• Journal of Industrial Technology
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• v.19
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• pp.245-251
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• 1999

The joint in the concrete pavement provides a control against transverse or longitudinal cracking at slab, which may be caused by temperature or moisture variation during or after hydration. Without control of cracking, random crack may cause more serious distresses and result in structural or functional failure of pavement system. Sometimes, joint itself, purposed to control crack, may cause a distresses in joint due to its inherent weakness in structural integrity. Thus, the load transfer capacity in joint is very important for serviceability and durability. The purpose of this dissertation was to develop an evaluation system at joints of jointed concrete pavement using finite element analysis was performed using ILLI-SLAB program with a selected variables which might affect fairly to on the performance of transverse joints. The most significant variables were selected from precise analysis. It was concluded that the variables which most significantly affect to pavement deflections are the modulus of subgrade reaction(K) and the modulus of dowel/concrete interaction(G), and limiting criteria on the performance of joints at JCP at 300pci, 500,000 lb/in. respectively.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.18-20
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• 2005

일반적으로 저압계통의 고장전류를 차단하기 위해 설치된 차단기의 차단원리는 주로 역전압발생법올 이용하고 있다. 역전압발생법은 효과적으로 저압계통의 고장전류를 차단할 수 있으나, 제한된 한류성능과 긴 아킹 시간은 차단기는 물론 주변 전력기기에 전기적/열적/기계적 스트레스를 주게 된다. 국내외 업체는 고장전류를 보다 빠르고 효과적으로 제한 및 차단을 할 수 있는 한류형 차단기를 제안하고 있는 실정이다. 저압계통의 경우, 정온도계수 (Positive Temperature Coefficient, PTC) 특성을 가지는 한류소자를 기존 차단기에 직렬 혹은 병렬로 연결하여 저압계통의 고장전류를 매우 빠르고 효과적으로 제한 및 차단하는 추세에 있으며, 또한 PTC 한류소자를 이용함으로써 저압계통의 차단보호협조를 효과적으로 구현하고자 하고 있다. PTC 한류소자는 소자는 열팽창이 큰 비전도성 성분과 열팽창이 작은 전도성 성분이 혼합되어 구성되며, 소자의 온도가 증가함에 따라 비전도성 성분이 상대적으로 큰 부피 팽창을 하여 저항이 증가하게 된다. 이러한 PTC 소자를 전력계통에 적용함으로써 고장전류에 따른 줄열에 의한 저항증가로 고장전류를 제한하게 된다. 본 연구에서는 일반적으로 배터리 보호용으로 사용되는 폴리에틸렌 수지 및 카본블랙으로 구성된 폴리머 PTC 한류소자를 이용하여, 기존의 저전력 배터리 보호 폴리머 PTC 소자로부터, 저압계통의 단락사고시 발생하는 단락전류를 효과적으로 제한할 수 있는 대전력 폴리머 PTC 소자를 개발하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.10
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• pp.2699-2709
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• 1995

This investigation reports on the study of the ambient turbulent effects on the droplet vaporization in the fuel spray combustion. For tractability, this discussion considers a single droplet in an infinite turbulent flow. In this numerical study, the low-Reynolds-number version of k-.epsilon. turbulence model was used to represent the turbulence effects. The set of two-dimensional conservation equations which describe the transport phenomena in turbulent flow using the mean flow quantities including the droplet internal laminar motion, are solved numerically with the finite difference procedure of Patankar(SIMPLER). The evaluation of the computational model is provided by two limiting cases: turbulent flow over the solid sphere and the laminar flow over a liquid drop. The results show that the turbulence effects are noticeable for the vaporization at high turbulence intensity (10-50%) which is encountered in a typical spray. The magnitude of turbulence effects mainly depends on the turbulent intensity. These effects are not sensitive to the Reynolds number in the range of 50 to 200, ambient temperature in the range of 700 to 1000.deg. K and the volatility.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.211.1-211.1
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• 2014

Recently, the scaling of conventional planar NAND flash devices is facing its limits by decreasing numbers of electron stored in the floating gate and increasing difficulties in patterning. Three-dimensional vertical NAND devices have been proposed to overcome these issues. Atomic layer deposition (ALD) is the most promising method to deposit charge trap layer of vertical NAND devices, SiN, with excellent quality due to not only its self-limiting growth characteristics but also low process temperature. ALD of silicon nitride were studied using NH3 and silicon chloride precursors, such as SiCl4[1], SiH2Cl2[2], Si2Cl6[3], and Si3Cl8. However, the reaction mechanism of ALD silicon nitride process was rarely reported. In the present study, we used density functional theory (DFT) method to calculate the reaction of silicon chloride precursors with a silicon nitride surface. DFT is a quantum mechanical modeling method to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. The bond dissociation energy of each precursor was calculated and compared with each other. The different reactivities of silicon chlorides precursors were discussed using the calculated results.

