• 제목/요약/키워드: A first principles study

검색결과 813건 처리시간 0.036초

수학교육과 구성주의 (Mathematics Education and Constructivism)

  • 이경화
    • 대한수학교육학회지:수학교육학연구
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    • 제9권1호
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    • pp.51-80
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    • 1999
  • The paper reviews of the constructivist view of mathematics and mathematics education. First of all, we shall study how mathematics has been treated as an object of cognition in philosophy or cognitive theories, what is changed in modern mathematics. It can lead us to understand the constructivist perspective on mathematics. Secondly, we will examine the view, the teaching and learning principles of mathematics education based on constructivism. Didactic transposition theory will be used as a frame of reference for this examination.

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First-principles Study of the Structure and Growth Mechanism of Allyl Alcohol Lines on the H-terminated Si(001)

  • Choi, Yun-Ki;Choi, Jin-Ho;Cho, Jun-Hyung
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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    • pp.184-184
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    • 2011
  • Using first-principles density-functional calculations, we investigate the chain reaction mechanism of allyl alcohol (ALA) molecules on the H-terminated Si(001)-2${\times}$1 surface. Recently, it was reported [1] that allyl mercaptan (ALM) molecules show a self-directed line growth across the dimer rows through a chain reaction involving several reaction processes: (i) The created radical at the C atom is transferred to the S atom, (ii) the resulting S-centered radical easily abstracts an H atom from the neighboring dimer row, and (iii) the generated S-H group further reacts with the neighboring dimer row to produce the Si-S bond on the neighboring dimer row, accompanying the associative desorption of H2. This H2-desorption process creates a new DB on the neighboring dimer row, setting off the chain reaction across the dimer rows. In the present study, we find that although the structure of ALA with -OH functional is analogous to that of ALM with -SH functional, ALA and ALM lines show a difference in their growth direction. We predict that ALA undergoes the chain reaction to show a line growth along the dimer row, contrasting with the ALM line growth across the Si dimer rows. Our analysis shows that the different growth direction of ALA is due to the strong instability of oxygen radical intermediate, which prevents from growing across the dimer rows. Thus, we demonstrate that the stability of the radical intermediate plays a crucial role in determining the direction of molecular line growth.

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관광서비스 부문 WTO 서비스 협상 동향과 우리나라의 대응방안 (A Study on Measures in the Tourism Service Sector of WTO Service Negotiations)

  • 신재기
    • 정보학연구
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    • 제8권2호
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    • pp.121-133
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    • 2005
  • The WTO(World Trade Organization) meetings for service negotiations started in February in 2000. Since then, the member countries have discussed the tourism sector and their expectations and methods of liberalization, based on the proposals they have submitted. The Republic of Korea had already opened hotels and restaurants, travel agencies and tour operator services, and tourist guide services, preceding of WTO service negotiations. However, to comply with the terms of the negotiations, the domestic laws and systems related to tourism should be analyzed according to their adherence to the principles of GATS(General Agreement on Trade in Services), which include market access and national treatment. Thus, the purposes of this study were two-fold: first, regarding the two basic principles of GATS(market access and national treatment), the articles of the administrative laws relating to tourism were examined. Second, proposals from the tourism sectors in the US, Canada, Dominique, EC, Switzerland, and Japan were also summarized and reviewed. Proper responses to service negotiations were proposed based on the results of this analysis. As a result, I can support the GATS classification(w/120) of tourism and the liberalization of tourism in other WTO member countries. I can also support the elimination of obstacles such as economic need tests and nationality requirement. 'Others' category should be considered more carefully according to the competitiveness of the given industry.

