665 research outputs found
Analysis of electric propulsion electrical power conditioning component technology. Volume 1 - Data bank Final report
Analysis of electric propulsion electric power conditioning component technology - data revie
Analysis of electric propulsion electrical power conditioning component technology, volume 2 Final report
Large solar arrays to provide power for electric propulsion engine for Mars mapper spacecraf
Letters of Credit—A Comparison of Article 5 of the Uniform Commercial Code and the Washington Practice [Part 2]
It is our hope that this discussion will serve a dual purpose: (1) provide a basis for evaluating the desirability of Article 5 and so aid in an over-all evaluation of the Uniform Commercial Code in this period of pre-enactment consideration of the Code\u27s merits, and (2) provide a point of departure for Washington bankers and lawyers who become concerned with letter of credit problems after enactment of the Code. The first of these objectives seems better served if we undertake with each section a critique of its operation in light of the existing practice. This we have done
Letters of Credit—A Comparison of Article 5 of the Uniform Commercial Code and the Washington Practice [Part 1]
It is our hope that this discussion will serve a dual purpose: (1) provide a basis for evaluating the desirability of Article 5 and so aid in an over-all evaluation of the Uniform Commercial Code in this period of pre-enactment consideration of the Code\u27s merits, and (2) provide a point of departure for Washington bankers and lawyers who become concerned with letter of credit problems after enactment of the Code. The first of these objectives seems better served if we undertake with each section a critique of its operation in light of the existing practice. This we have done
Caging dynamics in a granular fluid
We report an experimental investigation of the caging motion in a uniformly
heated granular fluid, for a wide range of filling fractions, . At low
the classic diffusive behavior of a fluid is observed. However, as
is increased, temporary cages develop and particles become increasingly
trapped by their neighbors. We statistically analyze particle trajectories and
observe a number of robust features typically associated with dense molecular
liquids and colloids. Even though our monodisperse and quasi-2D system is known
to not exhibit a glass transition, we still observe many of the precursors
usually associated with glassy dynamics. We speculate that this is due to a
process of structural arrest provided, in our case, by the presence of
crystallization.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Wavelength Scaling and Square/Stripe and Grain Mobility Transitions in Vertically Oscillated Granular Layers
Laboratory experiments are conducted to examine granular wave patterns near
onset as a function of the container oscillation frequency f and amplitude A,
layer depth H, and grain diameter D. The primary transition from a flat grain
layer to standing waves occurs when the layer remains dilated after making
contact with the container. With a flat layer and increasing dimensionless peak
container acceleration G = 4 pi^2 f^2 A/g (g is the acceleration due to
gravity), the wave transition occurs for G=2.6, but with decreasing G the waves
persist to G=2.2. For 2.2<G<3.8, patterns are squares for f<f_ss and stripes
for f>f_ss; H determines the square/stripe transition frequency
f_ss=0.33(g/H)^0.5. The dispersion relations for layers with varying H collapse
onto the curve L/H=1.0+1.1[f(H/g)^0.5]^(-1.32 +/- 0.03) (L is the wavelength)
when the peak container velocity v exceeds a critical value v_gm of
approximately 3 (Dg)^0.5. Local collision pressure measurements suggest that
v_gm is associated with a transition in the horizontal grain mobility: for
v>v_gm, there is a hydrodynamic-like horizontal sloshing motion, while for
v<v_gm, the grains are essentially immobile and the stripe pattern apparently
arises from a bending of the granular layer. For f at v_gm less than f_ss and
v<v_gm, patterns are tenuous and disordered.Comment: 21 pages, 15 figures, submitted to Physica
Shocks in supersonic sand
We measure time-averaged velocity, density, and temperature fields for steady
granular flow past a wedge and calculate a speed of granular pressure
disturbances (sound speed) equal to 10% of the flow speed. The flow is
supersonic, forming shocks nearly identical to those in a supersonic gas.
Molecular dynamics simulations of Newton's laws and Monte Carlo simulations of
the Boltzmann equation yield fields in quantitative agreement with experiment.
A numerical solution of Navier-Stokes-like equations agrees with a molecular
dynamics simulation for experimental conditions excluding wall friction.Comment: 4 pages, 5 figure
Rise and shine: The use of polychromatic short-wavelength-enriched light to mitigate sleep inertia at night following awakening from slow-wave sleep
Sleep inertia is the brief period of performance impairment and reduced alertness experienced after waking, especially from slow-wave sleep. We assessed the efficacy of polychromatic short-wavelength-enriched light to improve vigilant attention, alertness and mood immediately after waking from slow-wave sleep at night. Twelve participants (six female, 23.3 ± 4.2 years) maintained an actigraphy-confirmed sleep schedule of 8.5 hr for 5 nights, and 5 hr for 1 night prior to an overnight laboratory visit. In the laboratory, participants were awakened from slow-wave sleep, and immediately exposed to either dim, red ambient light (control) or polychromatic short-wavelength-enriched light (light) for 1 hr in a randomized crossover design. They completed a 5-min Psychomotor Vigilance Task, the Karolinska Sleepiness Scale, and Visual Analogue Scales of mood at 2, 17, 32 and 47 min after waking. Following this testing period, lights were turned off and participants returned to sleep. They were awakened from their subsequent slow-wave sleep period and received the opposite condition. Compared with the control condition, participants exposed to light had fewer Psychomotor Vigilance Task lapses (χ2[1] = 5.285, p = 0.022), reported feeling more alert (Karolinska Sleepiness Scale: F1,77 = 4.955, p = 0.029; Visual Analogue Scalealert: F1,77 = 8.226, p = 0.005), and reported improved mood (Visual Analogue Scalecheerful: F1,77 = 8.615, p = 0.004). There was no significant difference in sleep-onset latency between conditions following the testing period (t10 = 1.024, p = 0.330). Our results suggest that exposure to polychromatic short-wavelength-enriched light immediately after waking from slow-wave sleep at night may help improve vigilant attention, subjective alertness, and mood. Future studies should explore the potential mechanisms of this countermeasure and its efficacy in real-world environments
A Continuum Description of Vibrated Sand
The motion of a thin layer of granular material on a plate undergoing
sinusoidal vibrations is considered. We develop equations of motion for the
local thickness and the horizontal velocity of the layer. The driving comes
from the violent impact of the grains on the plate. A linear stability theory
reveals that the waves are excited non-resonantly, in contrast to the usual
Faraday waves in liquids. Together with the experimentally observed continuum
scaling, the model suggests a close connection between the neutral curve and
the dispersion relation of the waves, which agrees quite well with experiments.
For strong hysteresis we find localized oscillon solutions.Comment: paper has been considerably extended (11 instead of 6 pages; 6
instead of 4 figures) much better agreement with experiment. obtain now
oscillons in 1 dimensio
Stability of the Autism Diagnostic Interview—Revised from Pre-School to Elementary School Age in Children with Autism Spectrum Disorders
This study examined the stability of scores on the ADI-R from pre-school to elementary school age in children with autism spectrum disorders (ASD). Participants were 35 children who, at T1, all had a clinical diagnosis of ASD. On initial assessment (mean age 3.5 years; SD 0.6), all met ADI-R algorithm criteria for autism. ADI-R assessments were repeated at follow up (FU; mean age 10.5 years; SD 0.8). Changes in ADI-R total, domain and ADI-R algorithm item scores were assessed. Twentyeight children continued to score above the ADI-R cut-off for autism at FU, although significant decreases in ADI-R domain and item scores were also found. In conclusion, while classification of children according to ADI-R criteria, generally remained stable between pre-school and elementary school age, many children demonstrated significant improvements in symptom severity
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