15,138 research outputs found
International Governance of the Internet: An Economic Analysis.
ICANN currently determines which top level domains are available on the A-root server and so restricts the choices facing Internet users. Thus ICANN redistributes wealth and has become the focus of rent-seeking activities. Yet, despite my belief that the Internet will become substantially more regulated in the future, I am convinced that technology will trump the best efforts of regulators to âpromote the public interestâ.
The spatial stability of a class of similarity solutions
The spatial stability of a class of exact similarity solutions of the NavierâStokes equations whose longitudinal velocity is of the form xfâ˛(y), where x is the streamwise coordinate and fâ˛(y) is a function of the transverse, crossâstreamwise, coordinate y only, is determined. These similarity solutions correspond to the flow in an infinitely long channel or tube whose surface is either uniformly porous or moves with a velocity linear in x. Small perturbations to the streamwise velocity of the form x^Îťgâ˛(y) are assumed, resulting in an eigenvalue problem for Îť which is solved numerically. For the porous wall problem, it is shown that similarity solutions in which fâ˛(y) is a monotonic function of y are spatially stable, while those that are not monotonic are spatially unstable. For the acceleratingâwall problem, the interpretation of the stability results is not unambiguous and two interpretations are offered. In one interpretation the conclusions are the same as for the porous problemâmonotonic solutions are stable; the second interpretation is more restrictive in that some of the monotonic as well as the nonmonotonic solutions are unstable
Analysis of the Brinkman equation as a model for flow in porous media
The fundamental solution or Green's function for flow in porous media is determined using
Stokesian dynamics, a molecular-dynamics-like simulation method capable of describing the
motions and forces of hydrodynamically interacting particles in Stokes flow. By evaluating the
velocity disturbance caused by a source particle on field particles located throughout a
monodisperse porous medium at a given value of volume fraction of solids ø, and by
considering many such realizations of the (random) porous medium, the fundamental solution
is determined. Comparison of this fundamental solution with the Green's function of the
Brinkman equation shows that the Brinkman equation accurately describes the flow in porous
media for volume fractions below 0.05. For larger volume fractions significant differences
between the two exist, indicating that the Brinkman equation has lost detailed predictive value,
although it still describes qualitatively the behavior in moderately concentrated porous media.
At low ø where the Brinkman equation is known to be valid, the agreement between the
simulation results and the Brinkman equation demonstrates that the Stokesian dynamics
method correctly captures the screening characteristic of porous media. The simulation results
for ø ⼠0.05 may be useful as a basis of comparison for future theoretical work
Suspensions of prolate spheroids in Stokes flow. Part 2. Statistically homogeneous dispersions
The simulation method for prolate spheroids in Stokes flow introduced in a companion paper (Claeys & Brady 1993a) is extended to handle statistically homogeneous unbounded dispersions. The convergence difficulties associated with the slow decay of velocity disturbances at zero Reynolds number are overcome by applying O';Brien's renormalization procedure. The Ewald summation technique is employed to accelerate the evaluation of all mobility interactions. As a first application of this new method, the hydrodynamic transport properties of equilibrium hard-ellipsoid structures are calculated for aspect ratios ranging from 3 to 50. Calculated viscosities in the isotropic phase agree reasonably well with published experimental measurements
Suspensions of prolate spheroids in Stokes flow. Part 3. Hydrodynamic transport properties of crystalline dispersions
The short-time limit of the hydrodynamic transport properties is calculated for crystalline dispersions of parallel prolate spheroids using a moment expansion technique similar in concept to the simulation method known as Stokesian dynamics. The concentration dependence of the sedimentation rate, the hindered diffusivity and the Theological behaviour of face-centred lattices are examined for concentrations up to regular close packing (74% by volume). The influence of the detailed microstructure of the dispersion is also investigated by considering different arrangements of parallel ellipsoids. Useful reference configurations are proposed as standard geometries for regular arrays of prolate spheroids
The Muscadine Experience: Adding Value to Enhance Profits
The University of Arkansas Division of Agriculture received a grant from the National Research Initiative (NRI), CSREES USDA. The purpose was to help small- and medium-sized farmers and entrepreneurs enhance the viability of their farms through the establishment of vineyards, on-farm wineries, and production of value-added products from grapes and grape by-products. This publication looks at efforts by the UA Grape and Wine Research Program to enhance the profitability of muscadine grapes. Included are discussions of research designed to develop the market potential of muscadines as fresh fruit and as value-added products such as juice, wine, sweet spreads, vinegar, and dried products. The skin and seeds of muscadines have traditionally been considered waste; however, recent research has shown that they contain nutraceutical components. Reports are included of research to quantify these nutraceuticals and to develop products containing them
The Muscadine Experience: Adding Value to Enhance Profits
The University of Arkansas Division of Agriculture received a grant from the USDAâs Initiative for Future Agriculture and Food Systems (IFAFS) program. The purpose was to help small- and medium-sized farmers and entrepreneurs become more profitable and therefore add stability to the family farm. One approach to doing this is to investigate opportunities to enhance profits by adding value to traditional raw products
CONCEPTUAL UNDERPINNINGS OF POLICY ANALYSIS FOR RURAL DEVELOPMENT
Community/Rural/Urban Development,
Integrability of the Minimal Strain Equations for the Lapse and Shift in 3+1 Numerical Relativity
Brady, Creighton and Thorne have argued that, in numerical relativity
simulations of the inspiral of binary black holes, if one uses lapse and shift
functions satisfying the ``minimal strain equations'' (MSE), then the
coordinates might be kept co-rotating, the metric components would then evolve
on the very slow inspiral timescale, and the computational demands would thus
be far smaller than for more conventional slicing choices. In this paper, we
derive simple, testable criteria for the MSE to be strongly elliptic, thereby
guaranteeing the existence and uniqueness of the solution to the Dirichlet
boundary value problem. We show that these criteria are satisfied in a test-bed
metric for inspiraling binaries, and we argue that they should be satisfied
quite generally for inspiraling binaries. If the local existence and uniqueness
that we have proved holds globally, then, for appropriate boundary values, the
solution of the MSE exhibited by Brady et. al. (which tracks the inspiral and
keeps the metric evolving slowly) will be the unique solution and thus should
be reproduced by (sufficiently accurate and stable) numerical integrations.Comment: 6 pages; RevTeX; submitted to Phys. Rev. D15. Technical issue of the
uniqueness of the solution to the Dirichlet problem clarified. New subsection
on the nature of the boundary dat
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