Journal articles on the topic 'Non-radiating source'
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Cartlidge, Edwin. "Physicists fabricate a non-radiating antenna." Physics World 34, no. 9 (December 1, 2021): 6i. http://dx.doi.org/10.1088/2058-7058/34/09/06.
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SINAYOKO, SAMUEL, A. AGARWAL, and Z. HU. "Flow decomposition and aerodynamic sound generation." Journal of Fluid Mechanics 668 (December 3, 2010): 335–50. http://dx.doi.org/10.1017/s0022112010004672.
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An approximate decomposition of fluid-flow variables satisfying unbounded compressible Navier–Stokes equations into acoustically radiating and non-radiating components leads to well-defined source terms that can be identified as the physical sources of aerodynamic noise. We show that, by filtering the flow field by means of a linear convolution filter, it is possible to decompose the flow into non-radiating and radiating components. This is demonstrated on two different flows: one satisfying the linearised Euler equations and the other the Navier–Stokes equations. In the latter case, the corresponding sound sources are computed. They are found to be more physical than those computed through classical acoustic analogies in which the flow field is decomposed into a steady mean and fluctuating component.
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Shahir, Shahed, Mehrbod Mohajer, Arash Rohani, and Safieddin Safavi-Naeini. "PERMITTIVITY PROFILE ESTIMATION BASED ON NON-RADIATING EQUIVALENT SOURCE (2D CASE)." Progress In Electromagnetics Research B 50 (2013): 157–75. http://dx.doi.org/10.2528/pierb13012308.
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Xiao, Gaobiao, and Rui Liu. "Direct Method for Reconstructing the Radiating Part of a Planar Source from Its Far-Fields." Electronics 11, no. 23 (November 22, 2022): 3852. http://dx.doi.org/10.3390/electronics11233852.
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A planar current is generally divided into a radiating part that mainly generates propagation fields and a non-radiating part that mainly generates evanescent fields. This paper proposes a direct method to reconstruct the radiating part of a planar source from its far-fields based on their explicit relationships. A standard reconstruction process is provided in which the far-fields are sampled at the peaks of their propagation modes. An analysis shows that the achievable reconstruction resolution of the source distribution is about half a wavelength. The paper also demonstrates that it is possible to reconstruct the source by sampling the far-fields on a plane or along a linear path. The performance of the reconstruction algorithm is illustrated with numerical examples.
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Herrera, L., A. Di Prisco, and J. Ospino. "The transition of a gravitationally radiating, dissipative fluid to equilibrium." Canadian Journal of Physics 96, no. 9 (September 2018): 1010–15. http://dx.doi.org/10.1139/cjp-2017-0651.
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We describe the transition of a gravitationally radiating, axially and reflection symmetric, dissipative fluid to a non-radiating state. It is shown that very shortly after the end of the radiating regime, at a time scale on the order of the thermal relaxation time, the thermal adjustment time, or the hydrostatic time (whichever is larger), the system reaches the equilibrium state. This result is at variance with all the studies carried out in the past on gravitational radiation outside the source, which strongly suggest that after a radiating period, the conditions for a return to a static case look rather forbidding. As we shall see, the reason for such a discrepancy resides in the fact that some elementary, but essential, physical properties of the source have been overlooked in these latter studies.
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FREUND, JONATHAN B. "Noise sources in a low-Reynolds-number turbulent jet at Mach 0.9." Journal of Fluid Mechanics 438 (July 5, 2001): 277–305. http://dx.doi.org/10.1017/s0022112001004414.
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The mechanisms of sound generation in a Mach 0.9, Reynolds number 3600 turbulent jet are investigated by direct numerical simulation. Details of the numerical method are briefly outlined and results are validated against an experiment at the same flow conditions (Stromberg, McLaughlin & Troutt 1980). Lighthill's theory is used to define a nominal acoustic source in the jet, and a numerical solution of Lighthill's equation is compared to the simulation to verify the computational procedures. The acoustic source is Fourier transformed in the axial coordinate and time and then filtered in order to identify and separate components capable of radiating to the far field. This procedure indicates that the peak radiating component of the source is coincident with neither the peak of the full unfiltered source nor that of the turbulent kinetic energy. The phase velocities of significant components range from approximately 5% to 50% of the ambient sound speed which calls into question the commonly made assumption that the noise sources convect at a single velocity. Space–time correlations demonstrate that the sources are not acoustically compact in the streamwise direction and that the portion of the source that radiates at angles greater than 45° is stationary. Filtering non-radiating wavenumber components of the source at single frequencies reveals that a simple modulated wave forms for the source, as might be predicted by linear stability analysis. At small angles from the jet axis the noise from these modes is highly directional, better described by an exponential than a standard Doppler factor.
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CASADIO, R. "GAMMA-RAY BURSTS FROM GRAVITATIONAL COLLAPSE." International Journal of Modern Physics A 17, no. 20 (August 10, 2002): 2753. http://dx.doi.org/10.1142/s0217751x02011801.
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A possible origin of gamma-ray bursts is the gravitational collapse of compact objects. A semiclassical analysis, which employs the Born-Oppenheimer approximation in order to treat gravity as classical while matter is quantized1, was first applied to homogeneous spheres of dust2,3 and (thick) non-radiating shells 4. We later derived an effective Lagrangian for (thin) radiating shells5 which allowed us to study the evolution of a self-gravitating shell of bosonic matter coupled to a scalar radiation field. We showed that the matter can form a condensate and the matter degrees of freedom are excited, because of the non-adiabaticity of the collapse, at the expense of gravitational energy4,6. Upon decaying back to the ground state, the excited matter energy is subsequently transferred to the radiation field. In fact, the system can convert large fractions of its gravitational energy into radiation and the time evolution of the radius of the shell is then significantly slowed down with respect to the non-radiating case. This provides a new mechanism to extract energy from collapsing matter which might play a role as a source of gamma-ray bursts.
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Hoenders, Bernhard J., and Hedzer A. Ferwerda. "The non-radiating component of the field generated by a finite monochromatic scalar source distribution." Pure and Applied Optics: Journal of the European Optical Society Part A 7, no. 5 (September 1998): 1201–11. http://dx.doi.org/10.1088/0963-9659/7/5/025.
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Tang, Ming-Chun, Ting Shi, and Richard W. Ziolkowski. "Electrically Small, Broadside Radiating Huygens Source Antenna Augmented With Internal Non-Foster Elements to Increase Its Bandwidth." IEEE Antennas and Wireless Propagation Letters 16 (2017): 712–15. http://dx.doi.org/10.1109/lawp.2016.2600525.
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Zatta, Robin, Daniel Headland, Eamal Ashna, Ritesh Jain, Philipp Hillger, Janusz Grzyb, and Ullrich R. Pfeiffer. "Silicon Lens Optimization to Create Diffuse, Uniform Illumination from Incoherent THz Source Arrays." Journal of Infrared, Millimeter, and Terahertz Waves 42, no. 9-10 (September 2021): 947–59. http://dx.doi.org/10.1007/s10762-021-00828-0.
