CAPTURA. Repositorio Academico de la Universidad de Chile
(5.176 recursos)
Captura almacena y conserva la producción de conocimiento generado por docentes e investigadores de la Universidad de Chile, y la hace visible desde los portales académicos internacionales.
Mostrando recursos 1 - 20 de 555
1.
Compositional variations of syntectonic white-mica in low-grade ignimbritic mylonite - Arancibia, G.; Morata, Diego
The Silla del Gobernador Shear Zone (SGSZ), Coastal Range of central Chile (32 degrees S), is a low-grade mylonite generated from a Triassic acidic ignimbritic protolith. Different microstructures (e.g. quarter mats and pressure shadow structures) associated with pressure solution and solution transfer processes and well-preserved porphyroclasts can be observed. White-mica generation appears to be favoured by reaction-softening from dissolved quartz and feldspar porphyroclasts. According to the mylonite fabrics three different types of white-mica can be established (A, B and C) representing mylonites with evidences of relatively low, intermediate and high strain conditions. Deformation mechanisms suggest low-grade (350-400 degrees C) conditions...
2.
Space-efficient construction of LZ-index - Arroyuelo, Diego; Navarro, Gonzalo
A compressed full-text self-index is a data structure that replaces a text and in addition gives indexed access to it, while taking space proportional to the compressed text size. The LZ-index, in particular, requires 4uH(k)(1 + o(1)) bits of space, where u is the text length in characters and H-k is its k-th order empirical entropy, Although in practice the LZ-index needs 1.0-1.5 times the text size, its construction requires Much more main memory (around 5 times the text size), which limits its applicability to large texts. In this paper we present a practical space-efficient algorithm to construct LZ-index, requiring...
3.
Decomposition and reconstruction of multidimensional signals using polyharmonic pre-wavelets - Bacchelli, Bárbara; Bozzini, Mira; Rabut, Christophe; Varas, María-Leonor
In this paper, we build a multidimensional wavelet decomposition based on polyharmonic B-splines. The prewavelets are polyharmonic splines and so not tensor products of univariate wavelets. Explicit construction of the filters specified by the classical dyadic scaling relations is given and the decay of the functions and the filters is shown. We then design the decomposition/recomposition algorithm by means of downsampling/upsampling and convolution products.
4.
A global algorithm for nonlinear semidefinite programming - Correa, Rafael; Ramírez C., Héctor
In this paper we propose a global algorithm for solving nonlinear semidefinite programming problems. This algorithm, inspired by the classic SQP (sequentially quadratic programming) method, modifies the S-SDP (sequentially semidefinite programming) local method by using a nondifferentiable merit function combined with a line search strategy.
5.
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile - Belmar, Mauricio; Morata, Diego
Triassic-Jurassic volcano-sedimentary sequences in the Coastal Range of central Chile (34 degrees 45/35 degrees 20'S) from the Vichuquen-Tilicura and Hualane-Gualleco basins display metamorphic assemblages indicative of very low-grade conditions. Triassic and Lower Jurassic metapelites achieved anchizonal conditions (IC, b(o), coal-rank and fluid inclusions data: P approximate to 1.3, T approximate to 190) at 181-184 Ma, under geothermal gradient of approximate to 35 degrees C km(-1) during extensional geodynamic conditions. Nevertheless, in stratigraphically higher mafic volcanic sequences, of Middle to Late Jurassic age, the presence of chlorite (Xc =0.98-0.99), three types of epidote (XFe3+ = 41.14 +/- 0.90, 30.08 +/- 1.53...
6.
Semi-classical limit for radial non-linear Schrodinger equation - Castro, Rodrigo; Felmer Aichele, Patricio L.
We consider the nonlinear Schrodinger equation
epsilon(2)Delta u - V (x) u + | u|(p-1) u = 0, x is an element of R-N,
with superlinear and subcritical nonlinearity. Assuming that the potential is radially symmetric we find radial sign-changing solutions of the equation that concentrate in a ball, as the parameter e goes to zero. We study the asymptotic profile of these highly oscillatory solutions, completely characterizing their behavior by means of an envelope function.
7.
