Advanced Defense Science and Technology
Year:2018 | Volume:8 | Issue:4 |Papers Count:10

Mobile ad hoc networks (MANETs) are suitable option in many cases due to its simplicity and speed of deployment. However, MANETs are vulnerable against various types of security threats because of their dynamic topology and absence of a fixed infrastructure. Especially, the wide employment of this network in military and commercial applications makes its security more important. In recent years, considerable efforts have been made to design secure and robust routing protocol, and many security schemes have been proposed to tackle these security issues. In this paper, we design a defense strategy against black hole attack over the AODV routing protocol. The proposed solution employs the fuzzy logic system to identify malicious nodes in the network. In this design, each node is assigned by a fuzzy value which measures its probability of being an attacker. Extensive simulation, performed in the ns-2 simulator, show that the proposed algorithms outperforms previous methods in terms of number of dropped pockets.

Sometimes, the reliability in decision of a classifier is more important than its recognition rate. Military and security applications are clear examples to show the importance of this measure. For example, the inability of an automatic targets recognition system to distinguish all types of military planes increases its error rate but the decision of this system for recognition of military targets should be accompanied with maximum reliability and never should be considered a civilian as a military target. This paper presents an ensemble classifier with high reliability by using multi-objective heuristic methods. Moreover, ensemble size and error rate have been minimized. Multi-Objective Particle Swarm Optimization Algorithm and Multi-Objective Inclined Planes Optimization Algorithm are the multi-objective heuristic methods which are used in this paper. The recent method is applied to design ensemble classifiers for the first time. Due to the ability of multi-objective heuristic methods in presentation of the Pareto front, it's possible to create various and user-defined conditions; conditions in which the importance of each factor (ensemble size, error rate and reliability) can be strengthened and weakened.

In this study, barium hexaferrite nano particles were synthesized with different size distribution via sol-gel combustion method under different pH of 7, 9 and 11. Phase behavior, morphology and magnetic properties of final product were investigated respectively using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Also electromagnetic parameters of synthesized samples were evaluated using vector network analyzer (VNA) in the X and Ku bands. The XRD results showed the formation of pure single phase of barium hexaferrite with average crystallite size of about 70 nm while pH value was 11. The SEM micrographs showed no significant influence of pH on the crystal morphology. However, at the higher the pH value, the particle size was lowered. According to VSM results, all magnetic parameters increase with pH. The maximum value of saturation magnetization and coercivity force were obtained as 55. 61emu/g and 2805 Oe respectively for the synthesized sample at pH 11. Also, this sample had maximum reflection loss of about-6. 7 dB and-9. 8 dB at matching frequency of 11. 6 GHz and 14. 6 GHz in X and ku bands respectively.

A light element such as polyethylene is one of the neutron moderators. Polyethylene pile can be used for calibration of neutron dosimeters and detectors. The polyethylene pile was designed as a source for slowing down the fast neutrons and used in technology centers. Dimensions of the pile are 240 cm in length, 200 cm in width and 220 cm in height. 241Am-Be neutron source with intensity of 1. 1×107 n/s was placed in center of the pile. Measurement channels are available at any point of the pile by removing the polyethylene blocks. Spatial distribution of thermal and fast neutron flux was measured using BF3 neutron detector and cadmium cover. In order to obtain maximum thermal neutron population, this pile was simulated with MCNPX-2. 7. 0 code, and the results were in good agreement with experimental results. The quality of thermal neutron field was characterized by the cadmium ratio. Using a NaI(Tl) detector, gamma rays due to neutron source was measured in different directions inside the pile.

In this article, the multi-wavelength traveling wave model with rate equations are utilized to simulate the ASE spectrum in ytterbium-doped gain media. By solving the rate equations in time domain and in 0. 9-1. 1 μ m region, the model shows how the fiber length and amplifier configuration can affect amplifier operation and change the peak gain or bandwidth. The effect of various parameters including ratio of core area over inner cladding area, doping profile, pump wavelength and pumping scheme on the ASE spectrum are investigated. For a given pump power, wavelength, core over cladding area ratio and fiber concentration, by increasing the YDF length from 10 to 400 cm, the dominant peak in ASE spectrum, shifts from 1055. 42 to 1074 nm. Meanwhile the FWHM of the observed spectra decreases from 48 nm to 33 nm. For a given fiber length and by a sufficient increase of the pumping wavelength, we can further decrease the ASE (fluorescence) bandwidth by about 15 nm. These new results are consistent with those obtained from our experiments. In conclusion, by adjusting the fiber length, the pumping scheme and the wavelength, one can either form a nearly broad, symmetric and smooth or a narrow high gain spectrum.