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AbstractArrays of terahertz (THz) sources provide a pathway to overcoming the radiation power limitations of single sources. Several independent sources of THz radiation may be implemented in a single integrated circuit, thereby realizing a monolithic THz source array of high output power. Integrated THz sources must generally be backside-coupled to extended hemispherical dielectric lenses in order to suppress substrate modes and extract THz power. However, this lens also increases antenna gain and thereby produces several non-overlapping beams. This is because individual source pixels are relatively large. Hence, their spatial separation on-chip translates to angular separation in the far-field. In other words, there are gaps in their field of view into which very little THz power is projected. Therefore, they cannot homogeneously illuminate an imaging target. This article presents a simple, practical, and scalable method to convert arrays of incoherent THz sources into a diffuse, uniform illumination source without the need for reducing pixel size. Briefly, individual beam divergence is optimized by tailoring the dimensions of the extended hemispherical dielectric lens such that the far-field beams of adjacent source pixels overlap and combine to form a uniform far-field beam. We applied this method to an incoherent 8 × 8-pixel THz source array radiating 10.3 dBm at 0.42 THz as a proof of concept and thereby realized a 10.3-dBm 0.42-THz diffuse, uniform illumination source that was then deployed in a demonstration of THz active imaging.
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Kumar, Sure Geethan, S. Vijaya Kumar Varma, Putta Durga Prasad, Chakravarthula S. K. Raju, Oluwole Daniel Makinde, and Rohit Sharma. "MHD Reacting and Radiating 3-D Flow of Maxwell Fluid Past a Stretching Sheet with Heat Source/Sink and Soret Effects in a Porous Medium." Defect and Diffusion Forum 387 (September 2018): 145–56. http://dx.doi.org/10.4028/www.scientific.net/ddf.387.145.
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In this study, we numerically investigate the hydromagnetic three dimensional flow of a radiating Maxwell fluid over a stretching sheet embedded in a porous medium with heat source/sink, first ordered chemical reaction and Soret effect. The corresponding boundary layer equations are reduced into set of non-linear ordinary differential equations by means of similarity transformations. The resulting coupled non-linear equations are solved numerically by employing boundary value problem default solver in MATLAB bvp4c package. The obtained results are presented and discussed through graphs and tables. It is noticed that the Deborah number reduces the velocity fields and improves the temperature and concentration fields. Nomenclature
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Décréau, P. M. E., S. Aoutou, A. Denazelle, I. Galkina, J. L. Rauch, X. Vallières, P. Canu, S. Rochel Grimald, F. El-Lemdani Mazouz, and F. Darrouzet. "Wide-banded NTC radiation: local to remote observations by the four Cluster satellites." Annales Geophysicae 33, no. 10 (October 22, 2015): 1285–300. http://dx.doi.org/10.5194/angeo-33-1285-2015.
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Abstract. The Cluster multi-point mission offers a unique collection of non-thermal continuum (NTC) radio waves observed in the 2–80 kHz frequency range over almost 15 years, from various view points over the radiating plasmasphere. Here we present rather infrequent case events, such as when primary electrostatic sources of such waves are embedded within the plasmapause boundary far from the magnetic equatorial plane. The spectral signature of the emitted electromagnetic waves is structured as a series of wide harmonic bands within the range covered by the step in plasma frequency encountered at the boundary. Developing the concept that the frequency distance df between harmonic bands measures the magnetic field magnitude B at the source (df = Fce, electron gyrofrequency), we analyse three selected events. The first one (studied in Grimald et al., 2008) presents electric field signatures observed by a Cluster constellation of small size (~ 200 to 1000 km spacecraft separation) placed in the vicinity of sources. The electric field frequency spectra display frequency peaks placed at frequencies fs = n df (n being an integer), with df of the order of Fce values encountered at the plasmapause by the spacecraft. The second event, taken from the Cluster tilt campaign, leads to a 3-D view of NTC waves ray path orientations and to a localization of a global source region at several Earth radii (RE) from Cluster (Décréau et al., 2013). The measured spectra present successive peaks placed at fs ~ (n+ 1/2) df. Next, considering if both situations might be two facets of the same phenomenon, we analyze a third event. The Cluster fleet, configured into a constellation of large size (~ 8000 to 25 000 km spacecraft separation), allows us to observe wide-banded NTC waves at different distances from their sources. Two new findings can be derived from our analysis. First, we point out that a large portion of the plasmasphere boundary layer, covering a large range of magnetic latitudes, is radiating radio waves. The radio waves are issued from multiple sources of small size, each related to a given fs series and radiating inside a beam of narrow cone angle, referred to as a beamlet. The beamlets illuminate different satellites simultaneously, at different characteristic fs values, according to the latitude at which the satellite is placed. Second, when an observing satellite moves away from its assumed source region (the plasmapause surface), it is illuminated by several beamlets, issued from nearby sources with characteristic fs values close to each other. The addition of radio waves blurs the spectra of the overall received electric field. It can move the signal peaks such that their position fs satisfiesfs = (n+α) df, with 0 < α < 1. These findings open new perspectives for the interpretation of NTC events displaying harmonic signatures.
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Seth, Gauri Shenkar, Rohit Sharma, B. Kumbhakar, and R. Tripathi. "MHD Stagnation Point Flow over Exponentially Stretching Sheet with Exponentially Moving Free-Stream, Viscous Dissipation, Thermal Radiation and Non-Uniform Heat Source/Sink." Diffusion Foundations 11 (August 2017): 182–90. http://dx.doi.org/10.4028/www.scientific.net/df.11.182.
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An investigation is carried out for the steady, two dimensional stagnation point flow of a viscous, incompressible, electrically conducting, optically thick heat radiating fluid taking viscous dissipation into account over an exponentially stretching non-isothermal sheet with exponentially moving free-stream in the presence of uniform transverse magnetic field and non-uniform heat source/sink. The governing boundary layer equations are transformed into highly nonlinear ordinary differential equations using suitable similarity transform. Resulting boundary value problem is solved numerically with the help of 4th-order Runge-Kutta Gill method along with shooting technique. Effects of various pertinent flow parameters on the velocity, temperature field, skin friction and Nusselt number are described through figures and tables. Also, the present numerical results are compared with the earlier published results for some reduced case and a good agreement has been found among those results.
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Le, Tuan Tu, Huy Hung Tran, and Ayman Abdulhadi Althuwayb. "Wideband Circularly Polarized Antenna Based on a Non-Uniform Metasurface." Applied Sciences 10, no. 23 (December 3, 2020): 8652. http://dx.doi.org/10.3390/app10238652.
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This paper presents a non-uniform metasurface (MS)-based circularly polarized (CP) antenna that is able to perform with a wideband operation characteristic. A squared patch with truncated corners was chosen as a radiating CP source. Then, unlike the conventional CP MS antennas with a uniform MS, the proposed design employed a non-uniform MS placed above the driven patch. Apart from increasing the impedance bandwidth, the non-uniform MS was also capable of generating two additional CP bands in the high-frequency region, which contributed to significantly increasing the antenna’s overall performance. For demonstration, an antenna prototype was fabricated and experimentally tested. The measured operating bandwidth of the fabricated antenna was about 30% and the broadside gain within this band was around 6.6 dBic. Compared to the other reported CP MS antennas in the open literature, the proposed design has the advantages of very wideband operation with a comparable size and gain.
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Gore, J. P., U. S. Ip, and Y. R. Sivathanu. "Coupled Structure and Radiation Analysis of Acetylene/Air Flames." Journal of Heat Transfer 114, no. 2 (May 1, 1992): 487–93. http://dx.doi.org/10.1115/1.2911299.
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A coupled radiation-structure analysis of turbulent, non-premixed, strongly radiating acetylene/air flames is described. The analysis extends the laminar flamelet concept to include the effects of local radiative heat loss/gain. A new method for the calculation of the radiative source term is presented. New measurements of mean and fluctuating emission temperatures and radiation intensities, and previous data concerning flame structure are used to evaluate the predictions. Results show good agreement between measurements and predictions of flame structure similar to past uncoupled calculations. The mean emission temperatures and the mean visible radiation intensities are substantially underpredicted by the uncoupled analysis. The coupled calculations provide reasonable estimates of both quantities.
