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RISS 인기검색어
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- 저자 : Y. A. Amer (검색결과 4 건)
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Y. A. Amer,A. T. EL-Sayed,E. El Emam. Ahmed 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2
In this paper, we study how to improve the performance and reduce the vibration in a vertical conveyor system by using active control. The system is donated by a twodegree-of-freedom (2-DOF) under parametric and external excitations. The multiple time scales method (MTSM) is applied to get the approximate solution and all resonance cases for the considered system. The stability analysis for the nonlinear vibrating system examined using the frequency response equations near the simultaneous sub-harmonic and combined resonances numerically using the Runge-Kutta fourth-order order method (package ode45 in Matlab R2014a). The effects of various parameters are studied at the frequency response of the steady-state amplitudes for the worst resonance case. Numerical simulations have a good agreement with the analytical solution. A comparison is presented with the recently available published work.
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Nonlinear saturation controller for vibration supersession of a nonlinear composite beam
Y. S. Hamed,Y. A. Amer 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8
In this paper, a study for nonlinear saturation controller (NSC) is presented that used to suppress the vibration amplitude of a structuraldynamic model simulating nonlinear composite beam at simultaneous sub-harmonic and internal resonance excitation. The absorberexploits the saturation phenomenon that is known to occur in dynamical systems with quadratic non-linearities of the feedback gain and atwo-to-one internal resonance. The analytical solution for the system and the nonlinear saturation controller are obtained using method ofmultiple time scales perturbation up to the second order approximation. All possible resonance cases were extracted at this approximationorder and studied numerically. The stability of the system at the worst resonance case ( 2 sw W = andws = 2wc ) is investigated usingboth frequency response equations and phase-plane trajectories. The effects of different parameters on the system and the controller arestudied numerically. The effect of some types of controller on the system is investigated numerically. The simulation results are achievedusing Matlab and Maple programs.
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Y. A. Amer,A. T. EL-Sayed,F. T. El-Bahrawy 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4
Torsional vibration characteristics are important information for rotating machinery design and control. Jointed shaft is a commonlyused element in drive trains of rolling mill. The torsional vibrations of one- degree -of freedom nonlinear dynamical system are controlledusing active control. The multiple scale perturbation technique used to get the approximate solution of the differential equationdescribes the system. The worst resonance cases were deduced and the frequency response function are obtained. The stability and steadystate response of the system are studied and discussed numerically. The numerical solutions are focused on both the effects of the differentparameters and the system behavior at different resonance cases. To insure the validity of the results, a comparison between the numericaland analytical solution was presented.
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Sajeda Al-Tamimi,Mohammad Y.N. Saleh,Al-Mutez Gharaibeh,Farah Al-A’mar,Rasmieh Al-Amer 대한중환자의학회 2025 Acute and Critical Care Vol.40 No.2
Background: Exposure keratopathy is the most common ocular surface disorder in ventilated patients due to poor eyelid closure, decreased blink reflex, and the inability to produce tears. Healthcare providers in intensive care units (ICUs) play a significant role in preventing exposure keratopathy through appropriate eyelid taping and eye ointments.Methods: This is a cross-sectional study to describe the characteristics and factors associated with exposure keratopathy in all mechanically ventilated patients admitted to an adult ICU between February and June 2023. Patients were examined for corneal changes using a corneal fluorescein staining test with a cobalt blue filter indirect ophthalmoscope.Results: Of 156 ventilated patients included in this study, 42.3% had exposure keratopathy, 13.5% had lagophthalmos, and 26.9% of patients had chemosis. For patients with a Glasgow Coma Scale (GCS) score of 3, the odds ratio of exposure keratopathy was 21.47 (95% confidence interval [CI], 2.82–163.05). The use of inotropes increased the odds ratio to 35.55 (95% CI, 3.41–369.90), whereas a hospital stay >7.23 days increased the odds ratio to 43.59 (95% CI, 15.66–1,316.32).Conclusions: The frequency of exposure keratopathy is high and is underestimated in ventilated patients, with lower GCS and increased hospital length of stay as the main risk factors. Prioritizing eye care in ventilated patients with low GCS scores or prolonged ICU stays is essential to reduce exposure keratopathy.
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