• Title/Summary/Keyword: Spurious Frequency

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Modal identification of Canton Tower under uncertain environmental conditions

  • Ye, Xijun;Yan, Quansheng;Wang, Weifeng;Yu, Xiaolin
    • Smart Structures and Systems
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    • v.10 no.4_5
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    • pp.353-373
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    • 2012
  • The instrumented Canton Tower is a 610 m high-rise structure, which has been considered as a benchmark problem for structural health monitoring (SHM) research. In this paper, an improved automatic modal identification method is presented based on a natural excitation technique in conjunction with the eigensystem realization algorithm (NExT/ERA). In the proposed modal identification method, damping ratio, consistent mode indicator from observability matrices (CMI_O) and modal amplitude coherence (MAC) are used as criteria to distinguish the physically true modes from spurious modes. Enhanced frequency domain decomposition (EFDD), the data-driven stochastic subspace identification method (SSI-DATA) and the proposed method are respectively applied to extract the modal parameters of the Canton Tower under different environmental conditions. Results of modal parameter identification based on output-only measurements are presented and discussed. User-selected parameters used in those methods are suggested and discussed. Furthermore, the effect of environmental conditions on the dynamic characteristics of Canton tower is investigated.

System identification of a super high-rise building via a stochastic subspace approach

  • Faravelli, Lucia;Ubertini, Filippo;Fuggini, Clemente
    • Smart Structures and Systems
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    • v.7 no.2
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    • pp.133-152
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    • 2011
  • System identification is a fundamental step towards the application of structural health monitoring and damage detection techniques. On this respect, the development of evolved identification strategies is a priority for obtaining reliable and repeatable baseline modal parameters of an undamaged structure to be adopted as references for future structural health assessments. The paper presents the identification of the modal parameters of the Guangzhou New Television Tower, China, using a data-driven stochastic subspace identification (SSI-data) approach complemented with an appropriate automatic mode selection strategy which proved to be successful in previous literature studies. This well-known approach is based on a clustering technique which is adopted to discriminate structural modes from spurious noise ones. The method is applied to the acceleration measurements made available within the task I of the ANCRiSST benchmark problem, which cover 24 hours of continuous monitoring of the structural response under ambient excitation. These records are then subdivided into a convenient number of data sets and the variability of modal parameter estimates with ambient temperature and mean wind velocity are pointed out. Both 10 minutes and 1 hour long records are considered for this purpose. A comparison with finite element model predictions is finally carried out, using the structural matrices provided within the benchmark, in order to check that all the structural modes contained in the considered frequency interval are effectively identified via SSI-data.

Design and Implementation of Down-Converter for WCDMA Digital Optic Repeater (WCDMA 디지털 광 중계기용 Down-Converter 설계 및 제작)

  • 김성수;강원구;장인봉;양승인
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.9
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    • pp.974-978
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    • 2003
  • The down-converter of the WCDMA Digital Optic Repeater is developed. Based on the system specifications, the structure of the down-converter is accomplished and its block diagram is drawn. The down-converter is implemented according to these block diagrams. Subsequently a low pass filter, an automatic level controlled attenuator, a frequency synthesizer and other components for the down-converter are designed and implemented, and a main board to integrate these modules is also manufactured. To reduce the noise floor of system and suppress the RF spurious noise, a PCB layout is performed carefully. For each module consisting of the down-converter and the entire system, the performance tests are accomplished to check the performance about the specifications.

Waveform Generator for W-band Compact Radar (W-band 소형 레이다용 파형발생부)

  • Lee, Man-Hee;An, Se-Hwan;Kim, Young-Gon;Kim, Hong-Rak
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.5
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    • pp.97-102
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    • 2018
  • In this paper, W-band Waveform Generator for compact radar has been designed and fabricated. DDS (Direct Digital Synthesizer) is applied to generate CW (Continuous Wave) and FMCW (Frequency Modulation Continuous Wave) waveform at high speed. We designed two LO (Local Oscillator) paths for functions of distance delay and distance tracking tests at the prpposed system without extra test equipment. Two mode selections are provided by switch. It is observed that fabricated waveform generator performs -91 dBc/Hz phase noise at offset 1 kHz and -63.2 dBc spurious. Proposed W-band Waveform Generator is expected to apply for W-band compact radar transceiver module.

Controlling Linkage Disequilibrium in Association Tests: Revisiting APOE Association in Alzheimer's Disease

  • Park, Lee-Young
    • Genomics & Informatics
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    • v.5 no.2
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    • pp.61-67
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    • 2007
  • The allele frequencies of markers as well as linkage disequilibrium (LD) can be changed in cases due to the LD between markers and the disease allele, exhibiting spurious associations of markers. To identify the true association, classical statistical tests for dealing with confounders have been applied to draw a conclusion as to whether the association of variants comes from LD with the known disease allele. However, a more direct test considering LD using estimated haplotype frequencies may be more efficient. The null hypothesis is that the different allele frequencies of a variant between cases and controls come solely from the increased disease allele frequency and the LD relationship with the disease allele. The haplotype frequencies of controls are estimated using the expectation maximization (EM) algorithm from the genotype data. The estimated frequencies are applied to calculate the expected haplotype frequencies in cases corresponding to the increase or decrease of the causative or protective alleles. The suggested method was applied to previously published data, and several APOE variants showed association with Alzheimer's disease independent from the APOE ${\varepsilon}4$ variant, rs429358, regardless of LD showing significant simulated p-values. The test results support the possibility that there may be more than one common disease variant in a locus.

