检索结果-南通市图书馆

Impaired cellulose decomposition in a headwater stream receiving subsurface agricultural drainage

Ecological Processes 2022年第1期11卷 845-861页

作者： Rebecca Poisson Adam G.Yates Department of Geography Western UniversityLondonONCanada Department of Biology University of WaterlooWaterloo University200 University Avenue WestWaterlooON N2L 3G1Canada

Background:Agricultural development of former wetlands has resulted in many headwater streams being sourced by subsurface agricultural drainage systems.Subsurface drainage inputs can significantly influence stream environmental conditions,such as temperature,hydrology,and water chemistry,that drive ecological function.However,ecological assessments of subsurface drainage impacts are rare.We assessed the impact of an agricultural drainage system on cellulose decomposition and benthic respiration using a paired stream study in a headwater branch of Nissouri Creek,in Ontario,Canada.Adjacent first order segments sourced by a spring-fed marsh and a cropped field with subsurface drainage,as well as the adjoining trunk segment,were sampled over a year using the cotton strip assay to measure cellulose decomposition and benthic respiration.Results:Assessments of cellulose decomposition revealed a one-third reduction in the drainage-sourced segment compared to marsh-sourced segment.Between segment differences in cellulose decomposition were associated with reduced summer temperatures in the drainage-sourced segment.Impacts of stream cooling from the drainage-sourced segment were transmitted downstream as cellulose decomposition was slower than expected throughout the drainage-sourced segment and for several hundred meters down the adjoining trunk segment.Benthic respiration only differed between the drainage-and marsh-sourced segments in spring,when stream temperatures were similar.Conclusions:Our findings suggest there may be a widespread reduction in cellulose decomposition in streams across similar agricultural regions where subsurface drainage is prevalent.However,cooling of streams receiving significant amounts of water inputs from subsurface drainage systems may impart increased resiliency to future climate warming.

关键词： stream Agriculture Cotton strip assay Seasonality Organic matter breakdown Benthic respiration

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

Fashion Victims

引用

China Weekly 2024年第2期 40-44页

作者： Meng Qian Xie Ying 不详

Wholesale markets are taking a hit from livestream sales.Vendors and market bosses are scrambling to stay competitive,while others say they need to embrace the inevitable online future。

关键词： competitive market stream

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

A United Framework for Large-Scale Resource Description Framework stream Processing

引用

Journal of Computer Science & Technology 2019年第4期34卷 762-774页

作者： Hong Fang Bo Zhao Xiao-Wang Zhang Xuan-Xing Yang College of Arts and Sciences Shanghai Polytechnic UniversityShanghai 201209China College of Intelligence and Computing Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Cognitive Computing and Application Tianjin 300350China

Resource description framework(RDF)stream is useful to model spatio-temporal data.In this paper,we propose a framework for large-scale RDF stream processing,LRSP,to process general continuous queries over large-scale RDF streams.Firstly,we propose a formalization(named CT-SPARQL)to represent the general continuous queries in a unified,unambiguous way.Secondly,based on our formalization we propose LRSP to process continuous queries in a common white-box way by separating RDF stream processing,query parsing,and query execution.Finally,we implement and evaluate LRSP with those popular continuous query engines on some benchmark datasets and real-world datasets.Due to the architecture of LRSP,many efficient query engines(including centralized and distributed engines)for RDF can be directly employed to process continuous queries.The experimental results show that LRSP has a higher performance,specially,in processing large-scale real-world data.

关键词： resource description framework(RDF)stream continuous query united framework stream processing large-scale RDF stream processing(LRSP)

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

A Classifier Using Online Bagging Ensemble Method for Big Data stream Learning

引用

Tsinghua Science and Technology 2019年第4期24卷 379-388页

作者： Yanxia Lv Sancheng Peng Ying Yuan Cong Wang Pengfei Yin Jiemin Liu Cuirong Wang School of Computer Science and Engineering Northeastern University Laboratory of Language Engineering and Computing and also with School of Cyber SecurityGuangdong University of Foreign Studies School of Information Science and Engineering Central South University

By combining multiple weak learners with concept drift in the classification of big data stream learning, the ensemble learning can achieve better generalization performance than the single learning approach. In this paper,we present an efficient classifier using the online bagging ensemble method for big data stream learning. In this classifier, we introduce an efficient online resampling mechanism on the training instances, and use a robust coding method based on error-correcting output codes. This is done in order to reduce the effects of correlations between the classifiers and increase the diversity of the ensemble. A dynamic updating model based on classification performance is adopted to reduce the unnecessary updating operations and improve the efficiency of learning.We implement a parallel version of EoBag, which runs faster than the serial version, and results indicate that the classification performance is almost the same as the serial one. Finally, we compare the performance of classification and the usage of resources with other state-of-the-art algorithms using the artificial and the actual data sets, respectively. Results show that the proposed algorithm can obtain better accuracy and more feasible usage of resources for the classification of big data stream.

