基于时序多光谱影像的干旱草原区开采扰动信息提取方法

露天开采会彻底改变原有土地利用景观格局,直接破坏当地生态环境,甚至会影响附近居民的生产和生活,因此越来越多的学者开始关注开采扰动。先前有关利用时序多光谱影像提取开采扰动的研究区集中于扰动形式单一的森林区。而我国露天煤矿大多集中于草原区,且我国东北部的草原矿区因其脆弱的生态环境以及其他多种扰动形式的存在,使得开采扰动识别更加困难。为明确我国东北部生态脆弱区草原露采场的开采扰动,以胜利矿区为例,利用1986年-2017年27期Landsat多光谱遥感影像,基于归一化植被指数NDVI（normalized difference vegetation index）的长时间序列轨迹变化特征（为了去除物候、云和阴影等对时序多光谱影像的影响,利用BISE-WT滤波器对原始NDVI时间序列进行滤波处理, 有效地去除时序NDVI数据中的噪声并同时保留有效信息）,经过样本点训练,获得CV阈值（变异系数coefficient of variation）和Max阈值（植被阈值）,构建CV-Max扰动识别模型,提取研究区的扰动分布。并利用植被阈值,分析NDVI时序轨迹,获得扰动年际信息,重构扰动历史地图;进而通过分析研究区典型地物的光谱特征,构建裸煤提取规则,以此来提取研究区的裸煤分布;最后通过构建裸煤及扰动区两者间的拓扑关系,进行空间拓扑叠置分析,从而获得开采扰动信息。经过精度验证,开采扰动的提取精度达到93.17%（Kappa系数=0.85）,扰动年际信息提取精度达到83.35%（Kappa系数=0.81）。结果表明：在研究期间,空间上,开采扰动面积占研究区总面积的8.90%;时间上,开采扰动的发生集中于2000年-2009年,期间开采扰动像元占开采扰动总像元的76.70%;1988年-1998年矿区属于土地损毁初始期,2000年-2005年矿区属于土地损毁加速期,2006年-2009年矿区属于土地损毁高峰期,2010年-2017年开采扰动像元占比趋势比较平缓且持续处于较低水平,矿区土地损毁范围基本稳定。所提出的针对我国东北部生态脆弱性草原矿区,基于时序多光谱影像,利用植被指数NDVI和裸煤光谱特征提取开采扰动信息的方法是可行的,该研究结果可为干旱、半干旱草原露天矿区的可持续发展提供数据和理论方法支撑。     

Uncertainty Relations Based on Modified Wigner-Yanase-Dyson Skew Information

Uncertainty relation is a core issue in quantum mechanics and quantum information theory. We introduce modified generalized Wigner-Yanase-Dyson (MGWYD) skew information and modified weighted generalized Wigner-Yanase-Dyson (MWGWYD) skew information, and establish new uncertainty relations in terms of the MGWYD skew information and MWGWYD skew information.

     

Hexagonal La2O3 Nanocrystals Chemically Coupled with Nitrogen-Doped Porous Carbon as Efficient Catalysts for the Oxygen Reduction Reaction

The construction of nano-scale hybrid materials with a smart interfacial structure, established by using rare earth oxides and carbon as building blocks, is essential for the development of economical and efficient catalysts for oxygen reduction reactions (ORRs). In this work, hexagonal La₂O₃ nanocrystals on a nitrogen-doped porous carbon (NPC) derived from crop radish, served as building bricks, are prepared by chemical precipitation and then calcination at elevated temperatures. The obtained La₂O₃/NPC hybrid exhibits a very high ORR activity with a half-wave potential of 0.90 V, exceeding that of commercial Pt/C (0.83 V). Both DFT theoretical and experimental results have verified that the significantly enhanced catalytic performance is ascribed to the formation of the C−O−La covalent bonds between carbon and La₂O₃. Through the covalent bonds, electrons can transfer from the carbon to La₂O₃ and occupy the unfilled e_g orbital of the La₂O₃ phase. This results in the accelerated adsorption of active oxygen and the facilitated desorption of the surface hydroxides (OH_ad⁻), thereby promoting the ORR over the catalyst.     

Tests for p-regression Coefficients in Linear Panel Model When p is Divergent

Acta Mathematicae Applicatae Sinica, English Series - This paper evaluates the performance of the FW-test for testing part of p-regression coefficients in linear panel data model when p is...     

