The Degasperis-Procesi equation with self-consistent sources

The Degasperis-Procesi equation with self-consistent sources(DPESCS) is derived. The Lax representation and the conservation laws for DPESCS are constructed. The peakon solution of DPESCS is obtained.Comment: 15 page

Discovering causal interactions using Bayesian network scoring and information gain

Background: The problem of learning causal influences from data has recently attracted much attention. Standard statistical methods can have difficulty learning discrete causes, which interacting to affect a target, because the assumptions in these methods often do not model discrete causal relationships well. An important task then is to learn such interactions from data. Motivated by the problem of learning epistatic interactions from datasets developed in genome-wide association studies (GWAS), researchers conceived new methods for learning discrete interactions. However, many of these methods do not differentiate a model representing a true interaction from a model representing non-interacting causes with strong individual affects. The recent algorithm MBS-IGain addresses this difficulty by using Bayesian network learning and information gain to discover interactions from high-dimensional datasets. However, MBS-IGain requires marginal effects to detect interactions containing more than two causes. If the dataset is not high-dimensional, we can avoid this shortcoming by doing an exhaustive search. Results: We develop Exhaustive-IGain, which is like MBS-IGain but does an exhaustive search. We compare the performance of Exhaustive-IGain to MBS-IGain using low-dimensional simulated datasets based on interactions with marginal effects and ones based on interactions without marginal effects. Their performance is similar on the datasets based on marginal effects. However, Exhaustive-IGain compellingly outperforms MBS-IGain on the datasets based on 3 and 4-cause interactions without marginal effects. We apply Exhaustive-IGain to investigate how clinical variables interact to affect breast cancer survival, and obtain results that agree with judgements of a breast cancer oncologist. Conclusions: We conclude that the combined use of information gain and Bayesian network scoring enables us to discover higher order interactions with no marginal effects if we perform an exhaustive search. We further conclude that Exhaustive-IGain can be effective when applied to real data

Mineral processing simulation based-environmental life cycle assessment for rare earth project development: a case study on the Songwe Hill project

This is the final version. Available on open access from Elsevier via the DOI in this recordRare earth elements (REE), including neodymium, praseodymium, and dysprosium are used in a range of low-carbon technologies, such as electric vehicles and wind turbines, and demand for these REE is forecast to grow. This study demonstrates that a process simulation-based life cycle assessment (LCA) carried out at the early stages of a REE project, such as at the pre-feasibility stage, can inform subsequent decision making during the development of the project and help reduce its environmental impacts. As new REE supply chains are established and new mines are opened. It is important that the environmental consequences of different production options are examined in a life cycle context in order that the environment footprint of these raw materials is kept as low as possible. Here, we present a cradle-to-gate and process simulation-based life cycle assessment (LCA) for a potential new supply of REE at Songwe Hill in Malawi. We examine different project options including energy selection and a comparison of on-site acid regeneration versus virgin acid consumption which were being considered for the project. The LCA results show that the global warming potential of producing 1 kg of rare earth oxide (REO) from Songwe Hill is between 17 and 87 kg CO2-eq.A scenario that combines on-site acid regeneration with off-peak hydroelectric and photovoltaic energy gives the lowest global warming potential and performs well in other impact categories.This approach can equally well be applied to all other types of ore deposits and should be considered as a routine addition to all pre-feasibility studies.Natural Environment Research Council (NERC

Temporally explicit life cycle assessment as an environmental performance decision making tool in rare earth project development

This is the final version. Available from Elsevier via the DOI in this record.The study shows that a detailed LCA can be carried out for a proposed mining project as soon as Prefeasibility (PFS) data are available. The prefeasibility study is one of the key early steps in bringing a deposit towards production and results are often publically available. This study applies the technique to a rare earth deposit because rare earth element (REE) consumption is increasing owing to their use in low-carbon technologies such as electric vehicles and wind turbines. It is therefore particularly important to understand the environmental impacts of the raw materials. A number of REE deposits are under development to give additional supply and many possess novel mineral compositions and will require different processing methods than previously used. Assessing the environmental performance of the production of REE during the development of projects offers significant insights into how to improve the sustainability of a project. In this study we used life cycle assessment (LCA) to quantify the environmental impacts for producing rare earth oxide (REO) from the Bear Lodge Project, United States. The Life Cycle Impact Assessment results were produced for each year over the life of the project, generating insight about the relationships between ore composition, grade, processing method and environmental impacts. The environmental impacts vary significantly during the life of a project and a temporally explicit LCA can highlight these.Natural Environment Research Council (NERC

First-principles study of vibrational and dielectric properties of {\beta}-Si3N4

First-principles calculations have been conducted to study the structural, vibrational and dielectric properties of {\beta}-Si3N4. Calculations of the zone-center optical-mode frequencies (including LO-TO splittings), Born effective charge tensors for each atom, dielectric constants, using density functional perturbation theory, are reported. The fully relaxed structural parameters are found to be in good agreement with experimental data. All optic modes are identified and agreement of theory with experiment is excellent. The static dielectric tensor is decomposed into contributions arising from individual infrared-active phonon modes. It is found that high-frequency modes mainly contribute to the lattice dielectric constant.Comment: 15pages, 1 figure, 5 table