Sharif Digital Repository

Structures with time-varying electromagnetic properties can potentially yield non-reciprocity, amplification, harmonic generation, and other interesting wave propagation phenomena. To date, some studies have dealt with time-varying media and circuits, including time-varying optical ring resonators having degenerate travelling wave resonances. In time-varying ring resonators, the clockwise and counter clockwise resonances lose their degeneracy, and non-reciprocity is observed. One of the main challenges of such research is the need to induce time-variations in the entirety of the resonator or structure, which makes their implementation very limited or impossible in practice. The purpose of... 

Epidemics are one of the most important issues in social environments, economics systems, medicine, and other environments. In the study of the epidemics, some behaviors have been observed that are very similar to the phase transition in critical systems. For example, by changing the parameters that the epidemics process is characterized, the system’s epidemic behavior changes. Depending on the type of problem, this behavior change may be similar to continuous or discontinuous phase transitions. One of the fascinating issues that have just been taken into consideration in this area is the cooperation of two or more diseases. This means that the rate of transmission of a disease depends on...