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A Novel Despeckling Method for Medical Ultrasound Images Based on the Nonsubsampled Shearlet and Guided Filter
摘要： Porous maghemite (PM) was prepared by two-step calcinations. The crystallographic and magnetic changes of PM upon SO4^2? and CO3^2? adsorption were investigated. The crystallite size (~ 27 nm) and PM texture remain unchanged after adsorption. Fourier transform infrared spectra showed that SO4^2? and CO3^2? are adsorbed on the PM mainly through outer- and inner-sphere surface complexations, respectively. X-ray photoelectron spectra showed the increase and decrease of binding energy for Fe 2p3/2 electrons after SO4^2? and CO3^2? adsorption, respectively. Sulfate adsorption increases the magnetic susceptibility (χ) of PM by ~ 4.5%, and decreases the saturation magnetization (Ms) of PM by 24.6%. By comparison, carbonate adsorption decreases χ by ~ 3.7% and increases Ms by 17.8%. The magnetic changes upon SO4^2? and CO3^2? adsorption are attributed both to the electronegativity of anions and the size distribution of PM.
关键词： Adsorption,Electronegativity,Inorganic anion,Porous maghemite,Magnetic property
更新于2025-09-11 14:15:04
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Experimental investigation on premixed hydrogen/air combustion in varied size combustors inserted with porous medium for thermophotovoltaic system applications
摘要： Micro combustion stabilization is challenged by the large heat loss ratio, and the operating conditions are narrow because of the small combustor size. In this work, experimental tests combined with numerical simulations are carried out to investigate the premixed H2-air combustion with and without porous medium. The results indicate that the flame stabilization is greatly enhanced in the combustor with porous medium, and the wall temperature with porous medium is 188 K higher than that of the free flame in the tube with a length 22 mm, an outer diameter 7 mm and the wall thickness 0.5 mm. The appropriate porosity of porous medium is selected for each combustor to achieve a better thermal performance and high radiation temperature. With the increase of combustor diameter, the limitations in terms of inlet velocity and flame blowout are expanded and the radiation surface area is also increased for a higher energy output. The radiation temperature and surface area play important roles in the application of micro thermo-photovoltaic system. The combustor with a length 27 mm and an outer diameter 7 mm is able to achieve an optimal balance between the contingent negative variation of radiation surface area and radiation temperature, delivering an electrical power of 1.41 W with an efficiency 1.39% for the micro-TPV system with InGaAsSb PV cells when the H2 flow rate is 3.03 g/h and equivalence ratio Φ = 0.85.
关键词： Micro combustion,Porous medium,Porosity,Electrical power
更新于2025-09-11 14:15:04
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Biomass and Astaxanthin Productivities of Haematococcus pluvialis in an Angled Twin-Layer Porous Substrate Photobioreactor: Effect of Inoculum Density and Storage Time
摘要： The microalga Haematococcus pluvialis is mainly cultivated in suspended systems for astaxanthin production. Immobilized cultivation on a Twin-Layer porous substrate photobioreactor (TL-PSBR) has recently shown promise as an alternative approach. In Vietnam, a TL-PSBR was constructed as a low-angle (15°) horizontal system to study the cultivation of H. pluvialis for astaxanthin production. In this study, the biomass and astaxanthin productivities and astaxanthin content in the dry biomass were determined using different initial biomass (inoculum) densities (from 2.5 to 10 g dry weight m?2), different storage times of the initial biomass at 4 °C (24, 72, 120 and 168 h) and different light intensities (300–1000 μmol photons m?2 s?1). The optimal initial biomass density at light intensities between 400–600 μmol photons m?2 s?1 after harvest from suspension for immobilization on the TL-PSBR yielded the highest biomass and astaxanthin productivities, 8.7 g m?2 d?1 and 170 mg m?2 d?1, respectively; longer storage periods decreased productivity. Biomass and astaxanthin productivities were largely independent of light intensity between 300–1000 μmol photons m?2 s?1 but the efficiency of light use per mole photons was highest between 300–500 μmol photons m?2 s?1. The astaxanthin content in the dry biomass varied between 2–3% (w/w). Efficient supply of CO2 to the culture medium remains a task for future improvements of angled TL-PSBRs.
