Computational Investigation of Carbon Based Anode Materials for Li- and Post-Li- Ion Batteries

Due to its negligible capacity with respect to sodium intercalation, graphite is not suited as anode material for sodium ion batteries. Hard carbon materials, on the other hand, provide reasonably high capacities at low insertion potential, making them a promising anode materials for sodium (and potassium) ion batteries. The particular nanostructure of these functionalized carbon-based materials has been found to be crucially linked to the material performance. However, there is still a lack of understanding with respect to the functional role of structural units, such as defects, for intercalation and storage. To overcome these problems, the intercalation of Li, Na, and K in graphitic model structures with distinct defect configurations has been investigated by density functional theory. The calculations confirm that defects are able to stabilize intercalation of larger alkali metal contents. At the same time, it is shown that a combination of phonon and band structure calculations are able to explain characteristic Raman features typically observed for alkali metal intercalation in hard carbon, furthermore allowing for the quantification of the alkali metal intercalation inbetween the layers of hard carbon anodes.

The short- and long-term impacts of climate change on the irrigated barley yield in Iran: an application of dynamic ordinary least squares approach

Given the extensive impacts of climate change on the agricultural sector and their interactions, the climate change is known as one of the main factors influencing agricultural production. The present study aims to explore the short- and long-term impacts of climate change on the yield of irrigated barley in 28 Iranian provinces over the 1999-2015 period. The research uses panel data and dynamic ordinary least squares (DOLS) method. The study also estimated the threshold levels of temperature and rainfall which confirmed an inverted U-shaped relationship between climate change variables and irrigated barley yield. The threshold levels of temperature and rainfall are estimated to be 15.48 °C and 239 mm, respectively; beyond these threshold levels, the increase in temperature and rainfall have negative impact on barley yield in Iran. The long-term elasticity of temperature shows that the yield will be reduced with the increase in temperature in the long run. Same is the case with the precipitation and barley yield. The findings of the study suggest the need of a comprehensive national climate change policy and alignment of sectoral policies with it mitigate and adapt the climate change and global warming. Moreover, it also provided the guidelines for the government and policy-makers to introduce the use of modern eco-friendly and resource saving technologies such as water-saving methods of irrigation, use of fertilizer in required quantities, and improved seeds use. The government should also introduce the climate change awareness programs especially for farmers.

Interpretation of the hindered settling of calcium carbonate suspensions in terms of permeability

Many pharmaceutical formulations are produced in the form of concentrated suspensions. Calcium carbonate suspensions are used in this study and interpreted as the "model" for the behavior of such suspensions. The behavior of concentrated suspensions of powders in a liquid medium cannot be treated by the simple application of the normal principles of free fall and the use of Stokes Law pertaining to the viscous resistance offered by the surrounding fluid to fall. A single particle operating by the Stokes principle obeys this relationship. This law applies to the behavior of particles at low concentration in a liquid medium and is the basis for particle size distribution methods. At higher concentrations, however, the particles do not enjoy the freedom of unhindered fall. The system subsides "en bloc," and it is common practice to offer a modification to the Stokes equation which takes into consideration some function of the porosity of the system. There have been a considerable number of equations developed and modified based on this principle. However, an alternative method is to approach the problem by dealing with the permeability of a bed of powders in a liquid in which the bed is slowly altering with time. This is best achieved by the use of the permeability equation developed and presented by Kozeny-Carmen. This equation, as well as the Richardson-Zaki expression, are related to show that the Kozeny parameter K varies with the suspension porosity under sedimentation conditions. The values of K are often larger than the value normally reported (i.e., approximately 5). The data and treatment outlined here are extended to include not only the calcium carbonate suspensions, but other systems previously mentioned in the literature.