• Title/Summary/Keyword: noise measuring method

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A Study on the Noise Reduction Method for Data Transmission of VLBI Data Processing System (VLBI 자료처리 시스템의 데이터 전송에서 잡음방지에 관한 연구)

  • Son, Do-Sun;Oh, Se-Jin;Yeom, Jae-Hwan;Roh, Duk-Gyoo;Jung, Jin-Seung;Oh, Chung-Sik
    • Journal of the Institute of Convergence Signal Processing
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    • v.12 no.4
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    • pp.333-340
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    • 2011
  • KJJVC(Korea-Japan Joint VLBI Correlator) was installed at the KJCC(Korea-Japan Correlation Center) and has been operated by KASI(Korea Astronomy and Space Science Institute) from 2009. KJNC is able to correlate the VLBI observed data through KVN(Korean VLBI Network), VERA(VLBI Exploration of Radio Astrometry), and JVN(Japanese VLBI Network) and its joint network array. And it is used exclusively as computer in order to process the observed data for the scientific purpose KJJVC used the VSI(VLBI Standard Interface) as the VLBI international standard at the data input-output specification between each component. Especially, for correlating the observed data, the data is transmitted with 1024Mbps speed between Mark5B high-speed playback and RVDB(Raw VLBI Data Buffer). The EMI(Electromagnetic lnterference), which is occurred by data transmission with high-speed, cause the data loss and the loss occurrence is frequently often for long transmission cable. Finally it will be caused the data recognition error by decreasing the voltage level of digital data signal. In this paper, in order to minimize the data loss by measuring the EMI noise level in transmission of the VSI specification, the 3 methods such as 1) RC filtering method, 2) lmpedance matching using Microstrip line, and 3) Signal buffering method using Differential line driver, were proposed. To verify the effectiveness of each proposed method, the performance evaluation was conducted by implementing and simulations for each method. Each proposed method was effectively confirmed as the high-speed data transmission of the VSI specification.

A Study on the Speech Transmission Index Method for Estimating Articulation of Loudspeaking Telephony (음성전송지수를 이용한 확성전화기의 명료도 평가 방법)

  • Jang, Dae-Young;Kang, Seong-Hoon;Sim, Dong-Yeon;Kim, Chun-Duck
    • The Journal of the Acoustical Society of Korea
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    • v.13 no.5
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    • pp.32-39
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    • 1994
  • The speech transmission quality in telephone is quantified in terms of loudness rating, but this method has been validated only for the handset telephony. The transmission quality of loudspeaking telephony in any room must be evaluated not only with speech transmission but also with background noise, echo and reverberation since the effect of room acoustics is much stroger for loudspeaking telephoy. Therefore, it requires a better approach to specify the quality of loudspeaking telephony. By calcuating the speech transmission index (STI), a physical method for measuring the quality of speech transmission was proposed by Steeneken. In this paper, the application of a STI method for estimating articulation of loudspeaking telephony was discussed. And the STI measurement system with high speed calculation was also three rooms, having different reverberation times. The result show that the STI decreases as the reverberation time of rooms increases. It suggests that speech transmission index method can be useful evaluating articulation of a loudspeaking telephony including the sound field characteristics.

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Measurement of Joint Resistance of $(Bi,Pb)_2Sr_2Ca_2Cu_3O_x$/Ag Superconducting Tape by Field decay Technique (자장감쇠법을 이용한 $(Bi,Pb)_2Sr_2Ca_2Cu_3O_x$/Ag 초전도선재의 접합저항 측정)

  • Kim, Jung-Ho;Lee, Seung-Muk;Joo, Jin-Ho
    • Progress in Superconductivity
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    • v.14 no.1
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    • pp.1-10
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    • 2012
  • We fabricated a closed coils by using resistive-joint method and the joint resistance of the coils were estimated by field decay technique in liquid nitrogen. We used the Runge-kutta method for the numerical analysis to calculate the decay properties. The closed coil was wound by $(Bi,Pb)_2Sr_2Ca_2Cu_3O_x$/Ag tape. Both ends the tape were overlapped and soldered to each other. The current was induced in a closed coils by external magnetic flux density. Its decay characteristic was observed by means of measuring the magnetic flux density generated by induced current at the center of the closed coil with hall sensor. The joint resistance was calculated as the ratio of the inductance of the loop to the time constants. The joint resistances were evaluated as a function of critical current of loop, contact length, sweep time, and external magnetic flux density in a contact length of 7 cm. It was observed that joint resistance was dependent on contact length of a closed coil, but independent of critical current, sweep time, and external magnetic flux density. The joint resistance was measured to be higher for a standard four-probe method, compared with that for the field decay technique. This implies that noise of measurement in a standard four-probe method is larger than that of field decay technique. It was estimated that joint resistance was $8.0{\times}10^{-9}{\Omega}$ to $11.4{\times}10^{-9}{\Omega}$ for coils of contact length for 7 cm. It was found that 40Pb/60Sn solder are unsuitable for persistent mode.

