Multi-channel active noise cancellation using the DSP56001 (digital signal processor)

The authors report on the performance of a portable active noise cancellation (ANC) system based around a PC hosted 20-MHz Motorola DSP56001 processor with a four-channel analog input/output (I/O) board connected to the real world via standard consumer audio components. The system will perform active noise cancellation over the frequency range of 65-500 Hz. Quantitative results are presented for the cancellation of single tone noise and of narrowband noise, and a measure of the ANC power spectrum is calculated for various parameters of the filtered-X LMS algorithm in different acoustic environments. Qualitative results based on human hearing perception of the attenuation of various narrowband and real world noise sources are also discussed

Gross plastic deformation of axisymmetric pressure vessel heads

The gross plastic deformation and associated plastic loads of four axisymmetric torispherical pressure vessels are determined by two criteria of plastic collapse: the ASME twice elastic slope (TES) criterion and the recently proposed plastic work curvature (PWC) criterion. Finite element analysis was performed assuming small and large deformation theory and elastic–perfectly plastic and bilinear kinematic hardening material models. Two plastic collapse modes are identified: bending-dominated plastic collapse of the knuckle region in small deformation models and membrane-dominated plastic collapse of the cylinder or domed end in large deformation models. In both circumstances, the PWC criterion indicates that a plastic hinge bending mechanism leads to gross plastic deformation and is used as a parameter to identify the respective plastic loads. The results of the analyses also show that the PWC criterion leads to higher design loads for strain hardening structures than the TES criterion, as it takes account of the effect of strain hardening on the evolution of the gross plastic deformation mechanism

Design by analysis of ductile failure and buckling in torispherical pressure vessel heads

Thin shell torispherical pressure vessel heads are known to exhibit complex elastic-plastic deformation and buckling behaviour under static pressure. In pressure vessel Design by Analysis, the designer is required to assess both of these behaviour modes when specifying the allowable static load. The EN and ASME boiler and pressure vessel codes permit the use of inelastic analysis in design by analysis, known as the direct route in the EN Code. In this paper, plastic collapse or gross plastic deformation loads are evaluated for two sample torispherical heads by 2D and 3D FEA based on an elastic-perfectly plastic material model. Small and large deformation effects are considered in the 2D analyses and the effect of geometry and load perturbation are considered in the 3D analysis. The plastic load is determined by applying the ASME twice elastic slope criterion of plastic collapse and an alternative plastic criterion, the Plastic Work Curvature criterion. The formation of the gross plastic deformation mechanism in the models is considered in relation to the elastic-plastic buckling response of the vessels. It is concluded that in both cases, design is limited by formation of an axisymmetric gross plastic deformation in the knuckle of the vessels prior to formation of non-axisymmetric buckling modes

Drug interactions with lipid membranes: the effects of drug and lipid structure upon rates of ester hydrolysis

The transport of compounds around the body has been a topic of interest for many years, and the advent of non-invasive biological imaging in living tissue has made huge advances in the characterisation and localisation of cellular receptors for use in drug targeting. However, there remains a significant paucity of knowledge regarding how the majority of drug molecules are transported about the body, when they often exhibit negligible aqueous solubility and the body expresses no trans-membrane pumps or chaperone proteins that recognise them and facilitate their movement. This leads to large attrition rates in drug discovery programmes, as compounds with high binding constants or inhibitive activity in vitro fail to perform in vivo, due to poor bioavailability or non-specific sequestration away from the tissue of interest. In this study, the interactions between a number of drug and lipid molecules were investigated and the effects upon both the lipids’ chemical and bulk membrane structures were analysed. This revealed some of the mechanistic causes of the previously observed hydrolytic activity a number of common drug compounds exhibit toward lipid membranes and identified parameters affecting the observed rates of reaction. The findings also suggest approaches by which this behaviour might be predicted, or even tuned to deliver optimum pharmacological characteristics

The Age, Metallicity and Alpha-Element Abundance of Galactic Globular Clusters from Single Stellar Population Models

