• 한국자기학회지
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• 제15권6호
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• pp.303-306
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• 2005

Micromagnetics 전산 모사를 이용하여 국소적 층간교환상호작용이 있는 강자성/비자성/강자성 다층박막 구조에서 Bloch 자벽이나 Neel 자벽보다 더 얇은 두께의 자벽이 인위적으로 형성될 수 있음을 보였고, 이때 생성된 좁은 자벽의 두께가 강자성층의 두께에 의해 영향을 받음을 보였다. 국소적 층간교환상호작용을 가진 $Fe_1/Cr/Fe_2$ 구조에서 좁은 자벽이 생성됨을 보였고, $Fe_2$ 층의 두께를 20nm로 고정시키고 $Fe_1$층의 두께를 각각 1, 2, 4, 6nm으로 변화시켜가며 전산 모사를 수행하여 $Fe_1$ 층의 두께가 감소함에 따라 자벽의 두께가 얇아짐을 확인하였다.

• 한국음향학회지
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• 제15권1호
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• pp.23-33
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• 1996

본 논문에서는 bispectra를 위한 고전적 주영역 (classical principal domain)이 2계 Volterra 모델의 출력을 결정짓는데 사용되면 그 출력은 완전하지 못하게 될 것임을 지적한다. 이러한 불완전함은 DFT의 주기적 특성과 관련이 있다. 이런 이유로, 본 논문의 목적은 비선형 시스템의 응답의 추정을 향상기키는 Volterra 커널을 위한 확장된 주영역 (extended principal domain)을 제안하는데 있다. 확장된 주영역을 정의 내리기 위하여, 2차원 DFT와 Volterra 모델의 2계 요소와 정사각형 필터와의 관계를 사용하여 이산 시간 영역 Volterra 모델에서 새로운 이산 주파수 영역의 Volterra 모델을 유도하였다. 확장된 영역이 모델의 출력에 미치는 영향을 DFT의 주기성 측면에서 해석을 하였다. 컴퓨터 모의 실험을 통하여, Volterra 모델링에서 확장된 주영역의 영향을 살펴보았다. 모의 실험 결과에 의하면, Volterra 모델의 출력을 계산하는 과정과 Volterra 모델의 계수를 추정하는데 있어서 매우 중요한 역할을 함을 알 수 있었다.

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2002년도 International Symposium on Magnetic Resonance
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• pp.87-87
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• 2002

• Journal of Power Electronics
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• 제12권4호
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• pp.623-631
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• 2012

In this paper, a digital controller design procedure is presented for single-phase voltage-doubler boost rectifiers (VDBR). The model derivation of the single-phase VDBR is performed in the s-domain. After that the simplified equivalent z-domain models are derived. These z-domain models are utilized to design the input current and the output dc-link voltage controllers. For the controller design in the z-domain, the traditional K-factor method is modified by considering the nature of the digital controller. The frequency pre-warping and anti-windup techniques are adapted for the controller design. By using the proposed method, the phase margin and the control bandwidth are accurately achieved as required by controller designers in a practical frequency range. The proposed method is applied to a 2.5 kVA single-phase VDBR for Uninterruptible Power Supply (UPS) applications. From the simulation and the experimental results, the effectiveness of the proposed design method has been verified.

• ETRI Journal
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• 제35권5호
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• pp.739-747
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• 2013

This paper investigates the multifarious nature of the long-term evolution (LTE) scheme and that of the modified LTE scheme for symbol timing synchronization (STS). This investigation allows us to propose a new replica correlation-based STS scheme to overcome the inherent weaknesses of the other two schemes. The proposed STS signal combines a gold sequence and a half sine wave in the time domain, whereas conventional STS signals specify either binary sequences or complex sequences in the time domain or in the frequency domain. In the proposed scheme, a sufficient correlation property is realized by the gold sequence, and robustness against the frequency offset (FO) is achieved through the sine wave. Compared to the existing LTE-related schemes, the proposed scheme can better achieve immunity to FO and reduction in detector complexity, as well as a low peak-to-average power ratio and a low detection error rate. Performance evaluations through analysis and simulation are provided in the paper to demonstrate these attributes.

• ETRI Journal
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• 제41권5호
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• pp.574-584
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• 2019

A new Mirai variant found recently was equipped with a dynamic update ability, which increases the level of difficulty for DDoS mitigation. Continuous development of 5G technology and an increasing number of Internet of Things (IoT) devices connected to the network pose serious threats to cyber security. Therefore, researchers have tried to develop better DDoS mitigation systems. However, the majority of the existing models provide centralized solutions either by deploying the system with additional servers at the host site, on the cloud, or at third party locations, which may cause latency. Since Internet service providers (ISP) are links between the internet and users, deploying the defense system within the ISP domain is the panacea for delivering an efficient solution. To cope with the dynamic nature of the new DDoS attacks, we utilized an unsupervised artificial neural network to develop a hierarchical two-layered self-organizing map equipped with a twofold feature selection for DDoS mitigation within the ISP domain.

• 한국초등과학교육학회지:초등과학교육
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• 제24권3호
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• pp.268-280
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• 2005

Teaching with laboratory activities in school science, which are distinctive characteristic, is placed from other disciplines fur teaming almost 200 hundred years ago. A number of science educators have suggested that there are rich benefits in teaming from using laboratory activities. At these time, however, some educators have begun to seriously question the effectiveness and the role of laboratory activities. There are some causes related to obscure and vague aims of laboratory activities. The purposes of this paper is to review aims of laboratory activities presented in the literatures through historical overview, and to obtain implication for school science. There are various aims of laboratory activities by a number of researchers. Overall synthesizing, there are ffur domains of aims of science teaching through laboratory activities, (a) science knowledge has two sub-domains; scientific content knowledge and procedural knowledge, (b) nature of science, (c) science attitude has two sub-domain; scientific attitude and attitude toward science, and (d) ability of scientific inquiry has two sub-domain; manipulative skills and scientific thinking. But, it is necessary to continue the following study in order to obtain the aims of laboratory activities agreed by expert community, and setting up of lists of aims of laboratory activities for students to achieve hierarchies of school science curriculums.

