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International audience; The plastic blend (PLA-ABS) of polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) is a promising material with great toughness and environmental-friendly potentials. Nevertheless, little research has focused on PLA-ABS co-pyrolysis and combustion. This work explores the pyrolysis characteristics and flammability of PLA-ABS blend with a mass ratio of 1:1. The thermogravimetric analysis shows that during the co-pyrolysis of PLA-ABS the individual pyrolysis of PLA and ABS is much faster than the corresponding pyrolysis rate of PLA and ABS alone. The FTIR analyses of solid residues indicate that PLA and ABS do not react chemically in the solid phase, hence the volatile products of co-pyrolysis are similar to those of pure materials. Through Py-GC/MS experi-ments, characteristic products of ABS induced by PLA-ABS co-pyrolysis at 330 C were identified where the original ABS has not started to pyrolyze. This finding concludes that the co-pyrolysis enhances the depolymer-ization of components, leading to the characteristic products appearing at a lower temperature. Finally, the cone calorimeter experiments show that the PLA-ABS blend produces the highest peak heat release rate during combustion which is 93%-182% and 5%-15% higher than that of PLA and ABS, respectively. The cone calo-rimeter results further confirm the enhanced depolymerizations induced by co-pyrolysis.

International audience; The nucleation and crystallization of glass-ceramics are typically influenced by early phase separation, which can impact glass properties. However, it has been challenging to characterize the nanoscale phase separation and understand the nucleation mechanism of lithium disilicate (L2S) glass-ceramics, which has resulted in some controversy. Here, we raised the direct evidence of nanoscale clustering in the glassy phase prior to formal nucleation and crystallization by element distribution. Firstly, the amorphous Li3PO4 phase formed on the boundary between the phase separation area and residual glass matrix, and then nucleation tended to start on this phase boundary. Furthermore, the effect of phase-separation on nucleation and final crystallize products was illustrated. By sufficient phase-separation, the formation of desired Li2Si2O5 and LiAlSi4O10 microcrystals was effectively motivated, which is prerequisite for high mechanical properties and transparency. We hope this work provides guidance to rationally understand the early phase separation in glass for subsequent controlling crystallization.

International audience; The southeastern part of New Caledonia main island (Grande Terre) is the location of a large ophiolitic formation that hosts several hyperalkaline springs discharging high pH (~11) and warm (

International audience; The combination of operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy measurement and Density Functional Theory calculation reveals the counterintuitive HCHO sensing mechanism of In4Sn3O12. It is merely partial oxidation of HCHO into formate (or HCOOH) with medium activation energy (0.43–0.68 eV) and sufficient electron donation effect that is responsible for the sensor signal at the optimum temperature of 200 °C. The Sn (3a)-connected O is the active site and plays key roles in both HCHO adsorption and partial oxidation.

International audience; The (100) surface of alpha-MoO3 (α-MoO3) should possess overwhelmingly more exposed Mo than the (010), and the exposed Mo has been extensively considered as active site for amine adsorption. However, α-MoO3 (100) has drawn little attention concerning amine sensing mechanism. In this research, adsorption of ammonia (NH3), monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) is systematically investigated by density functional theory (DFT). All of these four molecules have high affinity to α-MoO3 (100) through interaction between the N and the exposed Mo, and the affinity is mainly influenced by number of methyl group and number of N-connected H. Adsorption and dissociation of water and oxygen molecule on stoichiometric or defective α-MoO3 (100) surface are then simulated to fully understand surface chemistry of α-MoO3 (100) in practical condition. At low temperature α-MoO3 (100) must be covered with lots of water molecule; the water can desorb or dissociate into hydroxyl groups at high temperature. Oxygen vacancy (VO) can be generated considering the annealing process during sensor device fabrication; VO must be filled with O2 molecule, which can further interact with adsorbed water nearby to form hydroxyl groups. According to this research, α-MoO3 (100) must be the active surface for amine sensing and its surface chemistry is well understood. In near future, further reaction and interaction will be simulated at α-MoO3 (100), and much more attention should be paid to α-MoO3 (100) not only theoretically but also experimentally.

International audience; Metal organic framework (MOF) glasses are a coordination network of metal nodes and organic ligands as an undercooled frozen-in liquid, and have therefore broadened the potential of MOF materials in the fundamental research and application scenarios. On the road to deploying MOF glasses as electrocatalysts, it remains several basic scientific hurdles although MOF glasses not only inherit the structural merits of MOFs but also endow with active catalytic features including concentrated defects, metal centers and disorder structure etc. The research on the ionic conductivity, catalytic stability and reactivity of MOF glasses has yielded scientific insights towards its electrocatalytic applications. Here, we first comb the history, definition and basic properties of MOF glasses. Then, we identify the main synthetic methods and characterization techniques. Finally, we advance the potentials and challenges of MOF glasses as electrocatalysts in furthering the understanding of these themes.