关键词： big data stream classification online bagging ensemble learning concept drift

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

A Task Allocation Method for stream Processing with Recovery Latency Constraint

引用

Journal of Computer Science & Technology 2018年第6期33卷 1125-1139页

作者： Hong-Liang Li Jie Wu Zhen Jiang Xiang Li Xiao-Hui Wei College of Computer Science and Technology Jilin University Changchun 130012 China Key Laboratory of Symbolic Computation and Knowledge Engineering of the Ministry of Education Changchun 130012 China Department of Computer and Information Sciences Temple University Philadelphia PA 19122 U.S.A. Department of Computer Science West Chester University of Pennsylvania West Chester PA 19383 U.S.A.

stream processing applications continuously process large amounts of online streaming data in real time or nearreal time. They have strict latency constraints. However, the continuous processing makes them vulnerable to any failures,and the recoveries may slow down the entire processing pipeline and break latency constraints. The upstream backupscheme is one of the most widely applied fault-tolerant schemes for stream processing systems. It introduces complexbackup dependencies to tasks, which increases the difficulty of controlling recovery latencies. Moreover, when dependenttasks are located on the same processor, they fail at the same time in processor-level failures, bringing extra recovery latencies that increase the impacts of failures. This paper studies the relationship between the task allocation and therecovery latency of a stream processing application. We present a correlated failure effect model to describe the recoverylatency of a stream topology in processor-level failures under a task allocation plan. We introduce a recovery-latency awaretask allocation problem （RTAP） that seeks task allocation plans for stream topologies that will achieve guaranteed recoverylatencies. We discuss the difference between RTAP and classic task allocation problems and present a heuristic algorithmwith a computational complexity of O（n log2 n） to solve the problem. Extensive experiments were conducted to verify thecorrectness and effectiveness of our approach. It improves the resource usage by 15%-20% on average.

关键词： stream processing task allocation fault-tolerance upstream backup, recovery latency

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

FAAD:an unsupervised fast and accurate anomaly detection method for a multi-dimensional sequence over data stream

引用

Frontiers of Information Technology & Electronic Engineering 2019年第3期20卷 388-404页

作者： Bin LI Yi-jie WANG Dong-sheng YANG Yong-mou LI Xing-kong MA Science and Technology on Parallel and Distributed Processing Laboratory College of ComputerNational University of Defense Technology Block Chain Research Institute of LianLian Pay

Recently, sequence anomaly detection has been widely used in many fields. Sequence data in these fields are usually multi-dimensional over the data stream. It is a challenge to design an anomaly detection method for a multi-dimensional sequence over the data stream to satisfy the requirements of accuracy and high speed. It is because:(1) Redundant dimensions in sequence data and large state space lead to a poor ability for sequence modeling;(2) Anomaly detection cannot adapt to the high-speed nature of the data stream, especially when concept drift occurs, and it will reduce the detection rate. On one hand, most existing methods of sequence anomaly detection focus on the single-dimension sequence. On the other hand, some studies concerning multi-dimensional sequence concentrate mainly on the static database rather than the data stream. To improve the performance of anomaly detection for a multi-dimensional sequence over the data stream, we propose a novel unsupervised fast and accurate anomaly detection(FAAD) method which includes three algorithms. First, a method called "information calculation and minimum spanning tree cluster" is adopted to reduce redundant dimensions. Second, to speed up model construction and ensure the detection rate for the sequence over the data stream, we propose a method called"random sampling and subsequence partitioning based on the index probabilistic suffix tree." Last, the method called "anomaly buffer based on model dynamic adjustment" dramatically reduces the effects of concept drift in the data stream. FAAD is implemented on the streaming platform Storm to detect multi-dimensional log audit data.Compared with the existing anomaly detection methods, FAAD has a good performance in detection rate and speed without being affected by concept drift.

关键词： Data stream Multi-dimensional sequence Anomaly detection Concept drift Feature selection

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

stream跨学科教学在线交互研究及其实践路径--基于35项国际实证研究的元分析

引用

远程教育杂志 2022年第6期40卷 74-82页

作者：徐慧芬张思杭沈忠华陆吉健杭州师范大学未来教育创新创业协会浙江杭州311121 杭州师范大学经亨颐教育学院浙江杭州311121 浙江药科职业大学基础学院浙江宁波315100

stream跨学科教学虽然是在STEM与STEAM理念的基础上发展而来,但它对“智能+”教育时代的跨学科教学与人才培养具有更重要的价值。跨学科教学的本质在于“超越学科”,纵观当前国内外的课程改革和教学实践,已开始转向对学生的阅读、交互... 详细信息

stream跨学科教学虽然是在STEM与STEAM理念的基础上发展而来,但它对“智能+”教育时代的跨学科教学与人才培养具有更重要的价值。跨学科教学的本质在于“超越学科”,纵观当前国内外的课程改革和教学实践,已开始转向对学生的阅读、交互、探究、设计等“软技能”的培养。为此,基于2003-2022年国际期刊上发表的35项stream跨学科教学在线交互相关实验与准实验研究(实验样本涉及美国、中国、澳大利亚等7个国家的7955名教师与学生),元分析的结果表明:在线交互对stream跨学科教学具有显著正向强作用,尤其是对科学与技术等学科侧重、内容交互、虚拟和视频辅助的stream跨学科教学。这一元分析结果充分揭示了:stream跨学科教学在线交互在当前各类教学中具有较大的借鉴与应用价值,需要深入探索混合式stream跨学科教学深度交互、面向读写能力培养的stream跨学科教学资源整合、扩展现实技术辅助下的沉浸式跨学科教学实践、利用在线交互数据等,进一步驱动与落实stream跨学科教学的实践应用。

