Search

International audience; Design for Additive Manufacturing (DfAM) aims at optimizing the product design based on design rules defined thanks to Additive Manufacturing (AM) constraints. To elaborate a functional design, several parameters like part orientation and layer thickness influence the results of mechanical strength, roughness, and manufacturing time. Surface roughness is an important input of Fused Deposition Modeling which impacts the product functionalities. To participate in product design optimization and DfAM development, this research suggests studying roughness models in order to clarify the best functional design methodology. This analysis permits to propose a meta-model that provides a better estimation for the surface roughness of the FDM products. A new roughness model is developed by a combination of genetic programming and symbolic regression due to the experimental data which helps the manufacturer to predict the surface quality of the products before fabrication. It enables us to estimate the surface roughness of all the AM products fabricated in a different value of layer thickness for all possible orientations in the space regarding part building direction.

In the present work, selective laser melting (SLM) technology was utilized for manufacturing CX stainless steel samples under a series of laser parameters. The effect of laser linear energy density on the microstructure characteristics, phase distribution, crystallographic orientation and mechanical properties of these CX stainless steel samples were investigated theoretically and experimentally via scanning electron microscope (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). Based on the systematic study, the SLM CX stainless steel sample with best surface roughness (Ra = 4.05 ± 1.8 μm) and relative density (Rd = 99.72 %±0.22 %) under the optimal linear density (η = 245 J/m) can be obtained. SLM CX stainless steel was primarily constituted by a large number of fine martensite (α’ phase) structures (i.e., cell structures, cellular dendrites and blocky grains) and a small quantity of austenite (γ phase) structures. The preferred crystallographic orientation (i.e., direction) can be determined in the XZ plane of the SLM CX sample. Furthermore, under the optimal linear energy density, the good combinations with the highest ultimate tensile strength (UTS = 1068.0 %±5.9 %) and the best total elongation (TE = 15.70 %±0.26 %) of the SLM CX sample can be attained. Dislocation strengthening dominates the strengthening mechanism of the SLM CX sample in as-built state.

Bound Powder Extrusion (BPE) is increasingly gaining popularity and makes metal additive manufacturing easier and more accessible for industrial production. The Markforged-Metal X technology with debinding and sintering, also called Atomic Diffusion Additive Manufacturing (ADAM), is a newcomer in the field of extrusion additive manufacturing. The main objective of this work is to investigate the mechanical properties of 17-4PH stainless steel samples produced by ADAM. Moreover, the effects of a mechanical post-treatment (SMAT) on surface and mechanical properties are also analyzed. The macroscopic tensile response and superficial residual stresses of as-fabricated and SMATed samples are compared.

International audience

International audience; The thermal comfort requirements of disabled people in healthcare buildings are an important research topic that concerns a specific population with medical conditions impacted by the indoor environment. This paper experimentally investigated adaptive thermal comfort in buildings belonging to the Association of Parents of Disabled Children, located in the city of Troyes, France, during the winter season. Thermal comfort was evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires adapted to their disability. Indoor environmental parameters such as relative humidity, mean radiant temperature, air temperature, and air velocity were measured using a thermal microclimate station during winter in February and March 2020. The main results indicated a strong correlation between operative temperature, predicted mean vote, and adaptive predicted mean vote, with the adaptive temperature estimated at around 21.65 °C. These findings highlighted the need to propose an adaptive thermal comfort strategy. Thus, a new adaptive model of the predicted mean vote was proposed and discussed, with a focus on the relationship between patient sensations and the thermal environment.

International audience

International audience; In this study, a Surface Mechanical Attrition Treatment (SMAT) is applied to a 17-4PH single edge notched tension (SENT) sample made by Atomic Diffusion Additive Manufacturing (ADAM). Grating of gold nanoparticles allowing multiscale characterizations is deposited on the surface of specimen by electron beam lithography. In-situ tensile test is carried out and images of the surface are recorded. The crack propagation is followed and the local parameters influencing the propagation are analyzed. The evolutions at the microstructure scale are compared with the macroscopic behavior of the specimen.

Enhancing the glazing areas in buildings could save energy by increasing solar gain and thus decreasing the demand for heating and artificial lighting during the cold season. However, relatively large glazed buildings often cause thermal discomfort to occupants due to the midseason heating, especially in the case of inertial heating systems. This study was conducted to examine the impact of direct solar radiation on the dynamic thermal behavior of a floor heating system. A series of experiments were conducted on a monitored full-scale controlled test cell facility simulating a dynamic sun patch on a radiant heating slab. A previously published bi-dimensional dynamic model based on the finite difference method was extended and validated to consider the additional heat flux brought by the sun patch. The findings show that the overheating time induced by the sun patch exposure was approximately 8.5 h after the disappearance of the solar patch. The average heating floor surface temperature attained 33.91 °C, whereas the indoor air temperature reached 26 °C. The conducted numerical parametric study revealed that when the sun patch occurs, ventilation remarkably decreases the indoor air temperature but keeps the average surface temperature almost unchanged and primarily over the standard upper limits. In contrast, water-based cooling technique appeared to be efficient under sun patch exposure since the average surface temperature and indoor air temperature can be decreased and maintained under acceptable limits in the average comfort zone.