International audience; There are numerous vital usages for mid-infrared (MIR) lasers in satellite communication, biomedicine, military, remote sensing, and environmental monitoring. In this work, a progression of Er3+ ions doped, Er3+/Pr3+ ions codoped Ga5Ge20Sb10S65 glasses were prepared, and their physical performances and structural characteristics were examined. To understand the non-phononassisted energy transfermechanism, we recorded the up-conversion and infrared fluorescence emission spectra by pumping with a commercial 980 nm LD. Then the 2.7 mu m strong fluorescence signal intensity can be obtained when the doped concentration of Pr3+ is proper. After the doping of Pr3+, fluorescence lifetime results revealed that the lifetimes of the Er3+:4I13/ 2 level fell dramatically from 7.33 to 1.90 ms, which experienced amuchmore significant decrease in lifetimes than the Er3+:4I11/ 2 level. The MIR fluorescence performances were assessed by the determined J-O parameters and relative emission cross sections. Additionally, the generally huge emission cross sections and the small pump energy show that it is possible to obtain population inversion with relatively small pump energy; thus the Er3+/Pr3+ glasses have great potential to be 2.7 mu m laser materials.

International audience; Infrared evanescent wave sensing based on chalcogenide fiber is an emerging technology for qualitative and quantitative analysis of most organic compounds. Here, a tapered fiber sensor made from Ge10As30Se40Te20 glass fiber was reported. The fundamental modes and intensity of evanescent waves in fibers with different diameters were simulated with COMSOL. The 30 mm length tapered fiber sensors with different waist diameters, 110, 63, and 31 mu m, were fabricated for ethanol detection. The sensor with a waist diameter of 31 mu m has the highest sensitivity of 0.73 a.u./% and a limit of detection (LoD) of 0.195 vol.% for ethanol. Finally, this sensor has been used to analyze alcohols, including Chinese baijiu (Chinese distilled spirits), red wine, Shaoxing wine (Chinese rice wine), Rio cocktail, and Tsingtao beer. It is shown that the ethanol concentration is consistent with the nominal alcoholicity. Moreover, other components such as CO2 and maltose can be detected in Tsingtao beer, demonstrating the feasibility of its application in detecting food additives.

International audience; Glass scintillators have several benefits compared to the currently used single or polycrystalline scintillators, including non-hygroscopicity, mechanical ruggedness, ease of producing customizable shapes, and low-cost synthesis. The combination of the inert glass matrix and the embedded highly scintillating center render them significant materials for medical imaging and therapy, non-destructive probing, nuclear monitoring, and high-energy physics. Recently, great progress has been made in exploring new kinds of glass scintillator materials, improving imaging resolution for radiation detection, and developing an enormous range of commercial products. However, the majority of efforts have been devoted to the variation of materials, while rationally designing this new family of scintillators toward expected properties and applications is still lacking. In this review, the focus is specifically on advances in glass scintillators, including the scintillation fundamentals, material designing rule, and current application status, as well as future challenges and future directions.

International audience; 2D Ruddlesden-Popper (RP) perovskites have demonstrated highperformance emitters, and large-sized perovskite single crystals have always been pursued for efficient optoelectronic devices. However, large-sized 2D RP perovskite single crystals with high quality are still difficult to achieve due to the weak interaction between layers and strong anisotropy. Here, we show a rational design strategy to synthesize centimeter-sized 2D BM2PbBr4 (BM = benzimidazole) perovskite single crystals by intermediate-phase engineering (IPE). 1D (DMF)2BMPbBr3 intermediate-phase single crystals were structurally decoupled and transformed to perfect 2D BM2PbBr4 seed crystals with a certain thickness, presenting a huge advantage over the extrathin crystal sheets in random stacking by natural crystallization. Furthermore, the new BM with conjugated structures we obtained as the A-site of the 2D RP perovskite enhances the exciton confinement, resulting in a surprisingly large excitonic binding energy of 368.2 meV. The emitting decay time is shortened to 0.98 ns, which is the smallest among all the perovskite materials. Tailoring of the X-site components for 2D RP BM2PbBr4 - xClx (x = 1, 2, 3, and 4) series with tunable luminescence and decay time was also synthesized by IPE. We believe IPE provides a new way for synthesizing large-sized perovskite single crystals with fine-tunable properties to satisfy the target applications.

