Abstract
The recently coupled INDRA-FAZIA apparatus offers unique opportunities to investigate heavy ion collisions at Fermi energies by combining the optimal identification capabilities of FAZIA and ...the large angular coverage of INDRA. We present a selection of the results of the analysis of the first experimental campaign performed with INDRA-FAZIA, in which the four reactions
58,64
Ni+
58,64
Ni have been studied at two different beam energies (32 and 52 MeV/nucleon) in the intermediate energy regime. The present work is focused on the isospin diffusion effects in semiperipheral and peripheral collisions. A stronger isospin equilibration is found at 32 MeV/nucleon than at 52 MeV/nucleon, as expected due to a shorter projectile-target interaction time in the latter case.
In this paper the technological aspects of the FAZIA array will be explored. After a productive commissioning phase, FAZIA blocks started to measure and give very useful data to explore the physics ...of Fermi energy heavy-ion reactions. This was possible thanks to many technical measures and innovations developed in the commissioning phase and tuned during the first experimental campaigns. This paper gives a detailed description of the present status of the FAZIA setup from the electronic and mechanical point of view, trying also to trace a path for new improvements and refinements of the apparatus.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In the last few years the FAZIA
1 collaboration has been investigating the properties of silicon detectors – in particular the crystal orientation and resistivity non-uniformity – in order to better ...pin down the detector characteristics that influence their performances for particle identification using
Δ
E
−
E
and Pulse Shape Analysis (PSA) techniques. In this paper we present the first particle identification results obtained with detectors selected for good resistivity uniformity and using a “non-channeled” configuration. A new digital electronics was also designed for the R&D phase of FAZIA and was tested under beam for the first time. A quantitative procedure to measure the observed performances is applied in order to quantify the particle identification thresholds. Particle identification thresholds of
∼
2.5
AMeV
for
Z
∼
3
–
10
have been reached with the studied reaction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The kinetics of P incorporation during Ni–P electrodeposition was investigated by means of interfacial pH measurements, cathodic polarization curves and electrochemical impedance spectroscopy. This ...process is strongly affected by solution pH. A buffering effect provided by sodium hypophosphite in the solution was observed at pH 1.5. By contrast, at pH 4.0, this effect was not observed and an increase in the degree of alkalination at the interface was verified. At pH 1.5, Ni
2+ reduction was strongly disfavored during Ni–P deposition. The impedance measurements indicated that the mechanism of Ni deposition was modified by the presence of NaH
2PO
2·H
2O in the solution. The characteristic time constants for the individual cathodic processes, H
+, Ni
2+ and NaH
2PO
2 reduction, could be identified during Ni–P electrodeposition. Moreover, at pH 4.0, Ni–P deposition occurs by means of a different mechanism than that observed at pH 1.5. These findings cannot be described by any of the models for Ni–P electrodeposition found in literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The 19F(p, α0)16O reaction at low energies plays an important role in fundamental physics. In particular in nuclear astrophysics it represents, together with the 19F(p, γ)20Ne reaction, the crossing ...point between the CNO and the NeNa cycles in stars. Further, in hydrogen-rich stellar environments, it is the most important fluorine destruction channel. In this paper we report new measurements on the 19F(p, α0)16O reaction at deeply sub-Coulomb energies (0.2–0.6 MeV), a region where, despite the key role of this reaction, very few and old data are reported. The deduced astrophysical S-factor is ≈1.5–2 times larger than currently adopted extrapolations with possibly important astrophysical consequences.