50,321 research outputs found
A Matrix Convexity Approach to Some Celebrated Quantum Inequalities
Some of the important inequalities associated with quantum entropy are
immediate algebraic consequences of the Hansen-Pedersen-Jensen inequality. A
general argument is given using matrix perspectives of operator convex
functions. A matrix analogue of Mar\'{e}chal's extended perspectives provides
additional inequalities, including a result of Lieb.Comment: 8 page
Suitability of commercially available laboratory cryogenic refrigerators to support shipboard electro-optical systems in the 10 - 77 Kelvin region
The primary development of cryogenically cooled infrared systems was accomplished by FLIR systems designed for airborne, passive night vision. Essential to the development of these FLIR systems was a family of closed cycle refrigerators which had to meet a limited envelope requirement, utilize a nonlubricated compressor module, and be light in weight. Closed cycle refrigerators accomplished the same cooling function, they use modified oil lubricated reciprocating compressors which are limited in their axis of orientation to an angle of approximately 15-20 degrees maximum from horizon
Electric vehicle power train instrumentation: Some constraints and considerations
The application of pulse modulation control (choppers) to dc motors creates unique instrumentation problems. In particular, the high harmonic components contained in the current waveforms require frequency response accommodations not normally considered in dc instrumentation. In addition to current sensing, accurate power measurement requires not only adequate frequency response but must also address phase errors caused by the finite bandwidths and component characteristics involved. The implications of these problems are assessed
Screened electrostatic interactions between clay platelets
An effective pair potential for systems of uniformly charged lamellar
colloids in the presence of an electrolytic solution of microscopic co- and
counterions is derived. The charge distribution on the discs is expressed as a
collection of multipole moments, and the tensors which determine the
interactions between these multipoles are derived from a screened Coulomb
potential. Unlike previous studies of such systems, the interaction energy may
now be expressed for discs at arbitrary mutual orientation. The potential is
shown to be exactly equivalent to the use of linearized Poisson-Boltzmann
theory.Comment: 23 pages, 10 figures, created with Revtex. To appear in Molecular
Physic
Self-Affinity in the Gradient Percolation Problem
We study the scaling properties of the solid-on-solid front of the infinite
cluster in two-dimensional gradient percolation. We show that such an object is
self affine with a Hurst exponent equal to 2/3 up to a cutoff-length
proportional to the gradient to the power (-4/7). Beyond this length scale, the
front position has the character of uncorrelated noise. Importantly, the
self-affine behavior is robust even after removing local jumps of the front.
The previously observed multi affinity, is due to the dominance of overhangs at
small distances in the structure function. This is a crossover effect.Comment: 4 pages, 4 figure
Tolerance and Sensitivity in the Fuse Network
We show that depending on the disorder, a small noise added to the threshold
distribution of the fuse network may or may not completely change the
subsequent breakdown process. When the threshold distribution has a lower
cutoff at a finite value and a power law dependence towards large thresholds
with an exponent which is less than , the network is not sensitive
to the added noise, otherwise it is. The transition between sensitivity or not
appears to be second order, and is related to a localization-delocalization
transition earlier observed in such systems.Comment: 12 pages, 3 figures available upon request, plain Te
Performance characteristics of the 12 GHz, 200 watt transmitter experiment package for CTS
The experiment package consists of a 200 W output stage tube (OST) powered by a power processing system (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 percent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 percent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, inter-modulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center)
A coalescence model for freely decaying two-dimensional turbulence
We propose a ballistic coalescence model (punctuated-Hamiltonian approach)
mimicking the fusion of vortices in freely decaying two-dimensional turbulence.
A temporal scaling behaviour is reached where the vortex density evolves like
. A mean-field analytical argument yielding the approximation
is shown to slightly overestimate the decay exponent whereas
Molecular Dynamics simulations give , in agreement with
recent laboratory experiments and simulations of Navier-Stokes equation.Comment: 6 pages, 1 figure, to appear in Europhysics Letter
Density profiles and surface tensions of polymers near colloidal surfaces
The surface tension of interacting polymers in a good solvent is calculated
theoretically and by computer simulations for a planar wall geometry and for
the insertion of a single colloidal hard-sphere. This is achieved for the
planar wall and for the larger spheres by an adsorption method, and for smaller
spheres by a direct insertion technique. Results for the dilute and semi-dilute
regimes are compared to results for ideal polymers, the Asakura-Oosawa
penetrable-sphere model, and to integral equations, scaling and renormalization
group theories. The largest relative changes with density are found in the
dilute regime, so that theories based on non-interacting polymers rapidly break
down. A recently developed ``soft colloid'' approach to polymer-colloid
mixtures is shown to correctly describe the one-body insertion free-energy and
the related surface tension
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