A Novel Approach to Optimize the Design of Parts for Additive Manufacturing

Additive Manufacturing (AM) is a term used to group the different manufacturing processes that use various techniques, each of which is capable of producing parts made from a wide variety of materials, such as polymers, ceramics, metals, wood, among others. All these technologies allow parts manufacturing by adding successive layers of material which can be liquid, powder or wire. In order to take advantages of the geometric freedom offered by AM, Topological Optimization (TO) is usually used. TO provides the optimal distribution of material for a given request. The main objective is weight reduction, without compromising the original resistance of an existing part produced by traditional processes. Taking advantage of the freedom allowed by the AM process and conciliating it with the CAE features, which allow to simulate the parts behavior when subjected to the expected loads, a new approach methodology was drawn in order to shorten the time needed to optimize parts design for AM. A case study was developed in order to validate the methodology established. The combination of AM and TO revealed promising results, attending to the component efficiency achieved.info:eu-repo/semantics/publishedVersio

Improving the Cut Surface Quality by Optimizing Parameters in the Fibre Laser Cutting Process

One of the main problems with laser cutting equipment is related to the wrong setting of cutting parameters. The mismatching of these parameters leads to a loss of cut surface quality, which is hardly re-established. This loss of quality is usually related to a burr problem. Thus, this study is aimed to improve and optimize this process using a fibre laser equipment. Three important laser cutting parameters were studied in order to investigate their importance in the cut surface quality: radiation power, cutting speed and gas pressure. The different values were performed cutting a stainless steel AISI 316L and a cold rolled steel St12. Metallographic and cut surface analysis, burr and roughness measurements were carried out, supported by a Scanning Electron Microscopy and profilometry. Through the Taguchi statistical analysis model, it is possible to indicate the best set of laser cutting parameters. It was verified that the values recommended by the equipment manufacturer can be optimized, being possible to use less radiation power in the laser beam with greater speed of cut, providing a better cut surface quality, improving and optimizing the entire process.info:eu-repo/semantics/publishedVersio

Improving manual assembly lines devoted to complex electronic devices by applying Lean tools

Manual assembly lines are usually deeply studied before implementation. Nevertheless, several problems upsurge when the product needs to be slightly changed. This is very common in complex electric and electronic devices usually produced in small batches, where the customers are demanding more and more features and the product needs to be continuously updated. However, these updates sometimes create huge difficulties for the previously installed assembly line, generating as well, line unbalancing and wastes of time regarding the initial situation. In this paper, a deep study of an adjusted assembly line of electronic devices was carried out using Value Stream Mapping (VSM) method to fully understand and document the different tasks and operations. The Lean Line Balancing (LLB) was also applied in order to reduce the line bottleneck by balancing the Task Time (TT) of each workstation so that there are no delays, and nobody is overburden with their task. Standardized processes and standardized work were also applied. During the line layout development stage, assembly fixtures, wastes reductions and visual management techniques were applied as well, different concepts were generated and, finally, the best solutions were selected. Throughout the study, many benefits for the studied manual assembly line were found, which can be considered as a strong motivation to apply Lean Manufacturing (LM) tools for better line efficiency and production rate.info:eu-repo/semantics/publishedVersio

