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81.
R. D. Mehta 《Experiments in fluids》1990,8(6):354-356
An experimental comparison method is proposed for the verification of mean flow and turbulence measurements obtained with a three-dimensional laser Doppler velocimeter system. Such measurements can include large errors caused by problems unique to three-dimensional systems. Direct comparisons of laser and hot cross-wire measurements obtained in two-dimensional flows, as is the common practice, will not bear out all the errors associated with three-dimensional laser systems. It is proposed here that the errors may be adequately quantified by making the direct comparisons in a weakly three-dimensional turbulent shear flow. The weak three-dimensional flow ensures high accuracy of the cross-wire data while still generating sufficiently strong secondary mean flow and Reynolds shear stresses so that all the laser measurements may be fully verified. This type of shear flow is easily generated by introducing a weak streamwise vortex into a nominally two-dimensional turbulent shear layer. 相似文献
82.
Inhibition effect of imidazole derivative 1,7′-dimethyl-2′-propyl-1H,3′H-2,5′-bibenzo[d]imidazole (DPBI) against mild steel corrosion in 1 M HCl solutions was evaluated using the conventional mass loss method,
potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy. The mass loss results showed
that DPBI is an excellent corrosion inhibitor; electrochemical polarizations data revealed the mixed mode of inhibition; and
the results of electrochemical impedance spectroscopy showed that the change in the impedance parameters, charge transfer
resistance, and double layer capacitance with the change in the concentration of the inhibitor is due to the adsorption of
the molecule leading to the formation of a protective layer on the surface of mild steel. The inhibition action of this compound
was assumed to occur via adsorption on the steel surface through the active centers of the molecule. 相似文献
83.
JPC – Journal of Planar Chromatography – Modern TLC - A rapid and reliable high-performance thin-layer chromatographic method has been established for analysis of prednisolone in a... 相似文献
84.
K.K. Bhasin Rishu Sukhjinder Singh H. Kumar S.K. Mehta 《Journal of organometallic chemistry》2010,695(5):648-2013
The present work reports an efficient one-pot synthesis of symmetrical pyridyl monoselenides by the reaction of bromo-/iodopyridines with the isopropylmagnesium chloride, iPrMgCl followed by quenching with selenyl chloride, SeCl2. The current methodology constitutes a convenient synthesis of bis(5-bromo-2-pyridyl) selenide (I), bis(2-bromo-5-pyridyl) selenide (II) and bis(2,5-dibromo-3-pyridyl) selenide (III) under cryogenic conditions requiring shorter time duration to give satisfactory yields. The hitherto unknown compounds have been characterized by elemental analysis and various spectroscopic techniques i.e., 1H NMR, 13C NMR, FT-IR, mass spectrometry and X-ray crystallography. 相似文献
85.
A conformationally locked fluoropentol undergoes an interesting transformation to (trans,anti,trans,anti,trans)-perhydro-2,3,4a,6,7,8a-naphthalenehexol essentially under conditions of base-induced transesterification. The proposed rationale for the observed metamorphosis involves a nucleophilic displacement of fluoride, and subsequent stereo- and regioselective anti-Fürst-Plattner-type ring-opening of the epoxide thus formed. 相似文献
86.
Souad Chaouche Rachid Ouarsal Brahim El Bali Mohammed Lachkar Michael Bolte Michal Dusek 《Journal of chemical crystallography》2010,40(6):526-530
Abstract
Crystal structure of Li2HPO3,H2O was determined by single-crystal X-Ray diffraction analysis at 173(2) K. It crystallizes in the monoclinic system (P21/c) with the parameters: a = 5.0322(9) ?, b = 8.9795(17) ?, c = 17.088(4) ?, β = 92.672(16)° and Z = 8. The structure was refined to R = 0.0237 and ωR = 0.0650 for 1449 reflexions. The framework of Li2HPO3, H2O can be described as layers perpendicular to the crystallographic c axis. The structure contains two types of Li-tetrahedrons. In one kind each O atom belongs to one HPO3 group, while in the second kind one apex is an O from water. A network of hydrogen bonds interactions insures the connection between the layers. 相似文献87.
Souad Chaouche Rachid Ouarsal Mohammed Lachkar Francesco Capitelli Brahim El Bali 《Journal of chemical crystallography》2010,40(6):486-490
Abstract
A new hybrid phosphate, (C6H5NH3)[ZnCl(HPO3)], has been synthesized and its structure characterized from single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Pbca (n. 61) with the unit-cell parameters: a = 9.8635(2) ?, b = 9.4516(10) ?, c = 22.2430(4) ?, Z = 8 and V = 2,073.62(6) ?3. The final R factors were R/ωR = 0.0361/0.0924. Its framework might be described as a layered structure with two (010)-parallel cationic and anionic layers. The IR spectrum of this phase shows characteristic bands of phosphite and anilinium groups. 相似文献88.
Zañartu M Mehta DD Ho JC Wodicka GR Hillman RE 《The Journal of the Acoustical Society of America》2011,129(1):326-339
Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory. 相似文献
89.
We study the stationary points of what is known as the lattice Landau gauge fixing functional in one-dimensional compact U(1) lattice gauge theory, or as the Hamiltonian of the one-dimensional random phase XY model in statistical physics. An analytic solution of all stationary points is derived for lattices with an odd number of lattice sites and periodic boundary conditions. In the context of lattice gauge theory, these stationary points and their indices are used to compute the gauge fixing partition function, making reference in particular to the Neuberger problem. Interpreted as stationary points of the one-dimensional XY Hamiltonian, the solutions and their Hessian determinants allow us to evaluate a criterion which makes predictions on the existence of phase transitions and the corresponding critical energies in the thermodynamic limit. 相似文献
90.
Cosmological models with variable G in C-field cosmology for barotropic fluid distribution in FRW space-time are investigated. To get the deterministic model of the
universe, we have assumed that G=R
n
where R is the scale factor and n the constant. To obtain the results in terms of cosmic time t, we have assumed n=−1. We find that for n=−1, Creation field (C) and spatial volume increase with time, G and ρ (matter density) decreases with time, the model represent accelerating universe. Thus inflationary scenario exists in the
model. The model is also free from horizon. The results so obtained match with the astronomical observations. 相似文献