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Rapoport, Yuriy G., Oleg K. Cheremnykh, Volodymyr V. Koshovy, Mykola O. Melnik, Oleh L. Ivantyshyn, Roman T. Nogach, Yuriy A. Selivanov et al. "Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment". Annales Geophysicae 35, n.º 1 (5 de enero de 2017): 53–70. http://dx.doi.org/10.5194/angeo-35-53-2017.
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Abstract. We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs), which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG) at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs) with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1). Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1) of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2) of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz) and VLF (kHz) ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system, measurements of electromagnetic and acoustic fields, study of the variations in ionospheric transparency for the radio emissions from galactic radio sources, optical measurements, and the impact on atmospheric aerosols. The proposed approach can be useful for better understanding the mechanism of the acoustic channel of seismo-ionospheric coupling.
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Carcione, José M. "Ground‐penetrating radar: Wave theory and numerical simulation in lossy anisotropic media". GEOPHYSICS 61, n.º 6 (noviembre de 1996): 1664–77. http://dx.doi.org/10.1190/1.1444085.
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Subsurface georadar is a high‐resolution technique based on the propagation of high‐frequency radio waves. Modeling radio waves in a realistic medium requires the simulation of the complete wavefield and the correct description of the petrophysical properties, such as conductivity and dielectric relaxation. Here, the theory is developed for 2-D transverse magnetic (TM) waves, with a different relaxation function associated to each principal permittivity and conductivity component. In this way, the wave characteristics (e.g., wavefront and attenuation) are anisotropic and have a general frequency dependence. These characteristics are investigated through a plane‐wave analysis that gives the expressions of measurable quantities such as the quality factor and the energy velocity. The numerical solution for arbitrary heterogeneous media is obtained by a grid method that uses a time‐splitting algorithm to circumvent the stiffness of the differential equations. The modeling correctly reproduces the amplitude and the wavefront shape predicted by the plane‐wave analysis for homogeneous media, confirming, in this way, both the theoretical analysis and the numerical algorithm. Finally, the modeling is applied to the evaluation of the electromagnetic response of contaminant pools in a sand aquifer. The results indicate the degree of resolution (radar frequency) necessary to identify the pools and the differences between the anisotropic and isotropic radargrams versus the source‐receiver distance.
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Molchanov, O., E. Fedorov, A. Schekotov, E. Gordeev, V. Chebrov, V. Surkov, A. Rozhnoi et al. "Lithosphere-atmosphere-ionosphere coupling as governing mechanism for preseismic short-term events in atmosphere and ionosphere". Natural Hazards and Earth System Sciences 4, n.º 5/6 (22 de noviembre de 2004): 757–67. http://dx.doi.org/10.5194/nhess-4-757-2004.
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Abstract. We present a general concept of mechanisms of preseismic phenomena in the atmosphere and ionosphere. After short review of observational results we conclude: 1. Upward migration of fluid substrate matter (bubble) can lead to ousting of the hot water/gas near the ground surface and cause an earthquake (EQ) itself in the strength-weakened area; 2. Thus, time and place of the bubble appearance could be random values, but EQ, geochemistry anomaly and foreshocks (seismic, SA and ULF electromagnetic ones) are casually connected; 3. Atmospheric perturbation of temperature and density could follow preseismic hot water/gas release resulting in generation of atmospheric gravity waves (AGW) with periods in a range of 6–60min; 4. Seismo-induced AGW could lead to modification of the ionospheric turbulence and to the change of over-horizon radio-wave propagation in the atmosphere, perturbation of LF waves in the lower ionosphere and ULF emission depression at the ground.
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Muhsin, Israa J. "Automated method for buried object detecting using ground penetrating radar (GPR) survey". Iraqi Journal of Physics (IJP) 12, n.º 23 (18 de febrero de 2019): 80–89. http://dx.doi.org/10.30723/ijp.v12i23.342.
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Ground Penetrating Radar (GPR) is a nondestructive geophysical technique that uses electromagnetic waves to evaluate subsurface information. A GPR unit emits a short pulse of electromagnetic energy and is able to determine the presence or absence of a target by examining the reflected energy from that pulse. GPR is geophysical approach that use band of the radio spectrum. In this research the function of GPR has been summarized as survey different buried objects such as (Iron, Plastic(PVC), Aluminum) in specified depth about (0.5m) using antenna of 250 MHZ, the response of the each object can be recognized as its shapes, this recognition have been performed using image processing such as filtering. Where different filters like (DC adjustment, triangular FIR, delete mean trace, FIR) have been applied on output image as well as the simulation of the soil and the buried objects layers have been obtained using GPR simulation program.
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Zhbankov, G. A. y N. P. Danilkin. "INTERACTION OF SHORT-WAVE ELECTROMAGNETIC WAVES WITH SMALL-SCALE IONOSPHERIC INHOMOGENEITIES OF THE POLAR IONOSPHERE (part II)". RADIO COMMUNICATION TECHNOLOGY, n.º 47 (23 de noviembre de 2020): 45–56. http://dx.doi.org/10.33286/2075-8693-2020-47-45-56.
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The results of a comparative analysis of the data of computational and field experiments reflecting the peculiarities of the impact of small-scale inhomogeneities of electron concentration in the Earth's ionosphere on the characteristics of radio wave propagation during vertical ground-based and satellite sounding of the ionosphere are presented. It has been proved that these inhomogeneities are the cause of noticeable distortions of traces in ionograms. The simulation results confirm the possibility of determining the degree of concentration change in a small-scale inhomogeneous structure from experimental data.
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Chen, Li, Jascha A. Lau, Dirk Schwarzer, Jörg Meyer, Varun B. Verma y Alec M. Wodtke. "The Sommerfeld ground-wave limit for a molecule adsorbed at a surface". Science 363, n.º 6423 (13 de diciembre de 2018): 158–61. http://dx.doi.org/10.1126/science.aav4278.
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Using a mid-infrared emission spectrometer based on a superconducting nanowire single-photon detector, we observed the dynamics of vibrational energy pooling of carbon monoxide (CO) adsorbed at the surface of a sodium chloride (NaCl) crystal. After exciting a majority of the CO molecules to their first vibrationally excited state (v = 1), we observed infrared emission from states up to v = 27. Kinetic Monte Carlo simulations showed that vibrational energy collects in a few CO molecules at the expense of those up to eight lattice sites away by selective excitation of NaCl’s transverse phonons. The vibrating CO molecules behave like classical oscillating dipoles, losing their energy to NaCl lattice vibrations via the electromagnetic near-field. This is analogous to Sommerfeld’s description of radio transmission along Earth’s surface by ground waves.
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Bi, Wenda, Yonghui Zhao, Cong An y Shufan Hu. "Clutter Elimination and Random-Noise Denoising of GPR Signals Using an SVD Method Based on the Hankel Matrix in the Local Frequency Domain". Sensors 18, n.º 10 (12 de octubre de 2018): 3422. http://dx.doi.org/10.3390/s18103422.
