Interactive visualization and analysis of transitional flow

A stand-alone visualization application has been developed by a multi-disciplinary, collaborative team with the sole purpose of creating an interactive exploration environment allowing turbulent flow researchers to experiment and validate hypotheses using visualization. This system has specific optimizations made in data management, caching computations, and visualization allowing for the interactive exploration of datasets on the order of 1TB in size. Using this application, the user (co-author Calo) is able to interactively visualize and analyze all regions of a transitional flow volume, including the laminar, transitional and fully turbulent regions. The underlying goal of the visualizations produced from these transitional flow simulations is to localize turbulent spots in the laminar region of the boundary layer, determine under which conditions they form, and follow their evolution. The initiation of turbulent spots, which ultimately lead to full turbulence, was located via a proposed feature detection condition and verified by experimental results. The conditions under which these turbulent spots form and coalesce are validated and presented.     

Application of single-level,pointwise algebraic,and smoothed aggregation multigrid methods to direct numerical simulations of incompressible turbulent flows

Single- and multi-level iterative methods for sparse linear systems are applied to unsteady flow simulations via implementation into a direct numerical simulation solver for incompressible turbulent flows on unstructured meshes. The performance of these solution methods, implemented in the well-established SAMG and ML packages, are quantified in terms of computational speed and memory consumption, with a direct sparse LU solver (SuperLU) used as a reference. The classical test case of unsteady flow over a circular cylinder at low Reynolds numbers is considered, employing a series of increasingly fine anisotropic meshes. As expected, the memory consumption increases dramatically with the considered problem size for the direct solver. Surprisingly, however, the computation times remain reasonable. The speed and memory usage of pointwise algebraic and smoothed aggregation multigrid solvers are found to exhibit near-linear scaling. As an alternative to multi-level solvers, a single-level ILUT-preconditioned GMRES solver with low drop tolerance is also considered. This solver is found to perform sufficiently well only on small meshes. Even then, it is outperformed by pointwise algebraic multigrid on all counts. Finally, the effectiveness of pointwise algebraic multigrid is illustrated by considering a large three-dimensional direct numerical simulation case using a novel parallelization approach on a large distributed memory computing cluster.     

Developments in shoulder arthroplasty

Indications for shoulder arthroplasty are numerous, mainly owing to glenohumeral osteoarthritis, rheumatoid arthritis, or fracture of the proximal humerus. However, the anatomy and the biomechanics of the shoulder are complex and shoulder arthroplasty has evolved significantly over the past 30 years. This paper presents the main recent evolutions in shoulder replacement, the questions not answered yet, and the main future areas of research. The review focuses firstly on the design, positioning, and fixation of the humeral component, secondly on the design, positioning, and fixation of the glenoid implant, and thirdly on other concepts of shoulder arthroplasty such as the reversed prosthesis, the cementless surface replacement arthroplasty, and the bipolar arthroplasty. This review demonstrates that more research is needed. Although, in the long term, large randomized trials are needed to settle the fundamental questions of what type of replacement and which kind of fixation should be used, biomechanical research in the laboratory should be focused primarily on the comprehension of glenoid loosening, which is a major cause of total shoulder arthroplasty failure, and the significance of radiolucent lines which are often seen but with no clear understanding about their relation with failure.     

Simulated train driving: fatigue, self-awareness and cognitive disengagement

Fatigue is a serious issue for the rail industry, increasing inefficiency and accident risk. The performance of 20 train drivers in a rail simulator was investigated at low, moderate and high fatigue levels. Psychomotor vigilance (PVT), self-rated performance and subjective alertness were also assessed. Alertness, PVT reaction times, extreme speed violations (>25% above the limit) and penalty brake applications increased with increasing fatigue level. In contrast, fuel use, draft (stretch) forces and braking errors were highest at moderate fatigue levels. Thus, at high fatigue levels, errors involving a failure to act (errors of omission) increased, whereas incorrect responses (errors of commission) decreased. The differential effect of fatigue on error types can be explained through a cognitive disengagement with the virtual train at high fatigue levels. Interaction with the train reduced dramatically, and accident risk increased. Awareness of fatigue-related performance changes was moderate at best. These findings are of operational concern.     

