共查询到20条相似文献,搜索用时 15 毫秒
1.
Influences of nonassociated flow rules on three-dimensional seismic stability of loaded slopes 总被引:1,自引:1,他引:0
The influences of soil dilatancy angle on three-dimensional (3D) seismic stability of locally-loaded slopes in nonassociated flow rule materials were investigated using a new rotational collapse mechanism and quasi-static coefficient concept. Extended Bishop method and Boussinesq theorem were employed to establish the stress distribution along the rupture surfaces that are required to obtain the rate of internal energy dissipation for the nonassociated flow rule materials in rotational collapse mechanisms. Good agreement was observed by comparing the current results with those obtained using the translational or rotational mechanisms and numerical finite difference method. The results indicate that the seismic stability of slopes reduces by decreasing the dilatancy angle for nonassociated flow rule materials. The amount of the mentioned decrease is more significant in the case of mild slopes in frictional soils. A nearly infinite slope under local loading, whether its critical failure surface is 2D or 3D, not only depends on the magnitude of the external load, but also depends on the dilatancy angle of soil and the coefficient of seismic load. 相似文献
2.
The robustly asymptotical stability problem for discrete-time nonlinear systems with time-delay was investigated. Positive
definite matrix are constructed through Lyapunov functional. With the identity transform, property of matrix inverse and S-procedure,
a new sufficient condition independent of the size of time-delay for robust stability of discrete-time nonlinear systems with
time-delay is established. With Schur complement, another equivalent sufficient condition for robust stability of discrete-time
nonlinear systems with time-delay is given. Finally, a sufficient condition dependent on the size of time-delay for robust
stability of discrete-time nonlinear systems with time-delay is obtained. A unified approach is used to cast the robust stability
problem into a convex optimization involving linear matrix inequalities.
Foundation item: Project (60425310) supported by the National Natural Science Foundation of China; project (2001AA4422200) supported by the
Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of the Ministry of Education
of China 相似文献
3.
A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the
method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield
function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based
on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone
and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions
to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of
the proposed method for rationally optimizing the design of compaction grouting operations.
Foundation item: Project (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China; Project
(09JJ1008) supported by Hunan Provincial Natural Science Foundation of China 相似文献
4.
Directly searching method for slip plane and its influential factors based on critical state of slope 总被引:3,自引:1,他引:2
In order to determine the slip plane of slope directly by the calculation results of strength reduction method, and analyze
the influential factors of slope stability, a numerical model was established in plane strain mode by FLAC3D for homogeneous
soil slope, whose parameters were reduced until the slope reached the critical state. Then FISH program was used to get the
location data of slip plane from displacement contour lines. Furthermore, the method to determine multiple slip planes was
also proposed by setting different heights of elastic areas. The influential factors for the stability were analyzed, including
cohesion, internal friction angle, and tensile strength. The calculation results show that with the increase of cohesion,
failure mode of slope changes from shallow slipping to the deep slipping, while inclination of slip plane becomes slower and
slipping volume becomes larger; with the increase of friction angle, failure mode of slope changes from deep slipping to shallow
slipping, while slip plane becomes steeper and upper border of slip plane comes closer to the vertex of slope; the safety
factor increases little and slip plane goes far away from vertex of slope with the increase of tensile strength.
Foundation item: Project(20060533071) supported by the Doctoral Program Foundation of Higher Education of China; Project (20060400264) supported
by China Postdoctoral Science Foundation; Project (50774093) supported by the National Natural Science Foundation of China;
Project (1343-74236000014) supported by Graduate Student Innovation Foundation of Hunan Province, China 相似文献
5.
Stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling
The stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling were analyzed. The
effects of the fluctuation of the cutting force, the mass eccentricity and the hydrodynamic forces of cutting fluid could
be taken into consideration in the model of drilling shaft system. Based on the isoparametric finite element method, the variational
form of Reynolds equation in hydrodynamic fluid was used to calculate nonlinear hydrodynamic forces and their Jacobian matrices
simultaneously. In the stability analysis, a new shooting method for rapidly determining the periodic orbit of the nonlinear
drilling shaft system and its period was presented by rebuilding the traditional shooting method and changing the time scale.
Through the combination of theories with experiment, the correctness and effectiveness of the above methods are verified by
using the Floquet theory. The results show that the mass eccentricity can inhibit the whirling motion of drilling shaft to
some extent.
Foundation item: Project(2007CB707706) supported by the Major State Basic Research Development Program of China; Projects(2007E213, 2007E203)
supported by the Natural Science Foundation of Shaanxi Province, China 相似文献
6.
