Limited Predictability and the Greenhouse Effect – A Scientific Review

1998 ◽  
Vol 9 (6) ◽  
pp. 633-646 ◽  
Author(s):  
A. Wiin-Nielsen
Keyword(s):  
Greenhouse Effect ◽  
General Strategy ◽  
Initial State ◽  
Scientific Review ◽  
Weather Forecasts ◽  
Non Linear ◽  
Model Equations ◽  
Non Linear System ◽  
Almost All ◽  
Aerosol Effects

The concept of limited predictability is reviewed followed by simple examples illustrating the sensitivity to small changes in the initial state and/or the forcing of a non-linear system. Limited predictability applies to almost all non-linear systems, and the concept is therefore important to geophysical systems governed by non-linear model equations. The limited predictability determines the upper limit to operational weather forecasts, but it will also be demonstrated that it has an impact on the determination of the effect of changes in the forcing of the system. The general strategy applied by researchers to estimate the atmospheric greenhouse effect is reviewed. It will be demonstrated that the adopted strategy, due to prescribed changes in the forcing of the climate system, is also influenced by limited predictability in the sense that predicted changes are much larger than observed changes in the temperatures at the surface of the Earth. It is therefore very unlikely that the predictions are reliable. The inclusion of the sulphur-aerosol effects are also discussed with the conclusion that although these cooling agents reduce the greenhouse warming, they do not behave as expected in the sulphur-rich and sulphur-poor regions.

scholarly journals On the existence of equations of evolution

1984 ◽  
Vol 7 (2) ◽  
pp. 409-411
Author(s):  
J. Lubliner
Keyword(s):  
Linear System ◽  
Evolution Equation ◽  
Closed Interval ◽  
The State ◽  
Initial State ◽  
Non Linear ◽  
Non Linear System

A time-independent, non-autonomous non-linear system governed by a principle of determinism (the state at a given time is determined by the initial state and by the control history during the intervening closed interval) is shown to obey a generalized evolution equation (1.2), wherenis such that the state is continuously differentiabie with respect to time whenever the control is of classCn.

scholarly journals Numerical approximation of nonlinear chromatographic models considering Bi-Langmuir isotherm

2020 ◽  
pp. 298-298
Author(s):  
Ambreen Khan ◽  
Sadia Perveen ◽  
Zarmeena Shaheen ◽  
Shamsul Qamar
Keyword(s):  
Case Studies ◽  
Approximate Solutions ◽  
Critical Parameters ◽  
Finite Volume Scheme ◽  
Test Case ◽  
Process Performance ◽  
Lumped Model ◽  
Non Linear ◽  
Model Equations ◽  
Non Linear System

In this research article, two standard models of liquid chromatograophy, namely the dispersive equilibrium model (DEM) and the kinetic lumped model (KLM) are approximated numerically. We studied the transport of multi components in a single column of chromatography considering non linear adsorption thermodynamics. The models are analyzed for standard Bi-Langmuir and generalized Bi-Langmuir types adsorption equilibrium isotherms using Danckwert (Robin) boundary conditions. Mathematically, the model equations form a non linear system of partial differential equations accounting for the phenomena of advection and diffusion, paired with an algebraic equation or a differential equation for adsorption isotherm. An extended semi-discrete high-resolution finite volume scheme is employed to obtain the approximate solutions of the governing model equations. The method has second to third order accuracy. Several test case studies are conducted to examine the influence of various critical parameters on the process performance. The contemplated case studies incorporate the elution process of liquid chromatography with an increasing number of components. In particular, single component, two component and three component mixtures are considered for the assessment of process performance. The formulated numerical algorithm provide an efficacious mechanism for investigating the retention behavior and the influence of mass transfer kinetics on the shapes of elution profiles.

A novel LSSVM-L Hammerstein model structure for system identification and nonlinear model predictive control of CSTR servo and regulatory control

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Akshaykumar Naregalkar ◽  
Subbulekshmi Durairaj
Keyword(s):  
Linear System ◽  
Regulatory Control ◽  
Hammerstein Model ◽  
Support Vector ◽  
Model Structure ◽  
Linear Dynamics ◽  
Vector Machines ◽  
Non Linear ◽  
Laguerre Filters ◽  
Non Linear System

Abstract A continuous stirred tank reactor (CSTR) servo and the regulatory control problem are challenging because of their highly non-linear nature, frequent changes in operating points, and frequent disturbances. System identification is one of the important steps in the CSTR model-based control design. In earlier work, a non-linear system model comprises a linear subsystem followed by static nonlinearities and represented with Laguerre filters followed by the LSSVM (least squares support vector machines). This model structure solves linear dynamics first and then associated nonlinearities. Unlike earlier works, the proposed LSSVM-L (least squares support vector machines and Laguerre filters) Hammerstein model structure solves the nonlinearities associated with the non-linear system first and then linear dynamics. Thus, the proposed Hammerstein’s model structure deals with the nonlinearities before affecting the entire system, decreasing the model complexity and providing a simple model structure. This new Hammerstein model is stable, precise, and simple to implement and provides the CSTR model with a good model fit%. Simulation studies illustrate the benefit and effectiveness of the proposed LSSVM-L Hammerstein model and its efficacy as a non-linear model predictive controller for the servo and regulatory control problem.

On a non-linear system for shape memory alloys

1990 ◽  
Vol 2 (1) ◽  
pp. 65-76 ◽  
Author(s):  
Ph. B�nilan ◽  
D. Blanchard ◽  
H. Ghidouche
Keyword(s):  
Linear System ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Non Linear ◽  
Non Linear System

Position Control of Hydraulic Actuators Using Fuzzy Pulse Width Modulation (PWM)

2015 ◽  
Vol 735 ◽  
pp. 294-298 ◽  
Author(s):  
Wei Ying Lai ◽  
Nurfarahin Onn ◽  
Collin Howe Hing Tang ◽  
Mohamed Hussein
Keyword(s):  
Fuzzy Logic ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Solenoid Valve ◽  
Operating Conditions ◽  
Hydraulic Actuators ◽  
Non Linear ◽  
Fuzzy Logic Approach ◽  
Logic Approach ◽  
Non Linear System

Hydraulic actuators are widely employed for industrial automation for its high power over weight ratio, functionality in tough operating conditions and low cost. However, the dynamics of hydraulic systems are non-linear and the system subjected to non-smooth and discontinuous non-linearities due to directional change of valve opening, friction, valve overlap and changes of hydraulic pressure acted on valve spool. Taking into account the effect of nonlinear parameter variations such as bulk modulus, compressibility of oil or viscosity of oil, fuzzy logic approach is chosen. Fuzzy control can adapt the inconstant working condition and non-linear system alongside of its robustness. For PWM controlled hydraulic component such as solenoid valve, effective approximation of the flow properties in a solenoid valve is essential. In this paper, the effect of fuzzy logic approach incorporated on pulse width modulation (PWM) controlled hydraulic system is to be investigated and experimentally verified.

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