190 research outputs found
Spacecraft attitude determination by fanscan technique
To determine orientation, or attitude, of spacecraft in flight relative to data-receiving antenna on earth use fanbeam antenna which is offset in angle from spin axis of spacecraft and provides fan-like radiation pattern
La messa in sicurezza dell'area industriale di Priolo-Augusta rispetto ai rischi da terremoto e maremoto
I recenti forti terremoti che hanno interessato zone particolarmente industrializzate in
Turchia ed in India (terremoto del 17.8.1999, Kocaeli, Turchia, Mw = 7.4; e terremoto
di Guyarat, India, del 26.01.2001, Mw =7.7) hanno messo in evidenza che al
danno prodotto dal terremoto si pu\uf2 aggiungere quello dovuto alle conseguenze di
incidenti e/o rotture negli impianti, cosiddetti, \u201ca rischio di incidente rilevante\u201d. Il rischio
totale nell\u2019area pu\uf2 quindi assumere valori estremamente elevati in termini economici,
ambientali, e talvolta con perdita di vite umane. Ad esempio, nel caso del terremoto turco,
il danneggiamento della raffineria Tupras di IZMIT ha provocato l\u2019incendio della stessa
e la fuoriuscita di una quantit\ue0 rilevante di olio (Foto 1). Sulla base di quanto sopra e di quanto conosciuto, il presente studio si propone come
elemento di base per l\u2019impostazione di interventi strutturali sugli impianti e sul territorio
con l\u2019obiettivo di mettere il tutto in condizioni di sicurezza a fronte del terremoto
(ed eventuale maremoto associato) atteso nell\u2019area.
A questo scopo \ue8 stata realizzata un\u2019analisi per mettere in evidenza l\u2019entit\ue0 e la frequenza
dei fenomeni naturali (terremoti e maremoti) che possono determinare significativi
impatti sia sull\u2019ambiente fisico che su quello antropizzato (infrastrutture) nell\u2019area
di Priolo-Augusta. Il progetto ha avuto come obiettivo iniziale la valutazione dei carichi
dovuti a fenomeni naturali che, trasformati in termini ingegneristici, devono essere utilizzati per la verifica della idoneit\ue0 progettuale degli impianti industriali presenti
nelle aree studiate. In particolare \ue8 stato valutato, dapprima, il terremoto di riferimento
per la progettazione, in termini di picco massimo di accelerazione e spettro di risposta
associato. In tale fase si \ue8 anche provveduto alla costruzione di scenari associati ad
un eventuale maremoto. I siti prescelti sono esposti ad un elevato rischio sismico la cui
definizione ha richiesto l\u2019adozione delle metodologie pi\uf9 avanzate disponibili. A tale
scopo sono stati applicati diversi approcci innovativi sia di tipo sismologico che ingegneristico
Microwave study of quantum n-disk scattering
We describe a wave-mechanical implementation of classically chaotic n-disk
scattering based on thin 2-D microwave cavities. Two, three, and four-disk
scattering are investigated in detail. The experiments, which are able to probe
the stationary Green's function of the system, yield both frequencies and
widths of the low-lying quantum resonances. The observed spectra are found to
be in good agreement with calculations based on semiclassical periodic orbit
theory. Wave-vector autocorrelation functions are analyzed for various
scattering geometries, the small wave-vector behavior allowing one to extract
the escape rate from the quantum repeller. Quantitative agreement is found with
the value predicted from classical scattering theory. For intermediate
energies, non-universal oscillations are detected in the autocorrelation
function, reflecting the presence of periodic orbits.Comment: 13 pages, 8 eps figures include
Recorded Motions of the Mw6.3 April 6, 2009 L’Aquila (Italy) Earthquake and Implications for Building Structural Damage: Overview.
