• Title/Summary/Keyword: Echo environmental

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Experimental Investigation of Impact-Echo Method for Concrete Slab Thickness Measurement

  • Popovics John S.;Cetrangolo Gonzalo P.;Jackson Nicole D.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.6
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    • pp.427-439
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    • 2006
  • Accurate estimates of in place thickness of early age (3 to 28 days after casting) concrete pavements are needed, where a thickness accuracy of ${\pm}6mm$ is desired. The impact-echo method is a standardized non-destructive technique that has been applied for this task. However, the ability of impact-echo to achieve this precision goal is affected by Vp (measured) and ${\beta}$ (assumed) values that are applied in the computation. A deeper understanding of the effects of these parameters on the accuracy of impact-echo should allow the technique to be improved to meet the desired accuracy goal. In this paper, the results of experimental tests carried out on a range of concrete slabs are reported. Impact-echo thickness estimation errors caused by material property gradients and sensor type are identified. Correction factors to the standard analysis method are proposed to correct the identified errors and to increase the accuracy of the standard method. Results show that improved accuracy can be obtained in the field by applying these recommendations with the standard impact-echo method.

Classification of Convective/Stratiform Radar Echoes over a Summer Monsoon Front, and Their Optimal Use with TRMM PR Data

  • Oh, Hyun-Mi;Heo, Ki-Young;Ha, Kyung-Ja
    • Korean Journal of Remote Sensing
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    • v.25 no.6
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    • pp.465-474
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    • 2009
  • Convective/stratiform radar echo classification schemes by Steiner et al. (1995) and Biggerstaff and Listemaa (2000) are examined on a monsoonal front during the summer monsoon-Changma period, which is organized as a cloud cluster with mesoscale convective complex. Target radar is S-band with wavelength of 10cm, spatial resolution of 1km, elevation angle interval of 0.5-1.0 degree, and minimum elevation angle of 0.19 degree at Jindo over the Korean Peninsula. For verification of rainfall amount retrieved from the echo classification, ground-based rain gauge observations (Automatic Weather Stations) are examined, converting the radar echo grid data to the station values using the inverse distance weighted method. Improvement from the echo classification is evaluated based on the correlation coefficient and the scattered diagram. Additionally, an optimal use method was designed to produce combined rainfalls from the radar echo and Tropical Rainfall Measuring Mission Precipitation Radar (TRMM/PR) data. Optimal values for the radar rain and TRMM/PR rain are inversely weighted according to the error variance statistics for each single station. It is noted how the rainfall distribution during the summer monsoon frontal system is improved from the classification of convective/stratiform echo and the use of the optimal use technique.

Hands-free Speech Recognition based on Echo Canceller and MAP Estimation (에코제거기와 MAP 추정에 기초한 핸즈프리 음성 인식)

  • Sung-ill Kim;Wee-jae Shin
    • Journal of the Institute of Convergence Signal Processing
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    • v.4 no.3
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    • pp.15-20
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    • 2003
  • For some applications such as teleconference or telecommunication systems using a distant-talking hands-free microphone, the near-end speech signals to be transmitted is disturbed by an ambient noise and by an echo which is due to the coupling between the microphone and the loudspeaker. Furthermore, the environmental noise including channel distortion or additive noise is assumed to affect the original input speech. In the present paper, a new approach using echo canceller and maximum a posteriori(MAP) estimation is introduced to improve the accuracy of hands-free speech recognition. In this approach, it was shown that the proposed system was effective for hands-free speech recognition in ambient noise environment including echo. The experimental results also showed that the combination system between echo canceller and MAP environmental adaptation technique were well adapted to echo and noise environment.

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동지나해의 초음파 산란층에 관한 연구 ( 1 ) ( Acoustic Scattering Layers in the East China Sea ( 1 ) )

  • Lee, Dae-Jae;Shin, Hyeong-Il;Park, Jung-Hee
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.1
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    • pp.14-19
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    • 1990
  • This paper describes on the characteristics of the acoustic echoes from the scattering layers by the aggregation of marine organisms which was measured by using a 50kHz echo sounder on board of the training ship SAEBADA belong to National Fisheries University of Pusan during the summer, 1989 in the East China Sea. A data acquisition system was used to record digitally the envelope of the echoes and the frequency distribution of echo amplitudes on the whole water column was examined as a function of time during the sunrise and sunset periods. Acoustic data showed that the abundance distribution of marine organisms according to depth in the servery area changed with time and that the organisms were most active during the twilight of morning, and the echo strength on the water column or scattering layer was also strongest during this time. Additional results of this survey suggest that other interest, such as the relationship between environmental conditions and biomass depth distribution, could be also investigated in hydroacoustic method.

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Nondestructive Assessment of Compressive Strength of Construction Materials Using Impact-Echo Response Signal (임팩에코 응답신호를 적용한 건설재료 비파괴 압축강도 산정)

  • Son, Moorak;Kim, Moojun
    • Journal of the Korean GEO-environmental Society
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    • v.18 no.8
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    • pp.17-21
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    • 2017
  • This paper is to grasp the use of impact-echo response signal induced from impacting an object for the assessment of compressive strength of construction materials nondestructively and to propose the test results. For this study, an impact device was devised and used for impacting an object by an initial rotating free falling impact and following repetitive impacts from the rebound action which eventually disappears. Concrete test specimens which had been mixed for different strengths were tested and the impact echo response signal was measured for each test specimen. The total sound signal energy which is assessed from integrating the impact-echo response signal was compared with the directly measured compressive strength for each specimen. The comparison showed that the total sound signal energy has a direct relationship with the directly measured compressive strength and the results clearly indicated that the compressive strength of construction materials can be assessed nondestructively using total sound signal energy which is assessed from integrating the impact-echo response signal induced from impacting an object.