关键词： Haematococcus pluvialis,a horizontal (low-angled) twin-layer photobioreactor,astaxanthin,porous substrate photobioreactor
更新于2025-09-11 14:15:04
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Facile fabrication of hierarchical micro-meso-macro porous metal oxide with high photochemical and electrochemical performances
摘要： A feasible route with a dual-templating method including both ice and SiO2 hard templates to fabricate hierarchical porous TiO2 with micro-, meso-, and macro-pores from inorganic/organic metal oxo cluster precursors is proposed. As-prepared TiO2 shows high photocatalytic activity and excellent electrochemical performances. The current strategy can be applied to fabrication of a broad range of metal oxide materials for catalysis and energy related applications.
关键词： Metal oxide,Lithium-ion batteries (LIBs),Photocatalytic,Hierarchical porous,TiO2
更新于2025-09-11 14:15:04
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Synthesis of Graphene on Porous Silicon for Vapor Organic Sensor by Using Photoluminescence
摘要： In this work, ultra-sensors of chemical solvents vapor were fabricated for chloroform, n-Hexane and Ethanol via modified porous silicon (PS) surface by the reduction of graphene oxide (rGO) layer. The rGO was conducted by electrochemical exfoliation of graphite electrodes with electrolyte solution at PH=4.6. Then porous silicon (PS) was prepared by employing electrochemical etching (ECE) method using silicon (Si) p-type at different etching current density J= 2, 4 and 6mA/cm2with constant HF concentration of 15%, and time of etching of 15min. The reduction graphene oxide competition with PS was studied as vapors organic sensor, morphological, structural, and surface bond configuration were characterized by Atomic Force Microscopic (AFM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) respectively, then the Photoluminescence (PL) quenching was measured by using sensor test system with three types of organic chemical solvents n-Hexane, chloroform and ethanol with nitrogen gas mixing, where they were prepared for testing humidity sensor towards the different organic solvents. The results revealed that the reduction graphene oxide layer on surface of PS lead to intensity increase of the PL, and modified the quality of PS sensor for chemical vapor.
关键词： porous silicon,organic vapor sensor,Photoluminescence,Graphene
更新于2025-09-11 14:15:04
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Reconstructing charge-carrier dynamics in porous silicon membranes from time-resolved interferometric measurements
摘要： We performed interferometric time-resolved simultaneous reflectance and transmittance measurements to investigate the carrier dynamics in pump-probe experiments on thin porous silicon membranes. The experimental data was analysed by using a method built on the Wentzel-Kramers-Brillouin approximation and the Drude model, allowing us to reconstruct the excited carriers’ non-uniform distribution in space and its evolution in time. The analysis revealed that the carrier dynamics in porous silicon, with ~50% porosity and native oxide chemistry, is governed by the Shockley-Read-Hall recombination process with a characteristic time constant of 375 picoseconds, whereas diffusion makes an insignificant contribution as it is suppressed by the high rate of scattering.
关键词： carrier dynamics,porous silicon,Drude model,Shockley-Read-Hall recombination,interferometric measurements
更新于2025-09-11 14:15:04
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Preparation of Nb2O5-decorated hierarchical porous ZnO microspheres with enhanced photocatalytic degradation of palm oil mill effluent
摘要： In the present work, Nb2O5-decorated hierarchical porous ZnO microspheres (ZnO/Nb2O5) were successfully prepared through a facile surfactant-free method. The as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and Brunauer–Emmett–Teller surface area analyses. Under UV light irradiation, the ZnO/Nb2O5 composites degraded palm oil mill effluent (POME) efficiently and demonstrated much higher photocatalytic activity compared to those of pure ZnO and Nb2O5. The enhanced photocatalytic degradation performance of ZnO/Nb2O5 composites was attributed to the high charge separation efficiency and hydroxyl radical generation ability as verified by the photoluminescence spectra. Phytotoxicity test upon the POME degradation over ZnO/Nb2O5 photocatalysis considerably decreased through the measurement of radicle lengths of Vigna radiata. Moreover, the ZnO/Nb2O5 composites were reused several times without appreciable loss of activity. This work revealed that the as-prepared ZnO/Nb2O5 composites have great potential for practical applications in the field of wastewater treatment.
