27,564 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
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
Research on the Application of E-commerce to Small and Medium Enterprises (SMEs): the Case of India
SMEs account for a large proportion and play an important role in the development of each country in the world, including India. The globalization will bring many advantages for enterprises however SMEs will face fierce competition at the local, national and International level. In order to maintain and promote the important role of SMEs in the context of increased competition, SMEs have to change and adopt new technologies. E-commerce and digital technologies are bringing opportunities to help SMEs improve their competitiveness, narrow the gap with big enterprises thanks to their fairness and flexibility of the digital business environment. According to UNIDO (2017), India is one of the countries successfully applying e-commerce to SMEs. Contributing to this success is the important role of the Indian government. Therefore, this paper focuses on researching the application of e-commerce to SMEs in terms of the role of government in promoting and creating an ecosystem for SMEs and e-commerce development
Isogeometric analysis for functionally graded microplates based on modified couple stress theory
Analysis of static bending, free vibration and buckling behaviours of
functionally graded microplates is investigated in this study. The main idea is
to use the isogeometric analysis in associated with novel four-variable refined
plate theory and quasi-3D theory. More importantly, the modified couple stress
theory with only one material length scale parameter is employed to effectively
capture the size-dependent effects within the microplates. Meanwhile, the
quasi-3D theory which is constructed from a novel seventh-order shear
deformation refined plate theory with four unknowns is able to consider both
shear deformations and thickness stretching effect without requiring shear
correction factors. The NURBS-based isogeometric analysis is integrated to
exactly describe the geometry and approximately calculate the unknown fields
with higher-order derivative and continuity requirements. The convergence and
verification show the validity and efficiency of this proposed computational
approach in comparison with those existing in the literature. It is further
applied to study the static bending, free vibration and buckling responses of
rectangular and circular functionally graded microplates with various types of
boundary conditions. A number of investigations are also conducted to
illustrate the effects of the material length scale, material index, and
length-to-thickness ratios on the responses of the microplates.Comment: 57 pages, 14 figures, 18 table
Evolution of structure of SiO2 nanoparticles upon cooling from the melt
Evolution of structure of spherical SiO2 nanoparticles upon cooling from the
melt has been investigated via molecular-dynamics (MD) simulations under
non-periodic boundary conditions (NPBC). We use the pair interatomic potentials
which have weak Coulomb interaction and Morse type short-range interaction. The
change in structure of SiO2 nanoparticles upon cooling process has been studied
through the partial radial distribution functions (PRDFs), coordination number
and bond-angle distributions at different temperatures. The core and surface
structures of nanoparticles have been studied in details. Our results show
significant temperature dependence of structure of nanoparticles. Moreover,
temperature dependence of concentration of structural defects in nanoparticles
upon cooling from the melt toward glassy state has been found and discussed.Comment: 12 pages, 6 figure
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