1,734 research outputs found

    Are Drivers\u27 Manuals Understandable?

    Get PDF
    In 1984, researchers determined that the readability of state drivers\u27 manuals exceeded the average literacy levels in the United States. Because text complexity threatened the ability of license applicants and practicing drivers to understand the information presented in the manuals, a potential safety risk was indicated. This study analyzes recent editions of the manuals using readability formulas and formal text presentation ratings. It was found that the average difficulty of the drivers\u27 manuals was reduced by more than one grade level and that the 1994 manuals are clearly superior to their earlier versions, but that, in the interest of highway safety, improvements should still be sought

    A Projective C*-Algebra Related to K-Theory

    Full text link
    The C*-algebra qC is the smallest of the C*-algebras qA introduced by Cuntz in the context of KK-theory. An important property of qC is the natural isomorphism of K0 of D with classes of homomorphism from qC to matrix algebras over D. Our main result concerns the exponential (boundary) map from K0 of a quotient B to K1 of an ideal I. We show if a K0 element is realized as a homomorphism from qC to B then its boundary is realized as a unitary in the unitization of I. The picture we obtain of the exponential map is based on a projective C*-algebra P that is universal for a set of relations slightly weaker than the relations that define qC. A new, shorter proof of the semiprojectivity of qC is described. Smoothing questions related the relations for qC are addressed.Comment: 11 pages. Added a result about the boundary map in K-theor

    Leistungen und Entwicklung von Öko- Milchviehbetrieben mit geringem Kraftfuttereinsatz in Baden-Württemberg

    Get PDF
    The aim of this study was the analysis of dairy farms in Baden-Württemberg producing milk without or with only a little amount of concentrate. 12 biological managed farms have been visited and consulted by questionnaire in 2010. Also the results of milk yield testing have been examined. Economic calculations were run for a comparison to conventionally working dairy farms. In 2015 the results were for 10 of these farms updated. Since 2010 the structure of the farms remained almost unchanged (number of cows, milk yield, cultivated area). The proportion of pasture from grassland increased from 45 to 53%. The ecological-low input drived production system leads to better conditions for profitable milk production compared to conventional dairy farms

    Disordered Topological Insulators via CC^*-Algebras

    Full text link
    The theory of almost commuting matrices can be used to quantify topological obstructions to the existence of localized Wannier functions with time-reversal symmetry in systems with time-reversal symmetry and strong spin-orbit coupling. We present a numerical procedure that calculates a Z_2 invariant using these techniques, and apply it to a model of HgTe. This numerical procedure allows us to access sizes significantly larger than procedures based on studying twisted boundary conditions. Our numerical results indicate the existence of a metallic phase in the presence of scattering between up and down spin components, while there is a sharp transition when the system decouples into two copies of the quantum Hall effect. In addition to the Z_2 invariant calculation in the case when up and down components are coupled, we also present a simple method of evaluating the integer invariant in the quantum Hall case where they are decoupled.Comment: Added detail regarding the mapping of almost commuting unitary matrices to almost commuting Hermitian matrices that form an approximate representation of the sphere. 6 pages, 6 figure

    Development and Short-Range Testing of a 100 kW Side-Illuminated Millimeter-Wave Thermal Rocket

    Get PDF
    The objective of the phase described here of the Millimeter-Wave Thermal Launch System (MTLS) Project was to launch a small thermal rocket into the air using millimeter waves. The preliminary results of the first MTLS flight vehicle launches are presented in this work. The design and construction of a small thermal rocket with a planar ceramic heat exchanger mounted along the axis of the rocket is described. The heat exchanger was illuminated from the side by a millimeter-wave beam and fed propellant from above via a small tank containing high pressure argon or nitrogen. Short-range tests where the rocket was launched, tracked, and heated with the beam are described. The rockets were approximately 1.5 meters in length and 65 millimeters in diameter, with a liftoff mass of 1.8 kilograms. The rocket airframes were coated in aluminum and had a parachute recovery system activated via a timer and Pyrodex. At the rocket heat exchanger, the beam distance was 40 meters with a peak power intensity of 77 watts per square centimeter. and a total power of 32 kilowatts in a 30 centimeter diameter circle. An altitude of approximately 10 meters was achieved. Recommendations for improvements are discussed
    corecore