• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1369-1375
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• 2007

The recent, a large capacity of telecommunication networks is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of internet, Video of internet protocol(VoIP), Audio/Video streaming. As a result, DWDM(Dense Wavelength Division Multiplexing)technologies are emerging to be a prevailing the method of solving it without additional optical fiber network building and high-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. When a separation distance of fiber and slab was $3{\mu}m$, The optical filter proposed as the simulation result was satisfied with a DWDM filter characteristic with FWHM of 0.1nm on TM mode and TE mode as 32nm polarization independence in a communication window of $1.3{\mu}m$ when center wavelength was each ${\lambda}_0=1.274755{\mu}m$ and ${\lambda}_0=1.30591{\mu}m$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.102-109
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• 2010

This paper investigates the bond behavior of reinforced concrete beams having high-strength transverse reinforcement. A total of four reinforced concrete beams were tested in this study to estimate the bond capacity of the proposed U-shape reinforcement. The proposed U-shape reinforcement not only has a simple structure to install, but also can increase the bond capacity of reinforced concrete beams by controling bond cracks. This study follow the test method proposed by Ichinose to obtain the bond stress and the bond slip of the specimens. The main test parameters were the yield strength, ratio, and reinforcing types of transverse reinforcements. It was found that the proposed U-shape reinforcement was able to effectively improve the bond performance of reinforced concrete beams with high-strength transverse reinforcement.

• Fire Science and Engineering
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• v.24 no.1
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• pp.40-45
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• 2010

Asymmetric Slimflor Beam had been unveiled with Thor beam (Hat beam) in Sweden since the late 1970s and had been developed by British Steen and SCI. In the major advanced countries in Europe after the early 1990s have interested in and developed this method, it has been concrened as the absence of hot-rolled section steel in the United Kingdom and welded of asymmetric section steel in Finland in the 2000s. It can be increase total floor area about 10%, save the interior and exterior materials, reduce the waste through reduction of the floor height. And it has more excellent fire resistance performance because less exposed than a regular composite steel beam in fire. This study is purpose that, a fire resistance performance of the Asymmetric Slimflor Beam in fire, it compared the temperature range with deflection of structure by fire behavior and load ratio of structure through change the shape of the steel cross-section in standard fire condition.

• Structural Engineering and Mechanics
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• v.67 no.2
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• pp.207-217
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• 2018

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and overloading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1359-1366
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• 2007

The recent, a large capacity of communication is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of Video of internet protocol(VoIP), Audio/Video steaming. DWDM(Dense Wavelength Division Multiplexing) technique has been emerged as the method of solving it without additional optical fiber network building and hish-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. The optical filter proposed as the simulation result satisfies DWDM filter characteristic; 1) when the separation distance between fiber and slab is $4.15{\mu}m$ at the communication window of $1.5{\mu}m$, the polarization independence is 65nm, 2) when the center wavelengths about TM mode and TE mode are each ${\lambda}_0=1.54946\;{\mu}m$ and ${\lambda}_0=1.6144\;{\mu}m$ and, FWHM(Full at Half Maximun) is 0.1nm.

• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.269-282
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• 2015

Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.73-79
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• 2018

In the west coast, south coast, and river basin, the use of geotextile mats has been increasing to improve the soft ground for making industrial facilities space and farmland. As an initial step to improve the vast and soft ground, the geotextile mats are laid and bonded to increase the bearing capacity of the wide ground for supporting construction equipment. Seam strength of geotextile mats exert a force only about 50% of the tensile strength of the fabric, which causes problems such as uplift and sinking in the soft ground. In this study, various types of geosynthetic matting techniques were investigated and the tensile strength of each method was compared and analyzed. Numerical analysis shows that stress increment in the ground due to the overburden load decreases when the seam strength of the geosynthetics mats is increased. When the seam strength was increased to 60, 70 and 80%, the bearing capacity of ground by geotextile mat was increased.

• Journal of Hydrogen and New Energy
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• v.32 no.6
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• pp.565-572
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• 2021

Hydrogen is currently produced from natural gas reforming or industrial process of by-product over than 90%. Additionally, there are green hydrogens based on renewable energy generation, but the import of green hydrogen from other countries is being considered due to the output variability depending on the weather and climate. Due to low density of hydrogen, it is difficult to storage and import hydrogen of large capacity. For improving low density issue of hydrogen, the gaseous hydrogen is liquefied and stored in cryogenic tank. Density of hydrogen increase from 0.081 kg/m³ to 71 kg/m3 when gaseous hydrogen transfer to liquid hydrogen. Density of liquid hydrogen is higher about 800 times than gaseous. However, since density and boiling point of liquid hydrogen is too lower than liquefied natural gas approximately 1/6 and 90 K, to store liquid hydrogen for long-term is very difficult too. To overcome this weakness, this paper introduces storage method of hydrogen based on liquid/solid (slush) and facilities for producing slush hydrogen to improve low density issue of hydrogen. Slush hydrogen is higher density and heat capacity than liquid hydrogen, can be expected to improve these issues.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.2
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• pp.169-176
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• 2022

Purpose : The purpose of this study is to investigate the effect of squat, bracing and aerobic exercise on lung function, which is known to be effective for strength training, on lung function. Methods : The study was conducted with 33 students from Busan K university. Eleven students were assigned to squats, bracing, and aerobic exercise, six weeks three times a week. In order to measure lung activity, pony Fx manufactured the change amount of FVC (forced vital capacity), FEV₁ (Forced expiratory volume at one second), and FEV₁/FVC % (forced vital capacity/forced expiratory volume at one second) was analyzed after inputting the information of experimental group A and B controls. As a method of measurement, the difference between the three groups was analyzed using repeated ANOVA. Results : As a result of analyzing the effects of squat, bracing, and aerobic exercise for 6 weeks, all values of FVC, FEV₁, FEV₁/FVC % were increased from 0 weeks to 6 weeks except FEV₁/FVC %. There was no significant difference in FVC from week 3 to week 6. In the squat, bracing, and aerobic exercise, the changes in spirometry showed that the FVC, FEV₁, and FEV₁/FVC % values in bracing exercise were significantly increased with time than before exercise. As a result of analyzing the changes in the spirometry of squat, bracing, and aerobic exercise, the FVC, FEV₁, FEV₁/FVC % values in the squat exercise showed statistically significant difference according to the period, but the lowest increase among the three groups. Conclusion : In conclusion, aerobic, bracing and squat exercises all had a significant impact on improving lung function. Therefore, even without aerobic exercise, squat or bracing exercise alone can be expected to improve lung function.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.1071-1081
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• 2022

As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.