• Structural Engineering and Mechanics
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• v.9 no.5
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• pp.417-432
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• 2000

A comprehensive analytic study has been conducted to investigate the instability problems of metal-plate-connected (MPC) joints in light frame trusses. The primary objective in this study is to determine the governing factors that constitute the buckling of the metal connectors and their effects on the structural response of joints. Another objective is to recommend design curves for the daily structural design of these joints. The numeric data presented in this paper has emerged from a broad base that was founded on over 350 advanced computer simulations, and was supported by available experimental results obtained by others. This basic-to-applied research includes practical engineering parameters such as size of gaps, shear lengths, gauge (plate thickness) of connectors, size of un-braced areas, failure modes, and progressive disintegration of joints. Square-end members have been emphasized though the results cover the custom-made fitted joints. The results indicate that chord shears cause and dominate the buckling of MPC joints, and the shear length has a more pronounced effect than the size of gaps. Further, large gauges and small un-braced areas improve the buckling response. Several practical recommendations have been suggested throughout the paper such as keeping the ratio of gap/shear length below 3/4 for improving the buckling strength. The study reveals that multi-area joints should not be simplified as single web-to-chord MPC joints such as keeping the ratio of gap/shear length below 3/4 for improving the buckling strength, even where one web is in tension and the other in compression. Finally, the results obtained from this study favorably agree with experimental data by others, and the classic buckling theories for other structural components.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.72-85
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• 2001

A study for the structural strength evaluation on the doubler plate subjected to the biaxial in-plane compression has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. A1so, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et a1. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Advances in concrete construction
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• v.8 no.4
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• pp.335-349
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• 2019

To investigate the axial compressive performance of the recycled aggregate concrete (RAC) filled glass fiber reinforced polymer (GFRP) tube and profile steel composite columns, static loading tests were carried out on 18 specimens under axial loads in this study, including 7 RAC filled GFRP tube columns and 11 RAC filled GFRP tube-profile steel composite columns. The design parameters include recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, slenderness ratio and RAC strength. The failure process, failure modes, axial stress-strain curves, strain development and axial bearing capacity of all specimens were mainly analyzed in detail. The experimental results show that the GFRP tube had strong restraint ability to RAC material and the profile steel could improve the axial compressive performance of the columns. The failure modes of the columns can be summarized as follow: the profile steel in the composite columns yielded first, then the internal RAC material was crushed, and finally the fiberglass of the external GFRP tube was seriously torn, resulting in the final failure of columns. The axial bearing capacity of the columns decreased with the increase of RCA replacement percentage and the maximum decreasing amplitude was 11.10%. In addition, the slenderness ratio had an adverse effect on the axial bearing capacity of the columns. However, the strength of the RAC material could effectively improve the axial bearing capacity of the columns, but their deformability decreased. In addition, the increasing profile steel ratio contributed to the axial compressive capacity of the composite columns. Based on the above analysis, a formula for calculating the bearing capacity of composite columns under axial compression load is proposed, and the adverse effects of slenderness ratio and RCA replacement percentage are considered.

• Journal of Korean Neurosurgical Society
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• v.37 no.2
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• pp.116-123
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• 2005

Objective: Percutaneous kyphoplasty using a balloon-catheter is an widely accepted method which achieves the restoration of vertebral height and the correction of kyphotic deformity with little complication in osteoporotic vertebral compression fractures. The authors assess the results of 59 patients who underwent kyphoplasty, and analyze the factors that could affect the prognosis. Methods: From December 2001 to May 2003, fifty-nine patients underwent kyphoplasty. The patients included 49 women and 10 men aged 52-85 years. Average t-score on bone marrow density was -3.58. About 7cc of polymethylmethacrylate(PMMA) was injected into the fractured vertebral body using $Kyphon^{(R)}$ under local anesthesia. The vertical height of all fractured vertebrae was measured both before and after surgery. Outcome data were obtained by comparing pre- and post-operative VAS score and by assessing postoperative satisfaction, drug dependency and activity. Various clinical factors were analyzed to assess the relationship with the outcome. Results: The VAS score improved significantly, and the mean percentage of restored vertebral height was 53%. The mean improvement in kyphosis was $3.6^{\circ}$. Eighty-nine percent of the patients gained excellent or good results. Any of the clinical factors including the interval between fracture and operation, the degree of height loss, the degree of the vertebral height restoration or the correction rate of kyphosis did not affect the clinical results. Conclusion: Kyphoplasty is associated with a statistically significant improvement in pain and function with little complication. The clinical results are not affected by any clinical parameters. Further follow-up study is needed to determine whether the restoration affects the long-term clinical results.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.685-691
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• 2013

Ibuprofen, non-steroidal anti-inflammatory drugs; NSAIDs, is a highly crystalline substance with the pharmaceutical properties of poor solubility and low bioavailability. The size reduction of ibuprofen is needed to improve the solubility. The objective of this study is to optimize the grinding condition of ibuprofen. Grinding of ibuprofen was carried out using a planetary mill. Grinding parameters were optimized using Box-Behnken experimental design method. The physical characteristics of ground ibuprofen were investigated for the particle size by particle size analyzer, for the crystal size by X-ray diffraction (XRD), and for the tensile strength by tensile/compression tester. The optimum conditions for the milling of ibuprofen were 290 rpm of the revolution number of mill, 24.6 g of the weight of sample, and 10 minutes of grinding time. The measured value of the particle size of ground ibuprofen at these optimum conditions was $13.5{\mu}m$. The results showed that the crystal size of ibuprofen was reduced by the planetary milling process. In case the relative density of the tablets formulated of ground ibuprofen was range of 0.85~0.90, the tensile strength of them was range of 1$2{\sim}14Kg_f/cm^2$.

