97,573 research outputs found
Ku-band field-effect power transistors
A single stage amplifier was developed using an 8 gate, 1200 micrometer width device to give a gain of 3.3 + or - 0.1 dB over the 14.4 to 15.4 GHz band with an output power of 0.48 W and 15% minimum efficiency with 0.255 W of input power. With two 8 gate devices combined and matched on the device carrier, using a lumped element format, a gain of 3 dB was attained over the 14.5 to 15.5 GHz band with a maximum efficiency of 9.9% for an output power of 0.8 W
The Ontological Basis of Strong Artificial Life
This article concerns the claim that it is possible to create living organisms, not merely models that represent organisms, simply by programming computers ("virtual" strong alife). I ask what sort of things these computer-generated organisms are supposed to be (where are they, and what are they made of?). I consider four possible answers to this question: (a) The organisms are abstract complexes of pure information; (b) they are material objects made of bits of computer hardware; (c) they are physical processes going on inside the computer; and (d) they are denizens of an entire artificial world, different from our own, that the programmer creates. I argue that (a) could not be right, that (c) collapses into (b), and that (d) would make strong alife either absurd or uninteresting. Thus, "virtual" strong alife amounts to the claim that, by programming a computer, one can literally bring bits of its hardware to life
Method and apparatus for producing microshells
A method is described for forming hollow particles, or shells, of extremely small size. The shell material is heated to a molten temperature in the presence of a gas that is at least moderately soluble in the shell material, to form a solution of the molten shell material and the soluble gas. The solution is atomized to form a multiplicity of separate droplets that are cooled while in free fall. Cooling of a droplet from the outside traps the desolved gas and forces it to form a gas bubble at the center of the droplet which now forms a gas filled shell. The shell is reheated and then cooled in free fall, in an environment having a lower pressure than the gas pressure in the shell. This causes expansion of the shell and the formation of a shell having a small wall thickness compared to its diameter
Changes of partitioning and increased root lengths of spruce and beech exposed to ambient pollution concentrations in southern England
International audienc
Analysis of enhanced diffusion in Taylor dispersion via a model problem
We consider a simple model of the evolution of the concentration of a tracer,
subject to a background shear flow by a fluid with viscosity in an
infinite channel. Taylor observed in the 1950's that, in such a setting, the
tracer diffuses at a rate proportional to , rather than the expected
rate proportional to . We provide a mathematical explanation for this
enhanced diffusion using a combination of Fourier analysis and center manifold
theory. More precisely, we show that, while the high modes of the concentration
decay exponentially, the low modes decay algebraically, but at an enhanced
rate. Moreover, the behavior of the low modes is governed by finite-dimensional
dynamics on an appropriate center manifold, which corresponds exactly to
diffusion by a fluid with viscosity proportional to
Use of active control technology to improve ride qualities of large transport aircraft
Analyses, construction and flight testing of two systems: Beta-vane and Modal Suppression Augmentation System (MSAS), which were developed to suppress gust induced lateral accelerations of large aircraft, are described. The 747 transport was used as the test vehicle. The purpose of the Beta-vane system is to reduce acceleration levels at the dutch roll frequency whereas the function of the MSAS system is to reduce accelerations due to flexible body motions caused by turbulence. Data from flight test, with both systems engaged shows a 50 to 70 percent reduction in lateral aft body acceleration levels. Furthermore, it is suggested that present day techniques used for developing dynamic equations of motion in the flexible mode region are limited
Finite Size Effects in the Anisotropic \lambda/4!(\phi^4_1 + \phi^4_2)_d Model
We consider the model on a
d-dimensional Euclidean space, where all but one of the coordinates are
unbounded. Translation invariance along the bounded coordinate, z, which lies
in the interval [0,L], is broken because of the boundary conditions (BC's)
chosen for the hyperplanes z=0 and z=L. Two different possibilities for these
BC's boundary conditions are considered: DD and NN, where D denotes Dirichlet
and N Newmann, respectively. The renormalization procedure up to one-loop order
is applied, obtaining two main results. The first is the fact that the
renormalization program requires the introduction of counterterms which are
surface interactions. The second one is that the tadpole graphs for DD and NN
have the same z dependent part in modulus but with opposite signs. We
investigate the relevance of this fact to the elimination of surface
divergences.Comment: 33 pages, 2 eps figure
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