical and optical properties of CNT coating mainly depended on the number of dip-coating, concentration of CNT solution. Consequently, the surface resistance and transmittance of CNT coating were sensitively controlled by the processing parameters. Surface resistance of CNT coating was measured using four-point method, and surface resistance of coated CNT could be better calculated by using the dual configuration method. Optical transmittance of PET film with CNT coating was evaluated using UV spectrum. Surface properties of coated CNT investigated by wettability test via static and dynamic contact angle measurement were consistent with each other. As dip-coating number increased, surface resistance of coated CNT decreased seriously, whereas the transmittance exhibited little lower due to the thicker CNT networks layer. Interfacial microfailure properties were investigated for CNT and indium tin oxide (ITO) coatings on PET substrates by electrical resistance measurement under cyclic loading fatigue test. CNT with high aspect ratio exhibited no change in surface resistance up to 2000 cyclic loading, whereas ITO with brittle nature showed a linear increase of surface resistance up to 1000 cyclic loading and then exhibited the level-off due to reduced electrical contact points based on occurrence of many micro-cracks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.137-147
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• 2012

In the steel-free bridge concrete deck, steel straps are generally used instead of conventional steel rebar while laterally restrained in the perpendicular direction to the traffic in order fir the arching effect of concrete deck. In this paper, the minimum amount of FRP bar is to be suggested based on the structural strength, crack propagation, stress level and others in order to control cracks. As a result of laboratory tests, the structural strength of deck with 0.15 percentage of steel strap showed improved structural strength including ductility. The long-term serviceability of steel strap deck with FRP bar proved to satisfy the requirements and to be structurally stable while showing the amount of crack and residual vertical displacement within the allowable limits after two million cyclic loadings. The structural failure of RC bridge deck is generally caused from the punching shear rather than moment. Therefore, the ultimate load at failure could be estimated using the shear strength formula in the two-way slab based on ACI and AASHTO criteria. However the design criteria tend to underestimate the shear strength since they don't consider the arching effects and nonlinear fracture in bridge deck with lateral confinement. In this paper, an equation to estimate the punching shear strength of steel strap deck is to be developed considering the actual failure geometries and effect of lateral confinement by strap while the results are verified in accordance with laboratory tests.

• The Journal of Korean Institute of Information Technology
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• v.16 no.11
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• pp.51-59
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• 2018

The Multi-Mission Unmanned Surface Vehicle(MMUSV), which is manufactured using glass Fiber Reinforced Plastic(FRP) material, is designed to perform a surveillance and reconnaissance on the sea. Various navigation sensors, such as RADAR, RIDAR, camera, are mounted on a mast to perform an autonomous navigation. And a dummy gun is mounted on the deck of the MMUSV for a target tracking and disposal. It is necessary to analyze a strength for structures mounted on the deck because the MMUSV performs missions under a severe sea state. In this paper, a strength analysis of the mast structure is performed on static loads and lateral external loads to verify an adequacy of the designed mast through a series of simulations. Based on the results of captive model tests, a strength analysis for a heave motion of the mast structure is conducted using a simulation tool. Also a simulation and fatigue test for a mounting part between the MMUSV and the dummy gun are performed using a specimen. The simulation and test results are represented that a structure of the mast and mounting part of the dummy gun are appropriately designed.he impact amount are performed through simulation and experiments.