• Journal of Korean Foot and Ankle Society
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• v.7 no.1
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• pp.109-114
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• 2003

Purpose: The purpose of this study is to evaluate the effectiveness and indications of the modified Essex-Lopresti reduction in calcaneal fractures. Materials and Methods: We reviewed retrospectively 41 cases of displaced intraarticular calcaneal fractures. The fracture was reduced with Essex-Lopresti technique with modification in compression of the lateral wall with the specially designed compression device instead of the operator's hands. We evaluated the results of treatment by AOFAS scale and the radiographic parameters including the Bohler's angle, calcaneal width, calcaneofibular distance and the congruency of the posterior facet. Results: Boler's angle was restored from 11 to 29.6 degrees on average, heel width was reduced to 112% of contralateral value, the calcaneofibular gap was restored up to 87.9% of contralateral side, and the articular surface of the posterior facet was restored less than 2 mm of step off and less than 2 mm of gap. AOFAS scale averaged 87 points. The quality of reduction was best in Sander's type II fractures. Small sized fragments in type III fractures could not be reduced. The results were better when the reductions were performed within 24 hours of injury. Conclusion: The modified Essex-Lopresti reduction was less invasive, easy to perform, and the results of treatment were similar to those of open reduction; it seemed to be a reasonable alternative for the selected intraarticular calcaneal fractures.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.4
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• pp.405-414
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• 2001

Plate tectonics is a dominant paradigm in modern geophysics. Because of its geological mechanism, Korea has a possibility of earthquake according to plate motion. Besides the disaster of earthquake grows rapidly, the importance of recognition for earthquake has been emphasized. This study attempts to decide crustal movement parameters with GPS data, analysed baseline after processing data with GIPSY-OASIS II S/W, observed from 6 stations in and around the Korean peninsula, and obtained from selected 11 stations in Korea. As a results, maximum shear strain was $0.04{\mu}/yr$ and the mean azimuth of the maximum compression axes$(A_{z2})$ is estimated as $97.75^{\circ}$ in and around the Korean peninsula. The average rate of the maximum shear strain($({\gamma}_max)$) is $0.17{\mu}/yr$. The mean azimuth of the maximum compression axes$(A_{z2})$ is estimated as $70.25^{\circ}$ in Korea. Such a pattern of strain distribution is harmonious with that of seismic activity in Korea both historically as well as today.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.4
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• pp.234-244
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• 2014

Recently it has been focused that the automobile engine has developed in a strong upward tendency for the use of the high viscosity and poorer quality fuels in achieving the high performance, fuel economy, and emission reduction. Therefore it is not easy to solve the problems between low specific fuel consumption and exhaust emission control at motor cars. In this study, it is designed and used the engine test bed which is installed with turbocharger and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters, and they were engine speeds(rpm), injection timing(bTDC), and engine load(%). From the result of an experimental analysis, peak cylinder pressure and the rate of pressure rise were increased, and the location of it was closer toward top dead center according to the increasing of engine speed and load, and with advancing injection timing. The combustion characteristics are effected by fuel injection timing due to be enhanced the mass burned fraction. Using the engine dynamometer for analyzing the engine performance, the engine torque and power have been enhanced according to advancing the fuel injection timing. In analyzing of exhaust emission, there has been a trade-off between PM and NOx with increasing of engine speed and load, and with advanced injection timing. The experimental data are shown that the formation of NOx has increased and PM, vice versa.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.67-73
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• 2006

In this study, basic physical tests and mechanical tests of crushed rock were performed in order to investigate the field application of crushed rock as substitute materials of sand that is commonly being used as foundation and backfill materials of sewer conduit. Particle-size distribution curve of crushed rock is similar to sand and also it is well-graded soil than common sand. Maximum dry unit weight in proctor compaction test for crushed rock is higher than the values of common sand. So we can estimate that the crushed rock has advantages in workability than sand for the backfill compaction after construction of sewer conduit. When we investigate the results of direct shear test and triaxial compression test on the crushed rock, it has a similar value of shear strength parameters to sand at the same stress state and as time goes by, it tends to increase the unconfined compression strength. But, because the strength reaches at the constant value after 6~7 days, we expect that it can absorb the lateral strain of flexible conduit well. All the above experimental results just proves that crushed rock can substitute for sand as backfill materials and foundation of sewer conduit.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.454-459
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• 2013

Pressure waves are generated and propagate in a tunnel when train enters tunnel high speed. A compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as an expansion wave. An expansion wave due to the entry of the train tail propagates along the tunnel and is reflected at tunnel exit as a compression wave. These pressure waves are repeatedly propagated and reflected at the tunnel entrance and exit. Severe pressure changes causes ear-discomfort for passengers in the cabin and micro pressure waves around the tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnels qualitatively and quantitatively, because pressure change rate is considered as one of the major design parameters for optimal tunnel cross sectional area and repeated fatigue force on car body. In this study, we developed a characteristics method based on a fixed mesh system and boundary conditions for crossing trains and analyzed this system using an X-t diagram. The results of the simulation show that offsetting of pressure waves occurs for special entry conditions of a crossing train.