摘要：
For the comprehensive utilization of antimony smelting arsenic-alkali residue, there are some problems such as the incomplete separation and low recoveries of arsenic and alkali, and the formation of arsenic-alkali mixed salts with secondary pollution. In order to solve these problems, the leaching solution of arsenic-alkali residue (arsenic-alkali solution) was used as a raw material in this study, and a novel process of twice alkali recovery with CO2, deep alkali removal with H2SO4, As(V) reduction with SO2 and evaporation concentration to recover arsenic was proposed to dispose of the arsenic-alkali solution. The total recovery of alkali was 87.8% by twice alkali recovery from the arsenic-alkali solution. After washing and thermal decomposition of crude NaHCO3, the obtained Na2CO3 product can be used as the reagent of arsenic removal in the refining process of crude antimony. In the process of deep alkali removal, compared with the direct treatment, the consumption of H2SO4 after twice alkali recovery was markedly reduced from the arsenic-alkali solution, and also no mirabilite was precipitated. The total recovery of arsenic was 80.6% in the process of arsenic recovery, and the purity of As2O3 in arsenic trioxide product reached 95.2% after washing, which meets the third grade standard of arsenic trioxide (GB 26721–2011). This process realizes the efficient separation and recovery of arsenic and alkali from the arsenic-alkali solution, and also no arsenic-alkali mixed salts are produced.
摘要：
Copper nanowires (CuNWs) are a key building block to facilitate carrier conduction across a broad range of nanodevices. For integration into nanoscale devices, manipulation and welding of these nanowires need to be overcome. Based on high energy density laser processing investigation, we report on innovative welding of single CuNWs to a silver film using a tightly focused laser beam combined with manipulation of CuNWs through the dielectrophoresis (DEP) method. Two types of lasers, femtosecond (FS) and continuous-wave (CW), were employed to analyze, improve, and control Cu-NW melting characteristics under high energy density irradiation. The FS laser welding of CuNWs resulted in a metallic joint with a low contact resistance suitable for functional electronic nanodevices. Computational simulations using the 1-D heat diffusion equation and finite difference method (FDM) were performed to gain an insight into metal-laser interactions for high performance welded contact development. Simulation studies on lasers established contrasting melting behavior of metal under laser irradiation. The device feasibility of CuNW based welded contacts was evaluated in terms of the electrical performance of a glucose sensor. It was possible to sense glucose concentration down to 10(-6) M, demonstrating a path towards integration of CuNWs into wearable, flexible nanoelectronic devices.
摘要：
Multi-term time-fractional partial differential equations (PDEs) have become a hot topic in the field of mathematical physics and are used to improve the modeling accuracy in the description of anomalous diffusion processes compared to the single-term PDE results. This research includes the numerical solutions of two-term time-fractional PDE models using an efficient and accurate local meshless method. Due to the advantages of the meshless nature and ease of applicability in higher dimensions, the demand for meshless techniques is increasing. This approach approximates the solution on a uniform or scattered set of nodes, resulting in well-conditioned and sparse coefficient matrices. Numerical tests are performed to demonstrate the efficacy and accuracy of the proposed local meshless technique.
摘要：
In this work, iron-manganese binary oxides (FMO) modified with different proportions of glucose addition (FMOCx) by co-precipitation method showed good activity in activating hydrogen peroxide (H2O2) for tetracycline degradation. The structure and surface characterizations of the FMO and FMOCx were measured by XRD, FTIR, TEM, BET and XPS. With increased glucose addition, FMOCx has more surface functional groups such as -OH and -COOH, particle size decreases, surface area gradually increases, and the ratio of high valence iron and manganese also increases. In addition, the glucose might be oxidized by KMnO4 to form amorphous carbon on the catalyst surface. Glucose modified iron-manganese binary oxides FMOC3 (with 0.003 mol glucose added) showed the highest efficiency removal capability for tetracycline up to 85%, which attribute to it has a larger surface area, more surface functional groups and higher surface active Mn(IV) site content. The results also demonstrated that FMOC3 could efficiently activate hydrogen peroxide. This study proves that glucose modified iron-manganese binary oxides (FMOCx) can offered a possibility of degradation of refractory organic pollutants as an environmentally friendly catalyst in the absence of H2O2 or not. (C) 2020 Elsevier Inc. All rights reserved.
摘要：
An esterification and amination of benzylic C-H bonds was developed by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under metal- and iodide-free conditions. Both carboxylic acids and amines could be used as ideal coupling partners for the oxidative coupling reactions with various diarylmethanes. A close to equal amount of coupling reagents was enough to afford the product in good to high yields.
