检索结果-南通市图书馆

Tracking chloride and metal diffusion in proofed and unproofed concrete matrices using ablative laser technology (ICP-MS)

引用

Natural Science 2010年第8期2卷 809-816页

作者： Avin Pillay Mirella Elkadi Fadi Feghali sai cheong fok Ghada Bassioni Sasi Stephen 不详

Depth profiling studies (laser ICP-MS) of ions (Cl-, Na+, Mg2+) in concrete-based material can be used to provide useful information on the migration paths of these ionic species. In particular, deterioration of concrete through infiltration of chloride could lead to costly corrosion problems with serious impact on the environment. Many modeling studies on concrete matrices depend on the tortuosity of these transport paths. Our work showed that dispersion paths of ionic species in concrete are intermittent and sporadic, suggesting that applications of simplifying assumptions in treatment of such data could lead to appreciable perturbations in related mathematical models. This paper examines the capability of using a high resolution ICP-MS laser ablation technique to track Cl– migration in concrete samples in the presence of other ions such as Na+ and Mg2+. Cationic migration in such materials is underexplored and data in this particular area could contribute to modeling studies. Concrete bricks (with and without surface coatings) were specially prepared in cubic configurations and allowed to saturate in a ponding medium (sea water). The study subsequently examined the distribution of Cl– , Na+ and Mg2+ with depth in protected (epoxy coated) and unprotected cored concrete slivers (5 mm diameter;2 mm thick) using an 80 μm- diameter laser beam coupled to an ICP-MS instrument. The laser (213 nm) was programmed to ablate a total depth of 50 μm at each point at 5-μm intervals. The results in unprotected samples indicated that chloride intensity showed a general decline with depth, suggesting that mobility of the chloride is a function of its interaction with the concrete matrix. In some cases ‘hotspots’ were observed at certain points indicating that transport of the intruding ion was limited. No significant mobility was observed in coated samples. The depth-profiling results for Na+ and Mg2+ were somewhat unexpected. Strong similarities in their spectra purported that th

关键词： Concrete Cl– Na+ Mg2+ Laser Ablation Depth-Profiling ICP-MS

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 perspective on recent methods on testing predictability of asset returns

引用

Applied Mathematics(A Journal of Chinese Universities) 2018年第2期33卷 127-144页

作者： LIAO Xiao-sai CAI Zong-wu CHEN Hai-qiang The Wang Yanan Institute for Studies in Economics MOE Key Laboratory of Econometrics (Xiamen University) Fujian Provincial Key Laboratory of Statistical Science Xiamen University Department of Economics University of Kansas

This paper highlights some recent developments in testing predictability of asset returns with focuses on linear mean regressions, quantile regressions and nonlinear regression models. For these models, when predictors are highly persistent and their innovations are contemporarily correlated with dependent variable, the ordinary least squares estimator has a finite-sample bias, and its limiting distribution relies on some unknown nuisance parameter, which is not consistently estimable. Without correcting these issues, conventional test statistics are subject to a serious size distortion and generate a misleading conclusion in testing pre- dictability of asset returns in real applications. In the past two decades, sequential studies have contributed to this subject and proposed various kinds of solutions, including, but not limit to, the bias-correction procedures, the linear projection approach, the IVX filtering idea, the variable addition approaches, the weighted empirical likelihood method, and the double-weight robust approach. Particularly, to catch up with the fast-growing literature in the recent decade, we offer a selective overview of these methods. Finally, some future research topics, such as the econometric theory for predictive regressions with structural changes, and nonparametric predictive models, and predictive models under a more general data setting, are also discussed.

