5,088 research outputs found

### Estimating a pressure dependent thermal conductivity coefficient with applications in food technology

In this paper we introduce a method to estimate a pressure dependent thermal
conductivity coefficient arising in a heat diffusion model with applications in
food technology. To address the known smoothing effect of the direct problem,
we model the uncertainty of the conductivity coefficient as a hierarchical
Gaussian Markov random field (GMRF) restricted to uniqueness conditions for the
solution of the inverse problem established in Fraguela et al. Furthermore, we
propose a Single Variable Exchange Metropolis-Hastings algorithm to sample the
corresponding conditional probability distribution of the conductivity
coefficient given observations of the temperature. Sensitivity analysis of the
direct problem suggests that large integration times are necessary to identify
the thermal conductivity coefficient. Numerical evidence indicates that a
signal to noise ratio of roughly 1000 suffices to reliably retrieve the thermal
conductivity coefficient

### The truth about freedom of choi

El presente es un análisis de los principales rasgos y tendencias que caracterizan
hoy a la triada Sociedad-Estado-Mercado. Hace énfasis en la hegemonía del mercado y ofrece
un recuento analítico de los hechos que la acompañan como son: la transnacionalización de
la cadena de valor, el ascenso de la sociedad del conocimiento, el protagonismo oligopólico
de la empresa transnacional, la nueva división social transnacional del trabajo, el proceso de
reconfiguración cultural, la exclusión social y la subordinación del Estado, entre otros. El planteamiento
que subyace a estas consideraciones es lo que acá se denomina “la verdad sobre
la libertad de elegir”, con lo cual se quiere hacer referencia al hecho de que las relaciones
Sociedad-Estado se encuentran hoy mediatizadas por el mercado, arrojando, como consecuencia,
una involución heterónoma de la Sociedad y del mismo Estado liberal.The actual is an academic analysis of the main features on the day has the triad
Society, State and Market. It emphasizes the market hegemony and offers an analytical recount
of the facts that go with, as the value chain internationalization, the knowledge society
rise, the translational enterprise powerful mark up, the new international social labour division,
the cultural reshape process, the social exclusion, the State subordination, among others.
The underlying outlining these issues is what the author calls “The truth under the free
to choose”, as a reference to the fact that the relationships between the Society and the State
are hindered by the Market with a heteronomous society involution as consequence

### A Natural Rank Problem for Homogeneous Polynomials and Connections with the Theory of Functions of Several Complex Variables

We study a natural extremal problem about the vector space consisting of all homogeneous polynomials of degree $d$ in $n+1$ variables with real coefficients, together with the zero polynomial. We define the {\it rank} of a polynomial to be the number of distinct monomials appearing in the polynomial with non-zero coefficient. We are particularly interested in those homogeneous polynomials whose quotient with the homogeneous polynomial $x_0+x_1+\cdots+x_n$ is a polynomial of degree $d-1$ with maximal rank. For each degree $d$, we seek the minimum rank for an element of this subfamily and we seek to describe those polynomials with minimum rank. We call such polynomials {\it sharp} polynomials.
These problems have a simple solution for polynomials in one and two variables. The three-variable case is interesting and non-trivial, but well-understood. This research question has its roots in the study of proper polynomial mappings between balls in complex Euclidean spaces of different dimensions and the degree estimates problem. D\u27Angelo, Kos and Riehl \cite{degree} and Lebl and Peters \cite{hyperplaneq} used a graph-theoretic approach to solve this problem in the case of proper monomial mappings. Lebl and Peters give a minimum rank estimate that answers our question in the three variable case. A family of sharp polynomials was described by D\u27Angelo and has been extensively studied. Brooks and Grundmeier \cite{notes} provided a new proof of the minimum rank theorem in the three-variable case using a commutative algebra approach. They reformulate the problem as a question about homogeneous ideals and address it by studying the Hilbert function and the graded Betti number of certain ideals.
Using the same method as Brooks and Grundmeier, we give a sharp estimate for the minimum rank of homogeneous polynomials of our subfamily in four variables as well as a family of sharp polynomials. Moreover, we state a general result on the minimum rank for polynomials in $n+1$ variables. Although this estimate is sharp in the three- and four- variable cases, the estimate is not sharp when the number of variables is greater than four

