Sharif Digital Repository

In this paper a magnetic levitation system is modeled and an eddy current based damping force is identified and used for position control of the levitated object in the system. In the magnetic levitation technology, contactless manipulation of a levitated object is done by use of magnetic fields. Also, the eddy-current based force is used to damp the motion of the levitated object. Eddy-current is generated in a plate which is placed underneath the levitated object due to the change of current in an electromagnet and the motion of the levitated object. First, using finite element method (FEM), the magnetic levitation system is modeled and the eddy-current based force acting on the levitated... 

The compound axle is a space saving suspension component that is relatively inexpensive and easy to install. Therefore it is used in rear suspension system of most front wheel drive passenger cars. This article present an optimum design algorithm for this component. A typical cross section for this the torsion beam of the axle is selected as a basis design. Using finite element methods, kinematics and elasto-kinematics behaviors of the section in vehicle normal maneuvers have been calculated. The acquired dynamic characteristics of the member was entered into a dynamic simulation program and the effect of geometrical parameters of torsion beam on the vehicle handling was studied. Using DOE... 

Stimuli-responsive controlled-release nanocarriers are promising vehicles for delivery of bioactive molecules that can minimize side effects and maximize efficiency. The release of the drug occurs when the nanocarrier is triggered by an internal or external stimulus. Mesoporous silica nanoparticles (MSN) can have drugs and bioactive cargos loaded into the high-capacity pores, and their release can be triggered by activation of a variety of stimulus-responsive molecular "gatekeepers" or "nanovalves." In this mini-review, we discuss the basic concepts of MSN in targeted drug-release systems and cover different stimulus-responsive gatekeepers. Internal stimuli include redox, enzymes, and pH,... 

An analytical solution for obtaining steady-state eddy-current-based force on a levitated permanent magnet above a plate with linear conductivity in the field of an electromagnet having cylindrical symmetry is presented in this paper. In literature, the force due to eddy current in this levitation system have been used for high precision positioning of a levitated permanent magnet without providing an explicit analytical model. In this system, a change in the coil's current and also the motion of the levitated permanent magnet in 3-D space generate eddy current in the plate. A novel explicit solution for obtaining damping forces due to these eddy currents is obtained as a function of... 

In this study, the unsteady three dimensional nanofluid flow, heat and mass transfer in a rotating system in the presence of an externally applied uniform vertical magnetic field is investigated. This study has different applications in rotating magneto-hydrodynamic (MHD) energy generators for new space systems and also thermal conversion mechanisms for nuclear propulsion space vehicles. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are non-dimensionalized using geometrical and physical flow field-dependent parameters. The velocity profiles in radial, tangential and axial directions, pressure gradient,... 

Magneto-rheological (MR) fluids consist of magnetic particles in carrying fluid. One of the drawbacks in using MR dampers in laboratory work is their price. At present, there is a compelling need for the production of the laboratory scale of MR fluids to lower their production cost. In this study, to show that the MR fluid is an applicable prototyped laboratory scale of single ended and mono-tube, MR dampers with a prototyped MR fluid are presented. The main features of produced MR fluid and dampers are simplifying in constructing and their low cost. These dampers are useful for laboratory research work. To illustrate the validity of the MR fluids, using this fluid, four MR dampers are made... 

Magnetic levitation is an appropriate solution for noncontact 3D manipulation. Workspace of the previously proposed maglev systems are confined to a relatively small cube, and this severely limits application of this technology. In addition, most of the previously given mechanisms require design and application of a subsystem for unifying their magnetic field. In this paper, a moving magnet is implemented which results in horizontally extendable work space; moreover, the field unifying section is not needed since one electromagnet only is used. Further, details of the mechanism and finite element based design procedure of the magnet are presented. Dynamic equations of the system derived by... 

In this study, the unsteady three dimensional nanofluid flow, heat and mass transfer in a rotating system in the presence of an externally applied uniform vertical magnetic field is investigated. This study has different applications in rotating magneto-hydrodynamic (MHD) energy generators for new space systems and also thermal conversion mechanisms for nuclear propulsion space vehicles. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are non-dimensionalized using geometrical and physical flow field-dependent parameters. The velocity profiles in radial, tangential and axial directions, pressure gradient,... 

In recent years miscellaneous smart micro/nanosystems that respond to various exogenous/endogenous stimuli including temperature, magnetic/electric field, mechanical force, ultrasound/light irradiation, redox potentials, and biomolecule concentration have been developed for targeted delivery and release of encapsulated therapeutic agents such as drugs, genes, proteins, and metal ions specifically at their required site of action. Owing to physiological differences between malignant and normal cells, or between tumors and normal tissues, pH-sensitive nanosystems represent promising smart delivery vehicles for transport and delivery of anticancer agents. Furthermore, pH-sensitive systems...