The Selective Laser Melting (SLM) process induces tensile residual stresses that impact negatively on the mechanical characteristics of the material. In literature, the well-known solution to overcome this issue is a post-process heat treatment. However, this solution is usually accompanied by a loss of the mechanical properties. Therefore, the aim of this investigation is to study the heat treatment impact and a Surface Mechanical Attrition Treatment on several characteristics. Different samples were characterized using several experimental observations such as surface roughness, micro-tensile testing, micro-hardness profiles, and X-ray diffraction. The results show beneficial impacts of SMAT on the As-Built SLM Ti-6Al-4V.

International audience; In France, the total heated surface area of educational buildings represents 19.5% of non-residential buildings, with an average total final energy consumption of 142 kWh/m2/y. Of this, the energy usage for heating is 97 kWh/m2/y. To save energy, building energy assessment seeks a trade-off between energy savings and the indoor environmental quality (IEQ) of the buildings. A long-term post-occupancy study was conducted on a two-story educational building with a total floor area of 3200 m2 located in Troyes, France. The Building Management System (BMS) programme was used to analyse the energy consumption for a period of three years from January 2015 to December 2017. Although the building complies with High Environmental Quality (HQE®) standards, the post-occupancy energy demand exceeded the predicted consumption levels owing to the auxiliary equipment. Furthermore, the indoor air quality (IAQ) was assessed by monitoring and analysing CO2 levels, which were satisfactory for 95% of occupancy period. Moreover, further investigations were performed in the building's foyer, area where indoor thermal comfort was assessed experimentally and numerically. Subjective evaluation was also conducted according to survey questionnaires completed by 41 students between the ages of 17 and 22. The results indicate that increasing the indoor temperature by 1 °C can improve the indoor thermal sensation but led to increased energy consumption of about 12%.

International audience

International audience

International audience; In biomechanics recent mathematical models allow to predict the muscular force response to functional electrical stimulations (in short, FES).The main concern of the present paper is to deal with the computation of optimized electrical pulses trains (for example in view of maximizing the final force response). Using the fact that FES are modeled as Dirac pulses, our problem is rewritten as an optimal sampled-data control problem where the control parameters are the pulses amplitudes and the pulses times. We establish the corresponding Pontryagin first-order necessary optimality conditionsand we show how they can be used in view of numerical simulations.

In this article, we analyze the time minimal control for the saturation of a pair of spins of the same species but with inhomogeneities of the applied RF-magnetic field, in relation with the contrast problem in Magnetic Resonance Imaging. We make a complete analysis based on geometric control to classify the optimal syntheses in the single spin case to pave the road to analyze the case of two spins. The Bocop software is used to determine local minimizers for physical test cases and Linear Matrix Inequalities approach is applied to estimate the global optimal value and validate the previous computations. This is complemented by numerical computations combining shooting and continuation methods implemented in the HamPath software to analyze the structure of the time minimal solution with respect to the set of parameters of the species. Symbolic computations techniques are used to handle the singularity analysis.

International audience; Additive Manufacturing or 3D Printing has a great potential to develop significant advances in materials, printers’ technology, and processes. Thus, the layer by layer manufacturing has existed for three decades and new developments recently appeared in smart materials. Laboratories discovered ways to design and manufacture advanced structured materials and responsive materials used in multi-functional and high-performance products. The current research and development efforts will have an impact on the traditional design and manufacturing process. 4D Printing announces a major modification in the product design and manufacturing process from static structures to dynamic structures like Shape Memory Material (SMM) with integrated functionalities. This article presents a review of smart materials based on a classification of advanced structured materials and responsive materials before beginning a description of current applications. The use of multi-materials and the study of predictive models to simulate the responsive materials behaviour accelerate the smart materials development.

International audience; In the time minimal control problem, singular arcs are omnipresent to determine the optimal solutions and leads to the well known turnpike phenomenon [1]. Very recently, this connection between singular arcs using a bang arc was shown to be relevant to saturate a single spin in Magnetic Resonance Imaging. Based on this example we propose a mathematical model to analyze such connection, which is called a bridge. This is applied to compute bridges in the optimization of chemical reaction networks using temperature control.

