Nonlinear free vibration analysis of the functionally graded beams

Nonlinear natural oscillations of beams made from functionally graded material (FGM) are studied in this paper. The equation of motion is derived according to the EulerBernoulli beam theory and von Karman geometric nonlinearity. Subsequently, Galerkin’s solution technique is applied to obtain the corresponding ordinary differential equation (ODE) for the FGM beam. This equation represents a kind of a nonlinear ODE containing quadratic and cubic nonlinear terms. This nonlinear equation is then solved by means of three efficient approaches. Homotopy perturbation method is applied at the first stage and the corresponding frequency-amplitude relationship is obtained. Frequency-amplitude formulation and Harmonic balance method are then employed and the consequent frequency responses are determined. In addition, Parameter Expansion Method is utilized for evaluating the nonlinear vibration of the system. A parametric study is then conducted to evaluate the influence of the geometrical and mechanical properties of the FGM beam on its frequency responses. Different types of material properties and boundary conditions are taken into account and frequency responses of the system are evaluated for different gradient indexes. The frequency ratio (nonlinear to linear natural frequency) is obtained in terms of the initial amplitude and compared for different materials and end conditions

Comparison between the Acute Effects of Intermittent Hypoxia and Aerobic Exercise on the Nitric Oxide Value, Blood Pressure and the Respiratory Function in Apnea

Background: Apnea is a common disorder in the community. The aim of the study was to compare the acute effects of activity and periodic hypoxia on the nitric oxide, blood pressure, and the pulmonary function in apnea. Methods: The study was as a clinical, pretest, and posttest intervention. A total of 11 males enrolled in the study and completed at least four options of the STOP-Bang inventory. They performed aerobic exercise on a treadmill with intensity of 70 0/0 heart rate reserve, during 40 minutes in intermittent hypoxia. The subjects inhaled intermittently 5 minutes normoxic and hypoxic (11%) air at sitting position for 1 hour. Nitric oxide, blood pressure, and lung function were measured before and after interventions. SPSS22 was used to analyze the collected data. Kolmogorov-Smirnov, ANOVA, and Pearson correlation tests were used. The significance level was set at 0.05. Results: Significantly elevated nitric oxide and reduced systolic blood pressure were observed at 40, 50 and 60 minutes in the intermittent aerobic exercise (Pvalue ≤ 0.05). We found a significant relationship between reduction in systolic blood pressure at 50 minutes and PEF in post 30 and 60 minutes. The results revealed heightened serum nitric oxide after aerobic exercise sessions and diminished systolic blood pressure. However, there was no difference in the lung function factors before and after the interventions. Conclusions: Aerobic exercise increases the nitric oxide better than hypoxia does and reduces blood pressure. Thus, it can be used in patients with obstructive sleep apnea. Keywords: Nitric oxide, Acute training, Lung function, Apnea

Active Transfer Learning for Persian Offline Signature Verification

Offline Signature Verification (OSV) remains a challenging pattern recognition task, especially in the presence of skilled forgeries that are not available during the training. This challenge is aggravated when there are small labeled training data available but with large intra-personal variations. In this study, we address this issue by employing an active learning approach, which selects the most informative instances to label and therefore reduces the human labeling effort significantly. Our proposed OSV includes three steps: feature learning, active learning, and final verification. We benefit from transfer learning using a pre-trained CNN for feature learning. We also propose SVM-based active learning for each user to separate his genuine signatures from the random forgeries. We finally used the SVMs to verify the authenticity of the questioned signature. We examined our proposed active transfer learning method on UTSig: A Persian offline signature dataset. We achieved near 13% improvement compared to the random selection of instances. Our results also showed 1% improvement over the state-of-the-art method in which a fully supervised setting with five more labeled instances per user was used

Full-Gradient Optimization of the Vibroacoustic Performance of (Non-)auxetic Sandwich Panels

This paper aims to optimize vibro-acoustic response of (non-) auxetic sandwich panels by use of topology optimization method. First, structural noise and vibration responses of the auxetic panel with the re-entrant hexagonal honeycomb core are studied. It is proved that the interactions between the structural vibrations and induced noise are more complex when expected for a low-frequency range, and the optimized noise reduction can be obtained by a proper combination of auxetic and non-auxetic properties within a single structure. Therefore, vibro-acoustic response of the sandwich panel with a re-entrant hexagonal honeycomb core by applying a full-gradient two-dimensional geometry optimization method is analyzed and optimized. It is shown that under various random loads, the sound power level can be reduced by about 20% at the cost of a slight increase (< 5%) of the total mass. Besides, the structural Eigen frequencies are shifted to lower values that are desirable for applications, e.g., in the aerospace industry. The obtained results ensure that the proposed optimization approach delivers extra noise reduction for auxetic sandwich panels as compared to the results available in the literature

