Hydrogen in polycrystalline silicon solar cell material: Its role and characteristics

The role and the characteristics of hydrogen in different polycrystalline silicon material are studied in this paper. The hydrogen diffusion through the grains and the grain boundaries, and its diffusion coefficient, are investigated. Moreover, the influence of the oxygen and the carbon contents on the diffusion mechanism of hydrogen in silicon is addressed. Also, it is found that the minority carrier diffusion length of polycrystalline silicon wafers considerably improves when annealed in hydrogen at high temperatures (>1000°C). Consequently, a significant amount of oxygen is out-diffused from the bulk of the wafers.     

Lattice Boltzmann simulation of natural convection in tall enclosures using water/SiO2 nanofluid

Natural convection in enclosures using water/SiO₂ nanofluid is simulated with Lattice Boltzmann method (LBM). This investigation compared with other numerical methods and found to be in excellent agreement. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number of base fluid, Ra = 10³-10⁵, the volumetric fraction of nanoparticles between 0 and 4% and aspect ratio (A) of the enclosure between 0.5 and 2. The thermal conductivity of nanofluids is obtained on basis of experimental data. The comparisons show that the average Nusselt number increases with volume fraction for the whole range of Rayleigh numbers and aspect ratios. Also the effect of nanoparticles on heat transfer augments as the enclosure aspect ratio increases.     

Causal density and integrated information as measures of conscious level

An outstanding challenge in neuroscience is to develop theoretically grounded and practically applicable quantitative measures that are sensitive to conscious level. Such measures should be high for vivid alert conscious wakefulness, and low for unconscious states such as dreamless sleep, coma and general anaesthesia. Here, we describe recent progress in the development of measures of dynamical complexity, in particular causal density and integrated information. These and similar measures capture in different ways the extent to which a system's dynamics are simultaneously differentiated and integrated. Because conscious scenes are distinguished by the same dynamical features, these measures are therefore good candidates for reflecting conscious level. After reviewing the theoretical background, we present new simulation results demonstrating similarities and differences between the measures, and we discuss remaining challenges in the practical application of the measures to empirically obtained data.     

Effect of cathode sheet resistance on segmented-in-series SOFC power density

Segmented-in-series solid oxide fuel cells with relatively short cell lengths of 1.4 mm were fabricated with varying LSM cathode current collector thicknesses. Increasing the LSM thickness from 11 to 91 μm yielded a factor of 2–3 area-specific resistance decrease and a similar power density increase. The maximum power density measured at 800 °C was 0.53 W cm⁻² calculated based on total array area (including interconnect), and 0.9 W cm⁻² calculated based on active cell area. A segmented-in-series electrical model was used to quantitatively explain the results based on the decreased cathode sheet resistance. The model also showed that the cell lengths were near optimal for maximizing the power density of these cells.     

A minimum parameter approach to crystal plasticity modelling

Plastic deformation processes in hexagonal metals are complex and are best analyzed using procedures such as visco-plastic self-consistent crystal plasticity modelling. These involve a large number of adjustable parameters and make limited use of independent input data. Using physical arguments, the authors show that several of the parameters can be replaced by experimentally measured values of critical resolved shear stresses from the literature. A further simplification derives from the argument that all deformation modes interact with the same substructure, and so a common work-hardening behaviour can be assumed as a reasonable first approximation. Furthermore, many microstructural contributions to the strength can be introduced through a single constant term. In these ways, the twelve or more adjustable parameters in the model are reduced to only three. This new approach is tested critically by applying it to a sheet magnesium alloy for which the plastic strain ratio varies markedly during the test. Its complex plastic behaviour, which arises from changes among the active deformation modes, is successfully predicted. A benefit of the present approach is that the effect of metallurgical variables such as grain size or precipitation strengthening can be readily investigated. Although tested here for a magnesium alloy, the same principles should be applicable to other hexagonal close-packed materials.     

Demonstrating the ascendancy of COVID-19 research using acronyms

Scientometrics - “COVID” which stands for corona virus disease, has become the world’s most infamous acronym. Previous analysis of acronyms in health and medical journals found a...     

MHD Turbulent and Laminar Natural Convection in a Square Cavity utilizing Lattice Boltzmann Method

In this study, the lattice Boltzmann method was used to solve the turbulent and laminar natural convection in a square cavity. In this paper a fluid with Pr = 6.2 and different Rayleigh numbers (Ra = 10³, 10⁴,10⁵ for laminar flow and Ra = 10⁷, 10⁸,10⁹ for turbulent flow) in the presence of a magnetic field (Ha = 0, 25, 50, and 100) was investigated. (Results show that the magnetic field drops the heat transfer in the laminar flow as the heat transfer behaves erratically toward the presence of a magnetic field in a turbulent flow. Moreover, the effect of the magnetic field is marginal for a turbulent flow in contrast with a laminar flow.The greatest influence of the magnetic field is observed at Ra = 10⁵ from Ha = 0 to 100 as the heat transfer decreases significantly.