• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.369-373
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• 1998

증기발생기에서 부식에 의한 전열관 손상은 전열관과 관판사이의 틈새에서 대부분 발생되고 이 틈새에서의 수질환경에 좌우된다. 틈새에서는 과열도가 높아 미량의 불순물이 농축되면서 틈새수화학 (crevice chemistry)은 증기발생기 내부수 수화학과는 달라진다. 전열관 손상을 억제하기 위해서는 틈새수질을 적절히 제어하여야 하는데 이는 틈새수화학을 정확히 분석평가할 수 있는 기술을 기반으로 하여야 한다. .기존의 틈새수질을 계산하는 방법으로는 증기발생기 내부수에 비해 틈새에서 화학종들이 얼마나 농축되는지를 가정하는 농축도 (concentration factor) 방법이 있으나 가정에 의한 불확실성으로 인해 틈새수질을 정확히 해석할 수 없었다. 그러나 원전 증기발생기의 잠복불순물 방출시험 자료로부터 틈새수질을 보다 정확히 평가할 수 있는 새로운 개념의 몰비지수(molar ratio index) 방법이 최근 EPRI에서 제시되었고 EPRI 산하의 많은 발전소에서 적용중이다. 본 연구에서는 PWR 원전 증기발생기의 틈새수화학을 평가할 수 있는 기술을 개발하기 위해 잠복불순물 방출시험 자료로부터 틈새에서의 몰비지수를 계산할 수 있는 CRAP (CRevice-chemistry Analysis Program) 전산프로그램을 작성하였다 CRAP를 국내원전에 적용하여 증기발생기 및 그 틈새에서의 수화학을 평가하였다.

• The Korean Journal of Applied Statistics
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• v.34 no.5
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• pp.711-721
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• 2021

In this paper, we propose the method of adjusting thresholds using impurity indices in classification analysis on imbalanced data. Suppose the minority category is Positive and the majority category is Negative for the imbalanced binomial data. When categories are determined based on the commonly used 0.5 basis, the specificity tends to be high in unbalanced data while the sensitivity is relatively low. Increasing sensitivity is important when proper classification of objects in minority categories is relatively important. We explore how to increase sensitivity through adjusting thresholds. Existing studies have adjusted thresholds based on measures such as G-Mean and F1-score, but in this paper, we propose a method to select optimal thresholds using the chi-square statistic of CHAID, the Gini index of CART, and the entropy of C4.5. We also introduce how to get a possible unique value when multiple optimal thresholds are obtained. Empirical analysis shows what improvements have been made compared to the results based on 0.5 through classification performance metrics.

• 한국전자현미경학회:학술대회논문집
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• 2004.11a
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• pp.136-138
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• 2004

• Journal of the Korean Institute of Telematics and Electronics
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• v.7 no.2
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• pp.33-42
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• 1970

This report is concerned with the fahrication with the falricationof silicon VVC diode by the double diffusion planer technique. At first, some design charts for VVC diode were derived by considering the voltage-capacitance relations, the critical field intensity at the metallurgical junction, and the cut-off frequency of the diode. These charts enables the fabrication engineers to design VVC diode easily without going into the sophisticated design theory. We started with a 2.5 ohm-cm n-type epitaxial silicon wafer. The phosphorous was diffused by POCl3 impurity source. Then boron diffusion followed make hyperabrupt p-n junction by BN source. The maximum to minimum capacitance ratio of the diode as a tuning diode for a TV tuner made in these experiments was 4:1. Measured electrical characteristics of the sample diodes showed in good agreement with the theoretical expectations. Slicing and polishing technique of the silicon wafer and diffusion technique of the impurity atoms, which were employed in our study, are also stated briefly in this report.

• Clean Technology
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• v.16 no.1
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• pp.1-11
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• 2010

As crude oil with heavier and/or highly oxidized components prevails, purification technologies such as desulfurization, denitrilization and demetalization have become important issues to control contents of sulfur and other impurities affecting the quality of petroleum. Also, the importance of catalyst technologies related with crude oil purification has been emphasized to control the production and yield of products. In this paper, technology trends of impurity removal such as sulfur, nitrogen and metal components from crude oil and catalysts related with purification of crude oil were studied through patent analysis. The patents published or registered in Korea, U. S. A., Japan, and Europe from mid 1970's to 2009 had been analyzed based on the application tendency, the distribution of major applicants, and their active indices, etc. The technology flow was figured out to see the technology trends.

