• 대한기계학회논문집A
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• 제20권9호
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• pp.2875-2886
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• 1996

This work present the experimental resutls for the free vibration of unstiffened, stiffened cylindrical shell filled with air, half water and full water. The natural frequencies and mode shapes of unstiffened, stiffened cylindrical shell are obtained experimentally also. The natural frequencies of stiffened cylindrical shell were generally highter than those of unstiffened cylindrical shell and natural requencies were decreased as cylindrical shell was filled with water. The effect of circumferential stiffener in the first mode was shown that natural frequency more increased 25% at air environment, 29% at half water environment and 37% at full water than those of unstiffened cylindrical shell, respectively. Also, the natural frequencies were decreased according to the added mass effect of fluid in the shell of unstiffened and stiffened cylindrical shell. The six mode shape results of all cases are simular and given. The natural frequencies are determined for a wide range of parameters : e.g. unstiffened shell, and filled with air, half and full water. The effects of varying the parameters on the free vibration frequencies and mode shapes are discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1777-1779
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• 2001

In this experiment, an attempt to use the sludge pellets as catalyst for NO removal from simulated gas is experimentally investigated by using cylinder type reactor. An experimental investigation has been conducted for NO concentration of 50[ppm], 100[ppm], 200[ppm] balanced with air. a gas flow rate of 5[1/min]. Cylinder type reactor is at upstream of system for corona discharge and packed bed type reactor filled with sludge pellets ate put at downstream of Cylinder type reactor for catalystic effect. And AC voltage to discharge the gases was supplied. In the result, NO removal with magnetic field is higher than that without magnetic field, when packed-bed reactor with sludge pellet is installed at downstream of cylinder reactor NO, $NO_2$ removal rate increased and $O_3$ is not generated.

• 설비공학논문집
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• 제7권4호
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• pp.556-565
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• 1995

The physical model of interest is based upon the concentric cylinder, where the outside cylinder is filled with optically thick and high temperature phase change material(PCM). The fluid is flowing through the inside cylinder to transfer the appropriate energy. The fluid is flowing through the inside cylinder to transfer the appropriate energy. The governing equations for the phase change material including internal thermal radiation and for the turbulent transfer fluid have been employed and numerically solved. The optically thick phase change justifies the P-l spherical harmonics approximation, which is believed to be appropriate choice particularly for the much coupled problem like in this study. The solid/liquid interface, temperature distribution within the PCM and the heat flux from the PCM to the transfer fluid have been obtained and compared with those of laminar transfer fluid. The numerical results show that the turbulent transfer fluid accelerates the solid/liquid interface and results in the increase of heat transfer rate from the PCM. The internal thermal radiation within the PCM, however, does not always playa role to increase the heat transfer rate throughout the inside cylinder. It is believed that the combined heat flux has been picked up more in the inflowing area than in the pure conductive phase change material.

• 설비공학논문집
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• 제9권1호
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• pp.55-63
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• 1997

A numerical investigation has been made for flows in an axisymmetric circular cylinder with an impulsively rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is only the vertex angle of the cone, otherwise Reynolds number and aspect ratio of the vessel are fixed. Main interest concerns on the vortex breakdown of meridional circulation by impulsive rotation of the cone with respect to the longitudinal axis of the cylinder. Numerical method has been used to integrate momentum and continuity equations on a generalized body-fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat endwall disks. The flow visualization photograph of the preceeding work by Escudier is compared with the present numerical results and the two results are in good agreements. Also flow data are plotted to gain a deep understanding for the present phenomena of the vortex breakdown. The conclusions of this work are clearly explained by the classical theory of the vortex flows in a finite geometry.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.683-688
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• 2003

Vibration characteristics of a fuel rod to be used in KALIMER(Korean Advanced LIquid MEtal Reactor) have been estimated through 3-dimensional finite element analysis and verified by experiment. The fundamental natural frequencies are found to be 6㎐ in air and 2.5㎐ in water. respectively. It has been found that in-water natural frequencies of the fuel rod are lower than in-air ones due to the added mass effect of the fluid filled inside the outer cylinder and they further decreases as the gap between the fuel rod and the outer cylinder increases, namely the added mass effect increases as the gap increases(maximum 54%). It has been also shown that the mass of the wire wrap axially coiled around the fuel rod do not affect the natural frequencies.

• 전기학회논문지
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• 제59권5호
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• pp.939-944
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• 2010

A high voltage air-cored helical strip/wire type pulse transformer has been fabricated for charging of a high voltage pulse forming line. As a primary coil, copper strip of 25mm width was wound helically around a MC nylon cylinder. For a secondary coil, copper enameled wire of 1mm diameter was wound around conical cylinder in order to provide insulation between two windings. The coupling coefficient of 0.53 was obtained when two coils were combined coaxially in the insulation oil filled chamber. Voltage gain and energy transfer efficiency were investigated by varying the parameters of primary and secondary circuit. Test results shows that the voltage gain increases up to 17 with increasing the primary capacitance up to 200nF. And highest energy transfer efficiency of 44% was obtained when the dual resonant operation condition was nearly satisfied. The pulse transformer developed in this study can be used for charging the middle conductor of a Blumlein pulse forming line.

