199 research outputs found
Droplet impact on a thin fluid layer
No full textThe initial stages of high-velocity droplet impact on a shallow water layer are described, with special emphasis given to the spray jet mechanics. Four stages of impact are delineated, with appropriate scalings, and the successively more important influence of the base is analysed. In particular, there is a finite time before which part of the water in the layer remains under the droplet and after which all of the layer is ejected in the splash jet
Twice Forty Years Of Learning: An Educational Biography of Robert Reid Howison (1820-1906)
No full textThe two primary purposes of this study were to develop an educational biography on the life of Robert Reid Howison, a nineteenth-century Virginia lawyer, minister, historian, and author, and to examine Howison's efforts as an educator.
Chapter One presents an approach to the study, guiding questions, and the research methodology of educational biography. Chapter Two examines Howison's learning experiences during his childhood and youth, from his birth in 1820 to 1841. These learning experiences were primarily connected with institutions of education, such as family, school, church, work, as well as his self-initiated learning and membership in a learning society. Chapter Two analyzes Howison's learning experiences during his prime adult years, 1841-1870, and discusses how, as an adult, family became less of an institution influencing his learning and became more of an opportunity to educate others. His self-initiated learning, coupled with institutions of education in the community, became more prominent during these years. His first book, A History of Virginia From Its Discovery and Settlement, revealed Howison both as a learner and educator as he conducted the necessary research for the book with the intent to teach the history of Virginia to the young men of the day. He also contributed other scholarship efforts such as writing a complete history of the Civil War. Chapter Four details Howison's later years, from 1870 to his death in 1906. During this time he authored two additional major works, God and Creation and A Students' History of the United States. Many of Howison's shorter works written during these years, such as newspaper and periodical articles, reveal his philosophy of education. Howison was also a lecturer on American History at Fredericksburg College, an event combining his work as an educator with his lifelong interest in reading and writing history. Chapter Five presents conclusions and recommendations to the study, particularly concerning the research methodology of educational biography as applied to the life of Robert Howison. His detailed description of his lifelong learning experiences, as described in his unpublished autobiography Twice Forty Years of American Life, were useful in establishing the significant learning experiences throughout his life as well as documenting the outcomes or results of his learning.Ph. D
A note on oblique water entry
No full textAn apparently minor error in Howison, Ockendon & Oliver (J. Eng. Math. 48:321–337, 2004) obscured the fact that the points at which the free surface turns over in the solution of the Wagner model for the oblique impact of a two-dimensional body are directly related to the turnover points in the equivalent normal impact problem. This note corrects some results given in Howison, Ockendon & Oliver (2004) and discusses the implications for the applicability of the Wagner\ud
model
A note on oblique water entry
No full textAbstract. A minor error in Howison, Ockendon & Oliver (J. Eng. Math. 48:321-337, 2004) obscured the fact that the points at which the free surface turns over in the solution of the Wagner model for the oblique impact of a two-dimensional body are directly related to the turnover points in the equivalent normal impact problem. This note corrects some of the earlier results given in Howison
A note on oblique water entry
No full textA minor error in Howison et al. (J. Eng. Math. 48:321-337, 2004) obscured the fact that the points at which the free surface turns over in the solution of the Wagner model for the oblique impact of a two-dimensional body are directly related to the turnover points in the equivalent normal impact problem. This note corrects some of the earlier results given in Howison et al. (J. Eng. Math. 48:321-337, 2004) and discusses the implications for the applicability of the Wagner model. © 2012 Springer Science+Business Media B.V.The authors wish to thank the reviewers for some helpful comments. This publication was based on work supported in part by award no. KUK-C1-013-04, made by King Abdullah University of Science and Technology (KAUST). M. R. M. would like to acknowledge the ESPRC for financial support via a studentship. J.R.O. was in receipt of a Leverhulme Emeritus Fellowship
Macroscopic dislocation modelling
No full textWork-hardened metals typically possess large numbers of dislocations in complex three-dimensional configurations about which little is known theoretically. Here these large numbers of dislocations are accounted for by means of a dislocation density tensor, which is obtained by applying an averaging process to families of discrete dislocations. Some simple continuous distributions are examined and an analogy is drawn with solenoids in electromagnetism before the question of the equilibrium of dislocation configurations is studied. It is then proved that the only finite, simply-connected distribution of dislocations in equilibrium in the absence of applied stresses are ones in which all components of stress vanish everywhere. Some examples of these zero stress everywhere (ZSE) distributions are then given, and the concept of 'plastic distortion' is used to facilitate their interpretation as rotations of the crystal lattice. Plastic distortion can also be understood as a distribution of infinitesimal dislocation loops ('Kroupa loops'), and this idea is used in Chapter 4 to investigate the dislocation distributions which correspond to elastic inclusions. The evolution, under an applied stress, of some simple ZSEs is analysed, and the idea of 'polarisation' is introduced, again in analogy with electromagnetism. Finally, a mechanism is conjectured for the onset of plastic flow
Data for numerical examples in "Generative Benchmark Models for Mesoscale Structure in Multilayer Networks"
No full textThis package includes the raw data used to generate the plots in Figures 8-10 of "Generative benchmark models for mesoscale structure in multilayer networks", by M. Bazzi, L. G. S. Jeub, A. Arenas, S. D. Howison, and M. A. Porter, arXiv:1608.06196. It was created using MATLAB and all variables are stored in .mat format. Please see the "Readme.txt" file for additional information on the data set
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Self-organized segregation of traders within a market
No full textWe study a simple competitive market, in which individual traders adapt their trading strategies according to past experience. Because of the limited knowledge available to them, they are forced to make decisions based on inductive, rather than deductive, thinking. We show that a population of competing traders with similar capabilities and knowledge will tend to self-segregate into opposing groups characterized by extreme behaviour. To be successful, a trader should behave in an extreme way by either always copying or rejecting past trends in the market's history. Cautious traders tend to perform poorly
SIMILARITY SOLUTIONS TO THE STEFAN PROBLEM AND THE BINARY ALLOY PROBLEM
No full textWe present a catalogue of explicit similarity solutions to the Stefan problem and the binary alloy problem; the most general case includes convective heat transfer due to a fluid motion driven by a density change at the solid-liquid interface. The free boundary is either an ellipsoid or a hyperboloid; in the latter case we note that for certain parameter regimes there may be two solutions (with different initial data), a situation which does not occur in the one-dimensional case. © 1988 Oxford University Press
BUBBLE-GROWTH IN POROUS-MEDIA AND HELE-SHAW CELLS
No full textSynopsisWe consider the characterisation of a class of free boundary problems arising in the flow of a viscous liquid in a porous medium (or, in two dimensions, a Hele–Shaw cell). Injected air forms a bubble which grows as time increases; it is shown that three kinds of behaviour can occur. Firstly, the solution may cease to exist in finite time; secondly, the solution may exist for all time and the free boundary may have one or more limit points as t tends to infinity; and thirdly, the bubble may exist for all time and fill the whole space as t tends to infinity. Two-dimensional explicit examples arc given of all three types of behaviour, and it is proved that the only solutions of the third kind are those in which the bubble is always elliptical; the proof uses the theory of null quadrature domains. It is shown that solutions for ellipsoidal bubbles exist in three dimensions and it is conjectured that the only three-dimensional null quadrature domains with finite complement are those whose complement is an ellipsoid.</jats:p
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