Analytical investigation of synchrophasing as a means of reducing aircraft interior noise

The noise control characteristics of synchrophasing are investigated using a simplified model of an aircraft fuselage. The analysis presented here includes directivity effects of the noise sources and solves in closed form the coupled motion between the interior and exterior acoustic fields and the shell vibrational response. The variation in sound pressure level at various locations inside the shell is studied for various synchrophase angles as well as the shell vibrational response and input power flow in order to uncover the principal mechanisms behind the transmission phenomena

Public health applications of remote sensing

Remote infrared and multispectral photography were used to identify coastal salt water-fresh water interfaces conducive to encephalitis vector mosquito breeding in Florida, and to determine the environmental conditions that caused an explosive outbreak of anthrax in Louisiana. Multiband photographic inventories were obtained by simultaneously processing three photographic negatives of the same view which record different wavelength portions of the same light. The process enhances differentiation of vegetative communities and sharply delineates edge effects by assigning false colors to differentiate subtle density differences

Information technology professionals and the new-rich middle class in Chennai (Madras)

Since 1991, when the policy of economic liberalisation began in earnest, the size and prosperity of India's middle class have grown considerably. Yet sound sociological and ethnographic information about its social structure and cultural values is still sparse, and as André Béteille comments: ‘Everything or nearly everything that is written about the Indian middle class is written by middle-class Indians…[who] tend to oscillate between self-recrimination and self-congratulation’. The former is exemplified by Pavan Varma's The Great Indian Middle Class (1998), which excoriates this class for its selfish materialism and the ‘retreat from idealism’ that was manifest in the smaller, ‘traditional middle class’ of the earlier, post-independence period. A good example of the opposite tendency is Gurcharan Das's India Unbound (2002), which celebrates ‘the rise of a confident new middle class’Das's diagnosis of what has changed is actually very similar to Varma's, but he insists that the new middle class is no ‘greedier’ than the old one, and the ‘chief difference is that there is less hypocrisy and more self-confidence

Traditional vocations and modern professions among Tamil Brahmans in colonial and post-colonial south India

Since the nineteenth century, Tamil Brahmans have been very well represented in the educated professions, especially law and administration, medicine, engineering and nowadays, information technology. This is partly a continuation of the Brahmans’ role as literate service people, owing to their traditions of education, learning and literacy, but the range of professions shows that any direct continuity is more apparent than real. Genealogical data are particularly used as evidence about changing patterns of employment, education and migration. Caste traditionalism was not a determining constraint, for Tamil Brahmans were predominant in medicine and engineering as well as law and administration in the colonial period, even though medicine is ritually polluting and engineering resembles low-status artisans’ work. Crucially though, as modern, English-language, credential-based professions that are wellpaid and prestigious, law, medicine and engineering were and are all deemed eminently suitable for Tamil Brahmans, who typically regard their professional success as a sign of their caste superiority in the modern world. In reality, though, it is mainly a product of how their old social and cultural capital and their economic capital in land were transformed as they seized new educational and employment opportunities by flexibly deploying their traditional, inherited skills and advantages

Quantification of channel planform change on the lower Rangitikei River, New Zealand, 1949-2007: response to management?

The Rangitikei River, a large gravel‐bed wandering river located in the North Island of New Zealand, has outstanding scenic characteristics, recreational, fisheries and wildlife habitat features. Recently concerns have been raised over the potential negative impact that perceived channel changes in the latter part of the 20th century may be having on the Rangitikei River recreational fishery. This study describes and quantifies the large‐scale morphological changes that have occurred in selected reaches of the lower Rangitikei River between 1949 and 2007. This research utilised historical aerial photography and analysis in ArcGIS® to quantify channel planform change in three reaches, encompassing ~18 km of the lower Rangitikei River. This showed that the lower Rangitikei was transformed from a multi‐channelled planform to a predominantly single‐thread wandering planform, with an associated reduction in morphological complexity and active channel width of up to 74%, between 1949 and 2007. Bank protection measures instigated under the Rangitikei River Scheme have primarily driven these changes. Gravel extraction has also contributed by enhancing channel‐floodplain disconnection and exacerbating sediment deficits. The findings of this study have implications for future management of the Rangitikei. Previous lower Rangitikei River management schemes have taken a reach‐based engineering approach with a focus on bank erosion protection and flood mitigation. This study has confirmed the lower river has responded geomorphologically to these goals of river control. However questions as to the economic and ecological sustainability of this management style may encourage river managers to consider the benefits of promoting a self‐adjusting fluvial system within a catchment‐framed management approach