International audience; Due to the high transparency, high Verdet constant, as well as easy processing properties, rare-earth ion-doped glasses have demonstrated great potential in magneto-optical (MO) applications. However, the variation in the valence state of rare-earth ions (Tb(3+) to Tb(4+)) resulted in the decreased effective concentration of the paramagnetic ions and thus degraded MO performance. Here, a strategy was proposed to inhibit the oxidation of Tb(3+) into Tb(4+) as well as improve the thermal stability by tuning the optical basicity of glass networks. Moreover, the depolymerization of the glass network was modulated to accommodate more Tb ions. Thus, a record high effective concentration (14.19 × 10(21)/cm(3)) of Tb ions in glass was achieved, generating a high Verdet constant of 113 rad/(T·m) at 650 nm. Lastly, the first application of MO glass for magnetic field sensors was demonstrated, achieving a sensitivity of 0.139 rad/T. We hope our work provides guidance for the fabrication of MO glass with high performance and thermal stability and could push MO glass one step further for magnetic sensing applications.

International audience; Inspired by the concept of intumescence, this research proposed and exemplified a strategy for reinforcing the carbonaceous structures to improve the fire retardancy of intumescent polybutylene succinate (PBS). Herein, intumescent PBS formulations were fabricated by incorporating ethylenediamine phosphate (EDAP) and melamine (MEL) or melamine cyanurate (MCA) as well as zinc borate (ZnB) into PBS at a relatively low loading (10 wt%). The reaction to fire of PBS formulations were assessed by mass loss calorimeter (MLC) and the reinforcement mechanism of the condensed phase was investigated by solid-state NMR technique. Compared to PBS/EDAP&MEL(5:1,10%) and PBS/EDAP&MCA(5:1,10%), the synergistic combination of ZnB and EDAP&MEL (or EDAP&MCA) significantly reduced the peak of heat release rate (pHRR) of PBS/EDAP&MEL(5:1,8%)/ZnB(2%) and PBS/EDAP&MCA (5:1,8%)/ZnB(2%) by 61% and 53%, respectively, exhibiting high degrees of intumescence. Meanwhile, the fire growth rate index (FIGRA) were reduced by 48.8% and 39.5%, respectively, and the maximum average rate of heat emission (MARHE) decreased by 47.9% and 53.3%, respectively. Moreover, the flameout time increased by 428 s (from 507 to 935 s) and 444 s (from 509 to 954 s), respectively. Those phenomena suggested a synergistic flame retardant effect of ZnB and intumescent additives on PBS. Solid-state NMR of 11B, 13C and 31P of the top and bottom of chars after MLC test demonstrated the strengthening of the protective char by the formation of borophosphate and other phosphate glasses, limiting cracking and increasing the char cohesion.; Inspirée par le concept d'intumescence, cette recherche a proposé et illustré une stratégie de renforcement des structures carbonées pour améliorer l'ignifugation du polybutylène succinate (PBS) intumescent. Des formulations de PBS intumescent ont été fabriquées en incorporant du phosphate d'éthylènediamine (EDAP) et de la mélamine (MEL) ou du cyanurate de mélamine (MCA) ainsi que du borate de zinc (ZnB) dans le PBS à une charge relativement faible (10 % en poids). La réaction au feu des formulations de PBS a été évaluée par calorimètre à perte de masse (MLC) et le mécanisme de renforcement de la phase condensée a été étudié par la technique de RMN à l'état solide. Comparée au PBS/EDAP&MEL(5:1,10%) et au PBS/EDAP&MCA(5:1,10%), la combinaison synergique de ZnB et d'EDAP&MEL (ou d'EDAP&MCA) a réduit de manière significative le pic du taux de dégagement de chaleur (pHRR) du PBS/EDAP&MEL(5 : 1,8 %)/ZnB(2 %) et du PBS/EDAP&MCA (5:1,8 %)/ZnB(2 %) de 61 % et 53 %, respectivement, montrant des degrés élevés d'intumescence. Parallèlement, l'indice de croissance de l'incendie (FIGRA) a été réduit de 48,8 % et 39,5 %, respectivement, et le taux moyen maximal d'émission de chaleur (MARHE) a diminué de 47,9 % et 53,3 %, respectivement. En outre, le temps d'extinction de la flamme a augmenté de 428 s (de 507 à 935 s) et de 444 s (de 509 à 954 s), respectivement. Ces phénomènes suggèrent un effet synergique de retardateur de flamme du ZnB et des additifs intumescents sur le PBS. La RMN à l'état solide des 11B, 13C et 31P de la partie supérieure et inférieure des chars après le test MLC a démontré le renforcement du charbon protecteur par la formation de borophosphate et d'autres verres de phosphate, limitant la fissuration et augmentant la cohésion du charbon.

