Detection Of Electromagnetic Waves Research Articles

Application of ZnO Nanoparticles EM Wave Detector Prepared by Sol-Gel and Self-Combustion Techniques

Zinc oxide (ZnO) has found many important applications such as optoelectronic devices, sensors and varistors. The challenging part however is synthesizing ZnO nanoparticles and its utilisation as EM detectors. Sol-gel and self-combustion techniques were chosen in this study due to the ability to produce single phase and nano-size samples. The starting mixture consists of 10 grams of zinc (II) nitrate, Zn(NO3)2.6H2O salt which was dissolved in 50 mL of nitric acid, HNO3.The solution was stirred at 250 rpm continuously for 1 day. The mixture was then gradually heated for every 15 minutes until it combusted at 110oC for the self-combustion technique. For the sol-gel technique, the dissolved mixture was heated at 40oC, 50oC, 60oC and 70oC until the gelatine was formed. After the drying process, the as-prepared samples were annealed at 100oC and 200 oC for 1 hour for each technique. Characterizations were performed by using X-Ray Diffraction (XRD), Raman Spectra and Scanning Electron Microscopy (SEM).The XRD analysis showed a major peak of [101] plane at 2Ө for the self-combustion technique and the sol-gel technique. Raman results for the samples prepared via sol-gel and self-combustion techniques had shown the major peak of ZnO that is located at the Raman shifts of 437.67 cm-1. Using the Scherrer equation, single crystal nano particle of ZnO was successfully obtained in the range of 38.49 nm to 50.70 nm for the sample prepared via the sol gel technique. By the self-combustion technique, the average dimension of the as-prepared sample is in the range of 34-49 nm. Further heat treatment resulted in a major change of the Raman shift corresponding to the single phase ZnO nano particles. The best samples were used as electromagnetic (EM) detectors. The EM detectors are polymer based composite which were prepared using a casting technique.

Detection of Anomalous ELF Band Environmental Electromagnetic Wave Based on Fluctuation in Magnetic Field Azimuth

Anomalous radiation of environmental electromagnetic wave is reported as a portent of earthquakes. Then, we are observing environmental electromagnetic waves of the ELF band all over Japan. We have been regarding the large amplitude in the observed signal as anomalous radiation. However, the observed signal contains a lot of slight amplitude anomalies hidden by background noise. To detect the earthquake precursor, it is necessary to detect not only large amplitude anomaly but also slight amplitude anomaly. In this paper, we propose the method of detecting anomalous radiation using the magnetic field azimuth which does not depend on the amplitude level. It is assumed that magnetic field azimuth has notable fluctuation when anomaly EM radiation occurs. We detect this fluctuation by the azimuthal standard deviation calculated every 20 minutes. Moreover, we show that it is dominant in anomaly detection to use the fluctuation in magnetic field azimuth instead of the amplitude level.

Conceal an entrance by means of superscatterer

Based on the fact that superscatterer can look like a scatterer bigger than its geometric size, we propose a design of hidden portal in which an entrance is concealed from the electromagnetic wave detection. Such a superscatterer is realized by coating a negative index material shell on a perfect electrical conductor rectangle cylinder. The results are numerically confirmed by full-wave simulations both in the far field and near field.

Ducted whistlers propagating in higher-order guided mode and recorded on board of Compass-2 satellite by the advanced Signal Analyzer and Sampler 2

[1] The advanced electromagnetic wave detector and analyzer, Signal Analyzer and Sampler 2, successfully operated on board of Compass-2 satellite (launched May 2006). One of the peculiarities of this experiment was that the efficient sensitivities of both electric and magnetic channels were very close to being identical. Between the interesting events detected we found the evidence of whistler mode signals propagating in higher- (third-) order guided mode, most probable between two layers (i.e., “onionskin” structure was in the plasmasphere at this time). We present in the paper the real full wave ultrawideband interpretation of these propagating signals using the exact solution of Maxwell's equations in this boundary problem.

エポキシ樹脂中のトリー伸展と放射電磁波

Detection of electro-magnetic waves is one of a good diagnosis tool that can be used for the condition assessment of insulating systems. Detection and frequency analysis of electro-magnetic wave caused by partial discharge in epoxy resin have been investigated. Electro-magnetic waves radiated by partial discharge could be detected by using simple system with a conventional discone antenna and a spectrum analyzer. Detected electro-magnetic wave spectra have two specific frequency regions: one is at lower than around 200MHz and another is higher than around 200MHz. From observation of electrical tree development and measurements of discharge current and partial discharge level, the former is associated with a void discharge in epoxy resin and the latter is identified as tree development. By using these specific frequency regions, it is applicable to detection of partial discharge and insulating assessment for power apparatus and their accessories including epoxy resin.

