Microwave Techniques Research Articles

Advanced Dielectric Anomaly Detection for Non-Destructive Fruit Inspection Using Electromagnetic Microwave Technique

This paper presents a comprehensive investigation into the application of an electromagnetic microwave technique combined with the dielectric anomaly approach algorithm for the non-destructive inspection of fruits. The proposed antenna configuration comprises eight elements arranged in a circular array, enabling the collection of signals scattered by objects, specifically fruits, placed in their path. The collected data undergoes a series of processing steps, including Fast Fourier Transform, covariance matrix estimation, eigenvalue and eigenvector computation, and spatial spectrum construction. The dielectric anomaly algorithm is then applied to detect defects in the fruits. The study covers five different types of fruits, both healthy and defective, and gathers essential dielectric properties. Furthermore, a novel hybrid IQR method is introduced for outlier detection in the dielectric data. The results demonstrate the effectiveness of the proposed methodology in providing valuable insights into the internal structures of fruits and detecting anomalies, contributing to the enhancement of quality assessment in fruit inspection processes.

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques Information for Authors

IEEE Transactions on Microwave Theory and Techniques Information for Authors

Ultrasound and microwave techniques for assisting ageing on lees of red wines.

Ageing on lees is a slow process that carries microbiological and economic risks in the wineries. This study evaluates the possibility of enhancing the extraction of different compounds from the lees, using combined strategies, such as ultrasound (US) or microwaves (MW) and the addition of inactive dry yeasts (IDY), to reduce the lees ageing time. The complete chemical analysis of the wine was done, amino acids, polysaccharides, colour and volatile compounds, together with the sensory analysis. The combined treatments increased the release of total polysaccharides, mannoproteins and total monosaccharides in the wines, and some amino acids like proline. However, wines treated with US and MW, with and without lees, showed a decrease in tannins and colour intensity, and in some volatile compounds like fatty acid esters, acetates and terpenes. The wines treated with IDY and MW were the best valued for their floral and red berry flavours and less astringency.

Synthesis and performance analysis of zeolitic imidazolate frameworks for CO2 sensing applications

In this paper, we investigate the potential use of Zeolitic Imidazolate Frameworks (ZIF-8) as a sensing material for CO2 detection. Three synthesis techniques are considered for the preparation of ZIF-8, namely room temperature, microwave-assisted, and ball milling. The latter is a green and facile alternative for synthesis with its solvent-free, room-temperature operation. In addition, ball milling produces ZIF-8 samples with superior CO2 adsorption and detection characteristics, as concluded from fluorescence measurements. Characterization tests including X-ray diffraction (XRD), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDS) are conducted to inspect the structural morphology, the thermal stability, and elements content of the ZIF-8 samples obtained from the different aforementioned synthesis techniques. The characterization tests revealed the appearance of a new phase of ZIF-8 which is ZIF-L when deploying the ball milling technique with different structure, morphology, response to CO2 exposure and thermal stability when compared to its counterparts. Fluorescence measurements are carried out to evaluate the limit of detection (LOD), selectivity, and recyclability of the different ZIF-8 samples. The LOD of the ZIF-8 sample synthesized based on ball milling synthesis technique is 815.2 ppm, while LODs of the samples obtained from microwave and room temperature-based synthesis techniques are 1780.6 ppm and 723.8 ppm, respectively. This indicates that the room temperature and ball milling produced MOFs have comparable LODs. However, the room temperature procedure requires the use of a harmful solvent. The range of LOD demonstrates the suitable use of ZIF-8 for indoor air quality monitoring and other industrial applications.

Unveiling the electron configuration‐dependent oxygen evolution activity of 2D porous Sr‐substituted LaFeO3 perovskite through microwave shock

AbstractDeveloping an efficient and stable oxygen evolution reaction (OER) catalyst is beneficial in various energy conversion and storage applications for achieving the “Carbon Neutrality” goal. Among the iron‐based perovskite oxides (AFeO3), LaFeO3 stands out as a preferred catalyst for electrocatalytic OER due to its exceptional selectivity in oxygen bonding at the A‐site. The introduction of A‐site substitution and controlled morphological engineering in perovskite structures has proven effective in enhancing the electrical conductivity and intrinsic catalytic activity. Nevertheless, the conventional A‐site substitution approach often involves prolonged high‐temperature calcination, leading to the agglomeration of nanostructures, particularly in two‐dimensional (2D) porous configurations. Herein, we introduce a novel method for synthesizing 2D porous LaFeO3 perovskite with A‐site Sr substitution using microwave shock. This microwave technique capitalizes on the benefits of transient heating and cooling, enabling simultaneous construction of 2D porous morphology and precise regulation of Sr substitution in one step. By conducting theoretical simulations of the electron configuration and analysis of crystal structure, we unveil the impact of Sr substitution on the OER activity of 2D porous LaFeO3. The synthesized La0.2Sr0.8FeO3 (LSFO‐8) catalyst exhibits an exceptional overpotential of 339 mV at 10 mA cm−2 and a small Tafel slope of 56.84 mV dec−1 in alkaline electrolyte. This investigation provides a fresh perspective for the design and engineering of electronic configuration in highly active 2D perovskite materials.

