• Progress in Medical Physics
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• v.9 no.3
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• pp.137-141
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• 1998

The purposes of this report are to evaluate whether lead ball and steel ball could be used as protective material of radiation and to acquire physical data of them for protecting 4-10 MV X-ray beams. Lead balls of diameter 2.0～2.5mm or steel balls of diameter 1.5～2.0 mm were filled in an acrylic box of uniform width. An MV radiograph of metal balls in a box were taken to ascertain uniformity of ball distribution in the box. Average density of metal ball and linear attenuation coefficient of metal balls for 4～10 MV X -rays were measured. At the time of measurement of linear attenuation coefficient, Farmer ionization chamber was used and to minimize the scatter effect, distance between the ball and the ionization chamber was 70 cm and field size was 5.5cm${\times}$5.5cm. For comparison, same parameters of lead and steel plates were measured. The distribution of metal balls was uniform in the box. The density of a mixture of lead-air was 6.93g/cm$^3$, 0.611 times density of lead, and the density of a mixture of steel-air was 4.75g/cm$^3$, 0.604 times density of steel. Half-value layers of a mixture of lead-air were 1.89 cm for 4 MV X-ray, 2.07 cm for 6 MV X-ray and 2.16 cm for 10 MV X-ray, and approximately 1.64 times of HVL of lead plate. Half-value layers of a mixture of steel-air were 3.24 cm for 4 MV X-ray, 3.70 cm for 6 MV X-ray and 4.15 cm for 10 MV X-ray, and approximately 1.65 times of HVL of lead plate. Metal balls can be used because they could be distributed evenly. Average densities of mixtures of lead-air and steel-air were 6.93g/cm$^3$, 4.75g/cm$^3$ respectively and approximately 1.65 times of densities of lead and steel. Product of density and HVL for a mixture of metal-air are same as the metal.

• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.118-122
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• 2002

A numerical study using linear finite element analysis is performed to investigate the behavior of basement wall subject to soil and water pressure. Currently, structural design of basement wall is based on the assumption for boundary condition of plate, which may lead to the erroneous results. In this study, parametric studies are performed to investigate the variation of moment and shear force according to column-to-wall stiffness ratios and aspect ratios. Scaled factors applicable to the design of basement wall are proposed with the illustration of desist examples.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.366-369
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• 2003

High T$_{c}$ superconducting lines will be applied as key materials in the areas of power transmission line; magnetic levitation of vehicle; magnetic separation; magnetic energy storage and marine propulsion. A combination method of electrophoresis deposition and zone-melting for preparation of YBaCuO tape is proposed. The submicron particle powder of YBaCuO made by sol-gel method is used in the electrophoresis process. A 40~50${\mu}{\textrm}{m}$ thickness of YBaCuO film on Ag plate could be deposited in about three minutes. After deposition the film is rolled and heat treated in order to increase the density and the adhesion of the film to the Ag plate. Silver(Ag) and lead oxide(PbO) were added in the YBaCuO powder in order to reduce its melting point. The YBaCuO coating with controlled Ag and PbO contents was preliminarily zone-melted at about 945$^{\circ}C$.>.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.251-258
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• 2000

Thermal deformation in an electronic package due to thermal strain mismatch is investigated. The warpage and the in-plane deformation of the package after encapsulation is analyzed using the laminated plate theory. An exact solution for the thermal deformation of an electronic package with circular shape is derived. Theoretical results are presented on the effects of the layer geometries and material properties on the thermal deformation. Several applications of the exact solution to electronic packaging product development are illustrated. The applications include lead on chip package, encapsulated chip on board and chip on substrate.

