10,902 research outputs found
Moving in to social housing and the dynamics of difference: 'neighbours from hell' with nothing to lose?
Integrated control and health management. Orbit transfer rocket engine technology program
To insure controllability of the baseline design for a 7500 pound thrust, 10:1 throttleable, dual expanded cycle, Hydrogen-Oxygen, orbit transfer rocket engine, an Integrated Controls and Health Monitoring concept was developed. This included: (1) Dynamic engine simulations using a TUTSIM derived computer code; (2) analysis of various control methods; (3) Failure Modes Analysis to identify critical sensors; (4) Survey of applicable sensors technology; and, (5) Study of Health Monitoring philosophies. The engine design was found to be controllable over the full throttling range by using 13 valves, including an oxygen turbine bypass valve to control mixture ratio, and a hydrogen turbine bypass valve, used in conjunction with the oxygen bypass to control thrust. Classic feedback control methods are proposed along with specific requirements for valves, sensors, and the controller. Expanding on the control system, a Health Monitoring system is proposed including suggested computing methods and the following recommended sensors: (1) Fiber optic and silicon bearing deflectometers; (2) Capacitive shaft displacement sensors; and (3) Hot spot thermocouple arrays. Further work is needed to refine and verify the dynamic simulations and control algorithms, to advance sensor capabilities, and to develop the Health Monitoring computational methods
Optimality of programmable quantum measurements
We prove that for a programmable measurement device that approximates every
POVM with an error , the dimension of the program space has to grow
at least polynomially with . In the case of qubits we can
improve the general result by showing a linear growth. This proves the
optimality of the programmable measurement devices recently designed in [G. M.
D'Ariano and P. Perinotti, Phys. Rev. Lett. \textbf{94}, 090401 (2005)]
Random quantum channels I: graphical calculus and the Bell state phenomenon
This paper is the first of a series where we study quantum channels from the
random matrix point of view. We develop a graphical tool that allows us to
compute the expected moments of the output of a random quantum channel. As an
application, we study variations of random matrix models introduced by Hayden
\cite{hayden}, and show that their eigenvalues converge almost surely. In
particular we obtain for some models sharp improvements on the value of the
largest eigenvalue, and this is shown in a further work to have new
applications to minimal output entropy inequalities.Comment: Several typos were correcte
Macrospin Tunneling and Magnetopolaritons with Nanomechanical Interference
We theoretically address the quantum dynamics of a nanomechanical resonator
coupled to the macrospin of a magnetic nanoparticle by both instanton and
perturbative approaches. We demonstrate suppression of the tunneling between
opposite magnetizations by nanomechanical interference. By approximating the
macrospin as a two-level system, we describe magnetopolaritons and their
destruction by interference. The predictions can be verified experimentally by
a molecular magnet attached to a nanomechanical bridge.Comment: 4.4 pages, 3 figures. Slightly revised presentation, results
unchange
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