4,098 research outputs found
Decoherent Histories and Non-adiabatic Quantum Molecular Dynamics
The role of quantum coherence loss in mixed quantum-classical dynamical
systems is explored in the context of the theory of quantum decoherence
introduced recently by Bittner and Rossky. (J. Chem. Phys. {\bf 103}, 8130
(1995)). This theory, which is based upon the consistent histories
interpretation of quantum mechanics, introduces decoherence in the quantum
subsystem by carefully considering the relevant time and length scales over
which one must consider the effects of phase interference between alternative
histories of the classical subsystem. Such alternative histories are an
integral part of any quantum-classical computational scheme which employ
transitions between discrete quantum states; consequently, the coherences
between alternative histories have a profound effect on the transition
probability between quantum states. In this paper, we review the Bittner-Rossky
theory and detail a computational algorithm suitable for large-scale quantum
molecular dynamics simulations which implements this theory. Application of the
algorithm towards the relaxation of a photoexcited aqueous electron compare
well to previous estimates of the excited state survival time as well as to the
experimental measurements.Comment: 22 pages, 3 figure
Soot formation and burnout in flames
The amount of soot formed when burning a benzene/hexane mixture in a turbulent combustor was examined. Soot concentration profiles in the same combustor for kerosene fuel are given. The chemistry of the formation of soot precursors, the nucleation, growth and subsequent burnout of soot particles, and the effect of mixing on the previous steps were considered
Unquenched complex Dirac spectra at nonzero chemical potential: Two-colour QCD lattice data versus matrix model
We compare analytic predictions of non-Hermitian chiral random matrix theory with the complex Dirac operator eigenvalue spectrum of two-color lattice gauge theory with dynamical fermions at nonzero chemical potential. The Dirac eigenvalues come in complex conjugate pairs, making the action of this theory real and positive for our choice of two staggered flavors. This enables us to use standard Monte Carlo simulations in testing the influence of the chemical potential and quark mass on complex eigenvalues close to the origin. We find excellent agreement between the analytic predictions and our data for two different volumes over a range of chemical potentials below the chiral phase transition. In particular, we detect the effect of unquenching when going to very small quark masses
Spin-dependent electron-hole capture kinetics in conjugated polymers
The recombination of electron-hole pairs injected in extended conjugated
systems is modeled as a multi-pathway vibron-driven relaxation in monoexcited
state-space. The computed triplet-to-singlet ratio of exciton formation times
increases from 0.9 for a model dimer to 2.5 for a 32-unit
chain, in excellent agreement with experiments. Therewith we rationalize
recombination efficiency in terms of spin-dependent interstate vibronic
coupling and spin- and conjugation-length-dependent exciton binding
energies.Our model calculations for various length polymers indicate that the
ratio of the singlet to triplet formation ratios, , is
inversely related to the ratio of the singlet and triplet binding energies,
Designing a Data-Tracking System for a Private Therapeutic Day School
The Children\u27s Institute on Mercer Island (CHILD) is a private therapeutic day school in the Seattle area serving students in elementary and secondary education. Their stated mission is to provide innovative school programs and therapies that promote social, emotional and academic development for children with special needs. In the fall of 2012 they engaged in a program evaluation that in many respects resembles a needs assessment in order to explore and improve aspects of their functioning. Through preliminary evaluation processes, including dialogue with CHILD\u27s Leadership Team and a survey of internal stakeholders, an area of interest in student mental health was uncovered and an initial evaluation question emerged: How does CHILD claim expertise, particularly in the area of mental health? Historically, evidence of CHILD\u27s impact in this regard has been largely anecdotal. Aside from a limited collection of behavioral data pertaining largely to IEP goals and objectives, CHILD does not track mental health, or long-term student outcomes. As a program interested in its own claims to expertise, members of the Leadership Team and other stakeholders have called for improved data collection in this regard. This program evaluation is an attempt to understand the types of data that would be most useful to CHILD\u27s interest in expertise and then design a program for tracking this data. Bronfenbrenner\u27s (1994) ecological model was used as a framework for guiding data collection, the results of which are synthesized and integrated into a series of recommendations constituting the final results of the project. This dissertation is available in open access at AURA, http://aura.antioch.edu/ and Ohio Link ETD Center, https://etd.ohiolink.edu/et
Lattice Models of Quantum Gravity
Standard Regge Calculus provides an interesting method to explore quantum
gravity in a non-perturbative fashion but turns out to be a CPU-time demanding
enterprise. One therefore seeks for suitable approximations which retain most
of its universal features. The -Regge model could be such a desired
simplification. Here the quadratic edge lengths of the simplicial complexes
are restricted to only two possible values , with
, in close analogy to the ancestor of all lattice theories, the
Ising model. To test whether this simpler model still contains the essential
qualities of the standard Regge Calculus, we study both models in two
dimensions and determine several observables on the same lattice size. In order
to compare expectation values, e.g. of the average curvature or the Liouville
field susceptibility, we employ in both models the same functional integration
measure. The phase structure is under current investigation using mean field
theory and numerical simulation.Comment: 4 pages, 1 figure
Computer-aided Melody Note Transcription Using the Tony Software: Accuracy and Efficiency
accepteddate-added: 2015-05-24 19:18:46 +0000 date-modified: 2017-12-28 10:36:36 +0000 keywords: Tony, melody, note, transcription, open source software bdsk-url-1: https://code.soundsoftware.ac.uk/attachments/download/1423/tony-paper_preprint.pdfdate-added: 2015-05-24 19:18:46 +0000 date-modified: 2017-12-28 10:36:36 +0000 keywords: Tony, melody, note, transcription, open source software bdsk-url-1: https://code.soundsoftware.ac.uk/attachments/download/1423/tony-paper_preprint.pdfWe present Tony, a software tool for the interactive an- notation of melodies from monophonic audio recordings, and evaluate its usability and the accuracy of its note extraction method. The scientific study of acoustic performances of melodies, whether sung or played, requires the accurate transcription of notes and pitches. To achieve the desired transcription accuracy for a particular application, researchers manually correct results obtained by automatic methods. Tony is an interactive tool directly aimed at making this correction task efficient. It provides (a) state-of-the art algorithms for pitch and note estimation, (b) visual and auditory feedback for easy error-spotting, (c) an intelligent graphical user interface through which the user can rapidly correct estimation errors, (d) extensive export functions enabling further processing in other applications. We show that Tony’s built in automatic note transcription method compares favourably with existing tools. We report how long it takes to annotate recordings on a set of 96 solo vocal recordings and study the effect of piece, the number of edits made and the annotator’s increasing mastery of the software. Tony is Open Source software, with source code and compiled binaries for Windows, Mac OS X and Linux available from https://code.soundsoftware.ac.uk/projects/tony/
- …