• Title/Summary/Keyword: overlapping error

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A design of FFT processor for EEG signal analysis (뇌전기파 분석용 FFT 프로세서 설계)

  • Kim, Eun-Suk;Kim, Hae-Ju;Na, Young-Heon;Shin, Kyung-Wook
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2010.10a
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    • pp.88-91
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    • 2010
  • This paper describes a design of fast Fourier transform(FFT) processor for EEG(electroencephalogram) signal analysis for health care services. Hamming window function with 1/2 overlapping is adopted to perform short-time FFT(ST-FFT) of a long period EEG signal occurred in real-time. In order to analyze efficiently EEG signals which have frequency characteristics in the range of 0 Hz to 100 Hz, a 256-point FFT processor based on single-memory bank architecture and radix-4 algorithm is designed. The designed FFT processor has high accuracy with arithmetic error less than 3%.

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A Survey on Qualitative Analysis of Directional VANET MAC Protocols

  • Kim, Bongjae;Cho, Kwangsu;Nam, Choonsung
    • International Journal of Contents
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    • v.10 no.2
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    • pp.9-17
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    • 2014
  • Since vehicles' trajectories are so complex and dense traffic changes in nature frequently, the VANET (Vehicles Ad-hoc Network), using Omni-directional Antenna, has many channel collisions (or overlapping) on Data Link phrases (MAC layers). It is not easy to keep a good seamless communication status for VANET because of its unpredictable network environment. Among VANET research, Directional Antenna have been proposed as one of the most common systematical solutions to reduce (or to mitigate) this miss-communication problems by narrowing communicational ranges and making use of its customized error-detection process. However, even though Directional Antennas help VANET keep good seamless communication, many VANET researchers have reported that Directional VANET still has miss-communicational problems - this has lead to problems like 'Directional Hidden Terminal Problem', 'Deafness', 'Un-accuracy Lobe Scopes' and 'High Deployment Cost' being reported in various papers. To establish well-organized design assessments for a good Directional VANET MAC protocol to overcome these problems, we rearranged and grouped current Directional VANET' qualitative criteria from several current survey papers using these categories- 'Directional Discovery', 'Directional Forwarding' and 'Directional Handover'. In addition, based on the results of the following analysis, we show the essential design concerns that need to be looked at in order to develop a well-designed Directional-VANET MAC protocol.

A Time-of-arrival Estimation Technique for Ultrawide Band Indoor Wireless Localization System (초광대역 방식의 실내 무선 위치인식 시스템에 적합한 도착시간 추정 알고리즘)

  • Lee, Yong-Up
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.8C
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    • pp.814-821
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    • 2009
  • In an ultrawide band (UWB) indoor wireless localization, time of arrival (TOA) parameter estimation techniques have some difficulties in acquiring a reasonable TOA estimate because of the clustered multipath components overlapping or random time intervals mainly due to non line-of-sight (NLOS) environment. In order to solve that problem and achieve an excellent UWB indoor wireless localization, we propose a UWB signal model and a robust TOA parameter estimation technique that has little effect on the clustered problems unlike the conventional technique. Through simulation studies, the validity of the proposed model and the TOA estimation technique are examined. The performance of estimation error is also analyzed.

Analysis of Intersymbol Interference due to Overlap m Overlap-Based DM-BPSK CSS Systems (오버랩 기반 DM-BPSK CSS 시스템에서 오버랩 횟수에 따른 심볼 간 간섭 분석)

  • Kim, Jun-Hwan;Lee, Young-Po;Song, Iick-Ho;Yoon, Seok-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.2C
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    • pp.99-104
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    • 2011
  • The chirp spread spectrum (CSS) technique spreads the data signal over a frequency bandwidth wider than minimum required bandwidth. By using time overlapping, the bit rate in CSS can be increased. However, for reliable transmission of data signal, the intersymbol interference (ISI) due to overlap should be analyzed. In this paper, the relation between the degree of overlap and ISI is analyzed in direct modulation binary phase shift keying CSS systems. In some cases, the overlap does not incur ISI at all and the ISI fluctuates or monotonically increases as the number of overlaps changes. It is also shown that the simulation results closely agree with the analytic results.

A Study on Noise Reduction Method using Wavelet Approximation Coefficient-based Distribution Characteristics (웨이브렛 근사계수 기반의 분포특성을 이용한 잡음 제거 방법에 관한 연구)

  • Bae, Sang-Bum;Kim, Nam-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.14 no.2
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    • pp.513-520
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    • 2010
  • The degradation phenomenon caused by noises significantly corrupts digitalized data. Therefore, a variety of methods to preserve the edge component of signals and remove noise simultaneously have been used in time domain and frequency domain. In this paper, we have proposed a new noise reduction algorithm using wavelet approximation coefficients to reduce the mixed noise overlapping the signal. The proposed algorithm adopts the distribution characteristics of the error function which is obtained by accumulating the wavelet approximation coefficients, in order to improve the capability to separate edges of the signal and noises.

A Watermarking Method Based on the Trellis Code with Multi-layer (다층구조를 갖는 trellis부호를 이용한 워터마킹)

  • Lee, Jeong Hwan
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2009.10a
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    • pp.949-952
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    • 2009
  • In this paper, a watermarking method based on the trellis code with multi-layer is proposed. An image is divided $8{\times}8$ block with no overlapping, and compute the discrete cosine transform(DCT) of each block, and the 12 medium-frequency AC terms from each block are extracted. Next it is compared with gaussian random vectors with zero mean and unit variance. As these processing, the embedding vectors with minimum linear correlation can be obtained by Viterbi algorithm at each layer of trellis coding. To evaluate the performance of proposed method, the average bit error rate of watermark message is calculated from different several images.

