2,386 research outputs found
On the Observability of Giant Protoplanets in Circumstellar Disks
We investigate the possibility to detect giant planets that are still
embedded in young circumstellar disks. Based on models with different stellar,
planetary, and disk masses, and different radial positions of the planet we
analyze the resulting submillimeter appearance of these systems. We find that
the influence of the planet on the spectral energy distribution could not be
distinguished from that of other disk parameters. However, dust reemission
images of the disks show that the hot region in the proximity of a young
planet, along with the gap, could indeed be detected and mapped with the
Atacama Large Millimeter Array in the case of nearby circumstellar disks
(d<100pc) in approximate face-on orientation.Comment: ApJ, in pres
Searching in Unstructured Overlays Using Local Knowledge and Gossip
This paper analyzes a class of dissemination algorithms for the discovery of
distributed contents in Peer-to-Peer unstructured overlay networks. The
algorithms are a mix of protocols employing local knowledge of peers'
neighborhood and gossip. By tuning the gossip probability and the depth k of
the k-neighborhood of which nodes have information, we obtain different
dissemination protocols employed in literature over unstructured P2P overlays.
The provided analysis and simulation results confirm that, when properly
configured, these schemes represent a viable approach to build effective P2P
resource discovery in large-scale, dynamic distributed systems.Comment: A revised version of the paper appears in Proc. of the 5th
International Workshop on Complex Networks (CompleNet 2014) - Studies in
Computational Intelligence Series, Springer-Verlag, Bologna (Italy), March
201
Gathering an even number of robots in an odd ring without global multiplicity detection
We propose a gathering protocol for an even number of robots in a ring-shaped
network that allows symmetric but not periodic configurations as initial
configurations, yet uses only local weak multiplicity detection. Robots are
assumed to be anonymous and oblivious, and the execution model is the non-
atomic CORDA model with asynchronous fair scheduling. In our scheme, the number
of robots k must be greater than 8, the number of nodes n on a network must be
odd and greater than k+3. The running time of our protocol is O(n2)
asynchronous rounds.Comment: arXiv admin note: text overlap with arXiv:1104.566
Hydromagnetic and gravitomagnetic crust-core coupling in a precessing neutron star
We consider two types of mechanical coupling between the crust and the core
of a precessing neutron star. First, we find that a hydromagnetic (MHD)
coupling between the crust and the core strongly modifies the star's
precessional modes when ; here is the
Alfven crossing timescale, and and are the star's spin and
precession periods, respectively. We argue that in a precessing pulsar PSR
B1828-11 the restoring MHD stress prevents a free wobble of the crust relative
to the non-precessing core. Instead, the crust and the proton-electron plasma
in the core must precess in unison, and their combined ellipticity determines
the period of precession. Link has recently shown that the neutron superfluid
vortices in the core of PSR B1828-11 cannot be pinned to the plasma; he has
also argued that this lack of pinning is expected if the proton Fermi liquid in
the core is type-I superconductor. In this case, the neutron superfluid is
dynamically decoupled from the precessing motion. The pulsar's precession
decays due to the mutual friction between the neutron superfluid and the plasma
in the core. The decay is expected to occur over tens to hundreds of precession
periods and may be measurable over a human lifetime. Such a measurement would
provide information about the strong n-p interaction in the neutron-star core.
Second, we consider the effect of gravitomagnetic coupling between the neutron
superfluid in the core and the rest of the star and show that this coupling
changes the rate of precession by about 10%. The general formalism developed in
this paper may be useful for other applications.Comment: 6 page
A stability with optimality analysis of consensus-based distributed filters for discrete-time linear systems
In this paper we investigate how stability and optimality of consensus-based distributed filters depend
on the number of consensus steps in a discrete-time setting for both directed and undirected graphs.
By introducing two new algorithms, a simpler one based on dynamic averaging of the estimates and
a more complex version where local error covariance matrices are exchanged as well, we are able to
derive a complete theoretical analysis. In particular we show that dynamic averaging alone suffices
to approximate the optimal centralized estimate if the number of consensus steps is large enough
and that the number of consensus steps needed for stability can be computed in a distributed way.
