4,504 research outputs found
Wave-coupled LiNbO_3 electrooptic modulator for microwave and millimeter-wave modulation
A new technique of phase velocity matching in electrooptic modulators was demonstrated. The results show that the phase velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguide's delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity of over 100°/W^(1/2)
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Iron Oxide Grains in Stardust Track 121 Grains as Evidence of Comet Wild 2 Hydrothermal Alteration
Stardust Track 121 terminal grains contain Fe-oxide. These are consistent with the presence of hydrothermal alteration on the Comet Wild 2 parent body
A variational principle for fluid sloshing with vorticity, dynamically coupled to vessel motion
A variational principle is derived for two-dimensional incompressible
rotational fluid flow with a free surface in a moving vessel when both the
vessel and fluid motion are to be determined. The fluid is represented by a
stream function and the vessel motion is represented by a path in the planar
Euclidean group. Novelties in the formulation include how the pressure boundary
condition is treated, the introduction of a stream function into the
Euler-Poincar\'e variations, the derivation of free surface variations, and how
the equations for the vessel path in the Euclidean group, coupled to the fluid
motion, are generated automatically.Comment: 19 pages, 3 figure
Constructive aspects of Riemann's permutation theorem for series
The notions of permutable and weak-permutable convergence of a series
of real numbers are introduced. Classically, these
two notions are equivalent, and, by Riemann's two main theorems on the
convergence of series, a convergent series is permutably convergent if and only
if it is absolutely convergent. Working within Bishop-style constructive
mathematics, we prove that Ishihara's principle \BDN implies that every
permutably convergent series is absolutely convergent. Since there are models
of constructive mathematics in which the Riemann permutation theorem for series
holds but \BDN does not, the best we can hope for as a partial converse to our
first theorem is that the absolute convergence of series with a permutability
property classically equivalent to that of Riemann implies \BDN. We show that
this is the case when the property is weak-permutable convergence
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Lithium and carbon isotopic fractionations between the alteration assemblages of Nakhla and Lafayette
Nakhla and Lafayette delta 7Li values for samples and extracts (4.1-14.2�) are consistent with brine evaporation. Relatively 13C-poor siderite in Lafayette suggests more than one carbon source was sampled
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