17,026 research outputs found
Chain Reduction for Binary and Zero-Suppressed Decision Diagrams
Chain reduction enables reduced ordered binary decision diagrams (BDDs) and
zero-suppressed binary decision diagrams (ZDDs) to each take advantage of the
others' ability to symbolically represent Boolean functions in compact form.
For any Boolean function, its chain-reduced ZDD (CZDD) representation will be
no larger than its ZDD representation, and at most twice the size of its BDD
representation. The chain-reduced BDD (CBDD) of a function will be no larger
than its BDD representation, and at most three times the size of its CZDD
representation. Extensions to the standard algorithms for operating on BDDs and
ZDDs enable them to operate on the chain-reduced versions. Experimental
evaluations on representative benchmarks for encoding word lists, solving
combinatorial problems, and operating on digital circuits indicate that chain
reduction can provide significant benefits in terms of both memory and
execution time
Calibrated Sub-Bundles in Non-Compact Manifolds of Special Holonomy
This paper is a continuation of math.DG/0408005. We first construct special
Lagrangian submanifolds of the Ricci-flat Stenzel metric (of holonomy SU(n)) on
the cotangent bundle of S^n by looking at the conormal bundle of appropriate
submanifolds of S^n. We find that the condition for the conormal bundle to be
special Lagrangian is the same as that discovered by Harvey-Lawson for
submanifolds in R^n in their pioneering paper. We also construct calibrated
submanifolds in complete metrics with special holonomy G_2 and Spin(7)
discovered by Bryant and Salamon on the total spaces of appropriate bundles
over self-dual Einstein four manifolds. The submanifolds are constructed as
certain subbundles over immersed surfaces. We show that this construction
requires the surface to be minimal in the associative and Cayley cases, and to
be (properly oriented) real isotropic in the coassociative case. We also make
some remarks about using these constructions as a possible local model for the
intersection of compact calibrated submanifolds in a compact manifold with
special holonomy.Comment: 20 pages; for Revised Version: Minor cosmetic changes, some
paragraphs rewritten for improved clarit
Closed trajectories of a particle model on null curves in anti-de Sitter 3-space
We study the existence of closed trajectories of a particle model on null
curves in anti-de Sitter 3-space defined by a functional which is linear in the
curvature of the particle path. Explicit expressions for the trajectories are
found and the existence of infinitely many closed trajectories is proved.Comment: 12 pages, 1 figur
Two universal results for Wilson loops at strong coupling
We present results for Wilson loops in strongly coupled gauge theories. The
loops may be taken around an arbitrarily shaped contour and in any field theory
with a dual IIB geometry of the form M x S^5. No assumptions about
supersymmetry are made. The first result uses D5 branes to show how the loop in
any antisymmetric representation is computed in terms of the loop in the
fundamental representation. The second result uses D3 branes to observe that
each loop defines a rich sequence of operators associated with minimal surfaces
in S^5. The action of these configurations are all computable. Both results
have features suggesting a connection with integrability.Comment: 1+12 pages. LaTeX. No figure
The importance of regional variation in the analysis of urbanization-agriculture interactions
La recherche gĂ©ographique sur l'agriculture dans les rĂ©gions mĂ©tropolitaines a Ă©tĂ© orientĂ©e vers l'Ă©tude des changements agricoles influencĂ©s par l'urbanisation. D'autres processus d'Ă©volution et les facteurs liĂ©s aux variations de l'environnement rĂ©gional ont Ă©tĂ© nĂ©gligĂ©s. Certaines recherches rĂ©centes faisant apparaĂźtre l'importance de l'environnement rĂ©gional Ă des Ă©chelles gĂ©ographiques diffĂ©rentes sont dĂ©crites. PremiĂšrement, une typologie de rĂ©gions basĂ©es sur les rĂ©gions mĂ©tropolitaines de recensement du Canada est prĂ©sentĂ©e. Certains groupes de la typologie ont connu des changements agricoles importants qui ne s'expliquent pas par les pressions du dĂ©veloppement mĂ©tropolitain. Des diffĂ©rences rĂ©gionales dans l'environnement agricole apportent des explications partielles. DeuxiĂšmement, pour la rĂ©gion de MontrĂ©al des variables agricoles (de 1961 Ă 1971) sont analysĂ©es avec une analyse factorielle. Les rĂ©sultats sont interprĂ©tĂ©s en termes a) de l'urbanisation et b) des variations dans l'environnement Ă l'intĂ©rieur de la rĂ©gion. En dernier lieu, pour une municipalitĂ© situĂ©e prĂšs de Toronto, une analyse est faite de la rĂ©partition gĂ©ographique du morcellement des parcelles cadastrales. Une fois encore, des liens sont apparents avec certaines caractĂ©ristiques de l'environnement. La conclusion est que les changements agricoles ne sont pas homogĂšnes, soit entre rĂ©gions, soit Ă l'intĂ©rieur d'une mĂȘme rĂ©gion, et que l'explication devrait ĂȘtre formulĂ©e aussi bien en termes de la variation de l'environnement rĂ©gional qu'en termes des influences mĂ©tropolitaines.Research into agriculture in metropolitan regions has concentrated on urban-induced agricultural land use changes. Other processes of change and factors related to variations in the regional environment have been neglected. Some recent research is reported here which points to the importance of the regional environment at a variety of scale levels. First, a typology of regions based on Census Metropolitan Areas in Canada is developed. Some groups of regions experienced significant agricultural changes quite unrelated to metropolitan development pressures. Regional differences in the agricultural environment are suggested as partial explanations. Second, for the MontrĂ©al region, a series of agricultural variables (1961 to 1971) are analysed using factor analysis. Results are interpreted in the light of a) urbanisation forces and b) internal variation in the regional environment. Finally, for a township near Toronto, an investigation is made of the distribution of severances. Once more, relationships appear with certain physical characteristics. The paper concludes that agricultural change is not uniform either between regions or within regions, and that part of the variation is related to differences in the "regional" environment and part to metropolitan forces
Can fundamental movement skill mastery be increased via a six week physical activity intervention to have positive effects on physical activity and physical self-perception?
