Relevant bibliographies by topics / Signals attenuation

Academic literature on the topic 'Signals attenuation'

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Published: 14 March 2023

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Journal articles on the topic "Signals attenuation"

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Lysenko, Iu Iu, Yu V. Kuts, V. M. Uchanin, and V. F. Petryk. "Research of oscillation mode in automated pulsed eddy current testing systems." Information extraction and processing 2021, no. 49 (December 17, 2021): 9–18. http://dx.doi.org/10.15407/vidbir2021.49.009.

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The formation and analysis of eddy current probe signals obtained in pulsed excitation mode is considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of inspected object parameters evaluation. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allowed proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signals phase and amplitude characteristics. Developed algorithm and the proposed methodology was implemented for evaluation of eddy current signals parameters and related characteristics of testing objects. This method was experimentally verified on a series of different test specimens. The obtained results confirm the possibility to apply the proposed informative signals to solve some problems concerned with automated eddy current testing. The formation and analysis of eddy current probe signals obtained in pulsed excitation mode are considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of automated eddy current testing. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allows proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signal phase and amplitude characteristics. Methods of increasing the accuracy of determining the eddy current probe signals attenuation and frequency using trends of signals phase and amplitude characteristics are considered. The proposed signal processing method was verified by modeling the process of determining the eddy current probe signals attenuation and the frequency from the signal with Gaussian noise. Algorithmic and software were developed based on the simulation results and the proposed improved methodology was implemented for determining signals parameters and related parameters and characteristics of testing objects.
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Matsushima, Jun, Makoto Suzuki, Ippei Matsugi, Yoshibumi Kato, and Shuichi Rokugawa. "Attenuation estimation using sweep signals in ultrasonic laboratory measurements." GEOPHYSICS 79, no. 3 (May 1, 2014): V115—V130. http://dx.doi.org/10.1190/geo2013-0281.1.

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It is important to obtain reliable attenuation results from experimental data to elucidate the physical mechanism responsible for ultrasonic wave attenuation. For attenuation estimation, a time window is often used to compute the frequencies of the direct-arrival waveforms. However, the effect of windowing distorts the spectral distribution due to a spectral leakage effect, degrading the attenuation estimates. We propose a method that enables accurate measurement of ultrasonic attenuation using sweep signals under the assumptions that velocity dispersion can be ignored and the quality factor [Formula: see text] is not dependent on frequency. We obtained the spectral amplitude of the sweep signal in the frequency-time domain using the continuous wavelet transform and estimated attenuation in the time-scale spectrum domain using the spectral-ratio method. This method is independent of the effect of windowing, whereas the windowing effect underestimates the attenuation results. In the absence of noise, the estimated attenuation results using sweep signals are in perfect agreement with the given input values, and the accuracy of the estimated attenuation results from windowed pulse waveforms depends on the extraction window length. However, our numerical experiments demonstrated that the proposed method is largely influenced by the existence of overlapping sweep events such as multiple reflections between the source and receiver transducer. Thus, applicability of the proposed method is limited to highly attenuative media, in which overlapping events are much smaller than direct sweep signals because these multiple reflected events are largely attenuated. Application of the proposed method to laboratory experimental data yielded similar underestimation of the attenuation results due to the windowing effect in the case of highly attenuative media. We also evaluated the usefulness of observing compressed pulse waveforms with shorter duration from the crosscorrelation of sweep waveforms than the case of pulse generation.
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Huang, Yaping, Hanyong Bao, and Xuemei Qi. "Seismic Random Noise Attenuation Method Based on Variational Mode Decomposition and Correlation Coefficients." Electronics 7, no. 11 (October 28, 2018): 280. http://dx.doi.org/10.3390/electronics7110280.

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Seismic data is easily affected by random noise during field data acquisition. Therefore, random noise attenuation plays an important role in seismic data processing and interpretation. According to decomposition characteristics of seismic signals by using variational mode decomposition (VMD) and the constraint conditions of correlation coefficients, this paper puts forward a method for random noise attenuation in seismic data, which is called variational mode decomposition correlation coefficients VMDC. Firstly, the original signals were decomposed into intrinsic mode functions (IMFs) with different characteristics by VMD. Then, the correlation coefficients between each IMF and the original signal were calculated. Next, based on the differences among correlation coefficients of effective signals and random noise as well as the original signals, the corresponding treatment was carried out, and the effective signals were reconstructed. Finally, the random noise attenuation was realized. After adding random noise to simple sine signals and the synthetic seismic record, the improved complementary ensemble empirical mode decomposition (ICEEMD) and VMDC were used for testing. The testing results indicate that the proposed VMDC has better random noise attenuation effects. It was also used in real-world seismic data noise attenuation. The results also show that it could effectively improve the signal-to-noise ratio (SNR) of seismic data and could provide high-quality basic data for further interpretation of seismic data.
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Wang, Xiang Hong, Hong Wei Hu, and Zhi Yong Zhang. "Attenuation of Acoustic Emission Signals in Structural Interfaces." Advanced Materials Research 569 (September 2012): 343–46. http://dx.doi.org/10.4028/www.scientific.net/amr.569.343.

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Received acoustic emission (AE) signals are transmitted across structural interfaces in many real-world applications. This paper studies attenuation of the signals across two common structural interfaces. The experimental results indicate that interface has effects on attenuation, which depends on the relative scales of structures. Signal energy is strengthened due to multiple flections of signals on the small-size structure when an interface is constructed by different scales. Thus the received signals are distorted worse than the original signals. So it is a better way to mount sensors on a simple structure with a size as much as a structure incurred AE sources.
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Salomonsson, Göran, and Benny Löfström. "Analysis of a System for Ultrasonic Imaging of Attenuation and Texture in Soft Tissue." Ultrasonic Imaging 7, no. 3 (July 1985): 225–43. http://dx.doi.org/10.1177/016173468500700303.