Condensation of classical nonlinear waves - Connaughton, Colm; Josserand, Christophe; Picozzi, Antonio; Pomeau, Yves; Rica, Sergio
We study the formation of a large-scale coherent structure (a condensate) in classical wave equations by considering the defocusing nonlinear Schrodinger equation as a representative model. We formulate a thermodynamic description of the classical condensation process by using a wave turbulence theory with ultraviolet cutoff. In three dimensions the equilibrium state undergoes a phase transition for sufficiently low energy density, while no transition occurs in two dimensions, in complete analogy with standard Bose-Einstein condensation in quantum systems. On the basis of a modified wave turbulence theory, we show that the nonlinear interaction makes the transition to condensation subcritical. The theory...
8.
On the consistency of the indirect lognormal correction - Emery, Xavier
The indirect lognormal correction is a change-of-support model commonly used in geostatistical applications when dealing with additive variables, for which the upscaling amounts to arithmetic averaging. It was designed as a generalization of the lognormal correction that states the permanence of lognormality, but so far its internal consistency has not been proven in the general case. After a recall of the theoretical conditions that change-of-support models must honor, the concept of conventional income is introduced and used to establish the mathematical consistency of the indirect lognormal correction. However, the suitability of this model is questionable in many situations, in particular...
9.
Properties and limitations of sequential indicator simulation - Emery, Xavier
The sequential indicator algorithm is a widespread geostatistical simulation technique that relies on indicator (co)kriging and is applicable to a wide range of datasets. However, such algorithm comes up against several limitations that are often misunderstood. This work aims at highlighting these limitations, by examining what are the conditions for the realizations to reproduce the input parameters (indicator means and correlograms) and what happens with the other parameters (other two-point or multiple-point statistics). Several types of random functions are contemplated, namely: the mosaic model, random sets, models defined by multiple indicators and isofactorial models. In each case, the conditions for...
10.
Testing the correctness of the sequential algorithm for simulating Gaussian random fields - Emery, Xavier
The sequential algorithm is widely used to simulate Gaussian random fields. However, a rigorous application of this algorithm is impractical and some simplifications are required, in particular a moving neighborhood has to be defined. To examine the effect of such restriction on the quality of the realizations, a reference case is presented and several parameters are reviewed, mainly the histogram, variogram, indicator variograms, as well as the ergodic fluctuations in the first and second-order statistics. The study concludes that, even in a favorable case where the simulated domain is large with respect to the range of the model, the realizations...
11.
Positive radial solutions to a 'semilinear' equation involving the Pucci's operator - Felmer Aichele, Patricio L.; Quaas, Alexander
In this article we prove existence of positive radially symmetric solutions for the nonlinear elliptic equation M-lambda,Delta(+)(D(2)u) - gammau + f(u) = 0 in B-R, u = 0 on partial derivativeB(R),
where M-lambda,Delta(+) denotes the Pucci's extremal operator with parameters 0
12.
Lime-concentrate roasting studies - effect of activated limestone - Riveros, Gabriel; Marín, Tanai; Puga, Carlos
The roasting in air of pellets consisting of copper-iron sulphides and limestone and activated limestone has been investigated to explore the possibility of developing a metal production process that eliminates sulphur dioxide gas emissions. The effects of pellet porosity, sulphide: limestone ratio, pellet sizes and temperature on reaction kinetics were investigated. Thermogravimetry was carried out under air atmosphere. The weight gain of pelletized samples was used to identify and study the phases present in the reaction products.
The experimental results indicated that at 500 degreesC using activated limestone, a completely reacted pellet can be produced in about 50 min with very...
13.
Thermodynamics of a dilute Bose gas with condensate - Rica, Sergio
The partition function of a dilute Bose gas with repulsive interaction, fixed number of particles and in the presence of a condensate is computed up to first order in the interactions. An equilibrium condition appears for the fraction of particles in the condensate and. the chemical potential of the particles. We show that for a dilute gas the Bose-Einstein transition is not of second order. Moreover, the thermodynamical quantities obtained may look different from those in the literature, because the chemical potential enters in a nontrivial way in the quasi particle spectrum.
14.
Environmental assessment of copper-gold-mercury mining in the Andacollo and Punitaqui districts, northern Chile - Higueras, Pablo; Oyarzún, Roberto; Oyarzún, Jorge; Maturana, Hugo; Lillo, Javier; Morata, Diego
The Coquimbo region has been one of the richest producers of Cu, Au and Hg in Chile, and some of the deposits have been mined almost continuously since the 16th century. To assess the potential environmental contamination in this region, the authors measured the concentration of Cu, As, Cd, Zn and Hg in samples of stream and mine waters, stream sediments, soils, flotation tailings, and mine wastes in the Andacollo (Cu, An, Hg) and Punitaqui (Cu-Au, Hg) districts. The concentration of Hg in the atmosphere in these districts were also measured. Although contamination is strongly controlled by the ore in...
