A DOE based approach for the design of RBF artificial neural networks applied to prediction of surface roughness in AISI 52100 hardened Steel turning

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Strings in horizons, dissipation and a possible interpretation of the Hagedorn temperature

We consider the entanglement of closed bosonic strings intersecting the event horizon of a Rindler spacetime, and, by using some simplified (rather semiclassical) arguments and some elements of the string field theory, we show the existence of a critical temperature beyond which closed strings cannot be in thermal equilibrium. The order of magnitude of this critical value coincides with the Hagedorn temperature, which suggests an interpretation consistent with the fact of having a partition function that is ill defined for temperatures higher than it. Possible implications of the present approach for the microscopical structure of stretched horizons are also pointed out.

Experimental and theoretical study of workpiece temperature when end milling hardened steels using (TiAl)N-coated and PcBN-tipped tools

The present work shows an experimental and theoretical study on heat flow when end milling, at high-speed, hardened steels applied to moulds and dies. AISI H13 and AISI D2 steels were machined with two types of ball nose end mills: coated with (TiAl)N and tipped with PcBN. The workpiece geometry was designed to simulate tool-workpiece interaction in real situations found in mould industries, in which complex surfaces and thin walls are commonly machined. The compressed and cold air cooling systems were compared to dry machining Results indicated a relatively small temperature variation, with higher range when machining AISI D2 with PcBN-tipped end mill. All cooling systems used demonstrated good capacity to remove heat from the machined surface, especially the cold air. Compressed air was the most indicated to keep workpiece at relatively stable temperature. A theoretical model was also proposed to estimate the energy transferred to the workpiece (Q) and the average convection coefficient ((h) over bar) for the cooling systems used. The model used a FEM simulation and a steepest decent method to find the best values for both variables. (c) 2007 Elsevier B.V. All rights reserved.

Mortar added by tyre rubber residues: Characterisation in fresh and hardened state

Due to the progressive increase of vehicles, the number of used tires is globally one of the serious environmental problems faced now. Therefore, several researches have being developed for its reuse. The use of tires' rubber in the concrete is a possible form of its application, aiming at the recycling of this material and the improvement of certain properties, as tenacity, impact resistance, thermal and acoustic isolation. This article presents conclusions that several researchers obtained using the rubberized concrete. Thus there were researched several works enclosing the period of 1993 to 2003, presenting then the results of some characteristics of this concrete such as: physical properties in fresh and hardened state, mechanical properties and properties that remit the durability. The bibliographical revision has as objective to subsidize future researches that can contribute to improve the use of this concrete in civil construction.

Grinding of hardened steels using optimized cooling

Grinding - the final machining process of a workpiece - requires large amounts of cutting fluids for the lubrication, cooling and removal of chips. These fluids are highly aggressive to the environment. With the technological advances of recent years, the worldwide trend is to produce increasingly sophisticated components with very strict geometric and dimensional tolerances, good surface finish, at low costs, and particularly without damaging the environment. The latter requirement can be achieved by recycling cutting fluids, which is a costly solution, or by drastically reducing the amount of cutting fluids employed in the grinding process. This alternative was investigated here by varying the plunge velocity in the plunge cylindrical grinding of ABNT D6 steel, rationalizing the application of two cutting fluids and using a superabrasive CBN (cubic boron nitride) grinding wheel with vitrified binder to evaluate the output parameters of tangential cutting force, acoustic emission, roughness, roundness, tool wear, residual stress and surface integrity, using scanning electron microscopy (SEM) to examine the test specimens. The performance of the cutting fluid, grinding wheel and plunge velocity were analyzed to identify the best machining conditions which allowed for a reduction of the cutting fluid volume, reducing the machining time without impairing the geometric and dimensional parameters, and the surface finish and integrity of the machined components.

