São Paulo Federal Institute of Education, Science and Technology

About: São Paulo Federal Institute of Education, Science and Technology is a education organization based out in São Paulo, Brazil. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 1707 authors who have published 2374 publications receiving 11333 citations.

Minimum chip thickness determination by means of cutting force signal in micro endmilling

Abstract: Issues related to ploughing affecting the performance of the micromilling process have recently been reported in literature. It is well known that there is a minimum chip thickness (hmin) below which ploughing is the main material removal mechanism and no shear occurs. This leads to a non-effective material removal, resulting in a poor surface quality. In order to solve this problem, the minimum chip thickness has been predicted by measuring the cutting forces. However, the determination of h min by means of the cutting force signal, at the instant the chip is being formed, has not been approached. In this article, a method of determining hmin, based upon the signal variation of the cutting forces and the effect of tool radial runout during chip formation is proposed. Carbide micro-endmills without coating were used to cut an aluminium alloy (RSA 6061-T6) sample and the cutting forces were measured using a micro-dynamometer. The microtopography of a microchannel wall was assessed using an optical profiler in order to establish the approximate position where the chip starts to form ( h min ) . As the cut progresses, the force component normal to the feed (FfN) reverses when the undeformed chip thickness is equal to the cutting edge radius (re). Simultaneously, the thrust force increases rapidly, and continues to grow but at a lower rate as FfN increase. The main cutting force and the active force present significant differences to each other. The minimum chip thickness was estimated as 0.3re by means of the behavior of the active force. A small quantity of material left on the wall of the microchannel could be observed in align with the cutting movement together with a deterioration of the surface finish attributed to the increase of re. Results show that the size of the material left is 2 to 4 times greater than h min . Conversely, the quality of the microchannel floor improves as re increase. This shows that there is a balance between h min and re and the effect upon the finish of the channel wall and floor. That should be important for microchannel fabrication in terms of performance of micro-scale heat exchangers depending on fluid viscosity. The topographic analyses of the wall and the images of the chips show an agreement with estimated h min under different cutting conditions and cutting edge radii. The proposed method in this paper not only permits the determination of the minimum chip thickness but also has the advantage of making it possible to estimate the cutting edge radius and to monitor the cutting edge wear.

Cellular to dendritic transition during transient solidification of a eutectic Sn-0.7 wt%Cu solder alloy

Abstract: The eutectic Sn–0.7 wt%Cu alloy is considered an important alternative to replace the classic eutectic Sn–Pb alloy, used to join metallic surfaces in electronic devices. The stable Sn–Cu eutectic is composed of a mixture of a tin-rich phase and fibrous Cu6Sn5 intermetallic particles. The morphology, size and distribution of stable and metastable intermetallic particles may affect the mechanical properties of the alloy. The distribution of these intermetallics is characterized by the interphase spacing, which depends on thermal parameters such as the growth rate (v) and the cooling rate ( T ˙ ) during solidification. The aim of this study is to investigate the microstructural evolution of a eutectic Sn–0.7 wt%Cu solder alloy during transient solidification. The resulting microstructural morphology depends on v and T ˙ , and in the case of soldering processes the control of these parameters is essential for the design of the final microstructure. A gradual cellular to dendritic transition was observed to occur for growth rates ranging from 0.3 to 0.5 mm s−1 and cooling rates from 0.9 to 1.5 K s−1. The cellular region was shown to be characterized by aligned eutectic colonies, and experimental growth laws relating cellular, dendritic and interphase spacings to both v and T ˙ have been proposed.

Effect of Imbalanced Datasets on Security of Industrial IoT Using Machine Learning

Abstract: Machine learning algorithms have been shown to be suitable for securing platforms for IT systems. However, due to the fundamental differences between the industrial internet of things (IIoT) and regular IT networks, a special performance review needs to be considered. The vulnerabilities and security requirements of IIoT systems demand different considerations. In this paper, we study the reasons why machine learning must be integrated into the security mechanisms of the IIoT, and where it currently falls short in having a satisfactory performance. The challenges and real-world considerations associated with this matter are studied in our experimental design. We use an IIoT testbed resembling a real industrial plant to show our proof of concept.

In vitro cytotoxic activity of Brazilian Middle West plant extracts

Abstract: Cytotoxic activity of eight plant extracts, native from the Mid-West of Brazil comprising Cerrado, Pantanal and semideciduous forest, was evaluated for MDA-MB-435, SF-295, and HCT-8 cancer cell strains. A single 100 µg.mL-1 dose of each extract was employed with 72 h of incubation for all tests. Doxorubicin (1 µg.mL-1) was used as the positive control and the MTT method was used to detect the activity. Cytotoxicity of distinct polarities was observed in thirty extracts (46%), from different parts of the following species: Tabebuia heptaphylla (Vell.) Toledo, Bignoniaceae, Tapirira guianensis Aubl., Anacardiaceae, Myracrodruon urundeuva Allemao, Anacardiaceae, Schinus terebinthifolius Raddi, Anacardiaceae, Gomphrena elegans Mart., Amaranthaceae, Attalea phalerata Mart. ex Spreng., Arecaceae, Eugenia uniflora L., Myrtaceae, and Annona dioica A. St.-Hil., Annonaceae. Extracts of at least two tested cell strains were considered to be highly active since their inhibition rate was over 75%.

A Robust Finite Control Set Applied to the DFIG Power Control

Abstract: This paper proposes a robust finite control set for doubly-fed induction generator power control. In this way, the proposed robust finite control has two components of the predicted rotor voltage. The first term calculates the voltage considering the rotor current references and the second term is designed considering the mistakes due to parameters’ estimation. The mentioned errors due to parameters’ variations were modeled as rotor current changes. Hence, the controller calculates the predicted rotor voltage considering parameter variations and rotor current references. So that, the minimized cost function selects the voltage vector to be supplied to the rotor of the machine. The influence of the estimation errors for variations on $R_{2}$ and $\sigma L_{2}$ was also investigated. The results obtained in a setup confirm the controller performance.