15.
Discovering geochemical patterns using self-organizing neural networks: a new perspective for sedimentary provenance analysis - Lacassie, Juan Pablo; Roser, Barry; Ruiz del Solar, Javier; Hervé, Francisco
An unsupervised neural network technique, Growing Cell Structures (GCS), was used to visualize geochemical differences between sandstones of four different sedimentary provenance groups: P1 (mafic), P2 (intermediate), P3 (felsic), and P4 (recycled). Multidimensional data of four sandstone data sets comprising major elements, log-normalized major elements, trace elements, and high field strength elements (HFSE) were projected into colored two-dimensional maps that can be visually and quantitatively interpreted. The cluster structure and variable distributions produced show that each sedimentary provenance group can be distinguished in the neural maps according to a unique combination of major or trace element concentrations. In these terms,...
16.
Modeling of subduction components in the Genesis of the Meso-Cenozoic igneous rocks from the South Shetland Arc, Antarctica - Machado, Adriane; Chemale, Farid Jr.; Conceicao, Rommulo V.; Kawaskita, Koji; Morata, Diego; Oteíza, Orlando; Van Schmus, William
Isotope data and trace elements concentrations are presented for volcanic and plutonic rocks from the Livingston, Greenwich, Robert, King George and Ardley islands (South Shetland arc, Antarctica). These islands were formed during subduction of the Phoenix Plate under the Antarctica Plate from Cretaceous to Tertiary. Isotopically (Sr-87/Sr-86), ratios vary from 0.7033 to 0.7046 and (Nd-143/Nd-144)(o) ratios from 0.5127 to 0.5129. epsilon Nd values vary from +2.71 to +7.30 that indicate asthenospheric mantle source for the analysed samples. Pb-208/Pb-204 ratios vary from 38.12 to 38.70, Pb-207/Pb-204 ratios are between 15.49 and 15.68, and Pb-206/Pb-204 from 18.28 to 18.81. The South Shetland...
17.
Average complexity of exact and approximate multiple string matching - Navarro, Gonzalo; Fredriksson, Kimmo
We show that the average number of characters examined to search for r random patterns of length m in a text of length n over a uniformly distributed alphabet of size a cannot be less than Omega(n log(sigma)(rm)/m). When we permit up to k insertions, deletions, and/or substitutions of characters in the occurrences of the patterns, the lower bound becomes Omega(n(k + log(sigma)(rm))/m). This generalizes previous single-pattern lower bounds of Yao (for exact matching) and of Chang and Marr (for approximate matching), and proves the optimality of several existing multipattern search algorithms.
18.
Pattern matching - Navarro, Gonzalo
An important subtask of the pattern discovery process is pattern matching, where the pattern sought is already known and we want to determine how often and where it occurs in a sequence. In this paper we review the most practical techniques to find patterns of different kinds. We show how regular expressions can be searched for with general techniques, and how simpler patterns can be dealt with more simply and efficiently. We consider exact as well as approximate pattern matching. Also we cover both sequential searching, where the sequence cannot be preprocessed, and indexed searching, where we have a data...
20.
Magnetic fabrics and compositional evidence for the construction of the Caleu pluton by multiple injections, Coastal Range of central Chile - Parada, Miguel; Roperch, Pierrick; Guiresse, Claudio; Ramírez, Ernesto
The Caleu pluton, which is located in the Coastal Range of central Chile, consists of three N-S elongated lithologic zones which define an across-pluton compositional variation characterized by a westward increase in SiO2 content, the Gabbro-Diorite (GDZ), Tonalite (TZ) and Granodiorite (GZ) Zones. A total of 547 cores were drilled at 68 sites within the different zones to carry out magnetic fabric and paleomagnetic studies. The highest values of magnetic susceptibility and remanent magnetization are found in the GDZ (0.04-0.1 SI), whereas the lowest values are observed in the GZ (0.01-0.02 SI). This is consistent with the significant decrease in...
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