M.F. de Oliveira

Uncovering Clusters in Crowded Parallel Coordinates Visualizations

The one-to-one strategy of mapping each single data item into a graphical marker adopted in many visualization techniques has limited usefulness when the number of records and/or the dimensionality of the data set are very high. In this situation, the strong overlapping of graphical markers severely hampers the users ability to identify patterns in the data from its visual representation. We tackle this problem here with a strategy that computes frequency or density information from the data set, and uses such information in parallel coordinates visualizations to filter out the information to be presented to the user, thus reducing visual clutter and allowing the analyst to observe relevant patterns in the data. The algorithms to construct such visualizations, and the interaction mechanisms supported, inspired by traditional image processing techniques such as grayscale manipulation and thresholding are also presented. We also illustrate how such algorithms can assist users to effectively identify clusters in very noisy large data sets

Corrosion resistance of amorphous and nanocrystalline Fe–M–B (MZr, Nb) alloys

Amorphous Fe‐M‐B (M‚Zr, Nb) based alloys with nanometer-sized crystallites have attracted attention due to their magnetic properties. Although corrosion resistance is a desirable property in such alloys, no study concerning this aspect has been reported. The eAect of metalloid content and partial crystallization on corrosion resistance of Fe‐M‐B (M‚Zr, Nb) amorphous alloys, Fe84Nb7B9 ,F e 84Zr7B9 and Fe83Zr3:5Nb3:5B9Cu1, was investigated. Corrosion resistance measurements were carried out by mass loss, potentiodynamic polarization, and thermogravimetric mass gain measurements. The partial crystallization of the amorphous alloy results in a decrease of the corrosion resistance for all the compositions analyzed. We also observed a greater corrosion resistance when Nb was present in comparison to the case when Zr was present. These results are an eAect of the superficial passive film protector formed. ” 2000 Published by Elsevier Science B.V. All rights reserved.

A Framework for Software Engineering Experimental Replications

Experimental replications are very important to the advancement of empirical software engineering. Replications are one of the key mechanisms to confirm previous experimental findings. They are also used to transfer experimental knowledge, to train people, and to expand a base of experimental evidence. Unfortunately, experimental replications are difficult endeavors. It is not easy to transfer experimental know-how and experimental findings. Based on our experience, this paper discusses this problem and proposes a Framework for Improving the Replication of Experiments (FIRE). The FIRE addresses knowledge sharing issues both at the intra-group (internal replications) and inter-group (external replications) levels. It encourages coordination of replications in order to facilitate knowledge transfer for lower cost, higher quality replications and more generalizable results.

Topological instability and electronegativity effects on the glass-forming ability of metallic alloys

The glass-forming ability (GFA) of metallic alloys is associated with a topological instability criterion combined with a new parameter based on the average electronegativity difference of an element and its surrounding neighbours. In this model, we assume that during solidification the glassy phase competes directly with the supersaturated solid solution having the lowest topological instability factor for a given composition. This criterion is combined with the average electronegativity difference among the elements in the alloy, which reflects the strength of the liquid. The GFA is successfully correlated with this combined criterion in several binary glass-forming systems.

Enhanced High Dimensional Data Visualization through Dimension Reduction and Attribute Arrangement

Researchers and users are well aware of the difficulties related to finding an appropriate configuration of the axes mapping attributes in multidimensional visualization techniques, particularly in visualizations that show a large number of attributes simultaneously. We address this problem with a simple strategy that offers both dimension ordering and dimension reduction. Dimension ordering is based on attribute similarity heuristics, and the basic rationale is extended to support dimension reduction. We discuss the performance of our algorithms and present some results of their application to several data sets. The algorithms improve the capability of visualization techniques to segregate clusters present in the data and reduce the visual clutter aggravated by arbitrary distributions of the axes

Coordinated views to assist exploration of spatio-temporal data: a case study

In this paper we focus on providing coordinated visual strategies to assist users in performing tasks driven by the presence of temporal and spatial attributes. We introduce temporal visualization techniques targeted at such tasks, and illustrate their use with an application involving a climate classification process. The climate classification requires extensive processing of a database containing daily rain precipitation values collected along over fifty years at several spatial locations in the Sao Paulo state, Brazil. We identify user exploration tasks typically conducted as part of the data preparation required in this process, and then describe how such tasks may be assisted by the multiple visual techniques provided. Issues related to the use of the multiple techniques by an end-user are also discussed.

