mohammadjavad karimi

In this present paper, the linear optical absorption coefficient in an array of quantum wires under the external electric and magnetic fields is studied. The effects of the external fields and structural parameters such as wires' radius, the number of wires, the distance between wires, and the Al composition on the optical absorption are investigated. Results indicate that the resonant peak of the absorption coefficient shifts toward the lower photon energies with increasing structural parameters. Also, results reveal that the absorption frequency is in the terahertz range and shifts to the higher (lower) energies by increasing the electric (magnetic) field.  The resonant peak value of the linear optical absorption decreases by increasing the wires' radius, the distance between wires, and the Al composition. However, it changes non-monotonically with the number of wires.  Also, the optical absorption reduces with the increase of the electric field and changes non-monotonically with the magnetic field.

Moving toward a sustainable energy future requires improving the efficiency of energy systems. The fact that about 22% of industrial electricity is consumed by induction-motor-driven centrifugal pumps, highlights the importance of continuous monitoring of such systems to ensure they are operating at their best efficiency points. This results in the overall reduction of energy consumption and consequently lowers the carbon footprint of pumping systems. This paper presents a non-intrusive approach towards estimating the efficiency of the whole motor pump chain. The motor efficiency is calculated using only motor electrical signals along with the nameplate information. To estimate the pump efficiency, a hybrid method is adopted which uses the pump characteristic curve, impeller speed, and affinity laws. Both estimation algorithms are based on electrical signature analysis (ESA) which requires only motor terminal quantities i.e. current and voltage. The proposed methods are tested on laboratory setups and the experimental results show their accuracy in estimating the efficiency of induction-motor-driven pumps. Given the non-intrusive nature of the proposed method, a simple data acquisition system to acquire motor current and voltage signals along with a microprocessor to implement the algorithms discussed here can be integrated into a single affordable board to be used in utilities for continuous efficiency monitoring purposes.

In this paper, a tunable absorber structure based on a graphene hexagonal array in the terahertz range is investigated. The graphene hexagonal absorber is simulated by the finite element method. The effects of the geometry, graphene Fermi energy level and incident light angle, and light polarization on the absorptance of the structure are investigated. The results show that the absorptance spectrum of the proposed absorber is tuned from 6.1 THz to 9.1 THz when the Fermi energy increases from 0.4eV to 0.9eV. The absorptance peak shifts to lower and higher frequencies with increasing hexagonal side length and Fermi energy level, respectively. The absorption of the structure is over 90% in the incident light angle range from 0 to 80º for the TE polarization and in the range of 0-40º for the TM polarization. Also, results indicate that the absorption peaks shift to the lower energies with increasing the dielectric constant of the dielectric layer.

In this research, biosynthesis of Ag nanoparticle investigated using Urtica extract. Different parameter such as temperature, pH, time and concentration of Ag salt optimize for this goal. Synthesized nanoparticle characterized by Uv-vis, XRD and TEM methods. Results show Ag nanoparticle synthesized in the size of 10 nm. In continuous, Ag nanoparticle was used for preparation of modified carbon paste electrode. And its effect investigated on electron exchange system for K4[Fe(CN6)] as a standard system. The obtained result shows that synthesized nanoparticle can be improved electrical conductivity of electron exchange in electrochemical systems.