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Ground-penetrating radar (GPR) is a kind of high-frequency electromagnetic detection technology. It is mainly used to locate targets and interfaces in underground structures. In addition to the effective signals reflected from the subsurface objects or interfaces, the GPR signals in field work also include noise and different clutters, such as antenna-coupled waves, ground clutters, and radio-frequency interference, which have similar wavelet spectral characteristics with the target signals. Clutter and noise seriously interfere with the target’s response signal. The singular value decomposition (SVD) filtering method can select appropriate singular values and characteristic components corresponding to the effective signals for signal reconstruction to filter the GPR data. However, the conventional time-domain SVD method introduces fake signals when eliminating direct waves, and does not have good suppression of random noise around non-horizontal phase axes. Here, an SVD method based on the Hankel matrix in the local frequency domain of GPR data is proposed. Different numerical models and real field GPR data were handled using the proposed method. Based on the power of fake signals introduced via different processes, qualitative and quantitative analyses were carried out. The comparison shows that the newly proposed method could improve efforts to suppress random noise around non-horizontal phase reflection events and weaken the horizontal fake signals introduced by eliminating clutter such as ground waves.
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Di Ninni, Paola, Pietro Bolli, Fabio Paonessa, Giuseppe Pupillo, Giuseppe Virone y Stefan J. Wijnholds. "Electromagnetic Analysis and Experimental Validation of the LOFAR Radiation Patterns". International Journal of Antennas and Propagation 2019 (27 de enero de 2019): 1–12. http://dx.doi.org/10.1155/2019/9191580.
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Low-frequency (<300 MHz) aperture array systems are one of the new trends in modern radio astronomy. Among the challenges they pose, the instrumental calibration is a key aspect requiring an accurate and reliable model of each element of such electrically large array. A full-wave electromagnetic analysis has been carried out for the lower frequency (30–80 MHz) array of the low frequency array (LOFAR) radio telescope taking into account the presence of soil ground, the mutual coupling between the antennas and the relevant receiver impedance loading effects. The impact of mutual coupling effects on the embedded element and array patterns is assessed for two subarray configurations with different degrees of sparseness. A simplistic array factor approach has been implemented as well to determine the accuracy in the antenna pattern evaluation with respect to the full-wave approach. Finally, results from an experimental campaign conducted by means of a micro hexacopter system show the reliability of the developed array numerical model.
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Leyser, Thomas B., H. Gordon James, Björn Gustavsson y Michael T. Rietveld. "Evidence of <i>L</i>-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith". Annales Geophysicae 36, n.º 1 (21 de febrero de 2018): 243–51. http://dx.doi.org/10.5194/angeo-36-243-2018.
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Abstract. The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The CASSIOPE (CAScade, Smallsat and IOnospheric Polar Explorer) spacecraft in the topside ionosphere above the F-region density peak detected transionospheric pump radiation, although the pump frequency was below the maximum ionospheric plasma frequency. The pump wave is deduced to arrive at CASSIOPE through L-mode propagation and associated double (O to Z, Z to O) conversion in pump-induced radio windows. L-mode propagation allows the pump wave to reach higher plasma densities and higher ionospheric altitudes than O-mode propagation so that a pump wave in the L-mode can facilitate excitation of upper hybrid phenomena localized in density depletions in a larger altitude range. L-mode propagation is therefore suggested to be important in explaining the magnetic zenith effect. Keywords. Space plasma physics (active perturbation experiments)
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Dulkarim, Nur Rabihah, Mohd Fairus Mohd Yusoff y Zaharah Johari. "Miniturize Flexible RFID Antenna Design using Metamaterial Structure". ELEKTRIKA- Journal of Electrical Engineering 18, n.º 2 (1 de septiembre de 2019): 55–59. http://dx.doi.org/10.11113/elektrika.v18n2.165.
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Radio Frequency Identification (RFID) is the application of electromagnetic fields to identify and track tags that attached on the objects. It transmits or reads the radio frequency waves in the system. However, due to rapid development of technology in telecommunication, a much more smaller and flexible device is needed. Therefore, in this paper, a new design of flexible RFID antenna using metamaterial structure has been proposed. At first, the basic rectangular microstrip patch antenna with resonant frequency of 900MHz is designed. Then, the CSRR metamaterial structure is introduced at the ground plane to reduce the size of the antenna while the polydimethylsiloxane (PDMS) material is being use as the antenna substrate for flexibility. All the simulation designs were done using CST software. The antenna performances such as resonant frequency, return loss, radiation pattern, gain and bandwidth are then be analyzed and presented. The results show good performances and can be applied for future application.
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Gao, Yong, Lijing Shao, Rui Xu, Ling Sun, Chang Liu y Ren-Xin Xu. "Triaxially deformed freely precessing neutron stars: continuous electromagnetic and gravitational radiation". Monthly Notices of the Royal Astronomical Society 498, n.º 2 (17 de agosto de 2020): 1826–38. http://dx.doi.org/10.1093/mnras/staa2476.
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ABSTRACT The shape of a neutron star (NS) is closely linked to its internal structure and the equation of state of supranuclear matters. A rapidly rotating, asymmetric NS in the Milky Way undergoes free precession, making it a potential source for multimessenger observation. The free precession could manifest in (i) the spectra of continuous gravitational waves (GWs) in the kilohertz (kHz) band for ground-based GW detectors, and (ii) the timing behaviour and pulse-profile characteristics if the NS is monitored as a pulsar with radio and/or X-ray telescopes. We extend previous work and investigate in great detail the free precession of a triaxially deformed NS with analytical and numerical approaches. In particular, its associated continuous GWs and pulse signals are derived. Explicit examples are illustrated for the continuous GWs, as well as timing residuals in both time and frequency domains. These results are ready to be used for future multimessenger observation of triaxially deformed freely precessing NSs, in order to extract scientific implication as much as possible.
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Fu, H. Y., W. A. Scales, P. A. Bernhardt, S. J. Briczinski, M. J. Kosch, A. Senior, M. T. Rietveld, T. K. Yeoman y J. M. Ruohoniemi. "Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT". Annales Geophysicae 33, n.º 8 (11 de agosto de 2015): 983–90. http://dx.doi.org/10.5194/angeo-33-983-2015.
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Abstract. Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.
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Gundersen, Rune, Richard Norland y Cecilie Rolstad Denby. "Geometric, Environmental and Hardware Error Sources of a Ground-Based Interferometric Real-Aperture FMCW Radar System". Remote Sensing 10, n.º 12 (19 de diciembre de 2018): 2070. http://dx.doi.org/10.3390/rs10122070.
