AMP: A Science-driven Web-based Application for the TeraGrid

The Asteroseismic Modeling Portal (AMP) provides a web-based interface for astronomers to run and view simulations that derive the properties of Sun-like stars from observations of their pulsation frequencies. In this paper, we describe the architecture and implementation of AMP, highlighting the lightweight design principles and tools used to produce a functional fully-custom web-based science application in less than a year. Targeted as a TeraGrid science gateway, AMP's architecture and implementation are intended to simplify its orchestration of TeraGrid computational resources. AMP's web-based interface was developed as a traditional standalone database-backed web application using the Python-based Django web development framework, allowing us to leverage the Django framework's capabilities while cleanly separating the user interface development from the grid interface development. We have found this combination of tools flexible and effective for rapid gateway development and deployment.Comment: 7 pages, 2 figures, in Proceedings of the 5th Grid Computing Environments Worksho

Chemical looping dry reforming of methane using mixed oxides of iron and cerium: Operation window

A series of the mixed oxides of iron and cerium, with an iron(III) oxide content ranging from 0 wt% to 100 wt% were tested as oxygen carriers in the chemical looping dry reforming of methane (CL-DRM). The reactivity during the CL-DRM significantly increased when iron and cerium are forming a mixed oxide. By careful control of the Fe2O3/CeO2 mass ratio, initial oxidation state and reaction time the activity of the oxygen carrier material can be adjusted so as to substantially favour oxidation of methane to syngas and discourage both total oxidation of methane and carbon deposition via decomposition of methane

Combining exsolution and infiltration for redox, low temperature CH4 conversion to syngas

Exsolution of surface and bulk nanoparticles in perovskites has been recently employed in chemical looping methane partial oxidation because of the emergent materials’ properties such as oxygen capacity, redox stability, durability, coke resistance and enhanced activity. Here we attempt to further lower the temperature of methane conversion by complementing exsolution with infiltration. We prepare an endo/exo-particle system using exsolution and infiltrate it with minimal amount of Rh (0.1 wt%) in order to functionalize the surface and induce low temperature activity. We achieve a temperature decrease by almost 220 °C and an increase of the activity up to 40%. We also show that the initial microstructure of the perovskite plays a key role in controlling nanoparticle anchorage and carbon deposition. Our results demonstrate that microstructure tuning and surface functionalization are important aspects to consider when designing materials for redox cycling applications

Effects of separation layer thickness on oxygen permeation and mechanical strength of DL-HFMR-ScSZ

It has been demonstrated in our previous studies that in order for greater methane conversion and less coke-formation, a higher oxygen permeation rate through the outer oxygen separation layer of a functional dual-layer ceramic hollow fibre membrane is needed. Besides new membrane materials with higher oxygen permeability, another way of improving oxygen permeation is to reduce the separation layer thickness, although this strategy is limited by the characteristic thickness, L c, where bulk diffusion and surface oxygen exchange are both important. As a result, a series of La 0.80Sr 0.20MnO 3-δ (LSM)-Scandia(10%)-Stabilized-Zirconia (ScSZ)/ScSZ-NiO functional dual-layer hollow fibres (DL-HF) with an outer oxygen separation layer thickness between approximately 8.0 and 72.4μm were fabricated in this study, by using the single-step co-extrusion and co-sintering process. The effects of separation layer thickness on oxygen permeation and mechanical strength were investigated. The oxygen permeation of the LSM-ScSZ separation layer is more likely to be controlled by surface exchange at higher temperatures, and changes to mixed control by both bulk diffusion and surface exchange at lower temperatures. A thicker separation layer also results in a thinner catalytic substrate layer, and subsequently decreases the mechanical strength of the dual-layer hollow fibre membrane

Towards efficient use of noble metals : via exsolution exemplified for CO oxidation