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Vien, Benjamin Steven, Nithurshan Nadarajah, Wing Kong Chiu, and L. R. Francis Rose. "Scattering of the Fundamental Symmetric Wave Mode Incident at a Defect on the Blind Side of a Weep Hole in an Isotropic Plate." Advanced Materials Research 891-892 (March 2014): 1237–42. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1237.
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The scattering of a fundamental symmetric wave mode by a notch on the blind side of weep hole is described in this paper. It will report on findings obtained from computational simulations to determine the effect and interaction of the impinging waves with the defect on the open hole located on the blind side of the incident wave. The finite element simulation results showed mode conversions of fundamental modes, leaky edge waves on the circumferential surface and source-like diffractions radiating from the tip of the notch and hole. These findings highlight the potential of applying this wave phenomenon to quantify defect located hard-to-inspect areas by positioning actuator and sensor in accessible regions of metallic structures and is relevant to the development and improvement of current techniques in non-destructive inspection of metallic structures
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Sreenivasulu, P., T. Poornima, and P. Bala Anki Reddy. "Soret and Dufour effects on MHD non-Darcian radiating convective flow of micropolar fluid past an inclined surface with non-uniform surface heat source or sink and chemical reaction." IOP Conference Series: Materials Science and Engineering 263 (November 2017): 062014. http://dx.doi.org/10.1088/1757-899x/263/6/062014.
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Akram, A., A. Rehman Jami, S. Ahmad, M. Sufyan, and R. Munir. "Role of modified scalar variables in the modeling of spherical fluids." International Journal of Geometric Methods in Modern Physics 15, no. 08 (June 22, 2018): 1850140. http://dx.doi.org/10.1142/s0219887818501402.
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The aim of this work is to analyze the role of shear evolution equation in the modeling of relativistic spheres in [Formula: see text] gravity. We assume that non-static diagonally symmetric geometry is coupled with dissipative anisotropic viscous fluid distributions in the presence of [Formula: see text] dark source terms. A specific distribution of [Formula: see text] cosmic model has been assumed and the spherical mass function through generic formula introduced by Misner-Sharp has been formulated. Some very important relations regarding Weyl scalar, matter variables and mass functions are being computed. After decomposing orthogonally the Riemann tensor, some scalar variables in the presence of [Formula: see text] extra degrees of freedom are calculated. The effects of the polynomial modified structure scalars in the modeling of through Weyl, shear, expansion scalar differential equations are investigated. The energy density irregularity factor has been calculated for both anisotropic radiating viscous with varying Ricci scalar and for dust cloud with present Ricci scalar corrections.
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Pietsch, W., W. Voges, E. Kendziorra, and M. Pakull. "Exosat Observations of H2252−035: Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission." International Astronomical Union Colloquium 93 (1987): 281–92. http://dx.doi.org/10.1017/s0252921100104993.
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AbstractThe 805 sec pulsing X-ray source H2252−035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ~ 100% in the 2.3–7.9 keV band it is only ~ 40%. X-ray dips that are more pronounced in low energies occur simultaneously with the orbital minimum of the optical light curve. The medium energy spectra during dips with respect to the non dip spectrum can be explained by just enhanced cold gas absorption of an additional absorbing column of 2 1022 cm−2. Model spectra for the 805 s minimum have to include a strong iron emission line at 6.55 keV with an equivalent width of 3 keV in addition to a reduced continuum intensity (radiating area) and enhanced low energy absorption.
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Ahmad, S., A. Rehman Jami, and Z. Aas. "Shear and expansion evolution for dissipative fluids." Modern Physics Letters A 33, no. 20 (June 28, 2018): 1850111. http://dx.doi.org/10.1142/s0217732318501110.
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The aim of this work is to analyze the role of shear evolution equation in the modeling of relativistic spheres in f(R) gravity. We assume that non-static diagonally symmetric geometry is coupled with dissipative anisotropic viscous fluid distributions in the presence of f(R) dark source terms. A specific distribution of f(R) cosmic model has been assumed and the spherical mass function through generic formula introduced by Misner–Sharp has been formulated. Some very important relations regarding Weyl scalar, matter variables and mass functions are being computed. After decomposing orthogonally the Riemann tensor, some scalar variables in the presence of f(R) extra degrees of freedom are calculated. The effects of the three parametric modified structure scalars in the modeling of Weyl, shear, expansion scalar differential equations are investigated. The energy density irregularity factor has been calculated for both anisotropic radiating viscous with varying Ricci scalar and dust cloud with present Ricci scalar corrections.
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Šimon, Vojtech. "NON-THERMAL EMISSION FROM CATACLYSMIC VARIABLES: IMPLICATIONS ON ASTROPARTICLE PHYSICS." Acta Polytechnica 53, A (December 18, 2013): 595–600. http://dx.doi.org/10.14311/ap.2013.53.0595.
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We review the lines of evidence that some cataclysmic variables (CVs) are the sources of non-thermal radiation. It was really observed in some dwarf novae in outburst, a novalike CV in the high state, an intermediate polar, polars, and classical novae (CNe) during outburst. The detection of this radiation suggests the presence of highly energetic particles in these CVs. The conditions for the observability of this emission depend on the state of activity, and the system parameters. We review the processes and conditions that lead to the production of this radiation in various spectral bands, from gamma-rays including TeV emission to radio. Synchrotron and cyclotron emissions suggest the presence of strong magnetic fields in CV. In some CVs, e.g. during some dwarf nova outbursts, the magnetic field generated in the accretion disk leads to the synchrotron jets radiating in radio. The propeller effect or a shock in the case of the magnetized white dwarf (WD) can lead to a strong acceleration of the particles that produce gamma-ray emission via pi0 decay; even Cherenkov radiation is possible. In addition, a gamma-ray production via pi0 decay was observed in the ejecta of an outburst of a symbiotic CN. Nuclear reactions during thermonuclear runaway in the outer layer of the WD undergoing CN outburst lead to the production of radioactive isotopes; their decay is the source of gamma-ray emission. The production of accelerated particles in CVs often has episodic character with a very small duty cycle; this makes their detection and establishing the relation of the behavior in various bands difficult.
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Salas-Matamoros, Carolina, and Karl-Ludwig Klein. "Polarisation and source structure of solar stationary type IV radio bursts." Astronomy & Astrophysics 639 (July 2020): A102. http://dx.doi.org/10.1051/0004-6361/202037989.
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The reconfiguration of the magnetic field during and after a coronal mass ejection (CME) may be accompanied by radio emission from non-thermal electrons. In particular, stationary type IV bursts (also called storm continua) are emitted by electrons in closed magnetic configurations usually located in the wake of the outward-travelling CME. Although stationary type IV bursts, which stand out by their long duration (up to several hours) and strong circular polarisation, have been known for more than fifty years, there have been no systematic studies since the 1980s. In this work we use the data pool of the Nançay Radioheliograph together with white-light coronagraphy, EUV imaging and magnetography from the SoHO, Proba2, SDO and STEREO spacecraft to revisit the source structure and polarisation of a sample of seven well-defined stationary type IV bursts at decimetre-to-metre wavelengths. The radio sources are most often found in one leg, in one case both legs, of the magnetic flux rope erupting into the high corona during the CME. The cross-correlation of the brightness temperature time profiles in the event with sources in both legs implies that the radiating electrons have energies of a few tens of keV. Comparison with the magnetic field measured in the photosphere and its potential extrapolation into the corona shows that the radio emission is in the ordinary mode. This result was inferred historically by means of the hypothesis that the magnetic field orientation in the radio source was that of the dominant sunspot in the parent active region. This hypothesis is shown here to be in conflict with noise storms in the same active region. It is confirmed that the polarisation of stationary type IV continua may be strong, but is rarely total, and that it gradually increases in the early phase of the radio event. We find that the increase is related to the gradual disappearance of some weakly polarised or unpolarised substructure, which dominates the first minutes of the radio emission.
