• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.5
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• pp.337-344
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• 2015

As many of armored vehicles are seriously exposed to threat of IEDs(Improvised Explosive Devices) in the Afghanistan war and the Iraq war. V-shaped military vehicles are deeply studied in order to protect crews and mounted soldiers against land mines. Generally the experiment on full-scaled V-shaped structure needs excessively high cost, which becomes a huge barrier to study. In this paper, we explore the possibility to make a half-scaled model of the V-shaped structure by using the geometric similarity scaling. We demonstrate the geometric similarity scaling between the original model and the half-scaled model is established on the momentum and deflections of structure via computer simulations and experiments. At this stage, we conduct only numerical analysis of predicting vibration of V-shaped structure because measuring vibration of structure is difficult in the mass-explosion experiment, which is remained as future work.

• Steel and Composite Structures
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• v.24 no.1
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• pp.37-52
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• 2017

To quantitatively assess the safety against seismic collapse of eccentrically braced steel frame (EBSF) system, 24 typical EBSFs with K-shape and V-shape braces with seismic precautionary intensities 8 and 9 were designed complying with China seismic design code and relative codes to constitute archetype space of this structure system. In the archetype space, the collapse probability of the structural system under maximum considered earthquakes (MCE) was researched. The results show that the structures possess necessary safety against seismic collapse when they respectively encounter the maximum considered earthquakes corresponding to their seismic precautionary levels, and their collapse probabilities increase with increasing seismic precautionary intensities. Moreover, the EBSFs with V-shape braces have smaller collapse probability, thus greater capacity against seismic collapse than those with K-shape braces.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.133-149
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• 1998

Clinical application of composite resin recently draw great concerns in dentistry. Especially due to advantages such as esthetics, adhesiveness, simple clinical procedures, various shapes and kinds of composite resins are widely being applied to prosthodontics, conservative dentistry, and orthodontics. But, clinical problems attributable to the polymerization shrinkage of composite resin have been proposed, and we have to regard clinical problems such as secondary caries, loss of restoration, fracture of the surrounding tooth structure, marginal discoloration, and tooth sensitivity, and many portions are remained to be overcome. Therefore, this study attempts to analyze stress distribution between resin and tooth structure which is generated during polymerization shrinkage of composite resin using three dimensional finite element method. Three dimensional finite element models with conventional box-shape cavity and erosion/abrasion type V-shape lesion cavity in upper central incisor were developed. These cavities were filled with four different types of placement techniques. (bulk filling, horizontal increment filling, oblique occlusal increment filling, oblique gingival increment filling) The stresses generated by polymerization shrinkage of composite resin were calculated. The results analyzed with three dimensional finite element method were as follows : 1. The increment filling technique showed the highest maximum normal stress in both conventional box-shape and V-shape cavities and showed a tendency to decrease after complete polymerization. 2. The bulk filling technique resulted in increased stresses during the curing process in both conventional box-shape and V-shape cavities and the highest maximum normal stress occurred after complete polymerization. 3. The bulk filling resulted in the lowest maximum normal stress in both box-shape and V-shape cavities 4. Regardless of placement method, in conventional box-shape cavity, the maximum normal stress increased in dentin floor, enamel, dentin sequence and in V-shape cavity, the maximum normal stress increased in enamel, dentin sequence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3410-3415
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• 2014

The heat generated by electronic devices can result in performance degradation. Therefore, a heat sink has been used to release the operating heat into the air outside. This study addressed a methodology for a heat sink with an inner tunnel. Under forced convection conditions, the heat transfer characteristics were different so the cooling and heating performances were studied for the heat sink with an inner tunnel. This was evaluated by performing the experimental test examining the heat transfer characteristics related to the variance in time and temperature distribution. In the cooling experiment, the temperature of the A-shape was lower than that of the B-shape, when the voltage was 10 V. These experimental results indicate the optimal cooling effect. In a heating experiment, the temperature of the A-shape was higher than that of the B-shape, when the voltage was 13 V. The experimental results showed that the temperature and efficiency of the A-shape were higher than those of the B-shape.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.2
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• pp.49-55
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• 2018

