7,464 research outputs found
An Improved Method for Calibrating Purchase Intentions in Stated Preference Demand Models
The Orbit demand model allows the magnitude of the calibration to stated purchase intentions to vary based on the magnitude of the stated quantities. Using an empirical example of stated trips, we find that the extent of calibration varies substantially with less correction needed at small stated trips (–25%) but larger corrections at higher quantities of stated visits (–48%). We extend the Orbit model to calculate consumer surplus per stated trip of $26. Combining the calibrations in stated trips and value per trip, the Orbit model provides estimates of annual benefits from 60% to 111% less than the count data model.hypothetical bias, Orbit, ordered probit model, travel cost model, recreation, stated preference, Agribusiness, Agricultural Finance, Consumer/Household Economics, Demand and Price Analysis, Financial Economics, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, Marketing, Production Economics, Productivity Analysis, Research Methods/ Statistical Methods, D12, H44, Q26, Q51,
A New Approach to Correct for Hypothetical Bias in Stated Preference Models
Many times economists are asked to estimate the demand for new consumer goods or services for which no market data exists. Typically market researchers and economists answer this challenge using surveys that ask about intended purchases (Louviere, et al. 2000) or what has become known as stated preference (SP) data. Tying this data to revealed preference (RP), or actual behavior, has been a target in a number of studies. Simplistic calibrations have been investigated in past RP-SP studies, such as Loomis, et al. 2001. This paper offers an alternative solution that allows the magnitude of the calibration correction to vary based on Klein and Sherman's (1997) Orbit procedure. This paper extends the original Orbit procedure of Klein and Sherman by Combining stated and revealed preference data on quantities and prices in the first stage, incorporating a correction for heteroskedasticity, and developing methods to calculate consumer surplus and elasticities.Research Methods/ Statistical Methods,
Sagnac effect in a chain of mesoscopic quantum rings
The ability to interferometrically detect inertial rotations via the Sagnac
effect has been a strong stimulus for the development of atom interferometry
because of the potential 10^{10} enhancement of the rotational phase shift in
comparison to optical Sagnac gyroscopes. Here we analyze ballistic transport of
matter waves in a one dimensional chain of N coherently coupled quantum rings
in the presence of a rotation of angular frequency, \Omega. We show that the
transmission probability, T, exhibits zero transmission stop gaps as a function
of the rotation rate interspersed with regions of rapidly oscillating finite
transmission. With increasing N, the transition from zero transmission to the
oscillatory regime becomes an increasingly sharp function of \Omega with a
slope \partialT/\partial \Omega N^2. The steepness of this slope dramatically
enhances the response to rotations in comparison to conventional single ring
interferometers such as the Mach-Zehnder and leads to a phase sensitivity well
below the standard quantum limit
Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts
A non-equilibrium Green function formalism (NEGF) is used to study the
conductance of a side-gated quantum point contact (QPC) in the presence of
lateral spin-orbit coupling (LSOC). A small difference of bias voltage between
the two side gates (SGs) leads to an inversion asymmetry in the LSOC between
the opposite edges of the channel. In single electron modeling of transport,
this triggers a spontaneous but insignificant spin polarization in the QPC.
