Search

The results of the numerical-analytical modeling of the photoconductivity of crystalline silicon with the inclusion of amorphous silicon are presented. These ones can be used in studying the principles of a new class of photovoltaic converters based on modified semiconductor materials. The initial data for such a model should be experimentally obtained layer parameters. During the calculations, it was assumed that the change in photoconductivity is caused by a change in the degree of disorder of amorphous inclusions. It was assumed that the semiconductor structure is dominated by cylindrical inclusions and the degree of sample disorder γ varies in the range from 0.040 to 0.065. That is, approximately 5 % of amorphous inclusions in the volume of the crystalline structure. The paper presents the results of calculations of changes in photoconductivity depending on the degree of disorder of the semiconductor structure. The results are in good agreement with obtained experimental data on amorphous-crystalline structures formed as a result of irradiation by γ-quanta. The photoconductivity of semiconductor samples irradiated with gamma rays was studied by microwave photomodulation methods using a resonator measuring transducer. [ABSTRACT FROM AUTHOR]

Moisture content is critical to concrete fabrication. Currently, concrete fabrication often involves experienced workers who can gauge whether the water volume is sufficient. This active human involvement requires appearance or thickness checks, which is not suitable for mass production. This method cannot also tell the actual moisture content. Moreover, different workers may give different assessments for the same concrete, which may further lead to different strengths of concrete. Thus, we propose and design a microwave-cavity-based online moisture sensing system to monitor concrete fabrication. Our system utilizes a microwave resonator as a front-end sensor to monitor moisture. This resonator is sensitive to the dielectric coefficient of a particular object. This dielectric coefficient of concrete notably changes when the water yield varies and hence can be readily detected. With this sensitive resonator, we built an online moisture-sensing system. Our prototype achieves moisture sensing with an error of as low as 0.5% and can check moisture content twice a second. [ABSTRACT FROM AUTHOR]

Hybrid quantum systems have attracted much attention due to the fact that they combine the advantages of different physical subsystems. Cavity QED (cavity quantum electrodynamics) with magnons is a hybrid quantum systems that combines a YIG (Yttrium Iron Garnet) sphere and a 3D (three-dimensional) rectangular microwave cavity. Based on this hybrid photon-magnon system, we obtain an approximate analytic solution by the RWA (rotating wave approximation) with an ingenious transformation. After skillfully diagonalizing the Hamiltonian, we show that the Kerr-nonlinearity interactions could yield a negativity value of the Wigner function, periodic quadrature squeezing effects, antibunching property, and field nonclassicality in the magnon. Our work may stimulate the study of nonclassicality of photon-magnon coupling systems and its potential applications in quantum information processing. [ABSTRACT FROM AUTHOR]

Herein, powders of SeO2 are subjected to hydraulic pressure in the range of 1.0–12 MPa and heating cycles in the range of 290–383 K. The pressure and temperature effects on the crystalline nature, plane orientations, structural parameters, surface morphology, composition, electrical resistivity, capacitance spectra and conductance spectra are explored. It is observed that hydraulic pressure value of 6.0 MPa is a critical value at which the tetragonal SeO2 grains prefer (020) plane orientation over (011) planes. The (020) plane orientations resulted in remarkable changes in the lattice parameters, structural parameters, electrical resistivity, capacitance and conductance spectra. In addition, the heating and cooling cycles of the samples pressed at 10 MPa have shown that the transition of the planes is permanent. The heated and cooled pellets displayed resonance–antiresonance in the capacitance spectra near 0.43 GHz. The resonance–antiresonance phenomena are accompanied with negative conductance effect near 0.43 GHz. The enhancements in the properties of SeO2 powders that are achieved via pressure and temperature effects make them appropriate for electronic circuit technological applications. [ABSTRACT FROM AUTHOR]

