28,101 research outputs found
The Desire for (Danish) Quality in High and Low Income Countries
We estimate the correlation between firm prices and sales within a CN8 product-country-year market. We do this for every market to which at least 16 different Danish firms exported between 1999 and 2006. Approximately 60% of Danish exports are to markets in which the price is negatively correlated with sales. These correlations are significantly different across destination countries within product categories, but across years for a given product-destination pair. While some existing theories perform better than others at predicting these patterns, none can reconcile the variation across countries. To fully explain the patterns, We introduce a model in which the price-sales correlation can be interpreted as the market's desire for high quality goods over low cost substitutes. We discover an inverted U shaped relation between a country's desire for quality and its per capita GDP, which we term a Quality Kuznets Curve. This curve has a turning point around 10 000 Euros for Danish exports. The Quality Kuznets Curve appears both when looking across products and within products.exports; firm heterogeneity; quality; productivity; Kuznets
Demand Uncertainty: Exporting Delays and Exporting Failures
This paper presents a model of trade that explains why firms wait to export and why many exporters fail. Firms face uncertain demands that are only realized after the firm enters the destination. The model retools the timing of uncertainty resolution found in productivity heterogeneity models. This retooling addresses several shortcomings. First, the imperfect correlation of demands reconciles the sales variation observed in and across destinations. Second, since demands for the firm's output are correlated across destinations, a firm can use previously realized demands to forecast unknown demands in untested destinations. The option to forecast demands causes firms to delay exporting in order to gather more information about foreign demand. Third, since uncertainty is resolved after entry, many firms enter a destination and then exit after learning that they cannot profit. This prediction reconciles the high rate of exit seen in the first years of exporting. Finally, when faced with multiple countries in which to export, some firms will choose to sequentially export in order to slowly learn more about its chances for success in untested markets.firm heterogeneity; exporting; trade failures; trade delay
Cost Linkages Transmit Volatility Across Markets
We present and test a model relating a firm's idiosyncratic cost, its exporting status, and the volatilities of its domestic and export sales. In prior models of trade, supply costs for domestic and exports were linear and thus additively separable. We introduce a nonlinear cost function in order to link the domestic and export supply costs. This theoretical contribution has two new implications for the exporting firm. First, the demand volatility in the foreign market now directly affects the firm's domestic sales volatility. Second, firms hedge domestic demand volatility with exports. The model has several testable predictions. First, larger firms have lower total and domestic sales volatilities. Second, foreign market volatility increases domestic sales volatilities for exporters. Third, exporters allocate output across both markets in order to reduce total sales volatility. We find evidence for these predictions with Danish firms operating between 1992 and 2006.
Hidden Markov Model Identifiability via Tensors
The prevalence of hidden Markov models (HMMs) in various applications of
statistical signal processing and communications is a testament to the power
and flexibility of the model. In this paper, we link the identifiability
problem with tensor decomposition, in particular, the Canonical Polyadic
decomposition. Using recent results in deriving uniqueness conditions for
tensor decomposition, we are able to provide a necessary and sufficient
condition for the identification of the parameters of discrete time finite
alphabet HMMs. This result resolves a long standing open problem regarding the
derivation of a necessary and sufficient condition for uniquely identifying an
HMM. We then further extend recent preliminary work on the identification of
HMMs with multiple observers by deriving necessary and sufficient conditions
for identifiability in this setting.Comment: Accepted to ISIT 2013. 5 pages, no figure
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The role of dwelling type when estimating the effect of magnetic fields on childhood leukemia in the California Power Line Study (CAPS).
