Aerodynamic noise from rigid trailing edges with finite porous extensions

This paper investigates the effects of finite flat porous extensions to semi-infinite impermeable flat plates in an attempt to control trailing-edge noise through bio-inspired adaptations. Specifically the problem of sound generated by a gust convecting in uniform mean steady flow scattering off the trailing edge and permeable-impermeable junction is considered. This setup supposes that any realistic trailing-edge adaptation to a blade would be sufficiently small so that the turbulent boundary layer encapsulates both the porous edge and the permeable-impermeable junction, and therefore the interaction of acoustics generated at these two discontinuous boundaries is important. The acoustic problem is tackled analytically through use of the Wiener-Hopf method. A two-dimensional matrix Wiener-Hopf problem arises due to the two interaction points (the trailing edge and the permeable-impermeable junction). This paper discusses a new iterative method for solving this matrix Wiener-Hopf equation which extends to further two-dimensional problems in particular those involving analytic terms that exponentially grow in the upper or lower half planes. This method is an extension of the commonly used "pole removal" technique and avoids the needs for full matrix factorisation. Convergence of this iterative method to an exact solution is shown to be particularly fast when terms neglected in the second step are formally smaller than all other terms retained. The final acoustic solution highlights the effects of the permeable-impermeable junction on the generated noise, in particular how this junction affects the far-field noise generated by high-frequency gusts by creating an interference to typical trailing-edge scattering. This effect results in partially porous plates predicting a lower noise reduction than fully porous plates when compared to fully impermeable plates.Comment: LaTeX, 20 pp., 19 graphics in 6 figure

How to discriminate between computer-aided and computer-hindered decisions: a case study in mammography

Background. Computer aids can affect decisions in complex ways, potentially even making them worse; common assessment methods may miss these effects. We developed a method for estimating the quality of decisions, as well as how computer aids affect it, and applied it to computer-aided detection (CAD) of cancer, reanalyzing data from a published study where 50 professionals (“readers”) interpreted 180 mammograms, both with and without computer support. Method. We used stepwise regression to estimate how CAD affected the probability of a reader making a correct screening decision on a patient with cancer (sensitivity), thereby taking into account the effects of the difficulty of the cancer (proportion of readers who missed it) and the reader’s discriminating ability (Youden’s determinant). Using regression estimates, we obtained thresholds for classifying a posteriori the cases (by difficulty) and the readers (by discriminating ability). Results. Use of CAD was associated with a 0.016 increase in sensitivity (95% confidence interval [CI], 0.003–0.028) for the 44 least discriminating radiologists for 45 relatively easy, mostly CAD-detected cancers. However, for the 6 most discriminating radiologists, with CAD, sensitivity decreased by 0.145 (95% CI, 0.034–0.257) for the 15 relatively difficult cancers. Conclusions. Our exploratory analysis method reveals unexpected effects. It indicates that, despite the original study detecting no significant average effect, CAD helped the less discriminating readers but hindered the more discriminating readers. Such differential effects, although subtle, may be clinically significant and important for improving both computer algorithms and protocols for their use. They should be assessed when evaluating CAD and similar warning systems

Effects of incorrect computer-aided detection (CAD) output on human decision-making in mammography

To investigate the effects of incorrect computer output on the reliability of the decisions of human users. This work followed an independent UK clinical trial that evaluated the impact of computer-aided detection(CAD) in breast screening. The aim was to use data from this trial to feed into probabilistic models (similar to those used in "reliability engineering") which would detect and assess possible ways of improving the human-CAD interaction. Some analyses required extra data; therefore, two supplementary studies were conducted. Study 1 was designed to elucidate the effects of computer failure on human performance. Study 2 was conducted to clarify unexpected findings from Study 1

Oil price changes and industrial output in the MENA region: nonlinearities and asymmetries

In this paper, we investigate the nature of asymmetry in the influence of oil price changes on output in six MENA countries. To get more observations for our analysis, we proxy GDP with industrial output and hence our inference is based on a relatively larger sample compared to previous studies. The results that we obtain are interesting and intuitive. First, we find that growth in MENA countries is linked to oil in the sense that it benefits from higher oil prices and it gets hurt by a fall in the oil market. Moreover, there are pronounced short- and long-term asymmetries in the influence of oil on output. In particular, the output is faster to respond to increases in the oil price than it responds to decreases. The long-term influence to a rise in oil is also higher, though it is realized over a longer period. These results are important and can be used to guide policies that are concerned with stabilizing the economies of the MENA region against oil price fluctuations