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Ground-based interferometric radar systems have numerous environmental monitoring applications in geoscience. Development of a relatively simple ground-based interferometric real-aperture FMCW radar (GB-InRAR) system that can be readily deployed in field without an established set of corner reflectors will meet the present and future need for real-time monitoring of the expected increased number of geohazard events due to climate changes. Several effects affect electromagnetic waves and limit the measurement accuracy, and a careful analysis of the setup of the deployed radar system in field is essential to achieve adequate results. In this paper, we present radar measurement of a moving square trihedral corner reflector from experiments conducted in both the field and laboratory, and assess the error sources with focus on the geometry, hardware and environmental effects on interferometric and differential interferometric measurements. A theoretical model is implemented to assess deviations between theory and measurements. The main observed effects are variations in radio refractivity, multipath interference and inter-reflector interference. Measurement error due to radar hardware and the environment are analyzed, as well as how the geometry of the measurement setup affects the nominal range-cell extent. It is found that for this experiment the deviation between interferometry and differential interferometry is mainly due to variations in the radio refractivity, and temperature-induced changes in the electrical length of the microwave cables. The results show that with careful design and analysis of radar parameters and radar system geometry the measurement accuracy of a GB-InRAR system without the use of deployed corner reflectors is comparable to the accuracy of differential interferometric measurements. A GB-InRAR system can therefore be used during sudden geo-hazard events without established corner reflector infrastructure, and the results are also valid for other high-precision interferometric radar systems.
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Korpisalo, Arto. "Tomographic reconstructions of borehole sections using the radio imaging method at Pyhäsalmi massive sulfide deposit in Finland". GEOPHYSICS 84, n.º 3 (1 de mayo de 2019): B217—B233. http://dx.doi.org/10.1190/geo2017-0332.1.
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We have used the radio imaging method (RIM) to delineate attenuating zones in two borehole sections in the area of the Pyhäsalmi volcanogenic massive sulfide (VMS) copper-zinc deposit located in central Finland. The frequency band (312.5–2500 kHz) is higher and thus provides better resolution and sensitivity to conductive targets than traditional ground-level and borehole electromagnetic (EM) methods. When EM waves are assumed to be propagated along straight rays, the simultaneous iterative reconstruction technique can be used and the decayed amplitudes of the electric field are converted to the attenuation coefficient in dB/m. The straight-ray assumption was, however, not met in this study. The reconstruction results of two borehole sections were compared with time-domain EM (TEM) data and electric logging data. Electric logging reveals the nearby conducive mineralizations, and when compared with RIM data, the continuation of attenuating formations can be better predicted. The intersections interpreted from the TEM data were consistent with the RIM data. However, continuation of the attenuating domains could only be established from RIM data. Low ray densities at the upper and lower edges, violation of the straight-ray assumption, and out-of-plane targets may generate artifacts. In addition, the constructions suffer from smearing in the direction of the raypath. According to the results, we can recover the shape and orientation of attenuating targets in the borehole sections, but the physical properties are underestimated due to the straight-ray assumption. The comparison studies confirmed that RIM is well-suited to estimating subsurface conductivity properties and to predicting the continuation of attenuating domains between the boreholes at the Pyhäsalmi VMS deposit.
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Lee, Gye-An, Darioush Agahi y Franco De Flaviis. "On-chip spiral inductor in flip-chip technology". International Journal of Microwave and Wireless Technologies 1, n.º 5 (octubre de 2009): 431–40. http://dx.doi.org/10.1017/s1759078709990663.
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Performance comparison is made between on-chip spiral inductor in flip-chip versus wirebond package technology. Full-wave electromagnetic simulation and on-strip measurement techniques were used to study the performance fluctuations of inductor within flip-chip environment. Results show that the performance of a flipped silicon-based spiral inductor is affected by the radio frequency (RF) current return path differences. The RF current return path for flip-chip is concentrated on the surface of silicon layer exclusively because back side ground under silicon is floating in flip-chip technology. In addition, the bump proximity effect is also considered. On-chip inductors in flip-chip environment must be optimized by reducing the eddy current in the silicon substrate and parasitic affects by adjusting design parameters. The equivalent circuit model of the flipped on-chip spiral inductor is verified with measured results over broadband frequencies. Also, the RF flip-chip characterization technique using on-strip measurement method is presented.
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Guinan, Edward F., Petr Harmanec y William Hartkopf. "Introduction & Overview to Symposium 240: Binary Stars as Critical Tools and Tests in Contemporary Astrophysics". Proceedings of the International Astronomical Union 2, S240 (agosto de 2006): 5–16. http://dx.doi.org/10.1017/s1743921307003730.
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AbstractAn overview is presented of the many new and exciting developments in binary and multiple star studies that were discussed at IAU Symposium 240. Impacts on binary and multiple star studies from new technologies, techniques, instruments, missions and theory are highlighted. It is crucial to study binary and multiple stars because the vast majority of stars (>60%) in our Galaxy and in other galaxies consist, not of single stars, but of double and multiple star systems. To understand galaxies we need to understand stars, but since most are members of binary and multiple star systems, we need to study and understand binary stars. The major advances in technology, instrumentation, computers, and theory have revolutionized what we know (and also don't know) about binary and multiple star systems. Data now available from interferometry (with milliarcsecond [mas] and sub-mas precisions), high-precision radial velocities (∼1-2 m/s) and high precision photometry (<1–2 milli-mag) as well as the wealth of new data that are pouring in from panoramic optical and infrared surveys (e.g., > 10,000 new binaries found since 1995), have led to a renaissance in binary star and multiple star studies. For example, advances have lead to the discovery of new classes of binary systems with planet and brown dwarf components (over 200 systems). Also, extremely valuable data about binary stars are available across the entire electromagnetic spectrum — from gamma-ray to IR space missions and from the ground using increasingly more powerful and plentiful optical and radio telescopes as well as robotic telescopes. In the immediate future, spectral coverage could even be extended beyond the radio to the first detection of gravity waves from interacting close binaries. Also, both the quality and quantity of data now available on binary and multiple stars are making it possible to gain unprecedented new insights into the structure, and formation and evolution of binary stars, as well as providing valuable astrophysical information (like precise stellar masses, radii, ages, luminosities and distances) to test and constrain current astrophysical theory. These major advances permit tests of current theories and ideas in stellar astrophysics and provide the foundations for the next steps in modeling and improvements in theory to be taken.
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Murmu, Lakhindar, Santasri Koley, Amit Bage y Sushrut Das. "A Simple WiMAX and RFID Band-Notched UWB Bandpass Filter and Its Susceptibility Study". Journal of Circuits, Systems and Computers 28, n.º 11 (octubre de 2019): 1950196. http://dx.doi.org/10.1142/s0218126619501962.
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An ultra-wideband (UWB) bandpass filter (BPF) with a fractional bandwidth (FBW) of about 110%, transmission zero at the high-frequency edge, and band notches at the worldwide interoperability for microwave access (WiMAX) and radio frequency identification (RFID) band is presented in this paper. The filter is based on single short-circuited stub, U-shaped defected ground structure (DGS) array, two U-shaped resonators and two stepped impedance resonators (SIRs). The filter is compact and exhibits a selective filtering characteristic equivalent to a three-pole Chebyshev filter. The design procedure has been described and verified by full-wave electromagnetic (EM) simulation and measurement. The proposed filter has low insertion loss, sharp rejection, and excellent in and out band performance. Due to its applications in WiMAX and RFID systems, the filter may be subjected to high EM radiation from the antenna and nearby sources. Therefore, susceptibility study of such a filter is very important. Hence, the susceptibility study of the band-notched UWB BPF has been carried out by subjecting the structure to an interference source.