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Attenuation in tissue decreases both the amplitude and the bandwidth of a reflected ultrasonic signal. Only the amplitude is restored in conventional ultrasonic equipment by amplifying the signal in a time-gain-compensator. This paper describes a method for restoring both the amplitude and bandwidth of the signal and an implemention of this method is proposed. This consists of two main parts: a device for estimating the attenuation and a time-variable circuit. The time-variable circuit is controlled by the estimated attenuation such that its transfer function approximates the inverse of the transfer function of the attenuation within the transducer passband. Its output is then almost independent of the attenuation and contains information on the texture of the tissue. Both the texture and attenuation estimates are displayed graphically. The quality of the image of the texture can be improved by choosing a wideband transducer, since it is almost exclusively dependent of transducer bandwidth. The performance of the method is studied using both simulated signals and signals measured in vitro.
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Kupchenko, L. F., A. S. Rybiak, and А. V. Ponomar. "Compensation method for atmospheric attenuation of laser radiation in active electro-optical systems with dynamic spectral processing of optical signals." Semiconductor Physics, Quantum Electronics and Optoelectronics 25, no. 02 (June 30, 2022): 211–18. http://dx.doi.org/10.15407/spqeo25.02.211.

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This paper describes the compensation method for atmospheric attenuation of laser radiation, which can be implemented in active electro-optical systems with pre-detector dynamic spectral processing of optical signals. In these electro-optical systems, the spectral flux of sensing radiation is formed using multispectral laser signals based on a priori information about the spectral reflectance of the target and background. The sensing signal formed in this way ensures maximum suppression of the background signal at the output of system with minimal attenuation of the target signal. The influence of atmospheric radiation attenuation on operation of an active electro-optical system with dynamic spectral processing has been analyzed. It has been shown that the laser radiation attenuation in the atmosphere significantly affects the efficiency of dynamic spectral processing of optical signals (leads to a decrease in the target image contrast). The developed compensation method for atmospheric attenuation of radiation in active electro-optical systems with dynamic spectral processing is based on the fact that the spectral intensity of the sensing radiation is formed not only on the basis of a priori data on spectral characteristics of the target and background, but also takes into account the spectral transmittance of the optical radiation propagation medium.
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Zribi, Mehrez, Erwan Motte, Pascal Fanise, and Walid Zouaoui. "Low-Cost GPS Receivers for the Monitoring of Sunflower Cover Dynamics." Journal of Sensors 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6941739.

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The aim of this research is to analyze the potential use of Global Navigation Satellite System (GNSS) signals for the monitoring of in situ vegetation characteristics. An instrument, based on the use of a pair of low-cost receivers and antennas, providing continuous measurements of all the available Global Positioning System (GPS) satellite signals is proposed for the determination of signal attenuation caused by a sunflower cover. Experimental campaigns with this instrument, combined with ground truth measurements of the vegetation, were performed over a nonirrigated sunflower test field for a period of more than two months, corresponding to a significant portion of the vegetation cycle. A method is proposed for the analysis of the signal attenuation data as a function of elevation and azimuth angles. A high correlation is observed between the vegetation’s water content and the GPS signals attenuation, and an empirical modeling is tested for the retrieval of signal behavior as a function of vegetation water content (VWC). The VWC was estimated from GNSS signals on a daily basis, over the full length of the study period.
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Abdorahimi, Danial, and Ali M. Sadeghioon. "Comparison of Radio Frequency Path Loss Models in Soil for Wireless Underground Sensor Networks." Journal of Sensor and Actuator Networks 8, no. 2 (June 22, 2019): 35. http://dx.doi.org/10.3390/jsan8020035.

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A wireless Underground Sensor Network (WUSN) is a group of sensors that collectively communicate through the underground medium. Radio Frequency (RF) signal transmission of the sensors through the ground is the most challenging aspects of a WUSN due to the high attenuation of the electromagnetic (EM) signal in the soil. Signals are often required to travel through soils with a high density or water content and generally through a non-isotropic and non-homogenous soil mixture with different boundaries, both of which can attenuate the signal sharply. The variability of the these conditions and complexity of the behaviour of signal attenuation with respect to these parameters makes accurate estimation of EM signal attenuation in soil challenging. Two main EM signal attenuation models exist to estimate attenuation (modified-Friis and Complex Refractive Index Model-Fresnel (CRIM-Fresnel). These were reviewed and a methodology was developed in order to measure the attenuation of the EM signals in the laboratory. Results from the laboratory measurements were compared with the estimation values calculated from the attenuation models. These comparisons showed a large difference between the estimated values by the models. In addition, analysis of the comparison tests showed that the CRIM-Fresnel model provides a better estimation of attenuation in samples with lower permittivity values while the modified-Friis model had a higher accuracy in samples with higher clay/water content which have higher permittivity values.
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Koda, Yusuke, Koji Yamamoto, Takayuki Nishio, and Masahiro Morikura. "Measurement Method of Temporal Attenuation by Human Body in Off-the-Shelf 60 GHz WLAN with HMM-Based Transmission State Estimation." Wireless Communications and Mobile Computing 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/7846936.

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This paper discusses a measurement method of time-variant attenuation of IEEE 802.11ad wireless LAN signals in the 60 GHz band induced by human blockage. The IEEE 802.11ad access point (AP) transmits frames intermittently, not continuously. Thus, to obtain the time-varying signal attenuation, it is required to estimate the duration in which the AP transmitted signals. To estimate whether the AP transmitted signals or not at each sampling point, this paper applies a simple two-state hidden Markov model. In addition, the validity of the model is tested based on Bayesian information criterion in order to prevent model overfitting and consequent invalid results. The measurement method is validated in that the distribution of the time duration in which the signal attenuates by 5 dB is consistent with the existing statistical model and the range of the measured time duration in which the signal attenuation decreases from 5 dB to 0 dB is similar to that in the previous report.
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RODRÍGUEZ, O. C., S. JESUS, Y. STEPHAN, X. DEMOULIN, M. PORTER, and E. COELHO. "NONLINEAR SOLITON INTERACTION WITH ACOUSTIC SIGNALS: FOCUSING EFFECTS." Journal of Computational Acoustics 08, no. 02 (June 2000): 347–63. http://dx.doi.org/10.1142/s0218396x0000025x.

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The problem of nonlinear interaction of solitary wave packets with acoustic signals has been intensively studied in recent years. A key goal is to explain the observed transmission loss of shallow-water propagating signals, which has been found to be strongly time-dependent, anisotropic, and sometimes exhibited unexpected attenuation versus frequency. Much of the existing literature considers the problem of signal attenuation in a static environment, without considering additional effects arising from groups of solitons evolving both in range and time. Hydrographic and acoustic data from the INTIMATE'96 experiment clearly exhibit the effects of soliton packets. However, in contrast with reported observations of signal attenuation, the observed transmission loss shows a pronounced signal enhancement that behaves like a focusing effect. This focusing is correlated with peaks in current, temperature, and surface tide. That correlation suggests that the nonlinear interaction of solitary wave packets with acoustic signals can lead to a focusing of the signal. To clarify this issue, hydrographic data was used to generate physically consistent distributions of "soliton-like" fields of temperature and sound velocity. These distributions were then used as input for a range-dependent normal-mode model. The results strongly support the hypothesis that the soliton field causes the observed signal enhancement.
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Dissertations / Theses on the topic "Signals attenuation"

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Smith, Patrick John. "Attenuation of volcanic seismic signals." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1131/.

