Seismic Analysis Capability in NASTRAN

Seismic analysis is a technique which pertains to loading described in terms of boundary accelerations. Earthquake shocks to buildings is the type of excitation which usually comes to mind when one hears the word seismic, but this technique also applied to a broad class of acceleration excitations which are applied at the base of a structure such as vibration shaker testing or shocks to machinery foundations. Four different solution paths are available in NASTRAN for seismic analysis. They are: Direct Seismic Frequency Response, Direct Seismic Transient Response, Modal Seismic Frequency Response, and Modal Seismic Transient Response. This capability, at present, is invoked not as separate rigid formats, but as pre-packaged ALTER packets to existing RIGID Formats 8, 9, 11, and 12. These ALTER packets are included with the delivery of the NASTRAN program and are stored on the computer as a library of callable utilities. The user calls one of these utilities and merges it into the Executive Control Section of the data deck to perform any of the four options are invoked by setting parameter values in the bulk data

Statistics of Pressure Fluctuations in Decaying, Isotropic Turbulence

We present results from a systematic direct-numerical simulation study of pressure fluctuations in an unforced, incompressible, homogeneous, and isotropic, three-dimensional turbulent fluid. At cascade completion, isosurfaces of low pressure are found to be organised as slender filaments, whereas the predominant isostructures appear sheet-like. We exhibit several new results, including plots of probability distributions of the spatial pressure-difference, the pressure-gradient norm, and the eigenvalues of the pressure-hessian tensor. Plots of the temporal evolution of the mean pressure-gradient norm, and the mean eigenvalues of the pressure-hessian tensor are also exhibited. We find the statistically preferred orientations between the eigenvectors of the pressure-hessian tensor, the pressure-gradient, the eigenvectors of the strain-rate tensor, the vorticity, and the velocity. Statistical properties of the non-local part of the pressure-hessian tensor are also exhibited, for the first time. We present numerical tests (in the viscous case) of some conjectures of Ohkitani [Phys. Fluids A {\bf 5}, 2570 (1993)] and Ohkitani and Kishiba [Phys. Fluids {\bf 7}, 411 (1995)] concerning the pressure-hessian and the strain-rate tensors, for the unforced, incompressible, three-dimensional Euler equations.Comment: 10 pages, 29 figures, Accepted for publication in Physical Review

BRAIN AND BEHAVIOUR IN BUMBLEBEES (BOMBUS IMPATIENS): SERIAL REVERSAL LEARNING AND ADULT MUSHROOM BODY DEVELOPMENT

This thesis explores learning in bumblebees (Bombus impatiens) and its relation to foraging and development of the mushroom bodies of the bee brain. The first experiment describes the performance of bees on a serial reversal task. Reversal learning requires animals to change their behavior with changes in reward contingencies and is a measure of behavioural flexibility. Results show that bumblebees are capable of improving in a serial reversal task. The second experiment explores the effects of foraging experience on bumblebee mushroom bodies. Mushroom body volume was compared in bees confined to the colony, bees actively foraging, and bees tested on the serial reversal task. In both experiments, bees were housed in simulated foraging environments differing in complexity, to determine the effect of environmental complexity on learning and brain development. The second experiment found no effect of foraging, learning experience or environmental complexity on mushroom body volume

A reconfigurable real-time morphological system for augmented vision

There is a significant number of visually impaired individuals who suffer sensitivity loss to high spatial frequencies, for whom current optical devices are limited in degree of visual aid and practical application. Digital image and video processing offers a variety of effective visual enhancement methods that can be utilised to obtain a practical augmented vision head-mounted display device. The high spatial frequencies of an image can be extracted by edge detection techniques and overlaid on top of the original image to improve visual perception among the visually impaired. Augmented visual aid devices require highly user-customisable algorithm designs for subjective configuration per task, where current digital image processing visual aids offer very little user-configurable options. This paper presents a highly user-reconfigurable morphological edge enhancement system on field-programmable gate array, where the morphological, internal and external edge gradients can be selected from the presented architecture with specified edge thickness and magnitude. In addition, the morphology architecture supports reconfigurable shape structuring elements and configurable morphological operations. The proposed morphology-based visual enhancement system introduces a high degree of user flexibility in addition to meeting real-time constraints capable of obtaining 93 fps for high-definition image resolution