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Froiz-Míguez, Iván, Peio Lopez-Iturri, Paula Fraga-Lamas, Mikel Celaya-Echarri, Óscar Blanco-Novoa, Leyre Azpilicueta, Francisco Falcone y Tiago M. Fernández-Caramés. "Design, Implementation, and Empirical Validation of an IoT Smart Irrigation System for Fog Computing Applications Based on LoRa and LoRaWAN Sensor Nodes". Sensors 20, n.º 23 (30 de noviembre de 2020): 6865. http://dx.doi.org/10.3390/s20236865.
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Climate change is driving new solutions to manage water more efficiently. Such solutions involve the development of smart irrigation systems where Internet of Things (IoT) nodes are deployed throughout large areas. In addition, in the mentioned areas, wireless communications can be difficult due to the presence of obstacles and metallic objects that block electromagnetic wave propagation totally or partially. This article details the development of a smart irrigation system able to cover large urban areas thanks to the use of Low-Power Wide-Area Network (LPWAN) sensor nodes based on LoRa and LoRaWAN. IoT nodes collect soil temperature/moisture and air temperature data, and control water supply autonomously, either by making use of fog computing gateways or by relying on remote commands sent from a cloud. Since the selection of IoT node and gateway locations is essential to have good connectivity and to reduce energy consumption, this article uses an in-house 3D-ray launching radio-planning tool to determine the best locations in real scenarios. Specifically, this paper provides details on the modeling of a university campus, which includes elements like buildings, roads, green areas, or vehicles. In such a scenario, simulations and empirical measurements were performed for two different testbeds: a LoRaWAN testbed that operates at 868 MHz and a testbed based on LoRa with 433 MHz transceivers. All the measurements agree with the simulation results, showing the impact of shadowing effects and material features (e.g., permittivity, conductivity) in the electromagnetic propagation of near-ground and underground LoRaWAN communications. Higher RF power levels are observed for 433 MHz due to the higher transmitted power level and the lower radio propagation losses, and even in the worst gateway location, the received power level is higher than the sensitivity threshold (−148 dBm). Regarding water consumption, the provided estimations indicate that the proposed smart irrigation system is able to reduce roughly 23% of the amount of used water just by considering weather forecasts. The obtained results provide useful guidelines for future smart irrigation developers and show the radio planning tool accuracy, which allows for optimizing the sensor network topology and the overall performance of the network in terms of coverage, cost, and energy consumption.
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Hurter, F. y O. Maier. "Tropospheric profiles of wet refractivity and humidity from the combination of remote sensing data sets and measurements on the ground". Atmospheric Measurement Techniques 6, n.º 11 (14 de noviembre de 2013): 3083–98. http://dx.doi.org/10.5194/amt-6-3083-2013.
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Abstract. We reconstruct atmospheric wet refractivity profiles for the western part of Switzerland with a least-squares collocation approach from data sets of (a) zenith path delays that are a byproduct of the GPS (global positioning system) processing, (b) ground meteorological measurements, (c) wet refractivity profiles from radio occultations whose tangent points lie within the study area, and (d) radiosonde measurements. Wet refractivity is a parameter partly describing the propagation of electromagnetic waves and depends on the atmospheric parameters temperature and water vapour pressure. In addition, we have measurements of a lower V-band microwave radiometer at Payerne. It delivers temperature profiles at high temporal resolution, especially in the range from ground to 3000 m a.g.l., though vertical information content decreases with height. The temperature profiles together with the collocated wet refractivity profiles provide near-continuous dew point temperature or relative humidity profiles at Payerne for the study period from 2009 to 2011. In the validation of the humidity profiles, we adopt a two-step procedure. We first investigate the reconstruction quality of the wet refractivity profiles at the location of Payerne by comparing them to wet refractivity profiles computed from radiosonde profiles available for that location. We also assess the individual contributions of the data sets to the reconstruction quality and demonstrate a clear benefit from the data combination. Secondly, the accuracy of the conversion from wet refractivity to dew point temperature and relative humidity profiles with the radiometer temperature profiles is examined, comparing them also to radiosonde profiles. For the least-squares collocation solution combining GPS and ground meteorological measurements, we achieve the following error figures with respect to the radiosonde reference: maximum median offset of relative refractivity error is −16% and quartiles are 5% to 40% for the lower troposphere. We further added 189 radio occultations that met our requirements. They mostly improved the accuracy in the upper troposphere. Maximum median offsets have decreased from 120% relative error to 44% at 8 km height. Dew point temperature profiles after the conversion with radiometer temperatures compare to radiosonde profiles as to: absolute dew point temperature errors in the lower troposphere have a maximum median offset of −2 K and maximum quartiles of 4.5 K. For relative humidity, we get a maximum mean offset of 7.3%, with standard deviations of 12–20%. The methodology presented allows us to reconstruct humidity profiles at any location where temperature profiles, but no atmospheric humidity measurements other than from GPS are available. Additional data sets of wet refractivity are shown to be easily integrated into the framework and strongly aid the reconstruction. Since the used data sets are all operational and available in near-realtime, we envisage the methodology of this paper to be a tool for nowcasting of clouds and rain and to understand processes in the boundary layer and at its top.
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Chen, Xuelei, Jingye Yan, Li Deng, Fengquan Wu, Lin Wu, Yidong Xu y Li Zhou. "Discovering the sky at the longest wavelengths with a lunar orbit array". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, n.º 2188 (23 de noviembre de 2020): 20190566. http://dx.doi.org/10.1098/rsta.2019.0566.
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Due to ionosphere absorption and the interference of natural and artificial radio emissions, astronomical observation from the ground becomes very difficult at the wavelengths of decametre or longer, which we shall refer to as the ultralong wavelengths. This unexplored part of the electromagnetic spectrum has the potential for great discoveries, notably in the study of cosmic dark ages and dawn, but also in heliophysics and space weather, planets and exoplanets, cosmic ray and neutrinos, pulsar and interstellar medium (ISM), extragalactic radio sources, and so on. The difficulty of the ionosphere can be overcome by space observation, and the Moon can shield the radio frequency interferences (RFIs) from the Earth. A lunar orbit array can be a practical first step to opening up the ultralong wave band. Compared with a lunar surface observatory on the far side, the lunar orbit array is simpler and more economical, as it does not need to make the risky and expensive landing, can be easily powered with solar energy, and the data can be transmitted back to the Earth when it is on the near-side part of the orbit. Here, I describe the discovering sky at the longest wavelength (DSL) project, which will consist of a mother satellite and 6–9 daughter satellites, flying on the same circular orbit around the Moon, and forming a linear interferometer array. The data are collected by the mother satellite which computes the interferometric cross-correlations (visibilities) and transmits the data back to the Earth. The whole array can be deployed on the lunar orbit with a single rocket launch. The project is under intensive study in China. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.
