601 research outputs found
Bounded LTL Model Checking with Stable Models
In this paper bounded model checking of asynchronous concurrent systems is
introduced as a promising application area for answer set programming. As the
model of asynchronous systems a generalisation of communicating automata,
1-safe Petri nets, are used. It is shown how a 1-safe Petri net and a
requirement on the behaviour of the net can be translated into a logic program
such that the bounded model checking problem for the net can be solved by
computing stable models of the corresponding program. The use of the stable
model semantics leads to compact encodings of bounded reachability and deadlock
detection tasks as well as the more general problem of bounded model checking
of linear temporal logic. Correctness proofs of the devised translations are
given, and some experimental results using the translation and the Smodels
system are presented.Comment: 32 pages, to appear in Theory and Practice of Logic Programmin
An Entailment Relation for Reasoning on the Web
Reasoning on the Web is receiving an increasing attention because of emerging fields such as Web adaption and Semantic Web. Indeed, the advanced functionalities striven for in these fields call for reasoning capabilities. Reasoning on the Web, however, is usually done using existing techniques rarely fitting the Web. As a consequence, additional data processing like data conversion from Web formats (e.g. XML or HTML) into some other formats (e.g. classical logic terms and formulas) is often needed and aspects of the Web (e.g. its inherent inconsistency) are neglected. This article first gives requirements for an entailment tuned to reasoning on the Web. Then, it describes how classical logic’s entailment can be modified so as to enforce these requirements. Finally, it discusses how the proposed entailment can be used in applying logic programming to reasoning on the Web
Theory of the Half-Polarized Quantum Hall States
We report a theoretical analysis of the half-polarized quantum Hall states
observed in a recent experiment. Our numerical results indicate that the ground
state energy of the quantum Hall and states versus spin
polarization has a downward cusp at half the maximal spin polarization. We map
the two-component fermion system onto a system of excitons and describe the
ground state as a liquid state of excitons with non-zero values of exciton
angular momentum.Comment: 4 pages (RevTeX), 3 figures (PostScript), added reference
Impact of reindeer grazing on ground-dwelling Carabidae and Curculionidae assemblages in Lapland
Reindeer Rangifer tarandus L. grazing shapes forest vegetation, microclimate, and
soil respiration in Lapland, especially due to grazing on lichens (Cladina). We studied
how these changes and their magnitude affect ground-dwelling species of beetle
families Carabidae (predators) and Curculionidae (herbivores), by using pitfall traps
to collect invertebrates from pairs of grazed and ungrazed study plots over a wide
range of site types. Changes in abundance, composition, richness and diversity of
beetle assemblage were tested in relation to magnitude of the impacts on vegetation.
The species compositions of Carabidae and Curculionidae differed between grazed
and ungrazed plots in all sites. The relative difference between grazed and ungrazed
plots in the number of individuals increased linearly with the impact of reindeer on
vegetation cover. Carabid beetles, as a family, were more common in grazed plots in
all sites. Curculionid beetles were more common in ungrazed plots in the birch
dominated sites. This difference was mainly due to the species that feeds on
deciduous leaves. In the pine dominated sites with high Cladina cover and more
changes in ground vegetation, the number of curculionids feeding on conifers was
higher in grazed plots. Species richness and diversity (H’) of both families were higher
in grazed plots. Of the total 27 species, 11 were found only in grazed plots, while not
a single species was found only in ungrazed plots. The relative difference between
plots in diversity and evennes (H’/H’max) had humped response to the difference in
Cladina cover. The diversity values were greater in grazed plots at the intermediate
levels of grazing impact, and only in sites with very low or extremely high Cladina
cover difference was the diversity higher in ungrazed plots. The response of beetle
diversity resembled the hypotheses suggested for the relationship between grazing and
vegetation diversity: greatest positive effect at intermediate grazing intensity and
negative effects at unproductive sites
Surface Instabilities and Magnetic Soft Matter
We report on the formation of surface instabilities in a layer of
thermoreversible ferrogel when exposed to a vertical magnetic field. Both
static and time dependent magnetic fields are employed. Under variations of
temperature, the viscoelastic properties of our soft magnetic matter can be
tuned. Stress relaxation experiments unveil a stretched exponential scaling of
the shear modulus, with an exponent of beta=1/3. The resulting magnetic
threshold for the formation of Rosensweig-cusps is measured for different
temperatures, and compared with theoretical predictions by Bohlius et. al. in
J. Phys.: Condens. Matter., 2006, 18, 2671-2684.Comment: accepted to Soft Matte
Theory of Incompressible States in a Narrow Channel
We report on the properties of a system of interacting electrons in a narrow
channel in the quantum Hall effect regime. It is shown that an increase in the
strength of the Coulomb interaction causes abrupt changes in the width of the
charge-density profile of translationally invariant states. We derive a phase
diagram which includes many of the stable odd-denominator states as well as a
novel fractional quantum Hall state at lowest half-filled Landau level. The
