We report operation of a single-longitudinal-mode WDMchannel-selectable fiber laser. The use of a tunable fiber Bragg grating and a linewidth narrowing saturable absorption filter in conjunction with an intracavity etalon enabled single-frequency emission and discretely tunable WDM channel operation without the need for external wavelength locking modules. Side mode suppression ratios (SMSRs) > 50 dB have been demonstrated with ~ 3 dBm individual channel output powers for 8 channel (f = 50 GHz) operation of this WDM source.
This paper presents an automated fish fry counting by detecting the pixel area occupied by each fish silhouette using image processing. A photo of the fish fry in a specially designed container undergoes binarization and edge detection. For every image frame, the total fish count is the sum of the area inside every contour. Then the average number of fishes for every frame is summed up. Experimental data shows that the accuracy rate of the method reaches above 95 percent for a school of 200, 400, 500, and 700 fish fry. To minimize errors due to crowding in the container, schooling behavior analysis is considered. The behavioral effects of different colored lights on milkfish and tilapia are thoroughly investigated. The system's effectiveness, efficiency, possible improvements, and other potential applications are discussed.
We propose, simulate, and experimentally demonstrate a circuit analogue of a special relativity phenomenon known as relativistic aberration of light (RAL) by using a surprisingly simple, low-cost, and easily accessible electronic circuit-based all-pass filter. This work is useful for two audiences: (i) physicists who are interested in research on circuit analogues; and (ii) physics educators who are interested in using the research results to raise interest among students by incorporating analogue-based learning into undergraduate physics lecture and laboratory courses. For the first type of audience, we present a rigorous theoretical framework describing this RAL-on-an-electronic-chip analogy. We show by (i) analytical modelling, (ii) commercial circuit software simulation, and (iii) experiment that the electrical phase shift Φ of the output signal is analogous to the RAL angle, Ψ. This parameter opens up a path among researchers to model the effects of other relativistic phenomena with electronic circuits. For the second type of audience, we discuss the potential role of RAL-on-an-electronic-chip in physics education (both in lectures and laboratory) that combines students’ learnings of both physics and electronic circuits, at the same time. We also explore briefly its relevance to engineering education.
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