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Blåsten, Eemeli, and Yi-Hsuan Lin. "Radiating and non-radiating sources in elasticity." Inverse Problems 35, no. 1 (November 20, 2018): 015005. http://dx.doi.org/10.1088/1361-6420/aae99e.
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Katsnelson, Boris, Ernst Uzhansky, Regina Katsman, Andrey Lun'kov, and Anatoliy N. Ivakin. "Geoacoustic inversion for gassy sediment parameters using reflection and scattering of acoustic signals." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A242. http://dx.doi.org/10.1121/10.0011196.
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Results of experimental study and theoretical modeling of acoustic propagation and reverberation in Lake Kinneret (Israel) with gassy sediments are presented. The presence of methane bubbles in sediments significantly influences reflection and scattering of sound signals from the bottom, which in turn allows estimating properties of sediment using acoustic sensing. Experiments were carried out using R/V Hermona with sound source located at a 7 m depth radiating 1 s-long 0.3–7 kHz LFM sweeps with intervals from 1 to 20 s. Acoustic pressure time series were received on a single hydrophone at ∼1 m from the source and two vertical arrays fixed in the lake center at either 40 m or 10 m from each other. Analysis of both monostatic and bistatic experimental data (including long range propagation) was aimed to estimate acoustic characteristics of the bottom and then to infer the related gas content and its spatial and temporal variability. The sound speed in sediments at different locations (with different depth of water layer, maximal depth 40 m) was estimated to be ∼170–250 m/s that corresponds to gas volume concentrations ∼1%, which is in accordance with direct measurements made using non-acoustic probes. [Work was supported by BSF grant 2018150.]
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Ardavan, H. "Asymptotic analysis of the radiation by volume sources in supersonic rotor acoustics." Journal of Fluid Mechanics 266 (May 10, 1994): 33–68. http://dx.doi.org/10.1017/s0022112094000923.
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The application of Lighthill's acoustic analogy to the generation of sound by rotating surfaces with supersonic speeds results in radiation integrals in which the stationary points of the phase function – that describes the sapce-time distance between each source point and a fixed observation point – have variable positions and coalesce at a caustic in the space of source points. Here, the leading term in the asymptotic expansion of the corresponding Green's function at this caustic is calculated, both in the time and the frequency domains, and it is shown that the radiation generated by volume sources, which are steady in the uniformly rotating blade-fixed frame, has an amplitude that does not obey the spherical spreading law, i.e. does not fall off like RP–1 with the radial distance RP away from the source. Within a finite solid angle, depending on the extent of the source distribution, the amplitude of this newly identified sound decays like RP–½, so that it is stronger in the far field than any previously studied element. That this is not incompatible with the conservation of energy is because the emission time intervals associated with the volume elements of the source distribution which contribute towards the non-spherically decaying component of the radiation are by a large (RP-dependent) factor greater than the time intervals during which the signals generated by these elements are received. The contributing source elements are those whose positions at the retarded time coincide witht the locus of singularities of the Green's function, i.e. with the one-dimensional locus of points, fixed in the rotating frame, which approach the observer with the wave speed and zero acceleration along the radiation direction. Because the signals received at two neighbouring instants in time arise from distinct, coherently radiating filamentary parts of the source which have both different extents and different strengths, the resulting overall waveform in the far zone consists of the superposition of a (continuous) set of narrow subpulses with uneven amplitudes. These subpulses are narrower the larger the distance from the source.The differences between the new results and those of the earlier works in the literature are shown to arise from the error terms in the far-field and high-frequency approximations, approximations that are inappropriate for volume sources moving supersonically.
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Musafir, Ricardo E. "On non-radiating sources." Journal of Sound and Vibration 332, no. 17 (August 2013): 3947–55. http://dx.doi.org/10.1016/j.jsv.2013.02.042.
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PINHEIRO, G., and R. CHAN. "RADIATING GRAVITATIONAL COLLAPSE WITH SHEARING MOTION AND BULK VISCOSITY REVISITED." International Journal of Modern Physics D 19, no. 11 (September 2010): 1797–822. http://dx.doi.org/10.1142/s0218271810018050.
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A new model is proposed to collapsing stars consisting of an anisotropic fluid with bulk viscosity, radial heat flow and outgoing radiation. In a previous paper one of us has introduced a time-dependent function into the grr, besides the time-dependent metric functions gθθ and gϕϕ. The aim of this work is to generalize this previous model by introducing bulk viscosity and comparing it to the non-viscous collapse. The behavior of the density, pressure, mass, luminosity and the effective adiabatic index is analyzed. Our work is also compared to the case of a collapsing fluid with bulk viscosity of another previous model, for a star with 6 M⊙. The pressure of the star, at the beginning of the collapse, is isotropic, but due to the presence of the bulk viscosity the pressure becomes more and more anisotropic. The black hole is never formed because the apparent horizon formation condition is never satisfied, in contrast to the previous model where a black hole is formed. An observer at infinity sees a radial point source radiating exponentially until it reaches the time of maximum luminosity, and suddenly the star turns off. This is in contrast to the former model where the luminosity also increases exponentially, reaching a maximum and decreases thereafter until the formation of the black hole. The effective adiabatic index diminishes due to the bulk viscosity, thus increasing the instability of the system, in both models, in the former paper as well as in this work.
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Borovkov, Dmitrii, and Adrià Canós Valero. "On the link between mean square-radii and high-order toroidal moments." Journal of Physics: Conference Series 2015, no. 1 (November 1, 2021): 012021. http://dx.doi.org/10.1088/1742-6596/2015/1/012021.
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Abstract Multipole expansions of the source play an important role in a broad range of disciplines in modern physics, ranging from the description of exotic states of matter to the design of nanoantennas in photonics. Within the context of the latter, toroidal multipoles, a third group of multipoles complementing the well-known electric and magnetic ones, have been widely investigated since they lead to the formation of non-radiating sources. In the last years, however, the photonics community has brought to light the existence of a fourth type of multipoles that is commonly overlooked. Currently, different groups have provided different mathematical expressions to describe such sources, and they have been coined with different names; on the one hand mean-square radii, and on the other hand, as high order toroidal moments. Despite their clear physical similarity, a formal relation between the two has not yet been established. While explicit formulas for both types have been derived, they are not expressed in the same basis, and therefore it is not possible to draw a clear physical connection between them. In this contribution, we will bridge this gap and rigorously derive the connection between the two representations, taking as an example the cases of the nth order mean square radius of the electric dipole and the nth order electric toroidal dipole. Our results conclusively show that both types of representations are exactly equivalent up to a prefactor.
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AZIZ, Jabir. "Analysis of Biological Effects of Microwave Energy and Safe Distance Calculations." Journal of Al-Rafidain University College For Sciences ( Print ISSN: 1681-6870 ,Online ISSN: 2790-2293 ), no. 2 (October 24, 2021): 1–14. http://dx.doi.org/10.55562/jrucs.v25i2.435.
