Relevant bibliographies by topics / Low Frequency Array (LOFAR)

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Low Frequency Array (LOFAR)'

Author: Grafiati
Published: 4 June 2021
Last updated: 10 February 2022

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Journal articles on the topic "Low Frequency Array (LOFAR)"

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van Haarlem, M. P. "LOFAR: The Low Frequency Array." EAS Publications Series 15 (2005): 431–44. http://dx.doi.org/10.1051/eas:2005169.

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van Haarlem, M. P., M. W. Wise, A. W. Gunst, et al. "LOFAR: The LOw-Frequency ARray." Astronomy & Astrophysics 556 (July 16, 2013): A2. http://dx.doi.org/10.1051/0004-6361/201220873.

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Mulrey, K., A. Bonardi, S. Buitink, et al. "Updated Calibration of the LOFAR Low-Band Antennas." EPJ Web of Conferences 216 (2019): 04006. http://dx.doi.org/10.1051/epjconf/201921604006.

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The LOw-Frequency ARray (LOFAR) telescope measures radio emission from air showers. In order to interpret the data, an absolute, frequency dependent calibration is required. Due to a growing need for a better understanding of the measured frequency spectrum, we revisit the calibration of the LOFAR antennas in the range of 30—80 MHz. Using the galactic radio emission and a detailed model of the LOFAR signal chain, we find a calibration that provides an absolute energy scale and allows us to study frequency dependent features in measured air shower signals.
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Bonardi, Antonio, Stijn Buitink, Arthur Corstanje, et al. "Towards real-time cosmic-ray identification with the LOw Frequency ARay." EPJ Web of Conferences 216 (2019): 04005. http://dx.doi.org/10.1051/epjconf/201921604005.

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The radio signals emitted by Extensive Air Showers have been successfully used for the last decade by LOFAR to reconstruct the properties of the primary cosmic rays. Since an effective real-time recognition system for the very short radio pulses is lacking, cosmic-ray acquisition is currently triggered by an external array of particle detector, called LORA, limiting the LOFAR collecting area to the area covered by LORA. A new algorithm for the real-time cosmic-ray detection has been developed for the LOFAR Low Band Antenna, which are sensitive between 10 and 90 MHz, and is here presented together with the latest results.
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Falcke, Heino D., Michiel P. van Haarlem, A. Ger de Bruyn, et al. "A very brief description of LOFAR – the Low Frequency Array." Proceedings of the International Astronomical Union 2, no. 14 (2006): 386–87. http://dx.doi.org/10.1017/s174392130701112x.

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AbstractLOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30–240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR will initially be on four key science projects (KSPs): (i) Detection of the formation of the very first stars and galaxies in the universe during the so-called epoch of reionization by measuring the power spectrum of the neutral hydrogen 21-cm line (Shaver et al. 1999) on the ∼ 5′ scale; (ii) Low-frequency surveys of the sky with of order 108 expected new sources; (iii) All-sky monitoring and detection of transient radio sources such as γ-ray bursts, X-ray binaries, and exo-planets (Farrell et al. 2004); and (iv) Radio detection of ultra-high energy cosmic rays and neutrinos (Falcke & Gorham 2003) allowing for the first time access to particles beyond 1021 eV (Scholten et al. 2006). Apart from the KSPs open access for smaller projects is also planned. Here we give a brief description of the telescope.
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Bilous, A. V., L. Bondonneau, V. I. Kondratiev, et al. "A LOFAR census of non-recycled pulsars: extending to frequencies below 80 MHz." Astronomy & Astrophysics 635 (March 2020): A75. http://dx.doi.org/10.1051/0004-6361/201936627.

