Academic literature on the topic 'System identification- Geophysical signals'
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Journal articles on the topic "System identification- Geophysical signals"
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Lubis, Muhammad Zainuddin, Kasih Anggraini, Husnul Kausarian, and Sri Pujiyati. "Review: Marine Seismic And Side-Scan Sonar Investigations For Seabed Identification With Sonar System." Journal of Geoscience, Engineering, Environment, and Technology 2, no. 2 (June 1, 2017): 166. http://dx.doi.org/10.24273/jgeet.2017.2.2.253.
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Marine seismic reflection data have been collected for decades and since the mid-to late- 1980s much of this data is positioned relatively accurately. Marine geophysical acquisition of data is a very expensive process with the rates regularly ship through dozens of thousands of euros per day. Acquisition of seismic profiles has the position is determined by a DGPS system and navigation is performed by Hypack and Maxview software that also gives all the offsets for the equipment employed in the survey. Examples of some projects will be described in terms of the project goals and the geophysical equipment selected for each survey and specific geophysical systems according to with the scope of work. For amplitude side scan sonar image, and in the multi-frequency system, color, becoming a significant properties of the sea floor, the effect of which is a bully needs to be fixed. The main confounding effect is due to absorption of water; geometric spread; shape beam sonar function (combined transmit-receive sonar beam intensity as a function of tilt angle obtained in this sonar reference frame); sonar vehicle roll; form and function of the seabed backscatter (proportion incident on the seabed backscattered signal to sonar as a function of the angle of incidence relative to the sea floor); and the slope of the seabed. The different angles of view are generated by the translation of the sonar, because of the discrete steps involved by the sequential pings, the angular sampling of the bottom.
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Abramovych, А. О. "IMPROVING THE EDDY CURRENT IDENTIFIER OF METALS BASED ON THE CORRELATION APPROACH." Radio Electronics, Computer Science, Control, no. 4 (December 3, 2022): 7. http://dx.doi.org/10.15588/1607-3274-2022-4-1.
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Context. The article considers the problem of improving the eddy current device for metal identification on the basis of the correlation approach. This approach is convenient for the accumulation of a database of known leading materials, as well as for the comparison of the signal from an unknown metal object with the available standards in the database. The proposed approach allows to determine the type of metal from which the sample is made, without damaging its surface.
Objective. The aim of the work is the identification of metals by type on the feedback signals from the eddy current converter, due to the identification of new informative features and the creation of a database of images of metals.
Method. The paper presents the results of an experimental study of the proposed approach to increase the reliability of identification of metal objects that are detected using an eddy current device. These studies are conducted on the basis of a radio system that operates on the eddy current principle and has low-frequency magnetic loop antennas. The eddy current method allows the identification of metals by type remotely and without damaging their surface, in contrast to X-ray fluorescence, optical emission or chemical methods. A correlation approach for processing the response signal spectrum from a hidden metal object is proposed. The correlation approach allows to increase the reliability of the identification of metals by type when processing the signal in the spectral region based on the Fourier transform. Studies have been conducted on the example of metals that have similar spectral characteristics (silver, gold, lead). The updated approach allowed to increase the percentage difference between the information parameters of signals – responses from 1.87% to 5.02% for silver and gold, from 2.24% to 4.34% for silver and lead and from 0.36% to 0.7% for gold and lead.
Results. The developed radio system is a laboratory model, which consists of an analog part and a digital one. The analog part is an antenna unit, a signal amplifier and a bandpass filter, a digital part – a microcontroller with an ADC for digitizing and transmitting data to a laptop, which software implements the proposed approaches to signal processing. The paper experimentally confirmed the possibility of using a radio engineering system to solve the problem of metal identification within a subset of nonmagnetic and magnetic materials.
Conclusions. The development of modern eddy current devices is aimed at increasing the reliability of the identification the hidden metal objects, which is relevant in geophysical exploration, archeology, and law enforcement agencies in the search for hidden non-ferrous metals. The development and improvement of such systems includes both the development the hardware and the discovery new information parameters in the feedback signals from metals. One such direction may be the correlation approach to signal processing in the spectral region.
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Abazarsa, Fariba, Fariborz Nateghi, S. Farid Ghahari, and Ertugrul Taciroglu. "Blind Modal Identification of Non-Classically Damped Systems from Free or Ambient Vibration Records." Earthquake Spectra 29, no. 4 (November 2013): 1137–57. http://dx.doi.org/10.1193/031712eqs093m.
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A significant segment of system identification literature on civil structures is devoted to response-only identification, simply because lack of measurements of input excitations for civil structures is a fairly common scenario. In recent years, several researchers have successfully adapted a second-order blind identification (SOBI) technique—a method originally developed for “blind source separation” of audio signals—to response-only identification of mechanical and civil structures. However, this development had been confined to fully instrumented classically damped systems. While several approaches have been proposed recently for extending SOBI to non-classically damped systems, they all require additional data such as velocity or analytic signals. Herein, we present a version of SOBI that requires only acceleration signals recorded during free or ambient vibration tests, and yields the system's complex mode shapes, natural frequencies, and damping ratios. Performance of the proposed technique is demonstrated through two synthetic examples: a ten-story structure possessing a passive control system, and a soil-structure system with seven degrees of freedom (seven-DOF).
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Bodin, Jacques, Gilles Porel, Benoît Nauleau, and Denis Paquet. "Delineation of discrete conduit networks in karst aquifers via combined analysis of tracer tests and geophysical data." Hydrology and Earth System Sciences 26, no. 6 (April 1, 2022): 1713–26. http://dx.doi.org/10.5194/hess-26-1713-2022.
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Abstract. Assessment of the karst network geometry based on field data is an important challenge in the accurate modeling of karst aquifers. In this study, we propose an integrated approach for the identification of effective three-dimensional (3D) discrete karst conduit networks conditioned on tracer tests and geophysical data. The procedure is threefold: (i) tracer breakthrough curves (BTCs) are processed via a regularized inversion procedure to determine the minimum number of distinct tracer flow paths between injection and monitoring points, (ii) available surface-based geophysical data and borehole-logging measurements are aggregated into a 3D proxy model of aquifer hydraulic properties, and (iii) single or multiple tracer flow paths are identified through the application of an alternative shortest path (SP) algorithm to the 3D proxy model. The capability of the proposed approach to adequately capture the geometrical structure of actual karst conduit systems mainly depends on the sensitivity of geophysical signals to karst features, whereas the relative completeness of the identified conduit network depends on the number and spatial configuration of tracer tests. The applicability of the proposed approach is illustrated through a case study at the Hydrogeological Experimental Site (HES) in Poitiers, France.
