2015 12th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), 2015
Hybrid energy harvesting system combining multiple sources is an alternative solution to harvest ... more Hybrid energy harvesting system combining multiple sources is an alternative solution to harvest energy continuously and to increase the output power to bias the electronic systems. In this work is presented a prototype for harvesting energy, which combined three different sources. It contains a piezoelectric cantilever based on Lead-Zirconate Titanate piezoelectric transducer (PZT) in order to harvest the ambient vibrations, a solar cell for sunlight and an antenna capable to harvest ambient Radio Frequency (RF) energy. The design, implementation and characterization of the circuits for signal conversion from AC to DC for the case of piezoelectric generator, and the RF to DC for the antenna are presented. The RF harvesting circuit operates at 2.4 GHz obtaining a voltage of 71mV. The prototype is capable to generate a maximum DC power around 241.3 mW when the piezoelectric, solar cell and RF devices are connected together. Thus, the output power of this hybrid harvesting circuit is very attractive for low power electronic applications.
We introduce a multilevel PDE solver for equations whose solutions exhibit large gradients. Expan... more We introduce a multilevel PDE solver for equations whose solutions exhibit large gradients. Expanding on Ami Harten's ideas, we construct an alternative to wavelet-based grid refinement, a multiresolution coarsening method capable of capturing sharp gradients across different scales and thus improving PDE-based simulations by concentrating computational resources in places where the solution varies sharply. Our scheme is akin to Finite
Mathematics and Computers in Simulation, Nov 1, 2006
In all higher organisms, oxygen transport from arterioles to the surrounding tissue is critical f... more In all higher organisms, oxygen transport from arterioles to the surrounding tissue is critical for survival. However, the exact nature of the transport of oxygen from the arteriole to the surrounding tissue remains shrouded in mystery, in part because the experimental data are not in accordance with the well-established Krogh diffusion model. In this paper, arteriolar pulsation is added to Krogh's model to show that simple vasomotor changes in the arterioles' diameter are insufficient to explain the high mobility of oxygen away from the arteriolar wall.
International Journal of Computational Science and Engineering, 2006
Miniaturisation of integrated circuits continues to shrink device lengths to such an extent that ... more Miniaturisation of integrated circuits continues to shrink device lengths to such an extent that quantum tunnelling and confinement effects change the behaviour of MOSFET devices. In this paper, we present a methodology by which to model the gate region of an n-Metal Oxide Semiconductor (MOS) device using a simplified version of the density-gradient equations. The resulting singularly perturbed ODEs are solved using an adaptive wavelet collocation method that adapts dynamically to the boundary layer. Our results are shown to be in good agreement with those from a direct numerical solution of the Schrödinger-Poisson system.
Mathematics and Computers in Simulation, Feb 1, 2009
Whether tracking the eye of a storm, the leading edge of a wildfire, or the front of a chemical r... more Whether tracking the eye of a storm, the leading edge of a wildfire, or the front of a chemical reaction, one finds that significant change occurs at the thin edge of an advancing line. The tracking of such change-fronts comes in myriad forms with a wide variety of applications expressible as PDEs. Expanding on Ami Harten's ideas, we construct an alternative to wavelet-based grid refinement, a multiresolution coarsening method that is capable of capturing sharp gradients across different scales, thus improving PDE-based simulations by concentrating computational resources where the solution varies sharply. We present this alternative grid coarsening method and compare its performance to other multiresolution methods by means of several examples.
Mathematics and Computers in Simulation, Dec 1, 2008
An analytic model for the I-V characteristics of a symmetric, undoped, double gate MOSFET is pres... more An analytic model for the I-V characteristics of a symmetric, undoped, double gate MOSFET is presented. The model is twodimensional and extends recent work by Chen and Taur. The formulae involve the LambertW function recently used by Ortiz-Conde to obtain threshold voltage approximations of an undoped single gate MOSFET. The drift diffusion equations are also solved numerically and our approximate solution for the Fermi potential is shown to be in close agreement with the exact numeric solution. We present a compact model for the complete I-V characteristics of an undoped double gate MOSFET.
As MOSFET device lengths have shrunk to submicron level there has been a corresponding reduction ... more As MOSFET device lengths have shrunk to submicron level there has been a corresponding reduction in the oxide thickness. At around 4-5nm thicknesses, quantum tunneling and confinement effects start to become noticeable. The Density-Gradient equation [1,2] is a way of calculating quantum corrections to existing formulae without solving the full Poisson-Schrödinger system. The DG equations have boundary layer behavior and in order to determine the solution in the boundary layer correctly, specialized numerical techniques are required. Several methods have been proposed, including finite-difference and custom nonlinear discretization schemes. The former require a very fine mesh and the latter have been shown to be sensitive to the boundary conditions. We propose a new way to solve the equations using interpolating wavelets, which captures the best aspects of both approaches.
