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Overdetermined Absolute Value Equations
Rohn, Jiří
2019 - anglický
We consider existence, uniqueness and computation of a solution of an absolute value equation in the overdetermined case.
Klíčová slova:
absolute value equations; overdetermined system
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Overdetermined Absolute Value Equations
We consider existence, uniqueness and computation of a solution of an absolute value equation in the overdetermined case.
Generalization of a Theorem on Eigenvalues of Symmetric Matrices
Rohn, Jiří
2019 - anglický
We prove that the product of a symmetric positive semide nite matrix and a symmetric matrix has all eigenvalues real.
Klíčová slova:
symmetric matrix; positive semide nite matrix; real spectrum
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Generalization of a Theorem on Eigenvalues of Symmetric Matrices
We prove that the product of a symmetric positive semide nite matrix and a symmetric matrix has all eigenvalues real.
Hybrid Methods for Nonlinear Least Squares Problems
Lukšan, Ladislav; Matonoha, Ctirad; Vlček, Jan
2019 - anglický
This contribution contains a description and analysis of effective methods for minimization of the nonlinear least squares function F(x) = (1=2)fT (x)f(x), where x ∈ Rn and f ∈ Rm, together with extensive computational tests and comparisons of the introduced methods. All hybrid methods are described in detail and their global convergence is proved in a unified way. Some proofs concerning trust region methods, which are difficult to find in the literature, are also added. In particular, the report contains an analysis of a new simple hybrid method with Jacobian corrections (Section 8) and an investigation of the simple hybrid method for sparse least squares problems proposed previously in [33] (Section 14).
Klíčová slova:
numerical optimization; nonlinear least squares; trust region methods; hybrid methods; sparse problems; partially separable problems; numerical experiments
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Hybrid Methods for Nonlinear Least Squares Problems
This contribution contains a description and analysis of effective methods for minimization of the nonlinear least squares function F(x) = (1=2)fT (x)f(x), where x ∈ Rn and f ∈ Rm, together with ...
Sort Program for Real Keys with Linear Time Complexity
Jiřina, Marcel
2019 - český
In this report we present a program for sorting data structures with sorting keys as real numbers, i.e. of type "real" or "float". The basis of the program is a modification of the countingsort algorithm for reals (instead of integers). It uses a comparision-type sorting for small part of data set given. The time complexity of this part of program can be bounded by linear function of n and thus, the total time complexity is also O(n) for n data items.
Klíčová slova:
sorting; real sorting keys; counting sort
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Sort Program for Real Keys with Linear Time Complexity
In this report we present a program for sorting data structures with sorting keys as real numbers, i.e. of type "real" or "float". The basis of the program is a modification of the countingsort ...
Does a Singular Symmetric Interval Matrix Contain a Symmetric Singular Matrix?
Rohn, Jiří
2019 - anglický
We consider the conjecture formulated in the title concerning existence of a symmetric singular matrix in a singular symmetric interval matrix. We show by means of a counterexample that it is generally not valid, and we prove that it becomes true under an additional assumption of positive semide niteness of the midpoint matrix. The proof is constructive.
Klíčová slova:
symmetric interval matrix; singularity; positive semide niteness
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Does a Singular Symmetric Interval Matrix Contain a Symmetric Singular Matrix?
We consider the conjecture formulated in the title concerning existence of a symmetric singular matrix in a singular symmetric interval matrix. We show by means of a counterexample that it is ...
Transforming hierarchical images to program expressions using deep networks
Křen, Tomáš
2018 - anglický
We present a technique describing how to effectively train a neural network given an image to produce a formal description of the given image. The basic motivation of the proposed technique is an intention to design a new tool for automatic program synthesis capable of transforming sensory data (in our case static image, but generally a phenotype) to a formal code expression (i.e. syntactic tree of a program), such that the code (from evolutionary perspective a genotype) evaluates to a value that is similar to the input data, ideally identical. Our approach is partially based on our technique for generating program expressions in the context of typed functional genetic programming. We present promising results evaluating a simple image description language achieved with a deep network combining convolution encoder of images and recurrent decoder for generating program expressions in the sequential prefix notation and propose possible future applications.
Klíčová slova:
deep networks; automatic program synthesis; image processing
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Transforming hierarchical images to program expressions using deep networks
We present a technique describing how to effectively train a neural network given an image to produce a formal description of the given image. The basic motivation of the proposed technique is an ...
