检索结果-南通市图书馆

Fractional Dynamics of Fluid-Conveying Pipes Made of Polymer-Like Materials

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2018年第2期31卷 243-258页

作者： ye Tang Tianzhi Yang Bo fang School of Mechanical and Automotive Engineering Anhui Polytechnic University School of Aerospace Engineering Shenyang Aerospace University Department of Mechanics Tianjin University School of Astronautics Harbin Institute of Technology

The fluid-conveying pipes made of polymer-like materials are widely applied in engineering fields. However, the fractional dynamics of fluid-solid interaction remain unknown. In this work, the fractional dynamics of the pipes subjected to the excitation of supporting foun- dation are studied. A new nonlinear, fractional-order dynamic model is presented. The method of multiple scales is adopted directly to solve the model for the case of primary resonances. Numerical results are presented to show the effects of fractional order, foundation vibration, and other physical parameters on the steady-state response and stability.

关键词： Fluid-conveying pipes Fractional dynamics Method of multiple scales Polymer- like materials

The Fejer-Riesz Inequality for the Besov Spaces

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2011年第10期27卷 1995-2004页

作者： Hasi WULAN fang Qin ye Department of Mathematics Shantou University Shantou 515063 P. R. China

A Fejer Riesz inequality for the weighted Besov spaces Bp,q is given. Some characteriza- tions of functions in Bp.q in terms of their Taylor coefficients are obtained.

关键词： Fejer-Riesz inequality Besov spaces Taylor coefficients

The study of the transmission of GHz waves in the oceanic low altitude waveguide in the PEM-based gridded method

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 Journal of China Universities of Posts and Telecommunications 2013年第6期20卷 24-29页

作者： CHEN Chao ZHANG ye-rong WANG fang-fang College of Electronic Science and Engineering Nanjing University of Posts and Telecommunications Suqian Branch of Jiangsu Company Limited China Mobile Communications Corporation

A parabolic equation method （PEM）-based discrete algorithm is proposed and is used to obtain the field distribution in the evaporation duct space. This method not only improves the computing speed, but also provides the flexibility to adjust the simulation accuracy. Numerical simulation of the wave propagation in the oceanic waveguide structure is done. In addition, the initial field distribution and progressive steps are determined. The loss model in the waveguide is solved through the numerical solution. By comparing the characteristics of the radio wave propagation in the duct and in the normal atmospheric structure, we analyses the radio transmission over the horizon detection in the oceanic waveguide.

关键词： evaporation duct the PEM-based gridded method transmission analysis

Comparison of paleoclimatic characteristics between monsoon and westerly areas,China

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2001年第S1期46卷 119-124页

作者： Wei ye fang Ji Zhejiang Normal Univ Coll Life & Environm Sci Jinhua 321004 Peoples R China

For past decades there have been many studies on the climate features during the last interglacial and glacial periods. A comparison between the loess record of western China with that of monsoon areas shows some regional differences. ( i) Generally, the climate of the Yili region since the late Pleistocene was dry, with fluctuations. Late Pleistocene climate change in the study area can be divided into 5 stages, corresponding to 5 marine isotopic stages (MIS 1-MISS), (ii) Evidence from grain size composition, magnetic susceptibility, carbonate content, pollen assemblage and geochemistry shows that the climate during the last glacial period was instable. During MIS4 the westerly winds were strong and the humidity was relatively high. Compared with the early stage, MIS2 was dry. In MIS3, westerly winds were relatively weak; pedogenesis prevailed, forming paleo-sols. (iii) In contrast to the Loess Plateau the deposition rate of dust at the early stage was higher than at the late stage of the last galical

关键词： paleoclimatic characteristics monsoon area western China.