Electronic Journal of Differential Equations (EJDE) [electronic only], 2009
We introduce a mesh refinement strategy for PDE based simulations that benefits from a multilevel... more We introduce a mesh refinement strategy for PDE based simulations that benefits from a multilevel decomposition. Using Harten's MRA in terms of Schröder-Pander linear multiresolution analysis [20], we are able to bound discontinuities in R. This MRA is extended to R n in terms of n-orthogonal linear transforms and utilized to identify cells that contain a codimension-one discontinuity. These refinement cells become leaf nodes in a balanced Kd-tree such that a local dyadic MRA is produced in R n , while maintaining a minimal computational footprint. The nodes in the tree form an adaptive mesh whose density increases in the vicinity of a discontinuity.
In all living organisms, oxygen transport from arterioles to the surrounding tissue is critical f... more In all living organisms, oxygen transport from arterioles to the surrounding tissue is critical for survival. However, the exact nature of the transport of oxygen from the arteriole to the surrounding tissue remains shrouded in mystery, in part because the experimental data are not in accordance with the well-established Krogh diffusion model. In this paper, arteriole pulsation is added to Krogh's model to show that simple vasomotor changes in the arterioles' diameter is insufficient to explain the high mobility of oxygen away from the arteriole wall.
We introduce an adaptive multilevel framework for the solution of numerical partial differential ... more We introduce an adaptive multilevel framework for the solution of numerical partial differential equations (PDEs) whose solution exhibits codimension-one discontinuities, or fast transitions. Our framework has three main components: grid generation, derivative evaluation and solution integration. The grid generation portion is based on a linear version of Harten's generalized multiresolution analysis (MRA), which we use to bound discontinuities in R . We then extend this MRA to Rn in terms of n-orthogonal linear transforms to identify cells that contain a codimension-one discontinuity. These refinement cells become leaf nodes in a balanced kD-tree such that a local dyadic MRA is produced in Rn , while maintaining a minimal computational footprint. The nodes in the tree form an adaptive mesh whose density increases in the vicinity of a fast transition. Utilizing the multilevel information encoded in the kD-tree, we developed a multilevel multiquadric radial basis function (RBF) that is scale-aware. These multilevel RBFs can interpolate nodal values between different kD-trees without generating Gibbs' effects near a codimension-one discontinuity. This interpolation technique was extended to form a scale-aware RBF differential quadrature method that can evaluate derivatives on the kD-trees. Our differential quadrature method is capable of representing derivatives of the sampled solution surface on balanced kD-trees without generating Gibbs' effects near codimension-one discontinuities, supposing there is some minimal separation distance between each fast transition. In addition to the grid generation and derivative portion of our framework, we detail our ongoing research on the adaptive multilevel integration, and show some preliminary results.
There are many statistical methods of tracking single and multiple targets; this manuscript will ... more There are many statistical methods of tracking single and multiple targets; this manuscript will focus on the state estimation problem. Ideally, a generalization of the recursive Bayes non-linear filter would track and resolve the state(s) of single or multiple targets, but that is currently computationally intractable. The Probability Hypothesis Density (PHD) makes the tracking problem computationally feasible by propagating only the first-order multi-target statistical moments by using a particle filter implementation for the PHD. The problem then becomes one of estimating the targets’ state based on the output of the PHD when using a particle filter implementation. This paper describes one heuristic method for obtaining a state estimator from the PHD. The approach used in this paper, based on the Expectation-Maximization (EM) algorithm, views the PHD distribution as a mixture distribution, and the particles as an i.i.d. sampling from the mixture distribution. Using this, a maximum likelihood estimator for the parameters of the distribution can be generated. The EM seems to work fairly well, particularly when targets are well spaced.
Journal of Non-Equilibrium Thermodynamics, Jan 20, 2005
Oxygen delivery to the tissues is crucial to survival but our understanding of the processes invo... more Oxygen delivery to the tissues is crucial to survival but our understanding of the processes involved in the transport of oxygen from blood to tissue is incomplete. The aim of the present work is to illustrate a long-standing paradox regarding such transport by reporting new state-of-the-art measurements and by analyzing the results in several ways, thereby exploring possible resolutions of the paradox. Our model calculations show that slight extensions of system parameters are su‰cient to overcome the apparent inconsistencies. Alternatively, so far unappreciated mild e¤ects like flow-assisted di¤usion in the interstitium will explain the supernormal di¤usion of oxygen.
