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Highlights • A new composite polynomial consisting of cubic polynomials and Bézier curves are generated for the trajectory planning of a 2-dof parallel mechanism. • The velocity and acceleration profiles achieved by the new polynomial are smoother, and maximum speed and acceleration values are lower than those obtained by the cubic spline method. • The new trajectory reduces the required actuator capacity, decreases vibration of the mechanism, and indicates energy saving potential. • A working prototype is manufactured and real-time experiments are carried out to demonstrate the validity and competency of the proposed composite polynomial approach. Abstract A new composite polynomial is generated, to be used in the trajectory planning of a 2-dof parallel mechanism; by combining cubic polynomials with Bézier curves based on quadratic Bernstein polynomials. By the cubic polynomials, a smooth trajectory is obtained in the vicinity of the starting and ending points, while a better convergence is obtained to the via points by the Bézier curves. The position, velocity, and acceleration profiles obtained using this new polynomial are compared with those obtained using the cubic polynomial spline method. The position, velocity, and acceleration profiles achieved by the new polynomial are smoother; and more, maximum speed and acceleration values are lower than those obtained by the cubic spline method. Due to these lower values, lower capacity actuators may be utilized and the life of the actuators may be extended. On the other hand, the continuous acceleration curve of the composite polynomial will prove less jerky motion, which means less vibration. It is also possible to indicate energy saving potential when considering the speed-torque characteristic curves of servomotors. Finally, a working prototype is manufactured and real-time experiments are carried out to demonstrate the validity and competency of the proposed composite polynomial approach. [ABSTRACT FROM AUTHOR]

Nonlinear free and forced vibrations of axially functionally graded Euler-Bernoulli beams with non-uniform cross-section are investigated. The beam has immovable, namely clamped-clamped and pinned-pinned boundary conditions, which leads to midplane stretching in the course of vibrations. Nonlinearities occur in the system due to this stretching. Damping and forcing terms are included after nondimensionalization. The equations are solved approximately using perturbation method and mode shapes by differential quadrature method. In the linear order natural frequencies and mode shapes are computed. In the nonlinear order, some corrections arise to the linear problem; the effect of these nonlinear correction terms on natural frequency is examined and frequency –response curves are drawn to show the unstable regions. In order to confirm the validity, our results are compared with others available in literature. [ABSTRACT FROM AUTHOR]

Objective: Previous studies show that serum fibrinogen levels are established risk factors for coronary artery disease (CAD) and that serum albumin levels are of a higher specificity and sensitivity in ST-elevation myocardial infarction (STEMI). In this study, we sought to evaluate the association between fibrinogen to albumin ratio (FAR) and the extent and severity of CAD evaluated by TAXUS Drug-Eluting Stent Versus Coronary Artery Bypass Surgery for the Treatment of Narrowed Arteries (SYNTAX) Score (SS) in patients with STEMI.Methods: A total of 278 patients with STEMI were included in the study. FAR was calculated using specified variables. The extent and severity of CAD were evaluated using the SS. The patients were divided into low- (SS <22) and high- (SS ≥22) risk groups. A Spearman rank correlation coefficient analysis was used for the relationship between FAR and SS. The cutoff points for sensitivity and specificity of FAR in predicting SS were estimated by performing a receiver operator characteristic curve analysis.Results: There were significant differences in the mean age (P=.016), admission serum albumin (P=.041), serum fibrinogen (P<.001), FAR (P<.001), and SS risk groups. Positive correlation was detected between FAR and SS (r=0.458, P<.001). A cutoff level of >87 FAR predicted SS (sensitivity, 70%; specificity, 70%), and an area under the curve of 0.758 serum fibrinogen and albumin level was an independent predictor for SS in patients with STEMI (b=0.039; 95% confidence interval, 0.016-0.062; P=.001 and b=-6.906; 95% confidence interval, -12.284 to -1.527; P=.013, respectively).Conclusion: In the present study, we showed that FAR is significantly related to SS in predicting the severity of CAD in patients with STEMI. [ABSTRACT FROM AUTHOR]

In this paper, a new matrix method based on orthogonal exponential (orthoexponential) polynomials and collocation points is proposed to solve the high-order linear delay differential equations with linear functional arguments under the mixed conditions. The convenience is that orthoexponential polynomials have shown to be effective in approximating a given function, fast and efficiently. An error analysis technique based on residual function is developed and applied to four problems to demonstrate the validity and applicability of the proposed method. It is confirmed that the present method yields quite acceptable results and the accuracy of the solution can significantly be increased by error correction and residual function. [ABSTRACT FROM AUTHOR]

In this paper, an exponential collocation method for the solution linear delay differential equations with constant delay is presented. The utility of this matrix based method is that it is very systematic and by writing a Maple program, any type of second order linear differential delay equation can be solved easily. The method is applied to three different types of delay equations; linear oscillator with delay (i) in the restoring force term, (ii) in the damping term, and (iii) in the acceleration term. Time response curves have been plotted for each type and the effect of the parameters of the delay terms has been shown. An error analysis based on residual function is carried out to show the accuracy of the results. [ABSTRACT FROM AUTHOR]

Abstract: Free vibration of a single degree of freedom system is a fundamental topic in mechanical vibrations. The present study introduces a novel and simple numerical method for the solution of this system in terms of Taylor polynomials in the matrix form. Particular and general solutions of the differential equation can be determined by this method. The method is illustrated by a numerical application and the results obtained are compared with those of the exact solution. [Copyright &y& Elsevier]

Abstract: Non-linear coupled vertical and torsional vibrations of suspension bridges are investigated. Method of Multiple Scales, a perturbation technique, is applied to the equations to find approximate analytical solutions. The equations are not discretized as usually done, rather the perturbation method is applied directly to the partial differential equations. Free and forced vibrations with damping are investigated in detail. Amplitude and phase modulation equations are obtained. The dependence of non-linear frequency on amplitude is described. Steady-state solutions are analyzed. Frequency–response equation is derived and the jump phenomenon in the frequency–response curves resulting from non-linearity is considered. Effects of initial amplitude and phase values, amplitude of excitation, and damping coefficient on modal amplitudes, are determined. [Copyright &y& Elsevier]

Tube bending is a widely used process in marine, automotive, construction and other industries. Different methods are available for this process during which various problems and defects are encountered. This paper aims to develop the most relevant model for bending the tubes using a computer numerical controlled (CNC) bending machine on the first attempt without any defects. To achieve this goal, the parameters affecting the tube bending process on the bending machine are defined. Based on these parameters, 150 bending experiments are conducted in an industrial plant to collect data and their results are used as dataset for machine learning (ML) algorithms. Seven different state-of-the-art ML algorithms –logistic regression, decision tree, k-nearest neighbor, random forest, Naïve Bayes, support vector machine and eXtreme gradient boosting (XGBoost)– are implemented using Python's Scikit-Learn library. Their performance is compared using confusion matrix and classification metrics such as accuracy, precision, recall, F1-score, receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) value. Considering all the performance metrics, logistic regression performed best in terms of prediction on our dataset. XGBoost and support vector machine were quiet successful based on F1 score and AUC, respectively. Overall, logistic regression, Naïve Bayes, Support Vector Machine, and XGBoost showed performances above 90% across all metrics. Decision tree, k-nearest neighbor and random forest performed poorly compared to other algorithms for our data. The proposed ML method is expected to save costs by reducing material waste and labor time and to increase the process efficiency and the product quality. [ABSTRACT FROM AUTHOR]