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Photocatalytic degradation of 4-chlorophenol with the use of FTO/TiO2/SrTiO3 composite prepared by microwave-assisted hydrothermal method
摘要： Microwave-assisted hydrothermal method was applied to obtain SrTiO3 photocatalyst by transformation of a thin TiO2 layer deposited on the conducting solid substrate (FTO-glass) via dissolution-precipitation reaction in alkaline solution. The influence of Sr2+ ions concentration on crystallinity, composition as well as photoelectrochemical and photocatalytic properties of the resultant materials was investigated. The XRD studies indicated the presence of some amount of co-deposited SrSiO3 due to reaction of metasilicates released from the glass substrate (not covered with FTO film). However, the process of glass dissolution was substantially prevented by protection of the back side of the sample with a Teflon tape. The best activity in photodecomposition of 4-chlorophenol under irradiation with 365 nm diode was obtained for FTO/TiO2/SrTiO3 composite fabricated in 6 h synthesis in the solution containing 0.1 M Sr(NO3)2, at temperature of 180 °C. The photoelectrochemical properties of the composites and FTO/TiO2 electrode were studied in the solution of Na2SO4 under illumination with a xenon lamp. The increased photocurrent density and longer electron lifetime for the hybrid system in comparison to those of TiO2 was discussed in terms of suppressed recombination rate due to formation of TiO2/SrTiO3 interface. It was also found that the side product, SrSiO3, reveals an excellent adsorption properties with respect to methylene blue and therefore, the system SrTiO3/TiO2/FTO/glass/SrSiO3 may be used as bifunctional composite for adsorption and photocatalysis.
关键词： 4-Chlorophenol photodecomposition,Photocatalysis,SrSiO3,Photoelectrochemical properties,Microwave-assisted hydrothermal synthesis,TiO2/SrTiO3,Electron lifetime
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Method of Detection of Thermal Microwave Radiation Increments
摘要： The optimal method for detecting objects of microwave radiation in a Ratio-type radiometer with an unstable receiver gain is synthesized. Analysis of the method indicates that the measurement results are not shifted, and the method itself can be practically implemented. The analytical expressions of the probabilistic and energy characteristics of objects detection against the background of the sky at various signal-to-noise conditions are obtained. The technical implementation of the detection method is proposed and experimental research is carried out.
关键词： Ratio-type microwave radiometer,unstable gain,Radar detection
更新于2025-09-23 15:21:21
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[IEEE 2017 IEEE 17th International Conference on Bioinformatics and Bioengineering (BIBE) - Washington, DC (2017.10.23-2017.10.25)] 2017 IEEE 17th International Conference on Bioinformatics and Bioengineering (BIBE) - A novel low-complexity framework in ultra-wideband imaging for breast cancer detection
摘要： In this research work, a novel framework is proposed as an efficient successor to traditional imaging methods for breast cancer detection in order to decrease the computational complexity. In this framework, the breast is divided into segments in an iterative process and in each iteration, the one having the most probability of containing tumor with lowest possible resolution is selected by using suitable decision metrics. After finding the smallest tumor-containing segment, the resolution is increased in the detected tumor-containing segment, leaving the other parts of the breast image with low resolution. Our framework is applied on the most common used beamforming techniques, such as delay and sum (DAS) and delay multiply and sum (DMAS) and according to simulation results, our framework can decrease the computational complexity significantly for both DAS and DMAS without imposing any degradation on accuracy of basic algorithms. The amount of complexity reduction can be determined manually or automatically based on two proposed methods that are described in this framework.
关键词： breast cancer detection,low complexity computational methods,DAS,DMAS,Microwave imaging
更新于2025-09-23 15:21:21
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Microwave dielectric properties of B and N co-doped SiC nanopowders prepared by combustion synthesis
摘要： B and N co-doped SiC nanopowders were prepared by combustion synthesis under a nitrogen atmosphere from the Si/C system, using α-Si3N4 powder and B powder as solid nitriding agent and dopant, respectively. The prepared particles had spherical morphology and narrow size distribution. XPS analysis demonstrated that B and N atoms successfully incorporated into SiC crystal and formed Si1-xBxC1-yNy solid solution. Results of dielectric properties showed that the real part ε′ and imaginary part ε″ of the complex permittivities of the samples decreased first, and then increased with increasing N content. The sample with 5% B and 15% N revealed the greatest values in ε′ and ε″ and better microwave absorption performance. The corresponding mechanism of the dielectric properties of SiC improved by co-doping was discussed in detail.
关键词： co-doping,SiC,dielectric property,microwave loss
更新于2025-09-23 15:21:21
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The Enhanced NO2 sensing properties of SnO2 nanoparticles/reduced graphene oxide composite
摘要： Multiple techniques were utilized to characterize the structure and morphology of the SnO2/reduced graphene oxide (rGO) composite, in which the composite was prepared by a facile one-pot microwave-assisted hydrothermal method. As a result, SnO2 nanoparticles with diameters of 3-5 nm were anchored uniformly on both sides of the rGO sheets. Meanwhile, a series of resistive-type gas sensors based on SnO2/rGO composite and pure SnO2 were fabricated and tested for analyzing the effects on introducing rGO. The results revealed that, the composite exhibited obviously enhanced gas sensing properties towards NO2 with high response, fast response and recovery speed, and good selectivity and reproducibility. At 75°C, the response of the composite to 350 ppb NO2 was about 6.6 times of that to pure SnO2. In addition, the response and recovery time of the sensor was greatly reduced from 39.2/54.7 to 6.5/1 minutes, and the detecting limit of the sensor was even as low as 50 ppb. Provided with the enlarged surface area and local p-n heterojunctions, the synergistic effect of SnO2 nanoparticles and rGO contributed to the enhanced gas sensing properties of SnO2/rGO composite.