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Akhi, A. V. "Akhi A.V. Efficiency of Identification of Complex Noise-Like Signal Classes by Dolphins (<i>Tursiops truncatus</i>) under Simultaneous Presentation Spatial Uncertainty." Fundamental and Applied Hydrophysics 16, no. 1 (April 23, 2023): 90–97. http://dx.doi.org/10.59887/fpg/vxe3-6531-nkup.
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The possibility of dolphin’s auditory system to solve the complex problem of identifying and classifying noise-like signals according to certain invariant features is considered under conditions of spatial uncertainty of their simultaneous presentation. There was studied the ability of bottlenose dolphins, which were trained to recognize and classify such signals, to select a certain class of signals from several that sound simultaneously. The dolphin had to recognize a positive class signal with a pair of simultaneously sounding signals: positive-negative (alternative choice) and with simultaneously sounding three signals: positive-negative-negative (multiple choice). It’s shown that the dolphin effectively solves the problem with a simple alternative choice of two signal sources, at the limit of reliability when choosing from three sources and unreliable when choosing from more sources.
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KOH, C. G., and M. J. PERRY. "STRUCTURAL DAMAGE QUANTIFICATION BY SYSTEM IDENTIFICATION." Journal of Earthquake and Tsunami 01, no. 03 (September 2007): 211–31. http://dx.doi.org/10.1142/s1793431107000134.
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After a disaster such as an earthquake has struck, the damage assessment of the affected buildings, bridges and other forms of structures is often urgently required for follow-up action. Research in using system identification for damage assessment in a quantifiable and non-destructive way has rapidly increased in recent years, due to advances in computing power and sensing technology. Though considerable progress has been made, many challenges still remain in achieving robust and effective identification of large structural systems using incomplete and noisy measurement signals. In this paper a novel strategy to tackle this problem is presented. A modified genetic algorithm (GA) strategy incorporating a search space reduction method, progressively and adaptively reduces the search space for each unknown parameter. By concurrent evolution of multiple species, it provides an excellent balance between exploration of the search space and exploitation of good solutions. The modified GA is incorporated into a damage detection strategy that works by comparing identified parameters for the undamaged and damaged structures and quantifies damage as a relative change in the stiffness of a member or a group of members. The additional information obtained from the analysis of the undamaged structure is used to greatly improve speed and accuracy in the identification of the damaged structure. Numerical studies on 10 and 20 degree-of-freedom (DOF) systems and an experimental study of a 7-storey small-scale steel frame are presented to illustrate the applicability of the method in accurately identifying even small amounts of damage.
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Zamora Santacruz, Mario Fernando, Mario RUIZ, and Jose OSORNO. "The Exploration of Hydrocarbons and Mining & Energy Resources Using Non-Seismic Methods - Nuclear Magnetic Resonance Technology." Technium: Romanian Journal of Applied Sciences and Technology 2, no. 7 (December 22, 2020): 372–89. http://dx.doi.org/10.47577/technium.v2i7.2258.
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Nuclear Magnetic Resonance-based technology is a geophysical method used in the exploration of hydrocarbons and other mineral resources, by studying electromagnetic signals from natural sources. The foregoing method has three phases: the first phase encompasses the identification of areas where hydrocarbons or other minerals are present at a regional level, using remote sensors; the anomalies identified are studied in detail in the second phase, during which the passive acquisition of electromagnetic signals on the surface with under 30m spacing be- tween points allows demarcating the areas with the highest and lowest intensity, to finally obtain stratigraphic columns at points selected after measuring the basic parameters using Vertical Probing with Electro – Resonance.
The study conducted for Agencia Nacional De Hidrocarburos (ANH) evaluated a total of 1083 Km2 spread over five areas whose topography, climate and vegetation restricted the acquisition of geological and geophysical data with traditional methods. Two of the five polygons are located in the part of the Chocó basin called Ánimas (163 km2) and Istmina (344 km2) while Timbiquí (159 km2), Remolino (200 km2) and Guayacana (217 km2) are in the Tumaco basin. The results of the satellite stage included the identification of 178 km2 of liquid hydrocarbon type anomalies in the Choco basin and 22 km2 of gaseous hydrocarbon-type anomalies in the Tumaco basin. The anomaly located in Animas was chosen for the field stage. It was detailed by demarcating the areas with the highest and lowest intensity, in which vertical probing took place, allowing for the in-depth characterization of nine parameters (H2O, CaCO3, Si, C10 H22, CH4, C21H44, Clays, Albite, Anorthite) in up to 4,000 m, identifying intervals showing a significant presence of hydrocarbons at 3,280 ft, 6,950 ft and 12,210 ft with a 36 ft.-average thickness, and an estimated basement depth of 12,650 ft. The correlation with seismic data allowed confirming the results, thus proving that the use of non-seismic methods in exploration and prospection processes allow for a better understanding of petroleum systems, while reducing uncertainty and exploratory hazards
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Munoz-Martin, Joan Francesc, Raul Onrubia, Daniel Pascual, Hyuk Park, Adriano Camps, Christoph Rüdiger, Jeffrey Walker, and Alessandra Monerris. "Untangling the Incoherent and Coherent Scattering Components in GNSS-R and Novel Applications." Remote Sensing 12, no. 7 (April 9, 2020): 1208. http://dx.doi.org/10.3390/rs12071208.
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As opposed to monostatic radars where incoherent backscattering dominates, in bistatic radars, such as Global Navigation Satellite Systems Reflectometry (GNSS-R), the forward scattered signals exhibit both an incoherent and a coherent component. Current models assume that either one or the other are dominant, and the calibration and geophysical parameter retrieval (e.g., wind speed, soil moisture, etc.) are developed accordingly. Even the presence of the coherent component of a GNSS reflected signal itself has been a matter of discussion in the last years. In this work, a method developed to separate the leakage of the direct signal in the reflected one is applied to a data set of GNSS-R signals collected over the ocean by the Microwave Interferometer Reflectometer (MIR) instrument, an airborne dual-band (L1/E1 and L5/E5a), multi-constellation (GPS and Galileo) GNSS-R instrument with two 19-elements antenna arrays with 4 beam-steered each. The presented results demonstrate the feasibility of the proposed technique to untangle the coherent and incoherent components from the total power waveform in GNSS reflected signals. This technique allows the processing of these components separately, which increases the calibration accuracy (as today both are mixed and processed together), allowing higher resolution applications since the spatial resolution of the coherent component is determined by the size of the first Fresnel zone (300–500 meters from a LEO satellite), and not by the size of the glistening zone (25 km from a LEO satellite). The identification of the coherent component enhances also the location of the specular reflection point by determining the peak maximum from this coherent component rather than the point of maximum derivative of the incoherent one, which is normally noisy and it is blurred by all the glistening zone contributions.
