Příspěvek vyhodnocuje ekonomické možnosti obnovitelných zdrojů energie ve srovnání s fosilními a jadernými palivy. Porovnává strukturu spotřeby primárních energetických zdrojů ve světovém měřítku a v ČR. V tabulkové formě uvádí výrobní a měrné investiční náklady pro vybrané technologie, specifikuje podmínky uplatnění obnovitelných zdrojů v konkurenci fosilních a jaderných paliv. V závěru si všímá výhledu možností využití obnovitelných zdrojů energie v ČR. and Jan Fiedler.
This paper contributes to Contradictions’ “Conceptual Dictionary” by exploring the history, theory, and practical implications of the notion of “ecosocialism”. The first part of the text follows the historical and ideological development of ecosocialism and examines its broad and diverse anarchist, feminist, and Marxist roots. This part of the text also introduces key authors of ecosocialism and their work. The subsequent part identifies critical ideas and offers a theoretical overview of scholarly and political debates about the relationship between ecosocialism and other environmental and socio-critical approaches. Finally, the text further explores the practical and political vision of the concept and reflects on the future of ecosocialist strategy.
The paper presents to Czech social scientists an introductory review of the concept of equivalence and the method of blockmodeling in social network analysis (SNA). After introducing the central concepts of SNA such as node and tie, along with their basic metrics such as centrality and cohesion, I present the concepts of role and position. These are treated by SNA as clusters of nodes with similar ties, something I juxtapose to algorithms to identify cohesive subgroups of nodes. Subsequently, I define and compare the two most frequently applied types of equivalence - structural, which is strict but broadly applicable, and regular, which is more liberal but has limited uses. Structural equivalence builds on a strict definition of similarity of ties, treating as equivalent only such nodes that have the same ties to the same other nodes. Regular equivalence works with looser criteria and better corresponds with both the theoretical and the intuitive notions of role; this, however, is outweighed by the absence of a unique regular-equivalent solution within a network and by the difficulty to process networks with undirected ties. Regular-equivalent nodes are such that have ties to other mutually equivalent nodes. I present examples to demonstrate the differences between both definitions. In the following section, I discuss measurement of similarity between the different nodes’ profiles of ties (e.g., correlation and Euclidean distance) and possible uses of the standard statistical methods of cluster analysis and multidimensional scaling to detect equivalent classes of nodes within networks. After pointing to the weaknesses of these techniques in network data analysis, I present blockmodeling as a method designed specifically to identify roles and positions within networks. Ischematize the blockmodeling procedure and present its basic terms before comparing classic inductive blockmodeling, which is primarily fit for the purposes of exploration and network reduction, with deductive generalized blockmodeling, which is applicable in testing hypotheses about basic structural characteristics of a network. I bring attention to the strengths and weaknesses of both approaches. Relatedly, I present an application of blockmodeling especially for the purposes of simplified network representation, comparing structural patterns across networks, and testing structural theories. In the following section, I demonstrate specific blockmodeling algorithms based on both structural equivalence (CONCOR and Tabu Search optimization) and regular equivalence (REGE and Tabu Search optimization). Then I verify the adequacy of their resulting assignment of positions to nodes using eta coefficient, Q modularity and correlation of the ideal blocked and the empirical adjacency matrices. In the concluding section, I demonstrate the entire blockmodeling procedure on an empirical case of a small network with undirected ties using the UCINET software tool, including interpretation of results. Finally, I reflect the contemporary position of blockmodeling among leading research approaches in SNA, referring to other empirically oriented studies that demonstrate the broad applicability and utility of position analysis., Tomáš Diviák., and Obsahuje použitou literaturu a poznámky
Several topologies of electrical machines can be used to meet requirements for application in a hybrid electric vehicle. This paper describes process of an electric motor-generator selection, considering electromagnetic, thermal and basic control design. The requested electrical machine must develop 45 kW in continuous operation at 1300 rpm with field weakening capability up to 2500 rpm. Both radial and axial flux topologies are considered as potential candidates. A family of axial flux machines is represented by a permanent magnet, single stator and two rotor plates topology. An induction machine was included into the selection process, alongside an embedded and inset permanent magnet synchronous machine, all of the radial type machines. and Obsahuje seznam literatury
Electromechanical system with one degree of freedom in mechanical oscillating part and with other degree in rotation a electrical subsystems is investigated by means of numerical solution of derived equations in dimensionless form. The most important nonlinearities are impacts of the main body on the stiff but deformable stop. Other nonlinear effects are introduced into system by the force transformation from unbalance exciter with limited power into the oscillating subsystem and also by nonlinear magnetic flux in the driving electromotor. Presented numerical simulation was focused on the study of the influence of exciting unbalance level on the time histories of oscillations and on phase trajectories. The various responses were shown and discussed in examples. and Obsahuje seznam literatury
The electro-ultrasonic spectroscopy was used as a non-destructive testing method for the magnesium composites evaluation. AC current varying with frequency fE and the ultrasonic signal varying with frequency fU are applied on the conducting sample and a new intermodulation signal on the frequency f m given by the superposition or subtraction of exciting frequencies is measured on the sample. We have measured on intermodulation frequency fm = fE – fU. This method can be used as a diagnostic tool for the quality and reliability assessment. The sample resistance is influenced by the ultrasonic signal. The ultrasonic signal changes the contact area between the conducting grains in the sample structure and then resistance is modulated by the frequency of ultrasonic excitation. The electrical charge and also the electrical current flowing through the sample structure are conserved. In case the contact area between the conducting grains is changing then the current density is changed. This leads to the resistivity change of measured structure. We suppose that for the sample with more defects in the structure the influence of the ultrasonic signal is more pronounced and the resistance change is higher. and Pomocí elektro-ultrazvukové nedestruktivní spektroskopie byl testován vzorek z hořčíkové slitiny. Tato metoda je založena na střídavém elektrickém proudu o frekvenci f e, který prochází vzorkem a ultrazvukovým vlněním o frekvenci f U. Na rozdílové a součtové frekvenci těchto dvou signálů vzniká nový intermodulační signál f m. Velikost tohoto signálu je závislá jak na velikosti budicích signálů, tak na struktuře testovaného materiálu a celkových defektech obsažených ve vzorku. rezistivita materiálu se mění v závislosti na ultrazvukovém vlnění. Ultrazvukový signál mění oblast kontaktu mezi vodivými zrny ve struktuře materiálu s frekvencí ultrazvukového vlnění f U. Tímto se mění proudová hustota ve vzorku, protože elektrický náboj a proud procházející vzorkem jsou konstantní. Předpokládáme, že vzorky, které obsahují více defektů ve své struktuře, budou mít vyšší hodnotu změny odporu než vzorky bez defektů.