• Journal of Chest Surgery
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• v.18 no.4
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• pp.663-666
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• 1985

Whatever a surgeon choose aortic prosthesis in aortic stenosis, it will always provoke some degree of obstruction to flow due to its smaller effective orifice area to tissue annulus. Occasionally, we meet small aortic annulus to his or her body surface area in aortic valve replacement. The small annulus remains a problem in that both tissue and mechanical prosthesis have significant pressure gradients between LV and aorta in resting or exercising states. In these circumstances, diverse surgical procedures, such as tilting disc prosthesis, supraannular position of aortic prosthesis, and enlargement of aortic root [including aortoventriculoplasty, translocation of aortic valve, & double outlet of LV by valved conduit], were applied. We experienced one case of aortic stenosis with small aortic annulus. Systolic pressure gradients between LV & aorta were 90 mmHg. Diameter of annulus was 19 mm. So we performed patch enlargement of aortic root by Manouguian and AVR with St. Jude medical valve 23 mm.

• Nuclear Engineering and Technology
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• v.36 no.5
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• pp.460-474
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• 2004

Effects of liquid subcooling on pool boiling heat transfer in an annulus with an open bottom have been investigated experimentally. A tube of 19.1mm diameter and the water at atmospheric pressure have been used for the fest. Up to $50^{\circ}C$ of liquid subcooling has been tested and experimental data of the annulus have been compared with the data of a single unrestricted tube. Temperatures on the heated tube surface fluctuate only slightly regardless of the heat flux in the annulus, whereas high variation is observed on the surface of the single tube. An increase in the degree of subcooling decreases heat transfer coefficients greatly both for the single tube and the annulus. Heat transfer coefficients increase suddenly at ${\Delta}T_{sub}\;{\le}\;10^{\circ}C$ and much greater change in heat transfer coefficients is observed at the annulus. To obtain effects of subcooling on heat transfer quantitatively, two new empirical equations have been suggested, and the correlations predict the empirical data within ${\pm}30\%$ error bound excluding some data at lower heat transfer coefficients.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1285-1292
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• 2009

The effects of the narrowed upside gap on nucleate pool boiling heat transfer in a vertical annulus were investigated experimentally. For the study, a stainless steel tube with a diameter of 25.4 mm and saturated water that kept an atmospheric condition were used. The ratio between the gaps measured at the upper and the lower regions of the annulus ranged from 0.18 to 1. Two different lengths of the modified gap also were investigated. The change in heat transfer due to the modified gap became evident as the gap ratio decreased and the length of the gap increased. As the gap ratio became less than 0.51, a significant decrease in heat transfer was observed compared to the plain annulus. The longer gap size resulted in an additional decrease in heat transfer. The major cause for the tendency was attributed to the formation of lumped bubbles around the upper region of the annulus followed by the increased flow friction between the fluid and the surface around the modified gap.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.8 s.251
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• pp.749-755
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• 2006

To improve pool boiling heat transfer in an vertical annulus with closed bottoms, the length of an outer tube has been changed from 0.2m to 0.6m. For the test, a heated tube of 19.1mm diameter and water at atmospheric pressure have been used. Annular conditions are made using glass tubes fabricated around the heated tube. The gap size of the annulus is 3.65mm. To elucidate effects of the outer tube length on heat transfer results of the annulus are compared with the data of a single unrestricted tube and the annulus with wider gap size of 6.35mm. Throughout the tests much higher heat transfer coefficients are observed for the annulus of 3.65mm gap size comparing to the other two cases. The change in the outer tube length results in much variation in heat transfer coefficients. Moreover, with shortening the length of outer tube the possibility of the CHF occurrence can be removed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.261-262
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• 2011

Conventional automatic transmission system includes a hydrodynamic torque converter to transfer engine torque from an engine crank shaft to a rotatable input members, which are of complex design permitting them to serve several functions. These are clutches or brakes which couple the rotatable input member to member of a planetary gear set. The annulus gear for an automatic transmission is a monolithic gear having a set of gear teeth formed on an inner surface which is coupling with a set of planetary gear. In this study, the flow forming method is applied to the manufacturing of the annulus gear. This cold forming is proper method in order to manufacture dimensionally precise and round hollow components such as annulus gear. By pre-calculated amount of wall thickness reduction, the seamless tube of SAE1026 is compressed above its yield strength, plastically deformed and made to flow in several roll passes. According to this study, the desired geometry of the annulus gear can be achieved when the outer diameter and the thickness of the tube are properly decreased by compressed roll passes and the available material volume is easily forced to flow longitudinally over the shape of mandrel.

