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241.
András Ványolos Balázs Dóra Attila Virosztek 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):643-645
We report of a theoretical study on quasi-one dimensional unconventional charge density wave (UCDW) driven by electron–phonon
interaction. Within mean field theory, we find that the wavevector dependence of the coupling leads to a momentum dependent
single particle gap on the Fermi surface. The presence of small energy single particle excitations around the gap nodes significantly
changes the optical conductivity compared to the conventional CDW result. In addition to that, the collective phase excitation
arising from fluctuation of the order parameter leads to further qualitative changes of the conductivity and results in an
effective mass that is nonmonotonic in temperature.
相似文献
242.
243.
Residual fracture energy of high-performance and normal concrete subject to high temperatures 总被引:2,自引:0,他引:2
Test data on the residual fracture energy of two significantly different concrete types are presented. About 80 beams of high
performance basalt concrete and ordinary gravel concrete have been tested in accordance with the RILEM work of fracture method.
The beams are heated at 1°C per minute up to a certain maximum temperature and kept at this temperature for 8 hours before
cooling them back to room temperature and testing in three-point bending.
The tests show that the two concretes behave almost identifical when the fracture energyG
F is considered as a function of maximum temperature. It is found that the damage introduced by a maximum temperature of 300
to 400°C increases the fracture energy by 50% compared with the reference tests at room temperature. A more tortuous crack
surface is one plausible explanation for the significant increase inG
F.
The article also presents temperature and weight loss recordings from the heating scenarios and finally, the characteristic
length and the cohesive tensile softening curve are shown to depend on the maximum temperature. Basically it is demonstrated
that the temperature exposure makes the concrete significantly more ductile.
Résumé Des données sur l'énergie résiduelle de rupture de deux bétons différents sont présentées. Environ 80 poutres de béton à base de basalte de très haute performance et de béton à base de gravier ordinaire ont été examinées conformément au travaux de la RILEM sur l'énergie de rupture. Les poutres sont chauffées à 1°C par minute jusqu'à une température maximale, puis maintenues à cette température pendant 8 heures avant d'être refroidies de nouveau à la température ambiante. Les poutres sont ensuite testées en flexion (système de flexion en trois points). Les essais prouvent que les deux bétons se comportent d'une manière presque identique quandG F est considéré comme une fonction de la température maximale. On peut aussi constater que le dommage occasionné par une température maximale de 300 à 400°C augmente l'énergie de rupture de 50% par comparaison aux essais de référence réalisés à la température ambiante. Une surface de rupture plus tortueuse semble être une explication plausible pour l'augmentation significative deG F. L'article présente également les évolutions de la température et de la perte de poids pour les scénarios de chauffage utilisés. En conclusion, cette étude montre que la longueur caractéristique et la courbe de post pic dépendent de la température maximale. Fondamentalement cela démontre que l'exposition à la température rend le béton sensiblement plus ductile.相似文献
244.
Guay Stéphane; Boisvert Jean-Marie; Freeston Mark H. 《Canadian Metallurgical Quarterly》2003,15(3):392
The goal of this study was to examine whether data from 3 different measures of communication (i.e., self-report, quasi-observational, and observational) can predict relationship adjustment and stability 1 year later when used conjointly in a sample of 62 young couples. The 3 measures of communication were the Communication Skills Test-Revised (CST-R), the Communication Box (CB), and the Demand/Withdraw Pattern Questionnaire (DWPQ). Through hierarchical multiple regression analyses, results revealed that the CST-R and the DWPQ predict both genders' relationship adjustment 1 year later when used conjointly. Logistic regression analyses revealed that none of the measures of communication significantly predicted relationship stability. In conclusion, the combination of the CST-R and the DWPQ appears to be useful for longitudinally predicting relationship adjustment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
245.
246.
Polycrystalline magnesium films were deposited under ultrahigh vacuum by thermal evaporation onto a cooled silica substrate. During the growth process of a film a number of lattice defects are incorporated. It was found that the defect density decreases with increasing thickness. An annealing study of the electrical resistance and defect density in magnesium films was made. The results were interpreted on the basis of Vand's theory. The function F0 expressing the law of distribution of the decay energies exhibited a maximum. For thick films there was no appreciable variation in the activation energy with thickness. In this case the evaluated activation energy E was found to be about 0.35 eV. For very thin films this energy decreases with increasing thickness. 相似文献
247.
The main purpose of the study reported here was to investigate the relative importance of complexity of syllable structure and task differences in measuring phonological awareness in low-literacy adults. This study is a replication of a study with children conducted by S. A. Stahl and B. A. Murray (1994). Results indicated that the complexity of syllable structure did indeed better describe the construct of phonological awareness in low-literacy adults. At the same time, the authors also found some differences in the pattern of literacy acquisition for their Spanish adults in comparison with child literacy acquisition in English. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
248.
Through two experiments, the study sought to emphasize the usefulness of the visual and kinesthetic imagery in mental practice. In Experiment 1, it was hypothesized that when the task to be learned through mental practice necessitates the reproduction of a form by drawing, the visual image, which provides a wide span of apprehension, is more suitable than the kinesthetic image. On the other hand, the kinesthetic image that supplies inputs from the muscles' positions and movements should be more appropriate for the acquisition of the duration of the drawing. In Experiment 2, it was hypothesized that the task, transformed into a motor task necessitating minute coordination of the two hands, would benefit more from kinesthetic imagery. To have optimal control over what was actually experienced during mental practice, the participants' imagery skills were measured. The participants also benefited from prior imagery training. The results demonstrate that when using mental practice to initially acquire a task, visual imagery is better for tasks that emphasize form while kinesthetic imagery is better for those tasks that emphasize timing or minute coordination of the two hands. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
249.
Nilgün Kzlcan Belks Ustamehmetolu Nesrin
z A. Sezai Sara Ahmet Akar 《应用聚合物科学杂志》2003,89(11):2896-2901
Soluble and processable conductive copolymers of silicone tegomers and pyrrole were developed. This was easily accomplished by the oxidative polymerization of pyrrole monomer by Ce(IV) salt in the presence of silicone tegomers with hydroxyl chain ends. The resulting copolymers were soluble in dimethylformamide. The products were characterized by Fourier transform infrared, 1H‐NMR, and four‐point probe conductivity, and their surface properties were investigated with contact‐angle measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2896–2901, 2003 相似文献
250.
In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within
the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour;
the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian
(ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several
representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental
data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle
with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks
to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present
spurious oscillations.
Received: 20 March 2002 / Accepted: 15 October 2002
The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged. 相似文献