International audience; In this study, anisotropic ductility and associated damage mechanisms of a grade X100 line pipe steel previously studied at the macroscopic scale, were investigated using in-situ synchrotron-radiation computed tomography (SRCT) of notched round bars. Line pipe materials have anisotropic mechanical properties, such as tensile strength, ductility and toughness. Specimens were tested for loading along both rolling (L) and transverse (T) directions. The in-situ data collected allowed quantifying both specimen deformation (evolution of the cross section) and microscopic damage parameters such as porosity, void shape and void orientation. Nucleation at small particles (CaS/TiO 2) aligned along the L direction was observed during plastic deformation. It was shown that only very few anisotropic particle clusters are present in the material. However, these clusters led to substantial early void growth for loading normal to the loading direction, thereby explaining the toughness anisotropy in this material. Significant void growth was observed at the beginning of load decrease for a relatively limited diameter reduction (about 10%). Coalescence of voids within clusters along L-direction (Necklace) clearly explained anisotropic rupture.

International audience; This paper deals with design for manufacturing (DFM) approach for additive manufacturing (AM) to investigate simultaneously the different attributes and criteria of design and manufacturing. The integrated design approach is provided in the product definition level and it gradually maps the customer requirements to the final product model. The main contribution of this paper is an interface processing engine that is an interface between the product model and manufacturing model. This study uses the Skin-Skeleton approach to model the first definition of the product and model the material flow of AM technology as the manufacturing process. This engine is developed through analysis of all AM technologies and identification of their parameters, criteria, and drawbacks. In order to evaluate some product and process parameters, a multi-objective problem is formulated based on the analysis of all AM technologies; production time and material mass are optimized regarding mechanical behavior of the material and roughness of product. The approach is validated by a case study through a bag hook example. From its requirement specification to the proposed approach, this article defines an optimized product and its manufacturing parameters for fused deposition modeling (FDM) technology.

International audience; Hemp shives is a lightweight material known for its insulating properties. Associating these bio-fibers with plant-based matrix instead of a mineral binder in insulation applications is of ecological interest. This article describes the study of a low environmental impact 100% plant-based material made solely from wheat starch and hemp shives. The hemp/starch ratio (H/S) influence and hemp shive size are studied. Samples are evaluated in terms of physical properties, mechanical behaviour and hygrothermal properties through an experimental approach. Results show that increasing 0–5 mm hemp shive proportion from 15% to 30% leads to a significant enhancement of the mechanical and hygric characteristics due to the load transfer and porosity. However, when the H/S ratio increases, mechanical and hygrothermal characteristics decrease slightly. Finally, the hemp-starch agro-material with H/S equal to 8 and 30% of 0–5 mm hemp shive seems to be the optimal composition between the studied samples.

International audience; In recent years, glass facades and extensive glassing areas have gained popularity in the built environment. However, thermal comfort and energy-savings in such buildings are still questionable. Advanced comfort-based control strategies have been proposed in order to fulfill a tradeoff between energy-saving and occupants’ thermal comfort. Yet, they could consume energy as the conventional control approach if the building is poorly designed. Thus, an adequate design of building envelope, namely glass facades, is essential to achieve the desired trade-off. The objective of this study is to understand and formulate the relationship between the mean radiant temperature (MRT) and glass facades design parameters in a comfort-controlled space in order to optimize building design for a trade-off between energy savings and thermal comfort. The combined use of numerical simulations, the design of experiments (DoE) technique and an optimization approach is adopted. For the investigations, a previously developed and validated dynamic simulation model is used. The combined use of numerical simulation and DoE aims to identify the significant parameters affecting the MRT, as well as to develop a metamodeling relationship between the considered design factors and MRT. Lastly, the developed meta-models are validated and used to determine a set of optimal solutions using the desirability function approach. The results indicate that the optimized design case allowed about 26% reduction of heating energy consumption compared to the base case design. Finally, the results show that an adequate design of the glazed envelope leads to improved thermal comfort conditions and reduce heating energy consumption.

International audience

International audience; Fused deposition modeling deposits a filament layer by layer and according to a trajectory. Based on stress criterion for filament deposition, this work suggests reproducing the principal directions of the stress in the sample through the control of the filament direction. A number of compact-tension (C-T) specimens have been printed with and without respecting this criterion. The fracture toughness test of these specimens was realized to compare the results. The results show that the suggested criterion leads to an improvement of 30% in the fracture toughness. Digital images correlation has been extensively used to study the local strain field in the specimens. Strain mapping reveals an important change in fracture behavior. The modification of filament direction leads to “ductile-like behavior” in crack extension, which is characterized by a large deformation zone associated with a slow crack growth rate during crack propagation.

