Majid Ghandchi | Islamic Azad University, Ahar branch (original) (raw)

Papers by Majid Ghandchi

2008 International Conference on Control, Automation and Systems, 2008

ABSTRACT Use of nonlinear loads, such as thyristor controlled inductors for FACTs devices, conver... more ABSTRACT Use of nonlinear loads, such as thyristor controlled inductors for FACTs devices, converters for HVDC transmission line and large adjustable speed motor drives, is expected to grow rapidly. All of these loads inject harmonic currents and reactive power into the power system. This paper presents a new control scheme for a 3 phase multi level parallel active filter. The presented control system is able to compensating current harmonics, reactive power and current unbalance of nonlinear loads. The conventional controllers based on pq theory need more calculations, since they need the use of Clark transformation (abc to alphabeta transformation). The proposed control system is very simple and therefore practical implementation of active filters is available. The presented simulation results carried out by Matlab/Simulink program show the validity of control strategy.

Projected density of states diagram (PDOS) of the bilayer ABhexC₁₃₂H<su... more Projected density of states diagram (PDOS) of the bilayer ABhexC₁₃₂H₄₀ GQDs, the E₁₁, and the E₂₂ showing the electronic transition E_ij from the <i>i</i>^th valence band to the <i>j</i>^thconduction band.

Density functional theory (DFT) and thermal DFT (thDFT) calculations were used to evaluate the en... more Density functional theory (DFT) and thermal DFT (thDFT) calculations were used to evaluate the energy band structure, bandgap, and the total energy of various graphene quantum dots (GQDs). The DFT calculations were performed using local density approximation for the exchange-correlation functional and norm-conserving pseudopotentials. We consider the triangular and hexagonal GQDs with zigzag and armchair edges and 1-3 nm dimensions with many hundred atoms. The simulation results show that all of these GQDs are direct bandgap semiconductors with a flat band structure, and they are suitable for electronics and optoelectronics applications. Analysis of GQDs in which the A and B sublattice symmetries were broken showed degenerate zero-energy shells. Using the thDFT calculations carried out at temperatures up to 1400 K, we evaluated the temperature dependence of the GQDs bandgaps and total energies via entropy-term and electron’s kinetic energy. The obtained results indicate that the gro...

Physical Chemistry Chemical Physics

We have developed the right atomic-molecular ab initio calculations-based model to investigate ph... more We have developed the right atomic-molecular ab initio calculations-based model to investigate photoelectrical properties of photodetectors based on graphene nanodot structures with two probes.

Using Photovoltaic systems is gradually expanded by increasing energy demand. Abundance and avail... more Using Photovoltaic systems is gradually expanded by increasing energy demand. Abundance and availability of this energy, has turned to one of the most important sources of renewable energy. Unfortunately, photovoltaic systems have two big problems: first, those have very low energy conversion efficiency (in act between 12 and 42 percent under certain circumstances). Second, the power produced by the solar cell depends on nonlinear conditions such as solar radiation, temperature and charge feature. According to this, received power maximum of photovoltaic cells depends on different non-linear variables, it is necessary to be continuously traced, as maximum received power of the cell (by controller). In this research, the increasing efficiency of photovoltaic systems has been investigated by using Maximum Power Point Tracking (MPPT) in two different modes contained connected to the Grid and disconnected from the grid with simulation by MATLAB software. The obtained results showed that...

Photonics

Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano... more Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano-graphene has been a topic of interest to researchers in recent years. Using a first-principles study based on density functional theory (DFT) and thermal DFT, we investigated the electronic structures and optical properties of bilayer graphene quantum dots (GQDs). The dielectric tensors, absorption spectra, and the refractive indexes of the bilayer GQDs were obtained for both in-plane and out-of-plane polarization. In addition, we calculated the absorption spectra via time-dependent DFT (TD-DFT) in the linear response regime. The TDDFT results show that a blue shift occurs in the absorption spectrum, which is consistent with the experimental results. In this investigation, we consider triangular and hexagonal GQDs of various sizes with zigzag and armchair edges. Our simulations show that unlike monolayer GQDs, for which light absorption for out-of-plane polarization occurs in the ultrav...

