Structural change and productivity growth 20 years later: old problems, new opportunities. Summary

Includes bibliography

Efeito túnel multidimensional em reações nucleares

Pós-graduação em Física - IFT

TCAD approaches to multidimensional simulation of advanced semiconductor devices

Technology scaling increasingly emphasizes complexity and non-ideality of the electrical behavior of semiconductor devices and boosts interest on alternatives to the conventional planar MOSFET architecture. TCAD simulation tools are fundamental to the analysis and development of new technology generations. However, the increasing device complexity is reflected in an augmented dimensionality of the problems to be solved. The trade-off between accuracy and computational cost of the simulation is especially influenced by domain discretization: mesh generation is therefore one of the most critical steps and automatic approaches are sought. Moreover, the problem size is further increased by process variations, calling for a statistical representation of the single device through an ensemble of microscopically different instances. The aim of this thesis is to present multi-disciplinary approaches to handle this increasing problem dimensionality in a numerical simulation perspective. The topic of mesh generation is tackled by presenting a new Wavelet-based Adaptive Method (WAM) for the automatic refinement of 2D and 3D domain discretizations. Multiresolution techniques and efficient signal processing algorithms are exploited to increase grid resolution in the domain regions where relevant physical phenomena take place. Moreover, the grid is dynamically adapted to follow solution changes produced by bias variations and quality criteria are imposed on the produced meshes. The further dimensionality increase due to variability in extremely scaled devices is considered with reference to two increasingly critical phenomena, namely line-edge roughness (LER) and random dopant fluctuations (RD). The impact of such phenomena on FinFET devices, which represent a promising alternative to planar CMOS technology, is estimated through 2D and 3D TCAD simulations and statistical tools, taking into account matching performance of single devices as well as basic circuit blocks such as SRAMs. Several process options are compared, including resist- and spacer-defined fin patterning as well as different doping profile definitions. Combining statistical simulations with experimental data, potentialities and shortcomings of the FinFET architecture are analyzed and useful design guidelines are provided, which boost feasibility of this technology for mainstream applications in sub-45 nm generation integrated circuits.

A novel multidimensional geriatric screening tool in the ED: evaluation of feasibility and clinical relevance

PURPOSES Geriatric problems frequently go undetected in older patients in emergency departments (EDs), thus increasing their risk of adverse outcomes. We evaluated a novel emergency geriatric screening (EGS) tool designed to detect geriatric problems. BASIC PROCEDURES The EGS tool consisted of short validated instruments used to screen 4 domains (cognition, falls, mobility, and activities of daily living). Emergency geriatric screening was introduced for ED patients 75 years or older throughout a 4-month period. We analyzed the prevalence of abnormal EGS and whether EGS increased the number of EGS-related diagnoses in the ED during the screening, as compared with a preceding control period. MAIN FINDINGS Emergency geriatric screening was performed on 338 (42.5%) of 795 patients presenting during screening. Emergency geriatric screening was unfeasible in 175 patients (22.0%) because of life-threatening conditions and was not performed in 282 (35.5%) for logistical reasons. Emergency geriatric screening took less than 5 minutes to perform in most (85.8%) cases. Among screened patients, 285 (84.3%) had at least 1 abnormal EGS finding. In 270 of these patients, at least 1 abnormal EGS finding did not result in a diagnosis in the ED and was reported for further workup to subsequent care. During screening, 142 patients (42.0%) had at least 1 diagnosis listed within the 4 EGS domains, significantly more than the 29.3% in the control period (odds ratio 1.75; 95% confidence interval, 1.34-2.29; P<.001). Emergency geriatric screening predicted nursing home admission after the in-hospital stay (odds ratio for ≥3 vs <3 abnormal domains 12.13; 95% confidence interval, 2.79-52.72; P=.001). PRINCIPAL CONCLUSIONS The novel EGS is feasible, identifies previously undetected geriatric problems, and predicts determinants of subsequent care.

