• International Journal of Aeronautical and Space Sciences
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• 제10권1호
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• pp.67-74
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• 2009

In general, the lunar landing stage can be divided into two distinct phases: de-orbit and descent, and the descent phase usually comprises two sub-phases: braking and approach. And many optimization problems of minimal energy are usually focused on descent phases. In these approaches, the energy of de-orbit burning is not considered. Therefore, a possible low perilune altitude can be chosen to save fuel for the descent phase. Perilune altitude is typically specified between 10 and 15km because of the mountainous lunar terrain and possible guidance errors. However, it requires more de-orbit burning energy for the lower perilune altitude. Therefore, in this paper, the perilune altitude of the intermediate orbit is also considered with optimal thrust programming for minimal energy. Furthermore, the perilune altitude and optimal thrust programming can be expressed by a function of the radius of a parking orbit by using continuation method and co-state estimator.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1329-1330
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• 2007

Phase-change random access memory(PRAM) has many advantages compare with the existing memory. For example, fast programming speed, low programming voltage, high sensing margin, low power consume and long cyclability of read/write. Though it has many advantages, there are some points which must be improved. So, we invented and studied new constitution of $Ge_{1}Se_{1}Te_{2}$ chalcogenide material. Actually, the performance properties have been improved surprisingly. However, crystallization time was as long as ever for amorphization time. In this paper, we studied in order to make set operation time and reset operation voltage reduced. In the present work, by alloying Sb in $Ge_{1}Se_{1}Te_{2}$. we could confirm that improved its set operation time and reset operation voltage. As a result, the method of Sb-alloyed $Ge_{1}Se_{1}Te_{2}$ can be solution to decrease the set operation time and reset operation voltage.

• 한국CDE학회논문집
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• 제19권4호
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• pp.368-389
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• 2014

There are many agendas and discussion subjects for BIM-based Criteria Design phase. At that time, some problems are occurred by software compatibility, simple repetitive tasks, rework caused by missing information etc. In this study, we focus on solving that problems by applying API(Application Programming Interface) method. For effective study, we construct Criteria Design process by using DSM (Dependency Structure Matrix) and study applicability of API. It will be effective for time-consuming task and simply labor-intensive tasks by applying API. we expect improving BIM-based Design Process and Data quality, work productivity without missing information and shapes for using API.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.199-199
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• 2008

이 실험은 NVM의 Oxide, Nitride, Oxide nitride층별 blocking, trapping and tunneling 속성에 대해서 밝히고자 한다. gate 전극은 값싸고 전도도가 좋은 알루미늄을 사용한다. 유리기판위에 Silicon nitride층을 20nm로 코팅하고 Silicon dioxide층을 10nm로 코팅한다. 그리고 amorphous Silicon material이 증착된다. Poly Silicon은 Solid Phase Crystallization 방법을 사용하였다. 마지막 공정으로 p-doping은 ion shower에 의한 방법으로 drain과 source 전극을 생성하였다. gate가 biasing 될 때, p-channel은 source와 drain 사이에서 형성된다. Oxide Nitride Oxide nitride (ONO) 층은 각각 12.5nm/20nm/2.3nm의 두께로 만들었다. 전하는 Program process 중에 poly Silicon층에서 Silicon Oxide nitride tunneling층을 통하여 움직이게 된다. 그리고 전하들은 Silicon Nitride층에 머무르게 된다. 그 전하들은 erasing process 중에 trapping 층에서 poly Silicon 층으로 되돌아 간다. Silicon Oxide blocking층은 trapping층으로 전하가 나가는 것을 피하기 위하여 더해진다. 이 논문에서 Programming process와 erasing process의 Id-Vg 특성곡선을 설명한다. Programming process에 positive voltage를 또는 erasing process에 negative voltage를 적용할 때, Id-Vg 특성 곡선은 왼쪽 또는 오른쪽으로 이동한다. 이 실험이 보여준 결과값에 의해서 10년 이상의 저장능력이 있는 메모리를 만들 수 있다. 그러므로, NVM의 중요한 두 가지 성질은 유지성과 내구성이다.

• 한국실내디자인학회논문집
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• 제19권5호
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• pp.95-104
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• 2010

One of 21st century's main paradigms is a 'Culture', and people started to express their 'cultural desires and demands' regarding public environments. Accordingly central and local governments are paying attention to these demands from their citizens and trying to establish the policies to meet these needs. This research is done to suggest the strategy programming model to support the executions of culture-centered public designs which are based on the local resources and identities. The entire research contains three sub-topics. First topic is setting the prototype phases of strategy programming. Second topic is analyzing the associated indices for each prototype phase. Third topic is suggesting Matrix Model in which the prototype phases and their associated indices are linked. Among three topics, this paper deals with the first one - the prototype phases of strategy programming. It studies this subject in relation with Place Marketing which emphasizes the local resources and identities. The prototype phases are comprised of 3 steps for Place Strategy and 4 steps for Marketing Strategy. Place Strategy should be considered prior to Marketing Strategy because in culture-centered public design, locality has priority over other concerns. The phases for Place Strategy includes 'Resource_analyzing of local resources', 'Mission_setting a purpose', and 'Targeting_segmenting target groups'. The phases for Marketing Strategy involves 'Organization_instituting the main body and/or partnership', 'Image Positioning_setting an unique local image', 'Point_realizing the product', and 'Channel_deciding the sales promotion tools'.