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Low frequency volcanic earthquakes, characterised by slowly decaying harmonic codas of 0.5-5Hz, have been observed on many volcanoes and are considered key tools in monitoring and eruption forecasting. The common element in a variety of models proposed for the origin of these earthquakes is resonance of a fluid body within a volcanic edifice. The source of the resonance is believed to consist of dispersive interface waves, trapped at the fluid-solid boundaries. The amplitude decay or attenuation of these earthquake signals can be decomposed into radiative and intrinsic components, and in this way yield information about both the geometry and fluid properties of the resonating source body. This thesis presents a study of the attenuation of low-frequency volcanic earthquakes, with particular emphasis on quantitatively linking seismic signals to magmatic processes and properties. The effect of the intrinsic attenuation of the fluid on the amplitude decay of low-frequency volcanic earthquakes is examined using a viscoelastic finite-difference model of seismic wave propagation. It is shown that the viscosity of the fluid contributes 23.6±2.26% less than previously thought to the apparent attenuation, and that its effect may have been substantially overestimated in previous studies. A physical explanation for this lies in understanding the fundamental differences between acoustic and interface waves. An analytical approach demonstrates that, for a set of realistic volcanic parameters, interface waves can be attenuated less than acoustic waves in a pure melt, if the longitudinal viscosity is at least 107 Pas. These results widen the set of possible resonators and imply that resonating volcanic conduits filled with high viscosity magma are viable sources for low-frequency seismicity. An automated method to measure the apparent attenuation of seismic signals is developed, tested, and applied to a dataset of low-frequency earthquakes from Soufri`ere Hills Volcano, Montserrat. Temporal trends in attenuation are observed and quantitatively interpreted as changes in magma viscosity. An estimate of the magma shear viscosity of 2.3 ± 2 × 105 Pas is obtained, demonstrating the ability of seismological data to place constraints on the magma properties.
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Johnston, Jerry W., and Steve LaPoint. "ROCKET MOTOR PLUME EFFECTS ON TM SIGNALS - MODEL CORROBORATION." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/607592.

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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California
This paper presents the interim results of an effort to corroborate analytic model predictions of the effects of rocket motor plume on telemetry signal RF propagation. When space is available, telemetry receiving stations are purposely positioned to be outside the region of a rocket motor's plume interaction with the RF path; therefore, little historical data has been available to corroborate model predictions for specific rocket motor types and altitudes. RF signal strength data was collected during the flight of HERA target missile by White Sands Missile Range (WSMR) using a transportable telemetry receiving site specifically positioned to be within the rocket plume region of influence at intermediate altitudes. The collected data was analyzed and compared to an RF plume attenuation model developed for pre-mission predictions. This work was directed by the US Army Kwajalein Atoll (USAKA)/ Kwajalein Missile Range (KMR) Safety Division.
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Doh, Yann. "Nouveaux modèles d'estimation monophone de distance et d'analyse parcimonieuse : Applications sur signaux transitoires et stationnaires bioacoustiques à l’échelle." Thesis, Toulon, 2014. http://www.theses.fr/2014TOUL0020/document.

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Les ondes acoustiques subissent peu de dispersion dans le milieu marin, comparé au milieu aérien. Certaines espèces de cétacés communiquent ainsi à grande distance, d'autres utilisent leurs émissions sonores pour s'orienter. La bioacoustique consiste à étudier ces espèces à partir de l'analyse de leurs sons, c'est-à-dire à les détecter, classer, localiser. Cela peut se faire via un réseau d'hydrophones au déploiement fastidieux. Afin de contribuer au passage à l'échelle de la bioacoustique, cette thèse propose des modèles originaux mono-hydrophone pour l'analyse de ces signaux stationnaires ou transitoires. Premièrement, nous dérivons un nouveau modèle d'estimation de la distance entre une source impulsive (ex. biosonar) et un hydrophone. Notre modèle théorique, l'Intra Spectral ATténuation(ISAT), dérive des lois acoustiques de déformation spectrale du signal transitoire induite par l'atténuation durant sa propagation. Ce modèle relie les rapports énergétiques des bandes de fréquences pondérés par un modèle de perte par atténuation fréquentielle (Thorp ou Leroy) à la distance de propagation. Nous approximons aussi ISAT par un modèle neuromimétique. Ces deux modèles sont validés sur le sonar du cachalot (Physeter macrocephalus) enregistré avec notre bouée acoustique autonome BOMBYX et notre système d'acquisition DECAV en collaboration avec le Parc National de Port-Cros et le sanctuaire Pelagos pour la protection des mammifères marins en Méditerranée. Les mesures d'erreur (RMSE) d'environ 500 mètres sur nos références du centre d'essai OTAN aux Bahamas présentent un intérêt opérationnel. Deuxièmement, nous proposons une analyse originale de l'évolution des voisements de cétacé par codage parcimonieux. Notre encodage des cepstres par apprentissage non supervisé d'un dictionnaire met en évidence l'évolution temporelle des bigrammes des chants que les baleines à bosse mâles émettent durant la période de reproduction. Nous validons ce modèle sur nos enregistrements du canal de Sainte-Marie à Madagascar entre 2008 et 2014, via notre réseau d'hydrophones BAOBAB qui constitue une première dans l'Océan Indien. Nos modèles s'inscrivent dans le projet Scaled Bioacoustics (SABIOD, MI CNRS) et ouvrent de nouvelles perspectives pour les passages à l'échelle temporelle et spatiale de la bioacoustique
Acoustic waves show low dispersion due to the underwater propagation, compared to the propagation in the air. Some species of cetaceans communicate at long distance, others use their sound production for orientation. The goal of the scientic area called bioacoustics is to study animal species based on the analysis of their emitted sound. Their sounds can be used to detect, to classify and to locate the cetaceans. Recordings can be done with an passive acoustic array of multiple hydrophones, but this method is expensive and difficult to deploy. Thus, in order to scale this approach, we propose in this Phd thesis several original single hydrophone models to analyze these stationary or transient signals.Firstly, we provide a new theoretical model to estimate the distance between the impulsive source (ex. biosonar of the cetacean) and the hydrophone. Our model, the Intra Spectral ATtenuation (ISAT), is based on the spectral signal alteration due to the underwater acoustic propagation, especially the differences in different frequency bands. We also approximated ISAT by an artificial neural network. Both models are validated on clicks emitted by sperm whales (Physeter macrocephalus) recorded by our sonobuoy BOMBYX and our data-acquisition system DECAV developed incollaboration with the National Park of Port-Cros (France) and the Pelagos sanctuary for the protection of marine mammals in the Mediterranean sea (France). The error (RMSE) measures on the recordings of the NATO test center in the Bahamas are about500 meters, promising further real applications. Secondly, we worked on the variations of the cetacean vocalizations using the sparse coding method. The encoding of thecepstrums by unsupervised learning of a dictionary shows bigrammic time changes of the songs of humpback whales (Megaptera novaeangliae). We validate this model on signals recorded in the Ste Marie Channel (Madagascar) between 2008 and 2014, through our network of hydrophones BAOBAB which is the first passive acoustic array deployed in the Indian Ocean.Our models are part of the Saled Bioacoustics project (SABIOD, MI CNRS) and open perspectives for temporal and spatial scaling of bioacoustics
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Maenou, Takatoshi, and Masaaki Katayama. "Study on Signal Attenuation Characteristics in Power Line Communications." IEEE, 2006. http://hdl.handle.net/2237/7798.

