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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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Global air quality and climate 总被引:1,自引:0,他引:1
AM Fiore V Naik DV Spracklen A Steiner N Unger M Prather D Bergmann PJ Cameron-Smith I Cionni WJ Collins S Dalsøren V Eyring GA Folberth P Ginoux LW Horowitz B Josse JF Lamarque IA Mackenzie T Nagashima FM O'Connor M Righi ST Rumbold DT Shindell RB Skeie K Sudo S Szopa T Takemura G Zeng 《Chemical Society reviews》2012,41(19):6663-6683
Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH(4)), ozone precursors (O(3)), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O(3) precursor CH(4) would slow near-term warming by decreasing both CH(4) and tropospheric O(3). Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NO(x)) emissions, which increase tropospheric O(3) (warming) but also increase aerosols and decrease CH(4) (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH(4) volatile organic compounds (NMVOC) warm by increasing both O(3) and CH(4). Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O(3) and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O(3) and SOA. 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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