Influence Of Microwave Field Research Articles

Интегрированные с ферритовым волноводом мультиэлектродные микроантены для возбуждения-приема спиновых волн

Multielectrode microantennas for spin waves integrated with a ferrite waveguide – yttrium iron garnet film – were fabricated and tested. Microantennas of two types were studied: with a parallel connection of conductors – “grating” and with a serial connection of conductors – “meander”. The performance of such microantennas for excitation of magnetostatic surface and backward volumec waves tens of micrometers in length has been demonstrated. It has been shown that for waves with a length of tens of micrometers, high (tens of megahertz) excitation selectivity can be achieved using the “grating” microantennas. Whereas, using the “meander” microantennas for the same wavelength range, it is possible not only to get selectivity, but also to significantly (up to 10 dB) increase the excitation efficiency compared to the microantenna with a single conductor. It is noted that the use of such microantennas for shorter spin waves can be hampered by the mutual influence of microwave fields from neighboring conductors, as well as the increasing role of ohmic losses in conductors.

Investigation of the dynamics of heating metal-dielectric structures with nanometer conductive film under the influence of microwave fields

The paper presents the results of experimental studies and analysis of the dynamics of heating of metal-dielectric structures (MDS) with aluminum conducting films on glass or sitall substrates when exposed to powerful microwave fields, as well as when exposed to direct and alternating currents.

Microwave assisted gain in inverted-Y type atomic system

The probe response in four-level inverted-Y configuration showsgainwithout population inversionin presence of microwave field.At on-resonant probe field, switching between superluminal and subluminal probe propagation under the influence of microwave field is discussed in details.Both the bandwidth and sharpness of optical switching can easilybe controlled by varying the microwave power. The switching action improves immensely if the control transition is chosen to be a Rydberg transition. The transient behavior of the atomic system ultimately settles into probe gain under the influence of the microwave field.A way of transferring population to the highest excited state through the application of microwave field is also discussed.

The Effect of Microwave on the Crystallization Behavior of CMAS System Glass-Ceramics.

The microwave sintering of glass-ceramics, non-thermal microwave effect, and crystal growth mechanism remain important challenges in materials science. In this study, we focus on developing approaches to affect crystal growth in the glass network of glass-ceramics by microwave heating, rather than performing a single study on the crystal structure and type. Raman spectroscopy is used to detect the structure of the glass network. We demonstrated that the non-thermal microwave effect promoted the diffusion of metal ions, which promoted the aggregation and precipitation of metal ions in the glass network to form crystals. The samples produced by microwave heating contain more non-bridging oxygen bonds than conventional sintered samples; therefore, the non-thermal microwave effect has a depolymerization effect on the glass network of the sample. Under the influence of microwave field, many metal ions precipitate, which precipitates many crystal nuclei. In addition, many active metal ions are captured during the crystal nucleus growth, which shortens the sintering process of glass-ceramics.

Direct-current-assisted microwave quenching of YBa2Cu3O7−δ coplanar waveguide to a highly dissipative state

The paper reports on revealing the effect of a strong change in the microwave losses in an high-temperature superconductor (HTS)-based coplanar waveguide (CPW) at certain values of the input power Pin and direct current Idc. CPW on the basis of 150 nm thick YBa2Cu3O7−δ epitaxial film on a single crystal MgO substrate was studied experimentally. A sharp and reversible transition of the CPW into a strongly dissipative state at the certain values of Pin and Idc depending on temperature were observed. Apparently, the effect can be explained by self-heating of HTS structure caused by magnetic flux flow under the joint influence of microwave field and direct current.

