Conditioning of Quasi-Newton Methods for Function Minimization

Shanno, David F.

doi:10.2307/2004840

Cited by 787 publications

(794 citation statements)

References 3 publications

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“…Parameters u *tot , z 0 , and C b are estimated by minimizing the root-mean-square error between measured velocity and suspended sand concentrations (U meas , C meas ) and the models (U mod , C mod [82] The quantities r and s are the number of velocity measurements (r = 5-40) and concentration measurements (s = 3-6). Equation (A12) was used in a minimization algorithm using the Broyden-Fletcher-Goldfarb-Shanno Quasi-Newton method with a cubic line procedure [Shanno, 1970] to produce the parameters u *tot , z 0 , and C b recorded in Table 3.…”

Section: Inverse Modelmentioning

confidence: 99%

The morphology and evolution of channels on the Wax Lake Delta, Louisiana, USA

Shaw

Mohrig

Whitman³

2013

JGR Earth Surface

105

108

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[1] River deltas are classic depositional systems, but a growing body of literature shows that their channel networks can be erosional. Furthermore, this erosion can attack channel beds of consolidated mud that acts as bedrock. To better understand the channel networks of natural deltas and engineered river diversions, we investigate bathymetric and planimetric change, bed cover, and sediment transport in the Wax Lake Delta (WLD) in coastal Louisiana, USA. Channels have eroded up to 40% of modern flow depth between the WLD's initiation in 1973 and 1999. Aerial image analysis shows that channels have widened by 11% between 1991 and 2009, forcing the downstream migration of islands. Channel beds are composed of 85-98% muddy bedrock, with the remainder covered by alluvial sands. Water velocity, grain size, and suspended sand concentration measurements during the 2009 spring flood show that almost all available grain sizes are transported in suspension. Flow was supply limited during this period, with the calculated sand concentration at the height of the bed load layer is 1-4 orders of magnitude smaller than predicted for saturated sand transport. We test "the cover effect" and "the tools effect" previously proposed for bedrock erosion in upland river channels. Bedrock erosion and alluvial cover are anti-correlated (the cover effect), but the observations do not closely follow previously proposed relationships. The difference in erosion rate between clear water and sand-rich water shows that abrasion by sand (the tools effect) accounts for 51% ± 56% of bedrock erosion when it is present.

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Section: Inverse Modelmentioning

confidence: 99%

The morphology and evolution of channels on the Wax Lake Delta, Louisiana, USA

Shaw

Mohrig

Whitman³

2013

JGR Earth Surface

105

108

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“…Os modelos foram obtidos a partir dos dados cristalográficos 31 . Os parâmetros geométricos das moléculas de CO, CO 2 e NH 3 foram totalmente otimizados, utilizando o algoritmo Broyden-Fletcher-Goldfarb-Shanno (BFGS) [63][64][65][66] , enquanto que os parâmetros geométricos do "cluster" foram mantidos congelados. Os efeitos da otimização não deixam de ser importantes, entretanto, os modelos estudados têm grande número de áto-mos e, conseqüentemente, elevado grau de liberdade.…”

