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71.
72.
73.
Using filament stretching rheometry to predict strand formation and “processability” in adhesives and other non-Newtonian fluids 总被引:1,自引:0,他引:1
The spinning of polymeric fibers, the processing of numerous foodstuffs and the peel and tack characteristics of adhesives
are all associated with the formation, stability and, ultimately, the longevity of thin fluid `strands'. This tendency to
form strands is usually described in terms of the tackiness of the fluid or by heuristic concepts such as `stringiness' (Lakrout
et al. J Adhesion 1999). The dynamics of such processes are complicated due to spatially and temporally non-homogeneous growth
of extensional stresses, the action of capillary forces and the evaporation of volatile solvents. We describe the development
and application of a simple instrument referred to as a microfilament rheometer (MFR) that can be used to readily differentiate
between the dynamical response of different pressure-sensitive adhesive fluid formulations. The device relies on a quantitative
observation of the rate of extensional thinning or `necking' of a thin viscous or viscoelastic fluid filament in which the
solvent is free to evaporate across the free surface. This high-resolution measurement of the radial profile provides a direct
indication of the ultimate time to break up of the fluid filament. This critical time is a sensitive function of the rheological
properties of the fluid and the mass transfer characteristics of the solvent, and can be conveniently reported in terms of
a new dimensionless quantity we refer to as a processability parameter P. We demonstrate the usefulness of this technique by presenting our results in the form of a case study in which we measure
the visco-elasto-capillary thinning of slender liquid filaments for a number of different commercial polymer/solvent formulations
and relate this to the reported processing performance of the materials. We also compare the MFR observations with the prediction
of a simple 1D theory derived from the governing equations that model the capillary thinning of an adhesive filament.
Received: 22 December 1999/Accepted: 4 January 2000 相似文献
74.
Amitabha Ghosh 《Pramana》1986,26(1):1-8
According to the model of inertial induction proposed earlier, the inertia force consists of an acceleration-dependent term
which comes out as identically equal to -ma. Besides, there is a velocity-dependent term which is exceedingly small to be easily detected. However, it has been shown
that this results in a cosmological red shift of light coming from distant stars and galaxies; the magnitude of the red shift
agrees very well with the observed values. Though this model yields correct results when applied to photons it needs modification
before applying to other bodies. A modified form of the inertial induction model is now proposed where the proposed velocity-dependent
inertia forces, when applied to the solar system, yields correct order of magnitude for the secular retardation of the earth’s
rotation. Moreover, a combined model using the velocity term and the tidal friction also does not suggest any close proximity
of the moon to the earth in the past. When the model is applied to the case of Phobos, a secular acceleration of the order
of magnitude of 10−3 deg yr−2 is obtained. 相似文献
75.
We study projective curvature tensor in K-contact and Sasakian manifolds. We prove that (1) if a K-contact manifold is quasi projectively flat then it is Einstein and (2) a K-contact manifold is ξ-projectively flat if and only if it is Einstein Sasakian. Necessary and sufficient conditions for a K-contact manifold to be quasi projectively flat and φ-projectively flat are obtained. We also prove that for a (2n + 1)-dimensional Sasakian manifold the conditions of being quasi projectively flat, φ-projectively flat and locally isometric to the unit sphere S
2n+1 (1) are equivalent. Finally, we prove that a compact φ-projectively flat K-contact manifold with regular contact vector field is a principal S
1-bundle over an almost Kaehler space of constant holomorphic sectional curvature 4. 相似文献
76.
The steady state and time domain spectroscopy of 9-aminoacridinium hydrochloride have been studied. 9-aminoacridine (I), 9-aminoacridinium
(II) and the double protonated ion (III) follow Waterman’s principle with respect to their spectra and lifetimes. It is established
that the excimer formation in (II) is from the ground state dimers which undergo either thermally-activated radiationless
excimer conversion or a geometrical rearrangement in the excited state at room temperature. The quenching of monomer emission
by dimers or foreign quenchers (KI) is found to be of transient nature as suggested by the continuum model.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
77.
78.
Jyoti Bhawan Singh Shakti Pratap Gupta Mohit Tripathi Sudhanshu Verma Alok Kumar Singh Devraj Yadav R. R. 《Acoustical Physics》2021,67(6):584-589
Acoustical Physics - We have estimated elastic, mechanical, thermal and ultrasonic properties, in high temperature regime, of cobalt nanowires (Co-NWs) having a hexagonal close-packed (HCP)... 相似文献
79.
A rapid and semi-quantitative immunochromatographic strip (ICS) test for cortisol analysis in serum was developed. The test strip was based on a competitive assay format. Colloidal gold nanoparticles were synthesized and coupled with cortisol-3-carboxymethyloxime-adipic acid dihydrazide-bovine serum albumin (F-3-CMO-ADH-BSA) antigen to directly compete with cortisol in human serum samples. F-3-CMO-ADH-BSA-gold label and uncoupled colloidal gold nanoparticles were appropriately characterized using UV-vis spectroscopy, transmission electron microscopy and atomic force microscopy. Anticortisol antibody raised against F-3-CMO-BSA immunogen in New Zealand white rabbits was coated on the NC membrane as test line. Anti-BSA antibody was used as control line. The lower detection limit of the ICS test was 30 ngmL(-1) with visual detection and was completed in 10 min. About 30 human serum samples were also analyzed by the developed strip test and their range of cortisol concentration was established. The developed ICS test is rapid, economic and user friendly. 相似文献
80.
Amitabha Chakraborty Moazzam Ali Swapan K. Saha 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1577-1583
Molecular interactions of five thiazine dyes with increasing alkyl substitution have been studied in aqueous and microemulsion media at 303 K within a concentration range of (1.35–7.00) × 10?4 M. The dimerization constant (Kd) values for the five dyes are ranged between 1.761 and 6.258 × 103 l mol?1 in bulk water media, where as in microemulsion media, Kd's are ranged between 1.760 and 4.110 × 103 l mol?1. Thionine (with no methyl substitution) and azure A (with two methyl substitution) displayed slightly larger Kd values in microemulsion water pools compared to bulk water while other dyes recorded significant drop in Kd values. The influence of microemulsion media on the molecular interaction of dyes has been explained in terms of electrostatic and hydrophobic factors. The monomer and the dimer spectra are explained in terms of molecular exciton model and the optical absorption parameters of both the species are reported in bulk and confined media. 相似文献