• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.84-92
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• 2023

As temporary storage facilities for spent nuclear fuels in domestic nuclear power plants are expected to be saturated, external intermediate storage facilities would be required in the future. Spent nuclear fuels are stored in metal canisters and then placed in a dry environment within concrete or metal casing for operation. In the United States, the dry storage method for spent nuclear fuels has been operated for an extended period. Based on the corrosion experiences of dry storage canisters in chloride environments, numerous studies have been conducted to reduce corrosion in welds. With the construction of intermediate storage facilities in Korea for spent nuclear fuels expected near coastal areas adjacent to nuclear power plants, there is a need for research on the corrosion occurrence of welds and mitigation methods for canisters in chloride environments. In this paper, we measured and compared the residual stresses in the Heat-Affected Zones (HAZ) after electron beam welding (EBW) and gas tungsten arc welding (GTAW) processes for candidate materials such as 304L, 316L, and duplex stainless steel(DSS). We investigated the possibility of microstructure control through the application of surface modification processes using friction stir processing (FSP). Corrosion tests on each welded specimen revealed a higher corrosion rate in EBW welds compared to GTAW. Furthermore, it was confirmed that corrosion resistance improved due to phase refinement and redistribution of precipitates when FSP was applied.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.225-232
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• 2023

In this study, poly(ethylene-co-vinyl acetate)/magnesium hydroxide (EVA/MDH) composites were prepared by electron beam crosslinking. EVA as a matrix resin and MDH as a flame retardant were melt-blended and compression molded to prepare EVA/MDH composites. The prepared EVA/MDH composites were electron beam-irradiated at various absorbed doses of 50~200kGy. The effects of electron beam irradiation on the gel content, tensile strength, elongation-at-break, thermal properties, and flame retardancy of the composites were investigated. The gel content and tensile strength increased, while the elongation-at-break decreased with an increase in the absorbed dose due to the formation of crosslinked network structures. In addition, the thermal stability and flame retardancy improved as the absorbed dose increased. Therefore, the EVA/MDH composites prepared in this study can be used as an insulation material for flame-retardant and heat-resistant wires and cables.

• Journal of the Korean Magnetics Society
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• v.12 no.5
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• pp.184-188
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• 2002

The Cu/Ni/Cu(002)/Si(100) films which have perpendicular magnetic anisotropy were deposited by e-beam evaporation methods. From the reflection high energy electron diffraction pattern, the films were confirmed to be grown epitaxially on silicon. After 2X lots ions/$\textrm{cm}^2$ C+ irradiation, magnetic easy-axis was changed from surface normal to in-plane as shown in the hysteresis loop of magneto-optical Kerr effects. It became manifest from analysis of X-ray reflectivity and grazing incident X-ray diffraction that even though interface between top Cu layer and Ni layer became rougher, the contrast of Cu and Ni's electron density became manifest after ion irradiation. In addition, the strain after deposition of the films was relaxed after ion irradiation. Strain relaxation related with change of magnetic properties and mechanism of intermixed layer's formation was explained by thermo-chemical driving force due to elastic and inelastic collision of ions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.58-61
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• 1995

Instead of using CCl$_4$CCl$_2$F$_2$ gases, we used a alternative reaction gas of CFCs which we have developed, for the experiment of laser induced dry etching of laser induced dry etching of GaAs, and compared with the etch profile of a usual reation gas. Laser powers(power density) on the sample surface were varied from 100 mW(12.7 MW/$\textrm{cm}^2$) to 210mW(27 MW/$\textrm{cm}^2$) The laser beam was scanned over the sample by moving the cell with a speed raging from 8.3$\mu\textrm{m}$/sec and the gas pressure also was varied form 260 Torr to 760 Torr, High etching rates up to 136 $\mu\textrm{m}$/sec and an aspect ratio of 2.6 have been achieved by single scan of laser beam. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron spectroscopy(AES) Etch profiles, including depth and width were observed by scanning electron microscopy(SEM)

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.6
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• pp.33-40
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• 1982

Although ultrasonic CT is one of the useful techniques for tissue characterization, the reconstructed images, such as the velocity distribution and attenuation constant distribution, are degraded by reflection and refraction of ultrasonic beam. This paper studied the degradation effects on attenuation images using agar gel phantoms which were developed to evaluate ultrasonic CT. We found that the reconstructed attenuation constants at the center of the phantoms were less than the actual values by 0.6 dB/cm when phantom velocity differs by 25 m/s from surrounding saline. We also studied a correction method for refraction and phase cancellation effects, where the correction was made using the maximum value in the received subdata, as obtained by sub-arraying microprobes located at each sampling point. Using this method, we could obtain an improvement in the reconstructed image by the correction on the attenuation effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.41-41
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• 2008