In the 21st century, the development of technologies to produce carbon free power sources remains... more In the 21st century, the development of technologies to produce carbon free power sources remains paramount. In this paper, we study an optimal power transmission strategy from a space-based satellite generation station to Earth using scalar diffraction theory. The resulting model is then solved via a spectral method that guarantees a compactly supposed profile from the transmitting antenna. Finally, the problem is then solved via a more general pseudo-spectral method using control theory.
International Conference on Mathematics and Engineering Techniques in Medicine and Biological Scienes, 2005
A robust algorithm is presented for labeling rows and columns in an irregular array. The algorith... more A robust algorithm is presented for labeling rows and columns in an irregular array. The algorithm is based on hierarchical pattern matching to a local lattice which is used as a template. Starting from the best local match, the pattern is expanded hierarchically to encompass the entire array. An application to labeling digitized images of an array of tissue sections mounted on a microscope slide is discussed.
There are many statistical methods of tracking single and multiple targets; this manuscript will ... more There are many statistical methods of tracking single and multiple targets; this manuscript will focus on the state estimation problem. Ideally, a generalization of the recursive Bayes non-linear filter would track and resolve the state(s) of single or multiple targets, but that is currently computationally intractable. The Probability Hypothesis Density (PHD) makes the tracking problem computationally feasible by propagating only the first-order multi-target statistical moments by using a particle filter implementation for the PHD. The problem then becomes one of estimating the targets’ state based on the output of the PHD when using a particle filter implementation. This paper describes one heuristic method for obtaining a state estimator from the PHD. The approach used in this paper, based on the Expectation-Maximization (EM) algorithm, views the PHD distribution as a mixture distribution, and the particles as an i.i.d. sampling from the mixture distribution. Using this, a maximum likelihood estimator for the parameters of the distribution can be generated. The EM seems to work fairly well, particularly when targets are well spaced.
A robust algorithm is presented for labeling rows and columns in an irregular array. The algorith... more A robust algorithm is presented for labeling rows and columns in an irregular array. The algorithm is based on hierarchical pattern matching to a local lattice, which is used as a template. Starting from the best local match, the pattern is expanded hierarchically to encompass the entire array. An application to labeling digitized images of an array of tissue sections mounted on a microscope slide is discussed.
2015 12th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), 2015
Hybrid energy harvesting system combining multiple sources is an alternative solution to harvest ... more Hybrid energy harvesting system combining multiple sources is an alternative solution to harvest energy continuously and to increase the output power to bias the electronic systems. In this work is presented a prototype for harvesting energy, which combined three different sources. It contains a piezoelectric cantilever based on Lead-Zirconate Titanate piezoelectric transducer (PZT) in order to harvest the ambient vibrations, a solar cell for sunlight and an antenna capable to harvest ambient Radio Frequency (RF) energy. The design, implementation and characterization of the circuits for signal conversion from AC to DC for the case of piezoelectric generator, and the RF to DC for the antenna are presented. The RF harvesting circuit operates at 2.4 GHz obtaining a voltage of 71mV. The prototype is capable to generate a maximum DC power around 241.3 mW when the piezoelectric, solar cell and RF devices are connected together. Thus, the output power of this hybrid harvesting circuit is very attractive for low power electronic applications.
We introduce a multilevel PDE solver for equations whose solutions exhibit large gradients. Expan... more We introduce a multilevel PDE solver for equations whose solutions exhibit large gradients. Expanding on Ami Harten's ideas, we construct an alternative to wavelet-based grid refinement, a multiresolution coarsening method capable of capturing sharp gradients across different scales and thus improving PDE-based simulations by concentrating computational resources in places where the solution varies sharply. Our scheme is akin to Finite
Mathematics and Computers in Simulation, Nov 1, 2006
In all higher organisms, oxygen transport from arterioles to the surrounding tissue is critical f... more In all higher organisms, oxygen transport from arterioles to the surrounding tissue is critical for survival. However, the exact nature of the transport of oxygen from the arteriole to the surrounding tissue remains shrouded in mystery, in part because the experimental data are not in accordance with the well-established Krogh diffusion model. In this paper, arteriolar pulsation is added to Krogh's model to show that simple vasomotor changes in the arterioles' diameter are insufficient to explain the high mobility of oxygen away from the arteriolar wall.
