On balanced CSPs with high treewidth

Tractable cases of the binary CSP are mainly divided in two classes: constraint language restrictions and constraint graph restrictions. To better understand and identify the hardest binary CSPs, in this work we propose methods to increase their hardness by increasing the balance of both the constraint language and the constraint graph. The balance of a constraint is increased by maximizing the number of domain elements with the same number of occurrences. The balance of the graph is defined using the classical definition from graph the- ory. In this sense we present two graph models; a first graph model that increases the balance of a graph maximizing the number of vertices with the same degree, and a second one that additionally increases the girth of the graph, because a high girth implies a high treewidth, an important parameter for binary CSPs hardness. Our results show that our more balanced graph models and constraints result in harder instances when compared to typical random binary CSP instances, by several orders of magnitude. Also we detect, at least for sparse constraint graphs, a higher treewidth for our graph models.

Statistical modelling of CSP solving algorithms performance

The goal of this work is to try to create a statistical model, based only on easily computable parameters from the CSP problem to predict runtime behaviour of the solving algorithms, and let us choose the best algorithm to solve the problem. Although it seems that the obvious choice should be MAC, experimental results obtained so far show, that with big numbers of variables, other algorithms perfom much better, specially for hard problems in the transition phase.

Generating hard SAT/CSP instances using expander graphs

In this paper we provide a new method to generate hard k-SAT instances. We incrementally construct a high girth bipartite incidence graph of the k-SAT instance. Having high girth assures high expansion for the graph, and high expansion implies high resolution width. We have extended this approach to generate hard n-ary CSP instances and we have also adapted this idea to increase the expansion of the system of linear equations used to generate XORSAT instances, being able to produce harder satisfiable instances than former generators.

How hard is a commercial puzzle: the eternity II challenge

Recently, edge matching puzzles, an NP-complete problem, have received, thanks to money-prized contests, considerable attention from wide audiences. We consider these competitions not only a challenge for SAT/CSP solving techniques but also as an opportunity to showcase the advances in the SAT/CSP community to a general audience. This paper studies the NP-complete problem of edge matching puzzles focusing on providing generation models of problem instances of variable hardness and on its resolution through the application of SAT and CSP techniques. From the generation side, we also identify the phase transition phenomena for each model. As solving methods, we employ both; SAT solvers through the translation to a SAT formula, and two ad-hoc CSP solvers we have developed, with different levels of consistency, employing several generic and specialized heuristics. Finally, we conducted an extensive experimental investigation to identify the hardest generation models and the best performing solving techniques.

Edge matching puzzles as hard SAT/CSP benchmarks

Recently, edge matching puzzles, an NP-complete problem, have rececived, thanks to money-prized contests, considerable attention from wide audiences. We consider these competitions not only a challenge for SAT/CSP solving techniques but also as an opportunity to showcase the advances in the SAT/CSP community to a general audience. This paper studies the NP-complete problem of edge matching puzzles focusing on providing generation models of problem instances of variable hardness and on its resolution through the application of SAT and CSP techniques. From the generation side, we also identify the phase transition phenomena for each model. As solving methods, we employ both; SAT solvers through the translation to a SAT formula, and two ad-hoc CSP solvers we have developed, with different levels of consistency, employing several generic and specialized heuristics. Finally, we conducted an extensive experimental investigation to identify the hardest generation models and the best performing solving techniques.

Llave electrónica basada en patrones de movimiento

Sistema embebido capaz de almacenar y posteriormente reconocer patrones de movimiento realizados con él y avisar de la detección de un patrón reconocido a otro sistema mediante una conexión TCP/IP vía Wi-Fi.

Aplicación Catalunya Cultura

Aplicación para dispositivos móviles de la plataforma Android que permite buscar y consultar las ofertas y propuestas de carácter cultural (teatro, conciertos, fiestas tradicionales, etc.) que se realizan en todos los pueblos y ciudades de Cataluña.

Nuevos datos sobre los yacimientos wurmienses del litoral catalán

We present a new bed of cold Malacological fauna of the Wrm in the Catalan littoral, one af its species is dated for the first time iii the hlediterranean (Sipho curtus). We point out the predorninance of Gasteropoda as regards Bivalves in comparison with the other cold beds known.

Applications of optically active metallacycles: new useful materials for the determination of the enantiomeric excess of Lewis bases and as resolving agents for monodentate phosphines

Es descriu la síntesi de nous compostos ciclopal·ladats derivats d'imines i amines primàries, òpticament actius, així com les seves aplicacions per a la determinació de l'excés enantiomèric i per a la resolució de bases de Lewis. També es comenta la síntesi i resolució de noves fosfines P-quirals, així com la seva aplicació a processos de catàlisi asimètrica. A més, es descriu la preparació d'algunes fosfines secundàries quirals i s'estudia la seva estabilitat configuracional.

Progress in a-Si:H/c-Si heterojunction emitters obtained by Hot-Wire CVD at 200°C

In this work, we investigate heterojunction emitters deposited by Hot-Wire CVD on p-type crystalline silicon. The emitter structure consists of an n-doped film (20 nm) combined with a thin intrinsic hydrogenated amorphous silicon buffer layer (5 nm). The microstructure of these films has been studied by spectroscopic ellipsometry in the UV-visible range. These measurements reveal that the microstructure of the n-doped film is strongly influenced by the amorphous silicon buffer. The Quasy-Steady-State Photoconductance (QSS-PC) technique allows us to estimate implicit open-circuit voltages near 700 mV for heterojunction emitters on p-type (0.8 Ω·cm) FZ silicon wafers. Finally, 1 cm 2 heterojunction solar cells with 15.4% conversion efficiencies (total area) have been fabricated on flat p-type (14 Ω·cm) CZ silicon wafers with aluminum back-surface-field contact.

Repercusiones de la anorexia y la bulimia en la salud oral, prevención y tratamiento

El presente artículo trata de aportar una puesta al día de los problemas que presentan los pacientes afectados de anorexia y de bulimia nerviosa. Se expone la información que el odontólogo debe tener en cuenta respecto al conocimiento de la enfermedad, sus manifestaciones orales, los criterios diagnósticos y los enfoques preventivos y terapéuticos necesarios.

Bulbochaete denticulata Wittrock (Oedogoniales, Chlorophyta), al Delta de l'Ebre (NE d'Espanya)

En unes campanyes limnológiques realitzades durant el mes de Setembre de 1986 al Delta de l'Ebre, observárem la presencia de Bulbochaete denticulata Wittrock, que creixia entre el plócon de la llacuna de la Tancäda (31TBF097023).

Bulbochaete denticulata Wittrock (Oedogoniales, Chlorophyta), al Delta de l'Ebre (NE d'Espanya)

En unes campanyes limnológiques realitzades durant el mes de Setembre de 1986 al Delta de l'Ebre, observárem la presencia de Bulbochaete denticulata Wittrock, que creixia entre el plócon de la llacuna de la Tancäda (31TBF097023).