Paula Ventura Martins

Correlation between Crystallization Kinetics and Electroactive Polymer Phase Nucleation in Ferrite/Poly(vinylidene fluoride) Magnetoelectric Nanocomposites

Poly(vinylidene fluoride) (PVDF) nanocomposites with different ferrite nanoparticle loadings are interesting as, depending on ferrite type and content, the electroactive β-phase of the polymer is nucleated and the magnetoelectric coupling is induced. The isothermal crystallization behavior of ferrite/PVDF nanocomposites is studied using polarized optical microscopy, and the crystallization kinetic is analyzed by the Avrami theory in order to understand the crystallization conditions leading to the nucleation of the electroactive polymer phase. It is found that the nucleation kinetics is enhanced by the presence of ferrite nanoparticles, as evidenced by the increasing number of spherulites with increasing nanoparticle content and by the variations of the Avrami exponent. The crystallization velocity is intimately related to the polymer α- or β-phase formation in the nanocomposites and follows the order NiFe(2)O(4)/PVDF > CoFe(2)O(4)/PVDF > Ni(0.5)Zn(0.5)Fe(2)O(4)/PVDF for a given temperature and nanoparticle loading, which results in larger amounts of β-phase for CoFe(2)O(4)/PVDF and Ni(0.5)Zn(0.5)Fe(2)O(4)/PVDF nanocomposites.

Tailored Magnetic and Magnetoelectric Responses of Polymer-Based Composites.

The manipulation of electric ordering with applied magnetic fields has been realized on magnetoelectric (ME) materials; however, their ME switching is often accompanied by significant hysteresis and coercivity that represents for some applications a severe weakness. To overcome this obstacle, this work focuses on the development of a new type of ME polymer nanocomposites that exhibits a tailored ME response at room temperature. The multiferroic nanocomposites are based on three different ferrite nanoparticles, Zn0.2Mn0.8Fe2O4 (ZMFO), CoFe2O4 (CFO) and Fe3O4 (FO), dispersed in a piezoelectric copolymer poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)) matrix. No substantial differences were detected in the time-stable piezoelectric response of the composites (∼-28 pC·N(1-)) with distinct ferrite fillers and for the same ferrite content of 10 wt %. Magnetic hysteresis loops from pure ferrite nanopowders showed different magnetic responses. ME results of the nanocomposite films with 10 wt % ferrite content revealed that the ME induced voltage increases with increasing dc magnetic field until a maximum of 6.5 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.26 T, and 0.8 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.15 T, for the CFO/P(VDF-TrFE) and FO/P(VDF-TrFE) composites, respectively. In contrast, the ME response of ZMFO/P(VDF-TrFE) exposed no hysteresis and high dependence on the ZMFO filler content. Possible innovative applications such as memories and information storage, signal processing, and ME sensors and oscillators have been addressed for such ferrite/PVDF nanocomposites.

Optimization of the Magnetoelectric Response of Poly(vinylidene fluoride)/Epoxy/Vitrovac Laminates

The effect of the bonding layer type and piezoelectric layer thickness on the magnetoelectric (ME) response of layered poly(vinylidene fluoride) (PVDF)/epoxy/Vitrovac composites is reported. Three distinct epoxy types were tested, commercially known as M-Bond, Devcon, and Stycast. The main differences among them are their different mechanical characteristics, in particular the value of the Young modulus, and the coupling with the polymer and Vitrovac (Fe39Ni39Mo4Si6B12) layers of the laminate. The laminated composites prepared with M-Bond epoxy exhibit the highest ME coupling. Experimental results also show that the ME response increases with increasing PVDF thickness, the highest ME response of 53 V·cm(-1)·Oe(-1) being obtained for a 110 μm thick PVDF/M-Bond epoxy/Vitrovac laminate. The behavior of the ME laminates with increasing temperatures up to 90 °C shows a decrease of more than 80% in the ME response of the laminate, explained by the deteriorated coupling between the different layers. A two-dimensional numerical model of the ME laminate composite based on the finite element method was used to evaluate the experimental results. A comparison between numerical and experimental data allows us to select the appropriate epoxy and to optimize the piezoelectric PVDF layer width to maximize the induced magnetoelectric voltage. The obtained results show the critical role of the bonding layer and piezoelectric layer thickness in the ME performance of laminate composites.

Algorithm Versus Physicians Variability Evaluation in the Cardiac Chambers Extraction

Congenital heart diseases are present in eight of every 1000 newborns. The diagnosis of those pathologies usually depends on the available imaging methods. A correct diagnosis requires a detailed observation of the heart chambers, wall motions, valves function, and quantitative evaluation of the cavity volumes. For that goal numerous automatic algorithms have been proposed to segment the echocardiographic images. In this paper, the authors evaluate the performance of a level set algorithm based on the phase symmetry approach and on a new logarithmic-based stopping function to extract the heart cavity contours simultaneously, and in a fully automatic way. The extracted cardiac borders are then statistically compared with the ones manually sketched by four physicians on a set of 240 cavities. Nonparametric statistical tests are conducted on the data using several figures of merit, in order to study the inter- and intraobserver variabilities among the four physicians and the level set algorithm, concerning to the extracted contours. The results show there is a great concordance about all the used similarity indexes. A higher interobserver variability was found among the physicians than the variability obtained when the algorithm versus physician performance is compared. The statistical analysis suggests the proposed algorithm produces results similar to the ones provided by the physicians.

