masoud hoseinzadeh

The main purpose of this article is to use metasurfaces to make objects invisible. The process is that, after examining how to analyze the electromagnetic plan metasurface of the plate, a method for the analysis of cylindrical metasurfaces is presented. Then, inspired by the modeling of plan metasurfaces, a method based on the physical characterization of cylindrical metasurfaces in order to model and extract their tensor parameters is expressed. The methods presented in this paper for analyzing, modeling and extracting the parameters of cylindrical metasurfaces can be implemented for any desired type of linear metasurfaces in a wide frequency range consisting of radio and microwave waves to light waves. In the next step, the proposed formulation is used to reduce the scattering of electromagnetic waves from objects or so-called invisibility. The proposed method for invisibility makes it possible to provide different configurations of metasurfaces to achieve any type of invisibility according to the limitations of practical implementation. In addition, the formulation is effective in providing a physical understanding and description of invisibility. To test the results, the formulation of this paper was applied to a designed metasurface sample. Finally, with the help of full-wave simulations, the metasurface tensor parameters are extracted and the desired invisibility is realized.

Polymer nanocomposites have high strength, low weight, thermal stability, electrical conductivity, and high chemical resistance. In this paper, graphene oxide nanoparticles are synthesized using the modified Hammers method and then to improve the thermal properties of the epoxy coating, prevent the accumulation of nanoparticles, and their proper distribution on the epoxy surface by triethoxysilane (3-aminopropyl) (APTES) Have become functional. The innovation of this paper is the synthesis of graphene oxide nanoparticles in an epoxy resin substrate which, in addition to investigating the microwave absorption properties, can also increase the thermal resistance. The results of the thermal analysis also show that the residual materials at 500 ° C for graphene oxide, GO and epoxy are 3.7, 62.4, and 8.21 percent, respectively. Due to the fact that the thickness of the sample has increased, when graphene oxide nanoparticles with 10% by weight are used, the losses at the frequency of 9.5 GHz reach their maximum value - 57 dB. Accordingly, because the number of casualties in this analysis was high, it is a good option to put the cover on a drone. The results of UAV modeling show that coatings containing graphene oxide nanoparticles at the highest wattage (10 wt%) can reduce the radar cross-section from -15 to -25 dB.

Today, knowledge is a competitive source and military power for the defense industry and one of the most important needs of defensive organizations to maintain national security in the country and defend borders is to have a Knowledge Management (KM) performance measurement model. The purpose of this study is to provide a causal model for measuring KM performance in one of the defensive organizations. Based on an in-depth review of previous studies and adjustment of defensive experts' opinions, indicators related to measuring the KM performance were extracted, and then, the constructions of the proposed model were determined using exploratory factor analysis and confirmatory factor analysis techniques. Finally, the causal relationships of the research model constructs were investigated using the structural equation modeling technique. The findings revealed that the four main criteria were identified and verified, namely "knowledge quality", "knowledge utility", "knowledge innovation" and "defensive results". Causal relationships between model criteria are also significant. This study could develop literature on KM performance measurement in defensive organizations. The obtained results could be utilized by policymakers and senior managers of defensive organizations to evaluate KM performance and improve the productivity of defensive projects.