• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.237-245
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• 2020

In decades, active sonar, which transmits signals and detects incident signals reflected by underwater targets, has been significantly studied since passive sonar in Anti-Submarine Warfare (ASW) detection performance becomes lowered, as underwater threats become their radiated noise reduced. In general, active sonar using Hull-Mounted Sonar (HMS) adjusts vertical tilt (depression) and sequentially transmits multiple Linear Frequency Modulation (LFM) subpulses which have non-overlapped bands, i. e. 1 kHz ~ 2 kHz, 2 kHz ~ 3 kHz, in order to reduce shadow zones. Recently, however, Generalized SFM (GSFM), which is generalized form of SFM, is proposed, and it is confirmed that subpulses of GSFM have orthogonality among each other depending on setting of GSFM parameters. Hence, in this paper, we applied GSFM to active target detection using HMS to improve the performance by the signal processing gain obtained from enlarged bandwidths of GSFM subpulses compared to those of LFM subpulses. Through simulation, we verified that when the number of subpulses is three, the matched filter gain of GSFM is approximately 5 dB higher than that of LFM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1678-1689
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• 2008

Recently, OOM(Object-Oriented Method) access method which begins to apply to software development is emphasizing development cost and time reduction through independent software reuse. But because of planning to the exclusion of the lack of knowledge and expansion or performance for development technology many problems are coming out. Therefore, this thesis suggests Effective Object-Oriented Modeling methods considering the plan for higher productivity enhancement of software in the software development life cycle. Effective Object-Oriented Modeling method includes, methods, Use Case modeling methods, Analysis Modeling methods, Design Modeling methods and others. This thesis suggests Framework model method read in characteristics as follows. First, suggestion about effective object-oriented standard model development, Second, retrenchment of software development or maintenance cost, Third, solution about uncertain problems of projects in line with the application of new technology.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.191-196
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• 2013

In this paper, the interaural intensity difference (IID)-based sounr source separation method in closely spaced stereo omnidirectional microphones is proposed. First, in order to improve the channel separability, a minimum variance distortionless response (MVDR) beamformer is employed to increase the intensity difference between stereo channels. After that, IID-based sound source separation method is applied. In order to evaluate the performance of the proposed method, source-to-distortion ratio (SDR), source-to-interference ratio (SIR), and sources-to-artifacts ratio (SAR), which are defined as objective evaluation criteria in stereo audio source separation evaluation campaign (SASSEC), are measured. As a result, it was shown from the objective evaluation that the proposed method outperforms a sound source separation method without applying a beamformer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.988-995
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• 2014

Two axis gimbal type X-band antenna system has been widely used to effectively transmit the real time image data from the observation satellite to the ground station. The micro-vibration generated by stepping motor actuation and imperfect intermeshed gear configuration of the antenna is one of the sources to degrade the image quality. To guarantee a high quality image of high resolution observation satellite, micro-vibration isolation of X-band antenna is required. In this paper, the X-band antenna vibration isolation system using pseudoelastic SMA(Shape Memory Alloy) mesh washer has been newly suggested. The basic characteristics of the SMA mesh washer isolator proposed in this study has been measured through static load tests and its effectiveness has been demonstrated by the micro-vibration isolation test of the X-band antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.603-610
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• 2005

Beam-forming method based on the estimated channel information at the base station degrade the performance mismatching directional vector in case of systems which Frequency Division Duplex (FDD) center frequency of uplink and downlink are different. Also blind estimation technique which is to obtain directional vector of reverse link through received signal has disadvantage of hardware complexity increase. To solve these problems, in present paper, a smart antenna algorithm which is to improve the beam-forming complexity increase due to user number by appling the spatial fourier transform to be able to beam- forming toward a wanted direction through adjusting a obtained uplink weight function by estimating Angle-of-Arrival (AoA) to the competable form at the downlink is proposed. The proposed algorithm is integrated to the CDMA downlink transmitter and simulations are performed to confirm the performance as frame error rate at the receiver. As a result, the beam forming effect is confirmed and the performance gain with the proposed algorithm is comparable to ordinary smart antenna system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.95-105
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• 2010

IEEE 802.15.4 is the one of the protocols for radio communication in a personal area network. Since it aims to provide low cost and low power communication for ubiquitous communication, it requires high level of optimization in implementation. Recently, there have been many studies on the performance evaluation of IEEE 802.15.4 MAC protocol. According to the results of the studies, it is tendency that the transceiver is implemented to SoC type. On the implementation, the specific functions of MAC like CSMA-CA and MAC frame handling is designed to hardwired functions. In this paper, we implemented the protocol with hardwired low MAC (HL-MAC) and its state machine for the optimization from the physical layer and MAC layer. it has the characteristics of the small code size and the enhanced power consumption.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.53-56
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• 2007

