2,818 research outputs found
Space Shuttle Lightning Protection
The technology for lightning protection of even the most advanced spacecraft is available and can be applied through cost-effective hardware designs and design-verification techniques. In this paper, the evolution of the Space Shuttle Lightning Protection Program is discussed, including the general types of protection, testing, and anlayses being performed to assess the lightning-transient-damage susceptibility of solid-state electronics
Design Practice in the UK Car Industry: How Coventry University is Addressing the Needs
This paper considers the needs of the UK car industry and identifies specific situations that have serious implications upon design practice. The response at Coventry University to these needs is discussed and our PAKTS model for Design Education introduced
Bright sand/dark dust: The identification of active sand surfaces on the Earth and Mars
Field studies and analysis of LANDSAT Thematic Mapper data in the Gran Desierto, Mexico may shed light on a technique to distinguish active from inactive (relict) sand surfaces. Active sand bodies in the study area are consistently brighter (by an average of 20%) at visual and near infrared wavelengths and darker at thermal infrared wavelengths than compositionally similar inactive sands. The reasons for the albedo difference between active and inactive sands are reviewed and the mixing model of Johnson et al. is examined for tracing the provenance of sands based on albedo and spectral variations. Portions of the wavelengths covered by the Mars Orbiter correspond to the Thematic Mapper data. The identification of active sands on Earth, with a priori knowledge of bulk composition and grain size distribution, may allow the remote mapping of active sand surfaces on Mars. In conjuction with thermal infrared remote sensing for composition, it may also provide a method for the remote determination of grain size distributions within sand/silt mixtures
ASTP simulated lightning test report
A simulated lightning test was conducted on the backup spacecraft for the Apollo Soyuz Test Project mission (CSM-119) to determine the susceptibility of the Apollo spacecraft to damage from the indirect effects of lightning. It is demonstrated that induced lightning effects from low-level injected currents can be scaled linearly to those which are obtained in a full threat lightning stroke. Test results indicate that: (1) many of the power and signal critical circuits would fail if subjected to full-threat lightning, (2) pyrotechnic circuits are safe for full-threat lightning, and (3) common-mode voltages exceeded the failure criteria level for all but three of the circuits tested
Optical matrix elements in tight-binding models with overlap
We investigate the effect of orbital overlap on optical matrix elements in
empirical tight-binding models. Empirical tight-binding models assume an
orthogonal basis of (atomiclike) states and a diagonal coordinate operator
which neglects the intra-atomic part. It is shown that, starting with an atomic
basis which is not orthogonal, the orthogonalization process induces
intra-atomic matrix elements of the coordinate operator and extends the range
of the effective Hamiltonian. We analyze simple tight-binding models and show
that non-orthogonality plays an important role in optical matrix elements. In
addition, the procedure gives formal justification to the nearest-neighbor
spin-orbit interaction introduced by Boykin [Phys. Rev \textbf{B} 57, 1620
(1998)] in order to describe the Dresselahaus term which is neglected in
empirical tight-binding models.Comment: 16 pages 6 figures, to appear in Phys. Rev.
Development of an Integrative Wellness Model: Supervising Counselors-in-Training
Supervision is an integral component of counselor development with the objective of ensuring safe and effective counseling for clients. Wellness also is an important element of counseling and often labeled as the cornerstone of the counseling profession. Literature on supervision contains few models that have a wellness focus or component; however, wellness is fundamental to counseling and the training of counselors, and is primary in developmental, strengths-based counseling. The purpose of this article is to introduce an integrative wellness model for counseling supervision that incorporates existing models of supervision, matching the developmental needs of counselors-in training and theoretical tenets of wellness
Development of a Bahiagrass \u3cem\u3ePaspalum Notatum\u3c/em\u3e Flugge With Increased Short-Day Biomass
Low herbage productivity of subtropical grasses during the short-day winter months of October through to March can place a severe burden on livestock producers in Southeastern U.S. Researchers at the University of Florida (Sinclair et al., 2001) hypothesised that the decrease in forage production might result from physiological dormancy induced by short day length. A study using artificial lights to extend the day length demonstrated that maintaining the day length at 15 hr during the short-day length period increased \u27Pensacola\u27 bahiagrass P. notatum Flugge saure Parodi forage yield 122% when compared with normal photoperiod (Mislevy et al., 2001). A Pensacola-derived bahiagrass population was selected for increased vegetative growth under short-day length using restricted recurrent phenotypic selection for three cycles (UF Cycle 3) to increase forage yield. Plants that comprise this population were less sensitive to short photoperiod and produced increased forage mass during the short days. The objective of this clipping study was to evaluate forage production and forage nutritive value of UF Cycle 3 compared with selected standard entries during short and long day length periods
Noncommutative geometry for three-dimensional topological insulators
We generalize the noncommutative relations obeyed by the guiding centers in
the two-dimensional quantum Hall effect to those obeyed by the projected
position operators in three-dimensional (3D) topological band insulators. The
noncommutativity in 3D space is tied to the integral over the 3D Brillouin zone
of a Chern-Simons invariant in momentum-space. We provide an example of a model
on the cubic lattice for which the chiral symmetry guarantees a macroscopic
number of zero-energy modes that form a perfectly flat band. This lattice model
realizes a chiral 3D noncommutative geometry. Finally, we find conditions on
the density-density structure factors that lead to a gapped 3D fractional
chiral topological insulator within Feynman's single-mode approximation.Comment: 41 pages, 3 figure
Small Leaf Mid-Rib Xylem Related to Leaf Freeze Tolerance Trait in Bahia (\u3cem\u3ePaspalum Notatum\u3c/em\u3e Flugge) Grass Lines
Controlled freeze (-60o C) trials of 31 bahiagrass selections from a breeding program for cold tolerance by Blount et al. (2001) showed diverse genotype Leaf Tissue Cold Damage (LTCD). Breman et al. (2003) defined LTCD on a rating scale (1 = no damage to 9 = 100% leaf damage). Unique midrib damage was observed as part of LTCD in bahiagrass under transpiration stress after a freeze trial. Small xylem conduit diameter and area has been strongly correlated with reduced cavitation caused by freeze thaw cycles which maintain leaf tissue in evergreen temperate woody plants; further shown in twelve woody species by Davis et al. (1999). Air bubbles in vessel ice columns prevent normal refill and function upon thawing. The purpose of this study was to test whether genotype xylem diameter and area could be used to predict LTCD
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