Search results for "Recursion"
showing 10 items of 61 documents
Reducing the irreducible: Dispersed metal atoms facilitate reduction of irreducible oxides.
2021
Oxide reducibility is a central concept quantifying the role of the support in catalysis. While reducible oxides are often considered catalytically active, irreducible oxides are seen as inert supports. Enhancing the reducibility of irreducible oxides has, however, emerged as an effective way to increase their catalytic activity while retaining their inherent thermal stability. In this work, we focus on the prospect of using single metal atoms to increase the reducibility of a prototypical irreducible oxide, zirconia. Based on extensive self-consistent DFT+U calculations, we demonstrate that single metal atoms significantly improve and tune the surface reducibility of zirconia. Detailed ana…
Logic, Computing and Biology
2015
Logic and Computing are appropriate formal languages for Biology, and we may well be surprised by the strong analogy between software and DNA, and between hardware and the protein machinery of the cell. This chapter examines to what extent any biological entity can be described by an algorithm and, therefore, whether the Turing machine and the halting problem concepts apply. Last of all, I introduce the concepts of recursion and algorithmic complexity, both from the field of computer science, which can help us understand and conceptualise biological complexity.
Bicommutants of reduced unbounded operator algebras
2009
The unbounded bicommutant $(\mathfrak M_{E'})''$ of the {\em reduction} of an O*-algebra $\MM$ via a given projection $E'$ weakly commuting with $\mathfrak M$ is studied, with the aim of finding conditions under which the reduction of a GW*-algebra is a GW*-algebra itself. The obtained results are applied to the problem of the existence of conditional expectations on O*-algebras.
Time and space efficient quantum algorithms for detecting cycles and testing bipartiteness
2016
We study space and time efficient quantum algorithms for two graph problems -- deciding whether an $n$-vertex graph is a forest, and whether it is bipartite. Via a reduction to the s-t connectivity problem, we describe quantum algorithms for deciding both properties in $\tilde{O}(n^{3/2})$ time and using $O(\log n)$ classical and quantum bits of storage in the adjacency matrix model. We then present quantum algorithms for deciding the two properties in the adjacency array model, which run in time $\tilde{O}(n\sqrt{d_m})$ and also require $O(\log n)$ space, where $d_m$ is the maximum degree of any vertex in the input graph.
Why (not) assess? Views from the academic departments of Finnish universities
2010
In Europe, national quality assurance systems of higher education have begun to be established. In Finland, this development has had the consequence of forcing universities to take notice of assessment procedures. However, little is known about the procedures taking place in individual academic departments as a result of this pan‐European trend. This article describes how academics currently comprehend quality assessment, paying particular attention to self‐evaluations and quality assurance systems. Altogether, the paper casts light on how academics are responding to the increasing university assessment activities.
Reduction of the glass transition temperature in polymer films: A molecular-dynamics study
2001
We present results of molecular dynamics (MD) simulations for a non-entangled polymer melt confined between two completely smooth and repulsive walls, interacting with inner particles via the potential $U_{\rm wall}\myeq (\sigma/z)^9$, where $z \myeq |z_{\rm particle}-z_{\rm wall}|$ and $\sigma$ is (roughly) the monomer diameter. The influence of this confinement on the dynamic behavior of the melt is studied for various film thicknesses (wall-to-wall separations) $D$, ranging from about 3 to about 14 times the bulk radius of gyration. A comparison of the mean-square displacements in the film and in the bulk shows an acceleration of the dynamics due to the presence of the walls. %Consistent…
Excitation of phase patterns and spatial solitons via two-frequency forcing of a 1:1 resonance.
2000
We show that a self-oscillatory system, driven at two frequencies close to that of the unforced system (resonance 1:1), becomes phase locked and exhibits two equivalent stable states of opposite phases. For spatially extended systems this phase bistability results in patterns characteristic for real order parameter systems, such as phase domains, labyrinths, and phase spatial solitons. In variational cases, the phase-locking mechanism is interpreted as a result of the periodic "rocking" of the system potential. Rocking could be tested experimentally in lasers and in oscillatory chemical reactions.
Drawing and extruding: Theoretical and approximate formulas
1969
The problem of drawing of wires and of strips has been treated in several studies; among these the studies of Sachs seem essential. However, the results deduced according to similar theories are not always in accordance with the experimental results: reduction of area or of thickness are in fact usually smaller than those resulting from the theory. This is in dependance of the fact that Sachs has adopted the Limiting Condition of Yielding by v. Mises, according to which the limit values of stress in traction and compression are equal. More recently other AA. (Alberti, Noto La Diega, Bugini), admitting the Limiting Condition of Yielding by A. (or of the Paraboloid of Revolution) of which we …
A singularly perturbed Kirchhoff problem revisited
2020
Abstract In this paper, we revisit the singularly perturbation problem (0.1) − ( ϵ 2 a + ϵ b ∫ R 3 | ∇ u | 2 ) Δ u + V ( x ) u = | u | p − 1 u in R 3 , where a , b , ϵ > 0 , 1 p 5 are constants and V is a potential function. First we establish the uniqueness and nondegeneracy of positive solutions to the limiting Kirchhoff problem − ( a + b ∫ R 3 | ∇ u | 2 ) Δ u + u = | u | p − 1 u in R 3 . Then, combining this nondegeneracy result and Lyapunov-Schmidt reduction method, we derive the existence of solutions to (0.1) for ϵ > 0 sufficiently small. Finally, we establish a local uniqueness result for such derived solutions using this nondegeneracy result and a type of local Pohozaev identity.
Rasiowa–Sikorski Sets and Forcing
2018
The paper is concerned with the problem of building models for first-order languages from the perspective of the classic paper of Rasiowa and Sikorski (1950). The central idea, due to Rasiowa and Sikorski and developed in this paper, is constructing first-order models from individual variables. The notion of a Rasiowa–Sikorski set of formulas of an arbitrary language L is introduced. Investigations are confined to countable languages. Each Rasiowa–Sikorski set defines a countable model for L. Conversely, each countable model for L is determined, up to isomorphism, by some Rasiowa–Sikorski set. Consequences of these facts are investigated.