eCollaboration — 'The Drive for Simplicity'

Technologies to allow users to collaborate together, independent of distance, have been available for a number of years. However, the usage of these technologies has remained limited even though companies have seen a steady increase in the need for communication between geographically dispersed staff. As a result, more travel is required than ever before—with all its associated costs, both monetary and social. This paper explores some of the reasons why eCollaboration has yet to deliver its full potential, and describes a number of solutions which BT is developing to address these issues.     

Nanoconfinement degradation in NaAlH4/CMK-1

An ordered mesoporous carbon scaffold (CMK-1) has been synthesized and infiltrated with NaAlH₄ nanoparticles by solvent- and melt-infiltration techniques. Small angle X-ray scattering (SAXS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and energy dispersive spectroscopy (EDS) are used to characterize the structure, composition and morphology before and after thermal treatment. This study illuminates some of the problems that can be associated with nanoconfinement of hydrogen storage materials including scaffold contamination, residual solvent contamination, sample morphology changes after heating, and other factors that can be detrimental to the application of these systems. Of particular interest is the expulsion of NaAlH₄ decomposition products from the scaffold after heating beyond its melting point under vacuum. This results in the surface of mesoporous carbon particles having arrays of multi-micron-long Al filaments that are >100 nm in diameter.     

Lapped nonlinear interpolative vector quantization and imagesuper-resolution

This article presents an improved version of an algorithm designed to perform image restoration via nonlinear interpolative vector quantization (NLIVQ). The improvement results from using lapped blocks during the decoding process. The algorithm is trained on original and diffraction-limited image pairs. The discrete cosine transform is again used in the codebook design process to control complexity. Simulation results are presented which demonstrate improvements over the nonlapped algorithm in both observed image quality and peak signal-to-noise ratio. In addition, the nonlinearity of the algorithm is shown to produce super-resolution in the restored images.     

High-aperture beams.

Beams of a high angle of convergence and divergence are called high-aperture beams. Different ways of defining high-aperture generalizations to paraxial beams are reviewed for both scalar beams and electromagnetic beams. The different approaches are divided into three types. The particular examples of Gaussian beams and Bessel beams are discussed. For Gaussian beams, beams that exhibit a Gaussian variation in the waist necessarily include evanescent components, which rules out their use in describing propagation over all space. Generalizations of the definitions of beam width and the beam-propagation factor M2 for high-aperture beams are described. The similarities among the three types of high-aperture beams and the different models of ultrashort-pulsed beams are discussed.     

Tantalum Enrichment in Tantalum‐Doped Titanium Dioxide

This investigation has assessed the behavior of Ta enrichment in Ta‐doped TiO₂ under various conditions of controlled oxygen activity and temperature. The aim has been to establish the relationships between specific processing conditions and the resulting compositional variation within the surface and near‐surface region. Under the application of oxidizing conditions [p(O₂) = 101 kPa], it has been observed that Ta will strongly enrich the surface of Ta‐doped TiO₂ irrespective of the annealing temperature (over the range of 1173–1523 K). However, under reducing conditions [p(O₂) in the vicinity of 10^?10 Pa], Ta enrichment is observed at 1173 K, but Ta depletion from the surface and near‐surface is observed at 1348 and 1523 K. This is attributed to an apparent lack of stability of the surface phase, which could possibly be TiTa₂O₇. The results for the investigation contribute to the engineering of TiO₂‐based photoelectrode materials that possess improved charge separation properties.     

