- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Deep and high precision cutting of alumina ceramics by picosecond laser
摘要： Ceramics possess high thermal and chemical resistance, low density, and high compressive strength; however, the machining complications imposed by their inherent brittleness limit their range of applications. Laser cutting technology can offer an automated manufacturing technique for machining these brittle materials. In this paper, a laser cutting method, so-called wobbling, was developed for performing deep, high precision, and defect-free laser cutting of industrial grade alumina ceramics. This work explored picosecond laser process parameters such as focal position, linear speed, and wobble amplitude in order to control cut depth and optimize cut quality in terms of kerf width, kerf taper, surface cleanness, while avoiding crack formation. The morphology and cut quality were evaluated using 3D laser scanning microscopy and scanning electron microscopy (SEM). Picosecond laser cutting process parameters were optimized, achieving a maximum material removal rate of ~10 mm3/min. It was shown that the laser cutting process developed via these experiments represents an effective and efficient manufacturing tool that can be incorporated in engineered net shaping systems.
关键词： Laser cutting,Material removal rate,Ablation,Ultrafast laser micromachining,Alumina ceramics
更新于2025-09-23 15:21:01
-
Photocatalytic reduction of U(VI) in wastewater by mGO/g-C3N4 nanocomposite under visible LED light irradiation
摘要： Efficient elimination of U(VI) from uranium wastewater is an urgent task for sustainable nuclear energy and environmental protection. In this study, magnetic graphene oxide decorated graphitic carbon nitride (mGO/g-C3N4) nanocomposite was prepared and used for photocatalytic reduction of U(VI) in wastewater under visible LED light irradiation for the first time. The batch experiments indicated that the mGO/g-C3N4 (mGCN) nanocomposite could efficiently reduce U(VI) under visible LED light, and a high U(VI) extraction capacity of 2880.6 mg/g was obtained with an extraction efficiency of 96.02 %. The transmission electron microscopy (TEM) elemental mapping, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses demonstrated that the soluble U(VI) was immobilized by transforming it to metastudtite ((UO2)O2?2H2O) by mGCN nanocomposite under visible LED light irradiation. This work indicated that the mGCN is a promising visible light catalyst for treatment of uranium wastewater.
关键词： removal,photoreduction,wastewater,uranium
更新于2025-09-23 15:21:01
-
Integration of 3D Macroscopic Graphene Aerogel with 0D-2D AgVO3-g-C3N4 Heterojunction for Highly Efficient Photocatalytic Oxidation of Nitric Oxide
摘要： The application of three-dimensional (3D) aerogels for immobilizing powder catalysts can greatly enhance the catalyst cycling stability. In this study, we modify two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets with zero-dimensional (0D) silver metavanadate (AgVO3) quantum dots. The resulting 0D-2D heterojunction facilitates the separation of electron-hole pairs, and exhibits high efficiency for removing nitric oxide (NO) at low concentrations (600 ppb) at room temperature. The removal efficiency is much higher than that of pure g-C3N4. The porous network framework of the 3D AgVO3-g-C3N4-graphene hybrid aerogel is formed by bridging of graphene oxide sheets. This results in the heterojunction further enhancing electron-hole separation. The modification of g-C3N4 promotes the separation of photogenerated carriers in a step by step manner, and enhances their oxidation-reduction ability. The AgVO3-g-C3N4-graphene hybrid aerogel exhibits excellent catalytic activity for NO removal (maximum of 65%). Cycling experiments verify the stability and recyclability of the aerogel.
关键词： 0D-2D heterojunction,NO removal,visible light,3D aerogel
更新于2025-09-23 15:21:01
-
Local Activity-Driven Structural-Preserving Filtering for Noise Removal and Image Smoothing
摘要： In this paper, a local activity measurement of the clipped and normalized variance or standard deviation is proposed to drive anisotropic diffusion and relative total variation (RTV) to work better for structural preservation. Firstly, two novel edge-stop functions are introduced for our local activity-driven anisotropic diffusion (LAD-AD) to efficiently remove severe artifacts and preserve the fine geometry structures in HEVC-compressed depth images. Secondly, we propose a simple yet effective local activity-driven RTV (LAD-RTV) with the way of the product between gradient and the local activity measurement for image smoothing and scale representation. Meanwhile, both color-sharing information and each-channel discriminative information are considered, which are significant to color image’s edge-preserving but not included in the RTV model. Besides, LAD-RTV leverages the form of the division of gradient and the local activity measurement to resolve the problem of general image de-noising by regarding the noises as the duplicate texture elements. Experimental results have validated that the proposed LAD-AD can greatly improve the precision of HEVC-compressed depth images and the quality of its synthesized image. Additionally, large numbers of results have shown our LAD-RTV is superior to several existing methods.
