• Corrosion Science and Technology
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• v.6 no.2
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• pp.37-43
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• 2007

Iodine sulfur (IS) process is one of the promising processes for a hydrogen production by using a high temperature heat generated by a very high temperature gas cooled reactor(VHTR) in the nuclear power industries. Even though the IS process is very efficient for a hydrogen production and it is not accompanied by a carbon dioxide evolution, the highly corrosive environment of the process limits its application in the industry. Corrosion tests of selected materials were performed in sulfuric acid to select appropriate materials compatible with the IS process. The materials used in this work were Fe-Cr alloys, Fe-Ni-Cr alloys, Fe-Si alloys, Ni base alloys, Ta, Ti, Zr, SiC, Fe-Si, etc. The test environments were 50 wt% sulfuric acid at $120^{\circ}C$ and 98 wt% at $320^{\circ}C$. Corrosion rates were measured by using a weight change after an immersion. The surface morphologies and cross sectional areas of the corroded materials were examined by using SEM equipped with EDS. Corrosion behaviors of the materials were discussed in terms of the chemical composition of the materials, a weight loss, the corrosion morphology, the precipitates in the microstructure and the surface layer composition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.136-142
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• 2019

Nuclear power plant concrete structures are in contact with the coast, and durability due to chloride attack is very important because it is used as cooling water by taking seawater. For this purpose, a 3-year long-term saltwater immersion test was carried out to evaluate chloride ion diffusion coefficient and age apponent (m) The m values of the foundation with 4,000 class was 0.35 ~ 0.39, similar to KCI or ACI suggested values. essential service water constructions and tunnels of 5,000 class were 0.44 ~ 0.53 and 6,000 class, and 0.62 of reactor containment buildings were similar to the proposed values of FIB. As a result of the prediction of the service life with the measured age coefficient, all the safety related concrete structures of the nuclear power plants satisfied the service life of more than 60 years.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.61-68
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• 2023

In this study, Sn-3.5Ag-15.0Fe composite solder was manufactured and applied to TLP bonding to change the entire joint into a Sn-Fe IMC(intermetallic compound), thereby applying it as a high-temperature solder. The FeSn₂ IMC formed during the bonding process has a high melting point of 513℃, so it can be stably applied to power modules for power semiconductors where the temperature rises up to 280℃ during use. As a result of applying ENIG surface treatment to both the chip and substrate, a multi-layer IMC structure of Ni₃Sn₄/FeSn₂/Ni₃Sn₄ was formed at the joint. During the shear test, the fracture path showed that cracks developed at the Ni₃Sn₄/FeSn₂ interface and then propagated into FeSn₂. After 2hours of the TLP joining process, a shear strength of over 30 MPa was obtained, and in particular, there was no decrease in strength at all even in a shear test at 200℃. The results of this study can be expected to lead to materials and processes that can be applied to power modules for electric vehicles, which are being actively researched recently.

• The Journal of the Korea Contents Association
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• v.11 no.6
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• pp.326-336
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• 2011

The Purpose of this study was to examine effects of mentoring function on career development and organizational effectiveness in private security service organization. Example number used on interpretation finally using purposive sampling method after this study establishes 5 places private security service company's security guard by population in Seoul on March, 2010 is total 227 people. Reliability of questionnaire appeared Cronbach's ${\alpha}$ value more than .667. Conclusions that appears in this study is as following. First, private security service organization's Mentoring function affects in career development. That is, if friendship, patronage, career management, society mind, and role model are mobilized, innovative own development, special capacity development, and information competitive power development are helped. Second, private security service organization's Mentoring function affects in organization effectiveness. If friendship, patronage, career management, society mind, and role model are mobilized, career satisfaction, organization immersion, and job satisfaction increase. On the other hand, change of jobs intention decreases if function of society mind is mobilized. Third, private security service organization's career development affects in organization effectiveness. If reform and special capacity development are helped, career satisfaction, organization immersion, and job satisfaction increase. While change of jobs intention decreases as development of information competition is helped. Fourth, Mentoring function exerts influence of causality on career development and organization effectiveness. That is, Mentoring exerts direct influence on organization effectiveness, but it exerts indirect effect through career development.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.90-90
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• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is the first astronomical spectrograph that uses a silicon immersion grating as its dispersive element. IGRINS fully covers the H and K band atmospheric transmission windows in a single exposure. It is a compact high-resolution cross-dispersion spectrometer whose resolving power R is 40,000. An individual volume phase holographic grating serves as a secondary dispersing element for each of the H and K spectrograph arms. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{{\prime}{\prime}}{\times}15^{{\prime}{\prime}}$. IGRINS has a plate scale of 0.27" pixel-1 on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with a SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized ($0.96m{\times}0.6m{\times}0.38m$) rectangular Dewar. The fabrication and assembly of the optical and mechanical components were completed in 2013. From January to July of this year, we completed the system optical alignment and carried out commissioning observations on three runs to improve the efficiency of the instrument software and hardware. We describe the major design characteristics of the instrument including the system requirements and the technical strategy to meet them. We also present the instrumental performance test results derived from the commissioning runs at the McDonald Observatory.