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Kaczmarek, Adrian, and Bernard Kontny. "Identification of the Noise Model in the Time Series of GNSS Stations Coordinates Using Wavelet Analysis." Remote Sensing 10, no. 10 (October 10, 2018): 1611. http://dx.doi.org/10.3390/rs10101611.
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Analysis of the time series of coordinates is extremely important in geodynamic research. Indeed, the correct interpretation of coordinate changes may facilitate an understanding of the diverse geophysical processes taking place in the earth’s crust. At present, when rigorously processing global navigation satellite system (GNSS) observations, the influence of deformations in the surface of the earth’s crust is not considered. This article presents signal modelling for the influence on the analysis of noise occurring in the time series of GNSS station coordinates. The modelling of coordinate time series was undertaken using the classic least-squares estimation (LSE) method and the inverse continuous wavelet transform (CWT). In order to determine the type of noise character, the coefficient spectral index was used. Analyses have demonstrated that the nature of noise in measurement data does not depend on the signal estimation method. The differences between classic modelling (LSE) of the time series with annual and semiannual oscillation and signal reconstruction are very small ( Δ κ = 0.0 ÷−0.2).
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Steinitz, G., P. Kotlarsky, and O. Piatibratova. "Indications for influence of artificial (man-made) activity on radon signals, in simulation experiments." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2195 (November 2016): 20160311. http://dx.doi.org/10.1098/rspa.2016.0311.
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Radon (Rn-222; a radioactive noble gas) is characterized by large temporal variations that differ significantly from variations of (i) other trace elements in geogas (noble gases); (ii) variation patterns of other dynamic geophysical systems (atmospheric, tidal). Consensus exists that there is no simple and straightforward understanding of the phenomena and its behaviour. This lacuna in the understanding of the underlying principles hampers the development of applications—such as radon as a proxy of processes in the seismogenic context. Using results from field investigations and simulation experiments the GSI suggested that an unidentified extraterrestrial component, probably in solar radiation, drives periodic radon signals in the diurnal and annual frequency bands. Recent findings from experimental investigations shed additional perspectives allowing a new evaluation of the issue. Particular transient signals, measured with alpha and gamma detectors, are interpreted to reflect the influence of artificial activity. Criteria are (i) signals lasting several hours that occur around midday on workdays (Sunday–Thursday); (ii) signals composed of a train of around 10 strong pulses, each lasting less than 15 min, occurring within several hours once a week, from Wednesday afternoon/evening to Thursday morning. A first interpretation is that an unidentified artificial activity of some sort (industrial?) generates and emits an unidentified agent that reaches enhanced confined mode experiments at the GSI laboratory, which respond to the incoming agent in the form of radon signals. Developing the capability of identification of such an earth-bound source generating an influencing agent is a key step towards understanding of external influence on radioactivity of radon.
Dissertations / Theses on the topic "System identification- Geophysical signals"
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AlHilal, M. H. "System identification using pseudorandom signals." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635747.
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Solomou, Michael. "System identification in the presence of nonlinear distortions using multisine signals." Thesis, University of South Wales, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289160.
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Deng, Qingwei 1968. "Identification of dendritic targeting signals of voltage-gated potassium channel 3." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82219.
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Members of voltage-gated potassium channel subfamily 3 (Kv3) have been extensively demonstrated to play a significant role in facilitating function of "fast-firing" neurons in the central nervous system. Kv3.1 and Kv3.3 channels, members of Kv3 channel subfamily, have different distribution profiles on the regional level of brain and on the subcellular level of neurons in mammals and in weakly electric fish, according to mRNA hybridizations in situ and immunohistochemical analysis. In mammals, Kv3.1 channels are expressed in soma, axon and proximal dendrites as well as presynaptic membrane of "fast-firing" neurons. In weakly electric fish (Apteronotus), Kv3.1 channels are distributed in the soma, in the basilar dendrites and in the proximal apical dendrites of pyramidal neurons; on the other hand, Kv3.3 channels are expressed in a larger region: soma, basilar dendrites and entire apical dendrites of these cells. Mechanisms underlying differential subcellular distribution of Kv3.1 and Kv3.3 channels in the apical dendritic compartment of pyramidal neurons are unknown. In order to identify peptide sequences responsible for the differential subcellular localization, I have used Semliki Forest virus as a modified viral expression system (PDE) in vivo to study dendritic targeting mechanisms in the pyramidal neurons of electrosensory lateral line lobe (ELL), where the primary processing for afferent input occurs in the apteronotid electrosensory system.
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PIOLDI, Fabio. "Time and Frequency Domain output-only system identification from earthquake-induced structural response signals." Doctoral thesis, Università degli studi di Bergamo, 2017. http://hdl.handle.net/10446/77137.
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Output-only Time and Frequency Domain system identification techniques are developed in this doctoral dissertation towards the challenging assessment of current structural dynamic properties of buildings from earthquake-induced structural response signals, at simultaneous heavy damping. Three different Operational Modal Analysis (OMA) techniques, namely a refined Frequency Domain Decomposition (rFDD) algorithm, an improved Data-Driven Stochastic Subspace Identification (SSI-DATA) procedure and a novel Full Dynamic Compound Inverse Method (FDCIM) are formulated and implemented within MATLAB, and exploited for the strong ground motion modal dynamic identification of selected buildings.
First, the three OMA methods are validated by the adoption of synthetic earthquake-induced structural response signals, generated from numerical integration on benchmark linear shear-type frames. Then, real seismic response signals are effectively processed, by getting even closer to real Earthquake Engineering identification scenarios. In the end, the three OMA methods are systematically applied and compared.
The present thesis demonstrates the reliability and effectiveness of such advanced OMA methods, as convenient output-only modal identification tools for Earthquake Engineering and Structural Health Monitoring purposes.
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Speckhahn, Marcus M. "Identification of acoustically active Arctic pressure ridges through the use of RADARSAT Geophysical Processor System (RGPS) sea ice products." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA351618.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, June 1998."June 1998." Thesis advisor(s): Robert H. Bourke, James H. Wilson. Includes bibliographical references (p. 301-304). Also available online.
