주파수 영역 등화기가 적용된 위성 DMB 시스템의 성능 분석

이재성,김덕경,Lee Jae-Sung,Kim Duk-Kyung 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.5a

위성 DMB(Digital Multimedia Broadcasting) 시스템은 중앙의 송신기인 위성과 지상보조 중계기인 Gap-filler로 구성되는 단일 주파수 망이다. NLOS 환경의 음영지역을 커버하기 위해서는 다수의 Gap-filler 설치가 필요한데, 이로 인해 다중경로 성분이 증가하여 Finger의 수가 제한된 현 RAKE 수신기의 성능을 저하시킨다. 이에 본 논문은 RAKE 수신기를 대신하여 주파수 영역 등화기를 사용하되, 현재 시스템의 변경을 최소화하기 위하여 기존 주파수 영역 등화기 기술에서 필요로 한 보호구간을 사용하지 않는 것으로 하고, 시뮬레이션을 통해 그 성능을 분석한다. 시뮬레이션 결과를 통해 주파수 영역 등화기는 현 RAKE 수신기보다 Gap-filer 개수의 증가에 둔감하고, 보다 큰 CDM 채널 용량을 가질 수 있음을 확인할 수 있다. 뿐만 아니라, 다양한 채널 모델에서의 결과는 주파수 영역 등화기가 기존의 시스템에서도 환경에 따라 충분히 사용가능할 수 있음을 말해준다. Satellite-Digital Multimedia Broadcasting(S-DMB) systems are single frequency networks which consist of a satellite and gap fillers. Though gap fillers are required to extend the coverage to NLOS(Non Line-of-Sight) area, the receiver performance can be degraded with a limited number of fingers due to the increased number of multi-paths. The paper proposes to use frequency domain equalizer(FDE) instead of conventional Rake receiver, where the guard interval is not considered in order to minimize the impact on the current S-DMB systems. Through a campaign of simulations, it is found that the proposed FDE is less sensitive to the number of gap fillers compared to the conventional Rake receiver, and can achieve a greater channel capacity in most channel environments.

소프트웨어 재활기법에 기반한 주-여분 서버 시스템의 작업전이 시간 분석

이재성,박기진,김성수,Lee, Jae-Sung,Park, Kie-Jin,Kim, Sung-Soo 한국정보처리학회 2001 정보처리학회논문지 A Vol.8 No.2

인터넷의 급속한 확산으로 인하여, 컴퓨터 시스템의 규모 및 복잡도가 점차 증가하고 있으며, 컴퓨터 시스템에 대한 높은 수준의 가용도 요구 조건을 충족시키기 위해, 하드웨어적.소프트웨어적 결함 허용 기법에 대한 연구가 활발하다. 소프트웨어 재활 기법은 서버에 탑재된 소프트웨어의 장시간 가동에 따른 소프트웨어 노화 현상을 다루고 있으며, 서버에서 실행중인 소프트웨어의 수행을 고의적으로 멈춘 후에 결함 발생 가능성이 낮은 초기 상태에서 이를 다시 가동시키는 소프트웨어적 결함 예방 방법의 일종이라 볼 수 있다. 본 연구에서는 주-여분 서버 시스템에서의 작업전이 시간이 소프트웨어 재활에 미치는 영향을 연구하였으며, 가용도 분석을 통해서 작업전이 시간이 재활 정책을 결정함에 있어서 중요한 요소임을 발견하였다. As the rapid growth of Internet, computer systems are growing in its size and complexity. To meet high availability requirements for the systems, one usually uses both hardware and software fault tolerance techniques. To prevent failures of computer systems from software-aging phenomenon that come from long mission time, we adopt software rejuvenation method that stops and restarts the software in the servers intentionally. The method makes the systems clean and healthy state in which the probability of fault occurrence is very low. In this paper, we study how switchover time affects software rejuvenation of primary-backup server systems. Through experiments, we find that switchover time is an essential factor for deciding the rejuvenation policy.

