18,909 research outputs found
On permanents of Sylvester Hadamard matrices
It is well-known that the evaluation of the permanent of an arbitrary
-matrix is a formidable problem. Ryser's formula is one of the fastest
known general algorithms for computing permanents. In this paper, Ryser's
formula has been rewritten for the special case of Sylvester Hadamard matrices
by using their cocyclic construction. The rewritten formula presents an
important reduction in the number of sets of distinct rows of the matrix to
be considered. However, the algorithm needs a preprocessing part which remains
time-consuming in general
On an inequivalence criterion for cocyclic Hadamard matrices
Given two Hadamard matrices of the same order, it can be quite difficult
to decide whether or not they are equivalent. There are some criteria to determine
Hadamard inequivalence. Among them, one of the most commonly used is the
4-profile criterion. In this paper, a reformulation of this criterion in the cocyclic
framework is given. The improvements obtained in the computation of the 4-profile
of a cocyclic Hadamard matrix are indicated.Ministerio de Ciencia e Innovación MTM2008-06578Junta de Andalucía FQM–296Junta de Andalucía P07-FQM-0298
Overview of business archives in Spain
The ICA Section of Business and Labour Archives is compiling several reports on the position of business archives around the world. The present communication is a state of the art in business archives in Spain, placed in several point: national and regional legislation, specific national policies for business archives, business archives
associations, training and current bibliography. A serious problem fort the future of business archives in Spain is the disinterest on the part of the businessmen about the
Archive’s importance in a compan
Strategic Interaction of International Markets: An Application to the Dairy Market
This paper studies the relation between the government´s objectives to sustain income in the dairy sector and the possibility to capture rent in the world market. To do this, two different governmental policies were considered: a direct export subsidy and a price discrimination scheme. These policies were analyzed under strategic and non-strategic scenarios. The results indicate that when there is non-strategic interaction and there exists a low opportunity cost of public funds, the two policies have the same effect on total welfare and lead to the same wealth transfer to producers. When there is a strategic interaction among producers, the price discrimination scheme leads to higher consumer welfare but lower producer benefit, being the net result on total welfare determined by the relative weights of the agents in the welfare function. From the producers´ point of view, the export subsidy is preferred to the price discrimination scheme when there is imperfect competition in the world market.dairy markets, strategic trade policy
Self-Dual codes from -matrices of skew symmetric type
Previously, self-dual codes have been constructed from weighing matrices, and
in particular from conference matrices (skew and symmetric). In this paper,
codes constructed from matrices of skew symmetric type whose determinants reach
the Ehlich-Wojtas' bound are presented. A necessary and sufficient condition
for these codes to be self-dual is given, and examples are provided for lengths
up to 52
Generalized binary arrays from quasi-orthogonal cocycles
Generalized perfect binary arrays (GPBAs) were used by Jedwab to
construct perfect binary arrays. A non-trivial GPBA can exist only if its energy
is 2 or a multiple of 4. This paper introduces generalized optimal binary arrays
(GOBAs) with even energy not divisible by 4, as analogs of GPBAs. We give a
procedure to construct GOBAs based on a characterization of the arrays in terms
of 2-cocycles. As a further application, we determine negaperiodic Golay pairs
arising from generalized optimal binary sequences of small length.Junta de Andalucía FQM-01
Optimization of a low weight electronic differential for LEVs
It is presented a performance analysis of an Electronic Differential (ED) system designed for Light Electric Vehicles (LEVs). We have developed a test tricycle vehicle with one front steering wheel and two rear fixed units is a same axis with a brushless DC integrated in each of them. Each motor has an independent controller unit and a common Arduino electronic CPU based that can plan specific speeds for each wheels as curves are being traced.
Different implementations of sensors (input current/torque, steering angle and speed of the wheels) are discussed related to hardware complexity, and performance obtained based on speed level requirements and slipping on the traction wheels.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Equivariant complex bundles, fixed points and equivariant unitary bordism
We study the fixed points of the universal G-equivariant n-dimensional
complex vector bundle and obtain a decomposition formula in terms of twisted
equivariant universal complex vector bundles of smaller dimension. We use this
decomposition to describe the fixed points of the complex equivariant K-theory
spectrum and the equivariant unitary bordism groups for adjacent families of
subgroups.Comment: Corrected version. To appear in AG&T. 27 page
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