Simulation of spatially coupling dynamic response of train-track time-variant system 总被引:11,自引:1,他引:10
There exist three problems in the calculation of lateral vibration of the train-track time-variant system at home and abroad and the method to solve them is presented. Spatially coupling vibration analysis model of train-track time-variant system is put forward. Each vehicle is modeled as a multi-body system with 26 degrees of freedom and the action of coupler is also considered. The track structure is modeled as an assembly of track elements with 30 degrees of freedom, then the spatially coupling vibration matrix equation of the train-track time-variant system is established on the basis of the principle of total potential energy with stationary value and the "set-in-right-position" rule. The track vertical geometric irregularity is considered as the excitation source of the vertical vibration of the system, and the hunting wave of car bogie frame is taken as the excitation source of lateral vibration of the system. The spatially coupling vibration matrix equation of the system is solved by Wilson-θ d 相似文献
7.
A robust decentralized H∞ control problem was considered for uncertain multi-channel discrete-time systems with time-delay. The uncertainties were assumed to be time-invariant, norm-bounded, and exist in the system, the time-delay and the output matrices. Dynamic output feedback was focused on. A sufficient condition for the multi-channel uncertain discrete time-delay system to be robustly stabilizable with a specified disturbance attenuation level was derived based on the theorem of Lyapunov stability theory. By setting the Lyapunov matrix as block diagonal appropriately according to the desired order of the controller, the problem was reduced to a linear matrix inequality (LMI) which is sufficient to existence condition but much more tractable. An example was given to show the efficiency of this method. 相似文献
8.
Application of empirical mode decomposition based energy ratio to vortex flowmeter state diagnosis 总被引:1,自引:0,他引:1
To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions
was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using
the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic
mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected
the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the
flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal
for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is
greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter.
Foundation item: Project(200801346) supported by the China Postdoctoral Science Foundation; Project(2008RS4022) supported by the Hunan Postdoctoral
Scientific Program; Project(2008) supported by the Postdoctoral Science Foundation of Central South University 相似文献
9.
The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete (HFC) were investigated.
The early-age cracking behavior of the HFC was analyzed by combining the tests of evaporation capacity and electrical resistivity
of the HFC. In these tests, a modified flat-type specimen was adopted. The results show that the HFC will have a lower evaporation
capacity when it is mixed with fine fly ash, while it will have a higher evaporation capacity when grade III fly ash is used
as mineral admixture. And the electrical resistivity rate of HFC reduces with the increase of the content of fly ash. A nonlinear
relationship exists between the cracking time of HFC and the minimum electrical resistivity. The early-age cracking behavior
of HFC with fly ash can be enhanced by appropriately increasing the fine particle content and MgO, K2O, and SO3 contents of fly ash. The optimal content of fly ash, which makes a satisfied early-age cracking behavior of HFC, is obtained.
And when the content of fly ash exceeds a critical value, the early-age cracking behavior of HFC will rapidly decrease.
Foundation item: Project(50478003) supported by the National Natural Science Foundation of China; Project(2002F007) supported by the Natural
Science Foundation of Fujian Province, China 相似文献
10.
By taking cross-wind forces acting on trains into consideration, a dynamic analysis method of the cross-wind and high-speed
train and slab track system was proposed on the basis of the analysis theory of spatial vibration of high-speed train and
slab track system. The corresponding computer program was written by FORTRAN language. The dynamic responses of the high-speed
train and slab track under cross-wind action were calculated. Meanwhile, the effects of the cross-wind on the dynamic responses
of the system were also analyzed. The results show that the cross-wind has a significant influence on the lateral and vertical
displacement responses of the car body, load reduction factor and overturning factor. For example, the maximum lateral displacement
responses of the car body of the first trailer with and without cross-wind forces are 32.10 and 1.60 mm, respectively. The
maximum vertical displacement responses of the car body of the first trailer with and without cross-wind forces are 6.60 and
3.29 mm, respectively. The maximum wheel load reduction factors of the first trailer with and without cross-wind forces are
0.43 and 0.22, respectively. The maximum overturning factors of the first trailer with and without cross-wind forces are 0.28
and 0.08, respectively. The cross-wind affects the derailment factor and lateral Sperling factor of the moving train to a
certain extent. However, the lateral and vertical displacement responses of rails with the cross-wind are almost the same
as those without the cross-wind. The method presented and the corresponding computer program can be used to calculate the
interaction between trains and track in cross-wind.
