2,065 research outputs found
Domains with a continuous exhaustion in weakly complete surfaces
No full textIn previous works, Tomassini and the authors studied and classified complex surfaces admitting a real-analytic plurisubharmonic exhaustion function; let X be such a surface and D⊆ X a domain admitting a continuous plurisubharmonic exhaustion function: what can be said about the geometry of D? If the exhaustion of D is assumed to be smooth, the second author already answered this question; however, the continuous case is more difficult and requires different methods. In the present paper, we address such question by studying the local maximum sets contained in D and their interplay with the complex geometric structure of X; we conclude that, if D is not a modification of a Stein space, then it shares the same geometric features of X
The death of William Golding: authorship and creativity in darkness visible and the paper men
No full textIn the seventies and eighties William Golding was deeply responsive to the critical, anti-authorial ethos that followed the publication of Roland Barthes's "La mort de I'auteur" (1968). In Darkness Visible (1979) and The Paper Men (1984) he investigates means by which to reaffirm authorial presence. Working through paradox, he performs the authorial death in these novels, and establishes language’s inadequacy as a means of conveying absolute meaning, authorial "vision," truth or revelation. Having done so he nonetheless gestures towards the divine, towards the possibility of a vatic communication. In this manner the novels work upon principles of contradiction and collapse. What remains is a discourse of hope, promise, desire, without means of substantiating such optimism. Thus Golding might be said to have practiced a form of negative theology, and to have anticipated in this respect some recent trends in literary theory
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Opinion polling in Central and Eastern Europe under communism
No full textWhilst political opinion polling occupies a well-entrenched position within contemporary capitalist political systems, the same cannot be said for the countries of Central and Eastern Europe. This article focuses primarily on the development of political opinion polling in these countries in the period prior to the collapse of communist regimes at the end of 1989. Polling was a feature of these communist-led societies, although it was limited in terms of its activities, the scope of issue coverage, and its ability to measure public opinion effectively. The major focus of the discussion concentrates on the methodological issues and problems confronting opinion pollsters in these societies during this time
Author´s book
No full textBakalářská práce v podobě autorské knihy nese název podle použitého textu od
Ernesta Hemingwaye Ostrovy uprostřed proudu. Ilustrace zhotovené na japonský papír jsou hlubinami oceánu, které omývají břehy textových ostrovů. Ty nás udržují v linii děje. Kniha je rozdělena do tří částí, stejně jako její předloha. Text je však zkrácen na ty nejdůležitější momenty z knihy a nechává tak prostor pro její obrazovou část.ObhájenoThe Author's book is called after Ernest Hemingway's book Islands in the Stream. The book is an expedition into the deep blue ocean which surrounds the isles of the leading text. These isles of the text keep us in the rythm of the book. The book consists of three parts - as well as the original book. The text has been shortened to the main moments of the story. Thanks to this reduction there is a space left for the illustrated part of the book
Bi2WO6‐based Z-scheme photocatalysts: Principles, mechanisms and photocatalytic applications
No full textThe development of novel photocatalysts for efficient utilization of solar energy is highly essential for the most critical humanitarian challenges, i.e., energy and water crises as well as environmental pollution. Bismuth tungstate (Bi2WO6), an outstanding Aurivillius phase perovskite, has attracted intensive attention as a visiblelight-responsive photocatalyst because of its non-toxicity, low cost, and outstanding physicochemical characteristics, i.e., nonlinear dielectric susceptibility, ferroelectric piezoelectricity, pyroelectricity, catalytic behavior, modifiable morphology, strong oxidation power, and good photochemical stability. However, the photocatalytic activity of bare Bi2WO6 is restricted because of the inherent drawbacks such as poor light-harvesting efficiency, weak reduction potential, relatively low specific surface area, the fast recombination rate of photoinduced charge carriers, and thus poor quantum yields of photocatalytic reactions. Moreover, the impossibility of simultaneous strong redox ability (demanding wide bandgap) and high light-harvesting efficiency (requiring narrow bandgap) is considered as a big challenge for the practical application of Bi2WO6. Undeniably, the construction of Z-scheme photocatalytic systems is recommended strategy to overcome the above-mentioned disadvantages because of the efficient spatial separation of photogenerated charge carriers and the boosting the redox performance. This review summarizes the principles and recent developments on Z-scheme photocatalytic systems with special emphasis on the Bi2WO6-based photocatalysts, including the types, photocatalytic mechanisms and practical applications. Moreover, major differences between type-II heterojunction and Z-scheme photocatalyst have also been discussed. Additionally, the significant role of unique structures (e.g., core-shell and 2D/2D) for the improvement of photocatalytic activity of Z-scheme photocatalyst has been presented. Indeed, Bi2WO6-based Zscheme photocatalysts have exhibited superior photocatalytic activity for various applications. For example, they show high photocatalytic activity towards water/wastewater treatment (removal of organic and inorganic pollutants, as well as microorganisms), air purification (decomposition of volatile organic compounds and inorganic matters), green energy conversion (e.g., generation of H2 and CH4 fuels under solar irradiation), and organic synthesis. It is thought that this remarkable activity of Bi2WO6-based Z-scheme photocatalysts might be attributed to the efficient solar light harvesting, separation and further transfer of charge carriers and strong redox ability. To the best of our knowledge, the present paper is the first attempt to summarize the Bi2WO6-based Zscheme photocatalytic reactions, providing important insights and up-to-date information for the scientific community to fully explore the potential of Bi2WO6-based photocatalysts for renewable environmental remediation, energy conversion, and chemical synthesis
