Fluid structure interaction of a two-dimensional membrane in a flow with a pressure gradient with application to convertible car roofs

Original article can be found at : http://www.sciencedirect.com/ Copyright ElsevierThe flow-induced deformation of a membrane in a flow with a pressure gradient is studied. The investigation focuses on the deformation of aerodynamically loaded convertible car roofs. A computational methodology is developed with a line-element structural model that incorporates initial slackness of the flexible roof material. The computed flow–structure interaction yields stable solutions, the flexible roof settling into static equilibrium. The interaction converges to a static deformation within 1% difference in the displacement variable after three iterations between fluid and structural codes. Reasonably accurate predictions, to within 7%, are possible using only a single iteration between the fluid and the structural codes for the model problem studied herein. However, the deformation results are shown to be highly dependent on the physical parameters that are used in the calculation. Accurate representation of initial geometry, material properties and slackness should be found before the predictive benefits of the fluid–structure computations are sought. The iterative methodology overcomplicates the computation of deformation for the relatively small displacements encountered for the model problem studied herein. Such an approach would be better suited to applications with large amplitude displacements such as those encountered in sail design or deployment of a parachute.Peer reviewedFinal Accepted Versio

The mechanics of composite corrugated structures: A review with applications in morphing aircraft

Corrugation has long been seen as a simple and effective means of forming lightweight structures with high anisotropic behaviour, stability under buckling load and energy absorption capability. This has been exploited in diverse industrial applications and academic research. In recent years, there have been numerous innovative developments to corrugated structures, involving more elaborate and ingenious corrugation geometries and combination of corrugations with advanced materials. This development has been largely led by the research interest in morphing structures, which seek to exploit the extreme anisotropy of a corrugated panel, using the flexible degrees of freedom to allow a structure’s shape to change, whilst bearing load in other degrees of freedom. This paper presents a comprehensive review of the literature on corrugated structures, with applications ranging from traditional engineering structures such as corrugated steel beams through to morphing aircraft wing structures. As such it provides an important reference for researchers to have a broad but succinct perception of the mechanical behaviour of these structures. Such a perception is highly required in the multidisciplinary design of corrugated structures for the application in morphing aircraft

Veterinary epidemiology and economics in Africa. A manual for use in the design and appraisal of livestock health policy

Discusses basic techniques involved in the planning, monitoring and evaluation of livestock disease control programmes in Africa i.e. the theory & application of epidemiology statistical analysis, economics, estimating costs and decision making

Multilocus sequence typing of the pathogenic fungus Aspergillus fumigatus

A multilocus sequence typing (MLST) scheme was devised for Aspergillus fumigatus. The system involved sequencing seven gene fragments and was applied to a panel of 100 isolates of A. fumigatus from diverse sources. Thirty different sequence types were found among the 100 isolates, and 93% of the isolates differed from the other isolates by only one allele sequence, forming a single clonal cluster as indicated by the eBURST algorithm. The discriminatory power of the MLST method was only 0.93. These results strongly indicate that A. fumigatus is a species of a relatively recent origin, with low levels of sequence dissimilarity. Typing methods based on variable numbers of tandem repeats offer higher levels of strain discrimination. Mating type data for the 100 isolates showed that 71 isolates were type MAT1-2 and 29 isolates were MAT1-1

Anomalous Chromomagnetic Moments of Quarks and Large Transverse Energy Jets

We consider the jet cross sections for gluons coupling to quarks with an anomalous chromomagnetic moment. We then apply this to the deviation and bounds from QCD found in the CDF and D0 Fermilab data, respectively, to find a range of possible values for the anomalous moments. The quadratic and quartic terms in the anomalous moments can fit to the rise of a deviation with transverse energy. Since previous analyses have been done on the top quark total cross section, here we assume the same moment on all quarks except the top and find the range $|\kappa'| \equiv |\kappa/(2 m_q)| = 1.0\pm 0.3$ TeV$^{-1}$ for the CDF data. Assuming the anomalous moment is present only on a charm or bottom quark which is pair produced results in a range $|\kappa'_{b,c}| = 3.5 \pm 1.0$ TeV$^{-1}$. The magnitudes here are compared with anomalous magnetic moments that could account for $R_b$ and found to be in the same general range, as well as not inconsistent with LEP and SLD bounds on $\Delta \Gamma_{\text{had}}$.Comment: REVTeX, 11 pages, 2 postscript figure

Nonlinear MEMS Piezoelectric Harvesters in the presence of geometric and structural variabilities

This paper investigates the use of an electrostatic device to improve the performance of MEMS piezoelectric harvesters in the presence of geometric and structural variabilities due to the manufacturing process. Different types of uncertain parameters including material and geometric uncertainties have been considered. The variability of these parameters are estimated based on available existing experimental data in the literature. Monte Carlo simulation (MCS) is used for uncertainty propagation and it is shown that the resonance frequencies of the majority of the samples are far away from the excitation frequency and consequently this results in less harvested power. This paper identifies these samples and uses electrostatic devices to improve the performance of the harvester. The proposed device is composed of an unsymmetric arrangement of two electrodes to decrease the resonance frequency of samples through a softening nonlinearity. The unsymmetric arrangement of two electrodes is inevitable and due to geometric variability of the harvester. There are also two arch shape electrodes which can be used to create a hardening effect to increase the resonance frequency of samples which have resonance frequencies smaller than the nominal value

A 5000-year record of relative sea-level change in New Jersey, USA

Stratigraphic data from salt marshes provide accurate reconstructions of Holocene relative sea level (RSL) change and necessary constraints to models of glacial isostatic adjustment (GIA), which is the dominant cause of late Holocene RSL rise along the U.S. mid-Atlantic coast. Here, we produce a new mid- to late-Holocene RSL record from a salt marsh bordering Great Bay in southern New Jersey using basal peats. We use a multi-proxy approach (foraminifera and geochemistry) to identify the indicative meaning of the basal peats and produce sea-level index points (SLIPs) that include a vertical uncertainty for tidal range change and sediment compaction and a temporal uncertainty based on high precision Accelerator Mass Spectrometry radiocarbon dating of salt-marsh plant macrofossils. The 14 basal SLIPs range from 1211 ± 56 years BP to 4414 ± 112 years BP, which we combine with published RSL data from southern New Jersey and use with a spatiotemporal statistical model to show that RSL rose 8.6 m at an average rate of 1.7 ± 0.1 mm/yr (1σ) from 5000 years BP to present. We compare the RSL changes with an ensemble of 1D (laterally homogenous) and site-specific 3D (laterally heterogeneous) GIA models, which tend to overestimate the magnitude of RSL rise over the last 5000 years. The continued discrepancy between RSL data and GIA models highlights the importance of using a wide array of ice model and viscosity model parameters to more precisely fit site-specific RSL data along the U.S. mid-Atlantic coast

Simultaneous NICER and NuSTAR Observations of the Ultracompact X-Ray Binary 4U 1543-624

We present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543−624 obtained in 2020 April. The source was at a luminosity of L0.5−50 keV = 4.9(D/7 kpc)2 × 1036 erg s−1 and showed evidence of reflected emission in the form of an O viii line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as xillverCO, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (Rin ≤ 1.07 RISCO). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be B ≤ 0.7(D/7 kpc) × 108 G at the poles. Given the lack of pulsations detected and position of Rin, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of RNS ≤ 12.1 km when assuming a canonical NS mass of 1.4 M⊙