Materials and Energy sciences

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An analysis of the droplet support fiber effect on the evaporation process


ABSTRACT

This paper presents an analysis of the effect of the droplet support fiber on the droplet evaporation process. This effect is evaluated for a droplet evaporating in a hot environment at atmospheric pressure using the experimental results of the present study and those in the literature. Selected published results are acquired using similar test conditions and experimental setups as the present data. The only main difference between these studies is the droplet support fiber diameter which varies between 14 µm and 225 µm. The ambient temperature explored in these studies ranges from room temperature up to 973 K. n-Heptane is selected because it is the most common fuel used in these studies. The main findings are that the cross-fiber technique, which uses 14 µm fiber diameters, induces no noticeable heat transfer into the droplet and consequently does not interfere with the evaporation process. In contrast, the classical fiber technique, which uses relatively larger fibers, greatly enhances the droplet evaporation rate as a consequence of increased conduction heat transfer through the fiber. A correlation is proposed to quantify the level of this increase as a function of ambient temperature and the fiber cross-sectional area.


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Solution of linear fractional partial differential equations based on the operator matrix of fractional Bernstein polynomials and error correction


ABSTRACT

In this paper, firstly, a new method which makes a modification of the Bern-stein polynomials is introduced to solve the linear fractional partial differential equations (FPDEs). The biggest advantage of the fractional Bernstein polynomials is that the order can be changed with the order of the fractional partial differential equations. For the first time, we try to use this method to solve the linear fractional partial differential equations. Secondly, convergence analysis and error correction are also given to make the calculation results more accurate. The concrete content of this method and error correction are explained briefly and numerical examples are given to demonstrate the validity and accuracy of the method.


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Shifted-Chebyshev-polynomial-based numerical algorithm for fractional order polymer visco-elastic rotating beam


ABSTRACT

In this paper, an effective numerical algorithm is proposed for the first time to solve the fractional visco-elastic rotating beam in the time domain. On the basis of fractional derivative Kelvin–Voigt and fractional derivative element constitutive models, the two governing equations of fractional visco-elastic rotating beams are established. According to the approximation technique of shifted Chebyshev polynomials, the integer and fractional differential operator matrices of polynomials are derived. By means of the collocation method and matrix technique, the operator matrices of governing equations can be transformed into the algebraic equations. In addition, the convergence analysis is performed. In particular, unlike the existing results, we can get the displacement and the stress numerical solution of the governing equation directly in the time domain. Finally, the sensitivity of the algorithm is verified by numerical examples.


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Dimerization of pentacyclopentacorannulene C30H10 as a strategy to produce C60H20 as a precursor for C60


ABSTRACT

The chemical synthesis of C 60 fullerene in the laboratory is still a challenge. In order to achieve this goal, we propose a synthetic route based on the dimerization between two pentacyclopentacorannulene (C 30 H 10) fragments employing the Diels-Alder cycloaddition reaction. Density functional calculations indicate that a step wise non-concerted dimerization mechanism of C 30 H 10 is favored over a one stage dimerization.


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Ultrasonic identification technique in recycling of lithium ion batteries


ABSTRACT

The recycling of lithium ion batteries has been mentioned as one of the near-future waste management necessities. In order for recycling to be economically viable, straightforward and cost effective techniques need to be developed to separate the individual materials in a composite electrode. Ultrasonic separation might be such a technique, provided that lithium ion battery microparticles respond predictably to a sound field. Lithium ion battery cathodes contain hydrophobic carbon. Owing to the incompressibility of a solid, the thin gaseous layer surrounding these hydrophobic particles must oscillate asymmetrically, when subjected to ultrasound. Consequently, the harmonic content of the ultrasound signal radiated from hydrophobic microparticles must be higher than that from hydrophilic microparticles with the same size. The question of whether the harmonic signal response generated by physical hydrophobic microparticles present in lithium ion battery cathodes is higher than the harmonic response of other component materials in the cathode is the focus of this paper. The scattering response of cathode materials subjected to 1-MHz ultrasound was measured and compared. The cathode materials C65, PVDF, and NMC respond differently to 1-MHz ultrasound. The superharmonic response of C65 has been attributed to asymmetric oscillations owing to its hydrophobicity. In addition, C65 hydrophobic microparticles might be suitable candidates for harmonic imaging.


