• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.4
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• pp.10-20
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• 2022

The performance analysis test of the scramjet engine intake was conducted under the Mach 5 condition of the scramjet engine test facility, a free-jet ground test facility of the Korea Aerospace Research Institute. A pitot/static pressure rake installed at the rear of the isolator was designed and manufactured to measure the total pressure recovery rate and mass capture ratio, which are typical performance factors of the scramjet engine intake. The effect of the rake mounted at the rear of the isolator on the intake, the performance analysis measured by the rake, and the change in wall static pressure distribution according to the angle of attack were performed. Finally, the point at which the intake unstart occurred was confirmed by using the rear back pressure adjusting device, which simulates pressure rise in the combustor, and the results are summarized in this paper.

• Proceedings of the Membrane Society of Korea Conference
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• 2002.05a
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• pp.169-171
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• 2002

• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.639-646
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• 2010

The APAM's quantitative effectiveness and comparative study in preventing and treating pressure ulcer has not been sufficiently evaluated mainly because of uncertainty of pressure load input and lack of interpretation of dynamic perfusion recovery characteristics of soft tissue. The purpose of this paper was to quantify and analyze the alternating pressure characteristics of APAM as a preventive measure for pressure ulcers. To quantify the alternating load to human body, we introduced alternating pressure profile concept and developed parametric model of the profile. Regarding pressure level and cycle time, 3 global and 7 local periodic parameters were used to define the profile such as light, standard, typical and heavy duty profile shape. Pressure impulse ratio of light duty is the lowest but pressure fluctuation is significantly high. For the same duty shape, contact conditions are changed with alternating cycle time and more dramatically in shorter alternating cycle time conditions. We can conclude that if we use shorter alternating cycle time on APAM's operation we can get more positive effects regarding to inflated contact time condition. We proposed the quantitative methods on tissue viability study of external loading by simultaneous measurement of interface pressure and tissue perfusion with proper alternating pressure profile conditions.

• Archives of Plastic Surgery
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• v.39 no.4
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• pp.417-421
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• 2012

We present a case of a near total amputation at the distal tibial level, in which the patient emphatically wanted to save the leg. The anterior and posterior tibial nerves were intact, indicating a high possibility of sensory recovery after revascularization. The patient had open fractures at the tibia and fibula, but no bone shortening was performed. The posterior tibial vessels were reconstructed with an interposition saphenous vein graft from the contralateral side and a usable anterior tibial artery graft from the undamaged ipsilateral distal portions. The skin and soft tissue defects were covered using a subatmospheric pressure system for demarcating the wound, and a latissimus dorsi myocutaneous free flap for definite coverage of the wound. At 6 months after surgery, the patient was ambulatory without requiring additional procedures. Replantation without bone shortening, with use of vessel grafts and temporary coverage of the wound with subatmospheric pressure dressings before definite coverage, can shorten recovery time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.839-848
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• 2005

Plastic plate heat exchangers have many advantages over the conventional heat exchangers such as aluminum plate heat exchangers, rotary wheel heat exchangers and heat pipe heat exchangers which have been used for ventilation heat recovery in the air-conditioning systems. In the present study, pressure drop and heat transfer characteristics of plastic plate heat exchangers are investigated for various design parameters and operating conditions which affect the performance of the plastic plate heat exchangers. In flat plate type heat exchanger, material thickness and channel height of heat exchanger are considered, and corrugate size and heat transfer area are considered in case of corrugate type heat exchanger. Pressure drop and effectiveness of the corrugate type heat exchanger increase as the corrugate size decreases.

