Microwave Energy Sources Research Articles

СВЧ ЭЛЕКТРОТЕХНОЛОГИЧЕСКАЯ УСТАНОВКА ДЛЯ МИКРОВОЛНОВОЙ ОБРАБОТКИ ПИЛОМАТЕРИАЛОВ И ПОЛИКАПРОАМИДНЫХ НИТЕЙ

Research was carried out to determine the optimal modes for the simultaneous processing of lumber and polycaproamide threads in a hybrid microwave electrotechnological installation. The work was carried out on an installation with a hybrid-type chamber with adjustment of the microwave power level of the magnetrons and the duration of exposure. Two possible designs of a hybrid installation for processing lumber and polycaproamide threads are presented, differing in that in one the lumber was processed inside the chamber, and the polycaproamide threads were pulled through waveguides using bobbins and an electric motor installed outside the chamber, and in the second, both materials were processed inside the installation chamber. The object of research is lumber and polycaproamide threads. Lumber was loaded into the working chamber in the form of a stack, which rotated along its axis, and a structure was examined in which polycaproamide threads were pulled through a waveguide extending from a source of microwave energy outside the chamber. The time of exposure to microwave radiation on lumber and half-caproamide threads was measured using electronic stopwatches; temperature and humidity were measured using a Testo 905T2 thermometer, a Testo 830T1 pyrometer, and a Testo 606-1 digital hygrometer. The use of a hybrid microwave electrotechnological installation reduced the processing time of lumber due to rotation in the microwave field to 15 hours, while ensuring the required quality of the dried material (final moisture content - 7.1%, reduction in chipping and impact bending strength within 5%). The relative breaking elongation of polycaproamide threads increased by 48.2%, and the breaking load – by 27.6%. Thanks to the simultaneous processing of lumber and polycaproamide threads, it is possible to reduce metal consumption and increase the energy efficiency of the installation.

Experimental studies of the plant raw material drying processes in the conditions of infrared and microwave fields

The object of research is the process of drying food plant raw materials. Among the existing methods of drying, convective has become the most common in industry, due to its practicality and ease of organization. However, modern convective drying technologies are accompanied by high-energy consumption, which is a serious problem in the conditions of global energy shortage. An analysis of options for solving drying problems proposed by the scientific community was carried out. The paper presents a solution to the problem through the use of electrodynamic dehydration technologies based on directed energy action. The principle of operation of such technologies is that the electromagnetic field directly interacts with polar molecules, which includes water, which leads to a significant increase in the energy efficiency of the drying process and a reduction in its duration. A set of experimental studies aimed at determining the effect of regime parameters, namely specific power, thickness of the product layer and type of edible vegetable raw materials on the drying process under the conditions of infrared and microwave fields, was carried out. The obtained graphic dependences indicate that the treatment of raw materials with ultra-high frequency radiation significantly reduces the time of the drying process and, as a result, is characterized by a low thermal load on the product, which is a significant advantage when processing heat-labile raw materials. This is due to the deeper penetration of the microwave field (up to 30 mm) compared to infrared (up to 0.003 m). In order to determine the effectiveness of innovative equipment, the paper presents the number of energy action, thanks to which a generalization of the experimental data base was carried out. As a result, criterion equations were obtained, which with an accuracy of ±16 % make it possible to calculate drying devices with infrared and microwave energy sources.

Development and justification of parameters of a microwave convective hop dryer

To solve the problem of low energy efficiency and the absence of small-sized hop dryers, a microwave convective continuous-flow hop dryer has been developed with reasonable parameters that allow preserving the consumer properties of hops. The scientific innovative idea of implementing the technology of drying hops in the working chamber of a microwave hop dryer, made in the form of tiered rotors located between stationary nonferromagnetic bases, forming coaxial resonators in which a traveling wave from microwave generators is excited, is considered. The rotors are made in the form of perforated non-ferromagnetic outer and inner shells, where ceramic perforated partitions are rigidly installed in the annular space, allowing to concentrate radiation energy in raw materials and reduce radiation losses. Having calculated the dimensions of the coaxial resonator, having created its three-dimensional model in the Compass 20 program, we imported it into the CST Microwave Studio program to substantiate the electrodynamic parameters. A hop dryer with a capacity of 5 kW microwave generators with spiral decelerating systems will ensure uniform drying of hops in compliance with electromagnetic safety, with a capacity of 100 kg/h when the rotor is located without microwave energy sources between two coaxial resonators to comply with a process duty cycle of 0.5.