El acceso al agua de los agricultores familiares de la región pampeana : Un análisis multidimensional

Este artículo presenta, en su primera parte, el enfoque conceptual y metodológico de un proyecto de investigación-acción participativa abordado de forma interdisciplinaria. La investigación refiere a las diferentes dimensiones que condicionan el acceso al agua de los agricultores familiares en distintos sitios de la región pampeana. La problemática se define en la dinámica con los actores involucrados, considerando que el agua mediatiza las relaciones sociales -de apropiación para el riego y la producción agrícola y de otros sectores, el consumo y la eliminación de residuos- entre diferentes actores. En las últimas secciones se presentan algunas de las observaciones y reflexiones del equipo de investigación en base a los primeros avances del trabajo de campo

El acceso al agua de los agricultores familiares de la región pampeana : Un análisis multidimensional

Este artículo presenta, en su primera parte, el enfoque conceptual y metodológico de un proyecto de investigación-acción participativa abordado de forma interdisciplinaria. La investigación refiere a las diferentes dimensiones que condicionan el acceso al agua de los agricultores familiares en distintos sitios de la región pampeana. La problemática se define en la dinámica con los actores involucrados, considerando que el agua mediatiza las relaciones sociales -de apropiación para el riego y la producción agrícola y de otros sectores, el consumo y la eliminación de residuos- entre diferentes actores. En las últimas secciones se presentan algunas de las observaciones y reflexiones del equipo de investigación en base a los primeros avances del trabajo de campo

El acceso al agua de los agricultores familiares de la región pampeana : Un análisis multidimensional

Este artículo presenta, en su primera parte, el enfoque conceptual y metodológico de un proyecto de investigación-acción participativa abordado de forma interdisciplinaria. La investigación refiere a las diferentes dimensiones que condicionan el acceso al agua de los agricultores familiares en distintos sitios de la región pampeana. La problemática se define en la dinámica con los actores involucrados, considerando que el agua mediatiza las relaciones sociales -de apropiación para el riego y la producción agrícola y de otros sectores, el consumo y la eliminación de residuos- entre diferentes actores. En las últimas secciones se presentan algunas de las observaciones y reflexiones del equipo de investigación en base a los primeros avances del trabajo de campo

A guided heuristic approach to the MEG inverse problem.

There is general agreement within the scientific community in considering Biology as the science with more potential to develop in the XXI century. This is due to several reasons, but probably the most important one is the state of development of the rest of experimental and technological sciences. In this context, there are a very rich variety of mathematical tools, physical techniques and computer resources that permit to do biological experiments that were unbelievable only a few years ago. Biology is nowadays taking advantage of all these newly developed technologies, which are been applied to life sciences opening new research fields and helping to give new insights in many biological problems. Consequently, biologists have improved a lot their knowledge in many key areas as human function and human diseases. However there is one human organ that is still barely understood compared with the rest: The human brain. The understanding of the human brain is one of the main challenges of the XXI century. In this regard, it is considered a strategic research field for the European Union and the USA. Thus, there is a big interest in applying new experimental techniques for the study of brain function. Magnetoencephalography (MEG) is one of these novel techniques that are currently applied for mapping the brain activity1. This technique has important advantages compared to the metabolic-based brain imagining techniques like Functional Magneto Resonance Imaging2 (fMRI). The main advantage is that MEG has a higher time resolution than fMRI. Another benefit of MEG is that it is a patient friendly clinical technique. The measure is performed with a wireless set up and the patient is not exposed to any radiation. Although MEG is widely applied in clinical studies, there are still open issues regarding data analysis. The present work deals with the solution of the inverse problem in MEG, which is the most controversial and uncertain part of the analysis process3. This question is addressed using several variations of a new solving algorithm based in a heuristic method. The performance of those methods is analyzed by applying them to several test cases with known solutions and comparing those solutions with the ones provided by our methods.

Preliminary results of the relation between ice viscosity and water content using an inverse method

One of the outstanding problems of the modelling of temperate ice dynamics is the limited knowledge on the rheology of temperate ice and, in particular, on how the rate factor depends on the liquid water content. Though it is well known that the rate factor depends strongly on the water content, in practice the only available experimentally-based relationship is that by Duval (1977), which is only valid for water contents up to 1%. However, actual water contents found in temperate and polythermal glaciers are sometimes substantially larger.

