检索结果-南通市图书馆

A spatial frequency/spectral indicator-driven model for estimating cultivated land quality using the gradient boosting decision tree and genetic algorithm-back propagation neural network

引用

International Soil and Water Conservation Research 2022年第4期10卷 635-648页

作者： Ziqing Xia Yiping Peng Chenjie Lin ya Wen Huiming liu Zhenhua liu College of Natural Resources and Environment South China Agricultural UniversityGuangzhou510642China

Cultivated land quality(CLQ)is related to national food *** and high-precision monitoring of CLQ is crucial for the sustainable development of ***,current satellite image-based evaluation methods that only consider the crop's spatial spectrum characteristics in the key growth stages cannot accurately estimate *** study proposes a new method based on time-series spectral data of crop growth to improve the accuracy of CLQ *** study was conducted in the Conghua District of guangzhou,guangdong Province,*** results showed that seven spectral indicators were determined as the optimal indicators based on the gradient boosting decision tree(gBDT)and variance inflation factor(VIF).And the genetic algorithm-back propagation neural network(gA-BPNN)model provided more accurate CLQ estimates than the partial least squares regression(PLSR)model,indicating a nonlinear relationship between CLQ and the *** addition,the gA-BPNN model with a normalized root mean square error(NRMSE)of 9.91%demonstrates the excellent potential for mapping CLQ over large *** model based on the seven optimal indicators of crop phenology provided higher accuracy than the gA-BPNN model based on the normalized difference vegetation index(NDVI)indicators in the spatial domain,significantly decreasing the NRMSE of the CLQ estimates by 3.17%.This further implied that the spectral indicators in the spatial frequency domain can improve the accuracy of estimating CLQ.

关键词： Cultivated land quality Time-series spectral data Spectral indicators Spatial frequency domain Conghua district

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

Mathematical Analysis on a general Delayed HBV Model with Capsids and Two Infection Routes

引用

Acta Mathematicae Applicatae Sinica 2024年第2期40卷 508-525页

作者： Li-li liu Hong-gang WANg ya-zhi LI Shanxi Key Laboratory of Mathematical Techniques and Big Data Analysis on Disease Control and Prevention Complex Systems Research CenterShanxi UniversityTaiyuan 030006China School of Mathematics and Statistics Qiannan Normal University for NationalitiesDuyun 558000China

Considering that HBV belongs to the DNA virus family and is hepatotropic,we model the HBV DNA-containing capsids as a *** this paper,a delayed HBV infection model is established,where the general incidence function and two infection routes including cell-virus infection and cell-cell infection are *** to some preliminaries,including well-posedness,basic reproduction number and existence of two equilibria,we obtain the threshold dynamics for the *** illustrate numerical simulations to verify the above theoretical results,and furthermore explore the impacts of intracellular delay and cell-cell infection on the global dynamics of the model.

关键词： delayed HBV model capsids general incidence function two infection routes global stability

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

空位缺陷硅烯纳米带结构与自旋极化电子性质的密度泛函紧束缚研究

引用

原子与分子物理学报 2025年第3期42卷 61-66页

作者：扶锦云吴丽君王爽迟中钰刘亚沈阳理工大学理学院沈阳110159

随着纳米电子器件和自旋电子学的不断发展,对小尺寸的纳米硅材料物理和化学性质的研究是研发新型微电子材料器件的基础.硅烯纳米带在实验制备和理论研究中均备受关注.本研究利用基于自洽电荷的密度泛函理论紧束缚方法,研究了不同宽度的... 详细信息

随着纳米电子器件和自旋电子学的不断发展,对小尺寸的纳米硅材料物理和化学性质的研究是研发新型微电子材料器件的基础.硅烯纳米带在实验制备和理论研究中均备受关注.本研究利用基于自洽电荷的密度泛函理论紧束缚方法,研究了不同宽度的硅烯纳米带的结构、稳定性和自旋极化电子性质.研究发现,稳定的完美和带有空位缺陷的硅烯纳米带表现为带有曲翘褶皱的蜂窝结构.纳米带边缘的曲翘度大于中心位置.空位缺陷更容易出现在纳米带边缘.纳米带的宽度可实现完美的硅烯纳米带的半导体性质和金属性之间的转换.硅烯纳米带中出现空位缺陷可有效调控纳米带自旋电子性质从半导体向金属性转变、半导体向半金属性转变,及金属性向为半导体或者半金属性质的转变.这种自旋电子性质的调控手段使得该种纳米材料在纳米电子自旋器件上有着潜在的应用价值.

