10,755 research outputs found
Implementing Session Centered Calculi
Recently, specific attention has been devoted to the development of service oriented process calculi. Besides the foundational aspects, it is also interesting to have prototype implementations for them in order to assess usability and to minimize the gap between theory and practice. Typically, these implementations are done in Java taking advantage of its mechanisms supporting network applications. However, most of the recurrent features of service oriented applications are re-implemented from scratch. In this paper we show how to implement a service oriented calculus, CaSPiS (Calculus of Services with Pipelines and Sessions) using the Java framework IMC, where recurrent mechanisms for network applications are already provided. By using the session oriented and pattern matching communication mechanisms provided by IMC, it is relatively simple to implement in Java all CaSPiS abstractions and thus to easily write the implementation in Java of a CaSPiS process
Linux kernel compaction through cold code swapping
There is a growing trend to use general-purpose operating systems like Linux in embedded systems. Previous research focused on using compaction and specialization techniques to adapt a general-purpose OS to the memory-constrained environment, presented by most, embedded systems. However, there is still room for improvement: it has been shown that even after application of the aforementioned techniques more than 50% of the kernel code remains unexecuted under normal system operation. We introduce a new technique that reduces the Linux kernel code memory footprint, through on-demand code loading of infrequently executed code, for systems that support virtual memory. In this paper, we describe our general approach, and we study code placement algorithms to minimize the performance impact of the code loading. A code, size reduction of 68% is achieved, with a 2.2% execution speedup of the system-mode execution time, for a case study based on the MediaBench II benchmark suite
Extreme Sensitivity of the Superconducting State in Thin Films
All non-interacting two-dimensional electronic systems are expected to
exhibit an insulating ground state. This conspicuous absence of the metallic
phase has been challenged only in the case of low-disorder, low density,
semiconducting systems where strong interactions dominate the electronic state.
Unexpectedly, over the last two decades, there have been multiple reports on
the observation of a state with metallic characteristics on a variety of
thin-film superconductors. To date, no theoretical explanation has been able to
fully capture the existence of such a state for the large variety of
superconductors exhibiting it. Here we show that for two very different
thin-film superconductors, amorphous indium-oxide and a single-crystal of
2H-NbSe2, this metallic state can be eliminated by filtering external
radiation. Our results show that these superconducting films are extremely
sensitive to external perturbations leading to the suppression of
superconductivity and the appearance of temperature independent, metallic like,
transport at low temperatures. We relate the extreme sensitivity to the
theoretical observation that, in two-dimensions, superconductivity is only
marginally stable.Comment: 10 pages, 6 figure
Weak Poisson structures on infinite dimensional manifolds and hamiltonian actions
We introduce a notion of a weak Poisson structure on a manifold modeled
on a locally convex space. This is done by specifying a Poisson bracket on a
subalgebra \cA \subeq C^\infty(M) which has to satisfy a non-degeneracy
condition (the differentials of elements of \cA separate tangent vectors) and
we postulate the existence of smooth Hamiltonian vector fields. Motivated by
applications to Hamiltonian actions, we focus on affine Poisson spaces which
include in particular the linear and affine Poisson structures on duals of
locally convex Lie algebras. As an interesting byproduct of our approach, we
can associate to an invariant symmetric bilinear form on a Lie algebra
\g and a -skew-symmetric derivation a weak affine Poisson
structure on \g itself. This leads naturally to a concept of a Hamiltonian
-action on a weak Poisson manifold with a \g-valued momentum map and hence
to a generalization of quasi-hamiltonian group actions
On the relative expressiveness of higher-order session processes
By integrating constructs from the λ-calculus and the Ï-calculus, in higher-order process calculi exchanged values may contain processes. This paper studies the relative expressiveness of HOÏ, the higher-order Ï-calculus in which communications are governed by session types. Our main discovery is that HO, a subcalculus of HOÏ which lacks name-passing and recursion, can serve as a new core calculus for session-typed higher-order concurrency. By exploring a new bisimulation for HO, we show that HO can encode HOÏ fully abstractly (up to typed contextual equivalence) more precisely and efficiently than the first-order session Ï-calculus (Ï). Overall, under session types, HOÏ, HO, and Ï are equally expressive; however, HOÏ and HO are more tightly related than HOÏ and Ï
Meson Form Factors and Non-Perturbative Gluon Propagators
The meson (pion and kaon) form factor is calculated in the perturbative
framework with alternative forms for the running coupling constant and the
gluon propagator in the infrared kinematic region. These modified forms are
employed to test the sensibility of the meson form factor to the
nonperturbative contributions. Its is a powerful discriminating quantity and
the results obtained with a particular choice of modified running coupling
constant and gluon propagator have a good agreement with the available data,
for both mesons, indicating the robustness of the method of calculation.
Nevertheless, nonperturbative aspects may be included in the perturbative
framework of calculation of exclusive processes.Comment: 18 pages, 7 figures. Discutions added, clarifing figures. Accepted to
be published in Phys. Rev.
The Machine Learning Landscape of Top Taggers
Based on the established task of identifying boosted, hadronically decaying
top quarks, we compare a wide range of modern machine learning approaches.
Unlike most established methods they rely on low-level input, for instance
calorimeter output. While their network architectures are vastly different,
their performance is comparatively similar. In general, we find that these new
approaches are extremely powerful and great fun.Comment: Yet another tagger included
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