检索结果-南通市图书馆

Variation of nutrient fluxes by rainfall redistribution processes in the forest canopy of an urban larch plantation in northeast China

引用

Journal of Forestry Research 2022年第4期33卷 1259-1269页

作者： Houcai sheng Na Guo Cunyong Ju Tijiu cai Center for Ecological Research Northeast Forestry UniversityHarbin 150040People’s Republic of China Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education Northeast Forestry UniversityHarbin 150040People’s Republic of China College of Food Engineering East University of HeilongjiangHarbin 150040People’s Republic of China

Atmospheric deposition(dry and wet deposition)is one of the primary sources of chemical inputs to terrestrial ecosystems and replenishes the nutrient pool in forest *** often acts as a primary transporting agent and solvent;thus,nutrient cycles in forests are closely linked to hydrological *** collected precipitation data during a growing season to explore variations in nutrient cycling and nutrient balances in the rainfall redistribution process(wet deposition)in a larch plantation in northeast *** measured nutrient(NO_(3)^(-),PO_(4)^(3−),Cl^(−),K,Ca,Na,and Mg)inputs via bulk precipitation,throughfall and stemfl ow,and used a canopy budget model to estimate nutrient fl uxes via canopy *** results suggest that the average concentrations of the base cation(K,Ca,Na,and Mg)showed the following order:stemfl ow>throughfall>bulk *** and stemfl ow chemistry dramatically fl uctuated over the growing season when net fl uxes(throughfall+stemfl ow—bulk precipitation)of NO−3,PO3−4,SO2−4,Cl−,K,Ca,Na,and Mg were−6.676 kg·ha^(-1),−1.094 kg·ha^(-1),−2.371 kg·ha^(-1),1.975 kg·ha^(-1),0.470 kg·ha^(-1),−5.202 kg·ha^(-1),−0.336 kg·ha^(-1),and 1.397 kg·ha^(-1),*** results suggest that NO−3,PO3−4,SO2−4,Ca,and Na were retained,while Cl−,K,and Mg were washed off by throughfall and stemfl ow.

关键词： Rainfall redistribution Aqueous fluxes Water chemistry Macronutrients input Plantation forest Harbin

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

Research progresses on equipment technologies used in safety inspection,repair,and reinforcement for deepwater dams

引用

Science China(Technological Sciences) 2022年第5期65卷 1059-1071页

作者： XIANG Yan sheng JinBao WANG Lei cai YueBo MENG Ying cai Wei Dam Safety Management Department Nanjing Hydraulic Research InstituteNanjing210029China State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing210029China Key Laboratory of Reservoir and Dam Safety Ministry of Water ResourcesNanjing210029China China Ship Scientific Research Center Wuxi214000China Hangzhou Hua-Neng Engineering Safety Technology Co. Ltd.Hangzhou310000China

China’s many dams are increasingly facing safety problems resulting from the natural aging of the dam hydraulic structure and geological disasters such as earthquakes under the operating condition of holding a vast amount of *** such as dam leakage and concrete cracking and erosion seriously affect the normal operation and effectiveness of a *** is impossible to empty a large reservoir with a high dam for many reasons,such as serious environmental consequences,and it is thus difficult to detect the working conditions of the underwater part of the *** is an increasingly urgent demand for detection and repair technologies that can be used in the deepwater ***,there are cutting-edge deepwater detection and processing technologies for hidden dangers in dam *** core technologies include underwater detection equipment,diving technologies,and underwater operation *** paper analyzes safety-oriented detection equipment recently used in unmanned detection,manned detection,and deepwater diver detection from the viewpoint of practical *** paper further reviews 100-m-depth-class technologies and applications of safety inspection,repair,and reinforcement equiment in the deepwater environment of reservoir *** outlook is provided on technology trends of deepwater detection,repair,and reinforcement and critical problems.

