592 research outputs found
Computing languages by (bounded) local sets
No full textWe introduce the definition of local structures as description of computations to recognize strings and characterize families of Chomsky's hierarchy in terms of projection of frontiers of local sets of structures. Then we consider particular grid structures we call bounded-grids and study the corresponding family of string languages by proving some closure properties and giving several examples
Quantum computing: 1-way quantum automata
No full textIn this paper we analyze several models of 1-way quantum finite automata, in the light of formal power series theory. In this general context, we recall two well known constructions, by proving:
1. Languages generated with isolated cut-point by a class of bounded rational formal series axe regular.
2. If a class of formal series is closed under f-complement, Hadamard product and convex linear combination, then the class of languages generated with isolated cut-point is closed under boolean operations.
We introduce a general model of 1-way quantum automata and we compare their behaviors with those of measure-once, measure-many and reversible 1-way quantum automata
Frequency of symbol occurrences in simple non-primitive stochastic models
No full textWe study the random variable Yn representing the number of occurrences of a given symbol in a word of length n generated at random. The stochastic model we assume is a simple non-ergodic model defined by the product of two primitive rational formal series, which form two distinct ergodic components. We obtain asymptotic evaluations for the mean and the variance of Yn and its limit distribution. It turns out that there are two main cases: if one component is dominant and non-degenerate we get a Gaussian limit distribution; if the two components are equipotent and have different leading terms of the mean, we get a uni-form limit distribution. Other particular limit distributions are obtained in the case of a degenerate dominant component and in the equipotent case when the leading terms of the expectation values are equal
Quantification of nuclear uncertainties in nucleosynthesis of elements beyond Iron
No full textNucleosynthesis beyond Fe poses additional challenges not encountered when studying astrophysical processes involving light nuclei. Generally higher temperatures and nuclear level densities lead to stronger contributions of transitions on excited target states. This may prevent cross section measurements to determine stellar reaction rates and theory contributions remain important. Furthermore, measurements often are not feasible in the astrophysically relevant energy range. Sensitivity analysis allows not only to determine the contributing nuclear properties but also is a handy tool for experimentalists to interpret the impact of their data on predicted cross sections and rates. It can also speed up future input variation studies of nucleosynthesis by simplifying an intermediate step in the full calculation sequence. Large-scale predictions of sensitivities and ground-state contributions to the stellar rates are presented, allowing an estimate of how well rates can be directly constrained by experiment. The reactions 185W(n,γ) and 186W(γ,n) are discussed as application examples. Studies of uncertainties in abundances predicted in nucleosynthesis simulations rely on the knowledge of reaction rate errors. An improved treatment of uncertainty analysis is presented as well as a recipe for combining experimental data and theory to arrive at a new reaction rate and its uncertainty. As an example, it is applied to neutron capture rates for the s-process, leading to larger uncertainties than previously assumed
Enhanced electron screening in d(d,p)t for deuterated metals
No full textThe electron screening effect in the d(d,p)t reaction has been studied for deuterated metals, insulators, and semiconductors, i.e. 58 samples in total. As compared to measurements performed with a gaseous D-2 target, a large effect has been observed in most metals, while a small (gaseous) effect is found, e.g., for the insulators, semiconductors, and lanthanides. The periodic table provides the ordering of the observed small and large effects in the samples. An explanation of the large effects in metals is possibly provided by the classical plasma screening of Debye applied to the quasi-free metallic electrons. The data also provide information on the solubility of hydrogen in the samples. RI Gyurky, Gyorgy/F-1078-2010; Fulop, Zsolt/B-2262-2008; Aliotta, Marialuisa /H-2567-201
Advertising and competition in theory practice and public policy
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This study analyses and compares the theories relating to advertising and competition in economics literature with their operation in the market-place, and with the attitudes and pronouncements of public policy towards advertising and competition. A survey of the main literature in economic theory concerned with advertising and competition includes the theory of value, the theory of the firm, and theories and empirical studies on the effects of advertising and imperfect competition on prices, profits, barriers to entry and product differentiation. Since no general agreement exists on these theories and research, the review is interspersed with criticisms which have been made about specific features of them, and also a short outline of alternative theories which are considered to give a more accurate
account of the behaviour of firms in the real world. Consumer behaviour in the market is then studied from three viewpoints: a summary of the major academic theories of consumer behaviour; the results of some empirical research into consumer behaviour; and eight case histories of products and services which show how products are developed and introduced on the market. Finally, the economic theories are compared with the results of the empirical research and the case histories. The theory and practice of advertising and competition is then compared with extracts from the reports of public bodies to illustrate the attitude of public policy towards advertising and competition. The conclusions draw attention to the major discrepancies which appear to exist between theory and practice, and the implications that follow for public policy which seems to be predominantly based on the theory of the firm and the need to eliminate imperfections in the market such as product differentiation, advertising and non-price competition
On the importance of low-energy beta beams for supernova neutrino physics
No full textWe show that low-energy beta beams are very well suited to obtain information about supernova-neutrino interactions. Linear combinations of low-energy beta-beam spectra are fitted to supernova-neutrino energy distributions. The resulting synthetic spectra are able to reproduce the response of a nuclear target to an incoming supernova neutrino flux in a very accurate way. This can provide important information about the neutrino response in a terrestrial detector. We illustrate this technique using deuterium and 16O as target material. The procedure provides an easy and straightforward way to apply the results of a beta-beam neutrino-nucleus measurement to a supernova neutrino detector, virtually eliminating potential uncertainties due to nuclear-structure calculations
Attributed Tree Transducers Cannot Induce All Deterministic Bottom-up Tree Transformations
No full textAbstractIn this paper we give a deterministic bottom-up tree transducer T and show that the tree transformation τ(T) induced by it can be induced by no attributed tree transducer
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