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We present a passive and non-intrusive sensing system for monitoring hand washing activity using structural vibration sensing. Proper hand washing is one of the most effective ways to limit the spread and transmission of disease, and has been especially critical during the COVID-19 pandemic. Prior approaches include direct observation and sensing-based approaches, but are limited in non-clinical settings due to operational restrictions and privacy concerns in sensitive areas such as restrooms. Our work introduces a new sensing modality for hand washing monitoring, which measures hand washing activity-induced vibration responses of sink structures, and uses those responses to monitor the presence and duration of hand washing. Primary research challenges are that vibration responses are similar for different activities, occur on different surfaces/structures, and tend to overlap/coincide. We overcome these challenges by extracting information about signal periodicity for similar activities through cepstrum-based features, leveraging hierarchical learning to differentiate activities on different surfaces, and denoting “primary/secondary” activities based on their relative frequency and importance. We evaluate our approach using real-world hand washing data across 4 different sink structures/locations, and achieve an average F1-score for hand washing activities of 0.95, which represents a 8.8X and 10.2X reduction in error over two different baseline approaches. 

Natural forsterite(Fo)-rich olivines represent the major constituent of the Earth's upper mantle. Collected at the surface in mantle xenoliths, they are commonly used in scientific research. Many electron microprobe labs use the San Carlos standard USNM111312/44 [1], provided by the Smithonian Institution, for calibrations. Non-USNMdistributed crystals of San Carlos olivine are also often used as starting material in experimental studies [e.g., 2, 3]. However, the potential inherent chemical variability of starting materials can affect results and their scientific interpretations. Hence, it is important to characterize the full chemical variability of the San Carlos olivine. Fournelle [4] showed that the USNM material shows limited variability (Fo89.6 to Fo90.5), but that non-standard San Carlos olivines can be significantly more variable, with Fo contents ranging from 87 to 92%. Following these results, we report new major and trace element analyses on grains (0.5 mm - >5mm) of non-USNM San Carlos olivine and compare them with analyses on USNM San Carlos standard compositions. We also investigate the presence of potential grain-scale chemical variations by looking at composition profiles on large (> 5mm) grains. Observed major-element variations (Fo88.4 to Fo91.4) are consistent with Fournelle’s results [4]. Additionally, we show that minor and trace element concentrations present significant and contrasted variations between grains (e.g., 17 % Ni, 28 % Mn, 44% V, 69 % Al, 285 % P, relative). At the scale of the individual grain, however, San Carlos olivines appear relatively homogeneous with no systematic core-rim variations. Results and implications for the use of this material in experimental studies and for interpretations of the petrogenetic processes will be discussed.