检索结果-南通市图书馆

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 Sinica 2009年第5期25卷 689-698页

作者： Yufeng Xing Bo Liu The Solid Mechanics research Center, beihang university,100191 beijing, china The Solid Mechanics research Center Beihang University 100191 Beijing China

A new two-eigenfunctions theory, using the amplitude deflection and the generalized curvature as two fundamental eigenfunctions, is proposed for the free vibration solutions of a rectangular Mindlin plate. The three classical eigenvalue differential equations of a Mindlin plate are reformulated to arrive at two new eigenvalue differential equations for the proposed theory. The closed form eigensolutions, which are solved from the two differential equations by means of the method of separation of variables are identical with those via Kirchhoff plate theory for thin plate, and can be employed to predict frequencies for any combinations of simply supported and clamped edge conditions. The free edges can also be dealt with if the other pair of opposite edges are simply supported. Some of the solutions were not available before. The frequency parameters agree closely with the available ones through pb-2 rayleigh-ritz method for different aspect ratios and relative thickness of plate.

关键词： Mindlin plate Free vibration Closed form solution Separation of variable

Filterless Photosensors with Intrinsic Color Perception and Flexibility

在线全文

学校读者我要写书评

暂无评论

Chemical research in Chinese Universities 2024年第5期40卷 894-900页

作者： ZHOU Hongtao XU beihang ZHENG Xinjia GONG Jinchao ZHANG Kaitong HE Yonglin Key Laboratory of Advanced Light Conversion Materials and Biophotonics School of Chemistry and Life ResourcesRenmin University of ChinaBeijing100872P.R.China School of Mathematics Renmin University of ChinaBeijing100872P.R.China

Sensing materials possessing intrinsic color perception are indispensable prerequisites for the development of filterless photosensors,which could eliminate the need for complex device designs and avoid color distortion in *** materials are constrained by complex processing methods and limited ***,a color-photosensitive array based on ionic liquid with selective photothermal conversion(ILSPC)has been developed for intrinsic color *** on the selective absorption,photothermal conversion,and thermosensitivity of ILSPC,a photo-thermo-electric sensing system has been ***,the versatility of the two algorithms has been validated in color reconstruction and electrical signal *** an exploration,the photosensitive array showcases promising color recognition capabilities,potentially propelling the evolution of flexible photosensors.

关键词： Ionic liquid Filterless Intrinsic color perception Selective photothermal conversion Photosensitive array

Adaptive neuro fuzzy inference system for classification of water quality status

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

Journal of Environmental Sciences 2010年第12期22卷 1891-1896页

作者： Han Yan,Zhihong Zou,Huiwen Wang School of Economics and Management,beihang university,beijing 100191,china [a] School of Economics Management Beihang University Beijing 100191 China

An adaptive neuro fuzzy inference system was used for classifying water quality status of river. It applied several physical and inorganic chemical indicators including dissolved oxygen, chemical oxygen demand, and ammonia-nitrogen. A data set （nine weeks, total 845 observations） was collected from 100 monitoring stations in all major river basins in china and used for training and validating the model. Up to 89.59% of the data could be correctly classified using this model. Such performance was more competitive when compared with artificial neural networks. It is applicable in evaluation and classification of water quality status.

关键词： adaptive neuro fuzzy inference system artificial neural networks water quality status classification

Conditions for Parallel realizable Configurations in Synthesis of Constraint-based Flexure Mechanisms

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第6期25卷 1086-1095页

作者： LI Shouzhong, YU Jingjun*, and ZONG Guanghua robotics Institute, beihang university, beijing 100191, china 1. robotics Institute Beihang University Beijing 100191 China

In synthesis of flexure mechanism, parallel arrangement is paid more attention due to its advantages, such as compact structure and higher stiffness. researchers have derived many parallel flexure mechanisms, but seldom discuss which kind of flexure mechanism can be realized via fully parallel arrangement. The realizable conditions proposed in current work are complicated to engineering applications. To solve two problems on how to judge whether a flexure mechanism can be realized via fully parallel arrangement and how to realize those flexure mechanisms which cannot be realized via fully parallel arrangement, the algebraic condition is derived to judge whether a freedom space is parallel realizable after introducing the definition of parallel realizable and some propositions, and the condition is there exist 6-n independent line constraints in constraint space reciprocal to dimensional freedom space. Then the realizable constraint spaces reciprocal to freedom spaces with 1-3 dimensions are provided. As a result, not all freedom spaces are parallel realizable. For freedom spaces that are not parallel realizable, the criterion of decomposing DOF is proposed to achieve all motion patterns via parallel or hybrid arrangement, that is a high dimensional freedom space can be realized via combining several low dimensional freedom spaces which are parallel realizable. Specific decomposing strategies for 4 and 5 DOF are provided and a complete flowchart is presented to guide designing flexure mechanisms, particularly those which are not parallel realizable. As case studies, synthesis processes of two helical and 3T1r motions are provided to illustrate the proposed approach. The proposed method provides a feasible approach to realize all motion patterns.

