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Search Results: 1 - 10 of 145486 matches for " Zachary B. Sharp "
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Improving Concrete Containment Structures Associated with Fixed-Cone Valves  [PDF]
B. Skyler Buck, Michael C. Johnson, Zachary B. Sharp
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.35051
Abstract: Fixed-Cone valves are often used to dissipate energy and regulate flow at the low level outlet works of dams. Fixed-Cone valves, also known as Howell-Bunger valves, create an expanding conical jet allowing the energy of the water to dissipate over a large area. However, in many applications constructing the large stilling basin necessary for these valves is either not possible or not feasible. In order to reduce the relative size of the stilling basin, hoods or concrete containment structures have been used in conjunction with Fixed-Cone valves. This paper discusses the use of baffles in concrete containment structures in order to dissipate energy in a considerably confined space. It was determined that using baffles, in place of a deflector ring and end sill (Used in traditional containment structures.), significantly improves the function of containment structures by reducing downstream flow velocities and improving flow patterns and stability. This information will be useful to engineers allowing them to minimize scour and erosion associated with concrete containment structures.
LIF Measurement of the Diluting Effect of Surface Waves on Turbulent Buoyant Plumes  [PDF]
David B. Sharp, Alistair Shawcross, Clive A. Greated
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2014, DOI: 10.4236/jfcmv.2014.23010
Abstract: In this paper, the diluting effect of surface waves on a buoyant plume has been measured using a Laser Induced Fluorescence (LIF) technique. The resulting time-averaged, full field concentration maps have allowed quantification of enhanced mixing due to surface waves as well as measurement of other plume parameters.
Partial Frequencies and Chladni’s Law in Church Bells  [PDF]
William A. Hibbert, David B. Sharp, Shahram Taherzadeh, Robert Perrin
Open Journal of Acoustics (OJA) , 2014, DOI: 10.4236/oja.2014.42007
Abstract: The rim partials of a church bell (those with an antinode at the soundbow) generate the strike pitch or perceived note of the bell. The spacing in frequency of the higher rim partials has an important effect on the tonal quality of the bell. Investigations into the partial frequencies of 2752 bells, both bronze and steel, of a wide variety of dates, founders and sizes, show a simple and unexpected relationship between the frequencies of the rim partials. This relationship explains why attempts to tune the higher rim partials independently have failed. A modified version of Chladni’s law provides insight into the musical relationship of the partials, and predicts the partials of individual bells well, but fails to give a simple model of the spacing between the partials seen in bells with different profiles.
Virtual Pitch and Pitch Shifts in Church Bells  [PDF]
William A. Hibbert, Shahram Taherzadeh, David B. Sharp
Open Journal of Acoustics (OJA) , 2017, DOI: 10.4236/oja.2017.73006
Abstract: It is well established that musical sounds comprising multiple partials with frequencies approximately in the ratio of small integers give rise to a strong sensation of pitch even if the lowest or fundamental partial is missing—the so-called virtual pitch effect. Experiments on thirty test subjects demonstrate that this virtual pitch is shifted significantly by changes in the spacing of the constituent partials. The experiments measured pitch by comparison of sounds of similar timbre and were automated so that they could be performed remotely across the Internet. Analysis of the test sounds used shows that the pitch shifts are not predicted by Terhardt’s classic model of virtual pitch. The test sounds used were modelled on the sounds of church bells, but a further experiment on seventeen test subjects showed that changes in partial amplitude only had a minor effect on the pitch shifts observed, and that a pitch shift was still observed when two of the lowest frequency partials were removed, so that the effects reported are of general interest.
Top Management Team Diversity, Quality Decisions and Organizational Performance in the Service Industry
Zachary B Awino
Journal of Management and Strategy , 2013, DOI: 10.5430/jms.v4n1p113
Abstract: Some past studies have found that the characteristics of the Top Management Team influence the performance of organizations while others have found that they do not. This study, which is founded on the Upper Echelon Theory, investigated the relationship between TMT diversity, quality decisions and organization performance. The study sought to find out the effect of TMT diversity and quality decisions in the performance of commercial banks in Kenya. The study found that quality decisions had a significant effect on the internal business processes and learning and growth perspectives of the balanced scorecard. The study sought to find the intervening effect of the quality decisions and the moderating effect of involvement culture and diversity management strategies. The study found that the two moderating variables had a significant effect on the relationship between TMT diversity and quality decisions and TMT diversity and organization performance.
Quantum Coherent Dynamics at Ambient Temperature in Photosynthetic Molecules
Zachary B. Walters
Physics , 2011,
Abstract: Photosynthetic antenna complexes are responsible for absorbing energy from sunlight and transmitting it to remote locations where it can be stored. Recent experiments have found that this process involves long-lived quantum coherence between pigment molecules, called chromophores, which make up these complexes. Expected to decay within 100 fs at room temperature, these coherences were instead found to persist for picosecond time scales, despite having no apparent isolation from the thermal environment of the cell. This paper derives a quantum master equation which describes the coherent evolution of a system in strong contact with a thermal environment. Conditions necessary for long coherence lifetimes are identified, and the role of coherence in efficient energy transport is illuminated. Static spectra and exciton transfer rates for the PE545 complex of the cryptophyte algae CS24 are calculated and shown to have good agreement with experiment.
An efficient parallel method for relaxing to the minimum action wavefunction
Zachary B. Walters
Physics , 2011,
Abstract: Efficient and accurate numerical propagation of the time dependent Schroedinger equation is a problem with applications across a wide range of physics. This paper develops an efficient, trivially parallelizeable method for relaxing a trial wavefunction toward a variationally optimum propagated wavefunction which minimizes the propagation error relative to a platonic wavefunction which obeys the time dependent Schroedinger equation exactly. This method is shown to be well suited for incorporation with multigrid methods, yielding rapid convergence to a minimum action solution even for Hamiltonians which are not positive definite.
Efficient wavefunction propagation by minimizing accumulated action
Zachary B. Walters
Physics , 2010, DOI: 10.1016/j.cpc.2010.12.030
Abstract: This paper presents a new technique to calculate the evolution of a quantum wavefunction in a chosen spatial basis by minimizing the accumulated action. Introduction of a finite temporal basis reduces the problem to a set of linear equations, while an appropriate choice of temporal basis set offers improved convergence relative to methods based on matrix exponentiation for a class of physically relevant problems.
A linear time quantum algorithm for 3SAT
Zachary B. Walters
Physics , 2015,
Abstract: A quantum algorithm for the NP complete problem of satisfying boolean formulas with three variables per clause (3SAT) is presented. Departing from traditional models of quantum computation, this algorithm makes extensive use of irreversible operations to incoherently transfer population from states which do not solve some problem of interest to states which do. Provided that a solution exists, the algorithm yields exponential decay of nonsolution probability, at a rate controlled by the user.
Quantum dynamics of the avian compass
Zachary B. Walters
Physics , 2012, DOI: 10.1103/PhysRevE.90.042710
Abstract: The ability of migratory birds to orient relative to the Earth's magnetic field is believed to involve a coherent superposition of two spin states of a radical electron pair. However, the mechanism by which this coherence can be maintained in the face of strong interactions with the cellular environment has remained unclear. This Letter addresses the problem of decoherence between two electron spins due to hyperfine interaction with a bath of spin 1/2 nuclei. Dynamics of the radical pair density matrix are derived and shown to yield a simple mechanism for sensing magnetic field orientation. Rates of dephasing and decoherence are calculated ab initio and found to yield millisecond coherence times, consistent with behavioral experiments.
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