Andreev reflection in bilayer graphene

We consider the conductance of a normal-superconductor junction in bilayer graphene in the framework of the Dirac-Bogoliubov-De-Gennes equation. A remarkable suppression of the conductance at voltages just below the superconducting gap is found. This can be understood in terms of the spinor structures of the electron and hole excitations, in particular the reflected valence band hole being orthogonal to the incoming electron at normal incidence. Minor changes in response to referee reports, references updated.Comment: 9 pages, 8 figure

Low-loss, circularly-polarized dichroic plate

Dichroic plate has orthogonally-disposed, loaded dipole apertures with their orientations arranged so as to cancel cross-coupling effects which would otherwise result in power loss to circularly polarized signal

Spiral groove seal

Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove produces a pumping action toward the fluid when the shaft rotates. This prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear. Provision is made for placing these spiral grooves in communication with the fluid to accelerate the generation of the hydraulic lifting force

Improved circumferential shaft seal

Comparative tests of modified and unmodified carbon ring seals showed that addition of helical grooves to conventional segmented carbon ring seals reduced leakage significantly. Modified seal was insensitive to shaft runout and to flooding by lubricant

Low loss dichroic plate

A low loss dichroic plate is disclosed for passing radiation within a particular frequency band and reflecting radiation outside of that frequency band. The dichroic plate is comprised of a configuration of dipole elements defined by slots formed in a conductive plate. The slots are dimensioned so as to pass radiation of a selected frequency and are shaped so as to minimize the relationship between that frequency and the tilt angle of the plate relative to the direction of radiation. The slots are arranged so as to minimize signal power loss due to cross polarization effects

Improved circumferential shaft seal for aircraft gear transmissions

Operation under simulated aircraft transmission conditions of speeds to 2850 m/min (9350 ft/min), lubricant temperatures to 394 K (250 F), shaft radial runouts to 0.254 mm (0.010 in.) F.I.R. (full indicator reading), and pressure differentials to 1.03 N/cm2 (1.5 psi) revealed that conventional circumferential seals leaked excessively. Modifying the conventional seal by adding helical grooves to the seal bore reduced leakage rates to within the acceptable level of 10 cm3/hr. The leakage rate of this modified seal was not significantly affected by lubricant flooding or by shaft radial runout

Digital computer analysis and design of a subreflector of complex shape

Digital computer technique for computing scattered pattern of complex hyperboloid subreflector in Cassegrain antenna feed system

Stochastic Generation of Particle Structures with Controlled Degree of Heterogeneity

The recently developed void expansion method (VEM) allows for an efficient generation of porous packings of spherical particles over a wide range of volume fractions. The method is based on a random placement of the structural particles under addition of much smaller "void-particles" whose radii are repeatedly increased during the void expansion. Thereby, they rearrange the structural particles until formation of a dense particle packing and introduce local heterogeneities in the structure. In this paper, microstructures with volume fractions between 0.4 and 0.6 produced by VEM are analyzed with respect to their degree of heterogeneity (DOH). In particular, the influence of the void- to structural particle number ratio, which constitutes a principal VEM-parameter, on the DOH is studied. The DOH is quantified using the pore size distribution, the Voronoi volume distribution and the density-fluctuation method in conjunction with fit functions or integral measures. This analysis has revealed that for volume fractions between 0.4 and 0.55 the void-particle number allows for a quasi-continuous adjustment of the DOH. Additionally, the DOH-range of VEM-generated microstructures with a volume fraction of 0.4 is compared to the range covered by microstructures generated using previous Brownian dynamics simulations, which represent the structure of coagulated colloidal suspensions. Both sets of microstructures cover similarly broad and overlapping DOH-ranges, which allows concluding that VEM is an efficient method to stochastically reproduce colloidal microstructures with varying DOH.Comment: 10 pages, 7 figure