A Monte Carlo simulation study of wind turbine loads in thunderstorm downbursts

The simulation of thunderstorm downbursts and associated loads on a utility‐scale wind turbine is the focus of this study. Using a deterministic–stochastic hybrid model, downburst‐related wind fields are generated separately from non‐turbulent and turbulent parts. The non‐turbulent part builds on available analytical models developed from field data that include recorded downburst events; the turbulent part is simulated as a stochastic process using standard turbulence power spectral density functions and coherence functions adjusted by information on parameters such as the downburst's translation velocity. Key thunderstorm downburst‐related parameters include the maximum radial velocity, the height and radial distance to the maximum radial velocity, the downburst intensity, the downburst translation velocity and the downburst translation direction. In addition, the streamwise ambient (environmental) velocity and the downburst touchdown location relative to the wind turbine are also important in turbine load computation. A utility‐scale 5‐MW wind turbine model is selected, and loads are generated using stochastic simulation of the aeroelastic response. Information available in the literature on recorded downbursts is used to define the cases studied. A single downburst simulation and associated turbine response simulation is first discussed to illustrate loads computation and highlight downburst‐related parameters of interest. Next, a Monte Carlo simulation study is performed to investigate the influence of touchdown locations and translation direction on turbine extreme loads. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of Thermal Aging and Chemical Treatment on Tensile Properties of Coir Fiber

Effect of thermal aging and chemical treatment on the physical properties of coir fiber was investigated. Coir fibers were treated with sodium hydroxide and glutaraldehyde for 2 h. The influence of alkali and aldehyde treatment on tensile strength and elongation at break was studied in detail. Enhancement in tensile strength of coir fiber was observed up to five days of aging at 50°C and further decreased. Thermal cross linking of cellulose present in the fiber may be the reason for the increase in tensile strength and thermal degradation due to the chain scission of cellulose reduced the tensile strength. Sodium-hydroxide-treated samples showed an increase in tensile strength and reduction in elongation at break. The removal of impurities such as waxy and fatty acid residues from the coir fiber by reacting with strong base solution improved the strength of fiber. Cross linking of cellulose with glutaraldehyde in the fiber reduced the elasticity and enhances the strength of the material. Scanning electron microscopy was employed to analyze the change in surface morphology upon chemical treatment. Improvement in the tensile strength suggests that NaOH and glutaraldehyde can be effectively used to modify coir fiber with excellent physical properties.     

Numerical correlation for thermal conduction in packed beds

The numerical conduction of heat in packed beds of particles is investigated, including the effects of inter-particle microasperity gaps and deformation contacts. A detailed numerical model of two half spheres in contact with interstitial fluid is constructed, including asperity (roughness) gaps and deformation contacts on the respective orders of 5 μm and 100 μm for 1 mm particle diameters. The resulting heat flux distributions at the diametrical planes of the particles are integrated to yield the overall thermal conductance, K, or resistance, R = 1/K, between the two diametrical planes. The results show K to be strongly dependent on the interstitial fluid gap and the deformation contact diameter, as well as on fluid and solid conductivities. The effective bed conductivity, k_e, is determined as a function of K and the void fraction, and correlated in terms of bed parameters. The resulting k_e correlation agrees well with published experimental data over a wide range of substances and temperatures.     

Challenges Based on Antiplasmodial and Antiviral Activities of 7-Chloro-4-aminoquinoline Derivatives

We report the structural functionalization of the terminal amino group of N¹-(7-chloroquinolin-4-yl) butane-1,4-diamine, leading to a series of 7-chloro-4-aminoquinoline derivatives, and their evaluation as potent anti-malarial and anti-viral agents. Some compounds exhibited promising anti-malarial effects against the Plasmodium falciparum 3D7 (chloroquine-sensitive) and Dd2 (chloroquine-resistant) strains. In addition, these compounds were assayed in vitro against influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Compound 5 h , bearing an N-mesityl thiourea group, displayed pronounced anti-infectious effects against malaria, IAV, and SARS-CoV-2. These results provide new insights into drug discovery for the prevention or treatment of malaria and virus co-infection.