• Journal of KSNVE
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• v.4 no.2
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• pp.137-146
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• 1994

An analytical method for linear free vibration of fully liquid-filled circular cylindrical shell with various boundary conditions is developed by the Fourier series expansion based on the Stokes' transformation. A set of modal displacement functions and their derivatives of a circular cylindrical shell is substituted into the Sanders' shell equations in order to explicitily represent the Fourier coefficients as functions of the end point displacements, forces, and moments. For the vibration relevant to the liquid motion, the velocity potential of liquid is assumed as a sum of linear combination of suitable harmonic functions in the axial directions. The unknown parameter of the velocity potential is selected to satisfy the boundary condition along the wetted shell surface. An explicit expression of the natural frequency equation can be obtained for any kind of classical boundary conditions. The natural frequencies of the liquid-filled cylindrical shells with the clamped-free, the clamped-clamped, and the simply supported-simply supported boundary conditions examined in the previous works, are obtained by the analytical method. The results are compared with the previous works, and excellent agreement is found for the natural frequencies of the shells.

• Journal of KSNVE
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• v.4 no.2
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• pp.163-175
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• 1994

An analytical method for nautral frequencies of a partially liquid- filled circular cylindrical shell with various boundary conditions is developed by means of the Stokes's transformation and Fourier series expansion on the basis of Sanders' shell equation. The liquid-shell coupled system is divided into two regions for convenient formulation. One is the empty shell region in which the Sanders' shell equations are formulated without the lipuid effect, the other is wetted shell region in which the shell equations are formulated with consideration of the liquid dynamic effect. The shell equations for each regions are combined by the geometry and the force continuities at the junction of the two regions. For the vibration relevant to the liquid motion, the velocity potential of liquid is assumed as a sum of linear combination of suitable harmonic functions in axial direction. The unknown parameters are selected to satisfy the boundary condition along the wetted shell surface. The natural frequencies of the liquid filled cylindraical shells with the clamped- free and the clamped-clamped boundary conditions examined in the previous works, are obtained by this analytical method. The results are compared with the previous works, and excllent agreement is found for the natural frequencies of the shells.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.69-73
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• 2011

Butterflies have been known to suck viscous liquids through a long, cylindrical proboscis using the large pressure difference formulated by the cyclic expansion and contraction of a muscular pump located inside their head. However, there are few studies on the liquid-feeding phenomena in a live butterfly, because it is hard to observe the internal morphological structures under in vivo condition. In this study, the dynamic motion of the pump system in a butterfly was in vivo visualized using synchrotron X-ray micro-imaging technique to analyze the liquid-feeding mechanism. The period of the liquid-feeding process is about 0.3sec. The expansion stage is about two times larger than the contraction stage in one cycle. The cyclic variation of pump volume generate large negative suction pressure and the pressure difference inside the long proboscis of a butterfly is estimated to be larger than 1atm.

• Polymer(Korea)
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• v.34 no.4
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• pp.369-375
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• 2010

We used melt polymerization method to prepare a series of aromatic liquid crystals (LCs) based on aromatic ester and amide units with the reactive methyl-maleimide end group, and then the resulting thermally cross-linked LCs to produce LC thermoset films by means of solution casting and the followed heat treatment. The synthesized LCs and LCTs were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), X-ray diffractometry (XRD), and polarizing optical microscopy (POM) with a hot stage. All of the LCs prepared by melt polymerization method formed smectic mesophases. The thermal properties of the LC and LCT films were strongly affected by the mesogen units in the main chain structures. The thermal expansion coefficients of samples were in the range of 27.72~50.95 ppm/$^{\circ}C$.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.646-652
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• 2009

Present study deals with a three phase flow problem of determining drag acting on spheres wetted by liquid flow by gas flow through the spheres in simple cubic (SC), body-center cubic (BCC) and face-centered cubic (FCC) array, respectively, when the inertia of gas is negligibly small. The liquid flow driven by gravity on the spheres is assumed to be unaffected by the countercurrent gas flow. A perturbation method coupled with a multipole expansion method is used to calculate the hydrodynamic interactions between spheres and hence determine the effect of liquid film and flow on the gas flow for each periodic array of spheres. An approximate method for evaluating the effect of the liquid film is also presented for simple estimations. It is found that the approximation results are in a reasonable agreement with the numerical calculations.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.828-833
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• 2014

In this paper, the performance characteristics for newly developed ejector refrigeration system, which is that the part of saturated vapor from liquid-vapor separator after ejector expansion process is entrained in ejector, and the saturated liquid flows in the evaporator and compressed with the rest of vapor in separator, is studied. The reasons of the performance improvement of refrigeration system are that the refrigeration capacity is increased due to quality reduction after iso-entropic expansion process by ejector and the compression work is reduced because of the relatively high pressure of vapor refrigerant before compression process. The comparison results of the ejector system entraining expansion gases with the present residential freezer show that the COP increases to 27.8% maximum in case of the pressure drop to 65% of high pressure of freezer, and to 40.1% for 75% pressure drop of refrigerant R401A. The COP improvement rate with 20%~60% pressure lift in diffuser of ejector is only 2.6%~3%.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.4
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• pp.451-459
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• 2024

This paper quantitatively analyzes the causes of ammonia-filled- cylinder rupture based on Tait equation and the safety guidelines, focusing on liquid expansion, internal temperature, and overfilling. When there exists a safety volume, i.e., gas-occupied volume within the ammonia cylinder, the internal pressure due to temperature rise corresponds to the vapor pressure at that temperature, with an approximate circumferential stress increase of 1.43 MPa/℃. In the absence of the safety volume, the internal pressure due to temperature rise matches the pressure of the compressed liquid ammonia at that temperature, and the resulting circumferential stress gradient in the cylinder shell is approximately 55.94 MPa/℃.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.384-393
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• 2002

The effects of hole expansion angle and the arrangement of nozzles on a film cooling system for a turbine-blade-shaped surface were experimentally investigated. Liquid crystal with flue-temperature correlation and an image processing system were employed to evaluate surface temperature. Distributions of cooling effectiveness were then presented to figure out the change of heat transfer characteristics with different geometric conditions of cooling-holes. It was found thats the averaged cooling efficiency on the suction surface was maximum with 10 degree of the cooling hole expansion angle. It was also shown that the averaged cooling efficiency on the pressure surface and the averaged cooling efficiency for dual array case were not affected by the hole expansion angle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.337-341
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• 2021

Phase evolution, thermal and microwave dielectric properties of cordierite-Al₂O₃ composite were investigated. As the content of Al₂O₃ increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al₂O₃. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al₂O₃ increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al₂O₃ composite sintered at 1,425℃ were 2.9×10^-6 K^-1, 5.1, and 34,844 GHz, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.314-319
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• 1995

The effect of liquid level on the natural frequencies and mode shapes of a partially liquid-filled circular cylindrical shell with various boundary conditions is investigated by means of a theoretical analysis based upon Fourier series expansion method and a finite element analysis using ANSYS computer program. Two dimensional mode shapes of the liquid-coupled shell structure are obtained by the ANSYS finite element analysis and show that the liquid level affect the nodal point movement. It is found that the variation of normalized naturalfrequencies (natural frequencies of liquid-filled shell/antural frequencies ofempty shell) to the liquid level is depend on the axial mode numbers and circumferential wave numbers. Additionally, it is found that the number of variational steps of normalized natural frequencies is identicial to that of axial nodal points of the mode shape.