• Journal of the Korean Society of Radiology
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• v.7 no.4
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• pp.301-305
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• 2013

This thesis intends to analyze tooth distortion by mandibular arch form by reproducing existing panorama image and reconstructed panorama image of Cone Beam CT data with the three-dimensional computer program. The diameter of tooth measured in Cone Beam CT's cross-section image and reconstructed panorama was synchronized without any big change from incisors to posteriors. But, panorama showed serious distortion as going to posteriors after showing a little distortion in incisors. The panorama reconstructed for patients' individual arch showed reduced distortion than panoramas used generally. In addition, panorama showed serious distortion from incisors to posteriors and it means that distortion is reduced in reconstructed panorama.

• Wind and Structures
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• v.39 no.1
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• pp.31-45
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• 2024

This paper examines the flow characteristics around an inclined prism with a U-shaped cross-section ("U-profile") and investigates the connection between the flow and flow-induced vibrations. The study employs a combined approach that involves wind tunnel experiments and computational fluid dynamics (CFD) using an unsteady Reynolds-averaged Navier-Stokes (RANS) turbulence model. Distinct vortex formation patterns are observed in the flow field surrounding the stationary inclined profile. When the cavity of the profile faces away from the incoming flow, large vortices develop behind the profile. Conversely, when the cavity is oriented towards the oncoming flow, these vortices form within the cavity. Notably, due to the slow movement of these large vortices through the cavity, the frequency at which vortices are shed in the negative inclination case is lower compared to the positive inclination, where they form in the wake. Wind tunnel experiments reveal an intermittent transition between the two vortex formation patterns at zero inclination. Large vortices sporadically emerge both in the cavity and behind the profile. The simulation results demonstrate that when these large vortices occur at a frequency close to the structure's natural frequency, they induce prominent pitch vibrations. This phenomenon is also sought after and presented in coupled vibration experiments. Additionally, the simulations indicate that when the natural frequency of the structure is considerably lower than the vortex shedding frequency, this type of vibration can be observed.

• Journal of Korean Association for Spatial Structures
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• v.7 no.3 s.25
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• pp.141-151
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• 2007

The appearance of many Glass Fiber Reinforced Plastic (GFRP) constructions look like ordinary steel construction, because GFRP has been imitated by the same way with the traditional steel's cross section as well as connection system. In terms of detachable connection, there was not enough appropriate option of GFRP connection, such as a traditional bolt connection for steel and wood structures. Most of all, from material characteristic of GFRP related to the deficient ductility, the shearstress principle of GFRP s not proper for the material property, which causes ineffective and not economic application of material. With this research problem, the innovative and detachable onnection system, which is more considered with appropriate material characteristic for FRP, is developed. Not only short time but also long time research with various connection variations is carried out.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.177-180
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• 2009

Tube hydroforming provides a number of advantages over the conventional stamping process, including fewer secondary operations, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. A hydroformed vehicle body component has an attachment flange or the like-formed as an integral part of the hydroforming process. For a given flange shape, a parting plane for the dies is established relative to which the various surfaces of the flange shape, in cross section, have no significant reverse curvature. This study shows analysis results that form the flanged tubular parts in the hydroforming. The thickness variations and defects during the hydroforming for flange forming could be analyzed by FE analysis. FE analysis was performed by LS-DYNA/Dynaform 5.5.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.32-37
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• 2010

Hydroforming has attracted a great deal of attention in the manufacturing industries for vehicles and transportation systems. Hydroforming technology contributes to weight reduction, increased strength, improved quality and reduced tooling cost. Hydroformed automotive parts used as structure components in vehichle body frame often have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. For a given flange shape, a parting plane for the dies is established relative to which the various surfaces of the flange shape, in cross section, have no significant reverse curvature. In this study, hydroforming process for flange forming was proposed. FE analysis to form flanged circular shape and flanged rectangular shape was preformed with Dynaform 5.5. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as tool geometry and hydraulic pressure has been performed and optimized. The results show that flanged automotive parts can be successfully produced with tube hydroforming.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.344-351
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• 2012

A disc spring consists of a conical disc. A load-displacement formula was newly developed in the form of energy method to consider both rigid and friction. The cross section of the disc spring has identical slope angles at the bottom of conical. To solve such a problem, an energy method calculation is proposed. To achieve the goal of this study, the proposed calculation is extended to a disc spring with friction. A firm basis background study based on Almen's work is presented in developing a new numerical approach to predict the available formulation for a disc spring with friction.

• Korean Journal of Materials Research
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• v.28 no.3
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• pp.189-194
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• 2018

Porous graphites were synthesized by removing the template in HF after cabothermal conversion for 3 h at $900^{\circ}C$, accompanied by intercalations of pyrolyzed fuel oil (PFO) in the interlayer of Co or Ni loaded magadiite. The X-ray powder diffraction pattern of the porous graphites exhibited 00l reflections corresponding to a basal spacing of 0.7 nm. The particle morphology of the porous graphites was composed of carbon plates intergrown to form spherical nodules resembling rosettes like a magadiite template. TEM shows that the cross section of the porous graphites is composed of layers with very regular spaces. In particular, crystallization of the porous graphite was dependent on the content of Co or Ni loaded in the interlayer. The porous graphite had a surface area of $328-477m^2/g$. This indicates that metals such as Co and Ni act as catalysts that accelerate graphite formation.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2130-2131
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• 2011

Electric fire breaks out by various causes such as electric short, overload(over current), leakage current, poor contact, static electricity, insulation deterioration, partial disconnection and etc. In this paper, we studied analysis technique for scientific and systematic judgment for distinction of electricity fire existence and nonexistence, and described about electricity fire cause analysis process for collecting physical evidences. We handled external form analysis, Substance extension analysis, X-ray transmission analysis, cross-section analysis, thermal analysis, chemical structure analysis, surface structure analysis, component analysis, electrical properties analysis, and circuit analysis by analysis technique for electricity fire cause judgment. We expect that analysis technic elevation and correct cause of fire analysis of scene of a fire investigators and analysts through this paper which see help.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.186-192
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• 1983

The purpose of this study is to determine the general frequency expression for a rotating shaft of uniform cross section, supported by two bearings, and carrying flywheel at the free end. The bearing spacing and the ratio of the weight of flywheel to the total distributed weight are used as parameters. The data have thus been reduced to dimensionless form so that the results are generally applicable for this type of rotor. Frequencies for the first three modes of vibration are determined. Experimental investigation with rotor/flywheel model confirmed the critical speed frequencies lie between analytical models with simply supported-simply supported boundary conditions and spring supported-spring supported boundary conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.112-117
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• 2007

With the Euro-4 regulation coming into effect, the domestic car industry is forced to look for newer options to reduce NOX in the exhaust. EGR(Exhaust Gas Recirculation) Cooler is an effective method for the reduction of NOX form a diesel engine. High efficiency, low pressure loss and compactness are desirable features of an EGR Cooler. The cooling performance of EGR depends on the shape of tubes and the location of the entrance and exit. This paper reports the computational work conducted to estimate the performance of EGR cooler with three different cross section tubes and a triangular spiral tube. Three dimensional computation results show that the triangular tube is more effective than circular and rectangular tube. The most effective geometry is a triangular spiral tube with offset inlet and outlet locations.