Using mobile metallic temperature sensors in continuous microwave assisted sterilization (MATS) systems

The goal of this study was to evaluate suitability of using mobile metallic temperature sensors in continuous microwave assisted sterilization (MATS) systems. A computer simulation model using the finite difference time domain method was developed to study the influence of microwave field on the accuracy of mobile metallic temperature sensors, ELLAB, in a MATS system in which food packages with embedded sensors traveled on a conveyor belt. Simulation results indicated that the metallic temperature sensors did not change the overall heating patterns within food samples. But when a metallic temperature sensor was placed in parallel to the electric field component within microwave cavities the field intensity had intense singularity at the sensor tip and caused localized overheating. The electric field singularity adjacent to the tip of the metallic temperature sensor can be avoided by placing the sensor perpendicular to the electric field component. The simulated heating patterns and temperature profiles were verified with experimental results. It was evident from both simulated and experimental results that the metallic temperature sensor could be used to capture temperature profile in a MATS system when placed in a suitable orientation.

Dehalogenation of polychlorinated biphenyls (PCB) by nucleofile reactants at the presence of ionic liquids and under application of microwaves

Laboratory-scale experiments were performed in order to examine the effect of microwave field on the effectiveness of KPEG method (nucleophilic substitution of the chlorine atoms in a molecule of PCBs by alkaline polyethylene glycol PEG) in the removal of PCBs from highly contaminated mineral oils with the content of indicator congeners (No 28,52,101,53,138 and 180) above 5500 mg kg-1. Results show that the microwave field significantly increases the reaction rate and the method’s effectiveness in the removal of chlorine from the molecules of PCBs. Addition of a small amount of an ionic liquid, in this case 1-butyl-3-methylimidazolium hexafluorophosphate–[bmim][PF6], significantly positively affects the results obtained under the influence of microwave field. The KPEG method enhanced by the application of microwaves could be used in practice for decontamination and recycling of PCB-containing dielectric fluids in electric capacitors and transformers. High efficiencies of the reaction were achieved even when microwaves were applied with no PEG added, only by the presence of alkaline hydroxide or by the presence of a small amount, up to ca. 2%, of an ionic liquid [bmim][PF6]. The microwave enhanced KPEG method might has some advantages for practical uses in decontamination applications.

Spin-Polarization Electronic Transport through a Quantum Dot in the Influence of Microwave Field

The evolution operator method is applied to studying the time-dependent and spin-related electron transport through a quantum dot coupled to two magnetic-metal leads. When the microwave field is applied on quantum dot there are additional peaks of PAT current besides the main peak of resonant tunneling current, and the energy distance between peaks relate to the frequency of microwave fields. Furthermore, Furthermore, owe to the magnetism of lead, the spin-up and spin-down current is different in the parallel magnetization configuration while the same in the antiparallel magnetization configuration.

Controllable Spin-Polarization of Electronic Transport through a Magnetic Quantum Dot in the Influence of Microwave Field

The evolution operator method is applied to studying the time-dependent and spin-related electron transport through a magnetic quantum dot coupled to two normal-metal leads. When the microwave field is applied on quantum dot there are additional peaks of PAT current besides the main peak of resonant tunneling current, and the energy distance between peaks relate to the frequency of microwave fields. Furthermore, owe to the spin non-degeneration in the magnetic quantum dot, the spin-up and spin-down current peaks are separated, and the separated distance depends on Zeeman energy. These effects allow us to propose a scheme to control the magnitude and spin polarization of current.

Microwave Sintering of YSZ Electrolyte Materials for SOFC

Microwave sintering behaviors of four different compositions of YSZ electrolyte materials were investigated. The samples were sintered in 2.45GHz microwave furnace. For comparison, conventional sintering was performed at 1821K.The densities of sintered samples showed considerable enhancement in the densification process under the influence of microwave fields. The samples with lower Y2O3 content are easy to sinter. The influence of the composition and sintering methods on the final phase composition and microstructure were investigated by X-ray diffraction and scanning electron microcopy. Finer and more uniform microstructures were observed in the microwave sintered samples comparing to the conventionally sintered samples.

Influence of microwave fields on electron transport through a quantum dot in the presence of direct tunneling between leads

We consider the time-dependent electron transport through a quantum dot coupled to two leads in the presence of the additional over-dot (bridge) tunneling channel. By using the evolution operator method together with the wide-band limit approximation we derived the analytical formulaes for the quantum dot charge and current flowing in the system. The influence of the external microwave field on the time-average quantum dot charge, the current and the derivatives of the average current with respect to the gate and source-drain voltages has been investigated for a wide range of parameters.

