Optimization of conventional spinning process parameters by means of numerical simulation and statistical analysis

Research in sheet metal spinning has increased due to a greater demand, especially in the transportation industries, for parts with very high strength-to-weight ratios with low cost. Spinning processes are efficient in producing such characteristics and there is great flexibility in the process with a relatively low tool cost. The objectives of this investigation are to define the critical working parameters in spinning, show the effects of these factors on product quality characteristics, and to optimize the working parameters. The example used is the conventional spinning of a cylindrical cup. Optimization of the process is undertaken through the use of statistical analysis tools applied to the data produced from three-dimensional finite element simulations of the process. This has been achieved by generating two ‘designs of experiments’.The first identifies the most critical parameters for product formability and the second shows how these critical parameters affect the product quality. The results show that feed rate,relative clearance, and roller nose radius are the most important working parameters and significantly affect average thickness, thickness variation, and springback of the cylindrical cup. An additional 22 per cent improvement in the product quality characteristic is gained through using the optimum working parameters

Experimental demonstration of the antiherbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates

The impact of plant-based factors on the population dynamics of mammalian herbivores has been the subject of much debate in ecology, but the role of antiherbivore defences in grasses has received relatively little attention. Silica has been proposed as the primary defence in grasses and is thought to lead to increased abrasiveness of foliage so deterring feeding, as well as reducing foliage digestibility and herbivore performance. However, at present there is little direct experimental evidence to support these ideas. In this study, we tested the effects of manipulating silica levels on the abrasiveness of grasses and on the feeding preference and growth performance of field voles, specialist grass-feeding herbivores. Elevated silica levels did increase the abrasiveness of grasses and deterred feeding by voles. We also demonstrated, for the first time, that silica reduced the growth rates of both juvenile and mature female voles by reducing the nitrogen they could absorb from the foliage. Furthermore, we found that vole feeding leads to increased levels of silica in leaves, suggesting a dynamic feedback between grasses and their herbivores. We propose that silica induction due to vole grazing reduces vole performance and hence could contribute to cyclic dynamics in vole populations

Evaluation of off-road terrain with static stereo and monoscopic displays

The National Aeronautics and Space Administration is currently funding research into the design of a Mars rover vehicle. This unmanned rover will be used to explore a number of scientific and geologic sites on the Martian surface. Since the rover can not be driven from Earth in real-time, due to lengthy communication time delays, a locomotion strategy that optimizes vehicle range and minimizes potential risk must be developed. In order to assess the degree of on-board artificial intelligence (AI) required for a rover to carry out its' mission, researchers conducted an experiment to define a no AI baseline. In the experiment 24 subjects, divided into stereo and monoscopic groups, were shown video snapshots of four terrain scenes. The subjects' task was to choose a suitable path for the vehicle through each of the four scenes. Paths were scored based on distance travelled and hazard avoidance. Study results are presented with respect to: (1) risk versus range; (2) stereo versus monocular video; (3) vehicle camera height; and (4) camera field-of-view

Moments of inertia of several airplanes

This paper, which is the first of a series presenting the results of such measurements, gives the momental ellipsoids of ten army and naval biplanes and one commercial monoplane. The data were obtained by the use of a pendulum method, previously described. The moments of inertia are expressed in coefficient as well as in dimensional form, so that those for airplanes of widely different weights and dimensions can be compared

Grasses and the resource availability hypothesis: the importance of silica-based defences

The resource availability hypothesis (RAH) predicts that allocation of resources to anti-herbivore defences differs between species according to their growth rate. We tested this hypothesis by assessing the growth and defence investment strategies of 18 grass species and comparing them against vole feeding preferences. In addition, we assessed the effectiveness of silica, the primary defence in many grasses, in influencing vole feeding behaviour. Across species, we found that there was a strong negative relationship between the overall investment in defence and growth rate, thus supporting predictions of the RAH. However, no such relationship was found when assessing the various individual anti-herbivore defences, suggesting that different grass species show significant variation in their relative investment in strategies such as phenolic concentration, silica concentration and leaf toughness. Silica was the most influential defensive factor in determining vole feeding preference. Experimentally induced increases in leaf silica concentration deterred vole feeding in three of the five species tested, and altered feeding preference ranks between species. The strong positive relationship between silica concentration and leaf abrasiveness, when assessed both within and between species, suggests that increased abrasiveness is the mechanism by which silica deters feeding. Although grasses are often considered to be tolerant of herbivore damage rather then defended against it, they do follow predictions of defence allocation strategy based on their growth rates, and this affects the feeding behaviour of generalist grass-feeding herbivores

Normal frames for non-Riemannian connections

The principal properties of geodesic normal coordinates are the vanishing of the connection components and first derivatives of the metric components at some point. It is well-known that these hold only at points where the connection has vanishing torsion and non-metricity. However, it is shown that normal frames, possessing the essential features of normal coordinates, can still be constructed when the connection is non-Riemannian.Comment: 4 pages, plain TeX. To appear in Class. Quantum Gra

Why Do Granular Materials Stiffen with Shear Rate? : Test of Novel Stress-Based Statistics

Peer reviewedPublisher PD

Support Vector Machine classification of strong gravitational lenses

The imminent advent of very large-scale optical sky surveys, such as Euclid and LSST, makes it important to find efficient ways of discovering rare objects such as strong gravitational lens systems, where a background object is multiply gravitationally imaged by a foreground mass. As well as finding the lens systems, it is important to reject false positives due to intrinsic structure in galaxies, and much work is in progress with machine learning algorithms such as neural networks in order to achieve both these aims. We present and discuss a Support Vector Machine (SVM) algorithm which makes use of a Gabor filterbank in order to provide learning criteria for separation of lenses and non-lenses, and demonstrate using blind challenges that under certain circumstances it is a particularly efficient algorithm for rejecting false positives. We compare the SVM engine with a large-scale human examination of 100000 simulated lenses in a challenge dataset, and also apply the SVM method to survey images from the Kilo-Degree Survey.Comment: Accepted by MNRA