关键词： dam unmanned detection manned submersible detection deepwater detection deep water repair and reinforcement

来源：

维普期刊数据库

同方期刊数据库

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

Collision-induced Rotational Energy Transfer in an Atom-Diatom System

引用

Chinese Journal of Chemical Physics 2008年第5期21卷 457-462页

作者： Yan-qing Ni jian Li Feng-cai Ma Department of Physics Liaoning University Shenyang 110036 China Department of Science Shenyang Institute of Aeronautical Engineering Shengyang 110036 China

As a further theoretical study of the collision-induced quantum interference on rotational energy transfer in an atom-diatom system, based on the first-Born approximation of time-dependent perturbation theory, taking into account the anisotropic Lennard-Jones interaction potential and the long-range interaction potential, the differential interference angles in singlet-triplet mixed states of CO A^1Π（v=9）-e3∑-（v=1） system in collision with He, Ne, Ar, and other partners were calculated theoretically. The relationships of differential interference angle versus impact parameters, including collision parameter b and velocity, are obtained.

关键词： Rotational energy transfer Collision-induced quantum interference Interference angle

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

Carbon nanotubes for flexible batteries: recent progress and future perspective

引用

National Science Review 2021年第5期8卷 158-174页

作者： sheng Zhu jian sheng Yuan Chen jiangfeng Ni Yan Li Beijing National Laboratory for Molecular Sciences Key Laboratory for the Physics and Chemistry of NanodevicesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsCollege of Chemistry and Molecular EngineeringPeking University School of Chemical and Biomolecular Engineering The University of Sydney School of Physical Science and Technology Center for Energy Conversion Materials & Physics(CECMP)Jiangsu Key Laboratory of Thin FilmsSoochow University Light Industry Institute of Electrochemical Power Sources

Flexible batteries, which maintain their functions potently under various mechanical deformations, attract increasing interest due to potential applications in emerging portable and wearable electronics. Significant efforts have been devoted to material synthesis and structural designs to realize the mechanical flexibility of various batteries. Carbon nanotubes(CNTs) have a unique one-dimensional(1 D) nanostructure and are convenient to further assemble into diverse macroscopic structures, such as 1 D fibers, 2 D films and 3 D sponges/aerogels. Due to their outstanding mechanical and electrical properties, CNTs and CNT-based hybrid materials are superior building blocks for different components in flexible batteries. This review summarizes recent progress on the application of CNTs in developing flexible batteries, from closed-system to open-system batteries, with a focus on different structural designs of CNT-based material systems and their roles in various batteries. We also provide perspectives on the challenges and future research directions for realizing practical applications of CNT-based flexible batteries.

关键词： carbon nanotube flexible battery electrochemical energy storage wearable electronics

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Synthesis of High Molecular Weight Polyethylene and E-MA Copolymers Using Iminopyridine Ni(Ⅱ) and Pd(Ⅱ) Complexes Containing a Flexible Backbone and Rigid Axial Substituents

引用

Chinese Journal of Polymer Science 2023年第2期41卷 233-239页

作者： Yu-Dan Liao Qi cai sheng-Yu Dai School of Chemical and Environmental Engineering Anhui Polytechnic UniversityWuhu241000China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefei230601China

Suppressing the chain transfer reactions during polymerization in late-transition metal-catalyzed olefin polymerization systems is the key to obtaining high molecular weight polyolefin materials. In this work, two efficient strategies(“sandwich” and rotation-restricted strategies)to retard chain transfer reactions in ethylene(co)polymerization were employed for the iminopyridyl system. Herein, a family of iminopyridyl Ni(Ⅱ)and Pd(Ⅱ) complexes with a flexible backbone and rigid axial bulky aryl substituents were designed, synthesized and characterized. In ethylene polymerization, the iminopyridyl Ni(Ⅱ) and Pd(Ⅱ) catalysts using the two strategies exhibited reasonable activities and generated highly branched polyethylenes with high molecular weights, where catalysts with dibenzosuberyl substituents exhibited significantly higher activities and produced higher molecular weight polyethylene than catalysts with 8-arylnaphthalenyl substituent. A similar trend of activities and molecular weights was also found in the copolymerization of ethylene with MA using the Pd(Ⅱ) catalysts. Moreover, highly branched E-MA copolymers with moderate to high molecular weights and high incorporation ratios(up to 17.4 mol%) were generated with the two Pd(Ⅱ) catalysts. Most interestingly, as compared with the dibenzhydryl Ni(Ⅱ) and Pd(Ⅱ) catalysts, the catalysts using the two strategies exhibited a superior ability to retard the chain transfer reactions and generated polymers and copolymers with 1-2 orders of magnitude higher molecular weights during ethylene(co)polymerization.

