NUMERICAL STUDIES ON RESONANT AND ENHANCEMENT EFFECTS FOR COUPLING OF MICROWAVE PULSES INTO NARROW SLOTS

In this paper, modifications to the finite-difference time-domain(FD-TD) method for modeling microwave pulse coupling into a slot, which is much narrower than one conventional FD-TD cell, are discussed. The coupling process of microwave pulse into a slot is studied by using the modified FD-TD method, and the dependence of microwave coupling on slot sizes, the carrier frequencies and the polarization directions of the incident waves is analysed. Resonant and enhancement effects which occur in this process are observed. The condition at which the resonant effect takes place is also presented.

Effects of Silane Coupling Agent on Microstructure and Mechanical Properties of EPDM/Carbonyl Iron Microwave Absorbing Patch

The effects of types and amounts of silane coupling agent on mechanical properties of vuleanized rubber microwave absorbing patch （VRMAP） were studied. The mechanisms of silane coupling agent＇s effects on mechanical properties of rubber microwave absorbing patch （ RMAP ） and microvave absorbing patch＇s （MAP＇s） mierostrueture were also discussed by using SEM and FT-IR. The experimental results show that the tensile strength of RMAP could be increased through adding the filler of carbonyl iron powder （CIP） modified by silane coupling agent. RMAP fiUed with CIP, which was treated by silane coupling agent KH550, possessed a high tensile strength of 11.5 MPa, which was 448% more than that of MAP whose filler wus not modified by any coupling agent. It was found that the optimal amount of KH550 was 1.0 phr to 100.0 phr carbonyl iron powder. The effects of different modifying techniques on RMAP＇s mechanical properties were also inrestigated. It is indieated that MAP whose filler is modified by the wet process has the highest tensile strength, but it is not the optimal modiifying technique due to complieated wet process. On the contrary, the dry process was very simple, and VRMAP possessed fairly high mechanical properties, therefore, it was the perfect modifying process.

Cathode position effects on microwave discharge cusped field thruster

The microwave discharge cusped field thruster is a novel concept of electric micropropulsion device,which operatesμN level thrust in low mass flow rate conditions,making use of a coaxial transmission line resonator.With its advantages of low thrust noise and high thrust resolution over a wide range of thrust,the thruster has emerged as a candidate thruster for the space-borne gravitational wave detection mission.The cathode effects commonly exist in many kinds of electric propulsion,and they are typically significant in micropropulsions.In order to find out the cathode position effects on a microwave discharge cusped field thruster,a thermionic cathode is mounted on a cross-slider for coupling.Under different cathode positions,the plume is analyzed by a Faraday probe and a retarding potential analyzer to analyze the performance and discharge characteristics.The results show that the magnetic mirror effect leads to significant degradation of anode current and an increase in low-energy ion ratio as the cathode moves away from the thruster exit.The electron conduction route also significantly impacts anode current efficiency,related to the cathode-exit distance and the thruster magnetic topology.

Microwave-promoted Palladium Catalyzed Suzuki Cross-coupling Reaction in Water

A simple, rapid and environmental friendly method for the synthesis of biaryl compounds under microwave irradiation is reported.

Microwave-assisted Palladium Catalyzed Cross-coupling Reaction of Sodium Tetraphenylborate with Carboxylic Anhydrides

A rapid and efficient method for synthesis of unsymmetrical ketones under microwave irradiation is reported.

Microwave Irradiated Cross Coupling of Carboxylic Acids and Crotyl Bromides: Efficient Application to Make Arachidonic Acid Esters

A microwave irradiated palladium-catalyzed reaction of carboxylic acids and crotyl type bromides creates series of esters in good to high yields. This facile ester synthesis then is applied to make esters from arachidonic acid, salicylic acid, folic acid, and aspirin efficiently.

Microwave Irradiated Palladium-Catalyzed Cascade Type Cross Coupling of Phenols and Halides for the Synthesis of Polyphenolic Ethers

A mild, cascade type methodology was developed for the synthesis of polyphenolic ethers by the palladium-catalyzed cross coupling of phenols and halo compounds under microwave heating. In most cases, reactions run in neat conditions and in some cases, IPA/water mixture, and 1,4-dioxane were employed as solvents to furnish the products. By applying this new method, we were able to synthesize and purify a good number of polyether compounds with complete spectral data.

