Improving secret key generation for wireless communications in FDD mode

Most recent research on channel‐based key generation oriented to time division duplex system because the channel reciprocity feature is applied directly for secret key generation. Most of commercial cellular systems depend on frequency division duplex (FDD) systems. In this paper, we investigate the impact of uplink and downlink of FDD systems for the generation of shared secret keys between two parties in the presents of passive eavesdropper. In addition, we are considering improving the rate of the secret key for wireless communication in FDD mode. The main idea is to use the fading coefficient of the channels between the relay and other parties as an additional random common source for the secret key generation. Also, explore the using of channel estimation techniques to reduce the channel training sequence and study its effect on the generation of shared key for wireless communications in FDD mode. We derive the upper bound of the generated shared key rate for four scenarios and give numerical examples to reveal the performance of our suggested improvement approaches.     

The electroremoval of copper from dilute waste solutions using Swiss-roll electrode cell

Copper is usually present in concentrations less than 5 g/L⁻¹ in dilute waste solutions. The low concentrations make these solutions unsuitable for the electro-flow owinning processes via conventional electrolysis cells. Unconventional, two-and three-dimensional electrode cells with relatively large cathodic area are essential for such treatment. Different types of cells are mentioned in the literature. Among these cells, the two-dimensional Swiss-roll cell (SR) is considered in this study. The effects of cathodic current densities, initial copper concentrations, free sulfuric acid concentration, the presence of iron and zinc cations, and the rate of flow of the solution on both the cathodic current efficiency and power consumption were studied. Copper was removed from synthetic and industrial mixtures of Cu/Fe/Zn sulfate solutions to less than 5 ppm with power consumptions of 10.326 kWh/kg⁻¹ and 8.61 kWh/kg⁻¹, respectively. The correlation between the SR cell and packed-column cell on such treatment was also considered.     

Zur anodischen auflösung von reineisen im bereich zwischen aktivem und passivem verhalten

The kinetics of anodic iron dissolution in sulphate ions containing solutions, which are free of oxygen, are investigated in a over potential range between active and passive states of the metal. The measurements were carried out on a rotating disk electrode in the pH-range between 3·5 and 5·5 using the potentiostatic triangular voltage sweep method under quasi-steady-state conditions. The measured current density-potential curves show two current maxima. At relatively low anodic overvoltages, i.e. before the maxima I is reached, the used recrystallized iron dissolves in the active state corresponding to the consecutive (Bockris-) mechanism. At high anodic overvoltages the passive state arises after passing the maxima II. In the transition range, i.e. in the potential range of the maximum I, a second mechanism of iron dissolution is discussed. This mechanism takes place parallel to the consecutive one. An intermediate [Fe (OH)₂]_ads will be formed, which dissolves in a following rate-determining chemical step or is changed in an oxide phase respectively.     

Palynological investigation of some selected species of family Fabaceae from Pakistan,using light and scanning electron microscopy techniques

Pollen morphology of 11 species of family Fabaceae that is, Trifolium alexandrinum, Trifolium resupinatum, Arachis hypogaea, Lathyrus aphaca, Medicago lupulina, Vicia sativa, Lathyrus odoratus, Pongamia pinnata, Melilotus indicus, Medicago polymorpha, Medicago sativa from Pakistan has been investigated by light and scanning electron microscopy. Pollen were generally tricolporate, radially symmetrical, isopolar, elliptic in equatorial view and triangular in polar view under LM. Results showed that pollens were per‐prolate (T. alexandrinum), prolate (T. resupinatum, V. sativa, L. odoratus, Melilotus indicus, M. polymorpha, M. sativa) and sub‐prolate (A. hypogaea, L. aphaca, M. lupulina, P. pinnata). The larger polar/equatorial (P/E) ratio was found in T. alexandrinum (2.26 μm) and the smallest was found in M. lupulina (1.21 μm). The exine of T. resupinatum was 3.00 μm in thickness while others posses smaller exine thickness. The larger pore diameter was found in P. pinnata (16.01 μm) while others have smaller. The length of colpi was larger in Arachis hypogaea (32.24) while others posses smaller. Eight types of surface ornamentation (Psilate, faintly rugulate). Perforate and rugulate to verrucate have been observed under SEM. The pollens were europalynous type. Pollen morphology proved to be useful for the specific delimitation and serve as a tool for the identification and classification of taxa at specific and generic levels and can also be used as a key for the taxonomic features. Diversity in exine sculpture is helpful indicative characters for the isolation of closely related species. Hence, it is clear that both qualitative and quantitative characters of pollen can be useful for differentiating between taxa at specific level.     

Micromorphology,pharmacognosy, and bio‐elemental analysis of an important medicinal herb: Verbascum thapsus L.

