180,987 research outputs found
Linking Focusing and Resolution with Selection
Focusing and selection are techniques that shrink the proof search space for respectively sequent calculi and resolution. To bring out a link between them, we generalize them both: we introduce a sequent calculus where each occurrence of an atom can have a positive or a negative polarity; and a resolution method where each literal, whatever its sign, can be selected in input clauses. We prove the equivalence between cut-free proofs in this sequent calculus and derivations of the empty clause in that resolution method. Such a generalization is not semi-complete in general, which allows us to consider complete instances that correspond to theories of any logical strength. We present three complete instances: first, our framework allows us to show that ordinary focusing corresponds to hyperresolution and semantic resolution; the second instance is deduction modulo theory; and a new setting, not captured by any existing framework, extends deduction modulo theory with rewriting rules having several left-hand sides, which restricts even more the proof search space
Linking Focusing and Resolution with Selection
International audienceFocusing and selection are techniques that shrink the proof-search space for respectively sequent calculi and resolution. To bring out a link between them, we generalize them both: we introduce a sequent calculus where each occurrence of an atomic formula can have a positive or a negative polarity; and a resolution method where each literal, whatever its sign, can be selected in input clauses. We prove the equivalence between cut-free proofs in this sequent calculus and derivations of the empty clause in that resolution method. Such a generalization is not semi-complete in general, which allows us to consider complete instances that correspond to theories of any logical strength. We present three complete instances: first, our framework allows us to show that ordinary focusing corresponds to hyperresolution and semantic resolution; the second instance is deduction modulo theory and the related framework called superdeduction; and a new setting, not captured by any existing framework, extends deduction modulo theory with rewriting rules having several left-hand sides, which restricts even more the proof-search space
Object-based selection of irrelevant features is not confined to the attended object
Attention to one feature of an object can bias the processing of unattended features of that object. Here we demonstrate with ERPs in visual search that this object-based bias for an irrelevant feature also appears in an unattended object when it shares that feature with the target object. Specifically, we show that the ERP response elicited by a distractor object in one visual field is modulated as a function of whether a task-irrelevant color of that distractor is also present in the target object that is presented in the opposite visual field. Importantly, we find this modulation to arise with a delay of approximately 80 msec relative to the N2pc-a component of the ERP response that reflects the focusing of attention onto the target. In a second experiment, we demonstrate that this modulation reflects enhanced neural processing in the unattended object. These observations together facilitate the surprising conclusion that the object-based selection of irrelevant features is spatially global even after attention has selected the target object
Three-dimensional microfabrication through a multimode optical fiber
Additive manufacturing, also known as 3D printing, is an advanced
manufacturing technique that allows the fabrication of arbitrary macroscopic
and microscopic objects. All 3D printing systems require large optical elements
or nozzles in proximity to the built structure. This prevents their use in
applications in which there is no direct access to the area where the objects
have to be printed. Here, we demonstrate three-dimensional microfabrication
based on two-photon polymerization (TPP) with sub diffraction-limited
resolution through an ultra-thin, 50 mm long printing nozzle of 560 micrometers
in diameter. Using wavefront shaping, femtosecond infrared pulses are focused
and scanned through a multimode optical fiber (MMF) inside a photoresist that
polymerizes via two-photon absorption. We show the construction of arbitrary 3D
structures of 500 nm resolution on the other side of the fiber. To our
knowledge, this is the first demonstration of microfabrication through a
multimode optical fiber. Our work represents a new area which we refer to as
endofabrication
Evolution of interactions and cooperation in the spatial prisoner's dilemma game
We study the evolution of cooperation in the spatial prisoner's dilemma game
where players are allowed to establish new interactions with others. By
employing a simple coevolutionary rule entailing only two crucial parameters,
we find that different selection criteria for the new interaction partners as
well as their number vitally affect the outcome of the game. The resolution of
the social dilemma is most probable if the selection favors more successful
players and if their maximally attainable number is restricted. While the
