检索结果-南通市图书馆

Traveling Waves in Degenerate Diffusion Equations

在线全文

学校读者我要写书评

暂无评论

Communications in Mathematical Research 2023年第1期39卷 36-53页

作者： tianyuan xu Jingxue Yin School of Mathematics South China University of TechnologyGuangzhou 510641P.R.China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631P.R.China

In this survey,we present a literature review on the study of travel-ing waves in degenerate diffusion equations by illustrating the interesting and singular wave behavior caused by *** main results on wave exis-tence and stability are presented for the typical degenerate equations,including porous medium equations,flux limited diffusion equations,delayed degener-ate diffusion equations,and other strong degenerate diffusion equations.

关键词： Traveling waves degenerate diffusion equation existence stability

Interaction of polyhydroxy fullerenes with ferrihydrite：adsorption and aggregation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2018年第2期30卷 1-9页

作者： Jing Liu Runliang Zhu tianyuan xu Mingwang Laipan Yanping Zhu Qing Zhou Jianxi Zhu Hongping He Key Laboratory of Mineralogy and Metallogeny Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangdong Provincial Key Laboratory of Mineral Physics and Material Research & Development Guangzhou 510640 China University of Chinese Academy of Sciences Beijing 100049 China

The rapid development of nanoscience and nanotechnology, with thousands types of nanomaterials being produced, will lead to various environmental impacts. Thus,understanding the behaviors and fate of these nanomaterials is essential. This study focused on the interaction between polyhydroxy fullerenes（PHF） and ferrihydrite（Fh）, a widespread iron（oxyhydr）oxide nanomineral and geosorbent. Our results showed that PHF were effectively adsorbed by Fh. The adsorption isotherm fitted the D-R model well, with an adsorption capacity of 67.1 mg/g. The adsorption mean free energy of 10.72 k J/mol suggested that PHF were chemisorbed on Fh. An increase in the solution p H and a decrease of the Fh surface zeta potential were observed after the adsorption of PHF on Fh; moreover, increasing initial solution p H led to a reduction of adsorption. The Fourier transform infrared spectra detected a red shift of C–O stretching from 1075 to 1062 cm-1 and a decrease of Fe–O bending, implying the interaction between PHF oxygenic functional groups and Fh surface hydroxyls. On the other hand, PHF affected the aggregation and reactivity of Fh by changing its surface physicochemical properties. Aggregation of PHF and Fh with individual particle sizes increasing from 2 nm to larger than 5 nm was measured by atomic force microscopy. The uniform distribution of C and Fe suggested that the aggregates of Fh were possibly bridged by PHF. Our results indicated that the interaction between PHF and Fh could evidently influence the migration of PHF, as well as the aggregation and reactivity of Fh.

关键词： Nanoparticles Polyhydroxy fullerenes Ferrihydrite Adsorption Aggregation

Modeling potential wetland distributions in China based on geographic big data and machine learning algorithms

在线全文

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2023年第1期16卷 3706-3724页

作者： Hengxing Xiang Yanbiao Xi Dehua Mao tianyuan xu Ming Wang Fudong Yu Kaidong Feng Zongming Wang State Key Laboratory of Black Soils Conservation and Utilization Northeast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunPeople’s Republic of China International Institute for Earth System Science Nanjing UniversityNanjingPeople’s Republic of China School of Foreign Languages Zhongnan University of Economics and LawWuhanPeople’s Republic of China College of Information and Technology Jilin Agricultural UniversityChangchunPeople’s Republic of China National Earth System Science Data Center BeijingPeople’s Republic of China

Climate change and human activities have reduced the area and degraded the functions and services of wetlands in *** protect and restore wetlands,it is urgent to predict the spatial distribution of potential *** this study,the distribution of potential wetlands in China was simulated by integrating the advantages of Google Earth Engine with geographic big data and machine learning *** on a potential wetland database with 46,000 samples and an indicator system of 30 hydrologic,soil,vegetation,and topographic factors,a simulation model was constructed by machine learning *** accuracy of the random forest model for simulating the distribution of potential wetlands in China was good,with an area under the receiver operating characteristic curve value of *** area of potential wetlands was 332,702 km^(2),with 39.0%of potential wetlands in Northeast *** features were notable,and potential wetlands were mainly concentrated in areas with 400-600 mm precipitation,semi-hydric and hydric soils,meadow and marsh vegetation,altitude less than 700 m,and slope less than 3°.The results provide an important reference for wetland remote sensing mapping and a scientific basis for wetland management in China.

