ABSTRACT
Objectives: Gingival pigmentation, the most common etiological factor of which is smoking, is a clinical condition that causes aesthetic complaints. Due to the dose-dependent effect of smoking, gingival pigmentation may present regression following cessation. This cross-sectional study aimed to evaluate gingival pigmentation in former tobacco consumers and compare with current ones. Material and Methods: A total of 110 people, 70 of whom were current smokers (Group CS) and 40 of whom were former smokers (Group FS), were included in the study. Participants filled out the data collection forms containing questions on demographic features and information related to tobacco consumption. In addition, all individuals were examined with Hedin's melanin index (HMI) to evaluate gingival pigmentation. Statistical significance was set at the P < 0.05 level. Results: The population consisted of 57.3% male, and the mean age of all participants was 39.43 (SD 12.3) years. The mean duration of tobacco consumption did not differ between groups, whereas the mean HMI score of Group FS was significantly lower (P = 0.001). The correlation analyses showed that while the HMI score of Group CS was in relation to both daily consumption amount and duration of consumption (for both, P < 0.01), the HMI score of Group FS showed a negative association with only time elapsed after cessation (P = 0.000). Conclusions: Considering the limitations of this study, the outcomes revealed a dose- and a time-dependent relation of gingival pigmentation in smokers. However, gingival pigmentation in former tobacco consumers was negatively correlated only with time elapsed after cessation.
ABSTRACT
Predictive maintenance is considered a proactive approach that capitalizes on advanced sensing technologies and data analytics to anticipate potential equipment malfunctions, enabling cost savings and improved operational efficiency. For journal bearings, predictive maintenance assumes critical significance due to the inherent complexity and vital role of these components in mechanical systems. The primary objective of this study is to develop a data-driven methodology for indirectly determining the wear condition by leveraging experimentally collected vibration data. To accomplish this goal, a novel experimental procedure was devised to expedite wear formation on journal bearings. Seventeen bearings were tested and the collected sensor data were employed to evaluate the predictive capabilities of various sensors and mounting configurations. The effects of different downsampling methods and sampling rates on the sensor data were also explored within the framework of feature engineering. The downsampled sensor data were further processed using convolutional autoencoders (CAEs) to extract a latent state vector, which was found to exhibit a strong correlation with the wear state of the bearing. Remarkably, the CAE, trained on unlabeled measurements, demonstrated an impressive performance in wear estimation, achieving an average Pearson coefficient of 91% in four different experimental configurations. In essence, the proposed methodology facilitated an accurate estimation of the wear of the journal bearings, even when working with a limited amount of labeled data.
ABSTRACT
HYPOTHESIS: During the evaporation of urea water solution (UWS), the wall temperature and surface properties influence the dynamics of deposit formation by affecting the internal mass transport. These effects are expected to be reflected in the resulting deposit morphology and allow different deposit regimes to be distinguished. EXPERIMENTS: The temperature of metallic substrates is varied for three different surface treatments to analyze the wetting, evaporation behavior and the crystallization process of single UWS droplets in situ using a high-speed camera. The deposit morphology is captured by confocal microscopy and analyzed via the power spectral density method (PSD). PSD is used to extract the height of different surface features for each deposit, providing valuable information about the local crystallization history. FINDINGS: A significant influence of the surface properties on the crystallization process as well as on the morphology of the final deposit is found. The influence of wettability is described by the resulting internal mass transport, which determine the urea distribution. PSD analysis quantified distinct trends in the scaling tendencies of the deposit aggregates under different wall conditions. The local crystal growth history extracted by PSD agrees well with proposed crystallization mechanisms, which is further supported by high-speed and SEM imaging.
