1,332 research outputs found
The Atmosphere Explorer power subsystem
The design and operation of the power subsystem for the Atmospheric Explorer spacecraft are discussed. The additional functional redundancy which was added in several component areas to improve the overall subsystem reliability is analyzed. The battery charging technique has been modified to include third electrode overcharge control. The automatic removal of all battery charge is provided to correct abnormally high battery voltages. An undervoltage detector has been added which removes all nonessential spacecraft loads when the battery voltage falls below a given level. All automatic functions can be over-ridden by ground command
Photoluminescence and photoluminescence excitation studies of lateral size effects in Zn_{1-x}Mn_xSe/ZnSe quantum disc samples of different radii
Quantum disc structures (with diameters of 200 nm and 100 nm) were prepared
from a Zn_{0.72}Mn_{0.28}Se/ZnSe single quantum well structure by electron beam
lithography followed by an etching procedure which combined dry and wet etching
techniques. The quantum disc structures and the parent structure were studied
by photoluminescence and photoluminescence excitation spectroscopy. For the
light-hole excitons in the quantum well region, shifts of the energy positions
are observed following fabrication of the discs, confirming that strain
relaxation occurs in the pillars. The light-hole exciton lines also sharpen
following disc fabrication: this is due to an interplay between strain effects
(related to dislocations) and the lateral size of the discs. A further
consequence of the small lateral sizes of the discs is that the intensity of
the donor-bound exciton emission from the disc is found to decrease with the
disc radius. These size-related effects occur before the disc radius is reduced
to dimensions necessary for lateral quantum confinement to occur but will
remain important when the discs are made small enough to be considered as
quantum dots.Comment: LaTeX2e, 13 pages, 6 figures (epsfig
Direct growth of graphene on GaN via plasma-enhanced chemical vapor deposition under N<sub>2</sub> atmosphere
One of the bottlenecks in the implementation of graphene as a transparent electrode in modern opto-electronic devices is the need for complicated and damaging transfer processes of high-quality graphene sheets onto the desired target substrates. Here, we study the direct, plasma-enhanced chemical vapor deposition (PECVD) growth of graphene on GaN-based light-emitting diodes (LEDs). By replacing the commonly used hydrogen (H2) process gas with nitrogen (N2), we were able to suppress GaN surface decomposition while simultaneously enabling graphene deposition at lt;800 °C in a single-step growth process. Optimizing the methane (CH4) flow and varying the growth time between 0.5 h and 8 h, the electro-optical properties of the graphene layers could be tuned to sheet resistances as low as ∼1 kΩ/D with a maximum transparency loss of ∼12. The resulting high-quality graphene electrodes show an enhanced current spreading effect and an increase of the emission area by a factor of ∼8 in operating LEDs. © 2020 The Author(s)
Elastic Scattering of Medium-Energy Protons
This work was supported by National Science Foundation Grant PHY 75-00289 and Indiana Universit
Roper excitation in reactions
We calculate differential cross sections and the spin transfer coefficient
in the reaction for proton
bombarding energies from 1 to 10 GeV and invariant masses spanning
the region of the N(1440) Roper resonance. Two processes --
excitation in the -particle and Roper excitation in the proton -- are
included in an effective reaction model which was shown previously to reproduce
existing inclusive spectra. The present calculations demonstrate that these two
contributions can be clearly distinguished via , even under kinematic
conditions where cross sections alone exhibit no clear peak structure due to
the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late
Study of the Giant Resonance Region by Inelastic Scattering of Polarized Protons
Supported by the National Science Foundation and Indiana Universit
Excitation of the Giant Resonance Region by Inelastic Scattering of Polarized Protons
This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit
Spin Flip Probabilities in 208-Pb Measured with 200 MeV Protons
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
The Optical Potential for Medium-Energy Proton Scattering
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
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