The present study was conducted on characterization of morpho‐anatomical, phytochemical, and bio‐elemental analysis of root, stem, and leaf of Verbascum thapsus. Morphologically Verbascum is a biennial plant that flowers for a month and a half in mid‐ to late summer. Various organoleptic features of root, leaf, and stem were recorded. Anatomically the T. S of the root, stem, and leaf showed a typical dicot histological differentiation. Leaf possessed anomocytic stomata, crescent shape vascular bundles, and covered with long and stellate type trichomes while, stem contained collateral type of vascular bundles and a well‐developed pith to store phytochemicals responsible for various pharmacological activities. The powder drug study through scanning electron microscopy revealed the presence of various types of tissues. Branched, tree like and stellate trichomes in root and leaf help in absorption and reduce loss of water. These anatomical features are responsible for the survival of the plant as biennial. Four macro elements (Na, K, Ca, and Mg) and seven microelements (Cr, Cu, Fe, Mn, Ni, Zn, and Cd) and their concentrations in ppm were also studied using Atomic Absorption Spectroscopy. Phytochemical screening of methanolic extract showed existence of various secondary metabolites, while mucilage and anthraquinones was not detected. The present study helps to understand the taxonomic identification of the plant based on morpho‐anatomical features and throws the attention of the researchers to carry out the work for developing its various formulations, which can ultimately be beneficial for the human beings as well as animals.     

Effect of nonionic side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious systems

Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.     

Application of Taguchi method for the optimization of Fe2+ removal from contaminated synthetic groundwater using a rotating packed bed contactor

Malaysia contains elevated levels of iron in shallow groundwater in the range of 3–7 mg Fe/L compared to the USEPA safe limit of 0.3 mg Fe/L. Air Kelantan Sdn Bhd in Malaysia uses the ‘River Bank Filtration’ (RBF) technology to harvest hyporheic water. The RBF treatment removes the turbidity of the river water through the river bed acting as a filter, but is unable to remove the Fe from the harvested water. This work proposes a technology to reduce Fe concentration in the extracted water using granular activated carbon in a laboratory‐scale rotating packed bed contactor (RPBC). The Taguchi method was used for optimizing the operating conditions for the adsorption of Fe onto activated carbon in the RPBC system. Taguchi optimization results showed that a removal efficiency of 87% Fe from a 50 mg Fe/L concentration could be achieved by a RPBC at an initial pH of 6.5, a feed rate of 40 L/h, a rotating speed of 1600 rpm and a packing density of 357 kg/m³.     

Recovery of nano-calcium fluoride and ammonium bisulphate from phosphogypsum waste

ABSTRACT

The production of phosphoric acid generates an enormous amount of phosphogypsum with emission of toxic fluorine acid gas. To remedy these environmental problems, a novel and a simple procedure permits converting phosphogypsum waste by recycled fluorine acid into valuable products. The obtained results confirm the efficiency of this procedure, which synthesises at room temperature the calcium fluoride in the form of nano-crystalline powder and the ammonium bisulphate salt from the exact stoichiometric proportions of phosphogypsum, hydrofluoric acid and ammonia. The total conversion of phosphogypsum is achieved after reaction time equal to one hour and a half. Generally, this novel procedure offers not only a solution for reducing phosphogypsum waste and fluorine gas emission, but also gives rise to valuable products, useful to industry and agriculture.     

Influence of biological and ecological factors on the bioaccumulation of polybrominated diphenyl ethers in aquatic food webs from French estuaries

Previous studies have shown the worldwide presence of six congeners of polybrominated diphenyl ethers (PBDEs) in marine biota (BDE-28, -47, -99, -100, -153 and -154). The objective of the present study was to document their presence, their level and their transfer in the food web of two major estuaries in France, the Loire and the Seine. PBDEs were quantified in eight principal species from the Loire, representing primary consumers (the bivalve Scrobicularia plana), omnivores (the worm Nereis diversicolor, the shrimps Crangon crangon, Palaemon elegans and Palaemon serratus, the flatfish Platichthys flesus and Solea solea) and supercarnivores (the eel Anguilla anguilla). In the Seine, only worms, bivalves, sole and eels have been studied. Parameters, which can interfere with the interpretation of contamination data (organ distribution, influence of weight or size of specimens, lipid richness, intrinsic variability), have been examined. BDE-47 was the predominant congener in all biota. Higher contamination was observed in most of the species collected from the Seine, in agreement with the higher human presence and economic activity in the Seine than in the Loire basin. PBDEs have been shown to biomagnify in both of the studied estuarine food webs. However, assessment of PBDE transfer from seafood products exposed to contaminants in the Seine estuary showed that human daily intake is far below the no observed adverse effect levels.     

智能打壳装置

在一台HAL 2 3 0电解槽上安装了 5个带有节能系统 (EnergySavingSystem)的汽缸和一个可用于快速测试寿命的“虚拟”ESS汽缸。测试的目的是使用ESS系统在正常操作中估计空气节省量和证明包括ESS系统在内的打壳装置的预期寿命周期能达到 8年。测试表明ESS系统的预期寿命超过 8年 ,与传统系统相比 ,可节省 5 9%的空气。如果全部使用该系统 ,可节省 65 %的能量。