• Corrosion Science and Technology
• /
• v.8 no.6
• /
• pp.243-250
• /
• 2009

When a steel sheet pipe applied to marine environment, an anti-corrosive coating should be treated to obtain long-term life-time for steels, especially, splash zone. Although anti-corrosive property of coatings is required to be tested in real marine environment, it is difficult because of long test time such as 20 years or more time. Therefore, we used cyclic corrosion tester in a laboratory, which has similar conditions with salt-dry-wet process such as real marine environment. Anti-corrosive properties of the coatings and two steels were tested their anti-corrosive properties under cyclic corrosion test conditions(KS D ISO 14993) and the results were compared with estimate life-time in real marine environment. According to cyclic corrosion test, accelerated corrosive factor of each anti-corrosive coating was investigated accelerated corrosive factor from impedance with EIS method. Accelerated corrosive factor of type SS400 carbon steel and A690 was also investigated their accelerated corrosive factor from the regression curves of weigh loss results. One of the anti-corrosive coatings showed about 50 years life-time compared with standard sample life-time. Carbon steel SS400 showed from 0.1 mm/yr to 0.06 mm/yr as its corrosion rate.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.1
• /
• pp.472-477
• /
• 2017

In this work, the current limiting and recovery characteristics of a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils were effectively improved by adding a third winding into the conventional flux-lock type SFCL with series connection of two coils. To confirm the contribution of the third winding to the current limiting and recovery characteristics of this type of the SFCL, short-circuit testing was carried out with consideration of the third winding, and the effect of the third winding on the current limiting and recovery characteristics was examined by comparative analysis of the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising the SFCL. Through the analysis of both the limiting impedance and the operational current as the main design parameter of the SFCL, the improved current limiting and recovery characteristics of the flux-lock type SFCL using the third winding could be verified.

• Journal of Korean Medicine for Obesity Research
• /
• v.9 no.1
• /
• pp.53-58
• /
• 2009

Objectives The purpose of this study was to investigate the clinical effect of oriental medical therapy on obesity and the progress of weight loss through an oriental obesity program. Methods The subjects were treated from January 2008 to February 2009 in J Korean Medical Hospital. Herbal medical Hospital. Herbal medicine, electrolipolysis, auricular acupuncture were performed during the treatment period. We checked the change of weight every treatment time and measured the body composition by bioelectrical impedance analysis(BIA) every 2 weeks. Results The progress of weight loss was steady in the first 4 weeks except for the sixth weight check. After 4 weeks treatment, the weight loss was 3.52${\pm}$1.98Kg and 4.83${\pm}$2.68%. Total fat mass measured by BIA significantly decreased 2.58${\pm}$1.30Kg after 4 weeks. Age and the weight loss were significantly negative correlated. Conclusions Oriental obesity treatment could be effective on obesity, but further studies would be needed for the foundation of a clinical guideline reflecting various factors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.2
• /
• pp.134-139
• /
• 2013

When the accident occurred in power distribution system, it needs to control efficiently the fault current according to the fault angle and location. The flux-lock type superconducting fault current limiters (SFCL) can quickly limit when the short circuit accidents occurred and be made the resistance after the fault current. The flux-lock type SFCL has a single triggering element, detects and limits the fault current at the same time regardless of the size of the fault current. However, it has a disadvantage that broken the superconductor element. If the flux-lock type SFCL has separated structure of the triggering element and the limiting element, when large fault current occurs, it can reduce the burden of power and control fault current to adjust impedance. In this paper, this system is composed by triggering element and limiting element to analyze operation of limiting current. When the fault current occurs, we analyzed the limiting and operating current characteristics of the two triggering current level, and the compensation characteristics of bus-voltage sag according to the fault angle and location.

• Computational Structural Engineering : An International Journal
• /
• v.2 no.1
• /
• pp.33-42
• /
• 2002

A computationally efficient stiffness design method for building structures is proposed in which dynamic soil-structure interaction based on the wave-propagation theory is taken into account. A sway-rocking shear building model with appropriate ground impedances derived from the cone models due to Meek and Wolf (1994) is used as a simplified design model. Two representative models, i.e. a structure on a homogeneous half-space ground and a structure on a soil layer on rigid rock, are considered. Super-structure stiffness satisfying a desired stiffness performance condition are determined via an inverse problem formulation for a prescribed ground-surface response spectrum. It is shown through a simple yet reasonably accurate model that the ground conditions, e.g. homogeneous half-space or soil layer on rigid rock (frequency-dependence of impedance functions), ground properties (shear wave velocity), depth of surface ground, have extensive influence on the super-structure design.

• Journal of the Korean Wood Science and Technology
• /
• v.48 no.5
• /
• pp.631-640
• /
• 2020

In this study, the effect of specimen size and layer thickness on the sound absorption of the leaves of two evergreen broad-leaved tree species, Dendropanax morbiferus and Fatsia japonica, was investigated. The specimen sizes of 0.5 × 0.5, 1.0 × 1.0, and 2.0 × 2.0 ㎠ and layer thicknesses of 1.00, 1.75, and 2.50 cm were considered. At the layer thickness of 2.5 cm, the leaf of the D. morbiferus showed no significant difference in sound absorption coefficients (SACs) as the sample size varied, however, a significant change in SACs was recorded in that of the F. japonica. At 1.0-cm thickness, the SACs of the F. japonica leaf varied more remarkably with the sample size. The 2.50-cm-thick F. japonica leaf with the specimen size 0.5 × 0.5 ㎠ exhibited the highest sound absorption effect among all samples investigated.