关键词： Nb2O5-decorated hierarchical porous ZnO microspheres,Photocatalytic degradation,Charge separation efficiency,Palm oil mill effluent,Hydroxyl radical generation
更新于2025-09-10 09:29:36
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Type II heterojunction in hierarchically porous zinc oxide/graphitic carbon nitride microspheres promoting photocatalytic activity
摘要： Graphitic carbon nitride (g-C3N4) is a visible light active semiconductor. However, low conductivity and high recombination rate of photogenerated electrons and holes limit its application in photocatalysis. In this work, we design and synthesize hierarchically porous zinc oxide/ graphitic carbon nitride (ZnO/g-C3N4) microspheres with type-II heterojunction to effectively degrade rhodamine B (RhB) via increasing the charge-separation efficiency. The ultraviolet-visible (UV-Vis) absorption spectra, Mott-Schottky plots and valence band X-ray photoelectron spectroscope confirm the formation of type-II heterojunction between ZnO nanocrystals and g-C3N4 nanosheets. As a result, the 1.5-ZnO/g-C3N4 composite (the mass ratio of zinc acetate dihydrate to g-C3N4 is 1.5) exhibits the highest photocatalytic activity with good stability and higher photocatalytic degradation rate comparing to pure g-C3N4 and pure ZnO. In addition, our results confirm that ?O2- and h+ are the main active species for ZnO/g-C3N4 in degradation of RhB.
关键词： Active species,Heterojunction,Photocatalytic activity,Hierarchically porous structure,ZnO/g-C3N4
更新于2025-09-10 09:29:36
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Preparation of Ni(OH)2/TiO2 porous film with novel structure and electrochromic property
摘要： Ni(OH)2/TiO2 nanorod composite porous film with a novel structure and remarkable electrochromic (EC) behavior was prepared on a fluorine doped tin oxide (F:SnO2; FTO) coated glass substrate by hydrothermal and solvothermal techniques. A pure Ni(OH)2 porous film was also prepared on another FTO substrate by the solvothermal technique for comparison. The growth process of Ni(OH)2 on the surface of TiO2 nanorod layer was investigated carefully. The component, morphology and microstructure of the films, as well as their EC performances including transmittance, cyclic voltammetry (CV), cycle life and response time were characterized. Compared with those of the pure Ni(OH)2 film, the EC performances of Ni(OH)2/TiO2 composite film have exhibited obvious enhancement owing to the good interface bonding, Ni(OH)2 porous structure, TiO2 nanorod layer and interpenetrating structure. Furthermore, it is noteworthy that the transmittance contrast in near infrared light area was distinctly improved, and even exceeded 95% after the 100th cycle, promising the Ni(OH)2/TiO2 nanorod composite porous film a potential EC application in near infrared light area in the future.
关键词： Composite porous film,Electrochromic property,Ni(OH)2/TiO2 nanorods,Solvothermal,Preparation
更新于2025-09-10 09:29:36
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Enhanced excitonic emission efficiency in porous GaN
摘要： We investigate the optical properties of porous GaN films of different porosities, focusing on the behaviors of the excitonic features in time-integrated and time-resolved photoluminescence. A substantial enhancement of both excitonic emission intensity and recombination rate, along with insignificant intensity weakening under temperature rise, is observed in the porous GaN films. These observations are in line with (i) the local concentration of electric field at GaN nanoparticles and pores due to the depolarization effect, (ii) the efficient light extraction from the nanoparticles. Besides, the porosification enlarges the surface of the air/semiconductor interface, which further promotes the extraction efficiency and suppresses non-radiative recombination channels. Our findings open a way to increasing the emission efficiency of nanophotonic devices based on porous GaN.
关键词： light extraction,exciton,porous GaN,photoluminescence,depolarization effect
更新于2025-09-10 09:29:36