Auditory frequency threshold comparisons of humans and pre-adolescent chimpanzees

Auditory frequency threshold comparisons of humans and pre-adolescent chimpanzee

An algorithm for quantifying dependence in multivariate data sets

We describe an algorithm to quantify dependence in a multivariate data set. The algorithm is able to identify any linear and non-linear dependence in the data set by performing a hypothesis test for two variables being independent. As a result we obtain a reliable measure of dependence. In high energy physics understanding dependencies is especially important in multidimensional maximum likelihood analyses. We therefore describe the problem of a multidimensional maximum likelihood analysis applied on a multivariate data set with variables that are dependent on each other. We review common procedures used in high energy physics and show that general dependence is not the same as linear correlation and discuss their limitations in practical application. Finally we present the tool CAT, which is able to perform all reviewed methods in a fully automatic mode and creates an analysis report document with numeric results and visual review.Comment: 4 pages, 3 figure

Correlation, Network and Multifractal Analysis of Global Financial Indices

We apply RMT, Network and MF-DFA methods to investigate correlation, network and multifractal properties of 20 global financial indices. We compare results before and during the financial crisis of 2008 respectively. We find that the network method gives more useful information about the formation of clusters as compared to results obtained from eigenvectors corresponding to second largest eigenvalue and these sectors are formed on the basis of geographical location of indices. At threshold 0.6, indices corresponding to Americas, Europe and Asia/Pacific disconnect and form different clusters before the crisis but during the crisis, indices corresponding to Americas and Europe are combined together to form a cluster while the Asia/Pacific indices forms another cluster. By further increasing the value of threshold to 0.9, European countries France, Germany and UK constitute the most tightly linked markets. We study multifractal properties of global financial indices and find that financial indices corresponding to Americas and Europe almost lie in the same range of degree of multifractality as compared to other indices. India, South Korea, Hong Kong are found to be near the degree of multifractality of indices corresponding to Americas and Europe. A large variation in the degree of multifractality in Egypt, Indonesia, Malaysia, Taiwan and Singapore may be a reason that when we increase the threshold in financial network these countries first start getting disconnected at low threshold from the correlation network of financial indices. We fit Binomial Multifractal Model (BMFM) to these financial markets.Comment: 32 pages, 25 figures, 1 tabl

Review on phase change materials (PCMs) for cold thermal energy storage applications

Thermal energy storage (TES) is a technology with a high potential for different thermal applications. It is well known that TES could be the most appropriate way and method to correct the gap between the demand and supply of energy and therefore it has become a very attractive technology. In this paper, a review of TES for cold storage applications using solid–liquid phase change materials has been carried out. The scope of the work was focussed on different aspects: phase change materials (PCMs), encapsulation, heat transfer enhancement, and the effect of storage on food quality. Materials used by researchers as potential PCM at low temperatures (less than 20 C) are summarized and some of their thermophysical properties are reported. Over 88 materials that can be used as PCM, and about 40 commercially available PCM have been listed. Problems in long term stability of the materials, such as corrosion, phase segregation, stability under extended cycling or subcooling are discussed. Heat transfer is considered both from theoretical and experimental point of view and the different methods of PCM encapsulation are reviewed. Many applications of PCM at low temperature can be found, such as, ice storage, conservation and transport of temperature sensitive materials and in air conditioning, cold stores, and refrigerated trucks.The work partially funded by the Spanish Government (ENE2008-06687-C02-01/CON and ENE2011-22722) and the European Union (COST Action COST TU0802 and project EFFIBUILDINGS – FP7-PEOPLE-2009-IIF-/-253914). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534). Eduard Oró would like to thank the University of Lleida for his research fellowship

Scalar--flat K\"ahler metrics with conformal Bianchi V symmetry

We provide an affirmative answer to a question posed by Tod \cite{Tod:1995b}, and construct all four-dimensional Kahler metrics with vanishing scalar curvature which are invariant under the conformal action of Bianchi V group. The construction is based on the combination of twistor theory and the isomonodromic problem with two double poles. The resulting metrics are non-diagonal in the left-invariant basis and are explicitly given in terms of Bessel functions and their integrals. We also make a connection with the LeBrun ansatz, and characterise the associated solutions of the SU(\infty) Toda equation by the existence a non-abelian two-dimensional group of point symmetries.Comment: Dedicated to Maciej Przanowski on the occasion of his 65th birthday. Minor corrections. To appear in CQ