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We present the results from the low-frequency (40–78 MHz) extension of the first pulsar census of non-recycled pulsars carried out with the LOw-Frequency ARray (LOFAR). We used the low-band antennas of the LOFAR core stations to observe 87 pulsars out of 158 that had been previously detected using high-band antennas. We present flux densities and flux-calibrated profiles for the 43 pulsars we detected. Of this sample, 17 have not, to our knowledge, previously been detected at such low frequencies. Here we recalculate the spectral indices using the new low-frequency flux density measurements from the LOFAR census and discuss the prospects of studying pulsars at very low frequencies using current and upcoming facilities, such as the New Extension in Nançay Upgrading LOFAR (NenuFAR).
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de Gasperin, F., M. Mevius, D. A. Rafferty, H. T. Intema, and R. A. Fallows. "The effect of the ionosphere on ultra-low-frequency radio-interferometric observations." Astronomy & Astrophysics 615 (July 2018): A179. http://dx.doi.org/10.1051/0004-6361/201833012.

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Context. The ionosphere is the main driver of a series of systematic effects that limit our ability to explore the low-frequency (<1 GHz) sky with radio interferometers. Its effects become increasingly important towards lower frequencies and are particularly hard to calibrate in the low signal-to-noise ratio (S/N) regime in which low-frequency telescopes operate. Aims. In this paper we characterise and quantify the effect of ionospheric-induced systematic errors on astronomical interferometric radio observations at ultra-low frequencies (<100 MHz). We also provide guidelines for observations and data reduction at these frequencies with the LOw Frequency ARray (LOFAR) and future instruments such as the Square Kilometre Array (SKA). Methods. We derive the expected systematic error induced by the ionosphere. We compare our predictions with data from the Low Band Antenna (LBA) system of LOFAR. Results. We show that we can isolate the ionospheric effect in LOFAR LBA data and that our results are compatible with satellite measurements, providing an independent way to measure the ionospheric total electron content (TEC). We show how the ionosphere also corrupts the correlated amplitudes through scintillations. We report values of the ionospheric structure function in line with the literature. Conclusions. The systematic errors on the phases of LOFAR LBA data can be accurately modelled as a sum of four effects (clock, ionosphere first, second, and third order). This greatly reduces the number of required calibration parameters, and therefore enables new efficient calibration strategies.
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Geyer, Marisa, and Aris Karastergiou. "Anomalous Pulsar Scattering at LOFAR Frequencies." Proceedings of the International Astronomical Union 13, S337 (2017): 275–78. http://dx.doi.org/10.1017/s1743921317008407.

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AbstractThe Low Frequency Array (LOFAR) is ideally suited to pulsar scattering studies, providing broad bands at low frequencies where the imprints of the ionized Interstellar Medium (IISM) are exaggerated. We analyse a set of sources at 110–190 MHz, and find unexpectedly shallow dependencies of pulse scatter broadening on frequency. These anomalous scattering values are discussed by considering evidence for anisotropic scattering and small scattering clouds.
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E. Kassim, Namir, T. Joseph W. Lazio, William C. Erickson, Patrick C. Crane, R. A. Perley, and B. Hicks. "The Low-Frequency Array (LOFAR): Opening a New Window on the Universe." Symposium - International Astronomical Union 199 (2002): 474–83. http://dx.doi.org/10.1017/s0074180900169591.

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Decametric wavelength imaging has been largely neglected in the quest for higher angular resolution because ionospheric structure limited interferometric imaging to short (< 5 km) baselines. The long wavelength (LW, 2—20 m or 15—150 MHz) portion of the electromagnetic spectrum thus remains poorly explored. The NRL-NRAO 74 MHz Very Large Array has demonstrated that self-calibration techniques can remove ionospheric distortions over arbitrarily long baselines. This has inspired the Low Frequency Array (LOFAR)—-a fully electronic, broad-band (15—150 MHz)antenna array which will provide an improvement of 2—3 orders of magnitude in resolution and sensitivity over the state of the art.
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Salas, P., M. A. Brentjens, D. D. Bordenave, J. B. R. Oonk, and H. J. A. Röttgering. "Tied-array holography with LOFAR." Astronomy & Astrophysics 635 (March 2020): A207. http://dx.doi.org/10.1051/0004-6361/201935670.

