31,284 research outputs found
A Discrete Model for Histogram Shaping
The aim of this article is to present a discrete model for histogram shaping. This is
an important image transformation with several practical applications. The model that is proposed is based on a generalization of the inferior part function. Finally, an algorithm based on this model is developed
A piezo-bar pressure probe
Piezo-bar pressure type probe measures the impact velocity or pressure of a moving debris cloud. It measures pressures up to 200,000 psi and peak pressures may be recorded with a total pulse duration between 5 and 65 musec
B-52 control configured vehicles: Flight test results
Recently completed B-52 Control Configured Vehicles (CCV) flight testing is summarized, and results are compared to analytical predictions. Results are presented for five CCV system concepts: ride control, maneuver load control, flutter mode control, augmented stability, and fatigue reduction. Test results confirm analytical predictions and show that CCV system concepts achieve performance goals when operated individually or collectively
Self-assembly of iron nanoclusters on the Fe3O4(111) superstructured surface
We report on the self-organized growth of a regular array of Fe nanoclusters
on a nanopatterned magnetite surface. Under oxidizing preparation conditions
the (111) surface of magnetite exhibits a regular superstructure with
three-fold symmetry and a 42 A periodicity. This superstructure represents an
oxygen terminated (111) surface, which is reconstructed to form a periodically
strained surface. This strain patterned surface has been used as a template for
the growth of an ultrathin metal film. A Fe film of 0.5 A thickness was
deposited on the substrate at room temperature. Fe nanoclusters are formed on
top of the surface superstructure creating a regular array with the period of
the superstructure. We also demonstrate that at least the initial stage of Fe
growth occurs in two-dimensional mode. In the areas of the surface where the
strain pattern is not formed, random nucleation of Fe was observed.Comment: 6 pages, 3 figure
Sub-2 cm/s passivation of silicon surfaces by aprotic solutions
Minimizing recombination at semiconductor surfaces is required for the accurate determination of the bulk carrier lifetime. Proton donors, such as hydrofluoric acid and superacids, are well known to provide highly effective short-term surface passivation. We demonstrate here that aprotic solutions based on bis(trifluoromethanesulfonyl)methane (TFSM) in hexane or pentane can also result in excellent passivation of (100)-orientation silicon surfaces. We show that the optimized TFSM-pentane passivation scheme can measure effective lifetimes up to 20 ms, with a surface recombination velocity of 1.7 cm s1 at an excess carrier density of 1015 cm3 . Fitting injection-dependent lifetime curves requires chemical passivation and field effect passivation from a negatively charged layer with a charge density of 1010–1011 q cm2 . The slightly higher recombination velocity of 2.3 cm s1 measured with TFSM-hexane can be explained by a lower charge density in the passivating layer, suggesting that the steric hindrance associated with the solvent size could play a role in the passivation mechanism. Finally, phosphorus nuclear magnetic resonance experiments confirm that TFSM-based solutions have Lewis acidity without being superacids, which opens up opportunities for them to be used in materials systems sensitive to superacidic environments
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What does the future hold for utility electricity efficiency programs?
This study develops projections of future spending and savings from electricity efficiency programs funded by electric utility customers in the United States through 2030 based on three scenarios. Our analysis relies on detailed bottom-up modeling of current state energy efficiency policies, demand-side management and integrated resource plans, and regulatory decisions. The three scenarios represent a range of potential outcomes given the policy environment at the time of the study and uncertainties in the broader economic and state policy environment in each state. We project spending to increase to 11.1 billion in 2030 and remains relatively flat in the low case ($6.8 billion in 2030). Our analysis suggests that electricity efficiency programs funded by utility customers will continue to impact load growth significantly at least through 2030, as savings as a percent of retail sales are forecast at 0.7 percent in the medium scenario and 0.98 percent in the high scenario
Constraints on quintessence and new physics from fundamental constant
Changes in the values of the fundamental constants mu, the proton to electron
mass ratio, and alpha, the fine structure constant due to rolling scalar fields
have been discussed both in the context of cosmology and in new physics such as
Super Symmetry (SUSY) models. This article examines the changes in these
fundamental constants in a particular example of such fields, freezing and
thawing slow roll quintessence. Constraints are placed on the product of a
cosmological quantity, w, the equation of state parameter, and the square of
the coupling constants for mu and alpha with the field, zeta_x, x = mu,alpha,
using the existing observational limits on the values of Delta x/x. Various
examples of slow rolling quintessence models are used to further quantify the
constraints. Some of the examples appear to be rejected by the existing data
which strongly suggests that conformation to the values of the fundamental
constants in the early universe is a standard test that should be applied to
any cosmological model or suggested new physics.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Society Letter
Characterizing Cosmic-Ray Propagation in Massive Star-forming Regions: The Case of 30 Doradus and the Large Magellanic Cloud
Using infrared, radio, and γ-ray data, we investigate the propagation characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus (30 Dor) star-forming region in the Large Magellanic Cloud (LMC) using a phenomenological model based on the radio-far-infrared correlation within galaxies. Employing a correlation analysis, we derive an average propagation length of ~100-140 pc for ~3 GeV CR electrons resident in 30 Dor from consideration of the radio and infrared data. Assuming that the observed γ-ray emission toward 30 Dor is associated with the star-forming region, and applying the same methodology to the infrared and γ-ray data, we estimate a ~20 GeV propagation length of 200-320 pc for the CR nuclei. This is approximately twice as large as for ~3 GeV CR electrons, corresponding to a spatial diffusion coefficient that is ~4 times higher, scaling as (R/GV)δ with δ ≈ 0.7-0.8 depending on the smearing kernel used in the correlation analysis. This value is in agreement with the results found by extending the correlation analysis to include ~70 GeV CR nuclei traced by the 3-10 GeV γ-ray data (δ ≈ 0.66 ± 0.23). Using the mean age of the stellar populations in 30 Dor and the results from our correlation analysis, we estimate a diffusion coefficient D_R ≈ (0.9-1.0) × 10^(27)(R/GV)0.7 cm^(2) s^(–1). We compare the values of the CR electron propagation length and surface brightness for 30 Dor and the LMC as a whole with those of entire disk galaxies. We find that the trend of decreasing average CR propagation distance with increasing disk-averaged star formation activity holds for the LMC, and extends down to single star-forming regions, at least for the case of 30 Dor
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