26,151 research outputs found

    Photovoltaic stand-alone modular systems, phase 2

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    The final hardware and system qualification phase of a two part stand-alone photovoltaic (PV) system development is covered. The final design incorporated modular, power blocks capable of expanding incrementally from 320 watts to twenty kilowatts (PK). The basic power unit (PU) was nominally rated 1.28 kWp. The controls units, power collection buses and main lugs, electrical protection subsystems, power switching, and load management circuits are housed in a common control enclosure. Photo-voltaic modules are electrically connected in a horizontal daisy-chain method via Amp Solarlok plugs mating with compatible connectors installed on the back side of each photovoltaic module. A pair of channel rails accommodate the mounting of the modules into a frameless panel support structure. Foundations are of a unique planter (tub-like) configuration to allow for world-wide deployment without restriction as to types of soil. One battery string capable of supplying approximately 240 ampere hours nominal of carryover power is specified for each basic power unit. Load prioritization and shedding circuits are included to protect critical loads and selectively shed and defer lower priority or noncritical power demands. The baseline system, operating at approximately 2 1/2 PUs (3.2 kW pk.) was installed and deployed. Qualification was successfully complete in March 1983; since that time, the demonstration system has logged approximately 3000 hours of continuous operation under load without major incident

    Polarization in the Lagoon nebula

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    A V-band polarimetric survey of stars associated with the Lagoon nebula was conducted. The data were combined with existing photometric and spectroscopic observations in order to investigate the alignment of magnetic field lines with identifiable symmetry axes and to evaluate the nature of dust in the immediate vicinity. Although stars are not in general highly polarized, electric vectors align with the minor axis of the Lagoon nebula, perpendicular to the major axis of the spatial distribution of massive stars. The observations indicate that the collapse of the molecular cloud progenitor was inhibited along directions perpendicular to magnetic field lines. Considering the low polarization efficiency and the high ratio of total to selective extinction, smaller grains of intranebular dust appear to have been destroyed

    A perturbation density functional theory for the competition between inter and intramolecular association

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    Using the framework of Wertheim's thermodynamic perturbation theory we develop the first density functional theory which accounts for intramolecular association in chain molecules. To test the theory new Monte Carlo simulations are performed at a fluid solid interface for a 4 segment chain which can both intra and intermolecularly associate. The theory and simulation results are found to be in excellent agreement. It is shown that the inclusion of intramolecular association can have profound effects on interfacial properties such as interfacial tension and the partition coefficient

    Volume of the set of unistochastic matrices of order 3 and the mean Jarlskog invariant

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    A bistochastic matrix B of size N is called unistochastic if there exists a unitary U such that B_ij=|U_{ij}|^{2} for i,j=1,...,N. The set U_3 of all unistochastic matrices of order N=3 forms a proper subset of the Birkhoff polytope, which contains all bistochastic (doubly stochastic) matrices. We compute the volume of the set U_3 with respect to the flat (Lebesgue) measure and analytically evaluate the mean entropy of an unistochastic matrix of this order. We also analyze the Jarlskog invariant J, defined for any unitary matrix of order three, and derive its probability distribution for the ensemble of matrices distributed with respect to the Haar measure on U(3) and for the ensemble which generates the flat measure on the set of unistochastic matrices. For both measures the probability of finding |J| smaller than the value observed for the CKM matrix, which describes the violation of the CP parity, is shown to be small. Similar statistical reasoning may also be applied to the MNS matrix, which plays role in describing the neutrino oscillations. Some conjectures are made concerning analogous probability measures in the space of unitary matrices in higher dimensions.Comment: 33 pages, 6 figures version 2 - misprints corrected, explicit formulae for phases provide

    Beyond uvulopalatopharyngoplasty for obstructive sleep apnoea: single surgeon case series of contemporary airway reconstruction

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    Objective: Adult patients with obstructive sleep apnoea can be a therapeutic surgical challenge if other treatments fail or are rejected. We report the outcomes of a series of 17 patients for whom standard device-based treatments failed or could not be used. These patients were considered unsuitable for a lesser operation and therefore underwent multilevel upper airway reconstruction. Method: Data from 17 consecutive patients were collected prospectively. This included pre- and post-surgery findings for clinical assessments, body mass index, sleep questionnaires, and laboratory polysomnograms. Patients underwent a combination of modified uvulopalatopharyngoplasty, transpalatal advancement and various tongue reduction procedures. Results: Analyses revealed statistically and clinically significant reductions in: mean apnoea-hypopnoea index scores (from 36.3 pre-operatively to 14.5 post-operatively, p \u3c 0.001), mean Epworth sleepiness scale scores (from 11.3 to 5.3, p \u3c 0.001) and mean snoring severity scores (from 6.9 to 1.3, p \u3c 0.001). Body mass index remained unchanged. Conclusion: Multilevel upper airway reconstructive surgery was associated with large reductions in both objective and patient-centred subjective measures of obstructive sleep apnoea severity

    Mesozooplankton Distribution and Abundance in the Pagan River: A Nutrient Enriched Subestuary of the James River, Virginia

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    The mesozooplankton in the Pagan River was dominated by calanoid copepods, with abundance peaks occurring during late winter-early spring and from late summer into early fall. This included spring, summer, and fall abundance maxima. The total mean abundance of the mesozooplankton was 3,008/m3

    Orbital order and ferrimagnetic properties of the new compound Sr8CaRe3Cu4O24Sr_8 Ca Re_3 Cu_4 O_{24}

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    By means of the LSDA+U method and the Green function method, we investigate the electronic and magnetic properties of the new material of Sr8_8CaRe3_3Cu4_4O24_{24}. Our LSDA+U calculation shows that this system is an insulator with a net magnetic moment of 1.01 μB\mu_{\rm B}/f.u., which is in good agreement with the experiment. Magnetic moments are mainly located at Cu atoms, and the magnetic moments of neighboring Cu sites align anti-parallel. It is the non-magnetic Re atoms that induce an orbital order of dd electrons of Cu atoms, which is responsible for the strong exchange interaction and the high magnetic transition temperature. Based on the LSDA+U results, we introduce an effective model for the spin degrees of freedom, and investigate the finite-temperature properties by the Green function method. The obtained results are consistent with the experimental results, indicating that the spin-alternating Heisenberg model is suitable for this compound.Comment: 8 pages and 5 figur

    Design description report for a photovoltaic power system for a remote satellite earth terminal

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    A photovoltaic (PV) power system has been installed as an adjunct to an agricultural school at Wawatobi on the large northern island of the Republic of Indonesia. Its purpose is to provide power for a satellite earth station and a classroom. The renewable energy developed supports the video and audio teleconferencing systems as well as the facility at large. The ground station may later be used to provide telephone service. The installation was made in support of the Agency for International Development's Rural Satellite Program, whose purpose is to demonstrate the use of satellite communications for rural development assistance applications. The objective of this particular PV power system is to demonstrate the suitability of a hybrid PV engine-generator configuration for remote satellite earth stations

    Migration of income-support recipients from non-metropolitan NSW and SA into Sydney and Adelaide

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    Nancy Marshall, Ian Burnley, Peter Murphy, Graeme Hug
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