Nonintrusive Nonlinear Reduced Order Models for Structures in Large Deformations: Validations to Atypical Structures and Basis Construction Aspects

The focus of this investigation is on reduced order models (ROMs) of the nonlinear geometric response of structures that are built nonintrusively, i.e., from standard outputs of commercial finite element codes. Several structures with atypical loading, boundary conditions, or geometry are considered to not only support the broad applicability of these ROMs but also to exemplify the different steps involved in determining an appropriate basis for the response. This basis is formed here as a combination of linear vibration modes and dual modes, and some of the steps involved follow prior work; others are novel aspects, all of which are covered in significant detail to minimize the expertise needed to develop these ROMs. The comparisons of the static and dynamic responses of these structures predicted by the ROMs and by the underlying finite element models demonstrate the high accuracy that can be achieved with the ROMs, even in the presence of significant nonlinearity.

Cardiac autonomic modulation and anti-TPO antibodies in Subclinical Hypothyroidism – Does any correlation exit?

Background Heart rate variability (HRV) reflects the balance of activities of sympathetic and parasympathetic components of the autonomic nervous system. Anti-thyroid antibodies have long been associated with thyroid dysfunction and influence thyroid profile testing, the most common being anti-Thyroid Peroxidase (TPO) and anti-Thyroglobulin antibodies. Subclinical hypothyroidism (SCHypo) is characterized by elevated TSH with normal thyroid hormones.We hypothesized that autonomic function may be deranged in anti-TPO positive sub-clinical hypothyroid cases even before the onset of overt hypothyroidism. Objectives To investigate the association between anti-TPO antibodies (anti-TPOAb) positive SCHypo and sympathovagal imbalance (SVI). Methodology: The study was conducted on age and BMI matched subclinical hypothyroid patients (n = 52) and healthy controls (n = 20). Cardiac autonomic activity was assessed by short term HRV in the time (SDNN, RMSSD, pNN50) and frequency domain (LFms2, HFms2, LFnu, HFnu, TP and LF/HF ratio). Nonlinear geometric measures (SD1, SD2, SD1/SD2, TINN, HRV triangular index) were also evaluated. Biochemical evaluation of serum thyroid profile, anti-TPOAb was done in all the subjects. Results Decreased HRV was observed in anti-TPOAb positive group when compared to negative and control groups. Significant positive correlation of anti-TPOAb with TSH, LF nu, LF/HF and negative correlation with SDNN, RMSSD, pNN50, SD1, SD1/SD2, HFnu and TP of HRV was observed. Conclusion Anti-TPOAb positive SCHypo group exhibited modifications in HRV characterized by decreased parasympathetic modulation, as compared to controls. The findings were also suggestive of increased risk of autonomic dysfunction in TPOAb- positive patients than negative. Anti-TPO antibody was significantly correlated with TSH and SVI in SCHypo patients.

Bifurcation and dynamic behavior analysis of a rotating cantilever plate in subsonic airflow

Turbo-machineries, as key components, have a wide utilization in fields of civil, aerospace, and mechanical engineering. By calculating natural frequencies and dynamical deformations, we have explained the rationality of the series form for the aerodynamic force of the blade under the subsonic flow in our earlier studies. In this paper, the subsonic aerodynamic force obtained numerically is applied to the low pressure compressor blade with a low constant rotating speed. The blade is established as a pre-twist and presetting cantilever plate with a rectangular section under combined excitations, including the centrifugal force and the aerodynamic force. In view of the first-order shear deformation theory and von-Kármán nonlinear geometric relationship, the nonlinear partial differential dynamical equations for the warping cantilever blade are derived by Hamilton’s principle. The second-order ordinary differential equations are acquired by the Galerkin approach. With consideration of 1:3 internal resonance and 1/2 sub-harmonic resonance, the averaged equation is derived by the asymptotic perturbation methodology. Bifurcation diagrams, phase portraits, waveforms, and power spectrums are numerically obtained to analyze the effects of the first harmonic of the aerodynamic force on nonlinear dynamical responses of the structure.

Nonlinear Geometric Framework for Software Defect Prediction

Humans use the software in every walk of life thus it is essential to have the best quality software. Software defect prediction models assist in identifying defect prone modules with the help of historical data, which in turn improves software quality. Historical data consists of data related to modules /files/classes which are labeled as buggy or clean. As the number of buggy artifacts as less as compared to clean artifacts, the nature of historical data becomes imbalance. Due to this uneven distribution of the data, it difficult for classification algorithms to build highly effective SDP models. The objective of this study is to propose a new nonlinear geometric framework based on SMOTE and ensemble learning to improve the performance of SDP models. The study combines the traditional SMOTE algorithm and the novel ensemble Support Vector Machine (SVM) is used to develop the proposed framework called SMEnsemble. SMOTE algorithm handles the class imbalance problem by generating synthetic instances of the minority class. Ensemble learning generates multiple classification models to select the best performing SDP model. For experimentation, datasets from three different software repositories that contain both open source as well as proprietary projects are used in the study. The results show that SMEnsemble performs better than traditional methods for identifying the minority class i.e. buggy artifacts. Also, the proposed model performance is better than the latest state of Art SDP model- SMOTUNED. The proposed model is capable of handling imbalance classes when compared with traditional methods. Also, by carefully selecting the number of ensembles high performance can be achieved in less time.