Search Results (571)

Breast cancer detection through non-invasive and accurate techniques remains a critical challenge in medical diagnostics. This study introduces a deep learning-based framework that leverages a microwave radar system equipped with an arc-shaped array of six antennas to estimate key tumor parameters, including position, size, and depth. This research begins with the evolutionary design of an ultra-wideband octagram ring patch antenna optimized for enhanced tumor detection sensitivity in directional near-field coupling scenarios. The antenna is fabricated and experimentally evaluated, with its performance validated through S-parameter measurements, far-field radiation characterization, and efficiency analysis to ensure effective signal propagation and interaction with breast tissue. Specific Absorption Rate (SAR) distributions within breast tissues are comprehensively assessed, and power adjustment strategies are implemented to comply with electromagnetic exposure safety limits. The dataset for the deep learning model comprises simulated self and mutual S-parameters capturing tumor-induced variations over a broad frequency spectrum. A core innovation of this work is the development of the Attention-Based Feature Separation (ABFS) model, which dynamically identifies optimal frequency sub-bands and disentangles discriminative features tailored to each tumor parameter. A multi-branch neural network processes these features to achieve precise tumor localization and size estimation. Compared to conventional attention mechanisms, the proposed ABFS architecture demonstrates superior prediction accuracy and interpretability. The proposed approach achieves high estimation accuracy and computational efficiency in simulation studies, underscoring the promise of integrating deep learning with conformal microwave imaging for safe, effective, and non-invasive breast cancer detection. Full article

Knowledge about the composition (volatile and non-volatile) and functionality of natural extracts from Mediterranean plants serves as a basis for their further application. In this study, five selected plants were used for the extraction of plant metabolites. Leaves and flowers of Critmum maritimum, Rosmarinus officinalis, Olea europea, Phylliera latifolia and Mellisa officinalis were collected, and a total of 12 extracts were prepared. Extractions were performed under microwave-assisted conditions, with two solvent types: water (W) and a hydroalcoholic (ethanolic) solution (HA). Detailed extract analysis was conducted. Phenolics were analyzed by detecting individual bioactive compounds using high-performance liquid chromatography and by calculating total phenolic and total flavonoid content through spectrophotometric analysis. Higher concentrations of total phenolics and total flavonoids were obtained in the hydroalcoholic extracts, with the significantly highest total phenolic and flavonoid values in the rosemary hydroalcoholic extract (3321.21 mg_GAE/L) and sea fennel flower extract (1794.63 mg_QE/L), respectively; and the lowest phenolics in the water extract of olive leaves (204.55 mg_GAE/L) and flavonoids in the water extracts of sea fennel leaves, rosemary, olive and mock privet (around 100 mg_QE/L). Volatile organic compounds (VOC) were detected using HS-SPME/GC–MS (Headspace Solid-Phase Microextraction coupled with Gas Chromatography-Mass Spectrometry), and antioxidant capacity was estimated using DPPH (2,2-diphenyl-1-picrylhydrazyl assay) and FRAP (Ferric Reducing Antioxidant Power) methods. HS-SPME/GC–MS analysis of samples revealed that sea fennel had more versatile profile, with the presence of 66 and 36 VOCs in W and HA sea fennel leaf extracts, 52 and 25 in W and HA sea fennel flower extracts, 57 in rosemary W and 40 in HA, 20 in olive leaf W and 9 in HA, 27 in W mock privet and 11 in HA, and 35 in lemon balm W and 10 in HA extract. The lowest values of chlorophyll a were observed in sea fennel leaves (2.52 mg/L) and rosemary (2.21 mg/L), and chlorophyll b was lowest in sea fennel leaf and flower (2.47 and 2.25 mg/L, respectively), while the highest was determined in olive (6.62 mg/L). Highest values for antioxidant activity, determined via the FRAP method, were obtained in the HA plant extracts (up to 11,216 mg_AAE/L for lemon balm), excluding the sea fennel leaf (2758 mg_AAE/L) and rosemary (2616 mg_AAE/L). Considering the application of these plants for fresh fish preservation, antimicrobial activity of water extracts was assessed against Vibrio fischeri JCM 18803, Vibrio alginolyticus 3050, Aeromonas hydrophila JCM 1027, Moraxella lacunata JCM 20914 and Yersinia ruckeri JCM 15110. No activity was observed against Y. ruckeri and P. aeruginosa, while the sea fennel leaf showed inhibition against V. fisheri (inhibition zone of 24 mm); sea fennel flower was active against M. lacunata (inhibition zone of 14.5 mm) and A. hydrophila (inhibition zone of 20 mm); and rosemary and lemon balm showed inhibition only against V. fisheri (inhibition zone from 18 to 30 mm). This study supports the preparation of natural extracts from Mediterranean plants using green technology, resulting in extracts rich in polyphenolics with strong antioxidant potential, but with no clear significant antimicrobial efficiency at the tested concentrations. Full article

