Pulse propagation

Another example of a relatively new technique for the noninvasive, nondestructive characterization of network structures involves ultrasound pulse-propagation measurements. The goal here is the rapid determi- 

This list is essentially an extension of parts of chapter 2, and many of the techniques described here are also useful for characterizing the composites described in chapter 9. 

Simulations and theoretical calculations have also been carried out for PDMS networks and single chains under deformation. Finally, investigations have clarified important aspects of polysiloxane permeabilities, - interfacial structure, and elasticity using an expansion approach.  

Rubber-like elasticity. Ann. Rev. Phys. Chem. 1989,40, 351-374. 

Treloar, L. R. G., The Physics of Rubber Elasticity, 3rd ed. Clarendon Press Oxford, 1975. 

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Agrawal G P 1989 Ultrashort pulse propagation in nonlinear dispersive fibers The Supercontinuum... 

Shock-compression processes are encountered when material bodies are subjected to rapid impulsive loading, whose time of load application is short compared to the time for the body to respond inertially. The inertial responses are stress pulses propagating through the body to communicate the presence of loads to interior points. In our everyday experience, such loadings are the result of impact or explosion. To the untrained observer, such events evoke an image of utter chaos and confusion. Nevertheless, what is experienced by the human senses are the rigid-body effects the time and pressure resolution are not sufficient to sense the wave phenomena. 

Romanchenko and Stepanov (1981) recognized that the impulse imparted at the spall plane to material downstream, because of the elastic-plastic nature of this material, led to an attenuating tensile stress pulse propagating toward the sample-window interface as is illustrated in Fig. 8.9. Thus, the maximum tension inferred from the measured spall signal should be adjusted for this attenuation in estimating a material spall strength at the spall plane. 

Product analysis polymer network s-NMR, gelation, swelling, birefringence, IR, NMR, STM, SANS, Brillouin scattering, pulse-propagation... 

Figure 12 Pulse propagation results, showing measurement of the time At required for a pulse to pass downward through an elastomer from Sensor 1 to Sensor 2. 

One example of a relatively new technique for the non-invasive, non-destructive characterization of network structures involves pulse-propagation measurements [288,289]. In this technique, the delay Af in a pulse passing through the network is used to obtain information on the network structure, for example, the chain length between cross-links or between entanglements. The technique is illustrated schematically in Figure 12 [282]. 

M. Sinha, Ph. D. Physics Probing Polymer Networks Using Pulse Propagation and Brillouin Light Scattering Techniques. University of Cincinnati, 2000. 

An alternative way to preform a channeled plasma consists in exploiting the nanosecond precursor that usually precedes a short femtosecond pulse in the output of a multi-terawatt laser system. In fact, the amplified spontaneous emission (ASE) pedestal has typically an intensity 106-1010 times lower than the main pulse, which, however, can be sufficient to ionize a gas-jet or a solid target. This drawback can be turned into a benefit assuming that this long precursor can prepare the plasma channel for the short pulse propagation. 

ISO 6721-9 1997 Plastics - Determination of dynamic mechanical properties - Part 9 Tensile vibration - Sonic-pulse propagation method ISO 3385 1989 Flexible cellular polymeric materials - Determination of fatigue by constant-load pounding... 

A. Melloni, F. Morichetti, and M. Martinelli, "Linear and nonlinear pulse propagation in coupled resonator slow-wave optical structures," Opt. Quant. Electron. 35, 365-379 (2003). 

Theoretical treatment of the femtosecond pulse propagation in a bulk Kerr medium with the dispersion of dielectric permittivity was based on the... 

A common way to treat the problem of a picosecond pulse propagation in regular dielectric waveguide with Kerr nonlinearity was to solve the nonlinear Schrodinger equation (NLSE) for the slowly varying temporal amplitude of electrical field ... 

Rigorous treatment of the self-action problem needs the transformation of Eq.(2.1), (2.5) into a system of integro-differential equations. However, if just some orders of group velocity dispersion and nonlinearity are taken into account, an approximate approach can be used based on differential equations solution. When dealing with the ID-i-T problem of optical pulse propagation in a dielectric waveguide, one comes to the wave equation with up to the third order GVD terms taken into account ... 

All the above results can be directly used in the problem of optical pulse propagation through the junctions provided that the quasi-static approximation is feasible. As the transmittance of a waveguide junction depends on power of a stationary component of the pulse, variation of an input pulse envelope behind the junction should be observed. 

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