International audience; ZrO2 is an effective nucleation agent for low-expansion lithium-aluminum silicate (LAS) glass-ceramic (GC) with high Al2O3 content. However, the effect of ZrO2 is still not fully understood in LAS glasses with low contents of Al2O3 and P2O5. In this work, the effect of ZrO2 on the phase separation and crystallization of Li2O-Al2O3-SiO2-P2O5 glasses were investigated. The results revealed that ZrO2 significantly increased T-g and the crystallization temperature of Li2SiO3 and Li2Si2O5 crystals. Li3PO4 crystals precipitated preferentially in the glass containing 3.6-mol% ZrO2, wherein Zr was stable in the network and no precipitation of ZrO2 nanocrystals was observed. Moreover, the separation of phosphate-rich phases in the as-quenched glasses increased with the addition of ZrO2. The findings of the study revealed a dual role of ZrO2. First, ZrO2 acted as a glass network former rather than a nucleation agent, increasing glass viscosity and the nucleation barrier of Li2SiO3 through its strong network connectivity. Second, as Zr preferentially combined with non-bridging oxygen to form Si-O-Zr linkages, a sufficient amount of charge-balancing Li+ ions existed in the network, which promoted the separation of phosphate-rich phases. It indicated that the incorporation of ZrO2 contributes to the activation of the nucleation role of P2O5, thus contributing to the formation of nanocrystals and fine microstructure of GCs.

This paper presents the experiment program which requires the students to incorporate the knowledge learned from both digital logic and computer organization courses to develop a multi-cycle MIPS CPU with FPGA. First, it introduces how to incorporate the knowledge of these two courses by conducting the experiments on the same FPGA platform. Then, it discusses how to teach the students to design a multi-cycle MIPS CPU which supports interruption han- dling. Later, it presents an analogous teaching approach which compares the FPGA development to the C program- ming to help the students master the intricate FPGA devel- opment process in an easy-to-understand way. This exper- iment program targets to help the students build the sys- tematic thinking way as well as cultivate them to develop a complicate computer system by integrating the knowledge of different courses. The experimental program has been carried out in the Internet-of-Things speciality for 6 years, and the survey results showed this experiment program had achieved the desired teaching objective effectively.

Pulsar Hα bow shocks provide rare opportunities to constrain the energetics and kinematics of the relativistic pulsar wind. We have acquired optical imaging and integral field unit spectroscopy of the bow shock of the millisecond pulsar PSR J1959+2048, measuring the shock symmetry axis at a position angle = 213.2 ± 0.°2 and showing that this slow nonradiative shock has a broad-to-narrow line component ratio I b /I n = 4. The data show that the pulsar’s velocity lies 2.°2 out of the plane of the sky. Coupled with a new fit for its timing proper motion, giving μ tot = 30.05 mas yr−1 and a Very Long Baseline Array (VLBA) interferometric parallax measurement giving d = 2.57 − 0.77 + 1.84 kpc (90% range), we have unusually complete information on the pulsar kinematics. The bow shock constraints on the wind momentum flux imply that, at the best-fit parallax distance, the pulsar moment of inertia must be very large and/or the Hα efficiency at its modest shock velocity must be very high.

International audience; Metal-organic framework (MOF) glasses feature numerous unique properties and potential applications, but many fundamental questions remain unanswered, especially concerning their glass transition. Here, we report a discovery about ZIF-62 glass (a typical MOF glass), namely, the hypersensitivity of its glass transition to pressure history. Specifically, upon quenching the ZIF-62 melt under a modest pressure of 60 MPa, the derived glass exhibited a significantly lower glass transition temperature (T-g) than the glass formed under ambient pressure. The sensitivity parameter of T-g to pressure for ZIF-62 glass is much higher than that of other glass systems, including polymer glasses that typically feature a huge increase in T-g upon compression. The origin of the hypersensitivity of T-g to pressure history was revealed by structural analyses, positron annihilation lifetime spectroscopy, and molecular dynamics simulations. We found that the medium-range structure change induced the drop in T-g.

This study presents an evaluation of the effects of pore diameter and porosity on the mechanical properties and biocompatibility of Ti6Al4V ELI periodic lattice structures, fabricated using SLM technology. Lattice structures of titanium alloys are in high demand for biomedical applications and are particularly useful as bone substitutes. A series of lattice structures with pore diameters of 500, 600, and 700 μm and porosities of 60% and 70% were designed by repeating an octahedral unit cell. Based on SEM and micro-CT observations, good morphological agreement was detected between the original designs and the SLM-produced structures. Microstructural analysis using TEM showed that the typically acicular α′ martensitic microstructure was obtained in the strut, which contributes to the brittle behavior of the lattice structure. Uniaxial compression tests were conducted, and the deformation behavior was recorded using a digital camera. Finite element analysis (FEA) of compression process was also conducted to enhance the understanding of the deformation mechanism. The surface chemistry of the lattice structure was analyzed using XPS methodology. The cytocompatibility of the lattice was also investigated with an in vitro test. The results show that the lattice structures with biocompatible surfaces have a comparable compressive strength (71–190 MPa) and elastic modulus (2.1–4.7 GPa) to trabecular bone.