These results shed light on the advantages as well as the fundamental limitations shared by all the
existing proposals for this class of algorithms in the basic case of linear time-invariant systems, that
are relevant for the analysis of more complex situations
Design and Development of the Engine Unit for a Twin-Rotor Unmanned Aerial Vehicle
Advanced computer-aided technologies played a crucial role in the design of an unconventional Uninhabited Aerial Vehicle (UAV), developed at the Turin Technical University and the University of Rome “La Sapienza”. The engine unit of the vehicle is made of a complex system of three two stroke piston engines coupled with two counter-rotating three-bladed rotors, controlled by rotary PWM servos. The focus of the present paper lies on the enabling technologies exploited in the framework of activities aimed at designing a suitable and reliable engine system, capable of performing the complex tasks required for operating the proposed rotorcraft. The synergic use of advanced computational tools for estimating the aerodynamic performance of the vehicle, solid modeling for mechanical components design, and rapid prototyping techniques for control system logic synthesis and implementation will be presented.
Tomographic test of Bell's inequality for a time-delocalized single photon
Time-domain balanced homodyne detection is performed on two well-separated
temporal modes sharing a single photon. The reconstructed density matrix of the
two-mode system is used to prove and quantify its entangled nature, while the
Wigner function is employed for an innovative tomographic test of Bell's
inequality based on the theoretical proposal by Banaszek and Wodkiewicz [Phys.
Rev. Lett. 82, 2009 (1999)]. Provided some auxiliary assumptions are made, a
clear violation of Banaszek-Bell's inequality is found.Comment: 7 pages, 3 figures: revised version with additional material;
accepetd for publication in Phys. Rev.
Seismic assessment and rehabilitation of a historical theatre based on a macro-element strategy
The structural and seismic assessment of the 19th-century Petruzzelli theater in Bari (Italy) is presented. The macro-elements strategy was adopted to dismantle the whole structure in parts. The steel dome was verified through dynamic multi-modal analysis based on finite element model. Each masonry macro-element was firstly verified through a kinematic analysis aiming at excluding local collapse mechanisms. Afterwards, a nonlinear static analysis was carried out in order to evaluate its overall seismic capacity. The effectiveness of linear or nonlinear analyses and of the macro-element strategy compared with other modeling techniques is also discussed. After highlighting the structural deficiencies of the theater, upgrading solutions are proposed with consideration of the safety needs and the architectural preservation requirements based on the historical importance of the buildin
Internationalisation, cultural distance and country characteristics: a Bayesian analysis of SME's financial performance
Relying on the accounting data of a panel of 403 Italian manufacturing SMEs collected over a period of 5 years, we find results suggesting that multinationality per se does not impact on the economic performance of international small and medium sized firms. It is the characteristics of the country selected i.e. the political hazard, the financial stability and the economic performance that significantly influence SMEs financial performance. The management implication for small and medium sized firms selecting and entering new geographic markets is significant, since our results show that for SMEs it is the market selection process that really matters and not the degree of multinationality
Con prisa y con pausas. Aproximaciones a la cuestión del financiamiento para la producción del hábitat popular en Campo Unamuno en la posconvertibilidad
Esta ponencia pretende reflexionar acerca de los procesos de producción del hábitat popular y de producción de ciudad que protagonizaron y protagonizan hogares del Conurbano Bonaerense durante la posconvertibilidad. Más específicamente, acerca de las estrategias de financiamiento para la producción del hábitat de hogares pertenecientes a tres barrios de Campo Unamuno, ubicado en el partido de Lomas de Zamora. El trabajo se inscribe en el marco de realización de una tesis de maestría en curso sobre esta temática. Aquí nos ocuparemos de sistematizar los modos en que estos hogares han financiado y financian la producción de su hábitat en la posconvertibilidad, en particular, en lo referido a la dimensión de acceso al suelo y a la vivienda y a su mejoramiento a lo largo del tiempo.
Los datos utilizados como insumo fueron obtenidos a partir de un relevamiento de campo coordinado por el equipo de investigación que la autora integra y realizado durante los meses de junio y julio de 2015. A través de una muestra representativa se han relevado los barrios: 17 de Marzo, Soledad y Libre Amanecer y se ha utilizado una estrategia metodológica combinada, cuanti y cualitativa.
Finalmente, el trabajo se inscribe en las líneas de investigación del equipo de la Undav arriba mencionado, el cual viene reelaborando un marco teórico de trabajo en el que están implicados conceptos como: sectores populares, economía popular, estrategias de reproducción social, estrategias de financiamiento, producción del hábitat, territorio.Mesa 29: “La cuestión urbana interrogada”: producción de la ciudad, actores y conflictos, una mirada desde los estudios urbanosFacultad de Humanidades y Ciencias de la Educació
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