Deposition and characterization of nickel–niobium composite electrocoatings

Ni–Nb composite electrocoatings were obtained on carbon steel from Watts bath, containing suspended 20 μm size niobium powders. The effect of cathodic current density, electrolyte stirring rate and concentration of Nb particles in the bath on the deposit morphology and texture, volume fraction of co-deposited Nb particles and microhardness was investigated. The Ni–Nb composite layers presented a rough morphology with randomly oriented Ni grains, whereas pure Ni coatings obtained under the same experimental conditions were smooth and showed highly preferred orientation in the [110] or [100] direction. Stirring rate of the electrolyte and concentration of Nb particles in the bath are the main parameters affecting the incorporation of Nb particles. The Nb incorporated volume fraction was 11–14%, 17–19%, 27–32% and 34–37% for the 20 g L⁻¹ Nb/550 rpm, 20 g L⁻¹ Nb/400 rpm, 40 g L⁻¹ Nb/400 rpm and 40 g L⁻¹ Nb/550 rpm conditions, respectively. The microhardness of the Ni–Nb composite coatings obtained at 20 and 40 mA cm⁻² was higher than that of pure Ni layers, due to grain refining. Incorporation of Nb particles in Ni coatings improved the corrosion resistance of the deposits in NaCl and H₂SO₄ solutions.     

Synthesis and characterization of block-copolymer surfactants with specific interactions with associative thickeners

It has been theorized that, in order to get some positive interaction with the associative thickeners, the surfactants should have, at the end of the hydrophilic sequence, a short hydrophobic group. On the other hand, in order to control the hydrophilic lipophilic balance (HLB), it is wise to use well controlled polymerization procedures to build the block-copolymer. Then, the safer and simplest way to reach such goal is to use the ring-opening living anionic polymerization of butylene oxide (hydrophobic sequence) and then ethylene oxide (hydrophilic sequence); this living block-copolymer is then killed using an alkyl or aryl chloride (or bromide). However, because such surfactants include at the end of the hydrophilic sequence a hydrophobic group, they tend to adopt, when adsorbed onto hydrophobic latex particles, a back-folded conformation. In order to get for them an extended conformation, the hydrophilic sequence should have charges able to repel each other. This was achieved upon preparing block-copolymers of acrylic acid and butylacrylate, using a controlled radical polymerization with reversible addition fragmentation transfer (RAFT) agents, starting with the poly(acrylic acid) (PAA) sequence. Then, the radical fragment coming from the RAFT agent is at the end of the PAA sequence. A few rheological data actually confirm the interest of the concept.     

Finite element simulation of nanoindentation tests using a macroscopic computational model

The aim of this work was to develop a numerical procedure to simulate nanoindentation tests using a macroscopic computational model. Both theoretical and numerical aspects of the proposed methodology, based on the coupling of isotropic elasticity and anisotropic plasticity described with the quadratic criterion of Hill are presented to model this behaviour. The anisotropic plastic behaviour accounts for the mixed nonlinear hardening (isotropic and kinematic) under large plastic deformation. Nanoindentation tests were simulated to analyse the nonlinear mechanical behaviour of aluminium alloy. The predicted results of the finite element (FE) modelling are in good agreement with the experimental data, thereby confirming the accuracy level of the suggested FE method of analysis. The effects of some technological and mechanical parameters known to have an influence during the nanoindentation tests were also investigated.     

Interoperable support for collaborative, mobile, and accessible health care

E-Health systems, through their use of Internet and wireless technologies, offer the possibility of near real-time data integration to support the delivery and management of health care. In practice, the wide range of choice in technologies, vendors, protocols, formats, and information representations can make even simple exchanges of information between systems problematic. Much of the focus on healthcare interoperability has been on resolving interoperability issues of system to system information exchanges. But issues around people to people interactions and people to system interactions are just as important to address from an interoperability point of view. In this paper, we identify interoperability deficiencies in collaborative care delivery and develop a methodology in two parts. In the first part, an ontology is developed to represent collaborative care delivery. In the second part, the ontology is used to design an architecture for interoperable clinical information system design. We then use a case study in palliative care to provide a proof of concept of the methodology. The case study provides an inventory of the interoperability requirements for palliative care and a perspective on the design and implementation of a people oriented clinical information system that supports collaborative health care delivery in palliative care.     

An experimental comparison of clustering methods for content-based indexing of large image databases

In recent years, the expansion of acquisition devices such as digital cameras, the development of storage and transmission techniques of multimedia documents and the development of tablet computers facilitate the development of many large image databases as well as the interactions with the users. This increases the need for efficient and robust methods for finding information in these huge masses of data, including feature extraction methods and feature space structuring methods. The feature extraction methods aim to extract, for each image, one or more visual signatures representing the content of this image. The feature space structuring methods organize indexed images in order to facilitate, accelerate and improve the results of further retrieval. Clustering is one kind of feature space structuring methods. There are different types of clustering such as hierarchical clustering, density-based clustering, grid-based clustering, etc. In an interactive context where the user may modify the automatic clustering results, incrementality and hierarchical structuring are properties growing in interest for the clustering algorithms. In this article, we propose an experimental comparison of different clustering methods for structuring large image databases, using a rigorous experimental protocol. We use different image databases of increasing sizes (Wang, PascalVoc2006, Caltech101, Corel30k) to study the scalability of the different approaches.     

Silica and alumina impregnated with dimethylformamide solutions of molybdophosphoric or tungstophosphoric acids for hydrotreatment reactions

Heteropolyacid (HPA) based catalysts were prepared by impregnation of silica and alumina with dimethylformamide solutions of molybdophosphoric and tungstophosphoric acids. This solvent allows the preservation of the Keggin unit during the impregnation independently of the nature of the support. Ni-promoted catalysts were prepared by impregnation with nickel nitrate solutions of the supported HPA. The stronger interaction of the HPA with alumina than with silica allows a better dispersion of the polyoxometallate species on the former one whereas the formation of bulk oxides is observed on silica. The performance of these HPA–Ni/support catalysts for hydrodenitrogenation and hydrodesulfurization reactions is related to the precursor–support interaction.     

Recent Advances on InAs/InP Quantum Dash Based Semiconductor Lasers and Optical Amplifiers Operating at 1.55 μm

This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm² per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T₀ larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time-jitter characteristics when QD lasers are actively mode-locked. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications     

Epitaxial and large area PLD ferroelectric thin film heterostructures on silicon substrates

Abstract

Epitaxial thin films of Bi₄Ti₃O₁₂ and SrBi₂Ta₂O₉ have been deposited by pulsed laser deposition (PLD) onto epitaxial thin film templates of CeO₂/YSZ as well as on epitaxial electrodes of (La_0.5Sr_0.5)CoO₃, in turn deposited onto CeO₂/YSZ template layers. These electrode and buffer layers have been deposited by PLD as well. The same heterostructures, namely ferroelectric Bilayered perovskite films on the same stack of epitaxial layers, have also been deposited by large area PLD. This technique allows deposition with a good uniformity onto entire silicon 3-inch wafers. Thickness and composition uniformity of the ferroelectric films, electrodes and buffer layers are important with regard to their possible application in microelectronics. Uniformities achieved are in the range of 5 to 15% of the mean thickness, depending on the material and deposition conditions.