Amirkabir International Journal of Electrical & Electronics Engineering
Volume:52 Issue: 1, Winter-Spring 2020

Weak microwave radiation (WMR) in our environment has raised health concerns in the public. Among those, communication frequencies are more than ever becoming widespread and their effects need thorough studies. A correct understanding of these effects in-vivo by in-vitro experiments shall preferentially use primary cells. In this study we compared non-modulated (CW) and modulated WMR exposure of biological cells in-vitro. Human ADMSC (Adipose-Derived Mesenchymal Stem Cells) were exposed to very weak non-thermal levels of microwave Electromagnetic fields at 1135 MHz ,SAR (Specific Absorption Rate) 0.002 W/kg (Watt per Kilogram) for 30 minutes daily for 4 days. A statistically significant decrease in proliferation rate of these stem cells was observed compared to the control group with no exposure. When amplitude-modulated exposure (15 Hz (Hertz) with a depth of 80%) was used with the same carrier frequency of 1135 MHz (Mega Hertz) and consistent average power, the cell numbers showed no statistically significant difference from the non-modulated exposure, but were nevertheless lower than the not-exposed control. The observed decrease in proliferation in response to -weak microwavefields supports the hypothesis that non-excitable cells, such as undifferentiated mesenchymal stem cells can interact with, and respond to weak electromagnetic radiation at communication frequencies. Possible mechanisms responsible for the observed results have been hypothesized and directions provided for future research.

This study presents a full-duplex Radio-over-Fiber (RoF) system providing the users' wireless access with a bit rate of 10 Gbps over 40 GHz radio carrier. This system can be used in a centralized radio access network (C-RAN) architecture because we provide a fully analog front haul link between central station and base station. We can consider it as infrastructure between remote radio heads (RRHs) and baseband units (BBUs). The most appropriate choices in our case are using left and right-side bands of the DSB spectrum for both uplink and downlink streams and modulation of the data signal on both polarization of the optical carrier, as well as simplifying system structure, the bit rate of the proposed system, raised significantly. Furthermore, a method was provided to create redundancy for the optical fiber path and enhance system stability in case of a fiber cut. Optical external modulation is considered to be a good possibility to generate the optical mm-wave signal with high spectral purity. The transmission performance of the signal is analyzed in detail by analytical formulations and a full-duplex RoF link is built to verify our theoretical analysis results based on the simulation. Furthermore, the impacts of the fiber chromatic dispersion have been compensated in the RoF system with the dual-polarization carrier signal.

In recent years, due to the fact that non-renewable energies come to an end, renewable energy is expected to provide a significant part of the future needs of Iran. Among these energies, solar energy is a suitable option for a wide range of the country, due to availability, proper radiation intensity, and high sunshine times during the year (about 300 sunny days per year). The purpose of this paper is to analyze the performance of a 1 MW solar power plant in Arak (Iran's first megawatt power plant) according to IEC-61724 standard using data recorded over a year (November 2017 to October 2018). The plant has the capacity of a 1 MW in a 1.6-hectare land with 3920 modules (split into 1920*260 Wp mono-crystals silicon technology and 2000*250 Wp multi-crystal silicon technology) in 200 strings and four inverters (each with a capacity of 250 kW). The information of this power plant is recorded in fifteen-minute intervals, which according to IEC-61724 this power plant is in class B, and we can do a one-year performance analysis. Also, the effect of the improper operation on the amount of injected energy into the grid is investigated. In this paper, the performance parameters of the system are presented, also a table to have a comparison to other PV plants in some parts of the world is provided.

