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Kamyar Modjtahedzadeh

Publications and source records attributed to Kamyar Modjtahedzadeh.

2 recordsLinked to original sources

Stability Analysis of Continuous-Time Linear Time-Invariant Systems

This paper focuses on the mathematical approaches to the analysis of stability that is a crucial step in the design of dynamical systems. Three methods are presented, namely, absolutely integrable impulse response, Fourier integral, and Laplace transform. The superiority of Laplace transform over the other methods becomes clear for several reasons that include the following: 1) It allows for the analysis of the stable, as well as, the unstable systems. 2) It not only determines absolute stability (a yes/no answer), but also shines light on the relative stability (how stable/unstable the system is), allowing for a design with a good degree of stability. 3) Its algebraic and convolution properties significantly simplify the mathematical manipulations involved in the analysis, especially when tackling a complex system composed of several simpler ones. A brief relevant introduction to the subject of systems is presented for the unfamiliar reader. Additionally, appropriate physical concepts and examples are presented for better clarity.

eess.SY

Wavelength and Refractive Indices from Interferometry

PASCO scientific 012-05187C Precision Interferometer is used in Michelson mode to investigate wavelengths and refractive indices. From varying the distance of the movable mirror in the Michelson setup the wavelength of the HeNe laser beam is found to be $630.6\pm7.9~\mathrm{nm}$; $0.28$ sigmas away from the accepted $632.8~\mathrm{nm}$ and agreeing with it. Then after considering the fact that the index of refraction for low pressure gasses varies linearly with pressure we place a vacuum cell in front of the movable mirror and pump out the air within it to find the individual slopes. By extrapolating the average slope we calculate the index of refraction for air to be $n=1.000226\pm0.000026$. This is $1.44$ sigmas away from the manufacturer's measured $1.000263$ and barely agreeing with it as we underestimated our error in the fringe count (which is caused by the change in pressure). Furthermore, the vacuum cell is replaced by a crown glass plate which is rotated to vary the length at which the EM wave travels in the Michelson interferometer. The angle of rotation is measured and utilized to find the refractive index of glass to be $1.514\pm0.006$; agreeing with the accepted value of $1.515$ as it is $0.125$ sigmas away from it. Thus, along with the wavelength observation this experiment is conducted successfully. Although the experiment to find the refractive index of air is conducted less successfully, it is also prosperous as the measured value is close to the accepted.

physics.ins-det