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Search Results: 1 - 10 of 133461 matches for " V. Fischer "
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The Heisenberg oscillator
Véronique Fischer
Bulletin of Mathematical Sciences , 2012, DOI: 10.1007/s13373-012-0021-z
Abstract: In this short note, we determine the spectrum of the Heisenberg oscillator which is the operator defined as $L+|x|^2+|y|^2$ on the Heisenberg group $H_1=\mathbb{ R} ^2_{x,y}\times \mathbb{ R} $ where L stands for the positive sublaplacian.
Testing of PLL-based True Random Number Generator in Changing Working Conditions
M. Simka,M. Drutarovsky,V. Fischer
Radioengineering , 2011,
Abstract: Security of cryptographic systems depends significantly on security of secret keys. Unpredictability of the keys is achieved by their generation by True Random Number Generators (TRNGs). In the paper we analyze behavior of the Phase-Locked Loop (PLL) based TRNG in changing working environment. The frequency of signals synthesized by PLL may be naturally influenced by chip temperature. We show what impact the temperature has on the quality of generated random sequence of the PLL-based TRNG. Thank to analysis of internal signals of the generator we are able to prove dependencies between the PLL parameters, statistical parameters of the generated sequence and temperature. Considering the measured results of experiments we form a new requirement in order to improve the robustness of the designed TRNG.
Background-Source Separation in astronomical images with Bayesian probability theory (I): the method
F. Guglielmetti,R. Fischer,V. Dose
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.14739.x
Abstract: A probabilistic technique for the joint estimation of background and sources with the aim of detecting faint and extended celestial objects is described. Bayesian probability theory is applied to gain insight into the coexistence of background and sources through a probabilistic two-component mixture model, which provides consistent uncertainties of background and sources. A multi-resolution analysis is used for revealing faint and extended objects in the frame of the Bayesian mixture model. All the revealed sources are parameterized automatically providing source position, net counts, morphological parameters and their errors.
Self-repairing material systems―a dream or a reality?  [PDF]
Hartmut Fischer
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.28110
Abstract: Currently, most industrial materials rely entirely on passive protection mechanisms; such me chanisms are readily applicable and universal for many different materials systems. However, they will always stay passive, and therefore their lifetime and functionality is limited and related to the amount of protective additives and the intensity of their consumption. Therefore, better, and preferentially active process for the protection/repair of damaged materials―selfrepairing processes―were developed and need to be developed further. Although it sounds futuristic or like a fiction in the modern, trendy times, which in many ways affects also directions of research; self healing of material systems exists already for a long time in all sorts of systems of materials or functionalities. The aim of this work is to go beyond the scope of a classical review the ones published recently in this field which almost entirely focused only onto polymeric systems. In this work, an analysis of the underlying functional and constructional principles of existing natural and synthetically selfhealing systems spanning over a range of classes of materials is given leading to general rules and principles for the design of new and application tailored selfhealing material systems.
The Definition of Density in General Relativity  [PDF]
Ernst Fischer
International Journal of Astronomy and Astrophysics (IJAA) , 2017, DOI: 10.4236/ijaa.2017.74025
Abstract: According to general relativity the geometry of space depends on the distribution of matter or energy fields. The relation between the local geometrical parameters and the volume enclosed in given limits varies with the distribution of matter. Thus properties like particle number, mass or energy density, defined in the Euclidean tangent space, cannot be integrated to give conserved integral data like total number, mass or energy. To obtain integral conservation, a correction term must be added to account for the curvature of space. For energy this correction term is the equivalent of potential energy in Newtonian gravitation. With this correction the formation of black holes in the sense of singularities by gravitational collapse does no longer occur and the so called dark energy finds its natural explanation as potential energy of matter itself.
On the Ontology of Structural Realism  [PDF]
Markus Fischer
Open Journal of Political Science (OJPS) , 2019, DOI: 10.4236/ojps.2019.91008
Abstract: Due to its systemic approach, structural realism (or neorealism) can be subsumed under methodological holism, which takes social phenomena to be wholes that cannot be reduced to their parts. The wholes posited by structural realism are the state and the international structure. Recent developments in the philosophy of social science suggest that methodological holism ought to be limited to causal explanation and complemented by ontological individualism, which requires an account of how social wholes derive from individuals. Structural realism lacks such an account because it takes the state as an empirical given, mistaking for a fact what is really a concept in need of deductive derivation from individuals. To bring the theory methodologically up to date, this essay undertakes such a derivation of the state from individuals, proceeding in the deductive manner of political theory. It thus provides structural realism with a methodologically valid ontology, which, in turn, enables the theory to better defend itself against liberal and constructivist critics who reduce the state to a transient phenomenon.
