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Artykuły w czasopismach na temat "Narrowband survey":
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Drew, Janet E. "New and old roles for narrowband Hα". Proceedings of the International Astronomical Union 5, H15 (listopad 2009): 778. http://dx.doi.org/10.1017/s1743921310011567.
AbstractUntil recently, Hα has been seen as the tracer of ionized gas, picking out both star formation and the late stages of stellar evolution. This has been reaffirmed, spectacularly, by the recent WHAM and SHS surveys. But the advent of large-area digital detectors creates a new role for narrowband Hα as a direct, simultaneous, measure of intrinsic stellar colour and reddening when e.g. r'-Hα is combined with a nearby broad band colour e.g. r'- i'. This new capability has been clearly demonstrated by the nearly-complete IPHAS survey.
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Feltrin, Luca, Galini Tsoukaneri, Massimo Condoluci, Chiara Buratti, Toktam Mahmoodi, Mischa Dohler i Roberto Verdone. "Narrowband IoT: A Survey on Downlink and Uplink Perspectives". IEEE Wireless Communications 26, nr 1 (luty 2019): 78–86. http://dx.doi.org/10.1109/mwc.2019.1800020.
Malse, Akhilesh J., i Reena Kulshreshtha. "A Survey on Narrowband filtering Design using Microstrip filters". International Journal of Engineering Trends and Technology 34, nr 7 (25.04.2016): 327–30. http://dx.doi.org/10.14445/22315381/ijett-v34p265.
Shara, M. M., M. Potter, A. F. J. Moffat i L. F. Smith. "A Deep Survey for Faint Galactic Wolf-Rayet Stars". Symposium - International Astronomical Union 143 (1991): 591–94. http://dx.doi.org/10.1017/s0074180900045952.
Surveys of the Galaxy for Wolf-Rayet (WR) stars are mostly based on objective prism searches, and are generally complete to only about 13th visual magnitude. We are using direct narrowband and broadband Schmidt plates to survey large areas of the southern Milky Way for WR stars to 17-18th magnitude. We expect to find more than 50 new WR stars. The newly detected stars should be among the most distant and/or reddened known in the Galaxy. The survey is also designed to test the completeness of previous bright WR star surveys, and thus to help settle debates over the Initial Mass Function of the most massive stars. We have now located 13 new WR stars in a 40 square degree region in Carina where 24 WR stars were already known. A 25% incompleteness in detection of WR stars as close as 2-3 kpc is suggested.
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Hickson, Paul, i Mark K. Mulrooney. "University of British Columbia–NASA Multi‐Narrowband Survey. I. Description and Photometric Properties of the Survey". Astrophysical Journal Supplement Series 115, nr 1 (marzec 1998): 35–42. http://dx.doi.org/10.1086/313080.
Corradi, R. L. M., L. Magrini, N. A. Walton, A. A. Zijlstra, J. R. Walsh, M. Perinotto, D. L. Pollacco, D. J. Lennon i R. Greimel. "First Results From the Local Group Census: Planetary Nebulae in Sextans B". Symposium - International Astronomical Union 209 (2003): 561. http://dx.doi.org/10.1017/s0074180900209704.
The Local Group Census is a narrowband survey of all the galaxies of the Local Group (LG) with Dec ≥ −30°, being carried out as part of the Isaac Newton Group's Wide Field Survey programme. Observations are being obtained with the Wide Field Camera at the 2.5m Isaac Newton telescope, equipped with a mosaic of four 2k x 4k EEV CCDs covering a field of view of 34′ x 34′.
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Thompson, D., F. Mannucci i S. V. W. Beckwith. "A Narrowband Imaging Survey for High Redshift Galaxies in the Near Infrared". Astronomical Journal 112 (listopad 1996): 1794. http://dx.doi.org/10.1086/118141.
