Error detection and control for nonlinear shell analysis

A problem-adaptive solution procedure for improving the reliability of finite element solutions to geometrically nonlinear shell-type problem is presented. The strategy incorporates automatic error detection and control and includes an iterative procedure which utilizes the solution at the same load step on a more refined model. Representative nonlinear shell problem are solved

Density-Dependent Convective Flow in Closed Basins

The Great Basin is a region of the Basin and Range Physiographic Province, which is completely isolated hydrologically from the sea. All precipitation that falls within the Great Basin is lost from the land surface or from the surf ace of closed inland lakes through evapotranspiration. Playas are often found at the base of these undrained basins. This study focuses on subsurface groundwater flow patterns in closed basins. Because all discharge from the basins occurs via evapotranspiration on and near the playa, the water table of the aquifer beneath the playa is often just below the ground surface. Fluctuations of the water table due to climatic events cause the water table to rise and dissolve the salts on the playa surface. This mass transfer can produce density gradients that in turn cause flow. This study is an extension of the work performed by Duffy and Al-Hassan (Duffy and Al-Hassan 1988) in which numerical experiments were used to show that the free convection, caused by the variation in density of the bulk fluid propenies, appears to play an important role in determining the patterns of groundwater flow beneath the playa. Their work considered only homogeneous, isotropic porous media in symmetric basins. The effects of anisotropy, periodic stratification, and asymmetric basins on the groundwater flow and transport patterns was studied here. Dimensionless parameters, the Rayleigh number and the salt nose length, L0*, were defined for each of the systems incorporated and were shown to be linearly related. The implication of this relationship is that the Rayleigh number can be used to predict basin-scale circulation patterns in the hypothetical closed basins studied. It was also determined that an equivalent anisotropic system could be defined for a horizontally stratified aquifer in order to predict basin-scale circulation patterns. An equivalent isotropic system was defined for each anisotropic system in a similar manner

A Content Analysis of Public School Education News in an Independently Owned Small Daily Newspaper

Newspapers and school districts form a tentative partnership in the dissemination of education news. Subjects preferred by readers have not been reflected in actual education news coverage. Emphasis on utility information at the expense of in-depth writing about what is going on in public education has been standard practice. Content analysis shows that while quantity of education news seems reasonable, the quality of that news fails to transmit to readers the substance of what teachers and children are accomplishing in the public schools

Nature’s Eden? The Production and Effects of ‘Pristine’ Nature in the Galápagos Islands

Best known for inspiring Charles Darwin's theory of evolution, the Galápagos Islands are often referred to as an “evolutionary Eden” and celebrated as one of the world’s few remaining bastions of “pristine” nature. However, recent concerns of a crisis of over-development prompted UNESCO to put the Galápagos on its list of World Heritage Sites “In Danger.” In this paper, we interrogate the conception of pristine nature which undergirds the recent crisis discourse and argue that such understandings of nature are not in fact natural, but are social productions that reflect particular ways of understanding island space. We then explore the material and political effects of understandings of “pristine” nature by showing how they work to structure the tourism industry and investment in public infrastructure in ways that have created social inequalities as well as negative environmental impacts. We then briefly discuss measures taken so far to address the crisis situation, arguing that they would benefit from critical attention to the complexity of social-environmental relations in the Galápagos and a re-thinking of the nature of the islands

Computational methods for global/local analysis

Computational methods for global/local analysis of structures which include both uncoupled and coupled methods are described. In addition, global/local analysis methodology for automatic refinement of incompatible global and local finite element models is developed. Representative structural analysis problems are presented to demonstrate the global/local analysis methods

Large-scale structural analysis: The structural analyst, the CSM Testbed and the NAS System

The Computational Structural Mechanics (CSM) activity is developing advanced structural analysis and computational methods that exploit high-performance computers. Methods are developed in the framework of the CSM testbed software system and applied to representative complex structural analysis problems from the aerospace industry. An overview of the CSM testbed methods development environment is presented and some numerical methods developed on a CRAY-2 are described. Selected application studies performed on the NAS CRAY-2 are also summarized

Digitally-produced image comparison of three, 90 diopter-equivalent lenses: Subjective and objective findings

Purpose: To evaluate the image quality of retinal structures as obtained by three high plus lenses manufactured by the Yolk company to determine if any of the lens types provided a better quality of digital image. Methods: Digital images of two different patients\u27 left and right optic nerve heads (ONH) and left and right maculae (MAC) were obtained with three high plus lenses in conjunction with a biomicroscope. One of each of the following three lenses were used during the study: 90 Diopter Classic (90D), Super Field (SF) and Digital Wide Field (DWF). A total of 10 optometric physicians, who were faculty of an accredited school of optometry at the time of the study, were then asked to view 30 pairs of simultaneously presented photographs and select the image of higher quality. The paired photographs consisted of images of either the same optic nerve head or same macula of the one specific patient, as taken with two different lenses. Three sets of identical images were randomly presented to screen for left- or righthandedness. The digital images were also evaluated by Adobe Photoshop for color and luminosity values within a defined area. Results: Objective results showed that there was no statistically significant difference between mean color and luminosity of the ONH and MAC images as produced by the 90D, SF and DWF lenses: p = 0.542, p = 0.587, p = 0.232 and p = 0.186. Subjective results were statistically significant for selecting the 90D lens as producing the better ONH image quality 1 (p == 0.041). While not statistically significant (p == 0.165), the subjects followed a similar trend in choosing the 90D lens as having better quality of the MAC images. Conclusions: The 90D lens appears to produce subjectively better quality in digital images of the posterior pole

A generic interface element for COMET-AR

The implementation of an interface element capability within the COMET-AR software system is described. The report is intended for use by both users of currently implemented interface elements and developers of new interface element formulations. Guidance on the use of COMET-AR is given. A glossary is provided as an Appendix to this report for readers unfamiliar with the jargon of COMET-AR. A summary of the currently implemented interface element formulation is presented in Section 7.3 of this report

CSM Testbed Development and Large-Scale Structural Applications

A research activity called Computational Structural Mechanics (CSM) conducted at the NASA Langley Research Center is described. This activity is developing advanced structural analysis and computational methods that exploit high-performance computers. Methods are developed in the framework of the CSM Testbed software system and applied to representative complex structural analysis problems from the aerospace industry. An overview of the CSM Testbed methods development environment is presented and some new numerical methods developed on a CRAY-2 are described. Selected application studies performed on the NAS CRAY-2 are also summarized