مجله علوم و فناوری های پدافند نوین
سال هفتم شماره 3 (پیاپی 25، پاییز 1395)

In this article to investigate the blast effects on structure and its performance determination, a building with reinforced concrete frames has been designed according to Iranian earthquake standard No.2800-05 and a single frame of it has been modeled with ABAQUS package and subjected to blast loads in accordance with the Iranian National Building Code of draft Part21 considering material and geometrical nonlinearities. The results indicate that the blast danger levels given in the Part21 do not have a reasonable relation with each others, neither in over pressure nor impulse. For example in the first blast danger level (the severe one), none of the columns could pass the life safety level (L.S.) of performance, but in all other blast danger levels, all column could pass Immediate Occupancy level (I.O.). Also the side way displacement is so little in the frame that in all blast loads could pass I.O. level. Also the code drift criterion is so that in all blast danger levels, I.O. level is achieved. According to these results, it seems that blast danger levels and also drift criterion should be revised.

Nowadays, RFID technology is using widely in our daily lives. This technology is used in many applications such as healthcare, military, identifying friend or foe of fighter-aircraft and etc. In order to provide security and privacy of RFID systems, different authentication protocols have been proposed. Pang proposed a RFID authentication protocol based on EPC C-1 G-2 standard. They claimed that their protocol is secure against various attacks and provides user privacy. It is shown that protocol proposed by pang is not safe and suffer from attacks such as tag ID exposure, tag impersonation, reader impersonation and de-synchronization. Also to enhance security of RFID users, an improved version of this protocol is proposed, showing that it is secure against aforementioned attacks. In addition, complexity and efficiency of the improved protocol is compared with some similar ones and it is shown that the improved protocol is completely secure. Eventually, security of the improved protocol is compared with some existed protocols.

By increasing the penetration of distributed generation in electrical distribution networks, especially in military areas, use of directional relay becomes a necessary device for protection of these networks. Due to the absence of potential transformers, the conventional directional relays cannot be applied in distribution networks for detection of fault direction. For this purpose, a new directional relay is presented that is able to detect the fault direction using only the through-fault current. The proposed approach is not affected by power flow direction and improves the performance of the previously introduced current based on directional relays employing pre-fault current. The present approach could eliminate the cost of the potential transformer in distribution systems. The extensive simulations, under different operation condition are carried out on two different distribution systems; including bidirectional 3 bus network and IEEE 14 bus test system. The obtained results approved the high efficiency of the proposed method.

On the base of the population areas and sensitive military centers and also developing underground civil projects such as buried tunnels in the north of Tehran such as Metro lines projects and military centers, there is the possibility of military threats due to the air attacks of the enemy countries because of the destructive effects on the urban operations. The penetrate missiles are of the dynamic instability factors that threaten the safety of the tunnels. In this study, by using of the numerical analysis, investigated resistance of the considered tunnel against explosion of bunker buster GBU-28 in the various deeps and finally the minimum distance among explosive cavity and crown of the tunnel that it remained stable in the explosive tensions situations determined about 25m. In the distances lower than 25m both critiques of replacement of crown of tunnel and the breaking point indicated instability of tunnel under load due to explosion.

One of the most dangerous insider threats in a supervisory control and data acquisition (SCADA) system is operational threat. An operational threat occurs when an SCADA operator does not perform his duties, or decides to abuse the privileges in order to perform malicious operations in remote substations. An operational threat on a critical infrastructure has the potential to cause large financial losses and irreparable damages at the national level. In this paper a new alarm-based anomaly detection system has been proposed to detect operational threats in SCADA system. The proposed system uses statistical quality control techniques for detecting anomalies and estimating control limits. The value of anomaly is calculated according to the severity of longed-unresolved alarms. The simulation results in power system SCADA as a case study show effectiveness of proposed system.

Generating and processing of spatial data for positioning of critical facilities increase the passive defence capability and security index, while decreasing the effects of possible attacks, significantly. Nowadays, accessing to satellite images with higher resolutions, due to the more accurate results, is an attractive issue in the field of defence systems. In this paper, a pushbroom imaging system has been implemented which is capable of receiving commands, storing and reloading images. The scanning-based camera plus an improved super-resolution algorithm will result in an output super-resolved image, in comparison with initial input. The proposed algorithm which incorporates less erroneous frames in the reconstruction process has been applied on the real-world camera outputs. Visual evaluation, the Q-Metric and CPBD factors show that the performance of our algorithm is better than the other methods.

Beside the various advantages of microgrids, continuous power generation impossibility in islanding mode threats the security of electrification of distribution network sensitive loads under emergencies. Solution introduced in this paper to provide passive defense of next generation of distribution networks in emergency situations is construction of distribution networks formed using microgrids connection in which the microgrids use each other power capacity when the power supply from the utility grid is not possible. A modular bidirectional DC-DC converter for connection of a DC microgrid to a DC distribution network is proposed which provides the bidirectional power transfer. Operation principle of the proposed converter is verified using experimental measurement, and proposed power management strategy for microgrid, connected to the distribution network, is investigated using PSCAD/EMTDC software. Analysis results show that connection of microgrids together increases the security of provision of electric power for microgrid loads under emergencies, which is frequently along with microgrids islanding mode.

In recent years, compared with stream ciphers more attention has been to block ciphers because of their proved security and wide application. Design of most block ciphers are based on substitution-permutation network (SPN) or Fiestel structure. Although Fiestel structures compared with SPN has many benefits, but since they have less active S-boxes in round function, it has a security weakness. In this paper, we introduce two new methods for designing 192-bit block cipher algorithms that use Switching Structure and Recursive Diffusion Layers to increase active S-boxes. The first method is based on switching structure and 3×3 multiple Recursive Diffusion Layers and the second method used switching structure and 2×2 multiple Recursive Diffusion Layers. Security of tow structures using linear programming offered analysed with linear programming and evaluated the results show of resistance to linear and differential cryptoanalysis. Also, since the Recursive Diffusion Layers are more efficient than MDS matrices in software and hardware, thus designed algorithms with these methods have high performance in various platforms.