5,753 research outputs found
Groups with Decomposable Set of Quasinormal Subgroups
A subgroup H of a group G is said to be quasinormal if HX =
XH for all subgroups X of G. In this article groups are characterized for
which the partially ordered set of quasinormal subgroups is decomposable
Verso una “sostenibilità programmata”: valutazioni LCA e LCC per la progettazione di coperture piane
Le sempre più chiare e pressanti indicazioni normative spingono i progettisti verso scelte più consapevoli sia in termini di sostenibilità, sia nei riguardi degli aspetti economici, che prendano però in considerazione tutte le fasi del ciclo di vita.
Attraverso una valutazione comparativa effettuata con l’ausilio delle note metodologie di Life Cycle Assessment e Life Cycle Costing, è possibile individuare, fra le diverse tipologie di componenti e di sistemi costruttivi, quelli che presentino un minor impatto sull’ambiente e che siano maggiormente sostenibili anche dal punto di vista economico, grazie a più appropriate strategie manutentive.
Anche l’analisi condotta con riguardo ad una semplice copertura piana da adeguare termicamente presenta spunti di interesse e di approfondimento a questa problematica rispetto alla quale troppo spesso si operano scelte non adeguate
How Noisy Data Affects Geometric Semantic Genetic Programming
Noise is a consequence of acquiring and pre-processing data from the
environment, and shows fluctuations from different sources---e.g., from
sensors, signal processing technology or even human error. As a machine
learning technique, Genetic Programming (GP) is not immune to this problem,
which the field has frequently addressed. Recently, Geometric Semantic Genetic
Programming (GSGP), a semantic-aware branch of GP, has shown robustness and
high generalization capability. Researchers believe these characteristics may
be associated with a lower sensibility to noisy data. However, there is no
systematic study on this matter. This paper performs a deep analysis of the
GSGP performance over the presence of noise. Using 15 synthetic datasets where
noise can be controlled, we added different ratios of noise to the data and
compared the results obtained with those of a canonical GP. The results show
that, as we increase the percentage of noisy instances, the generalization
performance degradation is more pronounced in GSGP than GP. However, in
general, GSGP is more robust to noise than GP in the presence of up to 10% of
noise, and presents no statistical difference for values higher than that in
the test bed.Comment: 8 pages, In proceedings of Genetic and Evolutionary Computation
Conference (GECCO 2017), Berlin, German
On Context Semantics and Interaction Nets
International audienceContext semantics is a tool inspired by Girard' s geometry of interaction. It has had many applications from study of optimal reduction to proofs of complexity bounds. Yet, context semantics have been defined only on -calculus and linear logic. In order to study other languages, in particular languages with more primitives (built-in arithmetic, pattern matching,...) we define a context semantics for a broader framework: interaction nets. These are a well-behaved class of graph rewriting systems. Here, two applications are explored. First, we define a notion of weight, based on context semantics paths, which bounds the length of reduction of nets. Then, we define a denotational semantics for a large class of interaction net systems
Hybrid fuel cell-based energy system with metal hydride hydrogen storage for small mobile applications
This paper describes the general architecture of a hybrid energy system, whose main components are a proton exchange membrane fuel cell, a battery pack and an ultracapacitor pack as power sources, and metal hydride canisters as energy storage devices, suitable for supplying power to small mobile non-automotive devices in a flexible and variable way. The first experimental results carried out on a system prototype are described, showing that the extra components, required in order to manage the hybrid system, do not remarkably affect the overall system efficiency, which is always higher than 36% in all the test configurations examined. in fact, the system allows the fuel cell to work most often at quasi-optimal conditions, near its maximum efficiency (i.e. at low/medium loads), because high external loads are met by the combined effort of the fuel cell and the ultracapacitors. For the same reason, the metal hydride storage system can be used also under highly dynamic operating conditions, notwithstanding its usually poor kinetic performance. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved
Bamboo trusses with low cost and high ductility joints