International audience; Tin oxide (SnO2) is an emerging electron transport layer (ETL) material in halide perovskite solar cells (PSCs). Among current limitations, open-circuit voltage (VOC) loss is one of the major factors to be addressed for further improvement. Here a bilayer ETL consisting of two SnO2 nanoparticle layers doped with different amounts of ammonium chloride is proposed. As demonstrated by photoelectron spectroscopy and photophysical studies, the main effect of the novel ETL is to modify the energy level alignment at the SnO2/perovskite interface, which leads to decreased carrier recombination, enhanced electron transfer, and reduced voltage loss. Moreover, X-ray diffraction reveals reduced strain in perovskite layers grown on bilayer ETLs with respect to single-layer ETLs, further contributing to a decrease of carrier recombination processes. Finally, the bilayer approach enables the more reproducible preparation of smooth and pinhole-free ETLs as compared to single-step deposition ETLs. PSCs with the doped bilayer SnO2 ETL demonstrate strongly increased VOC values of up to 1.21 V with a power conversion efficiency of 21.75% while showing negligible hysteresis and enhanced stability. Moreover, the SnO2 bilayer can be processed at low temperature (70 °C), and has therefore a high potential for use in tandem devices or flexible PSCs.

International audience; Evanescent wave absorption-based mid-infrared chalcogenide fiber sensors have prominent advantages in multicomponent liquid and gas detection. In this work, a new approach of tapered-fiber geometry optimization was proposed, and the evanescent efficiency was also theoretically calculated to evaluate sensing performance. The influence of fiber geometry (waist radius (R-w), taper length (L-t), waist deformation) on the mode distribution, light transmittance (T), evanescent proportion (T-O) and evanescent efficiency (tau) is discussed. Remarkably, the calculated results show that the evanescent efficiency can be over 10% via optimizing the waist radius and taper length. Generally, a better sensing performance based on tapered fiber can be achieved if the proportion of the LP11-like mode becomes higher or R-w becomes smaller. Furthermore, the radius of the waist boundary (R-L) was introduced to analyze the waist deformation. Mode proportion is almost unchanged as the R-L increases, while tau is halved. In addition, the larger the micro taper is, the easier the taper process is. Herein, a longer waist can be obtained, resulting in larger sensing area which increases sensitivity greatly.

Owing to their immense potential in energy conversion and storage, catalysis, photocatalysis, adsorption, separation and life science applications, significant interest has been devoted to the design and synthesis of hierarchically porous materials. The hierarchy of materials on porosity, structural, morphological, and component levels is key for high performance in all kinds of applications. Synthesis and applications of hierarchically structured porous materials have become a rapidly evolving field of current interest. A large series of synthesis methods have been developed. This review addresses recent advances made in studies of this topic. After identifying the advantages and problems of natural hierarchically porous materials, synthetic hierarchically porous materials are presented. The synthesis strategies used to prepare hierarchically porous materials are first introduced and the features of synthesis and the resulting structures are presented using a series of examples. These involve templating methods (surfactant templating, nanocasting, macroporous polymer templating, colloidal crystal templating and bioinspired process, i.e. biotemplating), conventional techniques (supercritical fluids, emulsion, freeze-drying, breath figures, selective leaching, phase separation, zeolitization process, and replication) and basic methods (sol-gel controlling and post-treatment), as well as self-formation phenomenon of porous hierarchy. A series of detailed examples are given to show methods for the synthesis of hierarchically porous structures with various chemical compositions (dual porosities: micro-micropores, micro-mesopores, micro-macropores, meso-mesopores, meso-macropores, multiple porosities: micro-meso-macropores and meso-meso-macropores). We hope that this review will be helpful for those entering the field and also for those in the field who want quick access to helpful reference information about the synthesis of new hierarchically porous materials and methods to control their structure and morphology.

This paper presents the experiment program which requires the students to incorporate the knowledge that they have learned from both digital logic and computer organization courses so as to develop a MIPS CPU with the reprogrammable FPGA. First, the top-to-down design concept and technical solutions on how to design and implement a MIPS CPU with FPGA is presented. Then, to help the students master the intricate FPGA development process in an easy-to-understand way, the analogous teaching method which compares the FPGA design to the C programming is investigated. This experiment program can help the students integrate the knowledge of different courses and develop a complicate computer system independently by their own ideas. It can not only improve the students' ability in solving the complex engineering problems, but can also help them build a systematic thinking way. The experimental program has been carried out in the Internet-of-Things speciality for 6 years, and the survey results showed that this experiment program had achieved its initial training objective effectively.

