Application Of Microwave Technology Research Articles

Pulsed microwave exposure real time and dynamically reduces reactive oxygen species in rat pheochromocytoma cells in vivo

ABSTRACTWith the widespread and ever‐increasing application of microwave technology in our daily lives, the potential adverse effects on biological systems from exposure to microwaves are extremely interesting based on thermal and nonthermal effects, especially nonthermal effects on the nervous system. To real time and dynamically elucidate the diversity of reactive oxygen species (ROS) in rat pheochromocytoma (PC12) cells using a real‐time‐pulsed microwave device combining laser confocal microscopy (LSCM). A LSCM system was designed, and its physical properties, including irradiation cavity simulation, field intensity distribution, and average specific absorption rate (SAR), were analyzed and a stable field intensity distribution as well as a precise average SAR were observed. Subsequently, the diversity of ROS in PC12 cells under pulsed microwave exposure was determined by LSCM online. Additionally, the total ROS in PC12 cells was determined by flow cytometry after pulsed microwave exposure. The ROS signal in single PC12 cell was rapidly quenched as the irradiation time was extended, whereas the total ROS showed no changes in flow cytometry after microwave exposure. This indicates that the change of intracellular ROS in PC12 cells by microwave exposure is a real‐time and dynamic process, and provides a significant reference for studying the biological effects of microwaves. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2395–2400, 2015

Topology optimization design of a lightweight ultra-broadband wide-angle resistance frequency selective surface absorber

In this paper, the topology design of a lightweight ultra-broadband polarization-independent frequency selective surface absorber is proposed. The absorption over a wide frequency range of 6.68–26.08 GHz with reflection below −10 dB can be achieved by optimizing the topology and dimensions of the resistive frequency selective surface by virtue of genetic algorithm. This ultra-broadband absorption can be kept when the incident angle is less than 55 degrees and is independent of the incident wave polarization. The experimental results agree well with the numerical simulations. The density of our ultra-broadband absorber is only 0.35 g cm − 3 and thus may find potential applications in microwave engineering, such as electromagnetic interference and stealth technology.

Reconfigurable Diffractive Antenna Based on Switchable Electrically Induced Transparency

Coupled electromagnetic resonances have various important applications in microwave engineering. Among them, the newly discovered electromagnetically induced transparency (EIT) has attracted much interest. In this paper, we explore the use of configurable electrically induced transparency to construct a microwave “diffractive medium” whose air-like optimally matched transparency and metal-like optimally reflective opacity can be conveniently switched by a binary dc voltage. Different from EITs based on closely coupled resonances, we use decoupled electrically induced resonances to achieve a low-loss transparency along with an optimal impedance matching with air. Satisfying the condition of a lossless perfectly matched layer, such transparency and opacity can be obtained in a wide range of incident angles. We validate our approach by experimentally demonstrating two electrically controlled steering antennas based on diffractive grating effect, both with thin planar apertures and binary digital control circuits. The proposed approach can be extended to higher frequencies, achieving configurable diffractive devices at millimeter-wave and terahertz frequencies.

Dont Sweat It: Treating Hyperhidrosis with Microwaves

When considering the medical applications of microwave technology, ablating sweat glands is probably not what initially comes to mind. However, hyperhidrosis (the medical term for excessive sweating) is a condition estimated to affect up to 3% of the population [1]. There is also evidence that an additional 17% of the population have symptoms that are similar to those diagnosed with the condition [2]. Imagine a scenario where someone is inactive, sitting at his or her desk in a cool, dry environment, yet is sweating from the hands, feet, or underarms as if exercising. This is the type of situation a hyperhidrosis sufferer might face on a daily basis. Beyond physical irritation, there is significant evidence that the condition can result in occupational, emotional, psychological, social, and physical impairment leading to increased amounts of depression and other negative effects [1]. The treatment of sweat is also common in the general population in addition to severe sufferers, as evident from the large amounts of money spent on deodorants and antiperspirants (e.g., US$2.9 billion in the United States in 2012) [3]. In this article, an overview of the current treatment options for axillary (underarm) hyperhidrosis, potential energy-based approaches, and the microwave technique developed for treating this potentially debilitating condition is presented. The challenges of commercializing such a medical microwave device are also discussed.

Analogue photonic link design charts for microwave engineering applications

A set of unique design charts for intensity-modulation direct-detection microwave photonics links is presented. The charts facilitate link design and analysis, clearly demonstrating performance trade-offs in terms of standard microwave performance metrics.