• 설비공학논문집
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• 제1권2호
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• pp.128-137
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• 1989

Numerical solutions for two-dimensional, steady, free convection are presented for a cylinder filled with saturated porous media. An annulus is bounded by inner wall with constant heat flux and two adiabatic horizontal walls with outer wall isothermally cooled. Governing equations are numerically solved for the range of Aspect Ratio 1 to 20, Radius Ratio, 1 to 20, and Rayleigh number, 50 to $10^4$ by Finite Difference method utilizing upwind scheme. Results are presented in terms of stream lines and isotherms, temperature distributions and local Nusselt numbers at the heated wall. Average Nusselt numbers are also presented for the comparisons.

• 한국음향학회지
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• 제24권8호
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• pp.441-446
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• 2005

수중에서 원통형 산란체의 산란 음장에서 발생하는 간섭 효과를 확인하기 위하여 한 개의 원통형 산란체와 동일한 두 원통형 산란체의 방위각에 따른 고주파 (120 kHz) 산란 패턴을 측정하였다. 실험은 가로, 세로, 높이가 각각 $5m\times5m\times5m$ 수조에서 공기가 채워진 원통형 PVC (poly vinyl-chloride)로부터 1.5m 거리에 위치한 수중 청음기를 $360^{\circ}$ 회전시키면서 실시하였다. 실험 결과 한 개 원통은 후방에서 무지향성으로 산란하는 특성을 보였으나 두 개 원통에서는 방위각에 따른 표적 강도의 변동성 (fluctuation)이 나타났다. Stanton이 제한한 이론 식과 측정한 산란 패턴을 비교한 결과 유사한 경향을 확인할 수 있었다.. 두 개 원통의 산란 패턴에서 나타나는 표적 강도의 변동성은 두 산란체의 중심으로부터 청음기까지의 거리차로 인한 산란 음장의 간섭 때문이다. 또한 두 개 원통의 산란 이론으로부터 원통의 간격이 커짐에 따라 표적 강도의 변동성이 심해지는 현상을 확인할 수 있었다.

• 농업과학연구
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• 제40권3호
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• pp.203-208
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• 2013

Differences in the filling amount of substrates in container can influence severely on the soil physical properties and crop growth. This research was conducted to secure the fundamental informations related to the changes in soil physical properties as influenced by the filling amount of coir dust-based substrates in container. For the experiment, three substrates were formulated by blending coir dust (CD) with expanded rice hull (CD+ERH, 8:2, v/v), carbonized rice hull (CD+CRH, 6:4, v/v) or ground and aged pine bark (CD+GAPB, 8:2, v/v). Based on the optimum bulk density, the amount of substrates filled in 347.5mL aluminum cylinder were adjusted to 90, 100, 110, 120, and 130%. Then the changes in total porosity (TP), container capacity (CC), and air-filled porosity (AFP) by various filling amounts were measured. The TP decreased linearly in CD+ERH and CD+GAPB and quadratically in CD+CRH as the filling amounts of the media increased from 90% to 130%. The CC in CD+ERH and CD+GAPB media increased as the filling amount increased from 90% to 120%, then decreased in 130%, showing quadratic change. The CC in CD+CRH was the highest in 90% filling amount and decreased gradually as the filling amount of root medea increased. The AFPs in CD+ERH and CD+GAPB media were 38 and 37%, respectively in 90% filling amount and they decreased drastically until 110% filling, then gradually in 120 and 130% filling amount showing the quadratic changes. The AFP of CD+CRH at 90% filling amount was 22% and it decreased as the filling amount increased until 130%, showing linear change. These results indicate that the increase in filling amount of substrates influenced more severely the AFP than CC, and careful consideration on container filling is required to provide a better root condition thus maximize crop growth.

• Radiation Oncology Journal
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• 제7권1호
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• pp.113-121
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• 1989

The inclusion of air filled cavities in treatment fields creates a potential dosimetric problem due to the rebuildup phenomenon near the air-tissue interface using a simulated phantom, such as air gap, air cylinder, and air cavity, the amount of rebuldup along the various field sizes and air cavity dimensions was measured. The results are as follows. 1. As the field size becomes larger in comparison with the cavity size, or as the cavity size gets bigger when the field size is equal to the cavity size, rebuildup decreases. 2. When the distance between the phantom surface and the air cavity is less than 1.5cm, there is prominent rebuildup. And when the distance is more than 1.5cm, rebuildup is relatively constant, 3. The change according to the depth of the cavity is affected by the field size and the cavity size, rebuildup usually increases when the depth of the cavity increases. 4. It is suggested that tissue equivalent material should be applied on the skin to make tissue thickness over the air cavity more than 1.5cm and that the field size should include the air cavity with at least 1cm margin.