• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.761-770
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• 2008

The report presents turbulent Navier Stokes computations on twin engine afterbody model with jet exhaust. The computations are carried out for free-stream Mach number of 0.8 to 1.20 and jet pressure ratio of 3.4 to 7.8. The Spalart-Allmaras turbulence model is used in the computations. Comparison is made with experimental data and Cp distribution around the afterbody is found to agree well with experiments. Flow features of the exhaust jet like under expansion, over expansion, Mach discs, etc are well captured. The effect of nozzle pressure ratio and flight Mach number are studied in detail. These computations serve as validation of the in-house code for twin jet afterbody.

• Transactions of Materials Processing
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• v.9 no.6
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• pp.561-566
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• 2000

Recently, the hydroforming technology has been recognized as a general technique in manufacturing industry, especially in automotive industry. Hydroforming is applied to increase strength, and to decrease weight, cost and parts. Hydroforming is based on the inflation of, for Instance, a tube, coupled with axial or radial compression and by subsequent expansion and sizing against the die wall. Expansion, axial feeding, calibration are important parameters in this process. In this paper, the effects of various parameters such as internal pressure, axial feeding and friction on hydroforming of automotive bumper rail have been considered.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.310-315
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• 2003

This paper presents the effect of boundary condition of failure pressure model for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with various corrosion defects for long exposure periods in years. A failure pressure model based on a failure function composed of failure pressure and operation pressure is adopted for the assessment of pipeline failure. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the corrosion pipeline.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.200-207
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX (Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. Critical tunnel lengths which are induced by x-t diagram analysis can be applied to the experimental results measured by using the running test with atmospheric pressure sensors and portable data acquisition system in previous study. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.239-240
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.167-168
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• 2008

• Wind and Structures
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• v.26 no.2
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• pp.99-114
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• 2018

Due to shortage of land and architectural aesthetics, sometimes the buildings are constructed as unconventional in plan. The wind force acts differently according to the plan shape of the building. So, it is of utter importance to study wind force or, more specifically wind pressure on an unconventional plan shaped tall building. To address this issue, this paper demonstrates a comprehensive study on mean pressure coefficient of 'E' plan shaped tall building. This study has been carried out experimentally and numerically by wind tunnel test and computational fluid dynamics (CFD) simulation respectively. Mean wind pressures on all the faces of the building are predicted using wind tunnel test and CFD simulation varying wind incidence angles from $0^{\circ}$ to $180^{\circ}$ at an interval of $30^{\circ}$. The accuracy of the numerically predicted results are measured by comparing results predicted by CFD with experimental results and it seems to have a good agreement with wind tunnel results. Besides wind pressures, wind flow patterns are also obtained by CFD for all the wind incidence angles. These flow patterns predict the behavior of pressure variation on the different faces of the building. For better comparison of the results, pressure contours on all the faces are also predicted by both the methods. Finally, polynomial expressions as the sine and cosine function of wind angle are proposed for obtaining mean wind pressure coefficient on all the faces using Fourier series expansion. The accuracy of the fitted expansions are measured by sum square error, $R^2$ value and root mean square error.

• Journal of The Korea Institute of Healthcare Architecture
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• v.28 no.4
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• pp.61-69
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• 2022

Purpose: In response to the rapid spread of COVID-19 in 2020, the government supported facilities and equipment through the 'Urgent Isolation Ward Expansion Project'. Design and remodeling of efficient negative pressure isolation facilities had to be done in a short period of time, and the performance gap between facilities was very large because the types of hospitals and wards of existing medical facilities were diverse. In order to secure the stability of isolation wards between medical facilities and reduce the facility gap, guidelines for planning isolation wards considering the diversity of each hospital should be appropriately presented. In consideration of these points, this study aims to provide basic data for future remodeling guidelines for each plan type of the negative pressure isolation ward first. Methods: We analyzed the plans before and after the change of 13 case hospitals that performed the urgent care bed expansion project for COVID-19 confirmed patients. Before the remodeling, the current status of the facility was analyzed according to the type of corridor, the location of the nursing station, and the location of the elevator. After remodeling, the flow of medical staff and patients, the flow of entry and exit of clean and contaminated items, and the space of negative pressure and non-negative pressure areas. Results: The ward type was divided into three types according to the corridor type and room arrangement: double loaded corridor type with two side wards, race track type with one side ward, and race track type with two side wards. Based on these three types, the standard floor plan type of the isolation ward was proposed in terms of the location of the elevator bank and Nurse station. Implications: When the existing general ward is converted into a negative pressure isolation ward, this study can be a basic data to present customized guidelines for each ward type.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.2
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• pp.95-100
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• 2022

PURPOSE: The purpose of this study was to compare the effect of depending on the location of applying chest expansion resistance exercise on the respiratory muscle strength stroke patients, and to suggest more effective interventions to improve respiratory function in stroke patients in clinical practice. METHODS: A total of 30 subjects were selected and divided into two groups, and chest cage extension resistance exercise was applied to the sternum and rib cage, respectively, and performed for 4 weeks, 3 times a week, for 20 minutes. In order to compare the general characteristics of the study subjects and the homogeneity of the group, the pre-experimental values were analyzed using the independent sample t-test. Paired-sample t-test was used for pre-post value comparison of maximum inspiratory pressure and maximum expiratory pressure in each group. Statistical significance was set to .05. RESULTS: Both the sternum application group and the rib cage application group showed a significant difference in the maximum inspiratory pressure according to the intervention. Also, there was a statistically significant difference in the maximum expiratory pressure in the sternum application group. CONCLUSION: As breathing exercise is important for stroke patients, based on the results of this study, if therapists perform sternal extension resistance exercise or rib extension resistance exercise according to the patient's condition and environment, it can help the breathing function of stroke patients.

• Archives of Plastic Surgery
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• v.47 no.5
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• pp.419-427
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• 2020

Background This study evaluated the Blossom system, an innovative self-filling, rate-controlled, pressure-responsive saline tissue expander (TE) system. We investigated the feasibility of utilizing this technology to facilitate implant-based and combined flap with implant-based breast reconstruction in comparison to conventional tissue expansion. Methods In this prospective, single-center, single-surgeon pilot study, participants underwent either implant-based breast reconstruction or a combination of autologous flap and implantbased breast reconstruction. Outcome measures included time to full expansion, complications, total expansion volume, and pain scores. Results Fourteen patients (TEs; n=22), were included in this study. The mean time to full expansion was 13.4 days (standard error of the mean [SEM], 1.3 days) in the combination group and 11.7 days (SEM, 1.4 days) in the implant group (P=0.78). The overall major complication rate was 4.5% (n=1). No statistically significant differences were found in the complication rate between the combination group and the implant group. The maximum patient-reported pain scores during the expansion process were low, but were significantly higher in the combination group (mean, 2.00±0.09) than in the implant group (mean, 0.29±0.25; P=0.005). Conclusions The reported average duration for conventional subcutaneous TE expansion is 79.4 days, but this pilot study using the Blossom system achieved an average expansion duration of less than 14 days in both groups. The Blossom system may accommodate single-stage breast reconstruction. The overall complication rate of this study was 4.5%, which is promising compared to the reported complication rates of two-stage breast reconstruction with TEs (20%-45%).