Advanced Defense Science and Technology
Year:2017 | Volume:7 | Issue:4|Papers Count:9

In this work, a chemiresistor gas sensor based on chemically reduced graphene oxide (CRGO) for selective detection of dimethyl methyl phosphonate (DMMP) as a nerve agent simulant was developed. The reduction of graphene oxide was performed by various reducing agents such as glucose, ascorbic acid, hydrazine hydrate and p-phenylenediamine (PPD). The efficient dispersion of CRGOs in distilled water were drop-cast onto an interdigitated electrode. Also tetrafluorohydroquinone (TFQ) was used as a second coating layer for improving sensor selectivity and sensitivity. LCR-Meter device is used for measurement of resistance changes. The sensor showed a linear dynamic range of 2-4.5 mg/L with a detection limit 0.3 mg/L for DMMP determination. Also the RSD to evaluate the repeatability of sensor for 4 replicate measurements was 1%.

Estimating the possibility of ground targets monitoring by imaging satellites is of the most challenging concerns in passive defense. In this research, two-line elements (TLE) data and SGP4 method which considers orbital perturbations have been used for modelling the orbits of low-altitude satellites in a specific period of time. The ability of SPG4 model for ground targets monitoring has been evaluated by using TLE data for estimating the accuracy of satellites’ position prediction in the next days. The ability of SPG4 for ground targets monitoring is appraised as well. Furthermore, a method has been proposed for estimating the possibility of ground targets monitoring based on based on the view geometry of optical imagery satellites in ordinary and critical situations and in-polygon algorithm. The proposed method has been presented as a MATLAB toolbox. For illustrating the applications of this toolbox, an investigation case study for three satellites EROS B, IKONOS, and SPOT 5 has been carried out as a case study, and then the results had been analyzed by using parameters such as range, angle of elevation and azimuth angles of target point from satellites.

The purpose of this paper is to present an index for evaluation of power network security after terrorist attacks against the network facilities using fuzzy set theory. In order to achieve this goal, a method based on probability and possibility theory is used. In the first step, by using Bayesian network which is a method based on probability theory, the probability of the attack as well as the risk value caused by terrorist activities against the power network facilities was calculated and the network facilities were ranked according to the level of the risk. In the second step, by employing fuzzy load flow and finding the fuzzy parameters related to network performance, the impact of the loss of each component ranked in the first step on power network was investigated. Finally, having calculated the risk value caused by terrorist attacks against the network facilities, an index was provided for evaluating power network security. Also, in order to validate the effectiveness of the proposed method, security index for a specific network was calculated.

In order to identify the best location for the construction of underground structures including equipment and installation of subsurface, magnetic anomalies in the southern part of Zanjan provinc by geomagnetic surveys were determined and investigated. Estimation of the magnetic anomalies was performed using standard Euler method. Then, to map upward constitution, three depth intervals were calculated for the anomaly. The result of qualitative interpretation represents a northwest-southeast trend of the anomaly on the study area. Anomaly modeling was performed using Vision software and the best locations for the construction of underground structures in accordance with the principles of magnetic hiding were proposed.

One of the important topics of passive defense is threats detection and waning alarm. One of the most widely used methods in detection field is video data investigation in order to identify unknown targets and warning alarm. In order to evaluate a fast and high-precision technique, video summarization is presented. Also, during the past years, creation of digital videos has caused exponential growth of video content. To increase the high volume of video usability, a lot of researches have been done and video summarization has been proposed to quick view of large video collection and quick understanding of the content of video data. In the video summarization, pictures are selected as a representative of each scene to obtain a visual overview of whole video. Recently, new methods using sparse formulation are suggested for video summarization being more effective in video data summarization than other methods. In this paper, video summarization is presented as a sparse dictionary selection problem. For this purpose, using a new method based on sparse coding, have been able to improve video data summarization compared to other video summarization methods based on sparse or other coding. Finally, the results for the ground truth data collection and State of the art methods, shows improvement our claim in the video summary on proposed method.

Risk assessment of infrastructures against threats, is one of the most important consideration in passive defence. Power system is an infrastructures on which other infrastructures are depended. This infrastructure is always regarded by terrorists as an attractive target. This paper presents a method for risk assessment of power system. It also presents a method for risk reduction of power system based on optimal allocation of defence budget for hardening facilities of power system. First, probability model of successful terrorist attack to power system’s facilities is presented and by combining of this probability and consequences of attack, risk of each scenario is achieved. Then, power system’s defence budget is optimally allocated for hardening its facilities. In order to indicate the effectiveness of these methods, IEEE 24-bus reliability test system is tested. Results show how system’s risk is reduced by the allocation of defence budget for system protection.

In this paper, a smart antenna system to be used in moving platforms is proposed. The designed system detects intelligently direction of the other moving platform and communicates with it in a poin to point manner. Compared to omnidirectional transmission, poin to point communication with a high accuracy in the required direction increases the link security and signal to noise ratio (SNR) in the receiver system. The fabricated smart antenna system consists of six sectors, the performance of which is controlled by an intelligent control board. First, the primary moving platform sends a signal to all directions and the second moving platform decides about direction of primary platform, considering the strongest SNR among sectors. In the next stage, aligning operation is performed. Each sector of the proposed smart antenna supports two frequency bands of UHF and C and the implementd adaptive array type is beam-switched. Antenna elements in C and UHF-band are Patch and Rubber duck, respectively. The results show that using the proposed smart antenna in the communication link, increases the security up to 4.7 times.

One of the most important parts in the aircraft avionic system is the electrical power supply, requiring special design considerations. Thus, many international standards have been adopted to achieve the best performance and highest system reliability. In this paper, a multi-output DC/DC switching converter with new forward-fly back structure for using in the military avionic system is presented. The proposed converter can provide a main high power output and an auxiliary output for control unit. It is performed without adding extra transformer winding, or change of switching frequency and duty cycle. Moreover, demagnetizing tertiary winding will be removed. The suitable electromagnetic interference (EMI) filter, inrush current suppressor circuit, and output ripple filter are designed according to MIL-STD standards. The proposed converter has many advantages such as simplicity of design, high processing speed of control system, high power density and efficiency, low size and weight, low electromagnetic noise, and good reliability.