also designed a few sensors with a standing pillar which can extend into the ambient flow. fabricated polymer MEMS sensors with a membrane structure to detect the moving of underwater objects. utilized SU-8 standing structures on thin silicon cantilever beams. The sensing elements of the devices typically consist of deformable flexural elements, such as cantilever beams, diaphragms and bridges. The inspiration has led to the design of novel sensors. Though it is blind, the blind fish is still capable of perceiving its surroundings and avoiding obstacles by relying on its lateral line.
The lateral line of blind fish is the most studied one. Recently, researchers have been paying attention to eliminating the issues of AUVs mentioned above by taking advantage of sensing principles inspired by Nature. Besides, they usually have a large size and heavy weight. Optical imaging will fail to work in dark and turbid water. However, sonar technology has a blind zone and the intense sound waves can be fatal to aquatic animals. Traditionally sensing strategies of AUVs to perceive their surroundings are sound navigation and ranging (SONAR) and optical imaging. Nowadays, autonomous underwater vehicles (AUVs) which can travel underwater without requiring input from an operator play an important role in underwater exploration and military applications. The present work provides a good application prospect for the underwater sensing of AUVs. Further, this sensor can work well under a disturbance with low frequency. Experimental results show that the sensitivity of the sensor is up to 1.16 mV/(mm/s), and the detectable oscillatory flow velocity is as low as 4 mm/s. By imitating the underwater disturbance and generating the oscillatory flow velocities with a vibrating sphere, the performance of the sensor in detecting the oscillatory flow was tested. The dynamic behaviors of the piezoelectric diaphragm were examined by the impedance spectrum. Sensor prototypes were fabricated by microfabrication technology. Finite element analysis was conducted to estimate the sensor behavior. This sensor is self-powered, does not need an external power supply, and works efficiently in d 33 mode by using inter-circulating electrodes to release the radial in-plane poling. Published by John Wiley & Sons Ltd.This paper presents a new sensor based on a radial field bulk piezoelectric diaphragm to provide energy-efficient and high-performance situational sensing for autonomous underwater vehicles (AUVs). Indoor air quality air circulation and ventilation chemical analysis household measurement humidifier indoor air pollutants particulate matter. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds. The transport and loss of PM 2.5 depended on the rate of air circulation and ventilation.
Operation of a single ultrasonic humidifier resulted in PM 2.5 concentrations up to hundreds of μg m -3, and its influence extended across the entire household. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Preliminary results of organic compounds being present in humidifier PM are also presented. Ion chromatography analysis revealed a large amount of SO 4 2- in PM, representing a previously unrecognized indoor source. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO 3 is likely making a major contribution to PM. In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. Household humidification is widely practiced to combat dry indoor air.
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