Adaptive power-controlled MAC protocols for improved throughput in hardware-constrained cognitive radio networks

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many MAC protocols for cognitive radio networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption comes at the cost of extra hardware. In this paper, we address the problem of assigning channels to CR transmissions in single-hop and multi-hop CRNs, assuming one transceiver per CR. The primary goal of our design is to maximize the number of feasible concurrent CR transmissions, and conserve energy as a secondary objective, with respect to both spectrum assignment and transmission power subject to interference constraint and user rate demands. The problem is formulated under both binary-level and multi-level spectrum opportunity frameworks. Our formulation applies to any power-rate relationship. For single-hop CRNs, a centralized polynomial-time algorithm based on bipartite matching that computes the optimal channel assignment is developed. We then integrate this algorithm into distributed MAC protocols that preserve fairness. For multi-hop ad hoc CRNs, we propose a novel distributed MAC protocol (WFC-MAC) that attempts to maximize the CRN throughput, assuming single transceiver radios but with “dual-receive” capability. WFC-MAC uses a cooperative assignment that relies only on information provided by the two communicating users. The main novelty in WFC-MAC lies in requiring no active coordination with licensed users and exploiting the dual-receive capability of radios, thus alleviating various channel access problems that are common to multi-channel designs. We conduct theoretical analysis of our MAC protocols, and study their performance via simulations. The results indicate that compared with CSMA/CA variants, our protocols significantly decrease the blocking rate of CR transmissions, and hence improve network throughput.     

Optical and structural properties of (PANI-CSA-PMMA)/NiNPs nanocomposites thin films for organic optical filters

Synthesized nanocomposite of protonated polyaniline with camphorsulfonic acid (PANI-CSA) hosted in poly(methyl methacrylate) (PMMA) and incorporated with nickel nanoparticles (NiNPs) were coated as thin films on activated fused silica substrates using oxygen-plasma and spin coating techniques. Weight percent ratios of 0, 10, 20, 30, 60, and 90% of NiNPs with respect to PANI-CSA thin films have been studied in order to investigate the optical, structural, and morphological properties of (PANI-CSA-PMMA)/NiNPs by employing UV–Vis spectrometer, XRD, scanning electron microscopy (SEM), contact angle (CA) goniometry, impedance analyzer, and thermogravimetric analysis. Deduced refractive indices (n) from UV–Vis data were in the range from 1.5 up to 2.2. SEM micrographs show the typical crystalline structure of PANI was vanishing gradually with increasing the NiNPs content. Optical properties such as refractive index (n), extinction coefficient (k), absorption coefficient (α) as well as the band-gap energies (E_g) were mathematically deduced throughout the experimental transmittance and absorbance UV–Vis spectra. Calculated refractive indices (n) were in the range from 1.5 up to 2.2. Optical band-gap energies decrease in a monoexponential decay for samples up to 60% NiNPs/PANI-CSA, samples with 90% concentration had substantial drop in its value due to the NiNPs percolations. The incorporation with NiNPs leads to the development of a new morphological states (sheet-like heterostructure) which start to be obvious at 30%, at this concentration the CA was maxima (54°), at this concentration and the crystallite size are maximum and the CA was maximum (highest hydrophobicity). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48643.     

Hardware Architecture for Guessing Random Additive Noise Decoding Markov Order (GRAND-MO)

Journal of Signal Processing Systems - Communication channels with memory are often sensitive to burst noise, which drastically reduces the decoding performance of standard channel code decoders,...     