CAD와 같이 계산위주의 응용을 지원하기 위해 개발된 초기의 객체지향 데이터베이스 시스템은 클라이언트에서 자료의 요구와 처리를 허용하는 자료 탑재방식이다. 이 방식은 클라이언트 워크스테이션에서 수행되는 작업의 대부분을 수행할 수 있는 지역 DBMS를 허용한다. 클라이언트 워크스테이션에서 자료와 잠금을 캐싱하는 것은 클라이언트-서버 데이터베이스 시스템의 성능 향상을 위한 중요한 기술이다. 이 논문에서는 클라이언트 워크스테이션이 자신의 지역 데이터베이스를 유지하면서 회피 또는 탐지 기반의 캐시일관성 유지 알고리즘들의 성능을 평가할 수 있도록 하는 클라이언트 워크스테이션을 모델링하고 구현하였다. 이 시스템은 3개의 클라이언트로 구성되고, 각 지역 동시성 제어 기법으로는 2PL을 사용하였다. 이 모델은 멀티데이터베이스 시스템 환경으로 확장 가능하다.

• Electronics and Telecommunications Trends
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• v.28 no.5
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• pp.145-155
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• 2013

현대인의 집밖 스마트 ICT 디바이스의 요구성능은 휴대 용이성, 끊김 없는 통신채널 확보, 저전력 소모, 편리한 UI, 다양한 기능의 통합제공, 필요한 기능의 손쉬운 추가 및 삭제 등이며, 이런 요구에 충족하기 위해서 HW는 경박단소, 고성능 및 저전력 소모 등으로, SW는 개방형 앱 스토어를 통한 기능추가로 진화하였고, 이를 포함하는 디바이스로는 스마트폰, 테블릿 PC가 대표적이다. 집안의 스마트 ICT 디바이스의 요구성능은 집밖 ICT 디바이스 성능을 포함하면서, 어떤 디바이스에서든 끊김없는 콘텐츠 및 데이터 수집과 이동성, 그리고 아직 정의되지 않은 미래 추가기능의 실행 가능성 등이며 이를 위해 STB(Set Top Box), IPTV, 미디어허브, SmarTV 등 다양한 디바이스가 혁신적인 변모를 준비하고 있다. 본고에서는 집안 ICT 디바이스 혁신의 결과물을 디지털 미디어 허브라 명명하고, 이를 지향하고 있는 후보군 디바이스 들의 동향을 살펴보며, 디지털 미디어 허브로의 신속한 변모를 위해 필요한 연구 개발 방안으로 플랫폼기반의 SW-SoC(System On a Chip) 개발 기술을 소개하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11a
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• pp.747-750
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• 2002

본 논문에서는 일반적으로 사용되는 마이크가 잡음에 민감하여 음성인식피치 성능을 저하시키기 때문에 잡음치 영향을 받지 않는 고지향성을 가지는 넥마이크로 입력되는 음성신호에 대한 특성을 고찰하고 기존의 일반마이크 입력 음성을 이용하는 인식시스템에서의 인식성능을 살펴본다. 넥마이크는 일반마이크와 동일한 원리로 음성을 채집하는 목부위에 장착된다. 실험에서 넥마이크에 의한 음성은 일반마이크 입력 음성에 비해 인식 성능이 저하되는 결과를 보여주어 앞으로 새로운 인터페이스의 연구대상으로 여겨진다.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.547-565
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• 2011

Different types of schemes have been used in stage prediction involving conceptual and physical models. Nevertheless, none of these schemes can be considered as a single superior model. To overcome disadvantages of existing physics based rainfall-runoff models for stage predicting because of the complexity of the hydrological process, recently the data-derived models has been widely adopted for predicting flood stage. The objective of this study is to evaluate model performance for stage prediction of the Neuro-Fuzzy and regression analysis stage prediction models in these data-derived methods. The proposed models are applied to the Wangsukcheon in Han river watershed. To evaluate the performance of the proposed models, fours statistical indices were used, namely; Root mean square error(RMSE), Nash Sutcliffe efficiency coefficient(NSEC), mean absolute error(MAE), adjusted coefficient of determination($R^{*2}$). The results show that the Neuro-Fuzzy stage prediction model can carry out the river flood stage prediction more accurately than the regression analysis stage prediction model. This study can greatly contribute to the construction of a high accuracy flood information system that secure lead time in medium and small streams.