• Journal of the Korean Society of Safety
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• v.23 no.2
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• pp.14-20
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• 2008

The objective of this study is to examine fatigue strength of the welded details. In order to attain the goal of this study, the bending fatigue tests was performed for four kinds of welded details used in steel bridges, such as in-plane gusset, out-of-plane gusset, cruciform, and cover plate. The effect of the length of welded attachment on fatigue strength was greater in out-of-plane gusset than in in-plane gusset. The fatigue strength of welded details with short attachment was superior to that with long attachment. Fatigue strength of welded details with transversely loaded welds was lower than that with longitudinally loaded welds, and those results were not satisfied with AASHTO specifications. For the fatigue strength of cover plate, cover plate with rectangular section was superior to that with tapered section. It was found that the fatigue crack initiates at the points of stress concentration which are the boundary between the base metal and the bead of weld in the part of the longitudinal edge of attachment, and propagates first along the boundary and along the perpendicular to the direction of the principle stress in the base metal of welded tip.

• Journal of Computational Design and Engineering
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• v.1 no.4
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• pp.266-271
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• 2014

The survivability of the naval ship is the capability of a warship to avoid or withstand a hostile environment. The survivability of the naval ship assessed by three categories (susceptibility, vulnerability and recoverability). The magnitude of susceptibility of a warship encountering with threat is dependent upon the attributes of detection equipment and weapon system. In this paper, as a part of a naval ship's survivability analysis, an assessment process model for the ship's susceptibility analysis technique is developed. Naval ship's survivability emphasizing the susceptibility is assessed by the probability of detection, and the probability of hit. Considering the radar cross section (RCS), the assessment procedure for the susceptibility is described. It's emphasizing the simplified calculation model based on the probability density function for probability of hit. Assuming the probability of hit given a both single-hit and multiple-hit, the susceptibility is accessed for a RCS and the hit probability for a rectangular target is applied for a given threat.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.5
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• pp.239-246
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• 2015

Reinforced concrete shear walls are effective for resisting lateral loads imposed by wind or earthquakes. Observed damages of the shear wall in recent earthquakes in Chile(2010) and New Zealand(2011) exceeded expectations. Various analytical models have been proposed in order to incorporate such response features in predicting the inelastic response of RC shear walls. However, the model has not been implemented into widely available computer programs, and has not been sufficiently calibrated with and validated against extensive experimental data at both local and global response levels. In this study, reinforced concrete shear walls were modeled with fiber slices, where cross section and reinforcement details of shear walls can be arranged freely. Nonlinear analysis was performed by adding nonlinear shear spring elements that can represent shear deformation. This analysis result will be compared with the existing experiment results. To investigate the nonlinear behavior of reinforced concrete shear walls, reinforced concrete single shear walls with rectangular wall cross section were selected. The analysis results showed that the yield strength of the shear wall was approximately the same value as the experimental results. However, the yielding displacement of the shear wall was still higher in the experiment than the analysis. The analytical model used in this study is available for the analysis of shear wall subjected to high axial forces.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.8
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• pp.686-691
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• 2016

This paper employs numerical tools to obtain an optimal thermal design of a heat exchanger with plain-fins. This heat exchanger is located at the condensing section of a crevice-type heat pipe. The plain-fins in the heat exchanger are radically mounted to two tubes in the condensing section. To obtain the optimal design parameters, a computational fluid dynamics technique is introduced and applied to different placement configurations in a system module. Owing to its effects on the heat pipe performance, the temperature difference between the tube surfaces and ambient air is investigated in detail. A greater heat dissipation rate occurs when the plain-fin offsets change from 2 to 3 mm. When this temperature difference is ${\Delta}T=70^{\circ}C$, the upper part of the plain-fins undergoes an accumulation of heat. At below $70^{\circ}C$, the dissipation of heat is accepted. A rectangular plain-fin geometry with varying widths and heights does not have a significant impact on the heat dissipation through-out the overall system. In addition, the temperature distributions between different plain-fin pitches show an equal profile even with different fin pitches.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2680-2687
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• 2000

The Reynolds equation, incorporating Elrods cavitation algorithm, is discretized on a rectangular grid in computational space through coordinate mapping in order to accurately analyze a herringbone grooved journal bearing of a spindle motor in a computer hard disk drive. The pressure distribution and cavitation area are determined by using the finite volume method. Predicted results are compared to experimental data of previous researchers. It was found that positive pressure is developed within the converging section of the bearing and that a cavity occurs in the diverging section. Cavitation has been neglected in the previous analysis of the herringbone grooved bearing. Load capacity and bearing torque are increased due to the increased of eccentricity and L/D and the decrease of the grooved width ratio. The maximum load capacity was found to occur at a groove angle of 30 degrees while bearing torque remains constant due to the variation of the groove angle. The cavitation region is significantly decreased with the inclusion of herringbone grooves. However, the region increases with the increase of the eccentricity, L/D, groove angle and the rotational speed and the decrease of the grooved width ratio.