International Journal of Computational Science and Engineering, 2006
Miniaturisation of integrated circuits continues to shrink device lengths to such an extent that ... more Miniaturisation of integrated circuits continues to shrink device lengths to such an extent that quantum tunnelling and confinement effects change the behaviour of MOSFET devices. In this paper, we present a methodology by which to model the gate region of an n-Metal Oxide Semiconductor (MOS) device using a simplified version of the density-gradient equations. The resulting singularly perturbed ODEs are solved using an adaptive wavelet collocation method that adapts dynamically to the boundary layer. Our results are shown to be in good agreement with those from a direct numerical solution of the Schrödinger-Poisson system.
Mathematics and Computers in Simulation, Feb 1, 2009
Whether tracking the eye of a storm, the leading edge of a wildfire, or the front of a chemical r... more Whether tracking the eye of a storm, the leading edge of a wildfire, or the front of a chemical reaction, one finds that significant change occurs at the thin edge of an advancing line. The tracking of such change-fronts comes in myriad forms with a wide variety of applications expressible as PDEs. Expanding on Ami Harten's ideas, we construct an alternative to wavelet-based grid refinement, a multiresolution coarsening method that is capable of capturing sharp gradients across different scales, thus improving PDE-based simulations by concentrating computational resources where the solution varies sharply. We present this alternative grid coarsening method and compare its performance to other multiresolution methods by means of several examples.
Mathematics and Computers in Simulation, Dec 1, 2008
An analytic model for the I-V characteristics of a symmetric, undoped, double gate MOSFET is pres... more An analytic model for the I-V characteristics of a symmetric, undoped, double gate MOSFET is presented. The model is twodimensional and extends recent work by Chen and Taur. The formulae involve the LambertW function recently used by Ortiz-Conde to obtain threshold voltage approximations of an undoped single gate MOSFET. The drift diffusion equations are also solved numerically and our approximate solution for the Fermi potential is shown to be in close agreement with the exact numeric solution. We present a compact model for the complete I-V characteristics of an undoped double gate MOSFET.
As MOSFET device lengths have shrunk to submicron level there has been a corresponding reduction ... more As MOSFET device lengths have shrunk to submicron level there has been a corresponding reduction in the oxide thickness. At around 4-5nm thicknesses, quantum tunneling and confinement effects start to become noticeable. The Density-Gradient equation [1,2] is a way of calculating quantum corrections to existing formulae without solving the full Poisson-Schrödinger system. The DG equations have boundary layer behavior and in order to determine the solution in the boundary layer correctly, specialized numerical techniques are required. Several methods have been proposed, including finite-difference and custom nonlinear discretization schemes. The former require a very fine mesh and the latter have been shown to be sensitive to the boundary conditions. We propose a new way to solve the equations using interpolating wavelets, which captures the best aspects of both approaches.
Electronic Journal of Differential Equations (EJDE) [electronic only], 2009
We introduce a mesh refinement strategy for PDE based simulations that benefits from a multilevel... more We introduce a mesh refinement strategy for PDE based simulations that benefits from a multilevel decomposition. Using Harten's MRA in terms of Schröder-Pander linear multiresolution analysis [20], we are able to bound discontinuities in R. This MRA is extended to R n in terms of n-orthogonal linear transforms and utilized to identify cells that contain a codimension-one discontinuity. These refinement cells become leaf nodes in a balanced Kd-tree such that a local dyadic MRA is produced in R n , while maintaining a minimal computational footprint. The nodes in the tree form an adaptive mesh whose density increases in the vicinity of a discontinuity.
In all living organisms, oxygen transport from arterioles to the surrounding tissue is critical f... more In all living organisms, oxygen transport from arterioles to the surrounding tissue is critical for survival. However, the exact nature of the transport of oxygen from the arteriole to the surrounding tissue remains shrouded in mystery, in part because the experimental data are not in accordance with the well-established Krogh diffusion model. In this paper, arteriole pulsation is added to Krogh's model to show that simple vasomotor changes in the arterioles' diameter is insufficient to explain the high mobility of oxygen away from the arteriole wall.
We introduce an adaptive multilevel framework for the solution of numerical partial differential ... more We introduce an adaptive multilevel framework for the solution of numerical partial differential equations (PDEs) whose solution exhibits codimension-one discontinuities, or fast transitions. Our framework has three main components: grid generation, derivative evaluation and solution integration. The grid generation portion is based on a linear version of Harten's generalized multiresolution analysis (MRA), which we use to bound discontinuities in R . We then extend this MRA to Rn in terms of n-orthogonal linear transforms to identify cells that contain a codimension-one discontinuity. These refinement cells become leaf nodes in a balanced kD-tree such that a local dyadic MRA is produced in Rn , while maintaining a minimal computational footprint. The nodes in the tree form an adaptive mesh whose density increases in the vicinity of a fast transition. Utilizing the multilevel information encoded in the kD-tree, we developed a multilevel multiquadric radial basis function (RBF) that is scale-aware. These multilevel RBFs can interpolate nodal values between different kD-trees without generating Gibbs' effects near a codimension-one discontinuity. This interpolation technique was extended to form a scale-aware RBF differential quadrature method that can evaluate derivatives on the kD-trees. Our differential quadrature method is capable of representing derivatives of the sampled solution surface on balanced kD-trees without generating Gibbs' effects near codimension-one discontinuities, supposing there is some minimal separation distance between each fast transition. In addition to the grid generation and derivative portion of our framework, we detail our ongoing research on the adaptive multilevel integration, and show some preliminary results.
