Aeroelastic analysis of a troposkien-type wind turbine blade

The linear aeroelastic equations for one curved blade of a vertical axis wind turbine in state vector form are presented. The method is based on a simple integrating matrix scheme together with the transfer matrix idea. The method is proposed as a convenient way of solving the associated eigenvalue problem for general support conditions

Brain glucose utilization in systemic lupus erythematosus with neuropsychiatric symptoms: A controlled positron emission tomography study

In contrast to morphological imaging [such as magnetic resonance imaging (MRI) or computed tomography], functional imaging may be of advantage in the detection of brain abnormalities in cases of neuropsychiatric systemic lupus erythematosus (SLE). Therefore, we studied 13 patients (aged 40±14 years, 11 female, 2 male) with neuropsychiatric SLE who met four of the American Rheumatism Association criteria for the classification of SLE. Ten clinically and neurologically healthy volunteers served as controls (aged 40±12 years, 5 female, 5 male). Both groups were investigated using fluorine-18-labelled fluorodeoxyglucose brain positron emission tomography (PET) and cranial MRI. The normal controls and 11 of the 13 patients showed normal MRI scans. However, PET scan was abnormal in all 13 SLE patients. Significant group-to-group differences in the glucose metabolic index (GMI=region of interest uptake/global uptake at the level of the basal ganglia and thalamus) were found in the parieto-occipital region on both sides: the GMI of the parieto-occipital region on the right side was 0.922±0.045 in patients and 1.066±0.081 in controls (P<0.0001, Mann WhitneyU test), while on the left side it was 0.892±0.060 in patients and 1.034±0.051 in controls (P=0.0002). Parietooccipital hypometabolism is a conspicuous finding in mainly MRI-negative neuropsychiatric SLE. As the parieto-occipital region is located at the boundary of blood supply of all three major arteries, it could be the most vulnerable zone of the cerebrum and may be affected at an early stage of the cerebrovascular diseas

Historical trend of polycyclic aromatic hydrocarbons in a sediment core from Osaka Bay during the Meghalayan

Polycyclic aromatic hydrocarbons (PAHs) are produced by incomplete combustion of biomass and fossil fuel, yet PAHs have been rarely analyzed in coastal sediment cores as a tracer for human activities before industrialization. The aim of this study was to assess if the historical trend of PAHs can be related to past human activities. To this end, we have determined the concentrations of PAHs in a 9 m-long sediment core from Osaka Bay, which records history of the last 2400 years. The concentration of PAHs before the beginning of the 17th century CE, the beginning of the peaceful Edo period, was consistently low (<100 ng g⁻¹) and mainly comprised of smoke-derived PAHs reflecting the natural background. A relative higher abundance of 4−6 ring PAHs from the early 17th century CE and a higher PAH concentration from the early 18th century CE until approximately 1800 CE agreed with a population increase, Cu smelting activities and increasing combustion of charcoal. The constant PAH concentration until the late 19th century CE overlapped with a decline in the population in the Osaka area. An increasing PAH concentration from the late 19th century CE marked the beginning of industrialization in the Modern age. The peak in PAH concentration in 1945 CE was likely caused by burning of wooden structures due to air raids on Osaka City. A second peak around 1980 CE indicated the introduction of cleaner energies. We conclude that PAHs in coastal sediment cores can be used to reconstruct past human activities

Harmonic Forcing Amplitude Effects in Globally Unstable Transonic Wing Flow

This work concerns the phenomenon of shock buffet and its mutual interaction with the flexible wing structure. The latter aspect is key to our contribution, since, even though renewed interest in edge-of-the-envelope flow unsteadiness can be observed in recent years, the multidisciplinary aeroelastic interaction is typically overlooked. Previous work by Timme [1] applied stability theory to a large aircraft wing, specifically the NASA Common Research Model, to reveal a global instability linked to shock buffet. Herein, we expand upon that work by adding the dimension of wing vibration to scrutinise its impact on the flow unsteadiness. We consider fluid-structure interaction solving the unsteady Reynolds-averaged Navier–Stokes equations with an industry-grade computational fluid dynamics solver to model the aerodynamics and a modal structural model of the actual wind-tunnel geometry to describe the flexible wing. Our focus experimental flow condition is a reference free-stream Mach number of 0.85 with a chord Reynolds number of 5 × 106 and a supercritical angle of attack of 3.75◦ . Results show that the initial aerodynamic unsteadiness, when started from a well converged static aeroelastic solution (validated with wind-tunnel data), is nearly independent of the presence of the flexible wing structure as long as the amplitudes are small. Indeed wing vibration follows the dominant shock-buffet excitation. Once transitioned into the non-linear aerodynamic regime (while noting that at the time of writing a longer time history is still required), most of the structural degrees-of-freedom are active close to their respective natural frequencies and also within the shock-buffet frequency range. An aeroelastic global stability analysis presented in our companion paper [2] has revealed that several of these modes become unstable due to the fluid-structure coupling. Overall the impact of the flexible wing results in lower amplitudes in integrated aerodynamic coefficients with a broader frequency content peaking around the first bending frequencies and the shock-buffet frequency range, which is in contrast to the rigid (yet statically deformed) wing where the shock-buffet excitation clearly dominates