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De, Villiers Wernich. "Prediction and measurement of power line carrier signal attenuation and fluctuation." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52410.

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Thesis (MScEng)--University of Stellenbosch, 2001,
ENGLISH ABSTRACT: A frequency domain Power Line Carrier (PLC) simulation program, with the ability to simulate signal attenuation including the coupling equipment, was developed. This simulation program was put to the test against the independent program of Professor L.M. Wedepohl and against practical field measurements. The predictions of the two programs were in precise agreement for a wide range of input parameters. Results from the field tests and predictions also showed close agreement. Further investigations, applying the simulation program, explained how ground conductors and soil resistivity influences PLC signal propagation. An experiment, which was developed to monitor PLC signal attenuation, was installed on the PLC system between Koeberg power station and Acacia substation, both near Cape Town. Data logged continuously over 28 days, indicated measurable and deterministic PLC signal attenuation variations with typical time constants of a few hours. Simulations of the PLC system indicated that the signal amplitude variations were influenced by changes in the height above the ground plane of the phase conductor. This significant finding creates the possibility to obtain real time knowledge of the sag of an Over Head Transmission Line (OHTL) by exploiting an operational PLC system. The knowledge about real time sag can be used in economical dynamic ampacity control systems. The practical and financial benefits to the electricity supply and distribution industry can be significant.
AFRIKAANSE OPSOMMING: 'n Frekwensie gebied "Power Line Carrier" (PLC) simulasie program wat die sein verswakking en die koppeling verliese kan naboots, is ontwikkel. Die program is getoets teen die onafhanklike program van Professor L.M. Wedepohl asook praktiese metings in die veld. Die vooruitskatings van beide programme is presies die selfde vir 'n wye reeks van parameters. Metings en nabootsings het ook noue ooreenstemming getoon. Verdere ondersoek, m. b. v. die program, is gedoen ten einde te verduidelik hoe grond-geleiers en grond weerstand die PLC sein se voortplanting beïnvloed. 'n Eksperiment om die PLC sein se verswakking mee te monitor is ontwerp. Die eksperiment was geïnstalleer in die PLC stelsel tussen Koeberg kernkragstasie en Acacia substasie, naby Kaapstad. Die eksperiment was vir 28 dae geaktiveer en die data wat die eksperiment opgelewer het toon meetbare PLC sein verswakking met tyd konstantes van 'n paar uur. Verdere nabootsings het gewys dat die veranderende verswakking in die PLC seinsterkte toegeskryf kan word aan die wisseling in hoogte van die fase geleiers bo die grondvlak. Hierdie bevinding is van besondere belang aangesien dit die moontlikheid oopmaak om die gemiddelde sak van kraglyne in reële tyd en onder bedryfs toestande te kan meet. Die informasie van die reële sak van kraglyne kan gebruik word in effektiewe stroomdrae-vermoë beheer stelsels. Die praktiese en finansiële voordele wat krag voorsieners en verspreiders hieruit kan put kan aansienlik wees.
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Pokorný, Rostislav. "Návrh programovatelného útlumového členu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413091.

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This Master´s thesis focuses on design and implementation of programmable attenuator. The main aim of this thesis is to create an electronical device that provide continuous setting of attenuation value in the range between 0–150 dB. Setting a value from the range can be performed using buttons and set values are shown on display. For this thesis an attenuator with working frequency between 0–6 GHz was chosen and four–layer printed circuit board was designed. As a result the device is fitted with an 8bit microcontroller ATmega328P–PU using five 6bit digital attenuators connected in series with manual and program settings of attenuation from 0–157,5 dB with step of 0,5 dB. Data are shown on a build–in display. The application for remote settings and value reading over integrated USB (Universal Serial Bus) interface, was created in C#. In conclusion of this thesis there is a measurement evaluation of attenuation measurement performed on the device.
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Viklund, Johan. "Atmospheric Attenuation for Lidar Systems in Adverse Weather Conditions." Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-184706.