• Korean Journal of Materials Research
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• v.8 no.6
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• pp.526-531
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• 1998

A hydride vapor phase epitaxy (HVPE) method was performed to grow the $10~240\mu{m}$ thick GaN films on (111) spinel $MgAl_2O_4$ substrate. The GaN films on $MgAl_2O_4$ substrate revealed a photoluminescence (PL) characteristics of the impurity doped GaN by the out-diffusion and auto-doping of Mg from $MgAl_2O_4$ substrate during GaN growth. The PL spectrum measured at 10K consists of free and bound excitons related recombination transitions and impurity-related donor-acceptor pair recombination and its phonon replicas. However, the deep-level related yellow band emission was not observed. The peak energy of neutral donor bound excitonic emission and the frequency of Raman $E_2$ mode were exponentially decreased with increasing the GaN thicknesses. and the frequency of E, Raman mode was shifted with the relation of $\Delta$$\omega$=3.93$\sigma$($cm^{-1}$/GPa), where l1 (GPa) is the residual strain in the GaN epilayers.

• The korean journal of orthodontics
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• v.26 no.5 s.58
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• pp.591-599
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• 1996

This study was undertaken to investigate the cytotoxicity of orthodontic wires after doing various treatments to the wires. 018x025 inch Stainless steel(A) and Co-Cr(B) wires were used and each of them were divided into 4 groups. A-1 and B-1 groups were as received state, and A-2 and B-2 groups were heat treated. A-3 and B-3 groups were electropolished after heat treatment, and A-4 and B-4 groups were soldered with Ag-solder. Each group had 3 wires and these were sterilized with Ethylene Oxide gas. We used human gingival fibroblast cell culture and agar overlay technique to investigate the cytotoxicity of each group of wires. The cytotoxicity of wire was assessed using reaction index (zone index/lysis index). The findings of this study were as follows. 1. Both of the stainless steel wire and Co-Cr wire showed no cytotoxicity in as received state. 2. Heat treatment or electropolishing of the wires had no effect on the cytotoxicity of the wires 3. Soldered stainless steel wires showed a little wider zone of discoloration than soldered Co-Cr wires, but the zone index and cytotoxicity(reaction index) was not different. 4. Soldered wires showed moderate cytotoxicity in both of the wires.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.713-716
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• 2013

The device performances of N-channel Tunneling FET have been characterized with different intrinsic length between drain and gate($L_{in}$), drain and source doping, permittivity and oxide thickness when the total effective channel length is constant. N-channel Tunneling FET of SOI structure have been used in characterization. $L_{in}$ was from 30nm to 70nm, dose concentration of drain and source were from $2{\times}10^{12}cm^{-2}$ to $2{\times}10^{15}cm^{-2}$ and from $1{\times}10^{14}cm^{-2}$ to $3{\times}10^{15}cm^{-2}$, permittivity was from 3.9 to 29, and oxide thickness was from 3nm to 9nm. The device performances were characterized by Subthreshold slope(S-slope), On/off ratio, and leakage current. From the simulation results, the leakage current have been reduced for long $L_{in}$ and low drain doping. S-slope have been reduced for high source doping, high permittivity and thin oxide thickness. With considering the leakage current and S-slope, it is desirable that are long $L_{in}$, low drain doping, high source doping, high permittivity and thin oxide thickness to optimize device performance in n-channel Tunneling FET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1582-1587
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• 2005

In coagulant control of water treatment plants, rule extraction, one of datamining categories, was performed for coagulant control of a water treatment plant. Clustering methods were applied to extract control rules from data. These control rules can be used for fully automation of water treatment plants instead of operator's knowledge for plant control. To perform fuzzy clustering, there are some coefficients to be determined and these kinds of studies have been performed over decades such as clustering indices. In this study, statistical indices were taken to calculate the number of clusters. Simultaneously, seed points were found out based on hierarchical clustering. These statistical approaches give information about features of clusters, so it can reduce computing cost and increase accuracy of clustering. The proposed algorithm can play an important role in datamining and knowledge discovery.

• Polymer(Korea)
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• v.37 no.5
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• pp.613-617
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• 2013

The effects of nano size kenaf cellulose fiber on mechanical property of polypropylene (PP) composite were investigated. The addition of nano-kenaf in place of natural kenaf showed higher tensile strength, flexural strength, impact strength, and heat deflection temperature compared to the natural kenaf filled PP composite, while it shows lower melt flow index, elongation%, and flexural modulus. These seemed to be due to the increased surface area of nano-kenaf fiber contacting PP matrix and reduced impurities such as volatile extractives on the fiber surface.