Microwaves See Thin Ice: A Review of Ice and Snow Sensing Using Microwave Techniques

Microwaves See Thin Ice: A Review of Ice and Snow Sensing Using Microwave Techniques

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques Information for Authors

IEEE Transactions on Microwave Theory and Techniques Information for Authors

Comparison of microwave moisture evaluation quality in time and frequency domain

The article presents the comparison of two methods of microwave data analysis for evaluation of moisture content in porous materials. The content of the paper covers the short description of microwave technique for moisture evaluation and the description of the two methods of microwave data analysis – the time domain and frequency domain. In the second part, the dependences between red brick moisture and apparent permittivity are presented. Apparent permittivity values are determined by microwave antenna and calculated in time and frequency domain. With the calculated values, regression models were estimated and quality of both evaluated. Using the analyzed data, the advantages and disadvantages of both techniques were defined and the measuring potential evaluated.

Microwave Photonic Filters and Applications

Microwave photonics is a promising and rapidly developing interdisciplinary field. It combines microwave and photonic techniques to generate, transmit, process, and manipulate microwave signals by using the advantages of broadband, high frequency, and low loss provided by photonics. As an important branch of microwave photonics, the microwave photonic filter (MPF) can overcome the limitations set by traditional electronic technology and can realize advanced signal processing in modern communication systems due to its higher performance, selectivity, and flexibility. This review provides a comprehensive overview of MPFs, including fundamental principles, typical structures, and key applications. Additionally, the microwave photonic integration is a very important tendence because of its advantages of small size, light weight, low power consumption, and low cost. The recent advances in integrated MPF are also reviewed.

New imidazole-2-ones and their 2-thione analogues as anticancer agents and CAIX inhibitors: Synthesis, in silico ADME and molecular modeling studies

The present study involves the synthesis of a series of new imidazole-2-ones derivatives and their 2-thione analogs using conventional heating and the environmentally friendly benign technique, the microwave technique. Structure of the compounds was well elucidated by considering the data of both elemental and spectral analyses. The obtained data and theoretical values of the synthesized molecules correlated with the proposed molecular structure. Moreover, all the synthesized compounds were evaluated in vitro for antitumor activity against HCT-116 and HeP2 human cancer cell panels and assessed as selective carbonic anhydrase IX isozyme (CA9/CAIX) inhibitors, thereby providing useful preliminary evidence for drug development. In addition, computational techniques were used to investigate the molecular and electronic characteristics of the investigated organic compounds. The 4b compound exhibited the best quantum chemistry features, as the highest occupied molecular orbital, softness, energy gap, and dipole moment, indicating the highest biological activity. This was supported by the experimental findings. Moreover, the in silico evaluation of drug candidates was also investigated. Thereafter, the anticancer activity of the most reactive candidate was studied via molecular docking to determine the types of interactions between this molecule and CAIX. According to the docking experiments, the 4b molecule generates five hydrogen bond interactions with active amino acid residues, Gln 92, Gln 67, and Thr 200.

Endoscopic Ultrasound-Guided Locoregional Treatments for Solid Pancreatic Neoplasms.

Solid pancreatic neoplasms are one of the most diagnosed gastrointestinal malignancies thanks to the current and progressive advances in radiologic methods. Endoscopic ultrasound-guided techniques have over time gained a prominent role in the differential diagnosis and characterization of these pancreatic lesions, including pancreatic cancer, neuroendocrine tumors, and metastases. Recently, several endoscopic ultrasound-guided locoregional treatment techniques, which are divided into thermal ablative techniques and non-thermal injection techniques, have been developed and applied in different settings for the treatment of solid pancreatic neoplasms. The most common ablative techniques are radiofrequency, microwave, laser, photodynamic therapy and hybrid techniques such as hybrid cryothermal ablation. The most common injection techniques are ethanol injection, immunotherapy and brachytherapy. In this review, we update evidence about the efficacy and safety of endoscopic ultrasound-guided locoregional treatments for solid pancreatic neoplasms.

Synthesis, spectroscopic, DFT calculations, biological activity, SAR, and molecular docking studies of novel bioactive pyridine derivatives

Enaminonitrile pyridine derivative was used as a precursor for preparation of fourteen heterocyclic compounds using both conventional thermal and microwave techniques. Diverse organic reagents, such as chloroacetyl chloride, acetic anhydride, chloroacetic acid, carbon disulfide, p-toluene sulfonyl chloride, maleic anhydride, phthalic anhydride, were used. The chemical formulae and structures of isolated derivatives were obtained using different analytical and spectroscopic techniques such as IR, 1H-, 13C-NMR as well as mass spectrometry. The spectroscopic analyses revealed diverse structure arrangements for the products. Molecular structure optimization of certain compounds were performed by the density functional theory (DFT/B3LYP) method and the basis set 6–31 G with double zeta plus polarization (d,p). The antimicrobial inhibition and the antioxidant activity of the reported compounds were screened. Compounds 5, 6, 11 and 13 exhibited the highest antibacterial inhibition, while compound 8 gave the highest scavenging activity (IC50 43.39 µg/ml) against the DPPH radical. Structure–activity relationship of the reported compounds were correlated with the data of antibacterial and the antioxidant activity. The global reactivity descriptors were also correlated with the biological properties of compounds. The molecular docking studies of reported compounds were investigated, and the analysis showed that the docked compounds have highly negative values for the functional binding scores. The binding interaction was found to be correlated with the substituent fragments of the compounds.

