Linear models with nearly frequency independent complex stiffness leading to causal behaviour in time domain

2006 ◽  
Vol 36 (1) ◽  
pp. 13-33 ◽  
Author(s):  
G. B. Muravskii
Keyword(s):  
Time Domain ◽  
Linear Models ◽  
Frequency Independent

Identifying linear models from time domain simulations

1997 ◽  
Vol 10 (2) ◽  
pp. 26-30 ◽  
Author(s):  
J.J. Sanchez-Gasca ◽  
K. Clark ◽  
N.W. Miller ◽  
H. Okamoto ◽  
A. Kurita ◽  
...  
Keyword(s):  
Time Domain ◽  
Linear Models

A Conjecture on the Interface Mechanics in Fractures Based on the Interpretation of Impulse Vests

1989 ◽  
Vol 203 (4) ◽  
pp. 203-205 ◽  
Author(s):  
J A Brandon ◽  
J Richards
Keyword(s):  
Fracture Healing ◽  
Linear Model ◽  
Time Domain ◽  
Linear Models ◽  
Callus Formation ◽  
Stiffness Model ◽  
Interface Mechanics ◽  
Static Mechanical ◽  
Characteristic Signal ◽  
Two Stages

Time-domain tests for monitoring fracture healing, undertaken by the authors and workers elsewhere, show a repeatable characteristic signal behaviour which is difficult to explain using the linear models prevailing in biomechanics. The paper proposes a simple non-linear model which, it is believed, will reproduce the observed signal behaviour and is consistent with the biphasic stiffness model previously identifed in static mechanical testing for monitoring of fracture healing. This, in turn, correlates with the two stages of callus formation in the accepted biological model.

scholarly journals Linear models of dissipation whose Q is almost frequency independent

2011 ◽  
Vol 19 (4) ◽  
Author(s):  
M. CAPUTO
Keyword(s):  
Fractional Derivatives ◽  
Linear Models ◽  
Solid Sphere ◽  
Inorganic Solids ◽  
The Earth ◽  
Single Substance ◽  
Stress Strain Relation ◽  
Frequency Independent ◽  
Experimental Values ◽  
Large Frequency

Laboratory experiments and field observations indicate<br />that tlie Q of many non ferromagnetic inorganic solids is almost frequency<br />independent in the range 10' to 10~2 cps; although no single substance has<br />been investigated over the entire frequency spectrum. One of the purposes<br />of this investigation is to find the analytic expression of a linear dissipative<br />mechanism whose Q is almost frequency independent over large frequency<br />ranges. This will be obtained by introducing fractional derivatives in the<br />stress strain relation.<br />Since the aim of this research is to also contribute to elucidating the<br />dissipating mechanism in the earth free modes, we shall treat the cases of<br />dissipation in the free purely torsional modes of a shell and the purely<br />radial vibration of a solid sphere.<br />The theory is checked with the new values determined for the Q of<br />the spheroidal free modes of the earth in the range between 10 and 5 minutes<br />integrated with the Q of the Railegh waves in the range between 5 and 0.6<br />minutes.<br />Another check of the theory is made with the experimental values<br />of the Q of the longitudinal waves in an alluminimi rod, in the range between<br />10-5 and 10-3 seconds.<br />In both clicks the theory represents the observed phenomena very<br />satisfactory.

A Time-Domain Solution to the Motions of a Steered Ship in Waves

1974 ◽  
Vol 18 (01) ◽  
pp. 32-45
Author(s):  
Leonardo Pérez y Pérez
Keyword(s):  
Time Domain ◽  
Experimental Results ◽  
Damping Coefficient ◽  
Convolution Integral ◽  
Roll Damping ◽  
Ship Model ◽  
Frequency Independent ◽  
Exciting Forces

The motions of a ship in waves are expressed as linear responses to arbitrary exciting forces by means of a convolution integral. Frequency-independent nonlinearities are considered to be part of the arbitrary forces. The method is used to numerically simulate the sway, roll, and yaw motions of a ship model in waves with nonlinear roll damping coefficient and an autopilot. The agreement of the simulation with experimental results is quite reasonable. This method is restricted neither to these modes of motion nor to these nonlinearities; it can be used for all six modes of motion and any frequency-independent nonlinearity.

