1,721,064 research outputs found
Dose-rate dependence of swelling and damage in ion-irradiated nickel
No full textThe results of an irradiation experiment using 46 MeV Ni6+ ions from the Variable-Energy Cyclotron facility in Harwell are presented. The doserate was varied, at a constant total dose, by a factor of 20 and the damage produced examined in the peak region of damage and at smaller depths. The temperature range 450–700°C was investigated. It was found that the temperature dependence of swelling varies with both the doserate and the dose
Local Antiferromagnetic Ordering in Ferromagnetic MnPt_{3} Alloys near the Stoichiometric Composition
No full textThe magnetic-moment density distribution in two alloys near the stoichiometric MnPt3 alloy composition has been measured by means of the polarized-neutron technique. It has been found that in the perfectly ordered lattice Mn and Pt atoms are ferromagnetically aligned, while in the presence of disorder the Mn atoms which happen to occupy the Pt sites give a negative contribution to the magnetization. The spherically averaged distribution for Mn atoms is independent of whether the atom is on a Mn or Pt site. However, Mn atoms on Mn sites are spherically symmetric, while Mn atoms on Pt sites have aspherical distributions
Concentration dependence of the phonon dispersion relations in substitutional fcc Co-Ni alloys
No full textThe concentration dependence of the phonon dispersion relations in fcc Co-Ni alloys have been determined by means of triple-axis spectrometry. Appreciable wave-vector-dependent frequency changes from pure Ni have been observed in this alloy system where practically no mass disorder is present because of the near-equal average mass of the costituents. The observed frequency shifts are discussed in connection with other experiments in similar alloy systems and with some estimates based on existing theories
Magnetic-moment distribution in ferromagnetic Fe-Cr alloys
No full textThe magnetic-moment distribution in disordered ferromagnetic bcc Fe3Cr has been determined by polarized-neutron diffraction. The measured magnetic structure factors, when compared with those of pure Fe obtained by Shull and co-workers and those for a Fe-Cr alloy of slightly smaller Cr content measured by Lander and Heaton, show an appreciably smaller asphericity. The composition dependence of the asphericity has been compared both with a localized-electron model and with calculations based on the coherent-potential approximation (CPA). The concentration dependences of the total spin magnetic moments, of the difference between the magnetic moments of the constituents, and of the density of states at the Fermi level are also compared with the CPA calculations. It is shown that the theory is able to reproduce the general trend of the experimental data in these alloys
Распределение магнитного момента в Fe−Ni сплавах. Эксперимент и вычисления
No full textThe magnetic structure factors of several ferromagnetic f.c.c. Fe−Ni alloys have been recently determined by means of the polarized-neutron technique in this and other laboratories. The amount of asphericity for each composition as determined by the population of thee g -sublevel was obtained from these measurements and these results are compared with a simple localized-electron model and with the predictions of coherent-potential approximation calculations. The agreement with these calculations is satisfactory
Indication of an electron redistribution in the d band of Fe alloyed with Si
No full textTwo alloys of the Fe-Si system have been investigated by means of polarised neutron diffraction: a 7.5 at.% Si alloy and a 14.3 at.% Si alloy. The alloy of higher Si content showed some long-range order. For Fe925Si75 both the spherical and aspherical form factors were found to be equal within errors to those of pure Fe; for Fe857Si143 the magnetic moments and form factors were obtained for the three different sites. The Si site was found to have a form factor very different from that of pure Fe. The authors discuss these results and show that they are probably due to the contribution of the electrons at the bottom of 3d band states of Fe atoms when they occupy the Si site
Hydrogen distribution in ice Ih
No full textNeutron scattering has been used to measure in ice Ih both the coherent scattering (D2O ice) and the incoherent scattering (H2O ice) in order to examine the nature of the disorder of the hydrogen in this system. The incoherent scattering has proved to be essentially elastic within experimental accuracy and to be Q-dependent after correction for the temperature factor. The coherent diffraction has shown the presence of a substantial contribution of Q-dependent diffuse scattering. Interpretation of the results of these determinations indicates that the hydrogen (or deuterium) atoms are in well defined positions along the H-bonds, that is the wavefunction is localised on one of the two possible sites along the bond. Moreover at low temperature tunnelling occurs to the other equilibrium position along the H-bond
Collective excitations in the liquid and amorphous state of D2O with soluted NaOD
No full textA triple-axis neutron spectrometer was used to investigate the scattering function of a 15 M NaOD solution in D2O. The solute acts as an amorphising agent, so that both the liquid and amorphous phases could be studied by changing the temperature from 300 K to 77 K. The experiment was directed to the study of the collective excitations. A dispersion relation could be established in both phases in the momentum range 0.4≤Q≤2.4Å−1 that was investigated in the experiment, though at the higherQ values the excitation energy width was found to be comparable to the energy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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