Single-degree-of-freedom model of displacement in vortex-induced vibrations

In contrast to the approach of coupling a nonlinear oscillator that represents the lift force with the cylinder’s equation of motion to predict the amplitude of vortex-induced vibrations, we propose and show that the displacement can be directly predicted by a nonlinear oscillator without a need for a force model. The advantages of the latter approach include reducing the number of equations and, subsequently, the number of coefficients to be identified to predict displacements associated with vortex-induced vibrations. The implemented single-equation model is based on phenomenological representation of different components of the transverse force as required to initiate the vibrations and to limit their amplitude. Three different representations for specific flow and cylinder parameters yielding synchronization for Reynolds numbers between 104 and 114 are considered. The method of multiple scales is combined with data from direct numerical simulations to identify the parameters of the proposed models. The variations in these parameters with the Reynolds number, reduced velocity or force coefficient over the synchronization regime are determined. The predicted steady-state amplitudes are validated against those obtained from high-fidelity numerical simulations. The capability of the proposed models in assessing the performance of linear feedback control strategy in reducing the vibrations amplitude is validated with performance as determined from numerical simulations.

     

Syrian hamster embryo (SHE) assay (pH 6.7) coupled with infrared spectroscopy and chemometrics towards toxicological assessment

The Syrian hamster embryo (SHE) assay (pH 6.7) is an in vitro candidate to replace in vivo carcinogenicity tests. However, the conventional method of visual scoring of foci (non-transformed vs. transformed colonies) can be time-consuming and is open to subjectivity. Infrared (IR) spectroscopy has the potential to provide objective assessment of such SHE colonies with the added advantage of potentially providing mechanistic information. In this study, SHE cells were treated with one of eight different chemical regimens, allowed in culture to attach and form foci on IR-reflective glass slides; these were subsequently interrogated by attenuated total reflection (ATR) Fourier-transform IR (FTIR) spectroscopy. Derived mid-IR spectra (n = 13,406) were subjected to chemometric analysis focusing primarily on the extraction of biochemical information related to test agent treatment and/or morphological transformation. The use of ATR-FTIR spectroscopy with chemometrics to analyze the SHE assay is a novel approach to toxicological assessment.     

Preparation, structure and spasmolytic activities of some derivatives of harmine series of alkaloids

Keeping in view the interesting chemistry and pharmacological importance of harmine series of bases -- the beta-carboline alkaloids, a number of new derivatives of tetrahydroharmine and harmalol have been prepared and characterized through spectral studies. Some of these derivatives showed spasmolytic activity. It was observed that all the N-acyl tetrahydroharmine derivatives are stable, not labile and no ring opening occurs in these compounds, as reported recently.     

Universal sound absorption in amorphous solids: A theory of elastically coupled generic blocks

Glasses are known to exhibit quantitative universalities at low temperatures, the most striking of which is the ultrasonic attenuation coefficient Q^?1. In this work we develop a theory of coupled generic blocks with a certain randomness property to show that universality emerges essentially due to the interactions between elastic blocks, regardless of their microscopic nature.     

Flow of Eyring-Powell liquid due to oscillatory stretchable curved sheet with modified Fourier and Fick’s model

Applied Mathematics and Mechanics - This study deals with the features of the mass and heat transport mechanism by adopting a modified version of Fourier and Fick’s model known as the...     

Maximum temperature analysis in a Li-ion battery pack cooled by different fluids

Journal of Thermal Analysis and Calorimetry - The use of Li-ion battery in electric vehicles is becoming extensive in the modern-day world owing to their high energy density and longer life. But...     

On the metric dimension of barycentric subdivision of Cayley graphs

Acta Mathematicae Applicatae Sinica, English Series - In a connected graph G, the distance d(u, v) denotes the distance between two vertices u and v of G. Let W = {w 1, w 2, ···, w...     

Effects of Graphene Nanoplatelets on Mechanical and Fire Performance of Flax Polypropylene Composites with Intumescent Flame Retardant

The integration of intumescent flame-retardant (IFR) additives in natural fiber-based polymer composites enhances the fire-retardant properties, but it generally has a detrimental effect on the mechanical properties, such as tensile and flexural strengths. In this work, the feasibility of graphene as a reinforcement additive and as an effective synergist for IFR-based flax-polypropylene (PP) composites was investigated. Noticeable improvements in tensile and flexural properties were achieved with the addition of graphene nanoplatelets (GNP) in the composites. Furthermore, better char-forming ability of GNP in combination with IFR was observed, suppressing HRR curves and thus, lowering the total heat release (THR). Thermogravimetric analysis (TGA) detected a reduction in the decomposition rate due to strong interfacial bonding between GNP and PP, whereas the maximum decomposition rate was observed to occur at a higher temperature. The saturation point for the IFR additive along with GNP has also been highlighted in this study. A safe and effective method of graphene encapsulation within PP using the fume-hood set-up was achieved. Finally, the effect of flame retardant on the flax–PP composite has been simulated using Fire Dynamics Simulator.