关键词：硅烯纳米带自旋极化电子性质密度泛函紧束缚空位缺陷

来源：

维普期刊数据库博看期刊

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

Electrochemical behavior of tungsten in(NaCl–KCl–NaF–WO_3)molten salt

引用

Rare Metals 2013年第5期32卷 512-517页

作者： Jie Li Xin-Yu Zhang ya-Bin liu Yun-gang Li Ri-Ping liu Key Laboratory of Metastable Materials Science & Technology Yanshan University Key Laboratory of the Ministry of Education for Modern Metallurgy Technology College of Metallurgy & Energy Hebei United University

Abstract The electrochemical reaction mechanism and electrocrystaUization process of tungsten in the NaCl- KCl-NaF-WO3 molten salt were investigated at 973 K （700℃） by means of cyclic voltammetry, chronopotentiometry, and chronoamperometry techniques. The results show that the electrochemical reaction process of tungsten in the NaCl-KCl-NaF-WO3 molten salt system is a quasireversible process mix-controlled by ion diffusion rate and electron transport rate. Tungsten ion in this system is reduced to W（0） in two steps. The electrocrystallization process of tungsten is found to be an instantaneous, hemispheroid three-dimensional nucleation process and the tungsten ion diffusion coefficient of 2.361 × 10^-4 cm2.s^-1 is obtained at experimental conditions.

关键词： NaCl-KClNaF-WO3 Tungsten Electrochemical reduction mechanism Electrocrystallization process

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

Increasing the Content of β Phase of Poly(9,9-dioctylfluorene) by Synergistically Controlling Solution Aggregation and Extending Film-forming Time

引用

Chinese Journal of Polymer Science 2019年第7期37卷 664-673页

作者： ya-Di liu Qiang Zhang Xin-Hong Yu Jian-gang liu yan-Chun Han State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China Hefei 230026China

For poly(9,9-dioctylfluorene)(PFO),β phase (coplanar conformation with the intra-chain torsion angle of 165°) has a greater conjugation length and higher degree of order compared to those of α phase, which favors charge carrier transport. However, the highest content of β phase obtained so far is 45%. We propose to increase the content of β phase by promoting the solution aggregation of PFO molecules and extending film-forming time. For this purpose, 1,8-diiodooctane (DIO) is added to PFO o-xylene solution, which enhances the interaction of PFO chains and improves the planarity of PFO backbone, resulting in the formation of ordered aggregation. The aggregates act as nucleation centers to promote the formation of β phase. The content of β phase increases with increasing DIO concentration and reaches a platform of 39% as DIO is more than 4 vol%. Furthermore, the film is kept in a sealed environment with oxylene atmosphere for 3 h, thus the PFO molecules have enough time to diffuse to the crystallization front and achieve disorder-order transition. As a result, the crystallinity of PFO is improved significantly and the content of β phase increases to 52%, reaching the highest value reported so far.

关键词： β Phase Ordered aggregation Film-forming time Disorder-order transition

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

Cathodic process of nickel electrodeposition from ammonia-ammonium chloride solutions

引用

Rare Metals 2023年第3期42卷 1061-1066页

作者： Liang Yuan Zhi-Ying Ding Shi-Jun liu ya-Ning He School of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China

Mechanism of cathodic process on nickel electrodeposition from ammonia-ammonium chloride solutions was studied by Tafel polarization curves,linear sweep voltammetry(LSV),cyclic voltammograms(CV)and chronopotentiometry(CE)*** the electrolyte with 1.0 mol·L^(-1) NiCl_(2)·6H_(2)O,4.0 mol·L^(-1) NH_(3)·H_(2)O and2.5 mol·L^(-1) NH4Cl,nickel ion mainly complexed with ammonia and almost no free nickel ion could be *** is confirmed that the dominant form of nickel ammonia complex ion in the system is Ni(NH_(3))_(4)^(2+)by measuring the equilibrium potential of the electrode at various concentrations of *** species of Ni(NH_(3))42+turns into Ni(NH_(3))_(2)^(2+)during pre-chemical reaction step before discharging reduction ***,Ni(NH_(3))_(2)^(2+)discharges at the cathodic interface to form metal nickel deposit *** process is involved during nickel electrodeposition according to CV *** reduction reaction of Ni(NH_(3))_(2)^(2+)is irreversible which is controlled by diffusion *** processes are also accompanied during the electrodeposition process,except for the diffusioncontrolled process.

关键词： Electrodeposition Nickel Cathodic process Ammoniacal solution

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 FINITE VOLUME PROJECTION METHOD WITH HYBRID UNSTRUCTURED TRIANgULAR COLLOCATED gRIDS FOR INCOMPRESSIBLE FLOWS

引用

Journal of Hydrodynamics 2009年第2期21卷 201-211页

作者： gAO Wei DUAN ya-li liu Ru-xun Department of Mathematics University of Science and Technology of China Hefei 230026 China

In this article a finite volume method is proposed to solve viscous incompressible Navier-Stokes equations in two-dimensional regions with corners and curved boundaries. A hybrid collocated-grid variable arrangement is adopted, in which the velocity and pressure are stored at the centroid and the circumcenters of the triangular control cell, respectively. The cell flux is defined at the mid-point of the cell face. Second-order implicit time integration schemes are used for convection and diffusion terms. The second-order upwind scheme is used for convection fluxes. The present method is validated by results of several viscous flows.