Innovative solutions of joints for bamboo trusses are presented. Experimental tests show the performances and the high level of ductility of the proposed technique, joined with simplicity in the concept of the joints, low level of technology and low cost of all used materials. It can permit a proper dissemination and a sustainable maintenance in developing countries
The transitional millisecond pulsar IGR J18245-2452 during its 2013 outburst at X-rays and soft gamma-rays
IGR~J18245--2452/PSR J1824--2452I is one of the rare transitional accreting
millisecond X-ray pulsars, showing direct evidence of switches between states
of rotation powered radio pulsations and accretion powered X-ray pulsations,
dubbed transitional pulsars. IGR~J18245--2452 is the only transitional pulsar
so far to have shown a full accretion episode, reaching an X-ray luminosity of
~erg~s permitting its discovery with INTEGRAL in 2013. In
this paper, we report on a detailed analysis of the data collected with the
IBIS/ISGRI and the two JEM-X monitors on-board INTEGRAL at the time of the 2013
outburst. We make use of some complementary data obtained with the instruments
on-board XMM-Newton and Swift in order to perform the averaged broad-band
spectral analysis of the source in the energy range 0.4 -- 250~keV. We have
found that this spectrum is the hardest among the accreting millisecond X-ray
pulsars. We improved the ephemeris, now valid across its full outburst, and
report the detection of pulsed emission up to keV in both the ISGRI
() and Fermi/GBM () bandpass. The alignment of the
ISGRI and Fermi GBM 20 -- 60 keV pulse profiles are consistent at a $\sim25\
\mu$s level. We compared the pulse profiles obtained at soft X-rays with \xmm\
with the soft \gr-ray ones, and derived the pulsed fractions of the fundamental
and first harmonic, as well as the time lag of the fundamental harmonic, up to
s, as a function of energy. We report on a thermonuclear X-ray burst
detected with \Integ, and using the properties of the previously type-I X-ray
burst, we show that all these events are powered primarily by helium ignited at
a depth of g cm. For such a helium
burst the estimated recurrence time of d is in
agreement with the observations.Comment: 10 pages, 6 Figures, 3 Tables Astronomy and Astrophysics Journal,
accepted for publication on the 13th of April 201
Phenomenological interpolation of the inclusive J/psi cross section to proton-proton collisions at 2.76 TeV and 5.5 TeV
We present a study of the inclusive J/psi cross section at 2.76 TeV and 5.5
TeV. The energy dependence of the cross section, rapidity and transverse
momentum distributions are evaluated phenomenologically. Their knowledge is
crucial as a reference for the interpretation of A-A and p-A J/psi results at
the LHC. Our approach is the following: first, we estimate the energy evolution
of the pt-integrated J/psi cross section at mid-rapidity; then, we evaluate the
rapidity dependence; finally, we study the transverse momentum distribution
trend. Whenever possible, both theory driven (based on pQCD predictions) and
functional form (data driven fits) calculations are discussed. Our predictions
are compared with the recently obtained results by the ALICE collaboration in
pp collisions at 2.76 TeV.Comment: 23 pages, 19 figures, updated text+figures, added comparison to ALICE
measurements at 2.76Te
Frequency of symbol occurrences in simple non-primitive stochastic models
We study the random variable Y-n representing the number of occurrences of a given symbol in a word of length n generated at random. The stochastic model we assume is a simple non-ergodic model defined by the product of two primitive rational formal series, which form two distinct ergodic components. We obtain asymptotic evaluations for the mean and the variance of Y-n and its limit distribution. It turns out that there are two main cases: if one component is dominant and non-degenerate we get a Gaussian limit distribution; if the two components are equipotent and have different leading terms of the mean, we get a uniform limit distribution. Other particular limit distributions are obtained in the case of a degenerate dominant component and in the equipotent case when the leading terms of the expectation values are equal
Frequency of symbol occurrences in bicomponent stochastic models
We give asymptotic estimates of the frequency of occurrences of a symbol in a random word Generated by any bicomponent stochastic model. More precisely, we consider the random variable Y-n representing the number of occurrences of a given symbol in a word of length n generated at random; the stochastic model is defined by a rational formal series r having a linear representation with two primitive components. This model includes the case when r is the product or the sum of two primitive rational formal series. We obtain asymptotic evaluations for the mean value and the variance of Yn and its limit distribution
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