Synthesis of Y_2O_2S：Eu^（3＋） Phosphor by Microwave Thermal Effectand Its Luminescent Properties

The phosphor Y2O2S:Eu3+ powder crystal has been synthesized by using the microwave thermal method.The data of X-ray powder diffraction showed that the phosphor structure belongs to hexagonal system with lattice parameters a=0.3785 nm,c=0.6590nm.The excitation spectrum of the phosphor is a broad band with peak at λ(ex)= 261 nm.The main emission peak at λ(em)=626nm and the other emission lines peak at 595,617 and 706 nm are assigned to transitions of the Eu3+ respectively.Under 254 nm excitation,the chromatic coordinates of phosphor are x=0.665, y=0.330.The relative luminescent intensity is about 62% compared with the standard phosphor Y2O3:Eu3+.Under 365nm excitation this phosphor gives rise to an intense red light.The phosphor particle size has a medium diameter of 7.3μm.

Dick Effect in a Microwave Frequency Standard Based on Laser-Cooled 113Cd+ Ions

The Dick effect is one of the main limits to the frequency stability of a passive frequency standard, especially for the fountain clock and ion dock operated in pulsed mode which require unavoidable dead time during interrogation. Here we measure the phase noise of the interrogation oscillator applied in the microwave frequency standard based on laser-cooled 113^Cd＋ ions, and analyze the Allan deviation limited by the Dick effect. The results indicate that the Dick effect is one of the key issues for the cadmium ion dock to reach expected frequency stability. This problem can be resolved by interrogating the local oscillator continuously with two ion traps.

Effects on the Behavior and Neuroimmunity of Pulsed Microwaves with Different Peak Densities

Pulsed microwaves are widely used inradar,navigation, and communication. The average power density is low at narrow pulse widths or large pulse intervals,but pulsed microwaves at certain peak densities exert numerous biological effects, including

Progress of the technique of coal microwave desulfurization

With the advantages of its fast speed,effective and moderate controllable conditions,desulfurization of coal by microwave has become research focus in the field of clean coal technology.Coal is a homogeneous mixture which consists of various components with different dielectric properties,so their abilities to absorb microwaves are different,and the sulfur-containing components are better absorbers of microwave,which makes them can be selectively heated and reacted under microwave irradiation.There still remain controversies on the principle of microwave desulfurization at present,thermal effects or non-thermal effects.The point of thermal effects of microwave is mainly base on its characters of rapidly and selectly heating.While,in view of non-thermal effect,direct interactions between the microwave electromagnetic field and sulfur containing components are proposed.It is a fundamental problem to determine the dielectric properties of coal and the sulfur-containing components to reveal the interaction of microwave and sulfur-containing compounds.However,the test of dielectric property of coal is affected by many factors,which makes it difficult to measure dielectric properties accurately.In order to achieve better desulfurization effect,the researchers employ methods of adding chemical additives such as acid,alkali,oxidant,reductant,or changing the reaction atmosphere,or combining with other methods such as magnetic separation,ultrasonic and microorganism.Researchers in this field have also put forward several processes,and have obtained a number of patents.Obscurity of microwave desulfurization mechanism,uncertainties in qualitative and quantitative analysis of sulfur-containing functional groups in coal,and the lack of special microwave equipment have limited further development of microwave desulfurization technology.

The Interaction of C-Band Microwaves with Large Plasma Sheets

A large plasma sheet 60 cm×60 cm×2 cm in size was generated using a hollow cathode, and measurements were conducted for interactions including transmission, reflection and absorption. With different discharge parameters, plasma sheets can vary and influence microwave strength. Microwave reflection decreases when the discharge current rises, and the opposite occurs in transmission. The C-band microwave is absorbed when it is propagated through large plasma sheets at higher pressure. When plasma density and collision frequency are fitted with incident microwave frequency, a large amount of microwave energy is consumed. Reflection, transmission and absorption all exist simultaneously. Plasma sheets are an attractive alternative to microwave steering at low pressure, and the microwave reflection used in receiving radar can be altered by changing the discharge parameters.

“Hot Nano Spots” as an Interpretation of So-Called Non-Thermal Biological Mobile Phone Effects

Indications exist that mobile phones may cause non-specific biological effects. They are classified as being of implausible non-thermal nature due to low quantum energy and low specific absorption rate levels, even if considering worst cases of "hot spots" of only millimeter size. The considerations of this paper demonstrate that classical theory of polarization offers a conventional interpretation for all three the existence of so far unclarified effects, their low reproducibility and their low intensity. The basis of this explanation is given by the assumption that hot spots contain even hotter “nano spots” on a molecular level according to well known mechanisms of γ-relaxation. In this paper, the concept is put for discussion assuming a heterogeneous system that consists of water molecules as well as larger-sized functional molecules. A consistent interpretation through temperature increase on the level of nanometer sized molecular compounds promises to favor interdisciplinary discussions with respect to safety regulations.