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Microwave energy has found wide range of applications in the fields of communications, industrial, scientific, medical, commercial and military. In the Public applications, microwave energy may produce biological effects which may sometimes, lead to adverse health effect.This paper introduces the relationship between microwave energy and the public health through the analysis of the effects of microwave energy on the biological systems and its hazardous effects on the health of the human body. It starts with the analysis of non-thermal and thermal effects of microwave energy on the tissue of the human body, and then it gives an analysis of the radiation limits of microwave radiation hazard and the different international standards. The safe distance from the radiating source was formulated and estimated for four scenarios, which represents different case studies (On-Beam-Axis of Continuous Transmission, On-Beam-Axis of Pulsating Transmission, Side-Lobe Transmission, and Rotating-Beam Transmission).The results of these estimations indicate that there is a hazardous distance varies from few meters up to few hundred of meters depending on the coverage, power and type of transmission.
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Eawsakul, Nitipat, and Chalermpol Reaungepattanawiwat. "Development of High Power LED Driver Using LNK418EG." Applied Mechanics and Materials 866 (June 2017): 345–49. http://dx.doi.org/10.4028/www.scientific.net/amm.866.345.
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Currently, the use of Light Emitting Diodes (LED) bulbs has been intensively increasing since LED possess various qualifications of high efficiency in light production, not radiating heat, no toxic substance, lifespan longer than other bulbs. However, when the circuit of LED Driver is connected directly to high power LED with an AC source, it causes high losses of energy and the occurrence of the non-sinusoidal waveforms thus causing the harmonic series in the power supply system. In the research, a circuit for driving high power LED at high power of 30 watts was created by using a Fly-Back converter converting AC into DC current. At the same time, IC LinkSwitch-PH model LNK418EG was applied to act as a factor correction for electric power and control the constant output currents and electromotive force. After the input AC current at 180-240 volts was applied on the experimental circuit, the input current which has the waveform close to a sine shape resulted in the low distortion of the input current but provided the constant output current and electromotive force. LED’s high luminance could be detected at 300 luxs at a distance of one meter and its performance was 90 percentages.
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Oshlakov, Victor G., and Anatoly P. Shcherbakov. "Optimisation of a Polarisation Nephelometer." Light & Engineering, no. 02-2021 (April 2021): 87–95. http://dx.doi.org/10.33383/2020-057.
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An analysis of the influence caused by polarization nephelometer parameters on the scattering matrix measurement accuracy in a non-isotropic medium is presented. The approximation errors in the actual scattering volume and radiation beam by an elementary scattering volume and an elementary radiation beam are considered. A formula for calculating the nephelometer base is proposed. It is shown that requirements to an irradiation source of a polarizing nephelometer, i.e. mono-chromaticity and high radiation intensity and directivity in a wide spectral range can be satisfied by a set of high brightness LEDs with a radiating (self-luminous) small size body. A 5-wavelength monochromatic irradiation source, with an emission flux of (0.15–0.6) W required for a polarization nephelometer, is described. The design of small-sized polarizing phase control units is shown. An electronic circuit of a radiator control unit based on an AVR-Atmega 8-bit microcontroller with feedback and drive control realized by means of an incremental angular motion sensor and a software PID controller is presented. Precise and smooth motion of the radiator is ensured by standard servo-driven numerical control mathematics and the use of precision gears. The system allows both autonomous adjustment of the radiator’s reference positions and adjustment by means of commands from a personal computer. Both the computer and microcontroller programs were developed with the use of free software, making it possible to transfer the programs to Windows‑7(10), Linux and embedded Linux operating systems. Communication between the radiator’s position control system and the personal computer is realised by means of a standard noise immune USB-RS485 interface.
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Kim, Kisik, and Emil Wolf. "Non-radiating monochromatic sources and their fields." Optics Communications 59, no. 1 (August 1986): 1–6. http://dx.doi.org/10.1016/0030-4018(86)90034-9.
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Kalyak, A. A., S. A. Kazantsev, V. M. Gruznov, and I. I. Zasypkina. "Instrumentation complex for measuring the thermophysical properties of rocks in natural occurrence temperature conditions." Journal of Physics: Conference Series 2388, no. 1 (December 1, 2022): 012137. http://dx.doi.org/10.1088/1742-6596/2388/1/012137.
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Abstract A schematic diagram and an operation algorithm of an instrumentation complex for measuring the thermal conductivity and thermal diffusivity of rocks by the non-stationary method of a linear source under natural occurrence temperature conditions up to 200 °C are proposed. Thermocouples are used to measure the temperature of the probes. The complex contains two linear (needle) probes, which are placed in a rock sample at a certain distance r from each other. One probe, containing a linear heater and a thermocouple, radiates heat, the other one, containing a thermocouple, is a measuring probe. The cold junction temperature of thermocouples is measured by a semiconductor sensor. To calculate the voltage of the cold junction from the value of its temperature, a direct conversion of thermoEMF by a power polynomial is used. To calculate the temperature of the hot junction of the probe, an inverse transformation by a power polynomial of the voltage values of the hot junction of thermocouples into temperature was applied. In direct and inverse transformations, the degree of polynomials is 10. To reduce the temperature measurement error, digital filtering of signals from thermocouples was used. A digital-to-analogue converter is included in the heater circuit of the radiating probe for flexible heating control. The results of measuring the thermal conductivity and thermal diffusivity of dry and wet sand samples are consistent with the literature data on the temperature dependence.
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Davidson, Mark P. "Quantum wave equations and non-radiating electromagnetic sources." Annals of Physics 322, no. 9 (September 2007): 2195–210. http://dx.doi.org/10.1016/j.aop.2006.10.005.
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Negrete, C. A., D. Dultzin, P. Marziani, D. Esparza, J. W. Sulentic, A. del Olmo, M. L. Martínez-Aldama, et al. "Highly accreting quasars: The SDSS low-redshift catalog." Astronomy & Astrophysics 620 (December 2018): A118. http://dx.doi.org/10.1051/0004-6361/201833285.
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Context. The most highly accreting quasars are of special interest in studies of the physics of active galactic nuclei (AGNs) and host galaxy evolution. Quasars accreting at high rates (L/LEdd ∼ 1) hold promise for use as “standard candles”: distance indicators detectable at very high redshift. However, their observational properties are still largely unknown. Aims. We seek to identify a significant number of extreme accretors. A large sample can clarify the main properties of quasars radiating near L/LEdd ∼ 1 (in this paper they are designated as extreme Population A quasars or simply as extreme accretors) in the Hβ spectral range for redshift ≲0.8. Methods. We use selection criteria derived from four-dimensional Eigenvector 1 (4DE1) studies to identify and analyze spectra for a sample of 334 candidate sources identified from the SDSS DR7 database. The source spectra were chosen to show a ratio RFeII between the FeII emission blend at λ4570 and Hβ, RFeII > 1. Composite spectra were analyzed for systematic trends as a function of Fe II strength, line width, and [OIII] strength. We introduced tighter constraints on the signal-to-noise ratio (S/N) and RFeII values that allowed us to isolate sources most likely to be extreme accretors. Results. We provide a database of detailed measurements. Analysis of the data allows us to confirm that Hβ shows a Lorentzian function with a full width at half maximum (FWHM) of Hβ ≤ 4000 km s−1. We find no evidence for a discontinuity at 2000 km s−1 in the 4DE1, which could mean that the sources below this FWHM value do not belong to a different AGN class. Systematic [OIII] blue shifts, as well as a blueshifted component in Hβ are revealed. We interpret the blueshifts as related to the signature of outflowing gas from the quasar central engine. The FWHM of Hβ is still affected by the blueshifted emission; however, the effect is non-negligible if the FWHM Hβ is used as a “virial broadening estimator” (VBE). We emphasize a strong effect of the viewing angle on Hβ broadening, deriving a correction for those sources that shows major disagreement between virial and concordance cosmology luminosity values. Conclusions. The relatively large scatter between concordance cosmology and virial luminosity estimates can be reduced (by an order of magnitude) if a correction for orientation effects is included in the FWHM Hβ value; outflow and sample definition yield relatively minor effects.