This paper proposes a new PI/PID controller tuning method within filtered Smith predictor (FSP) configuration in order to deal with various types of time delay processes including stable, unstable and integrating delay dominant and slow dynamic processes. The proposed PI/PID controller is designed based on the IMC principle and is tuned using a new constraint and without requiring any approximation or model reduction techniques. Meanwhile, the set-point weighting method plays a vital role in achieving a desired performance in both servo and regulatory problems. To have an enhanced disturbance rejection for integrating processes, an improved IMC filter is adopted to design a PID controller. The presented settings are applicable to a wide range of integrating processes. The trade-off between robustness and regularity performance is easily adjustable by tuning only one parameter. Guidelines are provided for the selection of the tuning parameter based on the maximum sensitivity value. Various performance indices are used to measure the performance of the closed-loop control system. Simulation results reveal the effectiveness of the proposed technique over some of the relevant techniques, particularly for integrating processes and stable processes with slow dynamics, by comparing performance indices such as IAE, total variation, overshoot and the maximum peak of error performance indices.

The power system nonlinearity and its profound impact on the individual states of power system is first evaluated and the interaction between their constituent modes during the occurrence of internal mode resonance (IMR) is discussed in this paper. A typical dynamical feature of nonlinear systems is the frequency-energy dependence of their states and their corresponding constituent modes which is also underlined in this paper. At first predominant state is identified which is defined as the one with highest energy level and the internal mode resonances and energy exchange between its constituent modes are explored accordingly. However, Perturbation Techniques such as Normal Form (NF) or Modal Series (MS) and several polynomial approximation are explored and it is demonstrated that such methodologies do not lead to the acceptable results and does not work well in near-resonant conditions. For this reason, the integrated algorithm consists of Shooting and Pseudo-Arclength is employed for obtaining Frequency-Energy Plot (FEP) to estimate and evaluate the involved modes behavior during the resonance and the energy level at which the internal resonance occurs. The studies are performed on 39-bus New England Test power System and the final results prove the accuracy and effectiveness of the proposed methodology and algorithm.

The exponential increase in carbon-dioxide resulting Global Warming would make the planet earth to become inhabitable in many parts of the world with ensuing mass starvation. The rise of digital technology all over the world fundamentally have changed the lives of humans. The emerging technology of the Internet of Things, IoT, machine learning, data mining, biotechnology, biometric, and deep learning facilitate the development of distributed green smart microgrids. We have gained godlike powers as to become unrecognizable, and we have the power to destroy ourselves through environmental mismanagement and nuclear calamities. The exponential increase in carbon-dioxide resulting Global Warming would make the planet earth to become inhabitable in many parts of the world with ensuing mass starvation. The rise of digital technology all over the world fundamentally have changed the lives of humans. The emerging technology of the Internet of Things, IoT, machine learning, data mining, biotechnology, biometric, and deep learning facilitate the development of distributed green smart microgrids. We have gained godlike powers as to become unrecognizable, and we have the power to destroy ourselves through environmental mismanagement and nuclear calamities.

In this paper, a simple but effective method for compensation of the quadrature error in MEMS vibratory gyroscope is provided. The proposed method does not require any change in the sensor structure, or additional circuit in the feedback path. The mathematical relations of the proposed feedback readout system were analyzed and the proposed solution assures good rejection capabilities. Based on the simulation results, the proposed method increases the dynamic range of the readout circuit by about 19 dB for the quadrature error with 10 times higher amplitude than the Coriolis signal. Furthermore, the feedback path reduces the effect of the 1 degree LO mixer phase error in the output path by about 95%, which causes our system to be less sensitive to this error. In addition, the 2nd harmonic component at the output of the proposed feedback readout is much lower than that of the conventional readout. As a result, proposed feedback readout can relax the requirement of the output low pass filter. In addition, the 2nd harmonic component at the output of the proposed feedback readout is much lower than that of the conventional readout. As a result, proposed feedback readout can relax the requirement of the output low pass filter.