Miniaturized microwave cavities constructed by the parallel-plate waveguide (PPW) becomes one of the main propagation pathways of the radio-frequency interference (RFI) in 3-D integrated circuits. It is still challenging to suppress RFI in the practical cavities, where the space is extremely constrained. In this work, the working mechanism and design method of the noise suppression sheet (NSS) is quantitatively studied, serving as an efficient approach to suppress RFI within an electrically small size in these microwave cavities. The analysis is based on the dispersion relationship derivation of the NSS-loaded PPW structure. Both the derived formulas and the numerical study reveal that the imaginary part of the permeability, that is, $\mu _{i}$ , of the NSS plays a key role in increasing the reflection and attenuation loss, and thus obtaining a high RFI suppression level. Further study indicates even when the NSS’s profile is lower than 10% of the cavity’s height and the length is lower than $0.1\lambda _{0}$ , its suppression level up to 10 dB can be well accomplished, which is deemed difficult to achieve by using conventional methods. Moreover, this method is, respectively, applied in three practical engineering scenarios for the RFI suppression, that is, heatsink package above a chip, power distributed network (PDN), and flexible circuit. Good agreement is observed between the measurement results and the simulated ones, which confirmed the efficacy of our quantitatively developed NSS. The proposed method is promising for broad industrial applications, such as tiny chip packages, multi-channel systems, and flexible electronics. [ABSTRACT FROM AUTHOR]

We report on the magnetic levitation of a millimeter-sized neodymium permanent magnet within the interior of a superconducting radio frequency (SRF) cavity. To the best of our knowledge, this is the first experimental work on levitating a magnet within an SRF cavity. The cavity is a coaxial quarter-wave microwave resonator made from 6061 aluminum, having a resonance frequency of 10 GHz and a loaded Q of 1400. The cylindrical magnet (N50) has a height of 1 mm, a diameter of 0.75 mm, a mass of 4 mg, and a remanence of 1.44 T. This produces a peak magnetic field 140 times greater than the critical field of aluminum. The magnet is placed either on the top of the coaxial portion of the cavity or on the cavity floor before cooling it below the superconducting transition temperature of aluminum. The coaxial mode's resonance frequency shifts as a function of the levitation height of the magnet and gives an idea of the magnet's position and mechanical motion. We observe a transition at a temperature of 650 mK where the Meissner effect levitates the magnet as the material beneath the magnet becomes superconducting. The magnet is levitated to a height of 2.5 mm above the surface of the cavity stub, which is a sufficient separation for the field strength of the magnet at the surface of the stub to be less than the critical field strength of the superconducting aluminum. We measure a 120 MHz upshift in the cavity resonance as the magnet is levitated from the top of the stub and 15 MHz downshift as it levitates from the floor of the cavity. Our measurements are consistent over several heating and cooling cycles. Our work provides a path towards a novel optomechanical system. [ABSTRACT FROM AUTHOR]

In this work, amorphous InSe thin films coated with 30–160-nm-thick SiO2 are used as an active material to fabricate multifunctional devices. The n-InSe/p-SiO2 layers that are deposited onto ytterbium substrates are optically and electrically characterized. It was observed that the coating of SiO2 nanosheets onto the surface of InSe enhances the light absorbability in the near-infrared range without remarkable altering of the bandgap. Significant increase in the steady-state photocurrent values accompanied by faster photocurrent responses resulted from the coating of SiO2 nanosheets. Electrically, while the Yb/InSe/Au channels display tunneling Schottky barrier characteristics, the Yb/InSe/SiO2/Au channels show pn junction features. Both channels displayed metal–oxide–semiconductors (MOS) capacitance–voltage characteristics. In addition, the analyses of the current–voltage characteristics have shown that the currents in the Yb/InSe/Au and Yb/InSe/SiO2(30 nm)/Au channel are dominated by electric field-assisted thermionic emission (tunneling) of charge carriers through barriers of widths of 18/14 and 30/16 nm under reverse-/forward-biasing conditions, respectively. Further increase in the oxide layer thickness lowered the barrier height of the devices. On the other hand, when an ac signal of low amplitude is imposed through the device channels, the conductance, capacitance, and reflection coefficient spectra displayed bandstop filter characteristics near 1.6 GHz. The microwave cutoff frequency spectra show a remarkable increase in the cutoff frequency values as a result of the coating of InSe with SiO2 nanosheets. The features of the device assure its applicability as rectifying diodes, fast photosensors, MOS capacitors, and microwave bandstop filters. [ABSTRACT FROM AUTHOR]