Bland-Hawthorn, Joss, i D. Heath Jones. "Taurus Tunable Filter: A Flexible Approach to Narrowband Imaging". Publications of the Astronomical Society of Australia 15, nr 1 (1998): 44–49. http://dx.doi.org/10.1071/as98044.
AbstractThe Taurus Tunable Filter (TTF) is a tunable narrowband interference filter covering wavelengths from 6300 Å to the sensitivity drop-off of conventional CCDs (∼9600 Å), although a blue ‘arm’ (4000–6500 Å) is to be added by the end of 1997. The TTF offers monochromatic imaging at the Cassegrain foci of both the Anglo-Australian and William Herschel Telescopes, with an adjustable passband of between 6 and 60 Å. In addition, frequency switching with the TTF can be synchronised with movement of charge (charge shuffling) on the CCD, which has important applications to many astrophysical problems. Here we review the different modes of TTF and suggest their use for follow-up narrowband imaging to the AAO/UKST Galactic Plane Hα Survey.
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Gajjar, Vishal, Dominic LeDuc, Jiani Chen, Andrew P. V. Siemion, Sofia Z. Sheikh, Bryan Brzycki, Steve Croft i in. "Searching for Broadband Pulsed Beacons from 1883 Stars Using Neural Networks". Astrophysical Journal 932, nr 2 (1.06.2022): 81. http://dx.doi.org/10.3847/1538-4357/ac6dd5.
Abstract The search for extraterrestrial intelligence at radio frequencies has largely been focused on continuous-wave narrowband signals. We demonstrate that broadband pulsed beacons are energetically efficient compared to narrowband beacons over longer operational timescales. Here, we report the first extensive survey searching for such broadband pulsed beacons toward 1883 stars as a part of the Breakthrough Listen’s search for advanced intelligent life. We conducted 233 hr of deep observations across 4–8 GHz using the Robert C. Byrd Green Bank Telescope and searched for three different classes of signals with artificial (or negative) dispersion. We report a detailed search—leveraging a convolutional neural network classifier on high-performance GPUs—deployed for the very first time in a large-scale search for signals from extraterrestrial intelligence. Due to the absence of any signal-of-interest from our survey, we place a constraint on the existence of broadband pulsed beacons in our solar neighborhood: ≲1 in 1000 stars have transmitter power densities ≳105 W Hz−1 repeating ≤500 s at these frequencies.
The main goals of this thesis are to classify, catalog and extract a redshift distribution
of galaxies in the UBC/NASA Multi-Narrowband Survey (UNMS), conducted
at the NASA Orbital Debris Observatory (NODO). We aim to classify sources using
a maximum of 39 photometric bands for any source observed. Two independent
classification schemes were implemented and compared. One used the photometric
information from all the filters available (X² fitting routine) and the other employed
a neural network, which based classification on isophotal shape parameters as input
(SExtractor). The classification efficiency of galaxies, based on independent confirmations
were 80% and 90% for the X² routine and SExtractor stellarity index respectively,
even though the comparison between the two methods was poor. The fitted redshifts
were compared with spectroscopically determined redshifts from the NASA/IPAC
Extra-Galactic Database (NED) for 19 galaxies. More than half of the sources had
seriously discrepant photometric redshifts. The spectral energy distributions (SEDs)
of the galaxies with redshifts that did match showed a smooth flux distribution (low
noise) that contained 1 or 2 emission features. Spectra that showed a somewhat scattered
distribution of flux points resulted in uncertain redshift estimates. Failure of
the photometric redshift estimation technique prevented us from pursuing more detailed
statistical analyses, such as the galaxy luminosity function. We discuss possible
interpretations for the apparent photometric/spectroscopic redshift discrepancy.
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Braglia, Katia. "Quasar detection in the UBC-NASA multi-narrowband survey". Thesis, 2002. http://hdl.handle.net/2429/12408.
