检索结果-南通市图书馆

Sources of methacrolein and methyl vinyl ketone and their contributions to methylglyoxal and formaldehyde at a receptor site in Pearl River Delta

引用

Journal of Environmental Sciences 2019年第5期31卷 1-10页

作者： zhenhao Ling Zhuoran He zhe Wang min Shao Xuemei Wang School of Atmospheric Sciences Sun Yat-sen University Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen University Department of Civil and Environmental Engineering Hong Kong Polytechnic University Institute for Environmental and Climate Research Jinan University

Methacrolein(MACR) and methyl vinyl ketone(MVK) are two major intermediate products from the photochemical oxidation of isoprene, the most important biogenic volatile organic compound. In addition, MACR and MVK have primary emissions. Investigating the sources and evolution of MACR and MVK could provide helpful information for the oxidative capacity of the atmosphere. In this study, hourly measurements of isoprene, MACR, and MVK were conducted at a receptor site in the Pearl River Delta region(PRD), i.e., the Heshan site(HS), from 22 October to 20 November, 2014. The average mixing ratios of isoprene,MACR and MVK were 151 ± 17, 91 ± 6 and 79 ± 6 pptv, respectively. The daily variations and the ratios of MVK/MACR during daytime and nighttime suggested that other sources besides isoprene photooxidation influenced the MACR and MVK abundances at the *** matrix factorization was utilized to resolve the sources of MACR and MVK. Five sources were identified and quantified, including biogenic emissions, biomass burning,secondary formation, diesel, and gasoline vehicular emissions. Among them, secondary formation made the greatest contribution to observed MACR and MVK with average contributions of ～ 45% and ～ 70%, respectively. Through the yields of secondary products from the oxidation of MACR and MVK by the OH radical and the concentrations of MACR and MVK, it was found that methylglyoxal and formaldehyde were the main oxidation products of MACR and MVK at the HS site. Overall, this study evaluated the roles of primary emissions on ambient levels of MACR and MVK and advanced the understanding of photochemical oxidation of MACR and MVK in the PRD.

关键词： Source apportionment Methacrolein Methyl vinyl ketone Pearl River Delta

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysis of imbibition of n-alkanes in kerogen slits by molecular dynamics simulation for characterization of shale oil rocks

引用

Petroleum Science 2022年第3期19卷 1236-1249页

作者： Qian Sang Xin-Yi Zhao Hui-min Liu ming-zhe Dong Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao266580ShandongChina School of Petroleum Engineering China University of Petroleum(East China)Qingdao266580ShandongChina Management Center of Oil&Gas Exploration of Shengli Oilfield Branch Company SINOPECDongying257001ShandongChina Department of Chemical and Petroleum Engineering University of CalgaryCalgaryABCanadaT2N 1N4

Shale oil formations contain both inorganic and organic *** organic matter holds both free oil in the pores and dissolved oil within the kerogen *** free oil flow in organic pores and the dissolved oil diffusion in kerogen molecules are coupled *** molecular flow of free n-alkanes is an important process of shale oil accumulation and *** study the dynamics of imbibition process of n-alkane molecules into kerogen slits,molecular dynamics(MD)simulations are *** of slit width,temperature,and n-alkane types on the penetration speed,dynamic contact angle,and molecular conformations were *** showed that molecular transportation of n-alkanes is dominated by molecular structure and molecular motion at this *** space-confinement conformational changes of molecules slow down the filling speeds in the narrow *** n-alkane molecules with long carbon chains require more time to undergo conformational *** high content of short-chain alkanes and high temperature facilitate the flow of alkane mixtures in kerogen *** obtained from this study are useful for understanding the underlying nanoscale flow mechanism in shale formations.

