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Search Results: 1 - 10 of 6006 matches for " Guillermo Jajamovich "
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Buenos Aires, sus transformaciones urbanas y la perspectiva de los investigadores: aproximaciones, críticas y problemas en torno a su dimensión internacional
Guillermo Jajamovich
Urbe : Revista Brasileira de Gest?o Urbana , 2009,
Abstract: El artículo analiza el tratamiento de las transformaciones urbanas en Buenos Aires en la producción académica centrándose alrededor de diversas posturas sobre el carácter internacional de las mismas. Se recorre una serie de investigadores prestando atención a los aportes realizados, los enfoques utilizados y al modo en que cada uno de los mismos construyen objetos diferentes que se recortan contra imágenes de lo que debiera ser la ciudad, intentando, mediante un trabajo interpretativo, leer políticas implícitas, o cierta dimensión operativa, en cada una de estas. Finalizando el recorrido, se puntualiza un aspecto poco explorado: la posibilidad de enfocar el análisis de Buenos Aires a partir de sus múltiples contactos con otras experiencias urbanas en la región, dejando de lado conceptos como el de globalización sin por eso perder de vista la pertinencia de abarcar escalas de análisis de carácter supranacional.
Políticas urbanas en un contexto de dictadura militar. Algunos interrogantes a partir de Buenos Aires (1976-1983)
Jajamovich Guillermo,Menazzi Luján
Bitácora Urbano-Territorial , 2012,
Abstract: El presente artículo busca reflexionar acerca del accionar de la última dictadura militar argentina sobre la ciudad de Buenos Aires. Así, se analizarán las políticas urbanas de la dictadura en general profundizando, en particular, en ciertas intervenciones, tales como los fallidos intentos de traslado del Mercado Nacional de Hacienda y el Plan de Autopistas Urbanas, que supuso una serie de demoliciones y expropiaciones en un área que sería testigo al poco tiempo de medidas de protección patrimonial. Estas intervenciones, entre otras, suponen ciertas fisuras o contradicciones que nos alejan de entender el accionar de la dictadura como algo unívoco. En ese sentido se se alan los distintos organismos estatales desde donde se producen estas intervenciones, las distintas perspectivas y lógicas de intervención y los efectos en ocasiones contradictorios sobre el territorio. A partir del análisis de estas intervenciones se problematizarán dos aspectos: la idea que supone un accionar unívoco, sin fisuras ni disputas internas por parte de la dictadura, y la imagen de un gobierno dictatorial omnipotente, sin actores sociales con capacidad de oponerse a sus distintas iniciativas.
Quantitative Liver MRI Combining Phase Contrast Imaging, Elastography, and DWI: Assessment of Reproducibility and Postprandial Effect at 3.0 T
Guido H. Jajamovich, Hadrien Dyvorne, Claudia Donnerhack, Bachir Taouli
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097355
Abstract: Purpose To quantify short-term reproducibility (in fasting conditions) and postprandial changes after a meal in portal vein (PV) flow parameters measured with phase contrast (PC) imaging, liver diffusion parameters measured with multiple b value diffusion-weighted imaging (DWI) and liver stiffness (LS) measured with MR elastography (MRE) in healthy volunteers and patients with liver disease at 3.0 T. Materials and Methods In this IRB–approved prospective study, 30 subjects (11 healthy volunteers and 19 liver disease patients; 23 males, 7 females; mean age 46.5 y) were enrolled. Imaging included 2D PC imaging, multiple b value DWI and MRE. Subjects were initially scanned twice in fasting state to assess short-term parameter reproducibility, and then scanned 20 min. after a liquid meal. PV flow/velocity, LS, liver true diffusion coefficient (D), pseudodiffusion coefficient (D*), perfusion fraction (PF) and apparent diffusion coefficient (ADC) were measured in fasting and postprandial conditions. Short-term reproducibility was assessed in fasting conditions by measuring coefficients of variation (CV) and Bland-Altman limits of agreement. Differences in MR metrics before and after caloric intake and between healthy volunteers and liver disease patients were assessed. Results PV flow parameters, D, ADC and LS showed good to excellent short-term reproducibility in fasting state (CV <16%), while PF and D* showed acceptable and poor reproducibility (CV = 20.4% and 51.6%, respectively). PV flow parameters and LS were significantly higher (p<0.04) in postprandial state while liver diffusion parameters showed no significant change (p>0.2). LS was significantly higher in liver disease patients compared to healthy volunteers both in fasting and postprandial conditions (p<0.001). Changes in LS were significantly correlated with changes in PV flow (Spearman rho = 0.48, p = 0.013). Conclusions Caloric intake had no/minimal/large impact on diffusion/stiffness/portal vein flow, respectively. PC MRI and MRE but not DWI should be performed in controlled fasting state.
Optimal Joint Target Detection and Parameter Estimation By MIMO Radar
Ali Tajer,Guido H. Jajamovich,Xiaodong Wang,George V. Moustakides
Mathematics , 2009, DOI: 10.1109/JSTSP.2010.2040104
Abstract: We consider multiple-input multiple-output (MIMO) radar systems with widely-spaced antennas. Such antenna configuration facilitates capturing the inherent diversity gain due to independent signal dispersion by the target scatterers. We consider a new MIMO radar framework for detecting a target that lies in an unknown location. This is in contrast with conventional MIMO radars which break the space into small cells and aim at detecting the presence of a target in a specified cell. We treat this problem through offering a novel composite hypothesis testing framework for target detection when (i) one or more parameters of the target are unknown and we are interested in estimating them, and (ii) only a finite number of observations are available. The test offered optimizes a metric which accounts for both detection and estimation accuracies. In this paper as the parameter of interest we focus on the vector of time-delays that the waveforms undergo from being emitted by the transmit antennas until being observed by the receive antennas. The analytical and empirical results establish that for the proposed joint target detection and time-delay estimation framework, MIMO radars exhibit significant gains over phased-array radars for extended targets which consist of multiple independent scatterers. For point targets modeled as single scatterers, however, the detection/estimation accuracies of MIMO and phased-array radars for this specific setup (joint target detection and time-delay estimation) are comparable.