In the context of improving energy efficiency and thermal comfort in the building, the use of phase change materials (PCMs) is one of the suggested solutions. The proposed integration solutions concern the building envelope as well as the applications related to its operation. The study of the incorporation of PCM in the walls of the building was the subject of numerous works. However, the antisymmetric character of storing/recovering energy management in the walls is less controlled and do not fit the optimal conditions. In this study, a solution based on the direct integration of a stabilized PCM (gel) in an envelope including ventilation channels, was proposed to overcome this problem of antisymmetry storing/recovering and fitting with different fixed ambient conditions. The final aim is to develop the optimization strategy of a wall combining the heavy inertia offered by the PCM, intra-ventilation control and the contribution to air renewal energy demand. In this context, an experimental study of a concrete block system is conducted to test the thermal response of this configuration by the application of cyclic solicitations. The comprehension of this integrated constructive solution essentially passes by the possession of validated numerical tools. For this, two models have been developed. The first model using the electrical–thermal analogy, based on an RC equivalence, is distinguished by its relative simplicity and weak time computing demand. Each of these two factors, R and C summarise the system properties and has a direct influence on the building transient simulations over a year. The second one is based on direct numerical simulation DNS of the energy and fluid flow equations using commercial code COMSOL Multiphysics. Such DNS is time consuming and could not be used to simulate over a year but aims only to validate the first RC circuit approach. A comparison of these two models with the idealised experimental data was carried out and allowed the validation of the thermal behaviour of the solution based on the integration of the PCM with core ventilation.

International audience; This work focuses on the implementation of mechanical behaviors from a previous Fused Depositing Modelling (FDM) method [1] into a Finite Element Modelling (FEM) in order to compare the mechanical and numerical results. Indeed, a former research reproducing the principal stress directions into Compact Tension (C-T) samples has been carried out by using fracture mechanics analysis [1,2]. We replicated these principal stress directions through an extrusion deposition by 3D printing in order to improve the fracture toughness. Then, the results were analyzed by comparing a C-T standard tensile test procedure with classical and optimized filament deposition. Eventually, this work observed that the fracture toughness was improved up to 20 % compared to a classical deposition. The objective of this new study is to obtain a reliable numerical simulation to reproduce the previous method and check the mechanical phenomena. The proposed method implies local elements to capture the filaments trajectories and to associate them with the Acrylonitrile Butadiene Styrene (ABS) material's reference on ABAQUS.

International audience; The objective of this article is to make the analysis of the muscular force response to optimize electrical pulses train using Ding et al. force-fatigue model. A geometric analysis of the dynamics is provided and very preliminary results are presented in the frame of optimal control using a simplified input-output model. In parallel, to take into account the physical constraints of the problem, partial state observation and input restrictions, an optimized pulses train is computed with a model predictive control, where a non-linear observer is used to estimate the state-variables.

International audience; The dynamics of mass reaction kinetics chemical systems is modeled by the Feinberg-Horn-Jackson graph and under the "zero deficiency assumption", the behavior of the solutions is well known and splits into two cases: if the system is not weakly reversible there exists no equilibrium, nor periodic solution and if the network is weakly reversible in each stoichiometric subspace there exists only one equilibrium point and this point is asymptotically stable. By varying the temperature, one gets a single input control system and in this article we study the problem of maximizing the production of one species during the batch time. Our aim is to present the geometric techniques and results based on the Pontryagin maximum principle to compute the closed loop optimal solution. The complexity of the problem is illustrated by using two test bed examples: a sequence of two irreversible reactions and the McKeithan scheme

Several solutions based on phase change materials (PCM) are used for the thermal regulation of buildings. In this study, a combination of the inertial effect of PCM and intra-ventilation regulation is proposed. The purpose is to increase the thermal inertia of the building envelope leading to a fast passive and active cooling of the indoor environment. The principle of the solution is the use of a polymer-stabilized paraffin in external walls integrating ventilation pipes. For that, an experimental study of a hollow concrete block with PCM and ventilation tubes is conducted to test its thermal response. Gathered to this part, a 3D numerical model is developed under COMSOL Multiphysics®. The obtained simulation results are in good agreement with the experimental data. A parametric study is then performed including its actual characteristics against several conditions; it is revealed that the use of PCM gathered to the ventilation tubes enhances the thermal phase shift. It is stated that the forced ventilation through the tubes makes it possible to manage the energy and contribute to the renewal of the air.

Talk; International audience; In this talk, we present the time minimal control problem about the saturation of a pair of spins of the same species but with inhomogeneities on the applied RF-magnetic field, in relation with the contrast problem in MRI. We make a complete analysis based on geometric control to classify the optimal syntheses in the single spin case, to pave the road to analyze the case of two spins. This points out the phenomenon of bridge, which consists in linking two singular arcs by a bang arc to bypass some singularities of the singular extremal flow. In the case of two spins, the question about global optimality is more intricate. The Bocop software is used to determine local minimizers for physical test cases and Linear Matrix Inequalities approach is applied to estimate the global optimal value and validate the previous computations. This is complemented by numerical investigations combining shooting and continuation methods implemented in the HamPath software to analyze the structure of the time minimal solution with respect to the set of parameters of the species. This reveals new complex structures, compare to the single spin case.

