5,899 research outputs found
Identification of Demand through Statistical Distribution Modeling for Improved Demand Forecasting
Demand functions for goods are generally cyclical in nature with
characteristics such as trend or stochasticity. Most existing demand
forecasting techniques in literature are designed to manage and forecast this
type of demand functions. However, if the demand function is lumpy in nature,
then the general demand forecasting techniques may fail given the unusual
characteristics of the function. Proper identification of the underlying demand
function and using the most appropriate forecasting technique becomes critical.
In this paper, we will attempt to explore the key characteristics of the
different types of demand function and relate them to known statistical
distributions. By fitting statistical distributions to actual past demand data,
we are then able to identify the correct demand functions, so that the the most
appropriate forecasting technique can be applied to obtain improved forecasting
results. We applied the methodology to a real case study to show the reduction
in forecasting errors obtained
Many-Body Density Matrices for Free Fermions
Building upon an analytical technique introduced by Chung and Peschel [M.
Chung and I. Peschel, Phys. Rev. B 64, art. 064412 (2001)], we calculated the
density matrix rho_B of a finite block of B sites within an infinite system of
free spinless fermions. In terms of the block Green function matrix G (whose
elements are G_ij = , where c_i^+ and c_j are fermion creation and
annihilation operators acting on sites i and j within the block respectively),
the density matrix can be written as rho_B = det(1 - G) exp[ sum_ij (log G(1 -
G^{-1})_ij c_i^+ c_j]. Implications of such a result to Hilbert space
truncation for real-space renormalization schemes is discussed.Comment: 12 pages in RevTeX4 format. Uses amsmath, bbold, dcolumn and mathrsfs
package
Mergers and Dynamic Oligopoly
Static oligopoly theories disagree on whether mergers are profitable. The Cournot model says that many potential mergers would be unprofitable whereas the Bertrand model says that all mergers are profitable. We show that, for economically sensible parameter values, mergers are profitable for merging firms when firms choose both price and output, using inventories to absorb differences between output and sales. Furthermore, substantial cost advantages are necessary for a merger to benefit consumers. The merger predictions of our dynamic model are most similarto predictions of static Bertrand analyses of differentiated products even though our model often behaves like the Cournot model in the long run.oligopoly, dynamic games, mergers
Exact ground states and correlation functions of chain and ladder models of interacting hardcore bosons or spinless fermions
By removing one empty site between two occupied sites, we map the ground
states of chains of hardcore bosons and spinless fermions with infinite
nearest-neighbor repulsion to ground states of chains of hardcore bosons and
spinless fermions without nearest-neighbor repulsion respectively, and
ultimately in terms of the one-dimensional Fermi sea. We then introduce the
intervening-particle expansion, where we write correlation functions in such
ground states as a systematic sum over conditional expectations, each of which
can be ultimately mapped to a one-dimensional Fermi-sea expectation. Various
ground-state correlation functions are calculated for the bosonic and fermionic
chains with infinite nearest-neighbor repulsion, as well as for a ladder model
of spinless fermions with infinite nearest-neighbor repulsion and correlated
hopping in three limiting cases. We find that the decay of these correlation
functions are governed by surprising power-law exponents.Comment: 20 pages, 18 figures, RevTeX4 clas
Phase transition in a super superspin glass
We here confirm the occurrence of spin glass phase transition and extract
estimates of associated critical exponents of a highly monodisperse and densely
compacted system of bare maghemite nanoparticles. This system has earlier been
found to behave like an archetypal spin glass, with e.g. a sharp transition
from paramagnetic to non-equilibrium behavior, suggesting that this system
undergoes a spin-glass phase transition at a relatively high temperature,
140 K.Comment: 4 pages, 3 figure
A generalized structure of Bell inequalities for bipartite arbitrary dimensional systems
We propose a generalized structure of Bell inequalities for arbitrary
d-dimensional bipartite systems, which includes the existing two types of Bell
inequalities introduced by Collins-Gisin-Linden-Massar-Popescu [Phys. Rev.
Lett. 88, 040404 (2002)] and Son-Lee-Kim [Phys. Rev. Lett. 96, 060406 (2006)].
We analyze Bell inequalities in terms of correlation functions and joint
probabilities, and show that the coefficients of correlation functions and
those of joint probabilities are in Fourier transform relations. We finally
show that the coefficients in the generalized structure determine the
characteristics of quantum violation and tightness.Comment: 6 pages, 1 figur
Equivalent Circuit Modeling of the Dielectric Loaded Microwave Biosensor
This article describes the modeling of biological tissues at microwave frequency using equivalent lumped elements. A microwave biosensor based on microstrip ring resonator (MRR), that has been utilized previously for meat quality evaluation is used for this purpose. For the first time, the ring-resonator loaded with the lossy and high permittivity dielectric material, such as; biological tissue, in a partial overlay configuration is analyzed. The equivalent circuit modeling of the structure is then performed to identify the effect of overlay thickness on the resonance frequency. Finally, the relationship of an overlay thickness with the corresponding RC values of the meat equivalent circuit is established. Simulated, calculated and measured results are then compared for validation. Results are well agreed while the observed discrepancy is in acceptable limit
Lines pinning lines
A line g is a transversal to a family F of convex polytopes in 3-dimensional
space if it intersects every member of F. If, in addition, g is an isolated
point of the space of line transversals to F, we say that F is a pinning of g.
We show that any minimal pinning of a line by convex polytopes such that no
face of a polytope is coplanar with the line has size at most eight. If, in
addition, the polytopes are disjoint, then it has size at most six. We
completely characterize configurations of disjoint polytopes that form minimal
pinnings of a line.Comment: 27 pages, 10 figure
Correlation density matrix: an unbiased analysis of exact diagonalizations
Given the ground state wavefunction for an interacting lattice model, we
define a "correlation density matrix"(CDM) for two disjoint, separated clusters
and , to be the density matrix of their union, minus the direct product
of their respective density matrices. The CDM can be decomposed systematically
by a numerical singular value decomposition, to provide a systematic and
unbiased way to identify the operator(s) dominating the correlations, even
unexpected ones.Comment: (4pp, 2 figures
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