Semi-Empirical Modelling of SLD Physics

2004 ◽  
Author(s):  
William Wright ◽  
Mark Potapczuk
Keyword(s):  
Empirical Modelling ◽  
Semi Empirical

scholarly journals Progress in semi-empirical modelling of main-sequence stellar chromospheres

1996 ◽  
Vol 176 ◽  
pp. 547-555
Author(s):  
E.R. Houdebine
Keyword(s):  
Main Sequence ◽  
Radiation Transfer ◽  
Research Programme ◽  
Significant Progress ◽  
Wave Dissipation ◽  
Empirical Modelling ◽  
Spectral Signatures ◽  
Outer Atmosphere ◽  
Semi Empirical

We present the results of a long term research programme on the outer atmospheres of main-sequence dwarfs. Combining NLTE-radiation transfer calculations with high resolution spectroscopic observations have led to significant progress in understanding chromospheric physical properties and spectral signatures. We emphasize that in order to unravel the extremely complex physics of the outer atmosphere and its energy source, magnetic field and acoustic wave dissipation, one must isolate the influence of all stellar parameters.

Interception of radionuclides by planophile crops: A simple semi-empirical modelling approach in case of nuclear accident fallout

2020 ◽  
Vol 266 ◽  
pp. 115308
Author(s):  
A. Cristina ◽  
R. Samson ◽  
N. Horemans ◽  
M. Van Hees ◽  
J. Wannijn ◽  
...  
Keyword(s):  
Nuclear Accident ◽  
Empirical Modelling ◽  
Semi Empirical ◽  
Modelling Approach

scholarly journals Semi-empirical modelling of stellar magnetic activity

2011 ◽  
Vol 7 (S286) ◽  
pp. 307-316
Author(s):  
Adriana Valio
Keyword(s):  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Magnetic Activity ◽  
Maunder Minimum ◽  
The Sun ◽  
Cyclic Activity ◽  
Empirical Modelling ◽  
Level Of Activity ◽  
Total Luminosity ◽  
Semi Empirical

AbstractSince Galileo, for four hundred years, dark spots have been observed systematically on the surface of the Sun. The monitoring of the sunspot number has shown that their number varies periodically every 11 years. This is the well-known solar activity cycle that is caused by the periodic changes of the magnetic field of the Sun. Not only do spots vary in number on a timescale of a decade, but the total luminosity and other signatures of activity such as flares and coronal mass ejections also increase and decrease with the 11-year cycle. Still unexplained to the present date are periods of decades with almost an absence of activity, where the best known example is the Maunder Minimum. Other stars also exhibit signs of cyclic activity, however the level of activity is usually thousand times higher than the solar one. Obviously, this is due to the difficulty of observing activity at the solar level on most stars. Presently, a method has been developed to detect and study individual solar like spots on the surface of planet-harbouring stars. As the planet eclipses dark patches on the surface of the star, a detectable signature can be observed in the light curve of the star during the transit. The study of a different variety of stars allows for a better understanding of magnetic cycles and the evolution of stars.

Molecular nanowires and their properties as electrical conductors

2017 ◽  
Author(s):  
George Kirczenow
Keyword(s):  
Ab Initio ◽  
Electrical Conduction ◽  
Future Development ◽  
Self Assembly ◽  
Empirical Modelling ◽  
Experimental Systems ◽  
The Future ◽  
Key Issues ◽  
Semi Empirical ◽  
Electrical Conductors

This article describes the properties of molecular nanowires as electrical conductors. It begins by defining a molecular nanowire and describing a specific example of a molecular nanowire, along with the concept of molecular nanowire self-assembly. It then considers how molecular nanowires are realized in the laboratory as well as the relationships between these methodologies, the systems that are produced and some experiments being performed on them. It also looks at the different kinds of molecules, electrodes and linkers out of which molecular nanowires are being or may be constructed; the Landauer approach to electrical conduction in molecular nanowires; the principles and limitations of ab-initio and semi-empirical modelling of molecular nanowires in the context of electrical conduction; and four specific experimental systems and the extent to which their observed behavior has been understood theoretically. The article concludes with a summary of key issues for the future development of the field.

Semi-empirical model for a hydraulic servo-solenoid valve

2002 ◽  
Vol 216 (3) ◽  
pp. 237-248 ◽  
Author(s):  
J A Ferreira ◽  
F Gomes de Almeida ◽  
M R Quintas
Keyword(s):  
Frequency Response ◽  
High Performance ◽  
Closed Loop ◽  
Optimization Techniques ◽  
Order System ◽  
Model Parameters ◽  
Empirical Modelling ◽  
Non Linear ◽  
Spool Valves ◽  
Semi Empirical

High-performance proportional valves, also called servo-solenoid valves, can be used today in closed-loop applications that previously were only possible with servo-valves. The valve spool motion is controlled in a closed loop with a dedicated hardware controller that enhances the valve frequency response and minimizes some non-linear effects. Owing to their lower cost and maintenance requirements as well as increasing performance they can compete with servo-valves in a large number of applications. This paper describes a new semi-empirical modelling approach for hydraulic proportional spool valves to be used in hardware-in-the-loop simulation experiments. The developed models use either data sheet or experimental values to fit the model parameters in order to reproduce both static (pressure gain, leakage flowrate and flow gain) and dynamic (frequency response) valve characteristics. Valve behaviour is divided into two parts: the static behaviour and the dynamic behaviour. A parameter decoupled model, with a variable equation structure, and a flexible model, with a fixed equation structure, are proposed for the static part. Spool dynamics are modelled by a non-linear second-order system, with limited velocity and acceleration, the parameters being adjusted using optimization techniques.

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