Beach face dynamics as affected by ground water table elevations

This report presents the results of laboratory studies which were carried out in the Coastal and Oceanographical Engineering Laboratory to investigate the effects of ground water table elevations on the beach profile changes over the swash zone. The experiment was conducted at three different water table levels while the other experimental conditions were fixed to constant values with regular waves. The water table levels included (1) normal water table level which is the same as mean sea level, (2) a higher level and (3) a lower level than the mean sea level. Special attention was given to the higher water level to investigate whether this level enhances erosion of the beach face and also to methods of interpreting the experimental data. The experiment described herein was carried out with a fairly fine sand and has demonstrated the significance of beach water table on profile dynamics. The increased water table level caused distinct effects in three definite zones. First, erosion occurred at the base of the beach face and the sand eroded was carried up and deposited on the upper portion of the beach face. Secondly, the bar trough deepened considerably and rapidly and the eroded sand was deposited immediately landward. This depositional area changed from mildly erosional to strongly depositional. Third, the area seaward of the bar eroded with a substantial deepening. The lowered water table appeared to result in a much more stable beach and the resulting effects were much less. The only noticeable trend was a limited deposition in the scour area at the base of the beach face. (Document has 37 pages.

Noncommutative open strings from Dirac quantization

We study Dirac commutators of canonical variables on D-branes with a constant Neveu-Schwarz 2-form field by using the Dirac constraint quantization method, and point out some subtleties appearing in previous works in analyzing constraint structure of the brane system. Overcoming some ad hoc procedures, we obtain desirable noncommutative coordinates exactly compatible with the result of the conformal field theory in recent literatures. Furthermore, we find interesting commutator relations of other canonical variables.Comment: 13 pages, revtex, Expressions are change

Conformally-coupled dark spinor and FRW universe

We study conformal coupling of dark spinor fields to gravity and calculate the energy density and the pressure of the spinor in FRW spacetime. We consider the renormalizable potential of the spinor field. In the cases where the field is proportional to some power of the cosmic scale factor $a(t)$, we determine the Hubble parameter as a function of the scale factor and find analytic solutions for $a(t)$ when the spinor field matter dilutes as the universe expands. We discuss the possibility that both matter- and dark energy-dominated eras of our universe can be described by the dark spinor.Comment: 4 pages, Revised argument in section III, results unchanged. To be published in PR

Isospin particle on S2S^{2} with arbitrary number of supersymmetries

We study the supersymmetric quantum mechanics of an isospin particle in the background of spherically symmetric Yang-Mills gauge field. We show that on $S^{2}$ the number of supersymmetries can be made arbitrarily large for a specific choice of the spherically symmetric SU(2) gauge field. However, the symmetry algebra containing the supercharges becomes nonlinear if the number of fermions is greater than two. We present the exact energy spectra and eigenfunctions, which can be written as the product of monopole harmonics and a certain isospin state. We also find that the supersymmetry is spontaneously broken if the number of supersymmetries is even.Comment: 6 page

Correlation of the transient energy margin to Out-of-step impedance relay operation

This research has developed a procedure in which the transient energy margin, for a multimachine power system obtained by the transient energy function method, is related to the apparent impedance of a line protected by the out-of-step relay;In this procedure, only the multimachine system parameters are used, and the conventional intermediate step of forming a two-machine equivalent is eliminated;Two types of energy-based criteria are derived to relate the apparent impedance to the transient energy margin obtained: (i) with the original multimachine system, and (ii) with the inertial equivalents of two groups of machines separated by the line protected by the out-of-step relay;An approximation of the post-disturbance trajectory is developed for the rotor angle positions between the instance of disturbance removal and the controlling u.e.p. Two such approximations are investigated: (i) a linear trajectory, and (ii) the Fourier series approximation. The energy-based criteria are then applied along this approximated trajectory. A technique for generating the swing impedance locus is also presented;The method is tested for a loss of generation distrubance on a 23-generator, 211-bus equivalent of the Florida Power & Light Company network. The results obtained are compared with time simulation results