作者机构：
[Liu, Hean] Hunan City Univ, Coll Sci, Yiyang 413000, Hunan, Peoples R China.;[Liu, Hean; Ki, Kim Yong] Sehan Univ, Grad Sch, Mokpo 58613, South Korea.
通讯机构：
[Liu, Hean] H;Hunan City Univ, Coll Sci, Yiyang 413000, Hunan, Peoples R China.
期刊：
Journal of Chromatography A,2020年1618:460905 ISSN：0021-9673
通讯作者：
Zhang, Xiao-Hua;Liu, Zhi
作者机构：
[Zhang, Xiao-Hua; Mu, Shu-Ting; Zhou, Qian; Liu, Pan-Hua; Zheng, Jing-Jing] Xuchang Univ, Food & Bioengn Coll, Key Lab Biomarker Based Rapid Detect Technol Food, Xuchang 461000, Peoples R China.;[Liu, Zhi] Zhejiang Acad Agr Sci, State Key Lab Managing Biot & Chem Threats Qual &, Inst Qual & Stand Agr Prod, Hangzhou 310021, Peoples R China.;[Qing, Xiang-Dong] Hunan City Univ, Coll Mat & Chem Engn, Hunan Prov Key Lab Dark Tea & Jin Hua, Yiyang 413049, Peoples R China.
通讯机构：
[Zhang, Xiao-Hua] X;[Liu, Zhi] Z;Xuchang Univ, Food & Bioengn Coll, Key Lab Biomarker Based Rapid Detect Technol Food, Xuchang 461000, Peoples R China.;Zhejiang Acad Agr Sci, State Key Lab Managing Biot & Chem Threats Qual &, Inst Qual & Stand Agr Prod, Hangzhou 310021, Peoples R China.
关键词：
Analysis of tea polyphenols;HPLC-DAD;Second-order advantage;Second-order multivariate methods;Time drift calibration
摘要：
Retention time shifts in second-order calibration-assisted chromatographic analysis seriously impact the modeling and quantitative accuracies in complex systems. In this work, three second-order methods, i.e. alternating trilinear decomposition (ATLD) algorithm, multivariate curve resolution-alternating least squares (MCR-ALS), alternating trilinear decomposition-assisted multivariate curve resolution (ATLD-MCR), were compared their performance to process liquid chromatographic data in the presence of retention time shifts and overlapped peaks. Firstly, the validation samples contain five tea polyphenols at three concentrate levels within the calibration ranges, helped to understand, visualize and interpret these features of three second-order multivariate methods. Secondly, experimental data were studied concerning the determination of polyphenols in Chinese tea samples by HPLC-DAD. The results showed that all three second-order multivariate methods realized satisfactory quantification for five targeted analytes in Pu-Er ripe tea samples and Green tea samples even with the interference of slight retention time shifts, average recoveries were 91.23% -113.16% for ATLD, 89.96%-115.96% for ATLD-MCR, 90.64%-117.60% for MCR-ALS, respectively. However, ATLD was disappointing in the case of larger time shifts (approx. 4.00 s and 6.40 s) occurring for the quantitative analysis of Black tea and Clinacanthus nutans tea, the average recoveries were just 67.33-84.05%. Relatively, MCR-ALS and ATLD-MCR were more significantly excellent, satisfactory results still can be obtained, the average recoveries for MCR-ALS and ATLD-MCR were in the range of 86.04-117.60% and 89.96-115.96%, respectively. (C) 2020 Elsevier B.V. All rights reserved.
关键词：
Mining and manufacturing;Rock weathering;Fertilizer and pesticide use;Principal component analysis;Mixed metal pollution;Surface water pollution
摘要：
This study collected past sampling data on total concentrations of 12 heavy metals (Cd, Pb, Cr, Hg, Zn, Cu, Ni, Al, Fe, Mn, As, and Co) in surface water bodies, i.e., 168 rivers and 71 lakes, from 1972 to 2017. The intent was to investigate the levels and sources of heavy metal pollution across five decades and five continents. Mean heavy metal concentrations in global river and lake water, and the number of heavy metals with concentrations greater than the published threshold limits as per the standards of both the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA) were generally lower in the 1970s and 1980s than in the 1990s, 2000s, and 2010s. Over time, heavy metal pollution in surface water has changed from single metal pollution to mixed metal pollution. Heavy metal concentrations in water, and the number of heavy metals with concentrations above the threshold limits for both WHO and USEPA standards were lower in the developed countries of Europe and North America, and higher in the developing countries of Africa, Asia, and South America. Over time, the main sources of metal pollution have changed from mining and manufacturing to rock weathering and waste discharge. The main metal sources differed across the five continents, with fertilizer and pesticide use, along with rock weathering, being dominant in Africa. Mining and manufacturing, along with rock weathering, were dominant in Asia and Europe. Mining and manufacturing, along with fertilizer and pesticide use, were dominant sources in North America, while four sources (mining and manufacturing, fertilizer and pesticide use, rock weathering, and waste discharge) were responsible for the majority of heavy metal pollution in the river and lake water bodies of South America. Additionally, implementing rigorous standards on metal emissions and recycling metals from wastewater are effective for controlling heavy metal source pollution. (C) 2020 The Authors. Published by Elsevier B.V.
