Life History, Diet, Abundance and Distribution, and Length-Frequencies of Selected Invertebrates in Florida Bay, Everglades National Park, Florida

This report presents information on the life history, diet, abundance and distribution, and length-frequency distributions of five invertebrates in Florida Bay, Everglades National Park. Collections were made with an otter trawl in basins on a bi-monthly basis. Non-parametric statistics were used to test spatial and temporal differences in the abundance of invertebrates when numbers were appropriate (i. e., $25). Invertebrate species are presented in four sections. The sections on Life History, and Diet were derived from the literature. The section on Abundance and Distribution consists of data from otter-trawl collections. In addition, comparisons with other studies are included here following our results. The section on Length-frequency Distributions consists of length measurements from all collections, except 1984-1985 when no measurements were taken. Length-frequency distributions were used, when possible, to estimate life stage captured, spawning times, recruitment into Florida Bay for those species which spawn outside the Bay, and growth. Additional material from the literature was added when appropriate. (PDF contains 39 pages)

Nonlinear copropagation of two optical pulses of different frequencies in photonic crystal fibers

A theoretical investigation of the nonlinear copropagation of two optical pulses of different frequencies in a photonic crystal fiber is presented. Different phenomena are observed depending on whether the wavelength of the signal pulse is located in the normal or the anomalous dispersion region. In particular, it is found that the phenomenon of pulse trapping occurs when the signal wavelength is located in the normal dispersion region while the pump wavelength is located in the anomalous dispersion region. The signal pulse suffers cross-phase modulation by the Raman shifted soliton pulse and it is trapped and copropagates with the Raman soliton pulse along the fiber. As the input peak power of the pump pulse is increased, the red-shift of the Raman soliton is considerably enhanced with the simultaneous further blue-shift of the trapped pulse to satisfy the condition of group velocity matching.

Unsteady shock motion on a NACA0012 aerofoil at low reduced frequencies

Using transonic blowdown windtunnel experiments, the 2D unsteady shock motion on a NACA0012 aerofoil is examined at various frequencies typical for helicopter blades in forward flight. The aerofoil is subjected to freestream velocities oscillating periodically between M = 0.66 and M = 0.77. Unsteady pressure traces and schlieren images are analyzed over a range of low reduced frequencies to provide information on shock location and strength throughout the cycle. Unsteady effects were noticeable even at very low reduced frequencies (down to O(0.01). However, through the range of frequencies investigated, and within experimental error, the unsteady shock location showed no discernible lag compared to the quasi-steady behaviour. On the other hand, significant variations were observed in shock strengths with the upstream running part of the cycle (decreasing Mach number) displaying considerably stronger shocks than during the accelerating part of the cycle. It could be shown that this variation in shock strength is primarily caused by the shock motion modifying the relative shock Mach number. As a result is was possible to use the quasi-steady results to predict the unsteady shock behaviour at the frequencies investigated here (below 0(0.1)).

Unsteady shock motion on a NACA0012 aerofoil at low reduced frequencies

Using transonic blowdown windtunnel experiments, the 2D unsteady shock motion on a NACA0012 aerofoil is examined at various frequencies typical for helicopter blades in forward flight. The aerofoil is subjected to freestream velocities oscillating periodically between M = 0.66 and M = 0.77. Unsteady pressure traces and schlieren images are analyzed over a range of low reduced frequencies to provide information on shock location and strength throughout the cycle. Unsteady effects were noticeable even at very low reduced frequencies (down to O(0.01). However, through the range of frequencies investigated, and within experimental error, the unsteady shock location showed no discernible lag compared to the quasi-steady behaviour. On the other hand, significant variations were observed in shock strengths with the upstream running part of the cycle (decreasing Mach number) displaying considerably stronger shocks than during the accelerating part of the cycle. It could be shown that this variation in shock strength is primarily caused by the shock motion modifying the relative shock Mach number. As a result is was possible to use the quasi-steady results to predict the unsteady shock behaviour at the frequencies investigated here (below 0(0.1)).