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21.
Frédéric Barbeu Vaclav Sobolik Serguei Martemianov Laurent Gbahoue 《Comptes Rendus Mecanique》2002,330(6):433-436
The present paper demonstrates how the directional characteristics of an actual three-segment electrodiffusional sensor can be calculated from the probe image. It was shown that utilization of ‘ideal’ directional characteristics lead to an important (up to 15°) error in flow angle determination. The directional characteristics calculated from the probe image improve significantly (up to 50%) the accuracy of the flow angle measurements. To cite this article: F. Barbeu et al., C. R. Mecanique 330 (2002) 433–436. 相似文献
22.
One of the most important problems in the turbulence theory is the process of turbulent mixing. Although many theoretical and experimental studies on the structure functions of a passive scalar as well as the probability density functions of its increment and gradient in a turbulent fluid have been published so far, the instantaneous feature of an advected scalar has not been explored very well. There are only a few experimental studies on a scalar concentration fluctuation analysis in turbulent flows. In this study the time‐series of both longitudinal velocity component and concentration analysis are to be presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
23.
Development of a flat plate boundary layer (grad P = 0) was investigated in the closed type wind tunnel (0.5 × 0.9 × 2.7 m3). The plate was either aerodynamically smooth or covered with a thin plate (10 mm thick) with the surface made from the sand paper (grits 80). FST is generated by square mesh plane grids/screens set across the flow as to produce homogeneous, close to isotropy turbulence with various scales of velocity and length. The surface roughness was of transient type. The comparison is made of the effect of various grouping of the wall roughness and FST on the boundary layer development. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
24.
For sufficiently smooth Banach spaces weak cotype 2 implies Hilbert space.Research supported in part by NSERC (Canada) 相似文献
25.
Vaclav Synek 《Talanta》2007,71(3):1304-1311
This paper continues in studying the coverage probability of uncertainty intervals. It particularly investigates the uncertainty intervals determined in compliance with the GUM and EURACHEM Guide in case of the results uncorrected for the systematic error, since the experimental bias has been found insignificant. The problem is solved for known values of the experimental bias, its standard uncertainty and the overall standard uncertainty. The obtained findings given in graphs and tables show that coverage probability of the uncertainty intervals defined by expanded uncertainty about the uncorrected results can considerably fall below the chosen level of confidence; this depression depends only on the ratio of the bias and the overall uncertainty. The bias uncertainty does not directly influence this depression, it only determines whether the bias is significant or not and thereby determines whether the results will be corrected or not. The paper proposes three methods how to remove this coverage probability reduction: to apply a higher level of confidence in the significance test, to correct the results with the insignificant but too high biases and to compute the uncertainty intervals defined by some type of the uncertainties enlarged with the insignificant bias. 相似文献
26.
Poly(4-styrenesulfonate) has been used to ionically cross-link (glue together) a single Langmuir-Blodgett bilayer derived from an amphiphilic calix[6]arene bearing six hexadecyl and six methylene-trimethylammonium groups. The resulting film is of high quality and robustness, as judged by its He/N2 permeation selectivity and by its ability to withstand exposure to chloroform solvent. The creation of a stable organic membrane, having a thickness that is less than 6 nm and a He/N2 permeation selectivity of ca. 305, represents a milestone for LB technology. 相似文献
27.
28.
Mentré O Ketatni el M Colmont M Huvé M Abraham F Petricek V 《Journal of the American Chemical Society》2006,128(33):10857-10867
The BiCu(2)(P(1-x)V(x))O(6) system shows the appearance of various phenomena that progressively change as a function of the average (P/V)O(4) groups size. Then, from x = 0 to x approximately 0.7, a solid solution exists with respect to the basic orthorhombic unit cell of BiCu(2)PO(6). For greater x values (0.7 < x <0.96), structural modulations with incommensurate q vector that slightly change versus x appear. The 4-D treatment of single-crystal XRD data of the modulated phase corresponding to x = 0.87 at 100 K (orthorhombic, a = 12.379(3)Angstrom, b = 5.2344(9) Angstrom, c = 7.8270(14) Angstrom, q = 0.268(3) b*, super space group: Xbmm(0gamma0) s00, X stands for the nonprimitive centering vector (1/2,0,1/2,1/2), R(obs)(overall) = 5.27%, R(obs)(fundamental) = 4.48%, R(obs)(satellite) = 6.58%) has evidenced strong positional modulated effects within the [BiCu(2)O(2)](3+) ribbons while three XO(4) configurations compete along the x(4) fourth dimension. There is no P/V segregation along x(4) in good agreement with steric-only origins of the modulation. Finally for 0.96 < x <1, two phases coexist, i.e., BiCu(2)VO(6) (X = 1) and a modulated phase of the previous domain.The BiCu(2)VO(6) crystal structure shows a unit cell tripling associated with monoclinic symmetry lowering. The VO(4) orientations between two ribbons proceed with respect to the interribbon distance. Then the full system shows flexible interactions between modulated Bi/M/O-based ribbons and surrounding tetrahedral groups, depending on the average XO(4) size. Furthermore, between two ribbons the Cu(2+) arrangement forms magnetically isolated zigzag copper two-leg ladders. Our preliminary results show a spin-gap behavior likely due to the existence of true S = (1)/(2) Heisenberg two-leg ladders. Modulated compositions are gapless, in good agreement with band-broadening toward a continuum in the magnetic excitation spectrum. The continuous distribution of Cu-Cu distances along the rungs and legs of the ladders should be mainly responsible for this magnetic change. 相似文献
29.