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Sol, Hélène, and Lourdes Vicente. "A Tentative Sketch for BL Lacertae Objects." Symposium - International Astronomical Union 159 (1994): 473. http://dx.doi.org/10.1017/s0074180900176521.
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VLBI polarization data show magnetic field configuration parallel to the nuclear jet in quasars and perpendicular to it in BL Lac objects. It appears difficult to account for this contrast within the unified scheme for AGN. To investigate a direct explanation of this peculiarity of BL Lac objects, we study the possibilities of propagation and radiation of beams of particles in transverse ambient magnetic field. High energy streams with kinetic energy density larger than the ambient magnetic one, Ekin > Emag, can easily propagate with enhancement of the transverse magnetic field at the leading edge of the stream and reconnection of magnetic lines in its wake. Synchrotron radiation in front shocks naturally leads to the observed polarization. Moreover self-polarization, with formation of charge layers and E × B drift velocity, allows substantial propagation for even lower energy streams with Ekin < Emag, as long as their density no is large enough, typically κ = 4πnomic2/B2 > 1. Such low energy streams are non diamagnetic and do not modify the ambient field. Any high energy tail of the total particle distribution in the jet therefore radiates in the transverse field pattern. This concerns for instance the BL Lac object W Comae if we assume a proton-electron jet with bulk velocity vo = 0.1c (as the source does not require relativistic beaming so far), an equipartition magnetic field B = 0.02 G and a density of radiating particles nr = 0.05cm−3 at about 7 pc from the nucleus (knot K3). For nr/no = 10−3, one gets the stream density no = 50cm−3 which allows good propagation as κ reaches 2 × 103, and still corresponds to a moderate mass outflow of 0.06 M⊙ /year for a VLBI jet cross-sectional area of 2pc2.
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Devaney, Anthony J., and Edwin A. Marengo. "A method for specifying non-radiating, monochromatic, scalar sources and their fields." Pure and Applied Optics: Journal of the European Optical Society Part A 7, no. 5 (September 1998): 1213–20. http://dx.doi.org/10.1088/0963-9659/7/5/026.
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Johnson, S., C. Miles, and D. A. Inglis. "First Report of Verticillium Wilt Caused by V. dahliae on Grafted Solanum aethiopicum in Washington." Plant Disease 97, no. 6 (June 2013): 840. http://dx.doi.org/10.1094/pdis-09-12-0870-pdn.
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Solanum aethiopicum L., previously S. integrifolium Poir. (4), has been used as a rootstock for commercial, grafted eggplant production throughout Asia (3). In August 2010 and 2011, symptoms of Verticillium wilt were observed on ‘Epic’ eggplant (S. melongena L.) grafted onto S. aethiopicum at two sites with a history of the disease: one in the irrigated, dryland Columbia Basin of eastern Washington near Eltopia, and the other in maritime western Washington near Mount Vernon. Interveinal chlorosis, V-shaped necrotic lesions, and wilting were evident at both sites in both years. Each year, stems of 20 symptomatic plants from each field site were cut at the soil line to a 20-cm length, surface sterilized for 5 min in a 10% bleach solution, rinsed in tap water for 30 s, cut longitudinally, and incubated in moisture chambers for 4 weeks at room temperature in the dark. Microsclerotia that formed in the stems were typical of those produced by V. dahliae. One isolate, ‘MVEgg301’, from an infected stem at Mount Vernon, developed dark microsclerotia and verticillate conidiophores in a radiating pattern, typical of Verticillium on half-strength potato dextrose agar (1/2 PDA) medium. The internal transcribed spacer (ITS) region of rDNA amplified by PCR assay using primers ITS6 and ITS4 from mycelia sampled directly from 1/2 PDA media revealed a 100% match with ITS rDNA sequences of >50 V. dahliae accessions in GenBank (1). Pathogenicity of ‘MVEgg301’ was assessed in two tests. In both, 12 each of non-grafted and grafted (with cv. Epic) S. aethiopicum plants were inoculated with ‘MVEgg301’ by cutting approximately 5 mm off the root tips and dipping the remaining roots in a suspension of 106 conidia/ml for 5 s. Similarly, 12 each of non-grafted and grafted S. aethiopicum plants were cut and dipped similarly in sterile water as controls. Chlorosis, necrosis, and wilting were observed in 11 of the 12 inoculated, non-grafted plants and 8 of the 12 inoculated, grafted plants in Test I. The same symptoms were observed in 10 of the 12 inoculated, non-grafted plants and 10 of the 12 inoculated, grafted plants in Test II. V. dahliae was reisolated and confirmed from symptomatic, inoculated non-grafted and grafted plants using the stem assay and direct PCR assay described above. Chlorosis, necrosis, and wilting were observed in one non-grafted control plant in Test I, and two non-grafted and four grafted control plants in Test II. The symptoms were mild and likely due to nutritional deficiencies; microsclerotia were not observed in any assayed water-inoculated plant stems. Although there are several reports of V. albo-atrum infecting S. aethiopicum in the United States (2), to our knowledge, this is the first report of V. dahliae causing Verticillium wilt on this eggplant species. This finding is significant because S. aethiopicum is used as a rootstock for control of soilborne diseases like Verticillium wilt in commercial grafted eggplant production (3). References: (1) G. Calmin et al. Biotechnol. Biotechnol. Equ. 21:40, 2007. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN, 1989. (3) M. Oda. Food Fert. Technol. Ctr. Ext. Bul. 480:1, 1999. (4) PBI Solanum Project. 2012. Solanaceae Source. Accessed at http://www.nhm.ac.uk/solanaceaesource/ . Natural History Museum, London, 29 Aug. 2012.
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Gragnani, G. L., and M. Diaz Mendez. "Improved electromagnetic inverse scattering procedure using non-radiating sources and scattering support reconstruction." IET Microwaves, Antennas & Propagation 5, no. 15 (2011): 1822. http://dx.doi.org/10.1049/iet-map.2011.0132.
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Bosneaga, I. A., M. C. Bologa, and E. I. Agarval. "К вопросу об оптимальной микробиологической деконтаминации воздушной среды и поверхностей." Elektronnaya Obrabotka Materialov 57, no. 6 (December 2021): 87–107. http://dx.doi.org/10.52577/eom.2021.57.6.87.