International audience; Low energy consumption buildings are rapidly spreading over Europe. Its underlying concept is based on improving the building envelope, and using high efficiency equipment. However, thermal comfort in such buildings is still questionable. Recently, advanced comfort-based control strategies have been proposed in order to fulfill a tradeoff between energy-saving and occupants comfort as well as reduce additional investments compared to conventional energy reduction solutions. Though few studies focused on the European climate conditions during a heating period, this study aims at investigating the sensitivity of energy-saving potential to outdoor climatic conditions and identifying the significant parameters affecting the heating energy consumption in a comfort-controlled highly glazed room under a European climatic condition. A validated model is used to carry out a comparative building simulation study between PMV-based comfort-control and conventional thermostatic-control, as well as a sensitivity study based on the Design of Experiments technique. The results show that PMV-based comfort-control is a reasonable solution to neutralize the trade-off between thermal comfort and heating energy consumption under the investigated European winter season. Moreover, the results demonstrate that energy consumption using the comfort-control is more sensitive to outdoor climatic conditions than the thermostatic-control. Furthermore, the results show that energy consumption in a comfort-controlled space is highly sensitive to occupants-related parameters (metabolic rate and clothing level) and the mean radiant temperature compared to other parameters, such as relative humidity. Finally, a meta-model is obtained to be used as a fast and simple way to predict the energy consumption in a comfort-controlled room.

The regular arrangement of metal nanoparticles influences their plasmonic behavior. It has been previously demonstrated that the coupling between diffracted waves and plasmon modes can give rise to extremely narrow plasmon resonances. This is the case when the single-particle localized surface plasmon resonance (λ LSP) is very close in value to the Rayleigh anomaly wavelength (λ RA) of the nanoparticles array. In this paper, we performed angle-resolved extinction measurements on a 2D array of gold nano-cylinders designed to fulfil the condition λ RA<λ LSP. Varying the angle of excitation offers a unique possibility to finely modify the value of λ RA, thus gradually approaching the condition of coupling between diffracted waves and plasmon modes. The experimental observation of a collective dipolar resonance has been interpreted by exploiting a simplified model based on the coupling of evanescent diffracted waves with plasmon modes. Among other plasmon modes, the measurement technique has also evidenced and allowed the study of a vertical plasmon mode, only visible in TM polarization at off-normal excitation incidence. The results of numerical simulations, based on the periodic Green’s tensor formalism, match well with the experimental transmission spectra and show fine details that could go unnoticed by considering only experimental data.

This study focuses on the thermal analysis and comparing a lattice model and an optimized model of open-cell metal foams manufactured thanks to a metal casting process. The topological optimization defines the complex geometry through thermal criteria and a plaster mold reproduces it in 3D printing to be used in casting. The study of the thermal behavior conducted on the two open foam metal structures is performed based on several measurements, as well as numerical simulations. It is observed that the optimized metal foam presented less and non-homogenous local temperature than the lattice model with the gap of about 10 °C between both models. The pore size and porosity significantly affect the heat transfer through the metal foam. The comparison between numerical simulations and experimental results regarding the temperature fields shows a good agreement allowing the validation of the developed three-dimensional model based on the finite element method.

The objective of this article is to present the seminal concepts and techniques of Sub-Riemannian geometry and Hamiltonian dynamics, complemented by adapted software to analyze the dynamics of the copepod micro-swimmer, where the model of swimming is the slender body approximation for Stokes flows in fluid dynamics. In this context, the copepod model is a simplification of the 3-link Purcell swimmer and is relevant to analyze more complex micro-swimmers. The mathematical model is validated by observations performed by Takagi’s team of Hawaii laboratory, showing the agreement between the predicted and observed motions. Sub-Riemannian geometry is introduced, assuming that displacements are minimizing the expanded mechanical energy of the micro-swimmer. This allows to compare different strokes and different micro-swimmers and minimizing the expanded mechanical energy of the micro-swimmer. The objective is to maximize the efficiency of a stroke (the ratio between the displacement produced by a stroke and its length). Using the Maximum Principle in the framework of Sub-Riemannian geometry, this leads to analyze family of periodic controls producing strokes to determine the most efficient one. Graded normal forms introduced in Sub-Riemannian geometry to evaluate spheres with small radius is the technique used to evaluate the efficiency of different strokes with small amplitudes, and to determine the most efficient stroke using a numeric homotopy method versus standard direct computations based on Fourier analysis. Finally a copepod robot is presented whose aim is to validate the computations and very preliminary results are given.

