• Progress in Superconductivity and Cryogenics
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• v.5 no.2
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• pp.66-70
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• 2003

Transient magnetic diffusion process in a melt-cast Bi2Sr2CaCu20X(Bi-2212) tube was studied by experimental and numerical analyses. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper. This experiment measure the magnetic flux density in the supercondutor after supply direct-current of Bi-2212 rounded by copper coil. This study was discussed of valid of a previous numerical solution which is compared by the penetrate time and the magnetic flux density difference of between the present results and the numerical solution.

• Journal of radiological science and technology
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• v.9 no.1
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• pp.73-81
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• 1986

This paper carried out an experiment on the characteristics of time, temperature, electric field and the dependense of electrode materials and gap length by the conduction current of the insulating oil used for x-ray tube housing. The obtained results can be summarized as following: 1. In the x-ray tube housing insulating oil with vacuum condition, conduction current is declined more than the x-ray tube housing insultaing oil with the air, and is held stable states. 2. At the low electric field the higher temperature of the x-ray tube housing insulating oil is increased, the more conduction current. 3. The dependence of electrode material is appeared at the low electric field and the short gap length than the high and the long with Fe> Cu >Al. 4. At the I-E characteristics, the low electric field than 1000 [V/cm] is appeared Ohm's law region, and the high become saturation region. 5. At the same electric field, the longer gap length become, the more conduction current is increased, and the same applied voltage, the longer, the less conduction current is decreased, the less low than high temperature x-ray tube housing insulating oil.

• Transactions of Materials Processing
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• v.23 no.3
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• pp.164-170
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• 2014

To predict the deformation and fracture during tube expansion using the finite element (FE) method, a material model is considered that incorporates the damage evolution due to the deformation. In the current study, a Rice-Tracey model was used as the damage model with inclusion of the hydrostatic stress term. Since OFHC Cu is not significantly affected by strain rate, a Hollomon flow stress model was used. The material parameters in each model were obtained by using an optimization method. The objective function was defined as the difference between the experimental measurements and FE simulation results. The parameters were determined by minimizing the objective function. To verify the validity of the FE modeling, cross-verification was conducted through a tube expansion test. The simulation results show reasonable agreement with the experiments. The design for a minimum diameter of expansion tube using the FE modeling was verified by a simplified tube expansion test and simulation results.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.301-307
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• 2015

We present a study of hydrogen liquefaction using the CFD (Computational Fluid Dynamics) program. Liquid hydrogen has been evaluated as the best storage method because of high energy per unit mass than gas hydrogen, but efficient hydrogen liquefaction and storage are needed in order to apply actual industrial. In this study, we use the CFD program that apply navier-stokes equation. A hydrogen is cooled by heat transfer with the while passing gas hydrogen through Cu tube. We change diameter and flow rate and observe a change of the temperature and flow rate of gas hydrogen passing through Cu tube. As a result of, less flow rate and larger diameter are confirmed that liquefaction is more well. Ultimately, When we simulate the hydrogen liquefaction by using CFD program, and find optimum results, it is expected to contribute to the more effective and economical aspects such as time and cost.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.137-152
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• 2023

Polarization behavior and corrosion inhibition of copper in acidic chloride solutions containing benzotriazole were studied. Pourbaix diagrams constructed for copper in NaCl solutions with different BTAH concentrations were used to understand the polarization behavior. Open circuit potential (OCP) depended not only on chloride concentration, but also on whether a CuBTA layer was formed on the copper surface. Only when the (pH, OCP) was located well in the CuBTA region of the Pourbaix diagram, a stable corrosion inhibiting CuBTA layer was formed, which was confirmed by X-ray Photoelectron Spectroscopy (XPS) and a long-term corrosion test. The OCP for the CuBTA layer decreased logarithmically with increasing [Cl^-] activity in the solution. A minimum BTAH concentration required to form a CuBTA layer for a given NaCl concentration and pH were determined from the Pourbaix diagram. It was found that 320 ppm BTAH solution could be used to form a corrosion-inhibiting CuBTA layer inside the corrosion pit in the sprinkler copper tube, successfully reducing water leakage rate of copper tubes. These experimental results could be used to estimate water chemistry inside a corrosion pit.

