Power Supply Options for a Naval Railgun

Large railguns require powerful power supply units. At the French-German Research Institute of Saint-Louis (ISL) most experimental railguns are driven by power supply units based on capacitors. Recent investigations at ISL explore the possibility to use coil based systems to increase the energy density of the power supply. In this study an electrical circuit simulation is used to investigate the difference for railgun operation in between a capacitor and a coil based power supply with respect to current amplitude behavior and projectile velocity. For this a scenario of a 25 MJ muzzle energy railgun is simulated with two different power supply options, replacing capacitors by coils and using a range of circuit resistances. The resistance determines to a large part the losses of the system and defines therefore the efficiency of the launch and the size of the power supply. The interpretation of the results of the performed simulations leads to the conclusion that the capacitor based system "naturally" pro- duces a favorable current pulse trace with respect to launching a mechanical delicate payload. Further simulations show that the disadvantage of the inductor based supply can be mitigated by increasing the power supply unit subdivision into smaller units.Comment: Submitted to IEEE Transactions on Plasma Physic

A Search for Rules for International Wheat Surplus Disposal

The general purpose of this study was to attempt to establish a basic rule for determining the level of commercial wheat imports, if any, that the underdeveloped countries should be required to maintain in addition to concessional purchases and to offer a rule and some procedures that the exporting countries might follow in supplying wheat on concessional terms

A device for feasible fidelity, purity, Hilbert-Schmidt distance and entanglement witness measurements

A generic model of measurement device which is able to directly measure commonly used quantum-state characteristics such as fidelity, overlap, purity and Hilbert-Schmidt distance for two general uncorrelated mixed states is proposed. In addition, for two correlated mixed states, the measurement realizes an entanglement witness for Werner's separability criterion. To determine these observables, the estimation only one parameter - the visibility of interference, is needed. The implementations in cavity QED, trapped ion and electromagnetically induced transparency experiments are discussed.Comment: 6 pages, 3 figure

A measurable entanglement criterion for two qubits

We propose a directly measurable criterion for the entanglement of two qubits. We compare the criterion with other criteria, and we find that for pure states, and some mixed states, it coincides with the state's concurrency. The measure can be obtained with a Bell state analyser and the ability to make general local unitary transformations. However, the procedure fails to measure the entanglement of a general mixed two-qubit state.Comment: 5 page

Conditional large Fock state preparation and field state reconstruction in Cavity QED

We propose a scheme for producing large Fock states in Cavity QED via the implementation of a highly selective atom-field interaction. It is based on Raman excitation of a three-level atom by a classical field and a quantized field mode. Selectivity appears when one tunes to resonance a specific transition inside a chosen atom-field subspace, while other transitions remain dispersive, as a consequence of the field dependent electronic energy shifts. We show that this scheme can be also employed for reconstructing, in a new and efficient way, the Wigner function of the cavity field state.Comment: 4 Revtex pages with 3 postscript figures. Submitted for publicatio

Strong-coupling expansions for the anharmonic Holstein model and for the Holstein-Hubbard model

A strong-coupling expansion is applied to the anharmonic Holstein model and to the Holstein-Hubbard model through fourth order in the hopping matrix element. Mean-field theory is then employed to determine transition temperatures of the effective (pseudospin) Hamiltonian. We find that anharmonic effects are not easily mimicked by an on-site Coulomb repulsion, and that anharmonicity strongly favors superconductivity relative to charge-density-wave order. Surprisingly, the phase diagram is strongly modified by relatively small values of the anharmonicity.Comment: 34 pages, typeset in ReVTeX, 11 encapsulated postscript files include

Contemporary changes and civil society in Portugal and the Russian Federation

Portugal and the Russian Federation share some aspects of traditional culture and similar experiences in modern history, but they also exhibit significant differences that determine specific modes of civil society’s development. Results of a comparative and diachronic analysis show that the major differences between the two countries reside in civil society’s openness and composition. Organized civil society is not very distinct in relative size when comparing Portugal and the Russian Federation, but it is globally more autonomous, expressive, trusted and institutionalized in Portugal than in the Russian Federation and among the factors that contribute to this condition are an earlier and revolutionary transition to democracy, a larger middle class, a greater prevalence of the value of interdependence, and a regime that endorses bigger public social expenditure in Portugal, all this within the framework of the European Union that has a longer history of social demand and institutional incentives for civil society. Despite those unequal conditions, civil society faces similar current challenges in both countries, mainly with the outsourcing of the public provision of social services.info:eu-repo/semantics/acceptedVersio

High-order nonlinearities in the motion of a trapped atom

Published versio

Health inequalities according to educational level in different welfare regimes: a comparison of 23 European countries

The object of this study was to determine whether the magnitude of educational health inequalities varies between European countries with different welfare regimes. The data source is based on the first and second wave of the European Social Survey. The first health indicator describes people's mental and physical health in general, while the second reports cases of any limiting longstanding illness. Educational inequalities in health were measured as the difference in health between people with an average number of years of education and people whose educational years lay one standard deviation below the national average. Moreover, South European welfare regimes had the largest health inequalities, while countries with Bismarckian welfare regimes tended to demonstrate the smallest. Although the other welfare regimes ranked relatively close to each other, the Scandinavian welfare regimes were placed less favourably than the Anglo-Saxon and East European. Thus, this study shows an evident patterning of magnitudes of health inequalities according to features of European welfare regimes. Although the greater distribution of welfare benefits within the Scandinavian countries are likely to have a protective effect for disadvantaged cities in these countries, other factors such as relative deprivation and class-patterned health behaviours might be acting to widen health inequalities