Scaling Evalutation of the Lattice Solid Model on the SGI Altix 3700

The Lattice Solid Model is a particle based method which has been successfully employed for simulating the fracturing of rocks, the dynamics of faults, earthquakes and gouge processes. However, results from initial simulations demonstrate that models consisting of only thousands of particles are inadequate to accurately reproduce the micro-physics of seismic phenomenon. Instead, models with millions or tens of millions of particles are required to produce realistic simulations. Parallel computing architectures, such as the SGI Altix 3700, provide the opportunity to solve much larger computational problems than traditional single processor systems. In order to take advantage of high performance systems, a Message Passing Interface version of the Lattice Solid Model has been implemented. Benchmarks, presented in this paper, demonstrate an 80% parallel efficiency for the parallel Lattice Solid Model on 128 processors of the SGI Altix 3700. These results, for a two--dimensional wave propagation problem, indicate the potential for the Lattice Solid Model to simulate more computationally challenging three-dimensional geophysical processes

Электроосаждение сплава свинец-олово из метансульфонатных растворов

Досліджено вплив різних чинників на склад сплаву свинець-олово, що осаджений з електроліту на основі метансульфонатної кислоти. Методом повного факторного експерименту ПФЕ2³ отримані рівняння регресії, що адекватно описують залежність вмісту олова в сплаві від умов осадження з електролітів із органічними добавками і без них.Effect of different factors on content of lead-tin alloys obtained from an electrolyte on the base of methanesulfonic acid is investigated. The method of full factor experiment FFE 2³ is used for obtaining of regression equations which adequately describe the relation between the electrodeposition condition and the contents of tin in alloys from electrolytes with and without some organic additives

The geomorphology and radar facies of Kaitorete Spit, Canterbury, New Zealand

Kaitorete Spit is a mixed sand and gravel barrier beach complex that is located at the northeastern end of the Canterbury Bight. Kaitorete Spit was examined during this study using a combination of ground penetrating radar surveys, sedimentological and geomorphological examinations of the barrier beach complex. The geomorphology formed on Kaitorete has developed in three different environments. At the northeastern end of Kaitorete low elevation spit recurves are formed. South of these are numerous parallel beach ridges, formed by the tops of prograded storm berms. Lacustrine geomorphic features have developed over the marine geomorphology. Small scale cuspate ridges have formed in shallow lake water and associated with lake bottom sediments. Lacustrine beach ridges, lacustrine beach ridge plains and lacustrine spit complexes all formed along the shore of a higher lake. Nine different radar facies were found developed in the radar profiles collected on Kaitorete Spit. The facies are defined on the basis of their internal reflector patterns. Generally, the reflector patterns could be predicted by interpreting the geomorphic features over which the radar profiles ran. Three of the radar facies revealed reflector patterns that could not be predicted using geomorphology alone. At the eastern end of Kaitorete Spit, the radar profiles revealed that the marine spit recurves comprise a spit beach overlying a spit platform. It also reveals that the distal end of the spit platform was reworked by tidal currents into a series of seaward prograding foresets. The radar profiles also revealed that immediately the barrier beach reached the edge of the spit platform, a rise in the elevation of the beach crest occurred due to an increase in the wave energy expended on the beach. In the centre of the barrier beach complex the radar profiles revealed that two long overwash barriers developed, which fill two long (up to 12 km), thin lake outlet lagoons. These lagoons developed as a result of breaching due to a large river overfilling the lake basin. After the initial breach, the longshore drift and lake outflow developed a dynamic equilibrium, resulting in the progressive eastward dislocation of the outlet mouth. The large volume of lake water acted to buffer the high flows of the river thereby, maintaining flow conditions at the outlet channel which were conducive to lagoon elongation. Associated with the lacustrine spit complexes are scarp-like ridges which have steep reflectors which dip away from the lake. These developed in a similar way to shore-parallel bars, with material moving up the stoss side and avalanching down the lee side. The combined application of ground penetrating radar and geomorphology reveals a much more complete geological history of an area where outcrop is sparse

The H1 Forward Proton Spectrometer at HERA

The forward proton spectrometer is part of the H1 detector at the HERA collider. Protons with energies above 500 GeV and polar angles below 1 mrad can be detected by this spectrometer. The main detector components are scintillating fiber detectors read out by position-sensitive photo-multipliers. These detectors are housed in so-called Roman Pots which allow them to be moved close to the circulating proton beam. Four Roman Pot stations are located at distances between 60 m and 90 m from the interaction point.Comment: 20 pages, 10 figures, submitted to Nucl.Instr.and Method

