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71.
The effect of spatial resolution and experimental noise on the kinematic fine-scale features in shear flow turbulence is investigated
by means of comparing numerical and experimental data. A direct numerical simulation (DNS) of a nominally two-dimensional
planar mixing layer is mean filtered onto a uniform Cartesian grid at four different, progressively coarser, spatial resolutions.
Spatial gradients are then calculated using a simple second-order scheme that is commonly used in experimental studies in
order to make direct comparisons between the numerical and previously obtained experimental data. As expected, consistent
with other studies, it is found that reduction of spatial resolution greatly reduces the frequency of high magnitude velocity
gradients and thereby reduces the intermittency of the scalar analogues to strain (dissipation) and rotation (enstrophy).
There is also an increase in the distances over which dissipation and enstrophy are spatially coherent in physical space as
the resolution is coarsened, although these distances remain a constant number of grid points, suggesting that the data follow
the applied filter. This reduction of intermittency is also observed in the eigenvalues of the strain-rate tensor as spatial
resolution is reduced. The quantity with which these eigenvalues is normalised is shown to be extremely important as fine-scale
quantities, such as the Kolmogorov length scale, are showed to change with different spatial resolution. This leads to a slight
change in the modal values for these eigenvalues when normalised by the local Kolmogorov scale, which is not observed when
they are normalised by large-scale, resolution-independent quantities. The interaction between strain and rotation is examined
by means of the joint probability density function (pdf) between the second and third invariants of the characteristic equation of the velocity gradient tensor, Q and R respectively and by the alignments between the eigenvectors of the strain-rate tensor and the vorticity vector. Gaussian
noise is shown to increase the divergence error of a dataset and subsequently affect both the Q–R joint pdf and the magnitude of the alignment cosines. The experimental datasets are showed to behave qualitatively similarly to the
numerical datasets to which Gaussian noise has been added, confirming the importance of understanding the limitations of coarsely
resolved, noisy experimental data. 相似文献
72.
73.
L. O. Buxton B. A. Dombrow D. M. Hegsted J. W. Porter W. H. Peterson A. Kienle A. Morgen C. Beger F. Westhauser J. Featherstone und F. Tanassijenko 《Fresenius' Journal of Analytical Chemistry》1941,121(3-4):150-152
Ohne Zusammenfassung 相似文献
74.
75.
From polymer gels to cytoskeletal structures, random networks of elastic material are commonly found in both materials science and biology. We present a three-dimensional micromechanical model of these networks and identify a "bending-to-stretching" transition. We characterize this transition in terms of concentration scaling laws, the stored elastic energy, and affinity measurements. Understanding the relationship between microscopic geometry and macroscopic mechanics will elucidate, for example, the mechanical properties of polymer gel networks or the role of semiflexible network mechanics in cells. 相似文献
76.
In this paper, by using the continuation theorem of coincidence degree theory and some analysis methods, we study a kind of periodic solutions to p-Laplacian neutral functional differential equation with a deviating argument,some new results on the existence of periodic solutions is obtained. 相似文献
77.
Cobranchi DP Botelho M Buxton LW Buck RC Kaiser MA 《Journal of chromatography. A》2006,1108(2):248-251
Two distinctly different capillary gas chromatographic methods were used to determine the vapor pressure of 8-2 fluorotelomer alcohol (8-2 FTOH) and 1-H perfluoroheptane at several temperatures. For measurements employing the relative retention-time method, a short polymethylsiloxane column was used from 25 to 65 degrees C. For the 8-2 FTOH, hydrocarbon alcohols and perfluoroalcohols were used as reference standards. For 1-H perfluoroheptane, hydrocarbons were used as reference standards. Vapor pressure estimates could differ by as much as an order of magnitude compared to published results determined by other (nonchromatographic) methods. This variance may be a function of solvent-solute interactions within the gas chromatographic column and the infinite dilution assumption, both used in the relative retention method. For comparison, data were also gathered using headspace gas chromatography (GC) with atomic emission detection (AED). The results from this novel GC/AED method were consistent with prior nonchromatographic results. A discussion of why headspace is the preferred technique for the determination of vapor pressure for fluorinated compounds is presented. 相似文献
78.
利用有限域上奇异伪辛几何构作了一个新的具有仲裁的认证码,计算了这个码的参数,当发方编码规则和收方解码规则按等概率分布选取时,计算出各种攻击成功的概率. 相似文献
79.
Verheijen JC Deiman BA Yeheskiely E van Der Marel GA van Boom JH 《Angewandte Chemie (International ed. in English)》2000,39(2):369-372
The introduction of a urea bond linking a protected diethylenetriamine (DETA) unit and the terminal amino group of a resin-bound peptide nucleic acid (PNA) decamer gave access to a PNA - DETA adduct (shown here), which hydrolyzed the target 25-mer RNA rapidly and sequence specifically. 相似文献
80.