Browsing by Author "He, Zhaoming (TTU)"
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Item Classification of Children's Heart Sounds With Noise Reduction Based on Variational Modal Decomposition(2022) Zhang, Anqi; Wang, Jiaming; Qu, Fei; He, Zhaoming (TTU)Purpose: Children's heart sounds were denoised to improve the performance of the intelligent diagnosis. Methods: A combined noise reduction method based on variational modal decomposition (VMD) and wavelet soft threshold algorithm (WST) was proposed, and used to denoise 103 phonocardiogram samples. Features were extracted after denoising and employed for an intelligent diagnosis model to verify the effect of the denoising method. Results: The noise in children's phonocardiograms, especially crying noise, was suppressed. The signal-to-noise ratio obtained by the method for normal heart sounds was 14.69 dB at 5 dB Gaussian noise, which was higher than that obtained by WST only and the other VMD denoising method. Intelligent classification showed that the accuracy, sensitivity and specificity of the classification system for congenital heart diseases were 92.23, 92.42, and 91.89%, respectively and better than those with WST only. Conclusion: The proposed noise reduction method effectively eliminates noise in children's phonocardiograms and improves the performance of intelligent screening for the children with congenital heart diseases.Item Detachment Force of the Helical Anchor in Mitral Annulus(2021) Zeng, Ganhe; Li, Gang; Jia, Yunchao; Chen, Si; Chen, Pengyang; He, Zhaoming (TTU)Helical anchors are used in transcatheter mitral valve repair. The aim of the current study was to investigate effect of helical anchor design, anchored position and biting depth on the detachment force in an in-vitro experiment. Mitral annulus was excised from 36 fresh porcine hearts and mounted in an unaxial test rig. Seven helical anchors were made of stainless steel based on the geometric parameters: outer diameter, wire diameter, and pitch. The helical anchors were screwed in at 3 to 9 o'clock positions of the posterior annulus, namely, P3-9, and pulled out. The pullout force was measured with the maximal pullout force defined as the detachment force. The detachment force within the medial, lateral and central positions were comparable (p > =0.069). The detachment force at P6 was lowest compared with the medial and lateral positions, and was 5.459 ± 0.193 N, 5.586 ± 0.113 N, 8.911 ± 0.250 N for the anchors in the outer diameters of 3, 4, 5 mm, respectively at the pitch of 2 mm and the wire diameter of 0.4 mm and biting depth of 3 coils. The detachment force increased with the outer and wire diameters, but was not affected by the pitch at the biting depth of 3 coils (p ≥ 0.279). The detachment force of the helical anchor is lowest in the central posterior annulus region, and the biting depth in 3 or more coils is recommended. The helical anchor is stronger than the suture.Item Two-phase flow investigation of sewage pumps with different tip clearance via computational fluid dynamics and multi-factor ANOVA(2024) Yang, Yang; Wang, Hui; Hu, Qixiang; Ji, Leilei; He, Zhaoming (TTU); Shi, Weidong; Song, Xiangyu; Zhou, LingSewage pumps are widely utilized in various applications, including municipal wastewater treatment plants, industrial processes, and residential sewage systems. These pumps are specifically designed to handle the transportation of mixtures consisting of solid and liquid components, commonly observed as two-phase flow. In this study, semi-open sewage pumps with varying clearance sizes have been examined through adjustment of the geometrical model. Multi-factor analysis of variance is employed to investigate the combined influence of different two-phase flow conditions and tip clearance sizes on the performance of sewage pumps. The results show that the performance of the pump decreases significantly as the clearance size increases. Also, the sensitivity of pump efficiency to variations in tip clearance size is contingent upon the flow rate. Under part-load conditions, both particle concentration and clearance size exhibit a notable effect on efficiency. The two-phase flow will greatly enhance the intensity of the unsteady flow near the inlet and outlet of the semi-open impeller, which is the main reason for the performance degradation of the sewage pump. The findings of this research provide valuable insights for enhancing the hydraulic performance and operational stability of semi-open sewage pumps operating under two-phase flow conditions.