Nonparametric Bootstrap Techniques for Implicitly Weighted Robust Estimators
Kalina, Jan
2018 - anglický
The paper is devoted to highly robust statistical estimators based on implicit weighting, which have a potential to find econometric applications. Two particular methods include a robust correlation coefficient based on the least weighted squares regression and the minimum weighted covariance determinant estimator, where the latter allows to estimate the mean and covariance matrix of multivariate data. New tools are proposed allowing to test hypotheses about these robust estimators or to estimate their variance. The techniques considered in the paper include resampling approaches with or without replacement, i.e. permutation tests, bootstrap variance estimation, and bootstrap confidence intervals. The performance of the newly described tools is illustrated on numerical examples. They reveal the suitability of the robust procedures also for non-contaminated data, as their confidence intervals are not much wider compared to those for standard maximum likelihood estimators. While resampling without replacement turns out to be more suitable for hypothesis testing, bootstrapping with replacement yields reliable confidence intervals but not corresponding hypothesis tests.
Klíčová slova:
robust statistics; econometrics; correlation coefficient; multivariate data
Dokument je dostupný na externích webových stránkách.
Nonparametric Bootstrap Techniques for Implicitly Weighted Robust Estimators
The paper is devoted to highly robust statistical estimators based on implicit weighting, which have a potential to find econometric applications. Two particular methods include a robust correlation ...
Detailní simulace proudění, teplot a znečištění vzduchu pro oblast Praha-Dejvice
Resler, Jaroslav; Geletič, Jan; Krč, Pavel; Eben, Kryštof
2018 - český
Simulations of Prague quarter Dejvice were performed with newly developed urban climate model PALM-4U based on LES model PALM. The modelling domain has extent 1000 x 800 m and the resolution of the model was 2 m. Two 24 hours episodes were simulated. The summer episode was intended to assess mainly the UHI effects and the winter episode to assess mainly the air quality issues. Two variants were simulated - the current real situation and the scenario with considered new buildings in the area of Victory Square (Vítězné náměstí). Some comments of the ressults are appended at the end of the report.
Klíčová slova:
PALM; LES; Urban Heat Island; Urban Air Quality; scenarios assessment
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Detailní simulace proudění, teplot a znečištění vzduchu pro oblast Praha-Dejvice
Simulations of Prague quarter Dejvice were performed with newly developed urban climate model PALM-4U based on LES model PALM. The modelling domain has extent 1000 x 800 m and the resolution of the ...
Datová sada pro detekci dezinformačního obsahu – případová studie Novičok v Česku
Řimnáč, Martin
2018 - český
Publikování dezinformací na webu hraje stále větší roli, proto vyvstává otázka, jak takovému obsahu čelit, a nebo na jeho potenciální závadnost alespoň upozornit. Propaganda využívá dezinformací k relativizaci skutečností, jejichž popis se snaží většinou nepřímo zpochybnit. Příspěvek formou případové studie v konkrétní kauze formálně popisuje výroky prezentované v článcích publikovaných na webu a to včetně účelu jejich publikování, všímá si některých zajímavých aspektů prezentovaných dezinformací a hledá model pro jejich popis. Cílem příspěvku je informovat o vznikající datové sadě a ilustrovat základní použité dezinformační techniky včetně důsledků jejich použití. The paper presents a case study of the propaganda usage on a real cause of double agent Sergei Skripal. The formal model describing statements published in web articles is announced and particular interesting aspects of used disinformation are provided together with the reasons, why the disinformation is published. The paper is aimed at the presentation of the data collection to have been created and provides a brief discussion on the used propaganda techniques.
Klíčová slova:
Dezinformace; Web; Entropie; Pravděpodobnost
Dokument je dostupný na externích webových stránkách.
Datová sada pro detekci dezinformačního obsahu – případová studie Novičok v Česku
Publikování dezinformací na webu hraje stále větší roli, proto vyvstává otázka, jak takovému obsahu čelit, a nebo na jeho potenciální závadnost alespoň upozornit. Propaganda využívá dezinformací k ...
Sparse Test Problems for Nonlinear Least Squares
Lukšan, Ladislav; Matonoha, Ctirad; Vlček, Jan
2018 - anglický
This report contains a description of subroutines which can be used for testing large-scale optimization codes. These subroutines can easily be obtained from the web page http://www.cs.cas.cz/~luksan/test.html. Furthermore, all test problems contained in these subroutines are presented in the analytic form.
Klíčová slova:
large-scale optimization; least squares; test problems
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Sparse Test Problems for Nonlinear Least Squares
This report contains a description of subroutines which can be used for testing large-scale optimization codes. These subroutines can easily be obtained from the web page ...
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