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151.
152.
This paper describes the experimental procedure to identify the predominant frequencies of the high speed testing machine
by conducting modal analysis. The effects due to the predominant frequencies of the system and loading rate on the magnitude
of system ringing and the flow stress were analyzed by using a single degree-of-freedom (SDOF) spring-mass-damper model. The
system was then used to study the dynamic tensile behavior of two engineering materials, i.e., polyethylene (PE) fabric-cement
composite and Alkaline Resistant (AR) glass fabrics at an intermediate strain rate. The stress oscillations in the response
of these materials due to system ringing were addressed. The failure behavior of each material was studied by examining high
speed digital camera images of specimens during the test. The validity of the dynamic tensile tests was investigated by examining
the condition of dynamic stress equilibrium—a criterion used in split Hopkinson pressure bar (SHPB) tests. The results show
that the quantitative criterion for a valid SHPB test is also applicable to dynamic tensile tests of these materials at the
intermediate strain rate. 相似文献
153.
Dette Holger Dhar Subhra Sankar Wu Weichi 《Annals of the Institute of Statistical Mathematics》2021,73(5):855-889
Annals of the Institute of Statistical Mathematics - This article studies the problem whether two convex (concave) regression functions modelling the relation between a response and covariate in... 相似文献
154.
Subramanian V. Sankar Derek Y. Kamemoto William D. Bachalo 《Particle & Particle Systems Characterization》1993,10(6):321-331
A combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro-balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow microballoons, the ability of large micro-balloons to respond to high frequency spatial and temporal flow field variations, and the overall advantages and disadvantages of using large microballoons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, the experimental facility, and the theoretical and experimental results. 相似文献
155.
We present a new approach that permits efficient performance analysis of kanban systems with general demand processes, material
arrival processes, and service times. The approach is based on parametric characterization of the traffic processes (arrival
and departure) in the network and uses two-moment approximations to estimate performance measures at individual stations.
We derive traffic flow constraints that are particular to closed queuing networks with synchronization stations and use these
to establish relationships between the parameters characterizing arrival and departure processes at the stations in the network.
The resultant set of non-linear equations is solved to estimate network performance measures. Numerical studies show that
the approach is not only fast but also reasonably accurate when compared to simulation. These studies also provide insights
with respect to the impact of different types of variability on the performance of a kanban system. This work also provides
a fundamental building block that can be used in the analysis of multi-stage kanban systems.
AMS Subject Classifications 68M20, 60K20, 90B05, 90B30 相似文献
156.
157.
We present a complete theoretical analysis of the periodic and non-periodic travelling waves in a diatomic chain model, in
the continuum limit by incorporating nonlinear sixth order polarization potential (φ6) at the anion site. We have formulated a nonlinear lattice dynamical theory in which various energy curves are obtained for
different types and magnitudes of the core-shell force constants. For periodic solutions, we have obtained two types of commensurate
wave amplitudes which propagate in the opposite direction with respect to each other. For nonperiodic solutions, we have obtained
various travelling excitations such as kink, antikink, excitons etc. for different values of the mass ratio and velocity parameter.
The dipole moment per unit charge for SrTiO3 has been calculated and it is found that the nonlinear excitations in this model carry large amount of energy as compared
to those obtained from harmonic and anharmonic optical phonons in the φ4-polarizable model. 相似文献
158.
The phonon spectra of unstrained and strained quasiperiodic semiconductor superlattices (QSSL) have been calculated using
one-dimensional linear chain model. We consider two types of quasiperiodic systems, namely cantor triadic bar (CTB) and Fibonacci
sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatch of about 7%. The calculations
have been made using transfer matrix method and also with and without the inclusion of strain. We present the results on phonon
spectra of two component CTB and two as well as three component FS semiconductor superlattices (SSL), thickness and order
dependence on LO mode of GaAs, effect of strain on LO frequency of GaAs. The calculated results show that the strain generated
due to lattice mismatch reduces significantly the magnitudes of the confined optical phonon frequency of GaAs. 相似文献
159.
We have investigated the lattice vibrational properties of a two-component strained layer semiconductor superlattice (GaAs)
n1 (GaSb)
n2 using a one-dimensional linear chain model and transfer matrix method [1]. Effect of strain, arising due to the lattice mismatch
(∼ 7%) has been considered explicitly in the equation of motion. We show for the first time that the optical vibrational frequency
increases (in the case of (GaAs)4 (GaSb)
n
) or decreases (in the case of (GaAs)
n
(GaSb)4) with increase of layer thicknessn, in either type of superlattices. Raman scattering measurements on some other similar systems support our findings. 相似文献
160.
We present detailed multi-channel experimental characterization of different configurations of single pump hybrid Raman-erbium doped fiber (EDF) amplifiers. The incorporation of an EDF section in a dispersion compensating Raman amplifier is demonstrated to provide superior performance than Raman only system. It is shown that the multi-channel gain spectrum is quite different form the single-channel case. We have also measured the polarization dependent gain (PDG) of the hybrid amplifier configurations and results show that different configurations of hybrid amplifiers have different PDG effects on long-haul optically amplified link. 相似文献