1,417 research outputs found
Large Area Crop Inventory Experiment (LACIE). LACIE transition year plan for the direct estimation of wheat from LANDSAT imagery
There are no author-identified significant results in this report
Mechanisms for current-induced conductivity changes in a conducting polymer
A layer of polyethylene dioxythiophene:polystyrene sulfonic acid (PEDT:PSS) spun onto the surface of an inorganic semiconductor forms a highly asymmetric rectifying junction when a small current is applied and can be permanently open circuited with application of a high current density. This allows the polymer/semiconductor junction to function as a write-once-read-many-times memory element. We use x-ray photoelectron spectroscopy and temperature induced conductivity measurements to study the morphological and chemical changes responsible for the large current-induced conductivity changes. It is found that by applying a large current to the organic-inorganic semiconductor rectifying heterojunction structure Au/PEDT:PSS/SiAuâPEDT:PSSâSi, the ratio of PEDT+PEDT+ to PSSâPSSâ near the interface changes due to phase segregation in the presence of both high electric field (>105âV/cm)(>105Vâcm) and temperature. This leads to a decrease in film conductivity by up to six orders of magnitude from its value in the conductive state.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87796/2/142109_1.pd
Geographical Analysis of US Green Sector Industry Concentration
This paper analyzes the geographic distribution of âgreen energyâ sector clustering in the lower 48 United States using recent developments in industry concentration analysis. Evidence suggests that the ten green energy subsectors and the aggregate of the firms comprising the green energy sector are regionally concentrated. Positive changes in industry concentration from 2002 to 2006 tended to be greatest in non-metropolitan counties, suggesting comparative advantage with respect to site location for the composite of firms making up these sectors.Agglomeration, Location Quotient, Renewable Energy, Community/Rural/Urban Development, Industrial Organization, Research and Development/Tech Change/Emerging Technologies,
A Laterally Modulated 2D Electron System in the Extreme Quantum Limit
We report on magnetotransport of a two-dimensional electron system (2DES),
located 32 nm below the surface, with a surface superlattice gate structure of
periodicity 39 nm imposing a periodic modulation of its potential. For low
Landau level fillings , the diagonal resistivity displays a rich pattern
of fluctuations, even though the disorder dominates over the periodic
modulation. Theoretical arguments based on the combined effects of the
long-wavelength, strong disorder and the short-wavelength, weak periodic
modulation present in the 2DES qualitatively explain the data.Comment: 4 pages, 5 figures. to appear in Phys. Rev. Let
Fluency Assistance Device
Currently about 1% of the world population (~70 million people) have a stutter considered a fluency disorder. Some fluency assistance devices are available for this population, but most are highly expensive or unreliable. Fluency Assistance Device (FAD) seeks to assist a niche community of these individuals for whom therapy has been unsuccessful but are currently depending on a device originally known as the Edinburgh Masker. FAD aims to redesign the masker to be more comfortable for the end user. FAD is developing versions 1.1 and 2.0 of the improved masker. Version 1.1 will update the original masker circuitry with surface mount devices. This will allow a slimmer circuitry enclosure, and enable upgrades of the original as requested. Version 2.0 will use Bluetooth technology and a microcontroller to achieve masker functionality with software code. FAD is now finalizing Version 1.1 and beginning Version 2.0.https://mosaic.messiah.edu/engr2020/1008/thumbnail.jp
Density functional theory based study of graphene and dielectric oxide interfaces
We study the effects of insulating oxides in their crystalline forms on the
energy band structure of monolayer and bilayer graphene using a \textit{first
principles} density functional theory based electronic structure method and a
local density approximation. We consider the dielectric oxides, SiO
(-quartz) and AlO (alumina or -sapphire) each with
two surface terminations. Our study suggests that atomic relaxations and
resulting equilibrium separations play a critical role in perturbing the linear
band structure of graphene in contrast to the less critical role played by
dangling bonds that result from cleaving the crystal in a particular direction.
We also see that with the addition of a second graphene layer, the Dirac cone
is restored for the quartz surface terminations. Alumina needs more than two
graphene layers to preserve the Dirac cone. Our results are at best
semi-quantitative for the common amorphous forms of the oxides considered.
However, crystalline oxides for which our results are quantitative provide an
interesting option for graphene based electronics, particularly in light of
recent experiments on graphene with crystalline dielectrics (hexagonal BN) that
find considerable improvements in transport properties as compared to the those
with amorphous dielectrics
Does browning-induced light limitation reduce fish body growth through shifts in prey composition or reduced foraging rates?
Browning of waters, coupled to climate change and land use changes, can strongly affect aquatic ecosystems. Browning-induced light limitation may have negative effects on aquatic consumers via shifts in resource composition and availability and by negatively affecting foraging of consumers relying on vision. However, the extent to which light limitation caused by browning affects fish via either of these two pathways is largely unknown. Here we specifically test if fish growth responses to browning in a pelagic food web are best explained by changes in resource availability and composition due to light limitation, or by reduced foraging rates due to decreased visual conditions. To address this question, we set up a mesocosm experiment to study growth responses of two different fish species to browning and conducted an aquaria experiment to study species-specific fish foraging responses to browning. Furthermore, we used a space-for-time approach to analyse fish body length-at-age across >40 lakes with a large gradient in lake water colour to validate experimental findings on species-specific fish growth responses. With browning, we found an increase in chlorophyll a concentrations, shifts in zooplankton community composition, and a decrease in perch (Perca fluviatilis) but not roach (Rutilus rutilus) body growth. We conclude that fish growth responses are most likely to be linked to the observed shift in prey (zooplankton) composition. In contrast, we found limited evidence for reduced perch, but not roach, foraging rates in response to browning. This suggests that light limitation led to lower body growth of perch in brown waters mainly through shifts in resource composition and availability, perhaps in combination with decreased visibility. Finally, with the lake study we confirmed that perch but not roach body growth and length-at-age are negatively affected by brown waters in the wild. In conclusion, using a combination of experimental and observational data, we show that browning of lakes is likely to (continue to) result in reductions in fish body growth of perch, but not roach, as a consequence of shifts in prey availability and composition, and perhaps reduced foraging
Global wave loads on a damaged ship
A computational tool was applied based on a two dimensional linear method to predict the hydrodynamic loads for damaged ships. Experimental tests on a ship model have also been carried out to predict the hydrodynamic loads in various design conditions. The results of the theoretical method and experimental tests are compared to validate the theoretical method. The extreme wave induced loads have been calculated by short term prediction. For the loads in intact condition, the prediction with duration of 20 years at sea state 5 is used, while for loads in damaged conditions the prediction in 96 hours exposure time at sea 3 is used. The maximum values of the most probable extreme amplitudes of dynamic wave induced loads in damaged conditions are much less than those in intact condition because of the reduced time. An opening could change the distribution of not only stillwater bending moment but also wave-induced bending moment. It is observed that although some cross sections are not structurally damaged, the total loads acting on these cross sections after damage may be increased dramatically compared to the original design load in intact condition
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