560 research outputs found
Solving AX-equations
No full textTitle: Solving AX-equations Author: Jan Butora Department: Department of algebra Supervisor: doc. RNDr. Jiří Tůma, DrSc., Department of algebra Abstract: In this work, we present concept of AX-equations and focus on two such equations. Using similiar techniques, we build a theory for both equations, which allows us to express number of their solutions based only on their parameters. Using this theory, we demonstrate on an example that differential steps, used in differential cryptanalysis of modular addition, are not independent. Moreover, based on this theory we introduce and implement fast algorithms for searching solutions. Keywords: differential cryptanalysis, AX-equations, modular addition, carry, sol- vability conditio
Theoretical investigation on radiation tolerance of Mn+1 AX(n) phases
No full textTernary M(n + 1)AX(n) phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination of ceramic and metallic properties. However, Mn + 1AXn materials behave differently in amorphization when exposed to energetic neutron and ion irradiations in experiment. We first analyze the irradiation tolerances of different M(n + 1)AX(n) (MAX) phases in terms of electronic structure, including the density of states ( DOS) and charge density map. Then a new method based on the Bader analysis with the first-principle calculation is used to estimate the stabilities of MAX phases under irradiation. Our calculations show that the substitution of Cr/V/Ta/Nb by Ti and Si/Ge/Ga by Al can increase the ionicities of the bonds, thus strengthening the radiation tolerance. It is also shown that there is no obvious difference in radiation tolerance between Mn (+ 1)AC(n) and Mn (+ 1)AN(n) due to the similar charge transfer values of C and N atoms. In addition, the improved radiation tolerance from Ti3AlC2 to Ti2AlC ( Ti3AlC2 and Ti2AlC have the same chemical elements), can be understood in terms of the increased Al/TiC layer ratio. Criteria based on the quantified charge transfer can be further used to explore other M(n + 1)AX(n) phases with respect to their radiation tolerance, playing a critical role in choosing appropriate MAX phases before they are subjected to irradiation in experimental test for future nuclear reactors
Ab initio study of irradiation tolerance for different M(n+1)AX(n) phases: Ti3SiC2 and Ti3AlC2
No full textLayered ternary M(n+1)AX(n) (MAX) materials are recently proposed to be promising candidates for future fission and fusion programmes because of their unique properties inherited from both ceramics and metals. However, different M(n+1)AX(n) materials demonstrate different behaviors when exposed to energetic neutron or ion irradiations. Based on first-principles calculations, we have investigated the irradiation tolerance of two typical M(n+1)AX(n) materials: Ti3SiC2 and Ti3AlC2 from two aspects. First, we make a detailed analysis on the interatomic bonding characters, which are believed to be responsible for the resistance to radiation-induced amorphization. Second, the formation energies of various intrinsic and antisite defects in these two compounds are calculated in order to elucidate their amorphization mechanism. Our results show that the absence of orbitals overlap of Al-C in Ti3AlC2 renders it more resistant to amorphization compared to Ti3SiC2. In addition, the antisite defects Al-Ti(1) and Al-Ti(2) in Ti3AlC2 have much lower formation energies compared to Si-Ti(1) and Si-Ti(2) in Ti3SiC2, which implies that the replacement of Ti with Al is easier than Si, thus providing an alternative way to accommodate the defects resulted from irradiation damage cascades. These results indicate that Ti3AlC2 is more irradiation tolerant than Ti3SiC2, in accordance with experimental observations. Our results have profound implications for the choice of appropriate MAX phase with best performance to be used in next reaction reactors. (C) 2014 AIP Publishing LLC
Minding the aesthetic: The place of the literary in education and research.
