741 research outputs found

    K-12 And Beyond: Tennessees Businesses Evaluate The States Educational System

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    A survey of Tennessee’s business leaders was conducted to determine their perceptions of the state’s educational system. Respondents indicated that lower grades were performing average or above, other grades and institutions must improve

    Global Measurements of Optically Thin Ice Clouds Using CALIOP

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    Optically thin ice clouds have been shown to have a net warming effect on the globe but, because passive instruments are not sensitive to optically thin clouds, the occurrence frequency of this class of clouds is greatly underestimated in historical passive sensor cloud climatology. One major strength of CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), onboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spacecraft, is its ability to detect these thin clouds, thus filling an important missing piece in the historical data record. This poster examines the full mission of CALIPSO Level 2 data, focusing on those CALIOP retrievals identified as thin ice clouds according to the definition shown to the right. Using this definition, thin ice clouds are identified and counted globally and vertically for each season. By examining the spatial and seasonal distributions of these thin clouds we hope to gain a better understanding these thin ice clouds and how their global distribution has changed over the mission. This poster showcases when and where CALIOP detects thin ice clouds and examines a case study of the eastern pacific and the effects seen from the El Nino-Southern Oscillation (ENSO)

    Office Building Uses Ice Storage, Heat Recovery, and Cold-Air Distribution

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    Ice storage offers many opportunities to use other tcchnologies, such as heat recovery and cold-air distribution. In fact, by using them, the designer can improve the efficiency and lower the construction cost of an ice system. This paper presents a case study of a large (550,000 square feet) office building which combines these ideas into one HVAC system. By integrating these technologies to take advantage of the unique characteristics of ice storage, the engineers created a system that provided a 1-1/2 year simple payback. The system reduces operating costs by over 0.16persquarefooteachyear,yetitincreasedthenetHVACbudgetbyonly0.16 per square foot each year, yet it increased the net HVAC budget by only 0.22 per square foot

    The investigation of smart magnetic nanoparticles for use in the hyperthermia treatment of cancer

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    Self-controlled temperature nanoparticles as a form of hyperthermia treatment to fight against cancer

    Magnetodielectric coupling in Mn3O4

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    We have investigated the dielectric anomalies associated with spin ordering transitions in the tetragonal spinel Mn3_3O4_4, using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering transitions in Mn3_3O4_4 lead to decreases in the temperature dependent dielectric constant at zero applied field. Applying a magnetic field to the polycrystalline sample leaves these two dielectric anomalies practically unchanged, but leads to an increase in the dielectric constant at the intermediate spin-ordering transition. We discuss possible origins for this magnetodielectric behavior in terms of spin-phonon coupling. Band structure calculations suggest that in its ferrimagnetic state, Mn3_3O4_4 corresponds to a semiconductor with no orbital degeneracy due to strong Jahn-Teller distortion.Comment: 6 pages, 7 figure

    Orthogonal Polynomial Projectors for the Projector Augmented Wave Method of Electronic Structure Calculations

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    The projector augmented wave (PAW) method for electronic structure calculations developed by Blochl [Phys. Rev. B 50, 17 953 (1994)] has been very successfully used for density functional studies. It has the numerical advantages of pseudopotential techniques while retaining the physics of all-electron formalisms. We describe a method for generating the set of atom-centered projector and basis functions that are needed for the PAW method. This scheme chooses the shapes of the projector functions from a set of orthogonal polynomials multiplied by a localizing weight factor. Numerical benefits of the scheme result from having direct control of the shape of the projector functions and from the use of a simple repulsive local potential term to eliminate ‘‘ghost state’’ problems, which can plague calculations of this kind. Electronic density of states results are presented for the mineral powellite (CaMoO4)

    Comparison of the Projector Augmented-Wave, Pseudopotential, and Linearized Augmented-Plane-Wave Formalisms for Density-Functional Calculations of Solids

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    The projector augmented-wave (PAW) method was developed by Blöchl as a method to accurately and efficiently calculate the electronic structure of materials within the framework of density-functional theory. It contains the numerical advantages of pseudopotential calculations while retaining the physics of all-electron calculations, including the correct nodal behavior of the valence-electron wave functions and the ability to include upper core states in addition to valence states in the self-consistent iterations. It uses many of the same ideas developed by Vanderbilt in his soft pseudopotential\u27\u27 formalism and in earlier work by Blöchl in his generalized separable potentials,\u27\u27 and has been successfully demonstrated for several interesting materials. We have developed a version of the PAW formalism for general use in structural and dynamical studies of materials. In the present paper, we investigate the accuracy of this implementation in comparison with corresponding results obtained using pseudopotential and linearized augmented-plane-wave (LAPW) codes. We present results of calculations for the cohesive energy, equilibrium lattice constant, and bulk modulus for several representative covalent, ionic, and metallic materials including diamond, silicon, SiC, CaF2, fcc Ca, and bcc V. With the exception of CaF2, for which core-electron polarization effects are important, the structural properties of these materials are represented equally well by the PAW, LAPW, and pseudopotential formalisms
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