In this article, Au/As2Se3/Ag/As2Se3/Yb Schottky barriers are formed and characterized. The devices prepared by the thermal evaporation technique under vacuum pressure of 10−5 mbar are observed to exhibit metal-induced crystallization process when coated onto Au substrates. Electrically, the arsenic selenide-based Schottky devices exhibited typical metal-oxide-semiconductor (MOS) characteristics with a built-in potential of 0.17 eV. The device shows resonance–antiresonance switching, negative capacitance (NC) effect, and high to low conductance switching features in the frequency domain of 10–1800 MHz. In addition, measurement of the impedance, amplitude of reflection coefficient, return loss (Lr), and voltage standing wave ratio (VSWR) spectra in the same domain have shown that the Au/As2Se3/Ag/As2Se3/Yb Schottky barriers display band stop features at 1180 MHz. The Lr and VSWR values at this critical frequency are 29.1 dB and 1.1, respectively. The electrical characterizations of the Au/As2Se3/Ag/As2Se3/Yb MOS devices have confirmed their suitability for use as parasitic capacitance cancellers, noise reducers, and as switching clock with selective switching time scales of switching delay time less than 0.40 ns. [ABSTRACT FROM AUTHOR]

Abatement of NO using microwave micro-plasma is presented in this paper. The micro-plasma is generated using granular activated carbon (GAC) particles of size (2–3 mm) in loosely fluidized bed in a microwave cavity operated at 2.45 GHz. A single-mode microwave cavity reactor (SMMCR) was constructed and microwave was injected through another slotted single-mode waveguide in a sandwiched manner. COMSOL Multiphysics software was used to investigate the microwave electric field and the power density within the SMMCR. Gas mixture of air and 500 ppm NO (in N2) at the flow rate of 2 l/min was passed through a quartz tube centered within the SMMCR, while the supplied microwave power was very low 10–80 W and corresponding NO reduction was greater than 98%. The mass of GAC used for generating the plasma was 5g. The efficiency of NO reduction is found to be 24.84 g(NO \text{2})/kWh. When air is mixed with NO (in N \text{2}), the efficiency of NOx reduction achieved vary greatly with respect to the supplied microwave energy, and behavior has become complex and is not predictable, which needs further investigation. A gas analyzer (testo 350) was used to measure the gas (NO, NO \text{2}, CO, and O \text{2}) concentration and temperature. [ABSTRACT FROM AUTHOR]

In this paper, a novel technique to achieve precise temperatures in food sterilization has been proposed. An accurate temperature profile is needed in order to reach a commitment between the total removal of pathogens inside the product and the preservation of nutritional and organoleptic characteristics. The minimal variation of the target temperature in the sample by means of a monitoring and control software platform, allowing temperature stabilization over 100 °C, is the main goal of this work. A cylindrical microwave oven, under pressure conditions and continuous control of the microwave supply power as function of the final temperature inside the sample, has been designed and developed with conditions of single-mode resonance. The uniform heating in the product is achieved by means of sample movement and the self-regulated power control using the measured temperature. Finally, for testing the sterilization of food with this technology, specific biological validation based on Bacillus cereus as a biosensor of heat inactivation has been incorporated as a distribution along the sample in the experimental process to measure the colony-forming units (CFUs) for different food samples (laboratory medium, soup, or fish-based animal by-products). The obtained results allow the validation of this new technology for food sterilization with precise control of the microwave system to ensure the uniform elimination of pathogens using high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, n-InSe/p-ZnSe/n-InSe (npn) thin-film transistors (TFTs) are deposited onto cubic (111)-oriented Ag, Au, and Al thin-film substrates. The properties of the structures are explored by means of X-ray diffraction and impedance spectroscopy in the frequency range of 10–1800 MHz. Although the Ag, Au, and Al substrates are observed to be well aligned with the cubic ZnSe, the electrical properties of these TFT for the np (InSe/ZnSe) and npn interfaces are different. Namely, while the capacitance of the TFT deposited onto the Ag substrate exhibited positive values, the capacitance of the TFT deposited onto Au and Al films is negative in the range of 10–1100 and 800–1800 MHz, respectively. In addition, even though the impedance of the Ag/np/Ag and Ag/npn/Ag heterojunction monotonically decreased with the increasing frequency, the impedance of Au/np/Au and Au/npn/Au interfaces exhibited resonance peaks at 1211 and 1148 MHz, respectively. When the wave trap features are read from reflection spectra, it is observed that the Ag/npn/Ag and the Al/np/Ag exhibit low-pass filter properties and the Au/npn/Au behaves as a bandstop filter at a notch frequency of 1176 MHz. These properties nominate the npn transistors for use as microwave traps and as high-speed CMOS amplifiers. [ABSTRACT FROM PUBLISHER]

