مجله علوم و فناوری های پدافند نوین
سال یازدهم شماره 4 (پیاپی 42، زمستان 1399)

In the recent years, advent of new technologies in the field of Structural Engineering, elements such as Sandwich Panels has attracted more attention, which are lightweight and highly resistant.Sandwich components are  the most widely used elements to resist against the pressure of explosion wave. The core of the sandwich panels does the most important role in absorbing and dissipating the energy of the explosion.And geometric shape of the core can have a decisive role in the amount of energy absorption. Accordingly, in this paper, the effect of geometric shape of the core of the steel sandwich panel on its behavior and amount of energy absorption against the explosion wave is analyzed by numerical methods. Abaqusfinite element software is used for simulation and analyzing. Validation of the responses obtained from numerical solution was performed with experimental data of valid papers. In the following, sandwich panels with four different types of regular and easily fabricated cores, were modeled under different pressures of explosive wave. And the effect of core geometry on the amount of energy absorption and displacement was investigated.Two important criteria in designing these types of sandwich panels are maximizing energy absorption and minimizing maximum displacement. The results show that at low pressures Model 4 with a quadrilateral horizontal core has the maximum energy absorption and minimum displacement value. However, at high pressures Model 2 with a hexagonal vertical core has the minimum displacement and Model 1 with a quadrilateral vertical has the maximum energy absorption. In other words related to the explosion pressure, a sandwich panel with the special geometry can have the best performance.

Several hazards often affect the stability of structures, and when designing and analyzing the structure, this should be considered. With increasing seismic strength of the structure, the strength of the structure increases against other forces, such as the explosion force. One of the most commonly used building design systems for lateral loads is the use of a cross bracing system. Using cross braces with friction damper can have more damping and energy absorption compared to cross braces without friction damper; it will behave better in big bangs. In this paper, the effect of cross braces with a friction damper and no friction damper on the performance of concrete structures against explosive force has been studied. For this purpose, the displacement and relative displacement of the floors in different modes of loading of the explosion have been calculated. Finally, the results show the effect of friction damper on reducing lateral displacement and relative displacement of the floors, so that in the structure with the damper compared with the structure without a damper, the lateral displacement and relative displacement of the floors significantly decreased. Studies show that adding a friction damper to the structure increases the stiffness of the structure, so the frequency of the structure is reduced.

Concrete retaining walls gratitude to their significant-high mass are considered a protective barrier and explosion resistance. The fabricated walls generally made of reinforced or fiber-reinforced concrete. This study deals with investigating the destructive effects of the explosion on retaining walls made of reinforced and fiber-reinforced concrete. For this purpose, the intended wall simulated by Abaqus software with various blast loads at different distances. Then, to investigate the damage caused by the explosion, the explosives were modeled in three positions attached to the wall, at a distance of one meter and at a distance of ten meters from the wall, perpendicular to the highest midpoint of the structure and the junction of wall and ground.The modeling results showed that the explosion at the connection of the wall to the ground has more destructive effects than the detonation at the highest point of the wall. The failure load of the reinforced concrete wall and fiber-reinforced concrete at the junction of the wall to the ground equals 5 kg C4 and 10 kg TNT and 15 kg C4 and 15 kg TNT at attached and distance of one meter from the wall respectively. The failure load was equal to 60 kg C4 and 70 kg TNT and 90 kg C4 and 100 kg TNT for reinforced concrete and fiber-reinforced concrete wall respectively at a distance of 10 meters from the wall and at the junction of the wall to the ground. Also, the explosion at the position attached to the wall and one meter from the wall showed local effects on the wall and occasion local damage. However, the explosion at a distance of ten meters did not act locally due to the large distance of the explosion from the wall, and more explosives are needed to destroy the wall at this distance.

In order to increase the resilience of distribution system against natural disaster and human attacks, before the events, the value of the monitored system assets should be identified according to different factors so that during the crisis, restoring of lost loads be done faster and qualitatively better. This paper is based on price-based modeling in which load value, to consider the importance of demand side; failure rate, line availability; intrinsic value of lines, to consider investment cost, as well as topology factor, to emphasize The configuration of grid was taken into consideration. In order to observe the impact of DG on the grid lines evaluation, it was investigated in two states: with and without DGs. The results, in addition to demonstrating the network sensitivity to the influential factors, show that distributed generation has a potential to change ranking of valuation and to help improve the process of restoring the distribution system.

