• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.66-71
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• 2015

Safety, resilience and comfort of pedestrian were assessed by the British Pendulum Test and SB/GB factor test at 8 kinds of sidewalk pavement. Sidewalk paving materials were normal concrete, porous concrete, concrete block, soil concrete, asphalt, rubber chip/resin mixture, wood chip/resin mixture and floor tile. In addition, a survey was conducted to investigate the perception of pedestrians on the sidewalk paving material. As a result, while the skid resistance value was measured in the most 60BPN above, the floor tile showed a low value of about 30BPN. The ratios of SB factor to GB factor of the elastic pavements(rubber/resin mixture and wood chip/resin mixture) appeared to be relatively large when compared with those of the conventional sidewalks. The survey showed that respondents perceived as more safe and comfortable elastic pavements compared to conventional pavements. Approximately 50% of respondents answered that hardened soil pavement was the most environmentally friendly.

• International Journal of Concrete Structures and Materials
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• v.7 no.3
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• pp.215-223
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• 2013

This study presents the effect of incorporating metakaolin (MK) on the mechanical and durability properties of high strength concrete for a constant water/binder ratio of 0.3.MK mixtures with cement replacement of 5, 10 and 15 % were designed for target strength and slump of 90 MPa and $100{\pm}25mm$. From the results, it was observed that 10 % replacement level was the optimum level in terms of compressive strength. Beyond 10 %replacement levels, the strength was decreased but remained higher than the control mixture. Compressive strength of 106 MPa was achieved at 10 % replacement. Splitting tensile strength and elastic modulus values have also followed the same trend. In durability tests MK concretes have exhibited high resistance compared to control and the resistance increases as the MK percentage increases. This investigation has shown that the local MK has the potential to produce high strength and high performance concretes.

• Journal of Ocean Engineering and Technology
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• v.9 no.1
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• pp.111-119
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• 1995

The elastic-plastic fracture toughness($J_{IC}$) and fracture resistance (J-R curve) of SA508-3 alloy steel used for nuclear reactor pressure vessel are investigated by using CT-type specimens. Fracture toughness tests are conducted by unloading compliance method and multiple specimen method at room temperature, -2$0^{\circ}C$ and 20$0^{\circ}C$. The apparent negative crack growth phenomenon which usually arises in partial unloading compliance test is well known. The negative crack growth phenomenon in determining J sub(IC) or J-R cure from partial unloading compliance experiments may be eliminated by the offset technique. In this study, the evaluation of $J_{IC}$ multiple specimen method recommended by the JSME gives the most reliable results by using half-size CT(similar-type) specimens.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.88-92
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• 2015

In order to study the semi-conductive characteristics of carbon black-filled ethylene-propylene-diene monomer (EPDM) composite film, which is used for measuring occlusal force, composite samples with volume ratios of carbon black to EPDM ranging from 30% to 70% were prepared. The process of making a composite film consists of two steps, which involve the preparation of a slurry composition and the fabrication of a thin film using solution casting and a lamination process. To prepare the slurry composition, we dispersed carbon black nanoparticles into an organic solvent before mixing with an EPDM solution in toluene. The mechanical and electrical properties of the resulting carbon black-filled EPDM film were then investigated, and the results showed that the electrical resistance of a film decreases with the increase in the carbon black content. Furthermore, improved elastic recovery was observed after cross-linking the EPDM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.578-585
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• 2004

Hardness test is performed for determination of the other properties, such as strength, wear resistance and deformation resistance, as well as hardness itself. And it is performed for prediction of residual lifetime by analysis of hardness reduction or hardness ratio. However, hardness test has limitation that observation of residual indent is needed for determination of hardness value, and that is the reason for not to be widely used in industrial field. Therefore, in this study, we performed researches to obtain Brinell hardness value from quantitative numerical formula by analysing relationship between indentation depths from indentation load-depth curve and mechanical properties such as work hardening exponent, yield strength and elastic modulus.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.25-34
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• 2008

