Influence of Machine Parameters on Ti-6Al-4V Small Sized Specimens Made by Laser Metal Powder Deposition

The present work is focused on one Additive Manufacturing (AM) process – Laser powder Metal Deposition (LMD-p) – and on one metallic alloy – Ti-6Al-4V. State of the art on LMD-p on Ti-6Al-4V alloy shows that three kinds of process parameters influence mechanical properties of building parts: raw materials (powder and substrate), machine parameters (Laser Power (P), Powder Flow (F) and Building Speed (V)), and building strategies (part orientation, waiting time between layers, etc.). Thus, this paper relates to first manufacturing investigations on small sized specimens (bead, wall and block) with the aim of providing a better knowledge about the first steps of manufacturing. Particularly, this paper is dedicated to the study of machine parameters (P, F and V). First, the influence of each machine parameter on 28 beads is studied separately. The geometrical aspect (high, width, dilution) of each bead is microscopically measured. Similarly, combinations of parameters (P/F, Energy Density and Powder Density) are introduced to increase parameters degree of freedom. First results show that P, V and F have a major influence on the beads’ geometry. In addition, a window process map is plotted and allows determining functional areas of machine parameters. From this map, walls (vertical superposition of one bead) are manufactured and microscopically observed. Functional sets of parameters from walls are selected and blocks can be built.

The Glory of the Past and Geometrical Concurrency

This paper contributes to the general understanding of the "geometrical model of concurrency" that was named higher dimensional automata (HDAs) by Pratt and van Glabbeek. In particular we provide some understanding of the modal logics for such models and their expressive power in terms of the bisimulation that can be captured.The geometric model of concurrency is interesting from two main reasons: its generality and expressiveness, and the natural way in which autoconcurrency and action refinement are captured.Logics for this model, though, are not well investigated, where a simple, yet adequate, modal logic over HDAs was only recently introduced.As this modal logic, with two existential modalities, "during" and "after", captures only split bisimulation, which is rather low in the spectrum of van Glabbeek and Vaandrager, the immediate question was what small extension of this logic could capture the more fine-grained hereditary history preserving bisimulation (hh)?In response, the work in this paper provides several insights. One is the fact that the geometrical aspect of HDAs makes it possible to use for capturing the hh-bisimulation, a standard modal logic that does not employ event variables, opposed to the two logics (over less expressive models) that we compare with. The logic that we investigate here uses standard backward-looking modalities (i.e., past modalities) and extends the previously introduced logic (called HDML) that had only forward, action-labelled, modalities.Since the direct proofs are rather intricate, we try to understand better the above issues by introducing a related model that we call ST-configuration structures, which extend the configuration structures of van Glabbeek and Plotkin. We relate this model to HDAs, and redefine and prove the earlier results in the light of this new model. These offer a different view on why the past modalities and geometrical concurrency capture the hereditary history preserving bisimulation.Additional correlating insights are also gained.

A Mathematical Proof Concerning the Geometrical Aspect of Very Low Index of Difficulty in Multidirectional Tapping Task of the ISO 9241 - Part 411

Through mathematics, this paper works to analyse the Index of Difficulty in ISO9241-Part 411: Evaluation methods for the design of physical input devices. It was proven that all the target circles always intersect for very low Index of Difficulty; which conjectured to disturb the experiment or affect the focus of the subject. Some examples are provided, in addition, to support the proof. We hope this proof will contribute to the improvement of ISO9241, where the result might become a special attention to the designer of the experiment in human-computer interaction field; especially in checking the influence of overlap area in the human factor.

GRAPHICAL PART OF LAND AND BUILDINGS REGISTRY BASED ON AERIAL PHOTOS FROM THE BOARD OF UNMANNED AERIAL VEHICLE (UAV)

The paper attempts to develop a new way of verifying and updating data collected in Land and Property Databases, containing information on land and buildings. The report examines currently existing law regulating for the collection of registration of data, mainly in their geometrical aspect, proposes possible ways of validating these data and enriches with some new elements based on UAS technology. By supplementing the databases with new Land and Property objects the study was prepared, taking into account some new legislative provisions related to the principles and scope of the collected data in the Land and Property's resources. The basic problem with the use of photogrammetry from the UAV level for measuring the location and shape of considered objects is ensuring the proper accuracy. The compliance of accuracy condition and the visibility of the objects makes it possible to significantly supplement the registration data databases with some new elements such as terraces, verandas, stairs, etc. The paper discusses these issues and presents the results performed on real objects, together with their accuracy rating. It has been found that images made from low altitude can be used to measure new object classes, update land and buildings database, and also, to a limited extent, validate Land and Property Databases for another, from the up-visible objects.

Involvement of Algebraic-Geometrical Duality in Shaping Fraction’s Meaning and Calculation Strategies with Fractions

Many mathematical concepts and processes, besides the algebraic form of their presentation, can be modeled as well geometrically through diagrams and graphics. Both these aspects of concepts demonstration (algebraic and geometrical aspect) are present on mathematical textbooks of pre-university education. In this paper we consider algebraic and geometrical aspect on 6th grade math textbooks and in particular algebraic-geometrical duality, aiming that the fraction concept and the fraction calculation strategy to be assimilated better by the students. A study was made with 78 students to understand their abilities to express using algebraic symbols and to introduce mathematical situations with geometrical models for “Fractions” chapter. After the analysis of calculative strategies applied by students, in the article it is suggested that algebraic-geometrical duality must be included in teaching based on a complete framework. This will enable students to fully realize the deep understanding of concepts and the calculative strategies they are using.

Effect of Wine Properties and Operating Mode upon Mass Transfer in Micro-Oxygenation

All along wine-making and during its ageing, oxygen plays an important role for the evolution of the wine. Solubilization of oxygen into musts or wines occurs when gaseous oxygen is brought into contact with the liquid. In this work, the specific technique of wine micro-oxygenation is addressed through the evaluation of transfer capacity for oxygen solubilization. This was done considering the parameters likely to influence the saturation concentration of dissolved oxygen and the conventional volumetric mass transfer coefficient kLa, which quantifies the efficiency of the oxygen transfer. The study has shown that the sugar concentration in the must induces a viscosity enhancement which leads to a significant decrease of the kLa value. Surprisingly, it was also observed that a very low quantity of ethanol in the liquid phase (0.05 percent volume) strongly favours the oxygen transfer. Conversely, the presence of dissolved carbon dioxide in the wine, which desorbs and dilutes the oxygen in the micro-bubbles, dramatically decreases the transfer of oxygen. The presence of anti-oxidant compounds (SO2) or oxygen consumer compounds (polyphenols) was shown to have no effect upon the efficiency of oxygen transfer. Operating parameters such as gas flow rate or geometrical aspect of the tank have also been considered.