The role of limit cycles in the admissibility of shock waves

1995 ◽  
Vol 8 (4) ◽  
Author(s):  
Sunčica Čanić
Keyword(s):  
Shock Waves ◽  
Limit Cycles

scholarly journals The Role of Mesh Generation, Adaptation, and Refinement on the Computation of Flows Featuring Strong Shocks

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Aldo Bonfiglioli ◽  
Renato Paciorri ◽  
Andrea Di Mascio
Keyword(s):  
Shock Waves ◽  
Mesh Generation ◽  
The Other ◽  
Shock Capturing ◽  
Structured Grids ◽  
Computational Mesh ◽  
Versatile Technique ◽  
Coarse Meshes ◽  
Shock Fitting

Within a continuum framework, flows featuring shock waves can be modelled by means of either shock capturing or shock fitting. Shock-capturing codes are algorithmically simple, but are plagued by a number of numerical troubles, particularly evident when shocks are strong and the grids unstructured. On the other hand, shock-fitting algorithms on structured grids allow to accurately compute solutions on coarse meshes, but tend to be algorithmically complex. We show how recent advances in computational mesh generation allow to relieve some of the difficulties encountered by shock capturing and contribute towards making shock fitting on unstructured meshes a versatile technique.

Role of laser-induced stress and shock waves in modification of the photoconductivity of films

1998 ◽  
Vol 13 (11) ◽  
pp. 1298-1303 ◽  
Author(s):  
V A Gnatyuk ◽  
A I Vlasenko ◽  
P O Mozol' ◽  
O S Gorodnychenko
Keyword(s):  
Shock Waves ◽  
Induced Stress ◽  
And Shock Waves

The Materialism Controversy

After Hegel ◽  
2014 ◽  
Author(s):  
Frederick C. Beiser
Keyword(s):  
Nineteenth Century ◽  
Shock Waves ◽  
Free Will ◽  
Natural Science ◽  
Main Question ◽  
Modern Natural ◽  
Modern Natural Science ◽  
Scientific Materialism ◽  
Reason And Faith

This chapter examines the so-called “materialism controversy,” one of the most important intellectual disputes of the second half of the nineteenth century. The dispute began in the 1850s, and its shock waves reverberated until the end of the century. The main question posed by the materialism controversy was whether modern natural science, whose authority and prestige were now beyond question, necessarily leads to materialism. Materialism was generally understood to be the doctrine that only matter exists and that everything in nature obeys only mechanical laws. If such a doctrine were true, it seemed there could be no God, no free will, no soul, and hence no immortality. These beliefs, however, seemed vital to morality and religion. So the controversy posed a drastic dilemma: either a scientific materialism or a moral and religious “leap of faith.” It was the latest version of the old conflict between reason and faith, where now the role of reason was played by natural science.

Key role of the expression of bone morphogenetic proteins in increasing the osteogenic activity of osteoblast-like cells exposed to shock waves and seeded on bioactive glass-ceramic scaffolds for bone tissue engineering

2014 ◽  
Vol 29 (5) ◽  
pp. 728-736 ◽  
Author(s):  
Giuliana Muzio ◽  
Germana Martinasso ◽  
Francesco Baino ◽  
Roberto Frairia ◽  
Chiara Vitale-Brovarone ◽  
...  
Keyword(s):  
Shock Wave ◽  
Alkaline Phosphatase ◽  
Shock Waves ◽  
Bioactive Glass ◽  
Bone Morphogenetic Protein ◽  
Bone Morphogenetic Proteins ◽  
Glass Ceramic ◽  
Osteogenic Activity ◽  
Morphogenetic Protein

