Experimental investigations static coefficient of friction in lubricated conditions and pre-heating of the sample pin at high temperatures is discussed in this paper. The static coefficient of ...friction was measured in the sliding steel copper pins per cylinder of polyvinylchloride. Pins are previously heated in a special chamber from room temperature to a temperature of 800 oC with a step of 50 °C. Tribological changes in the surface layer of the pins caused by pre-heating the pins at high temperatures and cooling systems have very significantly influenced the increase in the coefficient of static friction. The results indicate the possibility of improving the friction characteristics of metal materials based on their thermal treatment at elevated temperatures.
The observational {sup 19}F abundance in stellar environments systematically exceeds the predicted one, thus representing one of the unsolved challenges for stellar modeling. It is therefore clear ...that further investigation is needed in this field. In this work, we focus our attention on the measurement of the {sup 19}F(α,p){sup 22}Ne reaction in the astrophysical energy range, between 0.2 and 0.8 MeV (far below the Coulomb barrier, 3.8 MeV), as it represents the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct measurements is ∼0.66 MeV, covering only the upper tail of the Gamow window, causing the reaction-rate evaluation to be based on extrapolation. To investigate lower energies, the {sup 19}F(α,p){sup 22}Ne reaction has been studied by means of the Trojan horse method, applied to the quasi-free {sup 6}Li({sup 19}F,p{sup 22}Ne){sup 2}H reaction at E {sub beam} = 6 MeV. The indirect cross section of the {sup 19}F(α,p){sup 22}Ne reaction at energies ≲1 MeV was extracted, fully covering the astrophysical region of interest and overlapping existing direct data for normalization. Several resonances have been detected for the first time inside the Gamow window. The reaction rate has been calculated, showing an increase up to a factor of 4 with respect to the literature at astrophysical temperatures. This might lead to potential major astrophysical implications.
Clusters in neutron-rich light nuclei Jelavić Malenica, D.; Milin, M.; Di Pietro, A. ...
EPJ Web of Conferences,
01/2016, Letnik:
117
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly ...simple for investigations of α-particle clustering (because α-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay.
The
6He+
12C elastic and inelastic scattering and the
6He+
12C→
α+
14C reaction have been measured using a 18.0 MeV
6He beam. Experimental results for the elastic scattering are in fair agreement ...with optical model predictions, using the potentials found in the analysis of
6Li scattering on
12C at similar energies. In triple coincidences, the
6He+
12C→
10Be+2
α reactions were clearly seen, with the
10Be nucleus left in ground and several excited states. The dominant mechanism of this reaction is sequential decay through cluster states of
14C.
This paper is analyzing the impact of the construction element position of ship winch drum on the effects of torque transmission by friction in the mechanization welding process. The driving and ...driven wheels (construction elements) were examined for the general case of the load distribution. Based on this examination, the construction of the device that should provide the reliable torque transmission and the movement of the drum in the process of its welding are proposed. This construction is characterized by a high level of flexibility and ability to change the friction torque based on changing drum position in regard to the driving and driven wheels (construction elements). With this new construction, problems related to the movement synchronization are avoided, unlike the all previously known constructions of this type, which lead to the positive impact on the wear intensity of friction gears.
The abundance of 19F in the universe is strictly related to standard and extra-mixing processes taking place inside AGB-stars, that are considered to be the most important sites for its production. ...Nevertheless the way in which it is destroyed is far from being well understood. For this reason we studied the 19F(α,p)22Ne reaction, that is supposed to be the main destruction channel in the Helium-rich part of the star. In this experiment, the reaction has been studied in the energy range of relevance for astrophysics (0÷1 MeV) via the Trojan Horse Method (THM), using the three-body reaction 6Li(19F,p22Ne)d.
.
The paper describes a few practical methods for the analysis of data obtained by standard thin-thick silicon detector telescopes used in nuclear reaction measurements. The addressed issues are: 1) ...improvement in double-sided silicon strip detector (DSSSD) calibration based on the fact that each event is registered twice, both in horizontal and vertical strips, 2) improvements in particle identification and 3) simplified mapping of the non-uniformity of the thin detector, without a dedicated measurement of the thickness. The proposed procedures are applied on experimental data obtained for 30MeV
7
Li beam induced reactions on LiF and C targets, studied with a detection setup consisting of four telescopes placed at different angles and distances. The proposed methods aim at quicker and more reliable calibration and particle identification.
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