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Full-Text Articles in Engineering
Thermodynamic Modeling, Energy Equipartition, And Nonconservation Of Entropy For Discrete-Time Dynamical Systems, Wassim H. Haddad, Qing Hui, Sergey G. Nersesov, Vijaysekhar Chellaboina
Thermodynamic Modeling, Energy Equipartition, And Nonconservation Of Entropy For Discrete-Time Dynamical Systems, Wassim H. Haddad, Qing Hui, Sergey G. Nersesov, Vijaysekhar Chellaboina
Department of Electrical and Computer Engineering: Faculty Publications
We develop thermodynamic models for discrete-time large-scale dynamical systems. Specifically, using compartmental dynamical system theory, we develop energy flowmodels possessing energy conservation, energy equipartition, temperature equipartition, and entropy nonconservation principles for discrete-time, large-scale dynamical systems. Furthermore, we introduce a new and dual notion to entropy; namely, ectropy, as a measure of the tendency of a dynamical system to do useful work and grow more organized, and show that conservation of energy in an isolated thermodynamic system necessarily leads to nonconservation of ectropy and entropy. In addition, using the system ectropy as a Lyapunov function candidate, we show that our discrete-time, …
Annealing And Oxidation Of Silicon Oxide Films Prepared By Plasma-Enhanced Chemical Vapor Deposition, X. Y. Chen, Yongfeng Lu, L. J. Tang, Y. H. Wu, B. J. Cho, J. R. Dong, W. D. Song
Annealing And Oxidation Of Silicon Oxide Films Prepared By Plasma-Enhanced Chemical Vapor Deposition, X. Y. Chen, Yongfeng Lu, L. J. Tang, Y. H. Wu, B. J. Cho, J. R. Dong, W. D. Song
Department of Electrical and Computer Engineering: Faculty Publications
We have investigated phase separation, silicon nanocrystal (Si NC) formation and optical properties of Si oxide (SiOx, 0,x,2) films by high-vacuum annealing and dry oxidation. The SiOx films were deposited by plasma-enhanced chemical vapor deposition at different nitrous–oxide/silane flow ratios. The physical and optical properties of the SiOx films were studied as a result of high-vacuum annealing and thermal oxidation. X-ray photoelectron spectroscopy (XPS) reveals that the as-deposited films have a random-bonding or continuous-random-network structure with different oxidation states. After annealing at temperatures above 1000 °C, the intermediate Si continuum in XPS spectra (referring to the …
Parametric Investigation Of Laser Nanoimprinting Of Hemispherical Cavity Arrays, L. P. Li, Yongfeng Lu, D. W. Doerr, Dennis R. Alexander, X. Y. Chen
Parametric Investigation Of Laser Nanoimprinting Of Hemispherical Cavity Arrays, L. P. Li, Yongfeng Lu, D. W. Doerr, Dennis R. Alexander, X. Y. Chen
Department of Electrical and Computer Engineering: Faculty Publications
A monolayer of self-assembled silica particles can be imprinted into a silicon substrate by laser irradiation (KrF excimer laser, λ=248 nm). Periodical hemispherical cavities can be therefore created on the substrate surface. The influences of various particle sizes and laser fluence were investigated. In addition, preheating of the substrate significantly improves the performance. One-dimensional thermal calculation was employed to understand the thermal effect in this process. Three-dimensional optical simulation provided an accurate insight into the light intensity enhancement. Raman spectroscopy was used to examine the stress induced by the laser imprinting process resided in the cavity structures.
