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Identification of Damaged Teeth in Gears using Wavelet Transform Applied to the Angular Vibration Signal
Get PDFThis work represents a comparative study of Wavelet Transform of angular vibration signal and the traditional Fourier analysis applied to the signals of angular vibration, in one transmission which involve gears. How it is known, the elastic deformation of the material, together with the superficial irregularities of the teeth due to wear, provoke characteristic angular oscillations, which make it possible to distinguish between the regular functioning of a mechanism in good condition and the angular vibrations provoked by wear and the superficial irregularities of teeth in poor condition. However, the character of the vibrations produced in such circumstances means that Fourier’s analysis is not the most suitable processing technique for such cases. As the results of this work will show, wavelet transform applied to the angular vibration signal seems to be more suited to detecting and to identifying wear and other surface damage to the teeth of gears
Numerical Evaluation of Trabecular Bone Alterations: A Cell Method Application
Get PDFBone tissue is a complex multi-scale material and its morphological and functional characteristics are influenced during one’s life by constant changes, physiological and pathological. A recent technique can classify the mechanical response of trabecular bone by simulating the application of loads with a Cell Method model derived from plane radiographic images of the proximal epiphyses in the patient’s hand fingers, thus complementing the individual assessment with a low cost exam. The mesoscale pathological modifications (i.e. due to osteoporosis) can be detected and quantified, despite the simplification due to the use of radiograms. In this work, this approach is validated using four idealized structures, modelling different trabecular organizations in the site of interest. Then, the results obtained in six female subjects, age between 35 and 77, are discussed to highlight the potential relevance of this application for the study, in quantitative terms, of the trabecular bone alteration due to age, pathological conditions and lack of exposure to physiological mechanical stimuli (micro-gravity conditions)
Overview: Mechanism and Control of a Prosthetic Arm
Get PDFContinuous growth in industrialization and lack of awareness in safety parameters the cases of amputations are growing. The search of safer, simpler and automated prosthetic arms for managing upper limbs is expected. Continuous efforts have been made to design and develop prosthetic arms ranging from simple harness actuated to automated mechanisms with various control options. However due the cost constraints, the automated prosthetic arms are still out of the reach of needy people. Recent data have shown that there is a wide scope to develop a low cost and light weight upper limb prosthesis. This review summarizes the various designs methodologies, mechanisms and control system developed by the researchers and the advances therein.
Educating the patient to develop acceptability to prosthesis and using the same for the most basic desired functions of human hand, post amputation care and to improve patient’s independent life is equally important. In conclusion it can be interpreted that there is a wide scope in design in an adaptive mechanism for opening and closing of the fingers using other methods of path and position synthesis. Simple mechanisms and less parts may optimize the cost factor. Reduction in the weight of the prosthesis may be achieved using polymers used for engineering applications. Control system will remain never ending challenge for the researchers, but it is essential to maintain the simplicity from the patients perspective
The Fundamentals Underlying the Computations of Acceleration for General Dynamic Applications: Issues and Noteworthy Perspectives
Get PDFTo-date, with the exception of the Newmark method and the midpoint rule, most computational algorithms under the umbrella of LMS methods, which are predominantly employed in research and commercial software fail to properly evaluate acceleration computations accurately for conducting the numerical dynamic simulations. Indeed, this is not trivial and a sound theoretical basis of the fundamental underlying issues is described in detail. In this paper, we provide a resolution and point-out several noteworthy perspectives to address the proper evaluation of acceleration computations for structural dynamics applications with focus on the class of LMS methods as an illustration
A Meshless LBIE/LRBF Method for Solving the Nonlinear Fisher Equation: Application to Bone Healing
Get PDFA simple Local Boundary Integral Equation (LBIE) method for solving the Fisher nonlinear transient diffusion equation in two dimensions (2D) is reported. The method utilizes, for its meshless implementation, randomly distributed nodal points in the interior domain and nodal points corresponding to a Boundary Element Method (BEM) mesh, at the global boundary. The interpolation of the interior and boundary potentials is accomplished using a Local Radial Basis Functions (LRBF) scheme. At the nodes of global boundary the potentials and their fluxes are treated as independent variables. On the local boundaries, potential fluxes are avoided by using the Laplacian companion solution. Potential gradients are accurately evaluated without RBFs via a LBIE, valid for gradient of potentials. Nonlinearity is treated using the Newton-Raphson scheme. The accuracy of the proposed methodology is demonstrated through representative numerical examples. Fisher equation is solved here via the LBIE/LRBF method in order to predict cell proliferation during bone healing. Cell concentrations and their gradients are numerically evaluated in a 2D model of fractured bone. The results are demonstrated and discussed
