检索结果-南通市图书馆

EXACT SOLUTIONS FOR FREE IN-PLANE VIBRATIONS OF RECTANGULAR PLATES

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 Mechanica Solida Sinica 2011年第6期24卷 556-567页

作者： bo Liu Yufeng xing The Solid Mechanics Research Center Beijing University of Aeronautics and Astronautics Beijing 100191 China

All possible exact solutions are successfully obtained in terms of 10 sets of distinct eigensolutions for the free in-plane vibration of isotropic rectangular plates. The plates have simply supported condition at two opposite edges and any combination of classical boundary conditions at the other two edges. The exact solutions are validated through both mathematical proof and comparisons with the solutions of differential quadrature method. Some unusual phenomena are revealed in free in-plane vibrations of rectangular plates due to one of the eigenvalues being zero. This work constitutes an improved version of very recent corresponding work by the same authors lint. J. Mech. Sci., 2009, 51： 246-255]. both the solution forms and solving procedures in the previous work are substantially simplified. Some new results are also given, which are useful for validation purpose in future.

关键词： rectangular plate in-pane free vibration frequency mode shape exact solution

CHARACTERISTIC EQUATIONS AND CLOSED-FORM SOLUTIONS FOR FREE VIBRATIONS OF RECTANGULAR MINDLIN PLATES

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2009年第2期22卷 125-136页

作者： Yufeng xing bo Liu The Solid Mechanics Research Center Beijing University of Aeronautics and Astronautic Beijing 100083 China

The direct separation of variables is used to obtain the closed-form solutions for the free vibrations of rectangular Mindlin plates. Three different characteristic equations are derived by using three different methods. It is found that the deflection can be expressed by means of the four characteristic roots and the two rotations should be expressed by all the six characteristic roots,which is the particularity of Mindlin plate theory. And the closed-form solutions,which satisfy two of the three governing equations and all boundary conditions and are accurate for rectangular plates with moderate thickness,are derived for any combinations of simply supported and clamped edges. The free edges can also be dealt with if the other pair of opposite edges is simply supported. The present results agree well with results published previously by other methods for different aspect ratios and relative thickness.

关键词： Mindlin plate free vibration closed-form solution separation of variables

Analysis of a Shil’nikov Type Homoclinic Bifurcation

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2018年第5期34卷 901-910页

作者： Yan Cong XU xing bo LIU Department of Mathematics Hangzhou Normal University Hangzhou 310036 P. R. China Department of Mathematics Shanghai Key Laboratory of PMMP East China Normal University Shanghai 200241 P. R. China

The bifurcation associated with a homoclinic orbit to saddle-focus including a pair of pure imaginary eigenvalues is investigated by using related homoclinie bifurcation theory. It is proved that, in a neighborhood of the homoclinic bifurcation value, there are countably infinite saddle-node bifurcation values, period-doubling bifurcation values and double-pulse homoclinic bifurcation values. Also, accompanied by the Hopf bifurcation, the existence of certain homoclinie connections to the periodic orbit is proved.

关键词： Homoclinic bifurcation Hopf bifurcation Poincare map

Copper-Mediated Di- and Monofluoromethanesulfonylation of Arenediazonium Tetrafluoroborates： Probing the Fluorine Effect

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2018年第3期36卷 206-212页

作者： bo xing Chuanfa Ni Jinbo Hu Key Laboratory of Organofluorine Chemistry Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry University of Chinese Academy of Sciences Chinese Academy of Sciences 345Lingling Lu Shanghai 200032 China

A copper-mediated di- and monoffuoromethanesulfonylation of arenediazonium tetrafluoroborates using di- and monofluoromethanesul- finate reagents provides aryl difluoromethyl （or monofluoromethyl） sulfones in 8ood yields. It was found that the relative reactivity of these sodium fluoroalkanesulfinates in the present reactions decreases in the followin8 order： CH2FSO2Na 〉 CF2HSO2Na 〉 CF3SO2Na.

关键词： difluoromethanesulfonylation fluoromethanesulfonylation arenediazonlum sodium sulfinate fluorine effect

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

面向大规模图像检索的哈希学习综述

软件学报 2025年第1期36卷 79-106页

作者：张雪凝刘兴波宋井宽聂秀山王少华尹义龙山东大学软件学院山东济南250101 山东建筑大学计算机科学与技术学院山东济南250101 电子科技大学计算机科学与工程学院四川成都611731

随着互联网空间中图像数据的爆发式增长和图像应用领域的拓宽,大规模图像检索的需求与日俱增.哈希学习为大规模图像检索提供显著的存储与检索效率,并成为近年来一个研究热点.现有哈希学习综述存在着时效性弱与技术路线不清晰的问题,即... 详细信息

随着互联网空间中图像数据的爆发式增长和图像应用领域的拓宽,大规模图像检索的需求与日俱增.哈希学习为大规模图像检索提供显著的存储与检索效率,并成为近年来一个研究热点.现有哈希学习综述存在着时效性弱与技术路线不清晰的问题,即多总结5–10年前的研究成果,且较少总结哈希学习算法各组成部分间的关联关系.鉴于此,通过总结近20年公开发表的哈希学习文献,对面向大规模图像检索的哈希学习进行系统的综述性研究.首先,介绍哈希学习的技术路线和哈希学习算法的主要组成部分,包括损失函数、优化策略及样本外扩展映射.其次,将面向图像检索的哈希学习算法分为无监督哈希方法和监督哈希方法两类,并分别梳理每类方法的研究现状和演化过程.然后,介绍哈希学习算法评估通用的图像数据集与评估指标,并通过对比实验分析部分经典算法的性能.最后,结合哈希学习的局限性与新挑战对其发展前景进行阶段性总结与展望.