关键词： SnO2,Graphene,Heterojunctions,Microwave-assisted hydrothermal,Gas sensor
更新于2025-09-23 15:21:21
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Importance of carbon-monoxide-induced reaction in microwave heating synthesis of β-SiC from silicon powder in air
摘要： Microwave heating is known to provide extremely rapid synthesis of silicon carbide (SiC) from mixtures of silicon and carbon powders. The formation mechanism has long been considered to be a solid-state reaction among the powders in the mixture. Here, we present a new reaction mechanism via a gas-phase route. We have confirmed successful synthesis of ￠-SiC powder by microwave-heating of a small amount of Si powder that was entered into a quartz tube and then embedded in graphite powder, although no direct contact between the Si and graphite powders was allowed. Scanning electron microscopy observations revealed that the ￠-SiC powder was formed by direct carbonization of the Si powder. Since the atmosphere during the reaction comprises a vast majority of carbon monoxide (CO) gas according to the Boudouard equilibrium, the carbonization appears to have taken place via the CO gas. The contribution of such a gas-phase reaction could account in part for the rapidity of the microwave-heating reactions reported so far, which can hardly be explained solely by solid-state reactions among the mixed powders.
关键词： Carbon monoxide,Gas-phase reaction,Microwave heating,Silicon carbide,Air atmosphere,Silicon
更新于2025-09-23 15:21:21
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Treatment of graphene films in the early and late afterglows of N2 plasmas: comparison of the defect generation and N-incorporation dynamics
摘要： Graphene films grown on copper substrate by chemical vapor deposition were exposed to the flowing afterglow of a reduced-pressure N2 plasma sustained by microwave electromagnetic fields (surface-wave plasma). Two set of conditions were examined by controlling the gas flow rate: the late afterglow (LA) characterized by high number densities of reactive N atoms and the early afterglow (EA) in which significant populations of metastable N2(A) states and positive ions (N2+ and N4+) coexist with plasma-generated N atoms. LA treatments of graphene films show monotonous and steady incorporation of nitrogen atoms along with very low damage. However, given the very mild LA treatment conditions, a large part of the N atoms remains weakly bonded to the graphene surface; a feature ascribed to the plasma-induced functionalization of airborne hydrocarbon contaminants. In such conditions, graphitic inclusion of plasma-generated N atoms is limited to native defect sites. On the other hand, the presence of highly energetic species in the EA induces significant damage combined with much higher N-incorporation. Detailed Raman analysis of EA-treated samples further reveals a transition from vacancy-type defects to much larger multi-vacancies with increasing treatment time. This complete set of data indicates that, through a judicious control of the populations of reactive N atoms, metastable N2(A) states, and positive ions (N2+ and N4+), the flowing afterglow of microwave N2 plasmas represents a highly promising tool for precise, post-growth tuning of the defect generation and N-incorporation dynamics in graphene films.
关键词： Microwave plasmas,Plasma-graphene interactions,Flowing afterglows,Plasma-induced modification of materials and nanomaterials
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Soil Moisture Retrieval by Combining Using Active and Passive Microwave Data
摘要： Active and passive microwave remote sensing have their particular characteristics. Active microwave is more sensitive to vegetation cover and surface soil roughness, while passive microwave is more sensitive to the surface soil moisture. A new retrieval algorithm has been proposed by using Aquarius and SMAP satellites’ active and passive microwave observations to retrieve soil moisture products in different spatial scales. The retrieval results of soil moisture have been verified with the ground observations of soil moisture and temperature measurement (SMTM) stations in Naqu, China. The advantages and disadvantages of the algorithm have also been evaluated to analyze the practical value of the new soil moisture retrieval algorithm.
关键词： soil moisture retrieval algorithm,passive microwave,soil moisture,active microwave,active and passive microwave remote sensing,Aquarius satellite
更新于2025-09-23 15:21:01
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Heterogeneous multicore fiber for optical beamforming
摘要： We experimentally demonstrate, for the first-time to our knowledge, optical beamforming for microwave phased array antennas implemented with a heterogeneous multicore fiber link. The multicore fiber has been engineered to act as an optical sampled true time delay that allows to implement radiofrequency signal processing in a distributed way. It comprises 7 trench-assisted cores where each core is fabricated with different dimensions and core dopant concentration, as to feature a different group delay and chromatic dispersion behavior. We emulated different radio beamsteering scenarios where the beam-pointing angle is modified by tuning the optical wavelength in a 20-nm range, while squint-beam effects are avoided.
关键词： Microwave Photonics,optical beamforming networks,multicore fibers
更新于2025-09-23 15:21:01
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Terahertz Bragg Resonator based on a Mechanical Assembly of Metal Grating and Metal Waveguide
摘要： The physical contrast sensitivity of microwave imaging systems employing scattering-parameter measurements is defined. Methodologies are proposed for its evaluation through measurements and through simulations. This enables the estimation of the smallest detectable target permittivity contrast or size for the system under evaluation. The outcomes of the proposed simulation-based and measurement-based methods are compared for the case of a realistic tissue-imaging system. The agreement between the simulated and measured sensitivity estimation validates the proposed methods. The intention of the proposed methodology is to provide common means to quantify and compare the sensitivity performance of microwave systems used in tissue imaging as well as the antennas used as sensors. We emphasize that the proposed method targets the performance of the hardware and it is not concerned with the image-reconstruction algorithms.
关键词： microwave imaging,tissue sensing,Antenna measurements,receiver sensitivity,response sensitivity,physical contrast sensitivity (PCS)
更新于2025-09-23 15:21:01