3,255 research outputs found
The astronaut and the banana peel: An EVA retriever scenario
To prepare for the problem of accidents in Space Station activities, the Extravehicular Activity Retriever (EVAR) robot is being constructed, whose purpose is to retrieve astronauts and tools that float free of the Space Station. Advanced Decision Systems is at the beginning of a project to develop research software capable of guiding EVAR through the retrieval process. This involves addressing problems in machine vision, dexterous manipulation, real time construction of programs via speech input, and reactive execution of plans despite the mishaps and unexpected conditions that arise in uncontrolled domains. The problem analysis phase of this work is presented. An EVAR scenario is used to elucidate major domain and technical problems. An overview of the technical approach to prototyping an EVAR system is also presented
On the ubiquity of Beutler-Fano profiles: from scattering to dissipative processes
Fano models - consisting of a Hamiltonian with discrete-continuous spectrum -
are one of the basic toy models in spectroscopy. They have been succesfull in
explaining the lineshape of experiments in atomic physics and condensed matter.
These models however have largely been out of the scope of dissipative
dynamics, with ony a handful of works considering the effect of a thermal bath.
Yet in nanostructures and condensed matter systems, dissipation strongly
modulates the dynamics. In this article, we present an overview of the
theoretical works dealing with Fano interferences coupled to a thermal bath and
compare them to the scattering formalism. We provide the solution to any
discrete-continuous Hamiltonian structure within the wideband approximation
coupled to a Markovian bath. In doing so, we update the toy models that have
been available for unitary evolution since the 1960s. We find that the Fano
lineshape is preserved as long as we allow a rescaling of the parameters, and
an additional Lorentzian contribution that reflects the destruction of the
interference by dephasings. We discuss the pertinence of each approach -
dissipative and unitary - to different experimental setups: scattering,
transport and spectroscopy of dissipative systems. We finish by discussing the
current limitations of the theories due to the wideband approximation and the
memory effects of the bath.Comment: Expanded bibliography, minor typos correcte
Governance Infrastructure and U.S. Foreign Direct Investment
This paper examines the statistical importance of governance infrastructure as a determinant of U.S. foreign direct investment. In broad terms, governance infrastructure represents attributes of legislation, regulation, and legal systems that condition freedom of transacting, security of property rights and transparency of government and legal processes. Our econometric analysis employs a two-stage estimation procedure. In the first stage, the probability that a country is an FDI recipient is estimated. The results indicate that countries that fail to achieve a minimum threshold of effective governance are unlikely to receive any U.S. FDI. Countries that receive no U.S. FDI are typically countries that do not promote free and transparent markets, have ineffective governments, and are often countries whose legal systems are not rooted in English Common Law. In the second stage, the analysis is restricted to those countries that did receive FDI flows. The estimated equations focus on the determinants of the amount of FDI received. Given that a country is a recipient of U.S. FDI, governance infrastructure, including the nature of the legal system, is an important determinant of the amount received.foreign direct investment, capital flows, multinational corporations, infrastructure, governance
Thin-Slice Forecasts of Gubernatorial Elections
We showed 10-second, silent video clips of unfamiliar gubernatorial debates to a group of experimental participants and asked them to predict the election outcomes. The participants' predictions explain more than 20 percent of the variation in the actual two-party vote share across the 58 elections in our study, and their importance survives a range of controls, including state fixed effects. In a horse race of alternative forecasting models, participants' visual forecasts significantly outperform economic variables in predicting vote shares, and are comparable in predictive power to a measure of incumbency status. Adding policy information to the video clips by turning on the sound tends, if anything, to worsen participants' accuracy, suggesting that naïveté may be an asset in some forecasting tasks.
Kolmogorov's axioms for probabilities with values in hyperbolic numbers
We introduce the notion of a probabilistic measure which takes values in
hyperbolic numbers and which satisfies the system of axioms generalizing
directly Kolmogorov's system of axioms. We show that this new measure verifies
the usual properties of a probability; in particular, we treat the conditional
hyperbolic probability and we prove the hyperbolic analogues of the
multiplication theorem, of the law of total probability and of Bayes' theorem.
Our probability may take values which are zero--divisors and we discuss
carefully this peculiarity
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