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Tuffner, Francis K. "Computationally efficient weighted updating of statistical parameter estimates for time varying signals with application to power system identification." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1674094221&sid=4&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Kuramoto, André Seichi Ribeiro. "Projeto de sinais de excitação para identificação multivariável de plantas industriais." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3139/tde-07112016-144658/.
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Neste trabalho são discutidos e avaliados métodos de construção de conjuntos de sinais de excitação para identificação de sistemas. Esse estudo é realizado tendo como objetivo aplicações na indústria de processos, particularmente no refino de petróleo. As restrições operacionais da indústria de refino de petróleo estão cada vez mais severas em virtude do aumento da demanda energética, qualidade de derivados, variações de preço de petróleo, concorrência no mercado de derivados e outros fatores econômicos, ambientais e de eficiência energética. Nesse cenário, é crescente o uso de técnicas de controle preditivo por modelos e, consequentemente, a demanda por identificação de plantas de processamento. As características particulares das plantas de processamento e de sua operação impõem restrições ao projeto e à aplicação de sinais de excitação. Vários métodos de construção de sinais encontrados na literatura e outros três propostos neste trabalho são avaliados e comparados com referência ao atendimento a essas restrições. Uma das principais restrições para a aplicação de sinais de excitação para identificação é relativa ao tempo disponível para excitação da planta. Assim, para o bom uso desse período, faz-se necessário garantir o sucesso de um experimento previamente à sua realização. Na literatura, encontram-se várias medidas de desempenho de sinais de excitação possíveis de serem obtidas previamente ao experimento de identificação. Neste trabalho, s~ao propostas duas novas medidas que complementam essas na avaliação dos conjuntos de sinais previamente ao experimento. A eficácia dos métodos de construção e das medidas de desempenho de sinais de excitação é avaliada por meio de simulação de identificação multivariável de duas plantas típicas de refinarias. As conclusões deste trabalho apresentam em síntese essas avaliações, como também sugestões de trabalhos futuros que visam à continuidade da pesquisa desenvolvida aqui.In this work methods for generating sets of excitation signals for system identification are discussed and evaluated. This study is focused on applications in the process industries, particularly in oil refining. The operational constraints of the oil refining industry are becoming increasingly severe due to increased energy demand, quality of products, oil price variations,market competition and other economic, environmental and energy efficiency factors. In this scenario the use of model predictive control techniques is increasing, thus the demand for plant identification as well. The particular characteristics of the processing plants impose restrictions to the project and application of excitation signals. Various methods for generating signals accessible in the literature and three new others proposed in this work are compared with reference to these restrictions. One of the main constraints for applying excitation signals for identification is relative to the period available for excitation of the plant. Thus, for the proper use of this time interval, it is necessary to ensure the success of an experiment prior to its implementation. In the literature there are several performance measurements for evaluation of sets of excitation signals prior to the experiment. This work proposes two new measures to complement the evaluation. The effectiveness of the generating methods and performance measurements for excitation signals is evaluated by simulation of multivariable identification of two typical oil refining plants. The conclusions of this work briefly present these evaluations, as well as some suggestions of future work for the continuity of the current research.
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LIMA, Rafael Bezerra Correia. "Metodologia para identificação de sistemas em espaço de estados por meio de excitações pulsadas." Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1287.
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Nesse trabalho são apresentadas contribuições na área de identificação de sistemas representados em espaço de estados. E proposta uma metodologia completa para estimação de modelos que representem as principais dinâmicas de processos industriais. O fluxo natural das procedimentos de identificação consiste da coleta experimental dos dados, seguido pela escolha dos modelos candidatos e da utilização de um critério de ajuste que selecione o melhor modelo possível. Nesse sentido é proposta uma metodologia para estimativa de modelos em espaço de estados, utilizando excitações pulsadas. A abordagem desenvolvida combina algoritmos precisos e eficientes com experimentos rápidos, adequados a ambientes industriais. O projeto das excitações é realizado em tempo real, por meio de informações coletadas em um curto experimento inicial, baseado em uma única oscilação de uma estrutura realimentada por um relê. Esse mecanismo possibilita uma estimativa preliminar do atraso e da constante de tempo dominante do sistema. O método de identificação proposto é baseado na teoria de realizações de Kalman. É apresentada uma reformulação do problema de realizações clássico, para comportar sinais de entrada pulsados. Essa abordagem se mostra computacionalmente eficiente, assim como apresenta resultados semelhantes aos métodos de benehmark. A técnica possibilita também a estimativa de atrasos de transporte e a inserção de conhecimentos prévios por meio de um problema de otimização com restrições via LMI Linear Matrix Incqualities. Em muitos casos, somente as características principais do sistema são relevantes em um projeto de sistema de controle. Portanto é proposta uma técnica para obtenção de modelos de primeira ordem com atraso, a partir da redução de modelos balanceados em espaço de estados. Por fim, todas as contribuições discutidas nesse trabalho de tese são validadas em uma série de plantas experimentais em escala de laboratório. Plantas essas, projetadas e construídas com o intuito de emular o cotidiano operacional de instalações industriais reais.
This work Íntroduces contributions related to thc field of systems identification of state space models. It is proposed a complete methodology for modei estimation that encompasses the main dynamics of industrial processes. The natural flxix of the identification procedures rests on the the empirical collection of data followed by the choice of candidate modela and posterior use ot an adjusting criteria that drafts the best model amoug the contenders. In this sense. a uew methodology is proposed for models estimation in state spaces using pulsed excitation signal. The developed approach combines accurate and efhcient algorithms with quick experíments whose are suitable for the industrial environment. The excitatiou design is performed in real time by means of information collected in a snort mitíai experíment based in an single oscillation of a relay feedback. This mechanism allows a preliminary estimation of both delay and time constant prevalent in the system. The identification method proposed is based on Kalmairs realization theory. The thesis íntroduces a reformulation of the classic realization problem so it can admit pulsed input signals. This approaíth show itself as computationally efficient as well as provides similar results eompared to those obtained when perfonning the benchmark methods. Moreover, the technic allows the transport delay estimation and insertion of prior knowledge by means of an optimization problem with restrictions via linear matrix inequalities restrictions. In many cases only the characteristics of the main system are relevant in control systems design. Therefore a technique for the attainment first order models with time delay based on balanced state space models reduction. Lastly ali the contributions provided aíong the thesis are discussed and validated in a series of pilot scale plants. designed and built to emulate the operational cycle in real industrial plants.
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Kasaei, Shohreh. "Fingerprint analysis using wavelet transform with application to compression and feature extraction." Thesis, Queensland University of Technology, 1998. https://eprints.qut.edu.au/36053/7/36053_Digitised_Thesis.pdf.