Establishing the reliability with which stellar population parameters can be measured is vital to extragalactic astronomy. Galactic GCs provide an excellent medium in which to test the consistency of Single Stellar Population (SSP) models as they should be our best analogue to a homogeneous (single) stellar population. Here we present age, metallicity and $\alpha$-element abundance measurements for 48 Galactic globular clusters (GCs) as determined from integrated spectra using Lick indices and SSP models from Thomas, Maraston & Korn, Lee & Worthey and Vazdekis et al. By comparing our new measurements to independent determinations we are able to assess the ability of these SSPs to derive consistent results -- a key requirement before application to heterogeneous stellar populations like galaxies. We find that metallicity determinations are extremely robust, showing good agreement for all models examined here, including a range of enhancement methods. Ages and $\alpha$-element abundances are accurate for a subset of our models, with the caveat that the range of these parameters in Galactic GCs is limited. We are able to show that the application of published Lick index response functions to models with fixed abundance ratios allows us to measure reasonable $\alpha$-element abundances from a variety of models. We also examine the age-metallicity and [$\alpha$/Fe]-metallicity relations predicted by SSP models, and characterise the possible effects of varied model horizontal branch morphology on our overall results.Comment: 22 pages, 19 figures, accepted for publication in MNRA

1991 DA: An asteroid in a bizarre orbit

Asteroidal object 1991 DA has an orbit of high inclination, crossing the planets from Mars to Uranus. This is unique for an asteroid, but not unusual for a comet of the Halley-type: it therefore seems likely that 1991 DA is an extinct or dormant comet. Previous CCD imaging has shown no indication of a coma; spectroscopic observations of 1991 DA which lack any evidence of strong comet-like emissions are reported. Numerical integrations of the orbit of this object were performed which show that is has been remarkably stable for the past approximately 20,000 yr, but chaotic before that. This may allow a new estimate to be made of the physical lifetimes of comets

Homonymy and the Comparability of Goods in Aristotle

My dissertation will draw attention to an underexplored problem in Aristotle\u27s theory of the good and advance two alternative proposals about how it can be solved. Aristotle endorses an inconsistent triad of premises concerning homonymy, comparability, and goodness. First, he argues that the good is homonymous: there is no single characteristic, goodness, which is shared by all good things. Rather, he argues that different kinds of good things require different accounts specifying what it is for them to be good. Second, he holds that homonyms are incomparable. If two things are homonymously F, then we are not entitled to claim that one is more F than the other, or that they are F to an equal degree. The incomparability of homonyms entails, for example, that if two goods are homonymous, we cannot claim that that one is better than the other or that they are equally valuable. Finally, however, Aristotle holds that goods typically are comparable. Indeed, several passages throughout corpus suggest that he thinks of the cosmos as an axiological hierarchy in which every being can be ranked on a single scale of better and worse.This inconsistent triad constitutes a seldom recognized problem for Aristotle\u27s theory of the good which I call the incomparability problem. In the dissertation, I clarify the shape of the incomparability problem, explore the conceptual resources Aristotle has available to resolve it, and critically engage with the relatively small body of secondary literature that discusses it. Finally, I develop two possible solutions to it, both of which, I argue, are more promising than any alternatives in the literature thus far

The Playas Tudor Propaganda: Bale’s \u3cem\u3eKing John \u3c/em\u3eand the Authority of Kings

As the drama of John Bale of Suffolk (1495-1563) is an index to the controversies of the Reformation, so is his life an interesting parallel to the major events of that period of English history. He was born ten years after the battle of Bosworth, entered the Carmelite convent at Norwich two years before the accession of Henry VIII, was converted to Protestantism in the year Henry married Anne Boleyn, fled to the continent upon the fall of Cromwell in 1540, returned under Edward VI, and fled again when Mary became queen, only to return once more upon the enthronement of Elizabeth. Thus, both Bale\u27s drama and his life are significant expressions of the English Reformation