Search

Start Over Format bez média Data provider Academy of Sciences Library/Knihovna Akademie věd ČR

5912. Deflektometrická metoda rekonstrukce optických ploch

Creator:
Opat, Jan and Mikš, Antonín
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
optics and optika
Language:
Czech
Description:
Detailed theoretical analysis of the shape measurement of optical surfaces based on light reflection on the measured surface is provided. Relations are given for computing the parameters of the reflected beam on the measured surface and its record on the light detector. Deflectometric equation is derived for oblique incident beam on the measured surface and the method of its solution are given. and Je uvedena podrobná teoretická analýza měření tvaru optických ploch na základě odrazu světla na měřené ploše. Jsou uvedeny vztahy pro výpočet parametrů paprsku odraženého na měřené ploše a jeho stopy na detektoru záření. Je odvozena deflektometrická rovnice pro šikmý dopad paprsku na měřenou plochu a způsob jejího řešení.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5914. Deformation between African and Eurasian plate estimated from the European and the Egyptian GPS geodetic networks results from preliminary processing

Creator:
Antonín Zeman, Hassan, Khalil, Holešovský, Jan, Mohamed, Abdel Monem S., Novotný, Zbyněk, Salah, Mahmoud M., Jan Kostelecký, and Ali, Radwan M.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, GPS sítě, GPS netwoks, GPS coordinate time series, Egyptian GPS geodetic network, mechanics of continuum, deformation in the Eastern Mediterranean, 7, and 551
Language:
English
Description:
The article deals with estimating deformation between the African and the Eurasian Plate in the Eastern Mediterranean on the basis of GPS coordinate time series. Two sources of velocities were used for processing. The first was the freely available site velocities from the European Permanent Network (EPN). The second was the Egyptian GPS permanent network velocities. Their values were determined by the following technique. Firstly, the Egyptian site coordinates were computed from GPS daily observations, using the fiducial EPN stations. The daily site coordinates at a given time interval result in coordinate time series, which were analysed and used on velocity estimation of the Egyptian stations. Then the apparatus of the mechanics of continuum was applied to all resultant velocities. The regions of possible mutual interactions between the Eurasian and the African Plate in the Eastern Mediterranean were detected. The basic idea of this contribution is the common processing of GPS daily measurements from the Egyptian permanent network together with the EPN data. The available Egyptian GPS data cover almost the last three years, which represents a sufficient time interval for velocity estimation. Introducing the Egyptian permanent GPS measurements into processing enables a better estimate of deformations in the Eastern Mediterranean., Antonín Zeman, Khalil Hassan, Jan Holešovský, Abdel Monem S. Mohamed, Zbyněk Novotný, Mahmoud M. Salah, Jan Kostelecký and Radwan M. Ali., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5915. Deformation trends in the Jezeří castle massif, Krušné hory Mts

Creator:
Blahoslav Košťák, Bohumil Chán, and Jan Rybář
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, těžba uhlí, coal mining, Krušné hory (Česko a Německo), Krušné hory Mountains (Czechia and Germany), rock slope stability, deformation monitoring, 7, and 551
Language:
English
Description:
Brown coal open pit mining in the basin under Krušné Hory Mts. came to contact with slopes of the mountains, and a problem of the stability in high and steep slopes in the crystalline rock became an important question. The question concerns Jezeří Castle built on the top of one of the hills in a most endangered section where even a supporting pillar in the sediments under the slope toe was left to support the slope. As a result, an extensive monitoring program regarding deformations was initiated in the region. The program involved several methods and some important results are discussed. The results that are displayed concern mainly measurements done in geophysical tiltmeter stations in two underground galleries driven into the two steep slope sections showing most dangerous situation, as well as extensometers located in the same locations. Long-term monitoring revealed a tectonic deformation process of a natural origin that is registered as slow and systematic tilts. Besides, it revealed several periods of anomalies that are of basic importance. During a long period of observation from 1982 till 2005 three important deformation anomalies were registered: the event of 1994, the event of 2002, and the event of 2003/2004. The first and the third event have been classified as of a large regional character that affected a wide mountainous area and could be interpreted as a tectonic impulse originating within the mountainous structure of the so called "Dome of Hora Svaté Kateřiny". The second event has been considered different, strictly connected with extreme precipitation of August 2002. The anomaly was evidenced even deep in the crystalline, so that it could not be seen as of a superficial character only. The movement which was registered at that time was oriented right into the pillar supporting the slope., It is concluded that it was a short manifestation of instability in the critical profile "Jezeří - pillar", which stresses the important stabilisation function of the supporting pillar without which the profile will be probably destabilised., Blahoslav Košťák, Bohumil Chán and Jan Rybář., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5916. Deformed Heisenberg algebra with reflection and d-orthogonal polynomials

