External Validation of Models to Predict Unsuccessful Endometrial Ablation: a Retrospective Study

Study Objective: External validation of our previously presented and locally established prediction models to help counsel patients for failure of endometrial ablation (EA) or surgical re-intervention within 2 years after EA, called ‘Failure model’ and ‘Re-intervention model’ respectively. Design: Retrospective external validation study, minimal follow-up time of 2 years.Setting: Two non-academic teaching hospitals in the Netherlands.Patients: Pre-menopausal women (18+) who had undergone EA for abnormal uterine bleeding problems between January 2010 and November 2012. A total of 329 patients were eligible for analysis.Interventions: Interventions used for EA were Novasure (Hologic, Marlborough, Massachusetts, US) and ThermaChoice III (Ethicon, Sommerville, US). Measurements and Main Results: The Area Under the Receiver Operating characteristics Curve (AUROC) for the outcome parameter of failure within 2 years after EA was 0.59 (95% CI 0.53 – 0.65). Variables in this model were dysmenorrhea, age, parity ≥5 and preoperative menorrhagia. The Hosmer-Lemeshow test showed no significant difference between the observed and predicted outcome. (Chi-square: 4.62, P-value: .80) The AUROC for the outcome parameter surgical re-intervention within 2 years was 0.62 (95% CI 0.53 – 0.70) Variables in this model were dysmenorrhea, age, menstrual duration> 7 days, parity ≥5 and a previous caesarean section. The Hosmer-Lemeshow test showed no significant difference between the observed and predicted outcome (Chi-square 11.34, P-value .18).Conclusion: Both the failure model and the re-intervention model can be used to predict unsuccessful endometrial ablation in the general population within two years after the procedure. It can be used prior to surgery to facilitate tailor-made shared decision-making, and help counsel patients with regards to the potential outcome of their treatment with the use of a personally calculated percentage.

Analysis on Influence of Hydrogen Content Exceeding Standard in GaAs Device

Aiming at the problem of hydrogen content exceeding the standard in GaAs device, the influence mechanism of hydrogen content exceeding the standard on the device is analyzed, the failure model of hydrogen content exceeding the standard in GaAs device in engineering is given, the source of hydrogen is analyzed, and the protective measures of hydrogen content exceeding the standard are given. It is of certain guiding significance for future engineering application.

Percolation on interdependent networks with different group size distributions under targeted attack

Traditional research studies on interdependent networks with groups ignore the relationship between nodes in dependency groups. In real-world networks, nodes in the same group may support each other through cooperation and tend to fail or survive together. In this paper, based on the framework of group percolation, a cascading failure model on interdependent networks with cooperative dependency groups under targeted attacks is proposed, and the effect of group size distributions on the robustness of interdependent networks is investigated. The mutually giant component and phase transition point of networks with different group size distributions are analyzed. The effectiveness of the theory is verified through simulations. Results show that the robustness of interdependent networks with cooperative dependency groups can be enhanced by increasing the heterogeneity between groups under targeted attacks. The theory can well predict the numerical simulation results. This model provides some theoretical guidance for designing robust interdependent systems in real world.

Stating Failure Modelling Limitations of High Strength Sheets: Implications to Sheet Metal Forming

This article discusses the fracture modelling accuracy of strain-driven ductile fracture models when introducing damage of high strength sheet steel. Numerical modelling of well-known fracture mechanical tests was conducted using a failure and damage model to control damage and fracture evolution. A thorough validation of the simulation results was conducted against results from laboratory testing. Such validations show that the damage and failure model is suited for modelling of material failure and fracture evolution of specimens without damage. However, pre-damaged specimens show less correlation as the damage and failure model over-predicts the displacement at crack initiation with an average of 28%. Consequently, the results in this article show the need for an extension of the damage and failure model that accounts for the fracture mechanisms at the crack tip. Such extension would aid in the improvement of fracture mechanical testing procedures and the modelling of high strength sheet metal manufacturing, as several sheet manufacturing processes are defined by material fracture.

Reliability Evaluation of CNC Machine Tools Considering Competing Failures of Fault Failure Data and Machining Accuracy Degradation Data

Traditional reliability evaluation of CNC machine tools usually considers a single failure mode of fault failure or degradation failure, or considers fault failure and degradation failure to be independent of each other. However, in the actual working conditions, fault failure and degradation failure are mutually affected, and the reliability evaluation of the competing failure models of CNC machine tools by considering the two failure modes comprehensively can get more accurate evaluation results. Therefore, this paper proposes a reliability evaluation method for CNC machine tools considering fault failure data competing with machining accuracy degradation data. A fault failure model of CNC machine tools is established based on a non-homogeneous Poisson process. The fault failure model is updated according to the different effects of each maintenance result of the failure on machining accuracy. By integrating multiple geometric errors of CNC machine tools through multi-body system theory, the amount of machining accuracy degradation is extracted. A machining accuracy degradation failure model is established using the Wiener process. Considering the correlation between fault failure and degradation failure, a competing failure model based on the Coupla function is developed for evaluating the reliability of CNC machine tools. Finally, the effectiveness of the proposed method is verified by example analysis.