개인기업의 법인전환에 따른 세무효익 연구

이재성,서일,Lee Jae-Sung,Seo Il 대한경영정보학회 2001 경영과 정보연구 Vol.7 No.-

The form of company divides private and coporate companies. In general. private company has direct connection with owner's fortunes. On the contrary, cooperate company is established by a group of people who invest capital funds on their company and has an independent character. In the case of private company, their are many merits that owner can obtain all the benefits without divisions. However, the owner can mix up the control of accounting between public and private matters. As a result confusing, it is difficult to estimate financial situation of company and is limited to fund supply. Futhermore, owner has unlimited liabilities with law credit as a social cognition. Especially, the government tries to induce conversion of private company into cooperation one on the basis of benefits of tax and so on. In those situations, the purpose of this thesis is to study the management benefits with the conversion of private company into cooperate one focucing on the related tax reduction effect. To do this, I have reviewed all of the related textual achievements and tested the real significancy of tax reduction effect of conversion empirically. Finally, I have concluded that the conversion of private company into coporate one has many benefits including significant tax reduction effect. In other side, I have considered and reviewed many difficulties related conversion privated company into cooperate one and suggested some improvements as results. This thesis is comprises 5 chapters as follows; The first chapter explains purposes and methodologies and extents of this study. The second chapter deals the theoretical basis of conversion of private company into cooperate one and cooperates diverse benefits and types and processes of conversion. The preceding research achievements are also reviewed in this chapter. The third chapter deals empirical testing on the real tax reduction effect of the conversion. The analysis is proceeded through t-test of difference of tax between pre and after conversion. The result is presented so positively that I can conclude that cooperate conversion of private company has real benefit of tax reduction. The forth chapter deals the difficulties and improvements related with conversion. They are considered and reviewed at various aspects such as practical, financial and tax aspect. In fifth chapter, I summarise all of the significant points of this study and have conclusions in various aspects at last. In final point, this study is not enough in sample numbers and sample collecting area for empirical testing of significant tax reduction effect of cooperate conversion and research of more foreign achievements. Those are remained as continuing future studies.

H2 15O 양전자단층촬영술을 이용한 뇌기능 지도 작성 ( II ) - 작업 기억의 지도 작성

이재성,이동수,이상건,남현우,김석기,박광석,정재민,정준기,이명철 ( Jae Sung Lee,Dong Soo Lee,Sang Kun Lee,Hyun Woo Nam,Seok Ki Kim,Kwang Suk Park,Jae Min Jeong,June Key Chung,Myung Chul Lee ) 대한핵의학회 1998 핵의학 분자영상 Vol.32 No.3

Purpose: To localize and compare the neural basis of verbal and visual human working memory, we erforrned functional activation study using H2O PET. Materials and MethoDs: Repeated H213O PET scans with one control and three different activation tasks were performed on six right-handed narmal volunteers. Each activation task was composed of 13 matching trials. On each trial, four targets, a fixation dot and a probe were presented sequentially and subjects task was to press a response button to indicate whether or nat the probe was one of the previous targets. Short meaningful Korean words, simple drawings and monochromic pictures of human faces were used as matching objects for verbal or visual memory. All the images were spatially normalized and the differences between control and activation states were statistically analyzed using SPM96. Results: Statistical analysis of verbal memory activation with short words showed activation in the left Broca's area, premotor cortex, cerebellum and right cingulate gyrus. In verbal memory with simple drawings, activation was shown in the larger regions including where activated with short words and left superior temporal cortex, basal ganglia, thalamus, prefrontal cortex, anterior portion of right superior temporal gyrus and right infero-lateral frontal cortex. On the other hand, the visual memory task activated predominantly right-sided structures, especially inferior frontal cortex, supplementary motor cortex and superior parietal cortex. Conclusion: The results are :consistent with the hypothesis of the laterality and dissociation of the verbal and visual workmg memory from the invasive electrophysiological studies and emphasize the pivotal role of frontal cortex and cingulate gyrus in working memory system. (Korean J Nucl Med 1998;32:238-49)

