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111.
Large vortices occurring in the axial plane of a self-similar axisymmetric turbulent jet are educed by spatially filtering
PIV data. First, the instantaneous PIV frame is convolved with a Gaussian kernel to obtain a smooth (low-pass) field. Next,
the low-pass field is Galilean transformed to expose the large vortices residing near the edges of the jet. Large vortices
tend to organize themselves in preferred modes; evidence of ring and helical modes is revealed by Galilean transformation
of the low-pass filtered field. Both modes seem to occur prominently in jets, with the helical mode being the more frequent.
The overall diameter of both ring and helical modes is comparable with the local jet width. The low-pass field occasionally
exhibits arrowhead shaped structures with large entrainment at their downstream tips. Stochastic estimates computed from the
Galilean-transformed low-pass filtered field indicate that jet meander and a sweep-in of ambient fluid are sufficient to reconstruct
large vortices. The frequency of occurrence of modes agrees with previously quoted results.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
112.
An amine mediated C-Cl bond activation process of the solvent chloroform has been explored by a coordinatively labile trinuclear Cu(II) complex, [Cu3(L1)2(MeOH)(H2O)] (1), derived from N-(3-tert-butyl-2-hydroxybenzylidene)-4,6-O-ethylidene--D-glucopyranosylamine (H3L1). The effect of activation is extremely high with methylamine, resulting in the formation of [Cu(MeNH2)5]Cl2 (2) and [Cu(L2)2] (3; HL2 = 2-tert-butyl-6-[(methylimino)methyl]phenol), however, under identical conditions it is moderate with ethylamine resulting in the isolation of crystals of the intermediate amine bound trinuclear copper(II) complex, [Cu3(L1)2(EtNH2)2(MeOH)2] (5), which was further converted into the mononuclear complex, [Cu(HL1)(EtNH2)] (6), in a novel crystal-to-crystal transformation. The successive isolation of the ethylamine-bound tri- and mononuclear complexes, 5 and 6, supported the occurrence of proton transfer reactions, which might be a key step in C-Cl bond activation. The primary and secondary amines, 2-aminomethylpyridine, N,N-dimethylethylenediamine, and 1,4,7-triazacyclononane, also having chelating features further enhance the rate of activation. No activation has been noted in the case of triethylamine and N,N,N,N-tetramethylethylenediamine. Formation of a carbene-trapped compound, 2,6-xylyl isocyanide, was confirmed in the reaction of complex 1 with 1,4,7-triazacyclononane and 2,6-xylidine in CHCl3, suggesting that the C-Cl bond cleavage led to the generation of dichlorocarbene. In addition, the mononuclear complex 6 has been transformed into a homotrinuclear complex [Cu3(L1)2(MeOH)2] by treatment with Cu(II) ions in MeOH/CHCl3, suggesting the possibility that the former could be regarded as a suitable metalloligand for heterotrimetallic complex synthesis. 相似文献
113.
114.
Shih PI Chiang CL Dixit AK Chen CK Yuan MC Lee RY Chen CT Diau EW Shu CF 《Organic letters》2006,8(13):2799-2802
[reaction: see text] A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and FIrpic as the guest. 相似文献
115.
Jain AN 《Current protein & peptide science》2006,7(5):407-420
Virtual screening by molecular docking has become established as a method for drug lead discovery and optimization. All docking algorithms make use of a scoring function in combination with a method of search. Two theoretical aspects of scoring function performance dominate operational performance. The first is the degree to which a scoring function has a global extremum within the ligand pose landscape at the proper location. The second is the degree to which the magnitude of the function at the extremum is accurate. Presuming adequate search strategies, a scoring function's location performance will dominate behavior with respect to docking accuracy: the degree to which a predicted pose of a ligand matches experimental observation. A scoring function's magnitude performance will dominate behavior with respect to screening utility: enrichment of true ligands over non-ligands. Magnitude estimation also controls pure scoring accuracy: the degree to which bona fide ligands of a particular protein may be correctly ranked. Approaches to the development of scoring functions have varied widely, with a number of functions yielding similarly high levels of performance relating to the location issue. However, even among functions performing equally well on location, widely varying performance is observed on the question of magnitude. In many cases, performance is good enough to yield high enrichments of true ligands versus non-ligands in screening across a wide variety of protein types. Generally, performance is not good enough to correctly rank among true ligands. Strategies for improvement are discussed. 相似文献
116.
An electric-field poling process was established that yielded uniform periodically poled lithium niobate (PPLN) in 0.5 mm
thick lithium niobate substrate. We have fabricated 50 mm long fanned as well as multigrating PPLNs having period variations
from 25 μm to 32 μm. These PPLNs are required for quasi-phase-matched (QPM) optical parametric oscillator (OPO) applications.
We have also configured a bench-top OPO set-up based on these PPLNs. 相似文献
117.
Einstein-Rosen inflationary Universe is investigated in the presence of massless scalar field with a flat potential. To get
an inflationary Universe, we have considered a flat region in which the potential V is constant. Some physical properties of the model are discussed. 相似文献
118.
The Squeezing and sub-poissonian photon statistics of an optical field are a purely quantum mechanical phenomenon and has
been accepted as means of achieving noise below the quantum shot-noise limit. The effect of higher-order squeezing and sub-poissonian
nature of an optical field in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper Raman scattering
(CAHRS) are investigated under short-time approximation. The coupled Heisenberg equations of motion involving real and imaginary
parts of the quadrature operators are established and solved under short-time scale. The dependence of squeezing on the number
of photons is also investigated. It is also shown that higher-order squeezing allows a much larger fractional noise reduction
than lower-order squeezing. The occurrence of amplitude squeezing effects of the radiation field in the fundamental mode is
investigated in both the processes. The present work shows that squeezing is greater in CAHRS than the corresponding squeezing
in CARS. It is also shown that squeezing is greater in stimulated process than corresponding squeezing in spontaneous interaction.
The conditions for obtaining maximum and minimum squeezing are obtained. The photon statistics of the pump mode in the processes
has also been investigated and found to be sub-poissonian in nature. 相似文献
119.
In this paper, simulative analysis of 40 Gb/s long haul (500-2000 km) DWDM system with ultra high capacity upto 1.28 Tb/s has been carried out for carrier-suppressed return-to-zero (CSRZ), duobinary return-to-zero (DRZ) and modified duobinary return-to-zero (MDRZ) modulation formats. The DWDM system has been analyzed for the pre, post and symmetrical dispersion compensation schemes for 16 Channels with 25 GHz channel spacing in order to find the optimum modulation format for a high bit rate optical transmission system. The effect of variation in input power and transmission distances is observed in terms of Q value and eye opening for various formats. It is found that symmetrical compensation is superior to pre and post dispersion compensation schemes. It has also been observed that the performance of DWDM system is severely limited by the four-wave mixing (FWM) effect and is determined that MDRZ format seems to be the best choice for the transmission distance beyond 1550 km despite slightly more complex transmitter and receiver configuration. Further, symmetrical compensation scheme has been investigated for 32×40 Gb/s MDRZ format for faithful transmission over 1450 km. 相似文献
120.
Vivek V Rane 《Proceedings Mathematical Sciences》2018,128(2):19
For a Dirichlet character modulo an integer \(q\ge 3\), we use a highly simple elementary method to give an asymptotic formula for \(\sum _{\chi \ne \chi _0 ({\bmod q})} {|L(1, \chi )|^{4}} ,\) where \(\chi _0 ({\bmod \, q})\) is the principal character. This result seems to be new. 相似文献