• Ocean Systems Engineering
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• v.10 no.1
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• pp.1-23
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• 2020

Hydrodynamic Drag of Surface combatants pose significant challenges with regard to fuel efficiency and exhaust emissions. Stern flaps have been used widely as an energy saving device, particularly by the US Navy (Hemanth et al. 2018a, Hemanth Kumar and Vijayakumar 2018b). In the present investigation the effect of flap turning angle on drag reduction is numerically and experimentally studied for a high-speed displacement surface combatant fitted with a stern flap in the Froude number range of 0.17-0.48. Parametric investigations are undertaken for constant chord length & span and varying turning angles of 5° 10° & 15°. Experimental resistance values in towing tank tests were validated with CFD. Investigations revealed that pressure increased as the flow velocity decreased with an increase in flap turning angle which was due to the centrifugal action of the flow caused by the induced concave curvature under the flap. There was no significant change in stern wave height but there was a gradual increase in the stern wave steepness with flap angle. Effective length of the vessel increased by lengthening of transom hollow. In low Froude number regime, flow was not influenced by flap curvature effects and pressure recovery was marginal. In the intermediate and high Froude number regimes pressure recovery increased with the flap turning angle and flow velocity.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.65-74
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• 2002

Optimal supersonic diffuser shape of integrated rocket ramjet engine was derived which maximizes the total pressure recovery. Mass flux is considered as a design constraint and the second oblique shock angle of the external ramp, the cowl-lip angle and the throat area are selected as design variables. Refined response surface method through design space transformation technique was developed and employed, and high confidence level of the regression model could be obtained. Genetic algorithm was implemented for both system optimizer and subspace regression model optimization. Virtual nozzle was located at the end of throat to adjust the back pressure. With only 20 aerodynamic analyses, optimal supersonic diffuser shape which has 14% improved total pressure recovery characteristics was successfully designed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.120-125
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• 2011

As an effort to secure economically viable heat recovery units, innovative fin shapes for industrial boilers are studied for better performance. In the present study a numerical modeling for the analysis of heat exchanger performance is conducted using a commercial software, ANSYS CFX and the results are compared with the experimental data. Out of several candidate fin shapes curved wavy fin is selected for the present study. Both numerical and experimental data are directly compared for heat transfer rate and pressure drop with the assumed constant surface temperature of $60^{\circ}C$. Exhaust gas is obtained from a test apparatus which supplies variable flow rates. The numerical results show reasonable agreements with the experimental data within 10% in terms of both total heat transfer and pressure loss.

• Geosystem Engineering
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• v.21 no.6
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• pp.318-325
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• 2018

Eight tight sandstone reservoir samples from $He_8$ and $Shan_1$ Formations of the Sulige Gas field were selected to perform gas-water micro-displacement experiment based on authentic sandstone micro-model. The gas pressure-relief experiment was proposed for the first time to simulate the pressure change and gas-water percolation characteristics in the process of gas exploitation. The experiment results show that: (1) In the process of gas accumulation, the gas preferentially flows into the well-connected pores and throats with large radius, but rarely flows into the area without pores and throats. (2) Under sufficient gas drive, the water in pores and throats usually exists in the forms of 'thin water film', 'thick water film', and 'water column', but under insufficient gas drive, gas fails to flow into new pathways in time, so that the reservoirs with large pores and throats are high in water cut. (3) Under the same water saturation, the reservoirs with better petrophysical properties has higher gas recovery factor within unit time. Under the same petrophysical conditions, the reservoirs with lower water saturation show higher gas recovery factor within unit time. The higher the permeability, the stronger the liquid carrying capacity of reservoirs.

• Korean Journal of Clinical Laboratory Science
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• v.43 no.4
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• pp.138-144
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• 2011

Exaggerated blood pressure response during exercise has been found to increase the risk of future hypertension, left ventricular hypertrophy, cerebrovascular stroke, and CVD (cardiovascular disease) death. The aim of this study was to evaluate exercise capacity, cardiovascular factors in exaggerated blood pressure response during treadmill exercise testing. For research subjects, 72 subjects (normal blood response: 49 subjects, exaggerated blood response: 23 subjects) who received treadmill exercise test at J General Hospital were selected in this study. Exaggerated SBP (systolic blood pressure) response was defined as an SBP of 210 mmHg or greater during a maximal treadmill exercise test. The group with an exaggerated SBP response showed significantly higher values for RPP (rate pressure product) compared with the group with a normal SBP response. Subjects with METs (metabolic equivalents) had lower exaggerated SBP response than normal SBP response group. Subjects with recovery SBP had delayed exaggerated SBP response than normal SBP response group. Exaggerated SBP response to exercise is negative correlation with METs.