• Journal of Technologic Dentistry
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• v.40 no.1
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• pp.27-32
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• 2018

Purpose: This study was performed to investigate processability of the dental zirconia block. Most of the CAD/CAM zirconia restorations utilize the partially sintered blocks, which are sintered at a temperature lower than $1100^{\circ}C$. Methods: Partially sintered zirconia samples were prepared $40{\times}30{\times}10mm$ and surface treatment by #2000 sandpaper. Scratch hardness was determined by the procedure of ASTM G171-03 using a scratch hardness tester(KS TECH, Korea) equipped with a real time load detector to measure tangential force during scratching. The scratch rate was 30 mm/min. Results: Scratch hardness(Hs) increases steeply with increase in the loads. The highest Hs was sampl 1.42 GPa and lowest was sample 0.42 GPa. Conclusion : The machinability of partially sintered CAD/CAM zirconia blocks can be optivized by manipulation of Hs.

• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.10-15
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• 2008

The proper docking block arrangement, loading condition and structural reinforcement are required to ensure structural safety of ship, when she is in re-docking and launching for inspection or repair. The large reaction force due to narrow bottom tangent area, heavy weight and ballast loading are occurred at aft body and fore body of ship. Especially, in case of LNGC, the strength evaluation is necessary for cargo hold areas including mid-body because tank hydro test is performed in dry-dock. The analysis results and experiences to confirm structural safety for docking of conventional LNGC$(138K{\sim}151.7K)$ are introduced in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.435-440
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• 2004

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.107-116
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• 2014

A volume density of roughness correction blocks in a channel is defined and the corresponding roughness coefficient(n) is estimated by analyzing the diverse hydraulic characteristics of VR, the product of the average velocity and the hydraulic radius, block Reynolds number ($Re^*$), drag coefficient ($\acute{C}_D$), and the roughness coefficient ($n_b$) of bottom shear. The increase of VR and block Reynolds number causes the exponential decrease of roughness coefficient converged to a constant value as expected. The drag coefficient also exponentially decreases as block Reynolds number increases as well. The drag force is governed by the block shape defined by volume density in high block Reynolds number of turbulent flow region. For more accurate estimation of roughness coefficient the use of the correlation equation of it is required by block Reynolds number and volume density. The regression equations for n-VR, $\acute{C}_D-Re^*$, and $n_b-\acute{C}_D$ are presented. The regression equations of roughness coefficient are also presented by block Reynolds number and volume density. The developed equation of roughness coefficient by block Reynolds number and volume density has practical use by confirming the coincidence between the experimental results and the results of HEC-RAS using the developed equation.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.780-788
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• 1995

The purpose of this study was to compare the apical seal following root canal shaping by different methods. From fourty extracted mandibular 1st and 2nd molars, fourty mesial roots whose canals have some degree of curvature were selected. The mesiobuccal root portion including mesiobuccal portion of a crown was sectioned in each molar. After access cavity preparation for the mesiobuccal canal, working length was determined with # 10 K-file. The sectioned roots were implanted in acrylic resin block and randomly divided into four groups. The canals of group I were shaped by step-down/balanced force, group II by stepdown/step-back, group III by step-back and group IV by conventional method. All of the shaped canals were obturated by Thermafil method and access cavities were filled with IRM. The roots were removed from acrylic resin block and placed in 100 % humidity for 7days. Except the root surfaces of apical 2mm, the root surfaces were nail-varnished 3 times. After the roots were placed in 700 torr vacuum pressure for 15 minutes, they were immersed in 2% methylene blue solution for 4 days. Nail varnishes were removed with acetone. After that, the roots were decalcified in 5 % nitric acid and dehydrated with alcohol series. Transparent specimens were made by methyl salicylate and the quality of apical seal was assessed by measuring the leakage linearly. The results were as follows. 1. The leakage in canals shaped by step-down/balanced force method was significantly less than that in canals shaped by step-back method(P<0.05) and was less but not statistically than that in canals shaped by step-down/step-back method (P>0.05). 2. The leakage in canals shaped by step-down/step-back method was less than that in canals shaped by step-back method, but there was no statistical significance(P>0.05). 3. The leakage in canals shaped by conventional method was significantly more than that in canals shaped by step-down/balanced force, step-down/step-back and step-back method (P<0.05).

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.602-607
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• 2007

The heavy duty diesel engine must have a large output for maintaining excellent mobility. The compacted graphite iron (CGI) is a material currently under study for the engine demanded for high torque, durability, stiffness and fatigue. In this study, three dimensional finite element model of a heavy-duty diesel engine was developed to conduct the stress analysis by using property of CGI. The FE model of the heavy duty diesel engine section consisting with four half cylinder was selected. The heavy duty diesel engine section include cylinder block, cylinder head, liner, bearing cap, bearing and bolt. The loading conditions of engine are pre-fit load, assembly force and gas force.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.41-49
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• 1993

Piston slap is one of the major sources of noise in a 4-cycle diesel engine. Piston slap is not only one of major source mounted near the top and bottom of the piston thrust and antithrust skirts. Effects of engine speed, load and coolant temperature on piston motion were investigated. The measured piston motion showed 6 slapes per cycle resulting from the change of side force. Major piston slap timing was retarded as engine speeds became higher. The increase of engine load made large piston transverse movement toward thrust side of cylinder block. Piston transverse movement was due to reduced piston-liner clearance at higher coolant temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.411.2-411.2
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• 2014

The design of DNA nanostructures is of fundamental importance, the intrinsic value of DNA as a building-block material lies in its ability to organize other bio-molecules with nanometer-scale spacing. Here, we report the fabrication of DNA scaffolds with nano-pores (<10 nm size) that formed easily without the use of additives (i.e., avidin, biotin, polyamine, or inorganic materials) into large-scale structures by assembling DNA molecules at near room temperature ($30^{\circ}C$) and low pH (~5.5). Protein immobilization results also confirmed that a fibronectin (FN) proteins/large scale DNA scaffolds/aminopropylytriethoxysilane (APS)/SiO2/Si substrate with high sensitivity formed in a well-defined manner. The DNA scaffolds can be applied for use with DNA-based biochips, biophysics, and cell biology.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.3 s.258
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• pp.217-224
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• 2007

A numerical analysis for a silencer with three baffles of 120mm tank gun has been performed. The Reynolds-Averaged Wavier-Stokes equations with Baldwin-Lomax turbulence model were employed to compute unsteady, compressible flow inside the tank gun and the silencer. An axisymmetric computational domain was constructed by using 12 multi block chimera grids. The resolution of flow field is observed by depicting calculated pressure and muzzle brake force. The peak blast pressure and noise through the silencer reduced approximately 99% and 41dB in comparison to the tank gun without the silencer at near filed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.653-660
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• 1986

Two uppor bound solutions, by the force balance method and by a kinematically admissible velocity field, are compared for the metal forming problems in plane strain. It is concluded that these two approaches always give identical results when the geometrical configurations of the deformation model reman the same. By detailed derivations for plastic bending of a notched bar, closed die forging, compression of a rectangular block, machining with a restricted contact tool and plane strain backward extrusion, the identity of both approaches is verified.