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In this study, the weather impact on lidar signals has been researched. A lidar system was placed with a target at approximately 90 m and has together with a weather station collected data for about a year before this study. By using the raw detector data from the lidar, the full waveform can be obtained and the amplitude of the return pulse can be calculated. Atmospheric attenuation of lidar signals is often modeled using the lidar equation, which predicts an exponential decrease in energy over the distance. The factor in the exponent is referred to as the extinction coefficient and it is the main property studied in this thesis. By utilizing models for the extinction coefficient under different weather conditions, it is possible to simulate the performance of the lidar.  The extinction coefficient was calculated using different empirical models. The empirical models investigated in this thesis are the Kim and Kruse models for known visibility, the Al Naboulsi model for different types of fog with known visibility, the Carbonneau model for known precipitation amount in rainy conditions, and a similar model for snowy conditions. For the case of rain, a physical model was also used, which is derived through Mie theory. The physical model requires a particle size distribution, which is the number of particles of a certain radius per unit volume. A particle size distribution for rain was generated using the Ulbrich raindrop size distribution, using the precipitation amount recorded by the weather station. Particle size distributions for radiation and advection fog were also simulated.  The measured attenuation in lidar signals was compared to the predicted attenuation that was calculated using different models for the extinction coefficient in the lidar equation. Generally, the models tend to underestimate the amplitude of the return pulse. This can partially be explained by the assumptions used to derive the lidar equation, which neglects all augmentation of the beam. The visibility models gave more accurate results compared to the precipitation models. This was expected, since visibility is defined as a measure of attenuation and precipitation amount is not.  When a lidar signal is emitted, the light will be reflected from optical surfaces within the lidar and cause a pulse to be detected. This pulse is referred to as the zeropulse. In the first couple of meters of the transmission, we expect to see some backscattered light from adverse weather, since the detector has a larger solid angle at shorter distances. This returned light will be combined with the zeropulse and cause it to expand in width. By examining the zeropulse, it was possible to observe a difference between the average zeropulse under some different weather conditions. This leads to the conclusion that it may be possible to extract some information about current weather conditions from the zeropulse data, given that there is little ambient light and snowy weather conditions.  By integrating the zeropulse, variations in the shape of the zeropulse could be described by a single value. Then by separating the data into low and high visibility populations, the zeropulse integral could be used to predict the visibility. The conclusion was that the zeropulse integral can accurately predict whether visibility is above or below a threshold value, given that there is little ambient light and the visibility is known to be below 19950 m.
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White, John D. H. "A random signal ultrasonic test system for highly attenuating media." Thesis, Keele University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315234.

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Pollard, Kimberley Jeanne. "Study of slant path attenuation ratios derived from a dual-polarized radar." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040448/.

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Salchak, Iana. "Ingested Wireless Capsule Localisation Based on In-body RF Attenuation Path Loss." Thesis, Griffith University, 2022. http://hdl.handle.net/10072/417699.

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Engineering advancement over the last decade has significantly benefited the medical field, facilitating personalised and accessible healthcare. Various portable systems have been developed to obtain diagnostic parameters without the necessity for sedation or immobilisation of the patient, and even their presence at the medical facility. This can be especially important for populations that are at greater medical risk and are unable to undergo sedation, as well as for overall screening of the underlying conditions by continuous monitoring. This thesis provides engineering solutions aimed at improving the reliability of one of the modern medical diagnostic techniques – Wireless Capsule Endoscopy (WCE). It is a non-invasive approach for gastrointestinal (GI) tract examination that involves the natural propagation of a capsule through the entire tract of the patient while recording images of the lining. The video data are transmitted to a receiving unit outside the body, which is then accessed by medical practitioners for appropriate diagnostics. The Wireless Body Area Network (WBAN) technology describes the acquisition and transmission of the signal. One of the major challenges associated with WCE is the accurate localisation of the capsule due to the transit time being different for each individual. Localisation methods based on various physical principles are still under investigation by researchers. In this study, radiofrequency (RF) signal propagation analysis was used to provide accurate received signal strength (RSSI)-based localisation of the wireless endoscopy capsule. RSSI-based methods are widely used in indoor and outdoor positioning systems, allowing the estimation of the radial distance between reference sensors and an unknown transmitter position. Due to the significantly different electromagnetic (EM) properties of the human body as a propagation medium compared to air, one of the main objectives of this work was to develop an appropriate path loss propagation model. The advantage of the proposed solution is that it is based on an analytical approach and includes the attenuation constant defined by the EM properties of the soft tissues in the abdominal area. The theoretical basis of the developed attenuation path loss model (APLM) can be used to generalise and implement it for various In-to-On-Body communication systems at different operational frequencies. The APLM was numerically validated using CST Studio Software©, as well as by experiments on ex-vivo porcine tissues and in-vivo measurements on anesthetised living pigs. The experiments also served as the iii performance validation of a receiving inward cavity-backed slot antenna designed specifically for In-to-On-Body communications at 2.45 GHz, ISM band. In-vivo trials included implanting a wireless transmitter at several abdominal positions, which were then used for the 2-D and 3-D localisation accuracy assessment. Two trials were conducted separately at the medical facilities of The University of Southern Denmark (Odense, Denmark) and at the Herston Medical Research Centre, The University of Queensland (Brisbane, QLD, Australia). The research presents new knowledge for WBAN channel modelling for propagation media similar to the human body; confirms the reliability of the slot antenna performance for surface field measurements in WCE applications at 2.45 GHz; validates the application of the attenuation path loss model for In-to-On-Body communication channels; and it demonstrates high localisation accuracy when the proposed attenuation path loss model is used as an inverse solution for finding radial distances between the reference sensor and the unknown implant position.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Books on the topic "Signals attenuation"

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Lamczyk, Mark Anthony. Experimental and numerical investigations of the Gaussian suppression of sound by sound. Monterey, Calif: Naval Postgraduate School, 1997.

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R, Spilker Thomas, and United States. National Aeronautics and Space Administration., eds. Microwave resonator measurements of atmospheric absorption coefficients: A preliminary design study. Pasadena, Calif: National Aeronautics and Space Administration, Jet Propulsion Laborator[y], California Institute of Technology, 1995.

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National Institute of Standards and Technology (U.S.), ed. Electromagnetic signal attenuation in construction materials. Gaithersburg, Md: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

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Faramaz, Davarian, Jet Propulsion Laboratory (U.S.), and Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (7th : 1995 : Fort Collins, Colo.), eds. Proceedings of the nineteenth NASA Propagation Experimenters Meeting (NAPEX XIX) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (APSW VII) held in Fort Collins, Colorado, June 14-16, 1995. Pasadena, Calif: National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, 1995.

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Center, NASA Glenn Research, ed. Acousto-ultrasonics to assess material and structural properties. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2002.

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Center, NASA Glenn Research, ed. Acousto-ultrasonics to assess material and structural properties. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2002.

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Center, NASA Glenn Research, ed. Acousto-ultrasonics to assess material and structural properties. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2002.

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Kaufmann, Philipp A., and Oliver Gaemperli. Hybrid Cardiac Imaging. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199392094.003.0028.