Morphological budgeting in the Motueka River: an analysis of technique

Morphological budgeting is a key method for monitoring and studying sediment transfers within gravelly rivers. We assess the utility of traditional cross‐section approaches to budgeting using Digital Elevation Model (DEM) analysis. DEMs give a more accurate volume calculation within the constraint of sampling frequency compared with cross sections, since a greater area of river bed is sampled. DEM volume calculation within the 1.7 km ‘Three Beaches’ reach in the upper Motueka revealed a net loss of 3219 m3 in this reach between 2008‐2009. Comparisons of this value with cross section‐based volume calculations at a range of section spacing using (i) Mean Bed Level (MBL) analysis and (ii) DEMs generated from cross section data, suggest accuracy of the budget is maximised at a critical cross section spacing not exceeding 90 m. Careful positioning of cross sections could lengthen this distance further and is essential to accurately represent river channel morphology. MBL analysis using cross‐sections in the reach monumented by Tasman District Council (TDC) for river monitoring underestimates the magnitude of net sediment transfers by c. 30%

Prospects for Detecting Supernova Neutrino Flavor Oscillations

The neutrinos from a Type II supernova provide perhaps our best opportunity to probe cosmologically interesting muon and/or tauon neutrino masses. This is because matter enhanced neutrino oscillations can lead to an anomalously hot nu_e spectrum, and thus to enhanced charged current cross sections in terrestrial detectors. Two recently proposed supernova neutrino observatories, OMNIS and LAND, will detect neutrons spalled from target nuclei by neutral and charged current neutrino interactions. As this signal is not flavor specific, it is not immediately clear whether a convincing neutrino oscillation signal can be extracted from such experiments. To address this issue we examine the responses of a series of possible light and heavy mass targets, 9Be, 23Na, 35Cl, and 208Pb. We find that strategies for detecting oscillations which use only neutron count rates are problematic at best, even if cross sections are determined by ancillary experiments. Plausible uncertainties in supernova neutrino spectra tend to obscure rate enhancements due to oscillations. However, in the case of 208Pb, a signal emerges that is largely flavor specific and extraordinarily sensitive to the nu_e temperature, the emission of two neutrons. This signal and its flavor specificity are associated with the strength and location of the first-forbidden responses for neutral and charge current reactions, aspects of the 208Pb neutrino cross section that have not been discussed previously. Hadronic spin transfer experiments might be helpful in confirming some of the nuclear structure physics underlying our conclusions.Comment: 27 pages, RevTeX, 2 figure

Bearing detection in the presence of two sources of varying coherence using the complex cepstrum

The effect of the presence of two acoustic sources (one, the primary, whose location is to be detected) of varying coherence on a cepstral bearing finding procedure is experimentally studied. The coherence between the acoustic sources was altered by adding random noise of various SNR (signal-to-noise ratio) to the input signal of the primary source; the same base signal being fed to both sources. The results demonstrate that, when block liftering is used, the primary source bearing is reliably estimated for coherences as low as gamma sup 2 greater than or approx equal to 0.5. The results also imply that background noise (unreflected) of SNR greater than or approx equal to 10 dB will not markedly affect the accuracy of the bearing estimation algorithm

An experimental investigation of the interior noise control effects of propeller synchrophasing

A simplified cylindrical model of an aircraft fuselage is used to investigate the mechanisms of interior noise suppression using synchrophasing techniques. This investigation allows isolation of important parameters to define the characteristics of synchrophasing. The optimum synchrophase angle for maximum noise reduction is found for several interior microphone positions with pure tone source excitation. Noise reductions of up to 30 dB are shown for some microphone positions, however, overall reductions are less. A computer algorithm is developed to decompose the cylinder vibration into modal components over a wide range of synchrophase angles. The circumferential modal response of the shell vibration is shown to govern the transmission of sound into the cylinder rather than localized transmission. As well as investigating synchrophasing, the interior sound field due to sources typical of propellers has been measured and discussed