12,883 research outputs found
The Potential Impact of a Texas High Plains Ethanol Plant on Local Water Supplies
With the passage of the Energy Policy Act, the rapidly expanding number of ethanol plants, and the fury with which ethanol is being promoted, it is clear that ethanol will play a rising role in our domestic energy supply. Along with this rise there will be an increase in the consumptive use of water by ethanol production facilities. Regions, such as the Texas High Plains, that are already considered to be water stressed have the potential of being impacted. The objective of this research is to assess the potential impact the addition of an ethanol plant may have on the Texas High Plains and to determine how increased water costs will transform the economic viability of an ethanol plant.Resource /Energy Economics and Policy,
An atlas of ECMWF analyses (1980-1987). Part 1: First moment quantities
This document is an atlas of the European Center for Medium Range Weather Forecasts (ECMWF) initialized analyses for 1980 to 1987. Various first moment quantities are presented for monthly, seasonal, and annual averages on a global cylindrical projection, as well as, cross section maps of zonal averages. Global maps of winds, temperature, stream function, and velocity potential are presented at 850 and 200 mb. In addition, global maps of the 300 mb height field (total and eddy), the 500 mb vertical velocity, the 850 mb moisture field, and sea level pressure are presented. The average seasonal cycle and anomalies during the 8 year period are presented for selected quantities
Entanglement-enhanced measurement of a completely unknown phase
The high-precision interferometric measurement of an unknown phase is the
basis for metrology in many areas of science and technology. Quantum
entanglement provides an increase in sensitivity, but present techniques have
only surpassed the limits of classical interferometry for the measurement of
small variations about a known phase. Here we introduce a technique that
combines entangled states with an adaptive algorithm to precisely estimate a
completely unspecified phase, obtaining more information per photon that is
possible classically. We use the technique to make the first ab initio
entanglement-enhanced optical phase measurement. This approach will enable
rapid, precise determination of unknown phase shifts using interferometry.Comment: 6 pages, 4 figure
Farm Level Impacts of a Revenue Based Policy in the 2007 Farm Bill
Revenue-based policy alternatives are thought to be a potential component of the 2007 Farm Bill. This research provides an economic analysis of switching to a revenue assurance farm program for representative farms. Specifically, this research provides a monte-carlo stochastic simulation model that compares the effect of a revenue based safety net policy relative to continuing the 2002 Farm Bill policies for different types of U.S. crop farmers. The results show that both revenue assurance proposals by the National Corn Growers Association leave the majority of farmers, especially feed grain producers, with higher total receipts and higher government payments.Agricultural and Food Policy,
Adaptive Measurements in the Optical Quantum Information Laboratory
Adaptive techniques make practical many quantum measurements that would
otherwise be beyond current laboratory capabilities. For example: they allow
discrimination of nonorthogonal states with a probability of error equal to the
Helstrom bound; they allow measurement of the phase of a quantum oscillator
with accuracy approaching (or in some cases attaining) the Heisenberg limit;
and they allow estimation of phase in interferometry with a variance scaling at
the Heisenberg limit, using only single qubit measurement and control. Each of
these examples has close links with quantum information, in particular
experimental optical quantum information: the first is a basic quantum
communication protocol; the second has potential application in linear optical
quantum computing; the third uses an adaptive protocol inspired by the quantum
phase estimation algorithm. We discuss each of these examples, and their
implementation in the laboratory, but concentrate upon the last, which was
published most recently [Higgins {\em et al.}, Nature vol. 450, p. 393, 2007].Comment: 12 pages, invited paper to be published in IEEE Journal of Selected
Topics in Quantum Electronics: Quantum Communications and Information Scienc
Quantum-enhanced capture of photons using optical ratchet states
Natural and artificial light harvesting systems often operate in a regime
where the flux of photons is relatively low. Besides absorbing as many photons
as possible it is therefore paramount to prevent excitons from annihilation via
photon re-emission until they have undergone an irreversible energy conversion
process. Taking inspiration from photosynthetic antenna structures, we here
consider ring-like systems and introduce a class of states we call ratchets:
excited states capable of absorbing but not emitting light. This allows our
antennae to absorb further photons whilst retaining the excitations from those
that have already been captured. Simulations for a ring of four sites reveal a
peak power enhancement by up to a factor of 35 under ambient conditions owing
to a combination of ratcheting and the prevention of emission through
dark-state population. In the slow extraction limit the achievable power
enhancement due to ratcheting alone exceeds 20%.Comment: major revision with improved model (all data and figures updated
The distribution of extremal points of Gaussian scalar fields
We consider the signed density of the extremal points of (two-dimensional)
scalar fields with a Gaussian distribution. We assign a positive unit charge to
the maxima and minima of the function and a negative one to its saddles. At
first, we compute the average density for a field in half-space with Dirichlet
boundary conditions. Then we calculate the charge-charge correlation function
(without boundary). We apply the general results to random waves and random
surfaces. Furthermore, we find a generating functional for the two-point
function. Its Legendre transform is the integral over the scalar curvature of a
4-dimensional Riemannian manifold.Comment: 22 pages, 8 figures, corrected published versio
Superabsorption of light via quantum engineering
Almost 60 years ago Dicke introduced the term superradiance to describe a
signature quantum effect: N atoms can collectively emit light at a rate
proportional to N^2. Even for moderate N this represents a significant increase
over the prediction of classical physics, and the effect has found applications
ranging from probing exciton delocalisation in biological systems, to
developing a new class of laser, and even in astrophysics. Structures that
super-radiate must also have enhanced absorption, but the former always
dominates in natural systems. Here we show that modern quantum control
techniques can overcome this restriction. Our theory establishes that
superabsorption can be achieved and sustained in certain simple nanostructures,
by trapping the system in a highly excited state while extracting energy into a
non-radiative channel. The effect offers the prospect of a new class of quantum
nanotechnology, capable of absorbing light many times faster than is currently
possible; potential applications of this effect include light harvesting and
photon detection. An array of quantum dots or a porphyrin ring could provide an
implementation to demonstrate this effect
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