A systematic study of the electrodynamic coupling between the ferromagnetic resonance (FMR) and the cavity mode of a microwave cavity is presented. The nature of the FMR and cavity modes, described by their resonance position and line width, is measured and compared with a classical model based on the Landau–Lifshitz–Gilbert equation and an RLC circuit, which explicitly implement Faraday’s and Ampère’s laws. The relationship between the coupling gap, which can be accessed experimentally, and the coupling strength, which is a fundamental property of the FMR/cavity system, is discussed on the basis of this model. A straightforward method is experimentally developed to control the coupling gap. The capability of using such a tunable cavity-FMR coupling in combination with spin pumping could provide us with new technologies that utilize the light-matter interaction to control spin current in cavity spintronics. [ABSTRACT FROM PUBLISHER]

The hafnium doping effects on the performance of the Bi1.5Zn0.92Nb1.5O6.92 (BZN) varicaps are explored by means of impedance and signal power spectroscopes in the range of 10–1800 and 1000–3000 MHz, respectively. The Hf content that was varied in accordance with the Bi1.5Zn0.92–2xHfxNb1.5O6.92 formalism was observed to reach the solubility limit at the Hf content of 0.06. The free carrier concentration in the devices systematically increased with the increasing Hf content. The impedance spectral analysis revealed a series and parallel resonance exchange above 1000 MHz. The critical frequencies of resonance are observed to shift from 1638 to 1585 and reach 1476 MHz as the Hf content increases from 0.00 to 0.03 and reaches 0.06, respectively. It was also observed that the hafnium doping significantly increases the respective dielectric constant of BZN from 268 to 290 and to 470. In addition to the negative dielectric property that is useful in applications where the cancelation of parasitic capacitance is needed, the wave power spectral analysis revealed the microwave band-reject filter properties with the respective notch frequencies of 1580, 1845, and 2040 MHz. While the undoped ceramic filters can detect the signals of power down to 40 nW, the doped ones are functional for the signals of microwatt power. [ABSTRACT FROM AUTHOR]

Four decades after its prediction, the axion remains the most compelling solution to the strong- CP problem and a well-motivated dark matter candidate, inspiring a host of elegant and ultrasensitive experiments based on axion-photon mixing. This article reviews the experimental situation on several fronts. The microwave cavity experiment is making excellent progress in the search for dark matter axions in the μeV range and may plausibly be extended up to 100 μeV. Within the past several years, however, researchers have realized that axions are pervasive throughout string theories, but with masses that fall naturally in the neV range, for which an NMR-based search is under development. Both searches for axions emitted from the Sun's burning core and purely laboratory experiments based on photon regeneration have recently made great progress, with ambitious projects proposed for the coming decade. Each of these campaigns has pushed the state of the art in technology, enabling large gains in sensitivity and mass reach. Furthermore, each modality has been exploited in order to search for more generalized axion-like particles, which we also discuss in this review. We are hopeful, even optimistic, that the next review of the subject will concern the discovery of the axion, its properties, and its exploitation as a probe of early universe cosmology and structure formation. [ABSTRACT FROM AUTHOR]

