فصلنامه پدافند غیرعامل
سال دهم شماره 2 (پیاپی 38، تابستان 1398)

Progressive collapse begins by removing the local bearing capacity of a small part of the structures and causes structural failures which are not directly affected by the initial local event. In this research, the behavior of 3 and 6-story moment resisiting structures with tree column bending connections and span length to story height ratios (L/H) of 1.0, 1.5 and 2.0 were investigated under the effects of progressive collapse. In comparison between nonlinear static and dynamic analysis in terms of performance, the structure has almost the same response in two analysis. The deformations are slightly higher in nonlinear static analysis due to the fact that the dynamic load factor is more than actual in static nonlinear analysis. The maximum deformation occurs at the corner scenarios, which is higher if it is located in the middle story scenarios. Structures with more stories show better performance against progressive collapse, in other words, more structural elements in removed column connection area and upper stories means the structure has more alternate paths to carry and transfer the extra load. Therefore the number of critical members will decrease. Increasing the L/H ratio raises tensions and deformations in removed column connection zone. Three-story structures with L/H ratio of 1.0 are throughtly resistant to progressive collapse.and their resistance decreases by increasing L/H ratio. Six-story structures with L/H ratio of 2.0 are relatively resistant, because they have more structural members to carry extra load although their L/H ratio is relatively high.

International reports and statistics reveal that power grids have been one of the main targets for terrorist groups in recent years. Power grid has a vital role in all countries and, the functionality of all infrastructures depends on the performance of this network. In a country, the economy and the electric industry are highly interdependent and, consequently, the malfunction of the power grid results in a huge economic loss for that country. As a result, various models have been proposed by researchers, in an attempt to answer the question that how the available defensive resources should be optimally allocated to alleviate the negative consequences of intentional attacks. Power grid planner’s knowledge of these models can be helpful in selecting the best defense strategy for defending the power grid against intentional attacks. To the best of our knowledge, no review has been conducted on the proposed methods so far. Hence, in this paper, a comprehensive review of the most important models is conducted and a proper classification is provided. Then, the models belonging to each class are analyzed in detail, focusing on their flaws and merits.

Kernel rootkits have posed serious security threats due to their stealthy manner. To hide their presence and activities, many rootkits hijack control flows by modifying control data or hooks in the kernel space function pointers, especially those dynamically allocated from heaps and memory pools. These areas of kernel memory are currently not monitored by kernel integrity checkers. On the other hand, traditional host-based detection tools are executed inside the host they are protecting, therefore, since these tools are executed within the kernel, they could be easily detected by the rootkits. To solve this problem, current rootkit detection tools deploy virtual machine introspection technique that monitors the state of running virtual machine at hypervisor level, without rootkits interposition. The goal of this thesis is to present an approach based on virtual machine introspection, to detect rootkits which hide themselves and their associated malwares in the main memory using system control flow modification. The proposed approach monitors the integrity of windows kernel function pointers that are potentially prone to malicious exploits, based entirely on virtual machine introspection. This approach is evaluated with a set of rootkits which use advanced hooking techniques and it is shown that it detects all of the stealth techniques utilized

Nowadays, the close confrontation between structure and architecture has led to the invention of newly structural systems that are responsive to structural and architectural needs. In recent years, the diagrid structural system has attracted the attention of many architects and engineers due to the structural efficiency and aesthetic potential provided by its unique geometric configuration. In this study, the features of the structure and the architecture of the diagrid system are discussed. Also, with a description of the studies done in field of the diagrid system, the design challenges and optimal design of the geometric configuration of the structural system are fully examined. This system has more stiffness and strength, and less lateral displacement compared to other conventional systems. Other advantages include beautiful appearance, flexibility in architectural designs, possibility of creating freeform, twisted and irregular forms of buildings and building material reduction. According to the results of this study it can be admitted that the diagrid system is one of the most efficient systems for constructing high-rise buildings.

In passive defense projects, retrofitting of masonry walls has especial importance. One of the commonly used methods for seismic retrofitting of the walls is the implementation of a reinforced shotcrete layer. The behavior of walls strengthened with shotcrete against earthquakes have been studied by many researchers. However, the behavior of the walls against the explosion has received less attention and the effect of the mesh specification and the thickness of the shotcrete against this type of loading has not been investigated. In this research, the damage index is investigated for 700kg TNT explosion located at distances of 3,9 and 15 m from a masonry wall. In steel mesh, when the distance between the bars is 10 and 15 cm, and shotcrete layer thickness of 5, 10 and 15 cm damage index investigation is performed. Finally, 18 different models of steel mesh and thickness of shotcrete are introduced. With shotcrete strengthening, the wall failure index and the maximum displacement of the wall center is decreased. In all models, due to the closeness of the explosion to the wall, the wall was eventually destroyed and the effect of the reinforcement spacings on reducing the wall fracture was negligible. In contrast, the thickness of the wall has a greater role in reducing the tensile damage index of the wall.

The presence of an active population in each region will bring security and prosperity to the region forever. Creating attractive job opportunities, in proportion to the geography and climate of the area, is the key to maintaining the desired population coverage. In this regard, by stating the importance of developing the population of the southern shores of the country in national security, this study presents some solutions with the general models of industrial clusters and, by examining the upstream documents of the system in this area, proposes the establishment and management of continuous operation of three industrial clusters of fisheries, tourism, and date production in the country's southern provinces. Further, based on recent developments in building multipurpose ports in the country as a basement of the fishery activities, more discussion about the existing data has been presented. The results of these analyses indicate that, if the infrastructure and cluster supply chain complete the fishing industry, not only sustainable employment will be created on the southern coast of the country, but national security in these areas will be ensured through the expansion of sailor satisfaction and reverse migration.

In recent years with the advancement of military technology, societies have become decadent and observation of the ethical principles has declined; different countries attacking each other. One of the most important defensive strategies that have been taken into account by many developed countries, is using passive defense principles for the design of hidden systems according to the patterns of deception and camouflage. The built-in camouflage, has significant advantages compared to the additive camouflage, and it is considered in the original layout when new systems are being designed. This camouflage is a component of system composition and there is no need for personnel effort to activate it. The main objective of this research is to present new patterns for design of hidden buildings and development of resistant structures by the passive method as a defensive strategy. Another goal is to increase the possibility of continuity of their activity in the face of military and terrorist attacks.

Accurate and rapid diagnosis of biological threats has an important role in reducing vulnerability, sustaining essential activities, promoting national sustainability and facilitating crisis management in confronting these threats. The diagnostic systems of biological threats will lead to effectiveness in the passive biological defense. Currently, in the field of rapid and accurate detection of biological agents, various systems have been designed and constructed which are descriptive-analytic and based on functional characteristics, the most important ones of which have been introduced. By studying the approach of different countries, molecular diagnostic methods of biological agents due to high accuracy and speed have been considered and focused upon. The results of this research show that among various diagnostic systems of biological agents, high accuracy and high speed molecular diagnostic methods with field/operational applications, have high priority in the development and acquisition of biological threat detection technologies that can play an effective role in passive defense.