In nano TiO2 photocatalytic oxidation system, adding inorganic oxidizing species can efficiently trap photogenerated electrons and increase concentrations of hydroxyl radicals in the solution and enhance the photocatalytic oxidation rate of nano TiO2 to different organic matter. In this study, correlation of the production of hydroxyl radicals and the photoinduced electron tranfer of nano-TiO2 by inorganic oxidizing species (K2S2O8) was verified by means of the free radicals measured by spin trapping-ESR methods in which DMPO was selected as the spin-trap. The photocatalytic oxidation mechanism of glycine was studied.
Abstract A method for Ti/TiO 2 photoelectrode preparation using laser calcination instead of oven calcination process was introduced. The prepared TiO 2 film was investigated by X‐ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and amperometry, and it was found that the prepared electrode mainly consisted of anatase TiO 2 nanoparticles on its surface and exhibited a superior photocatalytic activity. The electrode was employed as a sensor to measure chemical oxygen demand (COD) of the wastewater. The measuring principle was based on the photocurrent responses of the electrode which were proportional to the COD values. Under the optimized experimental conditions, the linear range was 50–2000 mg L −1 , and the detection limit was 16 mg L −1 ( S/N =3). This method was characterized by short analysis time, simplicity, low environmental impact and long lifetime of the sensor. Additionally, the COD values obtained from the proposed and conventional methods agreed well as demonstrated by the high significant correlation between the two sets of COD values ( R =0.9895, n =25).
While the single-particle impact model is widely used in studying the cold spray process, its scope is restricted to the interaction between an individual particle and the substrate, providing very limited insight into the coating's internal structure and surface roughness. In this work, a multi-particle impact model was specifically established to investigate the microstructural characteristics and surface quality of nanostructured Cu coatings. It was found that with the increase of impact velocity from 100 m/s to 1500 m/s, three distinct coating structures can be identified: adhesion between nanoparticles, co-deformation, and liquefaction. Furthermore, due to the anisotropy of plastic deformation, coatings formed by particles with the initial orientation [110] displayed the roughest surface, while those aligned with [111] and [001] exhibited smoother surfaces. Additionally, as nano-scale particles possess limited kinetic energy, it is difficult for them to induce plastic deformation on the surface and within the substrate. Therefore, it was necessary to elevate the temperature to soften the substrate, only then could jetting be induced with larger adhesion areas. A successful approach to enhance surface quality and bonding strength of coatings involves simultaneous control of impact velocity, crystallographic orientation of particles, and substrate temperature.
Abstract An amperometric method that makes use of a nano‐PbO 2 modified electrode as an electrocatalytic sensor for the determination of chemical oxygen demand (COD) is described. The sensor signal was observed as a result of the detection of the oxidation current due to electrocatalytic oxidation of organic compounds in the sample solution. This sensor responded linearly to the COD Cr of standard samples in the range of 5–3 000 ppm and the detection limit was 2.5 ppm. When using the sensor to determine real samples, it displays short analysis time, simplicity and no sample pretreatment. The sensor was stable for over 20 days in real wastewater samples and has successfully been applied to the determination of COD in real wastewater samples.
With the wide application of video surveillance system, visual information has become the key research element of modern security technology.Computer vision related technology can be applied to the field of intelligent surveillance, so that computers can process video.People can use computers to understand video surveillance, directly get the number of people in an area, or get the distribution of people.This paper first analyzes the existing two types of target detection algorithms, and chooses Fast R-CNN algorithm as the research object of this paper.This paper combines the research method of background modeling with the research method of deep convolutional neural network based on statistical learning to fuse all the calibration boxes of pedestrian detection results.A pedestrian count evaluation method is proposed, and the pedestrian count results are smoothed and fused.
Graphene-based materials with a negative Poisson's ratio have numerous potential applications in various fields. However, the modification of graphene is cumbersome and may worsen the mechanical properties. The scale limitation and structural instabilities of suspended graphene are also unfavorable for practical applications. In the present study, we design several nanolayered graphene/Cu composites and investigate their tensile behavior using molecular dynamics simulations. The nanolayered composites exhibit an apparent auxetic behavior without any modification of graphene, as the graphene/Cu interface can significantly enhance the surface effect and lead to an earlier phase transformation of the Cu component. A simultaneous occurrence of a positive and negative Poisson's ratio can be achieved in an asymmetric composite due to the good blocking effect of graphene on two separated Cu films. Materials with simultaneous negative/positive Poisson's ratio have potential applications in scaffold design, where it is necessary to tune the magnitude and polarity of the Poisson's ratio in tissue engineering. Furthermore, we propose a composite consisting of alternating multilayer graphene and thin Cu films to overcome the scale limitation, whose negative Poisson's ratio persists when the total thickness exceeds 100 nm. It is found that the change in the absolute value of Poisson's ratio becomes smaller with an increase in total thickness. Graphene/Cu composites with only a slight deformation under external loading may be suitable for the fabrication of telecommunication cables, whose dimensions should remain unchanged when subjected to high hydrostatic pressure in the deep ocean.
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