The normal-faulting earthquake of 6 April 2009 in the Abruzzo Region of
central Italy caused heavy losses of life and substantial damage to centuriesold
buildings of significant cultural importance and to modern reinforcedconcrete-
framed buildings with hollow masonry infill walls. Although
structural deficiencies were significant and widespread, the study of the
characteristics of strong motion data from the heavily affected area indicated
that the short duration of strong shaking may have spared many more damaged
buildings from collapsing. It is recognized that, with this caveat of shortduration
shaking, the infill walls may have played a very important role in
preventing further deterioration or collapse of many buildings. It is concluded
that better new or retrofit construction practices that include reinforcedconcrete
shear walls may prove helpful in reducing risks in such seismic areas
of Italy, other Mediterranean countries, and even in United States, where there
are large inventories of deficient structures.Published651-6844.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve
Oxytocin and vasopressin systems in genetic syndromes and neurodevelopmental disorders
Oxytocin (OT) and arginine vasopressin (AVP) are two small, related neuropeptide hormones found in many mammalian species, including humans. Dysregulation of these neuropeptides have been associated with changes in behavior, especially social interactions. We review how the OT and AVP systems have been investigated in Autism Spectrum Disorder (ASD), Prader–Willi Syndrome (PWS), Williams Syndrome (WS) and Fragile X syndrome (FXS). All of these neurodevelopmental disorders (NDD) are marked by social deficits. While PWS, WS and FXS have identified genetic mutations, ASD stems from multiple genes with complex interactions. Animal models of NDD are invaluable for studying the role and relatedness of OT and AVP in the developing brain. We present data from a FXS mouse model affecting the fragile X mental retardation 1 (Fmr1) gene, resulting in decreased OT and AVP staining cells in some brain regions. Reviewing the research about OT and AVP in these NDD suggests that altered OT pathways may be downstream from different etiological factors and perturbations in development. This has implications for ongoing studies of the therapeutic application of OT in NDD
Black Holes in Quasi-topological Gravity
We construct a new gravitational action which includes cubic curvature
interactions and which provides a useful toy model for the holographic study of
a three parameter family of four- and higher-dimensional CFT's. We also
investigate the black hole solutions of this new gravity theory. Further we
examine the equations of motion of quasi-topological gravity. While the full
equations in a general background are fourth-order in derivatives, we show that
the linearized equations describing gravitons propagating in the AdS vacua
match precisely the second-order equations of Einstein gravity.Comment: 33 pages, 4 figures; two references adde
Quasinormal behavior of the D-dimensional Schwarzshild black hole and higher order WKB approach
We study characteristic (quasinormal) modes of a -dimensional Schwarzshild
black hole. It proves out that the real parts of the complex quasinormal modes,
representing the real oscillation frequencies, are proportional to the product
of the number of dimensions and inverse horizon radius . The
asymptotic formula for large multipole number and arbitrary is derived.
In addition the WKB formula for computing QN modes, developed to the 3rd order
beyond the eikonal approximation, is extended to the 6th order here. This gives
us an accurate and economic way to compute quasinormal frequencies.Comment: 15 pages, 6 figures, the 6th order WKB formula for computing QNMs in
Mathematica is available from https://goo.gl/nykYG
On the modelling of infilled RC frames through strut models
Infill panels largely affect the seismic response of framed constructions. The wide variety in their mechanical and geometrical features has produced many different models and assumptions in their analytical representation. In this paper the simplest and most diffuse analytical approach, based on the introduction of equivalent struts, has been checked. An overview is presented, focusing on the strut dimensions, strength and number. Two case-studies, taken by two different experimental campaigns, have been considered and reproduced. The obtained results have been compared to the experimental ones, and some parameters have been checked for selecting the model to use for analysis
Hawking emission from quantum gravity black holes
We address the issue of modelling quantum gravity effects in the evaporation
of higher dimensional black holes in order to go beyond the usual
semi-classical approximation. After reviewing the existing six families of
quantum gravity corrected black hole geometries, we focus our work on
non-commutative geometry inspired black holes, which encode model independent
characteristics, are unaffected by the quantum back reaction and have an
analytical form compact enough for numerical simulations. We consider the
higher dimensional, spherically symmetric case and we proceed with a complete
analysis of the brane/bulk emission for scalar fields. The key feature which
makes the evaporation of non-commutative black holes so peculiar is the
possibility of having a maximum temperature. Contrary to what happens with
classical Schwarzschild black holes, the emission is dominated by low frequency
field modes on the brane. This is a distinctive and potentially testable
signature which might disclose further features about the nature of quantum
gravity.Comment: 36 pages, 18 figures, v2: updated reference list, minor corrections,
version matching that published on JHE
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