### Energy prices in Europe. Evidence of persistence across markets

This paper deals with the behavior of energy price changes and how their shocks exert an impact on suppliers and
consumers in different markets. For this purpose, a fractional integration model is used to evaluate the persistence and mean reversion in prices across the major European markets (Germany, France, Italy, UK, Spain). We
compare the results with other major players as the US and Japan, to understand, first, if the European behavior
is different, and second, if geopolitical shocks that are affecting this market are expected to be permanent.
Empirical results show evidence of mean reversion properties in European prices, though some minor differences
arise from market to market that apparently, are not associated with the energy generation strategies followed by
each country. Thus, it will likely be expected following the current energy shocks the series will recover due to
natural market forces, without the need for additional policies

### The Effect Of Type-III Antifreeze Proteins (AFPs) On CO2 Hydrate Slurry Formation

CO2 hydrate slurry is a favourable direct coolant of fresh products due to its large latent heat and phase change temperature around 5°C. Continuous production of this slurry is, however, difficult to realise due to the high rate of hydrate formation. The use of additives is proposed with the purpose of decreasing the formation rate so that the controllability of the process is improved. Type-III Antifreeze Proteins (AFPs) are non-poisonous additives which have proven to be inhibitors of hydrate formation. These additives have also shown to protect the bio-cells of fresh products from damaging by freezing. The effect of these additives on the CO2 hydrate formation rate is experimentally investigated. The experiments have been performed in a coil heat exchanger with 6 mm internal diameter under operating conditions corresponding to hydrate formation conditions. The concentration of Type-III AFPs has been varied: no additives, 5 ppm and 10 ppm. The mixture of additives and CO2-water solution is cooled down until the hydrate formation conditions are attained. The growth rate of hydrates on the wall of the heat exchanger has been derived from the variation of the overall heat transfer coefficient with time. Results show that the addition of AFPs changes the supersaturation degree of CO2 water solution needed to initiate the hydrate formation process. A low concentration of the proposed additives is sufficient to slow down the formation rate of CO2 hydrate improving significantly the controllability of the hydrate production process

### Quasars Clustering at z approx 3 on Scales less sim 10 h^{-1} Mpc

We test the hypothesis whether high redshift QSOs would preferentially appear
in small groups or pairs, and if they are associated with massive, young
clusters. We carried out a photometric search for \Ly emitters on scales
$\lesssim 10 h^{-1}$ Mpc, in the fields of a sample of 47 $z\approx3$ known
QSOs. Wide and narrow band filter color-magnitude diagrams were generated for
each of the $6'.6\times6'.6$ fields. A total of 13 non resolved objects with a
significant color excess were detected as QSO candidates at a redshift similar
to that of the target. All the candidates are significantly fainter than the
reference QSOs, with only 2 of them within 2 magnitudes of the central object.
Follow-up spectroscopic observations have shown that 5, i.e., about 40% of the
candidates, are QSOs at the same redshift of the target; 4 are QSOs at
different z (two of them probably being a lensed pair at z = 1.47); 2
candidates are unresolved HII galaxies at z$\sim$0.3; one unclassified and one
candidate turned out to be a CCD flaw. These data indicate that at least 10% of
the QSOs at z$\sim$3 do have companions.
We have also detected a number of resolved, rather bright \Ly Emitter
Candidates. Most probably a large fraction of them might be bright galaxies
with [OII] emission, at z$\approx$ 0.3. The fainter population of our
candidates corresponds to the current expectations. Thus, there are no strong
indication for the existence of an overdensity of \Ly galaxies brighter than m
$\approx$ 25 around QSOs at $z\approx$ 3.Comment: 29 pages, 8 figures, tar gzip LaTex file, accepted to appear in Ap

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