Non-Abelian Discrete Dark Matter

We consider the minimal model in which dark matter is stabilized by a non-Abelian discrete symmetry. The symmetry group is taken to be D_3, which is the smallest non-Abelian finite group. The minimal model contains (nontrivial) singlet and doublet scalar representations of D_3 which couple to the Standard Model fields via the Higgs portal. This construction predicts two species of dark matter over much of the parameter space. Nontrivial interactions under D_3 lead to a novel thermal history of dark matter, while the multi-component nature of dark matter can be tested by future direct detection experiments.Comment: 12 pages, 6 figure

Supersymmetry Without Prejudice at the LHC

The discovery and exploration of Supersymmetry in a model-independent fashion will be a daunting task due to the large number of soft-breaking parameters in the MSSM. In this paper, we explore the capability of the ATLAS detector at the LHC ($\sqrt s=14$ TeV, 1 fb$^{-1}$) to find SUSY within the 19-dimensional pMSSM subspace of the MSSM using their standard transverse missing energy and long-lived particle searches that were essentially designed for mSUGRA. To this end, we employ a set of $\sim 71$k previously generated model points in the 19-dimensional parameter space that satisfy all of the existing experimental and theoretical constraints. Employing ATLAS-generated SM backgrounds and following their approach in each of 11 missing energy analyses as closely as possible, we explore all of these $71$k model points for a possible SUSY signal. To test our analysis procedure, we first verify that we faithfully reproduce the published ATLAS results for the signal distributions for their benchmark mSUGRA model points. We then show that, requiring all sparticle masses to lie below 1(3) TeV, almost all(two-thirds) of the pMSSM model points are discovered with a significance $S>5$ in at least one of these 11 analyses assuming a 50\% systematic error on the SM background. If this systematic error can be reduced to only 20\% then this parameter space coverage is increased. These results are indicative that the ATLAS SUSY search strategy is robust under a broad class of Supersymmetric models. We then explore in detail the properties of the kinematically accessible model points which remain unobservable by these search analyses in order to ascertain problematic cases which may arise in general SUSY searches.Comment: 69 pages, 40 figures, Discussion adde

Phase-field material point method for brittle fracture

The Material Point Method for the analysis of deformable bodies is revisited and originally upgraded to simulate crack propagation in brittle media. In this setting, phase field modelling is introduced to resolve the crack path geometry. Following a particle in cell approach, the coupled continuum/ phase-field governing equations are defined at a set of material points and interpolated at the nodal points of an Eulerian, i.e. non-evolving, mesh. The accuracy of the simulated crack path is thus de-coupled from the quality of the underlying finite element mesh and relieved from corresponding mesh-distortion errors. A staggered incremental procedure is implemented for the solution of the discrete coupled governing equations of the phase field brittle fracture problem. The proposed method is verified through a series of benchmark tests while comparisons are made between the proposed scheme, the corresponding finite element implementation as well as experimental results

A Search for Selectrons and Squarks at HERA

Data from electron-proton collisions at a center-of-mass energy of 300 GeV are used for a search for selectrons and squarks within the framework of the minimal supersymmetric model. The decays of selectrons and squarks into the lightest supersymmetric particle lead to final states with an electron and hadrons accompanied by large missing energy and transverse momentum. No signal is found and new bounds on the existence of these particles are derived. At 95% confidence level the excluded region extends to 65 GeV for selectron and squark masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure

Observable Consequences of Planet Formation Models in Systems with Close-in Terrestrial Planets

To date, two planetary systems have been discovered with close-in, terrestrial-mass planets (< 5-10 Earth masses). Many more such discoveries are anticipated in the coming years with radial velocity and transit searches. Here we investigate the different mechanisms that could form "hot Earths" and their observable predictions. Models include: 1) in situ accretion; 2) formation at larger orbital distance followed by inward "type 1" migration; 3) formation from material being "shepherded" inward by a migrating gas giant planet; 4) formation from material being shepherded by moving secular resonances during dispersal of the protoplanetary disk; 5) tidal circularization of eccentric terrestrial planets with close-in perihelion distances; and 6) photo-evaporative mass loss of a close-in giant planet. Models 1-4 have been validated in previous work. We show that tidal circularization can form hot Earths, but only for relatively massive planets (> 5 Earth masses) with very close-in perihelion distances (< 0.025 AU), and even then the net inward movement in orbital distance is at most only 0.1-0.15 AU. For planets of less than about 70 Earth masses, photo-evaporation can remove the planet's envelope and leave behind the solid core on a Gyr timescale, but only for planets inside 0.025-0.05 AU. Using two quantities that are observable by current and upcoming missions, we show that these models each produce unique signatures, and can be observationally distinguished. These observables are the planetary system architecture (detectable with radial velocities, transits and transit-timing) and the bulk composition of transiting close-in terrestrial planets (measured by transits via the planet's radius).Comment: Accepted to MNRAS. 14 pages, 4 figures, 1 tabl