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121.
Rami Haj-Ali Hagit Zemer Rani El-Hajjar Jacob Aboudi 《International Journal of Solids and Structures》2014
Piezoresistive composites are materials that exhibit spatial and effective electrical resistivity changes as a result of local mechanical deformations in their constituents. These materials have a wide array of applications from non-destructive evaluation to sensor technology. We propose a new coupled nonlinear micromechanical-microelectrical modeling framework for periodic heterogeneous media. These proposed micro-models enable the prediction of the effective piezoresistive properties along with the corresponding spatial distributions of local mechanical–electrical fields, such as stress, strain, current densities, and electrical potentials. To this end, the high fidelity generalized method of cells (HFGMC), originally developed for micromechanical analysis of composites, is extended for the micro-electrical modeling in order to predict their spatial field distributions and effective electrical properties. In both cases, the local displacement vector and electrical potential are expanded using quadratic polynomials in each subvolume (subcell). The equilibrium and charge conservations are satisfied in an average volumetric fashion. In addition, the continuity and periodicity of the displacements, tractions, electrical potential, and current are satisfied at the subcell interfaces on an average basis. Next, a one way coupling is established between the nonlinear mechanical and electrical effects, whereby the mechanical deformations affect the electrical conductivity in the fiber and/or matrix constituents. Incremental and total formulations are used to arrive at the proper nonlinear solution of the governing equations. The micro-electrical HFGMC is first verified by comparing the stand-alone electrical solution predictions with the finite element method for different doubly periodic composites. Next, the coupled HFGMC is calibrated and experimentally verified in order to examine the effective piezoresistivity of different composites. These include conductive polymeric matrices doped with carbon nano-tubes or particles. One advantage of the proposed nonlinear coupled micro-models is its ability to predict the local and effective electro-mechanical behaviors of multi-phase periodic composites with different conductive phases. 相似文献
122.
G. Chandra Sekhar Reddy M. Veera Narayana Reddy C. Radha Rani N. Bakthavatchala Reddy K. Uma Maheswara Rao S.K. Nayak C. Suresh Reddy 《Heteroatom Chemistry》2012,23(3):247-253
A new family of di(1‐oxo/thioxoper‐hydro‐1λ5‐[1,3,2]diazaphospholo[1,5‐a]pyridine‐1‐yl)(4‐substituted phenyl) boronates ( 4a – j ) has been synthesized in a two‐step process. A reaction of (±)‐piperidin‐2‐yl‐methanamine ( 1 ) phosphoryl/phosphorothioyl chloride in the presence of triethylamine in dry tetrahydrofuran formed the intermediate monochloride ( 2 ), which on condensation with p‐substituted phenylboronic acids ( 3a – j ) afforded the titled compounds ( 4a – j ). They were characterized by elemental, IR, 1H, 13C, 31P NMR, and mass spectral analyses. All these compounds showed moderate to high antiosteoclast and osteoblast activity. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:247–253, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21010 相似文献
123.
Juan Sabuco Samuel Zambrano Miguel A.F. Sanjuán James A. Yorke 《Communications in Nonlinear Science & Numerical Simulation》2012,17(11):4274-4280
Many discrete-time dynamical systems have a region Q from which all or almost all trajectories leave, or at least they leave in the presence of perturbations that we call disturbances. We partially control systems so that despite disturbances the trajectories of a dynamical system stay in the region Q at least for some initial points in Q. The disturbances can be thought of as either noise or as purposeful, hostile efforts of an enemy to drive the trajectory out of the region. Our goal is to keep trajectories inside Q despite the disturbances and our partial control of chaos method succeeds.Surprisingly this goal can be achieved with a control whose maximum allowable size is smaller than the maximum allowed disturbance. A fundamental step towards this goal is to compute a set called the safe set that had, until now, been found only in certain very special situations.This paper provides a general algorithm for computing safe sets. The algorithm is able to compute the safe sets for a specified region in phase space, the maximum disturbance value, and the maximum allowed control. We call it the Sculpting Algorithm. Its operation is analogous to removing material while sculpting a statue. The algorithm sculpts the safe sets. Our Sculpting Algorithm is independent of the dimension and is fast for one- and two-dimensional dynamical systems. As examples, we apply the algorithm to two paradigmatic nonlinear dynamical systems, namely, the Hénon map and the Duffing oscillator. 相似文献
124.
