Sharif Digital Repository

The creation of massless scalar particles from the quantum vacuum by spherical shell with time varying radius is studied. In the general case of motion the equations are derived for the instantaneous basis expansion coefficients. The examples are considered when the mean number of particles can be explicitly evaluated in the adiabatic approximation  

This paper presents an offline path planning method in 3D space for a surveillance aerial vehicle. In this method, the aerial vehicle is supposed to visit particular points on the path, and the collision between the vehicle and the fixed obstacles in the environment must be avoided. In order to accomplish the mission, first, the path is generated using B-splines. Then, the feasibility of tracking the designed path for the vehicle is considered by analyzing the vehicle's dynamic constraints, such as limitations on deflections of control surfaces. The analysis is supported by a simulation. Potential extension of the proposed analysis to multiple aerial vehicles has been also discussed at the... 

In this paper, one smart composite involving nitinol, piezoelectric and MMC is modeled. This simulation covers all criteria in these advanced materials and theoretically solves the five-order equation. Furthermore, numerical sample is investigated and results have been explored. The results represent the relationship between natural frequency of the structure, temperature, the lateral deflection and martensite ratio of shape memory alloy. The results show nonlinearity response in dynamic motion in lower natural frequency and linear behavior in higher frequency. In this simulation, numerical approximation has been avoided. Copyright © 2009 by ASME  

This paper presents an analytical approach to design a continuous time-invariant two-level control scheme for asymptotic stabilization of a desired period-one trajectory for a hybrid model describing walking by a planar biped robot with noninstantaneous double-support phase and point feet. It is assumed that the hybrid model consists of both single- and double-support phases. The design method is based on the concept of hybrid zero dynamics. At the first level, parameterized continuous within-stride controllers, including single- and double-support-phase controllers, are employed. These controllers create a family of 2-D finite-time attractive and invariant submanifolds on which the dynamics... 

INS-DVL integration is a common method for underwater navigation. However, inherent errors of sensors, especially in MEMS IMUs, lead to inaccuracies in estimating the position and attitude. In this paper, dynamic motion model of AUV is used to improve MEMS INS-DVL navigation. In this method, which is called model-aided or model-based navigation, the information of the kinetic model of the vehicle (obtained from Newton-Euler equations) is used to improve the navigation performance. Previous model-aided navigation studies about AUVs have been focused on the translational dynamic model of vehicles. As the best of our knowledge, this paper is the first one which suggests using a rotational... 

Aerodynamic coefficients on a two dimensional plunging airfoil, in a low-speed wind tunnel are presented. Dynamic motion was produced by plunging the model over a range of reduced frequencies, and mean angles of attack. The Reynolds number in the present test was held fixed (Re = 1.5×10 5), and the reduced frequency was varied in an almost wide range. Surface static pressure distribution was measured on the upper and lower sides of the model, during the oscillating motion. It was found that reduced frequency had strong effects on the pressure distribution, near the leading edge of the airfoil. For mean equivalent angles of attack of 0, 5 degrees, hysteresis loops on the upper surface of the...