• 컴퓨터교육학회논문지
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• 제22권6호
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• pp.43-55
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• 2019

4차 산업혁명으로 초지능, 초연결 사회가 도래했다. 4차 산업혁명의 핵심 기술들은 소프트웨어가 중요한 부분을 차지한다. 소프트웨어를 통해 문제를 해결하는 능력은 모든 사람이 갖추어야 할 핵심 역량이란 점에서 소프트웨어 교육이 필요하다. 소프트웨어 교육은 프로그래밍 과정을 통해 문제를 해결하는 능력인 컴퓨팅 사고력 향상을 목표로 한다. 지금까지 대부분의 문제해결 프로그래밍 교수학습 모형은 전통적 개발 방식인 폭포수 모형(분석-설계-개발-테스트)을 따른다. 이는 선행 단계에서 문제가 있는 경우 테스트 단계에서 발견되어 문제의 해결책을 다시 찾는 데 적지 않은 시간과 노력이 소요되어 학습에 부담으로 작용할 수 있다. 본 연구에서는 애자일(Agile) 개발 방식인 TDD(테스트주도개발)를 적용한 컴퓨팅 사고력 기반 테스트 중심 문제해결 학습 모형을 제안하고 전문가 검토를 통해 모형의 적절성을 검증하였다. 모형의 검증 결과 긍정적인 평가 결과를 보였다. 특히, 모형의 학습 단계 구성, 프로그래밍 학습에의 도움, 컴퓨팅 사고력 증진에의 도움 등에서는 높은 평점을 보여 향후 학습 적용 시 문제해결 프로그래밍 학습을 통한 컴퓨팅 사고력 발달에 긍정적인 효과가 있을 것으로 판단된다.

• Computers and Concrete
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• 제30권3호
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• pp.225-236
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• 2022

In this article, Multi-Gene Genetic Programming (MGGP) is proposed for the estimation of the compressive strength of concrete. MGGP is known to be a powerful algorithm able to find a relationship between certain input space features and a desired output vector. With respect to most conventional machine learning algorithms, which are often used as "black boxes" that do not provide a mathematical formulation of the output-input relationship, MGGP is able to identify a closed-form formula for the input-output relationship. In the study presented in this article, MGPP was used to predict the compressive strength of plain concrete, concrete with fly ash, and concrete with furnace slag. A formula was extracted for each mixture and the performance and the accuracy of the predictions were compared to the results of Artificial Neural Network (ANN) and Extreme Learning Machine (ELM) algorithms, which are conventional and well-established machine learning techniques. The results of the study showed that MGGP can achieve a desirable performance, as the coefficients of determination for plain concrete, concrete with ash, and concrete with slag from the testing phase were equal to 0.928, 0.906, 0.890, respectively. In addition, it was found that MGGP outperforms ELM in all cases and its' accuracy is slightly less than ANN's accuracy. However, MGGP models are practical and easy-to-use since they extract closed-form formulas that may be implemented and used for the prediction of compressive strength.

• 정보교육학회논문지
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• 제18권1호
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• pp.185-193
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• 2014

소프트웨어 제작 교육은 미래의 IT 기술을 능동적으로 사용하고, 컴퓨터와 대화할 수 있는 프로그래밍 언어를 가르치는 교육이다. 이를 위해 본 연구에서는 영국, 미국, 인도, 에스토니아를 중심으로 프로그래밍 교육과 관련된 교육과정을 분석하였다. 또한, 그 결과를 토대로 우리나라의 초등학교와 중학교에서 프로그래밍 교육을 할 수 있도록 정보 과학의 한 영역으로서 소프트웨어 제작 분야의 성취 목표와 교수학습 방법, 평가 방법 등을 제안하였다. 본 연구에서는 초등학교 1학년부터 중학교 3학년까지를 4단계로 구분하고, 각 단계별로 2~3개의 세부 영역과 그에 따른 성취 목표를 제시하였다.

• 전기학회논문지
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• 제60권3호
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• pp.538-543
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• 2011

In this paper, design and control of an interleaved boost converter for multi-string PV Inverter are discussed. Interleaved Boost converter can reduce current ripples at input and output side by cancelling an each phase of inductor currents. Therefore, it contributes to increase efficiency and downsize the whole system volume, cost. One of the advantages of the multi-string system is easy to expand power capacity by connecting the converter modules in parallel. In order to reduce current ripples, the inductor currents on each phase are controlled independently in the converter module, and communication between the converter modules is required for further ripple current reduction. Current control algorithm for the balance of the each phase ripple currents and synchronization of the converter modules based on communication are proposed and implemented in the DSP programming. 10kW prototype of the multi-string converter module is assembled and experimental results are presented to verify the proposed ripple current reduction methods.

• 대한산업공학회지
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• 제31권1호
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• pp.1-9
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• 2005

This paper proposes the heuristic algorithm for the generalized GT problems to consider the restrictions which are given the number of machine cell and maximum number of machines in machine cell as well as minimum number of machines in machine cell. This approach is split into two phase. In the first phase, we use the similarity coefficient which proposes and calculates the similarity values about each pair of all machines and sort these values descending order. If we have a machine pair which has the largest similarity coefficient and adheres strictly to the constraint about birds of a different feather (BODF) in a machine cell, then we assign the machine to the machine cell. In the second phase, we assign parts into machine cell with the smallest number of exceptional elements. The results give a machine-part grouping. The proposed algorithm is compared to the Modified p-median model for machine-part grouping.