检索结果-南通市图书馆

Strain Gradient Finite Element Formulation of Flexoelectricity in Ferroelectric Material Based on Phase-Field Method

引用

Acta Mechanica Solida Sinica 2024年第4期37卷 570-579页

作者： Shuai Wang Hengchang Su Min Yi li-hua Shao National Key Laboratory of Strength and Structural Integrity Institute of Solid MechanicsSchool of Aeronautic Science and EngineeringBeihang UniversityBeijing100191People’s Republic of China State Key Laboratory of Mechanics and Control for Aerospace Structures and Institute for Frontier Science and Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education and College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016People’s Republic of China

Flexoelectricity is a two-way coupling effect between the strain gradient and electric field that exists in all dielectrics,regardless of point group ***,the high-order derivatives of displacements involved in the strain gradient pose challenges in solving electromechanical coupling problems incorporating the flexoelectric *** this study,we formulate a phase-field model for ferroelectric materials considering the flexoelectric effect.A four-node quadrilateral element with 20 degrees of freedom is constructed without introducing high-order shape *** microstructure evolution of domains is described by an independent order parameter,namely the spontaneous polarization governed by the time-dependent Ginzburg–Landau *** model is developed based on a thermodynamic framework,in which a set of microforces is introduced to construct the constitutive relation and evolution *** the flexoelectric part of electric enthalpy,the strain gradient is determined by interpolating the mechanical strain at the node via the values of Gaussian integration points in the isoparametric *** model is shown to be capable of reproducing the classic analytical solution of dielectric materials incorporating the flexoelectric *** model is verified by duplicating some typical phenomena in flexoelectricity in cylindrical tubes and truncated pyramids.A comparison is made between the polarization distribution in dielectrics and *** model can reproduce the solution to the boundary value problem of the cylindrical flexoelectric tube,and demonstrate domain twisting at domain walls in ferroelectrics considering the flexoelectric effect.

关键词： Flexoelectricity Phase-field method Ferroelectrics Domain configuration

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

The Capture and Catalytic Conversion of CO2 by Dendritic Mesoporous Silica-Based Nanoparticles

引用

Energy & Environmental Materials 2024年第2期7卷 130-155页

作者： Yabin Wang liangzhu huang Songwei li Chuntai liu hua He College of Chemistry and Chemical Engineering Yan’an University Institute for Triazine Compounds & Hierarchical Porous Materials National Engineering Research Center for Advanced Polymer Processing Technology Key Laboratory of Materials Processing and Mold (Ministry of Education) Zhengzhou University

Dendritic mesoporous silica nanoparticles own three-dimensional centerradial channels and hierarchical pores,which endows themselves with superhigh specific surface area,extremely large pore volumes,especially accessible internal spaces,and so *** guest species（such as organic groups or metal nanoparticles） could be readily decorated onto the interfaces of the channels and pores,realizing the functionalization of dendritic mesoporous silica nanoparticles for targeted *** adsorbents and catalysts,dendritic mesoporous silica nanoparticles-based materials have experienced nonignorable development in CO2capture and catalytic *** comprehensive review provides a critical survey on this pregnant subject,summarizing the designed construction of novel dendritic mesoporous silica nanoparticles-based materials,the involved chemical reactions（such as CO2methanation,dry reforming of CH4）,the value-added chemicals from CO2(such as cyclic carbonates,2-oxazolidinones,quinazoline-2,4（1H,3H）-diones),and so *** adsorptive and catalytic performances have been compared with traditional silica mesoporous materials（such as SBA-15 or MCM-41）,and the corresponding reaction mechanisms have been thoroughly *** is sincerely expected that the in-depth discussion could give materials scientists certain inspiration to design brand-new dendritic mesoporous silica nanoparticles-based materials with superior capabilities towards CO2capture,utilization,and storage.