关键词： Molecular flow Imbibition n-Alkane Kerogen slit Molecular dynamics simulation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Modulation of stem cell fate in intestinal homeostasis,injury and repair

引用

World Journal of Stem Cells 2023年第5期15卷 354-368页

作者： zhe Wang Yan-Ji Qu min Cui Department of Gastroenterology Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430022Hubei ProvinceChina Department of Otorhinolaryngology Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430022Hubei ProvinceChina Department of Orthopedics Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430022Hubei ProvinceChina

The mammalian intestinal epithelium constitutes the largest barrier against the external environment and makes flexible responses to various types of *** cells are fast-renewed to counteract constant damage and disrupted barrier function to maintain their *** homeostatic repair and regeneration of the intestinal epithelium are governed by the Lgr5+intestinal stem cells(ISCs)located at the base of crypts,which fuel rapid renewal and give rise to the different epithelial cell *** biological and physicochemical stress may challenge epithelial integrity and the function of *** field of ISCs is thus of interest for complete mucosal healing,given its relevance to diseases of intestinal injury and inflammation such as inflammatory bowel ***,we review the current understanding of the signals and mechanisms that control homeostasis and regeneration of the intestinal *** focus on recent insights into the intrinsic and extrinsic elements involved in the process of intestinal homeostasis,injury,and repair,which fine-tune the balance between self-renewal and cell fate specification in *** the regulatory machinery that modulates stem cell fate would aid in the development of novel therapeutics that facilitate mucosal healing and restore epithelial barrier function.

关键词： Intestinal stem cell Epithelial repair Homeostasis Regeneration Selfrenewal Apoptosis

来源：

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

China agricultural outlook for 2015–2024 based on China Agricultural Monitoring and Early-warning System(CAMES)

引用

Journal of Integrative Agriculture 2015年第9期14卷 1889-1902页

作者： XU Shi-wei LI Gan-qiong LI zhe-min Agricultural Information Institute Chinese Academy of Agricultural Sciences Key Laboratory of Agricultural Information Service Technology Key Laboratory of Digital Agricultural Early-warning Technology and System Chinese Academy of Agricultural Sciences

The primary goal of Chinese agricultural development is to guarantee national food security and supply of major agricultural products. Hence, the scientiifc work on agricultural monitoring and early warning as wel as agricultural outlook must be strengthened. In this study, we develop the China Agricultural Monitoring and Early-warning System (CAMES) on the basis of a comparative study of domestic and international agricultural outlook models. The system is a dynamic and multi-market partial equilibrium model that integrates biological mechanisms with economic mechanisms. This system, which includes 11 categories of 953 kinds of agricultural products, could dynamical y project agricultural market supply and demand, assess food security, and conduct scenario analysis at different spatial levels, time scale levels, and macro-micro levels. Based on the CAMES, the production, consumption, and trade of the major agricultural products in China over the next decade are projected. The fol owing conclusions are drawn:i) The production of major agricultural products wil continue to grow steadily, mainly because of the increase in yield. i ) The growth of agricultural consumption wil be slightly higher than that of agricultural production. Meanwhile, a high self-sufifciency rate is expected for cereals such as rice, wheat, and maize, with the rate being stable at around 97%. i i) Agricultural trade wil continue to thrive. The growth of soybean and milk im-ports wil slow down, but the growth of traditional agricultural exports such as vegetables and fruits is expected to continue.

关键词： agricultural outlook projection China Agricultural Monitoring and Early-warning System(CAMES) agriculture of China

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects on soil quality of biochar and straw amendment in conjunction with chemical fertilizers

引用

Journal of Integrative Agriculture 2017年第3期16卷 704-712页

作者： HE Li-li ZHONG zhe-ke YANG Hui-min Key Laboratory of High Efficient Processing of Bamboo of zhejiang Province/China National Bamboo Research Center Hangzhou 310012 P.R.China Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 P.R. China University of Chinese Academy of Sciences Beijing 100049 P.R.China