The evolution of microwave-induced thermoacoustic signal characteristics generated during pulsed microwave ablation

Microwave-induced thermoacoustic (TA) signals are of emerging interest for monitoring microwave ablation (MWA) in real-time. TA signals can be generated using an interstitial ablation antenna with a pulsed microwave energy source. When a microsecond microwave pulse is absorbed by tissue, the tissue undergoes a small-scale temperature rise, inducing a thermoelastic expansion that leads to acoustic generation. TA signal characteristics are linked to the dielectric, thermal, and acoustic properties of the local ablation environment. These relevant properties evolve significantly during the ablation process. We conducted a simulation-based study to examine the evolution of microwave-induced TA signal characteristics generated during pulsed microwave ablation. We experimentally validated our multi-physics simulation model for a spatially uniform temperature profile. Then, using the validated simulation model, we investigated TA signals generated in tissue exhibiting spatially nonuniform temperature profiles that arise during MWA. We find that TA signal characteristics are highly influenced by the local environment temperature within the region of initial TA generation and, thus, contain rich information to be exploited for real-time ablation monitoring.

A Review on Space Based Solar Power

Energy conservation is the basic requirement of energy independence. Due to increased global warming, environmental planning becomes important factor for development. Space based solar power technology will help to achieve sustainable goals and for environmental planning by fulfilling requirement of energy. Hence Space Based Solar Power research has become one of prominent research work in the Aerospace domain. In SBSP, solar energy is normally collected by solar collectors or light structures of solar arrays and electronics devices convert it in some other form of energy i.e. microwave or laser for sending it on Earth. Microwave energy source is safer to living beings than other energy resources. Considering this things, the idea of generating solar power from space have attracted many space enthusiastic people for doing new innovations. This paper reviews cost effective technologies for Space Based Solar Power, orbital parameters which will affect on launching cost and efficiency and use of traditional Japan’s design method i.e. Origami for Space Based Solar Power.

Optimization of the plate drying process by electromagnetic radiation using the Green function method

An initial boundary value problem is formulated for calculating the heat-mass-energy fields in a homogeneous wet plate. To solve this problem, an original algorithm containing elements of analytical and numerical methods has been developed. In this method, solutions are written using the spatially one-dimensional Green function of the Neumann problem, which contains eigenvalues and eigenfunctions of the Sturm-Liouville boundary value problem. In comparison with the known numerical algorithms, the problems of the theory of electromagnetic drying for which its application can be effective are indicated. It is shown that the discrete supply of microwave energy significantly reduces the gradients of temperature, steam and moisture content, while reducing energy consumption by 11...12 %. The probability of an undesirable spontaneous temperature increase at the end of the drying cycle is significantly reduced, and the electrical and thermal conditions of the microwave energy source are improved.

An Experimental Study of a Regenerative Secondary Source of Microwave Energy

To create systems for remote metering of electric energy consumption, it is necessary to design new types of active microwave devices based on secondary signal sources that implement control of the electromagnetic field intensity. Current advances in the theory of electronic wave circuits let us to simulate correctly nonlinear and wave processes in circuits. At the same time, to use any components it is necessary to estimate the potential for technical implementation of the required electrical and geometric parameters, combining and embedding possibilities for proposed design solutions in the modern electronic equipment. Therefore, such an engineering approach requires experimental verification for the original calculations obtained analytically. The article presents the results for experimental modeling of a secondary microwave signal source, which allows to study the phenomenon of electrical energy regeneration by a negatron, a bipolar element with negative resistance. The experiments was carried out on the basis of the P2-67 meter, which allows to identify clearly the type of amplitude-frequency characteristics of the verification model in the three-centimeter wave range. The obtained information on its operating in the reflective and pass-through mode substantiate the choice of the active element and the microstrip realization for the resonant tuning system, which simultaneously functioning as a supply circuit. The possibility for constructive synthesis of a test model using a serial 2A706 avalanche-span diode is shown. Such a secondary source provides effective and controlled variation of the intensity of the re-emitted signal by recuperating and amplifying microwave power in practice.

Remotely Controlled Microscale 3D Self‐Assembly Using Microwave Energy

A novel, remotely controlled assembly process is developed to create microscale, self‐assembled 3D structures using remote‐controlled microwave energy. A nanometer thick chromium (Cr) film absorbs electromagnetic microwaves and generates heat energy, which induces reflow of polymeric hinges. This leads to self‐assembly of microscale 3D cubic structures. Since this assembly process does not require direct contact with a heat source or chemicals, microscale actuations can be achieved in a remote location without physical contact, resulting in the powerful capability to manipulate the 3D assembly process in situations where the heat sources and the environment around the microstructures are not controllable and accessible. Multiple folding configurations of the microstructures can also be achieved simultaneously with a single microwave energy source by forming different Cr thicknesses adjacent to the polymer hinges. Thus, remote‐controlled self‐assembly using microwave energy might be applied for the development of 3D microscale‐sensors, ‐microbots, and ‐metamaterials.

