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Morteza Hajimahmoodzadeh

Publications and source records attributed to Morteza Hajimahmoodzadeh.

5 recordsLinked to original sources
arXiv2021

Designing and manufacturing of interference notch filter with a single reflection band

Rugate, HL, and hybrid methods are used to design Notch Filters. Achieving a design that fits the notch characteristics of the filter and reducing transmission band ripples are the most influential factors in this topic. The ability of easy fabrication and choosing the right manufacturing method to have a notch filter with better characteristics should be noted. The main idea of this work is to design a notch filter structure with a narrow notch width and maximum reflection while reducing fabrication challenges. In addition, using anti-reflection layers in the outermost part of the designed structure, the pass-band ripples are reduced. In designed systems, various quarter-wave factors were used, which have less challenge in the manufacturing step. In addition, the stability of the deposition conditions and the density of the layers affect their quality and consequently the result of environmental tests. Therefore, the sputtering method with RF and DC sources is used to construct the designed structure. Finally, the samples were subjected to environmental tests such as abrasion, humidity, temperature, and adhesion. Some of the significant results of the manufactured single-band notch filter are presented.

physics.app-ph↗
arXiv2020

Investigating the effect of different quantum dots on the absorption spectrum and characteristics of quantum dot sensitized solar cells

Quantum dot sensitized solar cells are among the new generations of solar cells that have attracted much attention. Theoretical and simulation studies have predicted high efficiency for these cells so that in the future, these cells could be an excellent alternative to silicon solar cells. Other advantages of these cells are their ease of fabrication and cheaper manufacturing methods than existing cells. This paper's main idea is to simulate the effect of different quantum dots on the optical and electrical characteristics of these cells and, in particular, the efficiency. We then simulated the effect of simultaneous sensitizing by different quantum dots, and we observed that the cell's light absorption and the efficiency in simultaneous sensitizing, increased. Then we experimentally studied one of the cells that give the best simulation result (PbS/CdS co-sensitized). We deposited the quantum dots on transparent TiO2, and we obtained the light absorption, efficiency, and other characteristics of cells. Further, we investigated the effect of cobalt sulfide as the counter electrode in PbS/CdS, instead of platinum and gold, and we found that the efficiency has increased.

physics.app-ph↗
arXiv2004

Long-lived states of oscillator chain with dynamical traps

A simple model of oscillator chain with dynamical traps and additive white noise is considered. Its dynamics was studied numerically. As demonstrated, when the trap effect is pronounced nonequilibrium phase transitions of a new type arise. Locally they manifest themselves via distortion of the particle arrangement symmetry. Depending on the system parameters the particle arrangement is characterized by the corresponding distributions taking either a bimodal form, or twoscale one, or unimodal onescale form which, however, deviates substantially from the Gaussian distribution. The individual particle velocities exhibit also a number of anomalies, in particular, their distribution can be extremely wide or take a quasi-cusp form. A large number of different cooperative structures and superstructures made of these formations are found in the visualized time patterns. Their evolution is, in some sense, independent of the individual particle dynamics, enabling us to regard them as dynamical phases.

cond-mat.stat-mech↗
arXiv2003

Noised induced phase transition in an oscillatory system with dynamical traps

A new type of noised induced phase transitions is proposed. It occurs in noisy systems with dynamical traps. Dynamical traps are regions in the phase space where the regular forces are depressed substantially. By way of an example, a simple oscillatory system {x,v} with additive white noise is considered and its dynamics is analyzed numerically. The dynamical trap region is assumed to be located near the x-axis where the velocity v of the system becomes sufficiently low. The meaning of this assumption is discussed. The observed phase transition is caused by the asymmetry in the residence time distribution in the vicinity of zero value velocity. This asymmetry is due to a cooperative effect of the random Langevin force in the trap region and the regular force not changing the direction of action when crossing the trap region.

cond-mat.soft↗