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The main goal of this research is to design an efficient compression al~
gorithm for fingerprint images. The wavelet transform technique is the
principal tool used to reduce interpixel redundancies and to obtain a parsimonious
representation for these images. A specific fixed decomposition
structure is designed to be used by the wavelet packet in order to save on the
computation, transmission, and storage costs. This decomposition structure
is based on analysis of information packing performance of several decompositions,
two-dimensional power spectral density, effect of each frequency
band on the reconstructed image, and the human visual sensitivities. This
fixed structure is found to provide the "most" suitable representation for
fingerprints, according to the chosen criteria.
Different compression techniques are used for different subbands, based
on their observed statistics. The decision is based on the effect of each subband
on the reconstructed image according to the mean square criteria as
well as the sensitivities in human vision. To design an efficient quantization
algorithm, a precise model for distribution of the wavelet coefficients is developed.
The model is based on the generalized Gaussian distribution. A least
squares algorithm on a nonlinear function of the distribution model shape
parameter is formulated to estimate the model parameters. A noise shaping
bit allocation procedure is then used to assign the bit rate among subbands.
To obtain high compression ratios, vector quantization is used. In this
work, the lattice vector quantization (LVQ) is chosen because of its superior
performance over other types of vector quantizers. The structure of a lattice
quantizer is determined by its parameters known as truncation level and scaling
factor. In lattice-based compression algorithms reported in the literature
the lattice structure is commonly predetermined leading to a nonoptimized
quantization approach. In this research, a new technique for determining the
lattice parameters is proposed. In the lattice structure design, no assumption
about the lattice parameters is made and no training and multi-quantizing
is required. The design is based on minimizing the quantization distortion
by adapting to the statistical characteristics of the source in each subimage.
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Abstract Abstract
Since LVQ is a multidimensional generalization of uniform quantizers, it
produces minimum distortion for inputs with uniform distributions. In order
to take advantage of the properties of LVQ and its fast implementation,
while considering the i.i.d. nonuniform distribution of wavelet coefficients,
the piecewise-uniform pyramid LVQ algorithm is proposed. The proposed
algorithm quantizes almost all of source vectors without the need to project
these on the lattice outermost shell, while it properly maintains a small codebook
size. It also resolves the wedge region problem commonly encountered
with sharply distributed random sources. These represent some of the drawbacks
of the algorithm proposed by Barlaud [26). The proposed algorithm
handles all types of lattices, not only the cubic lattices, as opposed to the algorithms
developed by Fischer [29) and Jeong [42). Furthermore, no training
and multiquantizing (to determine lattice parameters) is required, as opposed
to Powell's algorithm [78).
For coefficients with high-frequency content, the positive-negative mean
algorithm is proposed to improve the resolution of reconstructed images.
For coefficients with low-frequency content, a lossless predictive compression
scheme is used to preserve the quality of reconstructed images. A method
to reduce bit requirements of necessary side information is also introduced.
Lossless entropy coding techniques are subsequently used to remove coding
redundancy.
The algorithms result in high quality reconstructed images with better
compression ratios than other available algorithms. To evaluate the proposed
algorithms their objective and subjective performance comparisons
with other available techniques are presented.
The quality of the reconstructed images is important for a reliable identification.
Enhancement and feature extraction on the reconstructed images
are also investigated in this research. A structural-based feature extraction
algorithm is proposed in which the unique properties of fingerprint textures
are used to enhance the images and improve the fidelity of their characteristic
features. The ridges are extracted from enhanced grey-level foreground areas
based on the local ridge dominant directions. The proposed ridge extraction
algorithm, properly preserves the natural shape of grey-level ridges as well as
precise locations of the features, as opposed to the ridge extraction algorithm
in [81). Furthermore, it is fast and operates only on foreground regions, as
opposed to the adaptive floating average thresholding process in [68). Spurious
features are subsequently eliminated using the proposed post-processing
scheme.
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Karthikeyan, E. "Studies of system identification and denoising for geophysical signals." Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7928.
Full textBooks on the topic "System identification- Geophysical signals"
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Keith, Godfrey, ed. Perturbation signals for system identification. New York: Prentice Hall, 1993.
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Coca, D. Smoothing chaotic signals for system identification: A multiresolution wavelet decomposition approach. Sheffield: University of Sheffield, Department of Automatic Control and Systems Engineering, 1995.
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Progri, Ilir. Geolocation of RF signals: Principles and simulations. New York: Springer, 2011.
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Speckhahn, Marcus M. Identification of acoustically active Arctic pressure ridges through the use of RADARSAT Geophysical Processor System (RGPS) sea ice products. Monterey, Calif: Naval Postgraduate School, 1998.
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Ogunfunmi, Tokunbo. Adaptive Nonlinear System Identification: The Volterra and Wiener Model Approaches (Signals and Communication Technology). Springer, 2007.
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Adaptive Nonlinear System Identification: The Volterra and Wiener Model Approaches (Signals and Communication Technology). Springer, 2007.
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Progri, Ilir. Geolocation of RF Signals: Principles and Simulations. Springer, 2011.
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Progri, Ilir. Geolocation of RF Signals: Principles and Simulations. Springer, 2014.
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Progri, Ilir. Geolocation of RF Signals: Principles and Simulations. Springer, 2011.
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Identification of Acoustically Active Arctic Pressure Ridges Through theUse of RADARSAT Geophysical Processor System (RGPS) Sea Ice Products. Storming Media, 1998.
Find full textBook chapters on the topic "System identification- Geophysical signals"
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Haber, Robert, and László Keviczky. "Test Signals for Identification." In Nonlinear System Identification — Input-Output Modeling Approach, 119–98. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4481-0_2.
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Tan, Ai Hui, and Keith Richard Godfrey. "Design of Pseudorandom Signals for Linear System Identification." In Industrial Process Identification, 25–58. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-03661-4_2.
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Tan, Ai Hui, and Keith Richard Godfrey. "Design of Computer-Optimised Signals for Linear System Identification." In Industrial Process Identification, 59–94. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-03661-4_3.
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Lingener, A. "Determination of Frequency Responses by Means of Pseudorandom Signals." In Application of System Identification in Engineering, 483–97. Vienna: Springer Vienna, 1988. http://dx.doi.org/10.1007/978-3-7091-2628-8_13.
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Pillonetto, Gianluigi, Tianshi Chen, Alessandro Chiuso, Giuseppe De Nicolao, and Lennart Ljung. "Classical System Identification." In Regularized System Identification, 17–31. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-95860-2_2.