• Steel and Composite Structures
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• v.19 no.3
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• pp.661-678
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• 2015

Buckling Restrained Braces (BRB) have been widely used in the construction industry as they utilize the most desirable properties of both constituent materials, i.e., steel and concrete. They present excellent structural qualities such as high load bearing capacity, ductility, energy-absorption capability and good structural fire behaviour. The effects of size and type of filler material in the existed gap at the steel core-concrete interface as well as the element's cross sectional shape, on BRB's fire resistance capacity was investigated in this paper. A nonlinear sequentially-coupled thermal-stress three-dimensional model was presented and validated by experimental results. Variation of the samples was described by three groups containing, the steel cores with the same cross section areas and equal yield strength but different materials (metal and concrete) and sizes for the gap. Responses in terms of temperature distribution, critical temperature, heating elapsed time and contraction level of BRB element were examined. The study showed that the superior fire performance of BRB was obtained by altering the filler material in the gap from metal to concrete as well as by increasing the size of the gap. Also, cylindrical BRB performed better under fire conditions compared to the rectangular cross section.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.373-381
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• 2002

The cost on transmission and erection of the precast prestressed concrete members largely depends on the weight of them. Optimum process is performed on a U-beam section to control the prestressing force, to reduce the self-weight, and to meet the required strength and stability. The strength, deflection, and concrete stress at the top and bottom of the section considered are required to check according to each construction step in this process. The weight of the original rectangular concrete beam could be reduced up to 39∼50％ from this method. Two full scale prototype U-beams were proposed and tested in this study. It was found that the U-beams in the test showed good performance in strength and serviceability within the limits of ultimate strength design method.

• Journal of Sensor Science and Technology
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• v.30 no.3
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• pp.170-174
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• 2021

As the rising attention to the medical and healthcare issue, Bio-MEMS (Micro electro mechanical systems) platform such as bio sensor, cell culture system, and microfluidics device has been studied extensively. Bio-MEMS platform mostly has high resolution structure made by biocompatible material such as polydimethylsiloxane (PDMS). In addition, three dimension structure has been applied to the bio-MEMS. Lithography can be used to fabricate complex structure by multiple process, however, non-rectangular cross section can be implemented by introducing optical apparatus to lithography technic. X-ray lithography can be used even for sub-micron scale. Here in, we demonstrated lines with round shape cross section using the tilted gold absorber which was deposited on the oblique structure as the X-ray mask. This structure was used as a mold for PDMS. Molded PDMS was applied to the cell culture platform. Moreover, molded PDMS was bonded to flat PDMS to utilize to the sub-micro channel. This work has potential to the large area bio-MEMS.

• Steel and Composite Structures
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• v.38 no.6
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• pp.637-656
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• 2021

The component-based method is widely used to analyze the initial stiffness of joint in steel structures. In this study, an analytical component model for determining the column face stiffness of square or rectangular hollow section (SHS/RHS) subjected to tension was established, focusing on endplate connections. Equations for calculating the stiffness of the SHS/RHS column face in bending were derived through regression analysis using numerical results obtained from a finite element model database. Because the presence of bolt holes decreased the bending stiffness of the column face, this effect was calculated using a novel plate-spring-based model through numerical analysis. The developed component model was first applied to predict the bending stiffness of the SHS column face determined through tests. Furthermore, this model was incorporated into the component-based method with other effective components, e.g., bolts under tension, to determine the tensile stiffness of the T-stub connections, which connects the SHS column, and the initial rotational stiffness of the joints. A comparison between the model predictions, test data, and numerical results confirms that the proposed model shows satisfactory accuracy in evaluating the bending stiffness of SHS column faces.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.131-140
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• 2003

The purpose of this study was to evaluate clinical applications of electroplating method through investigation of the physical properties of orthodontic rectangular wires according to varying their cross section. For the study, it was accomplished to electroplate the 0.016-inched orthodontic rectangular stainless steel wire. The cross section of stainless steel orthodontic rectangular wire increased from $0.016{\times}0.016inch\;to\;0.017{times}0.017inch$ by electroplating. The wire was heat treated to improve an adhesion between the wire and electroplated metal. h three-point bending test and torsion test were conducted in order to compare physical properties among three wire groups; $0.016{\times}0.016wires(group 016),\; electroplated\;0.016{\times}0.016wires(group\;016P)\;and\;0.017{\times}0.017$ wires (group 017). Through the investigations of each wire group, following results were obtained 1. At three-point bending test, the group Ol6P showed higher tendency in the degree of stiffness, yield strength and ultimate tensile strength than the group 016. Stiffness and ultimate tensile strength showed statistically significant differences between two groups at three-point bending test (p<0.05). 2. Stiffness, yield strength, and ultimate tensile strength of the group 016P showed lower tendency than those of the group 017 Stiffness showed statistically significant differences between two groups at three-point bending test (p<0.05). 3. Torque/twist rate, yield torsional moment, and ultimate torsional moment of the group 016P showed higher tendency than those of the group 016. All measurements showed statistically significant differences between two groups alter torsion test (p<0.05). 4. Torque/twist rate, yield torsional moment, and ultimate torsional moment of the group 0166P showed lower tendency than those of the group 017. Yield torsional moment, and ultimate torsional moment showed statistically significant differences between two groups after torsion test (p<0.05).