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S.Si, MT, Alam Tronics, y Ivan Bahder, S.Si, MTA. "PENGGUNAAN APLIKASI GPR (GROUND PENETRATING RADAR) DENGAN METODE NON-DESTRUCTIVE UNTUK KOLEKTIFITAS DATA KUALITATIF PADA ANALISA SUBSURFACE TANAH EKSTRIM LUNAK". Prosiding Temu Profesi Tahunan PERHAPI 1, n.º 1 (29 de marzo de 2020): 167–80. http://dx.doi.org/10.36986/ptptp.v1i1.60.
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ABSTRAK Ground-Penetrating Radar (GPR) adalah metode Geofisika dengan menggunakan teknologi radar untuk identifikasi perlapisan batuan dan “subsurface” pada investigasi geoteknik. Metode ini termasuk metode “non-destructive” (tanpa melakukan perusakan pada original base) menggunakan gelombang elektromagnetik dengan panjang gelombang mikro (Frekuensi UHF/VHF) yaitu pada garis spektrum gelombang radio dan dapat mendeteksi signal reflektif dari struktur bawah tanah. Kedalaman kemampuan alat GPR untuk “sensing” (penetrasi pembacaan) pada struktur batuan/tanah dengan GPR mencapai ketebalan 50m. GPR bisa mendeteksi (sensing) perubahan arah perlapisan batuan dan memprediksi ketebalan tanah ekstrim lunak, sehingga dapat mengidentifikasi resiko dan menekan biaya penanganan (reduction impact cost) dari perilaku extreme base sebelum proses “dumping” di area berawa atau gambut. Penggunaan instrumen GPR juga dapat menunjang detail interpretasi pengeboran geologi PT. KPC. Metode ini digunakan sebagai metode alternatif jika metode pengeboran geologi terlalu berbahaya dilakukan karena lereng yang diinvestigasi berada pada kondisi kritis atau area rawa yang tidak bisa dilalui mobilisasi rig drilling. Geoteknik KPC telah melakukan investigasi geoteknik dengan alat GPR yang telah dikorelasikan dengan data CPT. Pada korelasi nilai konstanta dielektrik dengan nilai CPT, dengan rentang 56.09 sampai 61.08 memiliki nilai konus terkoreksi, qt dengan rentang 0.12 MPa sampai 0.21 MPa. Hasil akhirnya akan diperoleh persamaan empiris data GPR vs data CPT.Kata kunci: investigasi geoteknik, non-destructive, sensing, dan reduction impact cost ABSTRACT Ground-Penetrating Radar (GPR) is Geophysical Method by using Radar Technology to purpose identification rock bedding and subsurface on geotechnical investigation. This method is classified for non-destructive application (without doing damage the original base) and applied by Electromagnetic Wave with microwave bandwidth (Frequency UHF/VHF) in spectrographic transmitting-wave (radio wave) and also to detect reflective pulse from the ground. Performance modulation depth of the GPR for sensing (beam penetration) rock/soil is for 50m. The GPR can detect (sensing) changes in the direction of rock bedding and for predicting extremely soft soil thickness, so as to identify risks and reduce handling cost (reduction impact cost) from extreme base behavior before the dumping process in marshy or peat areas. The use of GPR instruments can also support detailed interpretation of geological drilling in PT. KPC.This method is used as an alternative method if the geological drilling method is too dangerous to act, because the slopes investigated are in critical condition or swampy areas that cannot be traversed by drilling rig mobilization. KPC geotechnics have conducted geotechnical investigations with GPR tools that have been correlated with data CPT. The result of the correlation of dielectric constant values with CPT values, with a range of 56.09 to 61.08 has a corrected cone value, qt with a range of 0.12 MPa to 0.21 MPa. The final result is empirical correlation between data GPR and data CPT.Keynote: geotechnical investigation, non-destructive, sensing, and reduction impact cost
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Hachimi, Younes El, Yassine Gmih, El Mostafa Makroum y Abdelmajid Farchi. "A Miniaturized Patch Antenna Designed and Manufactured Using Slot's Technique for RFID UHF Mobile Applications". International Journal of Electrical and Computer Engineering (IJECE) 8, n.º 6 (1 de diciembre de 2018): 5134. http://dx.doi.org/10.11591/ijece.v8i6.pp5134-5143.
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In this research work, a novel compact antenna with rectangular slots is presented for radio frequency identification (RFID) handled applications in the ultrahigh frequency (UHF) band that can be manufactured and integrated into RFID readers without difficult. A prototype demonstrating the aforementioned features was constructed and measured. The proposed antenna is fed by 50-Ω coaxial cable and printed on a 1.6mm thick FR4 substrate which has a small size and occupies a volume of 68×66 ×1.6mm3. The patch, the feed-line and ground plane are made of PEC (Perfect Electric Conductor) with a thickness of 0.035 mm. Measured results indicate that the proposed antenna has a good impedance matching characteristic ranging from 889 to 939MHz, which covers the USA RFID-band (902–928MHz), the Chinese RFID-operating-band (920–924.5MHz), and the Korea and Japan RFID-band (917–923.5MHz). These results were achieved by the insertion of slots in the compact structure of the antenna. The electromagnetic simulators HFSS (High Frequency structure simulator) and CST (Computer Simulation Technology) microwave studio were used for the design, modeling and simulation of the antenna. The focus of the study of our antenna was on the parameters of return loss, bandwidth, Voltage Standing Wave Ratio (VSWR), input impedance and gain.
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Mundell, Carole y Mark Sullivan. "Workshop on Extreme Physics". Proceedings of the International Astronomical Union 7, S285 (septiembre de 2011): 270. http://dx.doi.org/10.1017/s1743921312000725.
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SummaryNever before has there been such a wealth of versatile ground- and space-based facilities with which to detect variable emission across the electromagnetic spectrum and beyond, to non-EM signals such as neutrinos and gravitational waves, to probe the most extreme phenomena in the Universe. The variable sky is already providing a wealth of new and surprising observations of phenomena such as GRBs, SNe and AGN that are pushing current theories beyond the state of the art. Multi-messenger follow-up will soon become de rigeur, and upcoming radio and optical all-sky transient surveys will revolutionise the study of the transient Universe. In addition to the technical and data challenges presented by such surveys, a major new challenge will be the interpretation of the wealth of available data and the identification of the underlying physics of new classes of variable (and potentially exotic) objects. Theoretical predictions will be vital for interpreting these future transient discoveries.The goal of this workshop was to bring together theorists and observers in order to identify unexplored synergies across three main research areas of extreme physics: gamma-ray bursts, supernovæ and, more generically, relativistic jets. It aimed to discuss key outstanding questions in these rapidly moving fields, such as the composition and acceleration of GRB and AGN jets, GRB progenitors and central engines, the origin of the wide range of observed variability time-scales in GRB prompt and after-glow light curves and related cosmological applications, the physics of the newly-discovered ultra-luminous SN-like optical transients—as well as to speculate on what we might hope to discover with future technology.The workshop absorbed two 90-minute sessions, selecting 3 main science topics (Relativistic Jets, GRBs and SNe) which it organised as structured discussions driven by a series of short but provocative questions. The final session featured a panel-led debate but with full audience participation.