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Modern civilization, providing economic and social progress, at the same time objectively creates – sometimes close to ideal – conditions for the spread of various infections. The catastrophic consequences of the SARS-CoV-2 pandemic clearly indicate that homo sapiens appeared to be unable to resist effectively the onslaught of the coronavirus. The purpose of this publication is an attempt to fill the gap in the development of effective methods and means for microbiological decontamination that are optimal in terms of critical parameters. Observational data indicate that a significant number of SARS-CoV-2 coronavirus infections occur by air without a direct contact with the source, including, over a long time interval. Precipitations help to cleanse the air from pollutants and viruses, reducing non-contact contamination, which additionally brings up to date the problem of optimal microbiological decontamination of the air environment and surfaces. A thermodynamic approach has been used to optimize microbiological sterilization. It is shown that irreversible chemical oxidation reactions are the shortest way to achieve sterility, and they are capable of providing high reliability of deconta-mination. It has been established that oxygen is an optimal oxidant, also from the point of view of ecology, since its reactive forms harmoniously fit into natural exchange cycles. The optimal method for obtaining reactive oxygen species for disinfection is the use of low-temperature (“cold”) plasma, which provides energy-efficient generation of oxidative reactive forms – atomic oxygen (O), ozone (O3), hydroxyl radical (·OH), hydrogen peroxide (H2O2), superoxide (O2-), and singlet oxygen O2(a1Δg). Due to a short lifetime for most of the above forms outside the plasma applicator, remote from the plasma generator objects should be sterilized with ozone (O3), the minimum lifetime of which is quite long. It has been substantiated that the microwave method of generating oxygen plasma is optimal for the energy efficient ozone production. A modular principle of generation is proposed for varying the productivity of ozone generating units over a wide range. The module has been developed on the base of an adapted serial microwave oven, in which a non-self-sustaining microwave discharge is maintained thanks to ionizers (igniters), including those based on radiating radionuclides-emitters. In case of massive contamination of surfaces, it is advisable – in addition to ozone (O3) air disinfecting – to use aqueous solutions of hydrogen peroxide (H2O2). It is essential that these reactive oxygen species for disinfecting remote from the plasma generator objects are highly efficient and, at the same time, environmentally neutral. Reliable and affordable personal protective equipment is proposed for activities in zones of increased ozone concentration. The considered optimal means of disinfection can be applicable not only in medicine, but also adapted for numerous practices in agriculture, industry, and in everyday life.
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Soria, Roberto, Zdenka Kuncic, and Anabela C. Gonçalves. "Chilled disks in ultraluminous X-ray sources." Proceedings of the International Astronomical Union 2, S238 (August 2006): 453–54. http://dx.doi.org/10.1017/s1743921307005911.
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AbstractIf the standard disk-blackbody approximation is used to estimate black hole (BH) masses in ultraluminous X-ray sources (ULXs), the inferred masses are ∼ 1000 M⊙. However, we argue that such an approximation cannot be applied to ULXs, because their disks are only radiating a small fraction of the accretion power, and are therefore cooler than they would be in a thermal-dominant state, for a given BH mass. Instead, we suggest that a different phenomenological approximation should be used, based on three observable parameters: disk luminosity, peak temperature, and ratio between thermal and non-thermal emission. This method naturally predicts masses ∼ 50 M⊙, more consistent with other theoretical and observational constraints.
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Atamanskyi, D. V., V. P. Riabukha, V. M. Kartashov, A. V. Semeniaka, and L. V. Procopenco. "SPECTRAL ESTIMATION METHODS FOR A JOINT SYSTEM OF THE NON-NOISE-LIKE TARGETS DETECTION AND THE NOISE RADIATING SOURCES LOCALIZATION." Radio Electronics, Computer Science, Control, no. 1 (April 1, 2022): 7. http://dx.doi.org/10.15588/1607-3274-2022-1-1.
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Context. For many radars, the autonomous systems of the non-noise-like aerial targets (AT) detection and the noise radiating sources (NRS) localization (direction-of-arrival estimation) may be replaced with a single detection-localization system, which carries out the common operations of the AT-detection and the NRS-localization only once. For such a system, groups of noneigenvalue and eigenvalue decomposition based “super-resolving” spectral estimation (SE) methods are considered to substantiate efficient one for the NRS-localization.
Objective. The comparative analysis efficiency of the SE-methods of different groups by a set of criteria and recommendations on their practical application.
Method. The methods’ efficiency is analyzed analytically, under simulation results and their comparison with new results presented in the open literature. In the simulation, a well-grounded and practically examined software-algorithmic basis of adaptive lattice filters for nonparametric SE-methods implementation is used.
The results. It is shown that the SE-methods of both groups have no restrictions on the antenna array configuration (flat, ring, etc.), including when used in non-equal spaced “sparse” antenna arrays with inter-element distances of more than half radar wavelength. A comparison is made on the resolution (determination of the NRS number) and the NRS-localization (direction-of-arrival estimation) efficiency by methods of different groups when using various antenna arrays. It is shown that the methods of the first group (non-eigenvalue based) in terms of the probability of correct resolution, are almost not inferior to the known and new methods of the second group (eigenvalue ones). Based on the set of criteria and practical application conditions for direction-of-arrival estimation of the noise radiating sources, it is recommended to use the Capon’s minimum variance method if there are limitations on the computational complexity of the method. In the absence of such restrictions, it is advisable to use the SE-bank of methods.
Conclusions. For the practical implementation of a joint system of the non-noise-like aerial target detection and the noise radiating sources localization, a structural-algorithmic basis of adaptive lattice filters is preferred. Using latter, along with the weight vector forming for the target detection, it is possible to implement not only the Capon’s method, but also a SE-bank of methods by combining the squares of absolute values of its original vectors’ components.
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Reddy, Konda Jayarami, N. P. Madhusudhana Reddy, Rama Krishna Konijeti, and Dasore Abhishek. "Numerical Investigation of Chemical Reaction and Heat Source on Radiating MHD Stagnation Point Flow of Carreau Nanofluid with Suction/Injection." Defect and Diffusion Forum 388 (October 2018): 171–89. http://dx.doi.org/10.4028/www.scientific.net/ddf.388.171.
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This research work is focused on the effects of combined heat and mass transfer on MHD stagnation point flow of Carreau nanaofluid embedded in porous medium with heat source. Thermal radiation and chemical reaction are also taken into account. The governing non-linear PDEs are transformed into a set of non-linear coupled ODEs which are then solved numerically by using the Runge– Kutta–Fehlberg fourth–fifth order method along shooting technique. The graphical and tabular results elucidate the influence of different non-dimensional governing parameters on the velocity, temperature and concentration fields along with the wall friction, local Nusselt and Sherwood numbers. We found the dual nature of the solutions for suction and injection cases. A good agreement of the present results has been observed by comparing with the existing literature results.
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Tucker, Robin. "On the effects of geometry on guided electromagnetic waves." Theoretical and Applied Mechanics 34, no. 1 (2007): 1–50. http://dx.doi.org/10.2298/tam0701001t.
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The method of moving (Cartan) coframes is used to analyze the influence of geometry on the behavior of electromagnetic fields in confining guides and the effect of such fields on their ultra-relativistic sources. Such issues are of relevance to a number of topical problems in accelerator science where the need to control the motion of high current-density micro-meter size bunches of relativistic radiating charge remains a technical and theoretical challenge. By dimensionally reducing the exterior equations for the sources and fields on spacetime using symmetries exhibited by the confining guides one achieves a unifying view that offers natural perturbative approaches for dealing with smooth non-uniform and curved guides. The issue of the back-reaction of radiation fields on the sources is approached in terms of a simple charged relativistic fluid model. .
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Yao, Ting, Jian Ye Zhang, Jia Ping Liu, and Qian Tian. "Non-Structural Cracking Analysis of early Age of Reinforcement Concrete Wall." Advanced Materials Research 446-449 (January 2012): 251–59. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.251.