作者机构：
Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang, China;[Tang, Yongjian] Sichuan Civil-Military Integration Institute, Mianyang, China;[Wu, Xuanguang; Huang, Zhen] School of National Defense Science and Technology, Southwest University of Science and Technology, Mianyang, China;[Yi, Yougen] College of Physics and Electronics, Central South University, Changsha, China;[Zhang, Guangfu] School of Communication and Electronic Engineering, Hunan City University, Yiyang, China
通讯机构：
[Zao Yi] J;[Guangfu Zhang] S;Joint Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang, China<&wdkj&>Sichuan Civil-Military Integration Institute, Mianyang, China<&wdkj&>School of Communication and Electronic Engineering, Hunan City University, Yiyang, China
作者：
Wang Song;Zhao Yunlin;Xu Zhenggang*;Yang Guiyan;Huang Tian;...
期刊：
Open Geosciences,2020年12(1):626-636 ISSN：2391-5447
通讯作者：
Xu Zhenggang
作者机构：
[Yang Guiyan; Xu Zhenggang; Zhao Yunlin; Wang Song] Cent South Univ Forestry & Technol, Key Lab Forestry Remote Sensing Based Big Data &, Changsha 410004, Hunan, Peoples R China.;[Xu Zhenggang] Northwest A&F Univ, Coll Forestry, Yangling 712100, Shaanxi, Peoples R China.;[Ma Nan; Wang Song; Huang Tian] Hunan City Univ, Hunan Urban & Rural Ecol Planning & Restorat Engn, Yiyang 413000, Hunan, Peoples R China.
通讯机构：
[Xu Zhenggang] C;[Xu Zhenggang] N;Cent South Univ Forestry & Technol, Key Lab Forestry Remote Sensing Based Big Data &, Changsha 410004, Hunan, Peoples R China.;Northwest A&F Univ, Coll Forestry, Yangling 712100, Shaanxi, Peoples R China.
关键词：
county scale;CA-Markov model;landscape indices;correlation analysis
摘要：
Understanding and modeling of land use change is of great significance to environmental protection and land use planning. The cellular automata-Markov chain (CA-Markov) model is a powerful tool to predict the change of land use, and the prediction accuracy is limited by many factors. To explore the impact of land use and socio-economic factors on the prediction of CA-Markov model on county scale, this paper uses the CA-Markov model to simulate the land use of Anren County in 2016, based on the land use of 1996 and 2006. Then, the correlation between the land use, socio-economic data and the prediction accuracy was analyzed. The results show that Shannon’s evenness index and population density having an important impact on the accuracy of model predictions, negatively correlate with kappa coefficient. The research not only provides a reference for correct use of the model but also helps us to understand the driving mechanism of landscape changes.
关键词：
cognitive radio networks;flow-adaptive spectrum leasing;channel aggregating
摘要：
Cognitive radio networks (CRNs), which allow secondary users (SUs) to dynamically access a network without affecting the primary users (PUs), have been widely regarded as an effective approach to mitigate the shortage of spectrum resources and the inefficiency of spectrum utilization. However, the SUs suffer from frequent spectrum handoffs and transmission limitations. In this paper, considering the quality of service (QoS) requirements of PUs and SUs, we propose a novel dynamic flow-adaptive spectrum leasing with channel aggregation. Specifically, we design an adaptive leasing algorithm, which adaptively adjusts the portion of leased channels based on the number of ongoing and buffered PU flows. Furthermore, in the leased spectrum band, the SU flows with access priority employ dynamic spectrum access of channel aggregation, which enables one flow to occupy multiple channels for transmission in a dynamically changing environment. For performance evaluation, the continuous time Markov chain (CTMC) is developed to model our proposed strategy and conduct theoretical analyses. Numerical results demonstrate that the proposed strategy effectively improves the spectrum utilization and network capacity, while significantly reducing the forced termination probability and blocking probability of SU flows.
