There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Functional π-Gelators and Their Applications

The molecular dynamics in the glass transition of the “quasi” ‐ van der Waals glass salol confined to nanopores (2.5, 5.0, and 7.5 nm) with lubricated inner surfaces is found to be faster ( by up to 2 orders of magnitude) than in the bulk liquid. This effect of confinement is more pronounced for smaller pores. It reflects the cooperativity of molecular motions in the glass transition and enables its length scale to be determined quantitatively. [S0031-9007(97)04009-X]

Length Scale of Cooperativity in the Dynamic Glass Transition

Broadband dielectric spectroscopy (10 Hz–10 Hz! is employed to study the dynamic glass transition of low-molecular-weight glass-forming liquids being confined to nanoporous sol-gel glasses with pore sizes of 2.5, 5.0, and 7.5 nm. As glass-forming liquids, salol ~one hydroxy group!, pentylene glycol ~two hydroxy groups!, and glycerol ~three hydroxy groups! were chosen. We interpret the dielectric spectra in terms of a two-state model with dynamic exchange between a bulklike phase in the pore volume and an interfacial phase close to the pore wall. This enables one to analyze in detail the interplay between the molecular dynamics in the two subsystems ~bulklike and interfacial!, its dynamic exchange, and hence their growth and decline in dependence on temperature and strength of the molecular interactions. For glycerol it is shown that a bulklike dynamic glass transition takes place in subvolumes as small as about 1 nm. @S1063-651X~96!08711-9#

Dielectric investigations of the dynamic glass transition in nanopores.

Granular physics has made considerable progress during the past decades in the understanding of static and dynamic properties of large ensembles of interacting macroscopic particles, including the modeling of phenomena like jamming, segregation and pattern formation, the development of related industrial applications or traffic flow control. The specific properties of systems composed of shape-anisotropic (elongated or flattened) particles have attracted increasing interest in recent years. Orientational order and self-organization are among the characteristic phenomena that add to the special features of granular matter of spherical or irregularly shaped particles. An overview of this research field is given.

Granular materials composed of shape-anisotropic grains

Novel approach to the analysis of broadband dielectric spectra.

Shear induced alignment of elongated particles is studied experimentally and numerically. We show that shear alignment of ensembles of macroscopic particles is comparable even on a quantitative level to simple molecular systems, despite the completely different types of particle interactions. We demonstrate that for dry elongated grains the preferred orientation forms a small angle with the streamlines, independent of shear rate across three decades. For a given particle shape, this angle decreases with increasing aspect ratio of the particles. The shear-induced alignment results in a considerable reduction of the effective friction of the granular material.

/pdf/orientational-order-and-alignment-of-elongated-particles-3j09r49m77.pdf

Ralf Stannarius

Papers

Length Scale of Cooperativity in the Dynamic Glass Transition

Dielectric investigations of the dynamic glass transition in nanopores.

Granular materials composed of shape-anisotropic grains

Novel approach to the analysis of broadband dielectric spectra.

Orientational order and alignment of elongated particles induced by shear.