4,080 research outputs found
Integrated control system for a gas turbine engine
A control system for a turbofan engine receives signals from a number of engine sensors and from the engine operator, and generates control signals. One control signal regulates the fan exhaust nozzle area in order to control inlet throat Mach number to maintain a low level of engine noise. Additional control signals regulate fuel flow to control engine thrust and fan pitch to control fan speed. A number of schedules are utilized to maintain a predetermined relationship between the controlled parameters and a number of fixed and calculated limits can override the control signals to prevent unsatisfactory engine performance
Electrical Switching in Metallic Carbon Nanotubes
We present first-principles calculations of quantum transport which show that
the resistance of metallic carbon nanotubes can be changed dramatically with
homogeneous transverse electric fields if the nanotubes have impurities or
defects. The change of the resistance is predicted to range over more than two
orders of magnitude with experimentally attainable electric fields. This novel
property has its origin that backscattering of conduction electrons by
impurities or defects in the nanotubes is strongly dependent on the strength
and/or direction of the applied electric fields. We expect this property to
open a path to new device applications of metallic carbon nanotubes.Comment: 4 pages and 4 figure
CORE and the Haldane Conjecture
The Contractor Renormalization group formalism (CORE) is a real-space
renormalization group method which is the Hamiltonian analogue of the Wilson
exact renormalization group equations. In an earlier paper\cite{QGAF} I showed
that the Contractor Renormalization group (CORE) method could be used to map a
theory of free quarks, and quarks interacting with gluons, into a generalized
frustrated Heisenberg antiferromagnet (HAF) and proposed using CORE methods to
study these theories. Since generalizations of HAF's exhibit all sorts of
subtle behavior which, from a continuum point of view, are related to
topological properties of the theory, it is important to know that CORE can be
used to extract this physics. In this paper I show that despite the folklore
which asserts that all real-space renormalization group schemes are necessarily
inaccurate, simple Contractor Renormalization group (CORE) computations can
give highly accurate results even if one only keeps a small number of states
per block and a few terms in the cluster expansion. In addition I argue that
even very simple CORE computations give a much better qualitative understanding
of the physics than naive renormalization group methods. In particular I show
that the simplest CORE computation yields a first principles understanding of
how the famous Haldane conjecture works for the case of the spin-1/2 and spin-1
HAF.Comment: 36 pages, 4 figures, 5 tables, latex; extensive additions to conten
Stratospheric General Circulation with Chemistry Model (SGCCM)
In the past two years constituent transport and chemistry experiments have been performed using both simple single constituent models and more complex reservoir species models. Winds for these experiments have been taken from the data assimilation effort, Stratospheric Data Analysis System (STRATAN)
DMTPC: A dark matter detector with directional sensitivity
By correlating nuclear recoil directions with the Earth's direction of motion
through the Galaxy, a directional dark matter detector can unambiguously detect
Weakly Interacting Massive Particles (WIMPs), even in the presence of
backgrounds. Here, we describe the Dark Matter Time-Projection Chamber (DMTPC)
detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this
detector, we have measured the vector direction (head-tail) of nuclear recoils
down to energies of 100 keV with an angular resolution of <15 degrees. To study
our detector backgrounds, we have operated in a basement laboratory on the MIT
campus for several months. We are currently building a new, high-radiopurity
detector for deployment underground at the Waste Isolation Pilot Plant facility
in New Mexico.Comment: 4 pages, 2 figures, proceedings for the CIPANP 2009 conference, May
26-31, 200
Smart urbanism in Barcelona: A knowledge-politics perspective
There is a risk in the ‘Smart City’ that plural forms of knowing the city become eclipsed by singular governance-oriented analyses produced through computational logics originating from undemocratic service providers. In light of this concern, this chapter considers three aspects of smart urbanism’s knowledge politics: i) the role of urban agencies – or understanding smart urbanism as a situated, socio-material practice; ii) the agency of smart city technologies’ materiality as well as the ownership and control of these technologies, and: iii) the political rationalities, values and assumptions embedded in smart city technologies’ design and use. Drawing on these insights, this chapter analyses smart knowledge politics in Barcelona, where the 2015 Council elections replaced a market-oriented political leadership enthusiastically implementing the Smart City with a political leadership whose origins in social movements and citizen democracy made it deeply sceptical towards smart urbanism. We analyse how this opened up space for different approaches to using technology in the city while at the same time giving rise to materially very different kinds of smart knowledge configuring technologies emphasizing citizen participation and democratic control of knowledge production. Indeed, political rationalities and smart knowledge configuring technologies intersected and co-evolved, rather than one
informing the other unidirectionally
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