2,282 research outputs found
Gravity-induced segregation of cohesionless granular mixtures
Working with the context of a theory proposed recently by Fried et al. (2001), we consider a one-dimensional problem involving granular mixture of K > 2 discrete sizes bounded below by an impermeable base, above by an evolving free surface, and subject to gravity. We demonstrate the existence of a solution in which the medium segregates by particle size. For a mixture of small and large particles (K = 2), we use methods of Smoller (1994) to show that the segregated solution is unique. Further, for a mixture of small, medium, and large particles (K = 3), we use LeVeque's (1994) CLAWPACK to construct numerical solutions and find that these compare favorably with analytical predictions.published or submitted for publicationis peer reviewe
Quantum process tomography via completely positive and trace-preserving projection
We present an algorithm for projecting superoperators onto the set of
completely positive, trace-preserving maps. When combined with gradient descent
of a cost function, the procedure results in an algorithm for quantum process
tomography: finding the quantum process that best fits a set of sufficient
observations. We compare the performance of our algorithm to the diluted
iterative algorithm as well as second-order solvers interfaced with the popular
CVX package for MATLAB, and find it to be significantly faster and more
accurate while guaranteeing a physical estimate.Comment: 13pp, 8 fig
Hearing the grass grow. Emotional and epistemological challenges of practice-near research
This paper discusses the concept of practice-near research in terms of the emotional and epistemological challenges that arise from the researcher coming 'near' enough to other people for psychological processes to ensue. These may give rise in the researcher to confusion, anxiety and doubt about who is who and what is what; but also to the possibility of real emotional and relational depth in the research process. Using illustrations from three social work doctoral research projects undertaken by students at the Tavistock Clinic and the University of East London the paper examines four themes that seem to the author to be central to meaningful practice-near research undertaken in a spirit of true emotional and epistemological open-mindedness: the smell of the real; losing our minds; the inevitability of personal change; and the discovery of complex particulars
Caution on Short Cuts for Lawns
This article, the first in a series of three, will be of special interest if you\u27re planning to build a new lawn. The following articles will deal more generally with caring for, maintaining and improving existing lawns
GO for a Better Lawn!
Your lawn is the setting for your house and other landscaping features. This article, the second in a series of three, offers tips on what you can do to improve a poor lawn or to maintain a good one
Displacement operators: the classical face of their quantum phase
In quantum mechanics, the operator representing the displacement of a system
in position or momentum is always accompanied by a path-dependent phase factor.
In particular, two non-parallel displacements in phase space do not compose
together in a simple way, and the order of these displacements leads to
different displacement composition phase factors. These phase factors are often
attributed to the nonzero commutator between quantum position and momentum
operators, but such a mathematical explanation might be unsatisfactory to
students who are after more physical insight. We present a couple of simple
demonstrations, using classical wave mechanics and classical particle
mechanics, that provide some physical intuition for the phase associated with
displacement operators.Comment: 14 pages, 4 figures, reorganized and reformatte
Comments: The Credit Card Act of 2009 Was Not Enough: A National Usury Rate Would Provide Consumers with the Protection They Need
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