An investigation of carbon nanotube jet grinding

Since their observation in 1976 and 1991, carbon nanotubes (CNTs) have generated much interest due to their properties and potential applications. CNTs are tubular carbon molecules with remarkable mechanical, electrical, chemical and thermal properties, which make them useful in various applications. Industries producing CNTs via the fluidized bed chemical vapor deposition technique face challenges related to the size of CNT bundles. The two main challenges are agglomeration and agglomerate size distribution control. A solution to these challenges involves the use of jet mills to grind the CNT agglomerates. The goal of this study was to determine whether the nanotubes could be ground with air jets using a commercial jet mill and apply a two-parameter model to describe the grinding process. The present study has indicated that air-jet grinding of CNTs is feasible with a typical commercial jet mill. This paper presents the effect of operational parameters on the arithmetic mean diameter of the ground product. Sonic velocity through the grinding nozzles was required to obtain reasonable grinding rates and relatively narrow particle size distributions. This occurs at high air to solids feedrate ratios. Additionally, a simple attrition model can describe the grinding process in the spiral jet mill.     

Electron spectroscopies and their use for materials characterization

We present here a general overview of electron spectroscopies from a practical point of view. The most frequently used ones are described and the type of structural information they can provide on materials is explained in relation to the physical processes on which they are based. Furthermore, we explore critically and in detail various tools that have been developed to allow a systematic solving of structures by these spectroscopies.     

SMC composites waste management as reinforcing fillers in polypropylene by combination of mechanical and chemical recycling processes

A new process of management of waste of composite materials from Sheet Moulding Compounds (SMC), as reinforcing fillers for thermoplastic materials, including both mechanical and chemical processes is proposed in this paper. Communited SMC being composed of coated glass fibres intimately mixed with calcium carbonate powder, their reinforcing power is low. First, the fibrous part was increased by partial dissolution of calcium carbonate present in the crushed products SMC. Second, a process of partial solvolysis was developed aiming at strong increasing the interfacial mechanical properties by functionalising of SMC load incorporated into polypropylene/grafted maleic anhydride polypropylene (PP/PP_gma). At this effect, we investigated a treatment with a hot triamine (diethylenetriamine, DETA) in order to create a functionalisation, after scission of the bond ester of unsaturated polyester, as bridging amino-succinimide.The effect of this recycling way by partial solvolysis was checked from the mechanical properties of the resulting reinforced PP/PP_gma material: Although a lower of Young modulus, better yield stress and especially resilience were observed.     

Effect of alkali halides on α-chymotrypsin activity in the plastein reaction

The influence of different alkali halides (LiF, LiCl. LiBr, NaF, NaCl, NaBr, KF, KCl and KBr) on α-chymotrypsin-catalysed plastein synthesis has been studied in aqueous medium at different substrate concentrations. The results showed an enhancing effect on the plastein synthesis enzyme action by the presence of salts, proportional to salt concentration, which was decreased when the substrate concentration was increased. Additionally, these facts allowed the ions to be classified as a function of their activation power (F^? > Cl^? > Br^?: K⁺ > Na⁺ > Li⁺), which was in agreement with the interpretation of the Hofmeister lyotropic series. The influence of the several phenomena produced by the presence of salts in the plastein reaction, such as, salt-substrate interactions and water activity, as well as the presence of deactivated enzyme was also analysed. The obtained results showed that the substrate concentration is the most important factor, and the activating effect of salts could be simultaneously involved with both a structural change on the substrate conformation and a reduction of water activity into the reaction media, enhancing the catalytic capability of the α-chymotrypsin towards a peptide synthesis action.     

Multivariate analysis of the correlation between noctuidae subfamilies and the chemical structure of their sex pheromones or male attractants

Female-emitted pheromones and sex attractants of Noctuidae were investigated using a specific computer procedure to analyze data collected from the literature. Correspondence analysis was used to survey the structure-activity relationships of sex pheromones in seven subfamilies. Structural, stereochemical, and functional features of active molecules were related to taxonomy. This multidimensional analysis revealed that the prevalent chemical frame of noctuid moth pheromones was a monounsaturated acetate withZ stereochemistry and a double bond on the fifth carbon closest to the nonfunctional branch of the molecule. Possible phylogenetic relationships within Noctuidae and between Noctuidae and other families are discussed in light of the sex pheromone biochemistry. Female sex pheromones appeared to be an additional character to be considered in the classification of noctuid moths.     

