A Higher order and stable method for the numerical integration of Random Differential Equations

Trabalho apresentado no Congresso Nacional de Matemática Aplicada à Indústria, 18 a 21 de novembro de 2014, Caldas Novas - Goiás

Otimização e análise mecânica de pastas geopoliméricas para uso em poços sujeitos à injeção cíclica de vapor

Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and thermal stability. Basic geopolymeric formulations can be found in the literature, which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21° for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3 for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204ºF (400ºC) and geopolymeric slurries are viable above 500ºF (260ºC)

Stochastic simulation of time-series models combined with geostatistics to predict water-table scenarios in a Guarani Aquifer System outcrop area, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Modeling for performance analysis of electromagnetic zero-sequence suppressor

The purpose of this work is to present a frequency domain model to demonstrate the operation of an electromagnetic arrangement for controlling the injection of zero-sequence currents in the electrical system. Considering the diversity of sequential distribution of harmonic components of a current, the device proposed can be used in the process of mitigation of zero-sequence components. This device, here called electromagnetic suppressor, consists of a blocker and filter both electromagnetic, whose joint operation can provide paths of high and low impedances that can be conveniently adjusted in order to search for a desired performance. This study presents physical considerations, mathematical modeling and computer simulations that clearly demonstrate the viability of this application as a more viable alternative in the conception of filtering systems. The performance analysis is based on the frequency response of harmonic transmittances. The efficacy of this technique in direct actions to maximize the harmonic mitigation process is demonstrated. ©2010 IEEE.

The collective memory and challenges of feminism

Includes bibliography

Information and communication technologies in the health sector: opportunities and challenges for the reduction of inequalities in Latin America and the Caribbean

Includes bibliography

The fractional and nonlinear magneto-flexible rod

This paper deals with a system involving a flexible rod subjected to magnetic forces that can bend it while simultaneously subjected to external excitations produces complex and nonlinear dynamic behavior, which may present different types of solutions for its different movement-related responses. This fact motivated us to analyze such a mechanical system based on modeling and numerical simulation involving both, integer order calculus (IOC) and fractional order calculus (FOC) approaches. The time responses, pseudo phase portraits and Fourier spectra have been presented. The results obtained can be used as a source for conduct experiments in order to obtain more realistic and more accurate results about fractional-order models when compared to the integer-order models. © Published under licence by IOP Publishing Ltd.

A single-phase single-stage buck-boost inverter intended for low power alternative energy conversion systems: Analysis, design and experimentation

This paper presents the operational analysis of the single-phase integrated buck-boost inverter. This topology is able to convert the DC input voltage into AC voltage with a high static gain, low harmonic content and acceptable efficiency, all in one single-stage. Main functionality aspects are explained, design procedure, system modeling and control, and also component requirements are detailed. Main simulation results are included, and two prototypes were implemented and experimentally tested, where its results are compared with those corresponding to similar topologies available in literature. © 2012 IEEE.

Free tools and strategies for the generation of 3D finite element meshes: Modeling of the cardiac structures

The Finite Element Method is a well-known technique, being extensively applied in different areas. Studies using the Finite Element Method (FEM) are targeted to improve cardiac ablation procedures. For such simulations, the finite element meshes should consider the size and histological features of the target structures. However, it is possible to verify that some methods or tools used to generate meshes of human body structures are still limited, due to nondetailed models, nontrivial preprocessing, or mainly limitation in the use condition. In this paper, alternatives are demonstrated to solid modeling and automatic generation of highly refined tetrahedral meshes, with quality compatible with other studies focused on mesh generation. The innovations presented here are strategies to integrate Open Source Software (OSS). The chosen techniques and strategies are presented and discussed, considering cardiac structures as a first application context. © 2013 E. Pavarino et al.

The employment situation in Latin America and the Caribbean: Advances and challenges in measuring decent work

At 6.4%, the unemployment rate for the Latin American and Caribbean region overall was the lowest for the past few decades, down from 6.7% in 2011. This is significant, in view of the difficult employment situation prevailing in other world regions. Labour market indicators improved despite modest growth of just 3.0% in the region’s economy. Even with sharply rising labour market participation, the number of urban unemployed fell by around 400,000, on the back of relatively strong job creation. Nevertheless, around 15 million are still jobless in the region. Other highlights of 2012 labour market performance were that the gender gaps in labour market participation, unemployment and employment narrowed, albeit slightly; formal employment increased; the hourly underemployment rate declined; and average wages rose. This rendering was obviously not homogenous across the region. Labour market indicators worsened again in the Caribbean countries, for example, reflecting the sluggish performance of their economies. The sustainability of recent labour market progress is also a cause for concern. Most of the new jobs in the region were created as part of a self-perpetuating cycle in which new jobs and higher real wages (and greater access to credit) have boosted household purchasing power and so pushed up domestic demand. Much of this demand is for non-tradable goods and services (and imports), which has stimulated expansion of the tertiary sector and hence its demand for labour, and many of the new jobs have therefore arisen in these sectors of the economy. This dynamic certainly has positive implications in terms of labour and distribution, but the concern is whether it is sustainable in a context of still relatively low investment (even after some recent gains) which is, moreover, not structured in a manner conducive to diversifying production. Doubt hangs over the future growth of production capacity in the region, given the enormous challenges facing the region in terms of innovation, education quality, infrastructure and productivity. As vigorous job creation has driven progress in reducing unemployment, attention has turned once again to the characteristics of that employment. Awareness exists in the region that economic growth is essential, but not in itself sufficient to generate more and better jobs. For some time, ILO has been drawing attention to the fact that it is not enough to create any sort of employment. The concept of decent work, as proposed by ILO, emphasized the need for quality jobs which enshrine respect for fundamental rights at work. The United Nations General Assembly endorsed this notion and incorporated it into the targets set in the framework of the Millennium Development Goals. This eighth issue of the ECLAC/ILO publication “The employment situation in Latin America and the Caribbean” examines how the concept of decent work has evolved in the region, progress in measuring it and the challenges involved in building a system of decent work indicators, 14 years after the concept was first proposed. Although the concept of decent work has been accompanied since the outset by the challenge of measurement, its first objective was to generate a discussion on the best achievable labour practices in each country. Accordingly, rather than defining a universal threshold of what could be considered decent work —regarding which developed countries might have almost reached the target before starting, while poor countries could be left hopelessly behind— ILO called upon the countries to define their own criteria and measurements for promoting decent work policies. As a result, there is no shared set of variables for measuring decent work applicable to all countries. The suggestion is, instead, that countries move forward with measuring decent work on the basis of their own priorities, using the information they have available now and in the future. However, this strategy of progressing according to the data available in each country tends to complicate statistical comparison between them. So, once the countries have developed their respective systems of decent work indicators, it will be also be important to work towards harmonizing them. ECLAC and ILO are available to provide technical support to this end. With respect to 2013, there is cautious optimism regarding the performance of the region’s labour markets. If projections of a slight uptick —to 3.5%— in the region’s economic growth in 2013 are borne out, labour indicators should continue to gradually improve. This will bring new increases in real wages and a slight drop of up to 0.2 percentage points in the region’s unemployment rate, reflecting a fresh rise in the regional employment rate and slower growth in labour market participation.

