Probabilistic parameter estimation in a 2-step chemical kinetics model for n-dodecane jet autoignition

This paper demonstrates the development of a simple chemical kinetics model designed for autoignition of n-dodecane in air using Bayesian inference with a model-error representation. The model error, i.e. intrinsic discrepancy from a high-fidelity benchmark model, is represented by allowing additional variability in selected parameters. Subsequently, we quantify predictive uncertainties in the results of autoignition simulations of homogeneous reactors at realistic diesel engine conditions. We demonstrate that these predictive error bars capture model error as well. The uncertainty propagation is performed using non-intrusive spectral projection that can also be used in principle with larger scale computations, such as large eddy simulation. While the present calibration is performed to match a skeletal mechanism, it can be done with equal success using experimental data only (e.g. shock-tube measurements). Since our method captures the error associated with structural model simplifications, we believe that the optimised model could then lead to better qualified predictions of autoignition delay time in high-fidelity large eddy simulations than the existing detailed mechanisms. This methodology provides a way to reduce the cost of reaction kinetics in simulations systematically, while quantifying the accuracy of predictions of important target quantities.     

MXenes as Emerging Materials: Synthesis,Properties, and Applications

Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising candidates for the solution of energy- and environmental-related problems. It is seen that the energy conversion and storage capacity of MXenes can be enhanced by changing the material dimensions, chemical composition, structure, and surface chemistry. Hence, it is also essential to understand how one can easily improve the structure–property relationship from an applied point of view. In the current review, we reviewed the fabrication, properties, and potential applications of MXenes. In addition, various properties of MXenes such as structural, optical, electrical, thermal, chemical, and mechanical have been discussed. Furthermore, the potential applications of MXenes in the areas of photocatalysis, electrocatalysis, nitrogen fixation, gas sensing, cancer therapy, and supercapacitors have also been outlooked. Based on the reported works, it could easily be observed that the properties and applications of MXenes can be further enhanced by applying various modification and functionalization approaches. This review also emphasizes the recent developments and future perspectives of MXenes-based composite materials, which will greatly help scientists working in the fields of academia and material science.     

COUPLING OF FINITE ELEMENT AND BOUNDARY ELEMENT METHODS FOR THE SCATTERING BY PERIODIC CHIRAL STRUCTURES

Consider a time-harmonic electromagnetic plane wave incident on a biperiodic structure in R^3. The periodic structure separates two homogeneous regions. The medium inside the structure is chiral and nonhomogeneous. In this paper, variational formulations coupling finite element methods in the chiral medium with a method of integral equations on the periodic interfaces are studied. The well-posedness of the continuous and discretized problems is established. Uniform convergence for the coupling variational approximations of the model problem is obtained.     

Thermal performance modeling of modified absorber wall of solar chimney-shaped channels system for building ventilation

Journal of Thermal Analysis and Calorimetry - This paper aims to compare the thermal performance of four different configurations of absorber wall for the solar chimney-shaped channels. A detailed...     

Fixed point theorems with respect to a contractive condition of integral type

We derive some fixed point theorems for mappings satisfying a contractive condition of integral type.     

The Hydrothermal Synthesis of Petalite Mineral Phases and their Morphological Changing by Increasing of Temperature

In this investigation the Petalite minerals were synthesized hydrothermally at different temperatures from a glass with the composition Li₂CO₃:Al₂O₃: SiO₂ and the relation 1: 1: 8. On that occasion the following mineral phases arised:

• at low temperatures (410°C) α-petalite (unit cell å = 11.737 Å/b̊ = 5.17 Å/c̊ = 7.63 Å, space group P₂/a);
• At 490 °C α-petalite was splitted to quartz and an orthorhombic β₁-petalite (unit cell å = 18.24 Å/c̊ = 10.54 Å/c̊ = 10.57 Å, space group P_mC_n). β₁-petalite could be observated until 1000 °C.
• at 560 °C tetragonal β₂-petalite (unit cell å = 7.50 Å/c̊ = 9.07 Å, space group P 4₃2₁2) in parallel with β₁-petalite;
• Behind 750 °C β₂-petalite was not observed.
• Behind 900 °C a pseudohexagonal mineral phase developed from β₁-petalite. May be it is possible to indicate this phase as hexagonal (unit cell å = 5.217 Å/c̊ = 5.464 Å, space group P 6₂22 or P 6₄22). The author suggests to denote this phase as β₃-petalite.

     

Novel experimental design paradigm for development of eco-friendly gradient chromatographic method for simultaneous determination of metronidazole and spiramycin

This work describes the innovative experimental design-assisted development of a green gradient chromatographic method for concomitant analysis of metronidazole (MTR) and spiramycin (SPR). Two different designs including fractional factorial and Box-Behnken designs were implemented for screening and optimization steps, respectively. The optimum chromatographic conditions involved a mobile phase consisting of ethanol and 20 mM sodium dihydrogen phosphate solution (pH adjusted to 2.5) in the ratio 2:98 (v/v) for 2 min then the ratio changed to 30:70 (v/v). The flow rate was 1.3 mL/minute. Separation and analysis were performed on X-bridge C18 (150 mm × 4.6 mm × 3.5 μm) column with diode array detector set at 230 nm. Column oven temperature was 40°C. A linear response was acquired over the range of 5–125 μg/mL for both drugs. Detection and quantitation limits were 0.86 and 2.62 μg/mL for MTR and 0.92 and 2.83 μg/mL for SPR, respectively. The method was implemented for determination of both drugs in three tablet formulations. The method was proved to be green as evaluated by three assessment tools. The application of experimental designs assists in development of a robust green chromatographic method in gradient elution mode for determination of both drugs within reasonable time.     

The Hydrothermal Effect on Crystal Development and Electrical Conductivity of Li2CO3

Lithiumcarbonat was treated hydrothermally in the range of temperature from 80 °C to 600 °C. The Li₂CO₃-crystals of the starting material were monoclinic with the unit cell a = 8.39 Å, b = 5.00 Å, c = 6.21 Å, β = 114.5° and the space group C2/c (Zemann). During the increase of temperature the habit of the Li₂CO₃-crystals changed in the ranges of higher temperatures that they could be described as pseudocubic. In parallel with this development the electrical conductivity of the crystals also changed.     

Transmission properties of space-time modulated metamaterials

We prove the possibility of achieving exponentially growing wave propagation in space-time modulated media and give an asymptotic analysis of the quasifrequencies in terms of the amplitude of the time modulation at the degenerate points of the folded band structure. Our analysis provides the first proof of existence of k-gaps in the band structures of space-time modulated systems of subwavelength resonators.