关键词： incompressible viscous flows Navier-Stokes equations finite volume method projection method unstructured collocated grid

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 electrochemical properties of Li FePO_(4) cathode material by ionic thermal method using eutectic mixture of tetramethyl ammonium chloride-urea

引用

Rare Metals 2021年第12期40卷 3477-3484页

作者： Si-Nan Li Shao-Hua Luo liu ya.g Qing Wang ya-Hui Zhang Xin liu School of Materials Science and Engineering Northeastern UniversityShenyang 110819China School of Resources and Materials Northeastern University At QinhuangdaoQinhuangdao 066004China Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province Qinhuangdao 066004China

In this study, the LiFePO_(4) cathode was synthesized by the ionic thermal method using the deep eutectic mixture of tetramethyl ammonium chloride and urea. The synthetic conditions were systematically investigated by orthogonal experiments, which indicate that the optimal reaction time, reaction temperature, molar ratio of Li to DES and rotate speed are 96 h, 220 ℃, 1:14 and20 r·min^(-1), respectively. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM) were characterized to investigate the crystalline structure and morphology of the obtained materials, indicating well-crystallized LiFePO_(4) with olivine structure. And the physical properties of LiFePO_(4) were explored through Fourier transform infrared spectroscopy(FTIR),57 Fe Mo¨ ssbauer absorption spectra and Raman spectra. An initial discharge capacity can reach 151 m Ah·g^(-1) at 0.1 C rate for LiFePO_(4) following by calcining at 600 ℃ under the optimal conditions, and it retains 125.1 m Ah·g^(-1) after 100 cycles. These results demonstrated that the addition of ionic liquids can improve the rate performance, cycle performance and ion diffusion rate of LiFePO_(4).

关键词： LiFePO_(4) Deep eutectic solvents Ionic thermal method Orthogonal experiments Electrochemical performance

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

Direct ink writing of conductive materials for emerging energy storage systems

引用

Nano Research 2022年第7期15卷 6091-6111页

作者： Ting Huang Wenfeng liu Chenliang Su ya-yun Li Jingyu Sun College of Materials Science and Engineering Shenzhen Key Laboratory of Special Functional Materials&Shenzhen Engineering Laboratory for Advance Technology of CeramicsShenzhen UniversityShenzhen 518060China College of Energy Soochow Institute for Energy and Materials InnovationsJiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy TechnologiesSoochow UniversitySuzhou 215006China Institute of Microscale Optoelectronics International Collaborative Laboratory of 2D Materials for Optoelectronic Science&Technology of Ministry of EducationShenzhen UniversityShenzhen 518060China

Direct ink writing(DIW)has recently emerged as an appealing method for designing and fabricating three-dimensional(3D)*** 3D structures can be built layer-by-layer via digitally controlled extrusion and deposition of aqueous-based colloidal *** formulation of well-dispersed suspensions with specific rheological behaviors is a prerequisite for the use of this *** this review article,the fundamental concepts of DIW are presented,including the operation principles and basic *** strategies used for ink formulation are discussed with a focus on the most widely used electrode materials,including graphene,Mxenes,and carbon *** recent progress in printing design of emerging energy storage systems,encompassing rechargeable batteries,supercapacitors,and hybrid capacitors,is *** and future perspectives are also covered to provide guidance for the future development of DIW.

关键词： direct ink writing energy storage ink formulation conductive materials structure-performance relationship

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

NUMERICAL INVESTIgATION ON NON-NEWTONIAN FLOWS THROUgH DOUBLE CONSTRICTIONS BY AN UNSTRUCTURED FINITE VOLUME METHOD

引用

Journal of Hydrodynamics 2009年第5期21卷 622-632页

作者： gAO Wei liu Ru-xun DUAN ya-li Department of Mathematics University of Science and Technology of China Hefei 230026 China

This article presents a numerical investigation on a steady non-Newtonian flow through a two-dimensional channel with double constrictions. The power-law mode is employed in describing the non-Newtonian behavior of the flow. An unstructured finite volume method combined with a fractional-step projection method is developed for the discretization of incompressible equations governing the non-Newtonian flows. The important flow dynamics related with the arterial diseases, such as the wall shear stress and vortex generation, are also numerically studied in detail. Numerical results reveal that there are marked differences between Newtonian and non-Newtonian models.

关键词： double constrictions power-law fluid finite volume method unstructured grids

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：