Considering the power grids automation and network data transferring in telecommunication infrastructure, the possibility of planning a cyber-attack grows up intensively. In this regard, the optimization of the budget for attack (BA) and budget for defense (BD) in a power network through cyber-attack is so crucial. In this paper, regarding the cyber invasion phase, the choice of the most vulnerable operating bus using the state estimation technique through a new algorithm is analyzed and simulated. For this purpose, false data injection is performed on the data sent from the PMU in such a way that it is not detectable to the network dispatching operator under the invasion. As a case study implementation of the suggested algorithm for a 14 IEEE bus network is carried out and the best bus in terms of exposure under attack is identified. The performance of this algorithm is based on the results obtained from state estimating of the grid after occurring a cyber-attack on different buses. Finally, the part of the grid, which the destruction of information in that part leads to the most damage to the grid, is determined.

Graffiti bombs are one of the modern non-destructive weapons that by causing short circuit in the power systems result in blackout in these networks. The main purpose of this paper is to propose a Special Protection System (SPS) to prevent long-term voltage instability after graffite attacks. In this SPS, the power grid is divided into several voltage control area (VCAs) in order to carry out corrective actions in a coordinated manner and reduce the risk of the instability. Then, according to the voltage stability status of each area determined by RPRI index, the proposed SPS will be used to prevent long-term voltage instability. In this paper, using the DPL environment of DIgSILENT PowerFactory software, the proposed SPS is implemented and tested on IEEE 39-Bus and Nordic32 networks. The results of simulations performed under different N-1, N-2 and N-3 contingencies and comparison of them with previous ones verify the appropriate performance of the proposed method.

Electric storage technologies have different levels of early stages of R&D, and today power systems, especially power grid in Iran, are highly regarded by planners and operators. Because of inherent characteristics of power networks and the presence of many vulnerabillities, using storage systems in power networks is inevitable in order to protect the critical infrastructures and maintain the economy and sustainability of electricity networks. The present study aims to develop the use of electrical storage devices in the distribution network from the passive defense perspective based on (qualitative) and descriptive statistics (quantitative) analysis with help of GAMS software. The country's peak courier survey shows that storage systems have more efficiency compared to power plants. In this investigation, seven types of best-performing batteries are analyzed, based on nominal power indices, efficiency, density, energy, daily insolubility and life span, and Lithium lion batteries are considered to be the most suitable for use in storage systems are introduced as most affordable.

The volume of advanced cyber attacks is increasing today; hence the use of intrusion detection systems in networks is inevitable. One of the major problems by using these systems are considered as the high volume of low-level alarms produced. In the present paper, one of the data mining techniques called Attribute-Oriented Induction is utilized. The basis of this approach is to generalize low-level data to high-level concepts. By the development of this strategy in the field of cyber attacks, the volume of intrusion detection alarms has been decreased. This reduction not only disrupts the detection of attacks but by more focusing on the common features of the attacks, it will increase the accuracy of detection. Moreover, one of the basic foundations of this method is a generalized hierarchy designed for effective attack features. Another highlight of this investigation is to provide an intuitive approach to selecting features for generalization. The new CICIDS2017 data set was employed to evaluate the proposed method, which overcame the shortcomings of its previous data set. In conclusion, the results show a 99% decrease in alarms at the lowest generalization level and an average of 25% at the other generalization levels. In addition to the normal traffic, 14 different attack types were identified, with the Dos Hulk attack being the most frequent with 8.16% and the Heartbleed attack having the lowest frequency 0.0004%. Other capabilities were offered in the proposed method include the possibility of online analytical processing and multidimensional data mining in cyber attack space by moving at different levels of generalization..

In smart home, most things interact with each other and with people at home. One of the benefits of smart home is the ability to control and monitor home, remotely. At the same time, smart home is potentially exposed to security problems and violates privacy of individuals. Considering that objects inside the smart home are constantly collecting private information about people's activities, if someone accesses unauthorized objects indoors, he takes control of objects and gives them data Private individuals have access to or damaged objects or disclosure of information. To prevent this, people who intend to use home-made objects must be authenticated before using it. In this paper, we propose a method for improving individual authentication based on a one-use password using smart card and elliptic curve cryptography algorithm in the smart home system. The results of the evaluations indicate improved interoperability between the user and the gateway to counteract the attacking attack compared to existing methods.

In this paper, a novel biosensor based on the photonic crystal for refractive index measurements is proposed and investigated. Three designs, known as single-cavity structure, duble and triple-cavities structures, are designed and studies. All the structures were composed of a main hole as a ring resonator localized between the input and output waveguides. Two-dimensional finite-difference time domain and plane-wave expansion methods are employed to study the output power spectrum of the structures. By absorbing DNA molecules in the PBS solution, the refractive index of the sensing holes differ which results to the output transmission spectrum of the structure shift and hence, the sensing process occure. We study the impact of different parameters on the sensing of the structures. Results show that the sensitivity of the sensor depends mainly on the geometrical properties of the defect region of the photonic crystal structure. Results shows that the single cavity and triplet structures have the best sensitivity equal to 345nm/RIU and 531compared to the other proposed sensors, respectivelly.