مجله علوم و فناوری های پدافند نوین
سال نهم شماره 3 (پیاپی 33، پاییز 1397)

User localization is one of the cutting edge research tops over the world and is very essential for defense science. Localization helps military and security forces to identify and disrupt terrorist plans before committing an offence. This paper proposes an effective and practical localization method in wireless networks. Cellular networks provide measurements regarding the signal attenuations from serving and neighboring base stations for managing radio resources. These measurements can be obtained by using an interceptor during the given call in passive manner from each mobile station. In this paper, we propose a passive mobile location technique which uses an interceptor for gathering these measured information and the timing advance parameter. We show by triangulation that the proposed algorithm can outperforms the angle-of-arrival (AOA) technique without any need for using array antennas and LOS propagation environment.

The use of Loran system is a strong defense for navigation due to its immunity against jamming and ability to penetrate indoor locations. This system can be used as a navigation aid system especially in times of crisis and GPS disconnection. Continuous Wave Interference (CWI) is one of the most important noise sources that make errors in signal phase tracking. Consequently, undesirable errors are constructed in time of arrival (TOA) measurement and ultimately navigation precision is reduced dramatically. In this paper, a new method is proposed in order to eliminate the CWI in Loran navigation system using linear adaptive algorithm. The specific innovation of this study is analyzing of Loran signal and obtaining the required delay to adopt the appropriate inputs in the adaptive filter. The used adaptive filter is the most relevant one in practical applications. The greatest advantage of the proposed method is that it dose not require knowledge of interference frequencies and frequency distribution. The proposed system is automatically obtained and eliminates interference frequency at the input. The simulation results show that the proposed algorithm provides a tremendous improvement in the SIR input. After applying the proposed algorithm, ratio of output to input of SIR, depending on the amount of SIR at the entrance of 36 to 80 dB is improved. Each iteration of the algorithm requires multiplication operator is 3N (N number of adaptive filter weights), and without any restrictions implemented hardware and computational time.

The Commanders are valuable resources of a team, group, brigade, division, and corps. They can provide valuable creative ideas, solve hard problems and so determine and manage the war strategy to win the battle. Their knowledge is valuable resources that should not go away with their deaths. In this paper, an expert system is presented that collect the knowledge of this man and build their knowledgebase that based on physical, intellectual, emotional and inner (The Sixth Sense) biorhythm cycle to predicting the level of fighter’s readiness to perform a military mission. In the knowledgebase, the importance of each cycle is modeled on various missions. With insert, the fighter’s information to the expert system, inferential mechanisms that are designed hierarchically, on the on hands prioritize them based on biorhythm and on the other hand, according to the mission requirements in the knowledgebase, prioritize the warriors. By doing so, the mission entrusted to warriors with respect to the preparation of them thus will lead to increased efficiency in the use of human capital.

In various applications of data communications of air born and space born, local profile recognition of atmosphere is very important. In many regions, achieving this profile from local data is impossible. This research aims to calculate and retrieve the atmospheric profile in Tehran Mehrabad Synoptic Station, using satellite data of MODIS. Radio sound data were analyzed for two cold and warm seasons. The retrieved data were also analyzed for a cold and a warm month. The vertical temperature, pressure, and humidity profiles were retrieved from data in clear, cloudless atmospheric conditions during day and night, and they were compared with radio sound data in the geographical region of the station. The atmospheric profile was retrieved using a statistical regression and fast radiative transfer model as well as radio sound data for determining regression coefficient. The results indicate that the retrieved atmospheric profiles are in good agreement with radio sound data. Mean squared error for temperature at a pressure of 700 mbar was at most 2.8ºK to 3ºK, and water vapor mixing ratio was obtained to be 1.2 (g/kg) to 1.3 (g/kg).

In this research, evaluation on of textile mechanical properties was performed with using of fiber pull-out method. that used for detection of their internal intraction with concern of fiber role. One of main hypothesis in this research, using of textile as a composite that consist of filaments. In this research, textiles was used in two types, pure and impregnated to shear thickening fluid. This experiments was performed in 50,250 and 500 mm.min-1 rates and with transverse force tensile for the effect of velocity on coefficient of friction. Results show that the present of shear thickening fluid cause to significantly increasing of friction between fibers and filaments. Therefore fibers conflict together effectively and suppressed their mobility and movements. Thus neccesery energy was increased for pull-out of fibers.