Air breakdown induced by the microwave with two mutually orthogonal and heterophase electric field components

The air breakdown is easily caused by the high-power microwave, which can have two mutually orthogonal and heterophase electric field components. For this case, the electron momentum conservation equation is employed to deduce the electric field power and effective electric field for heating electrons. Then the formula of the electric field power is introduced into the global model to simulate the air breakdown. The breakdown prediction from the global model agrees well with the experimental data. Simulation results show that the electron temperature is sensitive to the phase difference between the two electron field components, while the latter can affect obviously the growth of the electron density at low electron temperature amplitudes. The ionization of nitrogen and oxygen induces the growth of electron density, and the density loss due to the dissociative attachment and dissociative recombination is obvious only at low electron temperatures.

Lumped-equivalent circuit model for multi-stage cascaded magnetoelectric dual-tunable bandpass filter

A lumped-equivalent circuit model of a novel magnetoelectric tunable bandpass filter, which is realized in the form of multi-stage cascading between a plurality of magnetoelectric laminates, is established in this paper for convenient analysis.The multi-stage cascaded filter is degraded to the coupling microstrip filter with only one magnetoelectric laminate and then compared with the existing experiment results. The comparison reveals that the insertion loss curves predicted by the degraded circuit model are in good agreement with the experiment results and the predicted results of the electromagnetic field simulation, thus the validity of the model is verified. The model is then degraded to the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates. It is revealed that if the applied external bias magnetic or electric fields on the two magnetoelectric laminates are identical, then the passband of the filter will drift under the changed external field; that is to say, the filter has the characteristics of external magnetic field tunability and electric field tunability. If the applied external bias magnetic or electric fields on two magnetoelectric laminates are different, then the passband will disappear so that the switching characteristic is achieved. When the same magnetic fields are applied to the laminates, the passband bandwidth of the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates becomes nearly doubled in comparison with the passband filter which contains only one magnetoelectric laminate. The bandpass effect is also improved obviously. This research will provide a theoretical basis for the design, preparation, and application of a new high performance magnetoelectric tunable microwave device.

Ferromagnetic resonance frequency shift model of laminated magnetoelectric structure tuned by electric field

Based on Smith-Beljers theory and classical laminate theory, an explicit model is proposed for the ferromagnetic resonance （FMR） frequency shift of a stress-mediumed laminated magnetoelectric structure tuned by an electric field. This model can effectively predict the experimental phenomenon that the FMR frequency increases under a parallel magnetic field and decreases under a perpendicular magnetic field when the electric field ranges from - 10 kV/m to 10 kV/m. Besides, this theory further shows that the FMR frequency increases monotonically as the angle between the direction of the external magnetic field and the outside normal direction of the laminated structure increases, and the frequency will increase as great as 7 GHz. In addition, when the angle reaches a certain critical value, the external electric field fails to tune the FMR frequency. When the angle is above the critical value, the increase of the electric field induces the FMR frequency to increase, and the opposite scenario happens when it is below the critical value. When the angle is 90~ （parallel magnetic field）, the FMR frequency is the most sensitive to the change of the electric field.

Experimental and theoretical study of microwave enhanced catalytic hydrodesulfurization of thiophene in a continuous-flow reactor

Hydrodesulfiirization(HDS)of thiophene,as a gasoline model oil,over an industrial Ni-Mo/Al2O3 catalyst was investigated in a continuous system under microwave irradiation.The HDS efficiency was much higher(5%-14%)under microwave irradiation than conventional heating.It was proved that the reaction was enhanced by both microwave thermal and non-thermal effects.Microwave selective heating caused hot spots inside the catalyst,thus improved the reaction rate.From the analysis of the non-thermal effect,the molecular collisions were significantly increased under microwave irradiation.However,instead of being reduced,the apparent activation energy increased.This may be due to the microwave treatment hindering the adsorption though upright S-bind(η1)and enhancing the parallel adsorption(η5),both adsorptions were considered to favor to the direct desulfurization route and the hydrogenation route respectively.Therefore,the HDS process was considered to proceed along the hydrogenation route under microwave irradiation.