Directional Relays for Multi-Hop Cooperative Cognitive Radio Networks

In this paper, we investigate power allocation and beamforming in a relay assisted cognitive radio (CR) network. Our objective is to maximize the performance of the CR network while limiting interference in the direction of the primary users (PUs). In order to achieve these goals, we first consider joint power allocation and beamforming for cognitive nodes in direct links. Then, we propose an optimal power allocation strategy for relay nodes in indirect transmissions. Unlike the conventional cooperative relaying networks, the applied relays are equipped with directional antennas to further reduce the interference to PUs and meet the CR network requirements. The proposed approach employs genetic algorithm (GA) to solve the optimization problems. Numerical simulation results illustrate the quality of service (QoS) satisfaction in both primary and secondary networks. These results also show that notable improvements are achieved in the system performance if the conventional omni-directional relays are replaced with directional ones

Optimizing the technique for replacement of unicellular algae with agricultural by-products in feeding Artemia urmiana and parthenogenetic Artemia

In order to assess the maximum replacement possibility of unicellular green algae with cheap food sources for feeding Artemia, two strains of Artemia urmiana and parthenogenetic Artemia were fed under laboratory condition using wheat bran, soybean meal and 50/50% mixed diet of wheat bran/soybean, each in 12 different concentrations together with different rations of Dunaliella salina for 15 days. The results were compared with those fed only on algae D. salina as control group. At the end of the experiment, control groups in each two strains (with 9.11mm growth and 86.25% survival in A. urmiana and 8.55mm growth and 85% survival in parthenogenetic Artemia) had almost the best condition. In A. urmiana treatments 95.8-88% replacement for algae of wheat bran, treatment 94% replacement for algae of soybean and treatments 97-94% replacement for algae of mixed wheat bran/ soybean showed no significant differences with control in both growth and survival. In parthenogenetic Artemia treatments 94-82% replacement for algae of wheat bran, treatments 91-88% replacement for algae of soybean and treatments 91-82% replacement for algae of mixed wheat bran/soybean showed no significant differences with their control in both growth and survival. According to the results, it seems that single-cell algae and their production requires exorbitant spending and personnel which can be replaced with easily affordable agricultural wastes, without need to specialized staff

Two Reliable Methods for Solving the Modified Improved Kadomtsev-Petviashvili Equation

In this paper, the tanh-coth method and the extended (G\u27/G)-expansion method are used to construct exact solutions of the nonlinear Modified Improved Kadomtsev-Petviashvili (MIKP) equation. These methods transform nonlinear partial differential equation to ordinary differential equation and can be applied to nonintegrable equation as well as integrable ones. It has been shown that the two methods are direct, effective and can be used for many other nonlinear evolution equations in mathematical physics

An Empirical Ultra Wideband Channel Model for Indoor Laboratory Environments

Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. In this paper, the results of some UWB time-domain propagation measurements performed in modern laboratory (Lab) environments are presented. The Labs are equipped with many electronic and measurement devices which make them different from other indoor locations like office and residential environments. The measurements have been performed for both line of sight (LOS) and non-LOS (NLOS) scenarios. The measurement results are used to investigate large-scale channel characteristics and temporal dispersion parameters. The clustering Saleh- Valenzuela (S-V) channel impulse response (CIR) parameters are investigated based on the measurement data. The small-scale amplitude fading statistics are also studied in the environment. Then, an empirical model is presented for UWB signal transmission in the Lab environment based on the obtained results

New spiro (thio) barbiturates based on cyclohexanone and bicyclo [3.1.1]heptan-6-one by nonconcerted [1+5] cycloaddition reaction and their conformational structures

Crossed-aldol condensation reaction of aromatic aldehydes with ketones such as; acetone and cyclohexanone leads to the efficient formation of cross conjugated α,β-unsaturated ketones in excellent yield. The intermolecular and then intramolecular Michael addition reaction of α,β-unsaturated ketones derived from acetone and cyclohexanone with (thio)barbituric acids lead to synthesis new type of 7,11-diaryl-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone and 2,4-diaryl-1'H-spiro[bicyclo[3.3.1]nonane-3,5'-pyrimidine]-2',4',6',9(3'H)-tetraone, respectively in good yield. Structure elucidation is carried out by 1H NMR, 13C NMR, FT-IR, UV-Visible, mass spectroscopy and X-ray crystallography techniques. A possible mechanism of the formation is discussed. The structural conformation also demonstrated by coupling constants derived from dihedral angles between vicinal and geminal protons. The 1H NMR spectra of NH protons of spiro compounds derived from barbituric acid show a broad singlet peak instead, these protons in the spiro compounds derived from thiobarbituric acid show two distinct peaks. KEY WORDS: Crossed-aldol condensation, Michael addition, [1+5] Cycloaddition, Barbituric acid, Conformation, Spiro barbiturate Bull. Chem. Soc. Ethiop. 2014, 28(3), 423-440.DOI: http://dx.doi.org/10.4314/bcse.v28i3.1

Exact Solutions of the Generalized Benjamin Equation and (3 + 1)- Dimensional Gkp Equation by the Extended Tanh Method

In this paper, the extended tanh method is used to construct exact solutions of the generalized Benjamin and (3 + 1)-dimensional gKP equation. This method is shown to be an efficient method for obtaining exact solutions of nonlinear partial differential equations. It can be applied to nonintegrable equations as well as to integrable ones

An insight into the bioelectrochemical photoreduction of CO2 to value-added chemicals

Goal of sustainable carbon neutral economy can be achieved by designing an efficient CO2 reduction system to generate biofuels, in particular, by mimicking the mechanism of natural photosynthesis using semiconducting nanomaterials interfaced with electroactive bacteria (EAB) in a photosynthetic microbial electrosynthesis (PMES) system. This review paper presents an overview of the recent advancements in the biohybrid photoanode and photocathode materials. We discuss the reaction mechanism observed at photoanode and photocathode to enhance our understanding on the solar driven MES. We extend the discussion by showcasing the potential activity of EABs toward high selectivity and production rates for desirable products by manipulating their genomic sequence. Additionally, the critical challenges associated in scaling up the PMES system including the strategies for diminution of reactive oxygen species, low solubility of CO2 in the typical electrolytes, low selectivity of product species are presented along with the suggestions of alternative strategies to achieve economically viable generation of (bio)commodities