preferential selection of the best players promotes cooperation irrespective of
game parametrization, the optimal number of new interactions depends somewhat
on the temptation to defect. Our findings reveal that the "making of new
friends" may be an important activity for the successful evolution of
cooperation, but also that partners must be selected carefully and their number
limited.Comment: 14 pages, 6 figures; accepted for publication in PLoS ON
Deterministic control of broadband light through a multiply scattering medium via the multispectral transmission matrix
We present a method to measure the spectrally-resolved transmission matrix of
a multiply scattering medium, thus allowing for the deterministic
spatiospectral control of a broadband light source by means of wavefront
shaping. As a demonstration, we show how the medium can be used to selectively
focus one or many spectral components of a femtosecond pulse, and how it can be
turned into a controllable dispersive optical element to spatially separate
different spectral components to arbitrary positions.Comment: minor changes, with additional discussion of the results. Fig 4 now
split into two separate figure
Waltz - An exploratory visualization tool for volume data, using multiform abstract displays
Although, visualization is now widely used, misinterpretations still occur. There are three primary solutions intended to aid a user interpret data correctly. These are: displaying the data in different forms (Multiform visualization); simplifying (or abstracting) the structure of the viewed information; and linking objects and views together (allowing corresponding objects to be jointly manipulated and interrogated). These well-known visualization techniques, provide an emphasis towards the visualization display. We believe however that current visualization systems do not effectively utilise the display, for example, often placing it at the end of a long visualization process. Our visualization system, based on an adapted visualization model, allows a display method to be used throughout the visualization process, in which the user operates a 'Display (correlate) and Refine' visualization cycle. This display integration provides a useful exploration environment, where objects and Views may be directly manipulated; a set of 'portions of interest' can be selected to generate a specialized dataset. This may subsequently be further displayed, manipulated and filtered
Bullet Clusters in the MareNostrum Universe
We estimate the expected distribution of displacements between the dark
matter and gas cores in simulated clusters. We use the MareNostrum Universe,
one of the largest non radiative, SPH Lambda CDM cosmological simulations. We
find that projected 2-D displacements between dark matter and gas, equal or
larger than the observed in the Bullet Cluster, are expected in 1% to 2% of the
clusters with masses larger than 10^{14} Msun. The 2-D displacement
distribution is roughly the same between redshifts 0<z<0.5 when multiplied by a
factor of (1+z)^{-1/2}. We conclude that the separations between dark matter
and gas as observed in the bullet cluster can be easily found in a Lambda CDM
universe. Furthermore we find that the displacement distribution is not very
sensitive to the normalization of the power spectrum. Upcoming surveys could
extend the measurements of these displacements between dark matter and gas into
large samples of hundreds of clusters, providing a potential test for Lambda
CDM.Comment: 20 pages, 4 figures. Accepted for publication in Ap
Alliancing in Australia - No-Litigation Contracts: A Tautology?
A project alliance is a business strategy whereby client and commercial participants’ objectives are aligned. This paper takes an alliance project between public and private organizations in Queensland, Australia as a case study and reports the critical factors identified that influence the success of the alliance project. Alliancing is a system that provides a collaborative environment and a framework to adapt behavior to project objectives. It is about sharing resources and experiences, exposing the “hidden” risks. The case study suggests that leadership has a strong influence on the alliance climate. Commitment and action by the Project Alliance Board and, so, parent organizations have a strong impact on the team and alliance culture, indicating alliancing has a high chance of failure when there is inadequate support from top management. Like all relational contracting approaches, trust between alliance partners is important. This case study project takes a further step toward reinforcing the trust element by placing a No-Dispute clause in the alliance agreement. A review of the effects of the no-litigation clause upon the project team is presented. The writers conclude that without a positive approach to relationship management, a No-Dispute approach is impossible. Hence, they postulate that a “no-litigation” alliancing contract is essentially tautological, and go on to argue that a no-litigation contract cannot exist without the help of a clear relational vision, that leads to both soft and hard infrastructure to assist in decision making and relationship building
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