The synthesis of series of dysprosium-doped lithium manganese oxide in the general formula LiDyxMn2?xO4 (x?=?0.0, 0.05, 0.1, 0.15, and 0.2) using double stage coprecipitation method followed by microwave heat treatment is reported. The characterization results of X-ray diffraction and infrared spectroscopy have illustrated the cubic structure for all the compounds. The lattice parameter has been observed to decrease with dysprosium doping. The influence of doping in elastic property of the samples has been studied with infrared spectroscopy. The grain size of the LiDy0.05Mn1.95O4 has been observed to be less than 1???m. The Image J software has been used to further analyze the micrographs. The initial capacity of the samples are observed to decrease with Dy3+ doping, but the capacity retention after 50 cycles for Dy 0.05, 0.1, 0.15, and 0.2 samples are reported as 95.4%, 93.2%, 91.3%, and 87.7%, respectively. The electrochemical impedance spectra has been performed to analyze the effectiveness of Dy3+ ion doping and the act of Dy doping has been observed to reduce the charge transfer resistance and increase the Li ion diffusion coefficient. 相似文献
We introduce an adjusted likelihood ratio procedure for computing pointwise confidence intervals for survival functions from censored data. The test statistic, scaled by a ratio of two variance quantities, is shown to converge to a chi-squared distribution with one degree of freedom. The confidence intervals are seen to be a neighborhood of a semiparametric survival function estimator and are shown to have correct empirical coverage. Numerical studies also indicate that the proposed intervals have smaller estimated mean lengths in comparison to the ones that are produced as a neighborhood of the Kaplan-Meier estimator. We illustrate our method using a lung cancer data set. 相似文献
Although field-collected recordings typically contain multiple simultaneously vocalizing birds of different species, acoustic species classification in this setting has received little study so far. This work formulates the problem of classifying the set of species present in an audio recording using the multi-instance multi-label (MIML) framework for machine learning, and proposes a MIML bag generator for audio, i.e., an algorithm which transforms an input audio signal into a bag-of-instances representation suitable for use with MIML classifiers. The proposed representation uses a 2D time-frequency segmentation of the audio signal, which can separate bird sounds that overlap in time. Experiments using audio data containing 13 species collected with unattended omnidirectional microphones in the H. J. Andrews Experimental Forest demonstrate that the proposed methods achieve high accuracy (96.1% true positives/negatives). Automated detection of bird species occurrence using MIML has many potential applications, particularly in long-term monitoring of remote sites, species distribution modeling, and conservation planning. 相似文献
Transient numerical simulations of fluid flow and heat transfer over a bank of flat tubes have been carried for both in-line
and staggered configurations for the following boundary conditions: (a) isothermal and (b) isoflux. The effect of Reynolds
number, Prandtl number, length ratio, and the height ratio, on the Nusselt number, and the dimensionless pressure drop are
elucidated. Correlations are proposed for both pressure drop and Nusselt number and optimum configurations have been determined. 相似文献
Two-dimensional numerical studies of flow and temperature fields for turbulent natural convection and surface radiation in
inclined differentially heated enclosures are performed. Investigations are carried out over a wide range of Rayleigh numbers
from 108 to 1012, with the angle of inclination varying between 0° and 90°. Turbulence is modeled with a novel variant of the k–ε closure model. The predicted results are validated against experimental and numerical results reported in literature. The
effect of the inclination of the enclosure on pure turbulent natural convection and the latter’s interaction with surface
radiation are brought out. Profiles of turbulent kinetic energy and effective viscosity are studied to observe the net effect
on the intensity of turbulence caused by the interaction of natural convection and surface radiation. The variations of local
Nusselt number and average Nusselt number are presented for various inclination angles. Marked change in the convective Nusselt
number is found with the orientation of enclosure. Also analyzed is the influence of change in emissivity on the flow and
heat transfer. A correlation relevant to practical applications in the form of average Nusselt number, as a function of Rayleigh
number, Ra, radiation convection parameter, NRC and inclination angle of the enclosure, φ is proposed. 相似文献
The standard Gibbs transfer energies of 18-crown-6,dibenzo-18-crown-6, cryptands 21, 22 and 222 frommethanol to methanol + N-methyl-2-pyrrolidinone(NMP) mixtures were determined from solubility andpartition measurements at 30 °C. While the Gibbs energy of transfer of 18-C-6 is positive,increases up to XNMP = 0.7 and thereafter decreases, the transfer energy ofdibenzo-18-C-6 is negative and decreases with the addition of NMP. However,the transfer energy of cryptand 21becomes increasingly negative with theaddition of NMP while that of cryptand 22 ispositive and increases under the sameconditions. For cryptand 222, the transferenergy is slightly negative up toXNMP = 0.5 butdecreases markedly at higher compositions of NMP. These results have been explainedin terms of the various types of interaction between the ligand molecules, solventcomponents and the effect of solvent–solvent interactions on them. 相似文献
Summary: The effect of polydispersity on polymer blend phase behavior is studied by in situ small‐angle X‐ray scattering. In a polydisperse polyethylene (PE)/isotactic poly(propylene) (iPP) blend, the enthalpic portion of the interaction parameter is greater than that of a corresponding blend with lower polydispersity. This is attributed to the presence of long chains, which provide a higher interaction energy and packing constraint, reducing the system miscibility. As expected, the radius of gyration is higher in the system with higher polydispersity.
Comparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals. 相似文献
Global warming challenges are fueling the demand to develop an efficient catalytic system for the reduction of CO2, which would contribute significantly to the control of climate change. Herein, as-synthesized bismuthoxide-decorated graphene oxide (Bi2O3@GO) was used as an electro/thermal catalyst for CO2 reduction. Bi2O3@GO is found to be distributed uniformly, as confirmed by scanning electron and transmission electron microscopic analysis. The X-ray diffraction (XRD) pattern shows that the Bi2O3 has a β-phase with 23.4 m2 g−1 BET surface area. Significantly, the D and G bands from Raman spectroscopic analysis and their intensity ratio (ID/IG) reveal the increment in defective sites on GO after surface decoration. X-ray photoelectron spectroscopic (XPS) analysis shows clear signals for Bi, C, and O, along with their oxidation states. An ultra-low onset potential (−0.534 V vs. RHE) for the reduction of CO2 on Bi2O3@GO is achieved. Furthermore, potential-dependent (−0.534, −0.734, and −0.934 vs. RHE) bulk electrolysis of CO2 to formate provides Faradaic efficiencies (FE) of approximately 39.72, 61.48, and 83.00 %, respectively. Additionally, in time-dependent electrolysis at a potential of −0.934 versus RHE for 3 and 5 h, the observed FEs are around 84.20 % and 87.17 % respectively. This catalyst is also used for the thermal reduction of CO2 to formate. It is shown that the thermal reduction provides a path for industrial applications, as this catalyst converts a large amount of CO2 to formate (10 mm ). 相似文献
A fluorine-containing tetrasubstituted stereogenic center is a highly valued structural feature in medicinal chemistry. Herein, we describe the direct coupling of racemic α-fluoronitriles and aldehydes promoted by a chiral CuI/Barton's base catalytic system, delivering α-tetrasubstituted α-fluoro-β-hydroxynitriles with satisfactory stereoselection. The stereochemical course was positively biased by the combined use of asymmetrical achiral thiourea as a supplementary ligand for CuI, which significantly enhanced the stereoselectivity. Both aromatic and aliphatic aldehydes were implemented to provide densely and stereoselectively functionalized chiral building blocks with aliphatic and aromatic tails. 相似文献