Remote monitoring of structural health in composites

AbstractDedicated to Prof. Dr. Eng. Akimitsu Kurita on his 70th birthday, in honour of his scientific achievements, guidance and the education of his students.This paper explores a new interdisciplinary method for internal damage detection and tracking in composite materials using thermo‐chemical sensing. A micro‐sized network of strings is interwoven into the composites. Each string consists of a pair of tubes containing one of two different non‐polar reactants. A local defect within the composites causes straining and cracking of the tube shell, resulting in direct contact between the two non‐polar reactants. The latter undergo a chemical reaction resulting in a polar product. When exposed to a microwave energy source, a polar product heats up dramatically within seconds in comparison to the surrounding composite material or the non‐polar reactants. This localized thermal signature can be rendered visible by an infrared camera.This study summarizes the findings of an in‐depth computational and experimental study of this sensing technology which is expected to be applicable across industries using composites, among them aerospace, automotive, offshore and bridge engineering. Potential applications in steel offshore or steel bridge engineering involve using composite sensing patches to cover fatigue fracture‐critical components. Defects initiating on the steel substrate surface are expected to be sensed on demand with this proposed sensing technology.

Treatment of stand-alone atrial fibrillation with a right thoracoscopic approach employing a microwave or monopolar radiofrequency energy source: long-term results.

Minimally invasive surgery for atrial fibrillation (AF) has rapidly evolved recently. The long-term efficacy of most of these procedures is poorly known. Between 2006 and 2010, 38 drug-resistant, symptomatic patients with stand-alone AF underwent unilateral, thoracoscopic, off-pump ablation. The mean age was 60 ± 8.2 (range 42-75) years and the mean AF duration was 46 ± 62 (range 3-240) months. Sixteen patients (42%) had paroxysmal, 9 (24%) had persistent and 13 (34%) had long-standing persistent AF. A box lesion was created using a microwave (26 patients) or monopolar radiofrequency (12 patients) system. Patients were prospectively followed with repeat electrocardiograms (ECGs) and ECG Holters. Additional catheter ablation was offered to patients with recurrence of arrhythmia. All procedures were completed as planned with one conversion to sternotomy, zero mortality and minimal in-hospital complications. The mean follow-up duration was 70 ± 19 (range 20-88) months. Arrhythmia-free survival rates after the procedure were 50, 44.4, 24.1 and 10.8% at 6, 12, 36 and 60 months, respectively, with most recurrences in the first 6 months. Twelve patients underwent additional catheter ablation(s); from the last intervention, 75% of them were in sinus rhythm (SR) with a mean follow-up of 31 ± 23 (range 4-86) months. Overall, at the end of follow-up, only 3 patients were still in SR without any arrhythmia recurrence. Major complications (cerebral, peripheral embolism or bleeding) occurred in 5 patients. Unilateral, thoracoscopic AF ablation is safe and technically feasible. However, the results of the microwave and monopolar radiofrequency devices were less than satisfactory, with a gradual decline in arrhythmia-free survival over a very long-term follow-up.

Microwave-Assisted Synthesis of β-1,2,3-Triazolyl-α-amino Esters

The reaction of ethyl (p-methoxyphenylimino)acetate with propargyl bromide mediated by activated zinc powder afforded alkynyl amine, which was then reacted with a variety of organic azides using a microwave energy source, leading to β-1,2,3-triazolyl-α-amino esters in good yield.

Clay catalysed rapid valorization of glycerol towards cyclic acetals and ketals

Efficient clay catalyzed protocol for acetalization of glycerol. Utilization of non-conventional microwave and ultra-sonication energy sources. Value addition to the process by synthesizing chemicals of commercial importance.

Evaluation of Heat Absorption in Iron Ore Using Microwave Energy Source

The phosphorus content has significant effect on the steels quality and their applications. The iron ore resources around the world has continuously increased the amount of phosphorous due to the increase of the mining volume with less sterile generation aiming at the efficient utilization of the mining resources, as consequence larger amount of materials with high iron content but with higher phosphorous has been incorporated in the mining body. An alternative to enhance the mining efficiency is to perform a pre treatment of part of the mining body and subsequent blending to attain the acceptable phosphorous in the steelmaking. A viable alternative for reducing the phosphorus content of these residue is to use the acid leaching process which is considered an economical process for the dephosphorization of the iron ore, however, depending on the way the element phosphorus is contained in the ore it will demand additional energy. The objective of the present paper is to study the effective heating and cooling rates of iron ore using microwave energy and its subsequent cooling effect in a short period (thermal shock). Through the X-ray diffraction analysis and applying the Rietveld method it has been possible to demonstrate the mineralogical composition of the iron ore samples and the effect of rapid heating and cooling suitable to promote the fissure formation, thus enhancing the leaching efficiency. The scanning electron microscopy (SEM) was used to analyze the structure of ore due to the effect of its heating and cooling rates.

