New Methods of Quality of Service Assurance in Data Networks

Dizertační práce je zaměřena na výzkum v oblasti technologií pro zajištění kvality služeb v datových sítích. Moderní komunikační sítě se v dnešní době již neobejdou bez kvalitního nástroje pro poskytování odlišného zacházení různým třídám provozu. Jak studie ukázaly, v současnosti nejpoužívanější QoS mechanizmus v datových sítích je technologie diferencovaných služeb. Stěžejní částí práce je návrh nového QoS systému, který nabízí řešení jednoho z hlavních problémů technologie DiffServ. Nedostatkem tohoto mechanizmu je chybějící spolupráce mezi koncovou stanicí a hraničním prvkem DiffServ domény. Navržený systém proto nabízí síťové aplikaci možnost podílet se na procesu zajištění požadované úrovně kvality služby tím, že sama nastaví hodnotu DSCP v hlavičce svých paketů. Základem tohoto systému je znalost konfigurace technologie DiffServ na hraničním směrovači. Za tímto účelem používá koncová stanice protokol SNMP, pomocí kterého vyčítá potřebné konfigurační informace z MIB databáze síťového prvku. Navržený QoS systém byl ověřen v simulačních podmínkách. Výsledky simulací ukázaly, že navržený systém představuje efektivní řešení zmíněného problému technologie DiffServ, což dává dobrý předpoklad pro jeho úspěšné nasazení v reálných podmínkách.The doctoral thesis is focused on a research in the area of the quality-of-service support technologies in data networks. The current modern communication networks cannot operate correctly without an effective tool allowing differentiated treatment for various network traffic classes. Looking at the current trends in this area it turns out that the technology of Differentiated services is currently the most widely used mechanism for QoS assurance in data networks. The major part of this doctoral thesis concerns the design of a novel QoS system which offers a solution for one of the main problems of DiffServ technology. This disadvantage lies in the missing cooperation between the end station and edge node of the DiffServ domain. To overcome this limitation the system proposed introduces an improvement which enables the user application to actively participate in the resource reservation process by direct configuration of the DSCP value in the IP header of its own packets. This functionality is based on the identification of DiffServ configuration parameters available in the edge router. To retrieve the information required from network component the well-known SNMP protocol has been chosen, which has direct access to the components’s configuration stored in the MIB database. On the basis of this theoretical proposal several simulation scenarios have been created and analysed. The results show that the system designed presents an efficient solution for the mentioned problem of DiffServ. They also give good assumptions for the successful implementation of this system into a real environment.

Mechanical Properties of Medieval Bloomery Iron Materials - Comparative Tensile and Charpy-tests on Bloomery Iron Samples and S235JRG2

Ductility, toughness and strength of medieval bloomery iron materials were highly important mechanical properties, strongly affected by their microstructure and chemical composition. An attempt was made to characterize the most important mechanical properties of representative samples of main bloomery iron materials extracted in smelting experiments and compare them to the well know reference modern steel of S235JRG2. It was confirmed that notching and the stress concentration effect of slag inclusions strongly decrease all the characteristic values of ductility and toughness of bloomery iron materials. Typical medieval bloomery P-iron is a brittle material with almost zero or very low characteristic values of ductility and toughness but revealed similarly high strength as hardened and tempered bloomery steel

Dynamical fermion mass generation by a strong Yukawa interaction

We consider a model with global Abelian chiral symmetry of two massless fermion fields interacting with a complex massive scalar field. We argue that the Schwinger-Dyson equations for the fermion and boson propagators admit ultraviolet-finite chiral-symmetry-breaking solutions provided the Yukawa couplings are large enough. The fermions acquire masses and the elementary excitations of the complex scalar field are the two real spin-zero particles with different masses. As a necessary consequence of the dynamical chiral symmetry breakdown both in the fermion and scalar sectors, one massless pseudoscalar Nambu--Goldstone boson appears in the spectrum as a collective excitation of both the fermion and the boson fields. Its effective couplings to the fermion and boson fields are calculable.Comment: 9 pages, REVTeX4, uses feynmp, 1 eps figur

London model of dual color superconductor

The Meissner effect for the chromoelectric field E⃗a is a property of the non-perturbative QCD vacuum medium assumed to explain the observed confinement of color. The color dielectric function ϵ of such a medium should vanish. By Lorentz invariance ϵμ = 1 i.e., its color magnetic permeability μ should diverge. The assumption based on analogy is well motivated: Ordinary superconductor is the physical medium with μ = 0, confining the opposite magnetic charges (would they exist). For the first successful phenomenological description of both the Meissner effect and superconductivity within Maxwell equations Fritz London guessed two equations for the superconductivity current. We adapt his arguments to QCD and come with two analogous manifestly non-Abelian London-like equations. One equation describes the dual Meissner effect. The analogy is, however, not perfect: We can only speculate that there is some sort of chromo-magnetic superfluidity in QCD phenomena to which the second equation might be ascribed. Moreover, from more advanced Ginzburg-Landau (GL) theory of superconductivity it follows that the Meissner effect is a consequence of spontaneous breaking of the underlying global U(1) symmetry. This is certainly not the case of the dual Meissner effect. Fortunately, the derived London-like equations suggest a strongly color-paramagnetic behavior. We interpret it as a guide to the phenomenological Ginzburg-Landau-like manifestly gauge-invariant low-momentum QCD with the confining vacuum which behaves as a perfect color paramagnet (μ = +∞)

