• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1523-1530
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• 2007

The first reduction peak of the cyclic voltammogram (CV) for sulfur reduction in dimethyl sulfoxide has been studied using time resolved Fourier transform electrochemical impedance spectroscopic (FTEIS) analysis of small potential step chronoamperometric currents. The FTEIS analysis results reveal that the impedance signals obtained during short potential steps can be resolved into electron transfer reactions of two different time constants in a high frequency region. The FTEIS method provides snap shots of impedance profiles during an earlier phase of the reaction, leading to time resolved EIS measurements. Our results obtained by the FTEIS analysis are consistent with a series of electron transfer and chemical equilibrium steps of a complex reaction, making up an ECE (electrochemical-chemical-electrochemical) mechanism postulated from the results of computer simulation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.157-159
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• 2020

This paper presents an optimal planar transformer design of a 3-kW Low voltage DC-DC Converter (LDC) with 3.68 kW/L power density for electric vehicle (xEV) application. The transformer is optimized based on the trade-off between footprint and loss using the proposed figure-of-merit (FOM) based optimization. In order to achieve ZVS under entire load range, an external leakage inductance is added and implemented using the proposed magnetic integration technique. A comparison between non-integrated and integrated magnetic core using finite element analysis (FEA) is presented. The result shows that the integrated core can reduce the core loss up to 35 % and core boxed volume up to 15 % compared to the non-integrated core. Experimental results are also provided to validate the proposed magnetic integration technique.

• Journal of Power Electronics
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• 제14권2호
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• pp.257-264
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• 2014

A novel converter-free AC LED driver that is highly resistant to the fluctuation of AC voltage is proposed in this study. By removing large passive components, such as the bulky capacitor and the large-value inductor, the integration of the driver circuit is enhanced while the driving current remains stable. The proposed circuit provides LED lamps with a driving current that can follow the sinusoid waveform to obtain a very high power factor (PF) and low total harmonic distortion (THD). The LED input current produced by this driving current is insensitive to fluctuations in the AC voltage. Users will thus not feel that LED lamps are flashing during the fluctuation. Experiment results indicate that the proposed system can obtain PF of 0.999 and THD as low as 3.3% for a five-string 6 W LED load under 220 V at 50 Hz.

• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.35-42
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• 2008

Vibrio vulnificus produces siderophores, low-molecular-weight iron-chelating compounds, to obtain iron under conditions of iron deprivation. To identify genes associated with the biosynthesis of siderophore in V. vulnificus MO6-24/O, we screened clones with mini-Tn5 random insertions for those showing decreased production of siderophore. Among 6,000 clones screened, nine such clones were selected. These clones contain the transposon inserted in VV2_0830 (GenBank accession number) that is a homolog of a nonribosomal peptide synthase (NRPS). There is an another NRPS module, VV2_0831, 49-bp upstream to VV2_0830. We named these two genes vvs (Vibrio vulnificus siderophore synthase) A and B, respectively. Mutation of either vvsA or vvsB showed a decreased production of siderophore. The expression of an NRPS-lux fusion was negatively modulated by the presence of iron, and the regulation was dependent on Fur (ferric uptake regulator). However, the expression of the NRPS genes was still not fully derepressed in the iron-rich condition, even in furnull mutant cells, suggesting that some other unknown factors are involved in the regulation of the genes. We also demonstrated that the NRPS genes are important for virulence of the pathogen in a mice model.

• 한국과학교육학회지
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• 제1권1호
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• pp.35-44
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• 1978

In this study, concept centered approach and process centered approach in developing integrated science curriculum were compared and compromised between two approaches. It seems that two approaches are in antagonistic relations. The superficial conflictions getween two approaches are not because they are antagonistic in their nature, but because their interesting points are different. The concept centered approahc is interest in fundamental scientific concepts and the process centered approach is interested in scientific enquiry. If science is the composition of enquiry processes and concepts produced by enquiry processes, scientific enquiry process and scientific concept must not be inconsistant. Although concepts are not unchangeable, new concepts and advanced concepts are based on the old concepts. Enquiry activity which is not based on concepts also cannot be significant enquiry. Although fundamental concepts in science is very important, in order to apply concepts to varios phenomena, and to understand concepts more deeply the student should understand concept through the process by which the concepts are derived. As we have discussed above, only the concept centered approach or the process centered approach itself is not complete. Comparing these two uncomplete approaches to integrated science curriculum, we can find out that two approaches are in complementary relations. Because integrated science is based on the idea that natural phenomena should not be understood in fragments, but should be understood as mutually related system' the integrated science curriculum includes both the fundamental scientific concepts and scientific enquiry processes.