PurposeThe type of dwelling where a child lives is an important factor when considering residential exposure to environmental agents. In this paper, we explore its role when estimating the potential effects of magnetic fields (MF) on leukemia using data from the California Power Line Study (CAPS). In this context, dwelling type could be a risk factor, a proxy for other risk factors, a cause of MF exposure, a confounder, an effect-measure modifier, or some combination.MethodsWe obtained information on type of dwelling at birth on over 2,000 subjects. Using multivariable-adjusted logistic regression, we assessed whether dwelling type was a risk factor for childhood leukemia, which covariates and MF exposures were associated with dwelling type, and whether dwelling type was a potential confounder or an effect-measure modifier in the MF-leukemia relationship under the assumption of no-uncontrolled confounding.ResultsA majority of children lived in single-family homes or duplexes (70%). Dwelling type was associated with race/ethnicity and socioeconomic status but not with childhood leukemia risk, after other adjustments, and did not alter the MF-leukemia relationship upon adjustment as a potential confounder. Stratification revealed potential effect-measure modification by dwelling type on the multiplicative scale.ConclusionDwelling type does not appear to play a significant role in the MF-leukemia relationship in the CAPS dataset as a leukemia risk factor or confounder. Future research should explore the role of dwelling as an effect-measure modifier of the MF-leukemia association
Women Surrealist Photographers and Their Response to the Objectification of Women in Male Surrealist Art
Objectification of women in Male Surrealist art depicted the male gaze in its darkest form, through the ideas of the uncanny, fetish, and convulsive beauty. Women were treated as objects throughout Surrealist photography and painting instead of as human subjects. Their femininity and beauty were valued to the extent of held belief that a woman’s destiny is to be beautiful and be present for the male gaze. Women Surrealists have gained notoriety in the last sixty years for their presence in the Surrealist movement and for their diligence in providing the female perspective in opposition to the male perspective.
This study observes the photographic works of the Women Surrealists, Claude Cahun and Francesca Woodman, and their method of response to the objectification of women while also examining the political context of Claude Cahun’s involvement in the Surrealist movement and the influence of Andre Breton, Claude Cahun and other early surrealist artists on late surrealist artist Francesca Woodman. Photographs, surrealist texts, and journal entries are used as primary sources to approach and reason why these two artists chose the medium of photography as their method response, and how objectification, photography, and the self-portrait incited the modern artist-as-subject trend through Claude Cahun and Francesca Woodman.https://scholarscompass.vcu.edu/uresposters/1154/thumbnail.jp
Transport in bilayer graphene near charge neutrality: Which scattering mechanisms are important?
Using the semiclassical quantum Boltzmann equation (QBE), we numerically
calculate the DC transport properties of bilayer graphene near charge
neutrality. We find, in contrast to prior discussions, that phonon scattering
is crucial even at temperatures below 40K. Nonetheless, electron-electron
scattering still dominates over phonon collisions allowing a hydrodynamic
approach. We introduce a simple two-fluid hydrodynamic model of electrons and
holes interacting via Coulomb drag and compare our results to the full QBE
calculation. We show that the two-fluid model produces quantitatively accurate
results for conductivity, thermopower, and thermal conductivity.Comment: 10 pages, 3 figure
Quantum Boltzmann equation for bilayer graphene
A-B stacked bilayer graphene has massive electron and hole-like excitations
with zero gap in the nearest-neighbor hopping approximation. In equilibrium,
the quasiparticle occupation approximately follows the usual Fermi-Dirac
distribution. In this paper we consider perturbing this equilibrium
distribution so as to determine DC transport coefficients near charge
neutrality. We consider the regime (with the
inverse temperature and the chemical potential) where there is not a well
formed Fermi surface. Starting from the Kadanoff-Baym equations, we obtain the
quantum Boltzmann equation of the electron and hole distribution functions when
the system is weakly perturbed out of equilibrium. The effect of phonons,
disorder, and boundary scattering for finite sized systems are incorporated
through a generalized collision integral. The transport coefficients, including
the electrical and thermal conductivity, thermopower, and shear viscosity, are
calculated in the linear response regime. We also extend the formalism to
include an external magnetic field. We present results from numerical solutions
of the quantum Boltzmann equation. Finally, we derive a simplified two-fluid
hydrodynamic model appropriate for this system, which reproduces the salient
results of the full numerical calculations.Comment: 27 pages, 7 figures, fixed typos, add a section on a two-fluid mode
Minimum fuel rocket maneuvers in horizontal flight.
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76185/1/AIAA-6726-616.pd
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