Inverse kinematics of a humanoid robot with non-spherical hip: a hybrid algorithm approach

This paper describes an approach to solve the inverse kinematics problem of humanoid robots whose construction shows a small but non negligible offset at the hip which prevents any purely analytical solution to be developed. Knowing that a purely numerical solution is not feasible due to variable efficiency problems, the proposed one first neglects the offset presence in order to obtain an approximate “solution” by means of an analytical algorithm based on screw theory, and then uses it as the initial condition of a numerical refining procedure based on the Levenberg‐Marquardt algorithm. In this way, few iterations are needed for any specified attitude, making it possible to implement the algorithm for real‐time applications. As a way to show the algorithm’s implementation, one case of study is considered throughout the paper, represented by the SILO2 humanoid robot.

The Proper Generalized Decomposition With Application In Problems Of Dynamics

In this paper we address the new reduction method called Proper Generalized Decomposition (PGD) which is a discretization technique based on the use of separated representation of the unknown fields, specially well suited for solving multidimensional parametric equations. In this case, it is applied to the solution of dynamics problems. We will focus on the dynamic analysis of an one-dimensional rod with a unit harmonic load of frequency (ω) applied at a point of interest. In what follows, we will present the application of the methodology PGD to the problem in order to approximate the displacement field as the sum of the separated functions. We will consider as new variables of the problem, parameters models associated with the characteristic of the materials, in addition to the frequency. Finally, the quality of the results will be assessed based on an example.

Multi-valued control problems and mixture density network

We have proposed a novel robust inversion-based neurocontroller that searches for the optimal control law by sampling from the estimated Gaussian distribution of the inverse plant model. However, for problems involving the prediction of continuous variables, a Gaussian model approximation provides only a very limited description of the properties of the inverse model. This is usually the case for problems in which the mapping to be learned is multi-valued or involves hysteritic transfer characteristics. This often arises in the solution of inverse plant models. In order to obtain a complete description of the inverse model, a more general multicomponent distributions must be modeled. In this paper we test whether our proposed sampling approach can be used when considering an arbitrary conditional probability distributions. These arbitrary distributions will be modeled by a mixture density network. Importance sampling provides a structured and principled approach to constrain the complexity of the search space for the ideal control law. The effectiveness of the importance sampling from an arbitrary conditional probability distribution will be demonstrated using a simple single input single output static nonlinear system with hysteretic characteristics in the inverse plant model.

Inverse forecasting:a new approach for predictive modelling

In the last two decades there have been substantial developments in the mathematical theory of inverse optimization problems, and their applications have expanded greatly. In parallel, time series analysis and forecasting have become increasingly important in various fields of research such as data mining, economics, business, engineering, medicine, politics, and many others. Despite the large uses of linear programming in forecasting models there is no a single application of inverse optimization reported in the forecasting literature when the time series data is available. Thus the goal of this paper is to introduce inverse optimization into forecasting field, and to provide a streamlined approach to time series analysis and forecasting using inverse linear programming. An application has been used to demonstrate the use of inverse forecasting developed in this study. © 2007 Elsevier Ltd. All rights reserved.

Boundary integral equations for acoustical inverse sound-soft scattering

The shape of a plane acoustical sound-soft obstacle is detected from knowledge of the far field pattern for one time-harmonic incident field. Two methods based on solving a system of integral equations for the incoming wave and the far field pattern are investigated. Properties of the integral operators required in order to apply regularization, i.e. injectivity and denseness of the range, are proved.

Boundary-Value Problems for almost Nonlinear Singularly Perturbed Systems of Ordinary Differential Equations

A boundary-value problems for almost nonlinear singularly perturbed systems of ordinary differential equations are considered. An asymptotic solution is constructed under some assumption and using boundary functions and generalized inverse matrix and projectors.