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101.
We cloak a region from a known incident wave by surrounding the region with three or more devices that cancel out the field in the cloaked region without significantly radiating waves. Since very little waves reach scatterers within the cloaked region, the scattered field is small and the scatterers are for all practical purposes undetectable. The devices are multipolar point sources that can be determined from Green's formula and an addition theorem for Hankel functions. The cloaking devices are exterior to the cloaked region. 相似文献
102.
Cavitation structures in a large-scale (D = 8.25 mm), plain orifice style nozzle within a unique experimental rig are investigated using high-speed visualisation and
digital image processing techniques. Refractive index matching with an acrylic nozzle is achieved using aqueous sodium iodide
for the test fluid. Cavitation collapse length, unsteady shedding frequency and spray angles are measured for cavitation conditions
from incipient to supercavitation for a range of Reynolds numbers, for a fixed L/D ratio of 4.85. Periodic cavitation shedding was shown to occur with frequencies between 500 and 2,000 Hz for conditions in
which cavitation occupied less than 30% of the nozzle length. A discontinuity in collapse length was shown to occur once the
cavitation exceeded this length, coinciding with a loss of periodic shedding. A mechanism for this behaviour is discussed.
Peak spray angles of approximately θ ≈ 14° were recorded for supercavitation conditions indicating the positive influence
of cavitation bubble collapse on the jet atomisation process. 相似文献
103.
A theoretical study is presented of the effects of solvent molecular motion on nuclear spin-spin coupling constants. Solvent molecules are treated as point dipoles arranged around the solute molecule in a cubic closest packed arrangement. Average dipole moment vectors are given by a rotational Boltzmann average and the resulting perturbation is included in the Fock matrices. Calculations of nuclear spin-spin coupling constants were performed by self-consistent perturbation theory in the INDO (intermediate neglect of differential overlap) approximation of self-consistent-field molecular orbital theory. Calculated results are compared with the experimental data as well as the results of previous models. 相似文献
104.
Kimball A. Milton 《Letters in Mathematical Physics》1995,34(3):285-295
In this Letter, it will be demonstrated explicitly that the finite-element formulation of quantum electrodynamics is free from fermion doubling. We do this by (1) examining the lattice fermion propagator and using it to compute the one-loop vacuum polarization on the lattice, and (2) by an explict computation of vector and axial-vector current anomalies for an arbitrary rectangular lattice in the Schwinger model. There it is shown that requiring that the vector current be conserved necessitates the use of a square lattice, in which case the axial-vector current is anomalous. 相似文献
105.
M.J.T. Milton G. Ancellet A. Apituley J. Bösenberg W. Carnuth F. Castagnoli T. Trickl H. Edner L. Stefanutti T. Schaberl A. Sunesson C. Weitkamp 《Applied physics. B, Lasers and optics》1998,66(1):105-113
Received: 21 January 1997/Revised version: 20 May 1997 相似文献
106.
107.
108.
We have derived a precise thermodynamic definition of the standard free energy to form a cluster which is used in nucleation theory. The results [Eq. (9)] have a form differing slightly from the form usually used in nucleation theory and show that the Lothe-Pound correction factor is based on a misconception concerning the standard states involved. 相似文献
109.
110.
Milton Rosenberg 《Journal of multivariate analysis》1978,8(2):295-316
Let p, q be arbitrary parameter sets, and let be a Hilbert space. We say that x = (xi)i?q, xi ? , is a bounded operator-forming vector (?Fq) if the Gram matrix 〈x, x〉 = [(xi, xj)]i?q,j?q is the matrix of a bounded (necessarily ≥ 0) operator on , the Hilbert space of square-summable complex-valued functions on q. Let A be p × q, i.e., let A be a linear operator from to . Then exists a linear operator ǎ from (the Banach space) Fq to Fp on (A) = {x:x ? Fq, is p × q bounded on } such that y = ǎx satisfies yj?σ(x) = {space spanned by the xi}, 〈y, x〉 = A〈x, x〉 and . This is a generalization of our earlier [J. Multivariate Anal.4 (1974), 166–209; 6 (1976), 538–571] results for the case of a spectral measure concentrated on one point. We apply these tools to investigate q-variate wide-sense Markov processes. 相似文献