A failsafe analysis using NASTRAN's piecewise linear analysis and a nine node linear crack element

A two-dimensional crack element was implemented into NASTRAN as a user dummy element and used to study failsafe characteristics of the C5A fuselage. The element is formulated from Reitsner's functional requiring that it satisfy compatability with the linear boundary displacement elements in NASTRAN. Its accuracy is demonstrated by analyzing for the stress intensity factors of two simple crack configurations for which there are classic solutions

Research study on high energy radiation effect and environment solar cell degradation methods

The most detailed and comprehensively verified analytical model was used to evaluate the effects of simplifying assumptions on the accuracy of predictions made by the external damage coefficient method. It was found that the most serious discrepancies were present in heavily damaged cells, particularly proton damaged cells, in which a gradient in damage across the cell existed. In general, it was found that the current damage coefficient method tends to underestimate damage at high fluences. An exception to this rule was thick cover-slipped cells experiencing heavy degradation due to omnidirectional electrons. In such cases, the damage coefficient method overestimates the damage. Comparisons of degradation predictions made by the two methods and measured flight data confirmed the above findings

NASTRAN used in a production environment

A finite element analysis procedure built around the NASTRAN system is assessed. A number of support programs that were either written or modified to interface with NASTRAN and some improvements that were made to NASTRAN itself are noted. Some typical models are analyzed and an actual schedule is followed for constructing and analyzing the models to support a large design program

Accurate Reaction-Diffusion Operator Splitting on Tetrahedral Meshes for Parallel Stochastic Molecular Simulations

Spatial stochastic molecular simulations in biology are limited by the intense computation required to track molecules in space either in a discrete time or discrete space framework, meaning that the serial limit has already been reached in sub-cellular models. This calls for parallel simulations that can take advantage of the power of modern supercomputers; however exact methods are known to be inherently serial. We introduce an operator splitting implementation for irregular grids with a novel method to improve accuracy, and demonstrate potential for scalable parallel simulations in an initial MPI version. We foresee that this groundwork will enable larger scale, whole-cell stochastic simulations in the near future.Comment: 33 pages, 10 figure

Frequency-sweep examination for wave mode identification in multimodal ultrasonic guided wave signal

This article has been made available through the Brunel Open Access Publishing Fund.Ultrasonic guided waves can be used to assess and monitor long elements of a structure from a single position. The greatest challenges for any guided wave system are the plethora of wave modes arising from the geometry of the structural element which propagate with a range of frequency-dependent velocities and the interpretation of these combined signals reflected by discontinuities in the structural element. In this paper, a novel signal processing technique is presented using a combination of frequency-sweep measurement, sampling rate conversion, and Fourier transform. The technique is applied to synthesized and experimental data to identify different modes in complex ultrasonic guided wave signals. It is demonstrated throughout the paper that the technique also has the capability to derive the time of flight and group velocity dispersion curve of different wave modes in field inspections. © 2014 IEEE

ARCS, The Arcminute Radio Cluster-lens Search - I. Selection Criteria and Initial Results

We present the results of an unbiased radio search for gravitational lensing events with image separations between 15 and 60 arcsec, which would be associated with clusters of galaxies with masses >10^{13-14}M_{\sun}. A parent population of 1023 extended radio sources stronger than 35 mJy with stellar optical identifications was selected using the FIRST radio catalogue at 1.4 GHz and the APM optical catalogue. The FIRST catalogue was then searched for companions to the parent sources stronger than 7 mJy and with separation in the range 15 to 60 arcsec. Higher resolution observations of the resulting 38 lens candidates were made with the VLA at 1.4 GHz and 5 GHz, and with MERLIN at 5 GHz in order to test the lens hypothesis in each case. None of our targets was found to be a gravitational lens system. These results provide the best current constraint on the lensing rate for this angular scale, but improved calculations of lensing rates from realistic simulations of the clustering of matter on the relevant scales are required before cosmologically significant constraints can be derived from this null result. We now have an efficient, tested observational strategy with which it will be possible to make an order-of-magnitude larger unbiased search in the near future.Comment: Accepted for publication in MNRAS. 12 pages, 29 included PostScript figure

L’impact d’une zone de libre-échange entre le Canada et les États-Unis : examen critique de l’étude de Wonnacott

The Wonnacott study concludes that the most realistic and beneficial commercial policy Canada is likely to be able to pursue at the moment would be to negotiate a Canada-U.S. free trade arrangement. This paper consist primarily of assigning different weights to a variety of the considerations Wonnacott raises and analyzing the effects of these different weights on his conclusions regarding the appropriate free trade strategy for Canada. A number of issues are also raised which do not appear to have been examined in Wonnacott's analysis. The thrust of the paper is three-fold. First, there may not be as large a net economic benefits of Canada-United States free trade as the Wonnacott presentation suggests. Second, depending upon the weight one assigns to some of the political-economic factors, the advantages of the former policy may be reduced even more and accordingly we should not be stampeded into a bilateral Canada-United States agreement. And third, if any change in commercial policy is to have a maximum beneficial effect upon Canada, then regardless of what commercial policy is followed, more attention will have to be given to a number of broader issues such as Canadian practices and policies relating to its overall balance of payments (including capital inflows and their effects upon the Canadian dollar), and to protectionnist provincial policies encouraging the fragmentation of industry

Study of radiation hazards to man on extended near earth missions

Radiation hazards to man on extended near earth mission