Repository logo
 
Loading...
Profile Picture
Person

SOARES, CRISTIANO

Search Results

Now showing 1 - 10 of 46
  • Data acquisition and monitoring system (DAMS)
    Publication . Lopes, C.; Soares, C.
    In order to achieve specific requirements of their research programs under projects INTIMATE and INFANTE, a consortium formed by the Centro de Investigação ̧Tecnológica do Algarve (CINTAL), the Instituto Hidrográfico (IH) and the Instituto Superior Técnico (IST) have purchased an acoustic tomography and underwater communication system to the company CO.L.Mar. This system is composed of two hydrophone arrays, one surface buoy, one RF link and other electronic and mechanical devices, that can be referred to as distinct categories: • the Wet-end system and • the Dry-end system depending on their position when deployed. The Data Acquisition & Monitoring System ( DAMS ) described in this report connects to the Dry-end of Colmar’s tomographic system (as shown in figure 1) and provides the following capabilities: i) to read and monitor the data being acquired, ii) to demultiplex and store the data on digital format and iii) to provide absolute time-marking of the data for future use.In order to achieve specific requirements of their research programs under projects INTIMATE and INFANTE, a consortium formed by the Centro de Investigação ̧Tecnológica do Algarve (CINTAL), the Instituto Hidrográfico (IH) and the Instituto Superior Técnico (IST) have purchased an acoustic tomography and underwater communication system to the company CO.L.Mar. This system is composed of two hydrophone arrays, one surface buoy, one RF link and other electronic and mechanical devices, that can be referred to as distinct categories: • the Wet-end system and • the Dry-end system depending on their position when deployed. The Data Acquisition & Monitoring System ( DAMS ) described in this report connects to the Dry-end of Colmar’s tomographic system (as shown in figure 1) and provides the following capabilities: i) to read and monitor the data being acquired, ii) to demultiplex and store the data on digital format and iii) to provide absolute time-marking of the data for future use.
  • Large scale evaluation of primers for diagnosis of rupestris stem pitting associated virus-1
    Publication . Nolasco, Gustavo; Mansinho, A.; Santos, M. T.; Soares, C.; Sequeira, Z.; Sequeira, C.; Correia, P. K.; Sequeira, O. A.
    The unavailability of adequate immunological reagents has prevented the use of ELISA for the diagnosis of rupestris stem pitting disorder of grapevines. In this work, the performance of five primer pairs for broad-scale detection of rupestris stem pitting associated virus-1 by RT-PCR using ds-RNA templates was compared and contrasted with biological indexing. The virus was widespread among the budwood of 35 Portuguese grapevine varieties assayed, with a prevalence of 85%. The biological assay proved to be unreliable as an index of infection due to the high number of false negatives. Five sets of primers were assayed and compared by means of their relative sensitivity and negative predictive value. The primer pair specific for the coat protein gene was excluded because of the difficulty in identifying the specific amplified product. From the other four primer pairs, those specific for the helicase domain of the putative polymerase gene had the highest sensitivity and negative predictive value. However, a high confidence in the assay, as desirable for a certification scheme, could not be obtained by the sole use of this primer pair. An additional pair should be used in a separate or in a multiplex RT-PCR reaction.
  • Tomografia passiva costiera. Inversion results with active data - phase 2
    Publication . Jesus, S. M.; Soares, C.
    This report shows the acoustic inversion results obtained on the INTIFANTE'00 data set, Events II and V.
  • Shallow water tomography in a highly variable scenario
    Publication . Soares, C.; Jesus, S. M.
    In October 2000, SiPLAB and the Instituto Hidrográfico (IH - PN) conducted the IN-TIFANTE’00 sea trial in a shallow area off the Peninsula of Tróia, approximately 50 km south from Lisbon, in Portugal. The experiment itself and results obtained in most of the data set have been reported at various occasions in the last two years. This paper focuses on the data acquired during Event 2, where the acoustic propagation path was approximately range independent and the source ship was held on station at a constant range of 5.8 km from the vertical line array. Although these conditions were, in general, relatively benign for matched-field tomography, retrieval of water column and bottom parameters over a 14-hour-long recording revealed to be extremely difficult. This paper analysis in detail the characteristics of this data set and determines the causes for the observed inversion difficulties. Is is shown that the causes for the poor performance of the conventional methods are mainly the tide induced spatially correlated noise and the relative source-receiver motion during time averaging. An eigenvalue-based criterion is proposed for detecting optimal averaging time. It is shown that this data selection procedure together with hydrophone normalization and an appropriate objective function provide a better model fit and consistent inversion results and thus a better understanding of the environmental variability.
  • The INTIFANTE'00 sea trial: preliminary source localization and ocean tomography data analysis
    Publication . Jesus, S. M.; Coelho, E.; Onofre, J.; Picco, P.; Soares, C.; Lopes, C.
    The INTIFANTE'00 sea trial was a multidisciplinary experiment including testing of an autonomous surface vehicle, underwater communications, source localization and acoustic ocean tomography. The results shown here will concentrate on the source localization and ocean tomography data sets. The data gathered during a 24 hour run along a range independent track shows strong oceanographic features, possibly due to internal tide signature, both on the temperature data, as measured on the thermistor chain collocated with a vertical line array(VLA), and on the acoustic data. A range dependent track between 120 and 60 m water depth, shows a highly variable channel impulse response along time and range when the source was moving outwards from the VLA. In another acoustic track, the source was navigatated across a underwater canyon where the energy was rapidly distributed over a deep acoustic channel with sound trapped well below the thermocline. Good agreement between the modeled and measured channel responses represents the rst step towards matched- eld processinglike methods such as source localization and tracking and ocean tomography.