Crafting the Compelling User Experience

This article provides an introduction to the usage of software engineering approaches and tools for the design of user experience (UE). This approach was developed for three main reasons: (a) to provide UE design teams a rigorous, methodical, encompassing method that can be applied throughout the entire product development cycle; (b) to provide designers a way to work with abstract concepts to establish the conceptual design of the system before progressing to the realization of the design to the appropriate platform; and (c) to communicate the intended design to the implementation team in a manner that is concise, complete, and familiar. The approach is the application of Unified Modeling Language concepts to describe users and the UE design rather than the technical architecture. It is believed that designing the UE design separately from the technical architecture will help ensure teams deliver a usable and delightful UE. The methods in this article have been applied to a handful of real-world projects in the last year and a half. Thus far, the application of software engineering approaches and tools have been found to be very powerful aids that have enabled the creation of highly useful Web experiences as well as software applications.

Our intent is to address the full gamut of issues involved in creating a total user experience (UE)-from discovery of users needs through high-level and low-level design, ensuring fidelity during development, and deployment, with a full assessment of how well the design meets users' needs. We believe that through a concerted use of such a rigorous approach we can greatly improve not only the UE of products we create, but also the experience of designing and developing them. We are not the only team taking this direction in UE design. It has become clear to many in our field that a more rigorous, thorough, and accurate approach to UE design is not only possible-it is necessary, for many of the same reasons that software engineers long ago embraced such practices. As we are evolving our approaches in other phases, this article focuses on the discovery and design phase activities.     

The use of CFD modelling to optimise measurement of overflow rates in a downstream-controlled dual-overflow structure

The measurement of the flow through complex combined sewer overflow structures in the frame of automated monitoring remains difficult. In this paper, a methodology based on the use of computational fluid dynamics (CFD) modelling in order to improve the instrumentation of a downstream-controlled dual-overflow structure is presented. The dual-overflow structure is composed of two combined sewer overflows (CSOs) connected by a rectangular channel and controlled by a downstream gate located at the entry of the Meyzieu waste water treatment plant (close to Lyon, France). The analysis of the CFD results provides: (i) a better understanding of the interaction between the two CSOs--that means the hydraulic operation, the hydrodynamic behaviour, the backflow effect--and (ii) an ability to optimise the location of the water depth sensor. The measured water depth is used to assess the overflow rate by means of a numerical relationship. Uncertainties are also assessed.     

Parallel best-first search algorithms for planning problems on multi-core processors

The Journal of Supercomputing - The multiplication of computing cores in modern processor units permits revisiting the design of classical algorithms to improve computational performance in complex...     

Packing spherical discrete elements for large scale simulations

We introduce a new geometric method to generate sphere packings with restricted overlap values. Sample generation is an important, but time-consuming, step that precedes a calculation performed with the discrete element method (DEM). At present, there does not exist any software dedicated to DEM which would be similar to the mesh software that exists for finite element methods (FEM). A practical objective of the method is to build very large sphere packings (several hundreds of thousands) in a few minutes instead of several days as the current dynamic methods do. The developed algorithm uses a new geometric procedure to position very efficiently the polydisperse spheres in a tetrahedral mesh. The algorithm, implemented into YADE-OPEN DEM (open-source software), consists in filling tetrahedral meshes with spheres. In addition to the features of the tetrahedral mesh, the input parameters are the minimum and maximum radii (or their size ratio), and the magnitude of authorized overlaps. The filling procedure is stopped when a target solid fraction or number of spheres is reached. Based on this method, an efficient tool can be designed for DEMs used by researchers and engineers. The generated packings can be isotropic and the number of contacts per sphere is very high due to its geometric procedure. In this paper, different properties of the generated packings are characterized and examples from real industrial problems are presented to show how this method can be used. The current C++ version of this packing algorithm is part of YADE-OPEN DEM [20] available on the web (https://yade-dem.org).