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Zn–Ni–P and Zn–Fe–P alloys were electrodeposited on carbon steel plates and their morphology, composition and structure were evaluated as a function of electrolyte composition and pH. A mutual ...inhibitory effect between Zn and P co-deposition was observed. Amorphous alloys were only obtained with high Ni or Fe contents. Conversely, crystalline alloys presented high Zn contents. From this preliminary analysis electrodeposition conditions were selected to produce P-containing alloy coatings. Their corrosion properties were evaluated by means of a cyclic corrosion test in comparison with the corresponding P-free alloy coatings with and without an epoxy painting system. Crystalline Zn–Ni–P presented a remarkable performance, due to morphology changes in the alloy as a result of the effects of P compounds in the electrolyte. This alloy efficiently avoided corrosion propagation around an intentional defect in the painting layer. The corrosion behavior of amorphous Zn–Fe–P was similar to Zn–Fe. On the other hand, crystalline Zn–Fe–P presented the fastest corrosion rate. Corrosion propagation around the painting defect was better held by amorphous Zn–Fe–P due to an improved adhesion between painting and alloy layers. The presence of P in Zn alloys may effectively improve their anticorrosive properties. However, this phenomenon seems to be beyond the simple amorphism of the deposit.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The 802.11 DCF protocol was devised to achieve per-station fairness; conversely, an harsh per-station unfairness occurs when DCF is loaded by TCP traffic. We aim at extending theoretical knowledge on ...this fairness issue and at restoring per-station fairness. The contribution of the paper is threefold. First, we introduce two findings: (i) changing the physical transmission rate of the stations does not impact the per-station fairness; (ii) packet queuing occurs in the uplink buffer of a station and has a non-negligible impact on the fairness. Second, we derive a model for evaluating fairness performance. Our model accounts for the effect of several parameters and scenarios that no other model captures in a single analytic framework. Third, and finally, we propose a technique to enforce fairness, which is easy to deploy in real systems, without having to modify existing devices. Experimental results obtained with commercial devices confirm the validity of our solution and findings. Albeit the focus of this paper is on per-station (throughput) fairness, our technique can be easily modified, e.g. to enforce time-based fairness, or per-direction or per-flow fairness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We discuss new results concerning the investigation of the 19F(p,α0)16O reaction at very low energies (0.6-0.2 MeV). This reaction is important both in Nuclear Astrophysics, because it closes the ...CNOF cycle and it is an important fluorine destruction channel in hydrogen rich stellar environments, and in Nuclear Structure, because it allows to study the spectroscopy of the self-conjugated 20Ne compound nucleus. Despite its importance, very few direct data have been published at low energies in the literature. Our work allowed to deduce the S-factor down to ≈ 0.2 MeV and to point out the role played by broad resonances at low energies. The experimental S-factor is ≈1.5-2 times larger than non-resonant extrapolations reported by nacre with potentially important astrophysical consequences.
In this paper, we study the problem of maintaining fairness for TCP connections in wireless local area networks (WLANs) based upon the IEEE 802.11 standard. Current implementations of 802.11 use the ...so-called distributed coordination function (DCF), which provides similar medium access priority to all stations. Although this mode of operation ensures fair access to the medium at the MAC level, it does not provide any provisions for ensuring fairness among the TCP connections. TCP unfairness may result in significant degradation of performance leading to users perceiving unsatisfactory quality of service. We propose and analyze two solutions that are capable of enabling TCP fairness with minimal additional complexity. The proposed solutions are based on utilizing a rate-control mechanism in two modes: static or adaptive. They do not require modifying existing standards at the MAC or network layers. Hence, they are fully compatible with existing devices. Our performance analysis results prove the efficaciousness of our proposed solutions in achieving TCP fairness compared to existing approaches. We have, also, implemented the proposed solutions in an ad-hoc experimental test-bed, and performed measurements to demonstrate the validity of our approach and results
FAZIA front-end electronics Salomon, F.; Edelbruck, P.; Brulin, G. ...
EPJ Web of Conferences,
01/2015, Volume:
88
Journal Article, Conference Proceeding
Peer reviewed
Open access
FAZIA is a multi-detector specifically designed to optimize ion identification in heavy-ion experiments. Its electronic is fully digital; it was designed in the laboratories of the collaboration. ...This paper presents the front-end part of this electronic.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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