关键词：图像检索大规模数据近似最近邻检索哈希学习相似性保持

Quasi-steady aerodynamic characteristics of Terminal Sensitive Bullets with short cylindrical portion

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第2期17卷 633-649页

作者： Yong-liang Yang Rui Guo Rong-zhong Liu Liang Chen bo-yang xing bo-bo Zhao School of Mechanical Engineering Nanjing University of Science and TechnologyXiaolingwei 200210094NanjingChina The Seventh Design Department Aerospace Science and Technology CorporationThe Seventh Research Institute610100ChengduChina Unit 31102 of PLA 210000NanjingChina

The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal ***,there is little research in terms of the TSB andshort cylinder with two free ends,and particularly in this trajectory,where the scanning angleβand rollangle a vary over a broad range between 0°and *** this work wind tunnel experiments are firstconducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters forshort cylinder with aspect ratio L/D=*** to infinite cylinder,for the short cylinder with two freeends,the drag crisis phenomenon still exists in the critical regime 1.7×10^(5)≤Re≤6.8×10^(5).Then 3Dsimulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSbover a broad range of Re,L/D,a and *** sensitivity analysis of time step and grid are presented as ***β3=0,for short cylinder,the drag crisis phenomenon was also observed in the simulation,but notas obvious as in the wind tunnel *** some attitudes,there is an obvious Karman vortexin the wake ofshort cylinder and *** correlation between time-averaged aerodynamic coefficients and L/D,Re,a&l is *** vortex shedding frequency and shear layer behavior are obtained for quasi-steadyand unsteady ***,the effect of end's shape on drag reduction and vortex shedding frequency isanalyzed.

关键词： Turbulent flows around bluff body Critical regime Flow-induced structural vibration

Blind carrier frequency offset estimation for constant modulus signaling based OFDM systems: algorithm, identifiability, and performance analysis

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第1期11卷 14-26页

作者： Wei-yang XU bo LU xing-bo HU Zhi-liang HONG Department of Microelectronics Fudan University Shanghai 201203 China School of Information Science and Technology East China Normal University Shanghai 200241 China

Cartier frequency offset （CFO） estimation is critical for orthogonal frequency-division multiplexing （OFDM） based transmissions. In this paper, we present a low-complexity, blind CFO estimator for OFDM systems with constant modulus （CM） signaling. both single-input single-output （SISO） and multiple-input multiple-output （MIMO） systems are considered. Based on the assumption that the channel keeps constant during estimation, we prove that the CFO can be estimated uniquely and exactly through minimizing the power difference of received data on the same subcarriers between two consecutive OFDM symbols; thus, the identifiability problem is assured. Inspired by the sinusoid-like cost function, curve fitting is utilized to simplify our algorithm. Performance analysis reveals that the proposed estimator is asymptotically unbiased and the mean square error （MSE） exhibits no error floor. We show that this blind scheme can also be applied to a MIMO system. Numerical simulations show that the proposed estimator provides excellent performance compared with existing blind methods.

关键词： Orthogonal frequency-division multiplexing (OFDM) Constant modulus (CM) Carrier frequency offset (CFO) Blind estimation Multiple-input multiple-output (MIMO)

A high-performance biochar produced from bamboo pyrolysis with in-situ nitrogen doping and activation for adsorption of phenol and methylene blue

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2020年第11期28卷 2872-2880页

作者： Zhenhao Li bo xing Yan Ding Yunchao Li Shurong Wang State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China

Nitrogen doping is a promising method for the preparation of functional carbon *** this study,a nitrogen-doped porous coral biochar was prepared by using bamboo as raw material,urea as nitrogen source,and KHCO3 as green activator through in-situ *** structure of the obtained biochar was characterized by various techniques including nitrogen adsorption and desorption,Raman spectroscopy,X-ray photoelectron spectrometer,and *** adsorption properties of nitrogen-doped biochar were evaluated with phenol and methylene blue *** results showed that the nitrogen source ratio had a significant effect on the evolution of pore structure of *** urea addition ratio was beneficial to the development of pore *** optimum specific surface area of nitrogen-doped biochar could be up to 1693 m^2·g^-*** doping can effectively improve the adsorption capacity of biochar to phenol and methylene *** prepared at 973.15 K with low urea addition ratio exhibited the highest adsorption capacity for phenol and methylene blue,and the equilibrium adsorption capacity was 169.0 mg·g^-1 and 499.3 mg·g^-1,*** comparing the adsorption capacity of various adsorbents in related fields,it is proved that the nitrogen-doped biochar prepared in this study has a good adsorption effect.

关键词： In-situ pyrolysis Nitrogen doping Green activator Biochar Adsorption

The Analytic Eigenvalue Structure of the 1+1 Dirac Oscillator

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2020年第9期37卷 10-14页

作者： bo-xing Cao Fu-Lin Zhang Department of Physics School of ScienceTianjin UniversityTianjin 300072China

We study the analytic structure for the eigenvalues of the one-dimensional Dirac oscillator,by analytically continning its frequency on the complex plane.A twofold Riemann surface is found,connecting the two states of a pair of particle and *** can,at least in principle,accomplish the transition from a positive energy state to its antiparticle state by moving the frequency continuously on the complex plane,without changing the Hamiltonian after *** result provides a visual explanation for the absence of a negative energy state with the quantum number n=0.

关键词： transition. Dirac connecting