مجله علوم و فناوری های پدافند نوین
سال چهاردهم شماره 2 (پیاپی 52، تابستان 1402)

One of the significant problems of laser propagation in the atmosphere is the atmospheric turbulence and fluctuations of refractive index, which affects the laser parameters. In this article, the effects of atmospheric refractive index structure parameter (Cn2) on the intensity distribution, spot size, radius of curvature, and Rayleigh length of the laser beam propagated with Gaussian profile, wavelength 1064 nm, size of beam waist 1 cm and power 1 W have been investigated. In order to predict Cn2 parameter values, Hufnagel-Valley (HV) and Hufnagel-Andrews-Phillips (HAP) models were compared. The simulation results show that in both models, the Cn2 parameter decreases with the increase in height. Also, although the HV model is suitable for determining the Cn2 parameter at high altitudes with the presence of wind, it does not determine the behavior of the Cn2 parameter as well as the experimental results and the HAP model at low altitudes and at different hours of the day. The simulation of laser propagation in the atmosphere shows that with the increase of the Cn2 parameter, the average intensity distribution decreases and the spot size increases; Also, the radius of curvature is reduced and the Rayleigh length first goes up and then goes down. Despite the problems of laser propagation in the atmosphere, the results of this article and future investigations seem necessary to reduce and compensate for these effects.

Security is the most basic need of any society that affects different parts of it. Also, due to increasing security threats and limited resources to deal with them, it is necessary for security resources to be deployed in an optimal state. Furthermore, because of resources limitation, the use of deceptive resources is used by the attacker and the defender. Game theory is a common way to understand the concepts, strategies and consequently the allocation of limited resources of the attacker and defender. In this paper, a three-level Stackelberg security game between a defender and two attackers is modeled in a situation where the defender and the attacker try to deceive each other. The advantage of this research compared to the previous papers is to model the attacker and defender deception as well as considering the financial limitations and limitations related to attack and defense in a three-level model. The utility of the defender and the attackers is modeled along with their limitations. The model is converted into a single-level model using the Karush-Kuhn-Tucker method and solved, describing its application in defense decision-making. The obtained results show that by using the proposed model, limited security resources are optimally allocated, which leads to the improvement of security conditions and dealing optimally with security threats.

Today, Voice over Internet Protocol (VoIP) is widely used in real-time communication and social networks and has become a suitable carrier for steganography methods. To confronting these threats, many steganalysis methods have been invented, among the proposed solutions, the combination of signal processing and machine learning methods has made it possible to create steganalysis methods with high accuracy. In this paper, a combined approach of speech signal processing methods and artificial intelligence algorithms is used. In this research, first, data pre-processing is done on compressed audio signal with G.729 codec, which extracts intra-frame features and inter-frame correlations with good resolution. Then the obtained results are given to a deep learning network to train cover data from stego data. The results of the implementation include the improvement in both the detection accuracy and the computation time. This method has been analyzed for two important steganography families, QIM and PMS, and the proposed method has been tested and implemented for different embedding rates. Another important point is the real-time test of the presented method, which for 1000 millisecond files, the response time was less than 5 millisecond, which shows the high speed of the proposed model in the execution phase.

Power grid is one of the most important infrastructure of any society on which other infrastructures depend. Studies show that the false data injection cyberattack can cause transmission lines to overload. Usually, the power grid is capable of responding to the natural overloads of transmission lines, but if a cyberattack is accompanied by a targeted physical attack, the overload of transmission lines can become out of control, and consecutive outages can occur in the power grid’s transmission lines. This situation eventually leads to local or nationwide blackouts of the power grid. To confront the overload of transmission lines, the power grid’s operator removes the overloads by taking corrective measures such as using the upward and downward reserve power as well as load shedding. In this paper, we first show how a simultaneous cyber-physical attack can increase the amount of load shedding. Then a model based on game theory is presented to plan the load dispatch of the grid so that the operator can repel the cyber-physical attack with the lowest possible cost using corrective measures. The proposed model is simulated on a 5-bus test network and the results are analyzed.

In this paper, we discuss how to control the side lobe level of corrugated metallic periodic leaky wave Antenna by its artificial surface impedances. Leaky Wave Antenna have beam steering ability by Frequency Scan or by artificial Surface Impedance control in the constant frequency. Side Lobe Level of Leaky Wave Antenna is Worse level of Antennas Side Lobe Levels and This level worst if other Modes of Leaky wave antennas is activated. Therefore just minimize the Side Lobe Level as well as. In this paper we obtain 18dB of Side Lobe Level in HFSS Simulation and less than 16dB of Side Lobe Level in practical case in 10GHz frequenc

Unexpected events, whether natural, industrial or man-made, are considered as surprising events. If surprised at the time of unexpected events, irreparably reduces the public trust on the ability of the government to reduce the damage caused by these events. The purpose of this investigation is to pay attention to the crisis, to extract the factors of surprises in the crisis and to provide solutions to prevent it. Q method is used in this investigation and the statements related to surprise factors in crisis are extracted and scored by statistical society and research colleagues. By using the colonial competition algorithm and programming the algorithm in MATLAB software, viewpoint 4 was extracted as the most important one and appropriate solutions were presented, which include the study and proper location of the warehouses of the relief facilities and the investigating the appropriate number and location of these warehouse. and to prepare the people to familiarize themselves with the possible crises and analyze the response at the time of crisis, through public media and social media. Furthermore studying and predicting widespread crises and designing relief facilities and suitable routes to help the more vulnerable points are derived as the proper solutions in this investigation.