فهرست مطالب

  • سال نهم شماره 33 (Autumn-Winter 2018)
  • تاریخ انتشار: 1398/06/04
  • تعداد عناوین: 7
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  • Mahdi Omrani*, Masoud Shafiee, Siavash Khorsandi Pages 1-8
    Cyber ​​threats have been extraordinary increased in recent years. Cyber ​​attackers, including government agencies or hackers, have made significant advances in the use of various tools for attacking target systems in some countries particularly on Islamic republic of Iran. The complexity of cyber threats and the devastating effects of them on critical systems highlights necessity of cyber threats Foresight. This research can prepare the country for countering cyber threats based on existing and potential attack Vectors. First of all, 18 major cyber threats drivers base on attack Vectors through reviewing resources and interviewing with seven experts were identified. We use cross-impact analysis Future studies method to indicate main drivers of future cyber threats such as social engineering, Denial of service, ransomwares, spoofing and fraud and non-state actors. Mic Mac software will be used for this step. Finally, future scenarios for cyber threats were identified by using scenario-based approach. Scenario Wizard software will be used. The results of the research include two strong scenarios and 18 possible scenarios, based on the strongest scenario, ransomware, spoofing, fraud, social engineering and Denial of service are the most likely cyber threats by non-state actors through in a limited level
    Keywords: Foresight, cyber threats, attack Vector, cross-impact analysis, senario
  • Shima Tajeddini*, Habibollah Danyali, Mohammad Sadegh Helfroush, Yaghoub Fatemi Pages 9-14
    Alzheimer’s disease (AD) is a progressive and irreversible disease which gradually makes patients unable to do their daily routines. Although the present treatments can not cure the disease completely, its early detection can reduce symptoms and enhance the patients’ life quality. In the current literature, using the grey matter (GM) tissue which is known as an appropriate biomarker is highly common in AD diagnosis. However, two other brain tissues known as cerebrospinal fluid (CSF) and white matter (WM) seem to reveal beneficial information about the patients’ brain changes. The aim of the present study is to develop an automatic system for the early diagnosis of Alzheimer’s disease from structural MRI by simultaneously considering suitable features of all GM, CSF and WM tissues. A SVM-RBF classifier is trained and evaluated on the OASIS database to separate AD from healthy control (HC) subjects. The obtained results represent higher accuracy and sensitivity of the proposed algorithm in comparison with similar method.
    Keywords: Alzheimer’s disease, Biomarker, Classification, Feature extraction, Magnetic resonance imaging
  • Hamed Noroozy*, Shahrokh Jam Pages 15-19
    In this article an Archimedean spiral antenna is designed and analyzed that has good operation in broadband application. By analyzing this design, the effects that different parameters have on antenna operation will be studied and ways of optimization will be found.  Influences of cavity height and number of turns to obtain good matching and gain in a frequency interval of 4 to 18 GHz will be discussed. In addition, using cavity wall around the antenna, side lobes are decreased or deleted. By tapering the arms at feeding center, better matching will be attained. For making S11 bandwidth better, increasing the cavity height or reducing the number of turns can be used. Changing number of turns does not have a significant effect on the gain. To improve the antenna gain, the cavity height needs to be adjusted such that the reflected wave from cavity and radiated wave from spiral arms are constructing.
    Keywords: Archimedean spiral antenna, cavity, broadband antenna, gain, babinet principle
  • Masumeh Sharifi*, Najmeh Nozhat, Ehsan Zareian Pages 21-26
    Horn antennas can result in good impedance matching between the waveguide and free space due to the gradual increase in the aperture size. In this paper, a novel plasmonic sectoral horn nanoantenna based on using lens in the aperture is proposed. It is investigated that in addition to improvement of the directivity, the reflection coefficient is also reduced using the proper lens structure. The maximum directivity improvement is about 2 dBi compared to the structure without lens. Also, it is shown that the radiation pattern can be controlled by utilizing electro-optical material as the lens
    Keywords: Directivity, Electro-optic effect, Plasmonic Horn Nanoantenna, Reflection Coefficient
  • Samira Amiri*, Najmeh Nozhat Pages 27-33
    In this paper, the sensitivity of a plasmonic nanodipole antenna array for different materials of the metal nanodipole and substrate is calculated by changing the refractive index of the surrounding medium. The performance of our proposed array is studied at two wavelengths of 1310 and 1550 nm, the wavelengths of the second and third telecommunications windows. It is shown that by using the silver (Ag) nanodipole instead of the gold (Au) one, the bulk sensitivity of the nanostructure is improved. By replacing the substrate material from Si to SiO2, the sensitivity increases up to 1220 and 1150 nm/RIU at the wavelengths of 1310 and 1550 nm, respectively, that is very suitable for sensing applications. Moreover, the figure of merit (FoM) of the plasmonic sensor is calculated for both substrates and nanodipole materials. The maximum value of the FoM is obtained for the nanoantenna array with SiO2 substrate and Ag nanodipole and it is equal to 14.35. Furthermore, it is shown that by increasing the thickness of the nanodipole, the nanostructure sensitivity and FoM are enhanced
    Keywords: Figure of Merit (FoM), Nanoantenna, Optical Response, Sensitivity, Sensor
  • Hossein Ghavami*, Shahriar Shirvani Pages 35-44
    Minimizing the outage probability and maximizing throughput are two important aspects in device to device (D2D) communications, which are greatly related to each other. In this paper, first, the exact formulas of the outage probability for D2D communications underlaying or overlaying cellular network are derived which jointly experience Additive White Gaussian Noise (AWGN) and Rayleigh multipath fading. Then, simulation results of the exact formulas and previously respected approximate formulas are compared in MATLAB for both underlay and overlay scenarios. It is shown that the approximate formula in underlay scenario is a good estimate for exact one while approximate formula for overlaying scenario is a good approximation when the average distance between the transmit/receive nodes of D2D pair is less than half of the maximum distance between these nodes or variance of multipath fading is greater than 1.5. In addition, the probability density functions of Signal to Interference plus Noise Ratio (SINR) for underlay and overlay scenarios are found. Moreover, a new scenario is proposed which jointly considers overlay and underlay scenarios. Furthermore, exact and approximate formulas for outage probability and throughput of D2D users in the proposed scenario are derived. Finally, these formulas are compared to underlay and overlay scenarios in three special cases, low, moderate and high traffic loads
    Keywords: Device to Device Communications, Overlay, Underlay, Outage probability, Throughput
  • Hamed Niroomand*, Hossein Chabok, Samane Pakniyat Pages 45-48
    A design of a compact, easy to fabricate and applicable structure rectangular waveguide TM11 to TE10 mode converter is presented in this paper. The design procedure of the proposed structure can be divided into two parts in sequence. The beginning one is dedicated to the transformation from TM11 to TEM mode using a central conductor, while the second part is the transformation from TEM to TE10 mode using a dielectric loaded waveguide carrying out 180o phase shift. The proposed structure has the advantage of high efficiency of above 90 %, which are demonstrated in simulation results
    Keywords: Mode converter, S-band applications, TM11 to TE10 mode conveter, high power microwave (HPM) applications