Load-depth sensing of isotropic, linear viscoelastic materials using rigid axisymmetric indenters

An indentation experiment involves five variables: indenter shape, material behavior of the substrate, contact size, applied load and indentation depth. Only three variable are known afterwards, namely, indenter shape, plus load and depth as function of time. As the contact size is not measured and the determination of the material properties is the very aim of the test; two equations are needed to obtain a mathematically solvable system. For elastic materials, the contact size can always be eliminated once and for all in favor of the depth; a single relation between load, depth and material properties remains with the latter variable as unknown. For viscoelastic materials where hereditary integrals model the constitutive behavior, the relation between depth and contact size usually depends also on the (time-dependent) properties of the material. Solving the inverse problem, i.e., determining the material properties from the experimental data, therefore needs both equations. Extending Sneddon's analysis of the indentation problem for elastic materials to include viscoelastic materials, the two equations mentioned above are derived. To find the time dependence of the material properties the feasibility of Golden and Graham's method of decomposing hereditary integrals (J.M. Golden and G.A.C. Graham. Boundary value problems in linear viscoelasticity, Springer, 1988) is investigated and applied to a single load-unload process and to sinusoidally driven stationary state indentation processes.Comment: 116 pages, 29 figure

Habitat configuration matters when evaluating habitat-area effects on host–parasitoid interactions

Citation: With, K. A., & Pavuk, D. M. (2019). Habitat configuration matters when evaluating habitat-area effects on host–parasitoid interactions. Ecosphere, 10(2), e02604. https://doi.org/10.1002/ecs2.2604Higher trophic levels tend to be more sensitive to habitat fragmentation than lower trophic levels, which is why parasitism rates should decline in fragmented landscapes. Habitat loss and fragmentation (the subdivision of habitat) are typically interrelated processes, and thus, their effects are confounded in most studies. To address this, we quantified parasitism rates in pea aphids (Acyrthosiphon pisum) within an experimental model landscape system, in which we independently controlled the amount vs. the fragmentation of habitat (red clover, Trifolium pratense) within individual landscape plots (16 × 16 m). Aphid densities were generally unaffected by landscape pattern, except at the local scale for interior habitat cells within fragmented landscapes, which had significantly lower aphid densities than all other cell types. Aphid parasitism rates averaged about 40% and were significantly—albeit weakly—correlated with aphid density. Habitat amount had the greatest overall effect on parasitism rates, but fragmentation effects were evident in a shift in parasitism at intermediate habitat levels: Parasitism rates were higher in fragmented landscapes with 50% habitat. Edge effects alone did not explain this shift in parasitism rates. Parasitism rates were uniformly high within edge habitat and fragmented landscapes, and thus, the shift in parasitism at intermediate habitat levels was driven by increasing parasitism rates within interior cells and clumped landscapes at higher habitat amounts. Habitat configuration is thus important for evaluating habitat-area effects on species interactions, as habitat amount only affected parasitism rates within less-fragmented landscapes in this system

2 Girls with a Food Blog

We are two best friends that blog about food. We both started while at home with our kids and it has grown into a passion from there. We hope you enjoy our blog and please feel free to contact us with your comments or just to say hi

Spectroscopy of Hadrons with b Quarks from Lattice NRQCD

Preliminary results from an extensive lattice calculation of the B, B_c, and \Upsilon spectrum at quenched \beta = 6.0 are presented. The study includes radially and orbitally excited mesons, and baryons containing b quarks. The b quarks are formulated using NRQCD; for light and c quarks, a tadpole-improved clover action is used.Comment: talk given at LATTICE98(heavyqk), 3 pages LaTeX, 2 Postscript figure

Sapphic Modernists - Re-visiting Elizabeth McCausland and Berenice Abbott’s Changing New York

Within our research of female/sapphic collaborations of Modernity, a perpetual process of ‘erasure’ or the ‘writing out of art history’ of female collaborators is exposed. One such example is evident through analysis of the 1939 publication of Berenice Abbott’s photographs in Changing New York which has been acknowledged as a key contribution to urban photographic history. Little or nothing is known of the fact that all of the original captions for Changing New York were deemed not fit for publication and that the innovative spatial text-image design devised by Berenice Abbott and Elizabeth McCausland was rejected. Instead the publishers insisted on a very conservative approach to design and the blandness of the published captions read activate Berenice Abbott’s photographs much like a guide book to the city. We found the complete set of original captions to the book, written by Elizabeth McCausland, a communist and socially engaged journalist and long-time partner of Berenice Abbott. These highly critical texts act to place the photographs directly into the larger political and social context of the 1930s Depression in USA. The original attempt and idea for the book by Abbott and McCausland was intended to acknowledge both formats, text and photography, as equal in terms of activating meaning production and/or tools for critical reflection. The book was intended as a critical reflection on the harrowing social conditions and inequalities of the 1930s in New York City

Generalized coordinates on the phase space of Yang-Mills theory

We study the suitability of complex Wilson loop variables as (generalized) coordinates on the physical phase space of $SU(2)$-Yang-Mills theory. To this end, we construct a natural one-to-one map from the physical phase space of the Yang-Mills theory with compact gauge group $G$ to a subspace of the physical configuration space of the complex G^\C-Yang-Mills theory. Together with a recent result by Ashtekar and Lewandowski this implies that the complex Wilson loop variables form a complete set of generalized coordinates on the physical phase space of $SU(2)$-Yang-Mills theory. They also form a generalized canonical loop algebra. Implications for both general relativity and gauge theory are discussed.Comment: TeX, 11pp, revised version (minor clarifications added, Comment after (2.9) inserted); to appear in Class. Quant. Grav

An apparatus and method for detecting a tool

The apparatus is adapted to detect a tool based on a 3D image obtained by a 3D ultrasound imaging system. The apparatus comprises an image processing unit, which includes a tool detection module configured to perform a tool detection procedure. The tool detection procedure involves identifying a shadow of the tool in the 3D image and calculating the position of a "tool plane section" of the 3D image in which the entire length of the tool is represented