A MEMS Singlet Oxygen Generator—Part II: Experimental Exploration of the Performance Space

This paper reports the quantitative experimental exploration of the performance space of a microfabricated singlet oxygen generator (muSOG). SOGs are multiphase reactors that mix H₂O₂, KOH, and Cl₂ to produce singlet delta oxygen, or O₂ (a). A scaled-down SOG is being developed as the pump source for a microfabricated chemical oxygen-iodine laser system because scaling down a SOG yields improved performance compared to the macroscaled versions. The performance of the muSOG was characterized using O₂ (a) yield, chlorine utilization, power in the flow, molar flow rate per unit of reactor volume, and steady-state operation as metrics. The performance of the muSOG is measured through a series of optical diagnostics and mass spectrometry. The test rig, which enables the monitoring of temperatures, pressures, and the molar flow rate of O₂ (a), is described in detail. Infrared spectra and mass spectrometry confirm the steady-state operation of the device. Experimental results reveal O₂ (a) concentrations in excess of 10¹⁷ cm^-3, O₂ (a) yield at the chip outlet approaching 80%, and molar flow rates of 02(a) per unit of reactor volume exceeding 600 times 10^-4 mol/L/s.     

Synthesis of cobalt-doped barium cerate-zirconate and its evaluation for hydrogen production and electrochemical characterization

Cobalt-doped barium cerate-zirconate was synthesized using an oxalate co-precipitation route. The material was characterized using X-ray diffraction, transmission and scanning transmission electron microscopy coupled with X-ray energy dispersive spectroscopy. Results indicated that homogeneous cubic phase material was obtained at very high heat-treatment temperatures. Catalytic activity of the material toward CH₃OH partial-oxidation was tested at different temperatures and O₂:CH₃OH ratios. High hydrogen yields were obtained indicating that the material was a suitable catalyst for hydrogen generation. Impedance spectroscopy tests were conducted at different conditions to understand conduction processes occurring in the material. Results suggested mixed protonic–electronic conductivity in the presence of hydrogen. Thus, material is a potential candidate for the bi-functional role of electro-ceramic catalyst for simultaneous hydrogen generation and purification.     

Highlights of Drought Policy and Related Science in Australia and the U.S.A.

Abstract

Patterns of water supply and use in Australia and the U.S.A. differ in many ways. This results in different perceptions concerning the nature of drought and policy approaches to its management. This paper discusses the differences and similarities and explores lessons that policy makers in both countries can learn from one another. A key difference between the two countries is that whereas drought is perceived in Australia essentially in terms of its impact on agriculture, in the U.S. both perceptions and policy are also heavily influenced by the impact of drought on urban communities. This has led to different policy emphases. In 1992 Australia established its National Drought Policy; the U.S. is presently considering the adoption of a national drought policy. These policies highlight drought being accepted as part of natural climate variability, rather than as a natural disaster. They also emphasize the protection of the natural resource base.     

Technology Engineering: The Concurrent Development of Space Transportation Systems and Technology

Abstract:

This article develops and presents a technology engineering framework for the selection, development, and insertion of space transportation technologies concurrent with the systems engineering of the space transportation system(s) in which the technology will eventually be employed. The technology engineering framework developed and presented in this article draws on existing systems engineering processes, tools, and methods; takes into account the differences between systems engineering and technology engineering; and accounts for the high degree of interaction required between the concurrent technology and system development programs. The components of this technology engineering framework are discussed, and the major steps in the technology engineering process are outlined. An investigation is also conducted into facilitating the implementation of key portions of the framework using a state-of-the-art relational computer database referred to as the Reusable Launch Vehicle (RLV) Technology Database (RTDB). This database is demonstrated to provide an invaluable tool to collect, manipulate, analyze, document, and disseminate technology-related information, including previous research results, key technical parameters and characteristics, technology readiness levels, relationships to other technologies, costs, and potential barriers and risks.     

Theoretical investigation of a water‐gas‐shift catalytic membrane for diesel reformate purification

The novel application of a catalytic water‐gas‐shift membrane reactor for selective removal of CO from H₂‐rich reformate mixtures for achieving gas purification solely via manipulation of reaction and diffusion phenomena, assuming Knudsen diffusion regime and the absence of hydrogen permselective materials, is described. An isothermal, two‐dimensional model is developed to describe a tube‐and‐shell membrane reactor supplied with a typical reformate mixture (9% CO, 3% CO₂, 28% H₂, and 15% H₂O) to the retentate volume and steam supplied to the permeate volume such that the overall H₂O:CO ratio within the system is 9:1. Simulations indicate that apparent CO:H₂ selectivities of 90:1 to >200:1 at H₂ recoveries of 20% to upwards of 40% may be achieved through appropriate design of the catalytic membrane and selection of operating conditions. Under these conditions, simulations predict an apparent hydrogen permeability of 2.3 × 10^?10 mol m^?1 Pa, which compares favorably against that of competing hydrogen‐permselective membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4334–4345, 2013     

