Efficient Resource Allocation with Improved Interference Mitigation in FFR-Aided OFDMA Heterogeneous Networks

Fractional frequency reuse (FFR) has recently emerged as an efficient inter-cell interference coordination technique for orthogonal frequency division multiple access (OFDMA) based multi-tier cellular networks due to its low complexity, minimal signaling over-head, and coverage improvement. In this work, an intermediary region (IR) at the border of the center region (CR) and edge region (ER) is defined, which prevents severe cross-tier interference and is usually ignored by other schemes. Furthermore, a strategic resource allocation scheme is proposed, which allows macro users in this new region to be served more resources due to their good channel conditions close to the serving base station (BS), while femto users are assigned resource blocks from sub-bands that receive the least net interference from a set of usable sub-bands in any region. We find by analysis and simulation the optimal threshold for IR, which minimizes the cross-tier interference, and show that the femto throughput is also maximized for this threshold. Numerical results show the proposed scheme outperforms other notable schemes in terms of throughput and outage performances.     

Nitrite in soils: accumulation and role in the formation of gaseous N compounds

Nitrite is an intermediary compound formed during nitrification as well as denitrifiication. It occasionally accumulates in soils and drainage water. The nitrite can then undergo transformations to gaseous nitrogen compounds such as NO and NO₂. Soil pH controls the abiotic nitrite decomposition to a large extent. Under acidic conditions(pH <5.5), nitrous acid spontaneously decomposes preferentially to NO and NO₂. Nitrite also undergoes reactions with metallic cations (especially ferrous iron) and with organic matter. As a result of these reactions gaseous compounds such as NO, NO₂, N₂O and CH₃ONO can be formed. Through reaction of nitrite with phenolic compounds nitroand nitrosocompounds can be formed, building up organic N. With normal agricultural practices on slightly acidic soils, the nitrite instability usually does not lead to economically important N losses from soils. However, the compounds formed through its degradation or interaction with other soil constituents are linked to environmental problems such as tropospheric ozone formation, acid rain, the greenhouse effect and the destruction of the stratospheric ozone.     

Isolation and characterisation of locally isolated Gluconacetobacter xylinus BCZM sp. with nanocellulose producing potentials

Recently, attention has been given to nanocellulose produced by bacteria due to its unique properties and environmentally friendly nature when compared with plant cellulose. Bacterial nanocellulose (BNC) producing isolate was successfully isolated from rotten fruits via dilution and spread plates method. Based on the biochemical characterisation and molecular analysis of the 16S rDNA gene, the isolate was identified as Gluconacetobacter xylinus BCMZ sp. Nanocellulose productivity was confirmed by the formation of the white gelatinous layer between air/liquid surfaces when the culture was cultivated under a stationary condition at 30°C. Successful purification of nanocellulose was achieved using alkaline treatment method. The Fourier transformed infrared spectrum showed a characteristics band signature of pure nanocellulose, by displaying strong absorption peaks at 3335.36 and 2901.40 cm⁻¹ representing carbonyl and carbon–hydrogen bonding, respectively. Morphological characteristics of the BNC were determined by scanning electron microscopy (SEM). Elemental analysis of BNC was determined by energy dispersive X‐ray (SEM/EDX) analysis. The isolates BCZM showed significant nanocellulose production ability with a high degree of purity when compared with plant nanocellulose. BNC purification using 1 M NaOH solution is effective and eco‐friendly with no indication of recalcitrant formation as commonly found in plant nanocellulose purification steps.Inspec keywords: microorganisms, purification, scanning electron microscopy, X‐ray chemical analysis, Fourier transform infrared spectroscopy, biotechnologyOther keywords: locally isolated Gluconacetobacter xylinus BCZM sp, nanocellulose producing potentials, bacterial nanocellulose producing isolate, BNC producing isolate, rotten fruits, dilution, spread plates method, biochemical characterisation, molecular analysis, white gelatinous layer, air/liquid surfaces, nanocellulose purification, alkaline treatment method, Fourier transformed infrared spectrum, characteristics band signature, scanning electron microscopy, elemental analysis, energy dispersive X‐ray analysis, SEM analysis, EDX analysis, plant nanocellulose, BNC purification, recalcitrant formation     

Photocatalytic methanol reforming on Au/TiO2 for hydrogen production

Methanol can be reformed with water, at ambient temperature, using photocatalysis, and this reaction represents a possible low energy, more sustainable pathway to hydrogen production than (for instance) steam reforming. The requirements for the catalysts are rather strict since titania itself is almost inactive for anaerobic photocatalysis, whereas the addition of a very limited range of metals to the surface renders it active. Surprisingly, this includes gold, which shows one of the highest reactivities for hydrogen production. The mechanism is proposed to involve the methoxy and formate intermediates, the latter being implicated in the route to CO₂ and hydrogen production. One oxygen atom is supplied from the titania support, which is replaced in the catalytic cycle by oxygen from water. The threshold for the excitation is that for bandgap excitation into the titania conduction band, which stores the energy for reactivation, and this is mediated by electrophilic oxygen.     