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AbstractSystem identification as a field has been around since the 1950s with roots from statistical theory. A substantial body of concepts, theory, algorithms and experience has been developed since then. Indeed, there is a very extensive literature on the subject, with many text books, like [5, 8, 12]. Some main points of this “classical” field are summarized in this chapter, just pointing to the basic structure of the problem area. The problem centres around four main pillars: (1) the observed data from the system, (2) a parametrized set of candidate models, “the Model structure”, (3) an estimation method that fits the model parameters to the observed data and (4) a validation process that helps taking decisions about the choice of model structure. The crucial choice is that of the model structure. The archetypical choice for linear models is the ARX model, a linear difference equation between the system’s input and output signals. This is a universal approximator for linear systems—for sufficiently high orders of the equations, arbitrarily good descriptions of the system are obtained. For a “good” model, proper choices of structural parameters, like the equation orders, are required. An essential part of the classical theory deals with asymptotic quality measures, bias and variance, that aim at giving the best mean square error between the model and the true system. Some of this theory is reviewed in this chapter for estimation methods of the maximum likelihood character.
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De Moor, Bart, Peter Van Overschee, and Wouter Favoreel. "Algorithms for Subspace State-Space System Identification: An Overview." In Applied and Computational Control, Signals, and Circuits, 247–311. Boston, MA: Birkhäuser Boston, 1999. http://dx.doi.org/10.1007/978-1-4612-0571-5_6.
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Markovsky, Ivan, Anton Amann, and Sabine Van Huffel. "Application of Filtering Methods for Removal of Resuscitation Artifacts from Human ECG Signals." In System Identification, Environmental Modelling, and Control System Design, 273–91. London: Springer London, 2012. http://dx.doi.org/10.1007/978-0-85729-974-1_14.
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Bo, L. I. U., Z. H. A. O. Jun, and Q. I. A. N. Jixin. "Design and Analysis of Test Signals for System Identification." In Computational Science – ICCS 2006, 593–600. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11758532_78.
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Westwick, David T., and Robert E. Kearney. "Identification of Multiple-Input Nonlinear Systems Using Non-White Test Signals." In Advanced Methods of Physiological System Modeling, 163–78. Boston, MA: Springer US, 1994. http://dx.doi.org/10.1007/978-1-4757-9024-5_8.
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Faghih, Rose T. "From Physiological Signals to Pulsatile Dynamics: A Sparse System Identification Approach." In Dynamic Neuroscience, 239–65. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-71976-4_10.
Full textConference papers on the topic "System identification- Geophysical signals"
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Palma, Gabriel, Ana Aquino, Patricia Monticelli, Luciano Verdade, Charles Markham, and Rafael Moral. "A machine vision system for avian song classification with CNN’s." In 24th Irish Machine Vision and Image Processing Conference. Irish Pattern Recognition and Classification Society, 2022. http://dx.doi.org/10.56541/mhzn4111.
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Soundscape ecologists aim to study the acoustic characteristics of an area that reflects natural processes [Schafer, 1977]. These sounds can be interpreted as biological (biophony), geophysical (geophony), and human-produced (anthrophony) [Pijanowski et al., 2011]. A common task is to use sounds to identify species based on the frequency content of a given signal. This signal can be further converted into spectrograms enabling other types of analysis to automate the identification of species. Based on the promising results of deep learning methods, such as Convolution Neural Networks (CNNs) in image classification, here we propose the use of a pre-trained VGG16 CNN architecture to identify two nocturnal avian species, namely Antrostomus rufus and Megascops choliba, commonly encountered in Brazilian forests. Monitoring the abundance of these species is important to ecologists to develop conservation programmes, detect environmental disturbances and assess the impact of human action. Specialists recorded sounds in 16-bit wave files at a sampling rate of 44Hz and classified the presence of these species. With the classified wave files, we created additional classes to visualise the performance of the VGG16 CNN architecture for detecting both species. We end up with six categories containing 60 seconds of audio of species vocalisation combinations and background only sounds. We produced spectrograms using the information from each RGB channel, only one channel (grey-scale), and applied the histogram equalisation technique to the grey-scale images. A comparison of the system performance using histogram equalised images and unmodified images was made. Histogram equalisation improves the contrast, and so the visibility to the human observer. Investigating the effect of histogram equalisation on the performance of the CNN was a feature of this study. Moreover, to show the practical application of our work, we created 51 minutes of audio, which contains more noise than the presence of both species (a scenario commonly encountered in field surveys). Our results showed that the trained VGG16 CNN produced, after 8000 epochs, a training accuracy of 100% for the three approaches. The test accuracy was 80.64%, 75.26%, and 67.74% for the RGB, grey-scaled, and histogram equalised approaches. The method’s accuracy on the synthetic audio file of 51 minutes was 92.15%. This accuracy level reveals the potential of CNN architectures in automating species detection and identification by sound using passive monitoring. Our results suggest that using coloured images to represent the spectrogram better generalises the classification than grey-scale and histogram equalised images. This study might develop future avian monitoring programmes based on passive sound recording, which significantly enhances sampling size without increasing cost.
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Tristanov, Alexander, Olga Lukovenkova, Yuri Marapulets, and Alina Kim. "Improvement of methods for sparse model identification of pulsed geophysical signals." In 2019 Signal Processing: Algorithms, Architectures, Arrangements, and Applications (SPA). IEEE, 2019. http://dx.doi.org/10.23919/spa.2019.8936817.
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Tsumura, K., and J. Maciejowski. "Optimal quantization of signals for system identification." In 2003 European Control Conference (ECC). IEEE, 2003. http://dx.doi.org/10.23919/ecc.2003.7085053.
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"Identification of sediment-related disaster based on seismic and acoustic signals ("MM-Identification")." In Earth System Sciences (ESS). Vienna: Austrian Academy of Sciences Press, 2018. http://dx.doi.org/10.1553/ess-mmidentifications1.
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Naik, Manjish, and Douglas Cochran. "Nonlinear system identification using compressed sensing." In 2012 46th Asilomar Conference on Signals, Systems and Computers. IEEE, 2012. http://dx.doi.org/10.1109/acssc.2012.6489039.
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Bhat, Harish S. "System Identification via the Adjoint Method." In 2021 55th Asilomar Conference on Signals, Systems, and Computers. IEEE, 2021. http://dx.doi.org/10.1109/ieeeconf53345.2021.9723391.
