Application of Swept-Sine Excitation for Acoustic Impedance Education

The NASA Langley Normal Incidence Tube (NIT) and Grazing Flow Impedance Tube (GFIT) are regularly employed to characterize the frequency response of acoustic liners through the eduction of their specific acoustic impedance. Both test rigs typically use an acoustic source that produces sine wave signals at discrete frequencies (Stepped-Sine) to educe the impedance. The current work details a novel approach using frequency-swept sine waveforms normalized to a constant sound pressure level for excitation. Determination of the sound pressure level and phase from microphone measurements acquired using swept-sine excitation is performed using a modified Vold-Kalman order tracking filter. Four acoustic liners are evaluated in the NIT and GFIT with both stepped-sine and swept-sine sources. Using these two methods, the educed impedance spectra are shown to compare favorably. However, the new (Swept-Sine) approach provides much greater frequency resolution in less time, allowing the acoustic liner properties to be studied in much greater detail

Environmental determinants of landmine detection by dogs: Findings from a large-scale study in Afghanistan

This article’s purpose is to examine the strengths and weaknesses of mine-detection dogs in different environments. The experiments employed a total of 39 dogs in Afghanistan between October 2002 and July 2003. The results are discussed here

Non Linearity of the Ball/Rubber Impact in Table Tennis: Experiments and Modeling

AbstractAlong with comfort, the speed is a key metric used to qualify the performance of a table tennis racket. The restitution coefficient which corresponds to the ratio between the velocities of the ball right before and after normally impacting the racket relates to the speed performance: the higher the restitution coefficient, the greater the speed. Thus, understanding the normal impact problem is key and suggests investigating the effects of the intrinsic properties and architectures of the constituents of the racket. In this work, both experimental and numerical studies were pursued. Experimentally, normal impact tests were performed for varying launching velocities on samples made of isolated or associated constituents of a table tennis racket and the restitution coefficients calculated. Numerically, 3D finite elements simulations were conducted to replicate the normal impact conditions while incorporating the time-dependent constitutive behavior of the polymeric elements contributing during the impact: the racket constituents (the foam and the compact) and the ball. The restitution coefficients are seen to decrease with increasing launching velocity, while being minimum when the two racket polymeric constituents are associated. A fair agreement is obtained with the FE simulations in which the sample/ball contact zone is identified as a ring with its mean radius increasing till the maximum crushing. Ultimately, additional FE calculations confirm that the friction plays a key role in the energy dissipation process, alongside with the rate-dependent behavior and architecture of the polymeric constituents

The perception and management of risk in UK office property development

Risk is an ever-present aspect of business, and risk taking is necessary for profit and economic progress. Speculative property development is popularly perceived as a 'risky business' yet, like other entrepreneurs, developers have opportunities to manage the risks they face; techniques include phasing and joint ventures. The associated areas of investment portfolio risk, development risk analysis and construction risk management have all been addressed by research. This article presents new knowledge about how developers perceive risks and the means they subsequently adopt to manage them. The developers of office projects across the UK were sent questionnaires by post. Respondents were asked about their perceptions of risks at the first appraisal stage and currently and about the risk management techniques that they had adopted. In-depth interviews with a selection of respondents were then used to discuss and augment the findings. Developers were most concerned about market-based risks at both stages. Concern about production-orientated risks was lower and fell significantly between the two stages. A fixed price contract was the most common risk management technique. Risk management techniques were used more often outside London and the South East. Developer type affects both the perception and management of risk. While developers do manage risk, decisions are made on the basis of professional and business experience. These findings should help development companies manage risk in a more objective and analytical way

Nouvelle estimation de la fréquence du gène pour le noir dans la race ovine Bleu du Maine