Microwave-activated Coupling Reaction on Polyethylene Glycol

The two-step Sonogashira coupling reaction took place rapidly under microwave activation conditions. PEG bound substrates acted as PTC and polymer support as well. Its yields are 80~90% and the products are in high purity.

Determination on Heavy Metals Content of Achyranthes bidentata Blume. through Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

[Objective] The inductively coupled plasma mass spectrometry(ICP-MS)was constructed to determine the contents of lead,cadmium,mercury and arsenic in Archyranthes bidentata Blume.[Method]Under the optimum operation condition of ICP-MS,the samples were digested by microwave.The element 114In was taken as an internal standard element to compensate body effect and ICP-MS method was used to determine the contents of lead,cadmium,mercury and arsenic.[Result]For the determined elements,the correlation coefficient(r)of standard curve was over 0.9995 and recovery rate was from 96.7% to 106.4% while RSD was less than 11.2%.The result of determination showed that the heavy metal content in Archyranthes bidentata Blume.beyond standard was serious.[Conclusion]The constructed ICP-MS method with simple operation,rapid response,accuracy and high sensitivity in this experiment could be used for quality control of Chinese medicinal materials by detecting heavy metal contents in different Chinese medicinal materials from original places.

3D Seed-Germination-Like MXene with In Situ Growing CNTs/Ni Heterojunction for Enhanced Microwave Absorption via Polarization and Magnetization

Ti_(3)C_(2)Tx MXene is widely regarded as a potential micro-wave absorber due to its dielectric multi-layered structure.However,missing magnetic loss capability of pure MXene leads to the unmatched electromagnetic parameters and unsatisfied impedance matching condi-tion.Herein,with the inspiration from dielectric-magnetic synergy,this obstruction is solved by fabricating magnetic CNTs/Ni hetero-structure decorated MXene substrate via a facile in situ induced growth method.Ni2+ions are successfully attached on the surface and interlamination of each MXene unit by intensive electrostatic adsorption.Benefiting from the possible“seed-germination”effect,the“seeds”Ni^(2+)grow into“buds”Ni nanoparticles and“stem”carbon nanotubes(CNTs)from the enlarged“soil”of MXene skeleton.Due to the improved impedance matching con-dition,the MXene-CNTs/Ni hybrid holds a superior microwave absorp-tion performance of−56.4 dB at only 2.4 mm thickness.Such a distinctive 3D architecture endows the hybrids:(i)a large-scale 3D magnetic coupling network in each dielectric unit that leading to the enhanced magnetic loss capability,(ii)a massive multi-heterojunction interface structure that resulting in the reinforced polarization loss capability,confirmed by the off-axis electron holography.These outstanding results provide novel ideas for developing magnetic MXene-based absorbers.

Determination of trace multi-elements in coal fly ash by inductively coupled plasma mass spectrometry

The contents of Cr, Cu, Ni, As, Cd and Pb in coal fly ash were determined by a high resolution inductively coupled plasma mass spectrometry method. The sample digestions were performed in closed microwave vessels with HNO3, HClO4 and FIE The optimum conditions for the determination were obtained. The applicability of the proposed method was validated by the analysis of coal fly ash reference material （NIST SRM 1633a）. The results show that most of the spectral interferences can be avoided by measuring in the high resolution mode （maximum mass resolution R=9 000）. The detection limit is from 0.05 to 0.21 μg/g, and the precision is fine with relative standard deviation less than 4.3%.

Direct Determination of Trace Impurities in High Purity Zinc Oxide by High Resolution Inductively Coupled Plasma Mass Spectrometry

The determination of trace impurities in high purity zinc oxide by high resolution inductively coupled plasma mass spectrometry （ HR-ICP-MS ） was investigated. To overcome some poteutially problematic spectral iuterference, measurements were acquired in both middle and high resolution modes. The matrix effects due to the presence of excess HCl and zinc were evaluated. The optimum conditions for the determination were tested and discussed. The standard addition method was employed for quantitative analysis. The detection limits ranged from 0.02μg/ g to 6 μg/ g depending on the elements. The experimental resalts for the determination of Na, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, Sb and Pb in several high purity zinc oxide powders were presented.