The reliability assessment of structures under uncertainties in external loads including blast, gravity and lateral loads and also material properties change, is important to determine the reliable levels of structures. Therefore, the reliability analysis can be provided a suitable management from the reliable levels subjected to the increasing the loads and decreasing the resistance of structures. In this paper, three algorithms of first order reliability method (FORM) using steepest descent search direction are applied to evaluate the failure probabilities of structural steel problems which are designed by the Iranian National Building code. The FORM formula is modified based on a dynamic step size which is dynamically adjusted based on the merit functions between 0 and 1.5 named as modified Hasofer-Lind and Rackwitz-Fiessler (MHL-RF) method. The convergence performances for both robustness and efficiency of the gradient method, HL-RF and proposed MHL-RF were compared through four steel examples including a bar structure under tensile capacity, a multi-span beam under bending capacity, a connection under tension load and a column under axial force. The results illustrated that the all structural reliability methods-based steepest descent search direction are robustly converged, but the MHL-RF method is more efficient than the HL-RF and gradient method. The designed steel components by the Iranian National Building code where shown a good confidence levels with the reliability index in the range from 2.5 to 3.0.

In the present study, underground explosion and its iteraction with buried structures are modeled using Coupled Eulerian-Lagrangian Method (CEL). Modeling of explosive and its surrounding soil with Lagrangian approach is impossible due to large deformations and distortions which occure in soil. In order to develop a comprehensive model, the advantages of the Eulerian and Lagrangian approaches should be combined. The Eulerian approach is used for explosive and its surrounding medium to estimate near-field response such as dimensions of crater; and Lagrangian approach is used for far-field response of the blast such as pressure on buried structures. JWL equation of state is supposed for explosive behavior. Finally, the effect of different parameters of explosive (mass), soil (density, elastic modulus, internal friction angle, and cohesion) and buried structure (geometry and material) on the response of the medium are investigated.

The purpose of this study is the investigation of the behavior of ultra-high performance steel fiber reinforced concrete (UHPSFRC) under the low and high velocity impacts. The behavior of two types of concrete panels made of UHPSFRC and a type of conventional high strength concrete (HSC) under low velocity impact was investigated by the drop-weight tests. Experimental results, including required number of drops to initiate the crack and ultimate failure, crack pattern and the damage state for both types of concrete panel specimens are compared. Besides, numerical simulations using the LS-Dyna software package were implemented on both type concrete panels under high velocity impacts. The experimental test results proved the HSC specimens to be brittle and exhibit low impact strength by failure under the first impact incident. However, the UHPSFRC specimens with 2% fibers resulted in ductile behavior and could undergo at least ten consecutive drops. The numerical simulations revealed the identical specimens made of HSC and UHPSFRC under similar high velocity impact conditions resulted in different level of damage in panels. While the specimen composed of HSC experienced the penetration with full perforation at the impact location, the UHPSFRC specimens underwent penetration with no perforation under the impact load.

Nowadays, one of the most common methods for water transmission is through underground tunnels. Tunnels are in line with the fundamental principle of the passive defense for protection of water resources and are able to prevent any potential risks to water transmission lines. In this research, a numerical study has been employed to investigate the effects of surface explosion on the water transmission tunnels. Herein, by changing the distance of explosive materials as well as the thickness of concrete segments, response displacements and explosion effects on the concrete segments have been calculated. For this purpose, three concrete segments with the thicknesses of 0.2, 0.3 and 0.4 m were selected and subjected to the explosive materials located 0.5, 1 and 2 m away from them. The obtained results showed that the concrete segments with the thicknesses of 0.2 and 0.3 m experienced significant damage when subjected to 20 lb. explosive material at the distance of 0.5 m. It was found that burying the structures or embankments of the structures were among the best methods for damping the blast waves.

Investigating the possibility of underground structures detection is one of the complicated problems. In this paper, magnetic data have been used and both direct and inverse problems have been considered. In direct problem, with the assumption of the known size and position of the structure, magnetic response is modeled. Then, using the modeled signals, some points about the detectability of the structures are discussed. In inverse problem, position of the underground target is estimated based on the analytic signal and Euler deconvolution methods and 3D inversion of the magnetic data. Finally, both of the direct and inverse problems are implemented based on the simulated data and some suggestions are made to decrease the probability of detectability of the underground targets. The results show a concealed military structure with a susceptibility more than 0.05 SI and the depth of less than 200 m can be detected and located in a nonmagnetic host rocks using aeromagnetic survey with a resolution more than 60 m between lines. With increasing the magnetic susceptibility of structure, the possibility of detection will be increased; so that if the susceptibility exceeds 0.01 SI, the possibility of detection will be increased to depth of 400 m.

In this research a 3-storey metro station are selected. For assess the progressive collapse of these structures, the damaged walls should be modeled in software. The progressive collapse was assessed by nonlinear dynamic and static analysis. The alternative load path is the most important factor to the resistance, so the failure of the wall because of the high degree of freedom and existence of many shear walls, this structure wasn’t prone to progressive collapse. The explosion damages the metro, with the destruction of 30% of wall the tension ratio increase 3.9% and with the destruction of 60% of wall the tension ratio increase to 12.3% and with the total wall damage, the tension ratio increase to 16.4% .