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1.
Dynamical Behavior of Nonlinear Viscoelastic Timoshenko Beams with Damage on a Viscoelastic Foundation 总被引：2，自引：0，他引：2
Based on convolution-type constitutive equations for linear viscoelastic materials with damage and the hypotheses of Timoshenko beams with large deflections, the nonlinear equations governing dynamical behavior of Timoshenko beams with damage on viscoelastic foundation were firstly derived. By using the Galerkin method in spatial domain, the nonlinear integro-partial differential equations were transformed into a set of integro-ordinary differential equations. The numerical methods in nonlinear dynamical systems, such as the phase-trajectory diagram, Poincare section and bifurcation figure, were used to solve the simplified systems of equations. It could be seen that simplified dynamical systems possess the plenty of nonlinear dynamical properties. The influence of load and material parameters on the dynamic behavior of nonlinear system were investigated in detail. 相似文献
2.
Jane B. Keat Jane M. Wilburne 《美中教育评论》2009,6(7):61-67
This paper presents a mixed methods study that explored how storybooks influence kindergarten children＇s mathematical achievement and approaches to mathematics learning. Teachers＇ observations and research stating primary grade children＇s lack of mathematical knowledge and negative attitudes towards mathematics served as the impetus for the study. Three kindergarten teachers taught a mathematics unit using various children＇s storybooks and the characters in the stories as the context for mathematical problems. The results of the study show an impact on students＇ mathematical achievement as well as the identification of four themes that emerged on how students＇ approaches to learning were influenced when storybooks were integrated into the mathematics unit. 相似文献
3.
Cooperative system bridges comprise several basic structures that act jointly to improve structural characteristics. We delved into the historical development of cooperative system bridges. Cooperative systems are classified as different-load cooperative systems and same-load cooperative systems by distinguishing the modes of load distribution. For different-load cooperation, individual basic structures are at different positions in the direction along bridge axis and carry the loads separately. While for same-load cooperation, all basic structures overlap in geometrical locations and support the entire loads conjointly. The choosing of span ratios between basic structures, the design of connections of different-load cooperative systems were discussed as well as optimizations of relative rigidity for same-load cooperative systems which greatly influence structural characteristics. The general situation and several structural measurements of several cooperative bridges were demonstrated. This information can assist engineers in developing their concepts in cooperative systems and can lead to more efficient and economical cooperative bridges. 相似文献
4.
考虑剪切效应有限变形粘弹性板的动力稳定性 总被引：4，自引：0，他引：4
Based on Reddy‘s theory of plates with higher-order shear deformations and the Boltzmann superposition principles,the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects,The Galerkin method was applied to simplify the set of equations.The numerical methods in nonlinear dynamics were used to solve the simplified system.It could e seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads.The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelatic plates were investigated. 相似文献
5.
The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange＇s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge motions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions. 相似文献
6.
LIQ M 《天津大学学报(英文版)》2006,12(B09):22-30
In order to ensure the highest safety requirements, nuclear power plant structures （the containment structures, the fuel storages and transportation systems） should be assessed against all possible internal and external impact threats. The internal impact threats include kinetic missiles generated by the failure of high pressure vessels and pipes, the failure of high speed rotating machineries and accidental drops, The external impact threats may come from airborne missiles, aircraft impact, explosion blast and fragments. The impact effects of these threats on concrete and steel structures in a nuclear power plant are discussed. Methods and procedures for the impact assessment of nuclear power plants are introduced. Recent studies on penetration and perforation mechanics as well as progresses on dynamic properties of concrete-like materials are presented to increase the understanding of the impact effects on concrete containment structures. 相似文献
7.
LI Q M 《天津大学学报(英文版)》2006,12(Z1)
In order to ensure the highest safety requirements, nuclear power plant structures (the containment structures, the fuel storages and transportation systems) should be assessed against all possible internal and external impact threats. The internal impact threats include kinetic missiles generated by the failure of high pressure vessels and pipes, the failure of high speed rotating machineries and accidental drops. The external impact threats may come from airborne missiles, aircraft impact, explosion blast and fragments. The impact effects of these threats on concrete and steel structures in a nuclear power plant are discussed. Methods and procedures for the impact assessment of nuclear power plants are introduced. Recent studies on penetration and perforation mechanics as well as progresses on dynamic properties of concrete-like materials are presented to increase the understanding of the impact effects on concrete containment structures. 相似文献
8.
Menekse Seden TAPAN Cigdem ARSLAN 《美中教育评论》2009,6(3):54-60
The main purpose of this research is to elements and mathematical properties when they are axiomatic structure of the Euclidian geometry forms a determine to what extent preservice teachers use visual dealing with a geometrical construction activity. The coherent field of objects and relations of a theoretical nature; and thus it constitutes a favorable ground for the learning of the reasoning and justification. In geometry, even if the reasoning is assisted by concrete elements such as drawings, it is not based on actions or spatio-visual elements. Arguments based on mathematical properties are required in geometrical reasoning. A successful teaching of the geometry directly depends on the subject knowledge of the teachers. Another purpose is to map out the different kinds of justifications implemented by teachers related to such an activity. Analyses of the responses indicate that a large proportion of preservice teachers use visual elements for their geometrical constructions and they are tended to use naive empiricism concerning their justifications. 相似文献
9.
10.
Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of external simply supported beams, pulling the beams gradually. Then vertical loads were applied to the beams while the frequencies and related coefficients were measured at every step. We calculated natural frequencies and the results indicate that natural frequencies increase as the prestressing force rises in the pre-crack stage, and decrease significantly during the post-crack stage. Substantial incoincidences exist between the calculated and experimental results for the frequency and its tendency to changel Based on the experimental results, we modified the stiffness and other parameters in the equations. The results calculated using the modified equations agree with experimental results well, so the modified eauations can be used nractically. 相似文献
11.