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Structure monitoring has been increasingly valuable in recent years and has taken a leading role in the field of structural engineering. Date collected by early age monitoring represent a unique source of information for understanding the real behavior. In this paper, the temperatures evolution and concrete deformation evolution are obtained by real-time continuous monitoring of Reinforcement concrete(RC) wall. The result shows that the early age thermal cracking is one of the most important origin of several phenomena that imperil durability and shorten the lifespan of the structure. Though the wall is not considered as mass concrete, and has a big radiating surface, the maximum temperature can even reach up to 52°C due to heat generation of cement and the insulation of formwork, which can lead to shrinkage deformation when the temperature decreases. The measured experimental date can provide useful reference for early crack control and durability of RC concrete structure, and they can also be use to verify and improve the accuracy of the numerical results for RC wall, which is available in the future for basis to similar projects and research.
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P., Sreenivasulu, and Poornima T. "Combined Effects of Inclined Lorentzian forces and Melting heat transfer on Radiating Flow of Carbon Nanofluid past a Stretching Cylinder." International Journal of Engineering & Technology 7, no. 4.10 (October 2, 2018): 1070. http://dx.doi.org/10.14419/ijet.v7i4.10.27920.
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An analysis was made to study the effects of non-uniform heat source or sink and aligned magnetic field effect on boundary layer flow of carbon nanofluid past a stretching cylinder with melting heat transfer and radiation. The Prandtl boundary layer equations are transformed into highly nonlinear ordinary differential equations utilizing similarity variables. The final resolved system is explained with shooting method. The upshots of governing factors on the velocity, temperature, surface skin friction and rate of heat transfer are discoursed with the help of graphs. MWCNT performance is better than SWCNT in case of fluid flow. SWCNTs transfers more heat from the fluid rather than multi wall tubes.Comparison of our numerical results with available literature works and shown a good agreement.
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Yousaf, Z. "Structure of spherically symmetric objects: a study based on structure scalars." Physica Scripta 97, no. 2 (January 13, 2022): 025301. http://dx.doi.org/10.1088/1402-4896/ac4191.
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Abstract The aim of this paper is to explore the consequences of extra curvature terms mediated from f(R, T, Q) (where Q ≡ R μ ν T μ ν ) theory on the formation of scalar functions and their importance in the study of populations who are crowded with regular relativistic objects. For this purpose, we model our system comprising of non-rotating spherical geometry formed due to gravitation of locally anisotropic and radiating sources. After considering a particular f(R, T, Q) model, we form a peculiar relation among Misner-Sharp mass, tidal forces, and matter variables. Through structure scalars, we have modeled shear, Weyl, and expansion evolutions equations. The investigation for the causes of the irregular distribution of energy density is also performed with and without constant curvature conditions. It is deduced that our computed one of the f(R, T, Q) structure scalars (Y T ) has a vital role to play in understanding celestial mechanisms in which gravitational interactions cause singularities to emerge.
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Borovkov, Dmitrii, and Adrià Canós Valero. "Toroidal anapole with point magnetic dipoles." Journal of Physics: Conference Series 2388, no. 1 (December 1, 2022): 012018. http://dx.doi.org/10.1088/1742-6596/2388/1/012018.
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Abstract The role of multipolar expansion of the localized current is significant in a broad range of disciplines in the physics of nowadays. It is actively used in such problems as the design of nanoantennas in photonics or the description of exotic states of matter. The toroidal multipoles are the third group of multipoles which complements the electric and magnetic multipolar families. The investigation of toroidal multipoles is important because of their role in the formation of so-called anapole states, non-radiating sources. The further study showed that there are also exist the higher-order toroidal dipoles or mean-square radii, which are equivalent. Here we suggest the structure which consists of point magnetic dipoles and supports the toroidal anapole state, which is obtained with the destructive interference of electric toroidal dipole with the first mean-square radius of the electric toroidal dipole. We also present an analytical condition for toroidal anapole with this system of point magnetic dipoles placed in two circles.
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Maslov, V. P. "INVESTIGATION OF THERMAL RADIATION ANGULAR AND POLARIZATION CHARACTERISTICS OF ONE-DIMENSIONAL PHOTONIC STRUCTURES ON A FINITE SUBSTRATE." Optoelektronìka ta napìvprovìdnikova tehnìka 56 (December 7, 2021): 83–88. http://dx.doi.org/10.15407/iopt.2021.56.083.
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One-dimensional photonic structures (PS) are the layered metamaterials, which optical properties are due to interference effects within the structure. Due to the interaction of electromagnetic waves with the periodic structure, the thermal radiation (TR) of such PS has the features of coherent: it has a selective spectrum and a petal pattern. The relevance of TR PS research is due to the search for new materials to create sources of infrared (IR) radiation in the middle and far IR range (with a wavelength > 5 μm). The second important area of application of the radiating properties of the PS is the creation of non-radiating coatings to remove unwanted TR from the heated surfaces of the IR devices. Despite the fact that the irradiative properties of PS have been studied quite well, in the literature insufficient attention is paid to the influence of the finite substrate on the parameters of TR structures. The influence of a finite incoherent substrate on the angular and polarization characteristics of the thermal radiation of the system (photonic structure)/substrate has been investigated. Systems consisting of plane-parallel Ge or Si plates as PS and incoherent BaF2, BaF2/Al and Al substrates were used in experimental studies. It has been established, the contrast and amplitude of the directional diagram petals of the TR system depend on the ratio of the optical characteristics of the photonic structure and the substrate. The presence of a strongly reflective substrate eliminates the difference between the angular dependences of the s- and p-polarized components of the TR. In the case when the PS is placed on a transparent incoherent substrate with a lower refractive index, there is an increase in the p-polarized component of the TR and the suppression of the s-polarized. The thermal imaging picture of the TR angular distribution of the Si/Al system has been recorded and it was experimentally proved that the TR of photonic systems exhibits circular patterns. The results of the work can be used in the development of narrowband emitters in the middle and far infrared range, coatings to increase radiation energy exchange and coatings with minimal emissivity that are invisible in the thermal range.
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Terborgh, John, and Jeffrey Mathews. "Partitioning of the understorey light environment by two Amazonian treelets." Journal of Tropical Ecology 15, no. 6 (November 1999): 751–63. http://dx.doi.org/10.1017/s0266467499001157.
Full textAbstract:
Primary tropical forests comprise a mosaic of mature, gap and building phase patches, resulting in great spatial variation in the distribution of foliage. Light may consequently penetrate into the forest interior over a wide range of angles. It thus seems possible that understorey tree species might be adapted for distinct understorey light conditions. At the Cocha Cashu Biological Station in Madre de Dios, Peru, there are two understorey treelets distinguished by contrasting crown architectures. One, Neea chlorantha (Nyctaginaceae), possesses a much-branched superstructure and displays a smoothly contoured shell of drooping elliptical leaves. The other, Rinorea viridifolia (Violaceae), displays planar arrays of horizontally-oriented obovate leaves held on whorls of stiffly radiating horizontal branches.With the aid of hemispherical photography and the program CANOPY, the light environment at large within a 2.25-ha permanent tree plot, and above and below the crowns of Neea and Rinorea treelets, was investigated. Available light (measured as uncorrected indirect site factor (ISFU) in CANOPY) at control points showed a log-linear increase with height from 2.1 to 14.2 m. The relative amount of lateral illumination also increased with height. Photographs were taken just above and below the crowns of 50 Neea and 50 Rinorea treelets. Neea crowns were more effective at intercepting light from overhead sources, whereas Rinorea crowns were more effective at intercepting light from lateral sources. Adult Neea and Rinorea treelets occurred at locations in the forest where they were exposed to differing angular distributions of incident light, suggesting that the two species were engaged in a form of resource partitioning, a conclusion that is in conflict with the non-equilibrium model of tropical forest tree species diversity. It is suggested that tropical tree species diversity is, at least in part, a product of adaptive specialization to a spatially heterogeneous light environment.