Foundation item: Project (2007CB714706) supported by the Major State Basic Research and Development Program of China; Project (50678176) supported
by the National Natural Science Foundation of China; Project (NCET-07-0866) supported by the New Century Excellent Talents
in University 相似文献
11.
Based on the deficiency of time convergence and variability of Web services selection for services composition supporting
cross-enterprises collaboration, an algorithm QCDSS (QoS constraints of dynamic Web services selection) to resolve dynamic
Web services selection with QoS global optimal path, was proposed. The essence of the algorithm was that the problem of dynamic
Web services selection with QoS global optimal path was transformed into a multi-objective services composition optimization
problem with QoS constraints. The operations of the cross and mutation in genetic algorithm were brought into PSOA (particle
swarm optimization algorithm), forming an improved algorithm (IPSOA) to solve the QoS global optimal problem. Theoretical
analysis and experimental results indicate that the algorithm can better satisfy the time convergence requirement for Web
services composition supporting cross-enterprises collaboration than the traditional algorithms.
Foundation item: Project(70631004) supported by the Key Project of the National Natural Science Foundation of China; Project(20080440988)
supported by the Postdoctoral Science Foundation of China; Project(09JJ4030) supported by the Natural Science Foundation of
Hunan Province, China; Project supported by the Postdoctoral Science Foundation of Central South University, China 相似文献
12.
To avoid unstable learning, a stable adaptive learning algorithm was proposed for discrete-time recurrent neural networks. Unlike the dynamic gradient methods, such as the backpropagation through time and the real time recurrent learning, the weights of the recurrent neural networks were updated online in terms of Lyapunov stability theory in the proposed learning algorithm, so the learning stability was guaranteed. With the inversion of the activation function of the recurrent neural networks, the proposed learning algorithm can be easily implemented for solving varying nonlinear adaptive learning problems and fast convergence of the adaptive learning process can be achieved. Simulation experiments in pattern recognition show that only 5 iterations are needed for the storage of a 15×15 binary image pattern and only 9 iterations are needed for the perfect realization of an analog vector by an equilibrium state with the proposed learning algorithm. 相似文献
13.
A recently proposed model coupling with the solid-fluid of the saturated sand was utilized to study the deformation band.
Based on the critical state plasticity model by Borja and Andrade, the hydraulic conductivity tensor was naturally treated
as a function of the spatial discretization matrix about the displacement and the stress field, allowing a more realistic
representation of the physical phenomenon. The fully Lagrangian form of the Darcy law was resolved by Piola algorithm, and
then the flow law was gained, leading to the implementation of a modified model of the saturated sand. Then the criterion
for the onset of localization was derived and utilized to detect instability. The constitutive model was implemented in a
finite element program coded by FORTRAN, which was used to predict the formation and development of shear bands in plane strain
compression of saturated sand. At last, the formation mechanism of the shear band was discussed. It is shown that the model
works well, and the simulation sample bifurcates at 1.18% axial strain, which is in a good qualitative agreement with the
experiment. The pore pressure greatly affects the onset and development of the deformation band, and it obviously increases
around the localization-prone regions with the direction toward the outer side of the normal of the shear band, while the
pore stress flows nearly horizontally and is distributed equally far away the shear band region.
Foundation item: Project(2006G007-C) supported by the Foundation of the Science and Technology Section of Ministry of Railway of China; Project(77206)
supported by the Excellent PhD Thesis Innovation Foundation of Central South University, China 相似文献
14.
A design method for controllers and a comprehensive stability analysis for an acrobat based on Lyapunov functions are presented.
Three control laws based on three Lyapunov functions are designed to increase the energy so as to move the acrobot into the
unstable inverted equilibrium position, and solve the problem of posture and energy. The concept of a non-smooth Lyapunov
function is employed to analyze the stability of the whole system. The validity of this strategy is demonstrated by simulations.
Foundation item: Project (60425310) supported by the National Science Foundation of China; project (2001AA4422200) supported by the Teaching
and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of the Ministry of Education of
China 相似文献
15.
TheH
∞ control problem for a class of systems with time-varying and nonlinear uncertainties is considcred. A new sufficient condition
based on LMI is provided to judge their robust stability andL
2-gain finiteness. Solvability conditions are presented for both state feedback and output feedback cases, which are all reduced
to solutions of LMIs. The design procedure is also discussed via LMI approach.
Project supported by the National Natural Science Foundation of China (Grant No. 59704004). 相似文献
16.
