290 research outputs found
Investigation of a lattice Boltzmann model with a variable speed of sound
A lattice Boltzmann model is considered in which the speed of sound can be
varied independently of the other parameters. The range over which the speed of
sound can be varied is investigated and good agreement is found between
simulations and theory. The onset of nonlinear effects due to variations in the
speed of sound is also investigated and good agreement is again found with
theory. It is also shown that the fluid viscosity is not altered by changing
the speed of sound
Different Approaches to Managerial Support for Flexible Working: Implications for Public Sector Employee Well-Being
Improving well-being is an important human resource management issue within public sector organizations as it is linked with improved employee and organizational outcomes. A key antecedent to employee well-being is workālife balance, which can be supported or impeded by flexible working. The extent to which flexible working supports workālife balance and, ultimately, well-being depends on how flexible working is implemented, where managers play a central role. Managers can enable workālife balance by providing employees with work-family-specific support, which incorporates a range of behaviors, including facilitating access to flexible working. However, research to date says little about how and why managers engage in these behaviors and whether this differs within the same organizational context. This article addresses this gap, presenting four approaches to managerial support for flexible working: unconditional support, performance contingent support, no support, and support based upon the approval of others (transfer responsibility). It explores the reasons for each approach through the lens of Conservation of Resources (COR) theory. It suggests that different approaches create the potential for employee well-being to vary considerably within the same organizational and team context. These findings inform how to support and manage flexible working arrangements in ways that optimize well-being in the public sector
Drake Equation for the Multiverse: From the String Landscape to Complex Life
It is argued that selection criteria usually referred to as "anthropic
conditions" for the existence of intelligent (typical) observers widely adopted
in cosmology amount only to preconditions for primitive life. The existence of
life does not imply in the existence of intelligent life. On the contrary, the
transition from single-celled to complex, multi-cellular organisms is far from
trivial, requiring stringent additional conditions on planetary platforms. An
attempt is made to disentangle the necessary steps leading from a selection of
universes out of a hypothetical multiverse to the existence of life and of
complex life. It is suggested that what is currently called the "anthropic
principle" should instead be named the "prebiotic principle."Comment: 6 pages, RevTeX, in press, Int. J. Mod. Phys.
Organisational structures and processes for health and well-being: insights from work integration social enterprise
Background: Previous research on employee well-being for those who have experienced social and economic disadvantage and those with previous or existing mental health conditions has focused mainly on programmatic interventions. The purpose of this research was to examine how organisational structures and processes (such as policies and culture) influence well-being of employees from these types of backgrounds. Methods: A case study ethnographic approach which included in-depth qualitative analysis of 93 semi-structured interviews of employees, staff, and managers, together with participant observation of four social enterprises employing young people. Results: The data revealed that young people were provided a combination of training, varied work tasks, psychosocial support, and encouragement to cultivate relationships among peers and management staff. This was enabled through the following elements: structure and space; funding, finance and industry orientation; organisational culture; policy and process; and fostering local service networks. The findings further illustrate how organisational structures at these workplaces promoted an inclusive workplace environment in which participants self-reported a decrease in anxiety and depression, increased self-esteem, increased self-confidence and increased physical activity. Conclusions: Replicating these types of organisational structures, processes, and culture requires consideration of complex systems perspectives on implementation fidelity which has implications for policy, practice and future research
Lattice-Boltzmann and finite-difference simulations for the permeability for three-dimensional porous media
Numerical micropermeametry is performed on three dimensional porous samples
having a linear size of approximately 3 mm and a resolution of 7.5 m. One
of the samples is a microtomographic image of Fontainebleau sandstone. Two of
the samples are stochastic reconstructions with the same porosity, specific
surface area, and two-point correlation function as the Fontainebleau sample.
The fourth sample is a physical model which mimics the processes of
sedimentation, compaction and diagenesis of Fontainebleau sandstone. The
permeabilities of these samples are determined by numerically solving at low
Reynolds numbers the appropriate Stokes equations in the pore spaces of the
samples. The physical diagenesis model appears to reproduce the permeability of
the real sandstone sample quite accurately, while the permeabilities of the
stochastic reconstructions deviate from the latter by at least an order of
magnitude. This finding confirms earlier qualitative predictions based on local
porosity theory. Two numerical algorithms were used in these simulations. One
is based on the lattice-Boltzmann method, and the other on conventional
finite-difference techniques. The accuracy of these two methods is discussed
and compared, also with experiment.Comment: to appear in: Phys.Rev.E (2002), 32 pages, Latex, 1 Figur
Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere
Author Posting. Ā© National Academy of Sciences of the USA, 2007. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 14260-14265, doi:10.1073/pnas.0610903104.Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed
by thermal stress, are present in solvent extracts of 2,707-2,685 million year old (Ma)
metasedimentary rocks from Timmins, Ontario, Canada. These lipids appear in
conventional gas chromatograms as unresolved complex mixtures (UCMs) and include
cyclic and acyclic biphytanes, C36-C39 derivatives of the biphytanes, and C31-C35
extended hopanes. Biphytane and extended hopanes are also found in high pressure
catalytic hydrogenation (HPCH) products released from solvent-extracted sediments,indicating that archaea and bacteria were present in Late Archean sedimentary
environments. Post-depositional, hydrothermal gold mineralization and graphite
precipitation occurred prior to metamorphism (~2,665 Ma). Late Archean metamorphism
significantly reduced the kerogenās adsorptive capacity and severely restricted sediment
porosity, limiting the potential for post-Archean additions of organic matter to the
samples. Argillites exposed to hydrothermal gold mineralization have disproportionately
high concentrations of extractable archaeal and bacterial lipids relative to what is
releasable from their respective HPCH product and what is observed for argillites
deposited away from these hydrothermal settings. The addition of these lipids to the
sediments likely results from a Late Archean subsurface hydrothermal biosphere of
archaea and bacteria.This project was supported by NASA Exobiology grant #NAG5-13446 to Fabien Kenig.