Stability ball versus office chair: comparison of muscle activation and lumbar spine posture during prolonged sitting

OBJECTIVE: The objective of the study was to evaluate the differences between sitting on a stability ball and in an office chair in terms of trunk muscle activation and lumbar spine posture. BACKGROUND: Stability balls have become increasingly popular as an alternative to office chairs to help reduce the prevalence of low back pain; however, little research has been conducted on their use as office chairs. METHODS: The 14 participants (7 men, 7 women) were required to sit on both a stability ball and an office chair for 1 hour each while performing various computer workstation tasks throughout the sitting periods. The activation of eight muscles and lumbar spine posture were measured and analyzed. RESULTS: Increased muscle activation in thoracic erector spinae (p = .0352), decreased pelvic tilt (p = .0114), and increased perceived discomfort (p < .0001) while sitting on the stability ball were observed. CONCLUSIONS: The small changes in biological responses when sitting on a stability ball as compared with an office chair, combined with the increased reported discomfort while on the ball, suggests its use for prolonged sitting may not be advantageous. APPLICATION: Prolonged sitting on a stability ball does not greatly alter the manner in which an individual sits, yet it appears to increase the level of discomfort. Therefore, it is important to fully explore a new chair design and consult scientific research before implementing its use.     

High-temperature superconducting microwave devices: Fundamental issues in materials, physics, and engineering

High-T _c superconductivity has generated a great deal of interest because of the challenges it presents in the fields of material science, condensed matter physics, and electrical engineering, and because of the potential applications which may result from these research efforts. Thin-film passive microwave components may become the first high-temperature superconducting (HTS) devices available for widespread use and commercialization. In this article, we review aspects of material science, physics, and engineering which directly impact high-T _c superconducting microwave devices and discuss issues which determine the performance of these devices. Methods of growing HTS thin films on large-area substrates, techniques for fabricating single-level HTS passive microwave components, and the relevant properties of high-T _c superconducting films are discussed, with a focus on thin films of the HTS material YBa₂Cu₃O_7–. Several known mechanisms for microwave loss in both the superconductor and the dielectric substrate are presented. An overview of the general classes of superconducting passive microwave devices is given, and representative microwave devices which have been recently demonstrated are described in detail. Examples of a select few HTS active microwave components are also presented. Potential microwave applications are illustrated with comparisons to current technology.     

"Publishing opinions: A note on the usefulness of commentaries": Comment.

Comments on J. J. Christensen-Szalanski and L. R. Beach's (see record 1984-21471-001) conclusion that the attention given to commentaries and replies to articles did not justify the extra space and argues that citation indexes do not measure the major usefulness of these commentaries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficient simulated annealing on fractal energy landscapes

We present a new theoretical framework for analyzing simulated annealing. The behavior of simulated annealing depends crucially on the ldergy landscape associated with the optimization problem: the landscape must have special properties if annealing is to be efficient.We prove that certain fractal properties are sufficient for simulated annealing to be efficient in the following sense: If a problem is scaled to have best solutions of energy 0 and worst solutions of energy 1, a solution of expected energy no more than can be found in time polynomial in 1/, where the exponent of the polynomial depends on certain parameters of the fractal. Higher-dimensional versions of the problem can be solved with almost identical efficiency.The cooling schedule used to achieve this result is the familiar geometric schedule of annealing practice, rather than the logarithmic schedule of previous theory. Our analysis is more realistic than those of previous studies of annealing in the constraints we place on the problem space and the conclusions we draw about annealing's performance.The mode of analysis is also new: Annealing is modeled as a random walk on a graph, and recent theorems relating the conductance of a graph to the mixing rate of its associated Markov chain generate both a new conceptual approach to annealing and new analytical, quantitative methods.The efficiency of annealing is compared with that of random sampling and descent algorithms. While these algorithms are more efficient for some fractals, their run times increase exponentially with the number of dimensions, making annealing better for problems of high dimensionality.We find that a number of circuit placement problems have energy landscapes with fractal properties, thus giving for the first time a reasonable explanation of the successful application of simulated annealing to problems in the VLSI domain.This work was done while the author was on leave from IBM Research, and was also sponsored by DARPA and monitored by SNWSC under contract numbers N00039-87-C-0182 and N00039-88-C-0292. The author is completing his doctoral studies with Prof. Alberto Sangiovanni-Vincentelli. He is on leave from the I.B.M. Thomas J. Watson Research Center.     

“Erosion Control on Surface Mined Watersheds: a Modelling Approach”

ABSTRACT

This article describes the efforts of the Mexican government toward more efficient management of water resources. Inaccordance with the Mexican Constitution, municipal governments have been responsible for urban water and sanitation services. However; in practice most municipalities have weak finances and little expertise in managing water systems and the federal government still plays an important role in the management and financing of water infrastructure.

The article highlights the current state of the water sector in Mexico, including some of the main aspects of the legal and institutionalframework. It discusses the main difficulties faced by the municipalities in accomplishing their task. The strategy of the federal government, in order to achieve better urban water management, has focused on four main policies: changes in the legal and institutional framework for water management, further decentralization, new financing schemes, and greater private sector involvement. It concludes that flexible approaches should allow municipalities to find appropriate institutional, financial, and technical solutions.