• Title/Summary/Keyword: Linear Array

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A Fiber Laser Spectrometer Demodulation of Fiber Bragg Grating Sensors for Measurement Linearity Enhancement

  • Kim, Hyunjin;Song, Minho
    • Journal of the Optical Society of Korea
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    • v.17 no.4
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    • pp.312-316
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    • 2013
  • A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

Efficient Use of On-chip Memory through Profile-Driven Array Reorganization

  • Cho, Doosan;Youn, Jonghee
    • IEMEK Journal of Embedded Systems and Applications
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    • v.6 no.6
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    • pp.345-359
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    • 2011
  • In high performance embedded systems, the use of multiple on-chip memories is an essential architectural feature for exploiting inherent parallelism in multimedia applications. This feature allows multiple data accesses to be executed in parallel. However, it remains difficult to effectively exploit of multiple on-chip memories. The successful use of this architecture strongly depends on how to efficiently detect and exploit memory parallelism in target applications. In this paper, we propose a technique based on a linear array access descriptor [1], which is generated from profiled data, to detect and exploit memory parallelism. The proposed technique tackles an array reorganization problem to maximize memory parallelism in multimedia applications. We present preliminary experiments applying the proposed technique onto a representative coarse grained reconfigurable array processor (CGRA) with multimedia kernel codes. Our experimental results demonstrate that our technique optimizes data placement by putting independent data on separate storage. The results exhibit 9.8% higher performance on average compared to the existing method.

An Adaptive Algorithm for Array System in the Presence of Faulty Element

  • Kim, Ki M.;Il W. Cha;Dae H. Youn
    • Journal of Electrical Engineering and information Science
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    • v.1 no.1
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    • pp.156-159
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    • 1996
  • Element failure occurs with high probability for every array used in the real world ; that is, it is a common phenomenon that there are one or more elements with no output. Element failure produces an elevated sidelobe level and fails to reject the interference signals in an adaptive beamformer. In this paper, we present the adaptive beamforming algorithm for array with element failure. The presented method minimizes the array output power subject to a set of linear constraints which maintain the frequency response in the look direction and force the weights of the inoperative elements to zero. Numerical results have been included.

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Oscillation Criteria of Second-order Half-linear Delay Difference Equations

  • Saker, S.H.
    • Kyungpook Mathematical Journal
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    • v.45 no.4
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    • pp.579-594
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    • 2005
  • In this paper, we will establish some new oscillation criteria for the second-order half-linear delay difference equation $${\Delta}(Pn ({\Delta}Xn)^{\gamma})+q_nx_\array{{\gamma}\\n-{\sigma}}=0,\;n{\geq}n_0$$, where ${\gamma}>0$ is a quotient of odd positive integers. Our results in this paper are sharp and improve some of the well known oscillation results in the literature. Some examples are considered to illustrate our main results.

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Experiments on the stability of the spatial autocorrelation method (SPAC) and linear array methods and on the imaginary part of the SPAC coefficients as an indicator of data quality (공간자기상관법 (SPAC)의 안정성과 선형 배열법과 자료 품질 지시자로 활용되는 SPAC 계수의 허수 성분에 대한 실험)

  • Margaryan, Sos;Yokoi, Toshiaki;Hayashi, Koichi
    • Geophysics and Geophysical Exploration
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    • v.12 no.1
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    • pp.121-131
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    • 2009
  • In recent years, microtremor array observations have been used for estimation of shear-wave velocity structures. One of the methods is the conventional spatial autocorrelation (SPAC) method, which requires simultaneous recording at least with three or four sensors. Modified SPAC methods such as 2sSPAC, and linear array methods, allow estimating shear-wave structures by using only two sensors, but suffer from instability of the spatial autocorrelation coefficient for frequency ranges higher than 1.0 Hz. Based on microtremor measurements from four different size triangular arrays and four same-size triangular and linear arrays, we have demonstrated the stability of SPAC coefficient for the frequency range from 2 to 4 or 5 Hz. The phase velocities, obtained by fitting the SPAC coefficients to the Bessel function, are also consistent up to the frequency 5 Hz. All data were processed by the SPAC method, with the exception of the spatial averaging for the linear array cases. The arrays were deployed sequentially at different times, near a site having existing Parallel Seismic (PS) borehole logging data. We also used the imaginary part of the SPAC coefficients as a data-quality indicator. Based on perturbations of the autocorrelation spectrum (and in some cases on visual examination of the record waveforms) we divided data into so-called 'reliable' and 'unreliable' categories. We then calculated the imaginary part of the SPAC spectrum for 'reliable', 'unreliable', and complete (i.e. 'reliable' and 'unreliable' datasets combined) datasets for each array, and compared the results. In the case of insufficient azimuthal distribution of the stations (the linear array) the imaginary curve shows some instability and can therefore be regarded as an indicator of insufficient spatial averaging. However, in the case of low coherency of the wavefield the imaginary curve does not show any significant instability.

