SURFACE AND SUBSURFACE ALTERATIONS INDUCED BY HARD TURNING OF AISI 52100 BEARING STEEL

Over the last decades, turning of hardened steel for finishing purposes has earned visibility as a process that can potentially match grinding. This is due to the fact that economic advantages can be obtained when turning instead of grinding, however, turning of hardened steels has not been able to replace grinding to a greater extent owing to the difficulty of the former in providing the same level of dimensional accuracy achieved by the latter. The aim of this work is to assess the influence of cutting parameters (cutting speed, feed and depth of cut) on the dimensional and geometric deviations induced by finish turning of hardened AISI 52100 steel (60 HRC) with mixed alumina (Al2O3 + TiC) cutting tools. Additionally, the influence of the cutting parameters on the microstructure and subsurface microhardness profile is investigated. The novelty of the present work is to establish a relationship between surface (dimensional and geometric deviations) and subsurface (microstructure and microhardness variation) alterations induced by hard turning, which are crucial to the performance of the machined component. The results show that feed significantly affects diameter deviation, circularity, concentricity and surface roughness, while depth of cut affects diameter deviation and parallelism error. The influence of cutting speed is significant only with regard to the concentricity error. As far as subsurface alterations are concerned, higher surface microhardness values were obtained when combining higher cutting speed and lower feed and depth of cut. Clear evidence of microstructure alterations was observed under the most severe cutting condition only

Ficção científica na transposição didática do conceito de Entropia: a última pergunta de Isaac Asimov [Science fiction in the didactic transposition of the concept of Entropy: Isaac Asimov’s last question]

This paper presents and analyzes the methodology for teaching the concept of entropy supported by a science fiction text. In previous publications, we have presented ways of articulating Ausubel’s Meaningful Learning and Matthew Lipman’s Education theories, the object of his Philosophy Program. We show how this articulation considers the prerogatives of meaningful learning, linking it to higher-order thinking established by research communities and suggesting aggregating methods. As a theoretical-methodological expansion of these references, we transferred the notion of didactic transposition, via science fiction texts, to reinforce these postulates about teaching and cognition. The translational research involved researchers from the field of Physics teaching and 58 second-year high school students from a public institution. In the pedagogical mediation, as a basis for the discussion of the concept of entropy in the Second Law of Thermodynamics, we use one of the most acclaimed short stories by the popular Russian-American author, Isaac Asimov, entitled “The Last Question”. For data analysis, we resorted to techniques of semantic frequency and medium order of evocation as constructs of a taxonomy for the investigation of social representations arising from the implemented proposition. The results indicated consistency with the perspective of meaningful learning, consolidating reflections for similar interventions and contiguous research

Peginterferon plus ribavirin and sustained virological response rate in HCV-related advanced fibrosis: a real life study

Background: Tolerance and response to antiviral HCV treatment is poor in advanced fibrosis. The aim of this study was to assess SVR rate and its predictive factors in HCV advanced fibrosis patients treated in real life with full dose PEG-IFN plus RBV and to evaluate the adverse events related to treatment. Methods: A multicentric, retrospective study was conducted at six university hospitals. METAVIR F3 and F4 HCV monoinfected patients who were treated with PEG-IFN and RBV had their data analyzed. A stepwise logistic regression analysis was performed to identify the variables independently related to SVR. Adverse events were recorded during treatment. Results: 308 patients were included, 75% genotype 1 and 23% genotype 3. METAVIR F3 was present in 39% and F4 in 61% of patients. The median Child Pugh score for F4 patients was 5 (5–9). The global SVR rate was 34%, 11% were relapsers and 55% were nonresponders. SVR rates were similar between patients treated with PEG-IFN alfa 2a or alfa 2b (p = 0.24). SVR rates according to Child–Pugh score were 26% (Child A) and 18% (Child B). The independent factors related to SVR in F4 patients were genotype 3, RVR and fewer Child Pugh score points. Treatment interruption occurred in 31% patients and death occurred in 1.9%, all with liver cirrhosis. Conclusion: Treatment of HCV in patients with advanced fibrosis should not be postponed. However, a very careful evaluation of cirrhotic patients must be performed before treatment is indicated and careful monitoring is required during treatment.Universidade Estadual Paulista (UNESP) Botucatu School of MedicineUniversidade Federal do Rio de JaneiroUniversidade Estadual de CampinasUniversidade Federal de São Paulo (UNIFESP)Pontificia Universidade Catolica de São PauloUNIFESPSciEL

Performance of MISO Time Reversal Ultra-wideband over an 802.15.3a Channel Model

Abstract-This paper analyzes the performance of a baseband multiple-input single-output (MISO) time reversal ultrawideband system (TR-UWB) over the IEEE 802.15.3a channel model. Two scenarios are considered, CM1 based on LOS (0-4m) channel measurements and CM3 based on NLOS (4-10m) channel measurements. A semi-analytical performance expression is derived and compared with simulation results in terms of the number of antenna elements, number of users, and transmission rate. The results show that the system performance is improved with an increase in the number of transmit antenna elements and that additional equalization and multiple access enhancement schemes are necessary for high transmission rates