• Progress in Superconductivity
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• v.6 no.2
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• pp.129-132
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• 2005

The formation behavior of $YBa_2Cu_3O_{7-x}$(Y123) and CuO phases in the heat-treated Cu-sheathed YBCO thick films was studied. The thick films were prepared by screen-printing method using $BaCO_3$ and Y211 powders on Cu tapes. The screen-printed thick films were placed at the center of the tube furnace, heated to $930^{\circ}C$ in air atmosphere and then maintained at the temperature for 60 sec - 300 sec. The microstructure and phases formed in the thick films were investigated by using optical microscope, X-ray diffraction (XRD) and SEM image analysis. During the heat treatment, partial melting occurred rapidly in the printed layers by peritectic reaction between CuO and precursor powders, and then YBCO superconducting phases nucleated from the Cu tapes and grew in a form of thick films.

• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.23-25
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• 1994

A simple analytical method that allows direct monitoring of small amount of CO$_2$ in a CO$_2$ discharge tube which utilizes the optoacoustic detection technique is described. The dependence of the optoacoustic signal on the mole fraction of CO$_2$ was shown that the system responded linearly to the amount of CO$_2$ present in the miniature discharge cavity equipped with Cu electrodes. It was also found that fraction of dissociated CO$_2$ varied from 14 to 37% of the initial concentration which depended on the current and the pressure in the tube. This simple and easy detection method has proven to possess the practical advantages over the conventional systems for the study of CO$_2$ laser electrodes.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1977-1979
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• 1999

This work characterized in terms of the physical properties of heavy elements as reduction filter in the diagnostic radiology. From the results of experimental evaluation, it was founded that in the case of the Ho filter, the variety of X-ray property with kVp was less than those of Ba, Cu and Al. And the ratio of transit-dose to surface and the load of X-ray tube were increased in the order of Al, Ba, Cu and Ho. The contrast of X-ray image showed the higher value in the order of Cu, Al, Ba and Ho.

• Journal of radiological science and technology
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• v.23 no.1
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• pp.91-96
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• 2000

This work was on the reduction of exposure dose and contrast improvement by Use of Heavy Elements Filter From the result of experimental evaluation, it was found that the beam harding of X-ray was not showed in Ho and Gd, heavy elements filters, contrast to Cu and Al filters In which the harding showed. And the ratio of transit dose to surface dose and the load of X-ray tube increase in order of Al, Cu, Gd and Ho, respectively. The contrast of X-ray images using the intensifying screen and the input phosphor showed the higher value in order of Cu, Al, Gd and Ho. Therefore, in the case of using contrast media and phosphor in region of diagnostic radiology, X-ray image quality depends primarily on kVp and heavy elements filters.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.682-689
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• 1995

In order to refine the grain size of Mg-Zn alloy 0.5 to 6wt.%Cu or Si elements were added. Alloy ingot was made under vacuum atmosphere of 4 ${\times}$ 10$\^$-4/ Torr in the quartz tube coated by BN. Grain size and hardness were measured after solution treatment for 8 hours at 435$^{\circ}C$. Optimal condition for grain size refining effect was obtained at the minimum composition of 2wt.%Cu or 1.5wt.%Si addition to Mg-6wt%Zn alloy. Age hardening behavior was experimented at the optimal compositions of the Mg-6wt.%Zn, Mg-6wt.% Zn-2wt.%Cu and Mg-6wt.% Zn-1.5wt.%Si. The hardness increment due to fine grain size was higher at the Mg-Zn-Cu alloy system, but that due to age hardening was higher at the Mg-Zn-Si alloy system.