Continuous force excited bridge dynamic test and structural flexibility identification theory

  • Zhou, Liming;Zhang, Jian
    • Structural Engineering and Mechanics
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    • v.71 no.4
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    • pp.391-405
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    • 2019
  • Compared to the ambient vibration test mainly identifying the structural modal parameters, such as frequency, damping and mode shapes, the impact testing, which benefits from measuring both impacting forces and structural responses, has the merit to identify not only the structural modal parameters but also more detailed structural parameters, in particular flexibility. However, in traditional impact tests, an impacting hammer or artificial excitation device is employed, which restricts the efficiency of tests on various bridge structures. To resolve this problem, we propose a new method whereby a moving vehicle is taken as a continuous exciter and develop a corresponding flexibility identification theory, in which the continuous wheel forces induced by the moving vehicle is considered as structural input and the acceleration response of the bridge as the output, thus a structural flexibility matrix can be identified and then structural deflections of the bridge under arbitrary static loads can be predicted. The proposed method is more convenient, time-saving and cost-effective compared with traditional impact tests. However, because the proposed test produces a spatially continuous force while classical impact forces are spatially discrete, a new flexibility identification theory is required, and a novel structural identification method involving with equivalent load distribution, the enhanced Frequency Response Function (eFRFs) construction and modal scaling factor identification is proposed to make use of the continuous excitation force to identify the basic modal parameters as well as the structural flexibility. Laboratory and numerical examples are given, which validate the effectiveness of the proposed method. Furthermore, parametric analysis including road roughness, vehicle speed, vehicle weight, vehicle's stiffness and damping are conducted and the results obtained demonstrate that the developed method has strong robustness except that the relative error increases with the increase of measurement noise.

Channel estimation of OFDM System using Matching Pursuit method (Matching Pursuit 방식을 이용한 OFDM 시스템의 채널 추정)

  • Choi Jae Hwan;Lim Chae Hyun;Han Dong Seog;Yoon Dae Jung
    • Journal of Broadcast Engineering
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    • v.10 no.2
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    • pp.166-173
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    • 2005
  • In this paper, we propose a mobile channel estimation algorithm using matching pursuit algorithm for orthogonal frequency division multiplexing (OFDM) systems. Least square (LS) algorithm, which is used as a conventional channel estimation algorithm for OFDM systems, has error probability of channel estimation affected by effects of noise. By estimating the channel of sparse type, the proposed algorithm reduces effects of noise during time intervals that multi-path signal doesn't exist. The proposed algorithm estimates a mobile receivingchannel using pilot information transmitted consequently. We compare performance of the proposed algorithm with the LS algorithm by measuring symbol error rate with 64QAM under a mobile multi-path fading channel model.

Nonlinear and Independent Component Analysis of EEG with Artifacts (잡파가 섞인 뇌파의 비선형 및 독립성분 분석)

  • Kim, Eung-Soo;Shin, Dong-Sun
    • Journal of the Korean Institute of Intelligent Systems
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    • v.12 no.5
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    • pp.442-450
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    • 2002
  • In measuring EEG, which is widely used for studying brain function, EEG is frequently mixed with noise and artifact. In this study, the signals relevant to the artifact were distracted by applying ICA to EEG signal. First, each independent component which was assumed to be the source was separated by applying ICA to EEG which involved artifact relevant to the eye movement of a normal person. Next, the signal which was assumed to be artifact was removed from the separated 18 independent components, and the nonlinear analysis method such as correlation dimension and the Iyapunov exponent was applied to each reconstructed EEG signal and the original signal including artifact in order to find meaningful difference between the two signals and infer the anatomical localization of its source and distribution. This study shows it is possible not only to analyze the brain function visually and spatially for visually complex EEG signal, but also to observe its meaningful change through the quantitative analysis of EEG by means of the nonlinear analysis.

