Full-duplex overlay cognitive wireless powered communication network using RF energy harvesting

In this paper, a novel full-duplex overlay cognitive wireless powered communication network (FD-OCWPCN) is proposed where a full-duplex (FD) hybrid-access point (H-AP) supports the full access of all battery-free secondary users (SUs). The H-AP broadcasts wireless power to empower the nearby SUs in the downlink (DL) phase while decoding the information transmitted uplink (UL) phase by the SUs, simultaneously. To overcome the self-interference (SI) phenomenon in FD-OCWPCN, the problem of maximizing the system sum-throughput with optimal UL-DL transmission/reception time and H-AP’s transmit power allocation is considered. This problem is non-convex under perfect/imperfect SI cancelation (SIC), so we employ the active interference temperature control and the gradient projection techniques to effectively reduce it into a convex problem. Closed-form expressions for the perfect/imperfect SIC cases are also derived. To assess the performance of the FD-OCWPCN, a comparison with a half-duplex OCWPCN (HD-OCWPCN) is provided. The achievable average sum-throughput for different FD/HD-OCWPCN is compared in the context of the average and peak transmit power at the H-AP, the number of SUs, path loss exponent and fairness metric. The simulation results depict the superiority of the FD-OCWPCN over the HD-OCWPCN for the perfect SIC and the effective imperfect SIC.

     

Fabrication of superparamagnetic adsorbent based on layered double hydroxide as effective nanoadsorbent for removal of Sb (III) from water samples

In this study, the superparamagnetic adsorbent as Fe@Mg‐Al LDH was synthesised by different methods with two steps for the removal of heavy metal ions from water samples. An easy, practical, economical, and replicable method was introduced to remove water contaminants, including heavy ions from aquatic environments. Moreover, the structure of superparamagnetic adsorbent was investigated by various methods including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and vibrating sample magnetometer. For better separation, ethylenediaminetetraacetic acid ligand was used, forming a complex with antimony ions to create suitable conditions for the removal of these ions. Cadmium and antimony ions were studied by floatation in aqueous environments with this superparamagnetic adsorbent owing to effective factors such as pH, amount of superparamagnetic adsorbent, contact time, sample temperature, volume, and ligand concentration. The model of Freundlich, Langmuir, and Temkin isotherms was studied to qualitatively evaluate the adsorption of antimony ions by the superparamagnetic adsorbent. The value of loaded antimony metal ions with Fe@Mg‐Al LDH was resulted at 160.15 mg/g. The standard deviation value in this procedure was found at 7.92%. The desorption volume of antimony metal ions by the adsorbent was found to be 25 ml. The thermodynamic parameters as well as the effect of interfering ions were investigated by graphite furnace atomic absorption spectrometry.     

A new and applicable method to calculate mass and heat transfer coefficients and efficiency of industrial distillation columns containing structured packings

Most of the methods developed for efficiency estimation of distillation columns were based on the empirical mass transfer and hydraulic relations correlated to laboratory data. Therefore, these methods cannot estimate efficiency of industrial columns with sufficient accuracy. In this paper, a new and applicable method was developed for calculation of efficiency (and mass and heat transfer coefficients) of distillation columns containing structured packings. This method has potential advantages; e.g., it can calculate efficiency without using any empirical mass transfer and hydraulic correlations and models, and without the need to estimate the operational and hydraulic parameters of column. Therefore, it will be free of errors, limitations, and complexities of such empirical items. In addition, precision of the method does not decrease with increasing complexity of operating conditions and design parameters of column. The method can be used for efficiency calculation of any structured packing, including new ones, in distillation columns.     

Parallel‐series connected rectenna array using frequency selective surface (FSS) for power harvesting applications at 5.8 GHz

This article presents a frequency selective surface (FSS) and rectenna array in parallel‐series connection to harvest power of wireless power systems. To improve the basic antenna parameters, a frequency selective surface was mounted on the reverse side of the substrate. According to the results, the proposed method showed significant improvement in comparison to other methods in both single and rectenna array. Moreover, the conversion efficiency of the presented technique was increased to 76%. The output voltage of 4.5 and 9 V and the current of 60 and 120 mA were resulted for 5 and 10 rectenna units, respectively. The proposed arrays can be expanded to large scale integrated array without any significant degradation in conversion efficiency.     

