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391.
392.
Gyan Prakash Dubey Monika Sharma Neelima Dubey 《The Journal of chemical thermodynamics》2008,40(2):309-320
The densities (ρ) and speeds of sound (u) have been measured over the whole composition range for (butan-1-ol with hexane, or octane, or decane) at T = (298.15, 303.15, and 308.15) K and atmospheric pressure along with the properties of the pure components. Viscosities (η) of these binary mixtures have also been measured over the entire composition range at T = 298.15 K. Experimental values of density, viscosity and speed of sound have been used to evaluate excess properties viz. excess molar volumes (VE), deviation in viscosity (Δη), deviation in speeds of sound (Δu), deviation in isentropic compressibility (Δκs) and excess Gibbs free energy of activation of viscous flow (ΔG1E). The excess properties have been correlated using the Redlich–Kister polynomial equation. The sign and magnitude of these excess properties have been used to interpret the results in terms of intermolecular interactions and structural effects. The viscosity data have also been correlated by Grunberg and Nissan, Tamura–Kurata, and Hind correlation equations. 相似文献
393.
Photoelastic materials develop colored fringes under white light when subjected to mechanical stresses, which can be viewed
through a polariscope. This technique has traditionally been used for stress analysis of loaded components, however, this
can also be potentially used in sensing applications where the requirement may be measurement of the stimulating forces causing
the generation of fringes. This leads to inverse photoelastic problem where the developed image can be analyzed for the input
forces. However, there could be infinite number of possible solutions which cannot be determined by conventional techniques.
This paper presents neural networks based approach to solve this problem. Experiments conducted to prove the principle have
been verified with theoretical results and finite element analysis of loaded specimens. The developed technique, if generalized,
can be implemented for whole-field analysis of the stress patterns involving complex fringes under different loading conditions.
This can also provide direct visualization of the stress field, which may find application in a variety of specialized areas
including biomedical engineering and robotics.
相似文献
D. J. Claremont |
394.
Hard biomaterials such as bone, dentin, and nacre have primarily an organic phase (e.g. tropocollagen (TC)) and a mineral phase (e.g. hydroxyapatite (HAP) or aragonite) arranged in a staggered arrangement at the nanoscopic length scale. Interfacial interactions between the organic phase and the mineral phase as well as the structural effects arising due to the staggered arrangement significantly affect the strength of such biomaterials. The effect of such factors is intricately intertwined with the chemical environment of such materials. In the present investigation, an idealized TC–HAP composite system under tensile loading is analyzed using explicit three-dimensional (3-D) molecular dynamics (MD) simulations to develop an understanding of these factors. The material system is analyzed in three different environments: (1) in the absence of water molecules (non-hydrated), (2) in the presence of water molecules (hydrated), and (3) in the presence of water molecules with calcium ions (ionized water). The analyses focus on understanding the correlations among factors such as the structural arrangement, the peak stress during deformation, Young's modulus, the peak interfacial strength, and the length scale of the localization of peak stress during deformation. Analyses show that maximizing the contact area between the TC and HAP phases results in higher interfacial strength as well as higher fracture strength. Due to the staggered arrangement, the orientation of HAP crystals has insignificant effect on the biomaterial strength. Analyses based on strength scaling as a function of structural hierarchy level reveal that while peak strength follows a multiscaling relation, the fracture strength does not. The peak strain for failure was found to be independent of the changes in levels of structural hierarchy. Overall, the analyses, being limited in size due to the computational time constraint, point out important correlations between the mechanical strength and chemically influenced structural hierarchy of biomaterials. 相似文献
395.
396.
K. N. Jonnalagadda I. Chasiotis S. Yagnamurthy J. Lambros J. Pulskamp R. Polcawich M. Dubey 《Experimental Mechanics》2010,50(1):25-35
A new microscale uniaxial tension experimental method was developed to investigate the strain rate dependent mechanical behavior
of freestanding metallic thin films for MEMS. The method allows for highly repeatable mechanical testing of thin films for
over eight orders of magnitude of strain rate. Its repeatability stems from the direct and full-field displacement measurements
obtained from optical images with at least 25 nm displacement resolution. The method is demonstrated with micron-scale, 400-nm
thick, freestanding nanocrystalline Pt specimens, with 25 nm grain size. The experiments were conducted in situ under an optical
microscope, equipped with a digital high-speed camera, in the nominal strain rate range 10−6–101 s−1. Full field displacements were computed by digital image correlation using a random speckle pattern generated onto the freestanding
specimens. The elastic modulus of Pt, E = 182 ± 8 GPa, derived from uniaxial stress vs. strain curves, was independent of
strain rate, while its Poisson’s ratio was v = 0.41 ± 0.01. Although the nanocrystalline Pt films had the elastic properties
of bulk Pt, their inelastic property values were much higher than bulk and were rate-sensitive over the range of loading rates.
For example, the elastic limit increased by more than 110% with increasing strain rate, and was 2–5 times higher than bulk
Pt reaching 1.37 GPa at 101 s−1. 相似文献
397.
Achille Marchand Dr. Rituraj Mishra Aurélie Bernard Dr. Jean-Nicolas Dumez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201175
Online monitoring by flow NMR spectroscopy is a powerful approach to study chemical reactions and processes, which can provide mechanistic understanding, and drive optimisations. However, some of the most useful methods for mixture analysis and reaction monitoring are not directly applicable in flow conditions. This is the case of classic diffusion-ordered NMR spectroscopy (DOSY) methods, which can be used to separate the spectral information for mixture's components. We describe a fast and flow-compatible diffusion NMR experiment that makes it possible to collect accurate diffusion data for samples flowing at up to 3 mL/min. We use it to monitor the synthesis of a Schiff base with a flow-tube with a time resolution of approximately 2 minutes. The one-shot flow-compatible diffusion NMR described here open many avenues for reaction monitoring applications. 相似文献
398.
Kinetics and Catalysis - 4-Chloro-2,6-pyridinedicarboxylic acid (CPDA) functionalized mesoporous silica SBA-15 nanocomposites (SBA/5CPDA) were synthesized and characterized for the Knoevenagel... 相似文献
399.
Transport in Porous Media - The onset of double-diffusive convective instability of a horizontal throughflow induced by viscous dissipation in a fluid-saturated porous layer of high permeability is... 相似文献
400.
A. N. Dubey G. R. Relan S. Vaidyanathan 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):741-746
A derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at trace
levels in various process streams in 3M HNO3 medium using Arsenazo III. The method was developed with the objective of measuring both uranium and plutonium in the same
aliquot in fairly high burn-up fuels. The first derivative absorbances of the uranium and plutonium Arsenazo III complexes
at 632 nm and 606.5 nm, respectively, were used for their quantification. Mixed aliquots of uranium (20–28 μg/ml) and plutonium
(0.5–1.5 μg/ml) with U/Pu ratio varying from 25 to 40 were analysed using this technique. A relative error of about 5% was
obtained for uranium and plutonium. The method is simple, fast and does not require separation of uranium and plutonium. The
effect of presence of many fission products, corrosion products and complexing anions on determination of uranium and plutonium
was also studied. 相似文献