مجله علوم و فناوری های پدافند نوین
سال سوم شماره 3 (پیاپی 9، پاییز 1391)

Passive target localization has many applications in electronic warfare and passive defense. TDOA is the most accurate method in target localization. Following this method، one of the receivers is assigned as reference receiver and time difference of arrival between other receivers and reference receiver is measured. The target location is estimated by processing of these TDOA. The CTLS is one of TDOA based algorithm that has high accuracy and needs suitable initialization. In this paper، multi reference CTLS algorithm is proposed. CTLS algorithm accuracy was improved when multi reference receiver are considered instead of one reference receiver. Simulation results show that the proposed algorithm in different SNR، keep its improvement just with little increase of time processing and better performance compared to CTLS algorithm has been obtained.

In this research a mathematical model for surface radar sites’ location and a combination methodology for its resolution are presented. Hence after expressing the related conceptions، the goals and radar sites location method، mathematical model for radar sites location is expressed. Then a two-step method for solving this problem is offered. At the first step، the criteria parameters for selecting radar sites’ location based on passive and active defense are identified، classified، scored and prioritized. Since these kinds of problems are NP-hard، simulated annealing algorithm for solving this new mathematical model has been used. In this method the total score for each candidate location determines the position priority for radar network. So all of the possible states for the radar network are survived by stimulated annealing algorithm. Finally، a radar sites’ location problem in the Persian Gulf beaches using presented simulated annealing algorithm with hypothesis data has been resolved.

A new and highly efficient architecture for elliptic curve scalar point multiplication is presented. To achieve the maximum architectural and timing improvements، the critical path of the Lopez-Dahab scalar point multiplication architecture has been reorganized and reordered such that logic structures are implemented in parallel and operations in the critical path are diverted to noncritical paths. The results show that with G= 41، the proposed design is able to compute GF (2163) elliptic curve scalar multiplication in 11. 92μs with the maximum achievable frequency of 251 MHz on Xilinx Virtex-4 (XC4VLX200)، where G is the digit size of the underlying digit-serial finite field multiplier. The results of synthesis show that in this implementation 19606 slices or 22% of the chip area is occupied.

Due to limitations of mobile Ad Hoc networks، adding service quality to routing protocols of these networks improves their effectiveness and results in attaining requirements of passive defence. The main characteristics of mobile Ad Hoc networks are continuous changes in network structure as well as independency of nodes to any central unit. In this paper، using bandwidth calculation rules of multi-cast protocols a new routing method (named QB-ODMRP) is suggested based on a basic protocol (ODMRP) in order to avoid increasing delivery time (decreasing network speed) while increasing speed of individual nodes. Simulations on 60 dynamic and static nodes using ‘Glomusium v 2. 03’ software in various service quality scenarios show that the suggested method can improve delivery rate as much as %25 and decrease end-to-end delay %30، resulting in improving service quality.

The purpose of this article، is to present a pattern for the interior layout and arrangement of port elements from a passive defense view point. To this end، firstly the internal sections of port including piers، warehouse، human force concentrations and vital installations are recognized. Thereafter، different types of threats related to potential natural accidents- terrorist and military attacks- jeopardizing the port are determined and appropriate measures are taken accordingly. These provisions are effected within a systematic layout planning (SLP) frame work. So that، at the first stage، regarding provisions، the significance and the degree of relation between different port segments are delineated. In the second stage، the relations between different activities are dealt. Then، the required and the available space regarding partial and moderate limitation are compared. In the subsequent step، the space relation diagram and the diagram of relation activities are considered. The fourth step deals with the alternative layout design and drawing conclusions from the relation activities diagram. Finally an evaluation of the new layout is presented.

Based on the IEEE standards، distributed generation (DG) resources should not be operated over the critical situations in the interconnection power grid، because of the network instability considerations. These standards are severe restrictions for passive defense implementation in the power systems. In this paper، a new algorithm for employment of the micro grids equipped with the Gas Turbine Synchronous Generators (GTSG) is proposed. In an islanded distributed network، consumption and generation in the micro grids have a vital role. In this paper، two different types of load shedding methods، namely، traditional and intelligent methods are simulated considering frequency and derivative of the frequency in the system. Furthermore، according to the load and generation situations، «load shedding» and «changing the mode of the GTSG governors» are used as two different tools to prepare a robust stability in the system. Load following service is another subject which is studied in this paper. The proposed model has been applied to the load profile of an actual system using DIgSILENT software. The results show that over the critical conditions، operation of the DGs in the islanded mode is possible and reliable.

Synthesis of biocompatible polymer nanofibers is valuable، due to their use as a cover for burns and as a replacement bandage because of their antimicrobial properties. In this study، electrospinning of chitosan and nanofibers production with antibacterial properties was investigated. Nanofibers with average size ranges between 50-150 nm and appropriate size distribution were synthesized by electrospun of chitosan/poly ethylene oxide polymer solution. The results showed that the chitosan/poly ethylene oxide polymer solution with a ratio of 90 to 10 nm is the optimized polymer solution for nanofiber preparation. Afterwards، the thyme honey with antibacterial properties was used as additives (with different percentages) in the polymer solution. The scanning electron microscopy (SEM) images were showed appropriate size distribution of about 70-120 nm for chitosan/poly ethylene oxide nanofibers with low percentages of honey، like solution of chitosan/poly ethylene oxide without the addition of honey. However، with increase of the amount of honey to chitosan polymer solution، the nodes were increased، but the uniformity of spray droplets on the aluminum screen was observed.

In this paper، the performance and sensitivity of the cylindrical electromagnetic cloak considering the effect of different simplified cloaks are investigated. The performance of simplified cloak is less than ideal cloak; however، it can be realized in practice with acceptable level of RCS reduction. The exact wave solution for different regions of cylindrical cloak is derived and validated with full-wave simulations results based on COMSOL Multiphysics. Numerical experiments of RCS are performed for frequency band from 10MHz to 3GHz. The results of simulation show more than 18dB RCS reduction for simplified cloak.

In this paper، dynamic response of the two most common retaining walls in geotechnical engineering practices (conventional gravity retaining walls and geosynthetic reinforced soil (GRS) walls) to blast loading are investigated and compared using FLAC 2D. After large number of numerical simulations، it was concluded that performance of the GRS walls is better than conventional gravity retaining walls. Also it is observed that deformation modes of these two types of walls are different. In all analysis، dominant mode of lateral deformation for the gravity types of walls (for both 5 and 10 m) was overturning mode combination with sliding at base of wall، whereas for GRS walls in addition to sliding at base، deformation modes are start from bulging at low blast intensity loading and tends to overturning mode with increasing blast loading intensity. Therefore location of the maximum lateral displacement of gravity walls is occurred at wall crown in all the analysis، whereas in GRS walls، location of the maximum lateral displacement start from middle of the wall height in bulging mode and shift to the surface of the wall with increasing blast loading because of overturning mode domination. Also، it is concluded that soil damping and distance from blast loading adversely affected blast induced deformation of the walls.