The goal of this thesis is to select quasars by applying a novel analysis
to the UBC - NASA Multi-Narrow band Survey (UNMS1) catalog. The
database consists of drift-scan observations taken with the 3-m NASA Liquid
Mirror Telescope (LMT) in 1996-1997 and in 1999, using 35 narrow band
filters, from 4500 to 9500 Å, and 4 broad bands (B, V, R, I), necessary for
calibration purposes.
The method presented here is based on the comparison between UNMS1
catalog sources and stellar, galaxy, and quasar templates through a x² minimization procedure combined with Bayesian analysis. The x² parameter is
useful to determine which model is the best fit for an observed Spectral Energy
Distribution (SED); the odds ratio parameter, from the Bayes' theorem,
is necessary in order to know the most likely category the source belongs,
and it involves information such as the number of models for each category
and the surface densities of stars, galaxies and quasars at a given magnitude.
After the method was applied to templates, treated as test-objects, it is
concluded that more than 85% of quasar candidates, selected with at least
30 filter measurements, are correctly classified: the misclassification is due
mostly to the similarity between stellar models and quasars when important
spectral features are missed.
Of all the 39040 selected sources, 3056 quasar candidates were identified:
most of them have typical redshift (z ~ 0.3 - 4), apparent V magnitude (V
~ 16 - 20) and spectral index ( α ~ -2 - 0.8), but there is also a non-negligible
number of objects localized well outside these ranges. Analysing the position
of these sources in the redshift - V magnitude plane, redshift - spectral index
plane and V magnitude - spectral index plane, it is possible to identify
misclassified quasars and remove them away from the sample.
The final list of quasar candidates includes 2294 objects, among which 1
is in common with Veron's quasar catalog.
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Westra, Everhardus Antonius Metske. "A wide field narrowband survey for star forming galaxies at different epochs". Phd thesis, 2007. http://hdl.handle.net/1885/49404.
Narrowband surveys are a well-established tool for finding star-forming
galaxies at different epochs. This thesis presents the Wide Field Imager
Lyman Alpha Search (WFILAS), a survey originally designed to find
Lyman-a (Lya) emission-line galaxies at redshift z~5.7, and subsequently
utilised to find Hydrogen-a (Ha) emitting galaxies at redshift z~0.24.
The survey covers three 0.25 sq. deg. fields each observed in three
narrowband filters, an intermediate band filter (encompassing all
narrowband filters), and two broadband filters.
A sample of seven luminous Lya-emitting galaxies was identified (Lya
luminosity greater than or equal to 1.8e43 ergs), complementing existing
surveys by further constraining the bright end of the Lya luminosity
function. Three candidates identified in one of the three fields, the
well-studied Chandra Deep Field South, were grouped together, supporting
claims of an overdensity at this redshift by other groups.
Two of the seven candidate Lya emitting galaxies have been confirmed
through spectroscopy, one of which is the most luminous at this redshift
to date. The spectra of both objects displayed the asymmetric line
profiles common in Lya at these redshifts. Furthermore, tentative
evidence of a second Lya component, redward of the Lya line was found.
Additional high-resolution imaging showed that both objects were unresolved.
Spectroscopic follow-up was used to determine the fraction of
Ha-emitting galaxies in two of the fields from a total sample of 707
candidate emission line galaxies. This yielded two independent Ha
luminosity functions and star formation densities at z ~ 0.24 following
corrections for extinction, imaging and spectroscopic incompleteness.
These values were found to agree with those of other recent surveys
within the limits of uncertainty. A detailed error analysis found that
both cosmic variance and differences in selection criteria remain the
dominant sources of uncertainty between various Ha luminosity functions
at z smaller than or equal to 0.4. While the star formation rates were
consistent with the typical field galaxy densities probed by the fields,
a tentative increase in star formation rate per galaxy with increasing
density of star forming galaxies was found. This observation supports
galaxy formation scenarios in which galaxy-galaxy interactions are
triggers for star formation.
