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      • KCI등재

        위성 레이다용 QM급 주파수합성기 설계 및 제작

        김동식,김현철,허전,김완식 한국인터넷방송통신학회 2020 한국인터넷방송통신학회 논문지 Vol.20 No.3

        In this paper, Qualification Model of frequency synthesizer is designed for X-band SAR system and performed electrical and environment test. Designed frequency synthesizer generate 13.65 GHz with very low phase noise performance. The integrated phase noise from 10Hz to 1MHz is –37.91 dBc. IRF performances are analyzed according to phase noise and jitter. Also, thermal and structure analysis are achieved for stable operation in space environment. Designed frequency synthesizer is consist of 2 modules of 6U size and generate L-band, C-band, Ku-band. The result of this study would enhance the design ability of RF module and help the frequency synthesizer design for SAR payload system. 본 논문에서는 SAR 탑재체에 적용할 수 있는 X-band 주파수합성기 인증모델(QM)을 설계 및 제작하고, 우주환경모의 시험을 통해 그 성능을 검증하였다. 제작된 주파수합성기는 상하향변환에 필요한 13.XXGHz 의 저잡음 국부신호를 생성하는 역할을 수행하며, 10Hz에서 1MHz 까지 측정된 적분 위상잡음은 –37.91 dBc 이다. 측정된 위상잡음을통해 SAR 성능지표인 IRF성능 영향분석을 수행하였으며, 0.2 ps 의 지터로 PSLR과 ISLR에 영향 없이 SAR 시스템에적용 가능함을 확인하였다. 또한, 열분석, 구조분석을 수행하여 안정성을 확인하였으며, 열진공, 열주기, 진동, 충격 시험을 통해 우주환경 내성을 확인하였다. 제작된 QM 급 주파수합성기는 L-band, C-band, Ku-band 주파수를 출력하며, 6U모듈 2개로 설계를 하였다. 본 연구를 통해 국내 위성용 RF 모듈의 국산화 기술 확보와 SAR 위성용 주파수합성기기술 개발에 활용이 가능하다.

      • "暴力"論에 관한 社會學的 考察

        金東式 제주대학 1979 논문집 Vol.11 No.1

        In this study, we deal with 'violence' as a mode of human behavior to attempt to alter a 'given' order. And we demand to cleanse biases and prejudices that violence is always irrational or pathological. These biases and prejudices have been supported with assuming 'Violent Men', which means that they are biologically prone to do aggressive behavior in nature, or in behavioristic approach teamed violence in the subculture of violence. This assumption is held to be true, primarily by those who do not want any change in the given order. They are afraid that change in the connotation of violence might deprive them of any 'vested intrests,' so they argue social relations are composed of all of parts in consensus 'in the equilibriated social system.' But in conflict theory, social relations are composed of conflicting parts. Vio1ence is the deeplening of conflict in universal relations under a certain social condition. For the purpose of this clarifying, of 'Violence'-concept, in this study we examine the theories of 'violence' and require to establish new theory-arrangement. These discussion are oriented to a proposal that sociologists should not escape from the 'reality."

      • KCI등재

        GaMnAs 자성반도체의 박막 특성 및 후처리에 따른 특성 변화 연구

        김동식  (Dong Sik Kim) 대한전자공학회 2008 電子工學會論文誌 IE (Industry electronics) Vol.45 No.3

        본 연구에서는 비약적으로 발전하고 있는 반도체 소자가 요구하는 새로운 특성을 가진 신소재의 개발에 부응하여, 최근 세계적으로 많은 연구가 되고 있는 spintronics에 사용되는 화합물 자성반도체 박막에 관한 연구를 수행하였다. 본 연구에서 사용되는 GaMnAs 자성반도체 박막은 기존의 III-V족 화합물 반도체 소자에 적용이 쉽고, 그 응용범위가 넓어 앞으로의 전망이 매우 밝은 새로운 화합물 반도체라고 할 수 있다. 그러나 이런 GaMnAs 자성반도체 박막의 경우 현재까지 자성 특성을 나타내는 Curie 온도가 매우 저온에서만 나타나며, 또한 성장 조건에 따라 그 특성이 매우 달라지는 문제점을 가지고 있다. 따라서 본 논문에서는 GaMnAs 자성반도체 박막을 성장시키기 위한 최적조건과 자성특성을 향상시키기 위한 실험을 수행하였다. We investigate magnetic semiconductor thin films for application towards spintronics, which can overcome current limitations in semiconductor devices. GaMnAs magnetic semiconducting films studied are easily integrated into conventional semiconductor processes and also offer a wide range of application, therefore it shows much promise as a future material. However the Curie temperature at which magnetic properties exist for GnMnAs is very low, also depending on deposition conditons the properties of the film can vary widely. In order to study these issues we investigate the best possible deposition conditions for magnetic properties.

      • KCI등재

        레이아웃의 원리를 기반으로 민방위 대피시설 표지판 유형 및 부착 위치의 특성에 관한 연구

        김동식,허레이,백하영 한국실내디자인학회 2019 한국실내디자인학회논문집 Vol.28 No.5

        The current evacuation signs of civil defense facilities can be broadly divided into guide sign and guidance sign. It is very important role to guide the correct movement as well as provide evacuation information about civil defense facilities. Evacuation sign of civil defense facility currently inconsistently attached at each underground subway entrance which has different types of visual components including letters and pictograms along with different locations as a structural component. It caused huge visual confusion for users. In addition, due to the negligence of maintenance, many evacuation signs are corroded and discolored as well as even missed at some places. Therefore users may not be able to recognize evacuation signs of civil defense facilities. The purpose of this study is to elucidate various types and locations for evacuation signs of civil defense facilities which is attached at underground subway entrances based on the layout principle so that users can easily identify and access subway stations in emergency. It is also provided new standards as a unified guideline of evacuation sign for civil defense facilities with considering safety issues which is the most important aspect in our society.

      • KCI등재

        양자화 제약 집합에 여과된 데이터를 투영하는 기법의 이론적 고찰

        김동식,박섭형 한국통신학회 1996 韓國通信學會論文誌 Vol.21 No.7

        The postprocessing of compressed images based on the projections onto convex sets and the constrained minimization imposes several constraints on the procesed data. The quantization constraint has been commonly used in various algorithms. Quantization is many-to-one mapping, by which all the dat in a quantization region are mapped to the corresponding representative level. The basic idea behind the projection onto the QCS(quantization constraint set) is to prevent the processed data from diverging from the original quantization region in order to redue the artifacts caused by filtering in postprocessing. However, there have been few efforts to analye the POQCS(projection onto the QCS). This paper analyzed mathematically the POQCS of filtered data from the viewpoint of minimizing the mean square error. Our analysis shows that a proper filtering technique followed by the POQCS can reduce the quantization distortion. In the conventional POQCS, the outside data of each quantization region are mapped into the corresponding boundary. Our analysis also shows that mappingthe outside data to the boundary of a subregion of the quantization region yields lower distortion than does the mapping to the boundary of the original region. In addition, several examples and discussions on the theory are introduced.

      • KCI등재

        광열/광음 기법에 의한 나노초 폭발적 기화 과정 분석

        김동식,박희권,C.P.Grigoropoulos,최선락 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.6

        † 책임저자, 회원, 포항공과대학교 기계공학과E-mail: HYPERLINK "mailto:dskim87@postech.ac.kr" dskim87@postech.ac.krTEL: (054) 279-2179 FAX: (054) 279-3199* IBM, Storage Division, San Jose, USA

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