There are many statistical methods of tracking single and multiple targets; this manuscript will ... more There are many statistical methods of tracking single and multiple targets; this manuscript will focus on the state estimation problem. Ideally, a generalization of the recursive Bayes non-linear filter would track and resolve the state(s) of single or multiple targets, but that is currently computationally intractable. The Probability Hypothesis Density (PHD) makes the tracking problem computationally feasible by propagating only the first-order multi-target statistical moments by using a particle filter implementation for the PHD. The problem then becomes one of estimating the targets’ state based on the output of the PHD when using a particle filter implementation. This paper describes one heuristic method for obtaining a state estimator from the PHD. The approach used in this paper, based on the Expectation-Maximization (EM) algorithm, views the PHD distribution as a mixture distribution, and the particles as an i.i.d. sampling from the mixture distribution. Using this, a maximum likelihood estimator for the parameters of the distribution can be generated. The EM seems to work fairly well, particularly when targets are well spaced.
Journal of Non-Equilibrium Thermodynamics, Jan 20, 2005
Oxygen delivery to the tissues is crucial to survival but our understanding of the processes invo... more Oxygen delivery to the tissues is crucial to survival but our understanding of the processes involved in the transport of oxygen from blood to tissue is incomplete. The aim of the present work is to illustrate a long-standing paradox regarding such transport by reporting new state-of-the-art measurements and by analyzing the results in several ways, thereby exploring possible resolutions of the paradox. Our model calculations show that slight extensions of system parameters are su‰cient to overcome the apparent inconsistencies. Alternatively, so far unappreciated mild e¤ects like flow-assisted di¤usion in the interstitium will explain the supernormal di¤usion of oxygen.
In the 21st century, the development of technologies to produce carbon free power sources remains... more In the 21st century, the development of technologies to produce carbon free power sources remains paramount. In this paper, we study an optimal power transmission strategy from a space-based satellite generation station to Earth using scalar diffraction theory. The resulting model is then solved via a spectral method that guarantees a compactly supposed profile from the transmitting antenna. Finally, the problem is then solved via a more general pseudo-spectral method using control theory.
International Conference on Mathematics and Engineering Techniques in Medicine and Biological Scienes, 2005
A robust algorithm is presented for labeling rows and columns in an irregular array. The algorith... more A robust algorithm is presented for labeling rows and columns in an irregular array. The algorithm is based on hierarchical pattern matching to a local lattice which is used as a template. Starting from the best local match, the pattern is expanded hierarchically to encompass the entire array. An application to labeling digitized images of an array of tissue sections mounted on a microscope slide is discussed.
There are many statistical methods of tracking single and multiple targets; this manuscript will ... more There are many statistical methods of tracking single and multiple targets; this manuscript will focus on the state estimation problem. Ideally, a generalization of the recursive Bayes non-linear filter would track and resolve the state(s) of single or multiple targets, but that is currently computationally intractable. The Probability Hypothesis Density (PHD) makes the tracking problem computationally feasible by propagating only the first-order multi-target statistical moments by using a particle filter implementation for the PHD. The problem then becomes one of estimating the targets’ state based on the output of the PHD when using a particle filter implementation. This paper describes one heuristic method for obtaining a state estimator from the PHD. The approach used in this paper, based on the Expectation-Maximization (EM) algorithm, views the PHD distribution as a mixture distribution, and the particles as an i.i.d. sampling from the mixture distribution. Using this, a maximum likelihood estimator for the parameters of the distribution can be generated. The EM seems to work fairly well, particularly when targets are well spaced.
A robust algorithm is presented for labeling rows and columns in an irregular array. The algorith... more A robust algorithm is presented for labeling rows and columns in an irregular array. The algorithm is based on hierarchical pattern matching to a local lattice, which is used as a template. Starting from the best local match, the pattern is expanded hierarchically to encompass the entire array. An application to labeling digitized images of an array of tissue sections mounted on a microscope slide is discussed.
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Papers by Alfonso Limon