Semi-empirical modelling of radiation exposure to naturally occuring radioactive materials (NORMS) in a goldmine in Ghana

2006 ◽  
Vol 10 (1) ◽  
Author(s):  
EO Darko ◽  
GK Tetteh ◽  
EHK Akaho
Keyword(s):  
Radiation Exposure ◽  
Radioactive Materials ◽  
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.

Retrospection of Chernobyl Nuclear Accident for Decision Analysis Concerning Remedial Actions in Ukraine

2007 ◽  
Author(s):  
Vladimir Georgievskiy
Keyword(s):  
Radiation Exposure ◽  
Chernobyl Accident ◽  
Late Phase ◽  
Nuclear Accident ◽  
First Year ◽  
Radioactive Materials ◽  
Intermediate Phases ◽  
Radiological Data ◽  
Order Of Magnitude ◽  
Remedial Actions

It is considered the efficacy of decisions concerning remedial actions when of-site radiological monitoring in the early and (or) in the intermediate phases was absent or was not informative. There are examples of such situations in the former Soviet Union where many people have been exposed: releases of radioactive materials from “Krasnoyarsk-26” into Enisey River, releases of radioactive materials from “Chelabinsk-65” (the Kishtim accident), nuclear tests at the Semipalatinsk Test Site, the Chernobyl nuclear accident etc. If monitoring in the early and (or) in the intermediate phases is absent the decisions concerning remedial actions are usually developed on the base of permanent monitoring. However decisions of this kind may be essentially erroneous. For these cases it is proposed to make retrospection of radiological data of the early and intermediate phases of nuclear accident and to project decisions concerning remedial actions on the base of both retrospective data and permanent monitoring data. In this Report the indicated problem is considered by the example of the Chernobyl accident for Ukraine. Their of-site radiological monitoring in the early and intermediate phases was unsatisfactory. In particular, the pasture-cow-milk monitoring had not been made. All official decisions concerning dose estimations had been made on the base of measurements of 137Cs in body (40 measurements in 135 days and 55 measurements in 229 days after the Chernobyl accident). For the retrospection of radiological data of the Chernobyl accident dynamic model has been developed. This model has structure similar to the structure of Pathway model and Farmland model. Parameters of the developed model have been identified for agricultural conditions of Russia and Ukraine. By means of this model dynamics of 20 radionuclides in pathways and dynamics of doses have been estimated for the early, intermediate and late phases of the Chernobyl accident. The main results are following: • During the first year after the Chernobyl accident 75–93% of Commitment Effective Dose had been formed. • During the first year after the Chernobyl accident 85–90% of damage from radiation exposure had been formed. During the next 50 years (the late phase of accident) only 10–15% of damage from radiation exposure will have been formed. • Remedial actions (agricultural remedial actions as most effective) in Ukraine are intended for reduction of the damage from consumption of production which is contaminated in the late phase of accident. I.e. agricultural remedial actions have been intended for minimization only 10% of the total damage from radiation exposure. • Medical countermeasures can minimize radiation exposure damage by an order of magnitude greater than agricultural countermeasures. • Thus, retrospection of nuclear accident has essentially changed type of remedial actions and has given a chance to increase effectiveness of spending by an order of magnitude. This example illustrates that in order to optimize remedial actions it is required to use data of retrospection of nuclear accidents in all cases when monitoring in the early and (or) intermediate phases is unsatisfactory.

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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