A method for isogram extraction from topographic maps is proposed and analyzed. Main part of the extraction is done using automatic software based on nonlinear algorithms. Possibly needed final corrections are done in...
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ISBN:
(纸本)0819427446
A method for isogram extraction from topographic maps is proposed and analyzed. Main part of the extraction is done using automatic software based on nonlinear algorithms. Possibly needed final corrections are done in an interactive mode. Iterative procedures are used both to provide reliability and to minimize the number of operations performed by the user in the interactive mode. Illustrations are presented to clarify the operations, goals and obtained results. Also, techniques for relief recovery are proposed and their accuracy is studied.
The Kalman filter is the minimum-variance state estimator for linear dynamic systems with Gaussian noise. Even if the noise is non-Gaussian, the Kalman filter is the best linear estimator. For nonlinear systems it is ...
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The Kalman filter is the minimum-variance state estimator for linear dynamic systems with Gaussian noise. Even if the noise is non-Gaussian, the Kalman filter is the best linear estimator. For nonlinear systems it is not possible, in general, to derive the optimal state estimator in closed form, but various modifications of the Kalman filter can be used to estimate the state. These modifications include the extended Kalman filter, the unscented Kalman filter, and the particle filter. Although the Kalman filter and its modifications are powerful tools for state estimation, we might have information about a system that the Kalman filter does not incorporate. For example, we may know that the states satisfy equality or inequality constraints. In this case we can modify the Kalman filter to exploit this additional information and get better filtering performance than the Kalman filter provides. This paper provides an overview of various ways to incorporate state constraints in the Kalman filter and its nonlinear modifications. If both the system and state constraints are linear, then all of these different approaches result in the same state estimate, which is the optimal constrained linear state estimate. If either the system or constraints are nonlinear, then constrained filtering is, in general, not optimal, and different approaches give different results.
Fast approximate statistical nonlinear algorithms (capable of real-time operation) for solving direct and inverse problems in the diffusion optical tomography are described. These algorithms were tested by reconstruct...
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Fast approximate statistical nonlinear algorithms (capable of real-time operation) for solving direct and inverse problems in the diffusion optical tomography are described. These algorithms were tested by reconstructing a rather complicated internal structure (containing up to three strongly absorbing inclusions no smaller than 5 turn in size) of strongly scattering and weakly absorbing large (up to 140 mm) model objects (with scattering and absorption coefficients equal to 1.4 and 0.005-0.015 mm(-1) respectively). Experiments were performed using cw radiation of low-power diode lasers (with input power below 20 mW) in the near IR range (between 770 and 820 mn).
Compressed sensing (CS) theory has been recently applied in Magnetic Resonance Imaging (MRI) to accelerate the overall imaging process. In the CS implementation, various algorithms have been used to solve the nonlinea...
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ISBN:
(纸本)9781424441242
Compressed sensing (CS) theory has been recently applied in Magnetic Resonance Imaging (MRI) to accelerate the overall imaging process. In the CS implementation, various algorithms have been used to solve the nonlinear equation system for better image quality and reconstruction speed. However, there are no explicit criteria for an optimal CS algorithm selection in the practical MRI application. A systematic and comparative study of those commonly used algorithms is therefore essential for the implementation of CS in MRI. In this work, three typical algorithms, namely, the Gradient Projection For Sparse Reconstruction (GPSR) algorithm, Interior-point algorithm (l(1)_ls), and the Stagewise Orthogonal Matching Pursuit (StOMP) algorithm are compared and investigated in three different imaging scenarios, brain, angiogram and phantom imaging. The algorithms' performances are characterized in terms of image quality and reconstruction speed. The theoretical results show that the performance of the CS algorithms is case sensitive;overall, the StOMP algorithm offers the best solution in imaging quality, while the GPSR algorithm is the most efficient one among the three methods. In the next step, the algorithm performances and characteristics will be experimentally explored. It is hoped that this research will further support the applications of CS in MRI.
In many signal processing applications, the signals provided by the sensors are mixtures of many sources, The problem of separation of sources is to extract the original signals from these mixtures. A new algorithm, b...
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In many signal processing applications, the signals provided by the sensors are mixtures of many sources, The problem of separation of sources is to extract the original signals from these mixtures. A new algorithm, based on ideas of back propagation learning, is proposed for source separation. No a priori information on the sources themselves is required, and the algorithm can deal even with nonlinear mixtures. After a short overview of previous works in that field, we will describe the proposed algorithm, then some experimental results will be discussed.
A new algorithm for the computation of steady-state conditions of electric machines is presented, It is based on a large time increment method used in mechanics, It is applied to the electromagnetic field computation ...
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A new algorithm for the computation of steady-state conditions of electric machines is presented, It is based on a large time increment method used in mechanics, It is applied to the electromagnetic field computation in a generator. Compared with the step by step algorithm, the CPU time is strongly reduced.
In this paper, we present two families of second-order and third-order explicit methods for numerical integration of initial-value problems of ordinary differential equations. Firstly, a family of second-order methods...
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In this paper, we present two families of second-order and third-order explicit methods for numerical integration of initial-value problems of ordinary differential equations. Firstly, a family of second-order methods with two free parameters is derived by considering a suitable rational approximation to the theoretical solution of the problem at some grid points. Imposing that the principal term of the local truncation error of this family vanishes, we obtain an expression for one of the parameters in terms of the other. With this approach, a new one-parameter family of third-order methods is obtained. By selecting any 3(2) pair of second and third order methods, they can be implemented as an embedded type method, thus leading to a variable step-size formulation. We have considered one 3(2) pair of second and third order methods and made a comparison of numerical results with several ode solvers which are currently used in practice. The comparison of numerical results shows that the embedded 3(2) pair outperforms the methods considered for comparison.
We consider a nonlinear minimax allocation problem with multiple knapsack-type resource constraints. Each term in the objective function is a nonlinear, strictly decreasing and continuous function of a single variable...
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We consider a nonlinear minimax allocation problem with multiple knapsack-type resource constraints. Each term in the objective function is a nonlinear, strictly decreasing and continuous function of a single variable. All variables are continuous and nonnegative. A previous algorithm for such problem repeatedly solves relaxed problems without the nonnegativity constraints. That algorithm is particularly efficient for certain nonlinear functions for which there are closed-form solutions for the relaxed problems;for other functions, however, the algorithm must employ search methods. We present a new algorithm that uses at each iteration simple-to-compute algebriac expressions to check optimality conditions, instead of solving the relaxed minimax problems. The new algorithm is therefore significantly more efficient for more general nonlinear functions.
In this paper, we present PyPANCG, a Python library-interface that implements both the conjugate gradient method and the preconditioned conjugate gradient method for solving nonlinear systems. We describe the use of t...
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In this paper, we present PyPANCG, a Python library-interface that implements both the conjugate gradient method and the preconditioned conjugate gradient method for solving nonlinear systems. We describe the use of the library and its advantages in order to get fast development. The aim of this library is to develop high performance scientific codes for high-end computers hiding many of the underlying low-level programming complexities from users with the use of a high-level Python interface. The library has been designed for adapting to different stages of the design process, depending on whether the purpose is computational performance or fast development. Experimental results report the performance of our approach on different parallel computers.
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