The objective of this study was to evaluate the effects on chemical and microbiological properties of paddy soil of short-term biochar,straw,and chemical fertilizers compared with chemical fertilization *** soil fertilization treatments were evaluated：regular chemical fertilizers（RF）,straw＋regular chemical fertilizers（SRF）,straw biochar＋regular chemical fertilizers（SCRF）,bamboo biochar（BC）＋regular chemical fertilizers（BCRF）,and straw biochar＋70%regular chemical fertilizers（SC＋70%RF）.Their effects were investigated after approximately 1.5 *** soil p H and cation exchange capacity（CEC）were significantly higher in biochar-treated *** soil phosphorous（P）and potassium（K）contents increased with biochar *** soil Colwell P content was significantly increased with the addition of straw biochar in the treatments of SCRF and SC＋70%*** oxygen（O）：carbon（C）ratio doubled in BC picked from the *** indicated that BC underwent a significant oxidation process in the *** denaturing gradient gel electrophoresis（DGGE）fingerprints of microbial communities differed among the *** with added biochar had higher Shannon diversity and species richness indices than soils without *** results suggest that biochar can improve soil fertility.

关键词： biochar straw amendment fertilizer nutrient soil bacteria denaturing gradient gel electrophoresis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Comparison Study on the Semiconductive and Dissolution Behaviour of 316L and Alloy 625 in Hydrochloric Acid Solution

引用

Acta Metallurgica Sinica(English Letters) 2020年第3期33卷 403-414页

作者： Zhu Wang Zi-Ru Zhang Lei Zhang zhe Feng min-Xu Lu Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China

The corrosion behaviour of 316L and Alloy 625 was investigated using cyclic polarization,electrochemical impedance spectroscopy,X-ray photoelectron spectroscopy,Auger electron spectroscopy and induced coupled plasma-optical emis sion *** results indicated that Alloy 625 showed better corrosion resistance than 316L and the prolonging immersion time could enhance corrosion resistance of the two *** passive film formed on the surface of 316L exhibited an electronic structure of p-p heterojunction,with Fe3O4 and Cr2O3 enriched in the outer and inner layers,***,Alloy 625 presented the electronic structure of n-p heterojunction dominated by the outer Fe2O3/NiFe2O4 and inner *** resulted in the opposite semiconductive properties of the passive films formed on the two *** the acid solutions,Fe and Mo suffered from selective dissolution while Cr and Ni were relatively *** corrosion rates were mainly dominated by the dissolution of *** 625 presented better corrosion resistance than 316L due to the obviously lower content of Fe and the higher content of Cr and Ni in the passive *** continuously selective dissolution of iron resulted in the increase in Cr/Fe ratio in the passive film,which was responsible for the enhancement in corrosion resistance.

关键词： Stainless steel Induced coupled plasma(ICP) Polarization X-ray photoelectron spectroscopy(XPS) Passive films

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Potential dissemination mechanism of the tetC gene in Aeromonas media from the aerobic biofilm reactor under oxytetracycline stresses

引用

Journal of Environmental Sciences 2021年第7期33卷 90-99页

作者： Yanhong Shi Yu Zhang Xiangyang Wu Hong Zhang min Yang zhe Tian School of the Environment and Safety Engineering Jiangsu UniversityZhenjiang 212013China State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China

The tet C gene has been found to be one of the most widely distributed tetracycline resistance( tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tet C-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the Pac Bio RSII sequencing approach to reveal the genetic environment of tet C. The tet C gene was carried by an IS 26 composite transposon, named Tn 6434. The tet C-carrying Tn 6434 structure was detected in all of the A. media strains either in a novel plasmid p Aeme2( n = 9) or other DNA molecules( n = 2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn 6434. Inverse PCR and sequencing confirmed that Tn 6434 can form a circular intermediate and is able to incorporate into a preexisting IS 26 element, suggesting that Tn 6434 might be responsible for the dissemination of tet C between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.