Recent trend of the partial discharge measurement technique using the UHF electromagnetic wave detection method

AbstractThe ultra high frequency (UHF) electromagnetic wave detection method has been widely studied and used in partial discharge (PD) measurement and as a diagnostic technique for insulation performance in gas‐insulated switchgears (GIS) and transformers. The UHF method has advantages such as high sensitivity, wide detection range and reduced external disturbances. On the other hand, there are still some issues to be solved in the UHF methods, such as a clear understanding of the propagation characteristics of electromagnetic waves arising from the structure of the equipment, optimization of antenna design, calibration of charge, etc. This article deals with the present status and future trend of the technology of this promising UHF method of PD measurement, together with recent activities and results from our laboratory. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Plasma sheet stretching accompanied by field aligned energetic ion fluxes observed by the NUADU instrument aboard TC-2

The NUADU (NeUtral Atom Detector Unit) instrument aboard TC-2 recorded 4л solid angle images of charged particles (E >180 keV) spiraling around the magnetic field lines in the near-Earth plasma sheet (at ∼ −7 R E, equatorial dawn-to-night side) during a geomagnetic storm (Dst =−219 nT) on August 24, 2005. Energetic ion beam events characterized by symmetrical, ring-like, solid angle distributions around ambient magnetic field lines were observed during a 34-minute traversal of the plasma sheet by the TC-2 spacecraft. Also, observations during these multiple crossings of the plasma sheet were monitored by the magnetometer experiment (FGM) aboard the same spacecraft. During each crossing, a whistler-mode chorus enhancement was observed in the anisotropic area by the TC-2 low frequency electromagnetic wave detector (LFEW/TC-2) at a frequency just above that of the local lower hybrid wave. A comparison of the ion pitch angle distribution (PAD) map with the ambient magnetic field shows that an enhancement in the field aligned energetic ion flux was accompanied by tailward stretching of the magnetic field lines in the plasma sheet. In contrast, the perpendicular ion-flux enhancement was accompanied by a signature indicating the corresponding shrinkage of the magnetic field lines in the plasma sheet. Since both parallel ion-flux and perpendicular ion-flux enhancements occurred intermittently, the data were interpreted to imply a dynamical, oscillatory process of the magnetic field line (stretching and shrinking) in the near-Earth plasma sheet, which might have acted to help establish an interaction region in this area which would support continuous aurora-substorm triggering during the ongoing magnetic storm. The whistler-mode chorus may have been produced due to ion gyro-resonance during particle pitch angle diffusion after the plasma sheet compression.

A Finite Element Method Code to Analyse Waveguide Dispersion

The aim of our current work is to construct an algorithm for solving problems of radiation and detection of transient electromagnetic waves in the analysis of permeable bodies. The Time-Domain Finite Element Method (TDFEM) will be used in combination with other numerical techniques. TDFEM is necessary to design — with good precision — the broadband antennas to be used. Here we report the first step achieved in this goal. We designed a Finite Element Method (FEM) code to solve two-dimensional static problems in homogeneous waveguides. In order to test the algorithm constructed, it was applied to calculate dispersion features and to obtain the electromagnetic field in the transversal section of the waveguides for the propagation modes. The results obtained are in good agreement with the analytical results and those of other authors. Currently, we are developing a more complete code that includes time (TDFEM) and that focuses on three-dimensional problems.

Optical spectra of surface discharges in oil

The subject matter of this paper refers to the application of optical spectral diagnostics to the detection of electromagnetic waves generated by partial discharges. The research work refers to creeping discharges at bakelite/oil interface. The analysis of optical spectrum time changes was performed. The influence of voltage on the changes of the creeping discharge optical spectrum was determined. The spectrum distributions were determined in the area of creeping discharges. The results obtained at this stage of the research can constitute a source material for people dealing with issues connected with electrical material science and diagnostics of insulation systems

All Organic Terahertz Electromagnetic Wave Emission and Detection Using Highly Purified N-Benzyl-2-methyl-4-nitroaniline Crystals

We studied terahertz (THz) electromagnetic wave emission and detection using highly purified N-benzyl-2-methyl-4-nitroaniline (BNA) crystals. In THz emission experiments, we compared the efficiencies of THz emission via optical rectification for BNA, ZnTe, and GaP crystals, and confirmed that the BNA crystal is the most efficient THz emitter among these three crystals within the frequency range limits for observation. In the THz detection experiment, we also compared the modulation efficiencies of the BNA and ZnTe crystals, and found that the ZnTe crystal has a higher efficiency than the BNA crystal. However, the BNA crystal has a higher efficiency than the ZnTe crystal in high-frequency regions. Since the BNA crystal is suitable for detecting a high-frequency region even when using thick crystals, it is expected that the BNA crystal as a THz detector will be easy to prepare and handle.