Using the aeromagnetic data for mapping the basement depth and contact locations,at southern part of Tihamah region,western Yemen

The present study aims to produce an excellent picture for the basement depth and contact locations, deduced from the available aeromagnetic data. The total intensity aeromagnetic map was first corrected by the application of the reduction to the magnetic pole (for low latitude areas) technique. On the other hand, this map shows different anomalies of varying frequencies and amplitudes that reveal various causative sources, as well as varying compositions and depths. So, the fast Fourier transform is applied on the RTP map to show the regional and residual sources and their depths, using the radial averaged power spectrum which divided into three segments, according to the slope,: the maximum depth is 12,500 m that probably reflect the crustal thickness at this place, depths of deep sources which reflect the maximum depth to the basement complex is found to be 10,388 m and the shallow sources and noise (near-surface geological structures), its depth will be 2410 m. This slope probably represents the minimum depth to the basement, especially at the eastern part of the study area (along the great escarpment). At the western part, the basement will be deeper than the eastern part. Different edge detection processes, for example, tilt angle derivative (TDR) and its total horizontal derivative (HD_TDR) as well as 3D-Euler deconvolution; can determine the edges of these sources. These techniques were carried out on the aeromagnetic data of Tihamah region (the study area). The estimated Euler solutions were plotted on the tilt angle derivative map. An excellent correlation was noticed between these techniques indicating that both of them can be attributed in delineating the general structural framework of the area. These techniques indicated that the southern part of Tihamah region was highly affected by Red Sea–Gulf of Aden rift system, that represent two legs of Afar Triple Junction. Moreover that, two depth methods were applied, analytic signal (AS) and source parameter imaging (SPI). They reflected similar results for estimating the basement depths. From both of them the depth ranges from 2050 to 10,885 m. On the other hand, all the methods used in this study gave a similar results to the depth of the basement rocks, ranging in depth between 2250and 10,400 m.     

Recharge estimation in semi-arid karst catchments: Central West Bank,Palestine

Grundwasser - Knowledge of groundwater recharge constitutes a valuable tool for sustainable management in karst systems. In this respect, a quantitative evaluation of groundwater...     

Use of dolomite catalyst in biodiesel production via transesterification of waste cooking oil in oscillatory baffled reactor

Biodiesel has recently gained popularity due to its environmental issues and the fact that it is generated from renewable resources. However, the cost of the synthesis of biodiesel is the major impediment to commercialization. The utilization of leftover cooking oils as raw material, the adaptation of a continuous transesterification process, and the use of cheap catalysts are the major possibilities for investigating the cost of biodiesel. In this work, a dolomite catalyst was prepared from natural dolomite rocks and used for the evaluation of continuous transesterification of biodiesel from oleic acid as a model compound of waste cooking oil (WCO). The dolomite catalyst was prepared by activation under vacuum at a surface area of 34.5 m²/g. The characterization tests showed good thermal stability of the catalyst and evolution of the CaO and MgO compounds at high concentrations. A kinetic study was conducted to obtain kinetic parameters of catalytic transesterification of the WCO. The kinetic experiments were carried out at 298–333 K, and residence time up to 80 min. The results presented that the catalytic transesterification is the first-order reaction, and the activation energy was 43 kJ/mol. The oscillatory baffled reactor (OBR) was used to evaluate the dolomite catalyst for the continuous production of biodiesel via transesterification. The evaluation study was conducted at a methanol: oil mole ratio of 6:1 and the effect of different operation variables on oleic acid conversion to biodiesel was studied. These variables were temperature (323, 333, and 343 K), residence times (5–40 min), the amplitude of oscillation (2–8 mm), and frequency of oscillation (1, 2, 3, 4, and 4.3 Hz). The results showed an outstanding performance and stable activity of the dolomite catalyst as a conversion of 96% was obtained at 333 K, 4.3 Hz, 8 mm amplitude, and 40 min residence time.     

Properties of carbon nanotube-polymer composites aligned in a magnetic field

The goal of this study was to probe the effect of orientation and alignment of carbon nanotubes (CNTs) embedded in an epoxy polymer matrix under a magnetic field on the mechanical properties of the resulting nanocomposite. We showed that the changes in the mechanical properties of the nanocomposites, i.e. the glass transition temperature, Young’s modulus and elastic and viscous moduli, as a function of the magnetic field strengths used to align the carbon nanotubes, are dependent on the epoxy system used. Moreover, we showed that when CNT alignment actually occurs at high magnetic fields, the properties of the resulting composites are superior to those that were not exposed to a magnetic field.