Jay B. Benziger May Jean Cheah Vaclav Klika Michal Pavelka 《Journal of Polymer Science.Polymer Physics》2015,53(22):1580-1589
Water and proton transport across a Nafion membrane are measured as functions of water activity and applied electric potential with a polymer electrolyte hydrogen pump. Water and proton transport across the membrane must match water and proton transport entering and leaving the electrode/membrane/vapor three phase interfaces at the anode and cathode. At low applied electric potential proton and water fluxes are correlated. At moderate to high applied electric potential the proton current is constant, independent of applied electric potential, while the water transport increases with increasing electric potential. At high applied electric potential water and proton transport become uncoupled at the membrane interfaces; water is transported across the membrane/vapor interface and protons are transported across the membrane/electrode interface. The applied electric potential drives electro‐osmosis to redistribute the water in the membrane. Water redistribution is limited by the interfacial transport of water across the membrane/vapor interface. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2015 , 53, 1580–1589 相似文献
30.
Synthesis,Spectroscopy, X‐ray Crystallography,and DFT Computations of Nanosized Phosphazenes 下载免费PDF全文
Zahra Shariatinia Elnaz Jalali Moghadam Narges Maghsoudi Hourieh Sadat Mirhosseini Mousavi Michal Dusek Vaclav Eigner 《无机化学与普通化学杂志》2015,641(5):967-978
Nanoparticles of nine phosphazenes with general formula 4‐CH3C6H4S(O)2N=PX3 [X = Cl ( A ), NC4H8 ( 1 ), NC6H12 ( 2 ), NC4H8N–C(O)OC2H5 ( 3 ), NC4H8N–C(O)OC6H5 ( 4 ), NC4H8O ( 5 ), NHCH2–C4H7O ( 6 ), N(CH3)(C6H11) ( 7 ), NHCH2–C6H5 ( 8 ), and 2‐NH‐NC5H4 ( 9 )] were synthesized using ultrasonic method and characterized by 1H, 13C, 31P NMR, FT‐IR, fluorescence, as well as UV/Vis spectroscopy and additionally with XRD, FE‐SEM, N2 sorption, and elemental analysis. The 31P NMR spectra of compounds 1 – 9 reveal the most up field shift δ(31P) for 9 at –11.45 ppm reflecting the most electron donation of 2‐aminopyridinyl rings through resonance to the phosphorus atom. The 1H, 13C NMR spectra of 7 exhibit two sets of signals for the hydrogen and carbon atoms of its two isomers present in the solution state in 1:4 ratio. The FE‐SEM micrographs illustrate that the nanoparticles of compounds 1 – 9 have spherical morphology and a size of 27–42 nm. From the XRD patterns, the crystal sizes were estimated to about 24–86 nm. The highest bandgap was measured for 3 (3.81 eV) whereas the smallest was measured for 8 (3.50 eV). The structures of two polymorphs of compound 5 ( 5 , 5′ ) were determined by X‐ray crystallography at 120 K. Both of these polymorphs are triclinic with P1 space group but 5 has a doubled unit cell volume and two symmetrically independent molecules ( 5a and 5b ). In structures 5a and 5′ , the phosphorus and all endocyclic atoms of two morpholinyl rings display disorder, whereas the molecule 5b does not show disorder. The strong intermolecular O–H ··· O hydrogen bonds plus weak intermolecular C–H ··· O and C–H ··· N interactions create three‐dimensional polymers in the crystalline networks of 5 and 5′ . The DFT computations illustrate that molecule 5b is more stable than 5a by –1.1062 and –0.9779 kcal · mol–1 at B3LYP and B3PW91 levels, respectively. The NBO calculations presented sp3d hybridization for phosphorus and sulfur atoms and sp2, sp3 hybrids for the nitrogen and oxygen atoms. 相似文献