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Barbieri, C., O. S. Salafia, A. Perego, M. Colpi y G. Ghirlanda. "Light-curve models of black hole – neutron star mergers: steps towards a multi-messenger parameter estimation". Astronomy & Astrophysics 625 (mayo de 2019): A152. http://dx.doi.org/10.1051/0004-6361/201935443.
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In the new era of gravitational wave (GW) and multi-messenger astrophysics, the detection of a GW signal from the coalescence of a black hole – neutron star (BHNS) binary remains a highly anticipated discovery. This system is expected to be within reach of the second generation of ground-based detectors. In this context, we develop a series of versatile semi-analytical models to predict the properties of all the electromagnetic (EM) counterparts of BHNS mergers. We include the nuclear-decay-powered kilonova emission, its radio remnant, the prompt emission from the jet, and the related afterglow. The properties of these counterparts depend upon those of the outflows that result from the partial disruption of the NS during the merger and from the accretion disc around the remnant, which are necessary ingredients for transient EM emission to accompany the GW signal. We therefore define ways to relate the properties of these outflows to those of the progenitor binary, establishing a link between the binary parameters and the counterpart properties. From the resulting model, we anticipate the variety of light curves that can emerge after a BHNS coalescence from the radio up to gamma-rays. These light curves feature universal traits that are the imprint of the dynamics of the emitting outflows, but at the same time, they show a clear dependence on the BH mass and spin, but with a high degree of degeneracy. The latter can be deduced by a joint GW – EM analysis. In this paper, we perform a proof-of-concept multi-messenger parameter estimation of a BHNS merger with an associated kilonova to determine how the information from the EM counterpart can complement that from the GW signal. Our results indicate that the observation and modelling of the kilonova can help to break the degeneracies in the GW parameter space, leading to better constraints on the BH spin, for example.
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Shi, Kunpeng, Jinyun Guo, Yongming Zhang, Wang Li, Qiaoli Kong y Teng Yu. "Multi-Dimension and Multi-Channel Seismic-Ionospheric Coupling: Case Study of Mw 8.8 Concepcion Quake on 27 February 2010". Remote Sensing 13, n.º 14 (11 de julio de 2021): 2724. http://dx.doi.org/10.3390/rs13142724.
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GPS radio occultation (RO) technology can fully describe the subtle structure of the ionosphere. This paper discusses the dynamic abnormity observed by the RO data from the Constellation Observing System for Meteorology Ionosphere and Climate (FORMOSAT-3/COSMIC) before the great earthquake case in Concepcion, Chile (27 February 2010, Mw 8.8). Traditional ground-based GPS monitoring was considered as the external conditions and references to the excitation response. Using kriging interpolation, the global Nmf2 map (GNM) was first constructed to study the ionosphere deviation from the normal state. Successively, the ionosphere abnormality in the F2 region (Nmf2), vertical structure (RO profiles), and multiple heights (electron density) of traveling are unfolded. The Nmf2 disturbances in the possibility of seismic influences were excluded from non-seismic noise factors, including the external input (e.g., space weather activity, 15 February) and meteorological events (e.g., lower atmospheric forcing in quiet periods). However, the results show that there were apparent local Nmf2 perturbations for up to 5 h in the epicenter area on 21 and 25 February. The disturbances of the RO profiles and the interaction of other layers of the ionosphere implied the fluctuation signals of prominent long-wavelength fluctuations >50 km in the F layer. The ionospheric fluctuates wildly, and these wave signals considered as the trace of gravity wave propagating upward are mainly distributed at the elevation of 200–300 km. The simultaneous reaction of GNSS TEC further evidenced the potential possibility of acoustic gravity by the COSMIC RO profiles, reflecting the compounding couplings of seismo-ionosphere effects. In terms of the presentation of VLF radiation noise and the aerosol ion clusters, the electromagnetic and chemical channels have been previously completed by DEMETER and Terra/Aqua satellites. These findings implied the great potential of the FORMOSAT-7/COSMIC-2 system (now in the testing phase), with ~5000 soundings to investigate the subtle atmospheric stratification.
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Bokoyo Barandja, Vinci de Dieu, Bernard Zouma, Auguste Oscar Mackpayen, Martial Zoungrana, Issa Zerbo y Dieudonné Joseph Bathiebo. "Propagation of Electromagnetic Wave into an Illuminated Polysilicon PV Cell". International Journal of Antennas and Propagation 2020 (30 de enero de 2020): 1–7. http://dx.doi.org/10.1155/2020/6056712.
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The increasing cohabitation between telecommunication antennas generating electromagnetic waves and solar panels poses the problem of interaction between these radio waves and solar cells. In order to study the effect of radio waves on the performance of a polycrystalline silicon solar cell in a three-dimensional approach, it is necessary to assess the attenuation of the radio wave in the illuminated polysilicon grain and also to find the expressions of its components. This work investigated the attenuation of radio waves into a polycrystalline silicon grain by analyzing, firstly, the behaviour of the penetration length of the radio waves into the polysilicon grain and secondly, the behaviour of the attenuation factor. The propagation of the radio waves into the polycrystalline silicon grain can be considered without attenuation that can be neglected.
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Lyubarskii, Yu E. "Generation of pulsar radio emission". International Astronomical Union Colloquium 177 (2000): 387–88. http://dx.doi.org/10.1017/s0252921100060073.
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AbstractThe generation of radio emission from plasma waves excited by two-stream instability in pulsar magnetospheres is considered. Induced scattering transforms the excited longitudinal waves into waves that escape freely in the form of transverse electromagnetic waves. It is shown that the spectrum and the luminosity of the generated radio emission are compatible with those observed.
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van der Heide, Edwin. "Radioscape: Into Electromagnetic Space". Leonardo Music Journal 23 (diciembre de 2013): 15–16. http://dx.doi.org/10.1162/lmj_a_00143.
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Gangadhara, R. T. y V. Krishan. "Absorption of Electromagnetic Waves in Astrophysical Plasmas". Symposium - International Astronomical Union 142 (1990): 519–20. http://dx.doi.org/10.1017/s0074180900088562.
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We study Parametric Decay Instabilities(PDI) using the kinetic description, in the homogeneous and unmagnetized plasmas. These instabilities cause anomalous absorption of the incident electromagnetic (e.m)radiation. The maximum plasma temperatures reached are functions of luminosity of the non-thermal radio radiation and the plasma parameters.
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Naus, H. W. L. "Modeling of Buried Wire Detection by Radio-Frequency Electromagnetic Waves". IEEE Geoscience and Remote Sensing Letters 10, n.º 1 (enero de 2013): 160–64. http://dx.doi.org/10.1109/lgrs.2012.2196405.
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Wait, James R. y Khalid A. Nabulsi. "Wave tilt of radio waves propagating over a layered ground". GEOPHYSICS 61, n.º 6 (noviembre de 1996): 1647–52. http://dx.doi.org/10.1190/1.1444083.
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We call attention here to the limitation of the “Q approximation” in characterizing the complex wave tilt W over a layered half‐space. Using an improved formulation the frequency dependence of W is shown to be a discriminator of the electrical characteristic of the subsurface. The height dependence of the observer is also illustrated.
