University of West Bohemia

About: University of West Bohemia is a education organization based out in Pilsen, Czechia. It is known for research contribution in the topics: Sputter deposition & Band gap. The organization has 2587 authors who have published 7207 publications receiving 78537 citations. The organization is also known as: Západočeská Univerzita v Plzni & ZČU.

Pulsed reactive magnetron sputtering of high-temperature Si–B–C–N films with high optical transparency

Abstract: Multifunctional Si–B–C–N films with exceptionally high thermal stability are becoming increasingly attractive because of their potential applications in coating technologies, and in high-temperature electronics and optoelectronics. In the present work, amorphous Si–B–C–N films were deposited onto SiC and Cu floating substrates using pulsed dc magnetron co-sputtering of a single (B4C)25Si75 target in a 50% Ar + 50% N2 gas mixture. High-quality defect-free films with smooth surfaces (average roughness Ra = 4 nm) were produced. The films, possessing a composition (in at.%) of Si30–32B10–12C2–4N49–51, exhibited a hardness of 22 GPa, an effective Young's modulus of 170 GPa and an elastic recovery of 75%. The oxidation resistance of the Si–B–C–N films in air was found to be very high up to 1600 °C. The film materials retained their amorphous structure after annealing in inert gases (He and Ar) up to 1600 °C. Annealing of the as-deposited films in He from room temperature to 1400 °C led to a slight decrease in the refractive index from 1.92 to 1.91 and to an accompanying increase in the extinction coefficient from 3 × 10− 4 to 3 × 10− 3 (both at the wavelength of 550 nm).

Improved guaranteed computable bounds on homogenized properties of periodic media by the Fourier–Galerkin method with exact integration

Abstract: Summary Moulinec and Suquet introduced FFT-based homogenization in 1994, and 20years later, their approach is still effective for evaluating the homogenized properties arising from the periodic cell problem. This paper builds on the author's (2013) variational reformulation approximated by trigonometric polynomials establishing two numerical schemes: Galerkin approximation (Ga) and a version with numerical integration (GaNi). The latter approach, fully equivalent to the original Moulinec–Suquet algorithm, was used to evaluate guaranteed upper–lower bounds on homogenized coefficients incorporating a closed-form double-grid quadrature. Here, these concepts, based on the primal and dual formulations, are employed for the Ga scheme. For the same computational effort, the Ga outperforms the GaNi with more accurate guaranteed bounds and more predictable numerical behaviors. The quadrature technique leading to block-sparse linear systems is extended here to materials defined via high-resolution images in a way that allows for effective treatment using the FFT. Memory demands are reduced by a reformulation of the double-grid scheme to the original grid scheme using FFT shifts. Minimization of the bounds during iterations of conjugate gradients is effective, particularly when incorporating a solution from a coarser grid. The methodology presented here for the scalar linear elliptic problem could be extended to more complex frameworks. Copyright © 2015 John Wiley & Sons, Ltd.

Aspects and comparison of matrix decompositions in unscented Kalman filter

Abstract: The paper deals with state estimation of nonlinear Gaussian systems with a special focus on the unscented Kalman filter. Its algorithm is based on specification of a set of so-called sigma points which are generated according to the covariance matrix of the state decomposed into a product of a matrix and its transpose. The paper analyzes utilization of different matrix decompositions within the unscented transform, which is a core of the unscented Kalman filter. It is shown that different decompositions may lead to significant differences in quality of approximations provided by the transform. The influence of the decompositions on the filter is demonstrated in an example.