关键词： Aeromonas media tetC IS 26 Circular intermediate Inverse PCR

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Energy Efficiency Maximization Strategy for Sink Node in SWIPT-Enabled Sensor-Cloud Based on Optimal Stopping Rules

引用

China Communications 2021年第1期18卷 222-236页

作者： zhe Wang Lina Ge Taoshen Li Guifen Zhang min Wu Institute of Artificial Intelligence Guangxi University for NationalitiesNanning 530004China Guangxi Key Laboratory of Hybrid Computation and IC Design Analysis Nanning 530006China School of Computer Electronics and InformationGuangxi UniversityNanning 530006China Guangxi Power Grid Co. LtdNanning 530023China

Leveraging energy harvesting abilities in wireless network devices has emerged as an effective way to prolong the lifetime of energy constrained *** system gains are usually optimized by designing resource allocation algorithm ***,few works focus on the interaction that channel’s time-vary characters make the energy transfer *** address this,we propose a novel system operation sequence for sensor-cloud system where the Sinks provide SWIPT for sensor nodes opportunistically during downlink phase and collect the data transmitted from sensor nodes in uplink ***,the energy-efficiency maximization problem of the Sinks is presented by considering the time costs and energy consumption of channel *** is proved that the formulated problem is an optimal stopping process with optimal stopping *** optimal energy-efficiency(OEE)algorithm is designed to obtain the optimal stopping rules for ***,the simulations are performed based on the OEE algorithm compared with the other two strategies to verify the effectiveness and gains in improving the system efficiency.

关键词： sensor-cloud SWIPT optimal stopping theory energy efficiency channel quality

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

旋转流体中的二维惯性重力波-涡相互作用

引用

地球物理学报 2007年第4期50卷 1040-1052页

作者：王赟谈哲敏南京大学大气科学系中尺度灾害性天气教育部重点实验室南京210093

本文利用f-平面浅水模型讨论了二维情况下快速惯性重力波与平衡涡旋之间的相互作用问题.当快速的惯性重力波传入涡旋区域后,波-涡之间发生了相互作用,涡旋可被加深,涡旋区域的风场等可以出现非对称分布,当惯性重力波全部传出涡旋区域并... 详细信息

本文利用f-平面浅水模型讨论了二维情况下快速惯性重力波与平衡涡旋之间的相互作用问题.当快速的惯性重力波传入涡旋区域后,波-涡之间发生了相互作用,涡旋可被加深,涡旋区域的风场等可以出现非对称分布,当惯性重力波全部传出涡旋区域并远离之后,涡旋恢复到其初始状态,但此时惯性重力波可以出现非对称结构,这与一维情况不同.在波-涡发生相互作用过程中,其物理量变化的最大区域分布基本与波动传播方向一致,在波动进入或移出涡旋时,相对应存在两个最大物理量变化区域,此外,相互作用导致的物理量的最大变化与波动结构、强度、传播方向以及涡旋特性有关.非线性条件下的波-涡相互作用要强于线性过程.

关键词：惯性重力波涡旋相互作用旋转流体

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Classification of Natural Images Based on CNN-SVM and Algorithm Optimization

Classification of Natural Images Based on CNN-SVM and Algori...

引用

作者： zhe min 华中师范大学

学位级别：硕士

随着计算机技术和网络的飞速发展,图像数据库日益增多,如何从大量图像数据中快速地提取出视觉信息已成为智能视觉感知领域的研究热点。其中,如何对庞大的图像数据进行有效地分类一直都是获取图像信息领域的热门问题。至今为止,图像分类... 详细信息

