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Data-Driven Modeling of Linear and Nonlinear Dynamic Systems for Noise and Vibration Applications
No full textData-driven modeling can help improve understanding of the governing equations for systems that are challenging to model. In the current work, the Sparse Identification of Nonlinear Dynamical systems (SINDy) is used to predict the dynamic behavior of dynamic problems for NVH applications. To show the merit of the approach, the paper demonstrates how the equations of motions for linear and nonlinear multi-degree of freedom systems can be obtained. First, the SINDy method is utilized to capture the dynamic behavior of linear systems. Second, the accuracy of the SINDy algorithm is investigated with nonlinear dynamic systems. SINDy can output differential equations that correspond to the data. This method can be used to find equations for dynamical systems that have not yet been discovered or to study current systems to compare with our current understanding of the dynamical system. With this amount of flexibility, SINDy can be used for NVH applications to help analyze vibration-related datasets as the study shows that SINDy results are consistent with ODE solutions. This study demonstrates how SINDy can accurately replicate mature known dynamical system models to highlight its potential to extract equations for more complex systems whose dynamic equations are challenging or impossible to obtain
Why Do Patients Choose Skilled Nursing Facilities After Total Hip and Knee Arthroplasty?
No full textBackground Current research indicates that total joint arthroplasty patients who are discharged to skilled nursing facilities (SNFs) have higher complication rates as compared to home. Many factors like age, sex, race, Medicare status, and past medical history have been shown to influence discharge destination. The present study sought to gather patient-indicated reasons for SNF discharge and identify potentially modifiable factors influencing the decision. Methods Primary total joint arthroplasty patients were asked to complete surveys at their presurgical and 2-week postsurgical follow-up appointments. The surveys included home access and social support questions as well as patient-reported outcome measures: Patient-Reported Outcomes Measurement and Information System, Risk Assessment and Prediction Tool, Knee injury and Osteoarthritis Outcome Score for Joint Replacement, or Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement. Results Of 765 patients who met inclusion criteria, 3.9% were discharged to an SNF and these were more frequently post-THA, women, older, Black, and persons living alone. Regression analyses indicated that lower Risk Assessment and Prediction Tool score, higher age, no caregiver presence, and Black race were significantly associated with SNF discharge. Patients discharged to an SNF most commonly reported social concerns rather than medical or home access concerns as the main factor for SNF discharge. Conclusions While age and sex are nonmodifiable factors, the availability of a caregiver and social support represents an important modifiable factor in regard to discharge destination. Dedicated attention during the preoperative planning period may help augment social support and avoid unnecessary discharges to SNFs
Analysis of Shielding Effectiveness against Electromagnetic Interference (EMI) for Metal-Coated Polymeric Materials
Get PDFLightweight materials, such as polymers and composites, are increasingly used in the automotive and aerospace industries. Recently, there has been an increase in the use of these materials, especially in electric vehicles. However, these materials cannot shield sensitive electronics from electromagnetic interference (EMI). The current work investigates the EMI performance of these lightweight materials using an experimental setup based on the ASTM D4935-99 standard and EMI simulation using the ANSYS HFSS. This work studies how metal coating from zinc and aluminum bronze can improve the shielding performance of polymer-based materials, such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and polyphthalamide (PPA). Based on the findings of this study, a thin coating (50 μm) of Zn on the surface of PPS and a thin coating of 5 μm and 10 μm of Al-Bronze, respectively, on the surface of PEEK and PPA have indicated an increase in the shielding effectiveness (SE) when subjected to EMI. The shielding effectiveness significantly increased from 7 dB for the uncoated polymer to approximately 40 dB at low frequencies and up to approximately 60 dB at high frequencies for coated polymers. Finally, various approaches are recommended for improving the SE of polymeric materials under the influence of EMI