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Context. A radio interferometer uses time delays to maximize its response to radiation coming from a particular direction. These time delays compensate for differences in the time of arrival of the wavefront at the different elements of the interferometer, and for delays in the instrument’s signal chain. If the radio interferometer is operated as a phased array (tied array), the time delays cannot be accounted for after an observation, so they must be determined in advance. Aims. Our aim is to characterize the time delays between the stations in the core of the LOw Frequency ARray (LOFAR). Methods. We used radio holography to determine the time delays for the core stations of LOFAR (innermost 3.5 km). Using the multibeaming capability of LOFAR we map the voltage beam faster than with a raster scan, while simultaneously calibrating the observed beam continuously. Results. For short radio holographic observations (60 s and 600 s) of 3C196, 3C147, and 3C48 we are able to derive time delays with errors of less than one nanosecond. After applying the derived time delays to the beamformer, the beam shows residuals of less than 20% with respect to the theoretical beam shape. Conclusions. Tied-array holography could be a way towards semi-real-time beam calibration for the Square Kilometer Array.
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Dissertations / Theses on the topic "Low Frequency Array (LOFAR)"

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Ker, Louise Moira. "Radio AGN evolution with low frequency radio surveys." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7616.

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Supermassive black holes are leading candidates for the regulation of galaxy growth and evolution over cosmic time, via ‘feedback’ processes, whereby outflows from the Active Galactic Nuclei (AGN) halt star formation within the galaxy. AGN feedback is generally thought to occur in two modes, high-excitation (HERG, or ‘quasar-mode’) and low-excitation (LERG or ’radio-mode’) each having a different effect on the host galaxy. LERGs curtail the growth of the most massive galaxies, whereas HERGs are thought to be activated by mergers/interactions, switching off star formation at high redshift. A critical problem in current extragalactic astrophysics lies in understanding the precise physical mechanisms by which these feedback processes operate, and how they evolve over cosmic time. Radio-loud AGN are an essential tool for studying major feedback mechanisms, as they are found within the largest ellipticals, and hence are beacons for the most massive black holes across the bulk of cosmic time. In this thesis I develop and study existing complete radio samples with extensive new multi-wavelength data in the radio, optical and infrared, aiming to investigate the evolution of AGN feedback modes, and methods to locate and study such systems at the very highest redshifts. This will serve to inform further studies of radio-AGN planned with next generation radio instruments such as the LOw Frequency ARray (LOFAR). Very few radio-loud AGN systems are currently known at high redshifts, and the effectiveness of traditional high redshift selection techniques, such as selection based on steep spectral index, have not been well quantified. A purely evidence-based approach to determining the efficiency of various high redshift selection techniques is presented, using nine highly spectroscopically complete radio samples; although weak correlations are confirmed between spectral index and linear size and redshift, selection first of infrared-faint radio sources remains by far the most efficient method of selecting high-z radio galaxies from complete samples. Radio spectral curvature in four of the complete samples is analysed and the effect of radio spectral shape on the measurement of the radio luminosity function (RLF) of steep-spectrum radio sources is investigated. Below z=1, curvature has negligible effect on the measurement of the RLF, however at higher redshifts, where source numbers are low, the shape of the radio spectrum should be taken into account, as individual source luminosities can change up to 0.1-0.2 dex, and this can in some cases introduce errors in space density measurements of up to a factor of 2-3 where source numbers are low. Building upon these samples, the very first independent determinations of the separate RLFs for high and low excitation radio sources across the bulk of cosmic time are made, out to z=1. Here it is shown that HERGs show very clear signs of strong evolution, in line with theoretical predictions. LERGs also show some very weak evolution with redshift, showing increases in space density of typically around a factor of 2. These measurements are also used to estimate the contribution of LERGs, which typically show weak or no emission lines to the ‘missing redshift’ population, which are sources within the complete samples not identifiable spectroscopically. Complementary to this, a pilot study is presented in selecting ‘missing redshift’ sources which are classed as infra-red faint (IFRS), which show no optical or near-IR identification, and are compact in the radio. Follow up spectroscopy on these candidate high z sources detected no line emission. Finally, work carried out towards the testing and commissioning of the new LOFAR telescope is presented. The findings from this thesis will serve to both streamline and inform high redshift radio-AGN searches and studies planned to be carried out with LOFAR and other multi-wavelength complementary surveys in the near future, and help to open up an as yet unexplored epoch in radio-AGN formation and evolution.
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Trüstedt, Jonas Elias [Verfasser], Matthias [Gutachter] Kadler, and Marcus [Gutachter] Brüggen. "Long-wavelength radio observations of blazars with the Low-Frequency Array (LOFAR) / Jonas Elias Trüstedt ; Gutachter: Matthias Kadler, Marcus Brüggen." Würzburg : Universität Würzburg, 2017. http://d-nb.info/1125884630/34.