catena-Poly[[cobalt(II)-μ-aqua-μ-propanoato-κ2O:O′-μ-propanoato-κ2O:O] monohydrate]
A. I. Fischer,V. V. Gurzhiy,A. N. Belyaev
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810043540
Abstract: The title compound, {[Co(C2H5COO)2(H2O)]·H2O}n, was synthesized by the reaction of cobalt(II) carbonate hydrate with aqueous propionic acid. The structure consists of polymeric infinite linear chains with composition [Co(C2H5COO)4/2(H2O)2/2]∞ running along [010]. The chains are formed by Co2+ ions linked with bridging propionate groups and water molecules, with a Co...Co distance along the chains of 3.2587 (9) . The Co2+ ion is six-coordinated in a strongly distorted octahedral geometry. The chains are connected to each other by a network of O—H...O hydrogen bonds involving solvent water molecules.
catena-Poly[[cobalt(II)-μ-aqua-di-μ-butanoato-κ2O:O′;κ2O:O] 0.7-hydrate]
A. I. Fischer,V. V. Gurzhiy,A. N. Belyaev
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811019271
Abstract: In the title coordination polymer, {[Co(C3H7COO)2(H2O)]·0.7H2O}n, the Co2+ cation is coordinated by four bridging butanoate anions and two bridging water molecules in a severely distorted octahedral geometry. The Co2+ cations are linked by means of bridging ligands into polymeric chains along [010]. These chains are further connected to each other through hydrogen bonds involving partially occupied disordered water molecules; thus, sheets parallel to (001) are formed. One of the positions of disordered water O atom lies on a twofold axis. Two atoms of the aliphatic chain of one of the butanoate anions are disordered over two positions each.
Depth Profile Reconstruction from Rutherford Backscattering Data
U. V. Toussaint,K. Krieger,R. Fischer,V. Dose
Physics , 1998,
Abstract: An adaptive kernel method in the Bayesian framework together with a new simulation program for Rutherford backscattering spectroscopy (RBS) have been applied to the analysis of RBS data. Even in the case of strongly overlapping RBS peaks a depth profile reconstruction without noise fitting has been achieved. The adaptive kernel method leads to the simplest depth profile consistent with the data. Erosion and redeposition rates of carbon divertor plates in the fusion experiment ASDEX Upgrade could be determined by RBS-analysis of thin film probes before and after exposition to plasma discharges.
Prevalence, distribution and evolutionary significance of the IS629 insertion element in the stepwise emergence of Escherichia coli O157:H7
Lydia V Rump, Markus Fischer, Narjol Gonzalez-Escalona
BMC Microbiology , 2011, DOI: 10.1186/1471-2180-11-133
Abstract: The comparison of 4 E. coli O157:H7 genome and plasmid sequences showed numerous IS629 insertion sites, although not uniformly distributed among strains. Comparison of IS629s found in O157:H7 and O55:H7 showed the presence of at least three different IS629 sub-types. O157:H7 strains carry IS629 elements sub-type I and III whereby the ancestral O55:H7 carries sub-type II. Analysis of strains selected from various clonal groups defined on the E. coli O157:H7 stepwise evolution model showed that IS629 was not observed in sorbitol fermenting O157 (SFO157) clones that are on a divergent pathway in the emergence of O157:H7. This suggests that the absence of IS629 in SFO157 strains probably occurred during the divergence of this lineage, albeit it remains uncertain if it contributed, in part, to their divergence from other closely related strains.The highly variable genomic locations of IS629 in O157:H7 strains of the A6 clonal complex indicates that this insertion element probably played an important role in genome plasticity and in the divergence of O157:H7 lineages.Enterohemorrhagic Escherichia coli (EHEC) of serotype O157:H7 has been implicated in foodborne illnesses worldwide. It frequently causes large outbreaks of severe enteric infections including bloody diarrhoea, hemorrhagic colitis (HC) and haemolytic uremic syndrome (HUS) [1,2]. This serotype constitutively expresses the somatic (O) 157 and flagellar (H) 7 antigens, thus, these traits are used extensively in clinical settings to identify this highly pathogenic serotype [1]. However some O157:H7 strains, although being genotipically O157 or H7 do not express either of those antigens [3,4]. According to the latest CDC report, E. coli O157:H7 infections affect thousands of people every year accounting for 0.7%, 4% and 1.5%, of illnesses, hospitalizations and deaths, respectively of the total U.S. foodborne diseases caused by all known foodborne pathogens [5].Previously, we characterized two potentially pathogenic
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