Browsing by Subject "Arcs"

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Arc-related Mesozoic basins of northern Mexico : their origin, tectonic inversion and influence on ore localization
(2016-05) Lyons, James Irwin, 1948-; Kyle, J. Richard; Lawton, Timothy Frost; Cloos, Mark; Horton, Brian K; Elliott, Brent
New structural mapping and radiometric dating in northern Mexico integrated with previous studies indicate the need for revision of current regional tectonic models. The Mezcalera Marginal Basin, an autochthonous Jurassic-Lower Cretaceous basin exposed from southern Arizona to Guerrero replaces accreted terrane models. The lack of significant documentable offsets of this marginal basin provides evidence that contradict proposed major Mexican transform faults in northern Mexico. A left-lateral Cenomanian transpressional fault along which the Caborca and related terranes and offset Bisbee Group strata were displaced is documented by east-directed thrusting of the translated basement and supracrustal strata over the autochthonous Mezcalera Basin strata. Oxfordian (149 Ma) submarine volcanic domes at Batopilas, Chihuahua indicates the Nazas arc of central Mexico migrated across the Mezcalera Marginal Basin, and 124 to 138 Ma dates on Bisbee Group Morita Formation tuffs indicate Alisitos arc volcanism to the west. The well documented Late Cretaceous through Miocene arc migration can thus be projected to the Early Jurassic. Oceanic plate rollback toward the Pacific from the Jurassic through the Early Cretaceous explains the observed arc migration as well as the resulting extension of the Mexican continent. A previously unrecognized intracratonic basin, the Carrizal Basin, a probable northern extension of the Mexican Basin, is documented west of the Chihuahua Basin. The older usage Aldama Platform is divided into the Casas Grandes Platform to the west and the Florida-Aldama Ridge to the east of the Carrizal Basin. Basin inversion as defined by mapping of bivergent out-of-the-basin thrusting along both sides of both the Carrizal and Mexican Intracratonic Basins suggests inversion as the principal tectonic process that produced the Sierra Madre Oriental fold belts. Stratigraphic relationships document the inception of tectonic shortening as Late Cenomanian and a folded 43.7 Ma rhyolite flow at Division de Norte, Chihuahua documents continuing basin inversion well into the Eocene. Previous observations of spatial correlations between structurally complex basin margins and numerous major Cretaceous through Miocene mineral deposits are enhanced by the discovery of the large Cinco de Mayo polymetallic carbonate deposit hosted in stacked west-directed out-of-the-basin thrusting on the west margin of the Carrizal Basin.
Characterization of multi-Frobenius non-classical plane curves and construction of complete plane (N, d)-arcs
(2009-08) Borges Filho, Herivelto Martins; Voloch, José Felipe
This work is composed of two independent parts, both addressing problems related to algebraic curves over finite fields. In the first part, we characterize all irreducible plane curves defined over Fq which are Frobenius non-classical for different powers of q. Such characterization gives rise to many previously unknown curves which turn out to have some interesting properties. For instance, for n [greater-than or equal to] 3 a curve which is both q- and qn-Frobenius non-classical will have its number of Fqn-rational points attaining the Stöhr-Voloch bound. In the second part, we study the arc property of several plane curves and present new complete (N, d)-arcs in PG(2, q). Some of these arcs (viewed as linear (N, 3,N - d)-codes) are just a small constant away from the Griesmer bound and for some small values of q the bound is achieved. In addition, this part also answers a question of Voloch about the arc property of a certain family of curves with many rational points, and another question of Giulietti et al about the arc property of q-Frobenius non-classical plane curves.
Sustained and incipient fault location for utility distribution system
(2009-12) Chopra, Shivaz; Santoso, Surya; Grady, Mack
Automated fault location systems use power quality monitoring and circuit data to provide with a distance or impedance estimate to the fault. This can be used to avoid manual patrolling of the entire feeder in case of a main feeder lockout. It can also be used for circuits with repeated momentary interruptions to pinpoint the section of the circuit causing such problems. Self clearing sub cycle faults have been identified as the precursors of a number of sustained faults (requiring the operation of protective device) in utility distribution networks. The frequency of such incipient faults increases considerably as they are about to evolve into a full blown fault. This report proposes a modified and improved fault location algorithm that can be used to accurately identify sustained as well as temporary faults. The algorithm is based in the time domain and takes into account the arc voltage during a fault event. The proposed algorithm is developed, validated and applied to known distribution field data. Time domain simulation models are also used for validation purposes. The developed algorithm was observed to be very accurate when compared to other impedance based fault location algorithms proposed in the literature. Finally, sub cycle event identification and fault pre-location is proposed that can be very useful for electric utility operations. Highly accurate results were observed during this application study. For instance, a current waveform containing three incipient and one full fault event is shown in the figure given below. The estimated reactance to an incipient fault location is approximately 1.1 Ω. The fault location results obtained from the first three sub-cycle faults can be used to avert the final sustained fault event.