Improvement in Wind Vector from UHF Wind Profiler Radar through Removing Ground Echo (지형에코 제거를 통한 UHF 윈드프로파일러의 바람벡터 개선)

  • Kim, Kwang-Ho;Kim, Park-Sa;Kim, Min-Seong;Kang, Dong-Hwan;Kwon, Byung Hyuk
    • Journal of Environmental Science International
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    • v.25 no.2
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    • pp.267-280
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    • 2016
  • Ground echo is radar return from stationary targets such as buildings and trees. Wind vectors from the wind profile radar in Gangneung are affected by ground echoes due to the complex mountainous terrain located to the west and the south. These ground echoes make a spurious peak close to the direct current (DC) line signal in Doppler spectra. Wind vectors polluted by ground clutters were determined from spectra of oblique beams. After eliminated the terrain echoes, the accuracy of wind vector compared with radiosonde was improved about 68.4% and its relative coefficient was increased from 0.58 to 0.97.

Nondestructive Contactless Sensing of Concrete Structures using Air-coupled Sensors

  • Shin, Sung-Woo;Hall, Kerry S.;Popovics, John S.
    • International Journal of Safety
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    • v.7 no.2
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    • pp.17-22
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    • 2008
  • Recent developments in contactless, air-coupled sensing of seismic and ultrasonic waves in concrete structures are presented. Contactless sensing allows for rapid, efficient and consistent data collection over a large volume of material. Two inspection applications are discussed: air-coupled impact-echo scanning of concrete structures using seismically generated waves, and air-coupled imaging of internal damages in concrete using ultrasonic tomography. The first application aims to locate and characterize shallow delamination defects within concrete bridge decks. Impact-echo method is applied to scan defected concrete slabs using air coupled sensors. Next, efforts to apply air-coupled ultrasonic tomography to concrete damage imaging are discussed. Preliminary results are presented for air-coupled ultrasonic tomography applied to solid elements to locate internal defects. The results demonstrate that, with continued development, air-coupled ultrasonic tomography may provide improved evaluation of unseen material defects within structures.

Echo Noise Robust HMM Learning Model using Average Estimator LMS Algorithm (평균 예측 LMS 알고리즘을 이용한 반향 잡음에 강인한 HMM 학습 모델)

  • Ahn, Chan-Shik;Oh, Sang-Yeob
    • Journal of Digital Convergence
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    • v.10 no.10
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    • pp.277-282
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    • 2012
  • The speech recognition system can not quickly adapt to varied environmental noise factors that degrade the performance of recognition. In this paper, the echo noise robust HMM learning model using average estimator LMS algorithm is proposed. To be able to adapt to the changing echo noise HMM learning model consists of the recognition performance is evaluated. As a results, SNR of speech obtained by removing Changing environment noise is improved as average 3.1dB, recognition rate improved as 3.9%.

Application of Echo-Sounder Monitoring Technique as Ecological Impact Assessments of Fish on Artificial Weir Construction (인공보의 어류생태영향 평가를 위한 Echo-sounder 모니터링 기법 적용)

  • Han, Jeong-Ho;Lee, Jae Hoon;Choi, Ji-Woong;Lim, Byung Jin;Park, Jong-Hwan;An, Kwang-Guk
    • Journal of Environmental Impact Assessment
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    • v.21 no.6
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    • pp.859-877
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    • 2012
  • In this study, Echo-sounder($E_s$) monitoring methodology was applied to test environmental impacts of artificial weirs(SCW and JSW) in the Yeongsan River on fish community and habitat structures at first time, and was compared with conventional fish sampling methodologies($C_s$). For the Es monitoring in the fields, parallel transect methods was employed in determining the survey distance interval with every 125 m within the upper-lower 2 km of the weirs. Four different fish sampling gears such as casting nets, kick nets, fyke nets, and gill nets were used for applications of $C_s$ monitoring methodology. According to the Echo-sounder monitoring, fish density, expressed as a number of individuals per square meter, along the longitudinal axis of the weir was significantly greater(JSW, t = 3.506, n = 30, p < 0.001) in the down-river reach of the weir than in the up-river reach. Also, fish density along the vertical water column was highest at mid-depths of Seungchon weir, which has simple habitat substrates, while fish density was highest at hypolimnetic depth of Juksan weir. According to fish sampling by the $C_s$ methodology, the fish compositions decreased as the river goes upward, and significant differences(JSW, t = 0.248, n = 30, p < 0.05) in the compositions of fish species occurred between up-reach and down-reach of the weirs. The dominant species near the two weirs were Opsarichthys uncirostris amurensis, Hemiculter eigenmanni and Coilia nasus. Overall, our fish and habitat data, based on $E_s$ and $C_s$ monitoring methodologies, suggest that the weirs disturbed the rivers due to initial habitat disturbances by the weir constructions as well as the barrier roles of weirs on fish passage and migrations. More long-term scientific and systematic fish impact monitoring and assessments($E_s$ and $C_s$) are required in the future to predict changes of ecological structures and functions on the constructions of the weirs.