SESSION Ⅴ : 의사결정지원 ; 시스템 다이나믹스에 의한 돈육가격예측

이재성,박세권 ( Jae Sung Lee,Sei Kwon Park ) 대한산업공학회 1989 89년도 PKIIE Vol.- No.-

느타리 버섯균으로부터 wood meal-wheat bran 배지에서의 리그닌분해효소 생산

이재성,하효철,Lee, Jae-Sung,Ha, Hyo-Cheol 한국응용생명화학회 2002 한국농화학회지 Vol.45 No.2

수소 및 중수소가 포함된 실리콘 산화막의 전기적 스트레스에 의한 열화특성

이재성,백종무,정영철,도승우,이용현,Lee, Jae-sung,Back, Jong-mu,Jung, Young-chul,Do, Seung-woo,Lee, Yong-hyun 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.11

Experimental results are presented for the degradation of 3 nm-thick gate oxide $(SiO_2)$ under both Negative-bias Temperature Instability (NBTI) and Hot-carrier-induced (HCI) stresses using P and NMOSFETS, The devices are annealed with hydrogen or deuterium gas at high-pressure $(1\~5\;atm.)$ to introduce higher concentration in the gate oxide. Both interface trap and oxide bulk trap are found to dominate the reliability of gate oxide during electrical stress. The degradation mechanism depends on the condition of electrical stress that could change the location of damage area in the gate oxide. It was found the trap generation in the gate oxide film is mainly related to the breakage of Si-H bonds in the interface or the bulk area. We suggest that deuterium bonds in $SiO_2$ film are effective in suppressing the generation of traps related to the energetic hot carriers.

MeSH 시소러스를 이용한 한영 교차언어 키워드 자동 부여

이재성,김미숙,오영순,이영성,Lee Jae-Sung,Kim Mi-Suk,Oh Yong-Soon,Lee Young-Sung 한국정보처리학회 2006 정보처리학회논문지B Vol.13 No.2

의학용 시소러스인 MeSH (Medical Subject Heading)는 영어 의학 논문 색인을 위한 통제어 시소러스로서 오랫동안 사용되고 있다. 본 논문에서는 한국어 MeSH를 이용하여 한국어 의학 논문의 요약문에 자동으로 영문 MeSH 색인어를 부여하는 '교차언어 키워드 부여' 방법을 제안하고 색인 전문가 및 저자의 색인 효율과 비교한다. 이 색인어 부여 과정은 우선 한국어 MeSH 용어를 문장에서 인식하여 추출하고, 이 용어를 다시 영어 MeSH 용어로 바꾼 후, 용어의 중요도를 계산하여 상위의 용어를 색인어로 부여한다. 특히, 한국어 MeSH 용어 추출을 위해 효과적으로 띄어쓰기 변이를 처리할 수 있는 방법을 제안한다 실험 결과, 띄어쓰기 변이를 효과적으로 처리하여 한국어 MeSH의 크기를 약 42% 정도 줄였을 뿐만 아니라, 후보 색인어 추출의 효과도 높였다. 또 이 방법을 이용하여 색인어 자동 부여를 한 후, 색인 전문가 및 저자의 색인 결과를 비교한 결과, 이 자동 색인 방법이 전문가의 색인 능력보다는 부족했지만, 저자의 색인 능력과는 별 차이가 없음을 보였다. The medical thesaurus, MeSH (Medical Subject Heading), has been used as a controlled vocabulary thesaurus for English medical paper indexing for a long time. In this paper, we propose an automatic cross language keyword assignment method, which assigns English MeSH index terms to the abstract of a Korean medical paper. We compare the performance with the indexing performance of human indexers and the authors. The procedure of index term assignment is that first extracting Korean MeSH terms from text, changing these terms into the corresponding English MeSH terms, and calculating the importance of the terms to find the highest rank terms as the keywords. For the process, an effective method to solve spacing variants problem is proposed. Experiment showed that the method solved the spacing variant problem and reduced the thesaurus space by about 42%. And the experiment also showed that the performance of automatic keyword assignment is much less than that of human indexers but is as good as that of authors.