Hyperthermia is a form of cancer treatment in which affected human tissue is exposed to >40 °C temperature. In this paper, our goal is to assess the efficacy of fullerene agents to reduce heating time for cancer treatment. Such agents can accelerate heating of cancer cells and improve hyperthermia treatment efficacy. Typically, in vitro testing involves cancer cell culturing, heating cell cultures in accordance to specifications, and recording cancer cell viability after hyperthermia. To heat cell cultures, we design and evaluate a 2.4-GHz microwave cavity with controllable temperature. The cavity is comprised of a polystyrene cell culture dish (diameter = 54 mm, height = 13.5 mm) and a printed monopole antenna placed within the cavity for microwave heating. The culture temperature can be controlled through the intensity and duration of the antenna's microwave radiation. Heating experiments were carried out to validate the cavity's performance for F-12K culture medium (Kaighn's F-12K medium, ATCC). Importantly, fullerene agents were shown to reduce heating time and improve hyperthermia treatment efficacy. The culture medium temperature increased, on average, from 24.0 °C to 50.9 °C (without fullerene) and from 24.0 °C to 56.8 °C (with 3 mg/mL fullerene) within 15 minutes. [ABSTRACT FROM AUTHOR]

The axion is a light pseudoscalar particle which suppresses CP-violating effects in strong interactions and also happens to be an excellent dark matter candidate. Axions constituting the dark matter halo of our galaxy may be detected by their resonant conversion to photons in a microwave cavity permeated by a magnetic field. The current generation of the microwave cavity experiment has demonstrated sensitivity to plausible axion models, and upgrades in progress should achieve the sensitivity required for a definitive search, at least for low mass axions. However, a comprehensive strategy for scanning the entire mass range, from 1-1000 μeV, will require significant technological advances to maintain the needed sensitivity at higher frequencies. Such advances could include sub-quantum-limited amplifiers based on squeezed vacuum states, bolometers, and/or superconducting microwave cavities. The Axion Dark Matter eXperiment at High Frequencies (ADMX-HF) represents both a pathfinder for first data in the 20-100 μeV range (~5-25 GHz), and an innovation test-bed for these concepts. [ABSTRACT FROM AUTHOR]

Novel type of finite elements, based on independent three-dimensional higher-order modeling of geometry and electric fields using trivariate B-spline functions, is presented. The method is evaluated in simulations of rectangular, spherical, and ridged canonical microwave cavity problems. The examples demonstrate excellent accuracy and efficiency of the proposed method. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:619-624, 2014 [ABSTRACT FROM AUTHOR]

In the present study, the essential oil from the leaves of River Red Gum (Eucalyptus camaldulensis Dehnh) was distilled by microwave applied in situ hydrodistillation (MWHD) and the properties obtained were compared with hydrodistillation (HD) techniques. The chemical composition of essential oil obtained by the microwave method was analyzed by gas chromatography (GC) and GC–mass spectrometry (MS). The results showed that the essential oil from E. camaldulensis could successfully be distilled by using microwave irradiation power. Microwave power has been supplied from a cavity having a multimode microwave reactor 2455 MHz with a maximum power of 1000 W. Electromagnetic power distribution has been analyzed inside the cavity. The yield of essential oil increased with increasing microwave irradiation power. It was also found that the content of main compounds clearly varied according to methods applied. However, the yield of essential oil determined by MWHD was slightly lower than that of conventional HD method at conditions studied. [ABSTRACT FROM PUBLISHER]

The performance of a novel microwave ignition source was experimentally tested against a standard multi-spark ignition system. Comparison of the combustion and detonation performance was measured. The growth of combustion kernels and the discharge pattern of the igniters were recorded using high-speed video cameras for visual comparison. The results showed that the transition of deflagration to detonation transition was comparable between the two ignition systems. Significant improvement in ignition of lean mixtures of ethylene and ethane were observed for the microwave ignition system over the baseline multi-spark ignition and thus should be considered for application as a lean ignition source. [ABSTRACT FROM AUTHOR]

Atmospheric and higher pressure RF and microwave plasma sources have numerous applications including material processing and spectroscopy. More recently, advantages in using such discharges for combustion ignition are being investigated. A particularly simple and compact microwave discharge generating device is the quarter wave coaxial cavity resonator (QWCCR). This paper presents a new, compacted design of such a device. A simple approximate analysis of the quality factor, Q, which is a measure of the resonant electromagnetic potential step-up capability is given, and compared to experimentally measured quality factors showing reasonable agreement. Analytic results indicate that the foreshortened folded cavity quality factors are comparable to tapered coaxial cavity designs. [ABSTRACT FROM PUBLISHER]