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Koehler, Jana [Verfasser]. "Studying large-scale structures and polarization of the Northern sky facilitating single-station data of the Low Frequency Array (LOFAR) / Jana Koehler." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1113688378/34.

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Mangena. "Reconstruction of the ionization history from 21cm maps with deep learning." University of the Western Cape, 2020. http://hdl.handle.net/11394/7243.

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Masters of Science<br>Upcoming and ongoing 21cm surveys, such as the Square Kilometre Array (SKA), Hydrogen Epoch of Reionization Array (HERA) and Low Frequency Array (LOFAR), will enable imaging of the neutral hydrogen distribution on cosmological scales in the early Universe. These experiments are expected to generate huge imaging datasets that will encode more information than the power spectrum. This provides an alternative unique way to constrain the astrophysical and cosmological parameters, which might break the degeneracies in the power spectral analysis. The global history of reionization remains fairly unconstrained. In this thesis, we explore the viability of directly using the 21cm images to reconstruct and constrain the reionization history. Using Convolutional Neural Networks (CNN), we create a fast estimator of the global ionization fraction from the 21cm images as produced by our Large Semi-numerical Simulation (SimFast21). Our estimator is able to efficiently recover the ionization fraction (xHII) at several redshifts, z = 7; 8; 9; 10 with an accuracy of 99% as quantified by the coefficient of determination R2 without being given any additional information about the 21cm maps. This approach, contrary to estimations based on the power spectrum, is model independent. When adding the thermal noise and instrumental effects from these 21cm arrays, the results are sensitive to the foreground removal level, affecting the recovery of high neutral fractions. We also observe similar trend when combining all redshifts but with an improved accuracy. Our analysis can be easily extended to place additional constraints on other astrophysical parameters such as the photon escape fraction. This work represents a step forward to extract the astrophysical and cosmological information from upcoming 21cm surveys.
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LeBel-Buchanan, Nicholas. "Review of new instruments in low frequency radio interferometry and their calibration: LOFAR and MWA." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121206.

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Low frequency radio astronomy is experiencing a renaissance due to advances in computing power and efficiency. New instruments are being designed and built to take advantage of this. An introduction is given to radio astronomy. The physical mechanisms of radio emission are explained. The measurement of radio waves is discussed, particularly in regard to the properties and advantages of interferometric arrays. Two modern instruments currently being deployed and tested are described, with particular attention paid to their calibration techniques. These instruments are the Murchison Widefield Array (MWA) in Western Australia and the Low Frequency Array (LOFAR) in Europe, with most components in The Nether-lands. These instruments are compared with one another.<br>La radioastronomie de fréquence basse connaît une renaissance grâce aux progrès de la puissance de calcul et d'efficacité. De nouveaux instruments sont conçus et construits pour profiter de cette. Une introduction est donnée à la radioastronomie. Les mécanismes physiques de l'émission de radio sont expliqué. La mesure des ondes radio est discutée, en particulier en ce qui concerne les propriétés et avantages de réseaux interférométriques. Deux instruments modernes actuellement déployés et testés sont décrits, avec une attention particulière à leurs techniques d'étalonnage. Ces instruments sont le "Murchison Widefield Array" (MWA) en l' Ouest de l'Australie et le "Low Frequency Array" (LOFAR) en Europe, la plupart des composants dans les Pays-Bas. Ces instruments sont comparé l'un à l'autre.
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Sinclair, David Robert. "A study of the square kilometre array low-frequency aperture array." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:7b5047f4-5643-49be-aea8-e31512180267.

