On the Four-Color-Map Theorem

Coloring planar Feynman diagrams in spinor quantum electrodynamics, is a non trivial model soluble without computer. Four colors are necessary and sufficient.Comment: 8 page

Anisotropy beta functions

The flow of couplings under anisotropic scaling of momenta is computed in $\phi^3$ theory in 6 dimensions. It is shown that the coupling decreases as momenta of two of the particles become large, keeping the third momentum fixed, but at a slower rate than the decrease of the coupling if all three momenta become large simultaneously. This effect serves as a simple test of effective theories of high energy scattering, since such theories should reproduce these deviations from the usual logarithmic scale dependence.Comment: uuencoded ps file, 6 page

Sites for contemporary Gothic

No abstract

Employment at Will: The American Rule and Its Application in Alaska

In this thesis, secondary flow in a two stage, low aspect ratio turbine is investigated using CFD. A parameter study is carried out to investigate how the turbine performance is affected by the choice of aspect ratio. This is done in two steps, first by changing the blade height and then the blade size. The study shows that increasing the aspect ratio will lead to a significant increase of efficiency, but the effect diminishes for large aspect ratios, at which the efficiency moves towards an asymptotic value. Furthermore it is shown that increasing the aspect ratio to a certain value by changing the blade height results in a higher efficiency compared to changing the blade size, which is due to the difference in hub-to-tip ratio. An attempt to quantify the secondary losses is also made by looking at the radial kinetic energy at the outlet of a blade row. It turns out though, that the radial kinetic energy does not follow the same trend as the total pressure loss coefficient, which implies that it can not be used to quantify the secondary losses. Lastly, an effort to improve the method used for generating blade profiles is made, and the updated method is used to redesign rotor 2 to reduce losses

Laser phase noise to intensity noise conversion by lowest-order group-velocity dispersion in optical fiber: exact theory

An exact result for the spectral density of intensity variations that occur after propagation of ergodic light in a medium having lowest-order-only group-velocity dispersion is obtained and applied to the problem of semiconductor laser phase noise to intensity noise conversion in a single-mode optical fiber. It is shown that the intensity spectrum after propagation formally approaches, for a large laser linewidth or a long (or high-dispersion) fiber, the intensity spectrum of a thermal source having the same line shape as the laser