• 한국과학교육학회지
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• 제22권1호
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• pp.141-157
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• 2002

본 연구의 목적은 수 과학 통합 교육 활동 프로그램 모형 개발을 위한 기초 연구로서 수 과학 통합교육 활동에서 나타난 유아 수 과학 관련 개념 발달과 교사의 교수-학습 전략을 분석하는 것이다. 연구대상은 청주시의 K 초등학교 병설 유치원에 재원 중인 원아 4명을 대상으로 3주간 실시하여 얻어진 총 7회의 수업사례이다. 결과 분석은 수집된 7개의 수업사례에서 나타나는 유아들의 수 과학 관련 개념의 발달과 교사의 교수-학습 전략을 질적으로 분석하였으며, 분석 결과, 유아들은 물체의 무게와 모양 그리고 움직임 간의 관련성, 물체의 크기와 무게와의 관련성, 물체의 거리 측정에 대한 세 가지 측면에서의 개념 발달을 나타냈다. 유아들의 수 과학 개념 발달을 돕기 위한 교사의 교수-학습 전략은 발문 내용, 자료와 매체의 활용, 집단 구성의 측면에서 이루어지고 있는 것으로 나타났다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.298-298
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• 2006

There has been much interest in incorporating nanoscale voids into dielectric materials in order to reduce their k value, and thus in producing low-k porous interdielectric materials. One approach to the development of low-k dielectric materials is the templated polycondensation of organosilicate precursors in the presence of a thermally labile, organic polymeric porogen. The other is SiOCH films have low dielectric constant as well as good mechanical strength and high thermal stability through PECVD. In this article we explore the nanopore generation mechanism of organosilicate film using star-shape porogen and SiOCH film using bis-trimethylsilylmethane (BTMSM) precursor.

• BMB Reports
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• 제55권6호
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• pp.281-286
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• 2022

Hepatocellular carcinoma is a major health burden, and though various treatments through much research are available, difficulties in early diagnosis and drug resistance to chemotherapy-based treatments render several ineffective. Cancer stem cell model has been used to explain formation of heterogeneous cell population within tumor mass, which is one of the underlying causes of high recurrence rate and acquired chemoresistance, highlighting the importance of CSC identification and understanding the molecular mechanisms of CSC drivers. Extracellular CSC-markers such as CD133, CD90 and EpCAM have been used successfully in CSC isolation, but studies have indicated that increasingly complex combinations are required for accurate identification. Pseudogene-derived long non-coding RNAs are useful candidates as intracellular CSC markers - factors that regulate pluripotency and self-renewal - given their cancer-specific expression and versatile regulation across several levels. Here, we present the use of microarray data to identify stemness-associated factors in liver cancer, and selection of sole pseudogene-derived lncRNA ZNF204P for experimental validation. ZNF204P knockdown impairs cell proliferation and migration/invasion. As the cytosolic ZNF204P shares miRNA binding sites with OCT4 and SOX2, well-known drivers of pluripotency and self-renewal, we propose that ZNF204P promotes tumorigenesis through the miRNA-145-5p/OCT4, SOX2 axis.

• 경영과학
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• 제15권2호
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• pp.83-90
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• 1998

Today, ERP becomes very popular as a vehicle of implementing an integrated information system since this package not only facilitates reengineering but also provides the function of generating consolidated financial statements. Yet a successful introduction strategy on the integrated information system needs to be set up because ERP has weaknesses as well as strengths. The strengths include the prompt reaction to environmental changes, the integrated management of information, the adoption of open systems, and the selection of modules according to functionsl However, the weaknesses of ERP include the provision of only basic functions, the development of package on international standard processes, and possible disadvantages to small and medium-sized firms. This paper is to suggest recommendations on the implementation strategy of ERP as an integrated information system. According to the case study with Firm A that has successfully implemented an ERP package, the most significant advantage of adopting ERP was that Firm A was able to implement an integrated information system for only six months. Finally, this research generates suggestions, such as the importance of the project team structure, the sufficient amount of time for education, and the minimization of the package modification.

• Management Science and Financial Engineering
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• 제7권1호
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• pp.1-26
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• 2001

Assume a company sells two products (a and B) in a retail market. the company adopts a specific promotion mechanism, Tie-in Promotion, in which product A's promotional discount coupon is distributed whenever a consumer purchases product B. Product A will later e sold at a markdown price when consumers eventually take the opportunity to redeem the coupon. in the integrated tie-in promotion and stocking policy, we assume managers of two products coordinate by sharing information on the demand forecast and deciding the order quantities and tie-in promotion program to maximize joint profits. The optimal integrated tie-in policy is analyzed. The integrated tie-in promotion model is then compared with two other base models: (1) a decentralized Newsboy model in which no promotion is considered, and (2) an individual promotion model in which managers design a promotion program to promote one of the two products directly. The factors that make an integrated tie-in promotion a better approach are studied.