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483 results on '"Liu, Zhengang"'

12. The comparison of spectral analyses and flow features in upper airways with obstructive sleep apnea (OSA) between successful and failed surgeries

Author

Lu, Mingzhen, Chi, Tianxi, Liu, Zhengang, Wang, Shu, Liu, Yang, and Ye, Jingying

Subjects
Physics - Medical Physics, Physics - Biological Physics, Physics - Fluid Dynamics
Abstract

Obstructive sleep apnea (OSA) is a common sleep disorder and widening the upper airway is often used in clinical practice. However, the success rate of this surgery is limited; the failed surgery would even make the situation worse, indicating the widened airway is not the unique criterion to evaluate the breathing quality. Therefore, we carried out both experimental measurement and numerical simulation on OSA upper airways and found that there existed an intrinsic dominant 3-5 Hz signal and the signal-to-noise ratio (SNR) at 3-5 Hz is inversely correlated with apnea-hypopnea index (AHI). Firstly, to validate the suitability of simulation methods, we carried out Laser Doppler measurement in 3D-printing OSA upper airway models, and found excellent agreement between the measured and calculated velocity profiles in two upper airway models for the first time. Then we carried out large eddy simulation (LES) to investigate four pairs of OSA upper airway models with 8 different AHI values for both pre- and post-surgery; among them, three surgeries were successful and one failed. The decreased the pressure drop for failed case, proving that only widening airway cannot guarantee to improve OSA. In our analysis, it is indicating that a dominant recirculation downstream of the minimum cross-section should be a main feature of a successful surgery, and the strength of 3-5 Hz signal induced by flow separation in the upper airway plays an important role in appraising breathing quality. This provides a new guideline for surgery planning. Furthermore, we found a strong correlation between AHI and the area ratio of minimum cross-section near the retro-palate to the maximum cross-section behind the tongue base, and this correlation is highly significant, r = - 0.833, p = 0.01 < 0.05., Comment: 34 pages, 9 figures, 3 tables

Published
2020

20. Particles deposition on plates with different film cooling hole shapes for different blowing ratios and angles of attack.

Author

Liu, Zhengang, Ruan, Rongsheng, Zhang, Yixuan, Lyu, Yaguo, and Liu, Zhenxia

Subjects
*DUST, *SURFACE pressure, *ABSOLUTE value, *COOLING, *WAXES
Abstract

Turbine vanes may be subjected to the deposition of particles such as dust from the external environment. The deposition could affect their aerodynamic and cooling performances. As an effective cooling method, the film cooling could alter the deposition. In this paper, the deposition experiments at ambient temperature were conducted by using atomized wax as the substitute for real particles to investigate the influence of film cooling hole shapes on the deposition for different blow ratios and angles of attack. The results indicate that within the range of blowing ratios in this paper, the deposition on the pressure surface of different hole shapes increases with increasing blowing ratio. Among them, the cylindrical model exhibits the most significant variation in deposition, for example, with a relative increase of 94% in deposition when the blowing ratio was increased from 2.0 to 2.5. The CONSOLE test model showed a relative increase of 60%, while the conical and fan-shaped test model exhibited a relative increase of 20%. The conical, CONSOLE, and fan-shaped film cooling holes can mitigate the influence of the blowing ratio on the deposition of particles. Within the range of angle of attack in this paper, the deposition on the pressure surfaces with different hole shapes increases with the increase in the absolute value of angle of attack. The cylindrical test model exhibits the most significant variation. The conical and fan-shaped holes can mitigate the influence of the angle of attack on the deposition of particles. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Is Pyrolysis Treatment a Viable Solution to Detoxify Metal(loid)s in Sewage Sludge toward Land Application? Case Studies of Chromium and Zinc

Author

Luo, Lei, Wang, Jiawen, Yan, Aichu, Wang, Jiaxiao, Wu, Songlin, Xu, Xuehui, Chen, Wenxing, and Liu, Zhengang

Abstract

Metal(loid)s in sewage sludge (SS) are effectively immobilized after pyrolysis. However, the bioavailability and fate of the immobilized metal(loid)s in SS-derived biochar (SSB) following land application remain largely unknown. Here, the speciation and bioavailability evolution of SSB-borne Cr and Zn in soil were systematically investigated by combining pot and field trials and X-ray absorption spectroscopy. Results showed that approximately 58% of Cr existing as Cr(III)-humic complex in SS were transformed into Fe (hydr)oxide-bound Cr(III), while nano-ZnS in SS was transformed into stable ZnS and ferrihydrite-bound species (accounting for over 90% of Zn in SSB) during pyrolysis. All immobilized metal(loid)s, including Cr and Zn, in SSB tended to be slowly remobilized during aging in soil. This study highlighted that SSB acted as a dual role of source and sink of metal(loid)s in soil and posed potential risks by serving a greater role of a metal(loid) source than a sink when applied to uncontaminated soils. Nevertheless, SSB could impede the translocation of metal(loid)s from soil to crop compared to SS, where coexisting elements, including Fe, P, and Zn, played critical roles. These findings provide new insights for understanding the fate of SSB-borne metal(loid)s in soil and assessing the viability of pyrolyzing SS for land application.

Published
2024
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27. An Experimental Study on Reducing Depositing on Turbine Vanes with Transverse Trenches

Author

Liu, Zhengang, Zhang, Fei, Liu, Zhenxia, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Liang, Qilian, Series Editor, Martin, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zhang, Junjie James, Series Editor, and Zhang, Xinguo, editor

Published
2019
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43. Asymmetric acoustic splitting with the dual-layers of binary metagratings.

Author

Liu, Zhengang, Chang, Shuai, Xue, Shibei, Ju, Fangfang, and Qian, Shengyou

Abstract

Here, we exhibit the asymmetric acoustic splitting with the dual-layers of binary metagratings (BMs), i.e., BM1 and BM2. For the positive incidence (PI) normally from the BM1 side, acoustic waves are freely transmitted through the BM1 and split into two beams with the transmitted angles at and , then the two beams are freely transmitted through the BM2 with the transmitted angles at and . For the negative incidence (NI) normally from the BM2 side, acoustic waves are wholly reflected. Hence, the asymmetric acoustic splitting is observed. Here, the dual-layers of BMs are exemplified by the coating cells with different period lengths. Excellent agreement can be observed between the numerical simulations and the theoretical analysis. Our proposal may be applied in noise control and acoustic communication. [ABSTRACT FROM AUTHOR]

Published
2024
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