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This thesis primarily comprises simulations of SKA1-Low, the low-frequency aperture array of the Square Kilometre Array (SKA) radio telescope. Simulations assess how different design specifications would affect the telescope's performance and ability to undertake one of its key science projects: observing the Epoch of Reionisation (EoR). The simulations are based on the previous baseline design of ~ 260 000 dipole antennas in 1024 stations of 256 antennas each. It is found that errors in the gain and phase of signals at each antenna can significantly affect observations, with the greatest impact at the lowest frequencies. The EoR signal will be detectable at limited redshifts with gain errors of 10% and phase errors of 6 degrees, however to ensure the systematic noise contribution from these errors is always weaker than the EoR signal between z ~ 10 - 21 and spherical harmonic multipole coefficients l ~ 102 - 104 , the gain and phase errors may need to be less than or equal to approximately 5 x 10-6 and less than or equal to approximately 3 x 10-4 degrees, respectively. Alternative telescope layouts to the SKA1-Low baseline design of 1024 stations containing 256 antennas each are evaluated. Some telescope models which share antennas between stations, allowing stations to be formed in a flexible manner, are found to provide superior thermal noise sensitivity than the current design, but suffer greater detrimental effects from gain and phase errors when imaging. The implementation of the digital signal processing of a station beamformer is also discussed. Calculations show that five or nine Field Programmable Gate Arrays (FPGAs) with specifications comparable to the Virtex UltraScale+ XCVU13P could be used to beamform a single 256-antenna SKA1-Low station, depending on the utilisation rate of the FPGAs and the number of channels required.
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Schoeman, Dewald Hermanus. "Full scale low-cost ultra wide band antenna for SKA low frequency array." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80084.

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Thesis (MScEng)--Stellenbosch University, 2013.<br>ENGLISH ABSTRACT: This thesis is about the design, simulation and measuring of ultra wide band antennas for use in the Square Kilometre Array (SKA). The SKA is a radio astronomy project with one of the aims of detecting hydrogen particles in deep space. Several thousand antennas over a wide band of frequencies are needed to receive the radiation from these particles. This motivates the need for a low-cost ultra wide band antenna with the focus on the low frequency part of the SKA. In this thesis we present two design strategies: The first design strategy is for a printed LPDA on a substrate and design curves are generated. A scale model was built and measurements did not correlate with simulation results. This is due to manufacturing tolerances and assembly of the pyramidal structure. The second design strategy is for a full scale zig-zag antenna and design curves were also generated. The aim here is to produce a low-cost prototype by using brazing rods for the wire structure and mount it on a wooden frame. A full scale model was built and measurements on the roof produced much interference for the radiation pattern, but the reflection coefficient was good. We suggest doing measurements in an interference free environment in order to achieve the needed results. To conclude we suggest using the zig-zag antenna for the SKA. Some issues do however need more attention as the transformer has some losses, the cross polarisation is probably not good enough and the beamwidth does not reach the specification. We demonstrated a low cost prototype and there is the possibility of low-cost large scale manufacturing but this needs to be addressed. This has however not been analysed as many factors for large scale manufacturing are very difficult to predict beforehand and lies outside the scope of this thesis.<br>AFRIKAANSE OPSOMMING: Hierdie tesis gaan oor die ontwerp, simulasie en opmeting van ultrawyebandantennas vir gebruik in die SKA ("Square Kilometre Array"). Die SKA is ’n radioastronomie projek met die doel om waterstof partikels op te spoor in die ruimte. Duisende antennas wat oor ’n wye band van frekwensies strek is nodig om die energie van die partikels op te vang. Hieruit is daar ’n aanvraag vir lae-koste ultrawyebandantennas met die fokus op die lae frekwensie deel van die SKA. In hierdie tesis word twee ontwerpstrategieë voorgestel: Die eerste ontwerpstrategie is vir ’n gedrukte logaritmies periodiese dipool reeks (LPDR) op ’n substraat tesame met ontwerpskurwes wat gegenereer word. ’n Skaal model is gebou en die gemete resultate stem nie ooreen met die simulasie nie. Dit kan toegeskryf word aan vervaardigingstoleransies en die aanmekaar sit van die piramide struktuur. Die tweede ontwerpstrategie is vir ’n vol skaal sigsag ("zig-zag") antenna met ontwerpskurwes wat ook gegenereer word. Die doel is om ’n lae-koste prototipe te bou deur sweissoldeerdraad te gebruik vir die draadstruktuur en dan op ’n hout raam te plaas. ’n Vol skaal model is gebou en metings op die dak het baie interferensie veroorsaak vir die stralingsveld, maar tog was die weerkaatskoëffisient goed. Ons stel voor om die metings te herhaal in ’n steuringvrye omgewing om sodoende die korrekte resultate te verkry. Om af te sluit stel ons voor om die sigsag antenna vir die SKA te gebruik. Sekere kwessies soos die transformator wat verlieserig is, die kruispolarisasie wat moontlik nie goed genoeg is nie en die bundelwydte wat nie die spesifikasie haal nie moet nog aandag geniet. Ons het ’n lae-koste prototipe gedemonstreer en daar is die moontlikheid om dit op grootskaalse vervaardiging ook goedkoop te doen, maar dit moet nog uigesorteer word. Dit was wel nie geanaliseer nie, siende dat vele faktore ’n rol speel by grootskaalse vervaardiging wat uiters moeilik is om voor die tyd te voorspel en buite die omvang van die tesis lê.
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Bell, Martin. "The low frequency array and the transient and variable radio sky." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/208253/.