Comparison of dragonfly algorithm and Harris hawks optimization evolutionary data mining techniques for the assessment of bearing capacity of footings over two-layer foundation soils

Engineering with Computers - By assist of novel evolutionary science, the classification accuracy of neural computing is improved in analyzing the bearing capacity of footings over two-layer...     

Fractionation, solubility and functional properties of wheat bran proteins as influenced by pH and/or salt concentration

The content, fractionation, solubility and functional properties of wheat bran proteins as well as the effects of pH and/or NaCl concentration on some of these functional properties were investigated. The protein content of the bran was found to be 16.80%. Albumin and glutelin are the major fractions of wheat bran proteins. The minimal protein solubility was observed at pH 5.5, the maximum at pH 11.5. The emulsifying capacity, activity and emulsion stability as well as foaming capacity and foam stability were greatly affected by pH and salt concentrations. Lower values were observed at acidic pH and high salt concentration. The least gelation concentration of wheat bran proteins was found to be 16% when the proteins were dissolved in 1.0 M NaCl. The total protein was highly viscous and dispersable with water-holding capacity of 4.20 mL H2O/g protein, oil-holding capacity of 1.70 mL oil/g protein and bulk density of 0.29 g/mL while dispensability was found to be 77.30%.     

Relationships between rhizobial diversity and host legume nodulation and nitrogen fixation in tropical ecosystems

With recent advances in rhizobial phylogeny, questions are being asked as to how an ecological framework can be developed so that rhizobial classification and diversity could have greater practical applications in enhancing agricultural productivity in tropical ecosystems. Using the results of studies on tropical rhizobia which nodulate agroforestry tree legumes, three ecological aspects of rhizobial biodiversity were used to illustrate how its potential can be exploited. The results showed that legumes nodulate with diverse rhizobial types, thus contributing to the success of legumes in colonising a wide range of environments. There was an apparent shift in the relative dominance of rhizobia populations by different rhizobial types as soil pH changed. The Rhizobium tropici-type rhizobia were predominant under acidic conditions, Mesorhizobium spp. at intermediate pH and Sinorhizobium spp. under alkaline conditions. The R. tropici-type rhizobia were the most effective symbiotic group on all the host legumes. However, strains of Sinorhizobium spp. were as effective as the R. tropici types in N₂-fixation on Gliricidia sepium, Calliandra calothyrsus and Leucaena leucocephala; while Mesorhizobium strains were equally as effective as the R. tropici types on Sesbania sesban. Classification of rhizobia based on phenotypic properties showed a broad correlation with groupings based on 16S rRNA sequence analysis, although a few variant strains nested with the dominant groups in most of the clusters. Some of the phenotypic characters that differentiated different rhizobial groups are highlighted and a case is made for the need to standardise this method.     

Delay Analysis within Construction Contracting Organizations

Delayed completion of a construction project is often caused by a complex interaction of a combination of events, some of which are the contractor’s risks and others are the project owner’s. The apportionment of the liability to give effect to the risk allocation has therefore been a matter of great controversy. Many delay analysis methodologies have been developed over the years for performing this task. This paper reports on an empirical study into the current practice in the use of these methodologies in the United Kingdom, as part of a wider study aimed at developing a framework for improving delay claims analysis. The part of the study reported here was based on a questionnaire survey of key informants. The issues investigated include the categories of staff within contracting organizations who contribute to delay claims analyses, the awareness, use and reliability of existing delay analysis methods and the obstacles to their use in practice. The main findings of the study are that: (1) the preparation of delay claims often requires input from commercial managers (quantity surveyors), schedulers, site managers, external claim consultants and estimators; (2) commercial managers have the greatest involvement; (3) claims analyzed using the as-built versus as-planned and the impacted as-planned techniques are often successful although there is considerable literature on the shortcomings of these techniques; and (4) the main obstacles to the use of the methods relates to deficiencies in project records and scheduling practice.     

Aqueous processing of nickel spent catalyst for a value added product

Nickel was recovered from a fertilizer industry spent catalyst by leaching with nitric acid followed by nickel hydroxide precipitation. The optimization of temperature, initial acid concentration and particle size for leaching of the spent catalyst was done through 2³ factorial design. A maximum extraction of 91.9% was achieved at 90 °C, 1.5M HNO₃ and 62.5 μm particle size. Temperature and acid concentration showed positive effect, while particle size showed no effect. A regression equation was developed and employed to predict conditions for 100% extraction which were experimentally tested. Nickel hydroxide was electrochemically precipitated from the leach liquor and its maximum discharge capacity was found to be 155 mAh/g. A 3-stage counter current leaching circuit was designed to obtain a leach liquor of suitable pH. XRD characterization of the precipitated Ni(OH)₂ shows to consist of both α- and β-forms.