Extraction of coastal raft cultivation area with heterogeneous water background by thresholding object-based visually salient NDVI from high spatial resolution imagery

<p>The development of high spatial resolution satellite imaging has enabled the acquisition of mariculture area information. This data could play an important role in mariculture investigations, ocean disaster evaluations, and coastal management. Because chlorophyll is concentrated in the widely distributed raft culture (a major kind of mariculture), the Normalized Difference Vegetation Index (NDVI) can be used for extraction. However, extensive coastal raft culture is easily confused with the heterogeneous water background. This results in unsatisfactory extraction when surveying a large water area with heterogeneous water background. By combining object-based image analysis and the centre-surround mechanism of a visual attention model, we propose an object-based visually salient NDVI (OBVS-NDVI) feature. Comparison experiments using Gaofen-2 spectral imagery of Luoyuan Bay, Fuzhou, China, indicate that OBVS-NDVI can effectively discriminate raft cultivation areas over large areas with a heterogeneous water background.</p

Low-Cost Synthesis of Titanium Silicalite‑1 (TS-1) with Highly Catalytic Oxidation Performance through a Controlled Hydrolysis Process

Titanium silicalite-1 (TS-1) has been successfully synthesized in ultralow molar ratio of TPAOH/SiO₂ by two-step and multistep hydrolysis process, where the molar ratio of tetrapropylammonium hydroxide/silica (TPAOH/SiO₂) could be reduced to 0.08 and 0.065, respectively. Combined characterization of X-ray diffraction (XRD), N₂ adsorption–desorption, scanning electron microcopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, and thermal gravimetric (TG) analysis shows that currently synthesized TS-1 samples have the typical “blackberry” morphology, and the particle size is around 300–400 nm, similar to that of the conventional TS-1 synthesized at a high molar ratio of TPAOH/SiO₂ (>0.18). Additionally, currently synthesized TS-1 exhibits excellent catalytic oxidation performance in epoxidation of alkene and ammoximation of ketone, even better than that of conventional TS-1. Obviously, fast hydrolysis of a small part of TEOS at a high concentration of TPA⁺ in the first step induces more nuclei, which in turn accelerates crystallization in the subsequent step. Therefore, effective utilization of TPAOH to build the TS-1 framework is significantly increased. This strategy can greatly reduce the synthesis cost of TS-1, which is suitable for synthesis of TS-1 on an industrial scale

Lewis and Brønsted Acid Synergistic Catalysis for Efficient Synthesis of Hydroxylamine over Heteroatom Zeolites

Environmental and efficient synthesis of NH2OH is challenging. Herein, we have provided a route for efficient NH2OH formation by NH3 oxidation via the synergistic catalysis of Lewis acid sites of the framework Ti (Ti LAS) and Brønsted acid sites of the framework Al (Al BAS) in Ti–Al-MOR zeolites. Ti LAS was the active center for formation of transition-state NH2OH, while Al BAS could provide the proton H to convert transition-state NH2OH absorbed on Ti LAS to a [NH3OH]+ species. Protonation effect would not only promote the catalytic cycle process resulting from accelerating the desorption of transition-state NH2OH, but also improve the stability of NH2OH, being less prone to oxidative decomposition. In this work, we presented the synergistic catalysis between LAS and BAS over Ti-containing heteroatom zeolites to accelerate the catalytic cycle, which provided an environmental and efficient method for NH2OH formation

Core–Shell-Structured Titanosilicate As A Robust Catalyst for Cyclohexanone Ammoximation

Core–shell-structured MWW-type titanosilicate (Ti-MWW) with a well-defined micro-meso hierarchical porosity was fabricated by using self-assembly technique. This composite material Ti-MWW@meso-SiO₂ was applied as the catalyst for the ammoximation of cyclohexanone in a continuous slurry reactor. The combination of characterizations, such as XRD, SEM, HR-TEM, and N₂ adsorption, verified that the composite material was composed of zeolite crystallites as core and mesosilica as shell and that the micropores and mesopores were penetrated well with each other, which significantly facilitated the diffusion of large molecules. In continuous ammoximation of cyclohexanone as a probe reaction, the composite exhibited significantly prolonged lifetime in comparison to the parent Ti-MWW catalyst and the physical mixture of Ti-MWW and mesosilica. The unique catalytic behaviors of Ti-MWW@meso-SiO₂ were ascribed to protecting effect of the mesosilica shell. It served as a sacrificial lamb that protected the active component of zeolite core against rapid desilication and coke formation, leading to a stable duration of the catalysts