The synthesis of nanoscopic Ti based alloys and their effects on the MgH2 system compared with the MgH2 + 0.01Nb2O5 benchmark

The MgH₂ + 0.02Ti-additive system (additives = 35 nm Ti, 50 nm TiB₂, 40 nm TiC, <5 nm TiN, 10 × 40 nm TiO₂) has been studied by high-resolution synchrotron X-ray diffraction, after planetary milling and hydrogen (H) cycling. TiB₂ and TiN nanoparticles were synthesised mechanochemically whilst other additives were commercially available. The absorption kinetics and temperature programmed desorption (TPD) profiles have been determined, and compared to the benchmark system MgH₂ + 0.01Nb₂O₅ (20 nm). TiC and TiN retain their structures after milling and H cycling. The TiB₂ reflections appear compressed in d-spacing, suggesting Mg/Ti exchange has occurred in the TiB₂ structure. TiO₂ is reduced, commensurate with the formation of MgO, however, the Ti is not evident anywhere in the diffraction pattern. The 35 nm Ti initially forms an fcc Mg_47.5Ti_52.5 phase during milling, which then phase separates and hydrides to TiH₂ and MgH₂. At 300 °C, the MgH₂ + 0.02 (Ti, TiB₂, TiC, TiN, TiO₂) samples display equivalent absorption kinetics, which are slightly faster than the MgH₂ + 0.01Nb₂O₅ (20 nm) benchmark. All samples are contaminated with MgO from the use of a ZrO₂ vial, and display rapid absorption to ca. 90% of capacity within 20 s at 300 °C. TPD profiles of all samples show peak decreases compared to the pure MgH₂ milled sample, with many peak profiles displaying bi-modal splitting. TPD measurements on two separate instruments demonstrate that on a 30 min milling time scale, all samples are highly inhomogenous, and samplings from the exact same batch of milled MgH₂ + 0.02Ti-additive can display differences in TPD profiles of up to 30 °C in peak maxima. The most efficient Ti based additive cannot be discerned on this basis, and milling times ? 30 min are necessary to obtain homogenous samples, which may lead to artefactual benefits, such as reduction in diffusion distances by powder grinding or formation of dense microstructure. For the hydrogen cycled MgH₂ + 0.01Nb₂O₅ system, we observe a face centred cubic Mg/Nb exchanged Mg_0.165Nb_0.835O phase, which accounts for ca. 60% of the originally added Nb atoms.     

Titanium dioxide for solar-hydrogen I. Functional properties

The present work considers the concept of photoelectrochemical generation of hydrogen through water splitting using solar energy (solar-hydrogen). The focus is on functional material properties that are essential for the performance of photoelectrochemical cell for solar-hydrogen. The performance of the cell is discussed in terms of the energy conversion efficiency (ECE). It is argued that TiO₂ and TiO₂-based materials are the most promising candidates for photoelectrodes for solar-hydrogen. The modification of TiO₂ in order to achieve desired performance parameters is discussed in terms of the electronic structure, concentration of charge carriers and segregation-induced surface properties, which are critical to the ECE. Challenges to the development of a bi-photoelectrode cell, equipped with both n-type and p-type TiO₂, forming photoanode and photocathode, respectively, are discussed. The research strategies and pressing issues related to the optimization of key functional properties necessary for the commercialization of solar-hydrogen are outlined. It is shown that defect chemistry is the most appropriate framework for tailoring the functional properties of TiO₂-based oxide systems in order to obtain high-performance photoelectrodes. The present work provides an overview of the research progress on solar-hydrogen.     

Focal-length measurement by multiple-beam shearing interferometry

The application of multiple-beam shearing interferometry to lens focal-length measurement is described. A coated shearing plate interferometer was used in transmission to produce sharp multiple-beam fringes that rotate as the collimation of the incoming wave front from the lens under test changes. The test lens was used to collimate light from a point source that was translated longitudinally, and the focal length was determined from the rate of rotation of the fringes as the source moved. This method is simple, accurate, and lends itself to automatic determination of focal length.     

Straightness measurements by use of a reflection confocal optical system

Straightness measurement is a very important technique in the field of mechanical engineering. A particular application for straightness measurement is high-accuracy machining on a diamond-turning lathe. We propose a novel, to our knowledge, optical method for measuring the straightness of motion, and its mathematical analysis is outlined. The technique is based on measurement of the lateral displacement of point images by use of reflection confocal optical systems. The advantages of this method are that (i) the lateral displacements in the direction of the two axes perpendicular to the optical axis can be measured, (ii) the rotation angles around all three axes can be measured, and (iii) reflection optical systems are more compact in length than are transmission optical systems.