We characterized and imaged dental calculus using swept-source optical coherence tomography (SS-OCT). The refractive indices of enamel, dentin, cementum, and calculus were measured as 1.625 ± 0.024, 1.534 ± 0.029, 1.570 ± 0.021, and 2.097 ± 0.094, respectively. Dental calculus leads strong scattering properties, and thus, the region can be identified from enamel with SS-OCT imaging. An extracted human tooth with calculus is covered with gingiva tissue as an in vitro sample for tomographic imaging.
Most conventional FDC approaches are used to find the TDs required for monitoring and the TDs' related key parameters that need to be monitored, and then apply the SPC approach to detect the faults. However, in a practical situation, an abnormal key-parameter value may not be caused solely by its own TD; it may result from the other related parameters. Therefore, accurate fault classification or diagnosis may not be achieved. Moreover, most conventional PdM methods require a library of degradation patterns from previous run-to-failure data sets. Without those massive historical failure data, the PdM methods may not function properly. In this paper, we propose a virtual-metrology-(VM) based BPM scheme that possesses the capabilities of FDC and PdM. The BPM scheme contains the TD baseline model, FDC logic, and a RUL predictive module. The TD baseline model generated by the VM technique is applied to serve as the reference for detecting the fault. By applying the BPM scheme, fault diagnosis and prognosis can be accomplished, the problem of the conventional SPC method mentioned above can be resolved, and the requirement of massive historical failure data can also be released.
Index Terms-Automatic virtual metrology (AVM), baseline predictive maintenance (BPM) scheme, dynamic-moving-window (DMW) scheme, fault detection and classification (FDC), keep important sample (KIS) scheme, predictive maintenance (PdM).
Nomenclature Abbreviation List
AVMAutomatic virtual metrology. BDM Breakdown maintenance. BEI Baseline error index. BEI T Threshold of BEI. BPM Baseline predictive maintenance.
Diffuse optical multipatch technique is used to assess spatial variations in absorption and scattering in biological tissue, by monitoring changes in the concentration of oxyhemoglobin and deoxyhemoglobin. In our preliminary study, the temporal tracings of tissue oxygenation are measured using diffuse optical multipatch measurement and a venous occlusion test, employing normal subjects and ICU patients suffering from sepsis and heart failure. In experiments, obvious differences in tissue oxygenation signals were observed among all three groups. This paper discusses the physiological relevance of tissue oxygenation with respect to disease.
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