关键词： Potential wetland distribution machine learning algorithms geographic big data China wetland geographic features

Analysis of Epidemic Prevention Strategies of Omicron Variant Abroad

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Agricultural Biotechnology 2023年第1期12卷 53-54,60页

作者： Danling QIN Qian SHI xuetong ZHU Xijuan xu tianyuan xu Guizhou Academy of Testing and Analysis Guiyang 550000China Guizhou Electronic Certificate Co. Ltd.Guiyang 550081China

Omicron variant was first found in Botswana, southern Africa, on November 9, 2021. The variant has many mutations and spreads quickly. It also has immune escape to existing COVID-19 vaccines, and the infection rate and repeated infection rate have increased worldwide. For such variant, at this stage, foreign countries mainly adopt three strategies to prevent and control the epidemic. First, big data is used to track the potential infection of the epidemic, trace the spread of the epidemic, screen close contacts, and control the scope of infection. The second is to maximum the coverage rate of vaccination, especially the coverage rate of the third injection, so as to reduce the infection level of Omicron variant. At last, they are developing a general coronavirus vaccine to prevent infection caused by SARS-CoV-2 variants, including the Omicron variant, so as to fundamentally eliminate the potential threat of variants to human beings. In this paper, three major epidemic prevention strategies of Omicron variant abroad were summarized in detail.

关键词： Omicron mutant Novel coronavirus pneumonia Epidemic prevention strategy

高填方双层衬砌式明洞土压力和结构内力特性研究

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

铁道学报 2019年第2期41卷 146-153页

作者：徐湉源王明年于丽西南交通大学交通隧道工程教育部重点实验室四川成都610031

采用现场测试和数值分析方法对高填方双层衬砌明洞的土压力和结构内力进行研究,分析明洞上方和两侧土体的沉降差分布,结果表明:明洞垂直土压力系数在回填过程中先增大再减小最后趋于稳定,明洞上方与两侧土体沉降差使其土压力值高于土体... 详细信息

采用现场测试和数值分析方法对高填方双层衬砌明洞的土压力和结构内力进行研究,分析明洞上方和两侧土体的沉降差分布,结果表明:明洞垂直土压力系数在回填过程中先增大再减小最后趋于稳定,明洞上方与两侧土体沉降差使其土压力值高于土体自重;在相同的填方高度下,基础刚度对明洞荷载有较大影响,混凝土大坝基础明洞的土压力系数可达基岩基础明洞的1.5倍以上,内外侧土柱沉降差前者达到后者的6倍。在回填土达到拱顶前,衬砌结构内力变化缓慢,回填土达到拱顶后结构内力线性增大,且混凝土大坝基础明洞轴力值达到基岩基础明洞的1.2～1.6倍,弯矩值则为1.6～2.4倍;此外,外层和内层衬砌的轴力比与二者的厚度比基本一致,轴力分配与组合梁类似。

关键词：高填方明洞双层衬砌土压力系数结构内力明洞基础沉降差

考虑基础刚度的新型高填方双层衬砌式明洞的动态力学特性

在线全文

学校读者我要写书评

暂无评论

中国铁道科学 2017年第1期38卷 68-76页

作者：王明年徐湉源于丽罗勇西南交通大学土木工程学院四川成都610031 西南交通大学交通隧道工程教育部重点实验室四川成都610031

为解决高填方明洞整体式衬砌过厚导致的水化热裂缝问题,在渝利铁路重庆丰都高填方明洞工程中首次采用双层衬砌设计,通过现场实测及数值模拟2种方法分析该新型结构的动态力学特性。结果表明:在回填土达到明洞顶部前,即仅有侧向荷载时,明... 详细信息

为解决高填方明洞整体式衬砌过厚导致的水化热裂缝问题,在渝利铁路重庆丰都高填方明洞工程中首次采用双层衬砌设计,通过现场实测及数值模拟2种方法分析该新型结构的动态力学特性。结果表明:在回填土达到明洞顶部前,即仅有侧向荷载时,明洞结构的内力增量很小,在回填高度超过明洞顶部后,明洞的内力则随回填高度的增加而线性增长;双层衬砌明洞的外衬和内衬的轴力之比接近二者的厚度之比,而二者的弯矩之比则无类似规律,二者的相互作用方式与组合梁类似;采用混凝土坝基础时一定程度上增大明洞的荷载,其上明洞的轴力和弯矩分别为软岩基础上明洞的1.2~1.6倍和1.6~2.4倍;明洞拉应力集中现象主要出现在边墙位置。建议对混凝土坝基础上的明洞采取减载和优化边墙结构措施。

关键词：高填方明洞双层衬砌动态力学特性软岩基础混凝土坝基础

在线全文

学校读者我要写书评

暂无评论

焦粉高效活化过硫酸盐对苯胺的降解性能

化工进展 2022年第6期41卷 3314-3323页

作者：徐天缘郑茜王连娟陈婷魏鑫鹏中国矿业大学资源与地球科学学院江苏徐州221116 中国矿业大学国家煤加工与洁净化工程技术研究中心江苏徐州221116

焦粉作为焦化/煤化企业的低附加值副产物,用作污染控制材料是其高价值应用的一条重要途径。本文对焦粉形貌与成分进行表征分析,通过苯胺降解动力学和影响因素之间的交互作用评估焦粉活化过硫酸盐的催化性能,并初步探讨了相关机理。表征... 详细信息