Why don't people weatherize their homes? An ethnographic solution

The authors' analysis of energy decision-making in 60 households in Santa Cruz County. California, reveals a seeming anomaly in consumers' energy decision strategies. Few households have taken advantage of the low cost and high savings potential of weather-stripping and caulking, though many have spent thousands of dollars on other energy-conserving investments that are expensive and have long payback periods. An ethnographic model, which incorporates sociocultural and psychological goals, makes this perplexing pattern comprehensible. We conclude that a model of strict economic rationality is inadequate in explaining energy-conservation behavior. The notion of rationality must be expanded to incorporate noneconomic goals. The failure to do so may have serious consequences for the marketing of energy-conservation products and programs.     

Multidimensional modeling of a microfibrous entrapped cobalt catalyst Fischer‐Tropsch reactor bed

Thermal management of highly exothermic Fischer‐Tropsch synthesis (FTS) has been a challenging bottleneck limiting the radial dimension of the packed‐bed (PB) reactor tube to 1.5 in. ID. A computational demonstration of a novel microfibrous entrapped cobalt catalyst (MFECC) in mitigating hot spot formation has been evaluated. Specifically, a two‐dimensional (2‐D) model was developed in COMSOL^®, validated with experimental data and subsequently employed to demonstrate scale‐up of the FTS bed from 0.59 to 4 in. ID. Significant hot spot of 102.39 K in PB was reduced to 9.4 K in MFECC bed under gas phase at 528.15 K and 2 MPa. Improvement in heat transfer within the MFECC bed facilitates higher productivities at low space velocities (≥1000 h^?1) corresponding to high CO conversion (≥90%). Additionally, the MFECC reactor provides an eightfold increase in the reactor ID at hot spots ≤ 30 K with CO% conversions ≥ 90%. This model was developed for a typical FTS cobalt‐based catalyst where CO₂ production is negligible. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1723–1731, 2018     

The conditioning of comfort

This commentary considers how the insights from the Building Research & Information 2008 special issue on ‘Comfort in a Lower Carbon Society’ impact upon our understanding of the nature of comfort demand; their importance and relevance to the theory and policies of building comfort; and the commentary draws upon changing comfort practices in other parts of the world. One of the most important contributions of the collection is to situate comfort historically and technically, but also to give attention to the social consequences of air-conditioning. Air-conditioning has brought with it an encapsulation of home within house and has led to significant changes in the social geography of home and neighbourhood. The social, material and discursive facets of air-conditioning are globalizing at a rapid pace, fostered by the spread of inappropriate building practices, faith in modern scientific solutions to achieving comfort, and new ideas about the human body. Local knowledge about climate and comfort is waning in many parts of the world, and cooling comfort increasingly relegated to technical experts. This collection makes an important contribution to understanding how air-conditioning has become pervasive and suggests new lines of thinking in the crucial effort to move towards a less carbon-intensive comfort regime.

Ce commentaire explique comment les informations contenues dans le récent numéro spécial de Building Research & Information consacré au confort dans une société sobre en carbone ont une influence sur la nature de la demande de confort, sur son importance et sur sa pertinence par rapport à la théorie et aux politiques de confort; il s'appuie également sur des pratiques de confort qui évoluent dans d'autres parties du monde. L'une des contributions les plus importantes de cette collection est de resituer le confort sur le plan historique et technique mais aussi de prêter attention aux conséquences sociales de la climatisation. Avec la climatisation, le foyer se trouve encapsulé dans la maison, ce qui a conduit à des changements significatifs de la géographie sociale du foyer et du voisinage. Les aspects sociaux, matériels et discursifs de la climatisation se mondialisent à un rythme rapide, favorisés par des pratiques de construction inappropriées qui se répandent, par la foi dans des solutions scientifiques modernes pour obtenir le confort et de nouvelles idées sur le corps humain. Les connaissances locales sur le climat et le confort s'estompent dans de nombreuses parties du monde et le confort par le refroidissement est de plus en plus remis dans les mains d'experts techniques. Cette collection est une contribution importante qui explique comment la climatisation est envahissante et suggère de nouveaux axes de réflexion concernant l'effort à faire pour évoluer vers un état de confort exigeant moins de carbone.

Mots clés: comportement adaptatif, agence, climatisation, confort, consumérisme, demande d'énergie, satisfaction des occupants, géographie sociale, consommation durable