Coordenação no sistema agroindustrial da borracha natural : um estudo das relações entre produtores rurais e usinas beneficiadoras paulistas

O enfoque da Nova Economia Institucional é utilizado no estudo de sistemas agroindustriais brasileiros, mas ainda há poucos trabalhos sobre as relações entre produtores rurais e indústrias processadoras. O objetivo deste estudo é aferir o alinhamento das características das transações com os modos de governança adotados na comercialização de borracha natural entre produtores rurais e indústrias de beneficiamento primário. Busca-se confrontar os resultados com as previsões da teoria da Economia dos Custos de Transação, que prevê a adoção da governança mais eficiente, contingenciada ao ambiente transacional. Esta pesquisa utiliza um enfoque pioneiro para o setor. A primeira parte consiste na exploração qualitativa das transações entre produtores rurais e usinas beneficiadoras e na descrição dos elementos que compõe o sistema agroindustrial da borracha natural no Estado de São Paulo. Os resultados desta etapa são utilizados para refinar as hipóteses da etapa quantitativa, que relacionam os modos de governança adotados aos investimentos em ativos específicos, como o plantio de seringueiras, à frequência, à incerteza e à assistência técnica associadas à transação. Os resultados, apesar das limitações devido ao tamanho pequeno da amostra, sugerem que a quantidade de borracha comercializada influi positivamente na adoção de modos de governança mais coordenados e que a recorrência das transações provavelmente está associada a contratos relacionais. A hipótese da endogeneidade é rejeitada.

Avaliação e monitoramento de políticas públicas: criação de um modelo sistêmico aplicado ao Instituto de Assistência Técnica e Extensão Rural do Rio Grande do Norte (EMATER-RN)

The nature of this thesis is interventionist and aims to create an alternative on how to control and evaluate the public policies implementation developed at the Institute for Technical Assistance and Rural Extension of Rio Grande do Norte State. The cenarium takes place in a public institution , classified as a municipality that belongs to the Rio Grande do Norte government and adopts the design science research methodology , where it generates a set of artifacts that guide the development of a computerized information system . To ensure the decisions, the literature was reviewed aiming to bring and highlight concepts that will be used as base to build the intervention. The use of an effective methodology called Iconix systems analysis , provides a software development process in a short time . As a result of many artifacts created by the methodology there is a software computer able of running on the Internet environment with G2C behavior, it is suggested as a management tool for monitoring artifacts generated by the various methods. Moreover, it reveals barriers faced in the public companies environment such as lack of infrastructure , the strength of the workforce and the executives behavior

Alternative parameters for the continuation power flow method

The conventional Newton's method has been considered inadequate to obtain the maximum loading point (MLP) of power systems. It is due to the Jacobian matrix singularity at this point. However, the MLP can be efficiently computed through parameterization techniques of continuation methods. This paper presents and tests new parameterization schemes, namely the total power losses (real and reactive), the power at the slack bus (real or reactive), the reactive power at generation buses, the reactive power at shunts (capacitor or reactor), the transmission lines power losses (real and reactive), and transmission lines power (real and reactive). Besides their clear physical meaning, which makes easier the development and application of continuation methods for power systems analysis, the main advantage of some of the proposed parameters is that its not necessary to change the parameter in the vicinity of the MLP. Studies on the new parameterization schemes performed on the IEEE 118 buses system show that the ill-conditioning problems at and near the MLP are eliminated. So, the characteristics of the conventional Newton's method are not only preserved but also improved. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Proposal of a Transmission Line Model Based on Lumped Elements: An Analytic Solution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise dos projetos de desenvolvimento dos vales dos rios Tietê e Paraná

Este artigo avalia as alternativas propostas para a região dos vales dos rios Tietê e Paraná, no estado de São Paulo. Os projetos formalmente elaborados para a região foram analisados através do método da estrutura lógica. Tal método consiste em representar um projeto na forma de uma matriz 4 × 4 cujos elementos permitem a análise do projeto em questão pela utilização de critérios relacionados ao método científico, à análise de sistemas e ao ponto de vista da gerência de programas. Os resultados encontrados demonstraram a inconsistência nos planos e projetos existentes para a região.

A comparison of profilometer and AutoCAD software techniques in evaluation of implant angulation in vitro

Purpose: The aim of this study was to compare 2 different methods of assessment of implants at different inclinations (90 degrees and 65 degrees)-with a profilometer and AutoCAD software. Materials and Methods: Impressions (n = 5) of a metal matrix containing 2 implants, 1 at 90 degrees to the surface and 1 at 65 degrees to the surface, were obtained with square impression copings joined together with dental floss splinting covered with autopolymerizing acrylic resin, an open custom tray, and vinyl polysiloxane impression material. Measurement of the angles (in degrees) of the implant analogs were assessed by the same blinded operator with a profilometer and through analysis of digitized images by AutoCAD software. For each implant analog, 3 readings were performed with each method. The results were subjected to a nonparametric Kruskal-Wallis test, with P <= .05 considered significant. Results: For implants perpendicular to the horizontal surface of the specimen (90 degrees), there were no significant differences between the mean measurements obtained with the profilometer (90.04 degrees) and AutoCAD (89.95 degrees; P=.9142). In the analyses of the angled implants at 65 degrees in relation to the horizontal surface of the specimen, significant differences were observed (P=.0472) between the mean readings with the profilometer (65.73 degrees) and AutoCAD (66.25 degrees). Conclusions: The degrees of accuracy of implant angulation recording vary among the techniques available and may vary depending on the angle of the implant. Further investigation is needed to determine the best test conditions and the best measuring technique for determination of the angle of the implant in vitro.