Catalysts are ubiquitous in manufacturing industries and gas phase pollutant abatement but are not widely used in wastewater treatment, as high temperatures and concentrated waste streams are needed to achieve the reaction degradation rates required. Heating water is energy intensive, and alternative, low temperature solutions have been investigated, collectively known as advanced oxidation processes. However, many of these advanced oxidation processes use expensive oxidants such as perchlorate, hydroxy radicals or ozone to react with contaminants, and therefore have high running costs. This study has investigated microwave catalysis as a low-energy, low-cost technology for water treatment using NiO catalysts that can be heated in the microwave field to drive the decomposition of azo-dye contaminants. Using this methodology for the microwave-assisted degradation of two azo dyes (azorubine and methyl orange), conversions of >95% were achieved in only 10 s with 100 W microwave power. Full article

A novel and cost-effective methodology is introduced for the precise prediction of the melting time of metals and alloys in a 700 W domestic microwave oven, using a hybrid SiC–graphite susceptor to ensure efficient heating without direct interaction with microwaves. The study includes experimental trials with multiple alloys (Sn–Bi, Zn, Zamak, and Al–Si, among others) and variable masses, whose results made it possible to construct a dimensionless model, trained with XGBoost on easily measurable thermophysical properties (specific heat, density, thermal conductivity, mass, and melting temperature). The model achieves high accuracy, with a relative error below 5%, and metrics of MAE = 4.8 s, RMSE = 6.1 s, and R² = 0.9996. The generalization of the model to different microwave powers (600–1100 W) is also validated through analytical adjustment, without the need for additional experiments. The proposal is implemented as a Python application with a graphical interface, suitable for any academic or teaching laboratory, and its performance is compared with classical models. This approach effectively contributes to the democratization of thermal testing of metals in educational and research settings with limited resources, providing thermodynamic rigor and advanced artificial intelligence tools. Full article

The ability to perform instantaneous frequency measurement (IFM) of unknown microwave signals holds significant importance across various application domains. This paper presents a power-independent microwave photonic IFM system. The proposed system implements frequency measurement through the construction of an amplitude comparison function (ACF) curve, achieved by introducing a frequency-dependent time delay via an optical tunable delay line (OTDL) for the signal under test (SUT). System simulation demonstrates the measurement capability across a wide bandwidth of 0.1–40 GHz with high precision, exhibiting frequency errors ranging from −0.03 to 0.04 GHz. The scheme also maintains consistent performance under varying input power levels. Key implementation aspects, including single-sideband modulation selection and system extension methods, are analyzed in detail to optimize measurement accuracy. Notably, the proposed architecture features a simple and compact design with excellent integration potential. These characteristics, combined with its wide operational bandwidth and high measurement precision, make this approach particularly suitable for demanding applications in electronic reconnaissance and communication. Full article

