Ionic recombination in an ambient gas II. Computer experiment with specific allowance for binary recombination

1978 ◽  
Vol 359 (1698) ◽  
pp. 287-301 ◽  
Keyword(s):  
Rate Coefficient ◽  
Laboratory Data ◽  
Computer Experiments ◽  
Computer Experiment ◽  
Recombination Coefficient ◽  
Quasi Equilibrium ◽  
Low Density ◽  
Density Region ◽  
High Density Region ◽  
Ambient Gas

A method of conducting computer experiments on ionic recombination in an ambient gas is described. Account may be taken of binary recombination, and its contribution to the total recombination coefficient may be separated. Recombination in molecular oxygen is treated as an example. It is found that the recombination coefficient for ambient gas (or termolecular) recombination by itself is as predicted by the quasi-equilibrium statistical method in the low density region and as predicted by the Langevin-Harper formula in the high density region. The slightly modified Natanson formula which was introduced to bridge the very wide gap between these two regions is not successful, the pattern of its failure being that it underestimates the influence which the mobilities of the ions have on the recombination coefficient. An unsuspected characteristic of binary recombination revealed by the investigation is that its rate coefficient depends on the density of the ambient gas. Before attempting to extrapolate laboratory data on the total ionic recombination coefficient to zero ambient gas density it is essential to take cognisance of the steep rise of the binary recombination coefficient in the very low density region.

Monte Carlo and Perturbation Calculations for a Triangular Well Fluid

1974 ◽  
Vol 52 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Damon N. Card ◽  
John Walkley
Keyword(s):  
Monte Carlo ◽  
Hard Spheres ◽  
Low Density ◽  
Monte Carlo Data ◽  
Density Region ◽  
Wide Range ◽  
Model Fluid ◽  
High Density Region ◽  
Superposition Approximation ◽  
Triangular Well Potential

Monte Carlo data have been generated for a simple model fluid consisting of hard spheres with an attractive triangular well potential. The ranges spanned by the temperature and density are as follows. [Formula: see text] and [Formula: see text]. The machine data have been compared to the modern perturbation theories of (i) Barker, Henderson, and Smith and (ii) Weeks, Chandler, and Andersen. Comparison with the machine data shows that the latter theory is successful in the high density region only, but over a wide range of temperature. The Barker–Henderson approach is best in the low density region but the use of the superposition approximation limits the utility of this theory at high densities.

Ionic recombination in an ambient gas I. Extension of quasi-equilibrium statistical method into nonlinear region

1978 ◽  
Vol 359 (1698) ◽  
pp. 275-285 ◽  
Keyword(s):  
Statistical Method ◽  
Ion Pairs ◽  
Power Series Expansion ◽  
Radial Motion ◽  
Striking Similarity ◽  
Recombination Coefficient ◽  
Quasi Equilibrium ◽  
Inherent Limitation ◽  
The Past ◽  
Ambient Gas

In the past the quasi-equilibrium statistical method has been successfully applied in the calculation of the ionic recombination coefficient α in an ambient gas of sufficiently low density for a to be directly proportional to the density. As originally formulated the method contained nothing analogous to the nonlinearity predicted by the simple theory of Thomson (1924) and it was presumed that this was an inherent limitation. However the method has now been extended, nonlinearity being introduced by treating ion-pairs having inward radial motion separately from those having outward radial motion. This gives rise to coupled integro-differential equations which must be solved numerically. A certain power series expansion for a is obtained which bears a striking similarity to an expansion which may be derived from the closed formula of Thomson.

TRAFFIC FLOW ON A 3-LANE HIGHWAY

2004 ◽  
Vol 18 (31n32) ◽  
pp. 4161-4171 ◽  
Author(s):  
WEN-YAO CHEN ◽  
DING-WEI HUANG ◽  
WEI-NENG HUANG ◽  
WEN-LIANG HWANG
Keyword(s):  
Cellular Automaton ◽  
Traffic Flow ◽  
Low Density ◽  
Density Region ◽  
Lane Changing ◽  
Driving Behaviors ◽  
Control Scheme ◽  
High Density Region ◽  
Cellular Automaton Method ◽  
Changing Rate

The traffic flow on a 3-lane highway is investigated using a cellular automaton method. Two different kinds of vehicles, cars and trucks, with different driving behaviors are presented on the highway. It is found that in the high density region, a control scheme requiring passing from the inner lane will enhance the traffic flow; while restricting the trucks to the outer lane will enhance the flow in the low density region and also has the benefit of suppressing the unnecessary lane-changing rate.

