Fluctuation dynamo amplified by intermittent shear bursts in convectively driven magnetohydrodynamic turbulence

Intermittent large-scale high-shear flows are found to occur frequently and spontaneously in direct numerical simulations of statistically stationary turbulent Boussinesq magnetohydrodynamic (MHD) convection. The energetic steady-state of the system is sustained by convective driving of the velocity field and small-scale dynamo action. The intermittent emergence of flow structures with strong velocity and magnetic shearing generates magnetic energy at an elevated rate over time-scales longer than the characteristic time of the large-scale convective motion. The resilience of magnetic energy amplification suggests that intermittent shear-bursts are a significant driver of dynamo action in turbulent magnetoconvection

Extreme-value statistics from Lagrangian convex hull analysis for homogeneous turbulent Boussinesq convection and MHD convection

We investigate the utility of the convex hull of many Lagrangian tracers to analyze transport properties of turbulent flows with different anisotropy. In direct numerical simulations of statistically homogeneous and stationary Navier-Stokes turbulence, neutral fluid Boussinesq convection, and MHD Boussinesq convection a comparison with Lagrangian pair dispersion shows that convex hull statistics capture the asymptotic dispersive behavior of a large group of passive tracer particles. Moreover, convex hull analysis provides additional information on the sub-ensemble of tracers that on average disperse most efficiently in the form of extreme value statistics and flow anisotropy via the geometric properties of the convex hulls. We use the convex hull surface geometry to examine the anisotropy that occurs in turbulent convection. Applying extreme value theory, we show that the maximal square extensions of convex hull vertices are well described by a classic extreme value distribution, the Gumbel distribution. During turbulent convection, intermittent convective plumes grow and accelerate the dispersion of Lagrangian tracers. Convex hull analysis yields information that supplements standard Lagrangian analysis of coherent turbulent structures and their influence on the global statistics of the flow.Comment: 18 pages, 10 figures, preprin

On the engineering of crucial software

The various aspects of the conventional software development cycle are examined. This cycle was the basis of the augmented approach contained in the original grant proposal. This cycle was found inadequate for crucial software development, and the justification for this opinion is presented. Several possible enhancements to the conventional software cycle are discussed. Software fault tolerance, a possible enhancement of major importance, is discussed separately. Formal verification using mathematical proof is considered. Automatic programming is a radical alternative to the conventional cycle and is discussed. Recommendations for a comprehensive approach are presented, and various experiments which could be conducted in AIRLAB are described

Oxidized basalts on the surface of Venus: Compositional implications of measured spectral properties

Venera Lander reflectance data are compared with high temperature spectra of the same basaltic materials. The dark, flat unoxidized basalts are still inconsistent with the Venera data in the near-infrared. Basaltic material with a ferric component, however, would satisfy both the increase in reflectance beyond 0.7 microns as well as the dark, relatively colorless character in the visible. Therefore, it is concluded that besaltic surfaces of Venus represented by these measurements either contain minerals with uncommon characteristics, or, more likely, are relatively oxidized

Exploring the Importance of Criminal Legal Aid: A Canadian Perspective

There is a growing global recognition that, in order to address the current access to justice crisis, more research, together with a better understanding of data, is needed. This article, through an examination of existing legal aid research primarily in the area of criminal law, explores some of what we know and do not know about the relative benefits and costs of providing different kinds of criminal legal aid services. Although not a comprehensive review of all available research, this article identifies data strengths and gaps and the need for further research and reforms

Advanced analog television study final report, 4 nov. - 19 dec. 1963

Information bandwidth reduction for analog television signals - Description of multiple interlace syste