This paper presents the development and analysis of a planar microfluidic microwave sensor featuring three circular complementary split-ring resonators (CSRRs) fabricated on an RO3035 substrate. The sensor demonstrates enhanced sensitivity in characterizing liquids contained in a fine glass capillary tube by leveraging a novel configuration: a central 5-split-ring CSRR with a drilled hole to suspend the capillary, flanked by two 2-split-ring CSRRs to improve the band-stop filtering effect. The sensor’s performance is benchmarked against another CSRR-based microwave sensor with a similar configuration. High linearity is observed (R² > 0.99), confirming its capability for precise ethanol concentration prediction. Compared to the replicated square CSRR design from the literature, the proposed sensor achieves a 35.22% improvement in sensitivity, with a frequency shift sensitivity of 567.41 kHz/% ethanol concentration versus 419.62 kHz/% for the reference sensor. The enhanced sensitivity is attributed to several key design strategies: increasing the intrinsic capacitance by enlarging the effective area and radial slot width to amplify edge capacitive effects, adding more split rings to intensify the resonance dip, placing additional CSRRs to improve energy extraction at resonance, and adopting circular CSRRs for superior electric field confinement. Additionally, the proposed design operates at a lower resonant frequency (2.234 GHz), which not only reduces dielectric and radiation losses but also enables the use of more cost-effective and power-efficient RF components. This advantage makes the sensor highly suitable for integration into portable and standalone sensing platforms. Full article

This study employed high-pressure ultrasonic-microwave-assisted extraction (HP-UMAE) to extract gingerols from ginger. The extraction yield and total polyphenol content of the extracts were determined. Their antioxidant activity was assessed by DPPH and ABTS radical scavenging assays, and compared with extracts obtained by leaching extraction, reflux extraction, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and ultrasonic-microwave-assisted extraction (UMAE). The results demonstrated that HP-UMAE achieved the highest extraction yield and the strongest ABTS radical scavenging activity among the evaluated methods. Furthermore, HP-UMAE extracts exhibited the highest concentrations of key gingerol constituents: 6-gingerol (14.29 mg/L), 8-gingerol (0.38 mg/L), 10-gingerol (1.95 mg/L), and 6-shogaol (4.32 mg/L). This enhanced efficacy is attributed to the synergistic combination of ultrasonic cavitation and microwave-induced thermal effects under elevated pressure. This synergy creates conditions promoting cellular wall disruption, facilitating the release of intracellular components, while concurrently enhancing solvent penetration and gingerol solubility. Scanning electron microscopy (SEM) analysis confirmed the significant structural damage inflicted on ginger cell walls following HP-UMAE treatment. The process parameters for HP-UMAE were optimized using single-factor experiments. The optimal extraction conditions were determined as follows: microwave power 800 W, ultrasonic power 1000 W, liquid-to-solid ratio 55:1, and temperature 100 °C (corresponding pressure 2 MPa). Under these optimized parameters, the extraction yield and ABTS radical scavenging rate reached their peak performance, yielding values of 4.52% and 43.23%, respectively. Full article

As solid-state devices continue to advance, vacuum electron devices maintain critical importance due to their superior high-frequency power handling, long-term reliability, and operational efficiency. Among these, traveling-wave tubes (TWTs) excel in high-power microwave (HPM) applications, offering exceptional bandwidth and gain. However, developing THz-range TWT slow-wave structures (SWSs) presents significant design challenges. This work systematically outlines the SWS design methodology while addressing key obstacles and their solutions. As a demonstration, a staggered double vane (SDV) SWS operating at 1 THz (980–1080 GHz) achieves 650 mW output power, 23.35 dB gain, 0.14% electronic efficiency, and compact 21 mm length. Comparative analysis with deformed quasi-sine waveguide (D-QSWG) SWS confirms the SDV design’s superior performance for THz applications. Full article

