• Electronics and Telecommunications Trends
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• v.22 no.6
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• pp.24-32
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• 2007

지금까지 센서노드에 TCP/IP를 운용하는 것은 과도한 시스템 자원을 요구하기 때문에 부적절한 선택이라고 생각해 왔다. 그러나, 최소한의 기능만을 가진 TCP/IP를 센서 노드에 적용하여도 센서노드가 동작할 수 있으므로 센서 네트워크에 IP 기술을 접목시키려는 연구가 진행되고 있고, 이에 대한 표준 기술의 필요성이 대두되게 되었다. IETF 6LoWPAN WG는 L2 Layer에 IEEE 802.15.4를 기반으로 하는 센서 네트워크에 IPv6를 지원하기 위한 이슈를 다루는 그룹으로서 저전력, $20{\sim}250kbps$의 데이터 전송률, $900{\sim}2400MHz$의 주파수 대역에서 최소형 메모리와 최소형 프로세서만을 장착한 센서 응용을 대상으로 하고 있다. 이 그룹은 국제 표준화 기구 중 대표적으로 IP 기반의 센서 네트워크에 대한 표준 기술을 다루고 있는 그룹으로서, 우리나라에서 6LoWPAN 기술은 USN 기술에 IP를 도입한 IP-USN이라는 개념으로 소개되어 연구개발되고 있다. 본 고에서는 6LoWPAN WG에서 개발한 표준 기술을 소개하고, 향후 WG의 표준화 방향에 대하여 살펴본다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.12a
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• pp.370-373
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• 2002

본 논문에서는 단일영상들에 포함된 특징들을 효과적으로 추출하기 위하여 신경망 기반 독립성분분석기법의 이용을 제안하였다. 여기서 독립성분의 효과적인 분석을 위해 고정점 학습알고리즘의 신경망 기반 기법을 이용하였다. 이는 수치적 기법에 비해 신경망이 가지는 ？ㄱ습 등의 우수한 속성과 뉴우턴법의 고정점 알고리즘이 가지는 빠르고 간단한 계산속성을 동시에 살리기 위함이다. 제안된 기법을 512x412 픽셀의 L둠 영상과 480x225 픽셀의 지폐영상 각각에서 선택된 1,000개의 영상패치들을 대상으로 시뮬레이션 한 결과, 추출된 16x16 펙셀의 160개 독립성분 기저벡터는 지문영상과 지폐영상 각각에 포함된 공간적인 주파수 특성과 방향성을 가지는 경계 특성이 잘 드러나는 국부적인 특징들임을 확인할 수 있었다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.12a
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• pp.291-294
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• 2002

본 논문에서는 신경망 기반 독립성분분석기법을 이용하여 지문영상에 포함된 특징들을 효과적으로 추출하는 방법을 제안하였다. 여기서 독립성분의 효과적인 분석을 위해 고정점 학습알고리즘의 신경망 기반 기법을 이용하였다. 이는 수치적 기법에 비해 신경망이 가지는 학습 등의 우수한 속성과 뉴우턴법의 고정점 알고리즘이 가지는 빠르고 간단한 계산속성을 동시에 살리기 위함이다. 제안된 기법을 256$\times$256 픽셀의 8개 지문영상에서 선택된 10,000개의 영상패치를 대상으로 시뮬레이션 한 결과, 추출된 16$\times$16 펙셀의 160개 독립성분 기저벡터는 지문영상들에 포함된 공간적인 주파수 특성과 방향성을 가지는 경계 특성이 잘 드러나는 국부적인 특징들임을 확인할 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.155-163
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• 2009

In text-to-speech systems, the conversion of text into prosodic parameters is necessarily composed of three steps. These are the placement of prosodic boundaries. the determination of segmental durations, and the specification of fundamental frequency contours. Prosodic boundaries. as the most important and basic parameter. affect the estimation of durations and fundamental frequency. Break prediction is an important step in text-to-speech systems as break indices (BIs) have a great influence on how to correctly represent prosodic phrase boundaries, However. an accurate prediction is difficult since BIs are often chosen according to the meaning of a sentence or the reading style of the speaker. In Japanese, the prediction of an accentual phrase boundary (APB) and major phrase boundary (MPB) is particularly difficult. Thus, this paper presents a method to complement the prediction errors of an APB and MPB. First, we define a subtle BI in which it is difficult to decide between an APB and MPB clearly as a variable break (VB), and an explicit BI as a fixed break (FB). The VB is chosen using the classification and regression tree, and multiple prosodic targets in relation to the pith and duration are then generated. Finally. unit-selection is conducted using multiple prosodic targets. In the MOS test result. the original speech scored a 4,99. while proposed method scored a 4.25 and conventional method scored a 4.01. The experimental results show that the proposed method improves the naturalness of synthesized speech.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.4-13
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• 2005

