Research on a Fiber Optic Oxygen Sensor Based on All-Phase Fast Fourier Transform (apFFT) Phase Detection.

Fiber optic oxygen sensors based on fluorescence quenching play an important role in oxygen sensors. They have several advantages over other methods of oxygen sensing-they do not consume oxygen, have a short response time and are of high sensitivity. They are often used in special environments, such as hazardous environments and in vivo. In this paper, a new fiber optic oxygen sensor is introduced, which uses the all-phase fast Fourier transform (apFFT) algorithm, instead of the previous lock-in amplifier, for the phase detection of excitation light and fluorescence. The excitation and fluorescence frequency was 4 KHz, which was conducted between the oxygen-sensitive membrane and the photoelectric conversion module by the optical fiber and specially-designed optical path. The phase difference of the corresponding oxygen concentration was obtained by processing the corresponding electric signals of the excitation light and the fluorescence. At 0%, 5%, 15%, 21% and 50% oxygen concentrations, the experimental results showed that the apFFT had good linearity, precision and resolution-0.999°, 0.05° and 0.0001°, respectively-and the fiber optic oxygen sensor with apFFT had high stability. When the oxygen concentrations were 0%, 5%, 15%, 21% and 50%, the detection errors of the fiber optic oxygen sensor were 0.0447%, 0.1271%, 0.3801%, 1.3426% and 12.6316%, respectively. Therefore, the sensor that we designed has greater accuracy when measuring low oxygen concentrations, compared with high oxygen concentrations.

Time and the Anthropocene: Making more-than-human temporalities legible through environmental observations and creative methods.

The Anthropocene term invokes the multiple temporalities through which organisms, ecologies, and environments unfold - from the immediacy of the present moment to the sedimentary timescales of the geological record. Viewed from the perspective of anthropogenic climate change and environmental degradation, these organisms, ecologies, and environments, including the planet's human occupants, may well benefit if we took a view of time that was more-than-human in scope and scale. This paper demonstrates how design, creative practice, and technology can be used to make legible human and more-than-human timescales through local, planetary, and celestial imaginaries that are congruent with the Anthropocene term. It first considers various anthropogenic and non-anthropogenic phenomena that are used for time keeping, both human and non-human. It then discusses the design and development of a timepiece that uses observations of environmental light to imaginatively situate daily life within various temporal scales, from embodied, diurnal, circalunar, and annual to the sedimentary timescales of the geological record. Through the timepiece, the paper argues that a hybrid form of timekeeping that brings together human time standards and environmental observation could help align the temporal imaginaries of urban societies with biological, ecological, and planetary processes, while highlighting the presence of potentially damaging anthropogenic processes, such as artificial light at night. Such hybrid forms of timekeeping may help foster meaningful relationships between people and the environment, facilitate day-to-day awareness of the presence and extent of disruptive anthropogenic processes in our environments and provide an imaginative framework for thinking about urban time and life in an Anthropocene context.