Section: Modelos E Métodosunclassified

Análise teórica da interação de CO, CO2 e NH3 com ZnO

Martins¹,

Vasconcellos

Longo³

et al. 2004

Quím. Nova

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Recebido em 1/10/02; aceito em 16/7/03 THEORETICAL ANALYSIS OF THE INTERACTION OF CO, CO 2 , AND NH 3 WITH ZnO. This paper presents a study of the interaction of small molecules with ZnO surfaces by means of theoretical methods. The AM1 semi-empirical method was used for optimizing the geometric parameters of adsorbed molecules. The optimized AM1 structures were used in the calculations of the ab initio RHF method with the 3-21G* basis set. The interaction of CO, CO 2 and NH 3 molecules were studied with (ZnO) 22 and (ZnO) 60 cluster models. We have analyzed the interaction energy, SCF orbital energies, Mulliken charges and the density of states (DOS).Keywords: zinc oxide; interaction; theoretical methods. INTRODUÇÃOO óxido de zinco tem sido alvo de inúmeras pesquisas no decorrer dos últimos anos 1,2 com uma importante aplicação em materiais eletrônicos, tais como, células foto-voltaicas 1 , varistores 2,3 , além da grande diversidade de aplicações relacionadas a defeitos 4,5 , catálise 6-12 , sensores de gases 13 e quimissorção 14 . Superfícies de óxidos são sistemas de especial importância em ciências dos materiais 15,16 , dentre as quais, a superfície do ZnO tem uma diversificada atividade catalítica para um grande número de reações. A maioria dos catalisadores comerciais consiste de pequenas partículas de metal em grandes superfícies de óxidos, onde o metal é a fase ativa e os óxidos podem se comportar como materiais inertes ou modificar a atividade do metal, interagindo através de ligações 17,18 . Em outros, os óxidos formam parte da fase ativa onde a atividade catalítica total do sistema é determinada por interações cooperativas, que envolvem o metal e sítios ativos do óxido. Um completo entendimento destes sistemas catalíticos requer uma compreensão detalhada dos fatores que determinam as interações entre os vários constituintes: metal ↔ óxido, metal ↔ adsorvato e óxido ↔ adsorvato 19 O ZnO também é considerado um consagrado varistor, isto é, um dispositivo eletrônico de proteção contra sobrecarga de tensão ou ainda um dispositivo de descarga elétrica, que possui um elevado índice de não linearidade 30 . Suas propriedades elétricas dependem da microestrutura final do material que, por sua vez, pode ser controlada por diversos parâmetros físico-químicos, tais como processamento utilizado, temperatura de sinterização, taxa de aquecimento e resfriamento e natureza química dos dopantes. O ZnO é também um excelente protótipo para o estudo de estrutura eletrônica de interfaces e propriedades de transportes em óxidos semicondutores 1,3 .O ZnO cristaliza-se em uma estrutura hexagonal do tipo wurtizita, na qual cada átomo de zinco está no centro de um tetraedro distorcido coordenado a quatro outros oxigênios vizinhos 31 . Existem três superfícies naturais: a polar terminada em Zn, o plano hexagonal (0001), onde os íons zinco estão posicionados para fora, o plano polar (0001 -) terminado em oxigênio, onde os íons oxigênio estão posicionados para fora e o plano não polar prismático (101 -0) onde ambos, zinco e oxig...

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“…The particular nonlinear search used in this investigation was a quasi-Newton method, where the gradient is estimated using a numerical update; see, for instance, [16] and [17].…”

Section: Separating the Optimization Problem:m Odel Parameters Amentioning

confidence: 99%

System Identification From Multiple Short-Time-Duration Signals

Anderson

Dean

Kadirkamanathan

et al. 2007

IEEE Trans. Biomed. Eng.

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Article:Anderson, S.R., Dean, P., Kadirkamanathan, V. et ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract-System identification problems often arise where the only modeling records available consist of multiple short-timeduration signals. This motivates the development of a modeling approach that is tailored for this situation. An identification algorithm is presented here for parameter estimation based on minimizing the simulated prediction error, across multiple signals. The additional complexity of estimating the initial states corresponding to each signal is removed from the estimation algorithm. A numerical simulation demonstrates that the proposed algorithm performs well in comparison to the often-used least squares method (which leads to biased estimates when identifying systems from measurement noise corrupted signals). The approach is applied to the identification of the passive oculomotor plant; parameters are estimated that describe the dynamics of the plant, which represent the time constants of the visco-elastic elements that characterize the plant connective tissue.

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Conditioning of Quasi-Newton Methods for Function Minimization

Cited by 787 publications

References 3 publications

The morphology and evolution of channels on the Wax Lake Delta, Louisiana, USA

The morphology and evolution of channels on the Wax Lake Delta, Louisiana, USA

Análise teórica da interação de CO, CO2 e NH3 com ZnO

System Identification From Multiple Short-Time-Duration Signals

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