DRBEM Solution of MHD Flow with Magnetic Induction and Heat Transfer
Get PDFThis study proposes the dual reciprocity boundary element (DRBEM) solution for full magnetohydrodynamics (MHD) equations in a lid-driven square cavity. MHD equations are coupled with the heat transfer equation by means of the Boussinesq approximation. Induced magnetic field is also taken into consideration. The governing equations in terms of stream function, temperature, induced magnetic field components, and vorticity are solved employing DRBEM in space together with the implicit backward Euler formula for the time derivatives. The use of DRBEM with linear boundary elements which is a boundary discretization method enables one to obtain small sized linear systems. This makes the whole procedure computationally efficient and cheap. The results are depicted with respect to varying physical parameters such as Prandtl (0:005 ≤ Pr ≤ 1), Reynolds (100 ≤ Re ≤ 2500), magnetic Reynolds (1 ≤ Rem ≤ 100), Hartmann (10 ≤ Ha ≤ 100) and Rayleigh (10 ≤ Ra ≤ 106) numbers for discussing the effect of each parameter on the flow and temperature behaviors of the fluid. It is found that an increase in Ha slows down the fluid motion and heat transfer becomes conductive. Centered square blockage causes secondary flows on its left and right even for small Re. Strong temperature gradients occur around the blockage and near the moving lid for increasing values of Ra
Mixed Unsplit-Field Perfectly Matched Layers for Plane-Electromagnetic-Wave Simulation in the Time Domain
Get PDFThis study is concerned with the development of new mixed unsplitfield perfectly matched layers (PMLs) for the simulation of plane electromagnetic waves in heterogeneous unbounded domains. To formulate the unsplit-field PML, a complex coordinate transformation is introduced to Maxwell's equations in the frequency domain. The transformed equations are converted back to the time domain via the inverse Fourier transform, to arrive at governing equations for transient electromagnetic waves within the PML-truncated computational domain. A mixed finite element method is used to solve the PML-endowed Maxwell equations. The developed PML method is relatively simple and straightforward when compared to split-field PML techniques. It also allows the use of relatively simple temporal schemes for integration of the semi-discrete form, in contrast to the PML methods that require the calculation of complicated convolution integrals or the use of finite difference methods. Numerical results are presented for plane microwaves propagating through concrete structures, and the accuracy of these solutions is investigated via a series of error analyses
Numerical Solutions of Fractional System of Partial Differential Equations By Haar Wavelets
Get PDFIn this paper, time fractional one dimensional coupled KdV and coupled modified KdV equations are solved numerically by Haar wavelet method. Proposed method is new in the sense that it doesn’t use fractional order Haar operational matrices. In the proposed method L1 discretization formula is used for time discretization where fractional derivatives are Caputo derivative and spatial discretization is made by Haar wavelets. L2 and L∞ error norms for various initial and boundary conditions are used for testing accuracy of the proposed method when exact solutions are known. Numerical results which produced by the proposed method for the problems under consideration confirm the feasibility of Haar wavelet method combined with L1 discretization formula
Improved Adaptive Particle Filter for Integrated Navigation System
Get PDFParticle filter based on particle swarm optimization algorithm is not precise enough and easily trapping in local optimum, it is difficult to satisfy the requirement of advanced integrated navigation system. To solve these problems, an improved adaptive particle filter based on chaos particle swarm was proposed and used in GPS/INS integrated navigation system. This algorithm introduced chaos sequence to update the weight and threshold, which could improve the quality of samples and reduce the local optimization and enhance the global searching ability. In addition, the avoid factor was set which made the particles be away from low likelihood area. Finally, simulation results indicate that this algorithm improved the accuracy and robustness of GPS/INS integrated navigation system
Meshfree Method for the Topological Design of Microstructural Composites
Get PDFMeshfree methods have found good applications in many new researches, which show very good potential to be powerful numerical tools. As an alternative to the mesh based methods, meshfree methods have the advantage of not using a predefined mesh for the domain discretization. In this study, a mesh free scheme based on the radial point interpolation method was used to solve the topological design of microstructures for composite materials. The explicit form of the radial point interpolation method (RPIM) interpolation augmented with polynomials is presented, which satisfies range-restricted properties and is applicable to integrate a physically meaningful density interpolation. Meanwhile gauss quadrature scheme was applied in order to calculate the physical meaningful properties of microstructure, while the homogenization method is applied to evaluate the effective macroscopic properties of a periodic microstructure. Typical numerical examples are used to demonstrate the effectiveness of the proposed method for designing composite materials with expected effective elasticity tensor