Residual Filter to Improve Performance of H.264 Video Coding Standard (H.264 동영상 표준 부호화 방식의 성능 향상을 위한 잔여신호 필터)

  • Song, Won-Seon;Hong, Min-Cheol
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.11C
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    • pp.1066-1070
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    • 2006
  • In this paper, we present a residual filter to improve performance of H.264 compressed video. In general, noisy video sequences captured by imaging system result in decline of coding efficiency and unpleasant coding artifacts due to higher frequency components. By incorporating local statistics and quantization parameter into filtering process, the spurious noise is significantly attenuated and coding efficiency is improved, leading to improvement of visual quality and to bit-rate saving for given quantization step size. In addition, in order to reduce the complexity of the residual filter, noise induced by analyzing H.264 transformation and quantization processes are introduced. The simulation results show the capability of the proposed algorithm.

A Study on Performance Reduction Characteristics of Digital Wireless Communication by APD (APD 통계 모델에 의한 디지털 무선 통신 성능 저감 특성 연구)

  • Lim, Sung-Jin;Hur, Min-Ho;Kwon, Se-Woong;Yoon, Young-Joon
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.8-12
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    • 2003
  • To protect digital communications and broadcasting that are expected to be increasingly used at frequencies above 1GHz, there is a need to determine permissible disturbance limits for frequency bands above 1GHz according to indicates that better correlates with interference level in digital systems. The quality of digital communications is expressed in terms of bit error rate(BER) or throughput. In this regard, it has been reported that degradation of BER or throughput can be estimated from the amplitude probability distribution (APD) of disturbance amplitude. Therefore, if the APD can simply be measured with a high accuracy, APD will be an optimal index for the assessment of interference in digital communications. In this paper, we show that a measurement method using statistic model of APD has compatibility about performance reduction estimation of WLAN. And through approach of this inspection, we propose numeral models about interference effects of peak value and time rate of spurious.

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Current Status of KASI Solar Radio Observing System

  • Bong, Su-Chan;HwangBo, Jung-Eun;Park, Sung-Hong;Jang, Be-Ho;Lee, Chang-Hoon;Baek, Ji-Hye;Cho, Kyung-Suk;Park, Young-Deuk;Gary, Dale E.;Lee, Dae-Young
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.82.1-82.1
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    • 2011
  • Korea Astronomy and Space Science Institute (KASI) operates 2 solar radio observing facilities, e-CALLISTO (Earthwide network of Compound Astronomical Low-cost Low-frequency Instrument for Transportable Observatory) station and Korean Solar Radio Burst Locator (KSRBL). Although e-CALLISTO tracking system improvement.is underway, at least 6 new events were observed in this year. Software development for KSRBL is in progress. The antenna calibration software was updated and flux calibration software was developed. Also the automatic daily overview spectrum monitoring system is now operational. We found solutions to several problems including spurious data and FPGA board communication. However, a few minor unsolved hardware problems still persist. Meanwhile, at least 6 new events were observed by KSRBL in this year, and a comparative study with HXR is currently underway.

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Design and Implementation of LNA and BPF for RF System in Digital TRS Base Station (I) ; Receiving Part (디지털 TRS 기지국의 RF 시스템 수신부를 위한 저잡음증폭기와 대역통과필터의 설계 및 제작)

  • 구인모;이상설
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.10 no.6
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    • pp.900-909
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    • 1999
  • The receiving part of the RF system for the digital TRS base stations is developed in this paper. Based on the system specifications, the structure of the RF system is accomplished and its block diagram is drawn. The RF system is implemented according to these block diagrams. Subsequently the RF band-pass filter, the low noise amplifier, the automatic level controlled attenuator, the frequency synthesizer and other components for the system are designed and implemented, and a main board to integrate these modules is also manufactured. To lower the noise floor of the system and suppress the RF spurious noise, a PCB layout is performed carefully. For each module consisting of the RF system and the entire system, the performance tests are accomplished to check the specifications.

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A predictor-corrector algorithm of the generalized-$\alpha$ method for analysis of structural dynamics (동적해석을 위한 일반화된$\alpha$ 방범의 예측 수정자 알고리즘)

  • ;Hulbert, Gregory M.
    • Journal of KSNVE
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    • v.5 no.2
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    • pp.207-213
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    • 1995
  • A new predictor-corrector explicit time integration algorithm is presented for solving structural dynamics problems. The basis of the algorithm is the implicit generalized-.alpha. method recently developed by the authors. Like its implicit parent, the explicit generalized-$\alpha$ method is a one- parameter family of algorithms in which the parameter defines the high-frequency numerical dissipation. The algorithm can be utilized effectively for linear and nonlinear structural dynamics calculations is which numerical dissipation is needed to reduce spurious oscillations inherent in non-dissipative time integration methods used to solve wave propagation problems.

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