An ecofriendly and economical method of Knoevenagel condensation of aromatic aldehydes with malononitrile catalyzed by lemon juice, a natural catalyst, in the absence of any solvent is described. 相似文献
Perovskite type LaCoxFe1−xO3 nanoparticles was synthesized by a sol-gel citrate method. The structural, electrical and sensing characteristics of the LaCoxFe1−xO3 system were investigated. The structural characteristics were performed by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to examine the phase and morphology of the resultant powder. The XRD pattern shows nanocrystalline solid solution of LaCoxFe1−xO3 with perovskite phase. Electrical properties of synthesized nanoparticles are studied by DC conductivity measurement. The sensor shows high response towards ammonia gas in spite of other reducing gases when x = 0.8. The effect of 0.3 wt.% Pd-doped LaCo0.8Fe0.2O3 on the response and a recovery time was also addressed. 相似文献
The occurrence of synchronization and amplitude death phenomena due to the coupled interaction of limit cycle oscillators (LCO) has received increased attention over the last few decades in various fields of science and engineering. Studies pertaining to these coupled oscillators are often performed by studying the effect of various coupling parameters on their mutual interaction. However, the effect of system parameters (i.e., the amplitude and frequency) on the coupled interaction of such LCO has not yet received much attention, despite their practical importance. In this paper, we investigate the dynamical behavior of time-delay coupled Stuart–Landau (SL) oscillators exhibiting subcritical Hopf bifurcation for the variation of amplitude and frequency of these oscillators in their uncoupled state. For identical SL oscillators, a gradual increase in the amplitude of LCO shrinks the amplitude death regions observed between the regions of in-phase and anti-phase synchronization leading to its eventual disappearance, resulting in the occurrence of phase-flip bifurcations at higher amplitudes of LCO. We also observe an alternate existence of in-phase and anti-phase synchronization regions for higher values of time delay, whose prevalence of occurrence increases with an increase in the frequency of the oscillator. With the introduction of frequency mismatch, the region of amplitude death. The forced response of SL oscillator shows an asymmetry in the Arnold tongue and the manifestation of asynchronous quenching of LCO. An increase in the amplitude of LCO narrows the Arnold tongue and reduces the region of asynchronous quenching observed in the system. Finally, we compare the coupled and forced response of SL oscillators with the corresponding experimental results obtained from laminar thermoacoustic oscillators and the numerical results from van der Pol (VDP) oscillators. We show that the SL model qualitatively displays many features observed experimentally in coupled and forced thermoacoustic oscillators. In contrast, the VDP model does not capture most of the experimental results due to the limitation in the independent variation of system parameters.
We report the synthesis of CuO-poly(acrylic) acid/CNT hybrid thin films by a cost-effective spin-coating technique for supercapacitor
application. Hybrid films were annealed at 300, 400, and 500 °C to study its effect on the supercapacitor behavior. X-ray
photoelectron spectroscopy and Fourier transform-infrared spectroscopy techniques were used for the phase identification and
determination of the organic component in the hybrid films, respectively. Surface morphology of the films was examined by
scanning electron microscopy and revealed the novel ring-like structures. The average diameter of the ring changes from 0.5
to 1.2 μm with increase in annealing temperature. Cyclic voltammetry is employed to estimate the specific capacitance (Csp) of the films in 1 M H2SO4 electrolyte. It is observed that the Csp increases from 188 to 258 Fg−1 with increase in annealing temperature. 相似文献
Control on the wettability of solid materials by liquid is a classical and key issue in surface engineering. Optically transparent water-repellent silica films have been spin-deposited on glass substrates at room temperature (∼27 °C). The wetting behavior of silica films was controlled by surface silylation method using dimethylchlorosilane (DMCS) as a silylating reagent. A coating sol was prepared by keeping the molar ratio of methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent, water (H2O) constant at 1:8.8:2.64 respectively, with 4 M NH4OH as a catalyst throughout the experiments and the amount of DMCS in hexane was varied from 0 to 12 vol.%. It was found that with an increase in vol.% of DMCS, the water contact angle values of the films increased from 78° to 136°. At 12 vol.% of DMCS, the film shows static water contact angle as high as 136° and water sliding angle as low as 18°. The hydrophobic silica films retained their water repellency up to a temperature 295 °C and above this temperature the films show superhydrophilic behavior. These results are compared with our earlier research work done on silylation of silica surface using hexamethyldisilazane (HMDZ) and trimethylchlorosilane (TMCS). The hydrophobic silica films were characterized by taking into consideration the Fourier transform infrared (FT-IR) spectroscopy, thermo gravimetric-differential thermal (TG-DT) analyses, scanning electron microscopy (SEM), atomic force microscopy (AFM), % of optical transmission, thermal and chemical aging tests, humidity tests, static and dynamic water contact angle measurements. 相似文献
The concept of coloring is studied for graphs derived from lattices with 0. It is shown that, if such a graph is derived from
an atomic or distributive lattice, then the chromatic number equals the clique number. If this number is finite, then in the
case of a distributive lattice, it is determined by the number of minimal prime ideals in the lattice. An estimate for the
number of edges in such a graph of a finite lattice is given. 相似文献
Frequency spectra of the complex permittivity for 1,2-dichloroethane–alcohol binary mixtures have been determined over the frequency range 10 MHz to 20 GHz at 15, 25, 35, and 45°C, using the time-domain reflectometry (TDR) technique, for 11 compositions of each 1,2 dichloroethane–alcohol system. The alcohols used in the study were methanol, ethanol, and 1-propanol. The relaxation in these systems can be described by a single relaxation time using the Debye model. The static dielectric constant, relaxation time, the corresponding excess dielectric properties, Kirkwood correlation factor, and Bruggeman factor of the mixtures have been determined. The static dielectric constants for the mixtures have been fitted with the modified Bruggeman model. 相似文献
The endo:exo ratio of 0.35:1 for the reaction of cyclopentadiene with methyl methacrylate observed in organic solvents can be converted to 3:1 in chloroaluminate ionic liquids with their effective reuse in Diels-Alder reactions. 相似文献