The Improvement of an APEX Machine involved in the Tire Manufacturing Process

Over the years, there has been a huge expansion in the automotive component industry and its consequent innovation, which has evolved along with automation and robotics. Therefore, in order to ensure component quality, as well as the quality of the entire production process, it is crucial to enhance competitiveness in the sector. Since quality is a key feature in this industry, all manufacturers and suppliers are scrutinized by systematic audits to ensure constant improvements. This work was developed at a multinational industry and focuses on tire production for the automotive sector. Tires present a complex production process, which covers a wide range of activities from mixing, preparation, construction and vulcanization to the inspection departments, all of which are greatly predisposed to process improvement. In one of these departments (Preparation - APEX machines, responsible for the tire bead production), one of the main problems detected was directly related to a large number of failures in the pneumatic systems. These were found to be difficult to control, both in terms of speed and positioning. Some of the failures in automation were generating delays in certain processes, leading to lengthy setup times and culminating in higher production costs. In order to achieve greater quality, reliability and accuracy, a higher level of automation was applied to these kinds of machines by resorting to 5S methodology. A safety upgrade of the equipment was also undertaken, which will allow for the improvement of workplace safety.The performance improvement of the APEX machines was reached by implementing the following strategies: the automation of conveyor and tray movements between the cutting and application subprocesses; the implementation of 5S methodology; the automation of the cutting process; the updating of safety devices; and the automated control of the separation subprocess. A strong decrease in the breakdown time was recorded (-62%) resulting of the project implementation. The APEXmachine performance was also improved in 9%.info:eu-repo/semantics/publishedVersio

Magnetic Field Sensor With Terfenol-d Thin-film Coated Fbg

In this work a magnetic field sensor based on an FBG coated with a thin film of Terfenol-D is presented. The sensor was tested with two optical interrogation systems: one, a scanning laser system with a 1 pm resolution, and the other a differential white light interferometer (WLI). The results obtained in the magnetic field range of 20 mT to 100 mT, show the possibility of increasing the magnetic field measurement resolution, with temperature fluctuations invariance, by a factor of 4.5 when using the WLI system. © 2012 SPIE.8421Mora, J., Diez, A., Cruz, J.L., A magnetostrictive sensor interrogated by fiber gratings for DC-Current and temperature discrimination (2000) Ieee Photonic Tech L, 12 (12), pp. 1680-1682Satpathi, D., Moore, J.A., Ennis, M.G., Design of a terfenol-D based fiber-optic current transducer (2005) Ieee Sens J, 5 (5), pp. 1057-1065Li, M.F., Giant Magnetostrictive Magnetic Fields Sensor Based on Dual Fiber Bragg Gratings, pp. 490-495Mora, J., Martinez-Leon, L., Diez, A., Simultaneous temperature and ac-current measurements for high voltagelines using fiber Bragg gratings (2006) Sensor Actuat A-Phys, 125 (2), pp. 313-316Reilly, D., Willshire, A.J., Fusiek, G., A fiber-Bragg-grating-based sensor for simultaneous AC current and temperature measurement (2006) Ieee Sens J, 6 (6), pp. 1539-1542Davino, D., Visone, C., Ambrosino, C., Compensation of hysteresis in magnetic field sensors employing Fiber Bragg Grating and magneto-elastic materials (2008) Sensor Actuat A-Phys, 147 (1), pp. 127-136Yang, M.H., Dai, J.X., Zhou, C.M., Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials (2009) Opt Express, 17 (23), pp. 20777-20782Quintero, S.M.M., Braga, A.M.B., Weber, H.I., A magnetostrictive composite-fiber Bragg grating sensor (2010) Sensors-Basel, 10 (9), pp. 8119-8128Smith, G.N., Characterisation and performance of a Terfenol-D coated femtosecond laser inscribed optical fibre Bragg sensor with a laser ablated microslot for the detection of static magnetic fields (2011) Opt Express, 19 (1), pp. 363-370Quintero, S.M.M., Martelli, C., Braga, A., Magnetic field measurements based on terfenol coated photonic crystal fibers (2011) Sensors-Basel, 11 (12), pp. 11103-1111

Cholini (Coleoptera: Curculionidae, Molytinae) depositados na Coleção de Invertebrados do Instituto Nacional de Pesquisas da Amazônia