PIT-P2M: ProjectIT process and project metamodel

Within the constant evolution observed in IT/IS area, new processes emerged faced to new customer’s requirements and also due to new trends in software engineering community, such as unified or agile processes. Despite the great set of available tools in process and project management, still there is a real gap between “process” and “project” management approaches and respective tools. To assist team members on their work, the effort spend in a process customization could be used in other tasks, such as the project management task to control activities, work products and team members. In this paper, we describe a simplified SPEM-based metamodel for process specification and explain the motivation around this proposal. Considering this metamodel, we also propose a metamodel for project definition and configuration. To conclude, we demonstrate that this metamodel is better adapted to processes specification and can be applied in a project definition.

Business Alignment Methodology: The Discovery Phase

Current business process modeling methodologies offer little guidance regarding how to discover and maintain business process models aligned with their actual execution. This paper describes how to achieve this goal by uncovering, supervising and improving business process models based on actual work practices, using the Business Alignment Methodology BAM. BAM aims at enabling business process modeling, supervision and improvement through the distinction of two dimensions; 1 business processes and 2 work practices. BAM encompasses three phases; 1 Business Process Discovery, 2 Business Process Supervision and 3 Business Process Assessment and Improvement. This paper illustrates the business discovery phase of BAM with a case study in a real organizational setting.

ProPAMet: A Metric for Process and Project Alignment

Software Process Improvement (SPI) is one of the main software development challenges. Unfortunately, process descriptions generally do not correspond to the processes actually performed during software development projects. Process and project alignment is essential to really find out how process improvement is important to achieve an organization’s strategic objectives. Considering this approach, this paper presents a new software SPI methodology designated by Process and Project Alignment Methodology (ProPAM). As a complement to be aware about project changes and facilitate the migration to an improved process, we propose a metric called ProPAMet to analyze the alignment between process and projects. To conclude, a case study contributed to validate the effectiveness of ProPAM and ProPAMet.

A case study applying process and project alignment methodology

Software Process Improvement (SPI) is one of the main software development challenges. However, SPI standards and models (CMMI, SPICE) have not been always adopted with success. The current problem is a lack of strategy to implement successfully these standards and models. To undertake this objective is essential observe real life experiences and detect process and project mutual relationships. Without this alignment it will not be possible to find out how process management is really important to achieve organization’s strategic objectives. This paper proposes a methodology that allows the definition, evaluation and improvement of an organization software development process. This proposal, called a Process and Project Alignment Methodology (ProPAM), allows the specification of an organization development process, as well process and project alignment. ProPAM presents the following life cycle: (1) process definition; (2) project definition considering a base process model; (3) project coordination and monitoring and (4) process improvement assessment. This paper also provides an overview of the action plan to be taken within the software organizations that intent to conduct a SPI initiative. This plan includes two distinct phases: (1) specify the development process and (2) analyze projects, starting an SPI effort. In order to evaluate ProPAM, a study case is undertaken. The case study is performed following the action plan and presents all the steps of the ProPAM. Final results show that, when the organization started using ProPAM, process and project alignment reduced project planning time and effort. ProPAM also introduced new organizational practices that result in a SPI program.

BAM - Business Alignment Methodology

Information flows across the organization are complex and procedures employed to understand, share and control organizational knowledge and experiences should be properly supported by collaborative environments. Nevertheless, few collaborative methodologies had been proposed to describe and evolve business processes. In the future, business processes models should be the result of cross-team and cross-departmental collaboration, with involved business people sharing their personal knowledge and formalizing it. This paper focuses on a methodology for business process discovery and the importance to integrate local information into coherent and sound process definitions. Business Alignment Methodology (BAM) is a methodology that provides guidance about how organizational practices and knowledge are gathered to contribute for business process improvement against current BPM approaches.

A comparative study of SPI Approaches with ProPAM

Software process improvement (SPI) is one of the main software development challenges. Unfortunately, process descriptions generally do not correspond to the processes actually performed during software development projects. They just represent high-level plans and do not contain the information necessary for the concrete software projects. This deficient alignment between the process and project is caused by processes that are unrelated to project activities and failure in detecting project changes to improve the process. Process and project alignment is essential to really find out how process management is important to achieve an organizations strategic objectives. Considering this approach, this paper presents a comparative study of some of the most recognized SPI approaches and a new software process improvement methodology proposed, designed by Process and Project Alignment Methodology (ProPAM). Our intention is to show the problems observed in existing SPI approach and recognize that further research in process and project alignment based on actor oriented approaches is required.