Catalytic dehydrogenation of ammonia borane in non-aqueous medium

Dehydrogenation of Ammonia Borane (NH₃BH₃, AB) catalyzed by transition metal heterogeneous catalysts was carried out in non-aqueous solution at temperatures below the standard polymer electrolyte membrane (PEM) fuel cell operating conditions. The introduction of a catalytic amount (∼2 mol%) of platinum to a solution of AB in 2-methoxyethyl ether (0.02–0.33 M) resulted in a rapid evolution of H₂ gas at room temperature. At 70 °C, the rate of platinum catalyzed hydrogen release from AB was the dehydrogenation rate which was 0.04 g s⁻¹ H₂ kW⁻¹.     

Interactive machinability analysis of free-form surfaces using multiple-view image space techniques on the GPU

In this paper we present a set of graphics hardware accelerated algorithms to interactively evaluate the machinability of complex free-form surfaces. These algorithms work in image space and easily interface with all common formats available on CAD systems. The running time of these algorithms is independent of the complexity of the surface to be analyzed and depends only on the size of the projected image of the surface and the largest available tool head. Interactive speed is achieved through clever use of data-parallel techniques that map nicely onto the programming model of modern programmable graphics processing units. We demonstrate a method for pre-calculating and storing the machinability of a surface within a texture to further reduce rendering costs. The algorithms are implemented and tested on a complex set of parts and their performance has been analyzed.     

Parallelizing the Cellular Potts Model on graphics processing units

The Cellular Potts Model (CPM) is a lattice based modeling technique used for simulating cellular structures in computational biology. The computational complexity of the model means that current serial implementations restrict the size of simulation to a level well below biological relevance. Parallelization on computing clusters enables scaling the size of the simulation but marginally addresses computational speed due to the limited memory bandwidth between nodes. In this paper we present new data-parallel algorithms and data structures for simulating the Cellular Potts Model on graphics processing units. Our implementations handle most terms in the Hamiltonian, including cell–cell adhesion constraint, cell volume constraint, cell surface area constraint, and cell haptotaxis. We use fine level checkerboards with lock mechanisms using atomic operations to enable consistent updates while maintaining a high level of parallelism. A new data-parallel memory allocation algorithm has been developed to handle cell division. Tests show that our implementation enables simulations of >¹⁰⁶ cells with lattice sizes of up to 256³ on a single graphics card. Benchmarks show that our implementation runs ∼80× faster than serial implementations, and ∼5× faster than previous parallel implementations on computing clusters consisting of 25 nodes. The wide availability and economy of graphics cards mean that our techniques will enable simulation of realistically sized models at a fraction of the time and cost of previous implementations and are expected to greatly broaden the scope of CPM applications.     

Preparation of bipolar zeolite exchangers by gas-phase modification using NOx

Zeolites with varying Si/Al ratio, were synthesized using silica and alumina powder and by matching the XRD patterns with those given in the JCPDS files their chemical formula and crystal structure were determined. In order to make these into bipolar zeolite exchangers, they were modified (called Z₂ zeolite) using a gas-phase reaction with NO_x at 225°C and the formation of the oxynitride groups was confirmed with FTIR, ESCA and the elemental analysis. The XRD patterns of the modified zeolites were found to have changed and did not match with any of the patterns given in the JCPDS files. For these modified zeolites, we have determined the crystal structures and these were found to change from cubic for the unmodified to orthorhombic for the modified zeolites with Si/Al ?1.2 and to the tetragonal for Si/Al >1.2.The oxynitride covalent bond in Z₂ zeolites could be reduced by reacting with hydrazine hydrate to give bipolar zeolite exchangers (denoted as Z₃ zeolite) containing imine groups, thus making the zeolite bipolar in nature. The cation exchange capacities were determined and found to have the same order of magnitude as reported in the literature. The elemental analysis of the modified zeolites was carried out and the experimentally determined nitrogen value of gives 0.9-1.2 oxynitride group per formula unit of the material. The experimentally determined anion exchange capacity of the Z₃ zeolites ( for sample A1) suggests that for this value of exchange capacity, about two out of three formula units have an imine group. The difference between these two independent experiments suggests that not all imine groups participate in the anion exchange phenomena due to their non-availability. We found that Z₃ zeolite responds to organic reactions, and can be reacted with dichloroethane and subsequently quarternized with trimethylamine. Their anion exchange capacity is found to increase significantly.     

Availability of a two-unit standby system with switchover time and proper initialization of connect switching

A 2-unit standby redundant system with connect switching (CS) is considered. The standby unit takes random switchover-time when the operative unit fails and CS is properly initialized in a random time after each repair. Failure-time distributions of units are exponential whereas all other distributions are arbitrary. In this note we employ the method of semi-Markov process to obtain steady-state availability of the system.     

Preparation and characterization of PbS nanoclusters made by using a powder method on ionomers

By using a powder method, a new method for producing semiconductor/polymer nanocomposites, lead sulfide (PbS) nanoparticles were prepared and dispersed in either poly(methylmethacrylate-co-methacrylic acid) or poly(styrene-co-styrenesulfonic acid). The size of the nanoclusters was less than 2 nm, and the size distribution was rather sharp, determined by UV-vis absorption spectroscopy. The absorption spectra of the PbS-containing sheets showed a blue shift and the absorption edges were steep, reflecting the formation of nano-sized PbS clusters. The spectra also exhibited an absorption maximum, which is an indication of a narrow particle size distribution. The glass transition temperature (T_g) of the PbS-containing nanocomposites was higher than that of the corresponding ionomer. The effect of heat treatment on the aggregation of PbS is also discussed. The dissolution of powder samples, followed by neutralization of acidic groups, led to reduction of particle sizes, suggesting the usefulness of ionic groups for stabilizing PbS nanoclusters.     

Improving UAV imaging quality by optical sensor fusion: an initial study

The most frequent application of unmanned aerial vehicle (UAVs) is to collect optical colour images from an area of interest. Thus, high spatial resolution colour images with high amount of signal to noise ratio (SNR) are of great importance in UAV applications. Currently, most UAVs use single sensor colour filter array (CFA) cameras for image collection, within which the Bayer-pattern sensors are the most frequently used ones. Due to the limitations of the CFAs, the quality (in terms of spatial resolution, SNR, and sharpness) of UAV colour images is not optimal. In this article, a sensor fusion solution is proposed to improve the quality of UAV imaging. In the proposed solution, a high-resolution colour (HRC) Bayer-pattern sensor is replaced by a dual camera set containing a panchromatic (Pan) sensor, with the same pixel size and a Bayer-pattern colour (or a four-band multi-spectral) sensor with larger pixel size; the resulting images of the dual camera set are then fused. The enlarged pixel size of the colour sensor provides a higher SNR for the cost of lower spatial resolution. However, the accompanied Pan sensor provides single band images with high SNR and high spatial resolution. Fusing the images of the dual camera set generates colour (or MS) images with high spatial resolution, SNR, and sharpness compensating for the major problems of the Bayer-pattern filters.

This replacement solution is initially tested in a laboratory experiment. The results of quality assessments show that the SNR is increased by 2–3 times, the sharpness is improved by around 2 times, and the spatial resolution is increased up to the level of the pan images, while the colour errors remained almost as low as the original colour images. In addition, image classification capability of the images is examined using two methods: Support Vector Machine (SVM) and Maximum Likelihood (ML). The results of image classification also confirmed around 20–40% increase in accuracy. Therefore, the proposed sensor fusion can be a good alternative for UAV colour sensors.