In general, polyimides (PIs) are used in alignment layers in liquid crystal displays (LCDs). The rubbing alignment technique has been widely used to align the LC molecules on the PI layer. Although this method is suitable for mass production of LCDs because of its simple process and high productivity, it has certain limitations. A rubbed PI surface includes debris left by the cloth, and the generation of electrostatic charges during the rubbing induces local defects, streaks, and a grating-like wavy surface due to nonuniform microgrooves that degrade the display resolution of computer displays and digital television. Additional washing and drying to remove the debris, and overwriting for multi-domain formation to improve the electro-optical characteristics such as the wide viewing angle, reduce the cost-effectiveness of the process. Therefore, an alternative to non-rubbing techniques without changing the LC alignment layer (i.e, PI) is proposed. The surface of LC alignment layers as a function of the ion beam (IE) energy was modified. Various pretilt angles were created on the IB-irradiated PI surfaces. After IB irradiation, the Ar ions did not change the morphology of the PI surface, indicating that the pretilt angle was not due to microgrooves. To verify the compositional behavior for the LC alignment, the chemical bonding states of the ill-irradiated PI surfaces were analyzed in detail by XPS. The chemical structure analysis showed that ability of LCs to align was due to the preferential orientation of the carbon network, which was caused by the breaking of C=O double bonds in the imide ring, parallel to the incident 18 direction. The potential of non-rubbing technology for fabricating display devices was further conformed by achieving the superior electro-optical characteristics, compared to rubbed PI.

• Resources Recycling
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• v.20 no.5
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• pp.40-45
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• 2011

We carried out to investigate the refining effect of molybdenum by Ar-H$_2$ vacuum arc melting(VAM) process for recycling Mo scrap. The purity of the Mo metals refined by VAM was evaluated using glow discharge mass spectromety(GDMS). From the result of GDMS, most impurities in the Mo metals except for W were removed by Ar-H$_2$ VAM down to a few mass ppm levels. The purity of the refined molybdenum scrap was improved up to 4N5(99.995%) from 3N(99.95%) of the initial Mo scrap. The amount of gaseous impurities such as C, N, and O in Mo scrap were decreased from 1290 ppm to 132 ppm. As a result, it is considered that a possibility of refining and cost-effective method for recycling Mo scrap by Ar-H$_2$ vacuum arc melting process was confirmed in this study.

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.474-478
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• 2007

Nanostructures of $SiN_x$ were made by bombardment of ionized $N_2$ on Si surface and subsequent annealing. Atomic force micrograph showed the density of $SiN_x$ nanostructures was $3\times10^{10}/cm^2$. Their lateral size and height were 40$\sim$60 nm and 15 nm, respectively. The chemical state of the nanostructure was measured using X-ray photoelectron spectroscopy, which changed from $SiN_x$ to $Si_3N_4\;+\;SiN_x$ as the bombarding ionized gas current increases. Upon annealing, transmission electron micrograph showed a clear evidence for crystalline Si phase formation inside the $SiN_x$ nanostructures. Photoluminescence peak observed at around 400nm was thought to be originated from the interface states between the nanocrystalline Si and surrounding $SiN_x$ nanostructures.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.339-344
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• 2011

The Ohmic contact of Ti/Au metals on n-type ZnO thin film deposited on c-plane sapphire substrates by pulsed laser deposition was investigated by TLM (transfer length method) patterns. The Ti/Au metal films with thickness of 35 nm and 90 nm were deposited by electron-beam evaporator and thermal evaporator, respectively. By using the photo-lithography method, the $100{\times}100{\mu}m^2$ TLM patterns with $6{\sim}61{\mu}m$ gaps were formed. To improve the electrical properties as well as to decrease an interface states and stress between metal and semiconductor, the post-annelaing process was done in oxygen ambient by rapid thermal annealing system at temperature of $100{\sim}500^{\circ}C$ for 1 min. In this study, it appeared that the minimum specific contact resistivity shows about $1.1{\times}10^{-4}{\Omega}{\cdot}cm^2$ in $300^{\circ}C$ annealed sample, which may be originated from formation of oxygen vacancies of ZnO during an oxidation of Ti metal at the interface of Ohmic contacts.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.32-45
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• 2000

This paper presents the analytic derivation of the SINR, when a linear array antenna is accommodated into the cellular CDMA basestation receiver, in relation to the two major performance effecting factors in beamforming(BF) applications, i. e., the direction selectivity, which refers to the narrowness of the mainbeam width, and the direction-of-arrival(DOA) estimation accuracy. The analytically derived results are compared with the operation simulation of the receiver realized with the several BF algorithms and their agreements are confirmed, consequently verifying the correctness of the analysis and the operation simulation. In order to investigate separately the effects of the errors occurring in the direction estimation and in the interference suppression, which are the two major functional components of general BF algorithms, both the algorithms of steering BF and the minimum- variance- distortionless-response(MVDR) BF are applied to the analysis. A signal model to reflect the spatially scattering phenomenon of the RF waves entering into the .:nay antenna, which directly affects on the accuracy of the BF algorithm's direction estimation, is also suggested in this paper and applied to the analysis and the operation simulation. It is confirmed from the results that the enhancement of the direction selectivity of the away antenna is not desirable in view of both the implementation economy and the BF algorithm's robustness to the erroneous factors. Such a trade-off characteristics is significant in the sense that it can be capitalized to obtain an economic means of BF implementation that does not severely deteriorate its performance while ensuring the robustness to the erroneous effects, consequently manifesting the significance of the analysis results of this paper that can be used as a design reference in developing BF algorithms to the cellular CDMA system.