Obtaining multi-loop pursuit-control pilot models from computer simulation

2008 ◽  
Vol 222 (2) ◽  
pp. 189-199 ◽  
Author(s):  
R A Hess
Keyword(s):  
Computer Simulation ◽  
Time Domain ◽  
Flight Control ◽  
Linear Models ◽  
Degree Of Freedom ◽  
Pilot Model ◽  
Pursuit Control ◽  
The Time Domain ◽  
Frequency Domain Techniques ◽  
Six Degree Of Freedom

A method for generating simplified pursuit-control pilot models for computer simulation of multi-axis flight control tasks has been developed. The method involves a sequential loop closure synthesis procedure for creating the pilot model and includes handling qualities estimation. The original model formulation previously reported in the literature used frequency-domain techniques, primarily Bode diagrams to select model gains. The present research demonstrates how similar results can be obtained in the time-domain. This latter approach is particularly useful when complex, non-linear aircraft models are being used. The time-domain approach is exercised in a six-degree of freedom rotorcraft control simulation and in a six-degree of freedom tailless fighter simulation, both involving linear models.

scholarly journals CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO

Irriga ◽  
2005 ◽  
Vol 10 (2) ◽  
pp. 174-183
Author(s):  
Tibério Santos Martins da Silva ◽  
Vital Pedro da Silva Paz ◽  
Eugênio Ferreira Coelho ◽  
Maurício Antônio Coelho Filho ◽  
Gessionei Da Silva Santana
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Time Domain ◽  
Linear Models ◽  
Time Domain Reflectometry ◽  
Soil Electrical Conductivity ◽  
Bulk Electrical Conductivity

CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO  Tibério Santos Martins da Silva1; Vital Pedro da Silva Paz2; Eugênio Ferreira Coelho3; Maurício Antônio Coelho Filho3; Gessionei da Silva Santana41Universidade Federal da Bahia,  Cruz das Almas, BA, tibé[email protected] de Engenharia Agrícola, Universidade Federal da Bahia, Cruz das Almas-BA, 3Embrapa Mandioca e Fruticultura, Cruz das Almas-BA4Universidade Federal de Viçosa, Viçosa, MG,   1 RESUMO O trabalho teve como objetivo definir, em campo e em laboratório, modelos matemáticos que melhor relacionam a condutividade elétrica aparente (CEa), a umidade do solo (q) e a condutividade elétrica da solução do solo (CEw) sob aplicação de cloreto de potássio, via água de irrigação por gotejamento. O experimento consistiu de leituras de CEa e q com um analisador de umidade de reflectometria no domínio do tempo (TDR) em colunas de solo em laboratório e em várias posições de uma malha retangular de um perfil do solo, em condições de campo, seguido da extração de solução iônica nas respectivas posições. Foram ajustados modelos lineares e não lineares relacionando CEa, q e CEw. O resultados permitiram concluir que a CEw da solução do solo pode ser monitorada a partir de leituras de CEa pela TDR para fins de distribuição de solutos no solo sob fertirrigação, com uso dos modelos de Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) e empírico em condições de campo e laboratório. O modelo de Rhoades et al. (1989) e Rhoades et al. (1976) mostraram-se adequados apenas para os estudos em laboratório. UNITERMOS: fertirrigação, TDR  SILVA, T. S. M. DA; PAZ, V. P. DA S.; COELHO, E. F.; COELHO FILHO, M. A.; SANTANA, G. DA S. SOIL SOLUTION ELECTRICAL CONDUCTIVITY AS A FUNCTION OF BULK ELECTRICAL CONDUCTIVITY AND SOIL WATER CONTENT UNDER POTASSIUM CLORIDE APPLICATION USING TIME DOMAIN REFLECTOMETRY  2 ABSTRACT This study aimed to define mathematical models that suitably relate bulk electrical conductivity (CEa), soil water content (q) and soil solution electrical conductivity (CEw) under potassium chloride application by drip irrigation. The experiment consisted of readings of CEa and q using a Time Domain Reflectometry analyzer (TDR) in soil columns in laboratory and on several positions of rectangular soil profile grid under field conditions. Ionic solution was extracted in all positions of TDR readings. Linear and non-linear models relating CEa, q and CEw were adjusted to laboratory and field data. Results allowed to conclude that CEw may be monitored by readings of CEa from TDR for soil solute distribution under fertirrigation, using models of Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) and an empirical model in lab and in field. The models of de Rhoades et al. (1989) e Rhoades et al. (1976) were suitable only for laboratory studies. KEYWORDS: fertirrigation, soil electrical conductivity, TDR

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