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You searched for subject:(Nonlinear optical parameters). Showing records 1 – 2 of 2 total matches.

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1. William Júnio de Lima. Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos.

Degree: 2011, Federal University of Uberlândia

In this work, we have used a Ti3+:Safira laser tuned at 803nm to performed time-resolved measurements using the Z-scan technique to characterize the nonlinear optical properties of phosphate glasses. The glass matrix, labeled PAN (P2O5-Al2O3-Na2CO3), was doped with increasing Nd3+ concentration, ranging from 0.5 to 5 wt%. We have seen that the optical nonlinearity has a linear increase dependence with the doping ion concentration. Therefore, we propose a new approach to obtain the parameters polarizability difference, Δα, and absorption cross-section difference, Δσ, between the ground and excited states. We have also studied the upconversion Auger process in the same set of samples and we found a linear dependence of upconversion parameter γ in respect to the ion concentration. All results obtained are in good agreement with others found in the literature.

Neste trabalho, usando um laser de Ti3+:Safira sintonizado em 803nm como comprimento de onda de excitação, foram realizadas medidas de Z-scan resolvidas no tempo para caracterizar as propriedades óticas não lineares de matrizes vítreas à base de fosfato. Tal matriz denominada PAN (P2O5-Al2O3-Na2CO3) foi dopada com concentrações crescentes de Nd3+, variando de 0.5 a 5 peso%. Verificou-se que a dependência da não linearidade ótica destas amostras com a concentração do íon dopante, possui uma forma crescente e linear. A partir disso, foi proposto um novo procedimento para a obtenção dos parâmetros, diferença de polarizabilidade Δα e de seção de choque de absorção Δζ entre os estados excitado e fundamental do sistema. Fez-se também um estudo do processo de Conversão Ascendente de Energia Auger (CAA), para a mesma matriz e observou-se a dependência linear do parâmetro de CAA, γ, como função da concentração. Os resultados estão em bom acordo com outros encontrados na literatura.

Advisors/Committee Members: Djalmir Nestor Messias, Viviane Pilla, Sandro Marcio Lima.

Subjects/Keywords: Refração; Nonlinear refractive index; Upconversion Auger; Polarizability difference; Absorption cross section difference; Nonlinear optical parameters; Ótica não-linar; Índice de refração não linear; Conversão ascendente auger; Diferença de polarizabilidade; Diferença de seção de choque de absorção; Parâmetros óticas não lineares; FISICA

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lima, W. J. d. (2011). Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos. (Thesis). Federal University of Uberlândia. Retrieved from http://www.bdtd.ufu.br//tde_busca/arquivo.php?codArquivo=3325

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Lima, William Júnio de. “Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos.” 2011. Thesis, Federal University of Uberlândia. Accessed November 29, 2020. http://www.bdtd.ufu.br//tde_busca/arquivo.php?codArquivo=3325.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Lima, William Júnio de. “Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos.” 2011. Web. 29 Nov 2020.

Vancouver:

Lima WJd. Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos. [Internet] [Thesis]. Federal University of Uberlândia; 2011. [cited 2020 Nov 29]. Available from: http://www.bdtd.ufu.br//tde_busca/arquivo.php?codArquivo=3325.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Lima WJd. Estudos das propriedade óticas não lineares em meios dopados com absorvedores lentos. [Thesis]. Federal University of Uberlândia; 2011. Available from: http://www.bdtd.ufu.br//tde_busca/arquivo.php?codArquivo=3325

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Brigham Young University

2. Hakala, Tim. Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control.

Degree: PhD, 2006, Brigham Young University

A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.

Subjects/Keywords: control; position; adaptive; impulsive; settling-time; nonlinear friction; pulses; displacements; precise; tolerances; log-spaced; update; distributed; learning; Coulomb; Stribeck; Tomizuka; Yang; AIC; PID; MRAC; STR; RTAI; Linux; FreeBSD; kernel modules; microcontroller; convergence; practical; self-tuning; methods; techniques; limit-cycles; steady-state; error; zero; stable; stability; bound; envelope; partitioned; scheme; lookup-table; multi-point; adaptation; repeatable; mean; servo; motor; exponential; square-law; rise-time; real-time; log-log interpolation; pro-forma; curve-fit; sensitivity; compliance; variable; static; dynamic response; torque; acceleration; velocity; optical encoder; parameters; evolution; fixed-law; enhanced split; weighting; initialization; trajectory; layered processes; Mechanical Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hakala, T. (2006). Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control. (Doctoral Dissertation). Brigham Young University. Retrieved from https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2060&context=etd

Chicago Manual of Style (16th Edition):

Hakala, Tim. “Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control.” 2006. Doctoral Dissertation, Brigham Young University. Accessed November 29, 2020. https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2060&context=etd.

MLA Handbook (7th Edition):

Hakala, Tim. “Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control.” 2006. Web. 29 Nov 2020.

Vancouver:

Hakala T. Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control. [Internet] [Doctoral dissertation]. Brigham Young University; 2006. [cited 2020 Nov 29]. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2060&context=etd.

Council of Science Editors:

Hakala T. Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control. [Doctoral Dissertation]. Brigham Young University; 2006. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2060&context=etd

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