Many catalysts and in particular automotive exhaust catalysts usually consist of noble metal nanoparticles dispersed on metal oxide supports. While highly active, such catalysts are expensive and prone to deactivation by sintering and thus alternative methods for their production are being sought to ensure more efficient use of noble metals. Exsolution has been shown to be an approach to produce confined nanoparticles, which in turn are more stable against agglomeration, and, at the same time strained, displaying enhanced activity. While exsolution has been extensively investigated for relatively high metal loadings, it has yet to be explored for dilute loadings which is expected to be more challenging but more suitable for application of noble metals. Here we explore the substitution of Rh into an A-site deficient perovskite titante aiming to investigate the possibility of exsolving from dilute amounts of noble metal substituted perovskites. We show that this is possible and in spite of certain limitations, they still compete well against conventionally prepared samples with higher apparent surface loading when applied for CO oxidation

Exsolved nickel nanoparticles acting as oxygen storage reservoirs and active sites for redox CH4 conversion

The growing demand for H2 and syngas requires the development of new, more efficient processes and materials for their production, especially from CH4 that is a widely available resource. One process that has recently received increased attention is chemical looping CH4 partial oxidation, which, however, poses stringent requirements on material design, including fast oxygen exchange and high storage capacity, high reactivity toward CH4 activation, and resistance to carbon deposition, often only met by composite materials. Here we design a catalytically active material for this process, on the basis of exsolution from a porous titanate. The exsolved Ni particles act as both oxygen storage centers and as active sites for CH4 conversion under redox conditions. We control the extent of exsolution, particle size, and population of Ni particles in order to tune the oxygen capacity, reactivity, and stability of the system and, at the same time, obtain insights into parameters affecting and controlling exsolution

The effects of sulphur poisoning on the microstructure, composition and oxygen transport properties of perovskite membranes coated with nanoscale alumina layers

Perovskite oxides displaying mixed ionic and electronic conductivity have attracted a lot of interest for application in oxygen separation membranes. Such membranes could be used for a range of processes, including the conversion of natural gas to hydrogen or syngas. A major limitation of these materials is their tendency to segregate into simpler oxides under operating conditions, reacting with sulphur-based species often found in natural gas and leading to irreversible membrane degradation over time. Here we aim to delay or prevent this process by coating La0.6Sr0.4Co0.2Fe0.8O3-δ membranes with Alumina (Al2O3) layers of 1–100 nm thickness by using atomic layer deposition. We show that coatings of about 30 nm have negligible negative effect on O2 transport flux across the membrane and display good flux recovery when H2S is removed from the stream. Coatings thinner than this critical value provide little protection against irreversible poisoning while thicker coatings dramatically decrease overall O2 permeation fluxes. We also show that the irreversible sulphur poisoning under O2 permeation conditions is linked to microstructural and composition changes at the membrane surface caused predominantly by the formation of SrSO4 particles at the perovskite grain boundaries

Cosmic cookery : making a stereoscopic 3D animated movie.

This paper describes our experience making a short stereoscopic movie visualizing the development of structure in the universe during the 13.7 billion years from the Big Bang to the present day. Aimed at a general audience for the Royal Society's 2005 Summer Science Exhibition, the movie illustrates how the latest cosmological theories based on dark matter and dark energy are capable of producing structures as complex as spiral galaxies and allows the viewer to directly compare observations from the real universe with theoretical results. 3D is an inherent feature of the cosmology data sets and stereoscopic visualization provides a natural way to present the images to the viewer, in addition to allowing researchers to visualize these vast, complex data sets. The presentation of the movie used passive, linearly polarized projection onto a 2m wide screen but it was also required to playback on a Sharp RD3D display and in anaglyph projection at venues without dedicated stereoscopic display equipment. Additionally lenticular prints were made from key images in the movie. We discuss the following technical challenges during the stereoscopic production process; 1) Controlling the depth presentation, 2) Editing the stereoscopic sequences, 3) Generating compressed movies in display speci¯c formats. We conclude that the generation of high quality stereoscopic movie content using desktop tools and equipment is feasible. This does require careful quality control and manual intervention but we believe these overheads are worthwhile when presenting inherently 3D data as the result is signi¯cantly increased impact and better understanding of complex 3D scenes