Understanding of Void Formation in Cu/Sn-Sn/Cu System During Transient Liquid Phase Bonding Process Through Diffusion Modeling

Metallurgical and Materials Transactions B - Transient Liquid Phase (TPL) bounding of Sn foil sandwiched between two Cu foils involves, in the temperature range above the melting point of Sn...     

Preparation of new microporous titanium pillared kenyaite materials active for the photodegradation of methyl orange

In recent years, layered silicates have extensively been used to design new nanomaterials through functionalization. In this work, the lamellar sodium silicates magadiite and kenyaite have been hydrothermally synthesized in presence of ethanol as organic co-solvent. Materials of high purity and high crystallinity were obtained after only 24 h of crystallization at a temperature of 180 °C for kenyaite and a temperature of 150 °C for magadiite. It appears that the presence of ethanol in the synthesis medium tends not only to increase the crystallization rate, but also to stabilize the formation of magadiite.The as-synthesized Na-kenyaite was used as precursor for the preparation of titanium pillared clay materials. The resulting microporous titanium oxide pillared kenyaite materials exhibit large specific surface areas up to 180 m² g^?1 with a Ti contents up to 24 wt% and are active for the photocatalytic degradation under UV light irradiation of the organic dye methyl orange in water.     

Chemical recycling of glass fibre reinforced composites using subcritical water

A hydrolysis process is applied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibres. Subcritical conditions of water (200 °C < temperature < 374 °C and pressure < 221bars) were chosen regarding the involved chemistry for the case of simple esters. Several experiments were realised to measure the effects of the process parameters on the efficiency of hydrolysis, on the quality of the recovered fibres and finally on the nature of the recovered organic products. A washing of the fibres is necessary and appears to be an important step of the process realised in batch conditions. The identification of the recovered organic products indicates that monomers of the resin are obtained but also that secondary reactions occur during the hydrolysis process.     

Single-run separation of closely related cationic and anionic compounds by CE-ESI-MS: application to the simultaneous analysis of melamine and its analogs in milk

In recent years, two adulteration incidents concerning the addition of melamine, a nitrogen-rich industrial small polar compound, to pet food and infant formula products have occurred in China. These issues prompted laboratories to develop methods for the analysis of melamine and related compounds in a wide variety of food products and ingredients. In this context, a CE-ESI-MS method was developed to simultaneously analyze melamine and its related products (ammeline, ammelide and cyanuric acid) that possess close physico-chemical properties. This method allows the simultaneous analysis of both cations and anions in a single run, using CE to divide the run into two time segments in normal polarity mode. For this purpose, ESI polarity was switched once during the run, increasing sensitivity and data quality. The method was applied to spiked powdered milk and melamine-contaminated powdered milk, with two sample preparation procedures.     

Algorithmic-level Specification and Characterization of Embedded Multimedia Applications with Design Trotter

Designing embedded systems is a challenging task during which wrong choices can lead to extremely costly re-design loops, especially when these wrong choices are made during the algorithm specification and the mapping over the selected architecture. In this paper we propose a high-level approach for design space exploration, using a usual standard language as input. More precisely we present the two first steps of the Design Trotter framework: (i) the specification step and its underlying internal model (HCDFG: Hierarchical and Control Data Flow Graph) and (ii) the characterization step which takes place very early in the design flow. Indeed, once transformed into our internal representation, the specification is rapidly and automatically characterized and explored at the algorithmic level. The framework provides the designer with metrics so that he can evaluate, very early in the design process, the impact of algorithmic choices on resource requirements in terms of processing, control, memory bandwidth and potential parallelism at different levels of granularity. The overall aim of our approach is to improve the algorithm/architecture matching that sorely influences the implementation efficiency in terms of silicon area, performances and energy consumption. We give examples which illustrate how designers can refer to the outcomes of the Design Trotter framework in order to select or build suitable architectures for specific applications. Yannick Le Moullec received the M.S degree from the University of Rennes (France) in 1999 and the Ph.D degree from the University of South Brittany (France) in 2003. His thesis focused on Hardware/Software codesign, and more specifically on high-level design space exploration of embedded systems. His thesis work is part of the EDA framework “Design Trotter”. In 2003 he joined the center for embedded software (CISS) at Aalborg University (Denmark) as a post-doc fellow. His current work deals with design space exploration for wireless applications. Jean-Philippe Diguet received the M.S degree and the Ph.D degree from Rennes University (France) in 1993 and 1996 respectively. His thesis, carried out at LASTI lab., focused on the estimation of hardware complexity and algorithmic transforms for architectural synthesis. Then he joined the IMEC in Leuven (Belgium) where he worked as a post-doc fellow on the minimization of the power consumption of memories at the system-level. He has been a member of the LESTER lab. (Lorient, France) since 1998, where he initiated a research project in design space exploration both at the algorithmic and system levels. He has been an associated professor at the University of South Brittany (France) from 1998 until 2002. In 2002, he initiated a technology transfer and co-funded Dixip, a company in the domain of wireless embedded systems. Since 2004 he is a CNRS (French National Scientific Research Center) researcher. His work focuses on two topics. The first one is the management of the development of the EDA framework “Design Trotter” for design space exploration and combining the design space exploration with technology mapping over reconfigurable architectures. The second topic is the definition of environment-aware, predictive and self-adaptive architectures under QoS and power constraints, this topic includes new OS services, NOCs and architecture reconfiguration control. Nader Ben Amor is a PhD student at both University of South Brittany (France) and Sfax Engineering School (Tunisia). He received the Electrical Engineering Diploma in 2000 and the M.S Degree in Electronics in 2001 from Sfax Engineering School. His research interest is the design of embedded multimedia processors. Thierry Gourdeaux received the Engineer Title and the M.S degree from the ENSSAT school, Lannion (France), in 1997. Since 1999 he is a research engineer at the University of South Brittany. His work includes the analysis of DSP systems for spatial applications (with Alcatel Espace), technology and knowledge transfers to the industry community and the development of EDA tools such as “Design Trotter” and “Soft Explorer”. Jean-Luc Philippe is currently a full Professor at the University of South Brittany (France). He is leading a research group working on design methodologies for electronic systems executing under performances, consumption and safety constraints. Once implemented into tools, these methodologies are applied to several domains: signal and image processing, telecommunications, transitic systems, etc.     