Structural and optical properties of micro-diamonds with SiV− color centers

Isolated, micro-metre sized diamonds are grown by micro-wave plasma chemical vapour deposition technique on Si(001) substrates. Each diamond is uniquely identified by markers milled in the Si substrate by Ga+ focused ion beam. The morphology and micro-grain structure analysis, indicates that the diamonds are icosahedral or bi-crystals. Icosahedral diamonds have higher (up to = 2.3 GPa), and wider distribution ( = 4.47 GPa) of hydrostatic stress built up at the micro-crystal grain boundaries, compared to the other crystals. The number and spectral shape of SiV− colour centres incorporated in the micro-diamonds (MDs) is analysed, and estimated by means of temperature dependent photoluminescence measurements, and Monte Carlo simulations. The Monte Carlo simulations indicates that the number of SiV− colour centres is a few thousand per MD.

Enhancing the Extraction Process Efficiency of Thyme Essential Oil by Combined Ultrasound and Microwave Techniques

In this paper, the essential oil (EO) extraction from thyme by the consecutive use of ultrasound and microwave treatments is presented. The aim of this study was to apply an ultrasound pre-treatment of thyme leaves to enhance the thymol content and the extraction yield of the EO obtained by microwave-assisted hydro-distillation (MWHD). Compared with conventional hydro-distillation (CHD), the consecutive use of ultrasound pre-treatment and microwave extraction resulted in a 72% lower extraction time. When the ultrasound pre-treatment (using the ultrasonic processor with an amplitude of 70%) was applied, the EO content was 23% higher compared to the extraction without pre-treatment (2.67 ± 0.06 g EO/100 g DM for the MWHD with ultrasound pre-treatment compared with 2.18 ± 0.07 g EO/100 g DM for the MWHD without pre-treatment). The EO samples were analyzed by GC/MS. The results showed that the major component, thymol, varied from 43.54% (by CHD) to 65.94% (by the consecutive use of ultrasound and microwave treatments).

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques publication information

IEEE Transactions on Microwave Theory and Techniques Information for Authors

IEEE Transactions on Microwave Theory and Techniques Information for Authors

Metamaterial-Based Sensors Loaded Corona-Shaped Resonator for COVID-19 Detection by Using Microwave Techniques

Metamaterial-Based Sensors Loaded Corona-Shaped Resonator for COVID-19 Detection by Using Microwave Techniques

Design, synthesis, in vitro anticancer, molecular docking and SAR studies of new series of pyrrolo[2,3-d]pyrimidine derivatives

The current study involves the design and synthesis of a newly synthesized pyrrolo[2,3-d]pyrimidine derivatives to contain chlorine atoms in positions 4 and 6 and trichloromethyl group in position 2 using microwave technique as a new and robust approach for preparation of this type of pyrrolo[2,3-d]pyrimidine derivatives. The chemical structure of the synthesized pyrrolo[2,3-d]pyrimidine derivatives 3–19 was well-characterized using spectral and elemental analyses as well as single-crystal X-ray diffraction. All compounds were tested in vitro against seven selected human cancer cell lines, namely, MCF7, A549, HCT116, PC3, HePG2, PACA2 and BJ1 using MTT assay. It was found that compounds 14a, 16b and 18b were the most active toward MCF7 with IC50 (1.7, 5.7, and 3.4 μg/ml, respectively) relative to doxorubicin (Dox.) (26.1 μg/ml). Additionally, compound 17 exerted promising cytotoxic effects against HePG2 and PACA2 with IC50 (8.7 and 6.4 μg/ml, respectively) relative to Dox. (21.6 and 28.3 μg/ml, respectively). The molecular docking study confirmed our ELISA result which showed the promising binding affinities of compounds 14a and 17 against Bcl2 anti-apoptotic protein. At the gene expression level, P53, BAX, DR4 and DR5 were up-regulated, while Bcl2, Il-8, and CDK4 were down-regulated in 14a, 14b and 18b treated MCF7 cells. At the protein level, compound 14b increased the activity of Caspase 8 and BAX (18.263 and 14.25 pg/ml) relative to Dox. (3.99 and 4.92 pg/ml, respectively), while the activity of Bcl2 was greatly decreased in 14a treated MCF7 (2.4 pg/ml) compared with Dox. (14.37 pg/ml). Compounds 14a and 14b caused cell cycle arrest at the G1/S phase in MCF7. Compounds 16b and 18b induced the apoptotic death of MCF7 cells. In addition, the percentage of fragmented DNA was increased significantly in 14a treated MCF7 cells.