Optical Properties Of SioX Nanostructured Films By Pulsed-Laser Deposition At Different Substrate Temperatures, X. Y. Chen, Yongfeng Lu, Y. H. Wu, B. J. Cho, W. D. Song, D. Y. Dai
Optical Properties Of SioX Nanostructured Films By Pulsed-Laser Deposition At Different Substrate Temperatures, X. Y. Chen, Yongfeng Lu, Y. H. Wu, B. J. Cho, W. D. Song, D. Y. Dai
Department of Electrical and Computer Engineering: Faculty Publications
Silicon oxide sSiOxd nanostructured films have been formed by pulsed-laser deposition of Si in oxygen at different substrate temperatures, in order to study the structures and optical properties related to quantum confinement effects. After laser ablation, the single-crystal Si(100) target is converted to a polycrystal structure and shows weak photoluminescence (PL). The as-deposited SiOx nanostructured films show large particles (i.e., droplets) on a uniform background film. The droplets with weak PL emission have the same high crystallinity as the Si(100) target. Strong PL is observed from the amorphouslike background films rather than from the crystalline droplets. As …
Optical Modeling Of Iridium Thin Film Erosion Under Oxygen Plasma Exposure*, Li Yan, John A. Woollam
Optical Modeling Of Iridium Thin Film Erosion Under Oxygen Plasma Exposure*, Li Yan, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
This work is motivated by interest in use of iridium metal films in the space environment. Optical metrology is a sensitive tool for study of film roughness, optical constants, and microstructural properties. In the present paper, in situ spectroscopic ellipsometry is applied to monitor oxygen plasma etching of films of iridium/chromium on fused silica substrates, using an electron cyclotron resonance plasma source. Optical modeling allows for a fundamental understanding of the plasma etching mechanism. Analysis of spectroscopic psi and delta data at selected time slices suggests the iridium film is etched away gradually upon plasma irradiation, while showing no signs …
Laser-Assisted Nanoscale Deposition Of Diamond-Like Carbon Films On Tungsten Tips, J. Shi, Yongfeng Lu, R. S. Cherukuri, K. K. Mendu, D. W. Doerr, Dennis R. Alexander, L. P. Li, X. Y. Chen
Laser-Assisted Nanoscale Deposition Of Diamond-Like Carbon Films On Tungsten Tips, J. Shi, Yongfeng Lu, R. S. Cherukuri, K. K. Mendu, D. W. Doerr, Dennis R. Alexander, L. P. Li, X. Y. Chen
Department of Electrical and Computer Engineering: Faculty Publications
Diamond-like carbon (DLC) films were deposited on tungsten tips under KrF excimer laser irradiation in benzene solution. The deposition process was found to be highly dependent on tip sharpness. Tips with larger curvature radii and smaller aspect ratios could not be coated with DLC films under the same condition as that for sharp tips. Raman spectra showed that more sp3 tetrahedral structures were present in the DLC films on a tip with a smaller curvature radius. Simulation results showed that the tip sharpness dependent local optical enhancement played an important role in the DLC deposition process. An optical field …
Vector Dissipativity Theory For Large-Scale Impulsive Dynamical Systems, Wassim H. Haddad, Vijaysekhar Chellaboina, Qing Hui, Sergey Nersesov
Vector Dissipativity Theory For Large-Scale Impulsive Dynamical Systems, Wassim H. Haddad, Vijaysekhar Chellaboina, Qing Hui, Sergey Nersesov
Department of Electrical and Computer Engineering: Faculty Publications
Modern complex large-scale impulsive systems involvemultiplemodes of operation placing stringent demands on controller analysis of increasing complexity. In analyzing these large-scale systems, it is often desirable to treat the overall impulsive system as a collection of interconnected impulsive subsystems. Solution properties of the large-scale impulsive system are then deduced from the solution properties of the individual impulsive subsystems and the nature of the impulsive system interconnections. In this paper, we develop vector dissipativity theory for large-scale impulsive dynamical systems. Specifically, using vector storage functions and vector hybrid supply rates, dissipativity properties of the composite large-scale impulsive systems are shown to …
Investigation Of Femtosecond Laser-Assisted Micromachining Of Lithium Niobate, A. Malshe, D. Deshpande, E. Stach, Kamlakar Rajurkar, Dennis R. Alexander
Investigation Of Femtosecond Laser-Assisted Micromachining Of Lithium Niobate, A. Malshe, D. Deshpande, E. Stach, Kamlakar Rajurkar, Dennis R. Alexander
Department of Electrical and Computer Engineering: Faculty Publications
Lithium Niobate has a potential for applications in electronics and communication industries due to its unique electro-optical, piezoelectric and nonlinear properties. Femtosecond laser machining offers the best alternative to machine the mechanically fragile and optically delicate lithium niobate crystal. This paper reports a study of the effect of femtosecond laser machining on the surface integrity of lithium niobate. The transmission electron microscopy reveals a 100nm thin amorphous region and a void. The chemical analysis shows a loss of lithium and oxygen from the surface and sub-surface. Optical illumination facilitates the selective readout of the written spots of 2 microns size.