51,665 research outputs found
Impartial Evaluations of the Printing Quality of Paper
Several methods for the evaluation of paper have been investigated for their desirability as means of an impartial evaluation of the printing quality of paper. The halftone plate method showed the most desired results as an impartial evaluation of both coated and uncoated papers. The printing gage was not found to be a satisfactory method of evaluation. The drawdown method is especially significant in evaluating properties which influence the printing quality but lacks a suitable numerical evaluation
USDA Forest Service mobile satellite communications applications
The airborne IR signal processing system being developed will require the use of mobile satellite communications to achieve its full capability and improvement in delivery timeliness of processed IR data to the Fire Staff. There are numerous other beneficial uses, both during wildland fire management operations or in daily routine tasks, which will also benefit from the availability of reliable communications from remote areas
Use of extendible boom devices for space shuttle and EVA operations
Extended boom devices for orbital maintenance and safety of space shuttl
Use of Linear Perspective Scene Cues in a Simulated Height Regulation Task
As part of a long-term effort to quantify the effects of visual scene cuing and non-visual motion cuing in flight simulators, an experimental study of the pilot's use of linear perspective cues in a simulated height-regulation task was conducted. Six test subjects performed a fixed-base tracking task with a visual display consisting of a simulated horizon and a perspective view of a straight, infinitely-long roadway of constant width. Experimental parameters were (1) the central angle formed by the roadway perspective and (2) the display gain. The subject controlled only the pitch/height axis; airspeed, bank angle, and lateral track were fixed in the simulation. The average RMS height error score for the least effective display configuration was about 25% greater than the score for the most effective configuration. Overall, larger and more highly significant effects were observed for the pitch and control scores. Model analysis was performed with the optimal control pilot model to characterize the pilot's use of visual scene cues, with the goal of obtaining a consistent set of independent model parameters to account for display effects
Basic research in fan source noise: Inlet distortion and turbulence noise
A widely recognized problem in jet engine fan noise is the discrepancy between inflight and static tests. This discrepancy consists of blade passing frequency tones, caused by ingested turbulence that appear in the static tests but not in flight. To reduce the ingested distortions and turbulence in an anechoic chamber, a reverse cone inlet is used to guide the air into the fan. This inlet also has provisions for boundary layer suction and is used in conjunction with a turbulence control structure (TCS) to condition the air impinging on the fan. The program was very successful in reducing the ingested turbulence, to the point where reductions in the acoustic power at blade passing frequency are as high as 18 db for subsonic tip speeds. Even with this large subsonic tone suppression, the supersonic tip speed tonal content remains largely unchanged, indicating that the TCS did not appreciably attenuate the noise but effects the generation via turbulence reduction. Turbulence mapping of the inlet confirmed that the tone reductions are due to a reduction in turbulence, as the low frequency power spectra of the streamwise and transverse turbulence were reduced by up to ten times and 100 times, respectively
Optimal Hour-Ahead Bidding in the Real-Time Electricity Market with Battery Storage using Approximate Dynamic Programming
There is growing interest in the use of grid-level storage to smooth
variations in supply that are likely to arise with increased use of wind and
solar energy. Energy arbitrage, the process of buying, storing, and selling
electricity to exploit variations in electricity spot prices, is becoming an
important way of paying for expensive investments into grid-level storage.
Independent system operators such as the NYISO (New York Independent System
Operator) require that battery storage operators place bids into an hour-ahead
market (although settlements may occur in increments as small as 5 minutes,
which is considered near "real-time"). The operator has to place these bids
without knowing the energy level in the battery at the beginning of the hour,
while simultaneously accounting for the value of leftover energy at the end of
the hour. The problem is formulated as a dynamic program. We describe and
employ a convergent approximate dynamic programming (ADP) algorithm that
exploits monotonicity of the value function to find a revenue-generating
bidding policy; using optimal benchmarks, we empirically show the computational
benefits of the algorithm. Furthermore, we propose a distribution-free variant
of the ADP algorithm that does not require any knowledge of the distribution of
the price process (and makes no assumptions regarding a specific real-time
price model). We demonstrate that a policy trained on historical real-time
price data from the NYISO using this distribution-free approach is indeed
effective.Comment: 28 pages, 11 figure
The BHB stars in the Survey Fields of Rodgers et al. (1993): New Observations and Comparisons with other Recent Surveys
We study blue horizontal branch (BHB) and RR Lyrae stars in the Rogers et al.
(1993a) fields and compare their velocity and density distributions with other
surveys in the same part of the sky. Photometric data are given for 176
early-type stars in the northern field. We identify fourteen BHB stars and four
possible BHB stars, and determine the selection efficiency of the Century
Survey, the HK Survey, and the SDSS survey for BHB stars. We give light curves
and \gamma -radial velocities for three type-ab RR Lyrae stars in the northern
field; comparison with the nearby LONEOS Survey shows that there is likely to
be an equal number of lower-amplitude type-ab RR Lyrae stars that we do not
find. There are therefore at least twice as many BHB stars as type-ab RR Lyrae
stars in the northern field--similar to the ratio in the solar neighborhood.
The velocity distribution of the southern field shows no evidence for an
anomalous thick disk that was found by Gilmore et al. (2002); the halo velocity
peaks at a slightly prograde rotational velocity but there is also a
significant retrograde halo component in this field. The velocity distribution
in the northern field shows no evidence of Galactic rotation for |Z|>4 kpc and
a slight prograde motion for |Z|<4 kpc. The space densities of BHB stars in the
northern field agree with an extrapolation of the power-law distribution
recently derived by de Propris et al. (2010). For |Z|<4 kpc, however, we
observe an excess of BHB stars compared with this power-law. We conclude that
these BHB stars mostly belong to a spatially flattened, non-rotating inner halo
component of the Milky Way in confirmation of the Kinman et al. (2009) analysis
of Century Survey BHB stars.Comment: 24 pages, accepted in A
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