140,522 research outputs found
Dynamics of nearly unstable axisymmetric liquid bridges
The dynamics of a noncylindrical, axisymmetric, marginally unstable liquid bridge between two equal disks is analyzed in the inviscid limit. The resulting model allows for the weakly nonlinear description of both the (first stage of) breakage for unstable configurations and the (slow) dynamics for stable configurations. The analysis is made for both slender and short liquid brides. In the former range, the dynamics breaks reflection symmetry on the midplane between the supporting disks and can be described by a standard Duffing equation, while for short bridges reflection symmetry is preserved and the equation is still Duffing-like but exhibiting a quadratic nonlinearity. The asymptotic results compare well with existing experiments
New efficient constructive heuristics for the hybrid flowshop to minimise makespan: A computational evaluation of heuristics
This paper addresses the hybrid flow shop scheduling problem to minimise makespan, a well-known scheduling problem for which many constructive heuristics have been proposed in the literature. Nevertheless, the state of the art is not clear due to partial or non homogeneous comparisons. In this paper, we review these heuristics and perform a comprehensive computational evaluation to determine which are the most efficient ones. A total of 20 heuristics are implemented and compared in this study. In addition, we propose four new heuristics for the problem. Firstly, two memory-based constructive heuristics are proposed, where a sequence is constructed by inserting jobs one by one in a partial sequence. The most promising insertions tested are kept in a list. However, in contrast to the Tabu search, these insertions are repeated in future iterations instead of forbidding them. Secondly, we propose two constructive heuristics based on Johnson’s algorithm for the permutation flowshop scheduling problem. The computational results carried out on an extensive testbed show that the new proposals outperform the existing heuristics.Ministerio de Ciencia e Innovación DPI2016-80750-
On prime numbers of the form
Consider the set of integers for which there are infinitely
many primes such that is a power of . The aim of this paper is to
show a relationship between and the limits points of some set
rational numbers related to a sequence of polynomials introduced by
Kassel and Reutenauer [KasselReutenauer]
A relationship between the ideals of and the Fibonacci numbers
Let be the number of ideals of codimension of
, where is the
finite field with elements. Kassel and Reutenauer [KasselReutenauer2015A]
proved that is a polynomial in for any fixed value of .
For , this combinatorial interpretation of
is lost. Nevertheless, an unexpected connexion with Fibonacci numbers appears.
Let be the -th Fibonacci number (following the convention ,
). Define the series
We will prove that for each ,
where the integers are given by the following generating function
\prod_{m \geq 1} \left(1+F\left( t^m\right)\right) = 1 + \sum_{n \geq 1}
\lambda_n\,t^n. $
Non-Axisymmetric Effects on Long Liquid Bridges
The stability of long liquid bridges under non-axisymmetric disturbances like a microgravitational force acting perpendicular to the liquid bridge axis or a non-coaxiality of the disks is analyzed through an asymptotic method based on bifurcation techniques. Results obtained indicate that such non-axisymmetric effects are of higher order than those produced by axisymmetric perturbations
On a function introduced by Erd\"{o}s and Nicolas
Erd\"os and Nicolas [erdos1976methodes] introduced an arithmetical function
related to divisors of in short intervals . The aim of this note is to prove that is the largest
coefficient of polynomial introduced by Kassel and Reutenauer
[kassel2015counting]. We deduce that has a coefficient larger than
if and only if is the perimeter of a Pythagorean triangle. We improve a
result due to Vatne [vatne2017sequence] concerning the coefficients of
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