This work presents the characterization of a large-scale pilot plant for nitric acid production that employs atmospheric-pressure plasma in a closed-loop configuration. The primary objective here is to evaluate the scientific and practical feasibility of using high-power Cerawave™ plasma torch technology, manufactured by Radom Corporation, to enhance the rate of nitric acid production of plasma-assisted nitrogen fixation systems, while achieving specific energy consumption (SEC) comparable to that of smaller-scale setups reported in the literature. We provide a comprehensive overview of the components of the pilot plant, its operational strategy, and the analytical models underlying its processes. Preliminary system optimization results are discussed alongside the outcomes from a controlled batch run. After 30.9 h of operation at 50 kW plasma power, the system produced 198.9 L of nitric acid with a concentration of 28.6% by weight, corresponding to overall SEC of approximately 5.3 MJ/mol. This SEC could be improved to 3.7 MJ/mol using absorption columns with greater than 90% absorption efficiency. Additionally, around 60% of the plasma power was recovered as usable process heat via a heat exchanger. These results demonstrate that plasma-based nitrogen fixation is scientifically and technically viable at higher production scales while maintaining competitive specific energy consumption using microwave plasma. Full article

In industrial production, high-power microwaves are commonly used for heating and drying processes; however, their application in measurement is relatively limited. This paper presents a power measurement system to enhance the use of microwave measurements in industry and improve the efficiency of microwave drying for PET particles. Operating at 2.45 GHz, the system integrates four-port power measurements based on the multilayer perceptron (MLP). By introducing residual connectivity, the residual network is determined to detect the height of PET particles. Experimental results show that this system can perform rapid measurements without needing a vector network analyzer (VNA), significantly improving the efficiency of microwave energy utilization in the early drying stages. Furthermore, the system offers practical and cost-efficient predictions for low-loss particulate materials. This power measurement strategy holds promising application potential in future industrial production. Full article

Cannabis sativa L. is known for its high-value compounds, like Cannabidiol (CBD) and Cannabidiolic Acid (CBDA). It is widely used in the pharmaceutical and food industries. Different extraction methods, like Soxhlet and maceration, are commonly employed to obtain its extracts. High temperature and long extraction time can influence the yield and the purity of the extracts, affecting the quality of the final product. This study focused on optimizing CBD oil extraction from hemp inflorescences and its incorporation into a gluten-free bakery product for functionalization. Dynamic maceration (DME), assisted by ultrasound and microwave irradiation, was used. Our study explored the impact of varying sonication times (three distinct durations) and microwave powers (three levels, applied for two different irradiation times) on the resulting extracts. HPLC analysis was performed on these extracts. Subsequently, we used hemp flour and hemp oil to bake gluten-free cupcakes, which were fortified with the extracted CBD oil. Rheological characterization was used to investigate the cupcake properties, along with stereoscopic, color and puncture analysis performed on the baked samples. The most effective extraction parameters identified were 30 s of microwave irradiation at 700 W, yielding 45.2 ± 2.0 g of CBD extract, and 15 min of sonication, which resulted in 53.2 ± 2.5 g. Subsequent rheological characterization indicated that the product exhibited mechanical properties and a temperature profile comparable to a benchmark, evidenced by a height of 4.1 ± 0.2 cm and a hardness of 1.9 ± 0.2 N. These promising values demonstrate that hemp oil and hemp flour are viable ingredients for traditional cakes and desserts, notably contributing increased nutritional value through the CBD-enriched hemp oil and the beneficial profile of hemp flour. Full article

The aim of this study was to evaluate the impact of microwave treatment on the physical properties and bioactive compound content of acorn flour and its subsequent effects on the quality of muffins. Acorn flour, both dry and hydrated (flour-to-water mixture = 1:1, w/v), was subjected to microwave processing at varying power levels (925, 1295, and 1850 W) and exposure times (0.5, 1.0, 1.5, 2.0, and 3.0 min). The treated flour was incorporated into composite wheat–acorn muffins, which were analyzed for key physical attributes, including volume, porosity, crumb firmness, and color. In addition, the chemical composition of the muffins was assessed, with a particular focus on antioxidant activity and the content of bioactive compounds such as total free phenolics, flavonoids, and tannins. The results indicated that microwave treatment significantly influenced the antioxidant potential and technological properties of acorn flour-based muffins. Microwave treatment at 925 W for 3 min or 1295 W for 1.5 min under moist conditions resulted in muffins with enhanced antioxidant capacity (e.g., an increase in total free phenolics by up to 61.4% and flavonoids by up to 135.9%, and a reduction in tannin content by up to 38.2%), as well as improved volume and sensory acceptance. However, high-power treatment (1850 W) negatively affected muffin volume, porosity, and firmness. These findings emphasize the effectiveness of controlled microwave processing in improving both the nutritional and technological qualities of bakery products enriched with acorn flour. Full article

