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Search Results: 1 - 10 of 236058 matches for " R. Garcia Diaz "
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Inductive Lusternik-Schnirelmann category in a model category
J. M. Garcia-Calcines,P. R. Garcia-Diaz
Mathematics , 2006, DOI: 10.1016/j.jpaa.2007.05.005
Abstract: We introduce the notion of inductive category in a model category and prove that it agrees with the Ganea approach given by Doeraene. This notion also coincides with the topological one when we consider the category of (well-) pointed topological spaces.
A Cluster-Based Architecture to Structure the Topology of Parallel Wireless Sensor Networks
Jaime Lloret,Miguel Garcia,Diana Bri,Juan R. Diaz
Sensors , 2009, DOI: 10.3390/s91210513
Abstract: A wireless sensor network is a self-configuring network of mobile nodes connected by wireless links where the nodes have limited capacity and energy. In many cases, the application environment requires the design of an exclusive network topology for a particular case. Cluster-based network developments and proposals in existence have been designed to build a network for just one type of node, where all nodes can communicate with any other nodes in their coverage area. Let us suppose a set of clusters of sensor nodes where each cluster is formed by different types of nodes (e.g., they could be classified by the sensed parameter using different transmitting interfaces, by the node profile or by the type of device: laptops, PDAs, sensor etc.) and exclusive networks, as virtual networks, are needed with the same type of sensed data, or the same type of devices, or even the same type of profiles. In this paper, we propose an algorithm that is able to structure the topology of different wireless sensor networks to coexist in the same environment. It allows control and management of the topology of each network. The architecture operation and the protocol messages will be described. Measurements from a real test-bench will show that the designed protocol has low bandwidth consumption and also demonstrates the viability and the scalability of the proposed architecture. Our ccluster-based algorithm is compared with other algorithms reported in the literature in terms of architecture and protocol measurements.
NAO influence on extreme winter temperatures in Madrid (Spain)
L. Prieto,R. Garcia,J. Diaz,E. Hernandez
Annales Geophysicae (ANGEO) , 2003,
Abstract: Extremely cold days (ECDs), with minimum temperatures lower than -4.6°C, have been analysed for Madrid. This threshold corresponds to the 5th percentile of the period 1963–1999. Adopting a case analysis approach, five synoptic patterns have been identified that produce these extremely low temperatures. Three of them are associated with cold air flows over the Iberian Peninsula, and the other two with a lack of significant circulation over the region. A nonlinear association with the North Atlantic Oscillation (NAO) has been identified using log-linear models. The NAO positive phase leads to an increase in the winter frequency of those synoptic patterns associated with stagnant air flow over Iberia, while those characterised by cold, northern flows do not appear to be similarly influenced. Key words. Meteorology and atmospheric dynamics (climatology; synoptic-scale meteorology; general or miscellaneous)
Certainty relations between local and nonlocal observables
R. Garcia Diaz,J. L. Romero,G. Bjork,M. Bourennane
Physics , 2005, DOI: 10.1088/1367-2630/7/1/256
Abstract: We demonstrate that for an arbitrary number of identical particles, each defined on a Hilbert-space of arbitrary dimension, there exists a whole ladder of relations of complementarity between local, and every conceivable kind of joint (or nonlocal) measurements. E.g., the more accurate we can know (by a measurement) some joint property of three qubits (projecting the state onto a tripartite entangled state), the less accurate some other property, local to the three qubits, become. We also show that the corresponding complementarity relations are particularly tight for particles defined on prime dimensional Hilbert spaces.
Compound and scale mixture of vector and spherical matrix variate elliptical distributions
Jose A. Diaz-Garcia,R. Gutierrez-Jaimez
Mathematics , 2009,
Abstract: Several matrix variate hypergeometric type distributions are derived. The compound distributions of left-spherical matrix variate elliptical distributions and inverted hypergeometric type distributions with matrix arguments are then proposed. The scale mixture of left-spherical matrix variate elliptical distributions and univariate inverted hypergeometric type distributions is also derived as a particular case of the compound distribution approach.
Doubly noncentral singular matrix variate beta distributions
J. A. Diaz-Garcia,R. Gutierrez-Jaimez
Mathematics , 2009,
Abstract: In this paper, we determine the density functions of doubly noncentral singular matrix variate beta type I and II distributions.
Bimatrix variate generalised beta distributions
J. A. Diaz-Garcia,R. Gutierrez-Jaimez
Mathematics , 2009,
Abstract: In this paper, we extend the study of bivariate generalised beta type I and II distributions to the matrix variate case.