Investigation of unstable motion characteristics of vacuum arc cathode spots between transverse magnetic field contacts

With the improvement of the current level of power grids, the requirements of the opening level of the vacuum switches are also increasing. Vacuum arc cathode spots provide steam and electrons and, to a certain extent, determine the opening capacity of the vacuum switch. In this paper, a vacuum arc cathode spot research platform based on the de-mountable vacuum chamber is constructed. The characteristics of the vacuum arc cathode spots under the transverse magnetic field (TMF) contacts are assessed by a high-speed charge coupled device. The experimental results show that the cathode spot diffusion process can be divided into three processes through cathode spot distribution, arc voltage and current: initial diffusion stage of cathode spots, unstable motion stage of cathode spots, and extinguishing stage. The motion mode of cathode spots during unstable motion stage can be divided into cathode spots group stagnation (CSGS) to multi-cathode jet (MCJ) switch mode, cathode spots group motion (CSGM) to MCJ switch mode, CSGM mode, and MCJ mode. The effects of peak current and contact diameter on unstable motion mode were analysed.     

蓝宝石冲击消光晶向效应的第一性原理

蓝宝石的冲击消光现象是高压领域中的研究热点.低压段(86 GPa范围内)的实验研究表明蓝宝石的冲击消光与晶向相关,但在高压段(压力范围:131255 GPa)是否也具有晶向相关性目前尚不清楚.为此,利用第一性原理方法,分别计算了八个不同晶向的蓝宝石理想晶体和含氧离子空位缺陷晶体在高压段的光吸收性质,结果发现:1)蓝宝石在高压段的冲击消光表现出明显的晶向效应,且该效应还随压力增大而增强;一步的数据分析可以看出,在冲击实验采用的波段内,a晶向的消光最弱(透明性最好),c晶向的消光最强与c晶向的消光接近,g晶向的消光要弱于s晶向的消光.鉴于此,如果在高压段开展加窗冲击波实验,建议选择a晶向或m晶向的蓝宝石作为其光学窗口.本文结果不仅有助于深入地认识蓝宝石在极端条件下的光学性质,而且对未来的实验研究有重要的参考作用.     

An efficient synthesis of 9-anthrone lactone derivatives via the Knoevenagel condensation and intramolecular cyclization

One-step synthesis of 9-anthrone lactone derivatives from 1-acetyloxyanthraquinone with a variety of dicarbonyl substrates in the presence of K₂CO₃ by Knovenagel condensation and intramolecular cyclization is developed. Possible reaction mechanisms have been investigated using the density functional theory (DFT), which has been widely used in the study of reaction mechanism. The strategy could be useful for the synthesis of the core structure of marine natural product aspergiolide.     

In Vitro Light-Up Visualization of a Subunit-Specific Enzyme by an AIE Probe via Restriction of Single Molecular Motion

Enzymes contain several subunits to maintain different biological functions. However, it remains a great challenge for specific discrimination of one subunit over another. Toward this end, the fluorescent probe TPEMA is now presented for highly specific detection of the B subunit of cytosolic creatine (CK) kinase isoenzyme (CK-B). Owing to its aggregation-induced emission property, TPEMA shows highly boosted emission toward CK-B with a fast response time and very low interference from other analytes, including the M subunit of CK (CK-M). With the aid of a Job plot assay, ITC assay and molecular dynamics simulation, it was directly confirmed that the remarkably enhanced fluorescence of TPEMA in the presence of CK-B results from the restriction of single molecular motion in the cavity. Selective wash-free fluorescence imaging of CK-B in macrophages under different treatments was successfully demonstrated.     

Freeze–Thaw-Promoted Fabrication of Clean and Hierarchically Structured Noble-Metal Aerogels for Electrocatalysis and Photoelectrocatalysis

Noble-metal aerogels (NMAs) have drawn increasing attention because of their self-supported conductive networks, high surface areas, and numerous optically/catalytically active sites, enabling their impressive performance in diverse fields. However, the fabrication methods suffer from tedious procedures, long preparation times, unavoidable impurities, and uncontrolled multiscale structures, discouraging their developments. By utilizing the self-healing properties of noble-metal aggregates, the freezing-promoted salting-out behavior, and the ice-templating effect, a freeze–thaw method is crafted that is capable of preparing various hierarchically structured noble-metal gels within one day without extra additives. In light of their cleanliness, the multi-scale structures, and combined catalytic/optical properties, the electrocatalytic and photoelectrocatalytic performance of NMAs are demonstrated, which surpasses that of commercial noble-metal catalysts.