744 research outputs found
Lateral distribution calculation of multi-I beam composite curved bridge with slip effect
This paper presents a modified rigid cross beam method to study the lateral distribution of multi-I beam composite curved bridge with slip effect. First, the effective stiffness expression of single composite curved beam with slip effect were established and calculated by the FEM. Secondly, the lateral load distribution of multi-I beam composite curved bridge is obtained by substituting the effective stiffness of the main composite curved beam into the rigid cross beam method. Finally, The FEM numerical examples show that this method can accurately describe the load distribution characteristics of multi-I beam composite curved bridge with slip effect
Positive solutions for nonlinear semipositone nth-order boundary value problems
In this paper, we investigate the existence of positive solutions for a class of nonlinear semipositone th-order boundary value problems. Our approach relies on the Krasnosel'skii fixed point theorem. The result of this paper complement and extend previously known result
Existence of positive solutions for nth-order boundary value problem with sign changing nonlinearity
In this paper, we investigate the existence of positive solutions for singular th-order boundary value problem where , may be singular at and (or) and the nonlinear term is continuous and is allowed to change sign. Our proofs are based on the method of lower solution and topology degree theorem
Local Binary Fitting Segmentation by Cooperative Quantum Particle Optimization
Recently, sophisticated segmentation techniques, such as level set method, which using valid numerical calculation methods to process the evolution of the curve by solving linear or nonlinear elliptic equations to divide the image availably, has become being more popular and effective. In Local Binary Fitting (LBF) algorithm, a simple contour is initialized in an image and then the steepest-descent algorithm is employed to constrain it to minimize the fitting energy functional. Hence, the initial position of the contour is difficult or impossible to be well chosen for the final performance. To overcoming this drawback, this work treats the energy fitting problem as a meta-heuristic optimization algorithm and imports a varietal particle swarm optimization (PSO) method into the inner optimization process. The experimental results of segmentations on medical images show that the proposed method is not only effective to both simple and complex medical images with adequate stochastic effects, but also shows the accuracy and high efficiency
Direct and inverse problems on free vibration analysis of cracked non-uniform beams carrying spring-mass systems by finite element method
This paper presents an analytical approach to investigate the free vibration analysis of cracked non-uniform beam carrying spring-mass systems by finite element method and illustrates a valid and reliable damage identification method which using hybrid neural genetic technique. Firstly, based on the finite element method, the dynamic characteristics of non-uniform cracked beam carrying spring-mass systems are obtained. Then, the first five frequencies are used as input parameters by combining genetic algorithm with neural network to identify the damage. Finally, Numerical simulations of direct and inverse problems of non-uniform cracked beams carrying a spring-mass system are carried out
Stabilization diagrams to distinguish physical modes and spurious modes for structural parameter identification
A novel clustering stabilization diagram combined with self adaptive differential evolution algorithm is proposed to identify the modal parameters of civil engineering structures. Compared with the traditional stabilization diagram, the clustering diagram has drawn more attention because it can distinguish physical and spurious modes due to its automatic performance. In this paper, a self adaptive differential evolution algorithm is proposed to optimize the initial clustering centers so as to improve the clustering stabilization diagram. Moreover, this paper presents a new idea that the modal assurance criterion (MAC) composed of mode shapes is selected as the Y-axis to replace the model orders or damping ratios in existing stabilization diagrams. The results of a benchmark test of bridge Z24 and the numerical simulation of a continuous beam and a cable-stayed bridge demonstrate the advantages of the proposed approaches and the reliability of detecting the modal parameters
Signatures of a Pressure-Induced Topological Quantum Phase Transition in BiTeI
We report the observation of two signatures of a pressure-induced topological
quantum phase transition in the polar semiconductor BiTeI using x-ray powder
diffraction and infrared spectroscopy. The x-ray data confirm that BiTeI
remains in its ambient-pressure structure up to 8 GPa. The lattice parameter
ratio c/a shows a minimum between 2.0-2.9 GPa, indicating an enhanced c-axis
bonding through pz band crossing as expected during the transition. Over the
same pressure range, the infrared spectra reveal a maximum in the optical
spectral weight of the charge carriers, reflecting the closing and reopening of
the semiconducting band gap. Both of these features are characteristics of a
topological quantum phase transition, and are consistent with a recent
theoretical proposal.Comment: revised final versio
Ionization Induced by the Ponderomotive Force in Intense and High-Frequency Laser Fields
Atomic stabilization is a universal phenomenon that occurs when atoms
interact with intense and high-frequency laser fields. In this work, we
systematically study the influence of the ponderomotive (PM) force, present
around the laser focus, on atomic stabilization. We show that the PM force
could induce tunneling and even over-barrier ionization to the otherwise
stabilized atoms. Such effect may overweight the typical multiphoton ionization
under moderate laser intensities. Our work highlights the importance of an
improved treatment of atomic stabilization that includes the influence of the
PM force
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