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This thesis addresses the topic of exploring and characterising the transient and variable radio sky, using both existing radio telescopes, and the next generation of radio facilities such as the Low Frequency Array (LOFAR). Studies of well known variable radio sources are presented in conjunction with blind searches of parameter space for unknown sources. Firstly, a three year campaign to monitor the low luminosity Active Galactic Nucleus NGC 7213 in the radio and X-ray bands is presented. Cross-correlation functions are used to calculate a global time lag between inflow (X-ray) and outflow (radio) events. Through this work the previously established scaling relationship between core radio and X-ray luminosities and black hole mass, known as the ‘fundamental plane of black hole activity’ is also explored with respect to NGC 7213. Secondly, the technical and algorithmic procedures to search for transient and variable radio sources within radio images is presented. These algorithms are intended for deployment on the LOFAR telescope, however, they are heavily tested in a blind survey using data obtained from the VLA archive. Through this work an upper limit on the rate of transient events on the sky at GHz frequencies is placed and compared with those found from other dedicated transient surveys. Finally, the design, operation and data reduction procedure for the Low Frequency Array, which will revolutionise our understanding of low frequency time domain astrophysics is explored. LOFAR commissioning observations are reduced and searched for transient and variable radio sources. The current quality of the calibration limits accurate variability studies, however, two unique LOFAR transient candidates that are not present in known radio source catalogues are explored (including multi-wavelength followup observations). In the conclusion to this thesis the parameter space that future radio telescopes may probe - including the potential rates of such events - is presented. At the nano-Jansky level up to 107 transients deg−2 yr−1 are predicted, which will form an unprecedented torrent of data, followup and unique physics to classify
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Elbelazi, Issa. "Receiving Frequency Diverse Array Antenna for Tracking Low Earth Orbit Satellites." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1607728300235793.

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Laws, Michael Richard. "Low frequency strip waveguide array for flow measurement in hostile environments." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/77475/.