Microwave absorption properties of multi-walled carbon nanotube (outer diameter 20–30 nm)–epoxy composites from 1 to 26.5 GHz

In this work, multi-walled carbon nanotube (MWCNT) (outer diameters (OD) in the range of 20–30nm)–epoxy composites were fabricated. The MWCNT loadings in the polymer composites were controlled from 1–10wt.%. An Agilent PNA Network analyzer was utilized in the measurements of microwave absorption (MA) properties of these MWCNT–epoxy composites over a wide frequency range of 1–26.5GHz. The measurement results showed that MA strongly depends on MWCNT loadings in the composites. In addition, the microwave reflection, transmission, and dielectric permittivity of the MWCNT–epoxy composites are also investigated. The composite with 8wt.% MWCNT loading shows high microwave absorption as well as low reflection and transmission. These MWCNT–epoxy composites with 8–10wt.% MWCNT loadings show a significant potential for microwave technology applications.

Synthesis of highly decorated chiral 2-nitro-cyclohexane carboxylic esters through microwave-assisted organocatalyzed cascade reactions

Starting from (E)-β-substituted-β-nitroacrylates and α,β-unsaturated ketones, a stereoselective organocatalyzed one-pot methodology allowed to synthesize highly decorated chiral 2-nitro-cyclohexane carboxylic esters. The reaction is promoted by Cinchona alkaloid-derived primary amines in the presence of an acidic co-catalyst and affords two diastereoisomers, in good yields and high enantiomeric excess (often higher than 90% ee). By replacing conventional heating with microwave irradiation, cleaner reactions in shortened times (from 48h to 30min) were obtained, with improved dr (80:20) and high ee (up to 94%). The application of microwave technology to this organocatalytic methodology allowed also employing C1 substituted enones, leading to cyclohexanones with four contiguous stereocenters in two isomers only, and up to 99% enantioselectivity.

Structural order and dielectric properties of coal chars

For studying the influence of the structural evolution on the dielectric properties, X-ray diffraction and Raman spectroscopy were used to examine the phase and the degree of crystallite structure of coal chars prepared in the temperature range of 850–1600°C. Additionally, structural changes were visualized by high-resolution transmission electron microscopy. The dielectric properties were measured in the 2–18GHz frequency range using the transmission/reflection method. Generally, the fraction of carbon ordering of coal chars increased, while more parallel-aligned aromatic layers were presented, confirming that the crystallite structure of coal chars became ordered with increasing temperature. The dielectric properties of chars were found strongly dependent on heat-treatment temperature. Increasing temperature could produce higher values of the real part and imaginary part of the complex permittivity. Although mineral matters in coal chars were also observed to transform during heat treatment, the conversion of inorganic matters might have a marginal effect on the complex permittivity. As a result, it is reasonable to conclude that the dielectric properties primarily result from the crystallite structure of coal chars. Furthermore, the dielectric loss may contribute much more than the magnetic loss to the further application of microwave technology.

Study on Development and Application of Microwave Technology

<p>Microwave technology in just a few decades has penetrated into all walks of life, to social development and people's life had a profound impact. On the basis of the development of the microwave, the details of the mechanism of microwave heating and microwave sterilization of both technologies, and microwave heating conditions and characteristics of clarification, in addition, also includes microwave technology is widely used in various fields, while microwave technology for the existing problems are analyzed, and the prospects for the development of microwave technology is also discussed.</p>

Conversion of agricultural residues to carboxymethylcellulose and carboxymethylcellulose acetate

In view of continuing interest in the utilization of agricultural by-products, we have converted cellulose, wheat straw, barley straw, and rice hull into carboxymethylcellulose (CMC), using both conventional heat and microwave-assisted synthesis. The application of microwave technology has enabled an improved synthesis of CMC to be conducted, with similar degrees of substitution as conventional heat (3h) but reduced reactions times (30min). The CMC obtained can be acetylated to form carboxymethylcellulose acetate (CMC acetate). The FT-IR and solid state 13C NMR spectra of these materials have been characterized. With variations in the degrees of substitution of carboxymethyl and acetyl groups, a family of CMC acetate products can be made. The polymer may perhaps find applications as filtration membranes, functional fillers in polymers, and additives in commercial formulations.

Microwave demulsification of heavy crude oil emulsions: Analysis of acid species recovered in the aqueous phase

In this work, the application of microwave technology is investigated for breaking water-in-heavy crude oil emulsions focusing upon the identification of acidic species existing in the aqueous phase recovered by the microwave demulsification process. To accomplish this, a methodology for characterization of acidic species based on GC/qMS (gas chromatography coupled to mass spectrometry quadrupole type) has been developed. An experimental study was conducted to assess the effect of operating conditions, including the heating mode (microwaves/conventional heating), process time (30, 60min), pH of the aqueous phase (pH=2, 6, 10) and temperature (90, 120, 150°C) over the migration of acidic species from the crude oil to the aqueous phase during the demulsification of a heavy crude oil. The most influential variable was the temperature, which favors the partitioning of a larger number of acidic species, including cyclic compounds of low molecular weight that were not extracted at low temperature. The microwave heating allowed a wider distribution profile of monocyclic and bicyclic acids than the conventional heating scheme. Changing the aqueous phase pH from acid to the alkaline range modifies the profile of acidic compounds from predominantly acyclic to monocyclic and bicyclic species.

