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It is a formidable task to suppress the limit cycles for 2 × 2 systems with memory type nonlinearity in particular. The feasibility of suppression of such nonlinear self oscillations has been explored by using pole placement technique. The novelty of the work lies with the investigation in case of the memory type non linearity like backlash especially which is an inherent Characteristic of a Governor used for usual load frequency control of an inter-connected power system and elsewhere. Suppression of Limit Cycle using pole placement is adopted either arbitrary or optimal selection using Riccati Equation through State Feed Back. The analysis is based on harmonic linearization/harmonic balance method using graphical method which has been substantiated by digital simulation/use of SIMULINK Tool Box and the same have been illustrated through example.

Rivers play an integral part in the sustenance of life on earth. Flooding in rivers hinders the everyday lifestyle of the people in that region. Therefore, river engineers need to understand the characteristics of rivers (both in-bank and overbank flow conditions) and mitigate flood impacts using this study. The channel’s sinuous nature causes erosion of its outer wall and silt deposition on its inner wall. These changes in the terrain make it vital to design the meandering compound channel. The floodplains act as storage for floods during high flows. Levees, both straight and meandering, can be constructed on both sides of the channel to guard the surrounding lands. For doubly meandering levee alignment, the momentum transfer between the main channel and the adjoining floodplains affects the velocity distribution across the channel cross-section. So, hydraulic engineers must investigate this complex flow phenomenon in the case of a doubly meandering compound channel. This study investigates the flow in meandering compound channels using numerical and physical modelling, both of which are important in understanding non-uniform flow and its behaviour. Flood management, sediment transport, riverbank protection, and other critical engineering problems can be solved with accurate velocity and boundary shear distribution predictions along the open channel's cross-section. As a result, a research is presented on the sharing of shear stress throughout the channel bed, as well as boundary and velocity over the cross section of the main channel and the floodplains of meandering compound channels. The authors attempt to include flow complexity by modifying measurable properties of a meandering compound channel, such as width ratio, aspect ratio, and hydraulic parameter, relative depth, all of which have a significant impact on the flow. The geometry of meandering compound channels, having straight as well as sinuous floodplain levees, is chosen for this study. Unlike the experimental models, numerical hydraulic models are remarkably economical. So, in this research, the numerical hydraulic model is adopted to determine the different flow characteristics of compound meandering channels. In this paper, a complete three-dimensional and two-phase Computational Fluid Dynamics (CFD) model of the meandering compound channels is analyzed making use of the RNG K-ɛ turbulence model as we as Volume of Fluid (VOF) methodology. A comparison study between numerical results and experimental results are represent considering the two different experimental data of compound meandering channel having the main channel meandered with sinuosity (ratio of channel length to the down valley length) of 1.37 and were flanked by straight floodplains as well as meandered flood plains having sinuosity 1.06 on both sides. By error analysis, it is observed that the numerical results agree with that of the experimental ones.

We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6 × 1041 erg s−1, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (TBB ≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival Hubble Space Telescope data taken on 2003 August 3 reveals a ∼20 M⊙ progenitor candidate with log (L/L⊙) = 5.0 dex and Teff = 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17–24 M⊙ primary component.

Introduction: Boerhaavia diffusa Linn. (Family: Nyctaginaceae) is a widely used plant in India and Brazil as a traditional medicine for treatment of urolithiasis and other urinary disorders.Objectives: The aim of this study was to evaluate the antiurolithic activity of Boerhaavia diffusa root aqueous extract (BDE) as prophylaxis for renal stones.Methods: In vitro calcium oxalate (CaOx) crystallization inhibitory effect of BDE was determined by measuring change in turbidity at 620nm on addition of sodium oxalate in the synthetic urine. In a rat model of urolithiasis, induced by adding 0.75% ethylene glycol (EG) in drinking water and effect of simultaneous treatment of BDE (100-200 mg/kg) was observed for 28 days.Results: BDE inhibited CaOx nucleation, aggregation and crystal formation in the synthetic urine in vitro on addition of NaOx. The lithogenic treatment caused polyuria, weight loss, hyperoxaluria and impairment of renal function which was prevented by BDE. Hyperoxaluria and CaOx crystaldeposition in the renal tubules caused by EG intake was prevented by BDE treatment.Conclusion: This study indicates that the antiurolithic activity of Boerhaavia diffusa extract possibly mediated through inhibition of CaOx crystallization, diuresis and hypo-oxaluria may justify its prophylactic use in urolithiasis.