Examining Effects of Pilates Workout and Jujube Supplementation on Liver Fat Content, Enzymes, and Platelet Count

Introduction: Non-alcoholic fatty liver disease (NAFLD) is one of the fastest-growing health issues worldwide. This study aimed to assess the effect of an eight-week Pilates exercise program and jujube supplementation on liver fat content, liver enzymes, and platelet count in women with NAFLD. Materials and Methods: The current work is a pretest-posttest quasi-experimental study with a control group. Forty middle-aged women with NAFLD were selected via purposive sampling and allocated randomly to four equal groups, including jujube, Pilates, Pilates+jujube, and control. Liver enzymes measurement, platelet count, and ultrasonography were conducted to determine the fatty liver degree 24 hours before and 48 hours after the intervention.&nbsp;The Pilates protocol was performed three sessions weekly for eight weeks. The jujube supplementation group and the Pilates+jujube group consumed .4 g/kg jujube daily in the morning and evening. The collected data were analyzed in SPSS software, using the Kolmogorov-Smirnov, ANOVA, and dependent t-test. The level of significance was set at P &lt;.05. Results: AST, platelet count, waist-to-hip ratio, and fat levels in the Pilates, jujube, and Pilates+jujube groups changed significantly compared with the control group and baseline values (P &lt;.05). Conclusion: Pilates exercise and jujube consumption can lower serum enzyme concentrations along with fat content of the liver and raise blood platelet count. As a result, they may be regarded as efficient techniques to treat NAFLD

Comparison between the Acute Effects of Intermittent Hypoxia and Aerobic Exercise on the Nitric Oxide Value, Blood Pressure and the Respiratory Function in Apnea

Background: Apnea is a common disorder in the community. The aim of the study was to compare the acute effects of activity and periodic hypoxia on the nitric oxide, blood pressure, and the pulmonary function in apnea. Methods: The study was as a clinical, pretest, and posttest intervention. A total of 11 males enrolled in the study and completed at least four options of the STOP-Bang inventory. They performed aerobic exercise on a treadmill with intensity of 70 0/0 heart rate reserve, during 40 minutes in intermittent hypoxia. The subjects inhaled intermittently 5 minutes normoxic and hypoxic (11%) air at sitting position for 1 hour. Nitric oxide, blood pressure, and lung function were measured before and after interventions. SPSS22 was used to analyze the collected data. Kolmogorov-Smirnov, ANOVA, and Pearson correlation tests were used. The significance level was set at 0.05. Results: Significantly elevated nitric oxide and reduced systolic blood pressure were observed at 40, 50 and 60 minutes in the intermittent aerobic exercise (Pvalue ≤ 0.05). We found a significant relationship between reduction in systolic blood pressure at 50 minutes and PEF in post 30 and 60 minutes. The results revealed heightened serum nitric oxide after aerobic exercise sessions and diminished systolic blood pressure. However, there was no difference in the lung function factors before and after the interventions. Conclusions: Aerobic exercise increases the nitric oxide better than hypoxia does and reduces blood pressure. Thus, it can be used in patients with obstructive sleep apnea. Keywords: Nitric oxide, Acute training, Lung function, Apnea

Analytical Solution for the Sound Radiation Field of a Viscoelastically Supported Beam Traversed by a Moving Load

Sound radiation from a beam resting on a viscoelastic foundation is analytically studied when it is subjected to a moving load. The topic could cover a range of applications such as submerged floating tunnels, buried pipelines, and railway tracks. Galerkin&apos;s method is employed to obtain the transverse vibration of the beam. Based on the Rayleigh integral approach, acoustic pressure distribution around the beam is obtained in the time domain. In the second part of this paper, corresponding displacement and acoustic pressure are obtained by the use of the Rayleigh-Ritz approach in conjunction with the Laplace transform method and by the use of the Fourier transform, respectively. Durbin&apos;s numerical Laplace transform inversion scheme is eventually employed to obtain dynamic responses. A parametric study is then carried out and influences of the design parameters as well as the loading conditions on the acoustic pressure field are investigated