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1.
Phase-relations in the Cu-Se system were determined by evacuated silica-tube experiments. The phase diagram up to 1100° C was obtained from the results of differential thermal analyses of pure compounds and of their mixtures. The phases in the system are: Cu2Se — undergoes a polymorphic transformation at 150° C. The symmetry of the low temperature form is not yet known. The high form is cubic with a fluorite-type structure. Cu2–xSe — cubic, with x variable in a very narrow range, at room temperature. Cu3Se2 — tetragonal, breaks down to Cu2–xSe and CuSe at 150° C. CuSe — hexagonal below 60° C and, presumably, orthorhombic at higher temperature, melts incongruently at 387° C to Cu2–xSe and a Se-rich liquid. CuSe2 — orthorhombic, melts incongruently at 347° C to CuSe and a Se-rich liquid. The presence of an eutectic at 523° C was inferred from differential thermal heating and cooling curves.
Zusammenfassung Die Phasenbeziehungen im Cu-Se System wurden durch Versuche mit Hilfe evakuierter Quarzampullen bestimmt. Bis zu 1100° C wurden die Ergebnisse der Differential-Thermoanalyse verwendet. Die Phasen im System sind: Cu2Se: wandelt sich bei 150° C polymorph um. Die Symmetrie der Tieftemperaturform ist noch nicht bekannt, während die Hochtemperaturform kubisch ist (Flusspatstruktur). Cu2–xSe (kubisch) hat bei Raumtemperatur einen sehr kleinen x-Wert. Cu3Se2 (tetragonal) spaltet sich bei 150° C zu Cu2–xSe und CuSe. CuSe (hexagonal) ist unterhalb 60° C vermutlich rhombisch und bei höherer Temperatur (387° C) zersetzt es sich inkongruent zu Cu2–xSe und einer Se-reichen Schmelze. CuSe2 (rhombisch) zersetzt sich bei 347° C inkongruent zu CuSe und einer Se-reichen Schmelze. Die Anwesenheit eines Eutektikum bei 523° C wird aufgrund von DTA-Analysen angenommen.相似文献
2.
Ferraro G Bernardini A David M Meyer-Roux S Muellenhoff O Perkovic M Tarchi D Topouzelis K 《Marine pollution bulletin》2007,54(4):403-422
Studies of operational pollution carried out by European commission - Joint Research Centre in the Mediterranean Sea for the years 1999-2004 are briefly introduced. The specific analysis of the Adriatic Sea for the same period demonstrates that this area has been characterized by a relevant number of illegal discharges from ships. After setting the historical background of the project AESOP (aerial and satellite surveillance of operational pollution in the Adriatic Sea), the content, partners and aim of the project are presented. Finally, the results of the first phase of the AESOP project are presented. The results seem very encouraging. For the first time in the Adriatic, real time detection of oil spills in satellite images and an immediate verification by the Coast Guard has been undertaken. An exploratory activity has also been carried out in collaboration with the University of Ljubljana to use automatic information system (AIS) to identify the ships detected in the satellite images. 相似文献
3.
M. G. Bernardini F. Xie P. Sizun F. Piron Y. Dong J.-L. Atteia S. Antier F. Daigne O. Godet B. Cordier J. Wei 《Experimental Astronomy》2017,44(1):113-127
SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade, capable to detect and localise the GRB emission, and to follow its evolution in the high-energy and X-ray domains, and in the visible and NIR bands. The satellite carries two wide-field high-energy instruments: a coded-mask gamma-ray imager (ECLAIRs; 4–150 keV), and a gamma-ray spectrometer (GRM; 15–5500 keV) that, together, will characterise the GRB prompt emission spectrum over a wide energy range. In this paper we describe the performances of the ECLAIRs and GRM system with different populations of GRBs from existing catalogues, from the classical ones to those with a possible thermal component superimposed to their non-thermal emission. The combination of ECLAIRs and the GRM will provide new insights also on other GRB properties, as for example the spectral characterisation of the subclass of short GRBs showing an extended emission after the initial spike. 相似文献
4.
G. P.?Bernardini M.?Borgheresi C.?Cipriani F.?Di BenedettoEmail author M.?Romanelli 《Physics and Chemistry of Minerals》2004,31(2):80-84
A study on Zn replacement in sphalerite by divalent Mn has been performed by using EPR spectroscopy. Twelve natural and synthetic samples with different Mn-contents were selected for the spectroscopic investigation. The EPR spectra vary from an hyperfine sextet to a single broad line according to their Mn-content. Three components, attributed to Mn(II) in different chemical coordination (namely isolated ions, interacting ions, clusters) have been determined by means of spectral simulation. The variations of the EPR signals among the different spectra are due only to the mixing of these components, without any variation of each spectral parameter. Differing distribution of Mn(II) was, therefore, observed at a local scale. Consequently, the specific interactions driving the coalescence of Mn(II) ions to form clusters may be responsible for the banded pattern in sphalerite crystals. 相似文献
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6.
