Computer systems: What the future holds

Developement of computer architecture is discussed in terms of the proliferation of the microprocessor, the utility of the medium-scale computer, and the sheer computational power of the large-scale machine. Changes in new applications brought about because of ever lowering costs, smaller sizes, and faster switching times are included

Parallel tridiagonal equation solvers

Three parallel algorithms were compared for the direct solution of tridiagonal linear systems of equations. The algorithms are suitable for computers such as ILLIAC 4 and CDC STAR. For array computers similar to ILLIAC 4, cyclic odd-even reduction has the least operation count for highly structured sets of equations, and recursive doubling has the least count for relatively unstructured sets of equations. Since the difference in operation counts for these two algorithms is not substantial, their relative running times may be more related to overhead operations, which are not measured in this paper. The third algorithm, based on Buneman's Poisson solver, has more arithmetic operations than the others, and appears to be the least favorable. For pipeline computers similar to CDC STAR, cyclic odd-even reduction appears to be the most preferable algorithm for all cases

Precision in the perception of direction of a moving pattern

The precision of the model of pattern motion analysis put forth by Adelson and Movshon (1982) who proposed that humans determine the direction of a moving plaid (the sum of two sinusoidal gratings of different orientations) in two steps is qualitatively examined. The volocities of the grating components are first estimated, then combined using the intersection of constraints to determine the velocity of the plaid as a whole. Under the additional assumption that the noise sources for the component velocities are independent, an approximate expression can be derived for the precision in plaid direction as a function of the precision in the speed and direction of the components. Monte Carlo simulations verify that the expression is valid to within 5 percent over the natural range of the parameters. The expression is then used to predict human performance based on available estimates of human precision in the judgment of single component speed. Human performance is predicted to deteriorate by a factor of 3 as half the angle between the wavefronts (theta) decreases from 60 to 30 deg, but actual performance does not. The mean direction discrimination for three human observers was 4.3 plus or minus 0.9 deg (SD) for theta = 60 deg and 5.9 plus or minus 1.2 for theta = 30 deg. This discrepancy can be resolved in two ways. If the noises in the internal representations of the component speeds are smaller than the available estimates or if these noises are not independent, then the psychophysical results are consistent with the Adelson-Movshon hypothesis

Incompressibility in finite nuclei and nuclear matter

The incompressibility (compression modulus) $K_{\rm 0}$ of infinite symmetric nuclear matter at saturation density has become one of the major constraints on mean-field models of nuclear many-body systems as well as of models of high density matter in astrophysical objects and heavy-ion collisions. We present a comprehensive re-analysis of recent data on GMR energies in even-even $^{\rm 112-124}$Sn and $^{\rm 106,100-116}$Cd and earlier data on 58 $\le$ A $\le$ 208 nuclei. The incompressibility of finite nuclei $K_{\rm A}$ is expressed as a leptodermous expansion with volume, surface, isospin and Coulomb coefficients $K_{\rm vol}$, $K_{\rm surf}$, $K_\tau$ and $K_{\rm coul}$. \textit{Assuming} that the volume coefficient $K_{\rm vol}$ is identified with $K_{\rm 0}$, the $K_{\rm coul}$ = -(5.2 $\pm$ 0.7) MeV and the contribution from the curvature term K$_{\rm curv}$A$^{\rm -2/3}$ in the expansion is neglected, compelling evidence is found for $K_{\rm 0}$ to be in the range 250 $< K_{\rm 0} <$ 315 MeV, the ratio of the surface and volume coefficients $c = K_{\rm surf}/K_{\rm vol}$ to be between -2.4 and -1.6 and $K_{\rm \tau}$ between -840 and -350 MeV. We show that the generally accepted value of $K_{\rm 0}$ = (240 $\pm$ 20) MeV can be obtained from the fits provided $c \sim$ -1, as predicted by the majority of mean-field models. However, the fits are significantly improved if $c$ is allowed to vary, leading to a range of $K_{\rm 0}$, extended to higher values. A self-consistent simple (toy) model has been developed, which shows that the density dependence of the surface diffuseness of a vibrating nucleus plays a major role in determination of the ratio K$_{\rm surf}/K_{\rm vol}$ and yields predictions consistent with our findings.Comment: 26 pages, 13 figures; corrected minor typos in line with the proof in Phys. Rev.

Fluid sample collector Patent

Design and development of fluid sample collecto

Continuum

'Continuum' is a project which is a part of Sophie Stone's PhD research into 'Multiplicity as a Process of Experimental Music'. This folder comprises all documentation for 'Continuum', including images, scores, and video and audio recordings

Multiplicity as a process of experimental music

This PhD explores my practice through six new compositions of experimental music: Far Infrared (2015/18/19), “As Sure as Time…” (2016-), Amalgamations (2016-), Continuum (2017-), ُ وِيَّةُه (Huia) (2018-) and postcard-sized pieces (2020). Using the philosophical concept of multiplicity (discussed by Henri Bergson, Gilles Deleuze, and Alain Badiou) as a framework for the composition, realisation, and experience of this music, I highlight the heterogeneity of seemingly quantitative multiplicities. Key points of focus include considering the experience of sound, silence and durations, indeterminacy and interpretation, the notation, and musical situations (including space and collaboration) as qualitative multiplicities. Extensive research in experimental music, recent approaches to experimental music, and practice research methodologies form the background of this project. Prior knowledge within the field of experimental music is examined and extended, with case studies including Wandelweiser, and specific Wandelweiser composers such as Antoine Beuger and Emmanuelle Waeckerlé, as well as Éliane Radigue. Realisations of the six new compositions have been documented through audio recordings, videos, photographs, and scores, and are analysed and reflected upon in the exegesis, which influenced future situations and compositions in an iterative, reflexive cycle. As well as new compositions of experimental music, this research offers new perspectives on the concept of multiplicity as a paradigm to understand experimental music, particularly through the compositional process, realisation and listening experience. The compositions of this project explore multiplicity in various ways, such as series, flexibility of score and situations, types and experiences of silences, sustained sounds, duration, and instrumentation. Despite these traditionally being considered as quantitative multiplicities, I argue that they are qualitative through Badiou’s ontology of multiplicity due to their subjectivity, simultaneous and interwoven experiences of past and present, and all experiences not being complete. By considering multiplicities in this way, it highlights the complexity of experimental music practice

Amalgamations

'Amalgamations' is a project which is a part of Sophie Stone's PhD research into 'Multiplicity as a Process of Experimental Music'. This folder comprises all documentation for 'Amalgamations', including images, scores, and video and audio recordings

Far Infrared

'Far Infrared' is a project which is a part of Sophie Stone's PhD research into 'Multiplicity as a Process of Experimental Music'. This folder comprises all documentation for 'Far Infrared', including images, scores, and video and audio recordings