Study of spicy raw materials vacuum microwave concoction and microwave drying

The paper deals with defining the influence of microwave energy source power and vacuumizing depth on spicy raw materials heating duration, studying the mass and moisture content kinetics in the microwave concoction and microwave drying under vacuumizing conditions. The purpose of the paper is to establish the kinetics of microwave concoction and microwave drying of the mixture of crushed roots of spicy vegetables under vacuumizing conditions and to obtain practical information on rational modes of their implementation. The object of research is microwave concoction and microwave drying processes under vacuumizing conditions. A mixture of crushed roots of spicy vegetables such as parsley, parsnip, celery, dill was used as the subject of research. The microwave mixture concoction was carried out within the moisture content 560...100 %, and microwave drying - 100...10%.It was determined that the final temperature of the product decreases from 93oC to 76oC with the increase in the vacuumizing depth in the working chamber within 80...40 kPa. The duration of its achievement with increasing the heating power from 0.5 kW to 2 kW reduces by 3.9...4.1 times, and with increasing the vacuumizing depth from 80 kPa to 40 kPa - by 21...25 %.In microwave concoction, the change in vacuumizing depth from 80 kPa to 40 kPa affects the moisture removal intensity mainly during periods of warming and constant speed and generally leads to the process duration increase by 13...20 %. In microwave drying, slight difference in the results of changes in weight and moisture content is observed only at the initial stage, but there is almost no difference in achievement duration of the final value of moisture content. Rational values of processes duration at different values of heating power and vacuumizing depth were defined. It is recommended to maintain a residual pressure 40...60 kPa to preserve physicochemical properties of raw materials.

Experimental Investigation of Co-channel and Adjacent Channel Operations of Microwave Power and IEEE 802.11g Data Transmissions

SUMMARY We discuss the division of radio resources in the time and frequency domains for wireless local area network (WLAN) devices powered with microwave energy. In general, there are two ways to avoid microwave power transmission (MPT) from influencing data communications: adjacent channel operation of continuous MPT and WLAN data transmission and co-channel operation of intermittent MPT and WLAN data transmission. Experimental results reveal that, even when we implement these methods, several problems arise because WLAN devices have been developed without supposing the existence of MPT. One problem clarified in our experiment is that adjacent channel operation at 2.4 GHz does not necessarily perform well owing to the interference from MPT. This interference occurs regardless of the frequency separation at 2.4 GHz. The other problem is that intermittent MPT could result in throughput degradation owing to the data rate control algorithm and the association scheme of the WLAN. In addition, the experimental results imply that a microwave energy source and a WLAN device should share information on the timings

Laparoscopic thermal ablation of splenic metastases initial experience and present aspects

Splenic metastases develop in less than 1% of all metastatic cancers, and typically occur in a setting of disseminated disease. When isolated splenic metastasis occurs, the patient may be a candidate for aggressive treatment consisting mainly of splenectomy as described in the literature. However, the increased incidence of post-operative morbidity and severe infection after splenectomy are well known. We report a case of splenic metastasis that developed from colorectal cancer and was treated by laparoscopic-guided radiofrequency ablation. We reviewed the few reported cases of splenic metastasis (from colorectal and other primary cancers) treated by thermal ablation using radiofrequency (RF) or microwave (MW) energy sources. Many studies have proved that thermal ablation for benign splenic pathology is both feasible and safe with no sacrifice in efficacy. However only a few cases of MW or RF treatment of splenic secondary tumor have been described; no complications have been reported with this treatment in contrast to the 15 to 27% morbidity rate for splenectomy. When treatment of splenic metastasis is proposed with curative intent, thermal ablation by RF or by MW seems to be a feasible and safe technique resulting in spleen conservation with a low morbidity rate. Because of these features, thermal ablation seems an ideal treatment modality to obliterate splenic metastasis and may be an indispensable tool in the armamentarium of modern splenic surgery.

