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排序方式: 共有779条查询结果,搜索用时 78 毫秒
1.
M. Calin H. Grahl M. Adam J. Eckert L. Schultz 《Journal of Materials Science》2004,39(16-17):5295-5298
In this work the Al85Ni9Nd4Co2 alloy was used as a starting point for examining the possibility of forming bulk glassy Al-based materials by combining rapid quenching and ball milling techniques. Fine glassy powders were obtained by ball milling melt-spun amorphous ribbons using a severe cryogenic processing regime. The thermal stability data of the powders as obtained by constant-rate heating and isothermal DSC experiments together with viscosity measurements are discussed with respect to feasible consolidation conditions. The powder compaction was done by two methods (uni-axial hot pressing and extrusion) at 513 K for up to 15 min. Only the uni-axial hot pressing led to bulk Al85Ni9Nd4Co2 samples with similar glassy structure and Vickers microhardness values comparable to those of the initial melt-spun ribbons. 相似文献
2.
A national survey of school psychologists' acceptability of psychological assessment techniques in the area of externalizing problem behaviors was examined. School psychologists' ratings of 2 procedures, Behavioral Assessment (BA) and Traditional Assessment (TA), were compared using an analog case study methodology. Using a random sample of 500 National Association of School Psychologists members from the 1991–1992 membership directory, 339 Ss completed the Assessment Rating Profile after reading a hypothetical case summary describing a student with suspected externalizing problem behaviors. Results indicated statistically significant differences between assessment methods and ratings of acceptability. BA procedures were found to be more acceptable than TA procedures. Implications related to the acceptability of psychological assessment techniques, as well as implications for school psychology practitioners are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Petr A. Nikrityuk Kerstin Eckert Roger Grundmann 《Metallurgical and Materials Transactions B》2006,37(3):349-359
This paper presents a numerical study of the Lorentz force and fluid flow induced by a rotating magnetic field in a medium
with a nonhomogeneous electric conductivity placed in a cylindrical vessel with insulated walls. The nonhomogeneity is modeled
by the presence of a solid and a liquid phase of different electrical conductivity. The solid phase is located orthogonally
to the axis of rotation, which corresponds to the case of unidirectional solidification. The simulations were performed for
different locations of the solid front and different ratios of the electrical conductivity, σ
s
/σ
l
=0.2... 10. Here σ
s
and σ
l
are the electric conductivity of the solid and liquid phases, respectively. The results showed that the difference between
electrical conductivity of solid and liquid phases has a noticeable effect on the mean-time Lorentz force and the velocity:
namely, the presence of the solid phase (σ
s
>σ
l
) leads to an increase of the Lorentz force and fluid flow in the cylinder. 相似文献
4.
V. V. Tcherdyntsev S. D. Kaloshkin A. I. Salimon E. A. Leonova I. A. Tomilin J. Eckert F. Schurack V. D. Rogozin S. P. Pisarev Yu. P. Trykov 《Materials and Manufacturing Processes》2002,17(6):825-841
Al-Cu-Fe alloys were prepared from elemental powders in a high-energy planetary ball mill. A sequence of solid state reactions resulting in quasicrystal (QC) phase formation takes place during heating of the as-milled powder. These reactions were studied by both differential scanning calorimetry and x-ray diffraction methods. Mechanically alloyed powders were consolidated by cold and hot pressing, as well as by explosive compaction. After annealing at sufficiently high temperatures, the consolidated samples are single-phase QC, except the ones consolidated by explosion. The high reactivity of the as-milled alloys causes the appearance of high porosity of the consolidated samples after the annealing. 相似文献
5.
J. Granacher R. Tscheuschner K. Maile W. Eckert 《Materialwissenschaft und Werkstofftechnik》1993,24(10):367-377
Long Term Creep Crack Behaviour of Typical Power Plant Steels The creep crack behaviour of the steels was investigated in a wide loading range up to a test duration of 40 000 h and down to a creep crack growth rate of 2 · 10?5 mm/h with specimens of different shape and size. For steels of type l%Cr-l%Mo-0.6%Ni-0.3%V, 1%Cr-0.9%Mo-0.7%Ni-03.%V, 12%Cr-1%Mo-0.3%V-0.22%C and 12%Cr-l%Mo-0.3%V-0.20%C tested at 550°C, the creep crack growth rate could be described by the parameter C2* with significantly smaller scatter bands than by the parameter C1* or the stress intensity factor KI. For steel 12%Cr-2%Ni-1%Mo tested at 450°C, parameter KI leads to the smallest scatter band. The creep crack initiation can be described in a two-criteria diagram based on nominal stress and stress intensity factor. However the method is assumed to be over-conservative in case of increasing specimen size. As a result of several aperiodic creep fatigue crack tests, precracking under fatigue conditions gave a weak increase of the creep crack growth rate whereas by precracking under creep conditions the fatigue crack rate was strongly decreased. 相似文献
6.
The fluctuations observed by recording the picosecond pulses of a mode-locked laser with a synchroscan streak camera are due to the laser jitter and to the variations of the zero crossing of the synchronization. By means of a simple model, it is shown that the dispersions measured when the synchronization is generated from the mode-locker oscillator reflect the instantaneous time phase fluctuations of this oscillator. From the study of the experimental recordings with methods of time series analysis it results that the phase noise of the electronic oscillator is consistent with an underlying low-dimensional strange attractor. 相似文献
7.
Discusses the generalization effects of 7 commercially available student social-skills training (SST) curricula. A table listing strategy, curricula, S characteristics, and results is given. Maintenance of improved behavior was seen as least successful when the "train and hope" strategy was used. The combination of SST and alteration of consequences in the classroom led to the most significant maintenance of results. The most effective programs were those that combined a variety of techniques. Improvement of behavior was obtained more often with withdrawn students than with aggressive students. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
The macroscopic deformation behavior of a fiber-reinforced aluminum-boron composite is investigated. Different periodic and random arrangements of the microstructure are considered with macroscopic hardening behavior due to the evolution of plastic zones on the microscale being taken into account.
For the solution of the initial boundary value problem, a non-standard algorithm is applied. It consists of the direct solution of the whole set of equations, treating all variables as global quantities. Together with a higher order time integration method (BDF2), an automatic step size control is used in the FEM calculations. 相似文献
10.