Volume 1 Issue 1
Authors: Saeid Farokhzad; Hojjat Ahmadi
Abstract: A neural network simulator built for prediction of cavitation in centrifugal pump is discussed. A back propagation learning algorithm and a multi-layer network have been employed. The layers are constituted of nonlinear neurons and an input vector normalization scheme has been built into the simulator. This paper concentrates on a procedure for prediction of cavitation using acoustic signals and multi-layer perceptron neural network. Acoustic signals carry rich information about the condition of the system. Fast Fourier transform, proved itself a fast and strong technique for frequency analysis in the steady conditions and constant speed such as this work. Two classes were defined, namely i) healthy ii) cavitation. The extracted features were employed to feed the ANN classifier for cavitation detection. In developing the ANN models, different ANN architectures, each having different numbers of neurons in hidden layer, were evaluated. The optimal model was selected after several evaluations based on minimizing of mean square error (MSE) and correct classification rate (CCR). The network structure with 11 neurons in hidden layer and 11-11-2 structure is the best network. The mean square error achieved during training is 8.7204*10-8. Correct classification rate in system was 98.57%.
Keywords: Acoustic Emission; Cavitation; Fault Diagnosis; Centrifugal Pump.
Authors: Zeinab Khaksar; Hojjat Ahmadi; Seyed Saeid Mohtasebi
Abstract: Tractor driving is an occupation exposed to prolonged sitting, twisted postures, Whole Body Vibration (WBV) and mechanical shock which are considered as low back pain risk factors. As agricultural tractor drivers are exposed to the periodic, random and transient mechanical vibrations which can reduce driver comfort, activities and health and according to provisions of ISO 2631-1, hence in this research effectiveness of WBV on driver comfort was investigated. The comfort of ITM 399 tractor operator, exposed to vibration during plowing, disking, hay baling and trailer transportation operations, was assessed. In order to analysis the amount of transmitted vibration energy to operator’s body correctly, Power Spectral Density (PSD) of WBV in all three directions (vertical, horizontal and axial) were considered. This type of calculations helped to determine maximum amount of energy and its frequency that has most effect on operator’s comfort. According to the result, total weighted acceleration had the maximum value for disking, hay baling, trailer transportation and plowing operation, respectively. It was concluded that in the three directions and at different operations, except for trailer transportation, maximum amplitude of WBV energy which is transmitted to operator’s body through driver’s seat takes place at low frequencies (under 5 Hz).
Keywords: Whole Body Vibration; Tractor Operator; Power Spectral Density
Authors: M. Gorji; D. D. Ganji; M. Hatami; A. Hasanpour; A. K. Hossein
Abstract: In this study, the mathematical investigation of rocket motion path is presented using analytical and numerical methods. Differential transform method and fourth-order Runge-Kutta method are used for solving the current problem. A parametric study is performed which includes the effect of exhaust velocity (Ce), burn rate (BR) of fuel and diameter of cylindrical rocket (d) on the motion of a sample rocket. Also a realistic comparison of four on-line and active rockets is presented and the result is discussed. The main results indicate that the present analytical technique has high accuracy in comparison with the numerical solution. It is illustrated that the rocket velocity and altitude are increased with increasing the Ce and BR and decreased with increasing the rocket diameter. Finally it is concluded that Mu-3S-II rocket reaches to higher velocities and altitudes faster in comparison with the other introduced rockets.
Keywords: Modeling; Exhaust Velocity; Burn Rate; Rocket Motion Path
Authors: Mahinder Singh; Chander Bhan Mehta
Abstract: The thermosolutal convection in a compressible couple-stress fluid in a porous medium in the presence of uniform rotation and uniform magnetic field (separately) is studied. Using linearized stability theory and normal mode analysis, the dispersion relation is obtained in each case. In the case of incompressible magneto thermosolutal convection, the stable solute gradient, the magnetic field and couple-stress parameter postpone the onset of convection, whereas medium permeability hastens the onset of convection for stationary convection. For rotatory compressible thermosolutal convection the stable solute gradient and rotation have postponed the onset of convection whereas medium permeability and couple-stress have both hastened the onset of convection as well as postpone the onset of convection. We also found that the effect of compressibility is to postpone the onset of thermal instability. Further the solute gradient, magnetic field, and rotation are found to introduce oscillatory modes which were non-existent in their absence, and then principle of exchange of stability is valid. The sufficient conditions for non-existence of overstability are also obtained.
Keywords: Compressible Couple-Stress fluid; Thermosolutal Convection; Rotation; Magnetic Field and Porous Medium
Authors: Protsenko I. Yu; Odnodvorets L. V; Tyschenko K. V; Shumakova M.O.
Abstract: The analysis of one of the neglected problems of strain effect causes observation anomalous small longitudinal strain coefficient (l) in noble metal films. It is concluded that the value of l <3 units will take place in the case where in the quasi elastic or plastic deformation Poisson coefficient is more than 0.5. Our analysis suggests two reasons why this increases. They are connected with a decrease of the Debye temperature in thin films and smoothing of surface relief film at the surface diffusion of atoms on the grain boundaries.
Keywords: Strain Effect; Poisson Coefficient; Gruneisen Constant; Debay Temterature; Anomalous Small Strain Coefficient