• Journal of computational fluids engineering
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• v.22 no.1
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• pp.110-115
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• 2017

Natural convection of a fluid with the Prandtl number of 7(water) in a horizontal annulus with constant temperature walls is numerically investigated. The inner cylinder is hotter than the outer cylinder. The flows are classified by the number of eddies in a half annulus. It is found that dual or triple solutions exists above a critical Rayleigh number for an annulus with a aspect ratio $D_i/L=4$. Transitions of $3{\rightarrow}1$ and $2{\rightarrow}1$ eddy flow occur with decrease of Rayleigh number. However, reverse transitions of $1{\rightarrow}3$ and $1{\rightarrow}2$ eddy flow do not occur with increase of Rayleigh number, and no hysteresis phenomenon is observed. In the regime of triple solutions, the 3 eddy flow has the largest mean Nusselt number value and the 1 eddy flow has the smallest value.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.855-862
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• 2005

An experimental investigation has been carried out for aluminum foam heat sink inserted into the annulus to examine the feasibility as a heat sink for high performance forced water cooling in the annulus. The local wall temperature distribution, inlet and outlet pressures and temperatures, and heat transfer coefficients were measured for heat flux of 13.6, 18.9, 25.1, 31.4 $kw/m^2$ and Reynolds number ranged from 120 to 2000. Experimental results show that the friction factor is higher than clear annulus without aluminum foam, while the significant augmentation in Nu is obtained. This technique can be used for the compactness of the heat exchanger.

• Journal of KIISE
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• v.44 no.3
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• pp.246-252
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• 2017

In this paper, we present an algorithm that computes a minimum-width color spanning axis-parallel rectangular annulus. A rectangular annulus is a closed region between a rectangle and its offset, and it is thus bounded by two rectangles called its outer and inner rectangles. The width of a rectangular annulus is determined by the distance between its outer and inner rectangles. Given n points in the plane each of which has one of the prescribed k colors, we call a rectangular annulus color spanning if it contains at least one point for each of the k colors. Prior to this work, there was no known exact algorithm that computes a minimum-width color-spanning rectangular annulus. Our algorithm is the first to solve this problem and it runs efficiently in $O((n-k)^3nlogn)$ time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.237-244
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• 2011

An experimental study was carried out to investigate the effect of the inclination angle on the nucleate pool boiling of saturated water at atmospheric pressure. We considered an annulus with a gap of 5 mm and a bottom opening. The inner tube of the annulus was heated, and the outer diameter and the length of the tube were 25.4 mm and 500 mm, respectively. The inclination angle was varied from horizontal to vertical. The results were compared to those for an annulus with a larger gap and a single tube. In the small-gap annulus, the effect of the inclination angle on the heat transfer was not significant. However, an early onset of the critical heat flux was observed at 80 kW/$m^2$ when the annulus was horizontal. Liquid agitation and bubble coalescence were considered to be the major heat-transfer mechanisms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.217-222
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• 2006

Internal combustion engine is the main source of environmental pollutants and therefore advanced technology is required to reduce harmful elements from the exhaust gases all over the world. Especially, when the exhaust gas is released front the automotive muffler, exhaust noise has many bad influence on the surrounding environment. In order to reduce the exhaust noise, it is necessary that automotive muffler must be designed for best exhaust efficiency. The sound insulation room was installed for the analysis of an acoustics characteristics of the noise from automotive muffler, in this study. Exhaust gas noise, noise distribution characteristics, pressure and temperature of exhaust gas were investigated with the change of annulus temperature of air cooled annulus automotive muffler and cooled annulus automotive muffler. The following results were obtained with this study. From the frequency analysis of automotive muffler, high noise distribution was observed in the range $100{\sim}2000Hz$. It means that the noise in this range has an dominate influence for the overall noise. Noise reduction of automotive muffler was affected by the temperature of annulus. It is caused the result that the high temperature and pressure of exhaust gas are changed lower by the drop of annulus temperature. The tendencies of noise, the temperature and pressure of exhaust gas are similar to the performance curve of engine. Exhaust gas pressure is determined by the r.p.m. of engine and affected by the cooling performance of automotive muffler.