Influence of optimized lubrication-cooling and minimum quantity lubrication on the cutting forces, on the geometric quality of the surfaces and on the micro-structural integrity of hardened steel parts

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise da estabilidade da região externa do sistema Plutão-Caronte após a descoberta dos novos satélites NIX e HIDRA: aplicação à sonda new horizons

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Horizons 2030: Equality at the centre of sustainable development. Summary

The world is living a change of era. The 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals represent the international community’s response to the economic, distributive and environmental imbalances built up under the prevailing development pattern. This document, presented by the Economic Commission for Latin America and the Caribbean (ECLAC) to its member States at its thirty-sixth session, provides an analytical complement to the 2030 Agenda from a structuralist perspective and from the point of view of the Latin American and Caribbean countries. The proposals made here stem from the need to achieve progressive structural change in order to incorporate more knowledge into production, ensure social inclusion and combat the negative impacts of climate change. The reflections and proposals for advancing towards a new development pattern are geared to achieving equality and environmental sustainability. In these proposals, the creation of global and regional public goods and the corresponding domestic policies form the core for expanding the structuralist tradition towards a global Keynesianism and a development strategy centred around an environmental big push.

Horizons 2030: l’égalité au coeur du développement durable. Synthèse

Le monde traverse un changement d’époque. Face aux déséquilibres économiques, distributifs et environnementaux du mode de développement prédominant, la communauté internationale vient d’adopter le Programme de développement durable à l’horizon 2030 et ses 17 objectifs. Le document que la Commission économique pour l’Amérique latine et les Caraïbes (CEPALC) présente aux états membres à l’occasion de sa trente-sixième session a pour but d’apporter un complément analytique à ce Programme dans la perspective structuraliste du développement et de l’optique des pays d’Amérique latine et des Caraïbes. Les propositions contenues dans ce document sont centrées sur la nécessité de promouvoir un changement structurel progressif qui favorise l’incorporation du savoir à la production, garantisse l’inclusion sociale et combatte les effets néfastes du changement climatique. Les réflexions et les propositions visant à avancer sur la voie d’un nouveau mode de développement sont axées sur la promotion de l’égalité et de la pérennité de l’environnement. La création de biens publics mondiaux et leurs équivalents à l’échelle régionale, ainsi que l’application de politiques nationales sont au coeur d’une vision structuraliste qui est appelée à évoluer vers un keynésianisme mondial et une stratégie de développement centrée sur un élan majeur pour l’environnement.

Horizons 2030: Equality at the centre of sustainable development

The world is living a change of era. The 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals represent the international community’s response to the economic, distributive and environmental imbalances built up under the prevailing development pattern. This document, presented by the Economic Commission for Latin America and the Caribbean (ECLAC) to its member States at its thirty-sixth session, provides an analytical complement to the 2030 Agenda from a structuralist perspective and from the point of view of the Latin American and Caribbean countries. The proposals made here stem from the need to achieve progressive structural change in order to incorporate more knowledge into production, ensure social inclusion and combat the negative impacts of climate change. The reflections and proposals for advancing towards a new development pattern are geared to achieving equality and environmental sustainability. In these proposals, the creation of global and regional public goods and the corresponding domestic policies form the core for expanding the structuralist tradition towards a global Keynesianism and a development strategy centred around an environmental big push.

The sailboat island and the New Horizons trajectory

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of HSM cutting parameters on the surface integrity characteristics of hardened AISI H13 steel

The purpose of this study is to evaluate the influence of the cutting parameters of high-speed machining milling on the characteristics of the surface integrity of hardened AISI H13 steel. High-speed machining has been used intensively in the mold and dies industry. The cutting parameters used as input variables were cutting speed (v c), depth of cut (a p), working engagement (a e) and feed per tooth (f z ), while the output variables were three-dimensional (3D) workpiece roughness parameters, surface and cross section microhardness, residual stress and white layer thickness. The subsurface layers were examined by scanning electron and optical microscopy. Cross section hardness was measured with an instrumented microhardness tester. Residual stress was measured by the X-ray diffraction method. From a statistical standpoint (the main effects of the input parameters were evaluated by analysis of variance), working engagement (a e) was the cutting parameter that exerted the strongest effect on most of the 3D roughness parameters. Feed per tooth (f z ) was the most important cutting parameter in cavity formation. Cutting speed (v c) and depth of cut (a p) did not significantly affect the 3D roughness parameters. Cutting speed showed the strongest influence on residual stress, while depth of cut exerted the strongest effect on the formation of white layer and on the increase in surface hardness.