The paper summarizes results of investigations, design and development of ultra wideband antennas carried out during the last ten years in the Laboratory of Antennas and Telecommunication Systems of NTUU (''KP...
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ISBN:
(纸本)1424404908
The paper summarizes results of investigations, design and development of ultra wideband antennas carried out during the last ten years in the Laboratory of Antennas and Telecommunication Systems of NTUU (''KPI''). In particular it contains novel design of a linear 8-element horn array antenna with 45 degrees-slant polarization operating in octave bandwidth (4...8 GHz);ultra wideband horns with fan-type radiation patterns and coaxial to waveguide transitions for them with the frequency ratio up to 10:1;light-weight log-periodic radiators and arrays. The proposed designs were carefully investigated using different full wave numericalmethods and then finally optimized sets of parameters were achieved. Prototypes for telecommunication and radar applications have been manufactured, verified and all-round tested.
In this paper, different forms to construct convolutional codes from linear systems viewpoint are presented. For these purpose we consider that a convolutional code is essentially a linear system defined over a finite...
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In general, models of biological or technical applications are represented by nonlinear systems. Moreover, these systems contain multiple uncertain or unknown parameters. These uncertainties are the reason for some nu...
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ISBN:
(纸本)076952821X
In general, models of biological or technical applications are represented by nonlinear systems. Moreover, these systems contain multiple uncertain or unknown parameters. These uncertainties are the reason for some numerical and analytical problems in finding guaranteed bounds for the solution of the state space representation. Unfortunately, several industrial applications are demanding exactly these guaranteed bounds in order to fulfil regulations set by the state authorities. To get an idea of the solution of systems with uncertainties the numerical integration of the system's differential equations has to be done with randomly selected values for the unknown parameters. This computation is done several times, in some circumstances more than a thousand times. This approach is well known as the Monte-Carlo method, but this stochastic approach cannot deliver guaranteed bounds for the domain of the system's solution. Thus, we developed a method to find guaranteed bounds which uses linear Lyapunov-like functions to solve this problem. In this work we combine this method with a theory first introduced by Müller. Differential inequalities are used by Müller to obtain guaranteed bounds. Intersecting the results of both methods provides improved and tight bounds for the original uncertain system. Another approach is shown using a midpoint method providing guaranteed bounds. We achieve guaranteed and finite simulation bounds as a result of our approaches. The results can be used as an initial interval for further methods based on interval arithmetic. An example of a bioreactor with two state variables is shown in this paper to illustrate the methods.
In many high performance engineering and scientific applications there is a need to use parallel software libraries. Researchers behind these applications find it difficult to understand the interfaces to these librar...
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The numerical solution of optimization problems with partial differential equation (PDE) constraints is vital to a growing number of science and engineering applications. The development of robust and efficient algori...
The numerical solution of optimization problems with partial differential equation (PDE) constraints is vital to a growing number of science and engineering applications. The development of robust and efficient algorithms for the solution of these optimization problems presents many challenges that arise out of, e.g., the intricate mathematical structure of these problems, the complicated interactions between numericalmethods for PDE and optimization, the large-scale of the optimization problems, and the increasing complexity of applications. To identify and overcome these challenges an integrated approach is needed that builds on a variety of mathematical sub-disciplines, such as theory of PDEs, distributed parameter systems, numerical solution of PDEs, numerical optimization, and numericallinearalgebra. This international workshop has brought together some of the leading experts in the fast developing field of optimization problems with PDE constraints to present recent developments in this area as well as to identify open problems and further research needs.
In this paper, a three-dimensional non-linear finite element analysis is performed to study slender high strength "circular" CFT columns. Proper material constitutive models for columns subjected to an eccen...
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In this paper, we consider the optimal disturbance rejection problem for (possibly infinite dimensional) linear time-varying (LTV) systems using a framework based on operator algebras of classes of bounded linear oper...
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In this paper, we consider the optimal disturbance rejection problem for (possibly infinite dimensional) linear time-varying (LTV) systems using a framework based on operator algebras of classes of bounded linear operators. In particular, after reducing the problem to a shortest distance minimization in a space of bounded linear operators, duality theory is applied to show existence of optimal solutions, which satisfy a "time-varying" allpass or flatness condition. With the use of the theory of M-ideals of operators, it is shown that the computation of time-varying (TV) controllers reduces to a search over compact TV Youla parameters. This involves the norm of a TV compact Hankel operator and its maximal vectors. Moreover, an operator identity to compute the optimal TV Youla parameter is also derived. The results are generalized to the mixed sensitivity problem for TV systems as well, where it is shown that the optimum is equal to the operator induced of a TV mixed Hankel-Toeplitz operator generalizing analogous results known to hold in the LTI case. Finally, a numerical algorithm to compute optimal TV controllers is proposed
The paper summarizes results of investigations, design and development of ultra wideband antennas carried out during the last ten years in the laboratory of antennas and telecommunication systems of NTUU ("KPI&qu...
详细信息
The paper summarizes results of investigations, design and development of ultra wideband antennas carried out during the last ten years in the laboratory of antennas and telecommunication systems of NTUU ("KPI"). In particular it contains novel design of a linear 8-element horn array antenna with 45deg-slant polarization operating in octave bandwidth (4...8 GHz); ultra wideband horns with fan-type radiation patterns and coaxial to waveguide transitions for them with the frequency ratio up to 10:1; light-weight log-periodic radiators and arrays. The proposed designs were carefully investigated using different full wave numericalmethods and then finally optimized sets of parameters were achieved. Prototypes for telecommunication and radar applications have been manufactured, verified and all-round tested
A novel scaling method for preconditioning the classical matrix algebraic Riccati equation (ARE) is presented. The method is based on the assignment of predetermined values to the coefficients and the unknown matrices...
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A novel scaling method for preconditioning the classical matrix algebraic Riccati equation (ARE) is presented. The method is based on the assignment of predetermined values to the coefficients and the unknown matrices of the ARE. The proposed framework is independent of any numerical method and therefore its use is general. An Implementation of the method through the Newton algorithm is shown with a benchmark numerical example from the literature and comparisons with other existing methods are presented.
In the paper a perturbation method and robust approximation model of nonlinear dynamical systems, using sequence of time-invariant linear systems are applied. The sufficient conditions for robust application of the pe...
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In the paper a perturbation method and robust approximation model of nonlinear dynamical systems, using sequence of time-invariant linear systems are applied. The sufficient conditions for robust application of the perturbation method and the validity of the approximation are proven with a theorem, applying the theory of nonlinear operators of the functional analysis. Three examples comparing the numerical solution of the original system and the analytical solution of the approximate robust model are given. The method can be applied for analysis of dynamical systems, complex systems, optimization, synthesis of computer control and for investigation of classical perturbation problems.
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