25,719 research outputs found
A wave-function Monte Carlo method for simulating conditional master equations
Wave-function Monte Carlo methods are an important tool for simulating
quantum systems, but the standard method cannot be used to simulate decoherence
in continuously measured systems. Here we present a new Monte Carlo method for
such systems. This was used to perform the simulations of a continuously
measured nano-resonator in [Phys. Rev. Lett. 102, 057208 (2009)].Comment: 4 pages, revtex 4, 1 eps figure. v2: correction to Eqs (3),(9), and
(11); v3 added further informatio
An extension of the Kac ring model
We introduce a unitary dynamics for quantum spins which is an extension of a
model introduced by Mark Kac to clarify the phenomenon of relaxation to
equilibrium. When the number of spins gets very large, the magnetization
satisfies an autonomous equation as function of time with exponentially fast
relaxation to the equilibrium magnetization as determined by the microcanonical
ensemble. This is proven as a law of large numbers with respect to a class of
initial data. The corresponding Gibbs-von Neumann entropy is also computed and
its monotonicity in time discussed.Comment: 15 pages, v2 -> v3: minor typographic correctio
A Monte Carlo Method for Modeling Thermal Damping: Beyond the Brownian-Motion Master Equation
The "standard" Brownian motion master equation, used to describe thermal
damping, is not completely positive, and does not admit a Monte Carlo method,
important in numerical simulations. To eliminate both these problems one must
add a term that generates additional position diffusion. He we show that one
can obtain a completely positive simple quantum Brownian motion, efficiently
solvable, without any extra diffusion. This is achieved by using a stochastic
Schroedinger equation (SSE), closely analogous to Langevin's equation, that has
no equivalent Markovian master equation. Considering a specific example, we
show that this SSE is sensitive to nonlinearities in situations in which the
master equation is not, and may therefore be a better model of damping for
nonlinear systems.Comment: 6 pages, revtex4. v2: numerical results for a nonlinear syste
Extragalactic astronomy: The universe beyond our galaxy
This single-topic brochure is for high school physical science teachers to use in introducing students to extragalactic astronomy. The material is presented in three parts: the fundamental content of extragalactic astronomy; modern discoveries delineated in greater detail; and a summary of the earlier discussions within the structure of the Big-Bang Theory of evolution. Each of the three sections is followed by student exercises (activities, laboratory projects, and questions-and-answers). The unit close with a glossary which explains unfamilar terms used in the text and a collection of teacher aids (literature references and audiovisual materials for utilization in further study)
Description and simulation of an integrated power and attitude control system concept for space-vehicle application
An Integrated Power and Attitude Control System (IPACS) concept with potential application to a broad class of space missions is discussed. A description is given of the basic concept of combining the onboard energy storage and attitude control functions by storing energy in spinning flywheels which are used to provide control torques. A shuttle-launched Research and Applications Module (RAM) A303B solar-observatory mission having stringent pointing requirements (1.0 arc second) is selected to investigate possible interactions between energy storage and attitude control. A simulation of this spacecraft involving actual laboratory-model control-system hardware is presented. Simulation results are discussed which indicate that the IPACS concept, even in a failure-mode configuration, can readily meet the RAM A303B pointing requirements
Making connections and promoting the profession: social media use by World Federation of Occupational Therapy member organisations
BACKGROUND: World Federation of Occupational Therapists (WFOT) member organisations comprise 77 national occupational therapy organisations across the world. Each national organisation interacts with its members and the public using diverse methods. Increasingly, national organisations are broadening their communication methods.
OBJECTIVE: The objective of this study was to examine if and how occupational therapy organisations are using social media for communication, and if so, the types of concerns or barriers they experience and what role they anticipate social media might play in the near future.
METHODS: An online survey was developed; 57 of 77 WFOT member organisations responded.
FINDINGS: This study identified that WFOT national organisations are using social media, to varying degrees, with or without an individual formally assigned to manage social media. Respondents reported that they used social media to: communicate with members, promote the organisation and promote the profession. Commonly expressed needs included assistance with guide- lines for ethical social media use, developing technical expertise, and recognition of limits of time and competing priorities. Recommendations arising from this research are at the global, national, local and individual levels and incorporate active dissemination and pure diffusion approaches. Taking steps to increase the use of social media could indirectly impact occu- pational therapy practice through enhancing organisations’ abilities to support practitioners to enhance their practice.
LIMITATIONS AND RECOMENDATIONS FOR FURTHER RESEARCH: Although 57% of WFOT member organisations returned usable responses, there may be some additional perspectives that were not captured. It would be helpful to contact non-responding organisations to explore their social media use and plans. Further research could examine how future initiatives put in place by WFOT impact social media use by member organisations.Published versio
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