关键词： catalytic conversion CO2 adsorption CO2 capture dendritic mesoporous silica nanoparticles

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

Robust Correlation Clustering Problem with Locally Bounded Disagreements

引用

Tsinghua Science and Technology 2024年第1期29卷 66-75页

作者： Sai Ji Min li mei liang Zhenning Zhang Institute of Mathematics Hebei University of TechnologyTianjin 300401China School of Mathematics and Statistics Shandong Normal UniversityJinan 250358China College of Statistics and Data Science Beijing University of TechnologyBeijing 100124China Department of Operations Research and Information Engineering Beijing University of TechnologyBeijing 100124China

Min-max disagreements are an important generalization of the correlation clustering problem(CorCP).It can be defined as *** a marked complete graph G=(V,E),each edge in the graph is marked by a positive label"+"or a negative label"_"based on the similarity of the connected *** goal is to find a clustering C of vertices V,so as to minimize the number of disagreements at the vertex with the most ***,the disagreements are the positive cut edges and the negative non-cut edges produced by clustering *** paper considers two robust min-max disagreements:min-max disagreements with outliers and min-max disagreements with *** parameter δ∈(0,1/14),we first provide a threshold-based iterative clustering algorithm based on LP-rounding technique,which is a(1/δ,7/(1-14δ))-bi-criteria approximation algorithm for both the min-max disagreements with outliers and the min-max disagreements with outliers on one-sided complete bipartite ***,we verify that the above algorithm can achieve an approximation ratio of 21 for min-max disagreements with penalties when we set parameter δ=1/21.

关键词： min-max disagreements outliers penalties approximation algorithm LP-rounding

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

Regulating the crystal phase of bismuth-based semiconductors for promoted photocatalytic performance

引用

Science China Chemistry 2024年第6期67卷 1839-1864页

作者： Zhaohui Wu mei-Chi Chong Shiying Zhang Junshan li Yongfa Zhu Hunan Key Laboratory of Applied Environmental Photocatalysis Changsha UniversityChangsha410022China Department of Chemistry Tsinghua UniversityBeijing100084China Institute for Advanced Study Chengdu UniversityChengdu610106China

Numerous bismuth-based semiconductors(BBSs)with sophisticated and desirable structures used as photocatalysts for efficient photocatalytic degradation of water organic contaminants have attracted considerable ***,regulating the crystal phases and phase transition of BBSs for promoted photocatalytic performance is ***,the unique crystal structure and band structure features of each typical BBSs,and the vital roles on phase controlling of each phase were systematically presented based on the classification of ***,the critical factors for the phase transition of BBSs and intrinsic driving forces endowed by phases of BBSs for enhanced photocatalytic performance of organic contaminants removal were also *** review will provide systematical guidelines and horizons for regulating the crystal phase and phase transition of BBSs,promoting photocatalytic degradation and mineralization of organic contaminants.

关键词： bismuth-based semiconductors phase regulation photocatalytic performances organic contaminants

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

Catalytic asymmetric dearomative azo-Diels–Alder reaction of 2-vinlyindoles

引用

Chinese Chemical Letters 2024年第4期35卷 357-362页

作者： Yu-Hang Miao Zheng-Xu Zhang Xu-Yi huang Yuan-Zhao hua Shi-Kun Jia Xiao Xiao Min-Can Wang li-Ping Xu Guang-Jian mei Green Catalysis Center and College of ChemistryZhengzhou UniversityZhengzhou 450052China School of Chemistry and Chemical Engineering Shandong University of TechnologyZibo 255000China Institute of Pharmaceutical Science and Technology Zhejiang University of TechnologyHangzhou 310014China

Due to the high electrophilic nature of azo-dienophiles, azo-Diels–Alder proceeds rapidly even without the need of a catalyst and is therefore regarded as the “click reaction”. This spontaneity causes strong background reaction and poses a daunting challenge to chemists for developing the catalytic asymmetric version. Reported herein is the first catalytic asymmetric dearomative azo-Diels–Alder reaction between2-vinylindoles and triazoledione. This protocol makes use of the high energy barrier of dearomatization to avert the strong background reaction of azo-Diels–Alder reaction, allowing the implementation of the projected reaction at ambient temperature. Density functional theory calculations have been performed to gain insights into the reaction mechanism and the origins of the enantioselectivity. By using this method,a variety of tetracyclic indole derivatives have been readily prepared in good to excellent yields and with excellent diastereo-and enantio–selectivities(33 examples, up to 97% yield and >99% ee, >20:1 dr).

