Soot volume fraction from extinction in JP-8 and heptane pool fires

Journal ArticleTotal extinction measurements from a multiple beam experiment using a 10mW laser diode are presented and compared to calculate soot volume fraction in heavily sooting pool fires from a 150 mm diameter pan of Jet Propulsion fuel 8 (JP-8) and heptane. Trends in attenuation are critiqued for the two fuels, and estimates of the axi-symmetrical distribution of soot are established

Soot volume fraction from extinction in JP-8 and heptane pool fires

Journal ArticleTotal extinction measurements from a multiple beam experiment using a 10mW laser diode are presented and compared to calculate soot volume fraction in heavily sooting pool fires from a 150 mm diameter pan of Jet Propulsion fuel 8 (JP-8) and heptane. Trends in attenuation are critiqued for the two fuels, and estimates of the axi-symmetrical distribution of soot are established

A multi-site method to capture turnover in rare to common interactions in bipartite species networks

1. Ecological network structure is maintained by a generalist core of common species. However, rare species contribute substantially to both the species and functional diversity of networks. Capturing changes in species composition and interactions, measured as turnover, is central to understanding the contribution of rare and common species and their interactions. Due to a large contribution of rare interactions, the pairwise metrics used to quantify interaction turnover are, however, sensitive to compositional change in the interactions of, often rare, peripheral specialists rather than common generalists in the network. 2. Here we expand on pairwise interaction turnover using a multi-site metric that enables quantifying turnover in rare to common interactions (in terms of occurrence of interactions). The metric further separates this turnover into interaction turnover due to species turnover and interaction rewiring. 3. We demonstrate the application and value of this method using a host–parasitoid system sampled along gradients of environmental modification. 4. In the study system, both the type and amount of habitat needed to maintain interaction composition depended on the properties of the interactions considered, that is, from rare to common. The analyses further revealed the potential of host switching to prevent or delay species loss, and thereby buffer the system from perturbation. 5. Multi-site interaction turnover provides a comprehensive measure of network change that can, for example, detect ecological thresholds to habitat loss for rare to common interactions. Accurate description of turnover in common, in addition to rare, species and their interactions is particularly relevant for understanding how network structure and function can be maintained

Reasoning about Communicating Agents in the Semantic Web

Abstract. In this article we interpret the Semantic Web and Web Service issues in the framework of multi-agent interoperating systems. We will advocate the application of results achieved in the research area of reasoning about actions and change by showing scenarios and techniques that could be applied.

Design and modeling of cylindrical and falt-wound lithium-ion cells for the PNGV application.

In this study, 10-Ah cylindrical and flat-wound cells were designed and studied for use in batteries for the Partnership for a New Generation of Vehicles (PNGV). A low-cost current collection system was devised that results in a low resistance. Heat rejection from flat cells is much better than that from cylindrical cells and is an important safety factor. Very compact, powerful batteries of about 1.5 kW/L can be designed with wound lithium-ion cells

Equation of state and transport processes in self--similar spheres

We study the effect of transport processes (diffusion and free--streaming) on a collapsing spherically symmetric distribution of matter in a self--similar space--time. A very simple solution shows interesting features when it is matched with the Vaidya exterior solution. In the mixed case (diffusion and free--streaming), we find a barotropic equation of state in the stationary regime. In the diffusion approximation the gravitational potential at the surface is always constant; if we perturb the stationary state, the system is very stable, recovering the barotropic equation of state as time progresses. In the free--streaming case the self--similar evolution is stationary but with a non--barotropic equation of state.Comment: 9 pages, 2 figure

Kinematic Self-Similarity

Self-similarity in general relativity is briefly reviewed and the differences between self-similarity of the first kind and generalized self-similarity are discussed. The covariant notion of a kinematic self-similarity in the context of relativistic fluid mechanics is defined. Various mathematical and physical properties of spacetimes admitting a kinematic self-similarity are discussed. The governing equations for perfect fluid cosmological models are introduced and a set of integrability conditions for the existence of a proper kinematic self-similarity in these models is derived. Exact solutions of the irrotational perfect fluid Einstein field equations admitting a kinematic self-similarity are then sought in a number of special cases, and it is found that; (1) in the geodesic case the 3-spaces orthogonal to the fluid velocity vector are necessarily Ricci-flat and (ii) in the further specialisation to dust the differential equation governing the expansion can be completely integrated and the asymptotic properties of these solutions can be determined, (iii) the solutions in the case of zero-expansion consist of a class of shear-free and static models and a class of stiff perfect fluid (and non-static) models, and (iv) solutions in which the kinematic self-similar vector is parallel to the fluid velocity vector are necessarily Friedmann-Robertson-Walker (FRW) models.Comment: 29 pages, AmsTe

Gravitomagnetism and Relative Observer Clock Effects

The gravitomagnetic clock effect and the Sagnac effect for circularly rotating orbits in stationary axisymmetric spacetimes are studied from a relative observer point of view, clarifying their relationships and the roles played by special observer families. In particular Semer\'ak's recent characterization of extremely accelerated observers in terms of the two-clock clock effect is shown to be complemented by a similarly special property of the single-clock clock effect.Comment: 19 pages, LaTeX, IOP macros with package epsf and 1 eps figure, to appear in Classical and Quantum Gravity, slight revisio

The lower mass function of the young open cluster Blanco 1: from 30 Mjup to 3 Mo

We performed a deep wide field optical survey of the young (~100-150 Myr) open cluster Blanco1 to study its low mass population well down into the brown dwarf regime and estimate its mass function over the whole cluster mass range.The survey covers 2.3 square degrees in the I and z-bands down to I ~ z ~ 24 with the CFH12K camera. Considering two different cluster ages (100 and 150 Myr), we selected cluster member candidates on the basis of their location in the (I,I-z) CMD relative to the isochrones, and estimated the contamination by foreground late-type field dwarfs using statistical arguments, infrared photometry and low-resolution optical spectroscopy. We find that our survey should contain about 57% of the cluster members in the 0.03-0.6 Mo mass range, including 30-40 brown dwarfs. The candidate's radial distribution presents evidence that mass segregation has already occured in the cluster. We took it into account to estimate the cluster mass function across the stellar/substellar boundary. We find that, between 0.03Mo and 0.6Mo, the cluster mass distribution does not depend much on its exact age, and is well represented by a single power-law, with an index alpha=0.69 +/- 0.15. Over the whole mass domain, from 0.03Mo to 3Mo, the mass function is better fitted by a log-normal function with m0=0.36 +/- 0.07Mo and sigma=0.58 +/- 0.06. Comparison between the Blanco1 mass function, other young open clusters' MF, and the galactic disc MF suggests that the IMF, from the substellar domain to the higher mass part, does not depend much on initial conditions. We discuss the implications of this result on theories developed to date to explain the origin of the mass distribution.Comment: 18 pages, 15 figures and 5 tables accepted in A&