Joint Detection and Estimation: Optimum Tests and Applications
George V. Moustakides,Guido H. Jajamovich,Ali Tajer,Xiaodong Wang
Statistics , 2011,
Abstract: We consider a well defined joint detection and parameter estimation problem. By combining the Baysian formulation of the estimation subproblem with suitable constraints on the detection subproblem we develop optimum one- and two-step test for the joint detection/estimation case. The proposed combined strategies have the very desirable characteristic to allow for the trade-off between detection power and estimation efficiency. Our theoretical developments are then applied to the problems of retrospective changepoint detection and MIMO radar. In the former case we are interested in detecting a change in the statistics of a set of available data and provide an estimate for the time of change, while in the latter in detecting a target and estimating its location. Intense simulations demonstrate that by using the jointly optimum schemes, we can experience significant improvement in estimation quality with small sacrifice in detection power.
An Indoor Radon Survey in Three Different Climate Regions in Mexico, and the Influence of Climate in the Obtained Values  [PDF]
Guillermo Espinosa, Richard Gammage
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.29133
Abstract: In this paper we present the results of a survey of indoor radon concentration levels in Mexico. In order to investigate whether differences in climate translate into significant differences in indoor radon concentrations, the country was divided into three climate regions: the northern semi-desert region, the central semitropical region and the southern tropical region. The survey was carried out using nuclear track methodology. The dosimeters employed for the survey were based on the passive closed-end cup device, developed at the Physics Institute of the National Autonomous University of Mexico, and used PADC as detector material. A well-established protocol for chemically etching and reading the detectors was followed. Average annual temperatures differ between regions (from 15℃ to 28℃) but vary relatively little within each region. Atmospheric temperature is one of the most important factors which need to be considered when carrying out a survey of indoor radon concentrations because temperature largely determines building ventilation habits, and ventilation habits are known to have significant effects on indoor radon concentrations. Other factors, including building construction materials, architectural styles, geological and hydrological characteristics, and seismicity, vary from region to region and within each region. In each of the three regions low levels of indoor radon (from 37 to 179 Bq·m-3) were found.
The Flypaper and Teflon Effects: Evidence from China  [PDF]
Lyoe Lee, Guillermo Vuletin
Modern Economy (ME) , 2012, DOI: 10.4236/me.2012.37103
Abstract: In this paper, we analyze how public spending responds to income and intergovernmental fiscal transfer shocks in China. Similar to federations around the world, we find the flypaper effect at the provincial level since the country became a de facto federation in 1980. Before 1980 we find what we define as the teflon effect at the central government level. We rationalize the latter regularity using collection costs/distortionary taxation arguments
Modeling Walking with an Inverted Pendulum Not Constrained to the Sagittal Plane. Numerical Simulations and Asymptotic Expansions  [PDF]
Guillermo H. Goldsztein
Applied Mathematics (AM) , 2017, DOI: 10.4236/am.2017.81006
Abstract: Inverted pendulum models are commonly used to study the bio-mechanics of biped walkers. In its simplest form, the inverted pendulum consists of a point mass attached to two straight mass-less legs. Most works constrain the motion of the mass to the sagittal plane, i.e. the plane perpendicular to the ground that contains the direction toward the biped is walking. In this article, we remove this constrain to study the oscillations, the mass experiences in the direction perpendicular to the sagittal plane as the biped walks. While small, these lateral oscillations are unavoidable and of importance in the understanding of balance and stability of walkers, as well as walkers induced oscillations in pedestrian bridges.
Some relationships between the geometry of the tangent bundle and the geometry of the Riemannian base manifold
Guillermo Henry,Guillermo Keilhauer
Mathematics , 2009,
Abstract: We compute the curvature tensor of the tangent bundle of a Riemannian manifold endowed with a natural metric and we get some relationships between the geometry of the base manifold and the geometry of the tangent bundle.
Fracture Response of Reinforced Concrete Deep Beams Finite Element Investigation of Strength and Beam Size  [PDF]
Guillermo A. Riveros, Vellore Gopalaratnam
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.411212
Abstract: This article presents a finite element analysis of reinforced concrete deep beams using nonlinear fracture mechanics. The article describes the development of a numerical model that includes several nonlinear processes such as compression and tension softening of concrete, bond slip between concrete and reinforcement, and the yielding of the longitudinal steel reinforcement. The development also incorporates the Delaunay refinement algorithm to create a triangular topology that is then transformed into a quadrilateral mesh by the quad-morphing algorithm. These two techniques allow automatic remeshing using the discrete crack approach. Nonlinear fracture mechanics is incorporated using the fictitious crack model and the principal tensile strength for crack initiation and propagation. The model has been successful in reproducing the load deflections, cracking patterns and size effects observed in experiments of normal and high-strength concrete deep beams with and without stirrup reinforcement.
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