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Kazbegi, AZ, GZ Machabeli y G. Melikidze. "Radio Emission Model of a 'Typical' Pulsar". Australian Journal of Physics 40, n.º 6 (1987): 755. http://dx.doi.org/10.1071/ph870755.
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The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.
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Paranjape, B. V. y M. B. Paranjape. "On the interaction of electromagnetic waves with conductors". Canadian Journal of Physics 90, n.º 9 (septiembre de 2012): 849–53. http://dx.doi.org/10.1139/p2012-080.
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We study the interaction of electromagnetic waves with electrons. Our results can be applied to radio waves in the ionosphere or to lasers impinging on metals causing melting. We generalize the classical analysis of Zener to the case, which includes the interactions of the electrons with lattice vibrations or positive ions. We use the induced polarization to give a globally coherent and unifying analysis of the two cases: where collisions are important and where they are negligible.
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Wu, Z. "Tomographic imaging of isolated ground surfaces using radio ground waves and conjugate gradient methods". IEE Proceedings - Radar, Sonar and Navigation 148, n.º 1 (2001): 27. http://dx.doi.org/10.1049/ip-rsn:20010111.
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Jiang, Zhi Hao, Jeremy P. Turpin, Kennith Morgan, Bingqian Lu y Douglas H. Werner. "Spatial transformation-enabled electromagnetic devices: from radio frequencies to optical wavelengths". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, n.º 2049 (28 de agosto de 2015): 20140363. http://dx.doi.org/10.1098/rsta.2014.0363.
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Transformation optics provides scientists and engineers with a new powerful design paradigm to manipulate the flow of electromagnetic waves in a user-defined manner and with unprecedented flexibility, by controlling the spatial distribution of the electromagnetic properties of a medium. Using this approach, over the past decade, various previously undiscovered physical wave phenomena have been revealed and novel electromagnetic devices have been demonstrated throughout the electromagnetic spectrum. In this paper, we present versatile theoretical and experimental investigations on designing transformation optics-enabled devices for shaping electromagnetic wave radiation and guidance, at both radio frequencies and optical wavelengths. Different from conventional coordinate transformations, more advanced and versatile coordinate transformations are exploited here to benefit diverse applications, thereby providing expanded design flexibility, enhanced device performance, as well as reduced implementation complexity. These design examples demonstrate the comprehensive capability of transformation optics in controlling electromagnetic waves, while the associated novel devices will open up new paths towards future integrated electromagnetic component synthesis and design, from microwave to optical spectral regimes.
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Xing, Jiang Yong. "Electromagnetic Radiation on Human Health Hazards and Protective Measures in Modern Society". Advanced Materials Research 518-523 (mayo de 2012): 1022–26. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.1022.
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The discovery of electromagnetic waves and applications change the way people live in modern society, from the telephone, radio, TV to your computer, mobile phone, the electromagnetic wave for people to create a rich material life and spiritual life. Electromagnetic wave on the increasingly serious environmental pollution, electromagnetic radiation hazards on human health can not be ignored. Humans not only to continue to develop the application of electromagnetic waves, but recognize the dangers of electromagnetic radiation, to strengthen the protection, so that the electromagnetic waves more effectively for the benefit of mankind.
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Selormey, Paul y Yasumitsu Miyazaki. "Electromagnetic Compatibility Characteristics of Buildings in Mobile Radio Waves Propagation Channel". IEEJ Transactions on Electronics, Information and Systems 119, n.º 1 (1999): 97–104. http://dx.doi.org/10.1541/ieejeiss1987.119.1_97.
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Taghi, Mousavi, Riazi Gholamhosein y Rezayi-Zarchi Saeed. "Effect of Radio Frequency Waves of Electromagnetic Field on the Tubulin". Recent Patents on Endocrine, Metabolic & Immune Drug Discovery 7, n.º 3 (1 de septiembre de 2013): 252–56. http://dx.doi.org/10.2174/18722148113079990007.
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Jennison, R. C. "Relationship between photons and electromagnetic waves derived from classical radio principles". IEE Proceedings - Microwaves, Antennas and Propagation 146, n.º 1 (1999): 91. http://dx.doi.org/10.1049/ip-map:19990139.
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Meisenheimer, K., H. Hippelein y M. Neeser. "High Redshift Radio Galaxies". Symposium - International Astronomical Union 175 (1996): 571–76. http://dx.doi.org/10.1017/s0074180900081894.
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One hundred years after G. Marconi recorded radio waves over a distance of more than 1000 m, the most sensitive radio telescopes are able to detect the radio emission from light travel distances at least 1.4 × 1023 times greater. The electromagnetic waves from these distant objects are red shifted by Δλ/λ = z > 4. It is not the mere distance of high redshift objects which is fascinating, but rather the fact that one looks back into the early history of the universe by observing them: Objects at a redshift of 4 shined at a time when the universe had reached only about 1/5 of its present age.
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Jóźwik-Michałowska, Natalia y Andrzej Felski. "The Electromagnetic Field in the Vicinity of Radio-Navigation Systems". Annual of Navigation 25, n.º 1 (1 de diciembre de 2018): 109–24. http://dx.doi.org/10.1515/aon-2018-0008.
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AbstractToday, electromagnetic waves are the basic medium for all communication tasks. This applies also to navigation, where the most commonly waves have lengths measured in centimetres (radar, GPS) and longer, such as the waves used in the AIS or DGPS technologies. Navigators are mostly interested in the communication functionality of the used systems, i.e. such factors as range of the system and signal-to-noise ratio. This leads directly to increasing the transmitters’ power. However, it is important to bear in mind that the electromagnetic field can endanger human health, therefore, establishing the level of radiation both on vessels and near the shore transmitters is crucial in this context. The experience of authors shows that the knowledge of the most of navigators hereupon is not large. From this result extremely irresponsible behaviors of one persons, as well as inexplicable phobias others.This article presents the subject using the example of the electromagnetic field present near a lighthouse emitting AIS and DGPS signals. Relevant measurements were made at the Rozewie lighthouse by certified laboratory of Maritime Institute in Gdansk according the polish standards and internal, certified procedures. Results of the measurements were related to the national and European standards for electromagnetic field measurements in the context of occupational health and safety.
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Rucka, Magdalena y Jacek Lachowicz. "Numerical and experimental analysis of electromagnetic field propagation for ground penetrating radar inspection". Budownictwo i Architektura 13, n.º 2 (11 de junio de 2014): 307–15. http://dx.doi.org/10.35784/bud-arch.1909.
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This paper presents experimental tests by using the GPR method and numerical analysis of electromagnetic field propagation. The object of the experimental research was a ground floor structure. An antenna of frequency of emitted waves equal to 2 GHz was used for measurements. The paper also describes the numerical modelling of electromagnetic field with the use of the finite difference time domain method. Results of propagation of electromagnetic waves in a one-dimensional reinforced concrete specimen were presented.
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Centrella, Joan, Samaya Nissanke y Roy Williams. "Gravitational Waves and Time-Domain Astronomy". Proceedings of the International Astronomical Union 7, S285 (septiembre de 2011): 191–98. http://dx.doi.org/10.1017/s1743921312000592.
