830 research outputs found
EVIDENCE AND IMPLICATIONS OF NON-TRADABILITY OF FOOD STAPLES IN TANZANIA 1983-1998
Economic reform programs assume that major goods are tradable, such that depreciation of the real exchange rate raises the value of output compared to factor costs in domestic currency. In Tanzania, major food staples that account for most real income are non-tradables in at least one-quarter of the country. This is demonstrated and implications assessed for the constraints imposed on macroeconomic-led adjustment strategiesAgricultural and Food Policy,
Quantum Particles Constrained on Cylindrical Surfaces with Non-constant Diameter
We present a theoretical formulation of the one-electron problem constrained
on the surface of a cylindrical tubule with varying diameter. Because of the
cylindrical symmetry, we may reduce the problem to a one-dimensional equation
for each angular momentum quantum number along the cylindrical axis. The
geometrical properties of the surface determine the electronic structures
through the geometry dependent term in the equation. Magnetic fields parallel
to the axis can readily be incorporated. Our formulation is applied to simple
examples such as the catenoid and the sinusoidal tubules. The existence of
bound states as well as the band structures, which are induced geometrically,
for these surfaces are shown. To show that the electronic structures can be
altered significantly by applying a magnetic field, Aharonov-Bohm effects in
these examples are demonstrated.Comment: 7 pages, 7 figures, submitted to J. Phys. Soc. Jp
Electrically Driven Light Emission from Individual CdSe Nanowires
We report electroluminescence (EL) measurements carried out on three-terminal
devices incorporating individual n-type CdSe nanowires. Simultaneous optical
and electrical measurements reveal that EL occurs near the contact between the
nanowire and a positively biased electrode or drain. The surface potential
profile, obtained by using Kelvin probe microscopy, shows an abrupt potential
drop near the position of the EL spot, while the band profile obtained from
scanning photocurrent microscopy indicates the existence of an n-type Schottky
barrier at the interface. These observations indicate that light emission
occurs through a hole leakage or an inelastic scattering induced by the rapid
potential drop at the nanowire-electrode interface.Comment: 12 pages, 4 figure
Terahertz imaging and spectroscopy of large-area single-layer graphene
We demonstrate terahertz (THz) imaging and spectroscopy of a 15x15-mm^2
single-layer graphene film on Si using broadband THz pulses. The THz images
clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing
us to measure sheet conductivity with sub-mm resolution without fabricating
electrodes. The THz carrier dynamics are dominated by intraband transitions and
the THz-induced electron motion is characterized by a flat spectral response. A
theoretical analysis based on the Fresnel coefficients for a metallic thin film
shows that the local sheet conductivity varies across the sample from {\sigma}s
= 1.7x10^-3 to 2.4x10^-3 {\Omega}^-1 (sheet resistance, {\rho}s = 420 - 590
{\Omega}/sq).Comment: 6 pages, 5 figure
The shocklet transform: a decomposition method for the identification of local, mechanism-driven dynamics in sociotechnical time series
We introduce a qualitative, shape-based, timescale-independent time-domain transform used to extract local dynamics from sociotechnical time seriesātermed the Discrete Shocklet Transform (DST)āand an associated similarity search routine, the Shocklet Transform And Ranking (STAR) algorithm, that indicates time windows during which panels of time series display qualitatively-similar anomalous behavior. After distinguishing our algorithms from other methods used in anomaly detection and time series similarity search, such as the matrix profile, seasonal-hybrid ESD, and discrete wavelet transform-based procedures, we demonstrate the DSTās ability to identify mechanism-driven dynamics at a wide range of timescales and its relative insensitivity to functional parameterization. As an application, we analyze a sociotechnical data source (usage frequencies for a subset of words on Twitter) and highlight our algorithmsā utility by using them to extract both a typology of mechanistic local dynamics and a data-driven narrative of socially-important events as perceived by English-language Twitter
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