A Study on the Peak Sidelobe of the Random Array Antenna (I) On the Estimator of Linear Array (임의 배열 안테나의 부로브 첨두치에 관한 연구 (I) 선형배열의 에스티메이터에 관하여)

  • Kim, Yeong-Ju;Sin, Cheol-Jae;Park, Han-Gyu
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.19 no.5
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    • pp.43-47
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    • 1982
  • In this paper, we derived to anlyze the correlation between the peak sidelobe of the linear isotropic random array and the design parameters, such as the element numbers, wavelength, scanning angle, confidence level and the length of aperture, with the statistical theory of random processes. The Peak sidelobe estimator was tested by the computer simulations using Honte Carlo method. Consequently, it was evident that the results of the peak lidelobe estimator were consistent with those of the computer simulations over confidence level 0.7.

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Derivation of the ML Based Monopulse Ratio Curve (ML 기반 모노 펄스 MR 커브의 수학식 유도)

  • Lim, Jong-Hwan;Kim, Heung-Su;Yang, Hoon-Gee;Chung, Young-Seek;Bae, Kyung-Bin
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.10
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    • pp.960-965
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    • 2011
  • This paper presents the mathematical derivation of a maximum likelihood(ML)-based monopulse ratio(MR) curve. The derived form is, with the linear array assumed, shown to be the function of the number of array elements and the elements' spacing. Through some simulations, the acquired form is equivalent to the expected MR curve. Furthermore, we show the form, which consists of several terms, can be simplified by one tangent function.

A Study on Adaptive Sparse Matrix Beamforming Algorithm of Error Beam Steering Vector for Target Estimation (목표물 추정을 위한 오차 빔 지향벡터의 적응 회소 행렬 빔형성 알고리즘 연구)

  • Kang, Kyoung Sik
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.7 no.2
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    • pp.111-116
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    • 2014
  • In this paper, we estimates the direction of arrival of desired a target using linear array antenna in wireless communication. Direction of arrival estimation is to estimate for desired target position among incident signals on receiver array antennas. This paper improved estimation of direction of arrival for target using optimum weight, high resolution adaptive beamforming algorithm, and sparse matrix for driection of arrival estimation. Through simulation, we showed that we are performance the analysis to compare general algorithm with proposed algorithm. We show that propose algorithm more improve for direction of estimation than general beamforming algorithm.

Development and Experiment of a Linear Array Acoustic Lens with 31 Microphones (마이크로폰 31개로 이루어진 선형배열 음향렌즈의 구성과 실험)

  • Hyun, Seok-Bong;Min, Dong-Hyun;Kim, Su-Young
    • The Journal of the Acoustical Society of Korea
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    • v.13 no.5
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    • pp.15-23
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    • 1994
  • We developed an electronic lens for acoustic imaging systems, which is linear array with 31 microphones equally spaced with distance 34mm. Resonant frequency fo receiver circuit coupled to microphone is 20 kHz. We arranged 16 microphones horizontally and 15 microphones vertically, so that the array allows us to obtain a 2 dimensional angle of source, and to track the motion of source in real time. Due to the problem of aliasing in discrete Fourier Transfrom, the maximum observable angle of the lens is limited to 15${\circ}$. We also employed quadrature phase detection scheme to adjust the focus. We have tested the acoustic lens with a personal computer in an anechoic room and obtained the results agreed with the acoustic imaging theory.

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Realization of Optical Measurement using White Source and Fourier-domain (고휘도 백색 LED 및 CCD Array Detector를 사용한 Fourier-Domain 방식의 광 계측 시스템 구현)

  • Kim, Kwang-Yoo;Lee, Jung-Rul;Eom, Jin-Seob
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.45 no.1
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    • pp.25-30
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    • 2008
  • In this study, the Fourier-Domain optical measurement system, which use a commercial high power white LED as a light source and a CCD linear-array as a detector is realized. The proposed system shows the axial measurement range over $125{\mu}m$ and the axial resolution below $1.24{\mu}m$. This system has the advantage of the cost effective and compact structure and also the better resolution than the existing technologies, which have a resolution above a few of ${\mu}m$ and use bulky and/or expensive broadband light sources.