• Microbiology and Biotechnology Letters
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• v.22 no.6
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• pp.692-699
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• 1994

A bacterial strain which formed a distinct colony on agar plate containing phenol as a vapor phase and grew well in a liquid minimal medium was isolated and identified as Acinetobac- ter sp. GEM2. The optimal temperature and initial pH for the growth of Acinetobacter sp. GEM2 were 30$\circ$C and 7.0, respectively. Cell growth was inhibited by phenol at the concentration over 1500 ppm. Cell growth dramatically increased from 10 hours after cultivation and almost showed a stationary phase within 24 hours at which 95% of phenol was concomitantly degraded. Acinetobac- ter sp. GEM2 was capable of growing on aromatic compounds, such as benzoic acid, phenol, m- cresol, o-cresol, P-cresol, catechol, gentisic acid, and toluene, but did not grow on benzene, salicylic acid, p-toluic acid, and p-xylene. By the analysis of catechol dioxygenase, it seemed that catechol was degraded through both meta- and ortho-cleavage pathway. The growth-limiting log P value of Acinetobacter sp. GEM2 on organic solvents was 2.0.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.44-47
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• 2008

Organic semi-conductive materials have characteristics such as the advantages of easy formability, low-cost and diversity along with moderate semi-conductive properties. In this paper, we developed a flexible organic-inorganic hybrid solar cell fiber. First, we made a solar cell on the glass and attached the solar cell on the glass fiber similarly. In the latter case, thermal deposition method was employed in order to effectively apply ITO onto fiber surface. The amount of ITO was controlled by varying the temperature from 25, 150 to $300^{\circ}C$. Optimum result was obtained at $150^{\circ}C$ where maximize the deposition amount without significant decomposition of ITO. Despite of maximum open circuit voltage of 0.39V, the resulting current was quite unstable and weak, limiting realistic applications. It was, however, concluded that the flexible solar cell fiber developed showed a possibility of low-weight application from functional clothing for military to space suit mainly due to flexibility and thus wear ability.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.415-418
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• 2011

Thermal fatigue is one of the life-limiting damage mechanisms in the nuclear power plant conditions. The turbulent mixing of fluids of different temperatures induces rapid temperature changes to the pipe wall. The successive thermal transients cause varying cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack nucleation and growth similar to the cyclic mechanical stresses. The aim of this study was to fulfil the need by developing an real crack manufacturing method, which would produce realistic cracks. The test material was austenitic STS 304, which is used as pipelines in the reactor coolant system of a nuclear power plants. In order to fabricate thermal fatigue crack similar to realistic crack, successive thermal transients were applied to the specimen. Thermal transient cycles were combined with heating (60sec) and cooling cycle (30sec). And, In order to identify ultrasonic characteristic, it was performed the ultrasonic reflection measuring method for the fabricated specimen. From the results of ultrasonic reflection measuring testing, it was conformed that A-scan results(average 83% of real crack depth) for the TFC reference specimen was more enhanced NDT reliability than results(average 38% of real crack depth) for the EDM notch reference specimen.

• Journal of Korean Dental Science
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• v.3 no.2
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• pp.26-33
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• 2010

We searched at the "PubMed.gov" and "jendodon.com" sites to conduct a literature review on dental instruments that are reused in clinical settings and on infection control involving pre-disinfection or sterilization cleaning/rinsing. The keyword "dental clean" was used for the Web search. We found the present official definition of instrument cleaning performed prior to disinfection or sterilization rather limiting ("removal of foreign matter (soil, organism, etc.) from the instruments"). Thus, we proposed to expand the definition to include the removal of oils applied to protect the metallic instruments and from corrosion, stains, and rust resulting from the frequent reuse of the instruments. Clinicians are found to clean their dental instruments (a) immediately after treating their patients or (b) following their treatment but not immediately afterward. In the latter case, we recommend presoaking to be added. Ultrasonic sterilization of 5~15 minutes is found to be more effective in terms of eliminating residual matter from the instruments compared to other methods. To check on the cleaning results, we recommend visual inspection, which can be quick and practical in clinical settings. The latest products being developed and marketed on the market address the related problems. Nonetheless, research must be continued on the effects of presoak, cleaning/rinsing, disinfection, and high-temperature or heating-based sterilization on the dental instruments and on dental clinicians' practices in cleaning, disinfection, and sterilization. We advise dental clinicians to select the proper cleaning methods and detergents for their instruments to help eliminate or prevent corrosion, staining, and rusting, to reduce the maintenance costs, and to ensure user-friendly instruments/apparatuses.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.443-447
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• 2017

The initial reaction of hexachlorodisilane ($Si_2Cl_6$, HCDS) on amorphous silica ($SiO_2$) surface for atomic layer deposition was investigated using density functional theory. Two representative reaction sites on the amorphous $SiO_2$ surface for HCDS reaction, a surface hydroxyl and a two-membered ring, were considered. The reaction energy barrier for HCDS on both sites was higher than its adsorption energy, indicating that it would desorb from the surface rather than react with the surface. At high temperature range, some HCDSs can have kinetic energy high enough to overcome the reaction energy barrier. The HCDS reaction on top of the reacted HCDS was investigated to confirm its self-limiting characteristics.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.220-221
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• 2006

In recent, there have been several developments in lamp technology that promise savings in electrical power consumption and improved Quality of the lighting space. Above all, the advantages of ring-shaped electrodeless fluorescent lamp are the removal of internal electrodes and heating filaments that are a light-limiting factor of conventional fluorescent lamps. Therefore, the life time of ring-shaped electrodeless fluorescent lamps is substantially higher than that of conventional fluorescent lamps last up to 60,000 hours, There are intended as a highly efficient replacement for the incandescent reflector lamp in many applications. In this paper, maxwell 3D finite element analysis program (Ansoft) was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 250 kHz and some specific conditions. In addition, the optical characteristics of ring-shaped electrodeless fluorescent lamp were measured including light flux, efficiency and color temperature for each case.