International audience; This paper investigates the energy saving potential of a PMV-based thermal comfort control in a highly glazed room during the heating period. For the analysis, a PMV-based thermal comfort controller model is implemented in a validated Dymola® model to carry out the simulations. The results show that, PMV-based control provides consistent thermal comfort as well as energy-saving improvement. A parametric study is performed to investigate the effect of glass façades area and type on thermal comfort and energy saving. The results show that both thermal comfort and energy-savings could be improved under adequate glass façade configuration. Finally, a sensitivity study using the Design of Experiment (DoE) method is performed to study the effect of different parameters on the energy consumption in a PMV-based controlled space. Results demonstrate that energy consumption is highly sensitive to the metabolic rate, the mean radiant temperature and the clothing insulation more than those of the other parameters.

This series of notes have their origin into accelerated course in optimal control givento multidisciplinary Phd students in Mathematics, Physics or Control Engineeringand the purpose is to present the seminal results of this theory in view of applicationsto concrete problems. For that we choose to make the presentation using two reallife applications which are the core of current research projects on the academic sideand motivated by industrial applications. The two applications concern the swimming at low Reynolds number and the contrast problem in Magnetic Resonance Imaging.

In this article, we analyse the time minimal control for the saturation of a pair of spins of the same species but with inhomogeneities of the applied RF-magnetic field, in relation with the contrast problem in Magnetic Resonance Imaging. We make a complete analysis based on geometric control to classify the optimal syntheses in the single spin case to pave the road to analyze the case of two spins. The Bocop software is used to determine local minimizers for physical test cases and Linear Matrix Inequalities approach is applied to estimate the global optimal value and validate the previous computations. This is complemented by numerical computations combining shooting and continuation methods implemented in the HamPath software to analyze the structure of the time minimal solution with respect to the set of parameters species.

International audience; This paper presents an approach to analyze the critical drawbacks and attributes of Additive Manufacturing (AM) simultaneously to find the best manufacturing parameters to fabricate the AM products. In this study, Fused Deposition Modeling (FDM) is investigated as a common AM technology. For this purpose, a multi-optimization problem is formulated according to the analysis of FDM technology. In this problem, layer thickness and part orientation are determined as the decision variables which are the important parameters of manufacturing. As objective functions, production time and material mass are considered and the surface roughness of FDM products and mechanical behavior of material are defined as the constraint functions. Different methodologies are developed to model the AM criteria according to these decision variables. To find the optimal solutions for manufacturing, Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) is used. Finally, a case study highlighted the reliability of the proposed approach.

International audience; This book introduces readers to techniques of geometric optimal control as well as the exposure and applicability of adapted numerical schemes. It is based on two real-world applications, which have been the subject of two current academic research programs and motivated by industrial use – the design of micro-swimmers and the contrast problem in medical resonance imaging. The recently developed numerical software has been applied to the cases studies presented here. The book is intended for use at the graduate and Ph.D. level to introduce students from applied mathematics and control engineering to geometric and computational techniques in optimal control.

International audience; The design of customized product must correspond to users’ requirements to reach the expectations of the consumer. To include users in the design product process, we are interested in their perception of the product. We essentially realize a technical approach to guide the user for defining his personalized product. Based on the complexities of user’s profiles in order to translate his requirements, we define a systemic approach in a chain of design and additive manufacturing. The method is implemented into a web demonstrator. We defined a combinatory scheme and several illustrated scenari from Information Technology (IT) used as a template to analyze rich field data exchanges. The method provided a toolkit for leading the participation of multiple stakeholders in the design process (users, designers, advisers, community...). Finally, we determine a workflow required to product lifecycle management in the case where the user is in the center of the application to realize a customized product. The research framework shows that the community participation is central to the system so that the economic model is reliable. This paper presents the research method associated to the Internet platform creation.

Slow-fast affine control systems with one fast angle are considered. An approximation based on standard averaging of the extremal is defined. When the drift of the original system is small enough, this approximation is metric, and minimum time trajectories of the original system converge towards geodesics of a Finsler metric. The asymmetry of the metric accounts for the presence of the drift on the slow part of the original dynamics. The example of the J2 effect in the two-body case in space mechanics is examined. A critical ratio between the J2 drift and the thrust level of the engine is defined in terms of the averaged metric. The qualitative behaviour of the minimum time for the real system is analyzed thanks to this ratio.

International audience

International audience

Molecular dynamics simulations have been performed to study the mechanical properties of a columnar nanocrystalline copper with a mean grain size between 9.0 and 24 nm. A melting–cooling method has been used to generate the initial samples: this method produces realistic samples that contain defects inside the grains such as dislocations and vacancies. The results of uniaxial tensile tests applied to these samples reveal the presence of a critical mean grain size between 16 and 20 nm, for which there is an inversion of the conventional Hall–Petch relation. The principal mechanisms of deformation present in the samples correspond to a combination of dislocations and grain boundary sliding. In addition, this analysis shows the presence of sliding planes generated by the motion of perfect edge dislocations that are absorbed by grain boundaries. It is the initial defects present inside the grains that lead to this mechanism of deformation. An analysis of the atomic configurations further shows that nu...