Recycling of Cr/Ni/Cu plating wastes as black ceramic pigments

The non-ferrous metal industry, such as Cr/Ni/Cu plating, produces acid sludge which is usually neutralized with lime slurry in batch processes, and the resulting waste is dewatered by vacuum filtration or filter-pressing. Dewatered sludge contains calcium sulphate (CaSO4) coming from the neutralization process, as well as transition metals (Cr, Ni and Cu), oil, grease and suspended solids. In this communication, two residual sludges from Cr/Ni/Cu plating have been dried (110 C) and fired (1100 C), and both dried (gray coloured) and fired powders (black coloured) have been characterized by DTA-TG, XRD and SEMEDX techniques. XRD shows only quartz crystallization in dried samples, while NiCr2O4 chromite spinel and NiO periclase crystallize in fired powders, along with CaSO4 anhydrite and CaSiO3 wollastonite. The powders have been introduced as ceramic pigments into three different conventional glazes: a) a lead bisilicate (PbO.2SiO2) double fire frit (1000 C), b) a double fire frit with low lead content (1000 C), and c) a double fire frit without lead (1050 C). Glazed samples were characterized by UV-Vis-NIR (diffuse reflectance) and CIEL⁄a⁄b⁄ (color parameters). Dried powders induce glaze defects (pin-holing and crawling), but fired powders did not show these faults exhibiting more intense (higher L⁄ ) and yellowish (higher b⁄ ) black colors than the standard spinel

The spatial distribution of substellar objects in IC348 and the Orion Trapezium Cluster

Aims: Some theoretical scenarios suggest the formation of brown dwarfs as ejected stellar embryos in star-forming clusters. Such a formation mechanism can result in different spatial distributions of stars and substellar objects. We aim to investigate the spatial structure of stellar and substellar objects in two well sampled and nearby embedded clusters, namely IC348 and the Orion Trapezium Cluster (OTC) to test this hypothesis. Methods:Deep near-infrared K-band data complete enough to sample the substellar population in IC348 and OTC are obtained from the literature. The spatial distribution of the K-band point sources is analysed using the Minimum Spanning Tree (MST) method. The Q parameter and the spanning trees are evaluated for stellar and substellar objects as a function of cluster core radius R$_c$. Results: The stellar population in both IC348 and OTC display a clustered distribution whereas the substellar population is distributed homogeneously in space within twice the cluster core radius. Although the substellar objects do not appear to be bound by the cluster potential well, they are still within the limits of the cluster and not significantly displaced from their birth sites. Conclusions: The spatially homogeneous distribution of substellar objects is best explained by assuming higher initial velocities, distributed in a random manner and going through multiple interactions. The overall spatial coincidence of these objects with the cluster locations can be understood if these objects are nevertheless travelling slowly enough so as to feel the gravitational effect of the cluster. The observations support the formation of substellar objects as ``ejected stellar embryos''. Higher ejection velocities are necessary but net spatial displacements may not be necessary to explain the observational data.Comment: 4 pages. Accepted by A&A Letter

Balancing Minimum Spanning and Shortest Path Trees

This paper give a simple linear-time algorithm that, given a weighted digraph, finds a spanning tree that simultaneously approximates a shortest-path tree and a minimum spanning tree. The algorithm provides a continuous trade-off: given the two trees and epsilon > 0, the algorithm returns a spanning tree in which the distance between any vertex and the root of the shortest-path tree is at most 1+epsilon times the shortest-path distance, and yet the total weight of the tree is at most 1+2/epsilon times the weight of a minimum spanning tree. This is the best tradeoff possible. The paper also describes a fast parallel implementation.Comment: conference version: ACM-SIAM Symposium on Discrete Algorithms (1993

Strominger--Yau--Zaslow geometry, Affine Spheres and Painlev\'e III

We give a gauge invariant characterisation of the elliptic affine sphere equation and the closely related Tzitz\'eica equation as reductions of real forms of SL(3, \C) anti--self--dual Yang--Mills equations by two translations, or equivalently as a special case of the Hitchin equation. We use the Loftin--Yau--Zaslow construction to give an explicit expression for a six--real dimensional semi--flat Calabi--Yau metric in terms of a solution to the affine-sphere equation and show how a subclass of such metrics arises from 3rd Painlev\'e transcendents.Comment: 38 pages. Final version. To appear in Communications in Mathematical Physic

Long and short paths in uniform random recursive dags

In a uniform random recursive k-dag, there is a root, 0, and each node in turn, from 1 to n, chooses k uniform random parents from among the nodes of smaller index. If S_n is the shortest path distance from node n to the root, then we determine the constant \sigma such that S_n/log(n) tends to \sigma in probability as n tends to infinity. We also show that max_{1 \le i \le n} S_i/log(n) tends to \sigma in probability.Comment: 16 page