In this paper,the expected discounted penalty function is considered in the risk process with the time-correlated claims,that is,every main claim can cause a by-claim but the occurrence of the by-claim may be delayed.By the renewal argument,it is shown that the expected value satisfies a system of integro-differential equations.Moreover,the explicit expression for the Laplace transform of the expected value is derived by means of Rouchés theorem.A numerical example is 相似文献
12.
1 Introduction Inhomogenetiesintrafficrefertothosefactorsre sultingfromthechangeintrafficflowvolumes ,suchasthechangeinthenumberoflanes ,thedegradationofroads,andthedisturbanceatazebracrossingoratollstation ,etc .Theconsiderationoftheinhomo geneitiesgivesrisetospatiallyvaryingfluxintrafficcontinuummodels ,whichareusuallynon strictlyhy perbolicandhavenotbeenwellunderstoodmathemat ically .Therelatedstudiesinliteraturewerefewandthebehaviorandtheinfluenceoftheseinhomo geneitieswerenotclearenough… 相似文献
13.
A novel asymmetrical pitch system for rotary wing is presented. The pitch control characteristics are studied and analyzed.
Because elastic linkage is a key part in whole asymmetrical pitch system, in order to obtain the variation of the elastic
linkage deformation, an experimental platform mainly based on the device of micro aerial vehicles (MAVs) and a new control
system mounted on TMS320LF2407 are designed. This control system has its compacted configuration and reliability. Finally,
using this system to control the MAV for simulating the flying forward, experimental results show the MAV’s flight attitude
can be controlled based on the variation of the elastic linkage.
Project supported by the National Natural Science Foundation of China (Grant No.60605028), the National High-Technology Research
and Development Program of China (Grant No.2007AA04Z225), the Shanghai Rising-Star Program (Grant Nos.07QA14024, 07QH14006),
the Shanghai Shuguang Program (Grant No.07SG47), and the Shanghai Leading Key Laboratory of Mechanical Automation and Robotics
Science Foundation (Grant No.ZZ0805) 相似文献
14.
The bilinear Baecklund transformation (BT) provides a means of finding multisoliton solutions of some non-linear evolution equations, where Hirota‘s technique is used. In this paper, the bilinear BT for Toda lattice was modified and then some novel solutions of the Toda lattice was constructed through the modified BT. 相似文献
15.
A new algorithm is presented that generates developable Bézier surfaces through a Bézier curve called a directrix. The algorithm
is based on differential geometry theory on necessary and sufficient conditions for a surface which is developable, and on
degree evaluation formula for parameter curves and linear independence for Bernstein basis. No nonlinear characteristic equations
have to be solved. Moreover the vertex for a cone and the edge of regression for a tangent surface can be obtained easily.
Aumann’s algorithm for developable surfaces is a special case of this paper.
Project supported by the National Basic Research Program (973) of China (No. 2004CB719400), the National Natural Science Foundation
of China (Nos. 60373033 and 60333010) and the National Natural Science Foundation for Innovative Research Groups (No. 60021201),
China 相似文献
16.
In this paper we discuss a novel storage scheme for simultaneous memory access in parallel turbo decoder. The new scheme employs vertex coloring in graph theory. Compared to a similar method that also uses unnatural order in storage, our scheme requires 25 more memory blocks but allows a simpler configuration for variable sizes of code lengths that can be implemented on-chip. Experiment shows that for a moderate to high decoding throughput （40-100 Mbps）, the hardware cost is still affordable for 3GPP＇s （3rd generation partnership project） interleaver. 相似文献
17.
In the light of Ф-mapping method and the relationship between entropy and the Euler characteristic, the intrinsic topological structure of entropy of Kerr black holes is studied. From the Ganss-Bonnet-Chem theorem, it is shown that the entropy of Kerr black hole is determined by singularities of the Killing vector field of spacetime. These singularities naturally carry topological numbers, Hopf indices and Brouwer degrees, which can also be viewed as topological quantization of entropy of Kerr black holes. Specific results S = A/4 for non-extreme Kerr black holes and S = 0 for extreme ones are calculated independently by using the above-mentioned methods. 相似文献
18.
MAO Zhi-hong MA Li-zhuang ZHAO Ming-xi LI Zhong 《浙江大学学报(A卷英文版)》2006,7(9):1603-1608
INTRODUCTION With the proliferation of 3D scanning tools, in- terest in removing noise from meshes has increased. An important problem is how to suppress noise while preserving desirable geometric features of the model. In general, smoothing algorithms are roughly classi- fied into two categories: linear and nonlinear smoothing (Gonzalez and Woods, 2002). For linear smoothing, each mesh point is moved to the bary- center of its neighbors. Linear smoothing treats fea- ture (large variatio… 相似文献
19.
In this paper, we discuss a class of piecewise linear hyperbolic maps on the 2-torus. These maps arise in the second-order digital fdter with two＇ s complement arithmetic. By introducing codings underlying the map operations, we give some admissibility conditions for symbolic sequences and find some periodic properties of these symbolic sequences. Then we use these conditions to check the admissibility of periodic symbol sequences. 相似文献
20.
WANG Yong-cai ZHAO Qian-chuan ZHENG Da-zhong 《浙江大学学报(A卷英文版)》2006,7(6):927-936
INTRODUCTION With the prevalence of distributed computing and parallel programming languages (Barry and Allen, 1998), performance evaluation of the parallel execu-tion systems becomes important. In this work we derive bounds and an approximation of the mean response time of a particular type parallel program: program with Fork-Join tasks and executed in multi-processor with first come first served (FCFS) policy. This kind of program is general in large-scale simu-lation and numerical … 相似文献