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Matta, Rafik, Johnny K. H. Lau, Foteini Agrafioti, and Dimitrios Hatzinakos. "Real-time continuous identification system using ECG signals." In 2011 24th IEEE Canadian Conference on Electrical and Computer Engineering (CCECE). IEEE, 2011. http://dx.doi.org/10.1109/ccece.2011.6030676.
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Bingham, Jeffrey T., and Marco P. Schoen. "Characterization of Myoelectric Signals Using System Identification Techniques." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59904.
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Human muscle motion is initiated in the central nervous system where a nervous signal travels through the body and the motor neurons excite the muscles to move. These signals, termed myoelectric signals, can be measured on the surface of the skin as an electrical potential. By analyzing these signals it is possible to determine the muscle actions the signals elicit, and thus can be used in manipulating smart prostheses and teleoperation of machinery. Due to the randomness of myoelectric signals, identification of the signals is not complete, therefore the goal of this project is to complete a study of the characterization of one set of hand motions using current system identification methods. The gripping motion of the hand and the corresponding myoelectric signals are measured and the data captured with a personal computer. Using computer software the captured data are processed and finally subjected to several system identification routines. Using this technique it is possible to construct a mathematical model that correlates the myoelectric signals with the matching hand motion.
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Papi, F., D. Tarchi, M. Vespe, F. Oliveri, and G. Aulicino. "Radiolocation and tracking of automatic identification system signals." In 2014 IEEE Statistical Signal Processing Workshop (SSP). IEEE, 2014. http://dx.doi.org/10.1109/ssp.2014.6884686.
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Murphy, K. "System identification and modelling of a milk pasteurisation plant." In Irish Signals and Systems Conference 2004. IEE, 2004. http://dx.doi.org/10.1049/cp:20040592.
Full textReports on the topic "System identification- Geophysical signals"
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Corriveau, L., J. F. Montreuil, O. Blein, E. Potter, M. Ansari, J. Craven, R. Enkin, et al. Metasomatic iron and alkali calcic (MIAC) system frameworks: a TGI-6 task force to help de-risk exploration for IOCG, IOA and affiliated primary critical metal deposits. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/329093.
Full textAbstract:
Australia's and China's resources (e.g. Olympic Dam Cu-U-Au-Ag and Bayan Obo REE deposits) highlight how discovery and mining of iron oxide copper-gold (IOCG), iron oxide±apatite (IOA) and affiliated primary critical metal deposits in metasomatic iron and alkali-calcic (MIAC) mineral systems can secure a long-term supply of critical metals for Canada and its partners. In Canada, MIAC systems comprise a wide range of undeveloped primary critical metal deposits (e.g. NWT NICO Au-Co-Bi-Cu and Québec HREE-rich Josette deposits). Underexplored settings are parts of metallogenic belts that extend into Australia and the USA. Some settings, such as the Camsell River district explored by the Dene First Nations in the NWT, have infrastructures and 100s of km of historic drill cores. Yet vocabularies for mapping MIAC systems are scanty. Ability to identify metasomatic vectors to ore is fledging. Deposit models based on host rock types, structural controls or metal associations underpin the identification of MIAC-affinities, assessment of systems' full mineral potential and development of robust mineral exploration strategies. This workshop presentation reviews public geoscience research and tools developed by the Targeted Geoscience Initiative to establish the MIAC frameworks of prospective Canadian settings and global mining districts and help de-risk exploration for IOCG, IOA and affiliated primary critical metal deposits. The knowledge also supports fundamental research, environmental baseline assessment and societal decisions. It fulfills objectives of the Canadian Mineral and Metal Plan and the Critical Mineral Mapping Initiative among others. The GSC-led MIAC research team comprises members of the academic, private and public sectors from Canada, Australia, Europe, USA, China and Dene First Nations. The team's novel alteration mapping protocols, geological, mineralogical, geochemical and geophysical framework tools, and holistic mineral systems and petrophysics models mitigate and solve some of the exploration and geosciences challenges posed by the intricacies of MIAC systems. The group pioneers the use of discriminant alteration diagrams and barcodes, the assembly of a vocab for mapping and core logging, and the provision of field short courses, atlas, photo collections and system-scale field, geochemical, rock physical properties and geophysical datasets are in progress to synthesize shared signatures of Canadian settings and global MIAC mining districts. Research on a metamorphosed MIAC system and metamorphic phase equilibria modelling of alteration facies will provide a foundation for framework mapping and exploration of high-grade metamorphic terranes where surface and near surface resources are still to be discovered and mined as are those of non-metamorphosed MIAC systems.
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Phillips, Donald, and Yoram Kapulnik. Using Flavonoids to Control in vitro Development of Vesicular Arbuscular Mycorrhizal Fungi. United States Department of Agriculture, January 1995. http://dx.doi.org/10.32747/1995.7613012.bard.
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Vesicular-arbuscular mycorrhizal (VAM) fungi and other beneficial rhizosphere microorganisms, such as Rhizobium bacteria, must locate and infect a host plant before either symbiont profits. Although benefits of the VAM association for increased phosphorous uptake have been widely documented, attempts to improve the fungus and to produce agronomically useful amounts of inoculum have failed due to a lack of in vitro production methods. This project was designed to extend our prior observation that the alfalfa flavonoid quercetin promoted spore germination and hyphal growth of VAM fungi in the absence of a host plant. On the Israeli side of the project, a detailed examination of changes in flavonoids and flavonoid-biosynthetic enzymes during the early stages of VAM development in alfalfa found that VAM fungi elicited and then suppressed transcription of a plant gene coding for chalcone isomerase, which normally is associated with pathogenic infections. US workers collaborated in the identification of flavonoid compounds that appeared during VAM development. On the US side, an in vitro system for testing the effects of plant compounds on fungal spore germination and hyphal growth was developed for use, and intensive analyses of natural products released from alfalfa seedlings grown in the presence and absence of microorganisms were conducted. Two betaines, trigonelline and stachydrine, were identified as being released from alfalfa seeds in much higher concentrations than flavonoids, and these compounds functioned as transcriptional signals to another alfalfa microsymbiont, Rhizobium meliloti. However, these betaines had no effect on VAM spore germination or hyphal growth i vitro. Experiments showed that symbiotic bacteria elicited exudation of the isoflavonoids medicarpin and coumestrol from legume roots, but neither compound promoted growth or germination of VAM fungi in vitro. Attempts to look directly in alfalfa rhizosphere soil for microbiologically active plant products measured a gradient of nod-gene-inducing activity in R. meliloti, but no novel compounds were identified for testing in the VAM fungal system in vitro. Israeli field experiments on agricultural applications of VAM were very successful and developed methods for using VAM to overcome stunting in peanuts and garlic grown in Israel. In addition, deleterious effects of soil solarization on growth of onion, carrot and wheat were linked to effects on VAM fungi. A collaborative combination of basic and applied approaches toward enhancing the agronomic benefits of VAM asociations produced new knowledge on symbiotic biology and successful methods for using VAM inocula under field conditions
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Lers, Amnon, and Gan Susheng. Study of the regulatory mechanism involved in dark-induced Postharvest leaf senescence. United States Department of Agriculture, January 2009. http://dx.doi.org/10.32747/2009.7591734.bard.
