Hardware Parallel Architecture of a 3D Surface Reconstruction: Marching Cubes Algorithm

International audienceIn this paper we present a study of the algorithmic and architectural exploration methodology for a parallelism of the 3D reconstructing algorithm (Marching Cubes) and its optimized implementation on FPGA.We aim at defining a parallel multiprocessor architecture implementing this algorithm in an optimal way and Elementary Processor (EP) architecture dedicated to this algorithm. We use the SynDEx tool which adapts the AAA (Algorithm Architecture Adequacy) methodology, to find a good compromise between the computing power, the functionality of each PE, the optimization constraint (time, area), and the parallelization efficiency. Then, we describe a first implementation of PE on FPGA

Reconstruction of polygonal inclusions in a heat conductive body from dynamical boundary data

In this paper, we consider a reconstruction problem of small and polygonal heat-conducting inhomogeneities from dynamic boundary measurements on part of the boundary and for finite interval in time. Our identification procedure is based on asymptotic method combined with appropriate averaging of the partial dynamic boundary measurements. Our approach is expected to lead to an effective computational identification algorithms

FDM technology and the effect of printing parameters on the tensile strength of ABS parts

The effect of printing speed on the tensile strength of acrylonitrile butadiene styrene (ABS) samples fabricated using the fused deposition modelling (FDM) process is addressed in this research. The mechanical performance of FDM-ABS products was evaluated using four different printing speeds (10, 30, 50, and 70 mm/s). A numerical model was developed to simulate the experimental campaign by coupling two computational codes, Abaqus and Digimat. In addition, this article attempts to investigate the impacts of printing parameters on ASTM D638 ABS specimens. A 3D thermomechanical model was implemented to simulate the printing process and evaluate the printed part quality by analysing residual stress, temperature gradient and warpage. Several parts printed in Digimat were analysed and compared numerically. The parametric study allowed us to quantify the effect of 3D printing parameters such as printing speed, printing direction, and the chosen discretisation (layer by layer or filament) on residual stresses, deflection, warpage, and resulting mechanical behaviour

Effect of CNTs Additives on the Energy Balance of Carbon/Epoxy Nanocomposites during Dynamic Compression Test

International audiencePrevious research has shown that nanocomposites show not only enhancements in mechanical properties (stiffness, fracture toughness) but also possess remarkable energy absorption characteristics. However, the potential of carbon nanotubes (CNTs) as nanofiller in reinforced epoxy composites like glass fiber-reinforced polymers (GFRP) or carbon fiber-reinforced polymers (CFRP) under dynamic testing is still underdeveloped. The goal of this study is to investigate the effect of integrating nanofillers such as CNTs into the epoxy matrix of carbon fiber reinforced polymer composites (CFRP) on their dynamic energy absorption potential under impact. An out-of-plane compressive test at high strain rates was performed using a Split Hopkinson Pressure Bar (SHPB), and the results were analyzed to study the effect of changing the concentration of CNTs on the energy absorption properties of the nanocomposites. A strong correlation between strain rates and CNT mass fractions was found out, showing that an increase in percentage of CNTs could enhance the dynamic properties and energy absorption capabilities of fiber-reinforced composites

Experimental investigation of the effect of infill parameters on dynamic compressive performance of 3D-Printed carbon fiber reinforced polyethylene terephthalate glycol composites

International audienceThe current investigation evaluates the compressive response of 3D-printed carbon fiber-reinforced PETG thermoplastics to optimize different infill parameters when loaded at high impact pressures (strain rates). The selected parameters for the 3D printing of different samples are the filling pattern (rectilinear and honeycomb) and the filling density (25%, 50%, and 75%). Compression-split Hopkinson pressure bars (SHPBs) combined with a high-speed camera were used to monitor the evolution of the mechanical behavior and damage kinetics of 3D-printed samples in real-time with the variation in strain rate. The results revealed a significant improvement in compressive strength and compressive modulus when the filling density was increased from 20% to 75% for both patterns. However, the combination of a honeycomb pattern with 75% filling presented the best compressive strength, stiffness and damage resistance, irrespective of impact pressure. In particular, the highest compressive strengths, ranging from 35.5 to 56.16 MPa for impact pressures of 1.4 to 2.4 bar, respectively, were obtained with this configuration (75% honeycomb pattern). This represents a substantial difference of 25 to 38% compared with the 75% rectilinear pattern, which showed values below 35 MPa. Another significant result was observed for the compressive modulus, which reached 2787.8 MPa for the honeycomb-filled samples, whereas this value remained below 2000 MPa for the rectilinear pattern

Effect of carbon nanotubes on the in-plane dynamic behavior of a carbon/epoxy composite under high strain rate compression using SHPB