First results of low frequency electromagnetic wave detector of TC-2/Double Star program

Abstract. LFEW is a low frequency electromagnetic wave detector mounted on TC-2, which can measure the magnetic fluctuation of low frequency electromagnetic waves. The frequency range is 8 Hz to 10 kHz. LFEW comprises a boom-mounted, three-axis search coil magnetometer, a preamplifier and an electronics box that houses a Digital Spectrum Analyzer. LFEW was calibrated at Chambon-la-Forêt in France. The ground calibration results show that the performance of LFEW is similar to that of STAFF on TC-1. The first results of LFEW show that it works normally on board, and that the AC magnetic interference of the satellite platform is very small. In the plasmasphere, LFEW observed the ion cyclotron waves. During the geomagnetic storm on 8 November 2004, LFEW observed a wave burst associated with the oxygen ion cyclotron waves. This observation shows that during geomagnetic storms, the oxygen ions are very active in the inner magnetosphere. Outside the plasmasphere, LFEW observed the chorus on 3 November 2004. LFEW also observed the plasmaspheric hiss and mid-latitude hiss both in the Southern Hemisphere and Northern Hemisphere on 8 November 2004. The hiss in the Southern Hemisphere may be the reflected waves of the hiss in the Northern Hemisphere.

Shumann resonances and electromagnetic transparence in the atmosphere of Titan

Among the multiple questions that the CASSINI/HUYGENS mission tries to answer is the likelihood of electric discharges in Titan's atmosphere. The instruments “Huygens Atmospheric Structure Instrument” and “Radio and Plasma Wave Science” will probe the electromagnetic emissions during the Huygens descent and Cassini flybys, respectively. Although no lightning was observed during Voyager's encounters with Titan in 1980 and 1981, this does not exclude the existence of lightning phenomena. Recent investigations show that lightning discharges could occur in the lower atmosphere, such as the detection of methane condensation clouds in the troposphere and the theoretical prediction of an electric field that would be sufficient enough to cause lightning. We present a numerical model of Titan's atmosphere with the aim of calculating the resonance frequencies and the atmospheric transparency to electromagnetic waves. The detection and measurement of these resonances, Schumann frequencies, by the Huygens probe, would show the existence of electric activity connected with lightning discharges in the atmosphere. As it happens with the Schumann frequencies of Earth, losses associated with the electric conductivity will make these frequencies to be lower than the theoretically predicted, the fundamental one being located between 11 and 15 Hz. An analytical study shows that the strong losses associated with the high conductivity make it impossible that an electromagnetic wave generated near the surface with a frequency of 10 MHz or lower reaches the outer part of Titan's atmosphere. Therefore the detection of electromagnetic waves coming from Titan's lower atmosphere by the RPWS instrument is very unlikely.

Electromagnetic wave radiation by current-driven magnons in magnetic multilayers (invited)

We report the detection of electromagnetic waves radiated by current-driven magnons in Co/Cu magnetic multilayers. The magnons were excited by means of a high current density ∼108 A/cm2 injected into the multilayer through a point contact. The point contact itself was used as a high frequency mixer to mix electromagnetic waves radiated by the current-driven magnons with externally generated microwave radiation. Here the external microwaves are used as a direct probe of the high-frequency behavior and partial phase coherence of the current-induced excitations. When the external frequency equaled the frequency of the magnons generated in the multilayer a dc voltage was found to develop across the contact. Investigation of how this voltage varies with exciting current, magnetic field, and microwave frequency provides detailed information on the spectrum of the current-driven magnons. Our observations support the feasibility of a spin-wave maser, or spin-wave amplification by stimulated emission of radiation (SWASER).

Phase-coherent current-driven magnons in magnetic multilayers

We report the detection of electromagnetic waves radiated by current-driven magnons in a Co/Cu magnetic multilayer. The magnons were excited by means of a high current density ≈10 8 A/cm 2 injected into the multilayer through a point contact. The point contact itself was used as a high frequency mixer to mix electromagnetic waves radiated by the current-driven magnons with externally generated microwave radiation. Here the external microwaves are used as a direct probe of the high-frequency behavior and partial phase coherence of the current-induced excitations. When the external frequency equaled the frequency of the magnons generated in the multilayer a DC voltage was found to develop across the contact. Investigation of how this voltage varies with exciting current, magnetic field, and microwave frequency provides detailed information on the spectrum of the current-driven magnons. Our observations support the feasibility of a spin-wave maser, or spin-wave amplification by stimulated emission of radiation.