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AbstractThe gravitational-wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high-frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time-domain astronomy. In the decade, space-based observations of low-frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational-wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
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Tsubaki, Shuntaro, Shogo Hayakawa, Tadaharu Ueda, Tomohiko Mitani, Ei-ichi Suzuki, Satoshi Fujii y Yuji Wada. "Proton-Enhanced Dielectric Properties of Polyoxometalates in Water under Radio-Frequency Electromagnetic Waves". Materials 11, n.º 7 (13 de julio de 2018): 1202. http://dx.doi.org/10.3390/ma11071202.
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Electromagnetic waves, such as microwaves, have been used to enhance various chemical reactions over polyoxometalates. The dielectric properties of catalysts are among the relevant parameters facilitating catalytic reactions under electromagnetic radiation. This study describes the dielectric properties of polyoxometalate catalysts in aqueous and organic solutions to understand the mechanism of interactions between polyoxometalates and electromagnetic waves. Specific loss factors of polyoxometalates were observed at lower frequencies (<1 GHz) by the ionic conduction of the polyoxometalate solution. The evolution of ionic conduction depended strongly on cations rather than anions. Proton-type polyoxometalates exhibited significantly higher loss factors than other cations did. The activation energy for ionic conduction in protonated silicotungstic acid (H4SiW12O40) was significantly low in water (7.6–14.1 kJ/mol); therefore, the high loss factor of protonated polyoxometalates in water was attributed to the proton relay mechanism (i.e., Grotthuss mechanism). The results suggested that the proton relay mechanism at the radio-frequency band is critical for generating selective interactions of polyoxometalates with applied electromagnetic fields.
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Ganse, Urs, Felix Spanier y Rami Vainio. "Kinetic Simulations of Type II Radio Burst Emission Processes". Proceedings of the International Astronomical Union 6, S274 (septiembre de 2010): 470–72. http://dx.doi.org/10.1017/s1743921311007526.
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AbstractUsing a fully relativistic, 3D particle in cell code we have studied Langmuir- and electromagnetic wave processes in a CME foreshock plasma with counterstreaming electron beams. Langmuir wave excitation in resonance with the plasma frequency is observed, with timescales in accordance with theoretical predictions. However, no three wave interaction leading to emission of electromagnetic waves were detectable within the timeframe of our simulations.
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Safwat, Amr M. E. "Letter-shaped microstrip ground slots". International Journal of Microwave and Wireless Technologies 4, n.º 5 (16 de mayo de 2012): 523–28. http://dx.doi.org/10.1017/s1759078712000426.
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This paper proposes a systematic approach for designing and modeling letter-shaped microstrip ground slots. Twenty-three structures are investigated. For each one, a geometrical circuit model is developed. Interestingly, 21 letters have unique s-parameters (electromagnetic [EM] print). Results are confirmed by EM simulations and measurements. These results may pave the way to new applications, e.g. microwave character recognition, letter-based microwave circuits, or new radio frequency identification (RFID) structures
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Ligthart, L. P., A. I. Kozlov, A. I. Logvin y I. V. Avtin. "RADIO-WAVES REFLECTION AT REMOTE SENSING OF UNDERLYING COVERS". Civil Aviation High TECHNOLOGIES 22, n.º 3 (29 de junio de 2019): 57–66. http://dx.doi.org/10.26467/2079-0619-2019-22-3-57-66.
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Monitoring technologies are rapidly developing at present and allow to extract and use non-coordinate information about objects. Noncoordinate information is the information about the type and properties of an object under study. Remote sensing is the main method of solving monitoring problems where special positioning belongs to the radar methods, based on space-time processing of signals and, in particular, on methods of radio polarimetry. It is necessary to have information about the surface in order to solve the monitoring task. The slightest changes in the electrical and physical properties of such areas as salinity, humidity, soil composition, etc. will lead to a change in the basic electrodynamics of the surface, notably its complex dielectric permittivity. The article demonstrates the precise solutions to the problems of radio-waves reflection from a layered surface with various laws of changes of the complex permittivity in depth. Media with exponential and quadratic laws of variation for arbitrary angles of incidence of the radio wave on the surface are considered. Precise decision is obtained for layered media with the law of change in the complex permittivity the polynomial and linear characteristics. A similar problem for the parabolic layer is considered separately. The detailed analysis of radio waves reflection from the medium with a matching layer is carried out. The nature of the electromagnetic field inside the transition layer is studied in detail. The article is illustrated by the graphs showing the dependences of an electromagnetic wave reflection coefficient on the layered medium with linear and exponential laws of variation of the complex dielectric constant over depth.
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Smolyaninov, Igor, Quirino Balzano y Dendy Young. "Development of Broadband Underwater Radio Communication for Application in Unmanned Underwater Vehicles". Journal of Marine Science and Engineering 8, n.º 5 (23 de mayo de 2020): 370. http://dx.doi.org/10.3390/jmse8050370.
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This paper presents several novel designs of small form factor underwater radio antennas operating in the 2 MHz, 50 MHz and 2.4 GHz bands. These antennas efficiently excite surface electromagnetic waves (SEW) which propagate along the surface of seawater. The antenna operation is made possible due to implementation of an impedance matching enclosure, which is filled with de-ionized water. Enhanced coupling to surface electromagnetic waves is enabled by the enhancement of the electromagnetic field at the antenna apex. These features allow us to make antenna dimensions considerably smaller compared to typical free space designs. They also considerably improve coupling of electromagnetic energy to the surrounding seawater. Since SEW propagation length is considerably larger than the skin depth in seawater, this technique is useful for underwater broadband wireless communication. We conclude that the developed broadband underwater radio communication technique will be useful in networking of unmanned underwater vehicles.
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Pichugin, Vladimir N. "Features of control of characteristics of radio engineering devices in the multi-wave mode of operation". MATEC Web of Conferences 226 (2018): 04011. http://dx.doi.org/10.1051/matecconf/201822604011.
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In multi-wave elements of radio devices at frequencies, 1,2,..., 10 times the operating frequency, conditions arise for the propagation of several types of waves. This leads to the dependence of the characteristics of electronic devices and, consequently, the parameters of frequency selectivity on the spatial structure (spatial spectrum, mode composition) of the electromagnetic signal at the input of the element under study. The presence of such” spatial selectivity” requires taking into account the features of the multi-wave mode in solving various problems of electromagnetic compatibility. The article is devoted to the actual problemthe development of new methods of experimental research and control of the characteristics of electromagnetic waves of radio devices operating in multi-wave mode. The solution of the problem of studying the impact of a plane electromagnetic wave on the emitters of the radio-thnical system is carried out. The analytical calculation of the electrodynamics effects in the multi-wave mode is carried out.
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Friedman, M. "Extraction of radio frequency from electromagnetic surface waves guided by metallic strips". Review of Scientific Instruments 71, n.º 2 (febrero de 2000): 551–53. http://dx.doi.org/10.1063/1.1150239.
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