However, the spin polarization of the QPC is enhanced substantially when the
effect of electron-electron interaction is included. The spin polarization is
strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0
= 2e2/h) in the absence of any external magnetic field. In our simulations of a
model QPC device, the 0.5 plateau is found to be quite robust and survives up
to a temperature of 40K. The spontaneous spin polarization and the resulting
magnetization of the QPC can be reversed by flipping the polarity of the source
to drain bias or the potential difference between the two SGs. These numerical
simulations are in good agreement with recent experimental results for
side-gated QPCs made from the low band gap semiconductor InAs
Properties of seawater bitterns with regard to liquid-desiccant cooling
This study concerns the properties of the concentrated bittern solutions occurring as by-product from solar salt works, in relation to their potential use as liquid desiccants in cooling systems. Solutions of compositions similar to those of bitterns have been made up in the laboratory, as have concentrated mixtures of MgCl2–MgSO4–H2O. Measurements of vapour pressure have been carried out using an isoteniscope and are reported together with measurements of density and viscosity. Several theoretical models representing these properties are reviewed and compared against the experimental results; the average agreement between theory and experiment is within 5% for vapour pressure and better for the preferred models of the other two properties. Based on these findings, an expression is provided for the equilibrium relative humidity of bitterns as a function of concentration relative to raw seawater. The vapour pressures of bittern solutions are found to be similar to those of solutions containing only magnesium chloride but having the same mass fraction of total salts. Therefore magnesium chloride solution is a reasonable model for bitterns for the purpose of developing the proposed cooling system
Robustness of adiabatic quantum computation
We study the fault tolerance of quantum computation by adiabatic evolution, a
quantum algorithm for solving various combinatorial search problems. We
describe an inherent robustness of adiabatic computation against two kinds of
errors, unitary control errors and decoherence, and we study this robustness
using numerical simulations of the algorithm.Comment: 11 pages, 5 figures, REVTe
J.S. Bell's Concept of Local Causality
John Stewart Bell's famous 1964 theorem is widely regarded as one of the most
important developments in the foundations of physics. It has even been
described as "the most profound discovery of science." Yet even as we approach
the 50th anniversary of Bell's discovery, its meaning and implications remain
controversial. Many textbooks and commentators report that Bell's theorem
refutes the possibility (suggested especially by Einstein, Podolsky, and Rosen
in 1935) of supplementing ordinary quantum theory with additional ("hidden")
variables that might restore determinism and/or some notion of an
observer-independent reality. On this view, Bell's theorem supports the
orthodox Copenhagen interpretation. Bell's own view of his theorem, however,
was quite different. He instead took the theorem as establishing an "essential
conflict" between the now well-tested empirical predictions of quantum theory
and relativistic \emph{local causality}. The goal of the present paper is, in
general, to make Bell's own views more widely known and, in particular, to
explain in detail Bell's little-known mathematical formulation of the concept
of relativistic local causality on which his theorem rests. We thus collect and
organize many of Bell's crucial statements on these topics, which are scattered
throughout his writings, into a self-contained, pedagogical discussion
including elaborations of the concepts "beable", "completeness", and
"causality" which figure in the formulation. We also show how local causality
(as formulated by Bell) can be used to derive an empirically testable Bell-type
inequality, and how it can be used to recapitulate the EPR argument.Comment: 19 pages, 4 figure
CP Violating Bubble Wall Profiles
We solve the equations of motion for a CP violating phase between the two
Higgs doublets at the bubble wall of the MSSM electroweak phase transition.
Contrary to earlier suggestions, we do not find indications of spontaneous
``transitional'' CP violation in the MSSM. On the other hand, in case there is
explicit CP violation in the stop and chargino/neutralino sectors, the relative
phase between the Higgses does become space dependent, but only mildly even in
the maximal case. We also demonstrate that spontaneous CP violation within the
bubble wall could occur, e.g., if the Higgs sector of the MSSM were
supplemented by a singlet. Finally we point out some implications for
baryogenesis computations
The origin of switching noise in GaAs/AlGaAs lateral gated devices
We have studied the origin of switching (telegraph) noise at low temperature
in lateral quantum structures defined electrostatically in GaAs/AlGaAs
heterostructures by surface gates. The noise was measured by monitoring the
conductance fluctuations around on the first step of a quantum point
contact at around 1.2 K. Cooling with a positive bias on the gates dramatically
reduces this noise, while an asymmetric bias exacerbates it. We propose a model
in which the noise originates from a leakage current of electrons that tunnel
through the Schottky barrier under the gate into the doped layer. The key to
reducing noise is to keep this barrier opaque under experimental conditions.
Bias cooling reduces the density of ionized donors, which builds in an
effective negative gate voltage. A smaller negative bias is therefore needed to
reach the desired operating point. This suppresses tunnelling from the gate and
hence the noise. The reduction in the density of ionized donors also
strengthens the barrier to tunneling at a given applied voltage. Support for
the model comes from our direct observation of the leakage current into a
closed quantum dot, around for this device. The current
was detected by a neighboring quantum point contact, which showed monotonic
steps in time associated with the tunneling of single electrons into the dot.
If asymmetric gate voltages are applied, our model suggests that the noise will
increase as a consequence of the more negative gate voltage applied to one of
the gates to maintain the same device conductance. We observe exactly this
behaviour in our experiments.Comment: 8 pages, 7 figure
Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene
The interaction of CO with an attapulgite-supported Cu(II)Cl2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by a catalyst pre-treatment where the supported Cu(II)Cl2 sample is exposed to a diluted stream of chlorine. Subsequent CO exposure at ~ 370°C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of x-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu+ and a small amount of Cu2+. Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu+/Cu2+ catalyst is required to support CO chemisorption
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