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Automated Image Matching for Satellite Images with Different GSDs through Improved Feature Matching and Robust Estimation (특징점 매칭 개선 및 강인추정을 통한 이종해상도 위성영상 자동영상정합)

  • Ban, Seunghwan;Kim, Taejung
    • Korean Journal of Remote Sensing
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    • v.38 no.6_1
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    • pp.1257-1271
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    • 2022
  • Recently, many Earth observation optical satellites have been developed, as their demands were increasing. Therefore, a rapid preprocessing of satellites became one of the most important problem for an active utilization of satellite images. Satellite image matching is a technique in which two images are transformed and represented in one specific coordinate system. This technique is used for aligning different bands or correcting of relative positions error between two satellite images. In this paper, we propose an automatic image matching method among satellite images with different ground sampling distances (GSDs). Our method is based on improved feature matching and robust estimation of transformation between satellite images. The proposed method consists of five processes: calculation of overlapping area, improved feature detection, feature matching, robust estimation of transformation, and image resampling. For feature detection, we extract overlapping areas and resample them to equalize their GSDs. For feature matching, we used Oriented FAST and rotated BRIEF (ORB) to improve matching performance. We performed image registration experiments with images KOMPSAT-3A and RapidEye. The performance verification of the proposed method was checked in qualitative and quantitative methods. The reprojection errors of image matching were in the range of 1.277 to 1.608 pixels accuracy with respect to the GSD of RapidEye images. Finally, we confirmed the possibility of satellite image matching with heterogeneous GSDs through the proposed method.

Fine-image Registration between Multi-sensor Satellite Images for Global Fusion Application of KOMPSAT-3·3A Imagery (KOMPSAT-3·3A 위성영상 글로벌 융합활용을 위한 다중센서 위성영상과의 정밀영상정합)

  • Kim, Taeheon;Yun, Yerin;Lee, Changhui;Han, Youkyung
    • Korean Journal of Remote Sensing
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    • v.38 no.6_4
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    • pp.1901-1910
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    • 2022
  • Arriving in the new space age, securing technology for fusion application of KOMPSAT-3·3A and global satellite images is becoming more important. In general, multi-sensor satellite images have relative geometric errors due to various external factors at the time of acquisition, degrading the quality of the satellite image outputs. Therefore, we propose a fine-image registration methodology to minimize the relative geometric error between KOMPSAT-3·3A and global satellite images. After selecting the overlapping area between the KOMPSAT-3·3A and foreign satellite images, the spatial resolution between the two images is unified. Subsequently, tie-points are extracted using a hybrid matching method in which feature- and area-based matching methods are combined. Then, fine-image registration is performed through iterative registration based on pyramid images. To evaluate the performance and accuracy of the proposed method, we used KOMPSAT-3·3A, Sentinel-2A, and PlanetScope satellite images acquired over Daejeon city, South Korea. As a result, the average RMSE of the accuracy of the proposed method was derived as 1.2 and 3.59 pixels in Sentinel-2A and PlanetScope images, respectively. Consequently, it is considered that fine-image registration between multi-sensor satellite images can be effectively performed using the proposed method.

Contrast Enhancement based on Gaussian Region Segmentation (가우시안 영역 분리 기반 명암 대비 향상)

  • Shim, Woosung
    • Journal of Broadcast Engineering
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    • v.22 no.5
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    • pp.608-617
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    • 2017
  • Methods of contrast enhancement have problem such as side effect of over-enhancement with non-gaussian histogram distribution, tradeoff enhancement efficiency against brightness preserving. In order to enhance contrast at various histogram distribution, segmentation to region with gaussian distribution and then enhance contrast each region. First, we segment an image into several regions using GMM(Gaussian Mixture Model)fitting by that k-mean clustering and EM(Expectation-Maximization) in $L^*a^*b^*$ color space. As a result region segmentation, we get the region map and probability map. Then we apply local contrast enhancement algorithm that mean shift to minimum overlapping of each region and preserve brightness histogram equalization. Experiment result show that proposed region based contrast enhancement method compare to the conventional method as AMBE(AbsoluteMean Brightness Error) and AE(Average Entropy), brightness is maintained and represented detail information.

Delamination evaluation on basalt FRP composite pipe by electrical potential change

  • Altabey, Wael A.
    • Advances in aircraft and spacecraft science
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    • v.4 no.5
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    • pp.515-528
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    • 2017
  • Since composite structures are widely used in structural engineering, delamination in such structures is an important issue of research. Delamination is one of a principal cause of failure in composites. In This study the electrical potential (EP) technique is applied to detect and locate delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). The proposed EP method is able to identify and localize hidden delamination inside composite layers without overlapping with other method data accumulated to achieve an overall identification of the delamination location/size in a composite, with high accuracy, easy and low-cost. Twelve electrodes are mounted on the outer surface of the pipe. Afterwards, the delamination is introduced into between the three layers (0º/90º/0º)s laminates pipe, split into twelve scenarios. The dielectric properties change in basalt FRP pipe is measured before and after delamination occurred using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to delamination, a finite element simulation model for delamination location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Response surfaces method (RSM) are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured electrical potential changes of all segments between electrodes. The results show good convergence between the finite element model (FEM) and estimated results. Also the results indicate that the proposed method successfully assesses the delamination location/size for basalt FRP laminate composite pipes. The illustrated results are in excellent agreement with the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.