Using genetic algorithms for the optimization of mechanisms

This work examines the possibility of using genetic algorithms for the optimization of the loads transmitted in mechanisms. The variables of design are the relative positions of the various connections, considered in a comparative manner. The minimization of the loads transmitted in the connections is achieved by optimizing the respective positions of those lead to less expensive solutions for bearings and sections of beams. The examples show that using this stochastic method is an efficient way to minimize loads in mechanisms.     

Mechanism underlying cuticular hydrocarbon homogeneity in the antCamponotus vagus (SCOP.) (Hymenoptera: Formicidae): Role of postpharyngeal glands

The aim of the present study was to investigate the regulation and the homogeneity of the chemical signature between members ofCamponotus vagus after experimentally changing the cuticular chemical signature by topically applying hydrocarbons. Topical application of pentane (solvent) to the cuticle of isolated workers led to a significant decrease in the quantities of the cuticular hydrocarbons measured within 3 hr, followed by an increase within the following 3 hr and a period of relative stability from 9 hr to 14 days. On the other hand, after topical application to isolated workers ofn-tetracosane, a hydrocarbon existing only in trace quantity in this species, the quantity of this hydrocarbon measured over time in the epicuticular wax tended to level out at about 14 days after treatment. In contrast, topically applied (Z)-9-tricosene, an unsaturated hydrocarbon not normally synthesized by this species, decreased dramatically within a few hours and had completely disappeared within 14 days. (Z)-9-Tricosene applied to one member of a group was present in the postpharyngeal glands of the other members from 30 min to seven days of cohabitation. The highest levels were recorded in all six workers in each group after one day. GC-MS analyses showed that (Z)-9-tricosene was present in the cuticles of some untreated workers only after four and seven days of cohabitation with a treated worker. These data suggest: (1) that the deposited (Z)-9-tricosene decreased very quickly on the cuticle of the treated worker, although the total amount was spread over the cuticle and postpharyngeal gland and (2) that it was absorbed by the nontreated workers via the postpharyngeal glands during licking or grooming activities and reincorporated into the cuticle at four and seven days. When the treated worker was separated from the other ants by a wire mesh, (Z)-9-tricosene was detected neither in the cuticle nor in the postpharyngeal gland of nontreated workers.     

Importance of in-plane shear rigidity in finite element analyses of woven fabric composite preforming

A finite element made of woven unit cells under biaxial tension and in-plane shear is proposed for the simulation of fabric forming. The simulation is made within an explicit dynamic approach and is based on a simplified dynamic equation accounting for tension and in-plane shear strain energy. The biaxial tensile properties (given by two surfaces) and the in-plane shear properties (given by a curve) can be determined both by biaxial tensile tests and picture frame experiments or obtained by mesoscopic 3D finite element analyses of the woven unit cell. The interior load components of the proposed finite element are calculated explicitly and simply from the tensions and shear torque on four woven cells. The results obtained by the simulations of a hemispherical forming process on a very unbalanced fabric are compared to experiments. It is shown that the tension strain energy permits to describe the asymmetry of the response but that the computation of wrinkles and of the deformed states when the locking angle is exceeded needs to take the in-plane shear stiffness and its evolution with shear angle into account.     

Biomethanation: Its future development and the influence of the physiology of methanogenesis

Bioconversion of organic matter into methane by anaerobic bacteria is a process better understood each day. The technology of biomethanation takes advantage of this in a number of ways, three of them being examined in this paper. First, when biomethanation is conducted under continuous, completely mixed conditions without active biomass recycle, a bottleneck may arise from the limited number of methanogenic bacteria present in the digestion mixed liquor. As the specific methane production rate was shown to be also limited, the resulting overall methane production must remain low. ‘Second generation’ methane digesters are being designed so as to trap the methanogenic bacteria within the digester, a fact which was demonstrated by the accumulation in the methane digestion mixed liquor of coenzyme F₄₂₀. Second, when the feedstock for biomethanation consists of insoluble organic matter, the preliminary solubilisation of this insoluble matter is often rate-limiting. It was shown that the inverse of conversion varies linearily with the inverse of mean residence time, which allowed the calculation of ‘ultimate’ conversion. Application of this technique to the individual components of a complex feedstock, determined independently, allowed us to identify problems of rate limitation and of bacterial competency. Two-step methane digestion systems should help to overcome this second bottleneck. Third, monitoring of the biomethanation process needs major improvements. Even simple analytical methods such as dry organic matter or chemical oxygen demand determinations suffer major drawbacks and may lead to erroneous estimated efficiencies. A graph is proposed which attempts to correlate heats of combustion, mean oxidation stages and specific chemical oxygen demands with efficiencies with the aim of detecting anomalous values.