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수산물 Eco-label CoC에 대한 식품안전 접근방안 연구 : AHP 기법을 통한 요구사항 분석을 중심으로 (A study on food safety approach for seafood Eco-label chain of custody : Focused on Requirement Analysis by AHP Method)

  • 서종석;서영환;윤덕현;서원철;옥영석
    • 수산경영론집
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    • 제46권3호
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    • pp.51-61
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    • 2015
  • The purpose of this study is to find food safety approach in the Eco-label Chain of Custody(CoC) which is only focused to traceability. Because, consumers want to be assured the certified seafood comes from sustainable fishery as well as hygienic. In order to this approach, we used Analytic Hierarchy Process(AHP) method as belows. We first understood the CoC criteria for using pair-wise comparison and analyzed and selected each Eco-label certifications and standards. Second, we carried out a survey to the targeted standard Marine Stewardship Council(MSC) CoC auditors all over the world and analyzed the priorities of food safety approach to 4 principles and 12 criteria belong the MSC CoC Standard. As the results, we found out that 'Management System' has the highest priority in the principles and 'Documentation' and 'Keeping Record' are the most important criteria for this approach. In addition, 'Training' and 'Identification' are also higher priority of criteria. So, we suggested food safety approach method for improvement of these criteria in conclusion based on discussion with specialist in this field.

시소러스의 부가관계에 관한 연구 (A Study on Added-Term Relationship of Thesaurus)

  • 한상길
    • 정보관리학회지
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    • 제17권2호
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    • pp.119-138
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    • 2000
  • 이 연구의 목적은 새로운 정보검색 환경에 맞는 시소러스 부가관계의 확장 방안을 제시하는데 있다. 이를 위해 본 연구는 ISO 2788과 ANSI/NISO Z 39.19 기준, 그리고 현재 사용되고 있는 20개 시소러스의 부가용어관계를 비교 분석하여 문제점과 한계점을 도출하고, 새로운 정보검색환경에 맞는 부가관계 확장방안을 제시하였다. 이러한 문제점을 해결한 용어관계의 확장방안은 다음과 같다. 첫째, 범위주기에서 정의를 별도로 분리하고, 범위주기를 유형별로 구분했다. 둘째, 한정어 사용에 대한 원칙을 제시하였다. 셋째, 디스크립터 용어 정보의 확장방안을 제안했다.

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The Impact of Cruise Lines' Program on Tourism Industry in Incheon

  • KIM, Kyungmi;PARK, Hyunjun
    • 융합경영연구
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    • 제8권1호
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    • pp.20-28
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    • 2020
  • Purpose: This research explores possibilities for unique tourism programs in the Port of Incheon that would bring tourism benefits from the cruise line industry to Incheon. This research also tries to find practical strategies and principles for the cruise line industry by reviewing the current itinerary in the cruise line industry. Research design, data, and methodology: Because this study is exploratory research, it first reviews trends in global tourism, ocean tourism, and the cruise line industry. Then, this study compares the current status of cruise line industry in South Korea with those in Japan. Lastly, existing cruise itineraries are reviewed for practical strategies and principles. Results: Based on reviewing the example of a cruise ship itinerary from the cruise ship company, possible cruise line programs at stopover places are suggested for the Port of Incheon and if the program is planted, it will boost Incheon's economy and tourism industry. Conclusion: Basic data about tourism in coastal regions and data analyses are lacking. Therefore, this study not only recommends further research in itinerary development or evaluation of cruise stopover programs, but also future research should explore the impact of the cruise industry from many different perspectives.

티타늄 산화물과 유화물의 전지 전압을 결정하는 요소에 대한 제일원리계산 (First Principles Study on Factors Determining Battery Voltages of TiS2 and TiO2)