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"H-α Emitting Galaxies at z ∼ 0.6 in the Deep And Wide Narrowband Survey". Master's thesis, 2017. http://hdl.handle.net/2286/R.I.44164.
abstract: New measurements of the Hα luminosity function (LF) and star formation rate
(SFR) volume density are presented for galaxies at z∼0.62 in the COSMOS field.
These results are part of the Deep And Wide Narrowband Survey (DAWN), a unique
infrared imaging program with large areal coverage (∼1.1 deg 2 over 5 fields) and
sensitivity (9.9 × 10 −18 erg/cm 2 /s at 5σ).
The present sample, based on a single DAWN field, contains 116 Hα emission-
line candidates at z∼0.62, 25% of which have spectroscopic confirmations. These
candidates have been selected through comparison of narrow and broad-band images
in the infrared and through matching with existing catalogs in the COSMOS field.
The dust-corrected LF is well described by a Schechter function with L* = 10 42.64±0.92
erg s −1 , Φ* = 10 −3.32±0.93 Mpc −3 (L* Φ* = 10 39.40±0.15 ), and α = −1.75 ± 0.09. From
this LF, a SFR density of ρ SF R =10 −1.37±0.08 M○ yr −1 Mpc −3 was calculated. An
additional cosmic variance uncertainty of ∼ 20% is also expected. Both the faint
end slope and luminosity density that are derived are consistent with prior results at
similar redshifts, with reduced uncertainties.
An analysis of these Hα emitters’ sizes is also presented, showing a direct corre-
lation between the galaxies’ sizes and their Hα emission. Dissertation/Thesis Masters Thesis Astrophysics 2017
Książki na temat "Narrowband survey":
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Yankee Group. Consumer Communications Planning Service., red. Residential ISDN: Using and paying for narrowband. Boston, MA (200 Portland St., Boston 02114): The Group, 1991.
Lemarchand, Guillermo A. "A Full-Sky Survey for Ultra-Narrowband Artificial Signals". W Exobiology: Matter, Energy, and Information in the Origin and Evolution of Life in the Universe, 339–46. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5056-9_48.
Sun, Yuyi, Shibo He i Fei Tong. "Media Access Control for Narrowband Internet of Things: A Survey". W Encyclopedia of Wireless Networks, 795–99. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-78262-1_161.
Sun, Yuyi, Shibo He i Fei Tong. "Media Access Control for Narrowband Internet of Things: A Survey". W Encyclopedia of Wireless Networks, 1–4. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-32903-1_161-1.
Alagarsamy, Gautami, J. Shanthini i G. Naveen Balaji. "A Survey on Technologies and Challenges of LPWA for Narrowband IoT". W Trends in Cloud-based IoT, 73–84. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-40037-8_5.
E. Martínez Santos, Luis, Roberto Linares y Miranda i Fermín P. Espino-Cortés. "Electromagnetic Spectrum of the Corona Discharge and Their Fundamental Frequency". W Recent Topics in Electromagnetic Compatibility. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101550.
Historically, the Electromagnetic Compatibility (EMC) began with the disturbances at the radio navigation systems generated by the electrical power distribution lines; hence it was referred to as Radio Interference (RI). This disturbance is an Electromagnetic Interference (EMI). Although this type of EMI has been studied since the first decades of the past century, it still maintains a continued interest of the researchers, especially with the Corona Discharge (CD), generated by High Voltage Direct Current (HVDC) systems. Because of its design criterion and the concern that this phenomenon may affect the new radio communication systems in the very high frequency (VHF), ultra high frequency (UHF), and microwave bands, interest in their studies continues. In this chapter, an analysis of the electromagnetic spectrum of the CD is presented. The CD is generated at a short transmission line located within a semi-anechoic chamber. To be sure of the phenomenon, the CD is identified by its current pulse, which is well studied. The instruments used are an oscilloscope of 2 GHz and 2 GS/s, a spectrum analyzer, and an EMI test receiver. The results show that the CD concentrates its energy at frequencies below 70 MHz. In the UHF band, only narrowband signals very separated were found, with levels that cannot affect radio communication systems.