Use of computer-aided detection (CAD) tools in screening mammography: a multidisciplinary investigation

We summarise a set of analyses and studies conducted to assess the effects of the use of a computer-aided detection (CAD) tool in breast screening. We have used an interdisciplinary approach that combines: (a) statistical analyses inspired by reliability modelling in engineering; (b) experimental studies of decisions of mammography experts using the tool, interpreted in the light of human factors psychology; and (c) ethnographic observations of the use of the tool both in trial conditions and in everyday screening practice. Our investigations have shown patterns of human behaviour and effects of computer-based advice that would not have been revealed by a standard clinical trial approach. For example, we found that the negligible measured effect of CAD could be explained by a range of effects on experts' decisions, beneficial in some cases and detrimental in others. There is some evidence of the latter effects being due to the experts using the computer tool differently from the intentions of the developers. We integrate insights from the different pieces of evidence and highlight their implications for the design, evaluation and deployment of this sort of computer tool

Terrorism, Dread Risk and Bicycle Accidents

Following the airplane attacks of September 11th, 2001 it is claimed that many Americans, dreading a repeat of these events, drove instead of flying, and that, consequently, there were extra car accidents, increasing the number of fatalities directly caused by the attacks by 1,500. After the Madrid train bombings of March 11th, 2004, Spaniards, like Americans, avoided the attacked mode of travel, but no increase in car travel or fatal accidents resulted. Here we analyze behavioral concomitants of the July 7th 2005 bomb attacks on public transport in London. We find reduced underground train travel and an increase in rates of bicycling and, over the 6 months following the attacks, 214 additional bicyclist road casualties - a 15.4% increase. Nevertheless we found no detectable increase in car accidents. We conclude that, while fear caused by terrorism may initiate potentially dangerous behaviors, understanding the secondary effects of terrorism requires consideration of the environmental variables that enable fear to manifest in dangerous behaviors

The seductive allure of technical language and its effect on covid-19 vaccine beliefs and intentions

Previous research has demonstrated a ‘seductive allure’ of technical or reductive language such that bad (e.g., circular) explanations are judged better when irrelevant technical terms are included. We aimed to explore if such an effect was observable in relation to a covid-19 vaccinations and if this subsequently affected behavioural intentions to take up a covid-19 vaccine. Using a between subjects design we presented participants (N=996) with one of four possible types of vignette that explained how covid-19 vaccination and herd immunity works. The explanations varied along two factors: (1) Quality, explanations were either good or bad (i.e., tautological); (2) Language, explanations either contained unnecessary technical language or did not. We measured participants’ evaluation of the explanations and intentions to vaccinate. We demonstrate a ‘seductive allure’ effect of technical language on bad vaccine explanations. However, an opposite ‘repellent disdain’ effect occurred for good explanations which were rated worse when they contained technical language. Moreover, we show that evaluations of explanations influence intentions to vaccinate. We suggest that misinformation that includes technical language could be more detrimental to vaccination rates. Importantly, however, clear explanatory public health information that omits technical language will be more effective in increasing intentions to vaccinate

Molecular Dynamics Simulation of the ENTH Domain on Lipid Bilayer

This research study compares the effect of polypropylene and wool fibers on the mechanical properties of natural polymer based stabilized soils. Biocomposites are becoming increasingly prevalent and this growth is expected to continue within a number of sectors including building materials. The aim of this study was to investigate the influence of different fiber reinforced natural polymer stabilized soils with regards to mechanical properties and fiber adhesion characteristics. The polymer includes alginate, which is used in a wide range of applications but has not been commonly used within engineering and construction applications. In recent years, natural fibers have started to be used as an ecological friendly alternative for soil reinforcement within a variety of construction applications. Test results in this study have compared the effects of adding natural and synthetic fibers to clay soils and discussed the importance of an optimum soil specification. A correlation between the micro structural analysis using scanning electron microscope (SEM), fiber typology, fiber–matrix bonds and the mechanical properties of the stabilized soils is also discussed