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A low frequency, waveguide array transducer, for operation in hostile environments, is studied and optimised for operation in fluids. The design consists of multiple stainless steel, rectangular cross-section strips which are used to support Lamb-like guided waves, which with appropriate delays allows the steering of the emitted beam. Wave propagation within the waveguide strips is discussed and the effect of the strip geometry on the supported wave modes is studied using comprehensive finite element modelling that is validated experimentally. Deviations from Lamb wave behaviour is observed due to coupling that occurs across the finite width of the strip, leading to dispersive behaviour that is slightly different to that of Lamb waves in a plate of the same thickness. As a result of this study, suggestions are made for modifications to the waveguide geometry that may favourably change this dispersive behaviour, over a desired frequency range. The effect of thermal gradients on the propagation of ultrasonic waves within the waveguide strips is also studied. Using Lamb waves as a basis for the analysis, general trends in the wave behaviour were identified before a series of experiments were conducted to demonstrate similar effects in the waveguide strips. Computational fl uid dynamics models were also used to study the heat distribution within the waveguide strips of the transducer to allow the in uence of these effects in a practical application to be assessed. Finally, the phased array capabilities of the strip waveguide array transducer were demonstrated. Initially, finite element modelling was conducted to allow the optimisation of the array geometry before the construction of a prototype. Using this prototype and a custom low frequency phased array controller, experimental steering of the beam emitted from the transducer was demonstrated up to angles of 45°.
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Books on the topic "Low Frequency Array (LOFAR)"

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Heald, George, John McKean, and Roberto Pizzo, eds. Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2.

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Burns, Jack O. A Lunar Far-side Very Low Frequency Array: Proceedings of a workshop sponsored by the National Aeronautics and Space Administration, Washington, D.C., the University of New Mexico, Albuquerque, New Mexico, and the BDM Corporation, Albuquerque, New Mexico, and held at the BDM Corporation, Albuquerque, New Mexico, February 18-19, 1988. NASA, 1989.

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McKean, John, George Heald, and Roberto Pizzo. Low Frequency Radio Astronomy and the LOFAR Observatory: Lectures from the Third LOFAR Data Processing School. Springer, 2019.

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A Lunar far-side very low frequency array: Proceedings of a workshop. National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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A Lunar far-side very low frequency array: Proceedings of a workshop. National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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United States. Office of the Chief of Naval Operations., ed. Final suppelmental [i.e. supplemental] environmental impact statement for Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA) Sonar. Dept. of the Navy, Chief of Naval Operations, 2007.

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United States. Navy Dept. and United States. Office of the Chief of Naval Operations., eds. Final overseas environmental impact statement and environmental impact statement for surveillance towed array sensor system low frequency active (SURTASS LFA) sonar. Dept. of the Navy, 2001.

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United States. Navy Dept. and United States. Office of the Chief of Naval Operations., eds. Draft overseas environmental impact statement and environmental impact statement for surveillance towed array sensor system low frequency active (SURTASS LFA) sonar. Dept. of the Navy, 1999.

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(US), National Research Council. An Assessment of Potential Health Effects from Exposure to PAVE PAWS Low-Level Phased-Array Radiofrequency Energy. National Academies Press, 2005.

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An assessment of potential health effects from exposure to PAVE PAWS low-level phased-array radiofrequency energy. National Academies Press, 2005.

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Book chapters on the topic "Low Frequency Array (LOFAR)"

1

Brentjens, Michiel A., and Jan David Mol. "LOFAR Overview." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_2.

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Norden, Menne J. "LOFAR Station Processing." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_3.

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McKean, John, and Ger de Bruyn. "Calibration of LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_5.

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Brentjens, Michiel A. "Polarization Imaging with LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_10.

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Buitink, Stijn. "Particle Physics with LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_13.

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Moldón, Javier, and Eskil Varenius. "Long Baseline Imaging with LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_11.

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Hessels, Jason, and Richard Fallows. "High Time Resolution with LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_14.

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Mahony, Elizabeth. "Error Recognition in LOFAR Data." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_6.

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Heald, George. "The LOFAR Standard Imaging Pipeline." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_9.

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Oonk, J. B. Raymond. "Spectral Line Data Analysis with LOFAR." In Low Frequency Radio Astronomy and the LOFAR Observatory. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-23434-2_12.