Superconducting Thin Tin Film with PSCS and SNS in External Microwave Field

In the superconducting thin films of some metals (e.g. Al, Sn) at certain conditions (temperatures, dc current densities) the low frequency (compared to Josephson frequency) oscillation of electric potential takes place - so called non-Josephson oscillation (NJO). This phenomenon is related to nonequilibrium dynamics of phase-slip centers (PSC). We studied experimentally the conditions of NJO excitation and its characteristics in thin tin films both with PSCs and with artificial structures of the Superconductor-Normal metal-Superconductor (SNS) type under the influence of microwave field of frequency 10 10 Hz. It was found that NJO could be observed in narrow rf power range only when SNS have been transformed to SS'S by the field influence, but NJO characteristics differed from that in the unperturbed case.

Study on the Influence of Microwave Field on Heating in SrTiO<sub>3</sub> Synthesis

Study on the Influence of Microwave Field on Heating in SrTiO<sub>3</sub> Synthesis

Influence of microwave fields on the electron tunneling through a quantum dot

We consider a quantum dot coupled to two leads in the presence of external microwave (MW) fields which are applied to the dot and two leads, respectively. The amplitudes, phases, and frequencies of the MW fields are taken arbitrarily. Under the adiabatic approximation, the formula for the time-dependent current $j(t)$ and the average current $〈j(t)〉$ are obtained. Some analytical results for several special cases are presented and studied numerically. When the MW field is applied only to one lead, the detailed structure of the main resonant peak in the average current vs gate voltage is in good agreement with the experiment of Kouwenhoven et al. [Phys. Rev. Lett. 73, 3443 (1994)]. For the case with different frequencies of MW fields in different regions, some interesting effects occur, including multiple-photon-assisted tunneling, the combination of sidebands and the electron-photon pump effect, and the coherent effect.

Nonthermal Influence of Microwave Power on Chemical Reactions

To clarify the effect of microwave irradiation on acceleration of chemical reactions other than heating, Arrhenius' plots were taken for the disintegration reaction of sodium hydrogen carbonate water solution. Then to observe the influence of microwave field on the reaction, gas-generating velocities with different irradiated microwave powers were measured under a constant temperature condition. As a result, it was recognized that the microwave field acts to decrease the activation energy of the reaction. Next, pulsed and CW microwave powers, both having the same mean power, were applied to the solution and the pulsed microwave field was observed to accelerate disintegration more than CW. Although the molecular mechanism is not clear, a decrease of the activation energy seems to accelerate the reaction.

Microwave enhancement of evaporation of a polar liquid. II

The evaporation of a polar liquid at low pressure upon exposure to microwave radiation has been investigated. The conventional theories previously developed to describe the non-equilibrium conditions of the evaporating interface are found to be in poor agreement with the experimental results. It is possible to take into account the influence of microwave fields on the evaporating surface by modifying the expression for the entropy production. Another approach, based on the concept that microwaves would increase the pressure, has also been found to be satisfactory.

Microwave enhancement of evaporation of a polar liquid. I

The evaporation of a polar liquid at low pressure upon exposure to microwave radiation has been investigated. The conventional theories previously developed to describe the non-equilibrium conditions of the evaporating interface are found to be in poor agreement with the experimental results. It is possible to take into account the influence of microwave fields on the evaporating surface by modifying the expression for the entropy production. Another approach, based on the concept that microwaves would increase the pressure, has also been found to be satisfactory.

Influence of microwave field on the negative glow plasma characteristics in a helium glow discharge: G S Solntsev et al,Zh Tekh Fiz, 38 (5), May 1968, 893–896 ( in Russian).

Influence of microwave field on the negative glow plasma characteristics in a helium glow discharge: G S Solntsev et al,Zh Tekh Fiz, 38 (5), May 1968, 893–896 ( in Russian).