Search

In this paper, the problem of wind-induced vibration in tall buildings is addressed by utilizing a new type of damper, the tuned mass damper fluid inerter (TMDFI). The TMDFI incorporates an inerter in the classical tuned mass damper (TMD), which is physically realized using fluid in a helical channel. The device arrangement is optimized using a proposed nonlinear procedure and it is demonstrated through numerical simulations that the application of the TMDFI achieves excellent vibration control performance. Specifically, it has been found that the TMDFI requires lower mass and stroke requirements than traditional passive dampers while achieving comparable or better vibration reductions. It has been shown numerically that the damper demonstrates excellent vibration control capabilities by reducing the RMS displacement of the building by ≈50% and the RMS acceleration by 35%–80%. The results presented here show that the TMDFI is a damper capable of mitigating wind-induced vibrations in tall buildings with relatively simple design requirements. This new damper has the potential to significantly improve the safety, comfort, and durability of tall buildings subjected to wind loads. [ABSTRACT FROM AUTHOR]

The present study aimed to develop a methodology to estimate jute (Corchorus sp.) cultivated areas in the Indian subcontinent using sentinel-1A Synthetic aperture radar (SAR) C band dual polarization data. We developed a hierarchical decision tree (DT) model to estimate jute area and compared it with other supervised and unsupervised methods. The proposed DT model showed improved overall accuracy of 82–83% (Kappa coefficient, k = 0.78–0.79) over supervised or unsupervised methods and validated against Directorate of Economics and Statistics (DES) data, Government of India during 2016–2019. The VV backscatter record improved accuracy over VH backscatter. [ABSTRACT FROM AUTHOR]

Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well‐known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their rolling contact fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well‐known that these premature failures are attributed to surface damages such as white surface flaking (WSF), white etching cracks (WECs) and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied to demonstrate their TTR mitigation capabilities. Then, a novel idea of open‐loop high‐speed shaft mechanical brake control is proposed. The results presented here show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high‐speed shaft and reducing the risk of bearing slip by actuating the high‐speed shaft brake at the onset of the transient event. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time applied to it. This novel approach allows the wind turbines to protect the gearbox bearings from TTRs using the existing hardware on the turbine. [ABSTRACT FROM AUTHOR]

In the present work, we have studied the oxidation of HOSO˙ by O2 (3Σg−) employing quantum chemical and kinetic calculations. The present work reveals that HOSO˙ + O2 (3Σg−) is a barrierless reaction which proceeds through a stable hydrogen-bonded complex. The estimated atmospheric lifetime of HOSO˙ in the presence of O2 (3Σg−) is found to be several orders of magnitude less compared to the other oxidation paths of HOSO˙, suggesting that the oxidation of HOSO˙ by O2 (3Σg−) might be the most dominant oxidation path of HOSO˙ in the atmosphere. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of water is a burning global issue, and enormous importance has been given on easily applicable watertreatment methods namely adsorption. However, search for an efficient and reusable adsorbent is ever-evolving. In this study, activated carbon from highly ligno-cellulosic jute stick (JS-AC), the agricultural by-product of jute (Corchorus olitorius), was evaluated as a new adsorbent for removing cadmium (Cd) from the aqueous medium. The direct and interaction effects of four independent adsorption factors namely, initial Cd(II) concentration (20–100 mg/L), adsorbent dose (0.5–1 g/L), solution pH (3–7), and time (30–180 min) were investigated by applying response surface methodology (RSM). A 24 Box-Behnken matrix model with 3 centre points indicated that the maximum % Cd(II) removal was achieved at the initial concentration, dose, pH and time of 60.87 mg/L, 0.5 g/L, 7, and 30 min, respectively. The adsorption equilibrium was investigated by applying Freundlich, Langmuir, Temkin, and Jovanoic isotherm models while Langmuir isotherm exhibited the best fit (R2 = 0.99). The maximum Cd(II) adsorption capacity value of JS-AC was 73.53 mg/g. Finally, JS-AC was regenerated with 0.1M HNO3 as the desorption medium and reused for five successive cycles. This study indicated that jute stick, the under-utilised agro-residue of a cash crop, could be converted into a valuable product like JS-AC which offers immense application potential as an efficient and reusable adsorbent to treat Cd(II) contaminated aqueous medium before releasing in the environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The studied complexes could potentially form in the interstellar medium. • Binding energy increases from (CO) 2 to (CS) 2 with successive replacement of O by S. • The considerably higher polarizability of S over O results in extra stabilization. • Dispersion interaction plays a very important role in stabilizing all the complexes. The potential energy surfaces of two van der Waals complexes, namely CO-CS and (CS) 2 have been investigated and compared against the experimentally observed (CO) 2. Two stable conformers for (CO) 2 with very similar binding energies were identified, whose geometrical parameters and energetics were found to converge at CCSD(T)/CBS//MP2/aug-cc-pV5Z level. Therefore, CO-CS and (CS) 2 have also been optimized up to MP2/aug-cc-pV(5+d)Z level, where three and one stable conformers have been identified, respectively. Binding energy of (CS) 2 has been found to be over four times higher than (CO) 2. The same of CO-CS were found to lie in between that of (CO) 2 and (CS) 2. Energy decomposition analysis predicted dispersion interaction to play a major role in stabilizing the dimeric systems, its contribution increasing monotonically with decreasing binding energies. Atoms in molecule and non-covalent interaction analysis were also performed to visualize and analyze the nature of intermolecular interactions. [ABSTRACT FROM AUTHOR]