43,211 research outputs found
P/N InP homojunction solar cells by LPE and MOCVD techniques
P/N InP homojunction solar cells have been prepared by using both liquid phase epitaxy (LPE) and metallorganic chemical vapor deposition (MOCVD) growth techniques. A heavily doped p-In sub 0.53Ga sub 0.47As contacting layer was incorporated into the cell structure to improve the fill factor and to eliminate surface spiking at the front surface. The best conversion efficiencies (total area) obtained under AM 1 illumination are 14.2 percent for a LPE cell and 15.4 percent for a MOCVD cell
THE IMPACT OF SWINE PRODUCTION ON LAND VALUES IN ILLINOIS
Based on a spatiotemporal hedonic farmland price model and county-level data in Illinois from 1979 to 1999, we examined the impact of swine production on farmland values. Our results show that, in addition to the conventional determinants of farmland values, an increase in swine production intensity has a negative relationship with farmland values while an increase in swine operation scale had a positive association with farmland values at the county level in Illinois. We also estimate the impact of changes in the Illinois swine industry over the period 1980-1999 on farmland values at the state level and find that changes in swine inventory and scale of swine operations have led to changes in farmland prices from 62.96 per acre. In general, the changes in Illinois swine industry increase farmland values in Illinois.Land Economics/Use,
Dynamic Kerr Effect and Spectral Weight Transfer in the Manganites
We perform pump-probe Kerr spectroscopy in the colossally magnetoresistive
manganite Pr0.67Ca0.33MnO3. Kerr effects uncover surface magnetic dynamics
undetected by established methods based on reflectivity and optical spectral
weight transfer. Our findings indicate the connection between spin and charge
dynamics in the manganites may be weaker than previously thought. Additionally,
important differences between this system and conventional ferromagnetic metals
manifest as long-lived, magneto-optical coupling transients, which may be
generic to all manganites.Comment: 12 text pages, 4 figure
A Better Definition of the Kilogram
This article reviews several recent proposed redefinitions of the kilogram,
and compares them with respect to practical realizations, uncertainties
(estimated standard deviations), and educational aspects.Comment: 10 pages, no figure
Near-bandgap wavelength-dependent studies of long-lived traveling coherent longitudinal acoustic phonon oscillations in GaSb/GaAs systems
We report first studies of long-lived oscillations in optical pump-probe
measurements on GaSb-GaAs heterostructures. The oscillations arise from a
photogenerated coherent longitudinal acoustic phonon wave, which travels from
the top surface of GaSb across the interface into the GaAs substrate, providing
information on the optical properties of the material as a function of
time/depth. Wavelength-dependent studies of the oscillations near the bandgap
of GaAs indicate strong correlations to the optical properties of GaAs.Comment: 11 pages, 4 figure
Analysis of common attacks in LDPCC-based public-key cryptosystems
We analyze the security and reliability of a recently proposed class of
public-key cryptosystems against attacks by unauthorized parties who have
acquired partial knowledge of one or more of the private key components and/or
of the plaintext. Phase diagrams are presented, showing critical partial
knowledge levels required for unauthorized decryptionComment: 14 pages, 6 figure
Massey products in symplectic manifolds
The paper is devoted to study of Massey products in symplectic manifolds.
Theory of generalized and classical Massey products and a general construction
of symplectic manifolds with nontrivial Massey products of arbitrary large
order are exposed. The construction uses the symplectic blow-up and is based on
the author results, which describe conditions under which the blow-up of a
symplectic manifold X along its submanifold Y inherits nontrivial Massey
products from X ot Y. This gives a general construction of nonformal symplectic
manifolds.Comment: LaTeX, 48 pages, 2 figure
Spin Polarization at Semiconductor Point Contacts in Absence of Magnetic Field
Semiconductor point contacts can be a useful tool for producing
spin-polarized currents in the presence of spin-orbit (SO) interaction. Neither
magnetic fields nor magnetic materials are required. By numerical studies, we
show that (i) the conductance is quantized in units of 2e^2/h unless the SO
interaction is too strong, (ii) the current is spin-polarized in the transverse
direction, and (iii) a spin polarization of more than 50% can be realized with
experimentally accessible values of the SO interaction strength. The
spin-polarization ratio is determined by the adiabaticity of the transition
between subbands of different spins during the transport through the point
contacts.Comment: 4 pages, 4 figures; minor changes, published in J. Phys. Soc. Jp
Disorder-driven quantum phase transition from antiferromagnetic metal to insulating state in multilayered high-Tc cuprate (Cu,C)Ba2Ca4Cu5Oy
We report on superconducting(SC) characteristics for oxygen-reduced Cu-based
five-layered high-temperature superconductor (Cu,C)Ba2Ca4Cu5Oy(Cu-1245(OPT)),
which includes five-fold outer planes (OP) and four-fold inner planes (IP).As a
result of the reduction of the carrier density, the bulk SC for Cu-1245 (OPT)
takes place at the nearly optimally-doped OP with Tc= 98 K that is different
from previously-reported Cu-1245(OVD) where IP plays a primary role for the
onset of SC. It gives an evidence that the carrier density of the
optimally-doped layer determines its bulk Tc.Static antiferromagnetic(AFM)
order is evidenced at IP's by zero-field Cu-NMR at low temperature,
irrespective of the SC transition at OP's below 98K. This AFM state at IP's is
characterized by a carrier localization at low temperatures due to disorder
effect, whereas the carrier densities in each layer are similar to Hg-1245(OPT)
where the AFM metallic state are realized in IP's. This finding reinforces the
phase diagram in which the AFM metallic phase exists between AFM insulator and
SC states for the case of ideally-flat CuO2 plane without disorder.Comment: 4 pages, 5 figure
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