Development of protective coatings for tantalum T-22 alloy Final summary report

Oxidation resistance tests of protective coatings for tantalum allo

An analysis of the boundary layer in the 1D surface Cauchy–Born model

The surface Cauchy–Born (SCB) method is a computational multi-scale method for the simulation of surface-dominated crystalline materials. We present an error analysis of the SCB method, focused on the role of surface relaxation. In a linearized 1D model we show that the error committed by the SCB method is O(1) in the mesh size; however, we are able to identify an alternative "approximation parameter" – the stiffness of the interaction potential – with respect to which the relative error in the mean strain is exponentially small. Our analysis naturally suggests an improvement of the SCB model by enforcing atomistic mesh spacing in the normal direction at the free boundary. In this case we even obtain pointwise error estimates for the strain

The Paradox of United State Democracy

This program is about a paradox at the heart of American democracy. We take it for granted that elected officials, like President Bush and members of Congress, run America. In fact, many of the country\u27s most important decisions are taken by nine unelected lawyers accountable to no one. It is a paradox which is increasingly under scrutiny as more and more Americans are coming to question the power of their Supreme Court

Do correlations create an energy gap in electronic bilayers? Critical analysis of different approaches

This paper investigates the effect of correlations in electronic bilayers on the longitudinal collective mode structure. We employ the dielectric permeability constructed by means of the classical theory of moments. It is shown that the neglection of damping processes overestimates the role of correlations. We conclude that the correct account of damping processes leads to an absence of an energy gap.Comment: 4 page

Evolution of induced axial magnetization in a two-component magnetized plasma

In this paper, the evolution of the induced axial magnetization due to the propagation of an electromagnetic (em) wave along the static background magnetic field in a two-component plasma has been investigated using the Block equation. The evolution process induces a strong magnetic anisotropy in the plasma medium, depending nonlinearly on the incident wave amplitude. This induced magnetic anisotropy can modify the dispersion relation of the incident em wave, which has been obtained in this paper. In the low frequency Alfven wave limit, this dispersion relation shows that the resulting phase velocity of the incident wave depends on the square of the incident wave amplitude and on the static background magnetic field of plasma. The analytical results are in well agreement with the numerically estimated values in solar corona and sunspots.Comment: 7 pages, 1 figur

Student approaches and attitudes towards writing in German as a foreign language, using corpus-linguistic tools

Linguistic researchers are optimistic about what corpora can offer language learners; however, very little empirical assessment of the direct use of corpus tools is reported on in context, especially for languages other than English. One method of assessing the effectiveness and value of corpus tools is by collecting students’ experiences of using them and establishing if they perceive benefits through using corpus tools. Following a qualitative questionnaire which examined student approaches to writing in German as a  foreign language, and a quantitative analysis of their writing, a writing module was designed and instituted at Rhodes University for third-year German Studies students. The writing module made use of both indirect (paper-based) and direct (computer-based) corpus-based methods to teach everyday academic vocabulary and formulaic expressions, based on materials developed for the WHiG project in the UK. This study presents an overview of the students’ attitudes and perspectives (as recorded in questionnaires and interviews), in order to give voice to the qualitative and subjective dimension of foreign language learning, which is often neglected in corpus-based studies. The participating students perceived an improvement in their writing through a changed approach to researching and using everyday academic German. Keywords: German as a foreign language; student perceptions; teaching with corpora; everyday academic language; Deutsch als alltägliche Wissenschaftssprache; academic writing; students as co-creators of teaching materials

Non-linear exciton spin-splitting in single InAs/GaAs self-assembled quantum structures in ultrahigh magnetic fields

We report on the magnetic field dispersion of the exciton spin-splitting and diamagnetic shift in single InAs/GaAs quantum dots (QDs) and dot molecules (QDMs) up to $B$ = 28 T. Only for systems with strong geometric confinement, the dispersions can be well described by simple field dependencies, while for dots with weaker confinement considerable deviations are observed: most importantly, in the high field limit the spin-splitting shows a non-linear dependence on $B$, clearly indicating light hole admixtures to the valence band ground state

An Efficient Mechanism for Cross-border Support of Renewable Electricity in the European Union

The ability to exchange renewable electricity (RES-e) capacity between EU member states improves the welfare of all member states since potentials and demands for RES-e capacity vary across the EU. This notion is reflected in the promotion of so-called cooperation mechanisms by the European Commission. The existing mechanisms appear, unfortunately, to be insufficient to facilitate an efficient level of trade in capacity across the EU; only a small quantity of energy is expected to be subject to cooperation mechanisms (Klessmann et al. 2010). In order to address these challenges, in this paper we propose a new mechanism for cross-border support of renewable electricity in EU. The guiding idea is that the cross-border mechanism allocates new RES-e generating capacity across EU Member States to where it is most valuable. This can, but need not, coincide with the most cost efficient allocation. The mechanism consists of two main elements. Firstly, a cross-border impact matrix that indicates the spill-over of benefits between member states induced from the power injection of additional RES-e generating capacity. Secondly, an EU wide auction in which member states and generators of RES-e bid prices indicating their willingness to pay for additional RES-e generating capacity. Then for given parameters the auctioneer selects the set of bids that maximizes an EU-wide surplus. We find that the mechanism leads to a decentralized optimization of RES-e support in the EU, by matching high willingness to pay of member states with low cost potentials of RES-e generation, but only if the benefits of RES-e are actually delivered for the member state paying for it. Moreover, the mechanism offers the potential to significantly reduce the barriers of the current cooperation mechanism, such as transaction costs or uncertainty about costs and benefits

Incommensurate heterostructures in momentum space

To make the investigation of electronic structure of incommensurate heterostructures computationally tractable, effective alternatives to Bloch theory must be developed. In [Multiscale Model. Simul., 15(2017), pp. 476--499] we developed and analyzed a real space scheme that exploits spatial ergodicity and near-sightedness. In the present work, we present an analogous scheme formulated in momentum space, which we prove has significant computational advantages in specific incommensurate systems of physical interest, e.g., bilayers of a specified class of materials with small rotation angles. We use our theoretical analysis to obtain estimates for improved rates of convergence with respect to total CPU time for our momentum space method that are confirmed in computational experiments

Optimization and evaluation of electrophoretic protective coatings for tantalum T-222 alloy Final summary report, 1 Jul. 1966 - 27 Oct. 1967

Protective coating parameters for improving oxidation resistance and reliability of silicide coating systems for tantalum alloy