• 경영과학
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• 제11권2호
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• pp.43-63
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• 1994

A new model management framework is proposed to accommodate wide-spreading algebraic modeling languages (AMLs), and to facilitate a full range of model manipulation functions. To incorporate different modeling conventions of the leading AMLs (AMPL, GAMS, and SML) homogeneously, generic model concepts are introduced as a conceptual basis and are embodied by the structural and operational constructs of an Object-Oriented Database Management System(ODBMS), enabling the framework to consolidate components of DSSs(database, modelbase, and associated solvers) in a single formalism effectively. Empowered by a database query language, the new model management framework can provide uniform model management commands to models represented in different AMLs, and effectively facilitate integration of the DSS components. A prototype system of the framework has been developed on a commercial ODBMS, ObjectStore, and a C++ programming language.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.296-298
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• 2009

In this paper, we are performance analysis of IEEE 802.15.4b LR-WAPN(Low-Rate Wireless Personal Area Network; Zigbee) system noncoherent receivers at 915MHz under Jamming. IEEE 802.15.4b concerns itself with devices at 915MHz, which employ a higher data rate of up to 250 kbps, and which use O-QPSK(Offset Quradrature Phase Shift Keying modulation with DSSS(Direct Sequence Spread Spectrum). Communication between devices can still be hampered by the presence of interferers outside the network, whether the interference be intentional or not. Hence the receivers can not have stable receiving condition due to worse BER. To solve this problem, we present a mere stabilized receiver system of using noncoherent detection. In this paper, we look instead at the effect of jamming, i.e. intentional interference, on the BER performance of IEEE 802.15.4 devices.

• 항공우주시스템공학회지
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• 제8권2호
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• pp.40-48
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• 2014

In this paper, a prototype of GPS jammer localization system for precise landing is developed. The jammer localization system consists of the four jamming signal receivers for collecting RF signal, one central tracking station for estimating jammer position, and one monitoring station for displaying estimated position on the map. In order to estimate jammer location TDOA and AOA algorithm are introduced, and the function and design parameters of the developed prototype are proposed. CW, DSSS, Swept CW jamming signals were generated and used. From the results, it can be confirmed that developed system meets the performance goal.

• 한국전자통신학회논문지
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• 제9권4호
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• pp.455-468
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• 2014

RF-CBTC 열차제어시스템 무선 정보 송 수신의 이상적인 값을 도출하기 위하여 운영기관인 신분당선을 모델로 하여 터널환경에서 측정 및 시험하고, 알고리즘을 제시하여 끊임없는(Seamless) Hand off를 구현하기 위한 방안을 마련하였다. 또한 주파수 간섭 및 재 전송률을 줄이기 위하여 이상적인 값(-57dB)을 제시하고, 무선통신을 이용한 열차제어 시스템의 안정적인 데이터 통신이 가능하도록 주파수 최적화를 증명하였다. 이러한 결과를 토대로 신분당선 2단계구간에 실무적용 할 계획이다.

• Asia pacific journal of information systems
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• 제15권2호
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• pp.195-218
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• 2005

The emergence of ubiquitous computing environment will change the service architecture of business information systems such as Decision Support System(DSS), which will be a new application. Recent mobile DSSs allow the decision makers to be benefited from web and mobile technology. However, they seldom refer to context data, which are useful for proactive decision support. Meanwhile, ubiquitous applications so far provide restricted personalization service using context and preference of the user, that is, they do not fully make use of decision making capabilities. Hence, this paper aims to describe how the decision making capability and context-aware computing are jointly used to establish ubiquitous applications. To do so, an amended DSS paradigm: CKDDM(Context-Knowledge-Dialogue-Data-Model) is proposed in this paper. What will be considered for the future decision support systems when we regard ubiquitous computing technology as an inevitable impact that enforces the change of the way of making decisions are described. Under the CKDDM paradigm, a framework of ubiquitous decision support systems(ubiDSS) is addressed with the description of the subsystems within. To show the feasibility of ubiDSS, a prototype system, CAMA-myOpt(Context-Aware Multi Agent System-My Optimization) has been implemented as an illustrative example system.