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Assessment of both coronary anatomy and myocardial perfusion are equally important for the appropriate treatment of patients with stable coronary artery disease. Cardiac hybrid imaging allows integration of coronary anatomy and perfusion in one all-in-one image, thereby avoiding mental integration of findings. In selected subgroups of patients, cardiac hybrid imaging has demonstrated superior diagnostic accuracy compared to single modalities. The combination of coronary anatomy and function provides incremental prognostic information and improves risk stratification of patients with suspected or known CAD. Aside from CT coronary angiography, coronary artery calcium score (CACS) scans obtained from native ECG-triggered CT are used for hybrid imaging. They are used either for attenuation correction, or can be combined with radionuclide information to improve CAD detection and risk stratification. A large number of integrated hybrid scanners are commercially available and offer advantages for cardiac hybrid imaging. However, these devices are not mandatory, and hybrid imaging is perfectly feasible from two separate datasets using appropriate image fusion software. Cardiac magnetic resonance has entered the arena of hybrid imaging and several integrated PET/MRI devices are already commercially available. Its advantages include the lack of ionizing radiation and a high spatial resolution, particularly for soft tissue structures. In research, hybrid imaging moves beyond its conventional borders of perfusion imaging to target specific molecular or biological pathways that underlie cardiac disease, a concept known as molecular imaging. The combination of radionuclide imaging with CT or MRI offers attractive features to co-localize biological signals from radiolabeled targeted compounds with microanatomical structures.
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Ģēģere, Lilita. Research on Next Generation Fiber Optical Amplifiers and Their Evaluation in Dense Communication Systems. RTU Press, 2021. http://dx.doi.org/10.7250/9789934226878.

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In recent years, the information technology sector has developed rapidly and there has been a rapid increase in the amount of information transmitted. The demand for larger telecommunication network capacities is growing, therefore it is necessary to increase the number of channels and transmission speed in wavelength division multiplexed transmission systems. Various optical amplifiers can be used to compensate for the attenuation of the accumulated signal (over a wide wavelength range). The Doctoral Thesis did research on the use of EDFA, Raman, FOPA and combined optical amplifiers in wavelength division multiplexing systems. In the work, special emphasis is placed on erbium and ytterbium alloy fibers with the study of computer modeling of optical amplifiers in cladding pumping technology.
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Acousto-ultrasonics to assess material and structural properties. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2002.

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Book chapters on the topic "Signals attenuation"

1

Becerra-Luna, B., R. Martínez-Memije, J. C. Sánchez, and O. Infante. "Miokinetic Noise Attenuation in Photoplethysmographic Pulse Signals by LMS Adaptive Filtering with Adequacy of the Input Signals." In VI Latin American Congress on Biomedical Engineering CLAIB 2014, Paraná, Argentina 29, 30 & 31 October 2014, 128–31. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13117-7_34.

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Beura, Chandra Prakash, Michael Beltle, and S. Tenbohlen. "Attenuation of UHF Signals in a 420 kV Power Transformer Based on Experiments and Simulation." In Lecture Notes in Electrical Engineering, 1276–85. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-31680-8_122.

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Weik, Martin H. "signal attenuation." In Computer Science and Communications Dictionary, 1577. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_17340.

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Panetta, P. D., F. J. Margetan, I. Yalda, and R. B. Thompson. "Observation and Interpretation of Microstructurally Induced Fluctuations of Back-Surface Signals and Ultrasonic Attenuation in Titanium Alloys." In Review of Progress in Quantitative Nondestructive Evaluation, 1547–54. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-5947-4_202.

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Al-Shuhail, Abdullatif, and Saleh Al-Dossary. "Denoising Using Signal Model." In Attenuation of Incoherent Seismic Noise, 129–51. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-32948-8_7.

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Keiser, Gerd. "Optical Signal Attenuation and Dispersion." In Fiber Optic Communications, 93–145. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4665-9_3.

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Margetan, F. J., P. D. Panetta, and R. B. Thompson. "Ultrasonic Signal Attenuation in Engine Titanium Alloys." In Review of Progress in Quantitative Nondestructive Evaluation, 1469–76. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-5339-7_190.

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Porcino, Domenico. "Analysis of UWB Signal Attenuation Through Typical Building Materials." In Ultra-Wideband, 265–82. Chichester, UK: John Wiley & Sons, Ltd, 2006. http://dx.doi.org/10.1002/0470056843.ch13.

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Yoon, Myung-Hyun, and Tenkasi V. Ramabadran. "Accounting for Ultrasonic Signal Attenuation Through Model Parameter Interpolation." In Review of Progress in Quantitative Nondestructive Evaluation, 767–74. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2848-7_97.

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Rovelli, Antonio, Sandro Marcucci, and Giuliano Milana. "The Objective Determination of the Instantaneous Predominant Frequency of Seismic Signals and Inferences on Q of Coda Waves." In Scattering and Attenuations of Seismic Waves, Part I, 281–93. Basel: Birkhäuser Basel, 1988. http://dx.doi.org/10.1007/978-3-0348-7722-0_15.

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Conference papers on the topic "Signals attenuation"

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Zhao, Yumin, Yunyue Elita Li, Bei Li, Wei Luo, Zhaoyin Liu, and Yuxuan Zhou. "Seismic attenuation extracted from isolated traffic signals." In Second International Meeting for Applied Geoscience & Energy. Society of Exploration Geophysicists and American Association of Petroleum Geologists, 2022. http://dx.doi.org/10.1190/image2022-3746998.1.

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Lu, Yimin, Zhufeng Du, and Tiexia Huang. "Attenuation characteristics of underwater target lidar signals." In SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, edited by Wallace G. Fishell, Arthur A. Andraitis, Michael S. Fagan, Jerry D. Greer, and Mark C. Norton. SPIE, 1998. http://dx.doi.org/10.1117/12.330186.

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Shen, Yongna, Gongtian Shen, Pengcheng Gan, Junjiao Zhang, and Yilin Yuan. "Research on the Attenuation Characteristics of Acoustic Emission From Corrosion of Tank Bottom Plate." In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-96869.

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Abstract In order to clarify the detection range of acoustic emission technology for the tank bottom plate inspection, the attenuation characteristics of AE signal from lead-break on the tank bottom plate are investigated in this work. First the attenuation of AE signals from the lead-break on the upper surface of the tank bottom plate and that from the lead-break on the lower surface of the tank bottom plate are studied and compared when the tank is empty, which indicates that the upper surface corrosion of the tank bottom plate is much easier to detect than the lower surface corrosion. The weld perpendicular to the AE transport direction contributed much to the attenuation of the AE signals from tank floor. Then, the influence of liquid level on the attenuation and transport path of AE signals from tank bottom plate are investigated when water is added into the tank with a level of 10cm and 70cm, respectively. The liquid changes both the attenuation trend and the transport path of AE signals.
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Lopatin, M., N. Moskovitch, T. Trigano, and Y. Sepulcre. "Pileup attenuation for spectroscopic signals using a sparse reconstruction." In 2012 IEEE 27th Convention of Electrical & Electronics Engineers in Israel (IEEEI 2012). IEEE, 2012. http://dx.doi.org/10.1109/eeei.2012.6377045.

