Adaptive Reduced Basis Methods Applied to Structural Dynamic Analysis

The reduced basis methods (RBM) have been demonstrated as a promising numerical technique for statics problems and are extended to structural dynamic problems in this paper. Direct step-by-step integration and mode superposition are the most widely used methods in the field of the finite element analysis of structural dynamic response and solid mechanics. Herein these two methods are both transformed into reduced forms according to the proposed reduced basis methods. To generate a reduced surrogate model with small size, a greedy algorithm is suggested to construct sample set and reduced basis space adaptively in a prescribed training parameter space. For mode superposition method, the reduced basis space comprises the truncated eigenvectors from generalized eigenvalue problem associated with selected sample parameters. The reduced generalized eigenvalue problem is obtained by the projection of original generalized eigenvalue problem onto the reduced basis space. In the situation of direct integration, the solutions of the original increment formulation corresponding to the sample set are extracted to construct the reduced basis space. The reduced increment formulation is formed by the same method as mode superposition method. Numerical example is given in Section 5 to validate the efficiency of the presented reduced basis methods for structural dynamic problems.

A Real-Time Transient Analysis of a Functionally Graded Material Plate Using Reduced-Basis Methods

Based on the hybrid numerical method (HNM) combining with a reduced-basis method (RBM), the real-time transient response of a functionally graded material (FGM) plates is obtained. The large eigenvalue problem in wavenumber domain has been solved through real-time off-line/on-line calculation. At off-line stage, a reduced-basis space is constructed in sample wavenumbers according to the solved eigenvalue problems. The matrices independent of parameters are projected onto the reduced-basis spaces. At on-line stage, the reduced eigenvalue problems of the arbitrary wavenumbers are built. Subsequently, the responses in wavenumber domain are obtained by the approximated eigen-pairs. Because of the application of RBM, the computational cost of transient displacement analysis of FGM plate is decreased significantly, while the accuracy of the solution and the physics of the structure are still retained. The efficiency and validity of the proposed method are demonstrated through a numerical example.

Long-term outcomes of additional surgery versus non-gastrectomy treatment for early gastric cancer after non-curative endoscopic submucosal dissection: a meta-analysis

Background:Endoscopic resection is increasingly used in the treatment for early gastric cancer(EGC);however,about 15%of endoscopic submucosal dissection(ESD)cases report non-curative resection.The efficacy of different remedial interventions after non-curative ESD for EGC remains controversial.This meta-analysis aimed to compare the long-term outcomes of additional surgery and non-gastrectomy treatment for EGC patients who underwent non-curative ESD.Methods:All relevant studies published up to October 2021 were systematically searched in the PubMed,Web of Science,and Embase databases.The medical subject headings terms"early gastric cancer,""gastrectomy,""endoscopic submucosal dissection,"and their related free keywords were used to search relevant articles without restrictions on regions,publication types,or languages.The Newcastle–Ottawa Quality Assessment Scale was used to evaluate the quality of the included studies.Odds ratios(ORs)with 95%confidence intervals(CIs)of 5-year overall survival(OS),disease-specific survival(DSS),disease-free survival(DFS)and hazard ratios(HRs)with 95%CIs of OS were calculated using a random-or fixed-effects model.Results:This meta-analysis included 17 retrospective cohort studies with 5880 patients,of whom 3167 underwent additional surgery and 2713 underwent non-gastrectomy.We found that patients receiving additional gastrectomy had better 5-year OS(OR=3.63,95%CI=3.05–4.31),DSS(OR=3.22,95%CI=2.22–4.66),and DFS(OR=4.39,95%CI=1.78–10.82)outcomes than those receiving non-gastrectomy treatments.The pooled HR also showed that gastrectomy following non-curative ESD significantly improved OS(HR=0.40,95%CI=0.33–0.48).In addition,elderly patients benefited from additional surgery in consideration of the 5-year OS(HR=0.54,95%CI=0.41–0.72).Conclusions:Compared with non-gastrectomy treatments,additional surgery offered better long-term survival outcomes for patients with EGC who underwent non-curative ESD.

Adaptive cropping shallow attention network for defect detection of bridge girder steel using unmanned aerial vehicle images

Bridges are an important part of railway infrastructure and need regular inspection and maintenance.Using unmanned aerial vehicle(UAV)technology to inspect railway infrastructure is an active research issue.However,due to the large size of UAV images,flight distance,and height changes,the object scale changes dramatically.At the same time,the elements of interest in railway bridges,such as bolts and corrosion,are small and dense objects,and the sample data set is seriously unbalanced,posing great challenges to the accurate detection of defects.In this paper,an adaptive cropping shallow attention network(ACSANet)is proposed,which includes an adaptive cropping strategy for large UAV images and a shallow attention network for small object detection in limited samples.To enhance the accuracy and generalization of the model,the shallow attention network model integrates a coordinate attention(CA)mechanism module and an alpha intersection over union(α-IOU)loss function,and then carries out defect detection on the bolts,steel surfaces,and railings of railway bridges.The test results show that the ACSANet model outperforms the YOLOv5s model using adaptive cropping strategy in terms of the total mAP(an evaluation index)and missing bolt mAP by 5%and 30%,respectively.Also,compared with the YOLOv5s model that adopts the common cropping strategy,the total mAP and missing bolt mAP are improved by 10%and 60%,respectively.Compared with the YOLOv5s model without any cropping strategy,the total mAP and missing bolt mAP are improved by 40%and 67%,respectively.

Sharp recanalization using Chiba biopsy needle for the treatment of biliary occlusion after radiofrequency ablation

Introduction Biliary stricture is a less common complication after hepatic radiofrequency ablation(RFA)[1,2].Patients with biliary stricture often present with recurrent jaundice,fever or chills,and require endoscopic or percutaneous biliary drainage,and in some cases recanalization of the biliary tract[3].Establishing guide-wire passage through the stricture is essential for biliary recanalization.However,in some cases of complete biliary obstruction,a more aggressive technique is needed when ordinarymethods fail to establish.Herein,we report a novel technique of extraluminal recanalization for biliary strictures using a Chiba biopsy needle,which is similar to sharp endovascular recanalization.