Sharif Digital Repository

Earlier, we engineered a wireless power transfer (WPT) system whose key element is a self-activating and self-decoupling transmitting (Tx) antenna called the high-impedance coil (HIC) that grants a high efficiency for a receiving (Rx) antenna with a free position in front of the Tx array. When the Rx antenna is located in front of the Tx one, the input impedance of the last one drastically decreases, which results in efficient power transfer. This impedance is initially so high that the Tx antenna in the absence of the Rx one does not accept power, which implies negligible open-circuit losses. This feature grants the automatic activation/deactivation of the WT system. In the present work, we... 

In the area of life assessment, none-destructive methods of inspection and evaluation (NDI/NDE) play important role to ensure if astructure is still healthy enough to get used of. Using ultrasonic stress waves is one of the easiest and cheapest methods of NDI. Accordingly, different modes of lamb wave are mostly of interest..There are various methods for generating lamb waves. One of these methods is using piezoelectric wafer actuator/sensors (PWAS). Accordingly, one of the most important parts of this method is to generate right mode via an appropriate choose of actuating frequency. In this text using a new method for finding tuning frequencies of different lamb wave modes proposed. For... 

TiO2 nanotubes were synthesized using a modified autoclave-free thermal method from as-prepared initial powders. The size of initial powders (IP) was found to be critical in determining the morphology and crystal structure of the final product. Oleylamine (OA) was used as the polymer agent in the preparation of initial powders with different mol ratios of OA/Ti: 1, 5, and 10. X-ray diffraction analysis depicted that the increase of mole ratio up to 10 resulted in smaller nanoparticles with the sizes of about 8 nm. It was also deliberated that low temperature thermally treated IP showed the characteristic diffraction pattern of titanate phase of nanotubes. Scanning electron... 

The force experienced by a neutral dielectric object in the presence of a spatially non-uniform electric field is referred to as dielectrophoresis (DEP). The proper quantification of DEP force in the single-cell level could be of great importance for the design of high-efficiency micro-fluidic systems for the separation of biological cells. In this report we show how optical tweezers can be properly utilized for proper quantification of DEP force experienced by a human RBC. By tuning the temporal frequency of the applied electric field and also performing control experiments and comparing our experimental results with that of theoretically calculated, we show that the measured force is a... 

Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study...