• Computers and Concrete
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• v.13 no.3
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• pp.377-387
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• 2014

This paper presents an experimental study on socket base connections of precast reinforced concrete columns. The main purpose of this study is to determine socket base connection which has the closest behavior to monolithic casted column-base joints. For this purpose, six specimens having different column-socket base connection details were tested under cyclic loading. For each test, strength, stiffness, ductility and drift ratios of the specimens were determined. Test results indicated that a suggested connection type is 10%-30% stronger than the other type of connections under lateral loading. The welded connection (PC-5) had better lateral load carrying capacity and ductility. On the other hand, performance of standard connection (PC-1) which is commonly used in construction was weaker than other connections. Thus, decision of connection type should be referred not only performance but also applicability.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.36.2-36.2
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• 2008

This paper presents the impact of Japanese radio source on the S-Band communication between KOMPSAT-2 satellite and TT&C ground system. Major specifications such as transmitting EIRP (Effective Isotropic Radiated Power) and location of Japanese terrestrial station were informed from Radio Research Laboratory in Korea Communication Commission. To estimate path loss in S-Band, the distance between Japanese station and TT&C ground system was obtained by using COTS (Commercial Off-The-Shelf) software. After that the signal strength of Japanese radio source placed at the TT&C ground system was calculated from link parameters such as transmitting EIRP, path loss, and receiving antenna gain. Consequently, this paper shows that the degradation caused by Japanese radio source is acceptable to TT&C ground system for satellite operation.

• Steel and Composite Structures
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• v.24 no.3
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• pp.339-349
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• 2017

In this paper, a conventional refined plastic hinge analysis is improved to account for the effects of local buckling and lateral-torsional buckling. The degradation of flexural strength caused by these effects is implicitly considered using practical LRFD equation. The second-order effect is captured using stability functions to minimize modeling and solution time. An incremental-iterative scheme based on the generalized displacement control method is employed to solve the nonlinear equilibrium equations. A computer program is developed to predict the second-order inelastic behavior of space steel frames. To verify the accuracy and efficiency of the proposed program, the obtained results are compared with the existing results and those generated using the commercial finite element package ABAQUS. It can be concluded that the proposed program proves to be a reliable and effective tool for daily use in engineering design.

• Environmental Engineering Research
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• v.19 no.4
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• pp.355-361
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• 2014

The wastewater treatment with a two-phase expanded granular sludge bed (EGSB) system for anaerobic degradation of acetate, benzoate, terephtalate and p-toluate from purified terephtalic acid (PTA) production was studied. The feasibility and effectiveness of the system was evaluated in terms of organic oxidation by chemical oxygen demand (COD), gas production, bacterial adaptability and stability in the granular sludge. Average removal efficiencies 93.5% and 72.7% were achieved in the EGSB reactors under volumetric loading rates of $1.0-15kg-COD/m^3/day$ and terephtalate and p-toluate of 351-526 mg/L, respectively. Gas production reached total methane production rate of 0.30 L/g-COD under these conditions in the sequential EGSB reactor system. Higher strength influent COD concentration above 4.8 g-COD/L related to field conditions was fed to observe the disturbance of the EGSB reactors.

• Journal of Ship and Ocean Technology
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• v.1 no.1
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• pp.57-72
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• 1997

The larger trends related to cracking in ocean going vessels (primarily tankers and bulk carriers) are reviewed on the basis of available data. The typical interrelated causes of such cracking are: high local stresses, extensive use of higher strength steels, inadequate treatment of dynamic loads, adverse operational factors (harsh weather, improper vessel handling), and controllable structural degradation (corrosion, wear, stevedore damage). Three consequences of cracking are then discussed: structural failure, pollution, and increased maintenance. The first two, while rare, are potentially of high consequence including loss of life. The types of solutions that can be employed to improve the durability of ships in the face of fatigue cracking are then presented. For existing vessels, these solutions range from repairs based on structural analysis or service experience, control of corrosion, and enhanced surveys. For new vessels, the use of advanced design procedures that specifically address dynamic loads and fatigue cracking is necessary. As the preferred solution to the problem of cracking in ships, this paper advocates prevention by explicit design by first principles.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.291-291
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• 2006

Two different sources of clay, Na-Bentonite (Thai local clay) and Na-Montmorillonite were modified with Hexadodeccyltrimethyl ammonium bromide. The nanocomposites of polypropylene were successfully prepared via melt blending in a co-rotating twin screw extruder by using PP-g-MA as a compatibilizer at various contents of organoclays. The morphology of nanocomposites was investigated by using XRD and SEM. The results showed that the intercalated and exfoliated structures were obtained. The thermal behavior was also studied by using DSC and TGA. The degradation temperature of filled PP was greater than that of unfilled PP by 20%. And, the tensile strength and modulus were improved when a small amount of organoclays were added.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.2
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• pp.75-81
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• 2010

Characteristics of mixing biodegradable polymers and polymer impregnated paper for mulching mat for seedling were investigated. The mixed film of 70% PLA was most easily biodegradable. The surface of polymer films were changed to more rough due to enzymatic degradation of lipase. Tensile strength and breaking elongation of PLA mixed films were increased to the 0.04-0.31 kN/m and the 0.17-0.96%, respectively. With higher PLA contents, intensities of ester originated carboxyl group(about $1,748cm^{-1}$) were increased. Physical properties of prepared mulching mats were increased with PLA contents and stiffness of mulching mat was not so much changed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.453-460
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• 2001

The seismic capacity of columns usually has been tested in uniaxial loading condition. The seismic performance used to be evaluated under the same assumption. Since the real earthquake motion is multi-directional, the effects of multi-directional excitation on the seismic capacity of structures need to be carefully examined. In this paper, a frequency dependent alternate biaxial cyclic loading test is proposed as an evaluation method of seismic capacity under multi-directional excitation. Four test specimens were made and tested to study the degradation of strength, stiffness and ductility under biaxial loading condition. A multi- directional excitation. The capacity is obtained using frequency dependent alternate biaxial cyclic loading test. The orthogonal effect is taken into account by increasing the demand.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.323-328
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• 2001

The behavior of bridge column under multi-directional loading as well as uni-directional loading need to be studied because bridge columns will be subjected to the multi-directional cyclic loading during a strong earthquake. To evaluate the capacity of columns, uni-axial cyclic loading tests and bi-axial alternate cyclic loading tests were carried out. The number of cycles of alternate bi-axial loading were determined considering the ratio of natural frequencies in two orthogonal directions. From the test results, strength degradation and ductility reduction were observed in biaxial loading conditions. Their rates were found to be more rapid in the loading pattern that was determined considering the different natural frequencies.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.399-404
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• 2008

The influence of gas hydrate dissociation on submarine slope stability was studied in this paper. Gas hydrates are stable under high pressure and low temperature conditions. Once gas hydrate dissociates due to natural or human activities, it generates large amount of gas and water. During gas hydrate dissociation, a pore pressure between soil particles increases and results in the loss of an effective stress and degradation of soil stiffness. A pore pressures model was proposed to calculated excess pore pressures generated by gas hydrate dissociation at the Storegga Slide. A slope stability analysis for the Storegga Slide using a two dimensional finite difference method was carried out by considering excess pore pressures due to gas hydrate dissociation. Since the excess pore pressure calculated by the proposed method resulted in the considerable loss of stiffness and strength in slope, a submarine slope failure occurred at the Storegga slide was well simulated.