The methods of optical dispersion compensation on current traces

Tato práce pojednává o problému optických disperzí na stávajících trasách. V úvodu rozebírá jednotlivé vlastnosti a vliv chromatické a polarizační vidové disperze PMD, jednotlivé měřící metody těchto disperzí a jejich kompenzací. V závěru práce je nastíněna analýza výsledků měření stávající sítě a návrhy na kompenzaci a simulace stávajících optických tras a vyhodnocení výsledkůPolarization mode dispersion, PMD influence of fibres. Next includes optic dispersion measurement and compensation of optics dispersion follows. In the end thesis analyze measure of existing fibres, simulating and suggest optimal solutions.

Experimental testing of hydroinsulating injection screens efficiency in dependance on properties of building materials

Většina staveb v našem klimatu se potýká prakticky vždy s působením vlhkosti. V minulosti bylo dodatečné snižování vlhkosti prováděno pouze mechanickými metodami. Postupem času byla vynalezena a do praxe zavedena chemická sanace vlhkého zdiva tzv. metoda chemických infuzních clon. Tato metoda spočívá ve vytvoření vrtů ve zvolené výšce vlhkého zdiva, které jsou následně napouštěny speciálními roztoky, jež ve zdivu vyplní a utěsní póry v oblasti vrtů, díky čemuž následně dojde k vytvoření jednolité hydroizolační clony. Cílem této práce je navržení metody pro posouzení účinnosti penetrace injektážních prostředků ve stavebních zdících materiálech.The most of the buildings are almost always faced with moisture in our climate. In the past, the humidity was reduced and conducted only by mechanical methods. Over time, chemical wet masonry method also known as chemical infusion curtain was invented and introduced into practice. This method involves the creation of boreholes at a selected height of humid masonry. These boreholes are impregnated with special solutions. These solutions in humid masonry fill pores in the field of boreholes and thanks to this subsequence the monolithic waterproofing curtain is created. The objective of this work is to determine the methodology for verifying effectiveness of various types of waterproofing injection curtains depending on the properties of the various types of building materials.

Surface analysis of xGnP/PEI nanocomposite

Tato Diplomová práce se zabývá povrchovou analýzou nanokompozitní folie polyetherimidu (PEI) vyztuženého exfoliovanými grafitickými nanodestičkami (xGnP). Analyzovány byly take vzorky nevyztužené PEI folie a samostatné nanodestičky. Vzorky nanokompozitu a PEI folie byly plazmaticky leptány s využitím argonového plazmatu po dobu 1, 3 a 10 hod. Skenovací elektronová mikroskopie (SEM) byla použita pro charakterizaci samostatných nanodestiček rozptýlených na křemíkovém substrátu, původních či leptaných vzorků PEI folie a nanokompozitu. Nanodestičky byly identifikovány při povrchu leptané nanokompozitní folie. Mikroskopie atomárních sil (AFM) byla použita pro zobrazení povrchové topografie separovaných nanodestiček a odkrytých destiček při povrchu leptaného kompozitu. Povrchová drsnost (střední kvadratická hodnota, vzdálenost nejnižšího a nejvyššího bodu) leptaného nanokompozitu narůstala s prodlužující se dobou leptání. Akustická mikroskopie atomárních sil (AFAM) byla použita pro charakterizaci elastické anizotropie leptaných kompozitních vzorků. Nanoindentační měření umožnila charakterizaci lokálních mechanických vlastností PEI a nanokompozitních folií.This Diploma thesis deals with surface analysis of nanocomposite foil – polyetherimide matrix (PEI) reinforced by exfoliated graphite nanoplatelets (xGnP). The PEI foil without reinforcement and separate xGnP particles were also analysed. Samples of the nanocomposite and the PEI foil were etched for various times by argon plasma. Scanning electron microscopy (SEM) was used to characterize xGnP agglomerates dispersed over silicon wafer and pristine/etched samples of PEI foil and nanocomposite xGnP/PEI foil. Graphite nanoplatelets were identified at surface of etched nanocomposite foil. Atomic force microscopy (AFM) was used for surface topography imaging of separate nanoplatelets and those uncovered at the surface of etched nanocomposite. Surface roughness (root mean square, peak to peak) of etched nanocomposite increased with prolonged etching time. Atomic force acoustic microscopy (AFAM) was used to characterize elastic anisotropy of etched nanocomposite. Nanoindentation measurements were employed to characterize the local mechanical properties of PEI and nanocomposite foils.

Giant inelastic tunneling in epitaxial graphene mediated by localized states

Local electronic structures of nanometer-sized patches of epitaxial graphene and its interface layer with SiC(0001) have been studied by atomically resolved scanning tunneling microscopy and spectroscopy. Localized states belonging to the interface layer of a graphene/SiC system show to have an essential influence on the electronic structure of graphene. Giant enhancement of inelastic tunneling, reaching 50% of the total tunneling current, has been observed at the localized states on a nanometer-sized graphene monolayer surrounded by defects.Comment: 6 pages, 5 figures, accepted for publication in Phys. Rev.

