• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.803-808
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• 2006

This paper was a study about noise reduction through flow stabilization in duel using experimental method and numerical analysis at the same time. To determine the fan's type three kinds of fans(axial fan, centrifugal fan, and axial fan with centrifugal type) was examined to investigate the suitability for duct. As a result, under the equal number of rotation 2000 RPM, performance of an axial fan with centrifugal type was the most superior by 55dBA at 4.3CMM among other fans. After this, analyzed the results of the numerical analysis to find out the optimum design of pitch angle such as $0^{\circ},\;10^{\circ},\;15^{\circ}\;and\;20^{\circ}$. The intensity of turbulence was low when pitch angle was $15^{\circ}$ and air volume became peak by 5.08 CMM. It was observed that axis component of velocity increased gradually when pitch angle increased from $0^{\circ}\;to\;20^{\circ}$. Finally, designed the shapes of D/S(Down Stream) in duct that agreed inlet angle($\delta$) of stationary blades with pitch angle($\beta$) of axial fan with centrifugal type and derived flow to duct medial, and changed the shape of motor-mount to reduce occurance of unstable vortex in tip of impeller, and embodied noise reduction and improvement of air flow rate through flow stabilization.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.59-73
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• 2017

Numerical analysis using 3D finite element program (PLAXIS 3D) evaluated the interaction of soil - pile structure under dynamic surface loading. The dynamic p-y curve of the 1-g shaking table experiment by numerical analysis was calculated, and the parametric studies were presented by considering the pile-soil condition, the pile tip condition, and the loading condition. The frequency of 1.4 Hz is almost equal to the natural frequency of the pile - soil system. The p and y values of resonance phenomenon are significantly different from the results of other frequencies. The results can be summarized by a third order polynomial function representing the trend line in the p-y curve. In the case of a single pile, the shape of the dominant curve was found to be an ellipse by mathematical proof. The elliptic equation can be used for the dynamic design or analysis of soil-pile system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.703-713
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• 2002

Recently, an improved EFG(Element-Free Galerkin) crack analysis technique, which includes a discontinuous approximation and a singular basis function on the auxiliary supports, was developed. The technique is able to accurately analyze the crack propagation problem without any modification of the analysis model; however, it shows some dependency on the analysis parameters used. In this study, the effect of analysis parameters such as the size of compact support, dilation parameter, the smoothness of shape function around the crack tip, and the number of node using auxiliary supports on the accuracy of solution has been investigated. Through a patch test with a crack, relative L₂ error norm of stresses and the stress intensity factor were computed and compared for various analysis parameters and the results were presented as guidelines for adequate choice of analysis parameters.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.61-70
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• 1996

In cementless total hip arthroplasty(THA), an initial stability of the femoral component is mandatory to achieve bony inyowth and secondary long term fixation. Primary stability of the femoral component can be obtained by minimizing the magnitude of relative micromotions at bone stem interface. An accurate evaluation of interf'ace micromotion and stress/strain fields in the bone-implant system may be relevant for better understanding of clinical situations and improving THA design. Recently finite element method(FEM) was introduced in'orthopaedic research field due to its unique capacity to evaluate stress in structure of complex shape, loading and material behavior. The authors developed the 3-dimensional finite element model of proximal femur with $Multilock^{TM}$ stem of 1179 blick elements to analyse the micromotions and mechanical behaviors at the bone-stem inteface in early post-operative period for the load simulating single leg stance. The results indicates that the values of relative motion for this well fit stem were $150{\mu}m$ in maximum $82{\mu}m$ in minimum and the largest relative motion was developed in medial region of Proximal femur and in anterior-posterior direction. The motion in the proximal bone was much greater than in the distal bone and the stress pattern showed high stress concentration on the cortex near the tip of the stem. These findings indicate that the loading on the hip joint in the early postoperative situation before achieving bony ingrowth could produce large micromotion of $150{\mu}m$ and clinicaly non-cemented THA patient should not be allowed weight bearing strictly early in the postoperative period.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.2
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• pp.70-77
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• 1999

The disturbance of oil-water interface confined between tandem fences caused by a sequence of traveling vortices below the interface is investigated. The traveling vortices are assumed to be those detached from the tip of the fore fence. The potential flow is assumed and the density interface is replaced as a sheet of vortex. The shape of the interface is predicted by tracing a finite number of marker particles placed at the interface. The velocity of the marker particles is determined by the Biot-Savart integral along the vortex sheet plus the contribution from the traveling point vortices. The rate of change of vortex-sheet strength is predicted by using an evolution equation for vorticity. The calculated results obtained for various conditions demonstrate that the large amplitude of interfacial wave following the moving vortek can be generated by the vortices.