关键词： Catalytic asymmetric dearomatization Azo-Diels–Alder reaction 2-Vinylindoles Chiral phosphoric acid Tetracyclic indole derivatives

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

Detecting bulk and edge exceptional points in non-Hermitian systems through generalized Petermann factors

引用

Frontiers of physics 2024年第2期19卷 169-177页

作者： Yue-Yu Zou Yao Zhou li-mei Chen Peng Ye School of Physics State Key Laboratory of Optoelectronic Materials and Technologiesand Guangdong Provincial Key Laboratory of Magnetoelectric Physics and DevicesSun Yat-sen UniversityGuangzhou 510275China

Non-orthogonality in non-Hermitian quantum systems gives rise to tremendous exotic quantum phenomena,which can be fundamentally traced back to *** this paper,we introduce an interesting quantity(denoted asη)as a new variant of the Petermann factor to directly and efficiently measure non-unitarity and the associated non-Hermitian *** tuning the model parameters of underlying non-Hermitian systems,we find that the discontinuity of bothηand its first-order derivative(denoted as■η)pronouncedly captures rich physics that is fundamentally caused by *** concretely,in the 1D non-Hermitian topological systems,two mutually orthogonal edge states that are respectively localized on two boundaries become non-orthogonal in the vicinity of discontinuity ofηas a function of the model parameter,which is dubbed"edge state transition".Through theoretical analysis,we identify that the appearance of edge state transition indicates the existence of exceptional points(EPs)in topological edge *** the discontinuity of■η,we investigate a two-level non-Hermitian model and establish a connection between the points of discontinuity of■ηand EPs of bulk *** studying this connection in more general lattice models,we find that some models have discontinuity of■η,implying the existence of EPs in bulk states.

关键词： non-Hermitian Su−Schrieffer−Heeger(SSH)model exceptional point

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

Vanadium oxide nanospheres encapsulated in N-doped carbon nanofibers with morphology and defect dual-engineering toward advanced aqueous zinc-ion batteries

引用

Journal of Energy Chemistry 2024年第2期89卷 599-609,I0013页

作者： Yunfei Song Laiying Jing Rutian Wang Jiaxi Cui mei li Yunqiang Zhang School of Materials Science and Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353ShandongChina Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu 610054SichuanChina

Vanadium-based electrodes are regarded as attractive cathode materials in aqueous zinc ion batteries(ZIBs)caused by their high capacity and unique layered ***,it is extremely challenging to acquire high electrochemical performance owing to the limited electronic conductivity,sluggish ion kinetics,and severe volume expansion during the insertion/extraction process of Zn^(2+).Herein,a series of V_(2)O_(3)nanospheres embedded N-doped carbon nanofiber structures with various V_(2)O_(3)spherical morphologies(solid,core-shell,hollow)have been designed for the first time by an electrospinning technique followed thermal *** N-doped carbon nanofibers not only improve the electrical conductivity and the structural stability,but also provides encapsulating shells to prevent the vanadium dissolution and aggregation of V_(2)O_(3)***,the varied morphological structures of V_(2)O_(3)with abundant oxygen vacancies can alleviate the volume change and increase the Zn^(2+)***,the phase transition between V_(2)O_(3)and Zn_XV_(2)O_(5-m)·n H_(2)O in the cycling was also *** a result,the as-obtained composite delivers excellent long-term cycle stability and enhanced rate performance for coin cells,which is also confirmed through density functional theory(DFT)*** assembled into flexible ZIBs,the sample still exhibits superior electrochemical performance,which may afford new design concept for flexible cathode materials of ZIBs.

关键词： Aqueous zinc ion batteries Vanadium trioxide Oxygen vacancy Structure evolution Phase optimization

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

Effect of Sc on Al_(3)Fe phase and mechanical properties of as-cast AA5052 aluminum alloy

引用

China Foundry 2024年第3期21卷 257-264页

作者： Yang li Qing Yu Feng-feng Chen Jia-wen He Hong-mei Yang Meng-nie li Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650093China

The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical *** studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the *** this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%*** results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc *** ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.

