Search results for "Linear"
showing 10 items of 7165 documents
COOLING RATE DEPENDENCE AND DYNAMIC HETEROGENEITY BELOW THE GLASS TRANSITION IN A LENNARD–JONES GLASS
1999
We investigate a binary Lennard-Jones mixture with molecular dynamics simulations. We consider first a system cooled linearly in time with the cooling rate gamma. By varying gamma over almost four decades we study the influence of the cooling rate on the glass transition and on the resulting glass. We find for all investigated quantities a cooling rate dependence; with decreasing cooling rate the system falls out of equilibrium at decreasing temperatures, reaches lower enthalpies and obtains increasing local order. Next we study the dynamics of the melting process by investigating the most immobile and most mobile particles in the glass. We find that their spatial distribution is heterogene…
Spiking dynamics of frequency up-converted field generated in continuous-wave excited rubidium vapours
2020
We report on spiking dynamics of frequency up-converted emission at 420 nm generated on the 6P3/2-5S1/2 transition in Rb vapour two-photon excited to the 5D5/2 level with laser light at 780 and 776 nm. The spike duration is less than the natural lifetime of any excited level involved in the interaction with both continuous and pulsed pump radiation. The spikes at 420 nm are attributed to temporal properties of the directional emission at 5.23 {\mu}m generated on the population inverted 5D5/2-6P3/2 transition. A link between the spiking regime and cooperative effects is discussed. We suggest that the observed stochastic behaviour is due to the quantum-mechanical nature of the cooperative eff…
Tunable coaxial cavity resonator for linear and nonlinear microwave characterization of superconducting wires
2011
We discuss experimental results obtained using a tunable cylindrical coaxial cavity constituted by an outer Cu cylinder and an inner Pb-BSCCO wire. We have used this device for investigating the microwave response of the superconducting wire, both in the linear and nonlinear regimes. In particular, by tuning the different modes of the cavity to make them resonant at exactly harmonic frequencies, we have detected the power emitted by the superconducting inner wire at the second- and third-harmonic frequency of the driving field. The results obtained in the nonlinear regime, whether for the microwave surface impedance or the harmonic emission, are qualitatively accounted for considering inter…
Experimental and Theoretical Study of the Field Induced Phase Separation in Electro- and Magnetorheological Suspensions
1999
We present here the study of field induced phase separation in E.R. and M.R. fluids. Two thermodynamic models — one for the formation of chais of particles and the other for phase separation are presented and compared with experimental results obtained with two kinds of suspensions. One was made of silica particles in silicone oil and the other was made of magnetic polystyrene particles in water. In the presence of a flow the phase separation occurs with the dense phase forming a regular pattern of stripes. The dependence of the period of these stripes on the intensity of the magnetic field is well reproduced by the same kind of thermodynamic model if we add the effect of normal stresses i…
Fabrication of a biocompatible and continuous glucose biosensor with the poly(3,4-ethylenedioxythiophene) modified electrode
2019
Abstract In this study, we have explored the potentiality of using GOx/AuNP/PEDOT(BSA)/Pt electrode as an implantable, long-lasting, and sensitive glucose biosensor. We have examined the performance of the electrode for glucose calibration with three electrochemical measurements, such as cyclic voltammetry, linear sweep voltammetry, as well as chronoamperometry, which all exhibited strong linear correlation between resulting signal and glucose concentration. In comparison, linear sweep voltammetry gave the best linear sensitivity, whose average was about 3.124 µA/mM/cm2 within a wide glucose concentration range from 0.416 to 50 mM. Meanwhile, the stability of the electrode was confirmed by …
Three-Dimensional Printing of Nonlinear Optical Lenses.
2018
In the current paper, a series of nonlinear optical (NLO) active devices was prepared by utilizing stereolithographic three-dimensional printing technique. Microcrystalline NLO active component, urea, or potassium dihydrogen phosphate was dispersed in a simple photopolymerizable polyacrylate-based resin and used as the printing material to fabricate highly efficient transparent NLO lenses. The nonlinear activity of the printed lenses was confirmed by second-harmonic generation measurements using a femtosecond laser-pumped optical parametric amplifier operating at a wavelength of 1195 nm. The three-dimensional printing provides a simple method to utilize a range of NLO active compounds witho…
A quantitative electron-microscopic study of a linear polyethylene fraction crystallized at different temperatures
1981
Replica and thin-section electron microscopy was performed on a linear polyethylene fraction (Mw = 1.89 × 105, Mn = 1.79 × 10 5) which was either isothermally crystallized or quenched at difference temperatures. The results are numerically analyzed in such a manner so as to give the distribution of the total long spacing and of the crystallite and amorphous thicknesses. The quantitative information about the maximum and minimum values for these parameters at each crystallization temperature yields important clues as to possible molecular processes involved. Qualitative information regarding general morphology, molecular tilt with respect to the lamellar surface, and possible crystallographi…
A quantitative electron microscopic study of the crystallite structure of molecular weight fractions of linear polyethylene
1984
Utilizing thin-section techniques, transmission electron microscope studies were performed on a series of bulk-crystalized fractions of linear polyethylene covering the range M = 5 × 103−6 × 106. The crystallization conditions were varied from long-time isothermal to rapid quenching. Quantitative analysis could be carried out on such samples crystallized under controlled conditions. The crystallite thickness distributions and long periods are presented in terms of histograms. From these data the degree of crystallinity can be calculated and was found to compare favorably with that from other methods. The amorphous thickness increases significantly with molecular weight for all modes of crys…
Crack growth models for multiaxial fatigue in a ship’s propeller shaft
2021
Abstract A premature fatigue failure of a large intermediate propeller shaft in a shuttle tanker is discussed and analyzed. The short fatigue life consists mainly of a crack growth phase. Life predictions are carried out by crack growth modelling based on engineering fracture mechanics. The purpose of the present investigation is to identify the most likely loading modes based on the evolution of the crack propagation. A Linear Elastic Fracture Mechanics Model (LEFM) is applied with the stress intensity factor range entering the Paris law as a key parameter. Existing formulas for the geometry functions are supplemented by more detailed stress intensity factor calculations pertaining to smal…
On the strong closure of strains and stresses in linear elasticity
1999
We consider the following special problem related to the optimal layout problems of materials: given two linear elastic materials, the elasticity tensors of which are C1 and C2, and a force f, find the strong closure of strains and stresses as the distribution of the materials varies, or, alternatively, find the sets of elasticity tensors which generate these strong closures. In this paper, it is shown that the local incompatibility conditions depending on C1, C2 and the local properties of strains or stresses completely characterize these sets. A connection to multiple-well problems is established.