Infrared detectors can be used for a variety of applications such as: using in fiber-optic commun... more Infrared detectors can be used for a variety of applications such as: using in fiber-optic communications. Conventional technology for IR detectors is using p-i-n structure based on GaAs compound. This paper reports on the design and modeling of an IR detector using a p-i-n GaAs structure. Comsol software is used to simulate the model and the detector is discussed for terminal current, dopant profile, and energy band diagram. Finally, we have studied electric field according to layer depth under thickness, bias voltage, and field magnitude. We analyzed the electronic and optic behavior of IR detectors simultaneously, and detection spectrum was obtained in terms of wavelength

The aim of this paper is computing of the optimum duty cycle and inductance using Genetic Algorit... more The aim of this paper is computing of the optimum duty cycle and inductance using Genetic Algorithm to minimize tracking error and operating costs by means of a new current reference. Such a current reference is able to share the responsibilities in power quality deterioration between supply and customer, making the filter to deliver a current with a lower harmonic content, which means a lower power delivered and a lower switching frequency. The use of different control approach may be helpful to achieve a good current control since this approach allows to carry out a control action independent from the electrical parameters.

21 Design and Simulation of a Fast SAW Waveguide with Comsol Software Hadi Amos*, Majid Ghandchi ... more 21 Design and Simulation of a Fast SAW Waveguide with Comsol Software Hadi Amos*, Majid Ghandchi Department of Electrical Engineering Ahar Branch , Islamic Azad University , Ahar Iran Email: hadi.amos.iau.ahar@gmail.com, majid.ghandchi@gmail.com Abstract In this paper, the structure of SAW has been studied. In previous work in SAW, materials such as lithium niobium, lithium tantalite and gallium nitride were used in the structure of SAW, and thus had a low operating frequency and the highest reported operating frequency was about 4 GHz. In this paper, aluminum nitride and gallium nitride in the SAW structure are used in combination. The electrodes used in the structure are also made of aluminum. Comsol software was used to simulate the structure, and for the structure, the operating frequency was 7.02 GHz.

S7-1200 with Tia Portal technology has become a Standard function of distributed controlsystems. ... more S7-1200 with Tia Portal technology has become a Standard function of distributed controlsystems. Self-Tuning methods belong to Programmable Controllers (PLC) techniques. PLCtechniques contain software packages for advanced control based on mathematical methods. S7-1200 tools are designed to increase the Process Capacity, yield, and quality of products. Most ofthe present time digital industry regulators and PLCs are provided with some kinds of the SelfTuning constant algorithms. Practical part of the present paper deals with the design of thecontrol systems, which contain Self Tuning regulators and Zone PID features. A Control Systemwith PID Self Tuner is designed by Siemens along with visualization in Tia Portal to do so. Thereis a description of an implementation of the PID regulator as a function block, which can also beused for extension Zone PID control functions. Control Systems for relay and moment Self Tunerwith visualizations in Tia Portal are also designed and tested in ZA...

Microsystem Technologies, 2016

Proceedings of the European …, 2009

... in FarsiTeX Youssef Rezvan, Majid Ghandchi, and Farshad Rezvan ... In the conclusion we have ... more ... in FarsiTeX Youssef Rezvan, Majid Ghandchi, and Farshad Rezvan ... In the conclusion we have also dis-cussed the ways to upgrade this Farsi Spell-checker version 0.1, as well as other techniques. Y. Rezvan (*) Islamic Azad University, Ahar Branch, Dept. Electrical Eng. ...

MDPI AG, 2020

Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano... more Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano-graphene has been a topic of interest to researchers in recent years. Using a first-principles study based on density functional theory (DFT) and thermal DFT, we investigated the electronic structures and optical properties of bilayer graphene quantum dots (GQDs). The dielectric tensors, absorption spectra, and the refractive indexes of the bilayer GQDs were obtained for both in-plane and out-of-plane polarization. In addition, we calculated the absorption spectra via time-dependent DFT (TD-DFT) in the linear response regime. The TDDFT results show that a blue shift occurs in the absorption spectrum, which is consistent with the experimental results. In this investigation, we consider triangular and hexagonal GQDs of various sizes with zigzag and armchair edges. Our simulations show that unlike monolayer GQDs, for which light absorption for out-of-plane polarization occurs in the ultraviolet wavelength range of 85-250 nm, the out-of-plane polarization light absorption peaks in the bilayer GQDs appear in the near-infrared range of 500-1600 nm, similar to those in bilayer graphene sheets. The out-of-plane polarization light absorption peaks in the near-infrared range make bilayer GQDs suitable for integrated optics and optical communication applications.

