Temperature control during Spark Plasma Sintering and application to up-scaling and complex shaping

The determination and the homogeneity of the sample temperature during consolidation of powders by Spark Plasma Sintering (SPS) are addressed. Densifications were carried out in three different facilities differing by their constructors and their size. A structural transformation activated in a TiAl alloy was used as a marker of the sample temperature and finite element modeling were performed to evaluate the temperature at each point of the set-up. A good agreement between experimental and simulated data is exhibited. Alloys with identical microstructures were sintered and the homogeneity of the microstructure was better in the largest machines or when the sample was isolated by alumina disks.Large specimens with a diameter of 100 mm and a height of 60 mm were sintered, with the aim to achieve full densification and good microstructural control. On the basis of this temperature mastering, samples with complex shape were successfully densified. SEM post mortem observations confirmed the absence of porosities, and the expected microstructure as predicted by FEM calculations.     

Design of a walking cyclic gait with single support phases and impacts for the locomotor system of a thirteen-link 3D biped using the parametric optimization

The development of an algorithm of parametric optimization to achieve optimal cyclic gaits in space for a thirteen-link 3D bipedal robot with twelve actuated joints is proposed. The cyclic walking gait is composed of successive single support phases and impulsive impacts with full contact between the sole of the feet and the ground. The evolution of the joints are chosen as spline functions. The parameters to define the spline functions are determined using an optimization under constraints on the dynamic balance, on the ground reactions, on the validity of impact, on the torques, and on the joints velocities. The cost functional considered is represented by the integral of the torques norm. The torques and the constraints are computed at sampling times during one step to evaluate the cost functional for a feasible walking gait. To improve the convergence of the optimization algorithm the explicit analytical gradient of the cost functional with respect to the optimization parameters is calculated using the recursive computation of torques. The algorithm is tested for a bipedal robot whose numerical walking results are presented.     

Close-packed array of gold nanoparticles and sum frequency generation spectroscopy in total internal reflection: a platform for studying biomolecules and biosensors

An approach is introduced for studying the adsorption and recognition mechanisms of biomolecules, without using any markers. We show for the first time, that the sum frequency generation spectroscopy performed in the total internal reflection (TIR-SFG) geometry, combined with a regular close-packed array of gold nanoparticles allows to probe with a high sensitivity the changes in conformation and orientation induced by the recognition process of avidin by biocytin. This approach represents a new platform with potential use in biosensors, diagnostics and bioactive layers.     

How to make a European integrated market in small and isolated electricity systems? The case of the Canary Islands

This paper presents a geographic dimension not often studied in the dynamics of creating an internal market for electricity within the European Union, namely the case of small European electricity systems like those found on the Greek islands of Cyprus and Crete. Our question, then, is how to achieve a suitable internal market for electricity in small and isolated systems. To address this issue, we identify the main problems to be overcome by introducing a methodology in which the Canary Islands experience is taken as a case study for understanding the challenges in creating an “EU-like market for electricity”. Our results show that the design of the vertical industrial structure and the figure of the grid operator and its attributes are key features for the proper operation of any electrical system. We also stress the minor roles of other possible options to achieve this EU-compatible market by highlighting first, in the wholesale market, the call-for-tender solution to introduce more generation and the risk of using safety requirements as barriers to entry in these small markets, and second, in the supply activities, the potential problems of an improperly regulated tariff scheme.     

Analyzing the Substrate Specificity of a Class of Long-Horned-Beetle-Derived Xylanases by Using Synthetic Arabinoxylan Oligo- and Polysaccharides

Xylophagous long-horned beetles thrive in challenging environments. To access nutrients, they secrete plant-cell-wall-degrading enzymes in their gut fluid; among them are cellulases of the subfamily 2 of glycoside hydrolase family 5 (GH5_2). Recently, we discovered that several beetle-derived GH5_2s use xylan as a substrate instead of cellulose, which is unusual for this family of enzymes. Here, we analyze the substrate specificity of a GH5_2 xylanase from the beetle Apriona japonica (AJAGH5_2-1) using commercially available substrates and synthetic arabinoxylan oligo- and polysaccharides. We demonstrate that AJAGH5_2-1 processes arabinoxylan polysaccharides in a manner distinct from classical xylanase families such as GH10 and GH11. AJAGH5_2-1 is active on long oligosaccharides and cleaves at the non-reducing end of a substituted xylose residue (position +1) only if: 1) three xylose residues are present upstream and downstream of the cleavage site, and 2) xylose residues at positions −1, −2, +2 and +3 are not substituted.     

数字电视机顶盒,真的走到尽头了吗?

本文阐述了在大量采用广播DTT标准和最新视频压缩技术之后,全球的地面数字电视机顶盒(DTT/STB)在结构上的最新发展.最后一部分则描述了迪康(DiBcom)解决方案如何帮助OEM厂商继续使用成本优化的硬件,而不会影响机顶盒的扩展性,同时延长其使用寿命.     

Net Shape Fins for Compact Heat Exchanger Produced by Cold Spray

This work explores the manufacturability of pyramidal fin arrays produced using the cold spray process. Near-net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using masks made of commercially available steel wire mesh. The feedstock powders used to produce the fins are characterized using scanning electron microscopy. Obstruction of the masks was investigated. The standoff distances between the substrate, mesh, and nozzle were empirically determined. Fin array characterization was performed using digital microscopy. The fin arrays’ heat transfer performance was assessed experimentally for a range of Reynolds number relevant to the application sought. The fins produced using the cold spray process outperform traditional straight (rectangular) fins at the same fin density and it is hypothesized that this is due to increased fluid mixing and turbulence.