Numerical simulations, such as the finite element method have been widely used to predict noise and vibration behavior. This allows reducing the development time and production cost of products. However, these results have been calculated based on the governing equations at each physical areas as the idealized conditions. Then, these simulations are not taken into account the fluctuation of response characteristic by the uncertainties of noise factors. Therefore, it is important to restrain the fluctuation of products properties by the uncertainties. In this paper, focusing on the transient analysis, we propose a robust design for minimizing the time history amplitude fluctuation by structure uncertainties. The robust design is implemented based on the combined use of the stochastic finite element method and the structural optimization. Since this method is performed by minimizing the 1st sensitivity, we will formulate the 1st and 2nd sensitivity in the time domain. Then, the proposed method is validated by applying it to the simple mass-damper-spring system whether the fluctuation of the time history response amplitude is restrained.
Purpose
Over-the-scope clip (OTSC) is used for treatment of gastrointestinal perforation, postoperative anastomotic leakage, and for mucosal defect closure after duodenal endoscopic submucosal dissection (ESD). However, OTSCs are expensive and associated with fatal complications; therefore, proper OTSC usage is necessary. There are no clear criteria for OTSC use for mucosal defect closure after duodenal ESD. Therefore, we examined the closure outcomes achieved using OTSCs or conventional clips for patients that underwent duodenal ESD. We also analyzed the resected specimen area and preoperative estimated size of tumors treated with each method to determine the criteria for using either OTSC or conventional clip.
Methods
Endoscopic resection was performed for 133 superficial duodenal epithelial tumors at our institution from April 2017 to February 2022. Complete closure of mucosal defects after duodenal ESD was attempted for 82 tumors; these were divided into the OTSC group and the control group (for which conventional clips were used). Closure outcomes were analyzed.
Results
The overall rate of complete mucosal defect closure in the OTSC and control groups was 98.8% (95% confidence interval = 93.39–99.97%). There were significant differences in the median estimated tumor size (20 mm vs 15 mm; p < 0.001) and median resected specimen area (339.1 mm2 vs 169.6 mm2; p < 0.001) between the groups.
Conclusion
If the estimated preoperative tumor size is ≤ 18 mm, complete closure of mucosal defects after duodenal ESD can be achieved with only conventional clips. Based on this study, we suggest that OTSC is not necessary for small lesions.
Numerical simulations, such as the finite element method have been widely used to predict noise and vibration behavior. This allows reducing the development time and production cost of products.However, these results have been calculated based on the governing equations at each physical areas as the idealized conditions. Then, these simulations are not taken into account the fluctuation of response characteristic by the uncertainties of noise factors. Therefore, it is important to restrain the fluctuation of products properties by the uncertainties. In order to mitigate the fluctuation, robust optimization that is combined used of the stochastic finite element method and structural optimization will be introduced. Moreover, finite element models for vibro-acoustic simulations typically induce a high computational cost especially time history response analysis. In order to alleviate this problem, model order reduction is proposed to reduce the number of degrees of freedom while maintaining a desired accuracy. In this paper, focusing on the transient analysis, we propose a robust design method that combined use of the model order reduction and robust optimization. Then, the proposed method is validated by applying it to the vibro-acoustic systems whether the fluctuation of the time history response amplitude and the computational cost are restrained.
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