Vector Finite Elements and the Step by Step Eigenvalue Perturbation Methods

The electromagnetic resonant structures and their perturbations have been found their way in many applications in microwave engineering. Analysis of these structures using finite element method results in a generalized eigenvalue problem, where the eigenvalues correspond to the resonant frequencies, and the eigenvectors correspond to the resonant modes. The perturbations of resonant structures yield perturbed eigenvalue problem and can be solved by eigenvalue perturbation methods, effectively. Combining finite element method with step by step eigenvalue perturbation method yields parametric history with respect to perturbation parameter. In this study perturbation of a microwave ring resonator placed in a metalic enclosure has been examined, combining the vector finite element and the step-by-step generalized eigenvalue perturbation methods.

Applications of microwave technology to rapid synthesis of substituted imidazoles on silica-supported SbCl3 as an efficient heterogeneous catalyst

One-pot cyclo-condensation of benzil, aldehydes, ammonium acetate and primary amines were used to synthesize 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted-1H-imidazole derivatives under microwave irradiation with silica-supported SbCl3 (SbCl3/SiO2) as a heterogeneous catalyst. The operational simplicity, practicability and applicability of this protocol to various substrates make it an interesting alternative to previous procedures. From the environmental stand-point, this eco-friendly, green catalyst is stable, highly active, easy to prepare and handle.

Impact of Microwave Treatment on Chemical Constituents in Fresh Rhizoma Gastrodiae (Tianma) by UPLC-MS Analysis

Fresh Rhizoma Gastrodiae (Tianma) was processed in a microwave oven at 2450 MHz in order to study the effect on the main chemical component changes taking place during microwave treatment. It was found that microwave affected the chemical composition of Tianma. Seven compounds, including gastrodin, gastrodigenin (p-hydroxybenzylalcohol), p-hydroxybenzaldehyde, vanillyl alcohol, vanillin, adenine, and 5-hydroxymethylfurfural, were identified in this study. As major active compounds, the contents of gastrodin and gastrodigenin in MWT Tianma were both twice as much as those in raw Tianma. Besides, the MS data show that there are still some unidentified compositions in Tianma, and there are also many converted compounds in MWT Tianma, which is worthy of further work. The results have indicated that microwave treated fresh Tianma might be helpful in designing the processing of traditional Chinese medicine and the application of microwave technology in traditional Chinese medicine needs to be researched further in the future.

Wideband and large incident angle wave transparent material based on frequency selective surface with miniaturized elements

Different from the traditional frequency selective surface, the working frequency of a frequency selective surface with miniaturized elements (mFSS) is based on the intrinsic capacitance and inductance of its unit cell, but not the structure resonance. Focusing on the application of mFSS in wave transparent material (WTM), we have designed a band-pass WTM with unit cell of metal patch and wire, analyzed their intrinsic capacitance and inductance, and explored the parameters of the mFSS unit and its equivalent circuit on the performances of WTM. A bandpass WTM sample working at 10 GHz is designed and fabricated. Measurements demonstrate that the sample is wideband, insensitive to the incident angle, and polarization independent; the -1 dB bandwidth is over 40% at normal incidence and up to 20% even at large incident angles 60°. Experimental results are in good agreements with the calculations. The advantages of mFSS based WTM can expand its applications in microwave engineering, especially the radomes.

Enhanced magnetic properties of substituted Sr-hexaferrite nanoparticles synthesized by co-precipitation method

Nanoparticles of Mg–Co–Ti substituted strontium hexaferrite with nominal composition of SrFe12−2x(Mg,Co)x/2TixO19 (x=0–2.5) were synthesized by a co-precipitation method. The structural, magnetic and electromagnetic properties of samples were studied as a function of x by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analysis. It was found that the particle size decreases with an increase in Mg–Co–Ti substitution. The XRD results showed that the crystallite size of nanoparticles lies in the range of 40–45nm. The results of hysteresis loops indicated that for x>0.5, Ms and Hc decrease with an increase in x. Vector network analysis measurements showed that the doped samples had much more effective reflection loss values than those of undoped ferrites. As a result it was found that Mg–Co–Ti doped Sr-hexaferrite can be proposed as suitable absorbers for applications in microwave technology with a good deal of consistently.