In Brazilian Amazonia, Cholini (Coleoptera, Curculionidae, Molytinae) is represented by 53 species distributed in seven generaAmeris Dejean, 1821; Cholus Germar, 1824; Homalinotus Sahlberg, 1823; Lobaspis Chevrolat, 1881; Odontoderes Sahlberg, 1823; Ozopherus Pascoe, 1872 and Rhinastus Schoenherr, 1825. This work documents the species of Cholini housed in the Invertebrate Collection of the Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil and gives the geographical and biological data associated with them. A total of 186 Cholini specimens were identified as belonging to 14 species (13 from Brazilian Amazonia) and five genera (Cholus, Homalinotus, Odontoderes, Ozopherus and Rhinastus). Only 24% of the Cholini species reported from Brazilian Amazonia are actually represented in the INPA collection, underscoring the need for a more systematical collecting based on available biological information. The known geographical distribution was expanded for the following speciesCholus granifer (Chevrolat, 1881) for Brazil; C. pantherinus (Olivier, 1790) for Manaus (Amazonas); Cholus parallelogrammus (Germar, 1824) for Piraquara (Paraná); Homalinotus depressus (Linnaeus, 1758) for lago Janauacá (Amazonas) and rio Tocantins (Pará); H. humeralis (Gyllenhal, 1836) for Novo Airão, Coari (Amazonas) and Porto Velho (Rondônia); H. nodipennis (Chevrolat, 1878) for Carauari, Lábrea (Amazonas) and Ariquemes (Rondônia); H. validus (Olivier, 1790) for rio Araguaia (Brasil), Manaus (Amazonas), rio Tocantins (Pará), Porto Velho and BR 364, Km 130 (Rondônia); Odontoderes carinatus (Guérin-Méneville, 1844) for Manaus (Amazonas); O. spinicollis (Boheman, 1836) for rio Uraricoera (Roraima); and Ozopherus muricatus Pascoe, 1872 for lago Janauacá (Amazonas). Homalinotus humeralis is reported for the first time from "urucuri" palm, Attalea phalerata Mart. ex Spreng.Na Amazônia brasileira, Cholini (Coleoptera, Curculionidae, Molytinae) é representada por 53 espécies, distribuídas em sete gêneros: Ameris Dejean, 1821; Cholus Germar, 1824; Homalinotus Sahlberg, 1823; Lobaspis Chevrolat, 1881; Odontoderes Sahlberg, 1823; Ozopherus Pascoe, 1872 e Rhinastus Schoenherr, 1825. Este trabalho documenta as espécies de Cholini depositadas na Coleção de Invertebrados do Instituto Nacional de Pesquisas da Amazônia, Manaus, Brasil, além de apresentar a distribuição geográfica e informações sobre a biologia dessas espécies. Foram identificados 186 espécimes de Cholini, pertencentes a 14 espécies (13 da Amazônia brasileira) e cinco gêneros (Cholus, Homalinotus, Odontoderes, Ozopherus e Rhinastus). Somente 24% das espécies de Cholini registradas para a Amazônia brasileira estão representadas na coleção do INPA, ressaltando a necessidade de um esforço de coleta sistemático baseado na informação biológica disponível. Foi ampliada a distribuição geográfica conhecida das seguintes espécies: Cholus granifer (Chevrolat, 1881) para Brasil; C. pantherinus (Olivier, 1790) para Manaus (Amazonas); Cholus parallelogrammus (Germar, 1824) para Piraquara (Paraná); Homalinotus depressus (Linnaeus, 1758) para lago Janauacá (Amazonas) e rio Tocantins (Pará); H. humeralis (Gyllenhal, 1836) para Novo Airão, Coari (Amazonas) e Porto Velho (Rondônia); H. nodipennis (Chevrolat, 1878) para Carauari, Lábrea (Amazonas) e Ariquemes (Rondônia); H. validus (Olivier, 1790) para rio Araguaia (Brasil), Manaus (Amazonas), rio Tocantins (Pará), Porto Velho e BR 364, Km 130 (Rondônia); Odontoderes carinatus (Guérin-Méneville, 1844) para Manaus (Amazonas); O. spinicollis (Boheman, 1836) para rio Uraricoera (Roraima) e Ozopherus muricatus Pascoe, 1872 para lago Janauacá (Amazonas). Homalinotus humeralis é associado pela primeira vez com a palmeira urucuri Attalea phalerata Mart. ex Spreng