International audience; In this review, we address the use of numerical computations called Large-Eddy Simulations (LES) to study dust devils, and the more general class of atmospheric phenomena they belong to (convec-tive vortices). We describe the main elements of the LES methodology. We review the properties, statistics, and variability of dust devils and convective vortices resolved by LES in both terrestrial and Martian environments. The current challenges faced by modelers using LES for dust devils are also discussed in

Energy optimization and fault recovery are significant to ensure the embedded devices to work persistently and reliably. To achieve the energy optimization, a reconfigurable heterogeneous multi-core hardware platform is designed. Based on this hardware platform, a multi-core energy-efficient scheduling mechanism using reinforcement learning algorithm to search for the optimal scheduling solution is proposed. By the above hardware and software collaborative optimization mechanism, the energy cost of embedded system can be decreased significantly. To perform the fault recovery, a multi-core control-flow fault recovery mechanism is researched. This mechanism uses the Petri net model to detect the multi-core control-flow faults, and then recover these faults by a hardware-based quick recovery technique. The experimental results showed the energy cost of EMWSN could be optimized by more than 20% comparing to the traditional multi-core system. In addition, about 90% multi-core control-flow faults could be recovered, and the recovery time was nearly 40% less than the software-based recovery technique CFCSS.

International audience; Abnormal event detection is a challenging problem in video surveillance which is essential to the early-warning security and protection system. We propose an algorithm to solve this problem efficiently based on an image descriptor which encodes the movement information and the classification method. The new abnormality indicator is derived from the hidden Markov model which learns the histograms of optical flow orientations of the observed video frames. This indicator measures the similarity between the observed video frame and existing normal frames. The proposed method is evaluated and validated on several video surveillance datasets.

Energy efficiency and delay optimization are significant for the proliferation of wireless multimedia sensor network (WMSN). In this article, an energy-efficient, delay-efficient, hardware and software cooptimization platform is researched to minimize the energy cost while guaranteeing the deadline of the real-time WMSN tasks. First, a multicore reconfigurable WMSN hardware platform is designed and implemented. This platform uses both the heterogeneous multicore architecture and the dynamic voltage and frequency scaling (DVFS) technique. By this means, the nodes can adjust the hardware characteristics dynamically in terms of the software run-time contexts. Consequently, the software can be executed more efficiently with less energy cost and shorter execution time. Then, based on this hardware platform, an energy and delay multiobjective optimization algorithm and a DVFS adaption algorithm are investigated. These algorithms aim to search out the global energy optimization solution within the acceptable calculation time and strip the time redundancy in the task executing process. Thus, the energy efficiency of the WMSN node can be improved significantly even under strict constraint of the execution time. Simulation and real-world experiments proved that the proposed approaches can decrease the energy cost by more than 29% compared to the traditional single-core WMSN node. Moreover, the node can react quickly to the time-sensitive events.

International audience; For the elastic SV (transverse) waves in metals, a high-quality narrow passband filter that consists of aligned parallel thin plates with small gaps is designed. In order to obtain a good performance, the thin plates should be constituted by materials with a smaller mass density and Young’s modulus, such as polymethylmethacrylate (PMMA), compared to the embedded materials in which the elastic SV waves propagate. Both the theoretical model and the full numerical simulation show that the transmission spectrum of the designed filter demonstrates several peaks with flawless transmission within 0 KHz ~20 KHz frequency range. The peaks can be readily tuned by manipulating the geometrical parameters of the plates. Therefore, the current design works well for both low and high frequencies with a controllable size. Even for low frequencies on the order of kilohertz, the size of this filter can be still limited to the order of centimeters, which significantly benefits the real applications. The investigation also finds that the same filter is valid when using different metals and the reason behind this is explained theoretically. Additionally, the effect of bonding conditions of interfaces between thin plates and the base material is investigated using a spring model.

Memory optimization, energy conservation, real-time scheduling and fault tolerance are the essential research topics in the wireless sensor network (WSN). In this paper, a memory-efficient, energy-efficient, real-time and fault-tolerant WSN system LiveOS is designed and implemented. Compared to the other systems, LiveOS has several typical features. Firstly, the optimized Rate-Monotonic Scheduling (RMS) scheduling algorithm is implemented. By doing this, the memory cost of the multithreaded real-time operating system (RTOS) can be 47.3% optimized if compared to the traditional single-core node. Consequently, the RTOS becomes appropriate to run even on the memory-constrained WSN nodes. Secondly, the new research approach that addresses the WSN challenges by combining both the multi-core hardware technique and the software technique is applied in LiveOS. By means of the multi-core hardware support, the energy cost of LiveOS can be 35% optimized compared to the traditional single-core platform. Moreover, the real-time scheduling performance and the fault-tolerant ability of the WSN nodes can be optimized significantly. Due to the above features, LiveOS becomes the WSN system which has small memory footprint, long lifetime, high real-time scheduling performance and upstanding fault-tolerant ability. The evaluation on the different prototype nodes proves that LiveOS is appropriate to run on the resource-constrained WSN platforms and is competent to execute the outdoor real-time WSN applications.

