Journal Articles - Engineering Technology - 2021
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PublicationA Composite Method for Improving the Pulse Shape Discrimination Efficiency of a Scintillation Detector Using EJ-301 Liquid( 2021)This article presents a composite (COM) method to obtain the high-resolution pulse shape discrimination (PSD) for the neutron and gamma-ray pulses generated from scintillation detectors. The method, which is based on a selective combination of the digital charge integration (DCI) with the reference pulse method, aims to reduce the mixed radiation events in the low-energy range. An EJ-301 liquid scintillation detector together with a fast sampling analog-to-digital converter (ADC) is used to measure and digitize the pulses induced from the radioactive decays of 60 Co and 252 Cf, which are then analyzed by our COM method. The proposed method is evaluated using the figure of merit (FoM) and separation quality function F(u), and the results are compared with three known methods, namely the DCI, standard event fit (SEF), and artificial neural network (ANN) methods. We show that the average values of FoM and F(u) obtained within the COM method are about ten times higher than those obtained within the DCI and SEF in the whole energy range from 50 to 1000 keV electron equivalent (keVee). In particular, by using the COM method, the percentage of gamma events being confused as neutrons ranges from 0.32% to 8.80% when the energy is reduced from 400 to 50 keVee. This finding, which is significantly lower than those obtained by using the DCI and SEF, indicates that the proposed COM method should be considered as a leading method for producing a neutron/gamma PSD counter system with high resolution.
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PublicationRemoval of cationic dye using polyvinyl alcohol membrane functionalized by D-glucose and agar( 2021)The composite membranes of polyvinyl alcohol (PVA) functionalized by d-glucose and agar using the solution casting method were prepared for dye wastewater treatment. The composite membranes improved their hydrophobicity and thermal stability with respect to the parent PVA. The membranes possess good mechanical behaviors and have suitable pore sizes and pHpzc for the adsorption of cationic dyes as well as were sustainable in aqueous solution for more than 350 min. In which, the 6P2D2A membrane containing 60 % PVA, 20 % D-glucose and 20 % agar can adsorb cationic dye (methylene blue) at the maximum adsorption capacity of 29 mg/g for 120 min, whereas negligible adsorption for anionic dye such as Congo red. The high and selective adsorption capacity of the composite membranes makes them promising candidates for further filtration and separation of dye molecules. Also, the adsorption data well fitted with the nonlinear pseudo-first-order kinetic and Langmuir isotherm model.
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PublicationImproving Spectrum Efficiency in CR-NOMA over Rician Fading Channel Under Imperfection CSI( 2021)We present a downlink secondary network over Rician fading model since cognitive radio (CR) based non-orthogonal multiple access (NOMA) is adopted. Due to interference constraint, performance analysis of secondary destinations has further parameter to adjust performance as needed. We derive the closed-form expressions of outage probability for the case of two users in a group. Especially, we need to consider how system performance could be better in the case of imperfect channel state information. Then, we find main system parameters such as power allocation factor, condition of wireless channels as controlling factors of outage probabilities of two destinations. We perform Monte Carlo simulations to check the derived analytical expressions.
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PublicationSecrecy Outage Probability of Reconfigurable Intelligent Surface-Aided Cooperative Underlay Cognitive Radio Network Communications( 2021)With the introduction of wireless communications in a diverse range of security-sensitive scenarios such as healthcare, Smart Cities, internet-of-things (IoT) infrastructure, nuclear power plants, so forth, it has become necessary to protect the wireless network against malicious eavesdroppers via physical layer security (PLS). We analyze and study the impact of an eavesdropper located in an underlay cooperative cognitive radio network (CRN). A reconfigurable intelligent surface is used to improve the secrecy outage probability of the proposed system. CRs resolve spectrum scarcity by enabling spectrum sharing. On the other hand, RIS is a planar surface device equipped with signal enhancing reflecting elements that enhance signals at desired users and suppress signal power at undesired eavesdroppers in PLS networks. Therefore, the integration of RIS in cooperative underlay CR networks can enable secure wireless communications. To this end, we derive closed-form secrecy outage probability (SOP) expressions for a network that consists of a primary destination, secondary source, secondary user and a passive eavesdropper. The obtained equations are verified via simulation.
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PublicationOn The Performance of NOMA with Bi-directional in Weibull-Channel( 2021)Fading is considered to be one of the major issues in wireless communications. The non-Orthogonal Multiple Access (NOMA) technique proved to be efficient enough to overcome the fading issues if utilized efficiently. Since the signals transmitted in NOMA are superimposed, with the help of Channel State Information (CSI), the Successive Interference Cancellation (SIC) technique is applied to separate each user's signal. A lot of researches have been going on to study the performance of the NOMA system in various fading channels such as Nakagami-m channel distribution, Rayleigh channel distribution, Rician fading channel distribution, etc. Very few studies were conducted on Weibull-channel distribution applied in the NOMA network. This letter studies performance of the Weibull-channel fading distribution applied in the NOMA network in presence of two users and the presence of a bi-directional communication link between the devices. The analytical expressions were obtained to study the performance efficiency of the system and extensive simulations were generated comparing the performance in various parameters.