• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.169-174
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• 1995

A finite element scheme using the concept of PISO method has been developed to solve the viscous flow problems in all speed range. In this study, new pressure equation is proposed such that both the hyperbolic term related with the density variations and elliptic term reflecting the incompressibility constraint are included. Present method has been applied to incompressible flow in two-dimensional driven cavity(Re=100, 400 and 1,000), and its computed results are compared with other's. Also, Carter plate problem(M=3 and Re=1,000) is computed and the comparison is made with Carter's results. Finally, we simulate a shock-boundary layer interaction problem(M=2 and $Re=2.96{\times}10^5$) to illustrate the shock capturing capability of the present solution algorithm.

• Ocean Systems Engineering
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• v.1 no.3
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• pp.207-222
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• 2011

A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3196-3207
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• 1993

A second moment turbulent closure for the turbulent heat flux near a wall is developed by modification of model constants in pressure interaction term as the variables of the turbulent Reynolds number using the universal properties of turbulent heat flux near the wall. The present model shows that model constant for the wall reflection term in pressure interaction is most important in modelling of the near wall heat flux. Fully developed pipe flows with constant wall heat flux are tested to validate the proposed model. In most of calculation region, the predicted turbulent properties agree better with the experimetal data than the results from standard algebraic heat flux model which use the uniform model constants.

• Journal of Korean society of Dental Hygiene
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• v.10 no.4
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• pp.735-744
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• 2010

Objectives : The purpose of this study was to examine the stressors and stress-adaptation patterns of students preparing for the national dental hygiene certification examination. Methods : The subjects in this study were dental hygiene juniors in four selected colleges located in the metropolitan area. After a survey was conducted, the collected data were analyzed. Results : 1. Concerning motivation of choosing the department of dental hygiene, the largest group that accounted for 72.2 percent chose it due to employment prospects. As to satisfaction level with the department, 40.4 percent were satisfied. In relation to employment prospects, 54.1 percent thought the prospects were bright. 2. They got a mean of 3.23 in stressors. To be specific, they felt the most stress due to test anxiety(3.70), followed by leisure insufficiency (3.21), the uncertainty of the future(3.18) and parental pressure(2.64). 3. They got a mean of 2.02 in stress-adaptation method. They got 2.31 and 1.72 in long-term and short-term adaptation respectively, which showed that long-term stress adaptation method were more prevailing than short-term ones. 4. As for the relationship of the stressors, there was positive correlation among all the test anxiety, future uncertainty, leisure insufficiency and parental pressure, and their correlation was statistically significant(p<0.000). 5. Regarding connections between general characteristics and the stressors, whether they spent two years or more for college admission, satisfaction level with the dental hygiene department, employment prospects and health status made significant differences to the stressors (p<0.05), and there were significant gaps in adaptation patterns according to academic standing, satisfaction level with the department and health state(p<0.05). Conclusions : The dental hygiene students were under great pressure since they had to prepare for the national dental hygiene certification examination to become a certified dental hygienist, one of professional health care workers. Therefore stress counseling programs and stress-coping programs should be developed to relieve the stress of dental hygiene students who are going to take the national dental hygiene certification examination. And they should be assisted to stay away from stress and to handle their stress in a more active manner.

• Archives of Plastic Surgery
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• v.38 no.6
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• pp.871-874
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• 2011

Purpose: In some patients with velopharyngeal insufficiency (VPI), Hypernasality can persist after surgical management. Continuous Positive Airway Pressure (CPAP) is applied to these patients for treating hypernasality. The purpose of this study is to report follow-up results of postoperative CPAP therapy. Methods: After performing palatal lengthening, CPAP therapy was applied to three patients for eight weeks from July of 2008 to November of 2009. Perceptual evaluation, nasometry, and nasopharyngeal endoscopy were performed to evaluate hypernasality, nasalance and size of the gap at velopharyngeal port. Each evaluation was made before surgery, right after CPAP therapy and during follow-up of more than a year after CPAP therapy. Results: All of the patients showed improvement in hypernasality right after CPAP therapy according to the auditory perceptual evaluation, nasometry and nasopharyngeal endoscopy. But the improvement in hypernasality in these patients did not last during follow-up. Conclusion: In this study, our results suggest that CPAP therapy is effective in reducing hypernasality for postoperative VPI patients immediately after the therapy, but hypernasality may be worsen in some patients during follow-up. Therefore we recommend follow-ups after CPAP therapy to see if the efficacy of CPAP therapy lasts.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.431-438
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• 2009