No full textThe article discusses the significance of aesthetic as a mode of cognition and means of social cohesion. It notes the relation of aesthetic knowledge with the perception or intuition, the emergence of such awareness into something durable and the response to the embodiment. It describes the evolution of aesthetic delight in the human species, the sense of sense of beauty arising on one's realization of the formal qualities of something, through the poem presented by the author on achievement
ko-ax photo [Selected by Tate Curator of Photography, Simon Baker]
No full textko-ax photo was an open submission competition selected by Simon Baker (Curator of Photography, Tate), Sue Steward (Photography critic, Telegraph, Observer, Guardian, BBC) and John Gill (Curator Brighton Photo Biennial and Founder Photoworks). The 10 artists selected all presented fascinating artworks that conceal narratives and ask questions of the viewer. Questions of beauty, family, decay and fantasy were all explored across over 50 works.</p
Preconditioning Large Scale Iterative Solution of Ax = b Using a Statistical Method with Application to Matrix-Free Spectral Solution of Helmholtz Equation
No full textAbstractThe problem of preconditioning the linear system Ax = b where no entries of A are known but the matrix-vector product is given in the linear functional form Ax = L(x) is considered. A statistical multiregressor method is proposed whose convergence improves during Krylov iterations. It is shown that this method effectively improves the rate of convergence of the GMRES algorithm. The results are validated by applying the current preconditioner to a pseudo-spectral solution of Helmholtz equation
Veilig Getij, beheer en gebruik Stormvloedkering Oosterschelde: Ervaring en bijstelling
No full textDe rapportage van het project Evaluatie Oosterschelde bestaat uit de evaluatienota 'de evaluatie van de Oosterschelde na 5 jaar stormvloedkering' (AX91.089) en twee onderbouwende nota's: 'Beheer stormvloedkering Oosterschelde: ervaring en bijstelling' en 'De effecten van de waterbouwkundige werken op het getijdemilieu van de Oosterschelde'(AX91.091; GWWS91.088). Deze nota is gebaseerd op onderzoek dat is uitgevoerd in de periode 1987-1991. Het onderzoek bestond enerzijds uit veldwaarnemingen anderzijds uit nader theoretisch onderzoek betreffende de door de projektgroep BARCON ten tijde de aanleg van de kering geformuleerde uitgangspunten. Bij de interpretatie van de gegevens is gebruik gemaakt van de nieuwste wetenschappelijke inzichten. Tevens is gebruik gemaakt van nieuwe rekentechnieken. Het onderzoek is uitgevoerd in opdracht van direktie Zeeland van Rijkswaterstaat.KWP-collectio
A constructive proof of a unimodular transformation theorem for simplices
No full textMatrices;Linear Programming;Integer Programming
Combined effect of astaxanthin and squalene on oxidative stress in vivo
No full textObesity and diabetes, risk factors for metabolic syndrome, are characterized by oxidative stress and inflammatory responses. Marine biofunctionals, astaxanthin (Ax) and squalene (SQ), were evaluated for their combined effect. Groups of male KK-A (y) mice were fed high fat/sucrose diet for 4 weeks, supplemented with either 0.1 %Ax, 2 %SQ or 0.1 %Ax + 2 %SQ. In comparison to control, Sod was elevated in only Ax + SQ. However, Gpx was highest in Ax + SQ, indicating the combined antioxidant effect of Ax and SQ. This was supported by elevated mRNA expression of Sod1 and Gpx1. Except adiponectin (elevated in Ax and Ax + SQ), expression of other inflammatory markers was not altered. Blood glucose levels were decreased in SQ and Ax + SQ while liver triglycerides decreased in SQ group. This is the first in vivo study demonstrating combined effects of Ax and SQ resulting in antioxidant effects and modulation of glucose/triglyceride levels. This study highlights the benefit of utilizing Ax and SQ together for management of obesity/diabetes
Astaxanthin improves the developmental competence of invitro-grown oocytes and modifies the steroidogenesis of granulosa cells derived from bovine early antral follicles
No full textIn this study we investigated the effect of astaxanthin (Ax), which exhibits strong antioxidant activity, during invitro growth (IVG) on the developmental competence of oocytes and steroidogenesis of granulosa cells derived from early antral follicles. Bovine oocyte-cumulus-granulosa complexes collected from early antral follicles were cultured for 12 days in the presence or absence (control) of 500 mu M Ax. The viability of oocytes and antrum formation in the granulosa cell layer during IVG culture were greater in the presence than absence of Ax (P<0.05). Regardless of Ax treatment, 17-oestradiol production increased during IVG culture; however, progesterone production was significantly lower in the presence than absence of Ax (P<0.05). Reactive oxygen species levels were lower in Ax-treated oocytes than in controls after IVG (P<0.05). Although nuclear maturation and cleavage rates did not differ between the Ax-treated and control groups, Ax treatment led to weaker cathepsin B activity in oocytes and better blastocyst rates than in controls (P<0.05). Accordingly, Ax treatment during IVG increased the total number of cells in blastocysts (P<0.05). These results indicate that Ax supplementation of IVG medium improves the quality of bovine oocytes due to its antioxidative effects on growing oocytes and its suppression of the luteinisation of granulosa cells
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