EComment. New initiatives to get less invasive approaches for atrial fibrillation back on track

I have read with great interest the article by Starck et al. [1]. It seems to me that this report is an important and constructive tool for futures considerations. According to the Expert Consensus Document on Catheter and Surgical Ablation of Atrial Fibrillation [2], the pool of patients in this article was stratified as Class IIa indication with evidence supporting graded as Level C. In other words, surgical ablation for atrial fibrillation (AF) is reasonable for patients undergoing surgery for other indications. The surgical technique described by Cox et al. [3], termed as Cox-maze III procedure, when properly performed in a standard “cut-and-sew” fashion, cures AF in nearly 100% of the patients with or without concomitant disease [4]. However, this is an open procedure performed on a non-beating heart during cardiopulmonary bypass. In addition, despite the high success rate for curing AF, long aortic clamp times have always been the hallmark in this procedure. Simplification of the maze procedure has evolved with the use of different ablation tools such as microwave, cryotherapy, ultrasound, and radiofrequency energy sources to create the atrial lesions instead of employing the incisional technique used in the classic maze procedure. So the original Cox's concept is moving forward, but the procedure as a whole is respected only in appearance. These newer streamlined surgical approaches forget or do not consider the exclusion of the left atrial appendage (LAA) as an integral part of implementation in a global procedure. Indeed, all these less invasive approaches are almost exclusively focused in the pulmonary veins isolation when paroxysmal AF is treated. The high success rate of the Cox-maze III procedure lies not only in curing the AF, but also removing the LAA. As the authors in this article here have emphazised, the primary reason for occluding the LAA is to reduce the stroke risk arising from this anatomical structure. We need new initiatives to get the development of new technological approaches for AF back on track, and I feel that, beyond the elimination of a source of AF triggers, this report opens the way for new and more comprehensive proposals for AF treatment. If the LAA occlusion can be achieved by means of a thoracoscopic approach, as demonstrated by Benussi et al. [5], the central idea discussed here is that LAA occlusion must be understood as complementary to existing minimally invasive current approaches in the treatment of AF. Conflict of interest: none declared.

A novel combined manufacturing technique for rapid production of IRMOF-1 using ultrasound and microwave energies

The metal organic framework IRMOF-1 was successfully synthesized by applying a combination of ultrasonic (UTS) and microwave (MW) energy sources for rapid synthesis under various operating conditions including: sonication time and temperature as well as microwave irradiation time. Moreover sample activation was employed to improve surface area of the synthesized IRMOF-1. While the highest Langmuir surface area of the as-synthesized samples was 1315 m 2/g sample, surface area of the activated sample was 2473 m 2/g. The reaction products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), solid-state Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and BET.

Microwave plasma- enhanced chemical vapour deposition growth of carbon nanostructures

The effect of various input parameters on the production of carbon nanostructures using a simple microwave plasma-enhanced chemical vapour deposition technique has been investigated. The technique utilises a conventional microwave oven as the microwave energy source. The developed apparatus is inexpensive and easy to install and is suitable for use as a carbon nanostructure source for potential laboratory-based research of the bulk properties of carbon nanostructures. A result of this investigation is the reproducibility of specific nanostructures with the variation of input parameters, such as carbon-containing precursor and support gas flow rate. It was shown that the yield and quality of the carbon products is directly controlled by input parameters. Transmission electron microscopy and scanning electron microscopy were used to analyse the carbon products; these were found to be amorphous, nanotubes and onion-like nanostructures.

Epicardial High-intensity Focused Ultrasound Cardiac Ablation for Surgical Treatment of Atrial Fibrillation

The available alternatives to an effective but technically complex Cox maze procedure for surgical treatment of atrial fibrillation include ablation using radiofrequency, microwave, laser, cryotherapy or ultrasound energy sources. The purpose of this study was to evaluate the safety and efficacy profile of high-intensity focused ultrasound cardiac ablation for the surgical treatment of atrial fibrillation. 14 patients underwent epicardial high-intensity focused ultrasound treatment for atrial fibrillation using the Epicor cardiac ablation system between August 2006 and August 2007. The procedure was performed on the beating heart prior to the commencement of cardiopulmonary bypass for concomitant cardiac procedures. Physical examination, electrocardiography and 24-h Holter monitoring were used to determine the postoperative heart rhythm. There were no deaths directly related to the procedure. One patient with myelodysplastic syndrome died of septic complications. Three patients required cardioversion at 1 day, 3- and 4-month intervals postoperatively. The mean follow-up period was 9 months. Currently 10/13 (77%) patients are in sinus rhythm, one patient required insertion of a permanent pacemaker, one patient is in atrial fibrillation and another patient is in atrial flutter. Epicardial high-intensity focused ultrasound ablation is a viable alternative to the Cox maze procedure for the surgical treatment of atrial fibrillation. It is a safe and efficient procedure that does not require cardiopulmonary bypass and may potentially be performed using less invasive surgical techniques.