Solid-state configurations

Two prototype solid-state phased array systems concepts developed for the solar power satellite (SPS) are described. In both concepts, the beam was centered on the rectenna by means of phase conjugation of a pilot signal emanating from the ground. Also discussed are results of solid state studies

Creep at Elevated Temperatures and High Vacuum

High vacuum, high temperature, creep tests on copper and silve

Selection & Preliminary Design of Light-Weight, Low Cost X-Band Aircraft Antennas for Defense Satellite Communications

As satellite communications requirements increase and more functions are combined in the same frequency band in accordance with the ICNI concept, special requirements are being imposed on the aircraft antenna system. Depending on data rates to be transmitted via a satellite link, various bandwidths are required for the earth terminals. For high data rates, large relative bandwidths are necessary; and available frequency allocations generally indicate operation at X-band, with Ku-band as a possible additional choice. Mobile users require full hemispherical coverage of the antenna system. Aircraft users have the additional constraint that the antenna aperture has to be flush with the skin of the aircraft and to conform to the structure. In this paper, earth terminals utilizing an integrated military satellite communication (ICNI) system are tabulated, and typical parameters are summarized. A number of potential aircraft antenna configurations are analyzed, and a selection process leading to a minimum-cost, minimumweight, aircraft-antenna system for X-band operation is discussed. The chosen antenna system, a phased array using a combination of digital phase steering and traveling wave phase velocity steering, is described in detail. A comparison is presented between this antenna and several other systems

The Resonant Cavity Radiator (RCR)

The design of the resonant cavity radiator (RCR) is compared to that of the slotted waveguide array in terms of efficiency, weight, and structural integrity. It is shown that the RCR design has three significant potentials over the slotted waveguide array: (1) improvement in efficiency; (2) lighter weight; and (3) simpler structure which allows the RCR to be integrated with the RF tube to alleviate thermal interface problems

Energies of Quantum QED Flux Tubes

In this talk I present recent studies on vacuum polarization energies and energy densities induced by QED flux tubes. I focus on comparing three and four dimensional scenarios and the discussion of various approximation schemes in view of the exact treatment.Comment: 9 pages latex, Talk presented at the QFEXT 05 workshop in Barcelona, Sept. 2005. To appear in the proceeding

Appearance of the Single Gyroid Network Phase in Nuclear Pasta Matter

Nuclear matter under the conditions of a supernova explosion unfolds into a rich variety of spatially structured phases, called nuclear pasta. We investigate the role of periodic network-like structures with negatively curved interfaces in nuclear pasta structures, by static and dynamic Hartree-Fock simulations in periodic lattices. As the most prominent result, we identify for the first time the {\it single gyroid} network structure of cubic chiral $I4_123$ symmetry, a well known configuration in nanostructured soft-matter systems, both as a dynamical state and as a cooled static solution. Single gyroid structures form spontaneously in the course of the dynamical simulations. Most of them are isomeric states. The very small energy differences to the ground state indicate its relevance for structures in nuclear pasta.Comment: 7 pages, 4 figure

Twenty-five years of German unity - a success story? [25 Jahre Deutsche Einheit: eine Erfolgsgeschichte?]

Twenty­five years after reunification, economic fundamentals between East Germany and West Germany continue to differ. Massive financial transfers could not close the significant "prosperity gap" between the two former countries, but they did reduce it noticeably. This is most obvious with respect to indicators such as GDP per capita and unemployment. Fast convergence is unlikely to occur, as economic development is strongly driven by technology that might generate economies of scale, thereby favouring regions which are already well developed. Therefore, economic policy should no longer aim at convergence but rather at economic growth. Despite considerable progress, more structural change will be necessary for further convergence. Furthermore, the decades­long division generated fundamental political and psychological differences, which continue to be felt. One important factor in the continued economic disparity between the two is that East Germany has had to follow the West German development path, which only makes the catching up process more difficult