Duralumin

The use of duralumin in the construction of aircraft makes an account of the properties of this material desirable especially with reference to its working qualities as developed by experience

Continuous Time Monte Carlo for Lattice QCD in the Strong Coupling Limit

We present results for lattice QCD in the limit of infinite gauge coupling, obtained from a worm-type Monte Carlo algorithm on a discrete spatial lattice but with continuous Euclidean time. This is obtained by sending both the anisotropy parameter gamma^2 \sim a/a_t and the number of time-slices N_\tau to infinity, keeping the ratio \gamma^2/N_\tau \sim aT fixed. The obvious gain is that no continuum extrapolation N_\tau -> \infty has to be carried out. Moreover, the algorithm is faster and the sign problem disappears. We compare our computations with those on discrete lattices. We determine the phase diagram as a function of temperature and baryon chemical potential.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28, 2011, Annecy, Franc

MIA computer simulation test results report

Results of the first noise susceptibility computer simulation tests of the complete MIA receiver analytical model are presented. Computer simulation tests were conducted with both Gaussian and pulse noise inputs. The results of the Gaussian noise tests were compared to results predicted previously and were found to be in substantial agreement. The results of the pulse noise tests will be compared to the results of planned analogous tests in the Data Bus Evaluation Laboratory at a later time. The MIA computer model is considered to be fully operational at this time

Shear zones in granular media: 3D Contact Dynamics simulation

Shear zone formation is investigated in slow 3D shear flows. We simulate the linear version of the split-bottom shear cell. It is shown that the same type of wide shear zones is achieved in the presence as well as in the absence of gravity. We investigate the relaxation of the material towards a stationary flow and analyze the stress and the velocity fields. We provide the functional form of the widening of the shear zone inside the bulk. We discuss the growth of the region where the material is in critical state. It is found that the growth of the critical zone is responsible for the initial transient of the shear zone.Comment: 9 page

Force indeterminacy in the jammed state of hard disks

Granular packings of hard discs are investigated by means of contact dynamics which is an appropriate technique to explore the allowed force-realizations in the space of contact forces. Configurations are generated for given values of the friction coefficient, and then an ensemble of equilibrium forces is found for fixed contacts. We study the force fluctuations within this ensemble. In the limit of zero friction the fluctuations vanish in accordance with the isostaticity of the packing. The magnitude of the fluctuations has a non-monotonous friction dependence. The increase for small friction can be attributed to the opening of the angle of the Coulomb cone, while the decrease as friction increases is due to the reduction of connectivity of the contact-network, leading to local, independent clusters of indeterminacy. We discuss the relevance of indeterminacy to packings of deformable particles and to the mechanical response properties.Comment: 4 pages, 3 figures. Minor changes, journal reference adde

Shear band formation in granular media as a variational problem

Strain in sheared dense granular material is often localized in a narrow region called shear band. Recent experiments in a modified Couette cell provided localized shear flow in the bulk away from the confining walls. The non-trivial shape of the shear band was measured as the function of the cell geometry. First we present a geometric argument for narrow shear bands which connects the function of their surface position with the shape in the bulk. Assuming a simple dissipation mechanism we show that the principle of minimum dissipation of energy provides a good description of the shape function. Furthermore, we discuss the possibility and behavior of shear bands which are detached from the free surface and are entirely covered in the bulk.Comment: 4 pages, 5 figures; minor changes, typos and journal-ref adde

Cation Alloying as a Pathway to Reproducible olution Based Preparation of Efficient Metal Halide Perovskites Solar Cells with Increased Stability

With a certain amount of serendipity, research on dye sensitized solar cells led to the discovery of metal halide perovskite semiconductors as a solar energy conversion material1,2 that has inspired world wide research activities leading to efficiency increases from about 10 in 20123,4 to now 22 .5 8 Apart from their use as a single junction solar cell technology, metal halide perovskites can be processed as an add on layer onto other solar cells to realize efficient and low cost tandem architectures. The perovskite band gap can be tuned continuously from 1.1 to 3.0 eV by chemical engineering which makes them particularly relevant for multi junction devices.9 12 Experimental demonstrations of efficient tandem devices comprising metal halide perovskites as one13 15 or both10,16 components in a tandem stack highlight the potential for scalable and low cost multi junction devices17 with efficiencies approaching 30 is considered feasible.18,12,19,20 To reach this performance in a perovskite silicon tandem, the ideal band gap of the absorber material in top device should be about 1.7 eV18,12,21 sine silicon has a band gap of 1.1 eV .11,22,23 In this review, we dedicate section I to the discussion of the chemical tunability of metal halide perovskite with a particular focus on absorber materials with absorption onsets around 1.6 eV. Section II reflects on the benefit and role of including cesium Cs highlighting the work by Saliba et al.5,6 as this approach demonstrates a reliable pathway to obtain efficient solution processed metal halide perovskite absorbers with high reproducibility and extended operational device stability. Section III focuses on the state of the art of perovskite photovoltaics as a function of the absorption onset of the absorber layer highlighting materials with band gaps between 1.6 eV 1.75 eV as these are of great importance to the development of efficient tandem solar cells.12,18 20 In the conclusion section IV, we reflect on more general trends in metal halide alloys partially iscussed elsewhere23 highlighting cation alloying as an approach to obtain highly efficient devices in the band gap range between 1.6 and 1.7 eV. The data shown and discussed here is dominantly based on three of our recent publications and the interested reader is kindly referred to Unger et al.23 and Saliba et al.5,6 for more in depth discussions and experimental details

Unjamming of Granular Packings due to Local Perturbations: Stability and Decay of Displacements

We study the mechanical response generated by local deformations in jammed packings of rigid disks. Based on discrete element simulations we determine the critical force of the local perturbation that is needed to break the mechanical equilibrium and examine the generated displacement field. Displacements decay as a power law of the distance from the perturbation point. The decay exponent and the critical force exhibit nontrivial dependence on the friction: Both quantities are nonmonotonic and have a sharp maximum at the friction coefficient 0.1. We find that the mechanical response properties are closely related to the problem of force-indeterminacy where similar nonmonotonic behavior was observed previously. We establish direct connection between the critical force and the ensemble of static force networks.Comment: 4 pages, 4 figure

Integrating High Resolution Imagery with Spatial Analysis and Genealogical Analysis of Historic Cemeteries

Spatial and genealogical analysis of cemetery plot location and attribute data collected with a Trimble GeoExplorer 3 GPS unit was undertaken to understand the spatial arrangement and genealogical distribution of graves within one of the oldest cemeteries in the state of Texas. High spatial resolution multi-spectral imagery was incorporated as a base map to aid the visual interpretation of the spatial analyses