4,389 research outputs found
Mechanical Properties of Microstructural Components of Inorganic Materials
Disertační práce se zabývá studiem strukturních a mechanických vlastností anorganických materiálů. Cílem je nalezení jednotlivých fází ve zkoumaném materiálu a hlavně lokalizace (mechanicky) nejslabšího místa, jeho ovlivnění a následně výroba materiálu o lepších mechanických vlastnostech. Z důvodu velkého množství použitých metod je základní teorie vložena vždy na začátku příslušné kapitoly. Taktéž z důvodu značného množství výsledků jsou na konci kapitol uvedeny dílčí závěry. Práce je rozdělena na tři části, kdy první se zabývá seznámením s možnostmi modelování mikro-mechanických vlastností a provedením experimentů umožňujících posouzení rozsahu platnosti některého modelu. V druhé části je provedeno shrnutí současných možností indentačních zkoušek pro měření mechanických vlastností strukturních složek betonu a praktické zvládnutí metodiky vhodné k užití pro výzkum materiálů zkoumaných domovským pracovištěm. V třetí části je navržena metoda identifikace nejslabších článků struktury anorganických pojiv a její ověření na konkrétním materiálu zkoumaném na domovském pracovišti. V této dizertační práci jsou použity tyto metody: kalorimetrie, ultrazvukové testování, jednoosá pevnost v tlaku, nanoindentace, korelativní mikroskopie a rastrovací elektronová mikroskopie s energiově disperzním spektrometrem. Dílčími výsledky jsou kompletní charakterizace cementových materiálů, upřesnění stávajících poznatků a nalezení optimálního postupu pro charakterizaci. Hlavním výsledkem je inovativní přístup vedoucí k pozitivnímu ovlivnění materiálu.The doctoral thesis deals with study of structural and mechanical properties of inorganic materials. Goal is to find the weakest (mechanically) phases and interfaces of material. By affecting these structures it should be possible consequently produce a material with better mechanical properties. Due to the large amount of used methods the basic theory is discussed always in the beginning of relevant chapter. Similarly, due to the considerable amount of results every chapter includes partial conclusions. The work is divided in three parts. The first deals with the introduction of the possibilities of modeling micro-mechanical properties and performing of experiments that allow assessment of the scope of some model. In second part itis performed an overview of current possibilities of indentation tests for measuring mechanical properties of structural components of concrete and the practical managing of methods suitable for use for materials research examined at our faculty. In third part the method of identifying the weakest points in structure of inorganic binders is proposed and validation on the particular material examined at our faculty is performed. The methods used in this doctoral thesis are: calorimetry, ultrasonic testing, uniaxial compression, nanoindentation, correlative microscopy and scanning electron microscopy with energy dispersive spectrometer. Partial results are a complete characterization of cementitious materials, specification of existing knowledge and finding the optimal procedure for characterization. The main result is an innovative approach that leads to a positive effect on the material.
Exchange Rate Management and Inflation Targeting: Modeling the Exchange Rate in Reduced-Form New Keynesian Models
This paper introduces a strategy for modeling the exchange rate when the monetary authority targets inflation while also managing the exchange rate using interventions. It does so in the framework of a standard reduced-form New Keynesian model of monetary transmission used in many institutions for research, forecasting, and monetary policy analysis. We propose a microfounded modification to the UIP condition which allows for modeling of informal exchange rate bands. Our modeling strategy is useful for most hybrid IT regimes, including those with imperfect control over market interest rates.IT regimes, New Keynesian model, exchange rate, UIP
Czech Labor Market Flows 1993-2003 (in English)
This paper focuses on structural changes in employment in absolute and relative terms, using Czech labor force survey data. Gross flows, job-to-job flows, and industry flows are investigated to delineate the major movements on the Czech labor market. The overall analysis of mobility flows throughout 1993-2003 shows an increasing structural stagnation and diminishing labor market flexibility. The decisive mobility channel has been a direct job change without an episode of unemployment, but even this kind of mobility flow tends to diminish over time. Employment flows in and flows out between industries have decreased markedly over the last ten years.labor-market flows, structural adjustment, transition probabilities
Engineering quantum operations on traveling light beams by multiple photon addition and subtraction
We propose and investigate an optical scheme for probabilistic implementation
of an arbitrary single-mode quantum operation that can be expressed as a
function of photon number operator. The scheme coherently combines multiple
photon addition and subtraction and is feasible with current technology. As
concrete examples, we demonstrate that the device can perform approximate
noiseless linear amplification of light and can emulate Kerr nonlinearity.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
Spiders (Araneae) of stony debris in North Bohemia
The arachnofauna was studied at five stony debris sites in northern Bohemia. In Central Europe, the northern and montane species inhabiting cold places live not only on mountain tops and peat bogs but also on the lower edges of boulder debris, where air streaming through the system of inner compartments gives rise to an exceedingly cold microclimate. At such cold sites, spiders can live either on bare stones (Bathyphantes simillimus, Wubanoides ura/ensis), or in the rich layers of moss and lichen (Dip/oeentria bidentata). Kratoehviliella bieapitata exhibits a diplostenoecious occurrence in stony debris and on tree bark. Latithorax faustus and Theonoe minutissima display diplostenoecious occurrence in stony debris and on peat bogs. The occurrence of the species Seotina eelans in the Czech Republic was documented for the first time
Linear optical Fredkin gate based on partial-SWAP gate
We propose a scheme for linear optical quantum Fredkin gate based on the
combination of recently experimentally demonstrated linear optical partial SWAP
gate and controlled-Z gates. Both heralded gate and simplified postselected
gate operating in the coincidence basis are designed. The suggested setups have
a simple structure and require stabilization of only a single Mach-Zehnder
interferometer. A proof-of-principle experimental demonstration of the
postselected Fredkin gate appears to be feasible and within the reach of
current technology.Comment: 6 pages, 3 figures, RevTeX
Transformations of symmetric multipartite Gaussian states by Gaussian LOCC
Multipartite quantum correlations, in spite of years of intensive research,
still leave many questions unanswered. While bipartite entanglement is
relatively well understood for Gaussian states, the complexity of mere
qualitative characterization grows rapidly with increasing number of parties.
Here, we present two schemes for transformations of multipartite permutation
invariant Gaussian states by Gaussian local operations and classical
communication. To this end, we use a scheme for possible experimental
realization, making use of the fact, that in this picture, the whole N -
partite state can be described using two separable modes. Numerically, we study
entanglement transformations of tripartite states. Finally, we look at the
effect our protocols have on fidelity of assisted quantum teleportation and
find that while adding correlated noise does not affect the fidelity at all,
there is strong evidence that partial non-demolition measurement leads to a
drop in teleportation fidelity.Comment: 9 page
Linear optics quantum Toffoli and Fredkin gates
We design linear optics multiqubit quantum logic gates. We assume the
traditional encoding of a qubit onto state of a single photon in two modes
(e.g. spatial or polarization). We suggest schemes allowing direct
probabilistic realization of the fundamental Toffoli and Fredkin gates without
resorting to a sequence of single- and two-qubit gates. This yields more
compact schemes and potentially reduces the number of ancilla photons. The
proposed setups involve passive linear optics, sources of auxiliary single
photons or maximally entangled pairs of photons, and single-photon detectors.
In particular, we propose an interferometric implementation of the Toffoli gate
in the coincidence basis, which does not require any ancilla photons and is
experimentally feasible with current technology.Comment: 8 pages, 4 figures, RevTeX
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