检索结果-南通市图书馆

STEP-LIKE CONTRAST STRUCTURE OF SINGULARLY PERTURBED OPTIMAL CONTROL PROBLEM＊

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2012年第1期30卷 2-13页

作者： Mingkang Ni Limeng wu Department of Mathematics East China Normal UniversityShanghai 200241China

The existence of step-like contrast structure for a class of singularly perturbed optimal control problem is presented by contrast structure theory. By means of direct scheme of boundary function method, we construct the uniformly valid asymptotic solution for the singularly perturbed optimal control problem. As an application, an example is given to illustrate the main result in this paper.

关键词： Singular perturbation Optimal control problem Contrast structure.

Supported Pt-Ni bimetallic nanoparticles catalyzed hydrodeoxygenation of dibenzofuran with high selectivity to bicyclohexane

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

Chinese Chemical Letters 2022年第1期33卷 234-238页

作者： Pengyu wu Chun Cai Chemical Engineering College Nanjing University of Science and TechnologyNanjing 210094China

Catalytic hydrodeoxygenation(HDO)is one of the most effective methods to upgrade the oxygen-containing compounds derived from coal tar to valuable ***,an efficient bimetallic catalyst Pt_(1)Ni_(4)/MgO was prepared and applied in the HDO of dibenzofuran(DBF).High yield(95%)of the desired product bicyclohexane(BCH)was achieved at 240℃and 1.2 MPa of H_(2).Superior catalytic performance could be ascribed to the"relay catalysis"of Pt sites and Ni sites,and the reaction pathway is proposed as ***-up experiment and recyclability test were also performed,which demonstrated the recyclability and promising potential application of Pt_(1)Ni_(4)/MgO.

关键词： Hydrodeoxygenation Dibenzofuran Bicyclohexane Bimetallic catalyst Relay catalysis

A Meshless and Parallelizable Method for Differential Equations with Time-Delay

在线全文

学校读者我要写书评

暂无评论

Numerical Mathematics(Theory,Methods and Applications) 2018年第1期11卷 92-127页

作者： Shulin wu Chengming Huang School of Mathematics and Statistics Sichuan University of Science and EngineeringZigong 643000China School of Mathematics and Statistics Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratoryof Engineering Modeling and ScientificComputing Huazhong University of Science and TechnologyWuhan 430074China

Numerical computation plays an important role in the study of differential equations with time-delay,because a simple and explicit analytic solution is usually un ***-stepping methods based on discretizing the temporal derivative with some step-size∆t are the main tools for this *** get accurate numerical solutions,in many cases it is necessary to require∆t<τand this will be a rather unwelcome restriction whenτ,the quantity of time-delay,is *** this paper,we propose a method for a class of time-delay problems,which is completely *** idea lies in representing the solution by its Laplace inverse transform along a carefully de-signed contour in the complex plane and then approximating the contour integral by the Filon-Clenshaw-Curtis(FCC)quadrature in a few fast growing *** computations of the solution for all time points of interest are naturally parallelizable and for each time point the implementations of the FCC quadrature in all subintervals are also *** each time point and each subinterval,the FCC quadrature can be implemented by fast Fourier *** results are given to check the efficiency of the proposed method.

关键词： Delay differential equations meshless/parallel computatio contour integral Filon-Clenshaw-Curtis quadrature

Recent advances in improving performances of the lightweight complex hydrides Li-Mg-N-H system

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

Progress in Natural Science:Materials International 2017年第1期27卷 21-33页

作者： Bao Zhang Ying wu China Iron & Steel Research Institute Group Advanced Technology & Materials Co. Ltd

A brief review of state-of-the art advances in improving performances of the lightweight complex hydrides LiMg-N-H system is reported. Among the hydrogen storage materials, Li-Mg-N-H combination systems are regarded as one of the most potential candidates for the vehicular applications owing to their high hydrogen storage capacity( > 5 wt% H) and a more appropriate thermodynamic properties of hydrogen absorption and desorption. In the Li-Mg-N-H systems, tremendous efforts have been devoted to improving the hydrogen storage properties by adjusting composition, revealing reaction mechanisms, adding catalysts and refining the microstructures, etc. During the studies, different mechanisms, such as the coordinated two-molecule or multimolecule reaction mechanism and the ammonia-mediated mechanism, are proposed and applied under some certain conditions. Catalysis and nanosizing are very effective in enhancing the kinetic properties and thermodynamic destabilization of Li-Mg-N-H systems. Due to nano effects, the space-confinement and nanoconfinement seems to be more effective for improving the hydrogen storage performance, and it is great significant to develop hydrogen storage materials by studying the nanoconfined effects on the Li-Mg-N-H systems.