A Large Eddy Simulation (LES) of the flow in an inducer is carried out under flow rate oscillations. The present study focuses on the dynamic response of the backflow and the unsteady pressure performance to the flow rate fluctuations under non-cavitation conditions. The amplitude of angular momentum fluctuation evaluated by LES is larger than that evaluated by RANS. However, the phase delay of backflow is nearly the same as RANS calculation. The pressure performance curve exhibits a closed curve caused by the inertia effect associated with the flow rate fluctuations. Compared with simplified one dimensional evaluation of the inertia component, the component obtained by LES is smaller. The negative slope of averaged performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression show that the apparent decrease of inertia effects is caused by the response delay of Euler's head and that the increase of negative slope is caused by the delay of inertial term associated with the delay of backflow response. These results are qualitatively confirmed by experiments.

• Archives of Plastic Surgery
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• v.46 no.5
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• pp.470-474
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• 2019

Congenital absent sternum is a rare birth defect that requires early intervention for optimal long-term outcomes. Descriptions of the repair of absent sternum are limited to case reports, and no preferred method for management has been described. Herein, we describe the use of porcine acellular dermal matrix to reconstruct the sternum of an infant with sternal infection following attempted repair using synthetic mesh. The patient was a full-term male with trisomy 21, agenesis of corpus callosum, ventricular septal defect, patent ductus arteriosus, right-sided aortic arch, and congenital absence of sternum with no sternal bars. Following removal of the infected synthetic mesh, negative pressure wound therapy with instillation was used to manage the open wound and provide direct antibiotic therapy. When blood C-reactive protein levels declined to ${\leq}2mg/L$, the sternum was reconstructed using porcine acellular dermal matrix. At 21 months postoperative, the patient demonstrated no respiratory issues. Physical examination and computed tomography imaging identified good approximation of the clavicular heads and sternal cleft and forward curvature of the ribs. This case illustrates the benefits of negative pressure wound therapy and acellular dermal matrix for the reconstruction of absent sternum in the context of infected sternal surgical site previously repaired with synthetic mesh.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.328.1-328
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• 2001

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.35-44
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• 1991

This study was carried out for the purpose of pre-estimating long-term settlement under condition of actual field soil's property, in case of building up industrial sites on the marine deposit silty clay located at West Coast in Korea. This study analyzed Hyperbolic Method, Square Root Time Method and Exponential Function Method with utilization of measured survey values of settlement in In-Cheon Namdong Industrial Sites. In the future, for the continuos utilization, it seemed to be needed that further the survey values of fields should be accurartely measured for the analysis of more accurate pre-estimate about long-term settlement. Among the prediction methods of settlement Hyperbolic Method seemed to be the best fitting method for measured data. The settlement equations were derived from above three methods, for long-term settlements.

• Geomechanics and Engineering
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• v.29 no.2
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• pp.171-182
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• 2022

Reusing the used pile has not yet been implemented due to the unpredictability of the bearing capacity evolution. This paper presents an analytic approach to estimate the sides shear setup after the dissipation of pore pressure. Long-term evolution of adjacent soil is simulated by viscoelastic-plastic constitutive model. Then, an innovative concept of quasi-overconsolidation is proposed to estimate the strength changes of surrounding soil. Total stress method (α method) is employed to evaluate the long term bearing capacity. Measured data of test piles in Louisiana and semi-logarithmic time function are cited to validate the effectiveness of the presented method. Comparisons illustrate that the presented approach gives a reasonably prediction of the side shear setup. Both the presented method and experiment show the shaft resistance increase by 30%-50%, and this highlight the potential benefit of piles reutilization.