Report on expert group meeting on macroeconomic modelling in the Caribbean: new challenges and new directions

The purpose of the expert group meeting was to bring together modelling practitioners to share experiences and to reflect on how to overcome new and old challenges to model building in the Caribbean. As part of the rationale for such a meeting, it was argued that since a major objective of policymaking in the Caribbean was to create the conditions for growth with equity while reducing vulnerability to economic and environmental shocks, model builders must develop strategies to properly address those questions in a unified way. It was further suggested that those goals, though straightforward, required a concentrated technical effort to clarify and update understanding of the workings of Caribbean economies. The emphasis on addressing issues of growth, equity and vulnerability was urgent because Caribbean economies were at a crossroads, with major challenges to the foundations and premises on which the economies had been built.

Report on expert group workshop on macroeconomic modelling in the Caribbean: new challenges and new directions.

The purpose of the expert group meeting was to bring together modelling practitioners to share experiences and to reflect on how to overcome new and old challenges to model building in the Caribbean. As part of the rationale for such a meeting, it was argued that since a major objective of policymaking in the Caribbean was to create the conditions for growth with equity while reducing vulnerability to economic and environmental shocks, model builders must develop strategies to properly address those questions in a unified way. It was further suggested that those goals, though straightforward, required a concentrated technical effort to clarify and update understanding of the workings of Caribbean economies. The emphasis on addressing issues of growth, equity and vulnerability was urgent because Caribbean economies were at a crossroads, with major challenges to the foundations and premises on which the economies had been built.

Economic Survey of Latin America and the Caribbean 2015: Challenges in boosting the investment cycle to reinvigorate growth

The 2015 edition of the Economic Survey of Latin America and the Caribbean consists of three parts. Part I outlines the region’s economic performance in 2014 and analyses trends in the first half of 2015, as well as the outlook for the rest of the year. Part II analyses the dynamics of investment in Latin America and the Caribbean, the relationship between investment and the business cycle, the role of public investment, infrastructure gaps and the challenges in financing private investment. Part III of this publication may be accessed on the web page of the Economic Commission for Latin America and the Caribbean (http://www.cepal.org/en/node/33006). It contains the notes relating to the economic performance of the countries of Latin America and the Caribbean in 2014 and the first half of 2015, together with their respective statistical annexes, which present the main economic indicators of the countries of the region. The cut-off date for updating the statistical information in this publication was 30 June 2015.

Challenges and opportunities for knowledge organization at the intersection with information technologies

In this paper we study the intersection of Knowledge Organization with Information Technologies and the challenges and opportunities for Knowledge Organization experts that, in our view, are important to be studied and for them to be aware of. We start by giving some definitions necessary for providing the context for our work. Then we review the history of the Web, beginning with the Internet and continuing with the World Wide Web, the Semantic Web, problems of Artificial Intelligence, Web 2.0, and Linked Data. Finally, we conclude our paper with IT applications for Knowledge Organization in libraries, such as FRBR, BIBFRAME, and several OCLC initiatives, as well as with some of the challenges and opportunities in which Knowledge Organization experts and researchers might play a key role in relation to the Semantic Web.

Síntese e caracterização de filmes finos de ferrita de bismuto dopados com cálcio visando aplicação em memórias de múltiplos estados

The increasing demand for electro-electronic devices, with high performance and multi-functional and the rapid advances of the nanotechnology require the development of new methods and techniques for the production and characterization of nanostructure materials and phenomenological models to describe/to predict some of its properties. The demand for multifunctionality requires, at least, new materials, that can integrate ferroelectric and magnetic properties of high technological interest. Inside of this context, multiferroics material can be considered suitable to integrate two or more physical properties of high technological interest. It can also provides new challenges in the processes of synthesis of new materials, and development of new devices with controlling and simulation of its physical properties and modeling. For this Calcium (Ca)-doped bismuth ferrite (BiFeO3) thin films prepared by using the polymeric precursor method (PPM) were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), polarization and piezoelectric measurements.In order to study the behavior and determine which are the most important parameters to achieve the optimal property to be applied to a multiferroic materials