Search

The property of cathode in the microbial fuel cell (MFC) was one of the key factors limiting its output performance. MnO2 nanorods were prepared by a simple hydrothermal method as cathode catalysts for MFCs. There were a number of typical characteristic crystal planes of MnO2 nanorods like (110), (310), (121), and (501). Additionally, there were great many hydroxyl groups on the surface of nanorod-like MnO2, which provided a rich set of active adsorption sites. The maximum power density (Pmax) of MnO2-MFC was 180 mW/m2, which was 1.51 times that of hydrothermally synthesized MnO2 (119.07 mW/m2), 4.28 times that of naturally synthesized MnO2 (42.05 mW/m2), and 5.61 times that of the bare cathode (32.11 mW/m2). The maximum voltage was 234 mV and the maximum stabilization time was 4 days. The characteristics of MnO2, including rod-like structure, high specific surface area, and high conductivity, were conducive to providing more active sites for oxygen reduction reaction (ORR). Therefore, the air cathode modified by MnO2 nanorods was a kind of fuel cell electrode with great application potential. [ABSTRACT FROM AUTHOR]

The reaction mechanisms of vinyl acetate with OH radicals in the atmosphere have been studied using the density functional theory method. The geometry parameters and frequencies of all of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis sets. The single-point energy calculations are carried out at the MPWB1K/6311+G(3df,2pd)level. The detailed profiles of the potential energy surfaces for the reactions are constructed. Two OH addition and three H abstraction reaction pathways are considered for the reaction of vinyl acetate with OH radicals. The theoretical study shows that the most energetically favorable isomer is that of OH addition to the terminal carbon positions (C1 atom). The Å-ester rearrangement, which is characteristic of ester oxidation processes, is confirmed to be thermodynamically and kinetically favorable. The main products of the OH-initiated atmospheric oxidation of vinyl acetate are formaldehyde, formic acetic anhydride, and acetic acid. Key words: vinyl acetate, OH radicals, reaction mechanism, quantum chemical calculation. On a etudie les mecanismes reactionnels de l'acetate de vinyle avec les radicaux OH de l'atmosphere en faisant appel a la theorie de la fonctionnelle de la densite. On a calcule les parametres geometriques et les frequences des points stationnaires au niveau MPWBK1K de la theorie avec des ensembles de base 6-31G(d,p). Les calculs d'energie ponctuelle ont ete faits au niveau MPWB1K/6-311+G(3df,pd). On a construit les profils detailles des surfaces d'energie potentielle des reactions. On a considere l'addition de deux OH et l'enlevement de trois H comme voies reactionnelles pour la reaction de l'acetate de vinyle avec les radicaux OH. L'etude theorique montre que l'isomere le plus favorable d'un point de vue energetique est celui correspondant a l'addition d'un OH sur les positions carbonees terminales (C1). On a pu confirmer que le rearrangement de l'[alfa]-ester, qui est caracteristique des processus d'oxydation d'ester, est le plus favorable tant d'un point de vue thermodynamique que cinetique. Les produits principaux qui resultent d'une oxydation atmospherique de l'acetate de vinyle, initiee par un radical OH, sont le formaldehyde, l'anhydride mixte de l'acide formique et acetique et l'acide acetique. Mots-cles: acetate de vinyle, radicaux OH, mecanisme reactionnel, calculs de chimie quantique., Introduction Vinyl acetate (VA) ([C[H3.sub.]C(O)OCH=C[H.sub.2]]) is a synthetic unsaturated ester and has a wide variety of industrial applications. The major use of VA is to produce polyvinyl alcohol, polyvinyl acetate, [...]

Exploration of the water body extraction model based on GF - 6 satellite images can provide new data sources and technical support for water body monitoring. First, GF - 6 WFV satellite data of Zonag Lake was used to analyze the reflectance difference between water and other ground objects in each band of GF - 6 WFV satellite data. Based on this, a novel water index named red side water index ( RSWI) was constructed. Then, the overall accuracy and Kappa coefficient generated by the confusion matrix were used to verify RSWI and the other three water extraction models, which include the single - band threshold method, normalized difference water index, and modified shade water index. FinHy, six typical lakes with different types of areas larger than 100 km" in Hoh Xil were selected for analysis of general applicability. The results showed that compared with other methods, the decision tree model composed of RSWI and NIR bands effectively eliminates the influence of lake bottom sediments on water bodies and extracts shallow water bodies more completely, with an overall accuracy of 93. 78% and a Kappa coefficient of 0.87. Additionally, it has been found that the stability and general applicability of RSWI are better than those of other water body models with respect to different types of lakes. [ABSTRACT FROM AUTHOR]

• Spectral, texture, and structural information from UAV-based multispectral image were used to estimate SPAD values in leaves of walnut. • The accuracy of SPAD values estimation model constructed by combining remote sensing indices (spectral indices (SI), texture indices (TI) and structural indices (STI) are combined in pairwise or in full) is better than that of single remote sensing indices. • XGBoost model that combines spectral, texture, and structural indices provided the highest accuracy of SPAD values estimation. An important measure to describe the physiological status of vegetation is the chlorophyll concentration of the vegetation. For managing fields in precision agriculture, monitoring walnut growth, and estimating production, accurate determination of chlorophyll content is crucial. Spectral indices play a crucial role in the non-destructive and efficient monitoring of crop physiological parameters, especially in estimating chlorophyll content. However, spectral indices have low sensitivity to high chlorophyll levels and are susceptible to interference from background signals, which may result in decreased stability of the model. The unmanned aerial vehicle (UAV) captures high-resolution images that contain abundant spatial information, including texture and structural information. These spatial information can reflect crop canopy structure, may help to improve the estimation precision of crop chlorophyll content. However, research on utilizing drone-based spatial information for estimating crop chlorophyll content is relatively limited. The aim of this study is to explore the potential of integrating spectral, textural, and structural information to improve the accuracy of walnut leaf chlorophyll content estimation. This study used a drone equipped with a multispectral camera to capture images of walnut tree canopies. Based on these images, we extracted 17 spectral indices, 8 texture indices, and 5 structural indices. Then, we applied the Boruta algorithm to select the optimal spectral, texture, and structural indices, as well as their combinations. Finally, the SPAD (Soil and plant analyzer development) values estimation model for walnut leaves was established using the Decision Tree Regression (DTR), Random Forest Regression (RFR), and Extreme Gradient Boosting (XGBoost) methods. The research findings indicate that the accuracy of SPAD values estimation model constructed by combining remote sensing indices (spectral indices (SI), texture indices (TI) and structural indices (STI) are combined in pairwise or in full) is better than that of single remote sensing indices. In the combined remote sensing indices models, the accuracy of the model constructed by the pairwise combination of three remote sensing indices is relatively limited. However, when using the combination of spectral indices, texture indices, and structural indices, the estimation accuracy of SPAD values for walnut leaves can be effectively improved, and this combination is considered the best way to estimate SPAD values. Furthermore, among the trio of SPAD values estimation models considered (namely DTR, RFR, and XGBoost), the XGBoost model exhibited superior performance. Notably, when combining SI+TI+STI in the construction of the XGBoost model, it demonstrated the highest level of accuracy in estimating SPAD values (Training: R2 T =0.95, RMSE T =1.08; Validation: R2 v = 0.72, RMSE v =2.13). The findings of this research elucidate that the incorporation of spatial information from UAV multispectral imagery facilitates the monitoring of physiological parameters in walnut trees. By integrating the spatial and spectral information of UAV multispectral imagery, a feasible and accurate estimation method has been provided for monitoring the chlorophyll content in walnut leaves. [ABSTRACT FROM AUTHOR]