• Coupled systems mechanics
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• v.9 no.1
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• pp.29-46
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• 2020

In this paper we deal with stability problems of any complex structure that can be modeled by beam and shell finite elements. We use for illustration the steel plate girders, which are used in bridge construction, and in industrial halls or building construction. Long spans, slender cross sections exposed to heavy loads, are all critical design points engineers must take into account. Knowing the critical load that will cause lateral torsional buckling of the girder, or load that can lead to web buckling, as an important scenario to consider in a design process.Many of such problem, including lateral torsional buckling with influence of lateral supports and their spacing on critical load can be solved by the proposed method. An illustrative study of web buckling also includes effects of position and spacing of transverse and longitudinal web stiffeners, where stiffeners can be modelled optionally using shell or frame elements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.159-165
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• 2002

Currently structural design of basement exterior wall is based on the assumption of boundary condition of plate, which may lead to erroneous results. In this study, the behavior of basement exterior wall subject to earth pressure and hydraulic pressure is investigated using linear finite element analysis. Parametric studies are conducted to investigate the variation of moment and shear force according to column-to-wall stiffness and aspect ratios. Using these numerical results, modification factors applicable to the design of basement exterior wall are presented. Design example is illustrated, showing satisfactory results.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.457-460
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• 2008

CFRP plates has been established as an effective method for rehabilitation and strengthening of concrete structures. The CFRP reinforcements are bonded to beams and slabs using structural adhesives. Adhesive strength can be affected by environmental exposure. During freezing-and-thawing cycling, temperature-induced stresses in the adhesive layer, due to differential thermal expansion between the CFRP and the substrate concrete, may lead to bond damage and contribute to or cause premature CFRP composite separation. This paper presents the results of experimental program undertaken to investigate the effects of freeze-thaw cycling (from -18 to $4^{\circ}C$) on the behavior and failure characteristics of RC beams strengthened in shear with CFRP plate using acoustic emission (AE) technique.

• Journal of information and communication convergence engineering
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• v.1 no.2
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• pp.63-66
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• 2003

High $T_c$ superconducting lines will be applied as key materials in the areas of power transmission line; magnetic levitation of vehicle; magnetic separation; magnetic energy storage and marine propulsion. A combination method of electrophoresis deposition and zone-melting for preparation of YBaCuO tape is proposed. The submicron particle powder of YBaCuO made by sol-gel method is used in the electrophoresis process. A 40∼50 ${\mu}\textrm{m}$ thickness of YBaCuO film on Ag plate could be deposited in about three minutes. After deposition the film is rolled and heat treated in order to increase the density and the adhesion of the film to the Ag plate. Silver(Ag) and lead oxide(PbO) were added in the YBaCuO powder in order to reduce its melting point. The YBaCuO coating with controlled Ag and PbO contents was preliminarily zone-melted at about $945^{\circ}C$.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.21-27
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• 2023

In this article, a plate-type megasonic cleaning system with cooling pins is proposed for the sliced ingot, which is a raw material of silicon (Si) wafers. The megasonic system is operated with a lead zirconate titanate (PZT) actuator, which has high electric resistance, thus when it is being operated, it dissipates much heat. So this article proposes a megasonic system with cooling pins. In the design process, finite element analysis was performed and the results were used for the design of the waveguide. The frequency with the maximum impedance value was 998 kHz, which agreed well with the measured value of 997 kHz with 0.1 % error. Based on the results, the 1 MHz waveguide was fabricated. Acoustic pressures were measured, and analyzed. Finally, cleaning tests were performed, and 90 % particle removal efficiency (PRE) was achieved over 10 W power. These results imply that the developed 1 MHz megasonic will effectively clean sliced ingot wafer surfaces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.386-391
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• 1998

The effect of the changes in parameter angles(precone, droop, sweep) on the lead-lag damping was focused on. Experiment was made with hingeless 4-blade rotors and NACA 0012 airfoil. For the measurement of the rotating natural frequencies and lead-lag damping, non-rotating swash plate was oscillated at the regressing lag mode frequency and the data were acquired after the excitation was cut off. Analysis was made using a finite element formulation based on Hamilton's principle. The main blade is assumed as elastic beams. Quasi-steady strip theory is used to obtain aerodynamic forces, and non-circulatory forces are also included.