DEVELOPMENT OF AN ASTRONOMICAL INFRARED PtSi CAMERA (천문관측용 PtSi 전하결합소자 적외선 카메라의 개발)

  • Hong, Seung-Su;;Gu, Bon-Cheol;Kim, Kwang-Tae;Kim, Chil-Yeong;Oh, Gap-Su;Lee, Myeong-Gyun;Lee, Hyeong-Mok;Kang, Yong-Woo;Park, Won-Gi
    • Publications of The Korean Astronomical Society
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    • v.11 no.1
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    • pp.1-26
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    • 1996
  • We have built a near-infrared imaging camera with a PtSi array detector manufactured by the Mitsubishi Company. The PtSi detector is sensitive in the wavelength range 1 to $5{\mu}m$. Quantum efficiency of PtSi is much lower than that of InSb and HgCdTe types. However, the PtSi array has advantages over the latter ones: (i)The read-out noise is very low; (ii)the characteristics of the array elements arc uniform and stable; (iii)it is not difficult to make a large PtSi array; and (iv) consequently the price is affordably low. The array used consists of $512{\times}512$ pixels and its size is $10.2\;mm{\times}13.3\;mm$. The filter wheel of the camera is equipped with J, H, K filters, and an aluminum plate for measuring the dark noise. The dewar is cooled with liquid nitrogen. We have adopted a method of installing the clock pattern and the observing softwares in the RAM, which Gill he easily used for other systems. We have developed a software with a pull-down menu for operating the camera and data acquisition. The camera has been tested by observing $\delta$ Orionis.

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A Study on The Range Estimation of Underwater Acoustic Source using FDOA and TDOA of Multipath Signals (다중경로 신호의 도달 주파수와 시간 차를 이용한 수중음원 거리 추정 연구)

  • Son, Yoon-Jun;Son, Gi-Joong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.2
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    • pp.311-318
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    • 2021
  • Underwater, signals are transmitted by sound waves. Sound waves are transmitted through a multipath, either directly or through reflection, due to the variety of underwater environmental characteristics. In such diverse and complex underwater environments, tests must be conducted to determine the extent of the hazard from the survivability and pitfalls of submarines by measuring the underwater radiated noise. Usually, the sound source level measurement of underwater radiated noise should be made within the closest point (CPA: Closest Point of Approach) ± a few meters between the measurement sensor and the submarine. In this study, FDOA and TDOA methods were proposed to estimate the underwater source range. A simulation based on the underwater channel model confirmed the performance of the proposed method.

Range estimation of underwater acoustic moving source using Doppler frequency map (도플러 주파수 맵을 이용한 수중 이동 음원의 거리 추정)

  • Park, Woong-Jin;Kim, Ki-Man;Han, Min su;Choi, Jae-Yong
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.6
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    • pp.413-418
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    • 2017
  • When measuring the radiated noise of an underwater vehicle, range information between acoustic source and receiver is an important evaluating factor, but it cannot use GPS. There is a method of using the cross correlation for finding the range of the acoustic source instead of the GPS. However, this method has heavy computational loads. This paper proposes a fast Fourier transform based method with a relatively small amount of computation to estimate the range of a source. The proposed method estimates Doppler frequencies of CW signals received at multiple receivers by fast Fourier transform and estimates the source range by comparing theoretical Doppler frequencies map previously calculated by a receiver position and source depth information. Simulation and lake trial were performed to verify the performance.

A Study on Measurement of Internal Defects of Pressure Vessel by Digital Shearography(I) (전자 전단 간섭법을 이용한 압력용기의 내부결함 측정에 관한 연구(I))

  • Kang, Young-June;Park, Nak-Kyu;Ryu, Won-Jae;Kim, Kyung-Suk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.4
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    • pp.393-401
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    • 2002
  • Pipelines in power plants, nuclear facilities and chemical industries are often affected by corrosion effects. It is important to inspect the internal defects in pipelines in oder to guarantee safe operational condition. We have taken relatively much time, cost and manpower to use conventional NDT methods because these methods are contact measuring methods. In this paper, we used digital shearography, a laser-based optical method which allows full-field measurement of surface displacement derivatives. This method has many advantages in practical use, such as low sensitivity to environmental noise, simple optical configuration and real time measurement. The experiment was performed with pressure vessels which has different internal cracks and detected internal cracks in the pressure vessels at a real time using phase shifting method.