A physically based model for the evolution of dry, two-dimensional foams based on a combination of mass transfer, vertex movement, and edge relaxation, enables efficient and accurate simulation with and without wall r...
A physically based model for the evolution of dry, two-dimensional foams based on a combination of mass transfer, vertex movement, and edge relaxation, enables efficient and accurate simulation with and without wall rupture. The stochastic nature of topological transitions due to numerical error has been carefully examined and may explain the discrepancies found among various simulations. The separation of vertex and edge movements permits a study of foam evolution that includes wall rupture. Comparison with recent experimental results is presented that demonstrates that certain, semiempirical ``breaking rules'' are capable of reproducing both the overall topological evolution and certain scaling behavior observed in the experiments.
A new class of propagating fronts is proposed in which a spreading instability evolves through a singular configuration before saturating. As an example, we examine the viscous Rayleigh instability of a stationary flu...
A new class of propagating fronts is proposed in which a spreading instability evolves through a singular configuration before saturating. As an example, we examine the viscous Rayleigh instability of a stationary fluid column, using the marginal stability criterion to estimate the front velocity, front width, and the selected wavelength in terms of the surface tension and viscosity contrast. Systems that may display this phenomenon include droplets elongated in extensional flows, capillary bridges, liquid crystal tethers, and viscoelastic jets. The related problem of propagation in Rayleigh-like systems that do not fission is also considered.
This paper describes a general approach to signal detection with uncertainty in signal and/or background distributions. Attention is restricted to binary decision problems where the hypotheses can be expressed as sign...
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A method to obtain a new class of discrete eigenfunctions and associated real, nonsingular, decaying, “reflectionless” potentials to the time dependent Schrödinger equation is presented. Using the inverse scatt...
A method to obtain a new class of discrete eigenfunctions and associated real, nonsingular, decaying, “reflectionless” potentials to the time dependent Schrödinger equation is presented. Using the inverse scattering transform, related solutions of the Kadomtsev-Petviashvili equation are found. The eigenfunctions have poles of order m, m>1 in the complex plane and are also characterized by an index, or “charge,” which is obtained as a constraint in the theory.
We present an ultrafast nonlinear optical loop mirror (NOLM) switch based on multiple collisions between orthogonally polarized signal and control solitons in highly birefringent optical fiber. The 8-m circumference s...
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We probed the bending of actin subject to external forcing and viscous drag. Single actin filaments were moved perpendicular to their long axis in an oscillatory way by means of an optically tweezed latex bead attache...
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We probed the bending of actin subject to external forcing and viscous drag. Single actin filaments were moved perpendicular to their long axis in an oscillatory way by means of an optically tweezed latex bead attached to one end of the filaments. Shapes of these polymers were observed by epifluorescence microscopy. They were found to be in agreement with predictions of semiflexible polymer theory and slender-body hydrodynamics. A persistence length of 7.4±0.2 μm could be extracted.
In an era of fiscal austerity, downsizing and unforgiving pressure upon human and economic capital, it is an Augean task to identify resources for fresh and creative work. The realities of the day and the practical de...
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In an era of fiscal austerity, downsizing and unforgiving pressure upon human and economic capital, it is an Augean task to identify resources for fresh and creative work. The realities of the day and the practical demands of more immediate fleet needs can often dictate higher priorities. Yet, the Navy must avoid eating its seed corn. Exercising both technical insight and management foresight, the fleet, the R&D community, the Office of the Chief of Naval Operations (OpNav) and the product engineering expertise of the Naval Surface Warfare Center (NSWC) are joined and underway with integrated efforts to marry new, fully demonstrated technologies and operational urgencies. Defense funding today cannot sponsor all work that can be mission-justified over the long term because budgets are insufficient to support product maturation within the classical development cycle. However, by rigorous technical filtering and astute engineering of both marketplace capabilities and currently available components, it is possible in a few select cases to compress and, in effect, integrate advanced development (6.3), engineering development (6.4), weapon procurement (WPN), ship construction (SCN), operation and maintenance (O&M,N) budgetary categories when fleet criticalities and technology opportunities can happily meet. In short, 6.3 funds can be applied directly to ''ripe gateways'' so modern technology is inserted into existing troubled or aging systems, sidestepping the lengthy, traditional development cycle and accelerating practical payoffs to recurrent fleet problems. To produce such constructive results has required a remarkable convergence of sponsor prescience and engineering workforce excellence. The paper describes, extensively, the philosophy of approach, transition strategy, polling of fleet needs, technology assessment, and management team requirements. The process for culling and selecting specific candidate tasks for SHARP sponsorship (matching operational need with t
B. D. Coller, P. Holmes, John Lumley; Erratum: ‘‘Interaction of adjacent bursts in the wall region’’ [Phys. Fluids 6, 954 (1994)], Physics of Fluids, Volume 9,
B. D. Coller, P. Holmes, John Lumley; Erratum: ‘‘Interaction of adjacent bursts in the wall region’’ [Phys. Fluids 6, 954 (1994)], Physics of Fluids, Volume 9,
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