1,844 research outputs found
A hierarchical systems modelling approach based on neural networks for forecasting global waste generation: a case study of Chile
In this-first every study for Chile, a neural network
based hierarchical modelling approach is proposed
for forecasting domestic waste generation for the
whole country. Over 30 global variables from the
342 communes (municipalities) in the country
were analysed extensively using statistical tools
that led to 5 significant explanatory variables:
population, percentage of urban population, years
of education, number of libraries and number of
indigents. The five explanatory variables were
used to develop a feedforward neural network for
predicting volume of global waste generation for a
particular year (2002 in this case) in Chile and
assessing the contribution of variables. The model
had validation R² of 0.82
The Delta-Delta Intermediate State in 1S0 Nucleon-Nucleon Scattering From Effective Field Theory
We examine the role of the Delta-Delta intermediate state in low energy NN
scattering using effective field theory. Theories both with and without pions
are discussed. They are regulated with dimensional regularization and MSbar
subtraction. We find that the leading effects of the Delta-Delta state can be
absorbed by a redefinition of the contact terms in a theory with nucleons only.
It does not remove the requirement of a higher dimension operator to reproduce
data out to moderate momentum. The explicit decoupling of the Delta-Delta state
is shown for the theory without pions.Comment: 16 pages, 3 figures, uses harvma
Bound States and Power Counting in Effective Field Theories
The problem of bound states in effective field theories is studied. A
rescaled version of nonrelativistic effective field theory is formulated which
makes the velocity power counting of operators manifest. Results obtained using
the rescaled theory are compared with known results from NRQCD. The same ideas
are then applied to study Yukawa bound states in 1+1 and 3+1 dimensions, and to
analyze when the Yukawa potential can be replaced by a delta-function
potential. The implications of these results for the study of nucleon-nucleon
scattering in chiral perturbation theory is discussed.Comment: 23 pages, eps figures, uses revte
Renormalization of Singlet NN-Scattering with One Pion Exchange and Boundary Conditions
We present a simple and physically compelling boundary condition
regularization scheme in the framework of effective field theory as applied to
nucleon-nucleon interaction. It is free of off-shell ambiguities and
ultraviolet divergences and provides finite results at any step of the
calculation. Low energy constants and their non-perturbative evolution can
directly be obtained from experimental threshold parameters in a completely
unique and model independent way when the long range explicit pion effects are
removed. This allows to compute scattering phase shifts which are, by
construction consistent with effective range expansion to a given order in the
CM momentum and are free from finite cut-off artifacts. We illustrate how the
method works in the channel for the One Pion Exchange potential.Comment: (Latex, epsfig) 7 pages, 2 figure
Causality, delocalization and positivity of energy
In a series of interesting papers G. C. Hegerfeldt has shown that quantum
systems with positive energy initially localized in a finite region,
immediately develop infinite tails. In our paper Hegerfeldt's theorem is
analysed using quantum and classical wave packets. We show that Hegerfeldt's
conclusion remains valid in classical physics. No violation of Einstein's
causality is ever involved. Using only positive frequencies, complex wave
packets are constructed which at are real and finitely localized and
which, furthemore, are superpositions of two nonlocal wave packets. The
nonlocality is initially cancelled by destructive interference. However this
cancellation becomes incomplete at arbitrary times immediately afterwards. In
agreement with relativity the two nonlocal wave packets move with the velocity
of light, in opposite directions.Comment: 14 pages, 5 figure
Consequences of high-technology economic development for African Americans in Georgia, 1990-2000
Issued as final reportUniversity System of Georgia. Board of Regent
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