• 한국전자파학회논문지
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• 제12권6호
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• pp.906-911
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• 2001

본 논문에서는 비화 통신을 위하여 chirp 방식을 이용한 BPSK 시스템의 LPI(low probability of intercept)와 AJ(anti jamming) 성능을 분석하였다. Chirp 방식은 주파수를 전체 확산대역 내에서 임의적으로 변화시켜 신호의 주기적인 특성을 제거하기 때문에, feature parameter인 chip rate를 검출하는데 용이한 DAM(delay and multiplier)과 반송파 주파수 검출에 용이한 SC(Squaring Circuit)에 대항하여 뛰어난 LPI 특성을 가진다. chirp parameter의 변화에 따른 LPI 특성으로 chirp duration(Tc)이 커질수록 좋은 LPI 성능을 보인다. PBNJ(partial band noise jammer)환경에서, chirp 방식이 이론적인 DSSS(Direct Sequence Spread Spectrum) 방식에 비하여 AJ 성능이 우수함을 시뮬레이션으로 확인하였다. PBNJ와 MTJ(multi-tone jammer)를 비교하였을 때, chirped BPSK 시스템이 동일 JSR(jammer to signal power ratio)에서 MTJ에 더 우수한 AJ 성능이 있다.

• 항공우주기술
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• 제11권2호
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• pp.129-139
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• 2012

천리안위성의 안정적인 장기 일반운영과 예기치 못한 비상상황을 대비하기 위한 관제원 운영능력 유지를 위해 개발된 관제모의훈련시스템의 구조와 특징에 대해 설명한다. 본 논문에서 특히 교관 편의 기능을 강조한 GUI 환경의 고장주입 기능과 훈련 시나리오를 자동으로 동작시키는 스케줄러, 기존 시뮬레이터의 고장발생 기능개선 부분을 중점적으로 기술하여 훈련시스템의 차별적인 장점과 기대효과를 조명한다. 아울러 고장 복구 훈련 예제를 통하여 훈련시스템 동작과정의 이해를 돕는다.

• Journal of Communications and Networks
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• 제15권3호
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• pp.276-282
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• 2013

Self-encoded spread spectrum (SESS) is a novel modulation technique that acquires its spreading code from a random information source, rather than using the traditional pseudo-random noise (PN) codes. In this paper, we present our study of the SESS system performance under pulsed-noise jamming and show that iterative detection can significantly improve the bit error rate (BER) performance. The jamming performance of the SESS with correlation detection is verified to be similar to that of the conventional direct sequence spread spectrum (DSSS) system. On the other hand, the time diversity detection of the SESS can completely mitigate the effect of jamming by exploiting the inherent temporal diversity of the SESS system. Furthermore, iterative detection with multiple iterations can not only eliminate the jamming completely but also achieve a gain of approximately 1 dB at $10^{-3}$ BER as compared with the binary phase shift keying (BPSK) system under additive white gaussian noise (AWGN) by effectively combining the correlation and time diversity detections.

• Journal of Multimedia Information System
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• 제7권1호
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• pp.55-72
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• 2020

As the IT service environment grows, it is critical in terms of IT service quality to minimize the occurrence of failures due to changes in applications and to diagnose and recover in a short period of time how failure will affect the business. Thus, the Defense Acquisition Program Administration (DAPA) has been building and operating ITSMs to implement IT service management in a leading manner. Information Technology Service Management (ITSM) is divided into events, obstacles, changes, versions and setup management to ensure flexibility and stability in service delivery. It is also operated separately from service level, availability, capacity, financial and IT service continuity management to ensure service quality and cost efficiency. Based on ITSM military service history, this study looks at the impact of quality of service on value, satisfaction, and trust. The results of the analysis are highly valuable for future ITSM implementation and operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.465-467
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• 1999

The data transmission system in MAGLEV is required a high quality and high speed for a train safety and reliability driving. In the transmission channel between a vehicle and a ground-site, Gaussian noise is negligible, but impulse noise from the chopper controlled propulsoin unit and the Power supplying device is very severe. The transmission channel must be protected from these noise. In this paper, we propose a DSSS (direct-sequence spread spectrum) modulation as a new data transmission technique in the railway and analyze this data transmission characteristics.