Flowing gas, non-nuclear experiments on the gas core reactor

Flow tests were conducted on models of the gas core (cavity) reactor. Variations in cavity wall and injection configurations were aimed at establishing flow patterns that give a maximum of the nuclear criticality eigenvalue. Correlation with the nuclear effect was made using multigroup diffusion theory normalized by previous benchmark critical experiments. Air was used to simulate the hydrogen propellant in the flow tests, and smoked air, argon, or freon to simulate the central nuclear fuel gas. All tests were run in the down-firing direction so that gravitational effects simulated the acceleration effect of a rocket. Results show that acceptable flow patterns with high volume fraction for the simulated nuclear fuel gas and high flow rate ratios of propellant to fuel can be obtained. Using a point injector for the fuel, good flow patterns are obtained by directing the outer gas at high velocity along the cavity wall, using louvered or oblique-angle-honeycomb injection schemes

Copper cable theft: revisiting the price–theft hypothesis

Objectives: To test the commonly espoused but little examined hypothesis that fluctuations in the price of metal are associated with changes in the volume of metal theft. Specifically, we analyze the relationship between the price of copper and the number of police recorded 'live’ copper cable thefts from the British railway network (2006 to 2012)

Design of cryogenic tanks for launch vehicles

During the period since January 1990, work was concentrated on the problem of the buckling of the structure of an ALS (advanced launch systems) tank during the boost phase. The primary problem was to analyze a proposed hat stringer made by superplastic forming, and to compare it with an integrally stiffened stringer design. A secondary objective was to determine whether structural rings having the identical section to the stringers will provide adequate support against overall buckling. All of the analytical work was carried out with the TESTBED program on the CONVEX computer, using PATRAN programs to create models. Analyses of skin/stringer combinations have shown that the proposed stringer design is an adequate substitute for the integrally stiffened stringer. Using a highly refined mesh to represent the corrugations in the vertical webs of the hat stringers, effective values were obtained for cross-sectional area, moment of inertia, centroid height, and torsional constant. Not only can these values be used for comparison with experimental values, but they can also be used for beams to replace the stringers and frames in analytical models of complete sections of tank. The same highly refined model was used to represent a section of skin reinforced by a stringer and a ring segment in the configuration of a cross. It was intended that this would provide a baseline buckling analysis representing a basic mode, however, the analysis proved to be beyond the scope of the CONVEX computer. One quarter of this model was analyzed, however, to provide information on buckling between the spot welds. Models of large sections of the tank structure were made, using beam elements to model the stringers and frames. In order to represent the stiffening effects of pressure, stresses and deflections under pressure should first be obtained, and then the buckling analysis should be made on the structure so deflected. So far, uncharacteristic deflections under pressure were obtained from the TESTBED program using two types of structural elements. Similar results were obtained using the ANSYS program on a mainframe computer, although two finite element programs on microcomputers have yielded realistic results

500 TeV gamma rays from Hercules X-1

A signal (chance probability = .0002) with the 1.24 s period of Hercules X-1 has been observed using the Utah Fly's Eye. The signal's relatively long period and high shower energy conflict with some popular models of particle acceleration by pulsars. Optical and X-ray data suggest a picture in which energetic particles produce multi-TeV gamma rays by collisions with Hercules X-1's accretion disk

Design of cryogenic tanks for space vehicles shell structures analytical modeling

The initial objective was to study the use of superplastically formed corrugated hat section stringers and frames in place of integrally machined stringers over separate frames for the tanks of large launch vehicles subjected to high buckling loads. The ALS was used as an example. The objective of the follow-on project was to study methods of designing shell structures subjected to severe combinations of structural loads and thermal gradients, with emphasis on new combinations of structural arrangements and materials. Typical applications would be to fuselage sections of high speed civil transports and to cryogenic tanks on the National Aerospace Plane

Pion Production from Baked-Alaska Disoriented Chiral Condensate

We study the various stages of the evolution of chiral condensates disoriented via the ``baked-alaska'' mechanism, in which the condensates are described as the products of external sources localized on the light cone. Our analysis is based on the classical equations of motion of either the linear or the nonlinear sigma model. We use the associated framework of coherent states and, especially, their source functions to make the connection to the distribution functions for the produced particles. We also compare our classical approach with a mean-field calculation which includes a certain class of quantum corrections.Comment: replaced to correct misspelling of author's nam

Selection of Power Plant Elements for Future Reactor Space Electric Power Systems

Various types of reactor designs, electric power conversion equipment, and reject-heat systems to be used in nuclear reactor power plants for future space missions were studied. The designs included gas-cooled, liquid-cooled, and heat-pipe reactors. For the power converters, passive types such as thermoelectric and thermionic converters and dynamic types such as Brayton, potassium Rankine, and Stirling cycles were considered. For the radiators, heat pipes for transfer and radiating surface, pumped fluid for heat transfer with fins as the radiating surface, and pumped fluid for heat transfer with heat pipes as the radiating surface were considered. After careful consideration of weights, sizes, reliabilities, safety, and development cost and time, a heat-pipe reactor design, thermoelectric converters, and a heat-pipe radiator for an experimental program were selected

Supersymmetric Electroweak Corrections to the Higgs Boson Decays into Chargino or Neutralino Pair

We investigate the supersymmetric electroweak corrections to the decay widths of the CP-odd and the heavy CP-even Higgs bosons into chargino or neutralino pair in the framework of the Minimal Supersymmetric Standard Model. The corrections involve the contributions of the order $O(\alpha_{ew} m_{t(b)}^3/m_W^3)$, $O(\alpha_{ew} m_{t(b)}^2/m_W^2)$ and $O(\alpha_{ew} m_{t(b)}/m_W)$. The detailed calculations of the electroweak corrections to the following decay processes: $A^0/H^0 \to \tilde{\chi}^+_1 \tilde{\chi}^-_1$ and $A^0/H^0 \to \tilde{\chi}^0_2 \tilde{\chi}^0_2$ are presented in this paper. We find that these relative corrections maybe rather large quantitatively, and can exceed 10% in some regions of parameter space. The corrections to the decay $A^0/H^0 \to \tilde{\chi}^0_1 \tilde{\chi}^0_2$ can be obtained analogously, but our results show that they are very small and can be neglected.Comment: 25 pages, 9 figures,accepted by Physical Review