Upper critical field for underdoped high-T_c superconductors. Pseudogap and stripe--phase

We investigate the upper critical field in a stripe--phase and in the presence of a phenomenological pseudogap. Our results indicate that the formation of stripes affects the Landau orbits and results in an enhancement of $H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to a reduction of the upper critical field. This effect is of particular importance when the magnitude of the gap is of the order of the superconducting transition temperature. We have found that a suppression of the upper critical field takes place also for the gap that originates from the charge--density waves.Comment: 7 pages, 5 figure

An EOQ inventory model for items with Weibull deterioration, shortages and time varying demand

[[abstract]]An inventory model is considered in which inventory is depleted not only by demand, but also by deterioration. Hence, in this paper, we derive the EOQ model for inventory of items that deteriorates at a Weibull distributed rate, assuming the demand rate with a continuous function of time. Moreover, the proposed model cannot be solved directly in a closed form, thus we used the computer software IMSL MATH/LIBRARY (1989) to find the optimal service level and the optimal replenishment cycle time. Further, we also verify that the sufficient conditions of optimality of the service level and the replenishment cycle time are satisfied under certain conditions. Finally, three numerical examples and sensitivity analyses are provided to assess the solution procedure.[[notice]]補正完畢[[journaltype]]國