关键词： Li-Mg-N-H system Hydrogen storage Catalysis Nanosizing Mechanism

Sharp constants for a class of multilinear integral operators and some applications

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2016年第5期59卷 907-920页

作者： wu Di YAN DunYan School of Mathematics and Computational Science Sun Yat-Sen University School of Mathematics University of Chinese Academy of Sciences

We investigate a class of multilinear integral operators with the nonnegative kernels, and prove that the norms of the operators can be obtained by integral of the product of the kernel function and finitely many basic functions. Using the integral, we can easily calculate the sharp constants for the multilinear Hilbert inequality, the generalized Hardy-Littlewood-Sobolev inequality and the multilinear Hardy operator.

关键词： best constants multilinear integral operator Hardy operator Hardy-Littlewood-Sobolev inequality

The jet over a stretching wall with suction or injection

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第3期54卷 502-510页

作者： XU Hang wu GuoXiong State Key Laboratory of Ocean Engineering School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Mechanical Engineering University College London London WC1E7JE UK

The steady laminar wall jet over a stretching surface in the presence of lateral suction or injection is considered. Similarity solutions absent in previous publications are found in some new ranges of parameters in the governing equation. The accuracy and reliability of the solutions have been checked through detailed convergence study and compared with the solutions from the numerical method and analytic method, and excellent agreement has been found. This gives the strongest evidence that those solutions are indeed new ones.

关键词： wall jet stretching wall injection/suction similarity solution

Several fourth-order force gradient symplectic algorithms

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第2期10卷 173-188页

作者： Jia Xu Xin wu Department of Physics Nanchang University Nanchang 330031 China

By adding force gradient operators to symmetric compositions, we build a set of explicit fourth-order force gradient symplectic algorithms, including those of Chin and coworkers, for a separable Hamiltonian system with quadratic kinetic en- ergy T and potential energy V. They are extended to solve a gravitational n-body Hamiltonian system that can be split into a Keplerian part H0 and a perturbation part H1 in Jacobi coordinates. It is found that the accuracy of each gradient scheme is greatly superior to that of the standard fourth-order Forest-Ruth symplectic integra- tor in T ＋ V-type Hamiltonian decomposition, but they are both almost equivalent in the mean longitude and the relative position for H0 ＋//1-type decomposition. At the same time, there are no typical differences between the numerical performances of these gradient algorithms, either in the splitting of T ＋ V or in the splitting of H0 ＋//1. In particular, compared with the former decomposition, the latter can dra- matically improve the numerical accuracy. Because this extension provides a fast and high-precision method to simulate various orbital motions of n-body problems, it is worth recommending for practical computation.

关键词： celestial mechanics -- methods: numerical

Ten-Year Climatological Features and Air Origin of Midlatitude Double Tropopauses

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2015年第12期32卷 1592-1602页

作者： wu Xue Lü Daren Key Laboratory for Atmosphere and Global Environment Observation Institute of Atmospheric PhysicsChinese Academy of Sciences

The 10-year climatological features related to midlatitude double tropopause events （DTs） are examined using ERA- Interim data from 2003 to 2012. The analysis is based on tropopauses defined by lapse rate. Results show that DTs are permanent or semi-permanent in the midlatitudes, and high DT frequency bands move poleward in winter and equatorward in summer, which is consistent with the seasonal movement of the subtropical jet. Based on our statistics, the second tropopause is found at about 100 hPa in the subtropics and at slightly lower altitudes in sub-polar regions. The thickness between the first and second tropopause is smaller in the subtropics and increases with latitude. Next, the origin of air sandwiched between the first and second tropopause of DTs is studied with a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code （Version 3） diabatic trajectory model. The results show that, in the lower or middle troposphere, air is transported into the DTs from lower latitudes, mainly in the tropics. The dominant source regions are mainly areas of deep convection and steep orography, e.g., the western Pacific and Himalayan Mountains, and they show strong seasonality following the seasonal shift of these strong upwelling regions.

关键词： double tropopause trajectory model stratosphere-troposphere exchange

Estimation of Cloud Node Acquisition

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2014年第1期19卷 1-12页

作者： Waseem Ahmed Yongwei wu Department of Computer Science and Technology Tsinghua National Laboratory for Information Science and Technology (TNLIST) Tsinghua University Research Institute of Tsinghua University in Shenzhen

Over the past decade, there has been a paradigm shift leading consumers and enterprises to the adoption of cloud computing services. Even though most cases are still in the early stages of transition, there has been a steady increase in the implementation of the pay-as-you-go or pay-as-you-grow models offered by cloud providers. Whether applied as an extension of virtual infrastructure, software, or platform as a service, many users are still challenged by the estimation of adequate resource allocation and the wide variations in pricing. Customers require a simple method of predicting future demand in terms of the number of nodes to be allocated in the cloud environment. In this paper, we review and discuss existing methodologies for estimating the demand for cloud nodes and their corresponding pricing policies. Based on our review, we propose a novel approach using the Hidden Markov Model to estimate the acquisition of cloud nodes.

关键词： cloud computing resource allocation hidden states probability distribution