Memory optimization, energy conservation, over-the-air reprogramming, and fault tolerance are the critical challenges for the proliferation of the wireless sensor network. To address these challenges, a new wireless sensor network platform termed LiveWSN is presented in this article. In LiveWSN, several new design concepts are implemented, such as the hierarchical shared-stack scheduling and the pre-linking native-code reprogramming. By doing so, the data memory cost of the LiveWSN scheduling system can be optimized by 25% if compared with that of the traditional multithreaded MANTIS OS. Moreover, the application reprogramming code size can be decreased by 72.6% if compared with that of the Contiki dynamic-linking reprogramming. In addition to the new design concepts, the new research approach which addresses the energy conservation and fault tolerance challenges by combining the software technique and the multi-core hardware technique is applied in LiveWSN. By means of the multi-core hardware infrastructure, the lifetime of the LiveWSN nodes can be prolonged by 34% if compared with the single-core Live node. Moreover, the fault-tolerant performance of the wireless sensor network node can be optimized significantly. With the above features, LiveWSN becomes memory efficient, energy efficient, reprogrammable, and fault tolerant, and it can run on the high resource-constrained nodes to execute the outdoor real-time wireless sensor network applications.

International audience; Self-assembly is a fundamental concept and a powerful approach in molecular science. However, creating functional materials with the desired properties through self-assembly remains challenging. In this work, through a combination of experimental and computational approaches, the self-assembly of small amphiphilic dendrons into nanosized supramolecular dendrimer micelles with a degree of structural definition similar to traditional covalent high-generation dendrimers is reported. It is demonstrated that, with the optimal balance of hydrophobicity and hydrophilicity, one of the self-assembled nanomicellar systems, totally devoid of toxic side effects, is able to deliver small interfering RNA and achieve effective gene silencing both in cells - including the highly refractory human hematopoietic CD34(+) stem cells - and in vivo, thus paving the way for future biomedical implementation. This work presents a case study of the concept of generating functional supramolecular dendrimers via self-assembly. The ability of carefully designed and gauged building blocks to assemble into supramolecular structures opens new perspectives on the design of self-assembling nanosystems for complex and functional applications.

Glass-ceramics were fabricated from the 80GeS2⋅20Ga2S3 chalcogenide glass using an appropriate heat-treatment at a fairly low temperature (T g+30°C) for different durations. Compared with the base glass, they present much-improved thermal shock resistance and fracture toughness, and meanwhile remain an excellent mid-IR transmission in 2–10-μm spectral region. XRD results indicate that the enhanced mechanical properties are mainly due to the appearance of Ga2S3 crystals, and only a very small amount of GeS2 was precipitated on the surface. Bulk and powder samples heat-treated at 458°C for different durations were used to study the evolution of the two crystallization peaks using DSC measurement. It is found that the precipitation of Ga2S3 phase is responsible for the exotherm of first crystallization peak and that of GeS2 phase for the second one. The crystallization mechanism was also examined using the nonisothermal method, and the considerably low activation energy (E c) and high crystallization rate constant (K) for the first crystallization peak illustrate a much easier precipitation of Ga2S3 phase than that of GeS2 phase, which is in good accordance with the ceramization process.

International audience; Enhanced luminescence in rare-earth-doped chalcogenide glass-ceramics is of great interest for the potential integrated optoelectronic devices. However, fundamental mechanism on the enhancement of luminescence upon crystallization remains largely unknown. We report the fabrication and characterization of wide transmission chalcogenide glass and glass-ceramics based on the 25GeS2*35Ga2S3*40CsCl:0.3Er glass composition, and discuss the mechanism of enhanced luminescence. By monitoring the 4I9/2-4I15/2 of Er3+ transition, up-conversion luminescence of 12 times higher was observed in glass-ceramics compared with that in base glass. Electron paramagnetic resonance (EPR) and Raman scattering spectroscopies were employed to obtain the information of selective environment of Er3+ ions and microstructural evolution with the crystallization progress. Both of them evidenced that the enhanced up-conversion luminescence was mainly related to the local environmental evolution from a mixed chlorine-sulfur coordination to a low phonon energy chlorine coordination in the residual glassy matrix of glass-ceramics.

An alternative solution for producing logic devices in microelectronics is spintronics (SPIN TRansport electrONICS). It relies on the fact that in a magnetic layer, the electrical current can be spin polarized. To fabricate such components, a material whose electronic properties depend on its magnetic state is needed. The Mn-Ge system presents a lot of phases with different magnetic properties, which can be used for spintronics. The most interesting phase among the Mn-Ge system is Mn5Ge3 because of its stability at high temperatures, its Curie temperature which is close to room temperature and its ability of injecting spin-polarized electrons into semiconductors. In this paper, we have combined Reflection High-Energy Electron Diffraction (RHEED) and X-ray Diffraction (XRD), to study the sequence of formation of MnxGey phases during reactive diffusion of both a 50 nm and a 210 nm thick Mn films deposited by Molecular-Beam Epitaxy (MBE) on Ge (111).

