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This paper reports that the directional temperature is used to present a scheme for deducing the velocity of the reference frame where the black-body which produces the 2.7 K radiation background is at rest.The new renormalized relativistic thermodynamics lays the foundations of the method. 相似文献
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In this article we study the inverse problem of thermoacoustic tomography (TAT) on a medium with attenuation represented by a time-convolution (or memory) term, and whose consideration is motivated by the modeling of ultrasound waves in heterogeneous tissue via fractional derivatives with spatially dependent parameters. Under the assumption of being able to measure data on the whole boundary, we prove uniqueness and stability, and propose a convergent reconstruction method for a class of smooth variable sound speeds. By a suitable modification of the time reversal technique, we obtain a Neumann series reconstruction formula. 相似文献
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Benjamín Alemán Michael Rousseas Yisheng Yang Will Regan Michael Crommie Feng Wang Alex Zettl 《固体物理学:研究快报》2013,7(12):1064-1066
Graphene resonators are fabricated using a polymer‐free, direct transfer method onto metal reinforced holey carbon grids. The resonators are distinguished by the absence of organic residues and excellent crystallinity. The normal mode frequencies are measured using a Fabry–Perot technique; resonance curves indicate highly linear behaviour but very little built‐in strain, which is consistent with device geometry examined by atomic force microscopy. We conclude that the oscillators' restoring force is due instead to graphene's intrinsic bending rigidity; our measurements indicate a value of approximately 1.0 eV, consistent with previous theoretical and experimental work. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Archiv der Mathematik - In this note, we introduce a criterion to detect vanishing of essential algebras of a Green biset functor by means of morphisms. We introduce the inflation morphism and... 相似文献
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Structure elucidation of configurational isomers of nitrile‐substituted spirocyclopropyloxindoles by NMR spectroscopy,molecular modeling,and X‐ray crystallography 下载免费PDF全文
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Unambiguous and complete assignments of 1H and 13C NMR chemical shifts for five clerodane diterpenes, four of them isolated from Salvia splendens (salviarin, splendidin and splenolides A and B) and one obtained by acetylation of splenolide A, are presented. The assignments are based on 2D shift-correlated [1H,1H-COSY, 1H,13C-gHSQC-1J(C,H) and 1H,13C-gHMBC-nJ(C,H) (n=2 and 3)] and nuclear Overhauser effect (NOE) experiments. The conformation of the rings of these compounds is supported by the 3J(H,H) values and NOE results. 相似文献
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Benjamín M. Marín-Santibáñez José Pérez-González Lourdes de Vargas 《Rheologica Acta》2010,49(2):177-189
The nonlinear rheological behavior of short glass fiber suspensions has been investigated in this work by rotational rheometry
and flow visualization. A Newtonian and a Boger fluid (BF) were used as suspending media. The suspensions exhibited shear
thinning in the semidilute regime and weaker shear thinning in the transition to the concentrated one. Normal stresses and
relative viscosity were higher for the BF suspensions than for the Newtonian ones presumably due to enhanced hydrodynamic
interactions resulting from BF elasticity. In addition, relative viscosity of the suspensions increased rapidly with fiber
content, suggesting that the rheological behavior in the concentrated regime is dominated by mechanical contacts between fibers.
Visualization of individual fibers and their interactions under flow allowed the detection of aggregates, which arise from
adhesive contacts. The orientation states of the fibers were quantified by a second order tensor and fast Fourier transforms
of the flow field images. Fully oriented states occurred for shear rates around 20 s − 1. Finally, the energy required to orient the fibers was higher in step forward than in reversal flow experiments due to a
change in the spatial distribution of fibers, from isotropic to planar oriented, during the forward experiments. 相似文献
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Francisco Rodríguez-González José Pérez-González Lourdes de Vargas Benjamín M. Marín-Santibáñez 《Rheologica Acta》2010,49(2):145-154
The continuous extrusion of a metallocene linear low-density polyethylene through a transparent capillary die with and without
slip was analyzed in this work by rheometrical measurements and particle image velocimetry (PIV). For this reason, a comparison
was made between the rheological behaviors of the pure polymer and blended with a small amount of fluoropolymer polymer processing
additive. Very good agreement was found between rheometrical and PIV measurements. The pure polymer exhibited stick-slip instabilities
with nonhomogeneous slip at the die wall, whereas the blend showed stable flow. The slip velocity was measured directly from
the velocity profiles and was negligible for the pure polymer before the stick-slip but increased monotonously as a function
of the shear stress for the blend. The flow curves and the slip velocity as a function of the shear stress deviated from a
power law and were well fitted by continuous “kink” functions. Comparison of PIV data with rheometrical ones permitted a direct
proof of the basic assumption of the Mooney theory. Finally, the analysis of the velocity profiles showed that there is a
maximum in the contribution of slip to the average fluid velocity, which is interpreted as the impossibility for the velocity
profile to become plug like in the presence of shear thinning. 相似文献