Spectroscopic fingerprints of a surface Mott-Hubbard insulator: the case of SiC(0001)

We discuss the spectroscopic fingerprints that a surface Mott-Hubbard insulator should show at the intra-atomic level. The test case considered is that of the Si-terminated SiC(0001) sqrt{3}xsqrt{3} surface, which is known experimentally to be insulating. We argue that, due to the Mott-Hubbard phenomenon, spin unpaired electrons in the Si adatom dangling bonds are expected to give rise to a Si-2p core level spectrum with a characteristic three-peaked structure, as seen experimentally. This structure results from the joint effect of intra-atomic exchange, spatial anisotropy, and spin-orbit coupling. Auger intensities are also discussed.Comment: 4 pages, 2 figures, ECOSS-18 conferenc

Determination of convective diffusion heat/mass transfer rates to burner rig test targets comparable in size to cross-stream jet diameter

Two sets of experiments have been performed to be able to predict the convective diffusion heat/mass transfer rates to a cylindrical target whose height and diameter are comparable to, but less than, the diameter of the circular cross-stream jet, thereby simulating the same geometric configuration as a typical burner rig test specimen located in the cross-stream of the combustor exit nozzle. The first set exploits the naphthalene sublimation technique to determine the heat/mass transfer coefficient under isothermal conditions for various flow rates (Reynolds numbers). The second set, conducted at various combustion temperatures and Reynolds numbers, utilized the temperature variation along the surface of the above-mentioned target under steady-state conditions to estimate the effect of cooling (dilution) due to the entrainment of stagnant room temperature air. The experimental information obtained is used to predict high temperature, high velocity corrosive salt vapor deposition rates in burner rigs on collectors that are geometrically the same. The agreement with preliminary data obtained from Na2SO4 vapor deposition experiments is found to be excellent

Experimental verification of corrosive vapor deposition rate theory in high velocity burner rigs

The ability to predict deposition rates is required to facilitate modelling of high temperature corrosion by fused salt condensates in turbine engines. A corrosive salt vapor deposition theory based on multicomponent chemically frozen boundary layers (CFBL) has been successfully verified by high velocity burner rig experiments. The experiments involved internally air-impingement cooled, both rotating full and stationary segmented cylindrical collectors located in the crossflow of sodium-seeded combustion gases. Excellent agreement is found between the CFBL theory an the experimental measurements for both the absolute amounts of Na2SO4 deposition rates and the behavior of deposition rate with respect to collector temperature, mass flowrate (velocity) and Na concentration

Italy's Great Power Strategies in Central-Eastern Europe Between the World Wars: Cultural Institutions and Political Propaganda

This article addresses the issue of Italian penetration in Central-Eastern Europe in the interwar period, paying particular attention to the Czechoslovakian case and dwelling above all on some tools used by Italy to assert its influence among the heir countries of the Habsburg Empire. Among these tools, the article aims to highlight the importance of culture and propaganda, which, alongside politics and economics, allowed Italy to compete with the other great powers for hegemony in Central-Eastern Europe. The strategy of the other powers will be taken into consideration as well, in order to highlight, also in a comparative key, the role that cultural and propaganda institutions played in the policies of great power in the period considered. The complex of Italian cultural activities and institutions oriented towards the study of Central and Eastern Europe, established during the First World War, continued to operate in the post-war period at the time of the last liberal governments and was then strengthened by the fascist regime. Fascism made full use of the potential offered by cultural diplomacy to strengthen its positions in Central and Eastern Europe. Mussolini\u2019s unrealistic great power ambitions, however, rendered useless the network of cultural institutions responsible for the study of Eastern Europe, which collapsed with the fall of his regime

Vortex-induced extinction behavior in methanol gaseous flames: a comparison with quasi-steady extinction