Full textAbstract:
Postharvest leaf senescence contributes to quality losses in flowers and leafy vegetables. The general goal of this research project was to investigate the regulatory mechanisms involved in dark-induced leaf senescence. The regulatory system involved in senescence induction and control is highly complex and possibly involves a network of senescence promoting pathways responsible for activation of the senescence-associated genes. Pathways involving different internal signals and environmental factors may have distinctive importance in different leaf senescence systems. Darkness is known to have a role in enhancement of postharvest leaf senescence and for getting an insight into its regulatory mechanism/s we have applied molecular genetics and functional genomics approaches. The original objectives were: 1. Identification of dark-induced SAGs in Arabidopsis using enhancer/promoter trap lines and microarray approaches; 2. Molecular and functional characterization of the identified genes by analyzing their expression and examining the phenotypes in related knockout mutant plants; 3. Initial studies of promoter sequences for selected early dark-induced SAGs. Since genomic studies of senescence, with emphasis on dark-induced senescence, were early-on published which included information on potential regulatory genes we decided to use this new information. This is instead of using the uncharacterized enhancer/promoter trap lines as originally planned. We have also focused on specific relevant genes identified in the two laboratories. Based on the available genomic analyses of leaf senescence 10 candidate genes hypothesized to have a regulatory role in dark-induced senescence were subjected to both expression as well as functional analyses. For most of these genes senescence-specific regulation was confirmed, however, functional analyses using knock-out mutants indicated no consequence to senescence progression. The transcription factor WARK75 was found to be specifically expressed during natural and dark-induced leaf senescence. Functional analysis demonstrated that in detached leaves senescence under darkness was significantly delayed while no phenotypic consequences could be observed on growth and development, including no effect on natural leaf senescence,. Thus, WARKY75 is suggested to have a role in dark-induced senescence, but not in natural senescence. Another regulatory gene identified to have a role in senescence is MKK9 encoding for a Mitogen-Activated Protein Kinase Kinase 9 which is upregulated during senescence in harvested leaves as well as in naturally senescing leaves. MKK9 can specifically phosphorylate another kinase, MPK6. Both knockouts of MKK9 and MPK6 displayed a significantly senescence delay in harvested leaves and possibly function as a phosphorelay that regulates senescence. To our knowledge, this is the first report that clearly demonstrates the involvement of a MAP kinase pathway in senescence. This research not only revealed a new signal transduction pathway, but more important provided significant insights into the regulatory mechanisms underlying senescence in harvested leaves. In an additional line of research we have employed the promoter of the senescence-induced BFN1 gene as a handle for identifying components of the regulatory mechanism. This gene was shown to be activated during darkinduced senescence of detached leaves, as well as natural senescence. This was shown by following protein accumulation and promoter activity which demonstrated that this promoter is activated during dark-induced senescence. Analysis of the promoter established that, at least some of the regulatory sequences reside in an 80 bps long fragment of the promoter. Overall, progress was made in identification of components with a role in dark-induced senescence in this project. Further studies should be done in order to better understand the function of these components and develop approaches for modulating the progress of senescence in crop plants for the benefit of agriculture.
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Wagner, D. Ry, Eliezer Lifschitz, and Steve A. Kay. Molecular Genetic Analysis of Flowering in Arabidopsis and Tomato. United States Department of Agriculture, May 2002. http://dx.doi.org/10.32747/2002.7585198.bard.
Full textAbstract:
The primary objectives for the US lab included: the characterization of ELF3 transcription and translation; the creation and characterization of various transgenic lines that misexpress ELF3; defining genetic pathways related to ELF3 function regulating floral initiation in Arabidopsis; and the identification of genes that either interact with or are regulated by ELF3. Light quality, photoperiod, and temperature often act as important and, for some species, essential environmental cues for the initiation of flowering. However, there is relatively little information on the molecular mechanisms that directly regulate the developmental pathway from the reception of the inductive light signals to the onset of flowering and the initiation of floral meristems. The ELF3 gene was identified as possibly having a role in light-mediated floral regulation since elj3 mutants not only flower early, but exhibit light-dependent circadian defects. We began investigating ELF3's role in light signalling and flowering by cloning the ELF3 gene. ELF3 is a novel gene only present in plant species; however, there is an ELF3 homolog within Arabidopsis. The Arabidopsis elj3 mutation causes arrhythmic circadian output in continuous light; however, we show conclusively normal circadian function with no alteration of period length in elj3 mutants in dark conditions and that the light-dependent arrhythmia observed in elj3 mutants is pleiotropic on multiple outputs regardless of phase. Plants overexpressing ELF3 have an increased period length in constant light and flower late in long-days; furthermore, etiolated ELF3-overexpressing seedlings exhibit a decreased acute CAB2 response after a red light pulse, whereas the null mutant is hypersensitive to acute induction. This finding suggests that ELF3 negatively regulates light input to both the clock and its outputs. To determine whether ELF3's action is phase dependent, we examined clock resetting by light pulses and constructed phase response curves. Absence of ELF3 activity causes a significant alteration of the phase response curve during the subjective night, and overexpression of ELF3 results in decreased sensitivity to the resetting stimulus, suggesting that ELF3 antagonizes light input to the clock during the night. Indeed, the ELF3 protein interacts with the photoreceptor PHYB in the yeast two-hybrid assay and in vitro. The phase ofELF3 function correlates with its peak expression levels of transcript and protein in the subjective night. ELF3 action, therefore, represents a mechanism by which the oscillator modulates light resetting. Furthermore, flowering time is dependent upon proper expression ofELF3. Scientifically, we've made a big leap in the understanding of the circadian system and how it is coupled so tightly with light reception in terms of period length and clock resetting. Agriculturally, understanding more about the way in which the clock perceives and relays temporal information to pathways such as those involved in the floral transition can lead to increased crop yields by enabling plants to be grown in suboptimal conditions.