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Conference papers on the topic "Low Frequency Array (LOFAR)"

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Vermeulen, R. C. "LOFAR, the low frequency array." In SPIE Astronomical Telescopes + Instrumentation, edited by Larry M. Stepp, Roberto Gilmozzi, and Helen J. Hall. SPIE, 2012. http://dx.doi.org/10.1117/12.928196.

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Chiou, Mu-Min, and Jean-Fu Kiang. "Reconstruction algorithm applied to low-frequency array (LOFAR) image." In 2011 IEEE International Workshop on Electromagnetics; Applications and Student Innovation (iWEM). IEEE, 2011. http://dx.doi.org/10.1109/iwem.2011.6021486.

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White, Stephen, Namir E. Kassim, and William C. Erickson. "Solar radioastronomy with the LOFAR (low frequency array) radio telescope." In Astronomical Telescopes and Instrumentation, edited by Stephen L. Keil and Sergey V. Avakyan. SPIE, 2003. http://dx.doi.org/10.1117/12.460362.

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van Cappellen, Wim, and Dion Kant. "Design approaches to the Low Frequency Array (LOFAR) active antenna amplifier." In 32nd European Microwave Conference, 2002. IEEE, 2002. http://dx.doi.org/10.1109/euma.2002.339455.

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Kassim, Namir E., T. Joseph W. Lazio, William C. Erickson, Patrick C. Crane, Richard A. Perley, and Brian Hicks. "The Low-Frequency Array (LOFAR): opening a new window on the universe." In Astronomical Telescopes and Instrumentation, edited by Harvey R. Butcher. SPIE, 2000. http://dx.doi.org/10.1117/12.390454.

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Rottgering, Huub J. A. "LOFAR and the low frequency Universe." In ISKAF2010 Science Meeting. Sissa Medialab, 2010. http://dx.doi.org/10.22323/1.112.0050.

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"Low frequency solar scrutiny with the Polish LOFAR stations." In Planetary Radio Emissions VIII. Austrian Academy of Sciences Press, 2018. http://dx.doi.org/10.1553/pre8s437.

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Shulevski, Aleksandar, and Raffaella Morganti. "AGN life cycles - the low frequency story as told by LOFAR." In Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation. Sissa Medialab, 2013. http://dx.doi.org/10.22323/1.169.0027.

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Schoenmakers, Arno P. "Taming the beast: operating the world's largest low-frequency radio observatory LOFAR." In SPIE Astronomical Telescopes + Instrumentation, edited by Alison B. Peck, Robert L. Seaman, and Fernando Comeron. SPIE, 2012. http://dx.doi.org/10.1117/12.926521.

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Faulkner, A. J., and J. G. Bij de Vaate. "SKA low frequency aperture array." In 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2015. http://dx.doi.org/10.1109/aps.2015.7305073.

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Reports on the topic "Low Frequency Array (LOFAR)"

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Hald, J\atrgen, and Svend Gade. Array Designs Optimized for Both Low-Frequency NAH and High-Frequency Beamforming. SAE International, 2005. http://dx.doi.org/10.4271/2005-08-0014.

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Scandrett, C. L., and D. R. Canright. Low Frequency Active Array Calculations in a Shallow Channel. Defense Technical Information Center, 2001. http://dx.doi.org/10.21236/ada486572.

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Scatko, Thomas, and William Lipe. Frequency Diverse Array Component Characterization: An Evaluation of Low-Cost RF Components for Testing Frequency Diverse Array Antennas Used in Secure Communication Investigations. Defense Technical Information Center, 2015. http://dx.doi.org/10.21236/ada624158.

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Yilmaz, Ali, and Jeffery Gabelmann. A Low Frequency Electrode Array Tool for Fracture Diagnostics in Steel-Cased Wellbores. Office of Scientific and Technical Information (OSTI), 2017. http://dx.doi.org/10.2172/1475425.

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Chiu, Ching-Sang. 32-Channel Digitizer for a Moored Hydrophone Array for Low-to-Mid Frequency Shallow-Water Acoustics Experiments. Defense Technical Information Center, 2012. http://dx.doi.org/10.21236/ada574820.

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