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A Vanadium Redox Flow Battery based on a highly concentrated Protic Ionic Liquid Electrolyte


ABSTRACT

A protic ionic liquid is inctroduced for the first time as a solvent for a high energy density vanadium redox flow battery.  The proof-of-concept redox flow cell with a concentration of 3 mol L−1 vandyl sulfate electrolyte was tested for a total of 30 cycles at 40°C, showing an open circuit potential of 1.38 V, a nominal capacity of 1900 mAh at a current density of 40 mA cm−1 and energy and coulombic efficiencies of 64 and 90%, respectively. The continuous 16 hours of cycling suggest that the concentrated anolyte and catholyte are thermally stable and cycleable. This study underlines a new route to improve the energy-to-volume ratio of this promising energy storage system.

 

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Mechanisms of glass crystallization analyzed by electron backscatter diffraction (EBSD)


ABSTRACT

This Le Studium Fellowship was used to analyze the crystal growth in levitated melts. Furthermore, methodical questions concerning the method EBSD as well as XRD were addressed. Finally, the literature concerning oriented surface nucleation in glasses was completed. 


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Coordination compounds as antioxidants: activity evaluation by combining first-principle calculations and solid-state NMR


ABSTRACT

Inspired by the active site of the copper-zinc superoxide dismutase enzyme, we studied the reactivity of imidazolic ligands to improve the design and synthesis of coordination compounds, active against the superoxide radical (responsible of DNA, cellular and tissues damage, leading to illness like cancer, atherosclerosis, heart failures, etc.). By the joint use of first-principle calculations and solid state NMR spectroscopy, we identified the relationship between the structural characteristics and the reactivity of the synthesized compounds, that lead and modulates their antioxidant activity. 


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Catholyte formulations for high-energy Li-S batteries


ABSTRACT

The sulphur electrode in LiS batteries suffers from rapid capacity loss and low efficiency due to the solubility of long chain polysulphides formed during discharge. Herein, we demonstrate the beneficial effect of original catholyte formulations containing redox active organyl disulphides (PhS2Ph) on the capacity utilization and retention as well as the efficiency in LiS batteries. Resulting from the chemical equilibria in the electrolyte between the sulphur/polysulphides (S8/Sx2-) and disulphide/thiolates (PhS2Ph/PhSx-), the polysulphide redox shuttle phenomenon is minimized due to the suppression of formation of soluble polysulphides (Sx2-, x > 4). Using the catholyte containing 0.4 M Ph2S2 as an additive in a standard base electrolyte (DOL/DME + LiTFSI/LiNO3), a stable capacity of 1050 mAh.g-1 is obtained under galvanostatic cycling at C/5 with a coulombic efficiency of >99.5%. At 45°C, it is shown that the formulated catholyte enables galvanostatic cycling at a high c-rate of 1C over 500 cycles with a capacity above 900 mAh.g-1 and a high energy efficiency of 82%.


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Numerical Algorithms and Observer Design for Fractional Order Systems


ABSTRACT

During the past decades, fractional calculus has gained great interest and success in the field of automatic control. The research project was on numerical algorithms and observer design for fractional order systems. Various effective algorithms have been proposed to simulate different kinds of systems. Accurate and robust algebraic observers have been designed to estimate useful system information in noisy environment. An international conference has been held with the support of the project, which provided a platform for researchers to exchange results and advanced technology. Moreover, this project has provided an international collaboration opportunity for faculties and students both from INSA Centre Val de Loire and Yanshan University in China.