• Journal of KIISE
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• v.41 no.9
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• pp.625-632
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• 2014

With the trend of increasing needs for high-technology from customer and tightening regulation on automotive fuel efficiency and safety, application of E/E system has been expanding consistently in automotive industry. Thus, demand for core elements of E/E system has been growing: micro controller, analog IC and ASIC. But, development process of automotive semiconductor hasn't been clearly established in domestic area. This research aims to present a guide and an example for construction of requirement and design development process on semiconductor based on ISO/TS 16949 that is requirement for quality management system, CMMI that has been proven in various area and ISO 26262 widely used methodology for functional safety. It is expected that the result of this research is used as guidance for construction of semiconductor development process.

• Resources Recycling
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• v.23 no.2
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• pp.46-52
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• 2014

This study was conducted to observe the removal efficiency of oil-contaminated soil by various tests using microwaves and high-temperature heating elements. The water content was measured with the treatment amount, which was lowered to 300g in a relatively short amount of time. The treatment rate of TPH(Total Petroleum Hydrocarbons) showed the highest value with 70.1% when the SiC-activated carbon heating element was at 4 kW/kg, compared to the SiC heating element used alone. In particular, the higher electric power became, the higher treatment rate became, except at 3 kW. In the case of the heating element made by the fusion of SiC and activated carbon, the internal temperature exceeded $300^{\circ}C$ and again fell when it was treated at 4 kW for about 2 minutes. Then, after about 8 minutes, it rose again. On the basis of such results, the energy content necessary for the sample was calculated according to the electric power of microwaves, and tthe constant of TPH treatment was measured by tests on the treatment characteristics of oil-contaminated soil.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.23-35
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• 2004

The weathering characteristics of periodically submerged sedimentary rocks in the Sayeon dam, Ulsan was examined by field work, electron probe micro-analysis, X-ray diffraction, and X-ray fluorescence spectrometry. Analysis of fracture zone and exfoliation showed the submerged sedimentary rocks have undergone severe mechanical weathering. Mechanical weathering in the water-rock interface accelerated chemical weathering, such as dissolution and alteration of the most of minerals except for quartz in the weathering zone. The dissolution of carbonates specially calcite, is remarkable creating the cavities, whereas formation of minerals including clay minerals is not active. The sedimentary rocks have been periodically submerged for a certain period of time, and have repeated freezing and thawing. This mechanical weathering favored infiltration, which accelerated mineral dissolution. The high content of easily soluble carbonate of the sedimentary rocks is likely the major cause of intense chemical weathering. The dissolved elements within the infiltrated water interrupted the occurrence of clay and weathering minerals, and expend fractures by infiltrated water accelerated weathering process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.40-46
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• 1985

Some problems such as toughness decrement and stess relief cracking (SRC), many occur when post weld heat treatment (PWHT) is applied to remove residual stress adn hydrogen. In this paper PWHT was carried out under the stress of 0, 98, 196 and 294 MPa (0, 10, 20 and 30kgf/mm$^{2}$ each) to simulate residual stress in HAZ of Cr-Mo steel. The effect of applied stress during PWHT on fracture toughness was evaluated by COD fracture toughness test, micro-hardnes test and observation of SEM. The experimental results are as follows; (1) Fracture toughness of weld HAZ was improved by PWHT, but it decreased as heat treated under the stress. (2)Hardness ratio under the stress of 294MPa (30kg/mm$^{2}$) was lower and fracture toughness was decreased than that of the no stress. (3) Applied stress in weld HAZ during PWHT assisted precipitation of over saturated alloying elements in the structure, so fracture surface at the stress of 294MPa (30kg/mm$_{2}$) appeared the grain boundary failure possibly one of the reasons for PWHT embrittlenment.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.495-502
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• 2020

In this paper, a power management circuit was designed to drive the emergency lighting LED in the underground facility for public utilities using magnetic energy harvest. The magnetic energy harvest consists of a harvest elements and power management circuits. The proposed circuit was made of a rectifier, a battery charging circuit, and an LED driving circuit. In normal times, the battery is charged with the harvested power, and in the event of an emergency, the energy stored in the battery is used to drive the LED. As a result of the measurement, it took two minutes to charge the 47 mF capacitor. This is the amount of power that can drive an LED for emergency lighting for about three and a half minutes. Through this, it was confirmed that the power management circuit for magnetic energy harvest proposed in this paper can be used as an emergency lighting LED-driven power device in an underground facility for public utilities where it is difficult to draw separate power.

