Enhancements of small peaks using the moiré technique
Abstract A very simple technique is described for enhancing small peaks in 3D line drawings.
Modification of river tides by the discharge
The effect of an increased discharge on the tide progressing into a river is evaluated quantitatively by gaging the signal recorded at upstream stations against a reference station, during intervals of effectively constant discharge; this process is repeated for progressively larger values of the discharge. Upstream, the tidal range is reduced by an increased discharge; the time of arrival of low water is accelerated, while high water is retarded. The changes in range and in time may be represented by simple regression relations. Downstream an increased discharge causes a decrease in the effective friction during flood and an increase in it during ebb. Low water is retarded and high water is accelerated; some tidal components may actually be amplified over a segment of the river.
Modeling Coherent Backscattering Errors in Fiber Optic Gyroscopes for Sources of Arbitrary Line Width
We present a new model of the noise and drift induced by coherent backscattering in a fiber optic gyroscope (FOG) interrogated with a light source of arbitrary temporal coherence. This study is critical to understand whether a FOG driven with a laser instead of a broadband source can attain high sensitivity and stability, which would have the overwhelming benefit of improving the FOG scale factor stability by at least ten-fold and would enable the use of FOGs for inertial navigation of aircrafts. Analytical and numerical solutions bring to light two significant new predictions. First, coherent-backscattering noise can be made negligibly small by utilizing a laser with a very narrow linewidth (less than ~ 20 kHz), although in this regime the drift is high. Second, by using a laser with a broad linewidth (greater than ~ 10 MHz), both the noise and the drift are low enough for aircraft inertial navigation. The dependencies of the noise and drift on fiber loss, loop coupling coefficient, and backscattering coefficient are also presented to define the optimum mode of operation of this new class of FOGs.