A 3-D geometrical nonlinear model for the entire lift system of 1000-m sea trial system of China Ocean Mineral Resources R&D Association was established with finite element method. The model was utilized to analyze the dynamic characteristics of the vertical pipe under the influence of moving velocity, current direction and wave. The simulation results show that the axial stress is dominant on the vertical pipe, its maximum is located at the pipe top, all stresses are much less than the allowable value of the vertical pipe and joint; the heave motion leads to violent fluctuation of the force and stress, but a period of 8 s is not likely to resonate the present pipe; against the current, 0.50 m/s is the suggested moving velocity of the ship and miner, while along the current, the moving velocity can be slightly higher than 0.75 m/s. 相似文献
17.
The issue of reducing energy consumption for the job-shop scheduling problem in machining systems is addressed, whose dual
objectives are to minimize both the energy consumption and the makespan. First, the biobjective model for the job-shop scheduling
problem is proposed. The objective function value of the model represents synthesized optimization of energy consumption and
makespan. Then, a heuristic algorithm is developed to locate the optimal or near optimal solutions of the model based on the
Tabu search mechanism. Finally, the experimental case is presented to demonstrate the effectiveness of the proposed model
and the algorithm.
Foundation item: Project (50475062) supported by the National Natural Science Foundation of China; project (2004-47-19) supported by the
Natural Science Foundation of Chongqing City of China 相似文献
18.
Lattice constants, total energies and densities of states of transition metals Fe, Ru and Os with BCC, FCC and HCP structures
were calculated by the GGA+PBE functional and the ultrasoft pseudo-potential plane wave method, and compared with those of
the first-principles projector augmented wave (PAW) method, CALPHAD method and experimental data. The results show that the
lattice stability of this work is ΔG
BCC-HCP>ΔG
FCC-HCP>0, agreeing well with those of PAW method in the first-principles and CALPHAD method except for BCC-Fe. And the densities
of state of HCP-Ru and Os have an obvious character of stable phase, agreeing completely with the results of the total energy
calculations. Further analyses of atomic population show that the transition rate of electrons from s to p state for HCP,
FCC and BCC crystals increases from Fe to Os, and a stronger cohesion, a higher cohesive energy or a more stable lattice between
atoms of heavier metals are formed.
Foundation item: Project(20070533118) supported by the Doctoral Discipline Foundation of Ministry of Education of China; Projects(50471058,
50271085) supported by the National Natural Science Foundation of China; Project supported by the Postdoctoral Foundation
of Central South University, China 相似文献
19.
采用极限分析方法进行边坡稳定性分析通常采用线性MohrColumn破坏准则。但大量实验证明,岩土体的破坏包络线是非线性曲线。基于切线法和积分的思想,推导了基于非线性破坏准则的极限分析上限法求解竖直边坡稳定性和临界高度的计算公式。应用该方法计算了竖直边坡的稳定系数,并与文献中的计算结果进行了比较,结果相差很小。另外,对非线性破坏准则强度参数对竖直开挖边坡稳定性的影响分析结果表明,这些参数对边坡的稳定性分析结果起关键作用。 相似文献
20.
Using the orthogonal experimental design method involving three factors and three levels, the flexural strength and the compressive
strength of copolymer grouting material were studied with different compositions of water-cement ratio (mass fraction of water
to cement), epoxy resin content, and waterborne epoxy curing agent content. By orthogonal range and variance analysis, the
orders of three factors to influence the strength, the significance levels of different factors, and the optimized compound
ratio scheme of copolymer grouting material mixture at different curing ages were determined. An empirical relationship among
the strength of copolymer grouting material, the water-cement ratio, the epoxy resin content, and the waterborne epoxy curing
agent content was established by multivariate regression analysis. The results indicate that water-cement ratio is the most
principal and significant influencing factor on the strength. Epoxy resin content and waterborne epoxy curing agent content
also have a significant influence on the strength. But epoxy resin content has a greater influence on the 7-day and 28-day
flexural strength, and waterborne epoxy curing agent content has a greater influence on the 3-day flexural strength and the
compressive strength. The copolymer grouting material with water-cement ratio of 0.4, epoxy resin content of 8% (mass fraction)
and waterborne epoxy curing agent content of 2% (mass fraction) is the best one for repairing of cement concrete pavement.
The flexural strength and the compressive strength have good correlation, and the ratio of compressive strength to flexural
strength is between 1.0 and 3.3.
Foundation item: Projects(40728003, 40772180, 40802064) supported by the National Natural Science Foundation of China; Project (07JJ4012)
supported by the Hunan Provincial Natural Science Foundation of China; Project(20080430680) supported by China Postdoctoral
Science Foundation; Project(B308) supported by Shanghai Leading Academic Discipline Project 相似文献