关键词： asset returns Heteroskedasticity high persistency nonlinearity predictability quantile regressions

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

The dynamics of river confluences and their effects on the ecology of aquatic environment:A review

引用

Journal of Hydrodynamics 2022年第1期34卷 1-14页

作者： sai-yu Yuan Lei Xu Hong-wu Tang Yang Xiao Carlo Gualtieri State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing210024China Yangtze Institute for Conservation and Development Nanjing210024China Department of Structures for Engineering and Architecture University of Napoli Federico IINapoliItaly

Confluences act as critical nodes in a river *** affect hydrodynamics,sediment transport,bed morphology,and eco-hydraulics of the river *** of streams produces the complex mechanism of flow momentum and mass mixing which may affect the aquatic environment locally and even lasting for a long distance *** confluence creates a hotspot for the river system’s ecological change,which usually leads to changes in water temperature,suspended-sediment load,bed material,nutrient concentrations,water chemistry,and organic-matter ***,the dynamics of river confluences are very complex and have critical effects on river system’s water environment and *** this reason,a review summarizing turbulent flow,sediment transport,morphological-dynamics,mixing processes,and their effects on the ecology of the aquatic environment at river confluences is in order.A future research agenda and opportunities pertinent to river confluence are vitally emphasized as a multidisciplinary research topic.

关键词： River confluence hydrodynamics sediment transport morpho dynamics water environment water ecology

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

Experimental investigation of turbulent flows around high-rise structure foundations and implications on scour

引用

Water Science and Engineering 2022年第1期15卷 47-56页

作者： Dong-fang Liang Hao Jia Yang Xiao sai-yu Yuan Department of Engineering University of CambridgeCambridge CB21PZUK State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China Yangtze Institute for Conservation and Development Hohai UniversityNanjing 210098China

Many studies have been undertaken to predict local scour around offshore high-rise structure foundations(HRSFs),which have been used in constructing the Donghai Wind Farm in ***,there have been few works on the turbulent flow that drives the scour *** this study,the characteristics of the turbulent flow fields around an HRSF were investigated using the particle image velocimetry *** mean flow,vorticity,and turbulence intensity were analyzed in *** relationship between the flow feature and scour development around an HRSF was *** results showed that the flow velocity increased to its maximum value near the third row of the pile *** shear layer and wake vortices could not be fully developed downstream of the last row of the piles at small Reynolds *** strong flow and turbulent fluctuation near the third piles explained the existence of a longtail scour pattern starting from the HRSF shoulders and a trapezoidal deposition region directly downstream of *** laboratory experiment gains insight into the mechanism of the turbulent flow around HRSFs and provides a rare dataset for numerical model verifications.

关键词： High-rise structure foundations(HRSFs) Turbulent flow fields Particle image velocimetry(PIV) Scour Sediment transport

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

微胶囊型单组分环氧树脂胶粘剂的制备及其力学性能研究

引用

热固性树脂 2024年第2期39卷 15-22页

作者：安金亮汤胜孙赛玲申兆波河北工程大学土木工程学院河北邯郸056038 河北工程大学绿色功能材料研究所河北邯郸056038 广州市香港科大霍英东研究院工程材料及可靠性研究中心广东广州511458

以酚醛胺(T31)固化剂为芯材,聚脲(PUA)为壳材,采用界面聚合法制备了一种微胶囊型固化剂T31-PUA。通过热重分析仪、扫描电子显微镜对微胶囊的热稳定性、微观形貌进行了表征。将固化剂微胶囊与环氧树脂混合制备成单组分胶粘剂,利用示差扫... 详细信息

以酚醛胺(T31)固化剂为芯材,聚脲(PUA)为壳材,采用界面聚合法制备了一种微胶囊型固化剂T31-PUA。通过热重分析仪、扫描电子显微镜对微胶囊的热稳定性、微观形貌进行了表征。将固化剂微胶囊与环氧树脂混合制备成单组分胶粘剂,利用示差扫描量热仪、万能试验机对单组分胶粘剂的固化特性、耐久性能及力学性能进行表征。结果表明:微胶囊表面略有粗糙,平均粒径为150μm,芯材质量分数为60%。微胶囊在室温下压力解封,可在1 h内完成固化,其粘接件拉伸剪切强度为6.18 MPa。热解封可在120℃下30 min内固化,其粘接件拉伸剪切强度为6.95 MPa。该微胶囊型单组分胶粘剂室温储存期可达40 d以上,固化特性、耐久性和力学性能良好。

关键词：微胶囊固化剂酚醛胺聚脲环氧树脂单组分胶粘剂拉伸剪切强度

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

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

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：