  • 김희진;문원진;김영민;배경서;윤재식;이영미;국진선;김양수
    • 한국표면공학회지
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    • 제42권1호
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    • pp.8-12
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    • 2009
  • Electronic structures and chemical bonding of Li-intercalated $LiTiS_2$ and $LiTiO_2$ were investigated by using discrete variational $X{\alpha}$ method as a first-principles molecular-orbital method. ${\alpha}-NaFeO_2$ structure is the equilibrium structure for $LiCoO_2$, which is widely used as a commercial cathode material for lithium secondary battery. The study especially focused on the charge state of Li ions and the magnitude of covalency around Li ions. The average voltage of lithium intercalation was calculated using pseudopotential method and the average intercalation voltage of $LiTiO_2$ was higher than that of $LiTiS_2$. It can be explained by the differences in Mulliken charge of lithium and the bond overlap population between the intercalated Li ions and anions in $LiTiO_2$ as well as $LiTiS_2$. The Mulliken charge, which means the ionicity of Li atom, was approximately 0.12 in $LiTiS_2$ and the bond overlap population (BOP) indicating the covalency between Ti and S was about 0.339. One the other hands, the Mulliken charge of lithium was about 0.79, which means that Li is fully ionized. The BOP, the covalency between Ti and O, was 0.181 in $LiTiO_2$. Because of high ionicity of Li and the weak covalency between Ti and the nearest anion, $LiTiO_2$ has a higher intercalation voltage than that of $LiTiS_2$.

생애사적 접근을 통한 과학교사의 교수실행 변화과정에 관한 사례연구 (A Case Study on Changes in Science Teachers' Teaching Practices using the Biographical Approach)

  • 한혜진;이선경;김찬종;이경호;김희백;오필석;맹승호
    • 한국과학교육학회지
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    • 제29권1호
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    • pp.22-42
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    • 2009
  • 본 연구에서는 현직 교사가 자신의 생애, 특히 교직입문 이후 경력이 경과함에 따라서 접하게 되는 다양한 경험들 속에서 이루어진 교수실행의 연화과정을 탐색하고자 한다. 이를 위하여 구체적으로 교사의 관점에 근거해 교사의 삶을 살펴보는 생애사적 접근을 취하였고, 실천원리 (practical principle)의 변화 중심으로 개별 과학 교사의 교수실행 변화 과정을 상술하였다. 연구 참여자들은 각각 7년차, 10년차 중등 과학교사로 면담 및 수업관찰을 통해 연구 참여자의 교수실행 특징 및 변화 과정에 관한 자료를 수집하였다. 연구 결과로부터 연구 참여자들의 교수실행 변화과정의 특징을 다음과 같이 도출할 수 있었다. 연구 참여자들의 교수실행 변화는 1) 변화를 촉발한 결정적 경험, 이후 2) 기존 교수실행에 대한 적극적인 반성, 마지막으로 3) 교수실행의 구체적인 변화에 직접적인 영향을 미친 경험들이라는 3 요소의 상호작용을 통해 이해될 수 있었다. 이와 같은 교수실행 변화는 실천원리의 지형 (국면) 변화로 나타났다. 과거와 비교하여 변화원 주요 실천원리의 변화 양상은 (1) 기존 실천원리의 강화, (2) 기존 실천원리의 대체 (3) 새로운 실천원리의 형성으로 대별할 수 있었다.

비화학양론적 Na+β-alumina를 위한 Mg 원자의 치환: 제일원리 계산 (Mg Atom Substitution for Nonstoichiometric Na+ β-Alumina: A First Principles Study)

  • 김대현;김대희;정용찬;서화일;김영철
    • 한국재료학회지
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    • 제20권2호
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    • pp.55-59
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    • 2010
  • $Na^+$ ion conductivity can be improved by the substitution of an Mg atom for an Al atom to form a nonstoichiometric $Na^+$ $\beta$-alumina. We performed a first principles study to investigate the most stable substitution site of an Mg atom and the resulting structural change of the nonstoichiometric $Na^+$ $\beta$-alumina. Al atoms were classified as four different layers in the spinel block that are separated by conduction planes in the nonstoichiometric $Na^+$ $\beta$-alumina. The substitution of an Mg atom for an Al atom at a tetragonal site was more favorable than that at an octahedral site. The substitution in the spinel block was more favorable than that close to the conduction plane. This result was well explained by the volume changes of the polyhedrons, by the standard deviation of the Mg-O distance, and by the comparison with bulk MgO structure. Our result indicates that the most preferable site for the Mg atom was the tetrahedral site at the spinel block in the nonstoichiometric $Na^+$ $\beta$-alumina.