573 research outputs found
Colouring exact distance graphs of chordal graphs
For a graph and positive integer , the exact distance- graph
is the graph with vertex set and with an edge between
vertices and if and only if and have distance . Recently,
there has been an effort to obtain bounds on the chromatic number
of exact distance- graphs for from certain
classes of graphs. In particular, if a graph has tree-width , it has
been shown that for odd ,
and for even . We
show that if is chordal and has tree-width , then for odd , and for even .
If we could show that for every graph of tree-width there is a
chordal graph of tree-width which contains as an isometric subgraph
(i.e., a distance preserving subgraph), then our results would extend to all
graphs of tree-width . While we cannot do this, we show that for every graph
of genus there is a graph which is a triangulation of genus and
contains as an isometric subgraph.Comment: 11 pages, 2 figures. Versions 2 and 3 include minor changes, which
arise from reviewers' comment
EtnografÃa de la Planta Ballenera de Quintay: Reportajes, Informes, Historias
The processing of a whale in a shore whaling station began with their arrival. The whale was moored with a line to the winch and hoisted to the slipwayand on the platform flensing. At the platform,bubbler, meat and bones were separated and send to their own cooking units or “cocinerías”. From cookeries, oil and a mixture of liquids and solids were sent to be purified. Solid wastes were sent to the whale-meal or guanoplant. Eight shore whaling station was built in Chile, located between Punta Arenas in the south and Iquique in the north. In this paper, we construct a retrospective ethnography of Quintayshore whaling station,using the reports and written reports by people who observed the plant in full operation. In the reportages, the issues about whale processing, has been selectively represented by those who knew the practices in a “ethnographic present.”El procesamiento de una ballena en una planta costera terrestre comienza con la llegada de la ballena. La ballena era amarrada con una línea al huinche e izada a la rampa y luego a la plataforma de descuartizamiento. Allí se separaba el tocino, la carne y los huesos que iban a sus propias unidades de cocción o “cocinerías”. Se obtenía aceite y una mezcla de líquidos y sólidos que eran enviados a plantas de purificación. Los residuos sólidos eran enviados a la planta de harina o de guano. En Chile se construyeron ocho plantas industriales costeras localizadas entre Punta Arenas por el sur e Iquique por el norte. En este trabajo se intentará construir una etnografía retrospectiva de la planta ballenera de Quintay, utilizando los relatos en forma de reportajes, escritos por personas que observaron la planta en pleno funcionamiento. Nos interesa dar cuenta como han sido selectivamente representados determinados aspectos del procesamiento de las ballenas en una planta costera por aquellos que pudieron conocer las prácticas en un “presente etnográfico”
New automatic control system to improve the operation of PMD devices
In this thesis project, a functional PMD device was designed for the implementation of a control system and thus achieve a more efficient and controlled way of the propellant extraction process. For this design process, an analysis was carried out on the different types of PMD devices and which ones could be used in a control system, as well as the selection of certain conditions of the meteosat second generation (MSG) satellite, to focus the design to something more attached to in practice.Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::12 - Producció i Consum Responsable
Clique immersions in graphs of independence number two with certain forbidden subgraphs
The Lescure-Meyniel conjecture is the analogue of Hadwiger's conjecture for
the immersion order. It states that every graph contains the complete graph
as an immersion, and like its minor-order counterpart it is open
even for graphs with independence number 2. We show that every graph with
independence number and no hole of length between and
satisfies this conjecture. In particular, every -free graph
with satisfies the Lescure-Meyniel conjecture. We give
another generalisation of this corollary, as follows. Let and be graphs
with independence number at most 2, such that . If is
-free, then satisfies the Lescure-Meyniel conjecture.Comment: 14 pages, 3 figures. The statements of lemmas 3.1, 4.1, and 4.2 are
slightly changed from the previous version in order to fix some minor errors
in the proofs of theorems 3.2 and 4.3. Shorter proof of Proposition 5.2 give
Birth and death chains on finite trees: computing their stationary distribution and hitting times
Every birth and death chain on a finite tree can be represented as a random walk on the underlying tree endowed with appropriate conductances. We provide an algorithm that finds these conductances in linear time. Then, using the electric network approach, we find the values for the stationary distribution and for the expected hitting times between any two vertices in the tree. We show that our algorithms improve classical procedures: they do not exhibit ill-posedness and the orders of their complexities are smaller than those of traditional algorithms found in the literature
Quadratic Dynamical Decoupling with Non-Uniform Error Suppression
We analyze numerically the performance of the near-optimal quadratic
dynamical decoupling (QDD) single-qubit decoherence errors suppression method
[J. West et al., Phys. Rev. Lett. 104, 130501 (2010)]. The QDD sequence is
formed by nesting two optimal Uhrig dynamical decoupling sequences for two
orthogonal axes, comprising N1 and N2 pulses, respectively. Varying these
numbers, we study the decoherence suppression properties of QDD directly by
isolating the errors associated with each system basis operator present in the
system-bath interaction Hamiltonian. Each individual error scales with the
lowest order of the Dyson series, therefore immediately yielding the order of
decoherence suppression. We show that the error suppression properties of QDD
are dependent upon the parities of N1 and N2, and near-optimal performance is
achieved for general single-qubit interactions when N1=N2.Comment: 17 pages, 22 figure
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