• Journal of Environmental Science International
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• v.14 no.1
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• pp.71-80
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• 2005

Soil is one of the most fundamental elements as well as with water and air in studies associated with the environment, in addition, it is one of the important environmental mediums that constructs a basis of the bio­logical system and performs various roles of matter circulation. This study was carried out in Seoul, in May 2000 to evaluate variation in the concentration levels and distribution characteristics for PAH compounds in soil. Soil samples were collected from 33 sites covering traffic, factory, incineration and mountain groups and the PAHs were analyzed. The results show a wide dis­tribution range of PAHs concentrations between 14.66 ng/g and 1,219.35 ng/g. The highest concentration levels exist at Sungsu-2 of the factory group (FS-2). Daemo-3 of the Mountain group (MD-3) presents the lowest levels as compared with the other sites. PAH compounds including mutagenic and carcinogenic materials show high concentrations in the traffic and factory groups and a high ratio in the mountain group. Besides, these compounds absorbed with micro particles might be spread out over a wide region associated with particles' movement and diffusion. After principal component analysis of the soil samples, the results indicated that the sources of PAHs in the soil were divided into two groups, pesticides and vehicles.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.161-170
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• 2002

The Purpose of this study was to investigate the chemically improvement of metal-ceramics bond strength in the course of recasting Ni-Cr metal composite system with 10wt.%, 20wt.% and 30wt.% aluminum respectively. We have tested the bond strength, micro-structure, chemical composition of each metal composites and metal- ceramic bond interfaces by 3-point bending strength tester, SEM and EDS. We have made the conclusions through this study as follow: 1. The most suitable amount of aluminum to the Ni-Cr metal composite recasting is 20wt. % for improving metal-ceramics bond strength with debonding strength value of 49.54 kgf/mm2. 2. The aluminum must be changed to small spread alumina like phases and second aluminum-metal composites phases in the morphology of Ni-Cr metal composite system by adding during it's casting. These second phases have inclined functional oxide phases mixed with metal elements and they must take roll to improvement of metal-ceramics bond strength. 3. In the case of 30wt.% aluminum appended to Ni-Cr metal composite system, an excess of second inclined functional oxide phases produce cracks and spalling of them apart from it's base material. It must be a important factor of reduction of metal-ceramics bond strength.

• Journal of Korea Foundry Society
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• v.40 no.2
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• pp.16-24
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• 2020

The effect of a heat treatment on the microstructure and mechanical properties of Inconel 713C alloy vacuum investment castings were investigated. The microstructure of the as-cast state was observed, showing well-developed dendrite structures and distributed carbide particles and solidified massive precipitates in the grain or grain boundary during solidification, in this case the γ′ phase and MC particles. During a heat treatment, the γ phase matrix was reinforced by solid solution elements, carbide particles from the film morphology precipitated along the grain boundary, and many micro-precipitates of second γ′ phases 0.2 ㎛~2 ㎛ in size were newly formed in the γ phase matrix according to SEM-EDS analysis results. The tensile strength at a high temperature (850℃) decreased slightly becoming comparable with the room-temperature result, while the hardness value of the specimen after the vacuum heat treatment increased by approximately 19%, becoming similar to that of the as-cast condition. However, the impact values at room temperature and low temperature (-196℃) were approximated; this alloy was mostly not affected by an impact at a low temperature. In the observations of the fracture surface morphologies of the specimens after the tensile tests, the fractures at room temperature were a mix of brittle and ductile fractures, and an intergranular fracture in the inter-dendrite structure and some dimples in the matrix were observed, whereas the fractures at high temperatures were ductile fractures, with many dimples arising due to precipitation. It was found that a reinforced matrix and precipitates of carbide and the γ′ phase due to the heat treatment had significant effects, contributing greatly to the excellent mechanical properties.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.15-18
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• 2014

We present gas sensing performance based on $2{\times}2$ sensor array with four different elements ($TiO_2$, $SnO_2$, $WO_3$ and $In_2O_3$ thin films) fabricated by rf sputter. Each thin film was deposited onto the selected $SiO_2$/Si substrate with Pt interdigitated electrodes (IDEs) of $5{\mu}m$ spacing which were fabricated on a $SiO_2$/Si substrate using photolithography and dry etching. For 5 ppm $NO_2$ and 50 ppm CO, each thin film sensor has a different response to offers the distinguishable response pattern for different gas molecules. Compared with the conventional micro-fabrication technology, $2{\times}2$ sensor array with such remarkable response pattern will be open a new foundation for monolithic integration of high-performance chemoresistive sensors with simplicity in fabrication, low cost, high reliablity, and multifunctional smart sensors for environmental monitoring.

• Tribology and Lubricants
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• v.30 no.5
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• pp.303-310
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• 2014

In order to reduce friction and improve reliability, researchers have applied various surface texturing methods to highly sliding machine elements such as mechanical seals and piston rings. Despite extensive theoretical research on surface texturing, previous numerical results are only applicable to isothermal and iso-viscous conditions. Because the lubricant flow pattern of textured bearing surfaces is much more complicated than that for non-textured bearings, the Navier?Stokes equation is more suitable than the Reynolds equation for the former. This study carries out a thermohydrodynamic (THD) lubrication analysis to investigate the lubrication characteristics of a single micro-dimpled parallel thrust bearing cell. The analysis involves using the continuity, Navier?Stokes, energy, temperature?viscosity relation, and heat conduction equations with the commercial computational fluid dynamics (CFD) code FLUENT. This study discretizes these equations using the finite volume method and solves them using the SIMPLE algorithm. The results include finding the streamlines, pressure and temperature distributions, and variations in the friction force and leakage for various dimple radii and depths. Increasing the dimple radius and decreasing the depth causes a recirculation flow to form because of a strong vortex, and the oil temperature greatly increases compared with the non-textured case. The present numerical scheme and results are applicable to THD analysis of various surface-textured sliding bearings and can lead to further study.