检索结果-南通市图书馆

Acta Metallurgica Sinica(English Letters) 2013年第1期26卷 25-32页

作者： jun cai Daogang LU School of Nuclear Science and Engineering North China Electric Power University

The structure and energy of He impurities and vacancy on （001） surface of bcc iron are investigated by an ab initio method. Three cases for stabilities of a He atom at the surface are found： some of He atoms at surface atomic layers （SAL） relax into vacuum gap; some of surface He atoms at octahedral interstitial site relax into more stable tetrahedral interstitial site; some of surface He atoms still stay at tetrahedral interstitial site. The un-stability of the He atom at the surface system can be explained by deformation mechanism of charge densities and electronic densities of states. It is found that formation energy of the point defects from the topmost SAL to bulk-like atomic layer increase gradually, for example, the formation energies of a monovacancy at the first five topmost SALs are equal to 0.33, 1.56, 2.04, 2.02 and 2.11 eV, respectively. The magnetic moments of Fe atoms in the surface atomic layers are also calculated.

关键词： ab initio calculations Single point defects bcc Fe (001) surface Electronicstructure

Cure of a New Type Composite on Noise Control and Effect of Filler Modification

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2003年第z1期19卷 135-136页

作者： jun cai Fei XU Weimin cai School of Municipal and Environment Englineering Harbin Institute of Technology Harbin150001china School of Environment Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China School of Environment Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China

A new type composite of high efficiency sound attenuation was cured. The superfine tungsten powder, plasticizerand stabilizer are added into the PVC resin and blended in the mixing chamber of a HAAKE rheometer. The effect ofthe filler modification is considered in the composite cure. The properties of modified composite and unmodified oneare studied by SEM morphology viewing, acoustic and mechanical measurement. The test results indicate that thereason of the better soundproof and mechanical properties is the particle uniform dispersion and stronger adhesion.

关键词： Composite, Filler modification, Soundproof property, Mechanical property

Optimization of resource allocation in FDD massive MIMO systems

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

Digital Communications and Networks 2024年第1期10卷 117-125页

作者： jun cai Chuan Yin Youwei Ding School of Artificial Intelligence and Information Technology Nanjing University of Chinese MedicineNanjing 210046China School of Electronic and Information Hangzhou Dianzi UniversityHangzhou 310018ZhejiangChina

The performance of massive MIMO systems relies heavily on the availability of Channel State Information at the Transmitter(CSIT).A large amount of work has been devoted to reducing the CSIT acquisition overhead at the pilot training and/or CsI feedback *** fact,the downlink communication generally includes three stages,i.e.,pilot training,CsI feedback,and data *** three stages are mutually related and jointly determine the overall system ***,there exist few studies on the reduction of csIT acquisition overhead from the global point of *** this paper,we integrate the Minimum Mean Square Error(MMSE)channel estimation,Random Vector Quantization(RVQ)based limited feedback and Maximal Ratio Combining(MRC)precoding into a unified framework for investigating the resource allocation *** particular,we first approximate the covariance matrix of the quantization error with a simple expression and derive an analytical expression of the received Signal-to-Noise Ratio(SNR)based on the deterministic equivalence *** the three performance metrics(the spectral efficiency,energy efficiency,and total energy consumption)oriented problems are formulated *** practical system requirements,these three metrics can be collaboratively ***,we propose an optimization solver to derive the optimal partition of channel coherence *** results verify the benefits of the proposed resource allocation schemes under three different scenarios and illustrate the tradeoff of resource allocation between three stages.