Research on the Effect of High Power Microwave on Low Noise Amplifier and Limiter Based on the Injection Method

The reliability of electronic device is threatened in high power microwave (HPM) environment. In accordance with the situation that the emulation is ineffective in evaluating the accuracy and precision of the HPM effect to electronic device, the experimental method is used to resolve the problem. Low Noise Amplifier (LNA) and Limiter are selected as the objects for the experiments, the structural characteristic of the front-end of radar receiver is described, the phenomena and criterion are elaborated and analyzed using injection method due to its ability to get an accurate threshold avoiding the complex coupling, the basic principle of injection experiment is demonstrated, and the method and process of effect experiment about Low Noise Amplifier and Limiter are also explained. The experimental system is established, and the system is composed of low power microwave source such as TWT, test equipment for obtaining the effect parameters, and some of auxiliary equipments as camera, optical microscope or electron microscopy, attenuator, detector, and directional coupler etc. The microwave delivered from source is adjusted to the power infused by attenuator, and pour in the decanting point of effecter via directional coupler, then the couple signal created by directional coupler is input to the recording instrument after detecting by detector, finally the power of effecter is obtained. The value of power, which damages the effecter in the microwave pulse environment, is classified at the index of sensitivity, and the threshold is obtained by power diagnose and wave test. Some regular understandings of the HPM effect to electronic device are obtained based on the results of the experiments. It turns out that the index of electronic device is influenced significantly by the energy via front door coupling, the MOSFET made up of GaAs is the most wearing part to HPM in LNA, the damage threshold of LNA is about 40dBm under single pulse while in repetitive pulse the value is from 33.3dBm to 43.9dBm according to different wave band. The damage threshold of Limiter is about 56dBm to80dBm.

Advanced Synthesis Techniques for Microwave Filters

With the advent of the ‘digital revolution’ that has made possible services such as the world wide web, satellite broadcasting and mobile and trunk telephony, the finite RF spectrum allocated for terrestrial and satellite telecommunication systems is becoming increasingly crowded. This has impacted significantly upon the performance required from the microwave equipment that comprises these systems. In the case of microwave filters, greater in-band linearity to avoid signal distortion and out-of-band isolation to suppress interference are routinely specified, which can only be satisfied by advanced filtering characteristics. This article presents the coupling matrix approach to the synthesis of prototype filter networks, enabling the realization of the hardware embodying the enhanced performance needed by today’s high capacity systems.

Multiferroic and enhanced microwave absorption induced by complex oxide interfaces

NiFe204 （NFO）/ZnO composite nanoparticles with different ZnO components were investigated, which were pre- pared by a simple wet chemical route method. The magnetoelectric coupling between magnetostriction from NFO and piezoelectricity from ZnO was induced by the surface coating NFO nanoparticles of ZnO layer, NFO/ZnO composite showed ferroelectric properties and the remanent electric polarization reached 0.08 μC/cm. Moreover, the changes of resistance at different room temperatures reached about 2% under 3 T magnetic fields comparing with that of zero mag- netic fields. Furthermore, multiferroic NFO/ZnO resulted in enhancement of microwave absorption due to magnetoelectric coupling.

Analysis and FDTD Modeling of the Influences of Microwave Electromagnetic Waves on Human Biological Systems