关键词： scale representation,Image filtering,image smoothing,noise removal
更新于2025-09-23 15:21:01
-
Revisiting cocatalyst/TiO2 photocatalyst in blue light photothermalcatalysis
摘要： Coupling heat into photocatalysis (PC) has been found more efficient than PC for removal of volatile organic compounds (VOC). Therein, photothermal synergy induced photothermalcatalysis (PTC) sometimes tells different stories from PC. In this work, we revisit ST-01 TiO2 photocatalyst as photothermalcatalyst under blue light at 333 K and further investigate the role of surface grafted cocatalyst (CrxO, CoxO, CuxO, Pt) in catalytic removal of gaseous acetaldehyde pollutant. By comparison on the amount of cocatalyst, for PC, more CrxO cocatalyst (3 wt%) is favored for higher removal efficiency of acetaldehyde. For PTC, less CrxO cocatalyst (0.3 wt%) is favored. By further comparison on the type of cocatalyst, for PC, hole cocatalyst (CrxO and CoxO) gives inferior performance to that of electron cocatalyst (CuxO and Pt). For PTC, hole cocatalyst gives superior performance to that of electron cocatalyst. The difference between PC and PTC lies in synergistic effect between defect-related blue-light absorption, cocatalyst induced interfacial charge transfer and matched surface red-ox reaction rate. This work may provide new insight into the design and development of photothermalcatalyst for VOC removal.
关键词： Cocatalyst,VOC removal,Photothermal synergy,Photocatalytic,Photothermalcatalytic
更新于2025-09-23 15:21:01
-
Design of estimators for restoration of images degraded by haze using genetic programming
摘要： Restoring hazy images is challenging since it must account for several physical factors that are related to the image formation process. Existing analytical methods can only provide partial solutions because they rely on assumptions that may not be valid in practice. This research presents an e?ective method for restoring hazy images based on genetic programming. Using basic mathematical operators several computer programs that estimate the medium transmission function of hazy scenes are automatically evolved. Afterwards, image restoration is performed using the estimated transmission function in a physics-based restoration model. The proposed estimators are optimized with respect to the mean-absolute-error. Thus, the e?ects of haze are e?ectively removed while minimizing overprocessing artifacts. The performance of the evolved GP estimators given in terms of objective metrics and a subjective visual criterion, is evaluated on synthetic and real-life hazy images. Comparisons are carried out with state-of-the-art methods, showing that the evolved estimators can outperform these methods without incurring a loss in e?ciency, and in most scenarios achieving improved performance that is statistically signi?cant.
关键词： Image restoration,Haze removal,Image processing,Genetic programming
更新于2025-09-23 15:21:01
-
[Micro/Nano Technologies] Micro and Nano Fabrication Technology Volume 1 || Bonnet Polishing of Microstructured Surface
摘要： Microstructured surfaces have been adopted in various and wide applications. Different types of microstructures made of ductile materials can be generated by cutting process, for example, turning and milling with speci?ed diamond cutters. However, these processes generally are not capable to handle with hard and brittle materials which are called dif?cult-to-machine materials. Computer-controlled ultra-precision polishing with bonnet provides an enabling solution to generate microstructures due to its feasible in?uence function. With proper machining parameters, speci?ed shape of the tool in?uence function is hence obtained, and then with aid of tool path planning, microstructured surface topography is generated, especially for those dif?cult-to-machine materials. In this chapter, research work for generating microstructured surface by computer-controlled ultra-precision bonnet polishing is presented. The material removal characteris- tics and tool in?uence function of bonnet polishing are explained, and a multi- scale material removal model and a surface generation model were developed. Surface generation of microstructures by single precess polishing and swing precess polishing is explained in details. A series of simulation and real polishing experimental studies are undertaken based on a seven-axis ultra-precision freeform polishing machine. The generated microstructured surfaces with various patterns have been analyzed. The research results have demonstrated that the proposed bonnet polishing provides an enabling and effective approach for generating microstructured surfaces.