The Application of Microwave Technology in Demulsification of Water-in-Oil Emulsion for Missan Oil Fields

A series of batch demulsification runs were carried out to evaluate the final emulsified water content of emulsion samples after the exposure to microwave. An experimental study was conducted to evaluate the effects of a set of operating variables on the demulsification performance. Several microwave irradiation demulsification runs were carried out at different irradiation powers (700, 800, and 900 watt), using water-in-oil emulsion samples containing different water contents (20-80%, 30-70%, and 50-50%) and salt contents (10000, 20000, and 30000 ppm). It was found that the best separation efficiency was obtained at 900watt, 50% water content and 160 s of irradiation time. Experimental results showed that microwave radiation method can enhance the demulsification of water -in- oil emulsions in very short time compared to the conventional methods.

Guest Editorial

Over the past few years a significant growth of research involving the utilization of RF/microwave technologies in healthcare applications has been taking place. This "Special Issue on Biomedical Applications of RF/Microwave Technologies" is proof. Encouraged by funding from government agencies and private sources, and recognizing the emerging opportunities offered by high-frequency electronics and novel sensing technologies for advancing healthcare, researchers from various engineering disciplines have directed their interests to applications involving biological science and clinical medicine. The increase in RF/microwave-related activities targeting medical or biological problems is noticeable within the IEEE Microwave Theory and Techniques Society (IEEE MTT-S) community and beyond. These activities are broad in their scopes and involve multiple disciplines. They range from therapeutic, diagnostic, remote monitoring, and imaging applications of microwave technologies in clinical settings, as well as those involving sensing and communication over or through body tissues, where physiological or biochemical information are transmitted wirelessly, to the biological effects of these applications, in which the interaction of microwaves with tissues and living systems should be understood and manipulated. In addition, RF/microwave now serves as one of the key enabling technologies in innovative healthcare delivery and telemedicine. Three papers are on exposure systems for bioelectromagnetic research. Nine papers present radar-based systems for vital sign monitoring and object imaging. The remaining two radar papers focus on cancer detection by imaging. The Special Issue features papers from the US, UK, Japan, Korea, Australia, Canada, Saudi Arabia, Italy, Malaysia, Belgium, Germany, China, and France, indicating global efforts utilizing RF/microwave innovation for healthcare.

Recent Development of Novel Lead-Free Composite Solders Using Microwave-Assisted Sintering Powder Metallurgy Route

This review paper discusses on the recent lead-free composite solders developed using powder metallurgy (PM) routes. However, the review will focus on the sintering part in the powder metallurgy techniques which the application of microwave technology can be utilized in the development of robust lead-free composite solders. Comprehensive reviews of the published literatures were carried out to understand the requirements and problems in fabricating the lead-free composite solder by using microwave-assisted sintering PM route. This paper describes the improvement of the recent development of lead-free composite solders using microwave-assisted sintering application. It can be summarized that by adding appropriate amounts of a third element as reinforcement in lead-free base matrix system has mostly improved mechanical properties of the monolithic solder. Nevertheless, the review discovered with microwave-assisted sintering, most lead-free bulk samples exhibited a superior microstructural feature which has brought to surprisingly a better mechanical properties in the solder compared to conventionally sintered samples. With microwave-assisted sintering application, the issues related to the implementation of microwave-assisted sintering in lead-free solder development based solder system reinforced with ceramic particulates are also introduced. Furthermore, with the implementation of new hybrid microwave sintering technique which arises from the coalition of conventional and microwave sintering, will yield a staggering advancement in lead-free nanocomposite solder development.

An accurate macro-cell-method for extracting dispersion characteristics of 1D reciprocal microwave structures with finite periodicity

A novel macro-cell-method (MCM) has been proposed, which is capable of accurately extracting the dispersion characteristics of 1D reciprocal microwave structures with finite periodicity. In practice a single macro-cell consists of multiple periodic unit cells, therefore the electromagnetic coupling effects among unit cells can be rigorously considered. The eigen transfer factors ξN and 1/ξN corresponding to the forward and backward Bloch waves can be calculated in terms of the Bloch theory. Imposing complex logarithmic operation to ξN, the attenuation constant α can be univocally determined, while multiple integer branches exist in the solution of the phase shift constant β due to the multiroots property of the complex logarithm function. The rational integer branch is uniquely selected by comparing β from the MCM with that extracted from the unwrapping-method (UPM), regarding β from the UPM as the approximate value. Compared to the conventional eigenmode-method, UPM and single-cell-method, the MCM has no requirements to the coupling intensity among unit cells comprising finitely periodic structures, and with such good generality and accuracy, the MCM can be an effective tool for characterizing 1D reciprocal finitely periodic structures, facilitating their wide applications in microwave engineering.