Structural panel for engineering applications and method for manufacturing such a structural panel
No full textThe invention relates to a structural panel comprising a core of fibre material and outer layers on opposite sides of the core, wherein the core of fibre material is received in preshaped grooves provided in one outer layer's surface, the remaining area in said grooves being completely filled with resin material so as to avoid any air remaining in said grooves.Civil Engineering and Geoscience
Grupos autossimilares intransitivos
No full textTese (doutorado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Matemática, 2021.Neste trabalho estudamos representações autossimilares de grupos em Am, o grupo de automorfismos da árvore m-ária regular Tm. Um grupo abstrato é dito ser au- tossimilar se ele admite uma representação autossimilar fiel em alguma árvore Tm; quando a representação autossimilar induz ação transitiva no primeiro nível da árvore, dizemos que o grupo é autossimilar transitivo. Um procedimento pa- drão para construção de representação autossimilar transitiva de um grupo foi por meio de um único endomorfismo virtual do grupo em questão. Recentemente, foi mostrado que este procedimento, quando aplicado ao produto entrelaçado restrito Z o Z, não pode produzir representação autossimilar transitiva fiel para qualquer m ≥ 2 (veja [3]). Estudamos subgrupos autossimilares de Am sem assumir ação transitiva no primeiro nível de Tm. Esta ação geral é traduzida em um conjunto de endomorfismos virtuais correspondentes à diferentes órbitas da ação no primeiro nível de Tm. Com este novo procedimento, produzimos representações autossimi- lares fiéis, algumas das quais são também finita por estado, para vários grupos tais como Z (ω) , Z o Z e (Z o Z) o C2. Também estendemos resultados de Brunner-Sidki [5], sobre subgrupos abelianos autossimilares transitivos de Am ao caso geral, onde o grupo de permutação induzido no primeiro nível da árvore tem s ≥ 1 órbitas. Provamos que um tal grupo A, na sua representação na árvore, imerge em um único subgrupo abeliano de Am o qual é autossimilar e auto-centralizante. Por fim, mostramos que o grupo nilpotente de classe 3 e livre de torção, N3,4, de Bludov-Gusev [27], não é autossimilar.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).In this work we study self-similar representations of groups on Am, the group of automorphisms of a regular m-ary tree Tm. An abstract group is said to be self-similar provided it admits a faithful self-similar representation on some tree Tm; when a self-similar representation induces transitive action on the first level of the tree we say that the group is transitive self-similar. A standard approach for constructing a transitive self-similar representation of a group has been by way of a single virtual endomorphism of the group in question. Recently, it was shown that this approach when applied to the restricted wreath product ZoZ could not produce a faithful transitive self-similar representations for any m ≥ 2 (see [3]). We study self-similar subgroups of Am without assuming transitive action on the first level of the tree. This general action is translated into a set of virtual endomorphisms corresponding to the different orbits of the action on the first level of Tm. With this new approach we produce faithful self-similar representations, some of which are also finite-state, for a number of groups such as Z (ω) , Z o Z and (Z o Z) o C2. We also extend results from Brunner-Sidki [5], on transitive self-similar abelian subgroups of Am to the general case where the permutation group induced on the first level of the tree has s ≥ 1 orbits. We prove that such a group A, in its representation on the tree, embed into a unique abelian subgroup of Am which is self-similar and self-centralizing. Finally, we show that the nilpotent group of class 3 and torsion free, N3,4, of Bludov-Gusev [27], is not self-similar.Instituto de Ciências Exatas (IE)Departamento de Matemática (IE MAT)Programa de Pós-Graduação em Matemátic
Method and instrumentation for detection of rail defects, in particular rail top defects
No full textA method and instrumentation for detection of rail defects, in particular rail top defects, in a railway-track by measuring an axle box acceleration signal of a rail vehicle, wherein a longitudinal axle box acceleration signal is used as a measure to detect the occurrence of said rail defects, in particular rail top defects. The method also includes measuring a vertical axle box acceleration signal of said rail vehicle, whereby the longitudinal axle box acceleration signal is used in combination and simultaneously with said vertical axle box acceleration signal. It is further preferred that the longitudinal axle box acceleration signal is used to remove from said vertical axle box acceleration signal a signal-part that relates to vibrations of the rail vehicle's wheelset, including the bearing and axle box (3), and that the axle box acceleration signals are filtered for removing signal-parts contributed by vibrations of the track, including the rail (1), rail pads, fasteners, sleepers, and ballast.Design and ConstructionCivil Engineering and Geoscience
Birational Geometry of 3-fold Mori Fibre Spaces
No full textWe study the geography and birational geometry of 3-fold conic bundles over P and cubic del Pezzo fibrations over P. We discuss many explicit examples and raise several open questions
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