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41.
Let F= {C1,C2,...,C} be a family of ndisjoint convex bodies in the plane. We say that a set Vof exterior light sources illuminates F, if for every boundary point of any member of Fthere is a point in Vsuch that is visible from ,i.e. the open line segment joining and is disjoint from F. An illumination system Vis called primitive if no proper subset of Villuminates F. Let pmax(F) denote the maximum number of points forming a primitive illumination system for F, and letpmax(n) denote the minimum of F) taken over all families Fconsisting of ndisjoint convex bodies in the plane. The aim of this paper is to investigate the quantities pmax(F) and pmax(n). 相似文献
42.
A. Tumino C. Spitaleri A. Mukhamedzhanov G. G. Rapisarda S. Blagus M. Bogovać S. Cherubini V. Crucillá Z. Elekes Z. Fülöp M. Gulino G. Gyürky G. Kiss Dj. Miljanić M. Milin M. La Cognata L. Lamia R. G. Pizzone D. Rendić S. Romano M. L. Sergi E. Somorjai 《Few-Body Systems》2008,43(1-4):219-225
We address a successful indirect technique, the Trojan horse method, which allows one to measure the bare nucleus cross section for rearrangement reactions down to astrophysical energies. In particular, we consider here the application of the method to the p-p elastic scattering. This represents an important test of the main feature of the method, namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. In contrast to the on-energy-shell case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum, as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between the Trojan horse p-p data and the calculated on-energy-shell n-n, n-p and nuclear p-p cross sections. 相似文献
43.
M. La Cognata A. Del Zoppo P. Figuera A. Musumarra R. Alba S. Cherubini N. Colonna L. Cosentino V. Crucillà A. Di Pietro M. Gulino L. Lamia M.G. Pellegriti R.G. Pizzone S.M.R. Puglia G.G. Rapisarda C. Rolfs S. Romano M.L. Sergi C. Spitaleri S. Tudisco A. Tumino 《Physics letters. [Part B]》2008
The 8Li + 4He → 11B + n reaction at Ecm<2 MeV is a process of relevant astrophysical interest for which a remarkable experimental discrepancy between inclusive and exclusive cross-section measurements exists. In this Letter, a new inclusive neutron measurement at Ecm=1.05±0.16 MeV is given. The radioactive 8Li beam was delivered by the EXCYT facility. The cross section was determined by a low-background measurement of the time correlation between the 8Li projectile arrival to the target and the following neutron capture in a threshold-less 4π thermalization counter. This new data strengthens the reliability of the previous inclusive reaction cross-section data and altogether are consistent with a significant population of 11B levels at high excitation energy. 相似文献
44.
A. Tumino C. Spitaleri S. Cherubini M. Gulino M. La Cognata L. Lamia R. G. Pizzone S. M. R. Puglia G. G. Rapisarda S. Romano M. L. Sergi R. Spartà 《Few-Body Systems》2013,54(5-6):745-753
With the introduction of the Trojan Horse Method, nuclear cross sections between charged particles at astrophysical energies can now be measured. Here the basic features of the method are recalled together with recent results relevant for Nuclear Astrophysics. New applications in connection with plasma physics and industrial energy production are discussed. 相似文献
45.
F. Caruso V. Latora A. Pluchino A. Rapisarda B. Tadić 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):243-247
We investigate numerically the Self Organized Criticality (SOC)
properties of the dissipative Olami-Feder-Christensen model on
small-world and scale-free networks. We find that the small-world
OFC model exhibits self-organized criticality. Indeed, in this
case we observe power law behavior of earthquakes size
distribution with finite size scaling for the cut-off region. In
the scale-free OFC model, instead, the strength of disorder
hinders synchronization and does not allow to reach a critical
state. 相似文献
46.
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48.
M. La Cognata C. Spitaleri S. Cherubini M. Gulino L. Lamia R. G. Pizzone S. M. R. Puglia G. G. Rapisarda S. Romano M. L. Sergi A. Tumino 《Few-Body Systems》2008,44(1-4):353-356
The t(p,p)t and t(p,d)d channels have been investigated in an indirect way through the 2H(t,tp)n and 2H(t,dd)n three-body reactions performed at E t = 35.5?MeV in quasi-free kinematics. The agreement with direct data supports the pole approximation at energies above the Coulomb barrier. 相似文献
49.
We discuss an effective spin-glass Hamiltonian which can be used to study the glassy-like dynamics observed in the metastable states of the Hamiltonian mean field (HMF) model. By means of the Replica formalism, we were able to find a self-consistent equation for the glassy order parameter which reproduces, in a restricted energy region below the phase transition, the microcanonical simulations for the polarization order parameter recently introduced in the HMF model. 相似文献
50.
E. Rapisarda G. Raciti C. Sfienti F. Amorini L. Calabretta G. Cardella M. De Napoli 《The European physical journal. Special topics》2007,143(1):269-272
Microscopic modeling of complex systems by cellular automata, which deal
with particles at lattice sites interacting via simple local rules, involves
some arbitrariness besides a drastic simplification of nature. Here we
briefly report on some recent work on the influence of dynamic details on
the morphological and critical properties of one of such model systems. In
particular, we discuss on the similarities and differences between a kinetic
nonequilibrium Ising model—which is a prototype for nonequilibrium
anisotropic phase transitions—and its off–lattice counterpart, namely,
an analogue in which the spatial coordinates of the particles vary
continuously. We also pay attention to a related driven lattice model with
nearest-neighbor exclusion. 相似文献