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L. Seetha Lakshmi V Sridharan DV Natarajan V Sankara Sastry T S Radhakrishnan 《Pramana》2002,58(5-6):1019-1026
Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and
Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the
oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures
(T
p(ρ) and T
C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising
due to difference in the ionic radii between the substituent (r
M) and the Mn3+ ion (r
Mn
3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and
that of the neighboring Mn ion. 相似文献
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Richard DV. Espiritu Alberto V. AmorsoloJr. 《Journal of Thermal Analysis and Calorimetry》2012,107(2):483-487
Cu–Zn–Sn shape memory alloy strips with composition range of 13.70–46.30 mass% Sn were fabricated by electrodepositing Sn
on a shim brass surface and then subsequently annealed at a constant temperature of 400 °C for 120 min under flowing nitrogen.
Subjecting the Sn-plated strips to differential scanning calorimetry (DSC) analysis revealed that the austenitic start (A
s) temperature was essentially constant at 225 °C while the martensite start (M
s) temperature was consistently within the 221.5–222 °C interval. Austenite to martensite phase transformation showed two distinct
peaks on the DSC thermogram which can be attributed to the non-homogeneity of the bulk Cu–Zn–Sn ternary alloy. The latent
heats of cooling and heating were found to increase with the mass% Sn plated on the shim brass. Effect of annealing temperature
was also investigated wherein strips with an essentially constant composition of 26 mass% Sn were annealed at a temperature
range of 350–420 °C for 120 min under flowing nitrogen. Varying the annealing temperature has no significant effect on the
transformation temperatures of the ternary alloy. 相似文献
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Experimental observations of time-delay-induced amplitude death in two coupled nonlinear electronic circuits that are individually capable of exhibiting limit-cycle oscillations are described. The existence of multiply connected death islands in the parameter space of coupling strength and time delay for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds [Phys. Rev. Lett. 80, 5109 (1998); Physica (Amsterdam) 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay, and the onset of both in-phase and antiphase collective oscillations. 相似文献
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Experiments with reaction fronts (detonation waves and solidflames) reveal that, near the combustion limit, the fronts movein a spinning regime when localized zones of intensive reactiontravel along spiral trajectories. In the paper, the spinningwave is interpreted as an autosoliton and described phenomenologicallyby a nonlinear partial differential equation. The equation isstudied numerically, and the presence of the stable spinningand autosoliton solutions is shown. 相似文献
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We demonstrate the nonlinear recovery of diffused images in a self-focusing photorefractive medium. The method is based on the convolution property of nonlinearity, in which related modes reinforce each other as they propagate. The resulting mode coupling enables energy transfer from the scattered light to the underlying signal. The dynamics is well described by a model in which the signal seeds a modulation instability in the diffused background. 相似文献
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We demonstrate an all-optical bump-on-tail instability by considering the nonlinear interaction of two partially coherent spatial beams. For weak wave coupling, we observe momentum transfer with no variation in intensity. For strong wave coupling, modulations appear in intensity and evidence appears for wave (Langmuir) collapse at large scales. Borrowing plasma language, these limits represent regimes of weak and strong spatial optical turbulence. In both limits, the internal spectral energy redistribution is observed by recording and reconstructing a hologram of the evolving dynamics. The results are universal and can appear in any wave-kinetic system with short-wave-long-wave coupling. 相似文献
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