International audienceFiber reinforced composites have wide structural applications and vast research has been going on to improve their mechanical performance when subjected to quasi-static loading but, study of their dynamic behavior is still underdeveloped. For this reason, scientists have been continuously working on developing methods to improve their dynamic characteristics and addition of nanofillers suchs as Carbon Nanotubes (CNTs) as reinforcement is considered a possible solution for developing future generation high-quality fiber reinforced nanocomposites. In this study, composite specimens are manufactured using Epon 862 Epoxy resin and T300 6 k carbon fibers, and each specimen contained different weight percentages of multi-walled Carbon nanotubes (MWCNTs) i.e. 0% as a reference, 0.5%, and 2%. Specimens were tested experimentally using the Split Hopkinson pressure bar device (SHPB) under different pressures to examine their dynamic response and damage behavior at high strain rates. During the dynamic compression tests, a high-speed camera was used to monitor and record the damage kinetics. The experimental characterization showed that the integration of CNTs in matrix has greatly influenced the dynamic response and damage mechanism of the Carbon Fiber Reinforced Polymers composite (CFRP). Mechanical behavior of specimens with each percentage demonstrated the enhancement of the mechanical properties and showed the increase of the dynamic characteristics and fracture resistance because of the increase in stiffness of matrix material and interfacial bonding between matix and fiber reinforcement

Graphene nanofillers as a player to improve the dynamic compressive response and failure behavior of carbon/epoxy composite

International audienceVast research has been going on to improve the mechanical performance of Carbon Fiber Reinforced Polymers composite (CFRP) when subjected to quasi-static loading but, investigation and modification of their dynamic behavior is still underdeveloped. This paper presents an experimental investigation on the effect of random dispersed graphene nanoplatelets (GNPs) on mechanical properties of CFRP composites under dynamic loading. Four different mass fractions of GNPs, 0%, 0.5%, 1%, and 2%, were considered in the experiments. Specimens were tested experimentally using the Split Hopkinson pressure bar device (SHPB) to examine their dynamic response and damage behavior at high strain rates. During the dynamic compression tests, a high-speed camera was used to monitor and record the damage kinetics. The experimental characterization showed that the integration of GNPs has greatly influenced the dynamic response and damage mechanism of the CFRP. Composite doped with 1% GNPs demonstrates the optimum enhancement of the mechanical properties of the composite specimens and shows an increase of the dynamic characteristics and fracture resistance

Dynamic properties and toughening mechanisms of GNPs reinforced carbon fibers/epoxy textile composites under an SHPB impact load

International audienceIn the recent years, the mechanical and damping properties of fiber reinforced polymer composites have been improved by the addition of nanofillers such as titanium oxide, alumina oxide, carbon nanotube, and nanoclay. Recently, graphene nanoplatelets (GNPs) due to its exceptional characteristics, is getting significant attention. The literature that is currently available shows that adding graphene nanoplatelets can improve the stiffness, strength, and fracture toughness of fiber reinforced polymer composites when they are subjected to static and quasi-static loadings. However, there is currently a lack of information regarding how the incorporation of graphene nanoplatelets (GNPs) to the epoxy matrix can affect the dynamic response of carbon-epoxy composites, such as dynamic stress-strain behavior, stiffness, strength, and damage kinetics. The aim of this study is to examine the dynamic behavior of a composite made of carbon fibers and epoxy matrix filled with different mass fractions (0% as a reference, 0.5%, 1%, and 2%) of GNPs using Split Hopkinson Pressure Bar (SHPB). When compared to the findings obtained with carbon fiber reinforced polymer (CFRP) composites, the experimental results showed that adding up to 1% of GNPs resulted in significant improvements in strength and stiffness as well as decreases in delaminated area. However, a further increase in the mass fraction of GNPs in the epoxy matrix could lead to the presence of agglomerations and the non-uniform distribution of the filled resin between the carbon fibers, resulting in weak interfacial bonding, reducing the performance of the final composite, and leading to delamination failure

Etude algorithmique et conception d'architectures dédiées à la reconstruction 3D d'images médicales

electronic version (8 pp.

Growth promotion and protection against Orobanche foetida of chickpea (Cicer aerietinum) by two Rhizobium strains under greenhouse conditions

Fetid broomrape (Orobanche foetida Poir.) is a chlorophyll lacking holoparasite that subsists on the roots of plants and causes significant damage to the culture of leguminous plants particularly chickpea (Cicer aerietinum L.). The investigation was done about potential of Rhizobium strains for biological control of O. foetida using a commercial chickpea cultivar (Béja 1) and different Rhizobium strains. Firstly, benefit of bacterial inoculation on plant growth and efficiency in N-incorporation were demonstrated with four isolates, Azm, Bj, Sd.N2 and Sd.N1. Rhizobium strains were investigated for their ability to control O. foetida using pot and Petri-dish experiments. Inoculation of chickpeas with two (Azm and Bj) of the Rhizobium strains induced a significant decrease in O. foetida seed germination and in the number of tubercles on chickpea roots. Furthermore, other symptoms, including the non-penetration of the germ tube of germinated seeds into chickpea roots followed by radical browning and death of the parasite, were observed in the presence of these inoculated chickpea plants. The hypothesis that roots secrete toxic compounds related to Rhizobium inoculation is discussed.Keywords: Biological control, Rhizobium strains, Orobanche foetida, chickpea, necrotic symptomsAfrican Journal of Biotechnology Vol. 12(12), pp. 1371-137