关键词： Modelling,Bonnet polishing,Ultra-precision machining,Dif?cult-to- machine material,Precess polishing,Surface generation,In?uence function,Computer controlled polishing,Microstructured surface,Multi-scale material removal,Simulation
更新于2025-09-23 15:21:01
-
Theoretical model and experimental analysis of non-uniform material removal during full-aperture polishing
摘要： Full-aperture polishing is a key process in the fabrication of large flat optical elements with a high-precision surface figure. Controlling of the surface figure, which is primarily dependent on the material removal distribution, during the polishing process is challenging. In this study, a novel model is proposed to calculate the material removal distribution and the resultant surface figure. The model determines the material removal amount of points on the workpiece by considering the kinematic parameters and pressure distribution along the sliding trajectory relative to the pad. Moreover, the pressure distribution during the polishing process is acquired from the mechanical and morphological characteristic of polishing pad. With this model, the final surface figures under several polishing conditions were simulated and were found to be in close agreement with the experimental results.
关键词： Full-aperture polishing,Surface figure,Pressure distribution,Material removal distribution
更新于2025-09-23 15:21:01
-
Optimization and scale-up of an LED-illuminated microalgal photobioreactor for wastewater treatment
摘要： The use of LED-illuminated photobioreactors with microalgae has been extensively studied for wastewater treatment. Most studies have used isolated microalgae species; however, this practice does not match the reality of conditions in wastewater treatment plants. Operational conditions that promote greater growth of algal biomass and that remove pollutants most effectively are disputed in the literature. In this context, LED–illuminated photobioreactors with microalgae were evaluated using multivariate analysis in order to optimize removal of pollutants (nitrogen, phosphorus, and carbonaceous organic matter). Three variables were evaluated: operating time, LED wavelength, and luminous ?ux intensity. A microalgae consortium was used in the photobioreactor. In addition to the LED-illuminated photobioreactors, control photobioreactors illuminated by sunlight were also operated. Using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate if the behavior would be maintained. The best operational conditions for the removal of pollutants were observed in LED-illuminated photobioreactors operated under a light intensity of 700 μmol·m?2s?1 for 15 days. Under these conditions, it was possible to remove 89.97% of carbonaceous organic matter, 86.50% of nitrogen, and 30.64% of phosphorus. The scaled-up photobioreactor operated with similar performance.
关键词： multivariate optimization,Light-emitting diode,microalgae,scale-up,removal of pollutants
更新于2025-09-23 15:19:57
-
Synthesis and characterization of Bi-BiPO4 nanocomposites as plasmonic photocatalysts for oxidative NO removal
摘要： Bi metal–BiPO4 (Bi-BPO) nanocomposites formed by in situ solvothermal reduction were employed as plasmonic photocatalysts for oxidative NO removal, achieving a removal efficiency of 32.8% in a continuous NO flow (400 ppb) under illumination with visible light. This high performance was ascribed to the generation of energetic hot electrons (and their subsequent surface chemical reactions) due to the surface plasmon resonance (SPR) of Bi metal, as validated by numerical simulations. The combined results of density functional theory (DFT) calculations and electrochemical analysis revealed that hot electrons are transferred from Bi metal to BPO via the Bi-BPO interface. DFT calculations further showed that enhanced O2 activation on the Bi-BPO interface facilitates the generation of both superoxide (?O2?) and hydroxyl (?OH) radicals, as confirmed by electron spin resonance, while in situ DRIFTS analysis demonstrated that NO is activated on the Bi-BPO interface and then oxidized to nitrates. Thus, this work highlights the SPR effects of Bi metal and promoted O2 and NO activation in plasmonic photocatalysis, showing that the adopted approach can be generalized to design efficient and cost-effective photocatalytic systems for the removal of other gaseous pollutants.
关键词： Bi metal,O2 and NO activation,NO removal,plasmonic photocatalysis
更新于2025-09-23 15:19:57