Influence of the corrosion on the saturation magnetic density of amorphous and nanocrystalline Fe73Nb3Si15.5B7.5Cu1 and Fe80Zr3.5Nb3.5B12Cu1 alloys

Abstract Amorphous FeMBCu (M=Nb, Zr) and FeNbSiBCu alloys with nanometer size crystallites have attracted attention due to their soft magnetic properties. The mechanism through which crystallization affects the corrosion and the comparative effect of corrosion on magnetic properties of FeMBCu (M=Nb, Zr) and FeNbSiBCu alloys has not yet been evaluated. In this paper the effect of partial crystallization on corrosion resistance of amorphous Fe 73 Nb 3 Si 15.5 B 7.5 Cu 1 and Fe 80 Zr 3.5 Nb 3.5 B 12 Cu 1 alloy ribbons and the comparative effect of corrosion on saturation magnetic flux density, Bs, of these alloys were investigated. The samples were characterized by X-ray diffraction, differential scanning calorimetry and X-ray photoelectron spectroscopy. Corrosion resistance evaluation was carried out by measuring mass loss of samples immersed in 0.1 M H 2 SO 4 solution, and by measuring potentiodynamic polarization curves (potential vs. current). Saturation magnetic flux density, Bs, of the samples were measured. After partial crystallization of Fe 80 Zr 3.5 Nb 3.5 B 12 Cu 1 amorphous sample the corrosion resistance decreased, while for the Fe 73 Nb 3 Si 15.5 B 7.5 Cu 1 the corrosion resistance increased. The decrease of Bs after treatment in the corrosion solution as observed in the nanocrystalline Fe 80 Zr 3.5 Nb 3.5 B 12 Cu 1 sample was larger than that observed for both amorphous and the nanocrystalline Fe 73 Nb 3 Si 15.5 B 7.5 Cu 1 samples after the same treatment.

Electromechanical engraving and writing on bulk metallic glasses

Using the intrinsic materials properties of bulk metallic glasses (BMG), namely electrical resistivities two orders of magnitude higher than good conductors and a Newtonian viscous-flow regime of deformability, a new electromechanical process has been developed for engraving on BMGs. Viscous flow in the supercooled liquid region between the glass transition temperature Tg and the crystallization temperature Tx of the bulk metallic glass allows rapid electromechanical engraving at low applied stresses. Miniaturization of the process is expected to allow submicron engraving in the future.

Shaping of Bulk Metallic Glasses by Simultaneous Application of Electrical Current and Low Stress

Using the intrinsic materials properties of bulk metallic glasses (BMG), namely electrical resistivities two orders of magnitude higher than good conductors and a Newtonian viscous-flow regime of deformability, a new electromechanical process has been developed for shaping, joining and engraving of BMGs. The wider the liquid supercooled region between the glass transition temperature T g and the crystallisation temperature T x of the bulk metallic glass, the easier the application of the new process. In this range, the undercooled liquid deforms in a quasi-Newtonian way, allowing thermomechanical shaping in the low viscosity range as for oxide glasses. The new electromechanical processing technology has been used for economical and rapid shaping at low applied stresses by eliminating the thermal mass of the furnace and the need to heat the deformation dies. The process parameters are adaptable for the full maintenance of the glassy state or when desired, for appropriate compositions, for nanocrystallisation during the joining or shaping operation.

Reviewing Data Visualization: an Analytical Taxonomical Study

This paper presents an analytical taxonomy that can suitably describe, rather than simply classify, techniques for data presentation. Unlike previous works, we do not consider particular aspects of visualization techniques, but their mechanisms and foundational vision perception. Instead of just adjusting visualization research to a classification system, our aim is to better understand its process. For doing so, we depart from elementary concepts to reach a model that can describe how visualization techniques work and how they convey meaning