Modeling water penetration at dam-foundation joint

When fracture occurs in a concrete dam, the crack mouth is typically exposed to water. Very often this phenomenon occurs at the dam-foundation joint and is driven also by the fluid pressure inside the crack. Since the joint is the weakest point in the structure, this evolutionary process determines the load bearing capacity of the dam. In this paper the cracked joint is analyzed through the cohesive model proposed by Cocchetti et al. [Cocchetti G, Maier G, Shen X. Piecewise linear models for interfaces and mixed mode cohesive cracks. J Engng Mech (ASCE) 2002;3:279-98.], which takes into account the coupled degradation of normal and tangential strength. The water pressure inside the crack, which reduces fracture energy and increases the driving forces, is analyzed through the model proposed by Reich et al. [Reich W, Bruhwiler E, Slowik V, Saouma VE. Experimental and computational aspects of a water/fracture interaction. In: Bourdarot E, Mazars J, Saouma V, editors, Dam Fracture and Damage, The Netherlands: Balkema; 1994. p. 123-31.] and Bruhwiler and Saouma [Bruhwiler E, Saouma VE. Water fracture interaction in concrete. Part II: Fracture properties. Am Concr Inst J 1995;92:296-303; Bruhwiler E, Saouma VE. Water fracture interaction in concrete. Part II: Hydrostatic pressure in cracks. Am Concr Inst J 1995;92:383-90.]. Some numerical results are presented which refer to the benchmark problem proposed in 1999 by the International Commission On Large Dams. During the evolutionary process the horizontal dam crest displacement has been found to be a monotonic increasing function of the external load multiplier. As the fictitious process zone moves from the upstream to the downstream edge a transition occurs in the path of crack formation: the initial phase is dominated by the opening displacement, on the contrary afterwards the shear displacement dominates. Therefore, crack initiation does not depend on dilatancy. On the contrary the load carrying capacity depends on dilatanc

Modified carbon paste electrode as a tool for the evaluation of oxidative stability of rapeseed oil

Carbon paste electrode was used for evaluation of oxidative stability of rapeseed oil samples using cyclic voltammetry in 0.1 mol.L-1 HCl as a supporting electrolyte. Rapeseed oil samples were exposed to daylight and oxygen in open glass baker at the laboratory condition in order to obtain oils with accelerated primary and secondary products of oxidation. The oxidation status was determinated by peroxide value and p-anisidine value. Total oxidative stability was expressed as TOTOX index. The edible oils were used for preparation (modification) of the carbon paste composite material followed by the cyclic voltammetric measurement. Peroxide values significantly increased whereas p-anisinde value rather fluctuated during 40 days of storage in all the samples. Cyclic voltammograms showed anodic current peaks at 575 - 600 mV and cathodic current peaks at 400 - 425 mV. The oxidation and reduction waves diminished at pH ≥3.0 suggesting not only phenolic compounds contributed to the electrochemical characteristic of oil samples. The peroxide value or p-anisidine value did not correlate with oxidation or reduction peak currents at the potential 575 - 600 mV and 400 - 425 mV, respectively. Both cathodic and anodic currents increased with increasing TOTOX index exhibiting positive correlation with high Spearman correlation coefficient (r = 0.894 and r = 0.914 for anodic and cathodic current, respectively). Linear relationship was found for each sample individually. A caution has to be done when interpreting results since the correlation seems to be of oil sample specific. Nevertheless, the modified carbon paste electrode with rapeseed oil represents a suitable and alternative tool for determination of the oxidative state of edible oils without use of organic solvents

ELECTRODYNAMIC LOUDSPEAKER-DRIVEN ACOUSTIC COMPRESSOR

An acoustic compressor is  built  using the acoustic resonator which shape was optimized for a maximum acoustic pressure amplitude and a low-cost compression driver.  Acoustic compressor is built  by installing  a suction port in the resonator wall where the standing wave has its pressure node and a delivery port with a valve in the resonator wall where the standing wave has its pressure anti-node. Different reeds, serving  as delivery valves, are tested and their performance is investigated. It was shown that the performance of such simple compressor is comparable, or better, than the acoustic compressors built  previously by other researchers using non-optimally shaped resonators with more sophisticated driving mechanisms and valve arrangements

Stabilizing Agents for Calibration in the Determination of Mercury Using Solid Sampling Electrothermal Atomic Absorption Spectrometry

Tetramethylene dithiocarbamate (TMDTC), diethyldithiocarbamate (DEDTC), and thiourea were investigated as stabilizing agents for calibration purposes in the determination of mercury using solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). These agents were used for complexation of mercury in calibration solutions and its thermal stabilization in a solid sampling platform. The calibration solutions had the form of methyl isobutyl ketone (MIBK) extracts or MIBK-methanol solutions with the TMDTC and DEDTC chelates and aqueous solutions with thiourea complexes. The best results were obtained for MIBK-methanol solutions in the presence of 2.5 g L−1 TMDTC. The surface of graphite platforms for solid sampling was modified with palladium or rhenium by using electrodeposition from a drop of solutions. The Re modifier is preferable due to a higher lifetime of platform coating. A new SS-ETAAS procedure using the direct sampling of solid samples into a platform with an Re modified graphite surface and the calibration against MIBK-methanol solutions in the presence of TMDTC is proposed for the determination of mercury content in solid environmental samples, such as soil and plants

Temperature Effects in Acoustic Resonators

This paper deals with problems of nonlinear standing waves in axisymetrically shaped acoustic resonators where a mean temperature is distributed along the axis