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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Journal of Aerospace Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Bifurcation,Poincaré map,Preload,Tow-lobe bearing
- چکیده:
- چکیده انگلیسی: This paper presents the effect of preload on nonlinear dynamic behavior of a rigid rotor supported by two-lobe aerodynamic noncircular journal bearing. A finite element method is employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using Runge-Kutta method. To analyze the behavior of the rotor center in the horizontal and vertical directions under different operating conditions, the dynamic trajectory, the power spectra, the Poincare maps and the bifurcation diagrams are used. From this study, results show how the complex dynamic behavior of this type of system comprising periodic, -periodic and quasi-periodic responses of the rotor center varies with changes in preload values by considering two bearing aspect ratio. The results of this study contribute to a better understanding of the nonlinear dynamics of two-lobe aerodynamic noncircular journal bearing system.
- انتشار مقاله: 29-01-1389
- نویسندگان: R. Rashidi,A. Karami Mohammadi Karami Mohammadi,F. Bakhtiari Nejad Bakhtiari Nejad
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Aerospace Science and Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Bifurcation,Poincaré map,Preload,Tow-lobe bearing
- چکیده:
- چکیده انگلیسی: This paper presents the effect of preload on nonlinear dynamic behavior of a rigid rotor supported by two-lobe aerodynamic noncircular journal bearing. A finite element method is employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using Runge-Kutta method. To analyze the behavior of the rotor center in the horizontal and vertical directions under different operating conditions, the dynamic trajectory, the power spectra, the Poincare maps and the bifurcation diagrams are used. From this study, results show how the complex dynamic behavior of this type of system comprising periodic, -periodic and quasi-periodic responses of the rotor center varies with changes in preload values by considering two bearing aspect ratio. The results of this study contribute to a better understanding of the nonlinear dynamics of two-lobe aerodynamic noncircular journal bearing system.
- انتشار مقاله: 29-01-1389
- نویسندگان: R. Rashidi,A. Karami Mohammadi Karami Mohammadi,F. Bakhtiari Nejad Bakhtiari Nejad
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Science and Technology A:Science
- نوع مقاله: Journal Article
- کلمات کلیدی: Radial basis function,Reynold’s equation,noncircular gas bearings
- چکیده:
- چکیده انگلیسی: In this paper, the static characteristics of two-lobe, three-lobe and four-lobe noncircular gas journal bearing systems are studied in detail. The Reynold’s equation governing the noncircular gas bearing systems are analyzed by using Radial Basis Functions (RBF). The solutions are obtained numerically by solving systems of algebraic equations. The equilibrium position of the rotor is obtained without using the trial and error method; which is the merit of our method.
- انتشار مقاله: 11-11-1391
- نویسندگان: H. Rasooli Shooroki,R. Rashidi Meybodi,S. M. Karbassi,G. B. Loghmani
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Pharmaceutical Sciences
- نوع مقاله: Journal Article
- کلمات کلیدی: Xanthine Oxidase,Flavonoids,Quercetin,Rutin,Ruta graveolens
- چکیده:
- چکیده انگلیسی: Flavonoids could serve as potent inhibitors of xanthine oxidase (XO). In the present study, the effects of Ruta graveolens L. extract and its major isolated flavonoids, quercetin and rutin, on guinea pig liver XO have been investigated. The inhibitory effects of R. graveolens, quercetin and its glycoside form, rutin, were assayed spectrophotometrically. R. graveolens extract showed moderate inhibition on XO activity. Interestingly, bovine milk and guinea pig liver XO were inhibited significantly at different ranges by either the extract or its flavonoids, whereas allopurinol acted with almost the same potency on both enzymes. Rutin inhibited the enzymes in a competitive manner, while quercetin was found to be a competitive and mixed inhibitor of guinea pig liver and bovine milk XO, respectively. In conclusion, R. graveolens extract can act as a good inhibitor of XO. Interestingly, it was shown that the inhibitory effects of flavonoids on XO could be species dependent.
- انتشار مقاله: 26-06-1387
- نویسندگان: Saeed Pirouzpanah,Mohammad R. Rashidi,Abbas Delazar,Seyed Vali Razavieh,Ali Asghar Hamidi
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Nanoscience and Nanotechnology
- نوع مقاله: Journal Article
- کلمات کلیدی: debonding,Silica Nanoparticles,Crack deflection,Toughening
- چکیده:
- چکیده انگلیسی: In this paper, a systematic study on the effects of particle size and hybrid of two different size of silica nanoparticles on the toughening mechanisms of bisphenol-A epoxy was conducted. Nanosilica particles with mean diameter of 17 nm and 65 nm were blended into epoxy system. Probable synergy effects of these two nanoparticles on Young’s modulus and yield strength have been investigated. Results showed that the addition of the silica nanoparticles and also increasing content of nanoparticles improved Young’s modulus in all composites. In addition, the particle size did not show a considerable effect on the Young’s modulus and the use of both types of particles in a composite showed negligible synergy effect. On the other hands, results revealed that the addition of these nanoparticles did not change the yield stress of composites significantly. The fracture surfaces of composites were studied by Scanning electron microscopy. It was revealed that in all three series of nanocomposites, crack deflection, crack forking and debonding were the most important mechanisms.
- انتشار مقاله: 24-12-1391
- نویسندگان: M. Shariati,G. A. Farzi,A. Dadrasi,M. Amiri,R. Rashidi Meybodi
- مشاهده