This paper presents a novel microwave cavity sensor application for the detection of HEPA filter particulate loading. The sensor resonates at 3.435GHz and 8.570GHz when empty, where the TM010 and TM020 modes dominate respectively. Experimental results show that the resonant frequency of the sensor shifts significantly when filters of different particulate loadings are presented to it. This is a significant finding, and means that the sensor could present an effective solution for determining the loading of periodic use HEPA filters (e.g. those used in personal respirators), which are often disposed of unnecessarily. [ABSTRACT FROM AUTHOR]

We demonstrate a frequency-diverse aperture for microwave imaging based on a planar cavity at K-band frequencies (18–26.5 GHz). The structure consists of an array of radiating circular irises patterned into the front surface of a double-sided printed circuit board. The irises are distributed in a Fibonacci pattern to maximize spatial diversity at the scene. The printed cavity is a phase-diverse system and encodes imaged scene information onto a set of frequencies that span the K-band. Similar to recently reported metamaterial apertures, the printed cavity imager does not require any mechanically moving parts or complex phase shifting networks. Imaging of a number of targets is shown; these reconstructed images demonstrate the ability of the system to perform imaging at the diffraction limit. The proposed printed cavity imager possesses a relatively large quality factor that can be traded off to achieve higher radiation efficiency. The general mode characteristics of the printed cavity suggest advantages when used in computational imaging scenarios. [ABSTRACT FROM PUBLISHER]

New ignition sources are needed to operate the next generation of lean high-efficiency internal combustion engines. A significant environmental and economic benefit could be obtained from these lean engines. Towards this goal, the quarter wave coaxial cavity resonator (QWCCR), igniter was examined. A brief overview of the QWCCR's history is presented, followed by an electromagnetic analysis of the resonator. Microwave and radio-frequency gas breakdown at atmospheric and higher conditions are reviewed briefly. The presented analysis focuses on geometric and material parameter relations compared with performance characteristics, such as resonator quality factor and developed tip electric field which initiates a single-electrode high-pressure microwave gas breakdown. Conductor surface losses, dielectric losses, and radiation losses of the device are considered in the analysis, for which parameters of a prototype QWCCR were chosen for construction and evaluation of a resonator. Improved designs allowed successful integration of a QWCCR into a Briggs and Stratton engine. Given the capability of precise control, high power, and high energy delivery, and the opportunity for further optimization, the QWCCR has the potential to deliver more energy per ignition than a conventional spark plug and thus should be considered for application as a lean ignition source. [ABSTRACT FROM AUTHOR]

This article deals with the inverse scattering problem from scattered field data measured inside a closed microwave scanner. This system is presently being developed to demonstrate the potentiality of a non-invasive microwave imaging system for volumetric water content monitoring. The final goal is to retrieve soil moisture information as it is an important parameter for understanding fluid flow modelling, as well as water uptake by plants roots. Based on the actual state of the setup, we are proposing appropriate numerical tools, in particular a finite element formalism combined with a Lagrangian minimization scheme to provide a fast and accurate imaging tool. We will also show how we can improve the reconstruction algorithms by changing in a very simpler manner the measurement configuration, using either off-centred information or impedance boundary matching environment. [ABSTRACT FROM AUTHOR]

A combined knowledge-based neural-multilayer perceptron (KBN-MLP) model to account for a loading effect of arbitrary raised dielectric slab in a microwave cylindrical metallic cavity is presented. Existing partial knowledge about the resonant frequency behavior of loaded cavity is incorporated in the KBN part of suggested model. In comparison with the model based on classical MLP network, more accurate and efficient resonant frequencies calculation is achieved. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [ABSTRACT FROM AUTHOR]

