نشریه عصر برق
پیاپی 16 (زمستان 1400)

One of the most important factors in creating competition in future generations of satellite communications is to have a proper satellite system. For this reason, it is necessary for satellite operators to have a suitable choice among different satellite manufacturers, taking into account technical and economic considerations. Therefore, the necessary to select a manufacturer from among the existing manufacturers in this field is a serious challenge. In this paper, we review several methods and compare the evaluation criteria of satellite manufacturers based on the methods of MAXI MAX, Lexicography, non-compensatory decision making and compensatory decision making, which will be a booklet of common mathematical algorithms to compare parameters in a target problem. Finally, a more comprehensive and complete method than previous works has been presented based creating a cross-evaluation matrix according to the main- criteria and side-criteria to evaluate the satellite manufacturers by the satellite operator. In this paper, for better and more efficient selection, nine main criteria and twenty-six sidecriteria according to the type of service and favor of satellite communications are presented in order to evaluate and select among satellite manufacturers and compare with previous works.

Due to the high loss of propagation in millimeter wave (mmwave) and terahertz band (THz) used in fifth generation and Sixth generation telecommunication systems, the cells become much dense and more compact. On the other hand, because of the growing in the user’s demand on more bandwidth, employment of the beamforming techniques with Massive Multi-input Multi-output (Massive MIMO) are very important in order to increase spectral efficiency, proper and cost-effective coverage. Holographic beamforming technology is one of the latest techniques in the beamforming that has many advantages over the old these kinds of techniques such as Analog Beamforming and Digital Beamforming. Therefore, for taking the advantage of the next generation of telecommunication networks, it is necessary to be aware of the different sections of technologies like the antennas, and along with these technologies, entered into the equipment market of these growing technologies, also. In this research, some of the latest techniques and methods of beamforming are investigated and compared with each other. At the end, a suitable method is proposed according to the requierements of next telecommunication networks and technological trends.

Nowadays, due to different applications of cell phones and global approaches in the implementation of 5G networks, the level of public exposure to electromagnetic radiation has increased significantly. This increases concerns about the health effects of these exposures. Various methods such as power control, beamforming and massive MIMO are proposed to reduce the level of electromagnetic radiation in mobile networks. Furthermore, network topology and duration of exposure can be effective in reducing the level of exposure. In this paper, first, the definition of electromagnetic radiation, its criteria, effects and rules are mentioned. Then, the architecture of mobile communication networks and its effect on electromagnetic radiation are investigated. Afterwards, some technical solutions that can be used by network operator to reduce the level of electromagnetic radiation in the network are examined. Finally, some technical solutions are presented that can be used in cell phones to reduce the level of electromagnetic radiation of these devices.

After reading the ATC concepts and static ATC procedures, In this paper, the methods for determining Dynamic ATC (DATC) are collected. In this paper, researchers, efforts to provide new methods for determining DATC power systems have been compiled and the merits and weaknesses of these methods are highlighted. Uncertainty in ATC calculations is discussed and important methods of transient stability and voltage stability have been investigated in DATC determination. At the end of the paper, the strengths and weaknesses of all methods for determining DATC are specified. In order to be able to provide faster and more precise methods in the future.

Corona disease started in January 2020 in the wholesale fish market in Wuhan, China, and the World Health Organization declared it as a public disease and an international hazard, and in February 2020 named it Corona or Covid-19. Under this global pandemic, using artificial intelligence techniques especially convolutional neural networks based on deep learning for screening chest CT images are becoming more vital as before. The most studies in this field belong to the articles based on the deep learning methodologies using convolution neural networks. Already, obtained accuracies of detection and screening have benn reported in the article based on artificial intelligence and deep learning are more than 95 percent. The lack of comprehensive datasets of CT images with a large amount of samples is one of the most important problems in this field. Using hybrid architectures of convolutional neural networks have been increased the accuracy of these networks up to 99 percent.

In this paper we use SVR and MLP Neural Network for modelling and fault detection of KAHAK wind turbines. Electrical subsystems is our purpose for modelling and fault detection. We have actual data and real parameters about 2.5 MW wind turbines that installed in KAHAK wind farme. In first step we modelled and fault datect with two approach, Support Vector Regresion (SVR) and Multi Layer Perceptron (MLP), in second step we compare model error and accurase of SVR and MLP approach, that we can see SVR approach is better than MLP approach according modelling error. We use MATLAB software for this work.

Quantum teleportation protocol is one of the most important quantum information protocols. In this protocol, with the help of quantum entanglement and the classical channel, the state of a quantum particle is transmitted without traveling the physical distance from the sender to the receiver. Quantum teleportation, is the building block of quantum cryptographic protocols, quantum computing, and quantum networks. Therefore, since the initial ideas of the quantum teleportation protocol were proposed in 1993, many efforts have been made in the theoretical discussions and implementation of this protocol. In the present study, after introducing and classifying the theoretical ideas of quantum communication protocol, we will examine the practical implementations of this protocol. Next, the required technology requirements are presented along with the strengths and weaknesses of each.

Self-driving cars have been under intensive development in the last few years. These vehicles combine a variety of sensors, such as radar, lidar, sonar, and camera, to understand their surroundings. Each vehicle uses different sensors and installation locations. Although there is a great deal of variation in the set of sensors and their installation locations, some repetitive patterns can be seen among self-driving cars. In this paper, these patterns are examined and their different approaches are explained. First, the patterns used in some of the existing vehicles are presented. Then, general considerations in the design of sensor patterns are expressed. Next, the advantages and disadvantages of each pattern are examined. Finally, the results of this study are summarized.

According to wide variety of advantages of distributed generation units, especially those using clean and renewable energies, their installation are dramatically increasing in distribution networks. Among renewable energy generators, photovoltaic generation units have been paid more attention compared to other technologies because of clean energy generation, simple operation and maintenance, and availability in most areas. Despite the mentioned advantages, connecting the photovoltaic generation units to the distribution network will cause problems in the field of network protection. These include the possibility of overlapping relays and their non-coordination, bidirectional feeding network, and the occurrence of an islanding state. On the other hand, by increasing the penetration of these generators, the activation of advanced grid support functionalities such as active and reactive power regulations, low voltage ride through capability (LVRT) and seamless transition to islanded operation mode are included in current grid codes to compensate for their unpredictable energy production. Since these ancillary services can disrupt the operation of islanding detection methods, it is necessary to provide islanding detection method compatible with mentioned ancillary services. In this paper, islanding detection methods compatible with the advanced grid support functionalities such as power regulations, low voltage ride through, and seamless transition to islanded mode are reviewed.