Retraction of "Effect of Fluoride Layer Growth on the Deposition Rate under Different Microchannel Structures".

[This retracts the article DOI: 10.1021/acsomega.3c06182.].

Effect of Fluoride Layer Growth on the Deposition Rate under Different Microchannel Structures.

In the plasma-enhanced chemical vapor deposition (PECVD) process, a showerhead is used to enhance fluid uniformity in the chamber. The uniformity of the flow field will be affected by changing the microchannel on the showerhead, which in turn directly affects the uniformity of deposition. The showerhead will be etched during the cleaning process due to the presence of HF, which will form a fluoride layer. This layer will cause a decrease in the diameter of the microchannels, resulting in changes in the deposition uniformity. The impact of diameter changes can be reduced by making modifications to the microchannel structure. By adopting a coupling of the Navier-Stokes and Direct Simulation Monte Carlo (NS-DSMC) methods, we obtained the velocity variation of two typical microchannels (equal-diameter type and expansion type) under the same diameter change. The results indicate that compared to the equal-diameter type, the expansion type exhibits a smaller change in velocity for the same change in diameter. For the surface reaction limited regime, a stable velocity leads to a consistent residence time, which is advantageous for maintaining the uniformity of the film thickness. Therefore, compared to the equal-diameter type microchannel, the expansion type can reduce the impact of changes in diameter.

Experimental Research on the Preparation of K2CO3/Expanded Vermiculite Composite Energy Storage Material.

Thermochemical adsorption energy storage is a potential energy utilization technology. Among these technologies, the composite energy storage material prepared by K2CO3 and expanded vermiculite (EVM) shows excellent performance. In this paper, the influence of the preparation process using the impregnation method and vacuum impregnation method on K2CO3/EVM composite material is studied. The preparation plan is further optimized with the solution concentration and the expanded vermiculite particle size as variables. In the experiment, mercury intrusion porosimetry (MIP) is used to measure the porosity and other parameters. Additionally, with the help of scanning electron microscopy (SEM), the morphological characteristics of the materials are obtained from a microscopic point of view. The effects of different preparation parameters are evaluated by comparing the experimental results. The results show that the K2CO3 specific gravity of the composite material increases with the increase of the vacuum degree, up to 70.440 wt.% (the vacuum degree is 6.7 kPa). Expanded vermiculite with a large particle size (3~6 mm) can carry more K2CO3, and content per cubic centimeter of K2CO3 can be as high as 0.466 g.

Computational Fluid Dynamics Analysis of Carotid-Ophthalmic Aneurysms with Concomitant Ophthalmic Artery Infundibulum in a Patient-Specific Model.

BACKGROUND: Although previous studies have reported cases of coexistence of carotid-ophthalmic aneurysm and ophthalmic artery (OA) infundibulum, the hemodynamic characteristics of this complicated structure and its damaging effects on vision remain to be elucidated. The aim of the present study was to analyze this artery structure using computational fluid dynamics (CFD) techniques. METHODS: We have presented the case of a patient with a diagnosis of carotid-ophthalmic aneurysm, who had been experiencing blurred vision. A transient analysis was performed to investigate the blood flowing in the parent artery. Hemodynamic parameters such as streamline, wall shear stress (WSS), oscillatory shear index (OSI), and relative residence time were obtained. RESULTS: When the inlet velocity of the parent artery was at the second peak, the flow rate and intensity of the vortex reached their maximum. In the aneurysm neck, a region of high time-averaged WSS (TAWSS) and a region of low TAWSS with a high OSI coexisted. In addition, a relaxation area was found. In the aneurysm dome, the minimum TAWSS was 2.5 Pa, the maximum OSI was 0.48, and the 2 regions did not overlap. In the OA infundibulum, the maximum OSI and relative residence time were 0.47 and 39.2, respectively; the minimum TAWSS was 0.59 Pa. CONCLUSIONS: We detected aneurysm regions that were susceptible to further expansion and assessed the rupture risk of each region. The relaxation area could promote aneurysm progression. In addition, the location of the vortex shear force center varied with time. Finally, double vortex streamlines influenced the blood supply through the OA, impairing the vision. Infundibulum might promote thrombus formation and, hence, retard OA blood flow.

Mathematical method for analysis of the asymmetric retinal vascular networks.

PURPOSE: The purpose of this study was to quantitatively investigate the haemodynamics and oxygen transmission of the retina. METHODS: Considering the effect of Fåhraeus-Lindqvist effect on the apparent viscosity of blood and the actual haematocrit in blood vessels, this study used the currently known retinal parameters (e.g. blood flow obtained by Doppler Fourier domain optical coherence tomography, FD-OCT for short) to construct a retinal blood circulation model consisting of an asymmetric vascular network system. RESULTS: The blood flow velocity and the vascular diameter in the retinal blood vessels satisfied the exponential relationship. The wall shear stress was related to the release of nitric oxide synthase and endothelin-1 by endothelial cells and played an important role in retinal blood flow regulation. In the retinal arteries, the oxygen tension ranged from 98 to 65 mmHg, and the oxygen saturation ranged from 97.3% to 92.2%. In the retinal veins, the oxygen tension was approximately 41.8 mmHg, and the oxygen saturation ranged from 79.2% to 77.3%. The difference in oxygen content of the arteriovenous network was 5.4 (ml O2/dl blood), and the oxygen extraction of the superior temporal arteriovenous network was 86 (µl/min*ml O2/dl blood). CONCLUSION: Compared with previous relevant experimental data, the numerical model established in this article demonstrates reliability. It also helps advance our understanding of the retinal pathological processes related to hemodynamics and metabolism.