Development of a Robust Carrier Synchronizer for High Dynamic and Low Signal to Noise Ratio Signals in GPS Receivers

Wireless Personal Communications - In this paper, a robust carrier recovery loop for high dynamic and weak signals in GPS receivers is proposed. To achieve optimal tracking performance at...     

Design,synthesis, and nanoengineered modification of spherical graphene surface by layered double hydroxide (LDH) for removal of As(III) from aqueous solutions

In this study, new nano spherical graphene modified with LDH (Layered Double Hydroxide) was prepared and used to remove As(III) ion from aqueous solutions. At first, graphene oxide was synthesized from graphite using a well-known Hammer method. The obtained graphene oxide solution was sprayed in octanol solution under different temperatures and sprayed speed as influenced variables. The structure and physical characterization of synthesized spherical graphene oxide were determined by various techniques, including FT-IR, N₂ adsorption–desorption, SEM, TEM, and EDX. In the next step, the hydrothermal method was applied to deposition LDH on the spherical graphene oxide. The synthesized spherical graphene modified by LDH was used to remove As(III) as a toxic heavy metal ion. The effect of influenced variables including pH, contact time, amount of sorbent, and type eluent studied and the optimum values were as 8, 30, 50, and HCl (0.5 mol·L^-1), respectively. After optimization, the studied sorbent was shown a high adsorption capacity (149.3 mg·g^-1). The adsorption mechanism and kinetic models exhibited good agreement with the Langmuir isotherm and pseudo-second-order trends, respectively. Besides, the synthesized product was tested for seven times without significant loss in its sorption efficiency.     

Development of an undergraduate structured laboratory to supportclassical and new base technology experiments in communications

This paper describes an effective method of teaching a communications laboratory course that supports classical as well as new base technology experiments to undergraduate electrical engineering students. Primarily, experiments dealing with the design of the basic building blocks of analog and digital communications systems are targeted, which provides an opportunity for the student to become familiar with various signal processing techniques applied in modern communications systems, to learn how to operate the communication laboratory test equipment, and to obtain exposure to some hardware/software design and implementation of these subsystems. The second level of experimentation involves a small system in which discrete or integrated devices are used to build small systems. Level three involves experimentation with a complete communications system, such as a fiber optics communications system or a simulated satellite link. Four sample experiments are described in some detail     

Dehydrogenation of isobutane over Sn/Pt/Na-ZSM-5 catalysts: The effect of SiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ratio,amount and distribution of Pt nanoparticles on the catalytic behavior

Sn/Pt/Na-ZSM-5 was used as catalyst for the dehydrogenation of isobutane, and the effect of SiO₂/Al₂O₃ ratio and the dispersion of Pt nanoparticles on the conversion and product selectivity were studied under atmospheric pressure at 848 K. The catalysts were characterized by various techniques such as H₂ chemisorption, TEM, SEM, EDX, XRD, FT-IR, TG/DTG, elemental analysis by XRF and ICP techniques. Higher dispersion of Pt nanoparticles in the catalyst with SiO₂/Al₂O₃ ratio of 40 resulted in higher selectivity for isobutene.     

Performance of a multi-slit packed bed microstructured reactor in the synthesis of methanol: Comparison with a laboratory fixed-bed reactor

The performance of a multi-slit Integrated Micro Packed Bed Reactor-Heat Exchanger (IMPBRHE) for methanol synthesis from synthesis gas over Cu/ZnO/support commercial catalyst was experimentally investigated from a reaction engineering perspective. Through establishment of a systematic comparison strategy, performance comparison with a laboratory scale tubular Fixed-Bed Reactor (FBR) with three different dilution ratios was made to evaluate the IMPBRHE. The productivity, thermal behavior, activity of body materials, pressure drop and residence time distribution (RTD) of the two reactor types were investigated. The IMPBRHE outperformed the undiluted FBR and gave CO conversions comparable to the diluted FBRs. The main difference is ascribed to superior heat exchange properties of the IMPBRHE, which can improve reactor performance for an exothermic reaction such as methanol synthesis. The results reveal advantages of the IMPBRHE for robust scale up.