Abstract:Objective: To investigate the relationship between growth patterns and mandibular posterior tooth-alveolar bone complex morphology in a Chinese population with normal occlusion. Methods: Forty-five patients with normal occlusion (23 males, 22 females) were included in this study. Among these patients, 20 displayed the vertical growth pattern, and 20 had the horizontal growth pattern, while the remaining patients displayed the average growth pattern. All of the patients underwent dental cone beam computed tomography (CBCT), which included the region of the mandibular posterior teeth and the alveolar. A linear regression analysis and a correlation analysis between the facial height index (FHI) and the alveolar bone morphology were performed. Results: The inclination of the molars, the thickness of the cortical bone, and the height of the mandibular bone differed significantly between patients with the horizontal growth pattern and those with the vertical growth pattern (P<0.05). Significant positive correlations were found between: the FHI and the inclination of the molars; the FHI and the thickness of the cortical bone; and the FHI and the height of the mandibular bone. Conclusions: The mandibular posterior tooth-alveolar bone complex morphology may be affected by growth patterns.
In previous studies, the negative impedance electromagnetic shunt damping (EMSD) can increase the damping of host structures to reduce the unexpected vibration. This paper proposes a novel electromagnetic shunt mass (EMSM) concept, which can tune the natural frequency of an electro-mechanical system and simultaneously suppress vibration. The EMSM means that the mass of a system can be controlled with the EMSD. An electromagnetic transducer is designed and modeled. The negative inductance negative resistance (NINR) and the positive inductance negative resistance (PINR) shunts are proposed to investigate the tuning of the natural frequency characteristics. The governing equation of the coupling system is derived, and the EMSM model is established in frequency domain. The optimal resistance and inductance of the shunt are analyzed theoretically, and the root locus is employed to judge the stability of the coupling system. The laboratory experiment was setup to verify the EMSM concept. The results demonstrate that the EMSM can electrically tune the natural frequency of the electromagnetic transducer. Furthermore, the NINR-EMSM has the excellent performance in isolation region, and the PINR-EMSM is more effective to suppress the low frequency vibrations in resonant region.
Current studies on hemifacial microsomia (HFM) patients undergoing unilateral distraction osteogenesis (DO) mainly confined to description of facial morphology. This study was to investigate the effect of unilateral DO on upper airway in pediatric HFM patients using computational fluid dynamics. The investigators implemented the present retrospective study composed of 20 patients (age 9.5 ± 2.5 years, 11 males, 9 females) with moderate HFM performed unilateral DO on the ramus of mandible. Computational fluid dynamics models of the upper airway were obtained based on the computed tomography data sets which were taken before and 6 months after distraction. Morphologic and aerodynamic parameters were respectively computed and compared at peak inspiration. Paired t-tests were used to compare the differences between the before and after parameters with the significance set at P < 0.05. The authors observed that after DO, oropharynx and nasopharynx were the major expanded regions, average pressure increased in all cross-sections, average velocity decreased significantly except in the superior border of the epiglottis plane, and the airflow resistance significantly reduced in the whole upper airway (P < 0.05). The results indicate that unilateral DO may expand the constricted oropharynx and nasopharynx, obtain a relatively symmetrical airway shape and decrease the airflow resistance which consequently reduce the workload necessary for breathing and facilitate inspiration.
Mechanical tea harvesting using plucking machines is highly efficient, but harvested raw fresh tea leaves (FTLs) are always low quality because they contain a mixture of old leaves and leaf debris. To address this problem, this study developed an automatic sorting machine with a vision‐based recognition method to extract high‐quality FTLs from plucked raw FTLs. First, the raw FTLs were separated one by one after passing through three sequential conveyor belts with increasing speed, and were then classified into four grades using a vision‐based recognition method. Finally, the FTLs were blown by air nozzles into collection boxes according to their specific grade. In the recognition method, the shape‐based feature of each FTL is extracted by establishing the FTL's topological structure, and the support vector machine model is used for classification. The experimental results revealed that the vision‐based recognition method performed satisfactorily with an accuracy rate of 94% and precision rate of 85%. The sorting success rate and efficiency of the automatic sorting machine were approximately 80% and 15 kg hr−1, respectively. The results indicate that the developed automatic sorting machine can effectively and efficiently sort raw FTLs, which may improve the profitability and promote the automation of tea processing.
The immersed boundary-lattice Boltzmann method (IB-LBM) was used to examine the motion and deformation of three elastic red blood cells (RBCs) during Poiseuille flow through constricted microchannels. The objective was to determine the effects of the degree of constriction and the Reynolds (Re) number of the flow on the physical characteristics of the RBCs. It was found that, with decreasing constriction ratio, the RBCs experienced greater forced deformation as they squeezed through the constriction area compared to at other parts of the microchannel. It was also observed that a longer time was required for the RBCs to squeeze through a narrower constriction. The RBCs subsequently regained a stable shape and gradually migrated toward the centerline of the flow beyond the constriction area. However, a sick RBC was observed to be incapable of passing through a constricted vessel with a constriction ratio ≤1/3 for Re numbers below 0.40.
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