焦粉作为焦化/煤化企业的低附加值副产物,用作污染控制材料是其高价值应用的一条重要途径。本文对焦粉形貌与成分进行表征分析,通过苯胺降解动力学和影响因素之间的交互作用评估焦粉活化过硫酸盐的催化性能,并初步探讨了相关机理。表征结果显示焦粉表面粗糙,有清晰的孔隙。活性测试结果显示,1g/L焦粉可以高效活化5mmol/L过硫酸盐降解20mg/L苯胺,反应120min后苯胺去除率高于99%,其中灰分对苯胺降解无贡献。增加焦粉剂量和过硫酸盐浓度均可提高苯胺的降解效率。焦粉在pH 3~11范围内均可高效活化过硫酸盐降解苯胺,去除率维持在83%以上。此外,焦粉具有应用于修复复杂水体中有机污染物的潜能,在Cl^(-)、HCO^(-)_(3)和SO^(2)_(4)-干扰下,体系中苯胺去除率维持在90%以上。响应曲面分析表明,焦粉可以高效活化过硫酸盐降解苯胺,且焦粉剂量与过硫酸钠浓度的交互作用强,二者决定了苯胺的最终去除率。自由基淬灭实验证明焦粉活化过硫酸盐降解苯胺过程中,主要产生的活性氧物种为O_(2)·-和·OH。本文的研究结果可为低附加值的煤基副产物高价值应用提供指导,并为进一步发展环境友好的水污染控制与资源化技术提供新契机。

关键词：焦粉焦化废水污染控制活化过硫酸盐

维普期刊数据库博看期刊

草酸与铁氧化物相互作用及光化学活化分子氧过程的研究进展

在线全文

学校读者我要写书评

暂无评论

环境化学 2024年第2期43卷 405-415页

作者：陈婷陈振华徐天缘中国矿业大学国家煤加工与洁净化工程技术研究中心徐州221116 中国矿业大学资源与地球科学学院徐州221116

草酸与铁氧化物共存于自然环境中,二者之间的相互作用及光化学行为强烈影响着分子氧的活化.而分子氧活化影响共存体系中污染物的迁移与转化,是发展绿色污染控制氧化技术的关键.因此,探讨草酸与铁氧化物之间的相互作用与光化学活化分子... 详细信息

草酸与铁氧化物共存于自然环境中,二者之间的相互作用及光化学行为强烈影响着分子氧的活化.而分子氧活化影响共存体系中污染物的迁移与转化,是发展绿色污染控制氧化技术的关键.因此,探讨草酸与铁氧化物之间的相互作用与光化学活化分子氧是目前的研究热点之一.本文系统总结了近年来围绕草酸与铁氧化物相互作用以及草酸诱导铁氧化物活化分子氧的研究成果,论述了草酸在铁氧化表面的吸附与转化特性、草酸铁络合物光化学过程以及活性氧产生与转移途径,同时探讨了上述过程对环境污染物降解的影响,借此加深理解草酸诱导铁氧化物环境光化学行为与活化分子氧原理,并对今后的研究发展方向提出了展望,以期为利用天然铁氧化物和有机质发展原位环境修复技术提供依据.

关键词：草酸铁氧化物光化学活化分子氧光降解草酸铁络合物

基于分类-回归卷积神经网络的新能源电力系统可靠性评估方法

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

中国电机工程学报 2024年第23期44卷 9134-9144,I0002页

作者：邵成成任孟极徐天元钱涛王锡凡西安交通大学电气工程学院陕西省西安市710049

Monte Carlo模拟(Monte Carlo simulation,MCS)在复杂电力系统可靠性评估中广泛应用,但计算效率较低。针对此,该文提出一种基于卷积神经网络(conventional neural network,CNN)的可靠性评估方法,在时序MCS框架下采用CNN加速系统状态评... 详细信息

Monte Carlo模拟(Monte Carlo simulation,MCS)在复杂电力系统可靠性评估中广泛应用,但计算效率较低。针对此,该文提出一种基于卷积神经网络(conventional neural network,CNN)的可靠性评估方法,在时序MCS框架下采用CNN加速系统状态评估计算。首先,构造反映系统运行状态的特征向量,建立基于CNN的系统失负荷量回归模型;其次,针对可靠性评估样本不均衡、回归训练效率低的问题,进一步建立系统状态分类器,形成基于CNN的分类-回归模型;此外,针对CNN训练样本和实际评估样本不一致的问题,提出分类结果矫正机制,进一步提升模型的实用性;最后,通过改编IEEE-RTS系统的计算分析验证了所提方法的有效性和优越性。

关键词：卷积神经网络可靠性评估分类-回归数据驱动

维普期刊数据库博看期刊

同方期刊数据库