• Journal of the Korean Chemical Society
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• v.44 no.6
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• pp.573-580
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• 2000

MPT, which has been developed recently, is very tolerant to aqueous samples. Several types of MPT have been investigated and is found that the double concentric tube could sustain a stable plasma at a low plasma gas flow rate. However, the tip of torch is easily ruined. Triple concentric torch has shown the best stability and the plasma shape, much like that of ICP, especially when the central channel is quartz. The plasma is exposed and mixed with air as is suggested from the background spectrum, which leads to quenching of He MPT. Sensitivity of helium MPT equipped with a membrane desolvator has shown 10 times lower than that of Argon MPT for most of elements except for the ones with relatively high excitation energy. He MPT requires small plasma flow rate (about 1.6 L/min), stable and simple to use. Excitational temperature and electron number density measured are 4950 K and 3.28 ${\times}$ $10^{14}cm^{-3}$, respectively.

• Archives of Craniofacial Surgery
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• v.13 no.1
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• pp.11-21
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• 2012

Purpose: Mulliken's method allows for normal nasal and lip growth, which in turn forms a natural shape of the philtrum. Therefore, we used a modified Mulliken's method to correct unilateral and bilateral cleft lip nasal deformities and followed the patients for 10 years. Methods: Ninety-one patients, who had undergone repair of unilateral and bilateral cleft lip and nasal deformity simultaneously using Mulliken's method during the time period from June 1997 to June 2009, were enrolled into this study. To follow-up of the growth of the lips and nose after the operation, the following 5 anthropometric measurements were analyzed: nasal tip protrusion, columellar length, upper lip height, cutaneous lip height, and vermilion mucosa height. Results: Using this method, we obtained a result that there was no significant difference in the development of the lip compared to the normal control group, and that the bilateral cleft lip patients' nasal projection and columellar length was shorter than that in normal persons. Both measures were statistically significant. Conclusion: Mulliken's method is a superb surgical technique, which enables the normal development of the nose and lip, which further allows for the innate philtrum appearance. The author's result does not seem to be meaningful, because the normal rate of nasal growth is slow before adolescence; however, we recommend additional follow-up and accordant treatment, if needed, once the nasal growth is complete.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.5
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• pp.213-221
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• 2002

In order to improve the reliability of XLPE cables, it is necessary to find the useful diagnostic parameter according to long term aging. This paper described the change of partial discharge(PD) phase Properties of XLPE cable insulation with branch type electrical tree degradation. for long term aging. To understand the PD Properties with $\phi$ -q-n distributed shape of XLPE insulation, specimens were prepared by 22.9㎸ distribution cable and made in a type of block(16${\times}$16${\times}$3[mm]). Ogura needles having tip radius of l0${\mu}{\textrm}{m}$ were inserted into each block pieces. The measuring system was consisted of PD detector, digitizer for digital conversion, VXI system for signal processing. The PD properties of the specimens were measured from initiation of tree to breakdown and their characteristics were analyzed. We analyzed the relationship between electrical properties(PD Quantity, PD initiation angle, PD extinction angle, PD occurrence angle : (PD extinction angle - PD initiation angle)) and the normalized aging rate. We found PD parameter, PD initiation angle and occurrence angle, which are a useful diagnostic parameter in estimating the branch type electrical tree for XLPE insulation condition.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.389-398
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• 2002

The mixed mode problem (I and II) of a peny-shaped interface cracks in remote tension loading on a bi-material cylinder is studied using finite element method. The energy release rates for the tip of the crack in the interface were calibrated for several different moduli combinations and crack ratios using the modified crack closure integral technique and J-integral method, with numerical results obtained from a commercial finite element program. Numerical results show that non-dimensional value of$\sqrt{G_{II}E^*}/\sqrt[p]{\pi a}$ increases as the crack size or moduli ratio increases. Meanwhile, non-dimensional value of$\sqrt{G_{I}E^*}/\sqrt[p]{\pi a}$ decreases as the moduli ratio increases, but above the moduli ratio of 3 its value decreases then increases again as the crack size increases. Reliability of the numerical analysis in this study was acquired with comparison to an analytical solution for the peny-shaped interface crack in an infinite medium.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.1-9
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• 2017

Numerical computations are performed to investigate the effect of pintle stroke on the performance of an internal pintle thruster. Results show that the thrust control ratio was less than 2% and the aerodynamic load ratio was 22% as the pintle stroke increased. The flow past the nozzle throat rapidly expanding because of the shape of the pintle, and a shock wave was generated. Particularly, at the pintle stroke distance of 4 and 5 mm, the shock wave hit the wall of the nozzle, results in peeling bubbles. Depending on the altitude, the thrust increased and the aerodynamic load decreased, but the difference was as small as 1.5%. In the presence of the bore, the reduction of the pintle tip area resulted in a decrease in aerodynamic load.