关键词： AA5052 aluminum alloy Al3Fe phase mechanical properties grain boundary

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

Enhanced photocatalytic hydrogen production from Co-MOF/CN by nitrogen and sulfur co-doped coal-based carbon quantum dots

引用

Journal of Rare Earths 2024年第5期42卷 838-850,I0002页

作者： Shiyong Xu mei li Yijun Wang Caiyun Gao Rongsheng Xu Zhiliang jin School of Chemistry and Chemical Engineering North Minzu UniversityYinchuan750021China Ningxia Key Laboratory of Solar Chemical Conversion Technology.North Minzu University.Yinchuan 750021China State Key Laboratory of National Ethnic Affairs Commission Chemical Technology.North Minzu University Yinchuan750021China

A novel composite photocatalyst for photocatalytic decomposition of water for hydrogen evolution was successfully synthesized by in-situ growth of nitrogen and sulfur co-doped coal-based carbon quantum dots(NSCQDs)nanoparticles on the surface of sheet cobalt-based metal-organic framework(Co-MOF)and graphitic carbon nitride(g-C_(3)N_(4),CN).The structure and properties of the obtained catalysts were systematically *** effectively broaden the absorption of Co-MOF and CN in the visible *** new composite photocatalyst has high hydrogen production activity and the hydrogen production rate reaches 6254μmol/(g·h)at pH=*** the same time,NSCQDs synergy Co-MOF/CN composites have good *** four cycles of hydrogen production,the performance remains relatively *** tran sient photocurrent response and Nyquist plot experimental results further demonstrate the improvement of carrier separation efficiency in composite *** semiconductor type(n-type semico nductor)of the single-phase catalyst was determined by the Mott-Schottky test,and the band structure was *** conductive and valence bands of CN are-0.99 and 1.72 eV,respectively,and the conduction and valence bands of Co-MOF are-1.85 and 1.33 eV,*** e mechanism of the photocatalytic reaction can be inferred,that is,Z-type heterojunction is formed between CN an d Co-MOF,and NSCQDs was used as cocatalyst.

关键词： Nitrogen and sulfur co-doped Coal-based carbon quantum dots Co-MOF CN Photocatalytic hydrogen evolution Rare earths

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 Weakly-Supervised Crowd Density Estimation Method Based on Two-Stage linear Feature Calibration

引用

IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 965-981页

作者： Yong-Chao li Rui-Sheng Jia Ying-Xiang Hu Hong-mei Sun the College of Computer Science and Engineering Shandong University of Science and TechnologyQingdao 266590 the Faculty of Information Science and Engineering Ocean University of ChinaQingdao 266000China the College of Computer Science and Engineering Shandong University of Science and TechnologyQingdao 266590China the College of Computer Science and Engineering Nanjing University of Science and TechnologyNanjing 210000China

In a crowd density estimation dataset,the annotation of crowd locations is an extremely laborious task,and they are not taken into the evaluation *** this paper,we aim to reduce the annotation cost of crowd datasets,and propose a crowd density estimation method based on weakly-supervised learning,in the absence of crowd position supervision information,which directly reduces the number of crowds by using the number of pedestrians in the image as the supervised *** this purpose,we design a new training method,which exploits the correlation between global and local image features by incremental learning to train the ***,we design a parent-child network(PC-Net)focusing on the global and local image respectively,and propose a linear feature calibration structure to train the PC-Net simultaneously,and the child network learns feature transfer factors and feature bias weights,and uses the transfer factors and bias weights to linearly feature calibrate the features extracted from the Parent network,to improve the convergence of the network by using local features hidden in the crowd *** addition,we use the pyramid vision transformer as the backbone of the PC-Net to extract crowd features at different levels,and design a global-local feature loss function(L2).We combine it with a crowd counting loss(LC)to enhance the sensitivity of the network to crowd features during the training process,which effectively improves the accuracy of crowd density *** experimental results show that the PC-Net significantly reduces the gap between fullysupervised and weakly-supervised crowd density estimation,and outperforms the comparison methods on five datasets of Shanghai Tech Part A,ShanghaiTech Part B,UCF_CC_50,UCF_QNRF and JHU-CROWD++.

关键词： Crowd density estimation linear feature calibration vision transformer weakly-supervision learning

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：