2008 International Conference on Control, Automation and Systems, 2008

ABSTRACT Use of nonlinear loads, such as thyristor controlled inductors for FACTs devices, conver... more ABSTRACT Use of nonlinear loads, such as thyristor controlled inductors for FACTs devices, converters for HVDC transmission line and large adjustable speed motor drives, is expected to grow rapidly. All of these loads inject harmonic currents and reactive power into the power system. This paper presents a new control scheme for a 3 phase multi level parallel active filter. The presented control system is able to compensating current harmonics, reactive power and current unbalance of nonlinear loads. The conventional controllers based on pq theory need more calculations, since they need the use of Clark transformation (abc to alphabeta transformation). The proposed control system is very simple and therefore practical implementation of active filters is available. The presented simulation results carried out by Matlab/Simulink program show the validity of control strategy.

Projected density of states diagram (PDOS) of the bilayer ABhexC₁₃₂H<su... more Projected density of states diagram (PDOS) of the bilayer ABhexC₁₃₂H₄₀ GQDs, the E₁₁, and the E₂₂ showing the electronic transition E_ij from the <i>i</i>^th valence band to the <i>j</i>^thconduction band.

Density functional theory (DFT) and thermal DFT (thDFT) calculations were used to evaluate the en... more Density functional theory (DFT) and thermal DFT (thDFT) calculations were used to evaluate the energy band structure, bandgap, and the total energy of various graphene quantum dots (GQDs). The DFT calculations were performed using local density approximation for the exchange-correlation functional and norm-conserving pseudopotentials. We consider the triangular and hexagonal GQDs with zigzag and armchair edges and 1-3 nm dimensions with many hundred atoms. The simulation results show that all of these GQDs are direct bandgap semiconductors with a flat band structure, and they are suitable for electronics and optoelectronics applications. Analysis of GQDs in which the A and B sublattice symmetries were broken showed degenerate zero-energy shells. Using the thDFT calculations carried out at temperatures up to 1400 K, we evaluated the temperature dependence of the GQDs bandgaps and total energies via entropy-term and electron’s kinetic energy. The obtained results indicate that the gro...

Physical Chemistry Chemical Physics

We have developed the right atomic-molecular ab initio calculations-based model to investigate ph... more We have developed the right atomic-molecular ab initio calculations-based model to investigate photoelectrical properties of photodetectors based on graphene nanodot structures with two probes.

Using Photovoltaic systems is gradually expanded by increasing energy demand. Abundance and avail... more Using Photovoltaic systems is gradually expanded by increasing energy demand. Abundance and availability of this energy, has turned to one of the most important sources of renewable energy. Unfortunately, photovoltaic systems have two big problems: first, those have very low energy conversion efficiency (in act between 12 and 42 percent under certain circumstances). Second, the power produced by the solar cell depends on nonlinear conditions such as solar radiation, temperature and charge feature. According to this, received power maximum of photovoltaic cells depends on different non-linear variables, it is necessary to be continuously traced, as maximum received power of the cell (by controller). In this research, the increasing efficiency of photovoltaic systems has been investigated by using Maximum Power Point Tracking (MPPT) in two different modes contained connected to the Grid and disconnected from the grid with simulation by MATLAB software. The obtained results showed that...

Photonics

Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano... more Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano-graphene has been a topic of interest to researchers in recent years. Using a first-principles study based on density functional theory (DFT) and thermal DFT, we investigated the electronic structures and optical properties of bilayer graphene quantum dots (GQDs). The dielectric tensors, absorption spectra, and the refractive indexes of the bilayer GQDs were obtained for both in-plane and out-of-plane polarization. In addition, we calculated the absorption spectra via time-dependent DFT (TD-DFT) in the linear response regime. The TDDFT results show that a blue shift occurs in the absorption spectrum, which is consistent with the experimental results. In this investigation, we consider triangular and hexagonal GQDs of various sizes with zigzag and armchair edges. Our simulations show that unlike monolayer GQDs, for which light absorption for out-of-plane polarization occurs in the ultrav...

