29,544 research outputs found
Can randomness alone tune the fractal dimension?
We present a generalized stochastic Cantor set by means of a simple {\it cut
and delete process} and discuss the self-similar properties of the arising
geometric structure. To increase the flexibility of the model, two free
parameters, and , are introduced which tune the relative strength of the
two processes and the degree of randomness respectively. In doing so, we have
identified a new set with a wide spectrum of subsets produced by tuning either
or . Measuring the size of the resulting set in terms of fractal
dimension, we show that the fractal dimension increases with increasing order
and reaches its maximum value when the randomness is completely ceased.Comment: 6 pages 2-column RevTeX, Two figures (presented in the APCTP
International Symposium on Slow Dynamical Processes in Nature, Nov. 2001,
Seoul, Korea
Distributed photovoltaic systems: Utility interface issues and their present status
Major technical issues involving the integration of distributed photovoltaics (PV) into electric utility systems are defined and their impacts are described quantitatively. An extensive literature search, interviews, and analysis yielded information about the work in progress and highlighted problem areas in which additional work and research are needed. The findings from the literature search were used to determine whether satisfactory solutions to the problems exist or whether satisfactory approaches to a solution are underway. It was discovered that very few standards, specifications, or guidelines currently exist that will aid industry in integrating PV into the utility system. Specific areas of concern identified are: (1) protection, (2) stability, (3) system unbalance, (4) voltage regulation and reactive power requirements, (5) harmonics, (6) utility operations, (7) safety, (8) metering, and (9) distribution system planning and design
Analytical solution of Stokes flow inside an evaporating sessile drop: Spherical and cylindrical cap shapes
Exact analytical solutions are derived for the Stokes flows within
evaporating sessile drops of spherical and cylindrical cap shapes. The results
are valid for arbitrary contact angle. Solutions are obtained for arbitrary
evaporative flux distributions along the free surface as long as the flux is
bounded at the contact line. The field equations, E^4(Psi)=0 and Del^4(Phi)=0,
are solved for the spherical and cylindrical cap cases, respectively. Specific
results and computations are presented for evaporation corresponding to uniform
flux and to purely diffusive gas phase transport into an infinite ambient.
Wetting and non-wetting contact angles are considered with the flow patterns in
each case being illustrated. For the spherical cap with evaporation controlled
by vapor phase diffusion, when the contact angle lies in the range
0<theta_c<pi, the mass flux of vapor becomes singular at the contact line. This
condition required modification when solving for the liquid phase transport.
Droplets in all of the above categories are considered for the following two
cases: the contact lines are either pinned or free to move during evaporation.
The present viscous flow behavior is compared to the inviscid flow behavior
previously reported. It is seen that the streamlines for viscous flow lie
farther from the substrate than the corresponding inviscid ones.Comment: Revised version; in review in Physics of Fluid
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