Target threat estimation based on discrete dynamic Bayesian networks with small samples

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2022年第5期33卷 1135-1142页

作者： ye fang MAO Ying LI Yibing LIU Xinrui College of Information and Communication Engineering Harbin Engineering UniversityHarbin 150001China Key Laboratory of Advanced Marine Communication and Information Technology Ministry of Industry and Information TechnologyHarbin Engineering UniversityHarbin 150001China

The accuracy of target threat estimation has a great impact on command *** Bayesian network,as an effective way to deal with the problem of uncertainty,can be used to track the change of the target threat ***,the traditional discrete dynamic Bayesian network(DDBN)has the problems of poor parameter learning and poor reasoning accuracy in a small sample environment with partial prior information *** the finiteness and discreteness of DDBN parameters,a fuzzy k-nearest neighbor(KNN)algorithm based on correlation of feature quantities(CF-FKNN)is proposed for DDBN parameter ***,the correlation between feature quantities is calculated,and then the KNN algorithm with fuzzy weight is introduced to fill the missing *** this basis,a reasonable DDBN structure is constructed by using expert experience to complete DDBN parameter learning and *** results show that the CF-FKNN algorithm can accurately fill in the data when the samples are seriously missing,and improve the effect of DDBN parameter learning in the case of serious sample *** the proposed method,the final target threat assessment results are reasonable,which meets the needs of engineering applications.

关键词： discrete dynamic Bayesian network(DDBN) parameter learning missing data filling Bayesian estimation

DeepHGNN: A Novel Deep Hypergraph Neural Network

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2022年第5期31卷 958-968页

作者： LIN Jingjing ye Zhonglin ZHAO Haixing fang Lusheng Tibetan Information Processing and Machine Translation Key Laboratory of Qinghai Province College of Computer Qinghai Normal University Xining Urban Vocational & Technical College The State Key Laboratory of Tibetan Intelligent Information Processing and Application

With the development of deep learning,graph neural networks(GNNs) have yielded substantial results in various application fields. GNNs mainly consider the pair-wise connections and deal with graph-structured data. In many real-world networks, the relations between objects are complex and go beyond *** is a flexible modeling tool to describe intricate and higher-order correlations. The researchers have been concerned how to develop hypergraph-based neural network model. The existing hypergraph neural networks show better performance in node classification tasks and so on, while they are shallow network because of oversmoothing, over-fitting and gradient vanishment. To tackle these issues, we present a novel deep hypergraph neural network(Deep HGNN). We design Deep HGNN by using the technologies of sampling hyperedge, residual connection and identity mapping, residual connection and identity mapping bring from graph convolutional neural networks. We evaluate Deep HGNN on two visual object datasets. The experiments show the positive effects of Deep HGNN, and it works better in visual object classification tasks.

关键词： Deep neural networks Graph neural network Hypergraph neural network Deep hypergraph neural network

Udwadia–Kalaba Equation for Constrained Mechanical Systems:Formulation and 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

Chinese Journal of Mechanical Engineering 2018年第6期31卷 11-24页

作者： Xiao-Min Zhao ye-Hwa Chen Han Zhao fang-fang Dong School of Automotive and Transportation Engineering Hefei University of TechnologyHefei 230009China The George W.Woodruff School of Mechanical Engineering Georgia Institute of TechnologyAtlanta 30332USA School of Mechanical Engineering Hefei University of TechnologyHefei 230009China

There are many achievements in the field of analytical mechanics, such as Lagrange Equation, Hamilton’s Principle, Kane’s Equation. Compared to Newton–Euler mechanics, analytical mechanics have a wider range of applications and the formulation procedures are more mathematical. However, all existing methods of analytical mechanics were proposed based on some auxiliary variables. In this review, a novel analytical mechanics approach without the aid of Lagrange’s multiplier, projection, or any quasi or auxiliary variables is introduced for the central problem of mechanical systems. Since this approach was firstly proposed by Udwadia and Kalaba, it was called Udwadia–Kalaba Equation. It is a representation for the explicit expression of the equations of motion for constrained mechanical systems. It can be derived via the Gauss’ s principle, d’Alembert’s principle or extended d’Alembert’s principle. It is applicable to both holonomic and nonholonomic equality constraints, as long as they are linear with respect to the accelerations or reducible to be that form. As a result, the Udwadia–Kalaba Equation can be applied to a very broad class of mechani?cal systems. This review starts with introducing the background by a brief review of the history of mechanics. After that, the formulation procedure of Udwadia–Kalaba Equation is given. Furthermore, the comparisons of Udwadia–Kalaba Equation with Newton–Euler Equation, Lagrange Equation and Kane’s Equation are made, respectively. At last, three di erent types of examples are given for demonstrations.