Infrared detectors can be used for a variety of applications such as: using in fiber-optic commun... more Infrared detectors can be used for a variety of applications such as: using in fiber-optic communications. Conventional technology for IR detectors is using p-i-n structure based on GaAs compound. This paper reports on the design and modeling of an IR detector using a p-i-n GaAs structure. Comsol software is used to simulate the model and the detector is discussed for terminal current, dopant profile, and energy band diagram. Finally, we have studied electric field according to layer depth under thickness, bias voltage, and field magnitude. We analyzed the electronic and optic behavior of IR detectors simultaneously, and detection spectrum was obtained in terms of wavelength

The aim of this paper is computing of the optimum duty cycle and inductance using Genetic Algorit... more The aim of this paper is computing of the optimum duty cycle and inductance using Genetic Algorithm to minimize tracking error and operating costs by means of a new current reference. Such a current reference is able to share the responsibilities in power quality deterioration between supply and customer, making the filter to deliver a current with a lower harmonic content, which means a lower power delivered and a lower switching frequency. The use of different control approach may be helpful to achieve a good current control since this approach allows to carry out a control action independent from the electrical parameters.

21 Design and Simulation of a Fast SAW Waveguide with Comsol Software Hadi Amos*, Majid Ghandchi ... more 21 Design and Simulation of a Fast SAW Waveguide with Comsol Software Hadi Amos*, Majid Ghandchi Department of Electrical Engineering Ahar Branch , Islamic Azad University , Ahar Iran Email: hadi.amos.iau.ahar@gmail.com, majid.ghandchi@gmail.com Abstract In this paper, the structure of SAW has been studied. In previous work in SAW, materials such as lithium niobium, lithium tantalite and gallium nitride were used in the structure of SAW, and thus had a low operating frequency and the highest reported operating frequency was about 4 GHz. In this paper, aluminum nitride and gallium nitride in the SAW structure are used in combination. The electrodes used in the structure are also made of aluminum. Comsol software was used to simulate the structure, and for the structure, the operating frequency was 7.02 GHz.

S7-1200 with Tia Portal technology has become a Standard function of distributed controlsystems. ... more S7-1200 with Tia Portal technology has become a Standard function of distributed controlsystems. Self-Tuning methods belong to Programmable Controllers (PLC) techniques. PLCtechniques contain software packages for advanced control based on mathematical methods. S7-1200 tools are designed to increase the Process Capacity, yield, and quality of products. Most ofthe present time digital industry regulators and PLCs are provided with some kinds of the SelfTuning constant algorithms. Practical part of the present paper deals with the design of thecontrol systems, which contain Self Tuning regulators and Zone PID features. A Control Systemwith PID Self Tuner is designed by Siemens along with visualization in Tia Portal to do so. Thereis a description of an implementation of the PID regulator as a function block, which can also beused for extension Zone PID control functions. Control Systems for relay and moment Self Tunerwith visualizations in Tia Portal are also designed and tested in ZA...

Microsystem Technologies, 2016

Proceedings of the European …, 2009

... in FarsiTeX Youssef Rezvan, Majid Ghandchi, and Farshad Rezvan ... In the conclusion we have ... more ... in FarsiTeX Youssef Rezvan, Majid Ghandchi, and Farshad Rezvan ... In the conclusion we have also dis-cussed the ways to upgrade this Farsi Spell-checker version 0.1, as well as other techniques. Y. Rezvan (*) Islamic Azad University, Ahar Branch, Dept. Electrical Eng. ...

MDPI AG, 2020

Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano... more Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano-graphene has been a topic of interest to researchers in recent years. Using a first-principles study based on density functional theory (DFT) and thermal DFT, we investigated the electronic structures and optical properties of bilayer graphene quantum dots (GQDs). The dielectric tensors, absorption spectra, and the refractive indexes of the bilayer GQDs were obtained for both in-plane and out-of-plane polarization. In addition, we calculated the absorption spectra via time-dependent DFT (TD-DFT) in the linear response regime. The TDDFT results show that a blue shift occurs in the absorption spectrum, which is consistent with the experimental results. In this investigation, we consider triangular and hexagonal GQDs of various sizes with zigzag and armchair edges. Our simulations show that unlike monolayer GQDs, for which light absorption for out-of-plane polarization occurs in the ultraviolet wavelength range of 85-250 nm, the out-of-plane polarization light absorption peaks in the bilayer GQDs appear in the near-infrared range of 500-1600 nm, similar to those in bilayer graphene sheets. The out-of-plane polarization light absorption peaks in the near-infrared range make bilayer GQDs suitable for integrated optics and optical communication applications.