12,255 research outputs found
Scramjet nozzle design and analysis as applied to a highly integrated hypersonic research airplane
Engine-nozzle airframe integration at hypersonic speeds was conducted by using a high-speed research aircraft concept as a focus. Recently developed techniques for analysis of scramjet-nozzle exhaust flows provide a realistic analysis of complex forces resulting from the engine-nozzle airframe coupling. By properly integrating the engine-nozzle propulsive system with the airframe, efficient, controlled and stable flight results over a wide speed range
Rich-club connectivity dominates assortativity and transitivity of complex networks
Rich-club, assortativity and clustering coefficients are frequently-used
measures to estimate topological properties of complex networks. Here we find
that the connectivity among a very small portion of the richest nodes can
dominate the assortativity and clustering coefficients of a large network,
which reveals that the rich-club connectivity is leveraged throughout the
network. Our study suggests that more attention should be payed to the
organization pattern of rich nodes, for the structure of a complex system as a
whole is determined by the associations between the most influential
individuals. Moreover, by manipulating the connectivity pattern in a very small
rich-club, it is sufficient to produce a network with desired assortativity or
transitivity. Conversely, our findings offer a simple explanation for the
observed assortativity and transitivity in many real world networks --- such
biases can be explained by the connectivities among the richest nodes.Comment: 5 pages, 2 figures, accepted by Phys. Rev.
Colonial Guards : March And Two Step
https://digitalcommons.library.umaine.edu/mmb-ps/1784/thumbnail.jp
Orbiter/launch system
The system includes reusable turbojet propelled booster vehicles releasably connected to a reusable rocket powered orbit vehicle. The coupled orbiter-booster combination takes off horizontally and ascends to staging altitude and speed under booster power with both orbiter and booster wings providing lift. After staging, the booster vehicles fly back to Earth for horizontal landing and the orbiter vehicle continues ascending to orbit
Detecting periodicity in experimental data using linear modeling techniques
Fourier spectral estimates and, to a lesser extent, the autocorrelation
function are the primary tools to detect periodicities in experimental data in
the physical and biological sciences. We propose a new method which is more
reliable than traditional techniques, and is able to make clear identification
of periodic behavior when traditional techniques do not. This technique is
based on an information theoretic reduction of linear (autoregressive) models
so that only the essential features of an autoregressive model are retained.
These models we call reduced autoregressive models (RARM). The essential
features of reduced autoregressive models include any periodicity present in
the data. We provide theoretical and numerical evidence from both experimental
and artificial data, to demonstrate that this technique will reliably detect
periodicities if and only if they are present in the data. There are strong
information theoretic arguments to support the statement that RARM detects
periodicities if they are present. Surrogate data techniques are used to ensure
the converse. Furthermore, our calculations demonstrate that RARM is more
robust, more accurate, and more sensitive, than traditional spectral
techniques.Comment: 10 pages (revtex) and 6 figures. To appear in Phys Rev E. Modified
styl
Fabrication and Electric Field Dependent Transport Measurements of Mesoscopic Graphite Devices
We have developed a unique micromechanical method to extract extremely thin
graphite samples. Graphite crystallites with thicknesses ranging from 10 - 100
nm and lateral size 2 m are extracted from bulk. Mesoscopic
graphite devices are fabricated from these samples for electric field dependent
conductance measurements. Strong conductance modulation as a function of gate
voltage is observed in the thinner crystallite devices. The temperature
dependent resistivity measurements show more boundary scattering contribution
in the thinner graphite samples.Comment: 3 pages, 3 figures included, submitted to Appl. Phys. Let
Results of an aqueous source term model for a radiological risk assessment of the Drigg LLW Site, U.K.
A radionuclide source term model has been developed which simulates the biogeochemical evolution of the Drigg low level waste (LLW) disposal site. The DRINK (DRIgg Near field Kinetic) model provides data regarding radionuclide concentrations in groundwater over a period of 100,000 years, which are used as input to assessment calculations for a groundwater pathway. The DRINK model also provides input to human intrusion and gaseous assessment calculations through simulation of the solid radionuclide inventory. These calculations are being used to support the Drigg post closure safety case. The DRINK model considers the coupled interaction of the effects of fluid flow, microbiology, corrosion, chemical reaction, sorption and radioactive decay. It represents the first direct use of a mechanistic reaction-transport model in risk assessment calculations
Modulation of Thermoelectric Power of Individual Carbon Nanotubes
Thermoelectric power (TEP) of individual single walled carbon nanotubes
(SWNTs) has been measured at mesoscopic scales using a microfabricated heater
and thermometers. Gate electric field dependent TEP-modulation has been
observed. The measured TEP of SWNTs is well correlated to the electrical
conductance across the SWNT according to the Mott formula. At low temperatures,
strong modulations of TEP were observed in the single electron conduction
limit. In addition, semiconducting SWNTs exhibit large values of TEP due to the
Schottky barriers at SWNT-metal junctions.Comment: to be published in Phys. Rev. Let
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