随着计算机技术和网络的飞速发展,图像数据库日益增多,如何从大量图像数据中快速地提取出视觉信息已成为智能视觉感知领域的研究热点。其中,如何对庞大的图像数据进行有效地分类一直都是获取图像信息领域的热门问题。至今为止,图像分类一直遵循着如下思想:通过提取出所给的图像信息中所反映出来的图像特征,把这些图像进行归类,通过计算机对图像进行本质上的分析,将目标图像中的每个像素或者像素区域进行归类,从而代替人的视觉判断,最终达到应用于实际生活中的许多不同场景的目的。同时,图像分类在图像检索、人机交互、智能安防、视频监控、无人机平台等方面都有广阔的应用前景。然而,目前的图像分类算法仍然面临着巨大的挑战。图像分类技术是一个涉及图像处理、图像识别、算法搭建、信息统计等多个学科的重要研究方向,他能让使用者在庞大的数据中快速地筛选出想要的图像信息,能很好的运用于各种场合,节省了使用者大量的时间、精力。实现快速、准确的图像分类,不仅提高了人们的工作效率,还为一些诸如目标的检测与识别、行为分析等高级处理提供了保障。本文主要从图像分类技术、图像特征提取、特征编码技术、图像分类所使用的机器学习算法4个部分介绍目前图像分类技术的研究现状。(1)图像分类技术。目前,国内外的研究者已经研究出了许多图像分类算法,例如人工神经网络方法、支持向量机、统计方法等。Jinjun Wang和Amirreza Shaban分别在2010年和2013年提出了基于局部约束的线性特征编码和全局特征编码的图像分类算法。(2)图像特征提取。特征提取是指使用计算机提取图像信息,用一组特征向量来表示图像或者图像中某一区域,进而达到图像分类、目标检测识别的目的。2005年,Dalal和Triggs提出了HOG(Histograms of Oriented Gradients)特征描述子,其思想是通过将图像进行分块处理,较好地表示了图像中局部像素点之间的关系,同时将其与线性SVM结合运用于图像分类处理,取得了重大突破。(3)特征编码技术。2013年,Amirreza Shaban提出了局部相似性的全局编码,用高斯核方法来计算字典中两个字典元素的相似性,最终的图像特征编码结果不仅代表了特征描述子与局部字典元素之间的相似性,还表示了其与全局字典元素的相似性。(4)图像分类所使用的机器学习。传统的图像分类算法大部分是首先提取特征描述子,提取完特征后,通过有监督的学习来训练分类器,之后通过分类器来判断图像的类别。目前常用的学习算法主要有SVM、Adaboost、神经网络、随机森林等。SVM(Support Vector Machine),支持向量机的出现无疑使得机器学习的发展向前迈进了一大步,特别是在非线性高维模式识别上有明显的优势。其中心思想是将低维空间中线性不可分的问题转化到高维空间中从而变得线性可分,这个转换过程用到了核函数,其优点就是避免了维度灾难。在转化为线性可分问题后,通过找到样本之间的最大类间隔从而找到最优的分割超平面。同时,为了让分类器具有一定的容错性,避免由极少量的错误分类样本造成的不理想的分类效果,研究者们通常会在SVM中引入松弛因子。近年来,支持向量机在众多分类、识别问题中都得到了应用,最大的原因就是其在处理高维非线性问题上的明显优势。目前,许多研究者已经对SVM进行了多种改进从而使其能应用于不同的场景。而本文正是基于将目前较为热门的卷积神经网络(Convolutional Neural Network)与SVM相结合的改进后的CNN-SVM。今天,随着信息技术的不断发展,“精准林业”思想提出以后,林业立体视觉测量、林木农药精确对靶施用、基于图像的树木可视化重建、生长状态评估、树种自动识别与分类等课题被林业科研工作者提出,并在这些方面不断进行研究和探索。同时,图像分类技术在这些生态信息化管理的过程中开始被频繁使用。如何将自然图像分类为以上研究提供基础数据和技术支撑,是以上研究的重要基础和难点问题。在自然场景中拍摄的图像包含了丰富的信息,并受环境、光照、天气、噪声等干扰。因此,复杂背景下自然图像的分类的研究具有重要的实用价值和现实意义。这也是本文将要深入研究的话题。在介绍完图像分类技术的国内外研究现状后,本文对所涉及的理论基础及思想进行的介绍。首先,我们搭建了图像分类的主体框架及主要步骤。其次,我们介绍了SVM的主要思想以及不同的分类情况。在相关理论与算法的基础上,着眼于自然图像,分析了复杂背景下自然图像分类所面临的问题,提出了基于CNN-SVM的自然图像分类算法。分类器模型将传统的CNN网络与SVM分类器进行合理集成,利用CNN网络的隐藏层进行特征自动提取,同时采用分类效果更好的SVM分类器进行分类。同时考虑到CNN提取特征有可能遗漏掉部分强特征,因此本文提出了手动提取强特征,并与C

关键词：图像分类 CNN SVM 自然图像图像强特征图像抠图算法

来源：

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：