Advanced Defense Science and Technology
Year:2019 | Volume:10 | Issue:1 |Papers Count:14

For eavesdropping of modern telecommunications systems, which employ multiple transmit and receive antennas, the first step is to recognize the space-time code. In this paper, a method to classify within broad categories of space-time codes is proposed. The method is based on machine learning and pattern recognition. Compared to the previous reports, the novelty is including quasi-orthogonal space-time codes and also single antenna transmitter in identification set. Moreover, the method described in this paper outperforms the current classification methods. It is shown that the decision tree classifier based on several features extracted from correlation matrices, has practical advantages over the current classification methods, especially when data is very noisy.

Control, inspection, detection, and transmitting or receiving data in modern defence principles, essentially requires the low-power radio frequency systems with the ability of operating at various communication standards. In this paper, employing the modern method of active and passive N-path filters, a receiver front-end with the ability of tunablity at various standards and frequencies is proposed. In addition to the analysis of conventional and advanced N-path filters, the prior similar structures are discussed in details. Applying some modifications in the previous structure, not only the NF has been improved but also the power consumption has been considerably decreased, while the stability has been guaranteed. To verify the correctness of the proposed receiver front-end, the cadence IC design tool has been used to simulate the system. According to the simulation results, using CMOS90nm transistors, the amount of power consumption has been remarkably decreased with respect to the previous similar structures. The NF and S11 values in the whole of frequency range, DC to 1. 85GHz, are less than 3. 6dB and-10dB, respectively. The power consumption is less than 15mW including the power consumption of the recombiners. The out of band IIP3 is +8dBm.

It is an imperative necessity to take care of the country's space and air traffic. Usually radar systems will be used to control and discover possible targets. The received information from a radar system in a specific region must be sent online to the higher levels of command and control centers in order to detect possible threats and make appropriate decisions. This exchange of information requires a reliable communication backbone. However, having an online and secure transceiver communication backbone is still a demanding process. Moreover, errors in the current communication networks will cause an increasing percentage of packet loss and delay which affect the Quality of Service (QoS). In this paper, in order to handle these problems and increase the fault tolerance in command and control networks, a backup path is provided that uses the backup path in case of occurring faults in the main path. In addition, Software Defined networks (SDN) as a new architecture have been used in communication networks to provide desirable QoS. In the proposed method, the fault tolerance problem is modeled as a linear programming problem, which is solved through a combinational method of Genetic Algorithm and Fuzzy System. This solution creates an optimal response to dynamic changes and uncertainty accomplished in the communication network. The results of the performance evaluation showed that the proposed method achieves better fault tolerance compared to existing methods.

The vircator is one among several types of high power microwave sources. The reflex triode is one of the varieties of vircators. One of the defencive application of these tubes is the disruption of enemy systems by creating a strong electromagnetic field on the target. One of the factors that reduces the efficiency of these tubes is the distribution of power in non-dominant modes (dominant mode is TE11), the important issue is the relative power of the main frequency component, in this paper we first show that by placing two metal plates at the beginning and end of the axis of the anode and the cathode, we can simultaneously improve the relative power of the dominant mode and the main frequency. Distributed power in the dominant mode and the main frequency increased by 12% and 26%, respectively.

Microgrids are practical samples of the concept of decentralized power production. In this regard, after determination of appropriate technologies and the capacity of power generation and storage units for defensive objectives, the optimal scheduling of units in microgrids is of the crical importance. Thus, scheduling of distributed generations and energy storages in form of virtual power plant have gained significant attentions of both owner of these units and the operators of distributions aiming at increasing the system efficiency. This paper proposes a model for the optimal day-ahead scheduling of electrical and thermal units in a large scale virtual power plant. This plant includes a number of combined heat and power units, distribution consumers, a parking for plug-in hybrid electric vehicles with the ability to follow a smart charging pattern, boilers, renewable energy based generators and storage units. The presence of large number of storages, especially electrical vehicles, in these types of microgrids enhances the resiliency of the grids when encountering malicious attacks. Uncertaintie associated with electrical and thermal loads is modeled using a probabilistic programing while Monte-Carlo simulation has been utilized to model uncertainty in the behavior of electrical vehicles. Simulations have accomplished in two scenarios: 1) normal and 2) islanding operation after a deliberate attack. MATLAB software and cuckoo optimization algorithm are used for optimization task in this paper.