The Proposal for Improvement of the Business Strategy for the Firm

Předmětem této diplomové práce je analyzovat současnou obchodní strategii firmy JANTA s.r.o. a provést její optimalizaci, která povede ke zlepšení obchodní strategie firmy. Práce obsahuje teoretická východiska, analýzu společnosti, konkrétně externí a interní analýzy, SWOT analýzu a finanční analýzu, dále obsahuje doporučení a návody, která vedou v rámci navržené strategie ke stanoveným cílům tak, aby byla zlepšena konkurenceschopnost společnosti. Autor práce je jednatelem společnosti.The subject of this master's thesis is to analyze the current business strategy of the company JANTA s.r.o. and perform the optimization, that will improve business strategy. The work includes theoretical aspects, analysis of the company, specifically external and internal analysis, SWOT analysis and financial analysis, then contains recommendations and instructions, which lead up within the proposed strategy to set goals in order to improve the competitiveness of the company. The author is managing director of the company.

Analytical TCP Model for Millimeter-Wave 5G NR Systems in Dynamic Human Body Blockage Environment

Dynamic blockage of radio propagation paths between the user equipment (UE) and the 5G New Radio (NR) Base Station (BS) induces abrupt rate fluctuations that may lead to sub-optimal performance of the Transmission Control Protocol (TCP) protocol. In this work, we characterize the effects of dynamic human blockage on TCP throughput at the 5G NR air interface. To this aim, we develop an analytical model that expresses the TCP throughput as a function of the round-trip time (RTT), environmental, and radio system parameters. Our results indicate that the blockage affects TCP throughput only when the RTT is comparable to the blocked and non-blocked state durations when the frequency of state changes is high. However, such conditions are not typical for dynamic body blockage environments allowing TCP to benefit from the high bandwidth of 5G NR systems fully

Dynamical breakdown of Abelian gauge chiral symmetry by strong Yukawa interactions

We consider a model with anomaly-free Abelian gauge axial-vector symmetry, which is intended to mimic the standard electroweak gauge chiral SU(2)_L x U(1)_Y theory. Within this model we demonstrate: (1) Strong Yukawa interactions between massless fermion fields and a massive scalar field carrying the axial charge generate dynamically the fermion and boson proper self-energies, which are ultraviolet-finite and chirally noninvariant. (2) Solutions of the underlying Schwinger-Dyson equations found numerically exhibit a huge amplification of the fermion mass ratios as a response to mild changes of the ratios of the Yukawa couplings. (3) The `would-be' Nambu-Goldstone boson is a composite of both the fermion and scalar fields, and it gives rise to the mass of the axial-vector gauge boson. (4) Spontaneous breakdown of the gauge symmetry further manifests by mass splitting of the complex scalar and by new symmetry-breaking vertices, generated at one loop. In particular, we work out in detail the cubic vertex of the Abelian gauge boson.Comment: 11 pages, REVTeX4, 10 eps figures; additional remarks and references added; version published in Phys. Rev.

Examen metalográfico de la espada no. 438 en el marco de un estudio sistemático de las espadas de la fortaleza bajomedieval de Mikulčice, República Checa

The paper deals with a metallographic examination of a sword from grave No. 438, which was uncovered at the site of Mikulčice (Hodonín county), a former early medieval stronghold in Moravia (Czech Republic). Mikulčice was one of the main power centres of the Great Moravia – the first state formed by Slavs north of the Danube River – which was created in the first third of the 9th century and ended at the beginning of the 10th century. The sword, provided with a single flattened hemispherical pommel (Petersen X type), has a blade bearing an inscription that is no longer legible. According to the results of metallographic examination, the blade was hardened and consists of steel cutting edges welded on a core, which was composed of steel side-plates and a middle strip of iron or low-carbon steel. It was an excellent sword, undoubtedly one of the best swords excavated in Mikulčice.El artículo trata de un examen metalográfico de una espada de la tumba número 438, que fue descubierta en el yacimiento de Mikulčice (Hodonín Condado), antiguo bastión bajomedieval en Moravia (República Checa). Mikulčice fue uno de los centros de poder principales del Gran Moravia - la primera agrupación estatal de los eslavos del norte del río Danubio - que se creó en el primer tercio del siglo IX y fue abolido al comienzo del siglo X. La espada, que cuenta con un pomo aplanado hemiesféri-co (Petersen tipo X), tiene una hoja con una inscripción que ya no es legible. De acuerdo con los resulta-dos del examen metalográfico, la hoja fue endurecida y se compone de filos de corte de acero, soldados a un núcleo. Éste está compuesto de placas laterales de acero y una franja central de hierro o de acero dulce. Era una espada excelente, sin duda, una de las mejores espadas jamás excavadas en Mikulčice