关键词： Massive MIMO FDD CSIT Resource allocation

Integrability and Exact Solutions of the(2+1)-dimensional KdV Equation with Bell Polynomials Approach

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2022年第4期38卷 861-881页

作者： jun-cai PU Yong CHEN School of Mathematical Sciences Shanghai Key Laboratory of Pure Mathematics and Mathematical PracticeEast China Normal UniversityShanghai 200062China College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China

In this paper,the bilinear formalism,bilinear B?cklund transformations and Lax pair of the(2+1)-dimensional KdV equation are constructed by the Bell polynomials *** N-soliton solution is derived directly from the bilinear ***,based on the two-soliton solution,the lump solution is given out analytically by taking special parameters and using Taylor expansion *** the help of the multidimensional Riemann theta function,multiperiodic(quasiperiodic)wave solutions for the(2+1)-dimensional KdV equation are obtained by employing the Hirota bilinear ***,the asymptotic properties of the one-and two-periodic wave solution,which reveal the relations with the single and two-soliton solution,are presented in detail.

关键词： the bilinear formalism bilinear B?cklund transformations Lax pair lump solution periodic wave solution the asymptotic properties

A Generalization of Implicit Ore-condition for Hamiltonicity of k-connected Graphs

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2020年第3期36卷 620-626页

作者： jun-qing cai Lin WANG School of Management Qufu Normal UniversityRizhao 276826China

In 2005,Flandrin et *** that if G is a k-connected graph of order n and V(G)=X1∪X2∪···∪Xk such that d(x)+d(y)≥n for each pair of nonadjacent vertices x,y∈Xi and each i with i=1,2,···,k,then G is *** order to get more sufficient conditions for hamiltonicity of graphs,Zhu,Li and Deng proposed the definitions of two kinds of implicit degree of a vertex v,denoted by id1(v)and id2(v),*** this paper,we are going to prove that if G is a k-connected graph of order n and V(G)=X1∪X2∪···∪Xk such that id2(x)+id2(y)≥n for each pair of nonadjacent vertices x,y∈Xi and each i with i=1,2,···,k,then G is hamiltonian.

关键词： implicit degree Hamiltonian cycle cyclability

Flow characteristics in a rotor-stator cavity with cooling air inlet at low radius

在线全文

学校读者我要写书评

暂无评论

航空动力学报 2015年第4期30卷 775-783页

作者： cai Xu LUO Xiang ZHAO Xi XUGuo-qiang cai jun National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics School of Energy and Power Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China Dalian Airforce Department of Information Network Communicaiton Non-Commissioned Office Academy Dalian Liaoning 116600 China Guizhou Aero-Engine Research Institute Aviation Industry Corporation of China Guiyang 550081 China

Experiments were conducted on a typical rotor-stator system where air entered through an annular slot at low radius and flowed out of the cavity axially through a rim seal between the rotor and the *** the seal in this rotor-stator system,the stationary shroud overlapped the rotating *** distributions at the stator surface and flow resistance coefficients of the rotor-stator cavity with a maximum gap of 67mm were measured under different dimensionless mass flow rates from 1.32×104 to 4.87×104 with a large range of rotational Reynolds numbers from 0.418×106 to 2.484×*** results show that pressure on the stator surface decreases with the increase of rotational Reynolds number when the dimensionless mass flow rate is below 1.3×104;when the dimensionless mass flow rate is above 3.034×104,the trend *** is the so-called"pressure inversion effect".However,dimensionless pressure does not show the same changes when rotational dynamic pressure is chosen as the *** resistance coefficient of the rotor-stator cavity is determined by the dimensionless mass flow rate and rotational Reynolds number;for practical application,the resistance coefficient can also be estimated by the turbulent flow parameter in the range of turbulent parameter from 0.1to 1.6.