다결정 실리콘 박막으로 구성된 Metal-Semiconductor-Metal 광검출기의 제조

이재성,최경근,Lee, Jae-Sung,Choi, Kyeong-Keun 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.5

A polysilicon-based metal-semiconductor-metal (MSM) photodetector was fabricated by means of our new methods. Its photoresponse characteristics were analyzed to see if it could be applied to a sensor system. The processes on which this study focused were an alloy-annealing process to form metal-polysilicon contacts, a post-annealing process for better light absorption of as-deposited polysilicon, and a passivation process for lowering defect density in polysilicon. When the alloy annealing was achieved at about $400^{\circ}C$, metal-polysilicon Schottky contacts sustained a stable potential barrier, decreasing the dark current. For better surface morphology of polysilicon, rapid thermal annealing (RTA) or furnace annealing at around $900^{\circ}C$ was suitable as a post-annealing process, because it supplied polysilicon layers with a smoother surface and a proper grain size for photon absorption. For the passivation of defects in polysilicon, hydrogen-ion implantation was chosen, because it is easy to implant hydrogen into the polysilicon. MSM photodetectors based on the suggested processes showed a higher sensitivity for photocurrent detection and a stable Schottky contact barrier to lower the dark current and are therefore applicable to sensor systems.

메타 검색에서 외래어 질의 정제 효과

이재성,Lee, Jae-Sung 한국정보처리학회 2008 정보처리학회논문지B Vol.15 No.2

문서에서 외래어가 일관되게 사용되지 않고 여러 이형태로 사용되고 있기 때문에, 정확한 질의어 일치를 지원하는 검색 시스템에서 외래어 질의로 문서를 검색하는데 어려움이 많다. 본 논문에서는 하나의 외래어로 질의할 경우, 원 질의어와 같은 뜻의 다양한 이형태 외래어 질의로 자동 확장하고 정제하여 더 많은 관련 문서를 손쉽게 검색할 수 있는 메타 검색 방법을 제안한다. 이 방법은 1차로 원 질의어에서 다양한 외래어 이형태를 통계적 방법으로 확장하고, 2차로 그 결과를 각 검색 엔진에게 질의하여 일정 개수 이상의 질의어가 문서에 나타났는지, 원 질의어의 문맥과 유사한 문맥에서 그 질의어가 쓰였는지를 비교하여, 같은 뜻의 유효한 외래어를 판별해 내고 이를 이용하여 검색할 수 있도록 한다. 실험 결과, 기준점으로 쓰인 1차로 만든 이형태로 검색했을 때 F값은 평균 38%이었으나, 제안된 방법인 2차로 정제된 질의어로 검색했을 때의 F값은 평균 81%로 매우 향상된 결과를 보였다. Foreign word transliterations are not consistently used in documents, which hinders retrieving some important relevant documents in exact term matching information retrieval systems. In this paper, a meta search method is proposed, which expands and refines relevant variant queries from an original input foreign word transliteration query to retrieve the more relevant documents. The method firstly expands a transliteration query to the variants using a statistical method. Secondly the method selects the valid variants: it queries each variant to the retrieval systems beforehand and checks the validity of each variant by counting the number of appearance of the variant in the retrieved document and calculating the similarity of the context of the variant. Experiment result showed that querying with the variants produced at the first step, which is a base method of the test, performed 38% in average F measure, and querying with the refined variants at the second step, which is a proposed method, significantly improved the performance to 81% in average F measure.