The interactions of electromagnetic waves with the human body are complex and depend on several factors related to the characteristics of the incident wave, including its frequency, its intensity, the polarization of the tissue encountered, the geometry of the tissue and its electromagnetic properties. That’s to say, the dielectric permittivity, the conductivity and the type of coupling between the field and the exposed body. A biological system irradiated by an electromagnetic wave is traversed by induced currents of non-negligible density;the water molecules present in the biological tissues exposed to the electromagnetic field will begin to oscillate at the frequency of the incident wave, thus creating internal friction responsible for the heating of the irradiated tissues. This heating will be all the more important as the tissues are rich in water. This article presents the establishment from a mathematical and numerical analysis explaining the phenomena of interaction and consequences between electromagnetic waves and health. Since the total electric field in the biological system is unknown, that is why it can be determined by the Finite Difference Time Domain FDTD method to assess the electromagnetic power distribution in the biological system under study. For this purpose, the detailed on the mechanisms of interaction of microwave electromagnetic waves with the human body have been presented. Mathematical analysis using Maxwell’s equations as well as bio-heat equations is the basis of this study for a consistent result. Therefore, a thermal model of biological tissues based on an electrical analogy has been developed. By the principle of duality, an electrical model in the dielectric form of a multilayered human tissue was used in order to obtain a corresponding thermal model. This thermal model made it possible to evaluate the temperature profile of biological tissues during exposure to electromagnetic waves. The simulation results obtained from computer tools show that the temperature in the biological tissue is a linear function of the duration of exposure to microwave electromagnetic waves.

PHASE AND FREQUENCY LOCKING OF MICROWAVE AND MILLIMETER WAVE POWER COMBINING

The phase and frequency locking of microwave, millimeter wave power combining were analysed and summarized in an all-round way. The master/slave phase locking of cavity oscillators, the peer phase locking of mutually coupled oscillators, and the peer phase locking of ring-connected multiple oscillators were investigated. The results of numerical calculations, and the relations of phase to phase locking model and oscillator parameters were given. And the cavity and space power combining aspects for microwave and millimeter wave were presented.

Spin Transport in a Rashba Ring-Quantum Dot System Pumped by Microwave Fields

We report a theoretical study on producing electrically spin-polarized current in the Rashba ring with parallel double dots embedded, which are subject to two time-dependent microwave fields. By means of the Keldysh Green＇s function method, we present an analytic result of the pumped current at adiabatic limit and demonstrate that the interplay between the quantum pumping effect and spin-dependent quantum interference can lead to an arbitrarily controllable spin-polarized current in the device. The magnitude and direction of the charge and spin current can be effectively modulated by system parameters such as the pumping phase difference, Rashba precession phase, and the dynamic phase difference of electron traveling in two arms of ring; moreover, the spin-polarization degree of the charge current can also be tuned in the range [-∞, ＋∞]. Our findings may shed light on the all-electric way to produce the controllable spin-polarized charge current in the field of spintronics.

Determination of Palladium II in 5% Pd/BaSO₄by ICP-MS with Microwave Digestion, and UV-VIS Spectrophotometer

Determination palladiums have been reported 5% (w/w) Pd/BaSO4 known as Rosenmund Catalyst. The determination of palladium II known as Rosenmund Catalyst is always an expensive procedure usually involving procedures such as flame atomic absorption spectrophotometry, emission spectrometry, and many spectrophotometric methods. In this study, palladium II in 5% Pd/BaSO4, was synthesized and employed to develop an extractive UV-Visible Spectrophotometric, and an inductively coupled plasma mass spectrometry ICP/MS methods for the determination of palladium II. Specification for Pd is 4.85% to 5.10%;the result was 4.97% for the UV-Visible spectrophotometer and 4.90% for the ICP/MS. Both results meet the requirements.

微波消解-电感耦合等离子体质谱法同时测定有机肥料中9种有毒有害元素的含量

提出了微波消解-电感耦合等离子体质谱法(ICP-MS)同时测定有机肥料中As、Cd、Co、Cr、Ni、Pb、Sb、Tl、V等9种有毒有害元素含量的方法。取0.10 g有机肥料样品于聚四氟乙烯微波消解罐中,以2.5 mL盐酸、7.5 mL硝酸和2.0 mL氢氟酸为混合酸进行微波消解。消解结束后,于140℃赶酸,然后加入1.0 mL 50%(体积分数)硝酸溶液,再用水定容至50 mL,摇匀,过滤,取滤液待测,在线加入混合内标溶液。结果表明:9种元素标准曲线的线性范围均为2~100μg·L^(-1),方法检出限(3s)为0.59~66.75μg·kg^(-1);按照标准加入法对典型有机肥料样品进行回收试验,9种元素测定值的相对标准偏差(n=7)为2.0%~3.5%,回收率为81.5%~112%。