Multi-fragment decays of
129Xe,
197Au and
238U projectiles in collisions with Be, C, Al, Cu, In, Au and U targets at energies between
E
A
= 400
and 1000 MeV have been studied with the ALADIN ...forward-spectrometer at SIS. By adding an array of 84 SiCsI(Tl) telescopes the solid-angle coverage of the setup was extended to
θ
lab = 16°. This permitted the complete detection of fragments from the projectile-spectator source.
The dominant feature of the systematic set of data is the
Z
bound universality that is obeyed by the fragment multiplicities and correlations. These observables are invariant with respect to the entrance channel if plotted as a function of
Z
bound, where
Z
bound is the sum of the atomic numbers
Z
i
of all projectile fragments with
Z
i
⩾ 2. No significant dependence on the bombarding energy nor on the target mass is observed. The dependence of the fragment multiplicity on the projectile mass follows a linear scaling law.
The reasons for and the limits of the observed universality of spectator fragmentation are explored within the realm of the available data and with model studies. It is found that the universal properties should persist up to much higher bombarding energies than explored in this work and that they are consistent with universal features exhibited by the intranuclear cascade and statistical multifragmentation models.
According to many code requirements for concrete structures, the stress in the compressed part of reinforced concrete (RC) beams in bending is usually computed by means of uniaxial stress-strain ...relationships. These approaches sometimes are not able to reproduce the structural response of the beam when crushing of concrete in compression occurs. As a consequence, both the bearing capacity of RC structures and their ductility are roughly estimated. In this paper, the postpeak behavior of compressed concrete is modeled through sliding planes up to the expulsion of v-shaped block. The concrete damage on the surface of these-planes is the cause of the softening branch in the moment-curvature diagrams of RC beams. The proposed mathematical description of the sliding phenomenon also shows how it is impossible to define an univocal stress-strain relationship for concrete in compression, whose softening behavior depends both on the dimension of the compressive zone and on strain gradient (i.e., the curvature).
A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of
on the 3
level is ...derived. Comparing this value with the number of successfully reconstructed
hyperons allows to determine an upper limit on the ratio
, which is confronted with statistical and coalescence-type model calculations.
.
Results on the deep sub-threshold production of the short-lived hadronic resonance K*(892)
0
are reported for collisions of Ar + KCl at 1.76A GeV beam energy, studied with the High Acceptance ...Di-Electron Spectrometer (HADES) at SIS18/GSI. The K*(892)
0
production probability per central collision of
and the K*(892)
0
/K
0
ratio of
are determined at the lowest energy so far (
i.e.
deep below the threshold for the corresponding production in nucleon-nucleon collisions,
MeV). The K*
0
/K
0
ratio is compared with results of other experiments and with the predictions of the UrQMD transport approach and of the statistical hadronization model. The experimental K*
0
yield and the K*
0
/K
0
ratio are overestimated by the transport model by factors of about five and two, respectively. In a chemically equilibrated medium the ratio corresponds to a temperature of the thermalized system being systematically lower than the value determined by the yields of the stable and long-lived hadrons produced in Ar + KCl collisions. From the present measurement, we conclude that sub-threshold K* production either cannot be considered to proceed in a system being in thermal equilibrium or these short-lived resonances appear undersaturated, for example as a result of the rescattering of the decay particles in the ambient hadronic medium.
Quasi-projectile events from peripheral
35
A
MeV
Au+Au collisions are compared with
25
A
MeV
Au+C, 25 and
35
A
MeV
Au+Cu and
35
A
MeV
Au+Au central events. By fitting the measured charge yields with ...the Fisher droplet model technique, all the different data sets coherently point to a value
E
∗
c≈4.5
A
MeV
as the excitation energy where size distribution are best fitted by a power law. The physical parameters extracted from the fit strongly depend on the detailed shape assumed for the scaling function with the exception of
τ and
σ which are consistent with the critical exponents of the liquid-gas phase transition. Possible implications concerning the observation of a phase transition in multifragmentation experiments are discussed.
Flexural Deformability of Reinforced Concrete Beams Fantilli, Alessandro P; Ferretti, Daniele; Iori, Ivo ...
Journal of structural engineering (New York, N.Y.),
09/1998, Letnik:
124, Številka:
9
Journal Article
Recenzirano
In reinforced concrete beams, the sectional definition of the moment-curvature relationship is not straightforward owing to the presence of cracks. In general, this problem has been solved by ...considering a representative portion of the beam and by defining the curvature 1 r as the ratio between the rotation of the portion considered and its length. Large portions of the beam with many cracks lead to "average" moment-curvature relationship, while small portions delimited by two consecutive flexural cracks lead to "local" moment-curvature relationship. The difference between these two definitions is studied in this paper introducing a "general model." With this model the entire beam is modeled through a succession of blocks divided by flexural cracks taking into account the bond between steel and concrete. Due to the practical impossibility of univocal definition of the crack pattern evolution, it is proposed to use a "range model." This "range," delimited by the curves of maximum and minimum deformability, includes the moment-curvature relationship (locals and average) obtained from all possible crack patterns.
The HADES spectrometer and a time-of-flight detector based on long-sized (50–250 cm) scintillation counters are described. The detector is designed for identification of electrons, pions, and protons ...with momenta of 0.1–1.5 GeV/c at a flight distance of 220–250 cm. The operating conditions are analyzed, and the requirements to the detector and counter design are formulated. The design of the counters and their arrangement in the spectrometer are considered. The results of experimental studies of such characteristics of long counters as the light attenuation length in a scintillator and temporal and spatial resolutions, dependeing on the location of the point of the particle’s hit on the counter, are presented. Analysis of the data has shown that the main factor determining the spatial resolution of long counters is the quality of the polishing of the side faces of the scintillators, which determines the effective (averaged over the scintillator side surfaces) coefficient of total internal reflectionR. It is shown that, forR>-0.99, it is quite possible to achieve temporal and spatial resolutions of 100 ns and 2–3 cm, respectively, for scintillators with a length of up to 250 cm and a cross section of 1–20 cm2. Foreign and Russian photomultipliers were used in the counters.
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