In an attempt to discriminate different sources of organic matter and reconstruct the paleo-environment of the Taipei Basin, northern Taiwan over the past 250,000 years, organic carbon and nitrogen content (C/N ratios) and isotope composition (δ 13 C and δ 15 N) are measured for sediment samples collected from core Wu-ku drilled at the depocenter in western Taipei Basin. The high δ 13 C values (up to -17.0‰) and high C/N ratio (up to 14.9 and 13.0, respectively) indicate that this area underwent a period of relative aridity during MIS 2 and mid MIS 6. Another two periods of high and variable δ 15 N values (up to 15.5 and 13.5‰, respectively) in MIS 1 and MIS 7 represent different nutrient condition in the basin. In MIS 1, high δ 15 N variability along with increasing TOC may reflect an unstable trend of aquatic productivity related to the dynamic mixing ratios of seawater and fresh water. The high δ15 N values observed in the sediments of MIS 7 could be explained by the employment of a 15 N-enriched nitrate from denitrification as the main source of nitrogen for primary producers.
In this paper, we propose a dual-fiberoptic Fabry–Perot interferometer (FFPI) sensing system integrated with a low-cost and low-coherence light-emitting diode (LED) as a light source to detect dynamic vibration caused by acoustic waves with a cut-off frequency of 200 Hz. When the acoustic signals are applied, the sensing FFPI on a Styrofoam sheet provides the function of partially transforming the longitudinal energy as the transverse energy generates a phase shift in the sensing FFPI cavity. The light reflected from the sensor is demodulated by the reference FFPI to extract the measurand. The low-power (sub-nW) optical signals are transferred into electrical signals, processed by a designed optical receiver, and recorded for data analysis.
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