Experimental analysis and numerical simulation of sintered micro-fluidic

This paper investigates the use of numerical simulations to describe solid state diffusion of a sintering stage during a Powder Hot Embossing (PHE) process for micro-fluidic components. Finite element analysis based on a thermo-elasto-viscoplastic model was established to describe the densification process of a PHE stainless steel porous component during sintering. The corresponding parameters such as the bulk viscosity, shearing viscosity and sintering stress are identified from dilatometer experimental data. The numerical analyses, which were performed on a 3D micro-structured component, allowed comparison between the numerical predictions and experimental results of during a sintering stage. This comparison demonstrates that the FE simulation results are in better agreement with the experimental results at high temperatures

Elaboration and study of the thermo-mechanical properties of an aligned cnt - polypropylene nanocomposite by twin-screw mixer

This study presents first the fabrication of a nanocomposite material based on Multi-Walled Carbon Nanotubes, and on a thermoplastic polymer matrix. First, a twin-screw mixer had been employed for preparing polypropylene nanocomposites loaded at 0.1, 1, 2, and 5wt% of MWCNT. Second, a characterization of rheological behavior for polypropylene as well as polypropylene/multi-walled carbon nanotube mixtures, at three temperatures (180, 200, and 220 °C,) has been carried out using cone and plate rheometer. Then, its thermomechanical properties have been studied. The work demonstrates how the addition of functionalized CNTs to a polypropylene will allow it to act as thermal conductor rather than as insulator

RETRACTED : Composite parameters analysis with boundary element method

This article has been retracted at the request of the Editors-in-Chief, according to the Publication Ethics Policy and Publication Malpractice Statement.Please see: http://revue.ummto.dz/index.php/JMES/about/editorialPolicies#custom-2 This note is published, 26 June 202

Physical modelling of amorphous thermoplastic polymer and numerical simulation of micro hot embossing process

Micro hot embossing process is considered as one of the most promising micro replication processes for manufacturing of polymeric components, especially for the high aspect ratio components and large surface structural components. A large number of hot embossing experimental results have been published, the material modelling and processes simulation to improve the quality of micro replication by hot embossing process are still lacking. This paper consists to 3D modelling of micro hot embossing process with amorphous thermoplastic polymers, including the mechanical characterisation of polymers properties, identification of the viscoelastic behaviour law of the polymers, numerical simulation and experimental investigation of micro hot embossing process. Static compression creep tests have been carried out to investigate the selected polymers’ viscoelastic properties. The Generalized Maxwell model has been proposed to describe the relaxation modulus of the polymers and good agreement has been observed. The numerical simulation of the hot embossing process in 3D has been achieved by taking into account the viscoelastic behaviour of the polymers. The microfluidic devices with the thickness of 2 mm have been elaborated by hot embossing process. The hot embossing process has been carried out using horizontal injection/compression moulding equipment, especially developed for this study. A complete compression mould tool, equipped with the heating system, the cooling system, the ejection system and the vacuum system, has been designed and elaborated in our research. Polymer-based microfluidic devices have been successfully replicated by the hot embossing process using the compression system developed. Proper agreement between the numerical simulation and the experimental elaboration has been observed. It shows strong possibility for the development of the 3D numerical model to optimize the micro hot embossing process in the future

Multi-fidelity classification using Gaussian processes: accelerating the prediction of large-scale computational models

Machine learning techniques typically rely on large datasets to create accurate classifiers. However, there are situations when data is scarce and expensive to acquire. This is the case of studies that rely on state-of-the-art computational models which typically take days to run, thus hindering the potential of machine learning tools. In this work, we present a novel classifier that takes advantage of lower fidelity models and inexpensive approximations to predict the binary output of expensive computer simulations. We postulate an autoregressive model between the different levels of fidelity with Gaussian process priors. We adopt a fully Bayesian treatment for the hyper-parameters and use Markov Chain Mont Carlo samplers. We take advantage of the probabilistic nature of the classifier to implement active learning strategies. We also introduce a sparse approximation to enhance the ability of themulti-fidelity classifier to handle large datasets. We test these multi-fidelity classifiers against their single-fidelity counterpart with synthetic data, showing a median computational cost reduction of 23% for a target accuracy of 90%. In an application to cardiac electrophysiology, the multi-fidelity classifier achieves an F1 score, the harmonic mean of precision and recall, of 99.6% compared to 74.1% of a single-fidelity classifier when both are trained with 50 samples. In general, our results show that the multi-fidelity classifiers outperform their single-fidelity counterpart in terms of accuracy in all cases. We envision that this new tool will enable researchers to study classification problems that would otherwise be prohibitively expensive. Source code is available at https://github.com/fsahli/MFclass

RETRACTED : Positional finite element solutions for laminated composites

This article has been retracted at the request of the Editors-in-Chief, according to the Publication Ethics Policy and Publication Malpractice Statement. Please see: http://revue.ummto.dz/index.php/JMES/about/editorialPolicies#custom-2Reason : This paper duplicated parts of a master's thesis that had already appeared in the digital library of São Paulo University (Brazil) in May 2015, DOI:10.11606/D.18.2015.tde-27052015-171842.One of the conditions of submission of a paper for publication is that authors declare explicitly that they have written entirely original works, and should ensure that the sources of any ideas and/or words in the manuscript that are not their own have been properly attributed through appropriate citations and/or quotes. Plagiarism constitutes unethical publishing behaviour and is unacceptable. Any attempt of plagiarism should be followed by the rejection of the submitted manuscript.As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and we apologize to readers of the journal that this was not detected during the submission process.This note is published, 12 April 202

Tratamiento endodóncico de una lesión periapical causante de separación radicular

Se presenta un caso de lesión periapical de tamaño considerable que produjo una separación manifiesta de las raíces de dos incisivos inferiores. Se practicó un tratamiento de conductos radiculares, con sobreobturación de hidróxido de calcio. El control clínico y radiográfico a los dos años muestra una reparación total del periápice

Complicaciones en un caso de apicoformación

La apicoformación es un tratamiento de conductos radiculares cuya finalidad es conseguir el cierre del ápice radicular, en un diente con rizogénesis incompleta, mediante la aposición de tejidos calcificados por parte de células del periápice. A este tejido se le denomina osteocemento. En el transcurso de este tratamiento pueden surgir complicaciones tales como reagudizaciones, falta de formación de la barrera apical y fracturas dentarias

Perspectivas actuales del tratamiento endodóncico en dientes con lesiones periapicales crónicas

Se analizan los aspectos histopatológicos de las lesiones periapiciales, el fenómeno de la proliferación epitelial intragranulomatosa como mecanismo patogénico de formación de cavidades quísticas microscópicas, los problemas diagnósticos de las mismas así como las perspectivas terapéuticas más actuales

Observación radiográfica y estudio histológico de un caso de apicoformación en un molar humano

Se describe un caso de apicoformación en un segundo molar inferior derecho. La observación radiográfica revela un cierre apical con un patrón morfológico diferente al del segundo molar inferior izquierdo. Efectuada su exodoncia a los 15 meses, los cortes histológicos seriados muestran un tejido calcificado obturando el foramen apical y bien adaptado a las paredes iniciales de dentina y cemento. En su interior observamos unas pequeñas áreas conteniendo tejido conectivo con capi lares. Las observaciones histo lógicas y radiográficas demuestran que el cierre apica l se efectúa por diferenciación de las células del periodonto apical