• Clean Technology
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• v.3 no.2
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• pp.36-46
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• 1997

CFC and organic chlorine solvents has been used in the fine machinery and electronics industries for a long time since they have various excellent properties as cleaning agents. However, it is inevitable that alternative cleaning agents should be used since CFC and organic chlorine solvents were identified as ozone-depleting chemicals. There are various alternative cleaning agents. Among them, aqueous/semi-aqueous cleaning agents are environmentally friendly and promising in the long term. And their use and developement are on the increase in advanced countries, but few in our countries. In this paper, the charactistics and major components aqueous/semi-aqueous cleaning agents are analyzed and compared. And various cleaning equipments for aqueous/semi-aqueous cleaning agents such as immersion cleaner, ultronsonic cleaners, power spray cleaner, and vibration or rotational cleaners are compared and evaluated. Finally, important consideration points for selction of a cleaning system are analyzed and suggested in this paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.475-479
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• 2003

Traditional ultrasonic evaluation to detect micro/small surface cracks is the pulse-echo technique using the normal immersion transducer with high frequency, or the angle beam transducer with surface wave. It is difficult to make the automatic ultrasonic system that is to detect micro and small surface crack and position on the large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of transducer. The aim of this study using the high precision scanning acoustic microscope with 10MHz large aperture transducer was to display the real time A, B, C-scan for the automatic ultrasonic system in order to detect the existence and position of surface crack. The ultrasonic method with large aperture transducer was improved the scanning time and speed over 10times faster than traditional methods.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.155-158
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• 2012

In this work, AlON-$Al_2O_3$ coatings were prepared on Al2021 alloy by the electrolytic plasma processing (EPP) method. The experimental electrolytes include: 2 g/l NaOH as the electrolytic conductive agent, 10 g/l $Na_2AlO_2$ as the alumina formative agent, and 0.5 g/l $NaNO_2$, $NaNO_3$, and $NH_4NO_3$ as the nitride inducing agents. The effects of different nitrogen inducing agents were studied by a combined compositional and structural analyses of the ceramic coatings carried out by Xray diffractometry (XRD) and scanning electron microscopy (SEM) for the specimens EPP-treated at room temperature for 15 min under a hybrid voltage of 260 DC along with an AC 50 Hz power supply (200 V). Microhardness tests and wear tests were carried out to correlate the evolution of the microstructure and the resulting mechanical properties. Potentiodynamic polarizations and immersion corrosion tests were carried out in 3.5wt% NaCl water solutions under static conditions in order to evaluate the corrosion behavior of the coated samples. The results demonstrate that $NaNO_2$ is proven to be a good nitrogen inducing agent to produce high quality AlON-$Al_2O_3$ ceramic coatings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.681-686
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• 2017

Degradation is commonly observed in field-aged PV modules due to corrosion of the photovoltaic ribbon. The reduced performance is caused by a loss of fill factor due to the high series resistance in the PV ribbon. This study aimed to mitigate the degradation by corrosion using five sacrificial anodes - Al, Zn and their alloys - to identify the most effective material to mitigate the corrosion of the PV ribbon. The corrosion behavior of the five sacrificial anode materials were examined by open circuit potential measurements, potentiodynamic polarization tests, and galvanic current density and potential measurements using a zero resistance ammeter. Immersion tests for 120 hours were also conducted using materials and damp heat test tests were performed for 1500 hours using 4 cell mini modules. The Al-3Mg and Al-3Zn-1Mg sacrificial anodes had a low corrosion rate and reduced drop in power, making then suitable for long-term use.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.187-192
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• 2002

Applicability of laser micro welding process to the fabrication of medical devices was investigated. Austenitic stainless steel wire (SUS304) was spot melted and crosswise welded, which is one of the most possible welding process for the fabrication of medical devices, by using a Nd-YAG laser. Effects of welding parameters on the microstructure, tensile strength and corrosion resistance were discussed. In the spot melting, melted metal width decreased with decreasing the input energy and pulse duration. Controlling the laser wave to reduce laser noise which occurred in the early stage of laser irradiation made reasonable welding condition wider in the welding condition of small pulse duration such as 2ms. The microstructure of the melted metal was a cellular dendrite structure and the cell size of the weld metal was about 0.5~3.5 ${\mu}{\textrm}{m}$. Tensile strength increased with the decrease of the melted metal width and reached to a maximum about 660MPa, which is comparable with that for the tempered base metal. Even by immersion test at 318K for 3600ks in quasi biological environment (0.9% NaCl), microstructure of the melted metal and tensile strength hardly changed from those for as melted material. In the crosswise welding, joints morphologies were classified into 3 types by the melting state of lower wire. Fracture load increased with input energy and melted area of lower wire, and reached to a maximum about 80N. However, when input energy was further increased and lower wire was fully melted, fracture load decreased due to the burn out of weld metal.