关键词： flexure mechanism type synthesis screw theory line geometry constraint design

Simulation of three-dimensional nonideal MHD flow at high magnetic reynolds number

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

中国科学：技术科学英文版 2010年第1期53卷 206-212页

作者： LU HaoYu1 & Lee ChunHian2 1 School of Astronautics,beihang university,beijing 100191,china 2 National Laboratory for Computational Fluid Dynamics,beihang university,beijing 100191,china 1. School of Astronautics Beihang University Beijing 100191 China2. National Laboratory for Computational Fluid Dynamics Beihang University Beijing 100191 China

A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic *** eight-wave equations for magnetohydrodynamics(MHD) are proved to be a non-strict hyperbolic system,therefore it is difficult to develop its *** developed a new set of equations which cannot be numerically simulated by conservative TVD scheme directly due to its non-conservative form.A conservative TVD scheme augmented with a new set of eigenvectors is proposed in the *** validate this scheme,1-D MHD shock tube,unsteady MHD rayleigh problem and steady MHD Hartmann problem for different flow conditions are *** simulated results are in good agreement with the existing analytical *** this scheme can be used to effectively simulate high-conductivity fluids such as cosmic MHD problem and hypersonic MHD flow over a blunt body,etc.

关键词： magnetohydrodynamics(MHD) numerical simulation TVD MHD rayleigh flow MHD Hartmann flow

Design and Experiments of a robotic Fish Imitating Cow-Nosed ray

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2010年第2期7卷 120-126页

作者： Yueri Cai,Shusheng Bi,Licheng Zheng robotics Institute,beihang university,beijing 100191,P.r.china [a] robotics Institute Beihang University Beijing 100191 P. R. China

The cow-nosed ray is studied as natural sample of a flapping-foil robotic *** structure, motion discipline, and dynamicfoil deformation of cow-nosed ray are *** on the analysis results, a robotic fish imitating cow-nosed ray,named robo-ray Ⅱ, mainly composed of soft body, flexible ribs and pneumatic artificial muscles, is *** andswimming morphology of the robotic prototype are as that of a normal cow-nosed ray in *** propulsion parameters ofrobo-ray Ⅱ at normal conditions, including the St Number at linear swimming, thrust coefficient at towing are studied *** suitable driving parameters are confirmed considering the efficiency and swimming *** of 0.16 m·s’and thrust coefficient of 0.56 in maximum are achieved in experiments.

关键词： robotic fish cow-nosed ray flexible structure St Number thrust coefficient

A new control law based on characteristic exponent assignment for libration point orbit maintenance

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2010年第3期26卷 495-500页

作者： Jian Wei·Shi-Jie Xu Laboratory 504,School of Astronautics, beihang university,beijing 100191,china Laboratory 504 School of Astronautics Beihang University Beijing China

A new method is developed for stabilizing motion on collinear libration point orbits using the formalism of the circular restricted three body *** about the collinear libration point orbits yields an unstable linear parameter-varying system with periodic *** the variational equations,an innovative control law based on characteristic exponent assignment is introduced for libration point orbit maintenance.A numerical simulation choosing the richardson’s third order approximation for a halo orbit as a nominal orbit is conducted,and the results demonstrate the effectiveness of this control law.

关键词： Circular restricted three body problem Variational equations Libration point orbit maintenance Characteristic exponent assignment

An improved constrained steering law for SGCMGs with DPC

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第5期25卷 713-720页

作者： Lei Jin Shijie Xu dep.r.ment of Guidance, Navigation and Control,School of Astronautics, beihang university, 100191 beijing, china dep.r.ment of Guidance Navigation and Control School of Astronautics Beihang University 100191 Beijing China

An improved constrained （IC） steering law for single gimbal control moment gyros （SGCMGs） with deformed pyramid configuration （DPC） is proposed, First of all, the original system with five pyramid configuration （FPC） whose two adjacent gyros are in failure state is reconfigured as a degraded system with DPC. Then, the singular angular momentum hypersurfaces of the original and the degraded systems are plotted via the singular angular momentum equa- tion of SGCMGs. Based on singular surfaces, the differences between FPC and DPC in singularity and momentum envelope are obtained directly, which provide an important reference for steering law design of DPC. Finally, an IC steering law is designed and applied to DPC. The simulation results demonstrate that the IC steering law has advantages in simplicity of calculation, avoidance of singularity and exactness of output torque, which endow the degraded system with fine controllability in a restricted workspace.

关键词： Single gimbal control moment gyros (SGCMGs) - Deformed pyramid configuration (DPC) Failure Singularity - Steering law

Constructing a core framework of visual engine for Digital Earth system

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第S1期53卷 38-43页

作者： WENG JingNong,WANG YingJie & CAI Heng School of Computer,beihang university,beijing 100191,china beihang Univ Sch Comp Beijing 100191 Peoples R China

A visual engine is the core of a Digital Earth *** is a wide variety of functional requirements in Digital Earth system and different requirements correspond to different *** on the development of the visual engine for chinaStar,a 3D Digital china prototype software platform,and analysis of 3D Digital Earth platforms such as Google Earth,Virtual Earth,Skyline,etc,are discussed.A common core framework for a visual engine is proposed in this paper to construct a visual engine and then with this framework various Digital Earth application systems can be developed *** parametric model of the Earth,scheduling and optimization in visual field,choice of 3D graphics library,and designing component-based visual engine framework of Digital Earth are discussed in *** addition,the relationships among these four basic components and the construction of visualization applications of Digital Earth by this method are also discussed.

关键词： Digital Earth visual engine COMGIS core framework