384 research outputs found
Research project Mauretania: Satellites as development aids
A general discussion is presented of how satellite images and ground surveys are used to define land use. Specifically it deals with the Tagant region in Mauretania, West Africa
The optimal sink and the best source in a Markov chain
It is well known that the distributions of hitting times in Markov chains are
quite irregular, unless the limit as time tends to infinity is considered. We
show that nevertheless for a typical finite irreducible Markov chain and for
nondegenerate initial distributions the tails of the distributions of the
hitting times for the states of a Markov chain can be ordered, i.e., they do
not overlap after a certain finite moment of time.
If one considers instead each state of a Markov chain as a source rather than
a sink then again the states can generically be ordered according to their
efficiency. The mechanisms underlying these two orderings are essentially
different though.Comment: 12 pages, 1 figur
Lightweight Aggregate Potentialities of Some Indiana Shales
Indiana Geological Survey Report of Progress 12Laboratory tests show that some Indiana shales are potential sources of manufactured lightweight aggregate. Bloating, the process by which lightweight aggregates are manufactured, is caused by various constituents acting singly or in combination. Chemical composition and mineral composition of the shales and particle-size distribution of the mineral constituents are interrelated, and all of these factors contribute to the bloating of shales.
This study was made to test the potential use of some Indiana, shales as raw materials for manufacturing lightweight aggregate. Such aggregate was produced in Ohio, Illinois, and Kentucky before any interest was shown in Indiana. A new plant is now producing lightweight aggregate from shale of the Borden group near Brooklyn, Ind., but other plants are needed to meet the increasing demand for lightweight concrete in the State. It is hoped that this report will stimulate interest in developing lightweight aggregate from shale and will enable future producers of lightweight aggregate in Indiana to evaluate better the location, thickness, extent, and physical properties
of various shale formations.Indiana Department of Conservatio
WTAQ and the Green Bay Countree
A brochure that highlights the regions served by WTAQ. Each region has its own detailed section that includes history on its beginning. Throughout the brochure there are pictures and names of the WTAQ staff
Olfactory bulb hypoplasia in Prokr2 null mice stems from defective neuronal progenitor migration and differentiation.
New neurons are added on a daily basis to the olfactory bulb (OB) of a mammal, and this phenomenon exists throughout its lifetime. These new cells are born in the subventricular zone and migrate to the OB via the rostral migratory stream (RMS). To examine the role of the prokineticin receptor 2 (Prokr2) in neurogenesis, we created a Prokr2 null mouse, and report a decrease in the volume of its OB and also a decrease in the number of bromodeoxyuridine (BrdU)-positive cells. There is disrupted architecture of the OB, with the glomerular layer containing terminal dUTP nick-end labeling (TUNEL) -positive nuclei and also a decrease in tyrosine hydroxylase-positive neurons in this layer. In addition, there are increased numbers of doublecortin-positive neuroblasts in the RMS and increased PSA-NCAM (polysialylated form of the neural cell adhesion molecule) -positive neuronal progenitors around the olfactory ventricle, indicating their detachment from homotypic chains is compromised. Finally, in support of this, Prokr2-deficient cells expanded in vitro as neurospheres are incapable of migrating towards a source of recombinant human prokineticin 2 (PROK2). Together, these findings suggest an important role for Prokr2 in OB neurogenesis
Cost Models for MMC Manufacturing Processes
The quality cost modeling (QCM) tool is intended to be a relatively simple-to-use device for obtaining a first-order assessment of the quality-cost relationship for a given process-material combination. The QCM curve is a plot of cost versus quality (an index indicating microstructural quality), which is unique for a given process-material combination. The QCM curve indicates the tradeoff between cost and performance, thus enabling one to evaluate affordability. Additionally, the effect of changes in process design, raw materials, and process conditions on the cost-quality relationship can be evaluated. Such results might indicate the most efficient means to obtain improved quality at reduced cost by process design refinements, the implementation of sensors and models for closed loop process control, or improvement in the properties of raw materials being fed into the process. QCM also allows alternative processes for producing the same or similar material to be compared in terms of their potential for producing competitively priced, high quality material. Aside from demonstrating the usefulness of the QCM concept, this is one of the main foci of the present research program, namely to compare processes for making continuous fiber reinforced, metal matrix composites (MMC's). Two processes, low pressure plasma spray deposition and tape casting are considered for QCM development. This document consists of a detailed look at the design of the QCM approach, followed by discussion of the application of QCM to each of the selected MMC manufacturing processes along with results, comparison of processes, and finally, a summary of findings and recommendations
On the statistical distribution of first--return times of balls and cylinders in chaotic systems
We study returns in dynamical systems: when a set of points, initially
populating a prescribed region, swarms around phase space according to a
deterministic rule of motion, we say that the return of the set occurs at the
earliest moment when one of these points comes back to the original region. We
describe the statistical distribution of these "first--return times" in various
settings: when phase space is composed of sequences of symbols from a finite
alphabet (with application for instance to biological problems) and when phase
space is a one and a two-dimensional manifold. Specifically, we consider
Bernoulli shifts, expanding maps of the interval and linear automorphisms of
the two dimensional torus. We derive relations linking these statistics with
Renyi entropies and Lyapunov exponents.Comment: submitted to Int. J. Bifurcations and Chao
The compound Poisson limit ruling periodic extreme behaviour of non-uniformly hyperbolic dynamics
We prove that the distributional limit of the normalised number of returns to
small neighbourhoods of periodic points of non-uniformly hyperbolic dynamical
systems is compound Poisson. The returns to small balls around a fixed point in
the phase space correspond to the occurrence of rare events, or exceedances of
high thresholds, so that there is a connection between the laws of Return Times
Statistics and Extreme Value Laws. The fact that the fixed point in the phase
space is a repelling periodic point implies that there is a tendency for the
exceedances to appear in clusters whose average sizes is given by the Extremal
Index, which depends on the expansion of the system at the periodic point.
We recall that for generic points, the exceedances, in the limit, are
singular and occur at Poisson times. However, around periodic points, the
picture is different: the respective point processes of exceedances converge to
a compound Poisson process, so instead of single exceedances, we have entire
clusters of exceedances occurring at Poisson times with a geometric
distribution ruling its multiplicity.
The systems to which our results apply include: general piecewise expanding
maps of the interval (Rychlik maps), maps with indifferent fixed points
(Manneville-Pomeau maps) and Benedicks-Carleson quadratic maps.Comment: To appear in Communications in Mathematical Physic
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