The dynamical processes responsible for laser emission in the pulsed pumping of a transversely excited atmospheric (TEA) CO2 laser are investigated. An explanation for the formation of the giant pulse is proposed on the basis of a gain-switching mechanism in which it is assumed that with short strong-current pulses a high population inversion can be achieved prior to the onset of laser action. The kinetics of the mechanism are described by means of a set of nonlinear rate equations idealized to a four-energy-state system. With suitable initial conditions on the populations, the transient solution of these equations for the mixtures CO2–He and CO–N2–He appears to be consistent with the major features of experimental observation.
Remarkable density structures are observed in the plasma generated during the rise of a high-power COg laser. Jetlike structures and density bowls are seen in interferograms. Infrared imaging shows that these bowls are linked to localized Brillouin-instability backscatter. Depolarization measurements also exhibit filamentary structures that extend far into the underdense regions of the plasma.
This paper presents a new thermodynamic approach, based on the notion of power of separation, for the retrofit problem of finding the minimal energy requirement of an existing binary distillation column when coupling it in parallel with a membrane unit. A new geometric interpretation of this concept, which is supported by a rigorous mathematical proof, is introduced. From it results an efficient and accurate shortcut method to tackle the aforementioned problem. Numerical examples are considered for the energy intensive separation of olefins from paraffins, namely the retrofit of a C3-splitter and the retrofit of a C2-splitter through parallel hybridization with facilitated transport membranes. The results of the proposed shortcut method are compared to those obtained via the nonlinear programming optimization solvers GAMS-CONOPT and GAMS-CoinIpopt for a superstructure based problem formulation, which act as a reference. In both case studies, the shortcut method results in a significant reduction in problem size and in the number of solver iterations, while yielding only a small error on the minimal energy requirement of the column within the hybrid and on the hybrid architecture (i.e., the position of side-streams along the column). It could therefore be used to carry out a rapid screening of alternatives (e.g., different membrane technologies) in order to evaluate potential energy improvements. The proposed approach could also provide mathematical programming algorithms with a good initial guess of the solution.
The multilayer model of Al anodized selective surfaces has been revised by taking into account surface defects and incident angle of of illumination. This theory has been applied to Co-pigmented surfaces. Emphasis was put on extended experimental determination of all parameters used in the theory. With a detailed scanning and transmission electron microscope study of the structure, the size of the pores and their aerial density have been determined. Moreover, the surface roughness has been measured. This has permitted the calculation of the dielectric permeability for each layer. The permeabilities have then been used to compute spectral reflectance curves using the Bruggeman theory. Computer calculated reflectance curves based solely on experimental data agree well with experimental results for λ≥2 μm. At shorter wavelengths, interference peaks that were predicted, but not observed, were minimized by considering surface roughness.
Results of the interaction of gigawatt nanosecond CO2 pulses with various solid targets are reported. The x-ray emission as a function of focusing is not critical within ± 1 mm of the on-target position. The x-ray intensity has an approximate power law dependance of 2.5 with laser energy for all elements. Densitometer analysis of sections of the x-ray pinhole pictures indicate nonuniformities in the plasma and localized hot spots. Line spectra taken with a Bragg crystal indicate temperatures of 200 eV for 4 J of incident energy. Continuum spectra taken with absorbants show characteristic nonthermal behavior, which may be related to parametric instabilities. The x-ray yield as a function of atomic number exhibits a series of peaks which are similar in position to the predictions of a coronal model.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.