Density dependence of the Hanle effect of the 4s4p1P1 level of neutral calcium

1980 ◽  
Vol 58 (7) ◽  
pp. 1004-1009 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Density Dependence ◽  
High Density ◽  
Low Density ◽  
Density Region ◽  
Hanle Effect ◽  
Wide Range ◽  
High Density Region

The Hanle effect in the 4s21S0–4s4p1P1 (4226.7 Å) transition in Ca I has been observed over a wide range of densities. The low density observations determine the lifetime of the 1P1 level to be 4.49 ns. Collision parameters are obtained from observations in the high density region.

scholarly journals Cooperation mitigates diversity loss in a spatially expanding microbial population

2019 ◽  
Author(s):  
Saurabh Gandhi ◽  
Kirill S. Korolev ◽  
Jeff Gore
Keyword(s):  
Genetic Diversity ◽  
Genetic Drift ◽  
Founder Effect ◽  
Growth Dynamics ◽  
Low Density ◽  
Density Region ◽  
Diversity Loss ◽  
High Density Region ◽  
Expanding Population ◽  
Serial Founder Effect

AbstractThe evolution and potentially even the survival of a spatially expanding population depends on its genetic diversity, which can decrease rapidly due to a serial founder effect. The strength of the founder effect is predicted to depend strongly on the details of the growth dynamics. Here, we probe this dependence experimentally using a single microbial species, Saccharomyces cerevisiae, expanding in multiple environments that induce varying levels of cooperativity during growth. We observe a drastic reduction in diversity during expansions when yeast grows non-cooperatively on simple sugars, but almost no loss of diversity when cooperation is required to digest complex metabolites. These results are consistent with theoretical expectations. When cells grow independently from each other, the expansion proceeds as a pulled wave driven by the growth at the low-density tip of the expansion front. Such populations lose diversity rapidly because of the strong genetic drift at the expansion edge. In contrast, diversity loss is substantially reduced in pushed waves that arise due to cooperative growth. In such expansions, the low-density tip of the front grows much more slowly and is often reseeded from the genetically diverse population core. Additionally, in both pulled and pushed expansions, we observe a few instances of abrupt changes in allele fractions due to rare fluctuations of the expansion front and show how to distinguish such rapid genetic drift from selective sweeps.Significance statementSpatially expanding populations lose genetic diversity rapidly because of the repeated bottlenecks formed at the front as a result of the serial founder effect. However, the rate of diversity loss depends on the specifics of the expanding population, such as its growth and dispersal dynamics. We have previously demonstrated that changing the amount of within-species cooperation leads to a qualitative transition in the nature of expansion from pulled (driven by migration at the low density tip) to pushed (driven by migration from the high density region at the front, but behind the tip). Here we demonstrate experimentally that pushed waves, which emerge in the presence of sufficiently strong cooperation, result in strongly reduced genetic drift during range expansions, thus preserving genetic diversity in the newly colonized region.

scholarly journals Scalarons mimicking dark matter in the Hu–Sawicki model of f(R ) gravity

2021 ◽  
Vol 36 (37) ◽  
Author(s):  
Nashiba Parbin ◽  
Umananda Dev Goswami
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Scalar Field ◽  
Jordan Frame ◽  
Low Density ◽  
Density Region ◽  
Expansion Of The Universe ◽  
High Density Region ◽  
Spacetime Metric ◽  
The Universe

In this paper, we conduct a study on the scalar field obtained from [Formula: see text] gravity via Weyl transformation of the spacetime metric [Formula: see text] from the Jordan frame to the Einstein frame. The scalar field is obtained as a result of the modification in the geometrical part of Einstein’s field equation of General Relativity. For the Hu–Sawicki model of [Formula: see text] gravity, we find the effective potential of the scalar field and calculate its mass. Our study shows that the scalar field (also named as scalaron) obtained from this model has the chameleonic property, i.e. the scalaron becomes light in the low-density region, while it becomes heavy in the high-density region of matter. Then it is found that the scalaron can be regarded as a dark matter (DM) candidate since the scalaron mass is found to be quite close to the mass of ultralight axions, a prime DM candidate. Thus, the scalaron in the Hu–Sawicki model of [Formula: see text] gravity behaves as DM. Further, a study on the evolution of the scalaron mass with the redshift is also carried out, which depicts that scalaron becomes light with expansion of the Universe and with different rates at different stages of the Universe.

scholarly journals Computer Experiment Management in Virtual Environment

2021 ◽  
Vol 2066 (1) ◽  
pp. 012081
Author(s):  
Jianqing Deng
Keyword(s):  
Virtual Environment ◽  
Management System ◽  
Ant Colony Algorithm ◽  
Computer Experiments ◽  
Computer Experiment ◽  
Utilization Rate ◽  
Course Scheduling ◽  
Experiment Management ◽  
Function Modules ◽  
Computer Operation

Abstract With the development of the era of big data and the continuous updating of computer technology, the traditional teaching is not satisfied with the current diversified educational development concept, especially for the computer operation class, computer operation has become the mainstream of the current computer experiment class.With the increasing number of computer experiments and the extensive use of computers in open laboratories, how to manage computer experiments reasonably has become an urgent problem. The function of the computer is powerful, and students have different habits of using the computer, and the entertainment function of the computer is also loved by many students. Therefore, in the process of experiment, students often play games and watch movies, which is not easy to manage. In order to solve these problems, this paper studies the computer experiment management system under the virtual environment to help teachers manage the experiment process. This paper studies the function modules of the computer experiment management system, explains the key elements of the analysis of the implementation of the experiment management system, and explains the construction scheme of the virtual experiment teaching environment, and expounds the ant colony algorithm used in the design and management of the course scheduling system. This paper also analyzes the operation and load of computer experiment management through simulation experiment research, and tests and analyzes to prove the rationality of the management system. The experimental research shows that in the daily computer experiment management system, the most commonly used is the experimental teaching, and the conventional office, accounting for 27.35 and 26.33 respectively. The highest utilization rate of the computer experiment system is the daily teaching, accounting for 53.6%.

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