In this contribution, a numerical study of the optical properties of closely-packed gold nanorods was performed. The studied nano-objects are experimentally grown on a tilted polydimethylsiloxane (PDMS) substrate by using physical vapor deposition (PVD). This method creates nanorods tilted to a certain angle with respect to the substrate normal. This geometry allows exciting both transverse and longitudinal modes of the rods. As demonstrated in a previous experimental work, such PVD-grown nano-objects show promising possibilities both as strain gauges or strain-tunable metamaterials if fabricated on a stretchable dielectric substrate. This numerical study is based on experimental data from previous work and pushes further the subject by approaching an optimized nano-structure allowing better strain-sensitivity (particularly by changing the auto-organization of the said nanorods). Full Text: PDF References J.W.M. Chon, C. Bullen, P. Zijlstra, M. Gu, "Spectral encoding on Gold Nanorods Doped in a Silica Sol?Gel Matrix and Its Application to High-Density Optical Data Storage", Adv. Funct. Mater. 17, 875 (2007). CrossRef C.-C. Chen, Y.-P. Lin, C.-W. Wang, H.-C. Tzeng, C.-H. Wu, Y.-C. Chen, C.-P. Chen, L.-C. Chen, Y.-C. Wu, "DNA?Gold Nanorod Conjugates for Remote Control of Localized Gene Expression by near Infrared Irradiation", J. Am. Chem. Soc. 128, 3709 (2006). CrossRef J.N. Anker, W.P. Hall, O. Lyandres, N.C. Shah, J. Zhao, R.P. Van Duyne, "Biosensing with plasmonic nanosensors", Nat. Mater 7, 442 (2008). CrossRef B. Sepulveda, P.C. Angelome, L.M. Lechuga, L.M. Liz-Marzan?, "LSPR-based nanobiosensors", Nano Today 4, 244 (2009). CrossRef A. Haes, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Sensitivity and Selectivity of an Approach Based on the Localized Surface Plasmon Resonance Spectroscopy of Triangular Silver Nanoparticles", J. Am. Chem. Soc. 124, 10596 (2002). CrossRef J.C. Riboh, A.J. Haes, A.D. McFarland, C.R. Yonzon, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Real-Time Immunoassay in Physiological Buffer Enabled by Improved Nanoparticle Adhesion", J. Phys. Chem. B 107, 1772 (2003). CrossRef C.R. Yonzon, E. Jeoung, S. Zou, G.C. Schatz, M. Mrksich, R.P. Van Duyne, "A Comparative Analysis of Localized and Propagating Surface Plasmon Resonance Sensors: The Binding of Concanavalin A to a Monosaccharide Functionalized Self-Assembled Monolayer", J. Am. Chem. Soc. 126, 12669 (2004). CrossRef A.J. Haes, L. Chang, W.L. Klein, R.P. Van Duyne, "Detection of a Biomarker for Alzheimer's Disease from Synthetic and Clinical Samples Using a Nanoscale Optical Biosensor", J. Am. Chem. Soc. 127, 2264 (2005). CrossRef R. Caputo, G. Palermo, M.Infusino L. De Sio, "Liquid Crystals as an Active Medium: Novel Possibilities in Plasmonics", Nanospectroscopy 1, 40 (2015). CrossRef T. Maurer, J. Marae-Djouda, U. Cataldi, A. Gontier, G. Montay, Y. Madi, B. Panicaud, D. Macias, P.-M. Adam, G. Lev?que, T. Burgi, R. Caputo, "The beginnings of plasmomechanics: towards plasmonic strain sensors", Frontiers of Materials Science 9, 170 (2015). CrossRef X. Niu, S. P. Stagon, H. Huang, J.K. Baldwin, A. Misra, "Smallest Metallic Nanorods Using Physical Vapor Deposition", Phys. Rev. Lett. 110 136102 (2013). CrossRef Lumerical Solutions, Inc. DirectLink P.K. Jain, W. Huang, M.A.El-Sayed, "On the Universal Scaling Behavior of the Distance Decay of Plasmon Coupling in Metal Nanoparticle Pairs: A Plasmon Ruler Equation", Nanoletters 7, 2080 (2007). CrossRef P.K. Jain, M.A. El-Sayed, "Plasmonic coupling in noble metal nanostructures", Chem. Phys. Letters 487, 153 (2010). CrossRef