关键词： Ni(Ⅱ)and Pd(Ⅱ) Suppressing chain transfer High molecular weight Ethylene(co)polymerization

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

Synthesis and Characterization of Zirconia Nanocrystallites by Cationic Surfactant and Anionic Surfactant

引用

Chinese Journal of Structural Chemistry 2005年第10期24卷 1133-1139页

作者： YU jian-Chang HU sheng-Wei College of Material Science and Engineering Fuzhou University Fuzhou 350002 China

Study on nanomaterials has attracted great interests in recent years. In this article, zirconia nanocrystallites of different structures have been successfully synthesized via hydrothermal methods with cationic surfactant （CTAB） and anionic surfactant （SDS）, respectively. Differential Scanning Calorimeter （DSC-TG）, X-ray Diffractometer （XRD）, Transmission Electron Microscope （TEM）, Ultraviolet-Visible （UV-vis） and N2 adsorption-desorption analyses are used for their structure characteristics. The results show that the cationic surfactant has a distinctive direction effect on the formation of zirconia nanocrystallites, while the anionic surfactant has a self-assembly synergistic effect on them. The sample synthesized with the cationic surfactant presents good dispersion with the main phase of tetragonal zirconia, and the average nanocrystal size is around 15 nm after calcination at 500 ℃. While the sample synthesized with the anionic surfactant exhibits a worm-like mesoporous structure with pure tetragonal phase after calcination at 500 ℃ and with good thermal stability.

关键词： cationic surfactant anionic surfactant zirconia nanocrystallites,mesoporous zirconia

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

肇庆市城市低龄学生视力变化的家庭相关因素分析

引用

中国健康教育 2007年第7期23卷 508-510页

作者：梁碧绿郭赐贶蔡健生叶坚江瑞青关玲玉麦炜林绍良广东省肇庆市疾病预防控制中心广东肇庆526020 广东省肇庆市第十五小学广东肇庆526020 广东省肇庆市实验小学广东肇庆526020

目的了解和评估城市低龄学生家庭学习环境和行为习惯,为城市低龄学生视力的家庭相关因素干预研究提供科学依据。方法采用整群一级抽样的方法,应用自编调查表,对学校建筑卫生学达标的两所城市小学一年级学生进行视力的家庭相关因素调查,... 详细信息

目的了解和评估城市低龄学生家庭学习环境和行为习惯,为城市低龄学生视力的家庭相关因素干预研究提供科学依据。方法采用整群一级抽样的方法,应用自编调查表,对学校建筑卫生学达标的两所城市小学一年级学生进行视力的家庭相关因素调查,并对其家庭普遍使用的光源种类作读写书台视场布点测量光照度。结果有61.1%的学生用裸光荧光灯作读写灯具,其中56.1%的学生在低于150Lx光源下做功课;视力相关不健康习惯突出,其中以读写姿势不良为最多,占76.5%。结论低龄学生视力相关家庭因素和不健康习惯突出,必须引起社会和家庭的足够重视,并亟待加强低龄学生视力的家庭相关因素干预和指导。

关键词：城市低龄学生视力家庭学习环境健康行为

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

Quantized innovations Kalman filter: stability and modification with scaling quantization