Adaptive control charts for attributes

We develop a general model for adaptive c, np, u and p control charts in which one, two or three design parameters (sample size, sampling interval and control limit width) switch between two values, according to the most recent process information. For a given in-control average sampling rate and a given false alarm rate, the adaptive chart detects changes in the process much faster than a chart with fixed parameters. Moreover, this study also offers general guidance on how to choose an effective design.

Stick-slip chaos in a non-ideal self-excited system

In engineering practical systems the excitation source is generally dependent on the system dynamic structure. In this paper we analyze a self-excited oscillating system due to dry friction which interacts with an energy source of limited power supply (non ideal problem). The mechanical system consists of an oscillating system sliding on a moving belt driven by a limited power supply. In the oscillating system considered here, dry friction acts as an excitation mechanism for stick-slip oscillations. The stick-slip chaotic oscillations are investigated because the knowledge of their dynamic characteristics is an important step in system design and control. Many engineering systems present stick-slip chaotic oscillations such as machine tools, oil well drillstrings, car brakes and others.

A comparative study between two relaxed LMI-based fuzzy control designs

A comparative study, with theoretical analysis and digital simulations, of two conditions based on LMI for the quadratic stability of nonlinear continuous-time dynamic systems, described by Takagi-Sugeno fuzzy models, are presented. This paper shows that the methods proposed by Teixeira et. al. in 2003 provide better or at least the same results of a recent method presented in the literature. © 2005 IEEE.

Border detection in digital images: An approach by fuzzy numbers

The purpose of this paper is to introduce a new approach for edge detection in gray shaded images. The proposed approach is based on the fuzzy number theory. The idea is to deal with the uncertainties concerning the gray shades making up the image, and thus calculate the appropriateness of the pixels in relation to an homogeneous region around them. The pixels not belonging to the region are then classified as border pixels. The results have shown that the technique is simple, computationally efficient and with good results when compared with both the traditional border detectors and the fuzzy edge detectors. © 2007 IEEE.

Meta-heuristic approaches for a soft drink industry problem

The present paper evaluates meta-heuristic approaches to solve a soft drink industry problem. This problem is motivated by a real situation found in soft drink companies, where the lot sizing and scheduling of raw materials in tanks and products in lines must be simultaneously determined. Tabu search, threshold accepting and genetic algorithms are used as procedures to solve the problem at hand. The methods are evaluated with a set of instance already available for this problem. This paper also proposes a new set of complex instances. The computational results comparing these approaches are reported. © 2008 IEEE.

RBF circuits based on folded cascode differential pairs

We propose new circuits for the implementation of Radial Basis Functions such as Gaussian and Gaussian-like functions. These RBFs are obtained by the subtraction of two differential pair output currents in a folded cascode configuration. We also propose a multidimensional version based on the unidimensional circuits. SPICE simulation results indicate good functionality. These circuits are intended to be applied in the implementation of radial basis function networks. One possible application of these networks is transducer signal conditioning in aircraft and spacecraft vehicles onboard telemetry systems. Copyright 2008 ACM.

Digital system design process automation using place/transition petri nets

The constant increase in digital systems complexity definitely demands the automation of the corresponding synthesis process. This paper presents a computational environment designed to produce both software and hardware implementations of a system. The tool for code generation has been named ACG8051. As for the hardware synthesis there has been produced a larger environment consisting of four programs, namely: PIPE2TAB, AGPS, TABELA, and TAB2VHDL. ACG8051 and PIPE2TAB use place/transition net descriptions from PIPE as inputs. ACG8051 is aimed at generating assembly code for the 8051 micro-controller. PIPE2TAB produces a tabular version of a Mealy type finite state machine of the system, its output is fed into AGPS that is used for state allocation. The resulting digital system is then input to TABELA, which minimizes control functions and outputs of the digital system. Finally, the output generated by TABELA is fed to TAB2VHDL that produces a VHDL description of the system at the register transfer level. Thus, we present here a set of tools designed to take a high-level description of a digital system, represented by a place/transition net, and produces as output both an assembly code that can be immediately run on an 8051 micro-controller, and a VHDL description that can be used to directly implement the hardware parts either on an FPGA or as an ASIC.

Bandgap voltage reference with low susceptibility to electromagnetic interference (EMI)

In this paper, the susceptibility of a current-mode bandgap voltage reference to electromagnetic interference (EMI) superimposed to the power supply is investigated by simulation. Designed for AMS 0.35 CMOS process, the circuit provides a stable voltage reference in the temperature range of -40-150°C. When EMI disturbances are present, the circuit exhibits only 6.7 mV of offset for interfering signals in the frequency range of 150 kHz-1 GHz. © 2011 ACM.

Computational tool to support design of DAC Converter model AD7528 with the object code in XML

Based on literature review, electronic systems design employ largely top-down methodology. The top-down methodology is vital for success in the synthesis and implementation of electronic systems. In this context, this paper presents a new computational tool, named BD2XML, to support electronic systems design. From a block diagram system of mixed-signal is generated object code in XML markup language. XML language is interesting because it has great flexibility and readability. The BD2XML was developed with object-oriented paradigm. It was used the AD7528 converter modeled in MATLAB / Simulink as a case study. The MATLAB / Simulink was chosen as a target due to its wide dissemination in academia and industry. From this case study it is possible to demonstrate the functionality of the BD2XML and make it a reflection on the design challenges. Therefore, an automatic tool for electronic systems design reduces the time and costs of the design.