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Havana, Cuba

The chemical stabilization is one of the techniques that are used for the improvement of soils, using chemical substances that modify its characteristics. In Cuba an investigation is developed that leaves of the creation of a procedure of stabilization of soils using quaternary salts of ammonium, that It knows as ROCAMIX, that has as main advantages its economy and simplicity in its employment, besides getting the resistance increment and permeability reduction in the soils. In the article it shows up the way in that the quaternary salts produce the changes in the soils, as well as the modifications of the physical and mechanical properties of two types of stabilized soils with this system, comparing the properties of the soil in their natural state and after having improved, as well as the influence of the compaction energy and the evolution of the characteristics of the stabilized soils in the time. Source


Vilalta G.,CARTIF Centro Tecnologico | Nieto F.,CARTIF Centro Tecnologico | Vaquero C.,University of Valladolid | Vilalta J.A.,ISPJAE
World Academy of Science, Engineering and Technology | Year: 2010

Abdominal aortic aneurysms rupture (AAAs) is one of the main causes of death in the world. This is a very complex phenomenon that usually occurs "without previous warning". Currently, criteria to assess the aneurysm rupture risk (peak diameter and growth rate) can not be considered as reliable indicators. In a first approach, the main geometric parameters of aneurysms have been linked into five biomechanical factors. These are combined to obtain a dimensionless rupture risk index, RI(t), which has been validated preliminarily with a clinical case and others from literature. This quantitative indicator is easy to understand, it allows estimating the aneurysms rupture risks and it is expected to be able to identify the one in aneurysm whose peak diameter is less than the threshold value. Based on initial results, a broader study has begun with twelve patients from the Clinic Hospital of Valladolid-Spain, which are submitted to periodic follow-up examinations. Source


Garcia J.A.,University of Cantabria | Cabria L.,University of Cantabria | Marante R.,University of Cantabria | Rizo L.,ISPJAE | Mediavilla A.,University of Cantabria
Progress in Electromagnetics Research | Year: 2010

A zero-bias dual-mode mixing antenna for wireless transponders is proposed in this paper. Designed over an Enhancement-mode Pseudomorphic HEMT (E-PHEMT), the mixer takes advantage of the device nonlinear characteristics around cold operation. Simple closed form expressions, obtained from time-varying circuit analysis, predict good conversion efficiency in two different operating modes without requiring DC bias. For validation, a lab prototype has been implemented and tested, to be finally integrated in a compact active printed antenna suitable for wireless sensor networks or other radio frequency identification (RFID) applications. Source


Arias-Laso S.,ISPJAE | Diago-Cisneros L.,University of Habana
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

Events of giant conductance and anomalies of the phase transmission time for holes are theoretically investigated within the multicomponent scattering approach. Based on this model, new analytical expressions for unitarity relations in the uncoupled hole transport are obtained and directly applied to study the behavior of the conductance and the phase transmission time in a double barrier resonant tunneling (DBRT) and a superlattice GaAs-cladding layer/(AlAs/GaAs) n/GaAs-cladding layer. Clear-signature evidences of giant conductance phenomena for hole transmission without valence-band mixing through a DBRT and a superlattice were found. The giant conductance effect losses robustness by manipulating the number of superlattice layers and by including the valence-band particles coupling as well. Phase time through the heterostructure exhibits extremal dependencies in the gaps and in the barriers, as those reported before for electrons. We have detected an earlier arrival phase time for the propagation of both flavors of holes within the barrier, in the order of few tenths of picoseconds. An appealing filter-like effect is presented, whenever a selective confinement strength arises independently for both flavors of holes in the uncoupled regime. Our results also prescribe noticeable evidences for both uncoupled and coupled hole fluxes, similar to those foretold by Hartman, upon transmission of electrons through opaque barriers. © 2011 Elsevier B.V. Source


Torres A.E.,ISPJAE | Marante F.,ISPJAE | Tazon A.,University of Cantabria | Vassal'Lo J.,Antenna Technology Group
AEU - International Journal of Electronics and Communications | Year: 2015

We present a novel feeding system for microstrip radiators which is based on electromagnetic coupling. The effects of the antenna's key design parameters have been studied and discussed. This new feeding system was found to be very simple and useful in the design of flat arrays and reflectarrays using microstrip patches. A novel circularly polarized patch radiator fed from only one input line and based on the proposed feeding system is also presented in this paper. The result of the developed prototype in axial ratio bandwidth is double that obtained with a typical microstrip patch fed from two inputs. © 2015 Elsevier GmbH. All rights reserved. Source

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