Creator:
Bouzeffour, Fethi, Mansour, Hanen Ben, and Zaghouani, Ali
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
matematika, mathematics, d-ortogonální polynomy, koherentní stav, hypergeometrické funkce, Meixnerovy polynomy, d-orthogonal polynomials, matrix element, coherent state, hypergeometric functions, Meixner polynomials, d-dimensional linear functional vector, 13, and 51
Language:
English
Description:
This paper is devoted to the study of matrix elements of irreducible representations of the enveloping deformed Heisenberg algebra with reflection, motivated by recurrence relations satisfied by hypergeometric functions. It is shown that the matrix elements of a suitable operator given as a product of exponential functions are expressed in terms of d-orthogonal polynomials, which are reduced to the orthogonal Meixner polynomials when d = 1. The underlying algebraic framework allowed a systematic derivation of the recurrence relations, difference equation, lowering and rising operators and generating functions which these polynomials satisfy., Fethi Bouzeffour, Hanen Ben Mansour, Ali Zaghouani., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5918. Deformovatelné zrcadlo pro vysokovýkonové laserové aplikace

Creator:
Mrňa, Libor, Šarbort, Martin, and Holá, Miroslava
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
deformable mirror, high-power lasers, adaptive optics, deformovatelné zrcadlo, výkonové lasery, and adaptivní optika
Language:
Czech
Description:
The modern trend in high power laser applications such as welding, cutting and surface hardening lies in the use of solid-state lasers. The output beam of these lasers is characterized by a Gaussian intensity distribution. However, the laser beams with different intensity distributions, e.g. top-hat, are preferable in various applications. In this paper we present a new type of deformable mirror suitable for the corresponding laser beam shaping. The deformation of the mirror is achieved by an underlying array of actuators and a pressurized coolant that also provides the necessary cooling. We describe the results of the surface shape measurement using a 3D scanner for different settings of actuators. Further, we show the achieved intensity distributions measured by a beam profiler for a low power laser beam reflected from the mirror. and V poslední době nastává rozmach používání pevnolátkových laserů ve výkonových aplikacích, jako jsou laserové svařování, řezání a povrchové kalení. Výstupní svazek těchto laserů má gaussovské rozložení intenzity svazku. Pro výše uvedené aplikace by však v mnoha případech bylo žádoucí rozložení s konstantní intenzitou svazku v jeho průřezu, tzv. top-hat. Článek popisuje nový typ deformovatelného zrcadla vhodný pro transformaci rozložení intenzity ve svazku. Deformace zrcadla je vyvolána maticí tahových elementů připojených na zadní stranu tenkého zrcadla, které působí proti tlakové síle chladicí vody. Byl zhotoven funkční vzorek deformovatelného zrcadla. Bylo provedeno měření jeho tvaru povrchu pro tři nastavení tahových elementů pomocí 3D skeneru. Dále byla ověřena schopnost požadované transformace svazku užitím nízkovýkonového laseru s gaussovským rozložením a měřením odraženého svazku profilometrem intenzity.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5919. Degenerate Hopf bifurcations and the formation mechanism of chaos in the Qi 3-D four-wing chaotic system

Creator:
Liang, Hongtao, Tang, Yanxia, Li, Li, Wei, Zhouchao, and Wang, Zhen
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
four-wing chaotic attractors, Lyapunov coefficient, degenerate Hopf bifurcations, and period-doubling cascade
Language:
English
Description:
In order to further understand a complex 3-D dynamical system proposed by Qi et al, showing four-wing chaotic attractors with very complicated topological structures over a large range of parameters, we study degenerate Hopf bifurcations in the system. It exhibits the result of a period-doubling cascade to chaos from a Hopf bifurcation point. The theoretical analysis and simulations demonstrate the rich dynamics of the system.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5920. Degenerating Cahn-Hilliard systems coupled with mechanical effects and complete damage processes

Creator:
Heinemann, Christian and Kraus, Christiane
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Cahn-Hilliard system, phase separation, complete damage, elliptic-parabolic degenerating system, linear elasticity, energetic solution, weak solution, doubly nonlinear differential inclusion, and existence result; rate-dependent system
Language:
English
Description:
This paper addresses analytical investigations of degenerating PDE systems for phase separation and damage processes considered on nonsmooth time-dependent domains with mixed boundary conditions for the displacement field. The evolution of the system is described by a degenerating Cahn-Hilliard equation for the concentration, a doubly nonlinear differential inclusion for the damage variable and a quasi-static balance equation for the displacement field. The analysis is performed on a time-dependent domain which characterizes the nondegenerated elastic material regions. We choose a notion of weak solutions which consists of weak formulations of the Cahn-Hilliard system and the momentum balance equation, a variational inequality for the damage evolution and an energy inequality. For the introduced degenerating system, we prove global-in-time existence of weak solutions. The main results are sketched from our recent paper [WIAS preprint no. 1759 (2012)].
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

Limit your search

Show values starting with
more »

Show values starting with
more »

Show values starting with
more »

Show values starting with
more »

Show values starting with
more »

Show values starting with
more »

View distribution

Current results range from 1711 to 2022

View larger »