This paper presents KlyH, a new 1D (one-dimensional) large-signal simulation software for klystrons, designed to deliver efficient and accurate simulation and optimization tools. KlyH integrates a Fortran-based dynamic link library (DLL) as its computational core, which employs high-performance numerical algorithms to rapidly compute critical parameters such as efficiency, gain, and bandwidth. Compared with traditional 1D simulation tools, which often lack open interfaces and extensibility, KlyH is built with a modular and open architecture that supports seamless integration with advanced optimization and intelligent design algorithms. KlyH incorporates multi-objective optimization frameworks, notably the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) and Optimized Multi-Objective Particle Swarm Optimization (OMOPSO), enabling automated parameter tuning for efficiency maximization and interaction length optimization. Its bandwidth-of-klystron-analysis module predicts gain and output power across operational bandwidths, with optimization algorithms further enhancing bandwidth performance. A Java-based graphical user interface (GUI) provides an intuitive workflow for parameter configuration and real-time visualization of simulation results. The open architecture also lays the foundation for future integration of artificial intelligence algorithms, promoting intelligent and automated klystron design workflows. The accuracy of KlyH and its potential for parameter optimization are confirmed by a case study on an X-band relativistic klystron amplifier. Discrepancies observed between 1D simulations and 3D PIC (three-dimensional particle-in-cell) simulation results are analyzed to identify model limitations, providing critical insights for advancing high-performance klystron designs. Full article

This work proposes an ultrathin dual-polarized double-layer Huygens’ meta-atom, capable of generating Huygens’ resonance and achieving nearly 360° phase coverage and high transmission simultaneously. Two metalenses are designed based on the proposed meta-atom. The first is a dual-polarized metalens antenna with excellent directional radiation performance, achieving a peak gain of 30.4 dBi, an aperture efficiency of 47.8%, and a 3 dB bandwidth of 8.4% at 25 GHz. The second is a two-channel focusing metalens, with focusing efficiencies of 52.4% for x-polarization and 48.6% for y-polarization. The proposed meta-atom exhibits excellent transmission performance and offers a more flexible approach for designing transmissive devices, demonstrating significant application potential in the field of microwave communications, wireless power transfer, and imaging. Full article

Microwave Plasma Chemical Vapor Deposition (MPCVD) plays a crucial role in the growth of high-quality diamonds. However, during the MPCVD process, residues such as polycrystalline diamond, and graphite often adhere to the high-temperature growth substrate surfaces, potentially degrading diamond growth quality. To effectively remove these contaminants and improve the quality of diamond growth, this study employed an 800 kHz femtosecond laser to clean growth substrates with residual deposits. We assessed the effects of multiple cleaning cycles on residue removal from the Foundation Trench Region (FTR) and Inwall Region (IR) and on substrate quality. The results indicate that multiple scans at a laser power of 2.38 W, a repetition rate of 800 kHz, a scanning speed of 1800 mm/s, and a scan spacing of 10 μm significantly removed residues, reduced substrate surface roughness, and restored substrate cleanliness. This approach enhances the quality and efficiency of diamond growth via MPCVD. The application of high-repetition-rate femtosecond laser cleaning techniques for growth substrates significantly improves the quality of regenerated diamond films, providing crucial support for the preparation of high-quality diamond materials. Full article