Researchers in bioelectromagnetics often require realistic tissue, cellular and sub-cellular geometry models for their simulations. However, biological shapes are often extremely irregular, while conventional geometrical modeling tools on the market cannot meet the demand for fast and efficient construction of irregular geometries. We have designed a free, user-friendly tool in MATLAB that combines several known or new algorithms for easy production of three-dimensional complex cell shapes based on minimum data. We have considered four different methods of creating objects: Generalized Rotation, Super-Formula, 3D reconstruction of 2D parallel cross-sections and branching models. Besides, many transformations such as translation and rotation, Boolean operations for 3D objects including union and intersection, random copy, etc. are also included in the toolbox. By utilizing different methods, our toolbox generates a larger variety of realistic biological geometries, especially tailored for irregular and branching cellular and sub-cellular shapes. We present a group of biological shape examples in this paper. The toolbox can export the geometries to common standard stl or voxel formats to be used for simulations in other software. We have developed an open, user-friendly toolbox, with specialization in cellular and sub-cellular irregular models. This toolbox can provide the essential realistic cellular models for scientific simulations in biomedical engineering, biotechnology, bioelectromagnetics, cell biomechanics, and serve as an educational visualization tool in teaching cell biology. Examples of microdosimetric simulations for electromagnetic exposure to RF frequencies are given and discussed.

Typical cryptography schemes are not well suited for low complexity types of equipment, e.g., Internet of things (IoT) devices, as they may need high power or impose high computational complexity on the device. Physical (PHY) layer security techniques such as beamforming (in multiple antennas systems)  are possible alternatives to provide security for such applications. In this paper, we consider a network with multiple groups of users as receivers and a transmitter that intends to send different messages to each group of users. There are also some eavesdroppers (Eavs) at known locations of the environment. The goal of this paper is to find the beamforming vectors that minimize the total transmitting power while keeping the signal level above a threshold at the exact locations of the legitimate receivers (both angle and range) and keeping it less than another threshold at eavesdropping points.  We use frequency diverse arrays (FDA) at the transmitter; thus, the transmitter also needs to determine the frequency that each antenna element must use for data transmission. This condition makes the problem non-convex and so we propose an approximate solution for solving this optimization problem. Simulation results show the performance of the proposed scheme in a particular network setting.

This paper presents a robust control scheme for distributed generations (DGs) in islanded mode operation of a microgrid (MG). In this strategy, assuming a dynamic slack bus with constant voltage magnitude and phase angle, nonlinear equations of the MG are solved in the slack-voltage-oriented synchronous reference frame, and the instantaneous active and reactive power reference for the slack bus is obtained at each time step, based on Y_bus equation of the MG. The slack bus power references are robustly tracked by the proposed adaptive sliding mode based power controller. In addition, a hyper-plan sliding controller is suggested for other DGs that provides three regulators including active power, reactive power and voltage regulator for DG units and ensures protection of the power electronic interfaces to the faults assumed to have occurred in the MG. At each step time, DGs are modeled as positive and negative current sources that are controlled by their adaptive sliding mode controllers in the normal and abnormal operating conditions. All the parameters of controllers are derived via particle swarm optimization (PSO) algorithm in order to minimize an appropriate cost function. Performance of the proposed control strategy is compared to the performance of the conventional master-slave based control strategy. The validity and effectiveness of the presented method are supported by time domain simulation of a test microgrid in MATLAB.

This paper presents a multi-year scenario-based methodology for transmission expansion planning (TEP) in order to enhance the available transfer capability (ATC). The ATC is an important factor for all players of electricity market who participate in power transaction activities and can support the competition and nondiscriminatory access to transmission lines among all market participants. The transmission expansion planning studies deal with many uncertainties, such as system load uncertainties that are considered in this paper. The Latin hypercube sampling (LHS) method has been applied for generating different scenarios related to the load uncertainty. The objective function in the TEP model is to minimize the sum of investment costs (IC) and the expected operation costs (OC). Both ATC and TEP models are represented based on AC power flow constraints which are more accurate compared with the widely-used DC approach. In this respect, the nonlinear terms in power flow equations are linearized in order to obtain the efficient solutions by existing commercial solvers that can guarantee the achievement to the global optimal solution using branch and bound technique. The proposed model is applied to the IEEE 24-bus Reliability Test System and the results obtained show the efficiency, tractability and applicability of the proposed model.