  • Broadband matched-field tomography using simplified acoustic systems
    Publication . SOARES, CRISTIANO; Jesus, S. M.
    Ocean Acoustic Tomography is a remote sensing technique that has been proposed to infer physical properties of the ocean traversed by the sound field. Although its feasibility has been demonstrated, it is still not being used in a systematic way due, in a large extent, to cost and operational difficulties of standard acoustic systems. Current developments of acoustic systems go in the sense of simplifying them, both at the emitting and receiving end. Simplifying an acoustic system may represent a loss or a reduction of the amount of information contained in the observed acoustic field, possibly conducting to degradation in the inversion results. The objective of this thesis is to adapt existing array processing methods to be used in acoustic tomography and geoacoustic inversion taking into account the challenges posed by such simplifications, and to cope with the loss of available information they may represent. Two aspects are exploited with the objective of coping with the reduction of information: one is the development of a broadband data model, and the other is the development of matched-field processors based on that broadband data model, with particular emphasis in highresolution processors. Matched-field based approaches appear to be suitable to work in conjunction with the simplified acoustic systems used to collect several experimental data sets treated herein. Experimental results using simplified acoustic systems, sparse receiving arrays (active mode) on one hand, or an uncontrolled source (passive mode) on the other hand, show that it is possible to produce environmental estimates of the watercolumn and seafloor in close agreement with ground truth measurements.
  • Broadband MFP: coherent vs. incoherent
    Publication . Jesus, S. M.; Soares, C.
    Matched-Field Processing (MFP) is now a mature technique for source localization and tracking. There are at least two aspects that emerge, by their relevance, to the success of MFP: one is the ability of a given MFP processor to accurately pinpoint the source location while rejecting sidelobes, and the other is the impact of erroneous or missing environmental information (known as model mismatch) in the final source location estimate. This study addresses the first aspect regarding sidelobe rejection while considering that the processor is working on a mismatch free situation. One well known procedure to reduce sidelobes is to use a broadband MFP processor (whenever a band of frequencies is available). There are a number of different ways to combine MFP information across frequency that ran be classified in two broad groups: the conventional incoherent methods, that are based on the direct averaging of the auto-frequency inner products and the, say, less conventional methods, that perform a weighted average of the cross-frequency inner products where the weights are the frequency compensation phase-shifts. The later are generally termed as coherent broadband methods since they combine complex inner products. The coherent broadband methods proposed in the literature are either suboptimal or very computationally Intensive, even for a small number of frequencies. An alternative method is presented that combines cross-frequency information with the same localization performance than the standard coherent methods and a computation load similar to that of the incoherent processor. The performance of the various broadband processors is compared in simulated data.
  • The acoustic oceanographic buoy. A light acoustic data acquisition system
    Publication . Soares, C.; Zabel, F.; Martins, C.; Silva, A.; Jesus, S. M.
    The Acoustic Oceanographic Buoy (AOB) is a light acoustic receiving device that incorporates acoustic and non-acoustic signals received in various channels along a vertical line array that provide oceanographic and environment measurements all of which are uniquely GPS time referenced. The physical characteristics of the AOB, in terms of size, weight and autonomy, will tend to those of a standard sonobuoy with, however, the capabilities: of local data storage, dedicated signal-processing, GPS self localizing, real-time monitoring and online data transmission.
  • Source localization in a time-varying ocean waveguide
    Publication . Soares, C.; Siderius, M.; Jesus, S. M.
    One of the most stringent impairments in matched-field processing is the impact of missing or erroneous environmental information on the final source location estimate. This problem is known in the literature as model mismatch and is strongly frequency dependent. Another unavoidable factor that contributes to model mismatch is the natural time and spatial variability of the ocean waveguide. As a consequence, most of the experimental results obtained to date focus on short source-receiver ranges (usually <5 km), stationary sources, reduced time windows and frequencies generally below 600 Hz. This paper shows that MFP source localization can be made robust to time–space environmental mismatch if the parameters responsible for the mismatch are clearly identified, properly modeled and (time-)adaptively estimated by a focalization procedure prior to MFP source localization. The data acquired during the ADVENT’99 sea trial at 2, 5, and 10 km source-receiver ranges and in two frequency bands, below and above 600 Hz, provided an excellent opportunity to test the proposed techniques. The results indicate that an adequate parametrization of the waveguide is effective up to 10 km range in both frequency bands achieving a precise localization during the whole recording of the 5 km track, and most of the 10 km track. It is shown that the increasing MFP dependence on erroneous environmental information in the higher frequency and at longer ranges can only be accounted for by including a time dependent modeling of the water column sound speed profile.
  • Real-time environmental inversion using a network of light receiving systems
    Publication . Soares, C.; Jesus, S. M.
    This paper reports preliminary environmental inversion results of acoustic data collected simultaneously at two receiving systems during the RADAR’07 sea trial. These receiving systems have communication capabilities that allow for transfering acoustic and telemetric data to a base station with processing capabilities in order to produce environmental estimates during the acoustic experiment. During a large part of the experiment estimates on the temperature field appear to agree with concurrent ground truth data.