关键词： Udwadia–Kalaba Equation Mechanical system Constraint Moore–Penrose inverse

ZrC-SiC closed-cell ceramics with low thermal conductivity:Exploiting unique spherical closed-cell structure through tape casting and CVI techniques

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2024年第17期184卷 101-110页

作者： Kai Zhao fang ye Laifei Cheng Jinsong Yang Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China

Porous ultra-high temperature ceramics(UHTCs)are recognized as novel candidates for fulfilling the requirements of thermal protection systems of hypersonic aircrafts,as they possess excellent high-temperature resistance and low thermal ***,the reported porous UHTCs predominantly exhibit an open pore *** contrast,closed-cell UHTCs,formed by employing ceramic hollow microspheres(HMs)as pore-forming agents,hold great potential for achieving superior thermal insulation ***,the implementation of this strategy has been hindered by the scarcity of raw materials and preparation *** this paper,ZrC-SiC closed-cell ceramics were first successfully prepared through a combination of tape casting and chemical vapor infiltration(CVI)techniques,utilizing the self-developed ZrC HMs as the primary raw *** morphology,microstructure,and thermal insulation properties of the obtained ZrC-SiC closed-cell ceramics were *** results indicate that when the content of ZrC HMs is 30 vol.%,the density of the prepared porous ceramics is 2.09 g cm^(-3),with a closed porosity of 14.05%and a thermal conductivity of 1.69 W(m K)^(-1).The results clearly prove that the CVI process can successfully convert ZrC HMs into closed pore structures within porous *** introduction of ZrC HMs suppresses the contribution of free electrons to thermal conductivity and brings about a large number of solid-gas interfaces,which increases the interfacial thermal resistance and significantly reduces the phonon thermal ***,the as-prepared ZrC-SiC closed-cell ceramics show excellent thermal insulation *** study provides a new idea and method for the development of porous UHTCs and offers a more reliable material choice for thermal protection systems.

关键词： Closed-cell ceramics UHTCs Thermal insulation ZrC hollow microspheres CVI Interfacial thermal resistance

Application of the Modified nverse Design Method in the Optimization of the Runner Blade of a Mixed-Flow Pump

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 Journal of Mechanical Engineering 2018年第6期31卷 137-153页

作者： ye-Ming Lu Xiao-fang Wang Wei Wang fang-Ming Zhou School of Energy and Power Engineering Dalian University of TechnologyDalian 116000China Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of TechnologyDalian 116000China Collaborative Innovation Center of Major Machine Manufacturing in Liaoning Province Dalian 116000China

To improve the design speed and reduce the design cost for the previous blade design method, a modified inverse design method is presented. In the new method, after a series of physical and mathematical simplifications, a sail?like constrained area is proposed, which can be used to configure di erent runner blade shapes. Then, the new method is applied to redesign and optimize the runner blade of the scale core component of the 1400?MW canned nuclear coolant pump in an established multi?optimization system compromising the Computational Fluid Dynamics(CFD) analysis, the Response Surface Methodology(RSM) and the Non?dominated Sorting Genetic Algorithm?II(NSGA?II). After the execution of the optimization procedure, three optimal samples were ultimately obtained. Then, through comparative analysis using the target runner blade, it was found that the maximum e ciency improvement reached 1.6%, while the head improvement was about 10%. Overall, a promising runner blade inverse design method which will benefit the hydraulic design of the mixed?flow pump has been proposed.

关键词： Optimization Mixed?flow pump Inverse design method Runner blade Nuclear coolant