200,353 research outputs found
Knowledge-based vision and simple visual machines
The vast majority of work in machine vision emphasizes the representation of perceived objects and events: it is these internal representations that incorporate the 'knowledge' in knowledge-based vision or form the 'models' in model-based vision. In this paper, we discuss simple machine vision systems developed by artificial evolution rather than traditional engineering design techniques, and note that the task of identifying internal representations within such systems is made difficult by the lack of an operational definition of representation at the causal mechanistic level. Consequently, we question the nature and indeed the existence of representations posited to be used within natural vision systems (i.e. animals). We conclude that representations argued for on a priori grounds by external observers of a particular vision system may well be illusory, and are at best place-holders for yet-to-be-identified causal mechanistic interactions. That is, applying the knowledge-based vision approach in the understanding of evolved systems (machines or animals) may well lead to theories and models that are internally consistent, computationally plausible, and entirely wrong
Are the Kepler Near-Resonance Planet Pairs due to Tidal Dissipation?
The multiple-planet systems discovered by the Kepler mission show an excess
of planet pairs with period ratios just wide of exact commensurability for
first-order resonances like 2:1 and 3:2. In principle, these planet pairs could
have both resonance angles associated with the resonance librating if the
orbital eccentricities are sufficiently small, because the width of first-order
resonances diverges in the limit of vanishingly small eccentricity. We consider
a widely-held scenario in which pairs of planets were captured into first-order
resonances by migration due to planet-disk interactions, and subsequently
became detached from the resonances, due to tidal dissipation in the planets.
In the context of this scenario, we find a constraint on the ratio of the
planet's tidal dissipation function and Love number that implies that some of
the Kepler planets are likely solid. However, tides are not strong enough to
move many of the planet pairs to the observed separations, suggesting that
additional dissipative processes are at play.Comment: 20 pages, including 7 figures; accepted for publication in Ap
Temporal Aspects of Smart Contracts for Financial Derivatives
Implementing smart contracts to automate the performance of high-value
over-the-counter (OTC) financial derivatives is a formidable challenge. Due to
the regulatory framework and the scale of financial risk if a contract were to
go wrong, the performance of these contracts must be enforceable in law and
there is an absolute requirement that the smart contract will be faithful to
the intentions of the parties as expressed in the original legal documentation.
Formal methods provide an attractive route for validation and assurance, and
here we present early results from an investigation of the semantics of
industry-standard legal documentation for OTC derivatives. We explain the need
for a formal representation that combines temporal, deontic and operational
aspects, and focus on the requirements for the temporal aspects as derived from
the legal text. The relevance of this work extends beyond OTC derivatives and
is applicable to understanding the temporal semantics of a wide range of legal
documentation
Participant Recruitment of African American College Students at an Historically Black College and University (HBCU): Challenges and Strategies for Health-Related Research
Lack of research participation among African Americans is problematic for population relevant health disparity research. The purpose of this paper is to identify and describe challenges and strategies in recruitment of African American college students for health related research being conducted at a small Historically Black College or University (HBCU). Upon completion of a recruitment and retention literature review, study investigators constructed and tested a culturally-specific, direct-appeal protocol to recruit participants. Major barriers to recruitment of African American college students included discrete sources of distrust, lack of understanding of the research process, and logistical concerns. Implementation of a culturally-specific, direct appeal protocol led to a significant improvement in recruitment and retention of student participants. It is imperative that researchers demystify scientific investigation as a first step towards building trust between themselves and target populations, particularly those from traditionally underrepresented groups. Reasons for distrust, a need for trust and trust building strategies are offered here
Temperature Effects on Development of Three Cereal Aphid Parasitoids (Hymenoptera: Aphidiidae)
Temperature is an important climatological variable that influences the biology and ecology of insects. Poor climatic adaptation can limit the effectiveness of parasitic insects in biological control. Two exotic parasites (Syrian Diaeretiella rapae (M\u27Intosh) and Argentinean Aphidius colemani Viereck) imported for biological control of the Russian wheat aphid, Diuraphis noxia (Mordvilko), and one native parasite (Diaeretiella rapae) were reared in growth chambers in three fluctuating temperature regimes with average daily temperatures of 12, 18, and 24°C. Estimates of temperature thresholds for immature development were 3.3, 3.5, and 2.8°C, for Oklahoman D. rapae, Syrian D. rapae, and A. colemani, respectively. Estimates of thermal require- ments for development from egg to adult were 297, 278, and 301 degree-days for the three parasitoids. Dry weights of adults reared in different fluctuating temperature regimes did not differ significantly among sexes, but adults from regimes with low average temperatures of 12 and 18°C had significantly greater weights than those reared in a regime with an average temperature of 24°C. Results suggest that developmental response to temperature will not limit the effectiveness of the exotic parasites in biological control
Breakdown of counterflow superfluidity in a disordered quantum Hall bilayer
We present a theory for the regime of coherent interlayer tunneling in a
disordered quantum Hall bilayer at total filling factor one, allowing for the
effect of static vortices. We find that the system consists of domains of
polarized superfluid phase. Injected currents introduce phase slips between the
polarized domains which are pinned by disorder. We present a model of saturated
tunneling domains that predicts a critical current for the breakdown of
coherent tunneling that is extensive in the system size. This theory is
supported by numerical results from a disordered phase model in two dimensions.
We also discuss how our picture might be used to interpret experiments in the
counterflow geometry and in two-terminal measurements.Comment: 7 pages, 3 figure
- …