Previous research has suggested a positive relationship between fundamental movement skills (FMS) mastery and physical activity (PA) level. Research conducted on interventions to improve FMS mastery is equivocal and further research is needed.An intervention group of 82 children (35 boys and 47 girls) and a control group of 83 children (42 boys and 41 girls) were recruited from Years 4 and 5 (mean age ± SD = 8.3 ± 0.4 years) of two schools in Central England. The intervention included a combination of circuits and dancing to music. Pre and post intervention tests were conducted. Tests included: subjective assessment of eight FMS; objective measurement of two FMS; four day pedometer step count recording; height and mass for Body Mass Index (BMI); and the completion of Harter et al.'s (1982) self-perception questionnaire.Following a two (pre to post) by two (intervention and control group) mixed-model ANOVA it was highlighted that the intervention group improved mastery in all eight FMS, and increased both daily steps and physical self-perception.It can be concluded that focussing one Physical Education (PE) lesson per week on the development of FMS has had a positive benefit on FMS, PA level and physical self-perception for the children in this study
A settlers' guide: Designing for resilience in the hinterlands
© 2017 by the authors. There has often been a mutually beneficial relationship between cities and their rural hinterlands. The Kapiti region outside the city of Wellington in New Zealand is a prime example: it once provided Wellington's food, water and cultural diversity for both MÄori and European settlers. However, productivity-driven agriculture and extensive dormitory-suburbanization have affected significant parts of this once-abundant hinterland. Food production is becoming more mono-cultural, water quality is degrading, ecosystems' biodiversity is disappearing, provincial town centres are shrinking, emigrating youth are leaving unbalanced demographics, MÄori are increasingly disassociating their culture from their traditional lands and natural disasters are causing more impact-all of which is making Kapiti less resilient, and severing the once-healthy city-hinterland relationship. Our work on future settlement opportunities in Kapiti proposes alternatives, using experimental design-led research methods to develop speculative architectural and landscape architectural schemes. The schemes are framed by some of the spatial attributes of resilience: diversity, complexity, redundancy, interconnectivity and adaptability. Collectively, the work reveals design strategies that have a potential to rebuild hinterlands' culture, town centres, housing, agriculture, community and ecosystems and to recalibrate the broader relationship between hinterlands and metropolitan systems
Pore-scale Modeling of Viscous Flow and Induced Forces in Dense Sphere Packings
We propose a method for effectively upscaling incompressible viscous flow in
large random polydispersed sphere packings: the emphasis of this method is on
the determination of the forces applied on the solid particles by the fluid.
Pore bodies and their connections are defined locally through a regular
Delaunay triangulation of the packings. Viscous flow equations are upscaled at
the pore level, and approximated with a finite volume numerical scheme. We
compare numerical simulations of the proposed method to detailed finite element
(FEM) simulations of the Stokes equations for assemblies of 8 to 200 spheres. A
good agreement is found both in terms of forces exerted on the solid particles
and effective permeability coefficients
The SAMI Galaxy Survey: Satellite galaxies undergo little structural change during their quenching phase
At fixed stellar mass, satellite galaxies show higher passive fractions than
centrals, suggesting that environment is directly quenching their star
formation. Here, we investigate whether satellite quenching is accompanied by
changes in stellar spin (quantified by the ratio of the rotational to
dispersion velocity V/) for a sample of massive (10
M) satellite galaxies extracted from the SAMI Galaxy Survey. These
systems are carefully matched to a control sample of main sequence, high
central galaxies. As expected, at fixed stellar mass and
ellipticity, satellites have lower star formation rate (SFR) and spin than the
control centrals. However, most of the difference is in SFR, whereas the spin
decreases significantly only for satellites that have already reached the red
sequence. We perform a similar analysis for galaxies in the EAGLE
hydro-dynamical simulation and recover differences in both SFR and spin similar
to those observed in SAMI. However, when EAGLE satellites are matched to their
`true' central progenitors, the change in spin is further reduced and galaxies
mainly show a decrease in SFR during their satellite phase. The difference in
spin observed between satellites and centrals at 0 is primarily due to
the fact that satellites do not grow their angular momentum as fast as centrals
after accreting into bigger halos, not to a reduction of due to
environmental effects. Our findings highlight the effect of progenitor bias in
our understanding of galaxy transformation and they suggest that satellites
undergo little structural change before and during their quenching phase.Comment: 11 pages, 7 figures. Accepted for publication in MNRA
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