A quartz crystal microbalance can be used as a biosensor if biological receptor molecules (ligands) are attached to the crystal.
To improve the sensitivity, the surface area of the gold electrodes on the crystal was increased by rendering the electrodes
porous. This increased the response up to a factor of 3. A protein model system with human anti-myoglobin as ligand and sheep
skeletal myoglobin at different concentrations as analyte was used. The quartz crystal was mounted in a flow-cell, where immobilisation,
binding and regeneration of the surface were carried out. The kinetics of the model system was monitored under various experimental
conditions.
Received February 2, 2000. Revision June 30, 2000. 相似文献
125.
Lal Sohan Arora Sanjiv Kumar Vinod Rani Shikha Jagdeva Geetanjali 《Journal of Thermal Analysis and Calorimetry》2021,143(4):3267-3274
Journal of Thermal Analysis and Calorimetry - The different concentrations of chitosan were applied on cotton fabrics using glutaraldehyde as a cross-linking agent. The fabric samples were... 相似文献
126.
A new derivative of ursolic acid containing dual functionality was synthesized. Molecular docking studies and in vitro analysis indicated promising COX inhibition potential for the molecule. The synthesis, characterization, in silico and in vitro studies of the molecule are described here. 相似文献
127.
Saravanan M. Dhivakar S. Mohapatra M. Kutti Rani S. Vijayakumaran K. 《Journal of fluorescence》2022,32(4):1557-1563
The present work describes the synthesis and characterization of pyrene derivatives, N-(1-Pyrenoylmethyl) pyridinium bromide (PM-PB) and N-(1-Pyrenoylmethyl)-N,N,N-triethylammonium bromide (PM-TAB). The photophysical behavior of these molecules has been studied in various protic and aprotic solvents. Using steady state fluorescence intensity, fluorescence anisotropy and dynamic fluorescence lifetime studies, the sensitivity of these molecules towards the micellization process of bile salts has been monitored. These derivatives have been effectively used in estimating critical micellar concentration (CMC) of bile salt, sodium deoxycholate (NaDC).
相似文献128.
The γ- and conversion electron spectra following131Ba ε-decay are investigated, using HPGe detector and mini-orange electron spectrometer. Attention is particularly focussed
on identifying weak transitions associated with low energy high spin levels in131Cs level scheme earlier inferred in reaction studies but not yet observed in131Ba decay. Our experiment identifies 15 new gammas and 6 new conversion lines in this decay. Internal conversion coefficients
and multipolarities of several transitions are determined. Five new levels (3 with Iπ = 7/2+ and one each with Iπ 9/2+ and 11/2−) are introduced in the131Cs level scheme based on our observations taken together with the results from reaction studies. Spin-parity assignments to
a few other levels are also suggested 相似文献
129.
130.
Sol-Gel Synthesis of Nanocrystalline PZT Using a Novel System 总被引:2,自引:0,他引:2
Jacob K. Stanly Panicker N. Rani Selvam I. Packia Kumar V. 《Journal of Sol-Gel Science and Technology》2003,28(3):289-295
A simple system has been developed for the preparation of lead zirconate titanate, Pb(Zr
x
Ti1 – x
)O3 powders by sol-gel process. To achieve stable and homogeneous precursor solutions, chelating ligands such as acetic acid and acetylacetone have been used for the chemical modification of titanium and zirconium starting precursors. Phase-pure PZT powders were obtained, through a pyrochlore-free pathway, from the amorphous xerogel after heat treatment at 600°C. The formation of the crystalline phase, compositional homogeneity, sinterability, dielectric and piezoelectric characteristics of PZT are reported. 相似文献