مجله علوم و فناوری های پدافند نوین
سال نهم شماره 2 (پیاپی 32، تابستان 1397)

The explosion occurrence is the most likely events that may occur during a fire incident. This paper studies on nonlinear response of steel column against an explosion during fire event by using dynamic explicit finite element scheme. In this study, the effect of temperature of steel surface at the moment of explosion and scaled distance parameter are investigated. The results show that increasing temperature to more than 400 °C may cause large displacements and ultimately led to collapse the column. It is shown that increasing the temperature of the instant explosion for more intense explosions is less effective than explosions with larger scaled distance (Z).

One of the most important characteristics of a good structural design is its economic and optimal design against applied loads. Nowadays, with the increase of terrorist attacks, the economic design of buildings against blast load is important. Thus in this study, the effects of design methods on the economic design of steel moment frames with different number of floors against blast loading is evaluated. The studied frames were modeled in SAP2000 and were analyzed using linear and nonlinear dynamic methods. To ensure the accuracy of simulation, the model was first evaluated by a validated numerical studies and reasonable agreement was observed between them. Each of the structural models has been analyzed and designed using load and resistance factor design method as well as performance-based design method. Results show that in the low-rise frames, the performance based design method leads to more economical design (10 to 42 % depending on the severity of the blast load and the number of floors) in comparison with the load and resistance factor design method; but by increasing the number of floors, the load and resistance factor methods is more economical than the performance based design method.

Progressive collapse is the collapse of all or a large part of a structure precipitated by damage or failure of a relatively small part of it. These efforts tended to focus on improving redundancy and alternate load paths, to ensure that loss of any single component would not lead to a general collapse. To avoid of progressive collapse in structures, some criteria have been considered by regulations that after elimination of a member, structure should have ability to bear applied loads and transfer them to other members using substitution paths. In this study, the effect reinforced concrete slab in performance of steel moment resisting frame in progressive collapse was investigated.in this research a part of roof with structural members and connections were modeled and effective parameters of slab to increase structure capacity and crack propagation path due to corner, lateral and middle column elimination, were evaluated. In modelling, the effects of rebar, concrete strength and slab thickness on strength in different cases of column elimination were investigated. Results showed that moment resisting frame with composite slab have more capacity to bear loads due to column elimination in comparison with frame without composite slab. Also, the rate of increasing strength depends on location of column in the plan.

Increasing rate of scattered productions in electrical energy resources has led to pay more attention in planning accuracy. For example, location, capacity and DG incorrect numbers, can increase the rate of losses and damages to the power grids. Diversity and contradiction in objective functions, the uncertainty of the usefulness or having problem with a proper procedure, are the issues that are discussed in new techniques for energy resources. In this paper, in order to increase the accuracy and processing speed, instead of the conventional single-objective algorithms such as genetic algorithm, particle swarm algorithm, ant colony algorithm and etc, a multi-objective optimization location and determination of DG capacities in the power systems has been discussed. The sample network with planning horizon for implementing and using non-dominant sorting genetic algorithm, has been modeled in Matpower toolbox in MATLAB. DG initial and operational planning costs with respect to the certain proposed time period has been considered. The results show that the proposed multi objective plan, lets us to apply various solutions. It also gives the independency from the grid and maximum yield by choosing less objective functions.

Proper design and operation of transmission lines, known as transmission expansion planning, is known as the only efficient tool for optimization and continuous transmission of electrical energy to neighbor countries, affording economic and security interests to Iran. In order to achieve this goal, different items such as maintaining power system stability after the development of lines, the adequacy of lines after the end of the year planning horizon, are important. Along with the operation of the transmission network constraints and economic objectives, one of the concerns of passive defence is the determination of appropriate candidates to apply it to solving the problem of transmission expansion planning. In this paper, using the line stability indexes such as FSVI and Lmn indexes which are based on the load flow analysis, relation between passive defence and the transmission expansion planning has been created. Using these criteria, candidate lines which are used as input in transmission expansion planning methods, are determined.

Today, with the spread of social networks, the opposition's efforts to chill out people from government (known as “soft war”) are increased. Therefore, dealing with this type of networks is important for military and security organizations. Graph clustering is one of the first attempts toward analyzing social networks which can appropriately be modeled by a content graph. In contrast, most of the existing graph clustering methods independently focused on one of the content or structural aspects of a graph. The aim of this paper (implemented as CS-Cluster algorithm) is to achieve well connected clusters while their nodes benefits from homogeneous attribute values (content). In the second step of our research, after an intensive search, no measure has found which could simultaneously consider content and structural features of clustering algorithms. So to be able to appropriately evaluate our algorithm, a new content-structural measure (so-called “CS-Measure”) is proposed. Our experimentation shows that the proposed clustering algorithm outperforms two other well-known content-structural clustering algorithms, using the new content-structural, average similarity, and Error link measure as well as the previous content and structural measures, And it also performed relatively well in density measure.

