A study of the spectral characteristics of traffic noise attenuation by vegetation belts in Delhi

Traffic noise attenuation at different 1/3-octave frequencies is measured at three vegetation sites and a control site in Delhi, the capital city of India. The study indicates that attenuation generally increases with frequency. At low frequencies, maxima (between 10 and 16 dB) in relative attenuation are observed in the frequency interval between 315 and 400 Hz. Comparatively greater relative attenuation (>20 dB) is observed in the high frequency range between 10 and 12.5 kHz. A significantly higher relative attenuation of more than 24 dB is observed characteristically at 3.15 kHz at all the vegetation sites. The results indicate that vegetation belts could be used as effective barriers for traffic noise control along the roadsides.     

Investigation of factors influencing the performance of nanofluid-based direct absorption solar collector using Taguchi method

Journal of Thermal Analysis and Calorimetry - The performance of nanofluid-based solar collector depends on different factors like nanoparticle material, base fluid, mass fraction of nanoparticles,...     

Measurement of the resonance frequency of single bubbles using a laser Doppler vibrometer

The behavior of bubbles confined in tubes and channels is important in medical and industrial applications. In these small spaces, traditional means of experimentally observing bubble dynamics are often impossible or significantly perturb the system. A laser Doppler vibrometer (LDV) requires a narrow (<1 mm diameter) line-of-sight access for the beam and illumination of the bubble does not perturb its dynamics. LDV measurements of the resonance frequency of a bubble suspended in a small tank are presented to illustrate the utility of this measurement technique. The precision of the technique is similar to the precision of traditional acoustic techniques.     

System identification and early warning detection of thermoacoustic oscillations in a turbulent combustor using its noise-induced dynamics

Despite significant research, self-excited thermoacoustic oscillations continue to hinder the development of lean-premixed gas turbines, making the early detection of such oscillations a key priority. We perform output-only system identification of a turbulent lean-premixed combustor near a Hopf bifurcation using the noise-induced dynamics generated by inherent turbulence in the fixed-point regime, prior to the Hopf point itself. We model the pressure fluctuations in the combustor with a van der Pol-type equation and its corresponding Stuart–Landau equation. We extract the drift and diffusion terms of the equivalent Fokker–Planck equation via the transitional probability density function of the pressure amplitude. We then optimize the extracted terms with the adjoint Fokker–Planck equation. Through comparisons with experimental data, we show that this approach can enable prediction of (i) the location of the Hopf point and (ii) the limit-cycle amplitude after the Hopf point. This study shows that output-only system identification can be performed on a turbulent combustor using only pre-bifurcation data, opening up new pathways to the development of early warning indicators of thermoacoustic instability in practical combustion systems.     

A Facile,Sensitive and Rapid Sensing Platform Based on CoZnO for Detection of Fipronil; an Environmental Toxin

A sensitive detection of extremely toxic phenylpyrazole insecticide, ‘Fipronil’ is presented. Currently, the advancement of approaches for the detection of insecticides at low concentrations with less time is important for environmental safety assurance. Considering this fact, an effort has been made to develop an electrospun CoZnO nanofiber (NF) based label‐free electrochemical system for the detection of fipronil. The CoZnO NF were characterized using different techniques including field emission scanning electron microscopy (FE‐SEM), Energy Dispersive X‐Ray Analysis (EDX), X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and Raman Spectroscopy. Based on the experimental results, the proposed platform displayed a linear response for fipronil in the attogram/mL range despite the multiple interfering agents. The sensitivity of the device was found to be 3.99 KΩ (g/ml)^?1 cm^?2. Limit of detection (LOD) and limit of quantification (LOQ) were calculated and found to be 112 ag mL^?1 and 340 ag mL^?1 respectively. Further, this proposed sensor will be implemented in the fields for the rapid and proficient detection of the real samples.     

Enantioselective synthesis of functionalized medium-sized oxacycles

Enantioselective routes to functionalized, seven-, eight-, and nine-membered oxacycles that are amenable to further elaboration have been developed. Salient features of the methodology include highly diastereoselective and regioselective transformations of an ephedrine-derived epoxy morpholinone to functionalized precursors of the oxacycles. The ephedrine scaffold exerts remote stereocontrol in the functionalization of the appended oxacycle. [reaction: see text]     

Enantioselective synthesis of (R)-homocitric acid lactone

An expedient enantioselective approach to (R)-homocitric acid lactone from an ephedrine-derived morpholine-dione, a cationic glycolate equivalent, is described.     

Hydrolysis of Cyclic Ureas under Microwave Irradiation: Synthesis and Characterization of 7,8‐Diaminopelargonic Acid

A simple and efficient method for the synthesis of 7,8‐diaminopelargonic acid, a key intermediate in the biotin biosynthesis pathway, is reported. The d‐desthiobiotin powder was dissolved in concentrated hydrochloric acid, and the solution was exposed to microwave radiation of 2.45 GHz for varying lengths of time ranging from 60 s to 2 min. The product thus obtained was characterized by spectroscopic techniques and confirmed through bioassay. Further, the protocol was extended to the synthesis of several diamines from their corresponding cyclic ureas. The results show that the method is generally applicable and not only accelerates the hydrolysis reaction but also offers excellent yields.