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Kikkert, Cornelis Jan, and Geoffrey Reid. "Radiation and attenuation of communication signals on power lines." In Signal Processing (ICICS). IEEE, 2009. http://dx.doi.org/10.1109/icics.2009.5397568.

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Timothy D Drysdale, Toby Trevor Mottram, and David RS Cumming. "WSN: Modelling the Attenuation of Radio Signals by Bovines." In 2008 Providence, Rhode Island, June 29 - July 2, 2008. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2008. http://dx.doi.org/10.13031/2013.24842.

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Bai, Wenling, Lilin Dan, Yue Xiao, and Shaoqian Li. "Attenuation Factor Analysis for OFDM Signals with Peak Cancellation." In 2009 IEEE 69th Vehicular Technology Conference Spring. IEEE, 2009. http://dx.doi.org/10.1109/vetecs.2009.5073408.

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Li, Meng, and Zhonghua Huang. "Attenuation characteristic of UWB signals propagation in free space." In International Symposium on Optoelectronic Technology and Application 2016, edited by Bingheng Lu and Huaming Wang. SPIE, 2016. http://dx.doi.org/10.1117/12.2243759.

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Carcreff, Ewen, Sébastien Bourguignon, Jéro^me Idier, Laurent Simon, and Aroune Duclos. "Including frequency-dependent attenuation for the deconvolution of ultrasonic signals." In ICA 2013 Montreal. ASA, 2013. http://dx.doi.org/10.1121/1.4800850.

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Nazari, A., M. A. Riahi, and N. Abbasi. "The Influence of Attenuation on Frequency Component of Seismic Signals." In KazGeo 2012. Netherlands: EAGE Publications BV, 2012. http://dx.doi.org/10.3997/2214-4609.20142944.

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Reports on the topic "Signals attenuation"

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Becquet, Yann, D. G. Camell, Galen H. Koepke, Kate A. Remley, William F. Young, and Christopher L. Holloway. Attenuation of radio wave signals coupled into twelve large building structures. Gaithersburg, MD: National Bureau of Standards, 2008. http://dx.doi.org/10.6028/nist.tn.1545.

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Brown Horowitz, Sigal, Eric L. Davis, and Axel Elling. Dissecting interactions between root-knot nematode effectors and lipid signaling involved in plant defense. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598167.bard.

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Root-knot nematodes, Meloidogynespp., are extremely destructive pathogens with a cosmopolitan distribution and a host range that affects most crops. Safety and environmental concerns related to the toxicity of nematicides along with a lack of natural resistance sources threaten most crops in Israel and the U.S. This emphasizes the need to identify genes and signal mechanisms that could provide novel nematode control tactics and resistance breeding targets. The sedentary root-knot nematode (RKN) Meloidogynespp. secrete effectors in a spatial and temporal manner to interfere with and mimic multiple physiological and morphological mechanisms, leading to modifications and reprogramming of the host cells' functions, resulted in construction and maintenance of nematodes' feeding sites. For successful parasitism, many effectors act as immunomodulators, aimed to manipulate and suppress immune defense signaling triggered upon nematode invasion. Plant development and defense rely mainly on hormone regulation. Herein, a metabolomic profiling of oxylipins and hormones composition of tomato roots were performed using LC-MS/MS, indicating a fluctuation in oxylipins profile in a compatible interaction. Moreover, further attention was given to uncover the implication of WRKYs transcription factors in regulating nematode development. In addition, in order to identify genes that might interact with the lipidomic defense pathway induced by oxylipins, a RNAseq was performed by exposing M. javanicasecond-stage juveniles to tomato protoplast, 9-HOT and 13-KOD oxylipins. This transcriptome generated a total of 4682 differentially expressed genes (DEGs). Being interested in effectors, we seek for DEGs carrying a predicted secretion signal peptide. Among the DEGs including signal peptide, several had homology with known effectors in other nematode species, other unknown potentially secreted proteins may have a role as root-knot nematodes' effectors which might interact with lipid signaling. The molecular interaction of LOX proteins with the Cyst nematode effectors illustrate the nematode strategy in manipulating plant lipid signals. The function of several other effectors in manipulating plant defense signals, as well as lipids signals, weakening cell walls, attenuating feeding site function and development are still being studied in depth for several novel effectors. As direct outcome of this project, the accumulating findings will be utilized to improve our understanding of the mechanisms governing critical life-cycle phases of the parasitic M. incognita RKN, thereby facilitating design of effective controls based on perturbation of nematode behavior—without producing harmful side effects. The knowledge from this study will promote genome editing strategies aimed at developing nematode resistance in tomato and other nematode-susceptible crop species in Israel and the United States.
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Taylor, Oliver-Denzil, Amy Cunningham,, Robert Walker, Mihan McKenna, Kathryn Martin, and Pamela Kinnebrew. The behaviour of near-surface soils through ultrasonic near-surface inundation testing. Engineer Research and Development Center (U.S.), September 2021. http://dx.doi.org/10.21079/11681/41826.

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Seismometers installed within the upper metre of the subsurface can experience significant variability in signal propagation and attenuation properties of observed arrivals due to meteorological events. For example, during rain events, both the time and frequency representations of observed seismic waveforms can be significantly altered, complicating potential automatic signal processing efforts. Historically, a lack of laboratory equipment to explicitly investigate the effects of active inundation on seismic wave properties in the near surface prevented recreation of the observed phenomena in a controlled environment. Presented herein is a new flow chamber designed specifically for near-surface seismic wave/fluid flow interaction phenomenology research, the ultrasonic near-surface inundation testing device and new vp-saturation and vs-saturation relationships due to the effects of matric suction on the soil fabric.
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Brown, C. T., V. G. McDonnell, and D. G. Talley. Accounting for Laser Extinction, Signal Attenuation, and Secondary Emission While Performing Optical Patternation in a Single Plane. Fort Belvoir, VA: Defense Technical Information Center, January 2002. http://dx.doi.org/10.21236/ada410872.