International audience; Additive Manufacturing can produce three dimensional complex products based on the virtual CAD model. This new manufacturing method brings new possibilities in design and manufacturing cycle by its new parameters and Design For Manufacturing approach can be used to consider these issues. Therefore, an integrated methodology of Design for Manufacturing approach is proposed for additive manufacturing in this paper. This methodology investigates the characteristics related to Additive Manufacturing in design stage. For this purpose, Skin-Skeleton approach is used to model the procedure from the first step to final one. This skin-skeleton model consists of usage and manufacturing model which are used to present the customer requirement, product specification and design trend by usage model as well as manufacturing procedure and its constraints by manufacturing model. For this purpose, Topological optimization and Power Crust algorithm are utilized as tools to present optimized usage skin and skeleton. Also, manufacturing model is presented due to AM characteristics. Therefore, this model helps us to identify usage and manufacturing attributes to provide an interface model to define the product model by analysis of different parameter related to design and manufacturing and their relations comprehensively. Therefore, this model permits to consider manufacturing constraints and attributes as soon as possible in design stage to provide a better solution as a final product model for design and manufacturing concurrently as an integrated approach. In order to validate this approach, a bag hook that produced by Fused Deposition Modelling which is a well-known additive manufacturing technique is used.

We use molecular dynamics simulations to study the mechanical properties of a columnar nanocrystalline copper with a mean grain size between 8.91 nm and 24 nm. The used samples were generated by using a melting cooling method. These samples were submitted to uniaxial tensile test. The results reveal the presence of a critical mean grain size between 16 and 20 nm, where there is an inversion in the conventional Hall-Petch tendency. This inversion is illustrated by the increase of flow stress with the increase of the mean grain size. This transition is caused by shifting of the deformation mechanism from dislocations to a combination of grain boundaries sliding and dislocations. Moreover, the effect of temperature on the mechanical properties of nanocrystalline copper has been investigated. The results show a decrease of the flow stress and Young’s modulus when the temperature increases.

International audience; This paper presents a validated model based on the object-oriented modeling tool based on Modelica approach for the radiant floor heating system, located in thermal laboratory in a test building. The system consists of heat pump, radiant slab, circulation pump, three way valve and hydraulic loop. Single circuit radiant slab was the main component in our Modelica model. A comparison of simulated and measured data for two case studies resulted in maximum absolute error for room temperature, surface temperature, convective heat flow and radiative heat flow as 0.914°C, 0.772°C, 2.5W/m² and4.5W/m² for the first case study and 1.192°C, 1.463°C, 2.275W/m² and 3.9W/m² respectively for the second case study. The simulated results agreed very well with the measured data by taking the measurements errors and the simulation assumptions into account. Therefore, the developed model was validated to be applicable in other projects.

International audience; Based on copepod observations, Takagi proposed a model to interpret the swimming behavior of these microorganisms using sinusoidal paddling or sequential paddling followed by a recovery stroke in unison, and compares them invoking the concept of efficiency. Our aim is to provide an interpretation of Takagi’s results in the frame of optimal control theory and sub-Riemannian geometry. The Maximum principle is used to select two types of periodic control candidates as minimizers: sinusoidal up to time reparameterization and the sequential paddling, interpreted as an abnormal stroke in sub-Riemannian geometry. Geometric analysis combined with numerical simulations are decisive tools to compute the optimal solutions, refining Takagi computations. A family of simple strokes with small amplitudes emanating from a center is characterized as an invariant of SR-geometry and allow to identify the metric used by the swimmer. The notion of efficiency is discussed in detail and related with normality properties of minimizers.; A partir de l'observation du mécanisme de nage d'une famille de microorganismes appelées copépodes, Takagi propose un modèle pour interpréter ces nages. Deux types de contrôles périodiques associés sont proposés : le premier correspond à des contrôles sinusoïdaux formant une courbe de nage lisse et simple et le second est un contrôle constant par morceaux produisant untriangle. Notre objectif est d'interpréter cela dans le cadre du contrôle optimal et de la géométrie sous-Riemannienne. Le principe du Maximum est utilisé pour sélectionner des nages géodésiques de deux types : des nages formant des courbes simples associées à des contrôles sinusoïdaux à une reparamétrisation du temps près et le triangle est interprété comme une nage anormale. L'analysegéométrique combinée avec des simulations numériques permet de générer une famille de nages depetites amplitudes ce qui par continuation permet de calculer la nage la plus efficace. La notion d'efficacité est discutée en détails en relation avec le concept de normalité.

The use of phase change materials (PCMs) for improving the thermal comfort in buildings has become an attractive application. This solution contributes to increasing the thermal inertia of the building envelope and reducing power consumption. A building element filled with a PCM and equipped with ventilation tubes is proposed, both for increasing inertia and contributing to refreshing building envelope. A numerical simulation is conducted by the finite element method in COMSOL Multiphysics, which aims to test the thermal behaviour of the developed solution. An experimental study is carried out on a concrete block containing a PCM with ventilation tubes. The objective is to see the effect of PCM coupled with ventilation on increasing the inertia of the block. The results show the ability of this new solution to ensure an important thermal inertia of a building.