collective mode evaluated at the half-filled case is strikingly similar to that
for an odd-denominator fractional quantum Hall state.Comment: 4 pages, REVTEX, and 4 .ps file
Optical Spectroscopy of X-Mega targets in Carina Nebula : III. The multiple system Tr 16-104 (≡CPD -59° 2603)
We discuss the orbital elements of the multiple system Tr 16-104 which is usually believed to be a member of the open cluster Trumpler 16 in the Carina complex. We show that Tr 16-104 could be a hierarchical triple system consisting of a short-period (2.15 d) eclipsing O7 V+O9.5 V binary bound to a B0.2 IV star. Our preliminary orbital solution of the third body indicates that the B star most probably describes an eccentric orbit with a period of ∼285 or ∼1341 d around the close binary. Folding photometric data from the literature with our new ephemerides, we find that the light curve of the close binary exhibits rather narrow eclipses indicating that the two O stars must be well inside their Roche lobes. Our analysis of the photometric data yields a lower limit on the inclination of the orbit of the close binary of i≥77°. The stellar radii and luminosities of the O7 V and O9.5 V stars are significantly smaller than expected for stars of this spectral type. Our results suggest that Tr 16-104 lies at a distance of the order of 2.5 kpc and support a fainter absolute magnitude for zero-age main-sequence O stars than usually adopted. We find that the dynamical configuration of Tr 16-104 corresponds to a hierarchical system that should remain stable provided that it suffers no strong perturbation. Finally, we also report long-term temporal variations of high-velocity interstellar Ca ii absorptions in the line of sight towards Tr 16-104.Facultad de Ciencias Astronómicas y Geofísica
The DLV System for Knowledge Representation and Reasoning
This paper presents the DLV system, which is widely considered the
state-of-the-art implementation of disjunctive logic programming, and addresses
several aspects. As for problem solving, we provide a formal definition of its
kernel language, function-free disjunctive logic programs (also known as
disjunctive datalog), extended by weak constraints, which are a powerful tool
to express optimization problems. We then illustrate the usage of DLV as a tool
for knowledge representation and reasoning, describing a new declarative
programming methodology which allows one to encode complex problems (up to
-complete problems) in a declarative fashion. On the foundational
side, we provide a detailed analysis of the computational complexity of the
language of DLV, and by deriving new complexity results we chart a complete
picture of the complexity of this language and important fragments thereof.
Furthermore, we illustrate the general architecture of the DLV system which
has been influenced by these results. As for applications, we overview
application front-ends which have been developed on top of DLV to solve
specific knowledge representation tasks, and we briefly describe the main
international projects investigating the potential of the system for industrial
exploitation. Finally, we report about thorough experimentation and
benchmarking, which has been carried out to assess the efficiency of the
system. The experimental results confirm the solidity of DLV and highlight its
potential for emerging application areas like knowledge management and
information integration.Comment: 56 pages, 9 figures, 6 table
Colilert-menetelmän verifiointi sosiaali- ja terveysministeriön asetuksen 461/2000 mukaisiin koliformisten bakteerien ja Escherichia coli -bakteerin tutkimuksiin Suomessa
Colilert -18 Quanti-Tray -menetelmä (IDEXX Laboratories
Sairauspoissaolotarpeen määrittäminen : Kyselytutkimus lääkäreille
Kelan tutkimusosasto ja Suomen Lääkäriliitto toteuttivat vuonna 2014 lääkäreille kohdistetun kyselyn, jonka tarkoituksena on kartoittaa lääkäreiden näkemyksiä ja kokemuksia sairauspoissaoloihin liittyvistä käytännöistä ja kehittämistarpeista. Kysely perustuu vuonna 2012 Ruotsissa tehtyyn kyselyyn. Vastaava kysely toteutettiin myös Norjassa. Kysymykset on muokattu kunkin maan järjestelmään sopiviksi.
Kyselylomake lähetettiin 8 867 lääkärille loppuvuodesta 2014, ja siihen saattoi vastata joko paperisella tai sähköisellä lomakkeella. Vastausprosentti oli 34,8. Rakenteeltaan aineisto edusti perusjoukkoa, joskin työterveyshuolto oli hieman yliedustettuna.
Lääkärit pitivät julkisen sektorin palvelujen saatavuutta keskeisenä syynä sairauspoissaolojen pitkittymiseen. Myös vajaakuntoisten työntekijöiden työssä jaksamista tukevien toimenpiteiden saatavuus vaikutti sairauspoissaolojen kirjoittamiseen. Kelalta toivottiin enemmän palautetta lääkärien omasta toiminnasta. Lääkärien osaamisen kehittämistarpeet korostuivat erityisesti terveyskeskuksissa, mutta koulutusta tarvitsevien osuus on varsin suuri muillakin toimintasektoreilla. Lääkärit toivoivat laajasti, erikoistumisalasta tai toimipaikasta riippumatta, vähintäänkin joitakin sairauksia koskevia kansallisia suosituksia sairauspoissaolojen kestosta. Nykyisiä käytettävissä olevia ohjeita ja suosituksia monet lääkärit pitivät tärkeinä. Työterveyslääkärit erottuivat monissa kohdin omaksi ryhmäkseen. He näyttävät hallitsevan työkyvyn ja sairauspoissaolon tarpeen arviointiin liittyvät tehtävät parhaiten. Suomalaiset lääkärit kokivat ruotsalaisia ja norjalaisia perusterveydenhuollon lääkäreitä vähemmän ongelmia sairauspoissaoloon liittyvissä asioissa.
Tutkimuksen perusteella annetuissa suosituksissa esitetään puuttumista jatkohoidon ja kuntoutukseen pääsyn viiveisiin, työkyvyn arviointiin liittyvän koulutuksen lisäämistä, sairauspoissaolotarpeen siirtämistä enemmän työterveyshuollon vastuulle sekä sairauspoissaolojen kestoa koskevien suositusten laatimista ainakin joistakin sairauksista
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