In extensive air shower (EAS) experiments, the primary direction is reconstructed by the space–time pattern of secondary particles. Thus the equalization of the transit time of signals coming from different parts of the detector is crucial in order to get the best angular resolution and pointing accuracy allowed by the detector. In this paper an off-line calibration method is proposed and studied by means of proper simulations. It allows to calibrate the array repeatedly just using the collected data without disturbing the standard acquisition. The calibration method is based on the definition of a Characteristic Plane introduced to analyze the effects of the time systematic offsets, such as the quasi-sinusoidal modulation on azimuth angle distribution. This calibration procedure works also when a pre-modulation on the primary azimuthal distribution is present. 相似文献
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8.
M. Borgheresi G. P. Bernardini C. Cipriani F. Di Benedetto M. Romanelli 《Mineralogy and Petrology》2005,85(1-2):3-18
Summary A minero-chemical and spectroscopic characterisation has been performed on a natural bornite sample from the Natural History
Museum of the University of Florence, through the use of EPMA, XRD, continuous-wave (cw) and pulsed EPR spectroscopy. The
use of different EPR techniques allowed to fully investigate the distribution and valence states of Cu and Fe and to study
the early oxidation products of bornite.
The microanalytical and XRD characterisation proved bornite to be homogeneous and stoichiometric. Cw-EPR measurements confirmed
the presence of Fe(III) as fundamental valence state in bornite; moreover, no evidence of Cu(II) as a bulk transient species,
due to a charge transfer process, has been revealed. The broadening of the Fe(III) EPR spectrum is ascribed to a partial transfer
of spin density from Fe(III) to the surrounding cationic sublattice.
In contrast, the pulsed EPR experiments, registered at 4.2 K, revealed the presence of both Fe(III) and Cu(II). These species
were supposed to be present at the early stage of the surface alteration. The data provided by the electron spin-echo decay
and modulation suggest both the oxidised Cu(II) and Fe(III) species to belong to premature surface water adducts (evidenced
by proton nuclear modulation), which may evolve to sulphate species. 相似文献
9.
Ghirlanda G. Salvaterra R. Toffano M. Ronchini S. Guidorzi C. Oganesyan G. Ascenzi S. Bernardini M. G. Camisasca A. E. Mereghetti S. Nava L. Ravasio M. E. Branchesi M. Castro-Tirado A. Amati L. Blain A. Bozzo E. O’Brien P. Götz D. Le Floch E. Osborne J. P. Rosati P. Stratta G. Tanvir N. Bogomazov A. I. D’Avanzo P. Hafizi M. Mandhai S. Melandri A. Peer A. Topinka M. Vergani S. D. Zane S. 《Experimental Astronomy》2021,52(3):277-308
Gamma-ray Bursts (GRBs) are the most powerful transients in the Universe, over–shining for a few seconds all other γ-ray sky sources. Their emission is produced within narrowly collimated relativistic jets launched after the core–collapse of massive stars or the merger of compact binaries. THESEUS will open a new window for the use of GRBs as cosmological tools by securing a statistically significant sample of high-z GRBs, as well as by providing a large number of GRBs at low–intermediate redshifts extending the current samples to low luminosities. The wide energy band and unprecedented sensitivity of the Soft X-ray Imager (SXI) and X-Gamma rays Imaging Spectrometer (XGIS) instruments provide us a new route to unveil the nature of the prompt emission. For the first time, a full characterisation of the prompt emission spectrum from 0.3 keV to 10 MeV with unprecedented large count statistics will be possible revealing the signatures of synchrotron emission. SXI spectra, extending down to 0.3 keV, will constrain the local metal absorption and, for the brightest events, the progenitors’ ejecta composition. Investigation of the nature of the internal energy dissipation mechanisms will be obtained through the systematic study with XGIS of the sub-second variability unexplored so far over such a wide energy range. THESEUS will follow the spectral evolution of the prompt emission down to the soft X–ray band during the early steep decay and through the plateau phase with the unique ability of extending above 10 keV the spectral study of these early afterglow emission phases.
相似文献10.
Enrico Quagliarini Gabriele Bernardini Chiara Wazinski Luca Spalazzi Marco D’Orazio 《Bulletin of Earthquake Engineering》2016,14(4):1071-1101
One of the most influencing elements in inhabitants’ earthquake safety definition is represented by the interactions between people and post-event environment in urban scenarios. Understanding and simulating rules for pedestrians’ motion in earthquake evacuation could be useful to inquire the risk assessment introducing the “human” factor influence: integrated “risk maps” could be realized by combining results of similar analyses with the traditional site hazard, buildings vulnerability and exposition indices. This work proposes an innovative approach based on the analysis of these interactions. Two experimentally-based activities are required: an analysis of human behaviors towards the post-earthquake environment; a relation for defining environmental modifications. Results firstly show a summary of man-environment interactions in earthquake evacuations. A possible criterion for path choice in evacuation is also numerically defined. A theoretical agent-based model is developed on these bases and summarizes phases, motion rules and man-environment interactions in earthquake pedestrians’ evacuation in urban scenarios. Secondly, quick criteria for scenario modifications involving ruins formation are proposed and evaluated: for each building, the percentages of internal and external ruins area is a function of its vulnerability and the expected earthquake Richter magnitude. Moreover, the external ruins formation criterion is validated by comparing predicted and effective values of ruins area depth in real cases. The model could be proposed as a tool for evaluating probable pedestrians’ choices in post-event scenarios, in order to reduce the interferences between the built environment and the evacuation process through interventions on buildings, urban fabric and strategies for emergency management. 相似文献