Search results for " combinatorics"

EMERGENCE OF TRAVELLING WAVES IN SMOOTH NERVE FIBRES

2008

International audience; An approximate analytical solution characterizing initial condi- tions leading to action potential ¯ring in smooth nerve ¯bres is determined, using the bistable equation. In the ¯rst place, we present a non-trivial sta- tionary solution wave. Then, we extract the main features of this solution to obtain a frontier condition between the initiation of the travelling waves and a decay to the resting state. This frontier corresponds to a separatrix in the projected dynamics diagram depending on the width and the amplitude of the stationary wave.

A multi-local optimization algorithm

1998

The development of efficient algorithms that provide all the local minima of a function is crucial to solve certain subproblems in many optimization methods. A “multi-local” optimization procedure using inexact line searches is presented, and numerical experiments are also reported. An application of the method to a semi-infinite programming procedure is included.

The Serial Property and Restricted Balanced Contributions in discrete cost sharing problems

2006

We show that the Serial Poperty and Restricted Balanced Contributions characterize the subsidy-free serial cost sharing method (Moulin (1995)) in discrete cost allocation problems.

Hores: A timetabling system for Spanish secondary schools

1995

Constructing a timetable is a difficult problem faced by every school every year. A feasible solution has to satisfy many different requirements and constraints. A good solution has to provide compact timetables for classes and teachers. In order to help the schools, we have developed HORES, a robust and flexible timetabling system suited to the needs of Spanish secondary schools. HORES runs on a PC and is fast and user-friendly. It may handle virtually every condition required by the schools and obtains good quality solutions in very short computing times. It also allows the user to modify interactively the solutions. HORES is now being used by schools with satisfactory results.

Comparacion numerica de algoritmos para calcular distribuciones estacionarias de cadenas de Markov finitas

1992

En este trabajo se estudia la eficiencia de un conjunto de algoritmos, exactos e iterativos, para el problema de obtener la distribucion estacionaria de una cadena de Markov homogenea, irreducible y finita. Se presentan los resultados computacionales obtenidos al resolver problemas de diferentes tipos y tamanos, aleatoriamente generados, asi como el tratamiento estadistico realizado sobre los mismos. Se ha comparado la estabilidad de estos algoritmos frente a la perdida de irreducibilidad y la existencia de estados transitorios mediante su aplicacion a 26 problemas test. El trabajo concluye con una discusion del comportamiento de los diversos algoritmos.

Estudio bayesiano de los periodos de ocupacion y desocupacion en una cola M/M/1/∞/FIFO en equilibrio

1986

En este articulo, para un modelo de colas M/M/1/8/FIFO en equilibrio, se obtiene la distribucion predictiva del tiempo de duracion de un periodo de ocupacion, y de desocupacion de la cola, asi como la distribucion predictiva final del numero de personas atendidas en un periodo de ocupacion, y la probabilidad de que este sea finito. Finalmente, dichos resultados se aplican en una linea de espera concreta.

Searching for a strong double tracing in a graph

1998

Given a connected graph G, we present a polynomial algorithm which either finds a tour traversing each edge of G exactly two non-consecutive times, one in each direction, or decides that no such tour exists. The main idea of this algorithm is based on the modification of a proof given by Thomassen related to a problem proposed by Ore in 1951.

2021

Abstract We prove the existence of a smoothing for a toroidal crossing space under mild assumptions. By linking log structures with infinitesimal deformations, the result receives a very compact form for normal crossing spaces. The main approach is to study log structures that are incoherent on a subspace of codimension 2 and prove a Hodge–de Rham degeneration theorem for such log spaces that also settles a conjecture by Danilov. We show that the homotopy equivalence between Maurer–Cartan solutions and deformations combined with Batalin–Vilkovisky theory can be used to obtain smoothings. The construction of new Calabi–Yau and Fano manifolds as well as Frobenius manifold structures on moduli…

PROBABILISTIC QUANTIFICATION OF HAZARDS: A METHODOLOGY USING SMALL ENSEMBLES OF PHYSICS-BASED SIMULATIONS AND STATISTICAL SURROGATES

2015

This paper presents a novel approach to assessing the hazard threat to a locale due to a large volcanic avalanche. The methodology combines: (i) mathematical modeling of volcanic mass flows; (ii) field data of avalanche frequency, volume, and runout; (iii) large-scale numerical simulations of flow events; (iv) use of statistical methods to minimize computational costs, and to capture unlikely events; (v) calculation of the probability of a catastrophic flow event over the next T years at a location of interest; and (vi) innovative computational methodology to implement these methods. This unified presentation collects elements that have been separately developed, and incorporates new contri…

The smallest singular value of a shifted $d$-regular random square matrix

2017

We derive a lower bound on the smallest singular value of a random d-regular matrix, that is, the adjacency matrix of a random d-regular directed graph. Specifically, let $$C_1<d< c n/\log ^2 n$$ and let $$\mathcal {M}_{n,d}$$ be the set of all $$n\times n$$ square matrices with 0 / 1 entries, such that each row and each column of every matrix in $$\mathcal {M}_{n,d}$$ has exactly d ones. Let M be a random matrix uniformly distributed on $$\mathcal {M}_{n,d}$$ . Then the smallest singular value $$s_{n} (M)$$ of M is greater than $$n^{-6}$$ with probability at least $$1-C_2\log ^2 d/\sqrt{d}$$ , where c, $$C_1$$ , and $$C_2$$ are absolute positive constants independent of any other parameter…