Determining the position, edges and dimensions of underground tunnels has always been the challenging issues in protecting underground structures. In this paper, the gravity method is used to identify buried cavities and structures. After introducing the method, the gravity data is modeled directly using the horizontal derivatives filter and the Blakely algorithm. After determining the boundaries and corners of the fabricated models, the depth of the anomalies is estimated using the Analytic Signal-Euler (An-Euler) method. A multi-cube model is simulated in multistructure with different depths to evaluate the ability of the gravity method in exploration of structures at different depths. Then, to explore airborne capability, a multi-cube model is simulated at different altitudes. Finally, by exploring the results of this simulation, appropriate solutions have been proposed to reduce the probability of exploration and increase the probability of camouflage of buried structures.

In the present study, the uranium qualitative detector package containing Arsenazo and Bromo-PADAP indicators was designed; and also, the metalic ion detector package using Dithizone Indicator was built for detection and determination of some ionic interference via Uranium colorimetric method. The obtained results indicated that the detection limits of Uranium ions were equal to 50 ppm and 20 ppm respectively using detectors containing Arsenazo and Bromo-PADAP indicators. In the acidic media (pH=5), the uranium detectors had good detection performance. The metalic ion detector detected ions such as cobalt (II), copper (II), nickel (II), zinc (II), cadmium and silver until the detection limit 50 ppm. Arsenazo detector was superior to Bromo-PADAP detector for detection of Uranium since it prevented any ionic interference even in very high concentrations which with absorbtion of a solution containing Uranium ion, Arsenazo and Bromo-PADAP detectors in the presence masking agents in buffer solution produced miry green and purple colors respectively. While the operation time for Uranium ion detection in the presence of Arsenazo and Bromo-PADAP detectors was3 minutes and 1 minute respectively. Also, the quantitative evaluations based on image processing methods using MATLAB software show that the experimental results are consistent with the evaluation results.

Concrete Canvas is a flexible concrete impregnated fabric that hardens on hydration to form a thin, durable water proof and fire-resistant concrete layer. Strength properties of Canvas signify that it could be a blast resistant shell. In this paper, to investigate the concrete canvas shell behavior under blast loads, the blast behavior of reinforced concrete slabs are compared with prior experimental abservations using coupled analysis. Then the dynamic behavior of two-way concrete canvas shell under near-field blest load is modeled using finite element method. Analysis resultes illustrates failure development, distribution of diagonal and radial cracks on surface and central deflection of concrete canvas shall. Resultes shows that using concrete canvas shell with proper thickness is more resistant under blast loads than conventional slabs.

Various structures are subject to explosion for terrorist and non-terrorist reasons. The study of effective factors in reducing the damage caused by the explosion is one of the most important issues of passive defense. One of these factors is the presence of openings in the structure under confined explosion. In this study, the effect of opening on the loading caused by the explosion has been examined in terms of pressure-time and impulse-time graphs. In this regard, using the UFC 3-340-02 regulations and numerical simulation of the AUTODYN hydrocode, the confined explosion of a TNT explosive with different masses in a cubic chamber, with different openings in terms of size and location, has been investigated. The investigation results of the effect of each of the opening position factors specify the number of pop-ups with openings and the size of the opening on the loading exerted on the inner surface of the structure due to the confined explosion. Finally, in addition to determining the parametric optimal optimization, the results of the confined explosion resulting from numerical simulation are compared and examined with the UFC 3-340-02 regulations.

Underground structures such as sanctuaries and tunnels are considered as important and strategic structures. The response of an underground structure to loading from a surface explosion is a major issue in passive defence. So far, many studies have been carried out on various parameters such as ground response, structure response, field experiments, etc. However, there are still many unknown and vague aspects of the explosion and its impact on the soil and structure environment. In this study, the effect of soil moisture on the safety of an underground shelter has been investigated for the different amount of stress and displacement. Autodine software has been used to model the underground shelter, and two Lagrangian and Eulerian environments have been considered. The chosen explosive charge in this study is 52. 16 kg of TNT, and the data is recorded using the gauges enclosed in the model. The results show that increase in the degree of saturation of the soil layer has increased the excessive pressure from the soil, and as a result, the von Mises stress in the concrete and steel system has increased and led to the deterioration of the situation.

Underground structures, especially tunnels, are among the most strategic structures for all countries, and they are a potential target of enemy weapons. Therefore, the safety of these structures and the related studies are of the great importance. In the present study, the explosion phenomenon at the surface of the ground and the effect of its wave on the tunnels which are the most important buried structures is investigated by using nonlinear dynamic analysis by ANSYS-AUTODYN software. The effect of the blast wave propagation in soil was simulated with a full geometry in a 3D environment and after ensuring the accuracy of the results, the effect of the tunnel burial depth and the geometry of the cross section in reducing the destructive effects of the explosion on the tunnel were evaluated in a 2D environment. The results indicate that increasing the depth of the buried tunnel and also using sections such as circle, horseshoe, vertical ellipse and egg shape are effective in reducing the destructive effects of the explosion on buried tunnels.