The axion is a light pseudoscalar particle predicted to exist as a consequence of the Peccei-Quinn solution to the strong-CP problem. Its abundant production in the early Universe along with its stability and insignificant interaction cross-section make it a prime dark matter candidate. This report summarises the search for dark matter axions using resonant microwave cavities as well as searches for axions produced in the Sun and in the laboratory. All of these current experiments focus on the axion-photon interaction, as coherent axion-photon mixing in strong magnetic fields of large spatial extent can make up for the extraordinary weakness of the the coupling of axions to photons. [ABSTRACT FROM AUTHOR]

A novel kind of cavity-cell assembly for rubidium frequency standards has been developed. The assembly utilizes a new magnetron-type microwave cavity. The cavity is of small size, easily manufactured with high machining precision, and the cavity frequency can be easily adjusted. Either the integrated filter technique (IFT) or the separated filter technique (SFT) can be used in this cavity-cell assembly. The assembly has a high signal-to-noise ratio. The frequency stabilities of rubidium atomic frequency standards with this assembly are 4 × 10-12/τ1/2 for IFT and 2.7 × 10-12/τ1/2 for SFT, and its temperature coefficient and light shift are very low. [ABSTRACT FROM AUTHOR]

A knowledge-based neural (KBN) model of a microwave-loaded cylindrical metallic cavity is presented in this paper. The considered cavity is loaded with a homogeneous dielectric layer located on the cavity bottom. Unlike the model based on a classical multilayer perceptron (MLP) network, the proposed KBN model includes an existing partial knowledge about the resonant frequency behavior of the cavity, yielding more accurate determination of the resonant frequencies. A comparison of MLP and KBN models, as well as an advantage of using the KBN model, is given through an example referring to the experimental cylindrical metallic cavity with a circular cross section. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 580–585, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21057 [ABSTRACT FROM AUTHOR]

A cylindrical rod composed of a uniform mixture of metallic nanoparticles and alumina powder dissolved in paraffin was inserted in the center of a cylindrical microwave cavity. The real and imaginary parts of the complex dielectric constant of metallic nanoparticles at various microwave frequencies of the TM010 mode can be determined from the resonant frequency and quality factor, respectively, of the transmission resonance spectrum. This method involves the protection of the sample from adsorbed moisture and prevents the rod from filling with air, thus making the experimental values more accurately and stably determined than they are by the dielectric double-cavity method. The real parts of the dielectric constants of metallic nanoparticles are negative and their magnitudes decrease as the particle size decreases. This finding is consistent with theory, which states that conduction becomes weaker as the particle size is reduced. [ABSTRACT FROM AUTHOR]

A wet thermal paper method for measuring of mode patterns and heat distributions in a high-power microwave multimode cavity is developed. The exposure time of the paper is evaluated. It is shown that this method allows measuring and recording mode patterns in the loaded and unloaded cavity, and the heat distribution inside the cavity with a load movement The mode patterns and heat distributions along horizontal and vertical planes of the cavity are presented. Possible applications of the method in medicine and biology are discussed, and a calibration protocol of a microwave oven for microwave radiation exposure on cell cultures in the cavity is given. [ABSTRACT FROM AUTHOR]

The complex permittivity of liquids is measured with a microwave cavity. The measurements are conducted for the TE111, TE112, TM010, and TM011 modes in a circular cylindrical cavity. The loss tangent of the dirty oil (after 6000 mi) is found to be three times higher than the one of the clean oil. The relative dielectric constant is not noticeably effected. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 15–18, 1999. [ABSTRACT FROM AUTHOR]

Electron densit ies have been determined /or RF plasmas that were generated within a microwave resonant cavity by measuring the difference of the resonance frequencies with and without plasma. Since that method only yields a value of the electron density weighted ouer the microwave electric field distribution, to obtain real values an assumption on the spatial distribution of the electron density had to he made. Spatial profiles were taken of the emission of a 4s-5p Ar line at 419.8 not (with a small Ar admixture). The electron densities have been determined as a function of pressure and RF power in Ar, CF, C F and CHF, plasmas. The results indicate that the electron density for the last three gases decreases as a function of pressure above 50 m Torr. Typical values for the electron density for the investigated parameter range are 1-6 · 10 cm. Furthermore, the electron density is the lowest in gases with a high attachment cross .section. [ABSTRACT FROM AUTHOR]