This article investigates the problem of simultaneous attitude and vibration control of a flexible spacecraft to perform high precision attitude maneuvers and reduce vibrations caused by the flexible panel excitations in the presence of external disturbances, system uncertainties, and actuator faults. Adaptive integral sliding mode control is used in conjunction with an attitude actuator fault iterative learning observer (based on sliding mode) to develop an active fault tolerant algorithm considering rigid-flexible body dynamic interactions. The discontinuous structure of fault-tolerant control led to discontinuous commands in the control signal, resulting in chattering. This issue was resolved by introducing an adaptive rule for the sliding surface. Furthermore, the utilization of the sign function in the iterative learning observer for estimating actuator faults has not only enhanced its robustness to external disturbances through a straightforward design, but has also led to a decrease in computing workload. The strain rate feedback control algorithm has been employed with the use of piezoelectric sensor/actuator patches to minimize residual vibrations caused by rigid-flexible body dynamic interactions and the effect of attitude actuator faults. Lyapunov's law ensures finite-time overall system stability even with fully coupled rigid-flexible nonlinear dynamics. Numerical simulations demonstrate the performance and advantages of the proposed system compared to other conventional approaches.

This study proposes a new linear approximation for solving the dynamic response equations of a rocking rigid block. Linearization assumptions which have already been used by Hounser and other researchers cannot be valid for all rocking blocks with various slenderness ratios and dimensions; hence, developing new methods which can result in better approximation of governing equations while keeping simplicity is necessary. In this paper, a new linear approximation is derived for solving the deferential equations of a rocking block in order to include wider range of blocks with various slenderness. The proposed method is verified by numerical solutions of the governing equations utilizing two methods of: average acceleration and fourth order Runge-Kutta. Verifications revealed more reasonable accuracy of the proposed method in comparison with the current linearization assumptions.

Local bifurcation of the attitudinal dynamics of the torque free rigid body motion is discussed. Hamiltonian formalism is used to express equations of motion. To simplify attitudinal dynamics of a rigid body, six dimensional state space is reduced to a two dimensional one by Andoyer canonical transformation. Non-dimensional parameters of the system are defined and the effects of change in these parameters on the structural stability and the equilibrium points of the reduced space are discussed. The Poincaré surface of the section in the reduced phase space and heteroclinic orbits are derived. Based on the non-dimensional parameters of the system, two and three dimensional bifurcation diagrams are achieved. This study shows that various types of structural stability can be achieved for torque free rigid body attitudinal dynamics by changing relative magnitudes of the principal moments of inertia. These results are helpful when the chaotic behavior of a rigid body under perturbation is considered.

The aim of the current study was to determine the pattern, presentation and management of foreign body aspiration in our population. This prospective study comprised 55 patients with foreign body aspiration admitted to our department from January 2009 to December 2011. All patients underwent rigid bronchoscopy under local or general anesthesia. The patients’ demographic information along with clinical characteristics and their outcome were recorded and reported. The mean age of the children was 13.3±3.6 years. There were 32 (58.2%) females and 23 (41.8%) males. The frequent symptom was an attack of chocking followed by cough. The predominant sign was wheezing. Rigid bronchoscopy was successful in removing foreign body from 52 (94.5%) patients. Three (5.5%) patients who had undergone thoracotomy with bronchotomy needed exploration, after failure of bronchoscopy to remove the foreign body. There was no mortality in our series. Average hospital stay was 12 hours. It could be concluded that rigid bronchoscopy is modality of choice in management of foreign body aspiration especially in pediatric population.

In this study, the dynamics of bubble growth and collapse near a rigid wall is investigated using the modified volume of fluid method and the improved compressible interfoam solver in the OpenFoam open-source code. The research results indicate that the dimensionless gamma number has the most significant impact on the growth and collapse of the bubble near the wall. This study examined two gamma numbers 0.8 and 1.3. It was found that with a 60% increase in the gamma number, the maximum shear stress on the wall decreased by 37%, while the maximum absolute temperature inside the bubble increased by 12%. Additionally, as the gamma number increases, the area affected by the jet impact due to the bubble collapse increases. Within the scope of the present research, the initial pressure parameter of the bubble has the most significant impact on the maximum temperature inside the bubble. In the range of considered initial pressures, a 50% increase in the initial pressure results in a 6% decrease in the maximum temperature of the bubble. However, the values of other studied parameters, such as shear stress, change by less than one percent.

In performing vibration analysis of the car engine on the engine support, it is necessary to know the mass properties of the engine including mass, position of the center of mass and mass inertia moments. Because the car engine has a relatively complex geometric shape and is composed of different components with different densities, determining its mass properties faces many challenges. There are various methods to determine the mass properties of a car engine, one of the most common of which is the use of modal analysis (mass line method). In this paper, the mass line method is presented in order to finding the mass properties of rigid bodies. In order to evaluate the efficiency and accuracy of the method, dynamic modeling of a rigid body with known mass properties is performed in MSC Adams software. So according to the theory of mass line, the rigid body is hung from a soft suspension and a force is applied to it in different locations. Then, by performing Adams simulations, the corresponding acceleration values are extracted at various points. After that, the mass line method is coded in MATLAB software and the applied forces and accelerations obtained from Adams in the time domain are entered as input to the MATLAB code and by executing the MATLAB code, the mass properties of the rigid body are calculated. Finally, the values of the mass characteristics obtained from the MATLAB code are compared with the actual values of the rigid body simulated in Adams, and the accuracy of the mass line method in finding the mass properties is evaluated.

Experiments and numerical simulations were conducted in order to examine the flow field surrounding a flat-faced body impacting on a flat surface. In the experiments impact velocities ranged up to nearly 5 m/s. Visualisation was with a standard z-format schlieren system using a high-speed camera. The associated flow field exhibited ejected gas jets, shed vortices and weak compression waves in the external flow, as well as in the gap depending on pressure differences between the gap and the external field. A computational fluid dynamic simulation (CFD) was undertaken, enabling detailed evaluation of: the flow in the gap, the flow of the emerging jet near the impacting surface, and the development of the wave system and flow on the upper and lower surfaces of the impactor during its descent. It was found that very high pressures are generated in the gap between the impactor and impacting surface and that the jet emerging from the periphery of the impactor can reach supersonic velocities.