Using a combination of HCHO planar laser-induced fluorescence and laser Doppler velocimetry measurements, the extinction behavior of methanol counterflow diffusion flames was examined experimentally under conditions in which the extinction was brought about by a vortex generated on the oxidizer side. Comparisons were made with quasi-steady extinction results for the same flames. It was found that the flames can withstand instantaneous strain rates as much as two-and-a-half times larger than the quasi-steady ones. The finding was rationalized phenomenologically by comparing the characteristic times of the problem, that is, the mechanical time, the chemical time, and the vortex turnover time. Specifically, estimates of these times yielded the following ordering: τch < τvort < τm. As a result, the vortex introduced an unsteady effect in the outer diffusive-convective layer of the flame, while the inner reactive-diffusive layer behaved in a quasi-steady manner. Consequently, the flame was subject to a damped strain rate through the outer layer. Results from a simple analytical model showed that the difference between vortex-induced extinction and quasi-steady extinction was much more modest in terms of instantaneous scalar dissipation rate or Damköhler number. Furthermore, the temporal history of the strain rate was found to be necessary to determine the effective strain rate felt by the flame. Implications of these findings for turbulent diffusion flame modeling by the flamelet approach are discussed

Microgravity Combustion Diagnostics Workshop

Through the Microgravity Science and Applications Division (MSAD) of the Office of Space Science and Applications (OSSA) at NASA Headquarters, a program entitled, Advanced Technology Development (ATD) was promulgated with the objective of providing advanced technologies that will enable the development of future microgravity science and applications experimental flight hardware. Among the ATD projects one, Microgravity Combustion Diagnostics (MCD), has the objective of developing advanced diagnostic techniques and technologies to provide nonperturbing measurements of combustion characteristics and parameters that will enhance the scientific integrity and quality of microgravity combustion experiments. As part of the approach to this project, a workshop was held on July 28 and 29, 1987, at the NASA Lewis Research Center. A small group of laser combustion diagnosticians met with a group of microgravity combustion experimenters to discuss the science requirements, the state-of-the-art of laser diagnostic technology, and plan the direction for near-, intermediate-, and long-term programs. This publication describes the proceedings of that workshop

Faster annealing schedules for quantum annealing

New annealing schedules for quantum annealing are proposed based on the adiabatic theorem. These schedules exhibit faster decrease of the excitation probability than a linear schedule. To derive this conclusion, the asymptotic form of the excitation probability for quantum annealing is explicitly obtained in the limit of long annealing time. Its first-order term, which is inversely proportional to the square of the annealing time, is shown to be determined only by the information at the initial and final times. Our annealing schedules make it possible to drop this term, thus leading to a higher order (smaller) excitation probability. We verify these results by solving numerically the time-dependent Schrodinger equation for small size systemsComment: 10 pages, 5 figures, minor correction

In-Beam Background Suppression Shield

The long (3ms) proton pulse of the European Spallation Source (ESS) gives rise to unique and potentially high backgrounds for the instrument suite. In such a source an instrument capabilities will be limited by it's Signal to Noise (S/N) ratio. The instruments with a direct view of the moderator, which do not use a bender to help mitigate the fast neutron background, are the most challenging. For these beam lines we propose the innovative shielding of placing blocks of material directly into the guide system, which allow a minimum attenuation of the cold and thermal fluxes relative to the background suppression. This shielding configuration has been worked into a beam line model using Geant4. We study particularly the advantages of single crystal sapphire and silicon blocks .Comment: 12 pages, 8 figures, proceeding of NDS 2015, 4th International Workshop on Neutron Delivery Systems, 28 -30 September 2015, ILL Grenoble, Franc

Quantum annealing of the Traveling Salesman Problem

We propose a path-integral Monte Carlo quantum annealing scheme for the symmetric Traveling Salesman Problem, based on a highly constrained Ising-like representation, and we compare its performance against standard thermal Simulated Annealing. The Monte Carlo moves implemented are standard, and consist in restructuring a tour by exchanging two links (2-opt moves). The quantum annealing scheme, even with a drastically simple form of kinetic energy, appears definitely superior to the classical one, when tested on a 1002 city instance of the standard TSPLIB.Comment: 5 pages, 2 figure