Doubly singular matrix variate beta type I and II and singular inverted matricvariate $t$ distributions
J. A. Diaz-Garcia,R. Gutierrez-Jaimez
Mathematics , 2009,
Abstract: In this paper, the densities of the doubly singular beta type I and II distributions are found, and the joint densities of their corresponding nonzero eigenvalues are provided. As a consequence, the density function of a singular inverted matricvariate t distribution is obtained.
Effect of Management Practices on Soil Microstructure and Surface Microrelief
R. Garcia Moreno,T. Burykin,M. C. Diaz Alvarez,J. W. Crawford
Applied and Environmental Soil Science , 2012, DOI: 10.1155/2012/608275
Abstract: Soil surface roughness (SSR) and porosity were evaluated from soils located in two farms belonging to the Plant Breeding Institute of the University of Sidney. The sites differ in their soil management practices; the first site (PBI) was strip-tilled during early fall (May 2010), and the second site (JBP) was under power harrowed tillage at the end of July 2010. Both sites were sampled in mid-August. At each location, SSR was measured for three 1?m2 subplots using shadow analysis. To evaluate porosity and aggregation, soil samples were scanned using X-ray computed tomography with 5?μm resolution. The results show a strong negative correlation between SSR and porosity, 20.13% SSR and 41.38% porosity at PBI versus 42.00% SSR and 18.35% porosity at JBP. However, soil images show that when soil surface roughness is higher due to conservation and soil management practices, the processes of macroaggregation and structural porosity are enhanced. Further research must be conducted on SSR and porosity in different types of soils, as they provide complementary information on the evaluation of soil erosion susceptibility. 1. Introduction Soil surface roughness (SSR), which describes the microvariations in soil elevations primarily resulting from tillage practices and textural porosity, is one of the major factors affecting wind and water erosion [1–4]. SSR is a direct indicator of the degradation of soil microstructure, which is mainly due to a loss of physical, chemical, and biological properties [1, 2, 5]. In this case, SSR is closely related to erosion, which is the primary cause for the loss of soil structure and organic matter, and it leads to a decrease in soil productivity and reduced fauna diversity [4, 6]. SSR promotes soil biota activity, which plays an important role in the rehabilitation of sealed soil surfaces and the restructuring of soils, particularly after compaction events [7]. SSR is mainly affected by management practices and, depending on the techniques used, SSR can increase the number and variability of microorganisms through the improvement of soil porosity and flow water in the vadose zone [8]. The increase in microorganism activity is very important in most biogeochemical cycles within soils because it improves the physical and biological state of the soil [4, 9, 10]. Thus, tillage influences the development of different types of microorganisms. Techniques that conserve pore systems tend to enhance the activity of microorganisms and conserve the biota that are beneficial to the development of crops [7, 11, 12]. However, the study of soil
Effect of Urea Treatment on Chemical Composition and Digestion of Cenchrus ciliaris and Cynodon dactylon Hays and Zea mays Residues
G. R. Ramirez,J. C. Aguilera Gonzalez,G. Garcia Diaz,A. M. Nunez Gonzalez
Journal of Animal and Veterinary Advances , 2012,
Abstract: Buffelgrass (Cenchrus ciliaris), bermudagrass (Cynodon dactylon) hays, corn stover and corn cobs (Zea mays), with a moisture content of 50%, were ammoniated with feed grade urea at 0, 4.5 and 6.0% DM. Ammonia-treated forages were stored in plastic bags during 21 days. Crude Protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Acid Detergent Lignin (ADL), hemicellulose and cellulose were determined. The rate and extent of dry matter and NDF loss was estimated using the nylon bag technique. Rumen cannulated PelibueyxRambouillet sheep were used to incubate the nylon bags. During the trial, sheep were fed ad libitum 70% sorghum Sudan hay and 30% alfalfa hay. The CP content in buffelgrass hay (4.4, 9.9 and 16.3%, respectively) bermudagrass hay (6.2, 13.8, 22.9%), corn stover (7.4, 12.3, 15.6%) and corn cobs (3.0, 11.2, 16.7%) increased as urea treatment augmented. However, NDF was reduced as treatment increased (80.6, 74.7, 75.8; 79.9, 77.8, 75.5; 75.4, 66.0, 69.3; 92.5, 85.6 and 88.4%, respectively). Similar, pattern as NDF was found in hemicellulose content. Effective Degradability of Dry Matter (EDDM) and NDF (EDNDF) in buffelgrass hay (26, 42, 31; 20, 33 and 24%, respectively) and corn cobs 23, 36, 32; 25, 34, 31%, respectively) increased quadratically (p< 0.01) as urea treatment augmented. Whereas, EDDM and EDNDF in bermudagrass hay (30, 38, 39; 25, 32, 33%, respectively) and corn stover (42, 48, 53; 38, 41, 45%, respectively) increased linearly (p< 0.01). Urea ammoniation altered the chemical composition and digestibility of forages improving their nutritive value.
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