Possible expansion of the spectral emission range of electronic-transition chemical lasers

Abstract

Experimental investigations on superelastic shape-memory alloys (SMAs) show a dependence of the stress-strain relationship on the loading-unloading rate. This feature is of particular importance when utilizing SMA materials for seismic applications, since the loading rate may affect the structural response.Motivated by this observation and by the fact that there exist relatively few studies on the material modelling of SMAs in earthquake engineering, the present work addresses a uniaxial constitutive equation able to describe the rate-dependent behaviour of superelastic SMAs.The formulation of the model is based on two scalar internal variables, the static martensite fraction and the dynamic martensite fraction, for which three different types of evolutionary equations in rate form are proposed. Moreover, the model takes into account the different elastic properties between austenite and martensite. Finally, after discussing two possible approaches for the solution of the corresponding time-discrete framework, the ability of the model to simulate experimental data obtained from uniaxial tests performed on SMA wires and bars at frequency levels of excitation typical of earthquake engineering is assessed. reversible micromechanical phase transitions by changing the crystallographic structure from an austenitic phase to a martensitic phase. This capacity results in two major features at the macroscopic level, which are the superelastic effect and the shape-memory effect [9].Due to these unique characteristics, SMAs lend themselves to innovative applications in many scientific fields,

An extensive investigation of reactions involved in the nitrogen trifluoride dissociation

“…1 Added to this is the fact that nitrogen trifluoride decomposition is a source of fluorine atoms and NF 2 radicals, essential structures for a number of experimental physiochemical investigations. [2][3][4] These evidences led to a substantial rise in overall NF 3 consumption which, together with the fact that NF 3 is an important greenhouse gas, provides a necessity to investigate the decomposition process of this compound. Despite all recent efforts to understand this important mechanism, the kinetics of NF 3 decomposition remain controversial, particularly when it comes to the removal of this potent greenhouse gas from the atmosphere.…”