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,
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
We present total cross sections in the laboratory energy range 17.5-500 keV amu(-1) for electron capture by protons in collision with He+(1s). We describe this process theoretically by performing a close-coupling (CC)...
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We present total cross sections in the laboratory energy range 17.5-500 keV amu(-1) for electron capture by protons in collision with He+(1s). We describe this process theoretically by performing a close-coupling (CC) calculation using the symmetrized variational (SV) continuum distorted-wave (CDW) collision ansatz. We discuss the SVCDW results in conjunction with another CC variational CDW calculation, with CDW perturbation theory, and also with close-coupling calculations which involve a representation of the continuum by a set of pseudo-states which may include pseudo-states of the united atom. Moreover, we compare the SVCDW results with the available experimental data. The SVCDW results are found to be in very good agreement with the experiments of Peart et al, Rinn et al and Watts et al at all energies, and consequently to be at variance with the experimental results of Angel et al. The SVCDW results are also found to be in good accord with a CC calculation involving Sturmian-type pseudo-states. We investigate this agreement further by comparing impact-parameter profiles at 50 and 17.5 keV amu(-1).
A non-relativistic description of the differential cross section (DCS) for Thomas double-scattering electron capture at asymptotically high velocity is developed within the third-order continuum distorted-wave (CDW) p...
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A non-relativistic description of the differential cross section (DCS) for Thomas double-scattering electron capture at asymptotically high velocity is developed within the third-order continuum distorted-wave (CDW) perturbation theory for 1s --> 1s transitions in proton-hydrogen collisions. It is shown that at the critical proton scattering angles, namely the forward peak, Thomas maximum, small angles and the interference minimum, the CDW series has converged at second order. Moreover, it is proven that the third-order correction makes no contribution to the velocity-dependent upsilon-(11) and upsilon-(12) behaviour of the Thomas double-scattering total cross sections at the leading angles. The Oppenheimer-Brinkman-Kramers (OBK) travelling atomic orbital plane wave theory is compared to the CDW approximation. It is observed that the second-order OBK (OBK2) theory has not converged. It remains an open question as to whether fourth-order terms or higher in the OBK approximation contribute to the various differential cross sections. It is concluded that the CDW model gives a superior description of the Thomas double-scattering mechanism than the OBK model.
Numerical results for the Nikitin exponential model at non-zero impact parameters are presented. It is confirmed that in order to derive the correct strong-coupling approximation of the transition probability, one nee...
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Numerical results for the Nikitin exponential model at non-zero impact parameters are presented. It is confirmed that in order to derive the correct strong-coupling approximation of the transition probability, one need only include the leading terms of the asymptotic expansions of the confluent hypergeometric functions. Development beyond leading order is inappropriate to the particular model, because by construction the non-analytic wavefunction is discontinuous in its second-order derivative at the turning point, which follows from the cusp-like discontinuity in the first-order derivative of at least the off-diagonal Hamiltonian potential matrix elements. It is therefore concluded that the Stueckelberg phase-integral derivations of Crothers are essential if transition probabilities and cross sections are not to be underestimated at large impact parameters, due to neglecting the bending of the double Stokes line.
We show that the statistical properties of the large scales of the Kuramoto-Sivashinsky equation in the extended system limit can be understood in terms of the dynamical behavior of the same equation in a small finite...
A local alternating segment explicit - implicit method for the solution of 2D diffusion equations is presented in this paper .The method is unconditionally stable and has the obvious property of parallelism. Some nume...
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A local alternating segment explicit - implicit method for the solution of 2D diffusion equations is presented in this paper .The method is unconditionally stable and has the obvious property of parallelism. Some numerical experiments show the method is not only simple but also more accurate.
We present total cross sections in the energy range 7-1000 keV amu(-1) for electron capture by alpha-particles in collision with atomic hydrogen in the ground state. We describe this process theoretically by performin...
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We present total cross sections in the energy range 7-1000 keV amu(-1) for electron capture by alpha-particles in collision with atomic hydrogen in the ground state. We describe this process theoretically by performing a close-coupling calculation using the symmetrized variational (SV) continuum distorted-wave (CDW) collision ansatz. SVCDW views the collision in a unique way by including both incoming and outgoing CDWs in the wavefunctions at all finite times, while simultaneously guaranteeing the correct coulombic asymptotes. We compare the SVCDW results with the available experimental data, with a dose-coupling calculation in which outgoing CDWs only are used to describe the collision, and with CDW perturbation theory. At high energies the three theoretical curves converge, while at lower energies the SVCDW results are shown to reproduce experiments more accurately. We also compare the SVCDW results with other coupled-channel calculations which use pseudo-states to describe the interaction of the target and the projectile with the continuum.
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