Droplet migration: quantitative comparisons with experiment

An important practical feature of simulating droplet migration computationally, using the lubrication approach coupled to a disjoining pressure term, is the need to specify the thickness, H, of a thin energetically stable wetting layer, or precursor lm, over the entire substrate. The necessity that H be small in order to improve the accuracy of predicted droplet migration speeds, allied to the need for mesh resolution of the same order as H near wetting lines, increases the computational demands signicantly. To date no systematic investigation of these requirements on the quantitative agreement between prediction and experimental observation has been reported. Accordingly, this paper combines highly ecient Multigrid methods for solving the associated lubrication equations with a parallel computing framework, to explore the eect of H and mesh resolution. The solutions generated are compared with recent experimentally determined migration speeds for droplet ows down an inclined plane

Simple Wriggling is Hard unless You Are a Fat Hippo

We prove that it is NP-hard to decide whether two points in a polygonal domain with holes can be connected by a wire. This implies that finding any approximation to the shortest path for a long snake amidst polygonal obstacles is NP-hard. On the positive side, we show that snake's problem is "length-tractable": if the snake is "fat", i.e., its length/width ratio is small, the shortest path can be computed in polynomial time.Comment: A shorter version is to be presented at FUN 201

Membrane solitons in eight-dimensional hyper-Kaehler backgrounds

We derive the BPS equations satisfied by lump solitons in $(2+1)$-dimensional sigma models with toric 8-dimensional hyper-K\"ahler (${HK}_8$) target spaces and check they preserve 1/2 of the supersymmetry. We show how these solitons are realised in M theory as M2-branes wrapping holomorphic 2-cycles in the \bE^{1,2}\times {HK}_8 background. Using the $\kappa$-symmetry of a probe M2-brane in this background we determine the supersymmetry they preserve, and note that there is a discrepancy in the fraction of supersymmetry preserved by these solitons as viewed from the low energy effective sigma model description of the M2-brane dynamics or the full M theory. Toric ${HK}_8$ manifolds are dual to a Hanany-Witten setup of D3-branes suspended between 5-branes. In this picture the lumps correspond to vortices of the three dimensional ${\mathcal N}=3$ or ${\mathcal N}=4$ theory.Comment: 12+1 pages. LaTex. v2: Typos corrected and references adde

Managing Climatic Risks to Combat Land Degradation and Enhance Food security: Key Information Needs

This paper discusses the key information needs to reduce the negative impacts of weather variability and climate change on land degradation and food security, and identifies the opportunities and barriers between the information and services needed. It suggests that vulnerability assessments based on a livelihood concept that includes climate information and key socio-economic variables can overcome the narrow focus of common one-dimensional vulnerability studies. Both current and future climatic risks can be managed better if there is appropriate policy and institutional support together with technological interventions to address the complexities of multiple risks that agriculture has to face. This would require effective partnerships among agencies dealing with meteorological and hydrological services, agricultural research, land degradation and food security issues. In addition a state-of-the-art infrastructure to measure, record, store and disseminate data on weather variables, and access to weather and seasonal climate forecasts at desired spatial and temporal scales would be needed

Observed Asymmetry in pˉp→π+K−K0/π−K+Kˉ0\bar{p}p \to \pi^+ K^- K^0 / \pi^- K^+ \bar{K}^0 and Relation to Reciprocity

The charge-asymmetry observed in a recent CPLEAR experiment was interpreted by the authors as a direct observation of T-noninvariance. While this is the simplest and most natural inference, and the observed effect agrees in sign and magnitude with theoretical expectation, adherents of T-invariance may argue that other interpretations are also possible. If K^0 and \bar{K}^0 are produced equally in \bar{p} p annihilation, and T-invariance is assumed to hold, the asymmetry observed in CPLEAR must be attributed to TCP-noninvariance of kaon beta-decays. If that were the case, the charge-asymmetry in K_S^0 \to \pi l\nu decays should be three times larger than the one observed for K_L^0 decays.Comment: 8 pages, Late

POSTURAL CONTROL IN ELITE ARCHERS DURING SHOOTING

Archery is described as a static sport requiring fine movement control and proper endurance strength of the upper body (Soylu, Ertan, & Korkusuz, 2006).To investigate the differences of postural control (PC) between elite and general collegiate archers during static and shooting conditions

Bogomol'nyi equations for solitons in Maxwell-Chern-Simons gauge theories with the magnetic moment interaction term

Without assuming rotational invariance, we derive Bogomol'nyi equations for the solitons in the abelian Chern-Simons gauge theories with the anomalous magnetic moment interaction. We also evaluate the number of zero modes around a static soliton configuration.Comment: 9 pages, Revtex, SNUTP-94/6

Effective description of axion defects

Axion strings and domain walls exhibit a number of novel effects in the presence of gauge fields, in particular the electromagnetic field. It is shown how these effects are reproduced in a model of Nambu-Goto-type strings and open or closed membranes coupled to gauge fields. The generalization to `axionic p-branes' is considered and it is shown how worldvolume gauge fields that arise in certain cases can be interpreted as Goldstone fields.Comment: 9 pages NSF-ITP-93-3

The First Law for Boosted Kaluza-Klein Black Holes

We study the thermodynamics of Kaluza-Klein black holes with momentum along the compact dimension, but vanishing angular momentum. These black holes are stationary, but non-rotating. We derive the first law for these spacetimes and find that the parameter conjugate to variations in the length of the compact direction is an effective tension, which generally differs from the ADM tension. For the boosted black string, this effective tension is always positive, while the ADM tension is negative for large boost parameter. We also derive two Smarr formulas, one that follows from time translation invariance, and a second one that holds only in the case of exact translation symmetry in the compact dimension. Finally, we show that the `tension first law' derived by Traschen and Fox in the static case has the form of a thermodynamic Gibbs-Duhem relation and give its extension in the stationary, non-rotating case.Comment: 20 pages, 0 figures; v2 - reference adde

Processing of aluminum-graphite particulate metal matrix composites by advanced shear technology

Copyright @ 2009 ASM International. This paper was published in Journal of Materials Engineering and Performance 18(9) and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.To extend the possibilities of using aluminum/graphite composites as structural materials, a novel process is developed. The conventional methods often produce agglomerated structures exhibiting lower strength and ductility. To overcome the cohesive force of the agglomerates, a melt conditioned high-pressure die casting (MC-HPDC) process innovatively adapts the well-established, high-shear dispersive mixing action of a twin screw mechanism. The distribution of particles and properties of composites are quantitatively evaluated. The adopted rheo process significantly improved the distribution of the reinforcement in the matrix with a strong interfacial bond between the two. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (e) is obtained compared with composites produced by conventional processes.EPSR