Streszczenia konferencji na temat "Narrowband survey":
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Prasad, Sarita, i Edl Schamiloglu. "A survey of narrowband IEMI global threats". W 2013 IEEE International Symposium on Electromagnetic Compatibility - EMC 2013. IEEE, 2013. http://dx.doi.org/10.1109/isemc.2013.6670445.
Fernandez, Herman, Sandy Avella, Andres Jose Campuzano, David Balaguer, Vicent M. Rodrigo-Penarrocha, Juan Reig i Lorenzo Rubio. "A survey of channel measurement techniques and narrowband channel parameters for vehicular communications". W 2012 IEEE Colombian Communications Conference (COLCOM). IEEE, 2012. http://dx.doi.org/10.1109/colcomcon.2012.6233648.
Fleischman, Judith R., Peter G. Friedman, Christopher Martin i David Schiminovich. "Narrowband ultraviolet imaging experiment for wide-field surveys (NUVIEWS)". W SPIE's 1993 International Symposium on Optics, Imaging, and Instrumentation, redaktor Oswald H. W. Siegmund. SPIE, 1993. http://dx.doi.org/10.1117/12.162829.
Park, Jong H., Jongmin Kim, Muamer Zukic i Douglas G. Torr. "Reflective filters design for self-filtering narrowband ultraviolet imaging experiment wide-field surveys (NUVIEWS) project". W SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, redaktorzy Richard B. Hoover i Arthur B. C. Walker, Jr. SPIE, 1994. http://dx.doi.org/10.1117/12.193132.
Kohli, Indermeet, Alexis B. Lyons, Raheel Zubair, Bhavnit Bhatia, Amanda F. Nahhas, Taylor L. Braunberger, Henry W. Lim i Iltefat H. Hamzavi. "Optimizing parameters for inducing repigmentation in subjects with generalized vitiligo: comparing the efficacy of visible light with ultraviolet A1 versus narrowband ultraviolet B (Conference Presentation)". W Photonics in Dermatology and Plastic Surgery 2020, redaktorzy Bernard Choi i Haishan Zeng. SPIE, 2020. http://dx.doi.org/10.1117/12.2544864.
Wang, Jungao, Shixiao Fu i Rolf Baarholm. "Vortex-Induced Vibration of Steel Catenary Riser Under Vessel Motion". W ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23584.
A truncated steel catenary riser (SCR) model was experimentally tested in the ocean basin by oscillating the top end of the model to simulate the heave and surge vessel motion in order to investigate the vortex-induced vibration (VIV) features. Out-of-plane VIV responses were generally analyzed revealing that although the root mean square (RMS) strain distributed rather broadband, the displacement was quite consistent within a narrowband from 0.2D to 0.3D, and the touch-down point (TDP) area was found not to be the place suffering the maximum out-of-plane VIV response due to near wall effects. What’s more, strong wave propagations were firstly reported and summarized as a distinguished feature for VIV of a SCR under vessel motions, and further results reveal that wave propagation during the ‘lift up’ phase was quite different from that during ‘push down’ in terms of both wave speed and ‘power-in’ region location which is assumed to be caused by the tension variation along the model.
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Dehner, Rick, i Ahmet Selamet. "The Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System". W ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87716.
Deep surge is a violent fluid instability that occurs within turbomachinery compression systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. When a compressor transitions into deep surge, the time-averaged compressor outlet pressure and temperature decrease and increase, respectively, along with a drastic rise in narrowband, low-frequency noise. The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. The compressor breathes air from ambient through an inlet duct with a bellmouth opening. The downstream compression system consists of a compressor outlet duct attached to a plenum with increased cross-sectional area, and an additional duct that connects the plenum outlet to a control valve. A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of this compression system was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequency exhibit excellent agreement. The predicted flow-field throughout the compression system is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the center of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the compression system, along with harmonics at integer multiples of this fundamental frequency.