Une enquête faite en 1978 et 1979 parmi resp. 29 et 49 troupeaux ovins Bleu du Maine de Sarthe et de Mayenne a montré la persistance de l’apparition d’agneaux noirs. Ces agneaux sont de formule aa, a étant récessif par rapport à A wh l’allèle en Agouti responsable de la toison blanche des Bleu du Maine. Une estimation de la fréquence de a parmi les mâles et les femelles à la naissance (q) et au stade de reproducteurs (α) a été effectuée par deux méthodes différentes à partir de la fréquence des naissances noires et de celles des mâles hétérozygotes détectés. Il y avait respectivement en 77/78 et 78/79, 51 et 85 mâles qui ont donné respectivement 1 624 et 2 701 agneaux dont respectivement 56 et 104 étaient noirs. Le nombre des béliers hétérozygotes détectés était respectivement de 21 et 41. En supposant que la fréquence des hétérozygotes femelles est la même dans tous les troupeaux on prend comme estimation la moyenne des estimations par les deux méthodes ce qui donne (formule, voir document attaché) pour les fréquences de a chez les reproducteurs et q = 0,22 et 0,236. pour la fréquence à la naissance resp. en 77/78 et 78/79. En introduisant ces valeurs dans un programme de simulation, on obtient une estimation de 111 agneaux noirs et 44 béliers hétérozygotes détectés pour la deuxième campagne. Ces chiffres sont à rapprocher des deux effectifs observés : respectivement 104 et 41 ce qui justifie a posteriori la validité des estimations de fréquence. La fréquence chez les mâles est significativement plus élevée que chez les femelles, ce qui serait dû à une sélection plus intense chez les mâles que chez les femelles en faveur des hétérozygotes A wh a plus « bleus » que les hétérozygotes A wh A wh. Chez les femelles, si la pression de la sélection artificielle en faveur de l’hétérozygote est faible, celui-ci pourrait présenter en outre un avantage sélectif (une meilleure prolificité). C’est grâce à ces avantages naturels et artificiels des hétérozygotes que le gène se maintient à la fréquence élevée que nous observons, malgré l’élimination systématique des noirs de la reproduction. Toutefois, ces fréquences (environ 0,35 pour les mâles et 0,11 pour les femelles) sont actuellement inférieures à ce qu’elle a pu être dans le passé en races Wensleydale et Bleu du Maine (jusqu’à 050, pour les mâles et 0,42 pour les femelles). Cela est dû apparemment à un relachement récent de la pression de la sélection (surtout celle en faveur des mâles hétérozygotes) en zone Bleu du Maine. La présence d’un tel gène dans la population Bleu du Maine française présente un intérêt économique (production de 3 p. 100 d’agneaux en plus à la naissance) pour un désavantage réduit : diminution de 2 p. 100 de l’efficacité de la sélectionSurveys made in 1978 and 1979 among resp. 79 and 49 Bleu du Maine flocks in the departments of Sarthe and Mayenne have shown that black lambs still appear in the breed. These lambs have a aa formula at the A gouti locus, a being recessive to A wh the top allele of the series which gives the white fleece of the breed. An estimation of the frequency of a among males and females at birth (q) and at the reproductive age (formula, see attached document) has been performed by two methods based on the frequency of blacks at birth and the fequency of known heterozygous rams resp. In 77/78 and 78/79 lambings there were resp. 51 and 85 rams used giving resp. 1624 and 2701 lambs with resp. 56 and 104 black. The number of detected heterozygous rams was 21 and 41, resp. Supposing the same frequency of heterozygous females in all the flocks, the estimation used was the average estimation by the two methods, which gives (formula, see attached document) for the frequency of a among the male and female reproducers in resp. 78 and 79 surveys. The frequency among lambs at birth was .220 and .235 resp. By a program of simulation one get an estimation of 111 black lambs and 44 heterozygous sires for the 78/79 campaign, which may be compared to resp. 104 and 41. This is a fairly good a posteriori verification of the worth of the methods of estimation fot the gene frequencies. The gene frequency is ligher in male than in female reproducers, which could result from a stronger selection in favour of the heterozygotes A wh; among the males, the heterozygotes having a more intense a >coloration. If, among the ewes, the pressure of artificial selection for the heterozygotes is weak, this genotype may have a selective advantage in itself (better prolificacy). The a gene is probably kept at an equilibrium state at a rather high heterozygotes. Nevertheless, these frequencies (around .350 for the rams and . 11 for the ewes) are actually inferior to those observed in the past in Wensleydale and Bleu du Maine (up to .5 for the males and .42 for the females). This may be due to a recent relaxing of selection pressure in favour of heterozygous males in the Bleu du Maine zone which has been considered. The existence of such a gene in the Bleu du Maine population in France has an economic advantage of about 3 p. cent more lambs at birth. On the other hand the culling of black lambs reduces selection efficacy by 2 p. cent

Ambient Air Pollution, Social Inequalities and Asthma Exacerbation in Greater Strasbourg (France) Metropolitan Area: the PAISA Study

International audienceThe socio-economic status (SES) of populations has an influence on the incidence or mortality rates of numerous health outcomes, among which respiratory diseases (Prescott et al., 2003; Ellison-Loschmann et al., 2007). Considering asthma, the possible contribution of SES to overall prevalence –regardless of asthma severity-, remains controversial in industrialized countries. Several studies indicate that allergic asthma is more prevalent in more well-off populations whereas the non-allergic forms of asthma are more common in the deprived ones (Cesaroni et al., 2003; Blanc et al., 2006). On the other hand, severe asthma whatever its etiology appears to be more frequent in the latter populations, as compared to the more affluent (Basagana et al., 2004). Risk factors for exacerbations (e.g., passive smoking (Wright Subramanian, 2007), psychosocial stress (Gold & Wright, 2005), cockroach allergens (Kitch et al., 2000), and suboptimal compliance with anti-inflammatory medication (Gottlieb et al., 1995)) are generally more common among people with asthma and low SES than their better-off counterparts. These observations support the hypothesis that some factors more present in deprived populations contribute to asthma exacerbation (Mielck et al., 1996)

From witness to web sleuth: Does citizen enquiry using social media affect formal eyewitness identification procedures?

Eyewitnesses to crimes may seek the perpetrator on social media prior to participating in a formal identification procedure, but the effect of this citizen enquiry on the accuracy of eyewitness identification is unclear. The current study used a between-participants design to address this question. Participants viewed a crime video, and after a 1-2 day delay were either exposed to social media including the perpetrator, exposed to social media that substituted an innocent suspect for the perpetrator, or not exposed to social media. Seven days after viewing the crime video, all participants made an identification from a video lineup. It was predicted that exposure to social media that did not contain the guilty suspect would reduce the accuracy of subsequent identifications. Analysis revealed no association between social media exposure and lineup response for target present lineups. For target absent lineups there was a significant association between social media exposure and lineup response, but this was driven by a higher number of correct rejections for participants who saw the guilty suspect on social media. The results suggest that, at least in some circumstances, witnesses searching social media does not have a negative effect on formal ID procedures