引用

Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第2期13卷 118-130页

作者： jian XU jian-xun LI sheng XU Science and Technology on Avionics Integration Laboratory Shanghai Jiao Tong UniversityShanghai 200240 MOE Key Laboratory of System Control and Information Processing Shanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

The stability of quantized innovations Kalman filtering (QIKF) is analyzed. In the analysis, the correlation between quantization errors and measurement noises is considered. By taking the quantization errors as a random perturbation in the observation system, the QIKF for the original system is equivalent to a Kalman-like filtering for the equivalent state-observation system. Thus, the estimate error covariance matrix of QIKF can be more exactly analyzed. The boundedness of the estimate error covariance matrix of QIKF is obtained under some weak conditions. The design of the number of quantized levels is discussed to guarantee the stability of QIKF. To overcome the instability and divergence of QIKF when the number of quantization levels is small, we propose a Kalman filter using scaling quantized innovations. Numerical simulations show the validity of the theorems and algorithms.

关键词： Kalman filtering Quantized innovation Stability Scaling quantization Wireless sensor network

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

FRAMELET BASED DECONVOLUTION

引用

Journal of Computational Mathematics 2010年第3期28卷 289-308页

作者： jian-Feng cai Zuowei Shen Department of Mathematics University of California Los Angeles CA 90095 Department of Mathematics National University of Singapore 2 Science Drive 2 Singapore 117543

In this paper, two framelet based deconvolution algorithms are proposed. The basic idea of framelet based approach is to convert the deconvolution problem to the problem of inpainting in a frame domain by constructing a framelet system with one of the masks being the given （discrete） convolution kernel via the unitary extension principle of [26], as introduced in [6-9] . The first algorithm unifies our previous works in high resolution image reconstruction and infra-red chopped and nodded image restoration, and the second one is a combination of our previous frame-based deconvolution algorithm and the iterative thresholding algorithm given by [14, 16]. The strong convergence of the algorithms in infinite dimensional settings is given by employing proximal forward-backward splitting （PFBS） method. Consequently, it unifies iterative algorithms of infinite and finite dimensional setting and simplifies the proof of the convergence of the aluorithms of [6].

关键词： Framelet deconvolution wavelet tight frame soft-thresholding

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

HMFI分子筛Bronsted酸性位点与碱性分子的作用机制

引用

原子与分子物理学报 2025年第4期42卷 1-7页

作者：郑健秦康秦玉才宋丽娟中石化石油化工科学研究院有限公司北京100083 辽宁石油化工大学辽宁省石油化工催化科学与技术重点实验室抚顺113001

采用密度泛函理论(DFT)方法,以单铝、双铝和三铝酸性位点HMFI分子筛为模型分子筛,计算去质子化能考察HMFI分子筛的本征酸性,以NH_(3)分子作为模型分子,计算NH_(3)分子在HMFI分子筛中的吸附能与去质子化能进行关联性分析,并进一步考察NH_... 详细信息

采用密度泛函理论(DFT)方法,以单铝、双铝和三铝酸性位点HMFI分子筛为模型分子筛,计算去质子化能考察HMFI分子筛的本征酸性,以NH_(3)分子作为模型分子,计算NH_(3)分子在HMFI分子筛中的吸附能与去质子化能进行关联性分析,并进一步考察NH_(3)分子与HMFI分子筛的作用机制.研究表明分子筛Bronsted酸(简称B酸)强度与B酸数量没有强相关性,在考虑B酸位数量的同时须考虑B酸位的分布.酸性位点数量和分布的差异均可以调控NH_(3)分子的吸附构象,并且可以通过调节HMFI分子筛孔道对分子施加相互作用的模式,解析分子的结构和电子性质,精准调控分子的进一步转化.此项工作可以为未来高效多孔材料有效物种活性位的构建提供新思路.

关键词：密度泛函理论 HMFI分子筛 Bronsted酸性质吸附性能

来源：

维普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

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：