00/00004 Electromagnetic wave detection and imaging (EDIT) for reducing ash, sulfur, and heavy metals in run-of-mine coal

00/00004 Electromagnetic wave detection and imaging (EDIT) for reducing ash, sulfur, and heavy metals in run-of-mine coal

Development of a Novel Electromagnetic Technique for Detection of Cracks by Use of Micro Antenna.

When alternating current is applied to paramagnetic materials, such as austenitic stainless steels or aluminum alloys, the existence of cracks on the material surface or subsurface causes changes in current flow around them and, as a result, electromagnetic wave generated with this change in current flow can be detected on or near surface of a material. In this case, there is a possibility for detection of these defects by detecting electromagnetic wave by antenna. Hence, the measurements can be done without contact or without removing paint. In this paper, first results on detection of electromagnetic wave around defects with shielded loop antenna is described with a principle of this novel NDI method.

Direct detection of evanescent electromagnetic waves at a planar dielectric surface by laser atomic spectroscopy

The penetration depth and pseudomomentum (wave vector) of evanescent electromagnetic waves are measured at a planar dielectric surface by means of laser spectroscopy using the Cs ${\mathrm{D}}_{2}$ line with a wavelength of 852.1 nm. The same experimental setup is employed in all the experiments. The first result shows a sharp, asymmetric absorption profile, which is explained in terms of the thin penetration depth, and the second shows an actual transfer of the pseudomomentum of the surface electromagnetic mode to atoms via a resonance interaction. The measured penetration depth and pseudomomentum agree with the natural interpretation of the complex wave number characterizing evanescent waves at a planar dielectric-vapor interface. Direct excitation of evanescent waves by excited Cs atoms has also been observed as atomic fluorescence emitted into the dielectric material at the angle of total internal reflection. The results are in good agreement with the theoretical predictions and exhibit the characteristics of excitation transfer or tunneling from Cs atoms into the surface mode.

Emission of extremely strong magnetic fields from the head and whole body during oriental breathing exercises.

This article reports the result of an experiment that was designed to measure the biomagnetic field emanating from two individuals who were practising traditional Oriental Qi Gong breathing exercises. The biomagnetic field was measured with differential coils wound 80,000 turns, a magnetic needle compass and a digital electromagnetic wave detection device. It was found that an extremely strong magnetic field was emitted from the two individuals. One subject emitted a magnetic field at the level of 200-300 mT (2-3 mGauss) and the other at 0.13 mT (1.3 mGauss). In both cases, moreover, the magnetic needle compass rotated 30 degrees (this was tested 32 times). When the rotation of the needle occurred, a reproducible magnetic field of 800-1500 mT (8-15 mGauss) was indicated on the digital measuring device (this was tested 12 times). It is concluded that traditional Oriental Qi Gong breathing appears to stimulate an unusually large biomagnetic field emission.

Sheath waves observed on OEDIPUS A

An important novel feature of the tethered sounding rocket experiment OEDIPUS A (Observations of Electric‐field Distributions in the Ionospheric Plasma—A Unique Strategy) was its direct excitation and detection of electromagnetic waves on conductors in space plasmas. We present quantitative evidence about sheath waves excited in the ionosphere by a high‐frequency transmitter on one end of the 1‐km tether and detected by a synchronized receiver on the other end. An important characteristic of sheath waves is their sequence of sharply defined passbands and stop bands in the frequency range 0.1–5 MHz. The lowest passband is between 0.1 MHz and the plasma frequency near 2 MHz, the bandwidth where existing theory predicts sheath waves. Resonance fringes in this band have been scaled to determine the phase and group refractive indices of sheath waves. These agree reasonably well with the theory, considering the approximations therein. Passbands and stop bands observed in the range between 2 and 5 MHz are not expected on the basis of the current theory. In this range, band limits have clear signatures of the interaction of the tether fields with electrostatic cyclotron waves. Finite wire moment method modeling of the payload shows that in the low‐frequency passband, RF coupling along the tether is increased by 20 dB over vacuum conditions. Similarly, isolation is greater than vacuum isolation in the stop bands. Because sheath waves at frequencies up to 2 MHz are guided efficiently along conductors in plasma, they are a significant design issue in the electromagnetic compatibility of avionics at frequencies up to HF on large metal space structures.

Continued progress in electrophonic fireball investigations

The mechanism proposed in 1980 by Keay to explain the occasional observation of instantaneous electrophonic sounds from large meteor fireballs continues to gain support. This mechanism accounts for many of the empirical features of the phenomenon, and the detection of ELF electromagnetic waves by direct transduction explains various other geophysical electrophonic phenomena including early sounds from seismic events. The extension of Ceplecha's fireball model to include Revelle's criterion for turbulence leads to realistic estimates for the frequency of occurrence of electrophonic fireballs. It also appears possible that the type of electrophonic sound observed relates to the composition of the fireball.