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Farahbod, A. M., and J. F. Cassidy. An overview of seismic attenuation in the Northern Appalachians Seismic Zone, New Brunswick and Nova Scotia. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329702.

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In this study we investigated coda-wave attenuation (QC) from the northern Appalachian region of eastern Canada in the two provinces of New Brunswick and Nova Scotia. We used earthquake recordings from 8 broadband and 2 short period seismograph stations of the Canadian National Seismograph Network (CNSN) across the region. Our dataset is comprised of 476 earthquakes recorded between 1983 and 2021 with magnitudes ranging from 1.5 to 4.1, depths from 0 to 20 km (with the vast majority being <10 km) and epicentral distances of 5 to 100 km. This gives a total of 261 high signalto- noise (S/N) traces (S/N greater than or equal to 5.0) useful for QC calculation (with a maximum ellipse parameter, a2, of 100) across the region. Coda windows were selected to start at tc = 2tS (two times the travel time of the direct S wave), and were filtered at center frequencies of 2, 4, 8, 12 and 16 Hz. Our study reveals a consistent pattern. We find that in the northern New Brunswick, the lowest Q0 values (e.g., Q0 of 61) are at station KLN which is the closest station to the epicenter of the 1982 Miramichi earthquake (M 5.8). The highest Q0 values that we find (e.g., Q0 of 178) are at station GGN, located in the southern New Brunswick. Smaller Q0 values for stations in the north (closer to the Charlevoix-Kamouraska seismic zone or Miramichi source area) is explained by Jin and Aki's (1988) finding that Q0 is lower in the vicinity of large earthquakes. An average for all the data results in a Q relationship of QC = 99f0.96 for the frequency band of 2 to 16 Hz for the entire region.
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Farahbod, A. M., and J. F. Cassidy. An overview of seismic attenuation in the Eastern Canadian Arctic and the Hudson Bay Complex, Manitoba, Newfoundland and Labrador, Nunavut, Ontario, and Quebec. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330396.

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In this study we investigated coda-wave attenuation (QC) from the eastern Canadian Arctic in Nunavut and the Hudson Bay complex including portions of northern Manitoba, Ontario, Quebec and Labrador. We used earthquake recordings from 15 broadband and 3 short period seismograph stations of the Canadian National Seismic Network (CNSN) and 29 broadband stations of the POLARIS network across the region. Our dataset is comprised of 637 earthquakes recorded between 1985 and 2021 with magnitudes ranging from 1.3 to 6.1, depths from 0 to 20 km and epicentral distances of 5 to 100 km. This gives a total of 246 high signal-to-noise (S/N) traces (S/N[lesser/equal]5.0) useful for QC calculation (with a maximum ellipse parameter, a2, of 100) across the region. Coda windows were selected to start at tc = 2tS (two times the travel time of the direct S wave), and were filtered at center frequencies of 2, 4, 8, 12 and 16 Hz. Our study reveals a consistent pattern. We find that in the northern section of the study area, the highest Q0 values (e.g., Q0 of 110 and 112) are at station POIN and station RES, respectively, which are located in the older Archean province. The lowest Q0 values that we find (e.g., Q0 of 55 and 61) are at station AKVQ and IVKQ respectively, located in northern Quebec. Smaller Q0 values for stations in the south are explained by the younger age of the rocks and proximity to the main fault systems. An average for all the data results in a Q relationship of QC = 82f1.08 for the frequency band of 2 to 16 Hz for the entire region.
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Ron, Eliora, and Eugene Eugene Nester. Global functional genomics of plant cell transformation by agrobacterium. United States Department of Agriculture, March 2009. http://dx.doi.org/10.32747/2009.7695860.bard.

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The aim of this study was to carry out a global functional genomics analysis of plant cell transformation by Agrobacterium in order to define and characterize the physiology of Agrobacterium in the acidic environment of a wounded plant. We planed to study the proteome and transcriptome of Agrobacterium in response to a change in pH, from 7.2 to 5.5 and identify genes and circuits directly involved in this change. Bacteria-plant interactions involve a large number of global regulatory systems, which are essential for protection against new stressful conditions. The interaction of bacteria with their hosts has been previously studied by genetic-physiological methods. We wanted to make use of the new capabilities to study these interactions on a global scale, using transcription analysis (transcriptomics, microarrays) and proteomics (2D gel electrophoresis and mass spectrometry). The results provided extensive data on the functional genomics under conditions that partially mimic plant infection and – in addition - revealed some surprising and significant data. Thus, we identified the genes whose expression is modulated when Agrobacterium is grown under the acidic conditions found in the rhizosphere (pH 5.5), an essential environmental factor in Agrobacterium – plant interactions essential for induction of the virulence program by plant signal molecules. Among the 45 genes whose expression was significantly elevated, of special interest is the two-component chromosomally encoded system, ChvG/I which is involved in regulating acid inducible genes. A second exciting system under acid and ChvG/Icontrol is a secretion system for proteins, T6SS, encoded by 14 genes which appears to be important for Rhizobium leguminosarum nodule formation and nitrogen fixation and for virulence of Agrobacterium. The proteome analysis revealed that gamma aminobutyric acid (GABA), a metabolite secreted by wounded plants, induces the synthesis of an Agrobacterium lactonase which degrades the quorum sensing signal, N-acyl homoserine lactone (AHL), resulting in attenuation of virulence. In addition, through a transcriptomic analysis of Agrobacterium growing at the pH of the rhizosphere (pH=5.5), we demonstrated that salicylic acid (SA) a well-studied plant signal molecule important in plant defense, attenuates Agrobacterium virulence in two distinct ways - by down regulating the synthesis of the virulence (vir) genes required for the processing and transfer of the T-DNA and by inducing the same lactonase, which in turn degrades the AHL. Thus, GABA and SA with different molecular structures, induce the expression of these same genes. The identification of genes whose expression is modulated by conditions that mimic plant infection, as well as the identification of regulatory molecules that help control the early stages of infection, advance our understanding of this complex bacterial-plant interaction and has immediate potential applications to modify it. We expect that the data generated by our research will be used to develop novel strategies for the control of crown gall disease. Moreover, these results will also provide the basis for future biotechnological approaches that will use genetic manipulations to improve bacterial-plant interactions, leading to more efficient DNA transfer to recalcitrant plants and robust symbiosis. These advances will, in turn, contribute to plant protection by introducing genes for resistance against other bacteria, pests and environmental stress.
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