关键词： cooling system rotor-stator system flow characteristics pressure distribution resistance coefficient

Soliton, breather, and rogue wave solutions for solving the nonlinear Schrodinger equation using a deep learning method with physical constraints

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第6期30卷 77-87页

作者： jun-cai Pu jun Li Yong Chen School of Mathematical Sciences Shanghai Key Laboratory of Pure Mathematics and Mathematical Practiceand Shanghai Key Laboratory of Trustworthy ComputingEast China Normal UniversityShanghai 200241China Shanghai Key Laboratory of Trustworthy Computing East China Normal UniversityShanghai 200062China College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China Department of Physics Zhejiang Normal UniversityJinhua 321004China

The nonlinear Schrodinger equation is a classical integrable equation which contains plenty of significant properties and occurs in many physical ***,due to the difficulty of solving this equation,in particular in high dimensions,lots of methods are proposed to effectively obtain different kinds of solutions,such as neural networks among ***,a method where some underlying physical laws are embeded into a conventional neural network is proposed to uncover the equation’s dynamical behaviors from spatiotemporal data *** with traditional neural networks,this method can obtain remarkably accurate solution with extraordinarily less ***,this method also provides a better physical explanation and *** this paper,based on the above method,we present an improved deep learning method to recover the soliton solutions,breather solution,and rogue wave solutions of the nonlinear Schrodinger *** particular,the dynamical behaviors and error analysis about the one-order and two-order rogue waves of nonlinear integrable equations are revealed by the deep neural network with physical constraints for the first ***,the effects of different numbers of initial points sampled,collocation points sampled,network layers,neurons per hidden layer on the one-order rogue wave dynamics of this equation have been considered with the help of the control variable way under the same initial and boundary *** experiments show that the dynamical behaviors of soliton solutions,breather solution,and rogue wave solutions of the integrable nonlinear Schrodinger equation can be well reconstructed by utilizing this physically-constrained deep learning method.

关键词： deep learning method neural network soliton solutions breather solution rogue wave solutions

Exergy analysis and performance enhancement of isopropanol-acetone-hydrogen chemical heat pump

在线全文

学校读者我要写书评

暂无评论

Frontiers in Energy 2017年第4期11卷 510-515页

作者： Min XU jun cai Xiulan HUAI Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China

Exergy loss analysis was conducted to identify the irreversibility in each component of the isopropanol- acetone-hydrogen chemical heat pump （IAH-CHP）. The results indicate that the highest irreversibility on a system basis occurs in the distillation column. Moreover, the effect of operating parameters on thermodynamic performances of the IAH-CHP was studied and the optimal conditions were obtained. Finally, the potential methods to reduce the irreversibility of the IAH-CHP system were investigated. It is found that reactive distillation is apromising alternative. The enthalpy and exergy efficiency of the IAH-CHP with reactive distillation increases by 24.1% and 23.2%, respectively.

关键词： waste heat reuse chemical heat pump exergyanalysis isopropanol

An Implicit Degree Condition for Relative Length of Long Paths and Cycles in Graphs

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

Acta Mathematicae Applicatae Sinica 2016年第2期32卷 365-372页

作者： jun-qing cai Hao LI School of Management Qufu Normal University L.R.I UMR 8623 CNRS and Universit'e Paris-Sud 11 Institute for Interdisciplinary Research Jianghan University

For a graph G, we denote by p（G） and c（G） the number of vertices of a longest path and a longest cycle in G, respectively. For a vertex v in G, id（v） denotes the implicit degree of v. In this paper, we obtain that if G is a 2-connected graph on n vertices such that the implicit degree sum of any three independent vertices is at least n ＋ 1, then either G contains a hamiltonian path, or c（G）〉 p（G） - 1.

关键词： Hamiltonian path dominating cycles implicit degree longest paths longest cycles

Portfolio Optimization with Uncertain Exit Time in Infinite-Time Horizon

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2013年第4期29卷 673-684页

作者： Wen-jing GUO jun cai School of Finance University of Finance and Economics Department of Statistics ang Actuarial Science University of Waterloo

In this paper, we study infinite-period mean-variance formulations for portfolio selections with an uncertain exit time. We employ the convergence control method together with the dynamic programming algorithm to derive analytical expressions for the optimal portfolio policy and the mean-variance efficient frontier under certain conditions. We illustrate these results by an numerical example.

关键词： infinite-time horizon mean-variance formulation stochastic optimal control dynamic programming algorithm optimal investment policy efficient frontier exit time