The copyrolysis and cocombustion behaviors of Pingshuo
coal and
the biomasses (sawdust and rice straw) have been investigated using
a thermogravimetric analyzer. The experimental results indicate that
there exist synergetic effects between the biomasses and Pingshuo
coal during their coconversion process. The initial temperature of
volatile emission from Pingshuo coal and the temperature corresponding
to the maximum conversion rate during the copyrolysis change with
the biomass mixture ratio. Moreover, it can be deduced from the comparison
between the experimental and the calculated DTG curves that the copyrolysis
process is not the sum of Pingshuo coal and the biomass conversion.
During their cocombustion process, the larger the mixture
ratio of the biomass is, the lower the ignition temperature and the
burnout temperature are, and the larger the combustion characteristic
index is. In addition, the maximum combustion rate and the combustion
performance are the best when the mixture ratio of the biomass is
70 wt % in the research. Moreover, the activation energy and the frequency
factor of the copyrolysis and the cocombustion were calculated by
the Coats–Redfern method and the first-order reaction model.
The results show that the activation energy and the frequency factor
change with the mixture ratio of the biomass, and the regularity was
consistent with the above-mentioned conclusions. Therefore, it can
be deduced that the addition of the biomass can facilitate the pyrolysis
and the combustion of Pingshuo coal, and improve the utilization field
of Pingshuo coal.
Atomic force microscopy (AFM) has become the most commonly used tool to measure the mechanical properties of biological cells. In AFM indentation experiments, the Hertz and Sneddon models of contact mechanics are usually adopted to extract the elastic modulus by analyzing the load-indent depth curves for spherical and conical tips, respectively. However, the effects of surface tension, neglected in existing contact models, become more significant in indentation responses due to the lower elastic moduli of living cells. Here, we present two simple yet robust relations between load and indent depth considering surface tension effects for spherical and conical indentations, through dimensional analysis and finite element simulations. When the indent depth is smaller than the intrinsic length defined as the ratio of surface tension to elastic modulus, the elastic modulus obtained by classical contact mechanics theories would be overestimated. Contrary to the majority of reported results, we find that the elastic modulus of a cell could be independent of indent depths if surface tension is taken into account. Our model seems to be in agreement with experimental data available. A comprehensive comparison will be done in the future.
Polymer-based nanodielectrics have been intensively investigated for their potential application as energy storage capacitors. However, their relatively low energy density (Ue) and discharging efficiency (η) may greatly limit their practical usage. In present work, high insulating two-dimensional boron nitride nanosheets (BNNS), were introduced into a linear dielectric polymer (P(VDF-TrFE-CTFE)-g-PMMA) matrix to enhance the energy storage performance of the composite. Thanks to the surface coating of polydopamine (PDA) on BN nanosheets, the composite filled with 6 wt% coated BNNS (mBNNS) exhibits significantly improved breakdown strength (Eb) of 540 MV/m and an energy density (Ue) of 11 J/cm3, which are increased by 23% and 100%, respectively as compared with the composite filled with the same content of pristine BNNS. Meanwhile, η of both composites is well retained at around 70% even under a high voltage of 400 MV/m, which is superior to most of the reported composites. This work suggests that complexing polymer matrix with linear dielectric properties with surface coated BNNS fillers with high insulating 2D structure might be a facile strategy to achieve composite dielectrics with simultaneously high energy density and high discharging efficiency.
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