SEM analysis was supported by NSF grant EAR 0318769 to Juergen Schieber. GCĆGC
analysis was supported by NSF grant IIS-0430835 and the Seaver Foundation to
Christopher M. Reddy
Emission and economic performance assessment of a solid oxide fuel cell micro-combined heat and power system in a domestic building
Combined heat and power (CHP) is a promising technological configuration for reducing energy consumption and increasing energy security in the domestic built environment. Fuel cells, on account of their: high electrical efficiency, low emissions and useful heat output have been identified as a key technological option for improving both building energy efficiency and reducing emissions in domestic CHP applications. The work presented in this paper builds upon results currently reported in the literature of fuel cells operating in domestic building applications, with an emission and economic performance assessment of a real, commercially available SOFC mCHP system operating in a real building; under a UK context.
This paper aims to assess the emission and economic performance of a commercially available solid oxide fuel cell (SOFC) mCHP system, operating at The University of Nottingham's Creative Energy Homes. The performance assessment evaluates, over a one year period, the associated carbon (emission assessment) and operational costs (economic assessment) of the SOFC mCHP case compared to a ābase caseā of grid electricity and a highly efficient gas boiler.
Results from the annual assessment show that the SOFC mCHP system can generate annual emission reductions of up to 56% and cost reductions of 177% compared to the base case scenario. However support mechanisms such as; electrical export, feed in tariff and export tariff, are required in order to achieve this, the results are significantly less without. A net present value (NPV) analysis shows that the base case is still more profitable over a 15 year period, even though the SOFC mCHP system generates annual revenue; this is on account of the SOFC's high capital cost. In summary, grid interaction and incubator support is essential for significant annual emission and cost reductions compared to a grid electricity and gas boiler scenario. Currently capital cost is the greatest barrier to the economic viability of the system
A transient liquid-like phase in the displacement cascades of zircon, hafnon and thorite
The study of radiation effects in solids is important for the development of 'radiation-resistant' materials for fission-reactor applications'. The effects of heavy-ion irradiation in the isostructural orthosilicates zircon (ZrSiO4), hafnon (HfSiO4) and thorite (ThSiO4) are particularly important because these minerals are under active investigation for use as a waste form for plutonium-239 resulting from the dismantling of nuclear weapons(2-4). During ion irradiation, localized 'cascades' of displaced atoms can form as a result of ballistic collisions in the target material, and the temperature inside these regions may for a short time exceed the bulk melting temperature. Whether these cascades do indeed generate a localized liquid state(5-8) has, however, remained unclear. Here we investigate the irradiation-induced decomposition of zircon and hafnon, and find evidence for formation of a liquidlike state in the displacement cascades. Our results explain the frequent occurrence of ZrO2 in natural amorphous zircong(9-12) Moreover, we conclude that zircon-based nuclear waste forms should be maintained within strict temperature Limits, to avoid potentially detrimental irradiation-induced amorphization or phase decomposition of the zircon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62853/1/395056a0.pd
Characterization of xenotime from Datas (Brazil) as a potential reference material for in situ U-Pb geochronology
CITATION: Vasconcelos, A. D. et al. 2018. Characterization of xenotime from Datas (Brazil) as a potential reference material for in situ U-Pb geochronology. Geochemistry, Geophysics, Geosystems, 19:2262ā2282, doi:10.1029/2017GC007412.The original publication is available at https://agupubs.onlinelibrary.wiley.comThis study investigates five megacrysts of xenotime (XN01, XN02, XN03, XN04, and XN05) as potential reference materials (RMs) for UāPb geochronology. These crystals belong to a 300 g xenotime assortment, collected from alluvial deposits in SE Brazil. Electron microprobe and Laser AblationāInductively Coupled PlasmaāMass Spectrometry (LAāICPāMS) analyses show that the selected crystals are internally homogeneous for most rare earth element, (REE, except some light REE) but are relatively heterogeneous for U and Th. The xenotime REE patterns are consistent with an origin from hydrothermal quartz veins in the Datas area that cut greenschistāfacies metasediments and that locally contain other accessory phases such as rutile and monazite. Highāprecision UāPb Isotope DilutionāThermal Ionization Mass Spectrometry (IDāTIMS) analyses showed slight age heterogeneity for the XN01 crystal not observed in the XN02 sample. The two crystals have slightly different average 206Pb/238U ages of 513.4 Ā± 0.5 Ma (2 s) and 515.4 Ā± 0.2 Ma (2 s), respectively. In situ UāPb isotope data acquired via LAā(Q,SF,MC)āICPāMS are within the uncertainty of the IDāTIMS data, showing homogeneity at the 1% precision of the laser ablation (and probably ion microprobe) technique. UāPb LAā(MC, SF)āICPāMS analyses, using XN01 as a primary RM, reproduced the ages of other established RMs within less than 1% deviation. Other Datas crystals (XN03ā05) also display a reproducibility in Pb/U dates better than 1% on LAāICPāMS, making them good candidates for further testing by IDāTIMS.https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017GC007412Publisher's versio
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