Recognizing Potential Cyberspace Warriors through the Use of Suspicion Propensity Index

The Air Force currently suffers from excessively high attrition rates in the cyberspace career. The field is currently aiming to develop an entrance examination for the career, striving to improve personnel selection and decrease these high attrition rates. The attribute of suspicion is a key focus of the preliminary examination development, theorizing that it is a potential indicator present among competent cyber operators. This research makes use of the Suspicion Propensity Index (SPI), a reliable measure of one’s tendency to be suspicious, along with the highly cited Mayer’s trust questionnaire in order to compare the attributes that appear in successful cyberspace individuals compared to those with no cyber experience. These measures are analyzed in comparison to a cyber mission performance questionnaire, adapted to assess each participant’s cyberspace capabilities. The three aforementioned questionnaires were distributed to two distinct populations: a group of experienced cyber operators averaging 22.8 years in the career field and a group of Airmen from various career fields with no prior cyber experience. The research yields evidence that suspicion levels are significantly correlated to cyber mission performance scores among both the cyber and non-cyber populations, with cyber operators demonstrating higher overall levels of suspicion than those of non-cyber operators. Years of experience displays a more prominent effect on the suspicion levels of cyber personnel, with the non-cyber sample population displaying more constant levels of suspicion despite time in the Air Force. This evidence suggests that cyber operators gain suspicion over time in comparison to their non-cyber counterparts. The trust questionnaire scores were significantly correlated to SPI scores. However, results of the trust questionnaire do not appear to provide a prediction of cyber mission performance

Statistical correlation analysis for comparing vibration data from test and analysis

A theory was developed to compare vibration modes obtained by NASTRAN analysis with those obtained experimentally. Because many more analytical modes can be obtained than experimental modes, the analytical set was treated as expansion functions for putting both sources in comparative form. The dimensional symmetry was developed for three general cases: nonsymmetric whole model compared with a nonsymmetric whole structural test, symmetric analytical portion compared with a symmetric experimental portion, and analytical symmetric portion with a whole experimental test. The theory was coded and a statistical correlation program was installed as a utility. The theory is established with small classical structures

Data-driven pattern identification and outlier detection in time series

We address the problem of data-driven pattern identification and outlier detection in time series. To this end, we use singular value decomposition (SVD) which is a well-known technique to compute a low-rank approximation for an arbitrary matrix. By recasting the time series as a matrix it becomes possible to use SVD to highlight the underlying patterns and periodicities. This is done without the need for specifying user-defined parameters. From a data mining perspective, this opens up new ways of analyzing time series in a data-driven, bottom-up fashion. However, in order to get correct results, it is important to understand how the SVD-spectrum of a time series is influenced by various characteristics of the underlying signal and noise. In this paper, we have extended the work in earlier papers by initiating a more systematic analysis of these effects. We then illustrate our findings on some real-life data

Contrasting styles in cognition and behaviour in bumblebees and honeybees.

Bumblebees and honeybees have been the subjects of a great deal of recent research in animal cognition. Many of the major topics in cognition, including memory, attention, concept learning, numerosity, spatial cognition, timing, social learning, and metacognition have been examined in bumblebees, honeybees, or both. Although bumblebees and honeybees are very closely related, they also differ in important ways, including social organization, development, and foraging behaviour. We examine whether differences between bumblebees and honeybees in cognitive processes are related to differences in their natural history and behaviour. There are differences in some cognitive traits, such as serial reversal learning and matching-to-sample, that appear related to differences between bumblebees and honeybees in foraging and social behaviour. Other cognitive processes, such as numerosity, appear to be very similar. Despite the wealth of information that is available on some aspects of bumblebee and honeybee cognition and behaviour, there are relatively few instances, however, in which adequate data exist to make direct comparisons. We highlight a number of phenomena, including concept learning, spatial cognition, timing, and metacognition, for which targeted comparative research may reveal unexpected adaptive variation in cognitive processes in these complex animals. This article is part of a Special Issue entitled: In Honor of Jerry Hogan