• 영재교육연구
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• 제18권2호
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• pp.201-237
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• 2008

본 연구는 과학 및 시각예술 영역의 창의적 성취사례를 통해 두 영역의 영역보편성과 영역특정성에 대해 살펴보는 데 그 목적을 두었다. 연구를 위해 각각의 영역에서 세계적인 성취를 이룬 한국의 창의적 인물들(과학자: 10인, 시각예술가: 9인)에 대한 인터뷰를 실시하였고, 이로부터 수집한 질적 자료를 토대로 창의적 성취에서 영역보편적으로 드러나는 특성과 영역특정적으로 드러나는 특성을 요약, 기술하였다. 자료분석에는 본 연구의 근간이 되는 총괄적이고 체계적인 개념틀 '지식진화시스템(Knowledge-Evolving Systems: KES)'을 사용하였다. 분석 결과를 보면, 실재시스템에서 두 영역의 성취는 공통적으로 요동, 탐색, 산물을 통해 드러났다. 반면, 과학은 전문지식, 어려운 과제, 세계 최초의 객관적인 지식이 주요한 요인으로, 예술에서는 일상적인 지식, 다양한 주제, 새로운 변화에 대한 인간의 감성 전달이 주된 요인으로 드러났다. 개인시스템에서 두 영역은 모두 분명한 목표를 향한 집중과 독자적인 노력을 보편적으로 요구하였다. 반면 과학은 창조의지, 확산적 및 분석적 사고, 직관 및 통찰, 그리고 도전이 대표적인 요인으로, 시각예술은 즐거움, 민감성, 통합적 사고, 완벽성, 그리고 자유로움이 주요한 요인으로 산출되었다. 마지막으로 사회시스템에서 두 영역의 성취는 전문가의 승인에 의해 결정되었다. 그리고 과학자들의 성취에는 인간네트워크, 기관의 지원, 생존경쟁과 운이 큰 영향을 미쳤고, 시대적 요구와 민족성이 발전의 토대가 되었다. 반면, 시각예술가들은 주변의 반대와 부적인 예술문화 풍토로 인해 고독한 삶을 살아왔다.

• 한국초등과학교육학회지:초등과학교육
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• 제19권2호
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• pp.29-41
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• 2000

The purpose of this study is to examine the effects of the Portfolio applied science instruction on the students' scientific affective domain and perceptions of portfolio in elementary schools. Portfolio applied science instruction of the 6th grade science unit 'Environment pollution and Nature protection' was developed for this study. Traditional instruction was implemented to the control group and portfolio applied science instruction was implemented to the experimental group. Pretests of the scientific affective domain were administered to both groups. The treatment was given for about seven weeks for both groups. Instruments about scientific affective domain were administered to both groups. A questionnaire on perception of portfolio applied science instruction was given to the experimental group after the treatment. The results were analyzed using t-test on the students' scientific affective domain. The results of this study are as follows: 1. Portfolio applied science instruction program for elementary schools was developed. Students themselves determine the portfolio learning goal in a portfolio applied science instruction. Students construct the portfolio and they evaluate themselves and other colleagues. Also teachers go on portfolio applied science instruction considering portfolio purpose, concepts, evaluation. 2. There was not a statistically meaningful difference between an experimental group and a control group o]1 the students' scientific affective domain. In three sub categories of a scientific affective domain, the science perception, the interest on science and scientific attitude, there were not statistically meaningful difference among them. 3. As the results of the questionnaire on perceptions of portfolio, they didn't understand it very well but after learning portfolio, they showed positive attitude to perceptions of portfolio. Students in portfolio applied science instruction like more the portfolio applied science instruction than general instruction. 4. Portfolio applied science instruction has an useful value as a method of teaching and evaluation. Students and teachers can produce various portfolios products in portfolio applied science instruction. As a conclusion, portfolio applied science instruction was not statistically meaningful on the students' scientific affective domain, but it gives positive effects on perceptions of portfolio in elementary schools. Therefore, portfolio has an educational value as a method of teaching and evaluation for students' growth. In the future, teachers and students must have interaction and feedback in portfolio applied science instruction.

• 한국환경복원기술학회지
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• 제27권2호
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• pp.29-42
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• 2024

As a global response to climate and biodiversity challenges, there is an emphasis on the conservation and restoration of ecosystems that can simultaneously reduce carbon emissions and enhance biodiversity. This study comprised a text analysis and keyword extraction of 1,100 research papers addressing nature restoration in Korea, aiming to provide a quantative and systematic evaluation of domestic research trends in this field. To discern the major research topics of these papers, topic modeling was applied and correlations were established through network analysis. Research on nature restoration exhibited a mainly upward trend in 2002-2022 but with a slight recent decline. The most common keywords were "species," "forest," and "water". Research topics were broadly classified into (1) predictions of habitat size and species distribution, (2) the conservation and utilization of natural resources in urban areas, (3) ecosystems and landscape managements in protected areas, (4) the planting and growth of vegetation, and (5) habitat formation methods. The number of studies on nature restoration are increasing across various domains in Korea, with each domain experiencing professional development.