A new hybrid oedometer cell is designed and manufactured to investigate a behavior of soft soils by using elastic and electromagnetic waves during consolidation test. Bender elements, which generate and detect shear waves, are placed in the top cap and the bottom plate and mounted on the oedometer wall. Double wedge type electrical resistance probe, which measures local void ratio change, is positioned onto the top cap of the oedometer cell. The bender elements and the electrical resistance probe are anchored into a nylon set screw with epoxy resin. The nylon set screw with epoxy resin minimizes directly transmited elastic waves through the oedometer cell due to impedence mismatch and allows for easy replacement of defected bender elements and electrical resistance probe. Primary consolidation time can be estimated from the slope of electrical resistance versus log time curve and the evolution of shear wave velocity. The shear wave velocity can be used to assess inherent anisotropy when disturbance effects are minimized because particle alignment affects the shear wave velocity. The void ratios evaluated by the electrical resistance probe are similar to those by the settlement during consolidation. This study suggests that the shear wave velocity and the electrical resistance can provide complementary imformations to understand consolidation characteristics such as primary consolidation, anisotropy, and void ratio.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.1
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• pp.7-14
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• 2014

In this study, characteristic of elastic paving materials in bicycle road using polyurethane were studied experimentally. As a results, following their good result was obtained. Bicycle road packaging materials are flexural strength g test, ratio of mass change after freezing and thawing, repulsion elasticity test, water Permeation coefficient test and slip resistance test results showed good performance.

• Journal of Korean Academy of Nursing
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• v.42 no.7
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• pp.947-956
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• 2012

Purpose: To investigate the effect of progressive resistance training (PRT) on body composition, physical fitness, quality of life, lipid and nutritional profile of patients on hemodialysis (HD). Methods: A non equivalent comparison group pretest and posttest design study was used with 40 participants who were randomly assigned to the exercise group (20 participants) and the comparison group (20 participants). The exercise group received PRT for 30 minutes per session, 3 sessions a week, for 12 weeks, while the comparison group received usual care. The PRT consisted of upper and lower body exercises using elastic bands and sandbags. Outcome measures evaluated were: body composition, physical fitness, quality of life, and lipid profile. Results: Skeletal muscle mass, grip, leg muscle strength, and quality of life all improved significantly in the exercise group. Body fat rate, total cholesterol and triglyceride rate decreased significantly in the exercise group. Conclusion: These results suggest that PRT improves body composition, physical fitness, quality of life, and lipid profile of patients on HD. PRT using elastic bands and sandbags can be utilized as part of a regular care plan for these patients.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.4
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• pp.19-30
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• 2002

The stability of slope using root-pile like to the reinforcements is affected by the interaction behavior mechanism of soil-reinforcements. Through the studying on the interaction in joint of its, therefore, the control roles can be find out in installed slope. In study, the stress level ratio based on the insert angle of installed reinforcements in soil used to numerical analysis, which was results from the duty direct shear test in Lab. The maximum shear strain variation on the reinforcements was observed at insert angle, which was approximately similar to the calculated angle based on the equation proposed by the Jewell. The elasto-plastic joint model on the contact area of soil-reinforcements was presumed, the reinforced soil assumed non-linear elastic model and the reinforcements supposed elastic model, respectively. The finite element analysis of assumed models was performed. The shear strain variation of non-reinforced state obtained by the FEM analysis including elasto-plastic joint elements were shown the rationality of general limit equilibrium analysis for the slope failure mode on driving zone and resistance zone, which based on the stress level step according to failure ratio. Through the variation of shear strain for the variation of inserting angle of reinforcements, the different mechanism on the bending and the shear resistance of reinforcements was shown fair possibility.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.737-747
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• 2021

The objective of seismic resilience is to maintain or rapidly restore the function of a building after an earthquake. An efficient tilt mechanism at the member level is crucial for the restoration of the main structure function; however, the damage resistance of the members should be the main focus. In this study, through a comparison with the classical Flamant theory of local loading in the elastic half-space, an elastomechanical solution for the axial-stress distribution of a reinforced-concrete (RC) rocking column was derived. Furthermore, assuming that the lateral displacement of the rocking column is determined by the contact surface rotation angle of the column end and bending and shear deformation of the column body, the load-lateral displacement mechanical model of the RC rocking column was established and validated through a comparison with finite-element simulation results. The axial-compression ratio and column-end strength were analyzed, and the results indicated that on the premise of column damage resistance, simply increasing the axial-compression ratio increases the lateral loading capacity of the column but is ineffective for improving the lateral-displacement capacity. The lateral loading and displacement of the column are significantly improved as the strength of the column end material increases. Therefore, it is feasible to improve the working performance of RC rocking columns via local reinforcement of the column end.