Welding of heat - resistent steels by narrow gap SMAW method.

LUKOSZ Ondřej: Svařování žárupevných ocelí metodou 121 do úzké mezery. Projekt vypracovaný v rámci inženýrského studia, oboru 2307, předkládá návrh svařovacího postupu žáropevné oceli. Ta se užívá na výrobu energetických zařízení. Energetické zařízení typu parní turbína využívá materiálu 30CrMoNiV 5-11. Jedná se o svařování do úzké mezery automaticky pod tavidlem. Nejdůležitějším parametrem odstranitelnosti strusky je volba tavidla a přídavného materiálu. Na základě literární studie této problematiky byl navržen speciální postup svařování, zvoleno vhodné tavidlo a vhodný přídavný materiál. Pro experiment byla zvolena vhodná teplota předehřevu.LUKOSZ Ondřej: Welding of heat - resistent steels by method SMAW into the narrow gap. The project elaborated in frame of engineering studies branch 2307. The project is submitting design of technology production of the weld procedure creep metal. It uses in manufactory power equipment. The power equipment, the type of steam turbine, uses steel 30CrMoNiV 5-11. The welding into the narrow gap has its specifics. The most important parameter is the choice of flux and filler metal. We must decide appropriate flux for convenient disposing of slag. Based on the literature study these problems were proposed the specified welding procedure, appropriate flux and appropriate additional material. For the experiment was selected appropriate temperature of preheating.

Possibility of the new type phase transition

The scalar field theory and the scalar electrodynamics quantized in the flat gap are considered. The dynamical effects arising due to the boundary presence with two types of boundary conditions (BC) satisfied by scalar fields are studied. It is shown that while the Neumann BC lead to the usual scalar field mass generation, the Dirichlet BC give rise to the dynamical mechanism of spontaneous symmetry breaking. Due to the later, there arises the possibility of the new type phase transition from the normal to spontaneously broken phase. The decreasing in the characteristic size of the quantization region (the gap size here) and increasing in the temperature compete with each other, tending to transport the system in the spontaneously broken and in the normal phase, respectively. The system evolves with a combined parameter, simultaneously reflecting the change in temperature and in the size. As a result, at the critical value of this parameter there occurs the phase transition from the normal phase to the spontaneously broken one. In particular, the usual massless scalar electrodynamics transforms to the Higgs model

Twin-Photon Confocal Microscopy

A recently introduced two-channel confocal microscope with correlated detection promises up to 50% improvement in transverse spatial resolution [Simon, Sergienko, Optics Express {\bf 18}, 9765 (2010)] via the use of photon correlations. Here we achieve similar results in a different manner, introducing a triple-confocal correlated microscope which exploits the correlations present in optical parametric amplifiers. It is based on tight focusing of pump radiation onto a thin sample positioned in front of a nonlinear crystal, followed by coincidence detection of signal and idler photons, each focused onto a pinhole. This approach offers further resolution enhancement in confocal microscopy

Confined Maxwell Field and Temperature Inversion Symmetry

We evaluate the Casimir vacuum energy at finite temperature associated with the Maxwell field confined by a perfectly conducting rectangular cavity and show that an extended version of the temperature inversion symmetry is present in this system

Cryptocurrencies as a Store of Value Versus Selected Alternative Assets

Bakalářská práce se zabývá zhodnocením role uchovatele hodnoty nejvýznamnějších kryptoměn a jejich komparace s vybranými aktivy. Práce je rozdělena na teoretickou a praktickou část. Teoretická část je zaměřena na charakteristiku peněž, kryptoměn a investic. Rovněž je zde popsán historický vývoj peněž a kryptoměn se zaměřením na dvě nejvýznamnější kryptoměny (Bitcoin a Ethereum). V poslední části jsou popsány akciové a komoditní trhy. Praktická část je zaměřena na porovnání vybraných kryptoměn s ostatními aktivy na základě míry volatility, následuje vyhodnocení výsledků a v závěru je formulováno několik doporučení.The bachelor thesis deals with the store of value function of the most prominent cryptocurrencies and their comparison with selected assets. The thesis is divided into theoretical and practical parts. The theoretical part focuses on the characteristics of money, cryptocurrencies and investments. It also describes the historical development of money and cryptocurrencies, focusing on the two most important cryptocurrencies (Bitcoin and Ethereum). The last section describes the stock and commodity markets. The practical part focuses on comparing the selected cryptocurrencies with other assets on the basis of volatility, followed by an evaluation of the results and concludes with several recommendations.114 - Katedra ekonomievýborn

Quantum Spring from the Casimir Effect

The Casimir effect arises not only in the presence of material boundaries but also in space with nontrivial topology. In this paper, we choose a topology of the flat $(D+1)$-dimensional spacetime, which causes the helix boundary condition for a Hermitian massless scalar field. Especially, Casimir effect for a massless scalar field on the helix boundary condition is investigated in two and three dimensions by using the zeta function techniques. The Casimir force parallel to the axis of the helix behaves very much like the force on a spring that obeys the Hooke's law when the ratio $r$ of the pitch to the circumference of the helix is small, but in this case, the force comes from a quantum effect, so we would like to call it \textit{quantum spring}. When $r$ is large, this force behaves like the Newton's law of universal gravitation in the leading order. On the other hand, the force perpendicular to the axis decreases monotonously with the increasing of the ratio $r$. Both forces are attractive and their behaviors are the same in two and three dimensions.Comment: 6 pages, 7 figures, published in PL

Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface

We report on two orders of magnitude reduction in the fluorescence lifetime when a single molecule placed in a thin film is surrounded by two gold nanospheres across the film interface. By attaching one of the gold particles to the end of a glass fiber tip, we could control the modification of the molecular fluorescence at will. We find a good agreement between our experimental data and the outcome of numerical calculations