An equalization algorithm is proposed to guarantee a stable performance in fast fading channels for digital television (DTV) systems from the advanced television system committee (ATSC) standard. In channels with high Doppler shifts, the conventional equalization algorithm shows severe performance degradation. Although the conventional equalizer compensates poor channel conditions to some degree, long filter taps required to overcome long delay profiles are not suitable for fast fading channels. The Proposed sparse equalization algorithm is robust to the multipaths with long delay Profiles as well as fast fading by utilizing channel estimation and equalizer initialization. It can compensate fast fading channels with high Doppler shifts using a filter tap selection technique as well as variable step-sizes. Under the ATSC test channels, the proposed algorithm is analyzed and compared with the conventional equalizer. Although the proposed algorithm uses small number of filter taps compared to the conventional equalizer, it is stable and has the advantages of fast convergence and channel tracking.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.5
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• pp.624-630
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• 2010

As electrocardiogram(ECG) signals are generally sampled with a frequency of over 200Hz, a method to compress diagnostic information without losing data is required to store and transmit them efficiently. In this paper, an ECG signal compression method, which uses feature points based on curvature, is proposed. The feature points of P, Q, R, S, T waves, which are critical components of the ECG signal, have large curvature values compared to other vertexes. Thus, these vertexes are extracted with the proposed method, which uses local extremum of curvatures. Furthermore, in order to minimize reconstruction errors of the ECG signal, extra vertexes are added according to the iterative vertex selection method. Through the experimental results on the ECG signals from MIT-BIH Arrhythmia database, it is concluded that the vertexes selected by the proposed method preserve all feature points of the ECG signals. In addition, they are more efficient than the AZTEC(Amplitude Zone Time Epoch Coding) method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.697-708
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• 2016

As the needs for fast wireless communication technology in various fields, including companies, individuals, etc., grows, many research projects related to the coverage of propagation are being carried out for plaining optimized communication services. On the other hand, there are some limitations in surveying and analyzing propagation in highland areas. To provide a better communication service of a new service, a range of radio environment conditions based on a wide radio bandwidth (selection of propagation model, correction of value in accordance with radio bandwidth, etc.) should be considered. In particular, radio environment conditions are becoming increasingly sophisticated. By the early detection of real-time changes in the radio spectrum, which is based on an examination and research of regional occupied band width condition, proper measures should be established. To make a proper solution of above, the basic real-time analysis of spectrum distribution status by regional groups is necessary. In addition, the establishment of prompt measures should be enable by stored or analyzed radio data. In an attempt to predict reliable propagation coverage, this thesis examines the limited propagation data with HTZ Warfare, which were collected from domestic high land sites faced with limited access. Furthermore, a comparative result value evaluation for an optimized propagation model was performed through testing simulations, and frequency-dependent and propagation model-dependent analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.343-350
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• 2015

Extensive discussion on the optimal types of offshore wind turbine(OWT) among monopile, tripod and jacket in the intermediate depth of water has been actively carried out in worldwide wind turbine industry. Selecting the optimal types of OWT among several substructural types, it is required to consider the economic and technical feasibility including dynamically stable design of a wind turbine system. In this study, the effects of loading levels and uncertainties of soil properties on the natural frequency of OWT have been quantitatively investigated. In conclusion, the natural frequency of monopile-type OWTs has a significant level of uncertainty, hence it is very important to minimize the level of uncertainties in soil properties when the monopile is selected as a foundation for an OWT.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.6
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• pp.9-16
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• 2013

Bio-impedance measurement system(BMS) is non-invasive and easy to implement a measurement method that allows determining the water content of a patient. The measurement conditions, the hardware specifications and the configurations of BMS devices must be well chosen in order to get correct and reproducible results. BMS was then conducted for the limbs and the thoracic using a lock-in amplifier and LabView control system with a frequency range of 1kHz-100kHz. From both the measurement data and the simulation results, we verified that the parameters in the proposed equivalent model and the trend of impedance variation according to the multi-frequency of applied current source are similar to those of human body. We believe that the real-time BMS developed in this study is highly reliable and applicable to the research on the clinical characteristics of the human being's impedance.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.109-117
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• 2010

Digital watermarking has drawn extensive attention for protecting digital contents from unauthorized copying. This paper proposes a new watermarking scheme in frequency domain for copyright protection of digital audio. In our proposed watermarking system, the original audio is segmented into non-overlapping frames. Watermarks are then embedded into the selected prominent peaks in the magnitude spectrum of each frame. Watermarks are extracted by performing the inverse operation of watermark embedding process. Simulation results indicate that the proposed scheme is robust against various kinds of attacks such as noise addition, cropping, resampling, re-quantization, MP3 compression, and low pass filtering. Our proposed watermarking system outperforms Cox's method in terms of imperceptibility, while keeping comparable robustness with the Cox's method. Our proposed system achieves SNR (signal-to-noise ratio) values ranging from 20 dB to 28 dB. This is in contrast to Cox's method which achieves SNR values ranging from only 14 dB to 23 dB.