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Numerical analysis of the effects of canal wall-up and canal wall-down mastoidectomy on the sound transmission characteristics of human ears

Liu Peihan, Liu Wen, Zhao Yu, Yan Shanshan, Jiang Wen, Liu Houguang, Wan Jin

Acta of Bioengineering and Biomechanics

2023

Vol. 25, no. 2

133--145

The aim of this work was to study the effect of canal wall-up (CWU) and canal wall-down (CWD) and mastoid obliteration in conjunction with CWD (CWD-MO) mastoidectomy on the sound transmission characteristics of the human ear. Methods: Three mastoidectomy surgical methods, CWU, CWD and CWD-MO, were simulated on the freshly dissected cadaver heads. Then, the finite element (FE) models corresponding to these surgical methods were established by micro-computed tomography (Micro-CT) and reverse engineering technology, and the accuracy of the models was verified. Finally, the FE Models were used to analyze the effects of different surgical methods on the sound transmission characteristics of the human ear. Results: For CWU, since the integrity of the outer wall of the ear canal is ensured, the sound pressure (SP) gain of the ear canal and the stapes footplate displacement (FPD) gain after this operation are close to normal values. For CWD, due to severe damage to the outer wall of the ear canal, a negative gain of the ear canal SP occurs in the high-frequency range, and the resonance frequency is significantly reduced. For CWD-MO, the frequency range of SP negative gain in the ear canal is reduced due to the addition of fillers in the ear canal to reduce the degree of damage, and the resonance frequency is increased compared to CWD. Conclusions: The impact of three types of mastoidectomy, including CWU, CWD, and CWDMO, on the sound transmission characteristics of the human ear after surgery is relatively small.

A dynamic model for the heat transfer behavior of a cooling system

Liu Wen, Zhang Chi, Hu Xiao-Xiong, Cao Jian-Bo, Liu Li-Jiao, Ye Xin-Y, Lin Li, Qi Xun-Ji

Control and Cybernetics

2020

Vol. 49, No. 3

315--332

For purposes of studying the heat transfer behavior of various fluids in a refrigeration system, a dynamic model is established, obtained on the basis of analysis concerning the effects of adsorption velocity, adsorbent bed temperature, condensing temperature, and heat transfer fluids, as well as changes of external conditions. It is demonstrated that adsorption velocity increases sharply in the initial phase of adsorption process and gradually declines after reaching a peak value, whereas condensing temperature increases sharply in the initial phase of desorption process and decreases after reaching a peak value with the desorption quantity decreasing. Furthermore, the increase of heat source temperature and the decrease of cooling water temperature can advance the adsorption process. The present study therefore suggests some ways of improving the performance of such a refrigeration system by increasing heat source temperature, decreasing ambient air temperature, increasing return air temperature and decreasing cooling water temperature.