• Geomechanics and Engineering
• /
• v.29 no.1
• /
• pp.53-63
• /
• 2022

Simplified analytical solutions are developed for the dynamic analyses of an axially loaded pile foundation embedded in a transverse-isotropic, fluid-filled, poro-visco-elastic soil with rigid substratum. The pile is modeled as a viscoelastic Rayleigh-Love rod, while the surrounding soil is regarded as a transversely isotropic, liquid-saturated, viscoelastic, porous medium of which the mechanical behavior is represented by the Boer's poroelastic media model and the fractional derivative model. Upon the separation of variables, the frequency-domain responses for the impedance function of the pile top, and the vertical displacement and the axial force along the pile shaft are gained. Then by virtue of the convolution theorem and the inverse Fourier transform, the time-domain velocity response of the pile head is derived. The presented solutions are validated, compared to the existing solution, the finite element model (FEM) results, and the field test data. Parametric analyses are made to show the effect of the soil anisotropy and the excitation frequency on the pile-soil dynamic responses.

• Earthquakes and Structures
• /
• v.14 no.5
• /
• pp.411-424
• /
• 2018

This study explores the inelastic behavior of systems with flexible base. The use of a single degree of freedom system (ESDOF) with equivalent ductility to represent the response of flexible base systems is discussed. Two different equations to compute equivalent ductility are proposed, one which includes the contribution of rigid body components, and other based on the overstrength of the structure. In order to asses the accuracy of ESDOF approach with the proposed equations, the behavior of a 10-story regular building with reinforced concrete (RC) moment resisting frames is studied. Local and global ductility capacity and demands are used to study the modifications introduced by base flexibility. Three soil types are considered with shear wave velocities of 70, 100 and 250 m/s. Soil-foundation stiffness is included with a set of springs on the base (impedance functions). Capacity curves of the building are computed with pushover analysis. In addition, non linear time history analysis are used to asses the ductility demands. Results show that ductility capacity of the soil-structure system including rigid body components is reduced. Base flexibility does not modify neither yield and maximum base shear. Equivalent ductility estimated with the proposed equations is fits better the results of the numerical model than the one considering elastoplastic behavior. Modification of beams ductility demand due to base flexibility are not constant within the structure. Some elements experience reduced ductility demands while other elements experience increments when flexible base is considered. Soil structure interaction produces changes in the relation between yield strength reduction factor and structure ductility demand. These changes are dependent on the spectral shape and the period of the system with fixed and flexible base.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.16 no.3
• /
• pp.1-12
• /
• 2012

In this study, an analysis method for the earthquake response of an offshore wind turbine model is developed, considering the effects of the fluid-structure-soil interaction. The turbine is modeled as a tower with a lumped mass at the top of it. The tower is idealized as a tubular cantilever founded on flexible seabed. Substructure and Rayleigh-Ritz methods are used to derive the governing equation of a coupled structure-fluid-soil system incorporating interactions between the tower and sea water and between the foundation and the flexible seabed. The sea water is assumed to be a compressible but non-viscous ideal fluid. The impedance functions of a rigid footing in water-saturated soil strata are obtained from the Thin-Layer Method (TLM) and combined with the superstructure model. The developed method is applied to the earthquake response analysis of an offshore wind turbine model. The method is verified by comparing the results with reference solutions. The effects of several factors, such as the flexibility of the tower, the depth of the sea water, and the stiffness of the soil, are examined and discussed. The relative significance of the fluid-structure interaction over the soil-structure interaction is evaluated and vice versa.

• Journal of The Korean Society of Integrative Medicine
• /
• v.10 no.2
• /
• pp.37-47
• /
• 2022

Purpose : We aimed to investigate the effects of nutritional foods on sarcopenia prevention and physical function among the elderly living in rural communities during the COVID-19 pandemic by providing customized nutrition. Methods : This study was conducted in the rural community of SCC. Participants (n=24, over age 65) were randomly assigned into a Protein group (n=12) and a Vitamin group (n=12). The protein group was given 23 g/d of protein (whey, soybean, BCAA) for 8 weeks and the Vitamin group 23 g/d of vitamin (B, C, D, E and mixed minerals such as calcium, magnesium, zinc) for 8 weeks. All participants had their body composition such as height, weight, skeletal muscle mass, body mass index, and body fat percentage, measured using bioelectrical impedance analysis (BIA) and physical function assessed using grip strength and the short physical performance battery (SPPB). Results : At the end of the intervention, there was a significant increase in skeletal muscle mass (p<.01) in the Protein group (p=.002, 4.92 %) compared to the baseline: it increased by 2.33 %. The Vitamin group had a significant increase in body fat percentage after the intervention (p=.001, 15.35 %) compared to the baseline: body fat percentage decreased by 4.49 %. There were no significant differences in left and right Grip strength/Weight, SPPB, 4-m gait speed, chair stand test, and sense of balance in both groups. Conclusion : The findings from this study suggest that 8 weeks of protein intake have a significant effect on skeletal muscle mass and body fat percentage. Protein intake helped promoting the health of the elderly in rural community during the COVID-19 pandemic. It will assist creating a foundation for providing customized nutrition for the elderly in rural community in the future.