Today, the crisis and its consequences, is one of the main threatening factors in organizations, and to determine efficient and sustainable strategies, according to the terms of defense and attack, proper planning must be done. In this study, with the aim of improving reliability, first, modeling the optimal strategies to defend and attack in the stationary state is presented, provided that the attacker to deceive the defender will create a number of false attacks. In the static model, considering the probability of a successful attack, defender capability in identifying false attacks, reliability block diagram and game theory approach in finding the balance point, a nonlinear programming model is proposed to determine the amount of investment defend and attack. Then, according to the results of the static model, system dynamics and implications of evolutionary game theory, a new and dynamic approach to determine sustainability strategies of defense and attack is presented, that defender use two strategies based on actual or 90% of all adopted attacks and the attacker also use two strategies use or not to use false attacks. Finally, presented model is illustrated for an applied case and final findings are analyzed.

In most studies done in the field of design of structures against explosion, uncertainties in explosive loading are not directly considered. By considering these uncertainties and using reliability analysis, more accurate and reasonable estimation of structural safety and probability of failure can be reached. In this paper, using Mont-Carlo simulation method and considering uncertainties associated with blast loading, the probability of failure of steel columns under different blast loads is calculated. Then, the minimum required protective distance is determined to prevent significant damage of structure. The single degree of freedom and finite element simulation methods are utilized for structural analysis. Finally, safe protective distances are proposed as 4. 5, 9. 5, 12 and 14 meters for charge weights of 30, 200, 400 and 600 kg TNT, respectively.

Graphite bomb is a non-destructive weapon that is used for disturbing electrical power supply and blackouts. Cascading failures and blackouts are the most significant threats for power system security. A power system will be collapsed if the process of cascading failures proceeds by further line tripping. In this paper, a new method for Tehran power system islanding is proposed to encountering graphite attack and substation outage. Based on the proposed method, after the graphite bombs is released on electric substations, substation outage and islanding power system commands is occured. Thus, a new approach for identifying coherent groups of generators in power systems based on the correlation coefficients between rotor angle oscillations of generators is presented. The method uses a newly proposed clustering index based on the correlation coefficients of generators oscillations which is able to classify any number of generators into coherent groups. The proposed approach uses real time data of generators oscillations via PMUs, so it is able to easily take into account the effect of system detailed modeling. Simulation results, obtained using MATLAB and DIgSILENT software on the Tehran power system show that the proposed algorithm is efficient and have a well performance regarding voltage and transient stability when solving the controlled islanding problem.

One of the important research areas in protection of underground structures is evaluation of projectiles penetration depth in ground as a protective cover. The phenomenon of impact and projectile penetration is dependent on several factors, one of the most important of them is the effect of soil moisture. Therefore, this paper is aimed to study the GBU-28 penetration depth in sandy and clayey soils and the effect of groundwater level on penetration depth by means of AUTODYN software. The results have shown that soil moisture plays an important role in projectile penetration depth in different times of explosion. Generally, projectile penetration depth in clayey soil is more than sandy soil with same densities, but increasing rate of projectile penetration depth compared to dry soil in sandy soil is a little more than clayey soil.

Physical protection of critical installations is one of the most important methods for passive defense of infrastructures. Physical protection reduces the success probability of a physical or sabotage attack. In this article, an efficient model is presented to evaluate the physical protection of critical installations based on critical detection point concept. In this model there is no need to calculate the success probability of the attack for all adversary paths of that critical installation. Furthermore, the abilities and capabilities of the saboteurs are also considered in calculating the success probability of an attack against the critical installation. Calculation of the model and determination of the success probability of attack against the critical installation is implemented by Monte-Carlo method which avoid the complex deterministic calculation methods with complex conditional probabilities. The simulation of presented model is compared with other models and the results are tested.