In this work, the role of shock wave-induced increase of bone morphogenetic proteins in modulating the osteogenic properties of osteoblast-like cells seeded on a bioactive scaffold was investigated using gremlin as a bone morphogenetic protein antagonist. Bone-like glass-ceramic scaffolds, based on a silicate experimental bioactive glass developed at the Politecnico di Torino, were produced by the sponge replication method and used as porous substrates for cell culture. Human MG-63 cells, exposed to shock waves and seeded on the scaffolds, were treated with gremlin every two days and analysed after 20 days for the expression of osteoblast differentiation markers. Shock waves have been shown to induce osteogenic activity mediated by increased expression of alkaline phosphatase, osteocalcin, type I collagen, BMP-4 and BMP-7. Cells exposed to shock waves plus gremlin showed increased growth in comparison with cells treated with shock waves alone and, conversely, mRNA contents of alkaline phosphatase and osteocalcin were significantly lower. Therefore, the shock wave-mediated increased expression of bone morphogenetic protein in MG-63 cells seeded on the scaffolds is essential in improving osteogenic activity; blocking bone morphogenetic protein via gremlin completely prevents the increase of alkaline phosphatase and osteocalcin. The results confirmed that the combination of glass-ceramic scaffolds and shock waves exposure could be used to significantly improve osteogenesis opening new perspectives for bone regenerative medicine.

scholarly journals Testing predator - prey theory by studying fluctuating populations of small mammals.

1995 ◽  
Vol 22 (1) ◽  
pp. 89 ◽  
Author(s):  
S. Boutin
Keyword(s):  
Population Dynamics ◽  
Small Mammals ◽  
Limit Cycles ◽  
Functional Responses ◽  
Predator Satiation ◽  
Linear Type ◽  
Small Component ◽  
Wide Range ◽  
Fluctuating Populations

Fluctuating populations of small mammals provide an excellent opportunity to study the functional and numerical responses of predators because of the wide range in prey density that occurs. I reinterpret data from six studies that have examined the role of predation in the population dynamics of voles in California, southern Sweden and western Finland, of snowshoe hares in northern Canada, and of house mice and rabbits in Australia. Most studies have measured functional responses by relying on changes in diet as reflected by scat or stomach contents. These methods are probably biased toward showing predator satiation. Contrary to previous conclusions I find that there is little evidence for non-linear (Type 111) functional-response curves or predator satiation at high prey densities. Recent studies indicate that the functional and numerical responses of predators can be rapid and strong enough to initiate cyclic declines, dampen fluctuations, or even cause stable numbers. The exception to this appears to be the irruptions of mice and rabbits in Australia. I propose a general explanation for the role of predation whereby the effect of predation is largely dependent on the entire prey community. When potentially cyclic prey are a small component of the overall prey biomass, generalist predators are able to prevent fluctuations by strong functional or numerical responses. As the prey community becomes dominated by a few species that fluctuate, limit cycles predominate. Limit cycles turn into irruptive population dynamics when seasonal prey reproduction is eliminated because of extended periods of vegetation growth (vegetation flushes following drought). In the future we must test assumptions underlying the way we study predation by telemetric monitoring of prey mortality and by experimentally manipulating predation.

Development of a Large Diameter Diaphragmless Shock Tube for Gas-Dynamic Laser Studies

2007 ◽  
Vol 566 ◽  
pp. 9-14 ◽  
Author(s):  
I. da S. Rego ◽  
K.N. Sato ◽  
S. Kugimiya ◽  
T. Aoki ◽  
Y. Miyoshi ◽  
...  
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
Large Diameter ◽  
Gaseous Mixtures ◽  
Gas Dynamic ◽  
Diaphragmless Shock Tube ◽  
Good Accordance ◽  
Basic Characteristics ◽  
And Performance

This paper reports on the design and performance of a large diameter diaphragmless shock tube that has been recently developed in order to experimentally study various basic characteristics of the gas-dynamic laser (GDL). The main engineering element of the shock tube is a diaphragm-like sliding piston (in place of a rupturing diaphragm) by which normal shock waves are formed. The role of such a structure in generating repeatable shock waves is discussed. The shock tube performs in good accordance with the simple shock tube theory, as has been verified so far by experiments with some conventional lasing gases (gaseous mixtures of CO2 and N2 and those diluted with an excess of He) at shock wave Mach numbers ranging from 1 to 5. Recent results of the stagnation conditions achieved in the shock tube with application to GDL experiments are included as well.

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