In recent years, Software Defined Networking (SDN) facilitates the most of management and configuration issues for network administrators. In SDN, data plane and control plane are separated from each other and the control plane is responsible for all management functionality issues. Although, this mechanism provides effective and centralized management, it introduces some security problems which might have adversary effect on the performance of network. Freeloading is one of the most important attacks in SDN, in which a malicious user can hiddenly use the network resources. This paper explains the freeloading attack in detail and proposes an effective countermeasure for mitigating the attack. Due to the some components of the proposed method is implemented in data plane; it has low overhead and high accuracy. Simulation results confirm that the proposed method can detect and prevent the freeloading attack effectively without adverse effects on the network performance.

Each channel of the phased array antenna intrinsically has the phase errors. This is because of the position and orientation error of antenna elements due to assembling tolerance or mechanical distortion, and the electric length error of each RF channel. These errors can decrease the antenna performance, for instance the gain reduction, sidelobe level enhancement, and inaccurate beam direction. In order to improve the performance of the antenna in the presence of phase errors, a phase correction method using Genetic Algorithm (GA) is proposed. By using the proposed method, the antenna overall radiation pattern is recovered close to ideal radiation pattern without error. By applying the simulation data to a large array of 32 40 elements at the frequency of S-band the effectiveness of the proposed method is verified.

In this paper, a combined method to detect buildings from satellite imagery is presented. This method is based on combining data obtained by the local feature vectors and decision-making by applying adaptive thresholding the estimated probability distribution function, is conducted. Local Features serve as observations and location of buildings are used as joint random variables in order to estimate the probability density function. Then the locations of buildings are determined by considering modes of estimated probability density function and extracted features. To evaluate the efficiency of proposed method some satellite imagery of northern Tehran is used. Satellites North of Tehran building images are used in order to evaluate our proposed method. Tested images have different spatial contrast and resolution. Furthermore, tested buildings contain variety of characteristics which allows us representing our simulation with sufficient diversity. Experimental results of 32 different images in Tehran have shown that proposed method can be detected existing buildings in satellite imagery with fewer errors and more accurately.

The high sensitivity and precision of the distribution optical fiber newfound sensors led to special attention to them and use them in the modern industry, and in particular applications such as monitoring of borders security and leakage of energy pipes, monitoring the safety of large urban structures, Railway lines and so on. The spatial resolution and sensing length are two basic characteristic parameters for researchers. It is obvious that in the military and industrial affairs, whatever the spatial resolution is better will be observed more safety and less damages. The highest obtained spatial resolution between the Brillouin scattering sensors is corresponds to Brillouin dynamic grating sensors which is less than 1 cm. In this sensors, grating was generated by two pump waves and was read by probe wave that senses the intruder. This spatial resolution is achieved using phase correlation technique. In this technique pump waves are modulated by a phase modulator PRBS that generated a periodic and random phase shift equal to 0 or π. Of course, the heavy signal processing and complicated mathematical equations are disadvantages of this technique. In this article, we simulate phase correlation technique using a straightforward matrix relations and calculated first, spatial resolution and then sensing length. finally, with this innovative technique is obtained 9 mm spatial resolution over a 295 m of sensing length and 14 mm spatial resolution over a 460 m of sensing length that is full matching with the results of phase correlation tecnique without having its complexities.

There are many methods for converting the beta particle energy to electrical energy. Conversion of the beta particle energy to the electrical energy using semiconductors, is one of the important methods that can be used in radioisotopic batteries. In this work, a photo-betavoltaic semiconductor battery has been designed and constructed. The battery produce electric energy by converting photon energy from the sun or kinetic energy of beta particles. Doping process of silicon to fabrication of the p-i-n diode has been investigated. Thus, diffusion of dopants in 1000°C, SEM analysis, calculation of doping concentration, calculation of the diffusion depth and electric resistance of the doped silicon have been investigated. The measured betavoltaic current was 50 pA for a 58 μCi 90Sr/90Y. The photo-betavoltaic battery has been simulated by Monte-Carlo MCNP5 code and 45.2 pA electric current has been obtained. A fairly good agreement was observed between experimental and numerical results. Also, this battery is responds to visible light, sensitivity of which is comparable with the sun cells.