A T-shape structure was manufactured by the superplastic forming and diffusion bonding process using two Ti-3Al-2.5V alloy tubes. A Ti-3Al-2.5V tube was prepared for the hydroforming in the superplastic condition until it reaches a surface area such as a roof welded in the hole of another Ti-3Al-2.5V tube. Afterward, the superplastic forming process and the diffusion bonding process were carried out simultaneously until the appropriate bonding along the interface area of two Ti-3Al-2.5V tubes was obtained. The bonding qualities were different at each location of the entire interface according to the applied process conditions such as strain, pressure, temperature, holding time, geometries, etc. The microstructures of bonding interface have been observed to understand the characteristics of the applied processes in this study.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.112-117
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• 2002

The effects of shield gas on the structure of methane-air nonpremixed counterflow flames were numerically investigated. The near extinction flame of a low global strain rate 20 $s^{-1}$ of 19% methane diluted by 81% nitrogen by volume and undiluted air was computed. The flame shape, centerline temperature and axial velocity profiles were compared for different velocity of the shield gas and with and without the shield gas. The effects of the velocity of the shield gas were negligible for $V_{S}/V_{F}{\leq}2$ in normal gravity. Under normal gravity conditions, the flame shape and its position with the shield gas were different from those of the flame without the shield gas, whereas no discernible effects of the shield gas along the centerline were observed in zero gravity.

• Journal of Powder Materials
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• v.22 no.3
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• pp.169-174
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• 2015

The optical film for light luminance improvement of BLU that is used in LCD/LED and retro-reflective film is used as luminous sign consist of square and triangular pyramid structure pattern based on V-shape micro prism pattern. In this study, we analyzed machining characteristics of Cu-plated flat mold by shaping with diamond tool. First, cutting conditions were optimizing as V-groove machining for the experiment of micro prism structure mold machining with prism pattern shape, cutting force and roughness. Second, the micro prism structure such as square and triangular pyramid pattern were machined by cross machining method with optimizing cutting conditions. Burr and chip shape were discussed with material properties and machining method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.4
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• pp.118-124
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• 2016

In this paper, the model to develop the forming process for turbine seal is suggested. And numerical approach for the shape design of the turbine seal is examined. Because of the thin thickness of the turbine seal, the seal is easily fractured in the manufacturing process. The main factors of the seal manufacturing consist of addendum angle and dedendum angle, fillet on the addendum face, number of the gear teeth, sheet initial location and gear initial location, rake and vertical clearance. The structure and shape of seal are modeled using the commercial 3D mechanical design program, CATIA(V5/R20). Also, rolling process to manufacture the turbine seal is analyzed using DEFORM$^{TM}$-3D(V11), commercial forming analysis software and runs under PC workstation. This study focused on the shape design of turbine seal. Through this research, the main factors to make the turbine seal for airplane turbine engine can be obtained. This study results are reflected to the shape design for turbine seal.

• Structural Engineering and Mechanics
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• v.68 no.5
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• pp.519-526
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• 2018

In this article, experimental training of the commercial available shape memory alloy fibre (SMA) fibre under the combined thermomechanical loading is reported. SMA has the ability to sense a small change in temperature (${\geq}10^{\circ}C$) and activated under the external loading and results in shape change. The thermomechanical characteristics of SMA at different temperature and mechanical loading are obtained through an own lab-scale experimental setup. The analysis is conducted for two types of the medium using the liquid nitrogen (cold cycle) and the hot water (heat cycle). The experimental data indicate that SMA act as a normal wire for Martensite phase and activated behavior i.e., regain the original shape during the Austenite phase only. To improve the confidence of such kind of behavior has been verified by inspecting the composition of the wire. The study reveals interesting conclusion i.e., while SMA deviates from the equiatomic structure or consist of foreign materials (carbon and oxygen) except nickel and titanium may affect the phase transformation temperature which shifted the activation phase temperature. Also, the grain structure distortion of SMA wire has been examined via the scanning electron microscope after the thermomechanical cycle loading and discussed in details.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.40-47
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• 1998

This paper report sthe design, fabrication and characterization of an AlGaAs/GaAs HBT (heterojunction bipolar transistor) with an air-bridge isolation structure which is made to improve high frequency characteristics for the application to the mobile communication system in the next genration. We found that the size, shape and structure of HBT have an effect on the high frequency operation. The measured dc and ac characteristics of the four type HBTs were compared and analyzed. An E-type HBT with an air-bridge structure by undercut etching exhibited .beta.=56, $V_{off-set}$ = 0.3 V, B $V_{CEO}$=7.0V with $f_{T}$=40 GHz and $f_{max}$=45GHz at a collector current density of 7.1*10$^{4}$ A/c $m^{2}$.>.