Gamma-irradiated human amniotic membrane decellularised with sodium dodecyl sulfate is a more efficient substrate for the ex vivo expansion of limbal stem cells

yesThe gold standard substrate for the ex vivo expansion of human limbal stem cells (LSCs) remains the human amniotic membrane (HAM) but this is not a defined substrate and is subject to biological variabil-ity and the potential to transmit disease. To better define HAM and mitigate the risk of disease transmis-sion, we sought to determine if decellularisation and/or c-irradiation have an adverse effect on culture growth and LSC phenotype. Ex vivo limbal explant cultures were set up on fresh HAM, HAM decellularised with 0.5 M NaOH, and 0.5% (w/v) sodium dodecyl sulfate (SDS) with or without c-irradiation. Explant growth rate was measured and LSC phenotype was characterised by histology, immunostaining and qRT-PCR (ABCG2, DNp63, Ki67, CK12, and CK13). Ƴ-irradiation marginally stiffened HAM, as measured by Brillouin spectromicroscopy. HAM stiffness and c-irradiation did not significantly affect the LSC phe-notype, however LSCs expanded significantly faster on Ƴ-irradiated SDS decellularised HAM (p < 0.05) which was also corroborated by the highest expression of Ki67 and putative LSC marker, ABCG2. Colony forming efficiency assays showed a greater yield and proportion of holoclones in cells cultured on Ƴ-irradiated SDS decellularised HAM. Together our data indicate that SDS decellularised HAM may be a more efficacious substrate for the expansion of LSCs and the use of a c-irradiated HAM allows the user to start the manufacturing process with a sterile substrate, potentially making it safer

The Convex Geometry of Linear Inverse Problems

In applications throughout science and engineering one is often faced with the challenge of solving an ill-posed inverse problem, where the number of available measurements is smaller than the dimension of the model to be estimated. However in many practical situations of interest, models are constrained structurally so that they only have a few degrees of freedom relative to their ambient dimension. This paper provides a general framework to convert notions of simplicity into convex penalty functions, resulting in convex optimization solutions to linear, underdetermined inverse problems. The class of simple models considered are those formed as the sum of a few atoms from some (possibly infinite) elementary atomic set; examples include well-studied cases such as sparse vectors and low-rank matrices, as well as several others including sums of a few permutations matrices, low-rank tensors, orthogonal matrices, and atomic measures. The convex programming formulation is based on minimizing the norm induced by the convex hull of the atomic set; this norm is referred to as the atomic norm. The facial structure of the atomic norm ball carries a number of favorable properties that are useful for recovering simple models, and an analysis of the underlying convex geometry provides sharp estimates of the number of generic measurements required for exact and robust recovery of models from partial information. These estimates are based on computing the Gaussian widths of tangent cones to the atomic norm ball. When the atomic set has algebraic structure the resulting optimization problems can be solved or approximated via semidefinite programming. The quality of these approximations affects the number of measurements required for recovery. Thus this work extends the catalog of simple models that can be recovered from limited linear information via tractable convex programming

Stochastic Acceleration by Turbulence

The subject of this paper is stochastic acceleration by plasma turbulence, a process akin to the original model proposed by Fermi. We review the relative merits of different acceleration models, in particular the so called first order Fermi acceleration by shocks and second order Fermi by stochastic processes, and point out that plasma waves or turbulence play an important role in all mechanisms of acceleration. Thus, stochastic acceleration by turbulence is active in most situations. We also show that it is the most efficient mechanism of acceleration of relatively cool non relativistic thermal background plasma particles. In addition, it can preferentially accelerate electrons relative to protons as is needed in many astrophysical radiating sources, where usually there are no indications of presence of shocks. We also point out that a hybrid acceleration mechanism consisting of initial acceleration by turbulence of background particles followed by a second stage acceleration by a shock has many attractive features. It is demonstrated that the above scenarios can account for many signatures of the accelerated electrons, protons and other ions, in particular $^3$He and $^4$He, seen directly as Solar Energetic Particles and through the radiation they produce in solar flares.Comment: 29 pages 7 figures for proceedings of ISSI-Bern workshop on Particle Acceleration 201