• Journal of Chest Surgery
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• 제20권3호
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• pp.610-618
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• 1987

A 23-y-o male patient was suffered from intermittent fainting and dyspnea on exertion [NYHA Class IIIIV]. 2-D - Echocardiogram and cardiac catheterization with cineangiogram showed typical IHSS findings those were asymmetrical septal hypertrophy [ASH], systolic anterior motion of anterior mitral leaflet [SAM] which induced mild mitral regurgitation [Seller Grade I/IV] and pressure gradient about 60 mmHg between left ventricle and the aorta. Medical treatment with 8-adrenergic blockade [propranolol] and Ca" channel antagonist [Verapamil] had no response. So, we performed trans-aortic ventricular septal myotomy and mymectomy. Resected rectangular muscle bar was 1 Cm x 1 Cm x 4.5 Cm. Post-operative pressure gradient between the left ventricle and the aorta was less than 10 mmHg and SAM. was disappeared with decreased mitral regurgitation grade. Post-operative course was smooth and his symptoms and signs were free without any medication during 12 months follow-up.w-up.

• Journal of Chest Surgery
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• 제20권4호
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• pp.765-772
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• 1987

Double-chambered right ventricle [DCRV] as a clinical and anatomic entity was separated from other forms of right ventricle obstruction, and frequently associated with VSD. We experienced surgical treatment of 6 cases of DCRV with VSD. Among them, PDA in a case, PFO in two cases and one case of mild infundibular PS were associated. Preoperative cardiac catheterizations and RV cineangiograms showed about 69 mmHg. of pressure gradient in average between RV inflow and outflow portion, and filling defect by anomalous muscle bundles in the sinus portion of RV. On operation, VSD and other associated anomaly were corrected after resection of anomalous muscle bundle for relief of the obstruction through the vertical RV-tomy site. Postoperative EKG showed complete RBBB, but hemodynamic problems were not developed. Postoperative cardiac catheterizations showed markedly decreased pressure gradient between two chambers, that was about 15 mmHg. in average. Postoperative course was smooth and discharged without any problems.

• Journal of Chest Surgery
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• 제25권9호
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• pp.925-929
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• 1992

Supravalvular aortic stenosis is relatively uncommon form of congenital heart disease and the most important lesion of this anomaly is various narrowing of the aortic lumen just above the sinus of Valsalva. We experienced a case of hourglass type of supravalvular aortic stenosis involving lcm from length from lcm above the sinus of Valsalva. The patient was associated with mental retardation, peculiar facies and dental anomaly. The diagnosis was confirmed preoperatively by retrograde left heart catheterization and left ventriculography. An incision was made in the ascending aorta and into the right coronary and noncornary sinus. Care was taken to protect the right coronary artery. A Y-shaped patch of Dacron was made to enlarge the stenotic portion of aorta. Postoperative pressure gradient between the aorta and left ventricle markedly reduced 36 mmHg in comparison with preoperative pressure gradient 150mmHg. The boy was discharged without any event.

• 한국수소및신에너지학회논문집
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• 제19권1호
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• pp.64-70
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• 2008

This paper briefly discusses the main sources of errors and their solutions for measuring hydrogen uptake from gas phase by the Sieverts technique. Correction of volumetric errors of apparatus, density of hydrogen storage material, estimation of temperature gradient are investigated. Systematic errors and the change of density of the host material according to the pressure have been the subject of much controversy in recent years. We considered the standard ball calibration, temperature gradient distribution, pretreatment of hydrogen storage materials to minimize errors. We could lessen the miscalculations after applying those methods to Equilibrium pressure-composition isotherm data.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.571-574
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• 2010

Large-eddy simulation has been conducted to simulate turbulent boundary-layer flows over an array of regularly distributed obstacles considering various cases of a wind incident angle. The effect of wind direction was investigated in the square cube array that periodic boundary condition was imposed. Characteristics of the turbulent flow over the obstacle array have been found to be very sensitive to the direction of prevailing wind or of mean wind or of mean pressure gradient but varied with height, specially below the urban canopy. Turbulent statistics are changed sensitively with the direction of mean pressure gradient around 10 degree.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2053-2060
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• 2005

The unsteady Couette flow of an electrically conducting, V1SCOUS, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1915-1918
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• 2003

Atherosclerosis, which is a degenerate disease, is believed to occur in the vascular system due to deposition of cholesterol and low density lipoprotein(LDL) or thrombosis on the blood vessel. Atherosclerosis narrows arterial lumen, which is known as stenosis phenomenon of blood vessel. Pathogenesis of atherosclerosis is thought to occur mainly by aging. Restenosis phenomenon is observed in the same site of insertion of a stent and balloon angioplasty after treatment of interventional theraphy. Several hypothetical theories related to the generation of atherosclerosis have been reported: high shear stress theory, low shear stress theory, high shear stress gradient theory, flow separation and turbulence theory and high pressure theory. However, no one theory clearly explains the causes of atherosclerosis. In the present study the generation of atherosclerosis in the left coronary artery is investigated. The hypotheses are verified by using the computer simulation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.341-344
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• 2008

The complicated helical flow formed in the regenerative turbomachines is usually decomposed into a peripheral component and a circulatory component. On the basis of the momentum exchange theory, the circulatory flow plays a critical role of imparting angular momentum to the peripheral flow. Therefore, the accuracy of performance prediction is dominated by the circulatory flow modeling. Until now the circulatory flow has been accounted of a standstill flow normal to the peripheral flow. However, the circulatory path from the impeller exit to the re-entrance inlet is exposed to the adverse pressure gradient, so it would be more realistic to describe that the circulatory flow is formed on the skewed plane not perpendicular to the peripheral flow. Present study suggests new circulatory flow loss model including the effect of adverse pressure gradient and modifies the effective circulatory flow rate and circulatory pivot which were previously published.

• 대한기계학회논문집
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• 제17권6호
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• pp.1541-1546
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• 1993

본 연구에서는 새로운 유형의 저레이놀즈수 레이놀즈응력모델을 개발하기 위해 Launder등과 Gibson과 Launder에 의해 제시된 레이놀즈응력모델을 벽근처의 저 레이놀즈수 영역까지 확장하였다. 개발된 모델의 성능을 시험하기 위해 두 평판사이 에서 완전히 발달된 2차원 유동을 계산하여 그 결과를 Kimm등에 의해 수행된Navier- Stokes방정식의 직접계산결과와 비교하였으며, 아울러 Launder와 Shima가 제시한 모델로도 계산을 수행하여 그 결과를 비교 검토하였다.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1232-1239
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• 2006

In the present study, the unsteady Hartmann flow with heat transfer of a viscous incompressible electrically conducting fluid under the influence of an exponentially decreasing pressure gradient is studied. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is acted upon by an external uniform magnetic field applied perpendicular to the plates. The equations of motion are solved analytically to yield the velocity distributions for both the fluid and dust particles. The energy equations for both the fluid and dust particles including the viscous and Joule dissipation terms, are solved numerically using finite differences to get the temperature distributions.