关键词： stream STEAM STEM 跨学科教学在线交互

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

SIZE DISTRIBUTION OF DROPLETS ABOVE A ROTATING stream TRAY AND MODEL OF DROPLET MOTION THEREIN

引用

Chinese Journal of Chemical Engineering 1997年第2期5卷 35-42页

作者：陈建孟谭天恩 Department of Chemical Engineering Zhejiang University of Technology Department of Chemical Engineering Zhejiang University

Droplet size distributions have been investigated with a two-probe system above a rotatingstream tray of 300 mm diameter.The measured distributions are found to follow the upper limitedlognormal distribution with three parameters dependent primarily on gas hole F-factor.A probabilitymethod is used to describe the initial state of the droplet population above the tray,and a model fordroplet motion is presented.The results computed with model agree well with experimental data.

关键词： rotating stream tray droplet size distribution model for droplet motion

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

Water quality and sediment contamination assessment of Pazarsuyu stream, Turkey using multivariate statistical methods and pollution indicators

引用

International Soil and Water Conservation Research 2019年第1期7卷 47-56页

作者： Fikret Ustao(g)lu Yal(c)in Tepe Biology Department Faculty of Arts and Science Giresun UniversityGure28200 GiresunTurkey

The spatio-temporal variations of surface water quality and the level of metal contamination in the sediment of Pazarsuyu stream were determined by using multivariate statistical techniques and pollution indicators,respectively.The water and sediment samples were collected monthly from four different stations along the Pazarsuyu stream between June 2014 and May 2015 and analyzed using standard methods.Results were assessed according to national and international water quality criteria and the water quality parameters in some stations were found to be over these criteria levels.The present study showed that statistical techniques such as Pearson Correlation Index (PCI),Principal Component Analysis (PCA),Cluster Analysis (CA),One Way ANOVA need to be used to get better information for the studies on the water quality of surface waters.PCA identified six factors accounting for 82.88% of the total variation in the data.The abundance of sediment heavy metals was in the order of Fe > Mn > Zn > Pb > Cu> Cr > Co > Cd.The heavy metal contamination in the sediments was evaluated by applying the enrichment factor (EF),contamination factor (CF),geoaccumulation index (lgeo) and potential ecological risk index (PERI).Pb was heavily contaminated and has a significant enrichment of contamination according to calculated EF values.Therefore,the stream water can be used for irrigation with precaution but extensive treatment required before using for domestic purposes to prevent adverse public health effects.

关键词： Pazarsuyu stream Water quality Multivariate statistical techniques sediment Heavy metals Pollution indicators

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

Hillslope coupled stream morphology, flow conditions, and their effects on detrital sedimentology in Garnet Canyon, Teton Range,Wyoming

引用

Geoscience Frontiers 2018年第4期9卷 1193-1202页

作者： Lisa M.Tranel Department of Geography Geology and the Environment Illinois State University

Characterizing stream erosion in any steep mountain landscape is arduous, but the challenge level increases when the stream flows through a glaciated catchment frequently modified by hillslope debris.Glacial landforms and stochastic mass wasting in alpine systems may interfere with sediment delivery to downstream sites where detrital sediments are often collected to represent upstream bedrock sources.To use detrital sediments as indicators of erosion, we need to understand potential sediment accumulation in flat glaciated reaches or behind rockfall barriers. This study investigates the stream channel in Garnet Canyon, a glaciated catchment located in the central Teton Range, to describe hillslope coupled channel morphology and the subsequent effects on sediment transport throughout the catchment.stream cross-section surveys and sediment size measurements of the surface bedload were collected in the field within a glacially flattened segment of Garnet Canyon. Calculations of shear stress conditions allowed evaluation of the importance of mineral densities on potential grain entrainment. The length of the Garnet Canyon stream observed in this study was coupled with hillslope deposits. Critical shear stresses were sufficient to move gravel-sized sediments through all sections when calculated with quartz mineral density and through most sections when applying apatite mineral density. These results verify the application of detrital sediments to evaluate erosion rates or spatial bedrock sources because snowmelt stream flow efficiently moves entrained sediment past glacially reduced slopes and potential talus barriers.

关键词： stream Morphology Garnet Canyon Sediment Talus

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

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：