International audience; The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS2-Ga2S3 glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14-15 mol% Ga2S3. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS2*14.3 mol% (1/7) Ga2S3, six-coordinated [S3Ga-X-GaS3] units (X=S or None) are well isolated by the [GeS4] structures, which contributes to the decreasing of precipitation of Ga2S3 crystals in (100-x)GeS2-xGa2S3 (x≤14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range structural order, firstly, includes the arrangement of structural units which is consistent with and provides an atomistic explanation of the compositional evolution of phase transformation behavior in these glasses.Graphical abstractSynopsis: network demixing in GeS2-Ga2S3 chalcogenide glasses.

In recent years, spintronics whose principle is based on controlling the spin of electrons in semiconductor layers is presented as a complementary or even an alternative solution for production of logic devices in microelectronics. It relies on the fact that electric current in a magnetic layer can be spin polarized. Manufacture of such components is based on the use of materials or heterostructures whose electronic properties depend on their magnetic state. The magnetic Mn-Ge system is interesting because of its possible development at high Curie temperature and its integration on Si substrate. Among all of the Mn-Ge phase compounds of the diagram, Mn5Ge3 seems the most interesting one for spintronics applications: it is a stable and ferromagnetic phase at room temperature. In this paper, we present first results of the study, by Reflection High Energy Electron Diffraction (RHEED), X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), of the sequence of formation of the MnxGey phases in the case of reaction of a nanometric-thick Mn film (200nm) deposited by MBE on Ge (111).

International audience; With the increase of the complexity of automotive control, it is necessary to develop AEIICS (Automotive Electronic and Information Integrated Control System) for exchanging information between ECUs (Electronic Control Units) based on in-vehicle network technology. We named the parameter (or variable) contained in and transmitted by frame as signal. Period and deadline are basic temporal characteristics for signal and frame. Designers mainly focus on directly designing the period and deadline of frame but omit the temporal characteristic relationship between signal and frame. In this paper, we researched on the calculation method of period and deadline of frame according to the temporal characteristic of signal. Based on the period of signal, we proved the period of frame is the minimal period of signals composing this frame. Considering the possible time offset between the production time of data of signal and the first transmission time of frame containing this data, we deduced the calculation formula of deadline of frame by applying GCRT (Generalized Chinese Remainder Theorem).

In this thesis, we are interested in a wide-area PLC (Power Line Communication) network to provide a communication infrastructure for monitoring and control of energy distribution and consumption. This work has been carried out as a part of REMPLI (Real-time Energy Management via Power Line and Internet) European project and resulted in the definition of REMPLI PLC. For achieving high network performance and real-time data transfer using medium voltage and low voltage electricity grids, major problems such as dynamic packet routing, quality of service management and real-time event reporting are addressed. We designed an efficient routing protocol to cope with dynamic electricity grid topology changes and to relay packets to reach the destination. REMPLI PLC performance is evaluated using simulations and complemented by analytic studies. It is proved that most of the application requirements can be satisfied by REMPLI PLC. We proposed and implemented a new traffic dispatcher providing differentiated quality of service for applications. Based on ALOHA protocol, some variants have been designed and evaluated for enabling efficient real-time event notification.; Dans cette thèse, nous nous intéressons à la problématique liée à la communication numérique sur courant porteur dans l'objectif de fournir une infrastructure de communication qui permet la surveillance et le contrôle de la distribution et de la consommation de l'énergie. Ce travail a été effectué dans le cadre du projet européen REMPLI (Real-time Energy Management via Power Line and Internet) et a produit la spécification REMPLI PLC (Power Line Communication). Pour fournir une meilleure performance de la communication et effectuer le transfert de données en temps réel, en utilisant les réseaux électriques de moyenne tension et de basse tension, les problèmes principaux qui sont le routage dynamique de paquets de données, la gestion de la qualité de service et la notification des événement en temps réel, ont été traités. Nous avons développé un protocole de routage efficace pour s'adapter au changement dynamique de topologie du réseau électrique. Les performances de REMPLI PLC sont évaluées en utilisant des approches de simulation couplée avec des approches analytiques. Il est prouvé que la majorité des besoins applicatifs peuvent être satisfaite par REMPLI PLC. Nous avons proposé et implanté un nouvel “ordonnançeur de traffic” fournissant différents niveaux de qualité de service pour les applications. Des variantes de protocole ALOHA ont été proposées et évaluées afin de vérifier que les propriétés temps réel requises sur les notifications d'événements sont respectées.