Resilient BBU placement in 5G C-RAN over optical aggregation networks

Photonic Network Communications - The huge data demand envisioned for the 5G requires radical changes in the mobile network architecture and technology. Centralized radio access network (C-RAN) is...     

Modelling of through silicon via and devices electromagnetic coupling

This paper is essentially composed of two parts for future synthesis. We developed 2D and 3D simulations, starting from a 0.35 μm standard CMOS technology, focusing on through silicon via or redistribution layer induced coupling; nMOSFET, pMOSFET, and the sensitive regions of the CMOS inverter are investigated. We also study stacked devices in 3D circuits, in the radiofrequency range, and propagation of electromagnetic waves along some interconnections with discontinuities. This study is performed in the time domain—a finite-difference time-domain method is applied to the analysis of some vias flanked by two striplines, all embedded in silicon. Electric and magnetic field distributions, transmission and reflexion parameters, and pulse propagations along a transverse via are presented.     

Modeling and characterization of a 5.2 GHz VCO for UWB applications in 0.13 μm CMOS process

This paper describes a 5.2 GHz voltage-controlled oscillator (VCO) as a key component in RF transceivers. The circuit includes a complementary cross-coupled MOSFET as a negative conductance, beside a tank circuit which consists of an optimal on-chip spiral inductor (L), and an accumulation mode MOS varactor (C(V)). A model for phase noise and figure merit is introduced and verified through simulation in a standard 0.13 μm CMOS process. The VCO core drew a 4.2 mA of current from a 1.2 V power supply and a phase noise of −98.5 dBc/Hz at 1 MHz offset from the 5.2 GHz carrier was calculated. The whole performance of the circuit specifically the tuning range was found to be 26%.     

Alkali retention/separation during bagasse gasification: a comparison between a fluidised bed and a cyclone gasifier

Biomass fuelled integrated gasification/gas turbines (BIG/GTs) have been found to be one of the most promising technologies to maximise electricity output in the sugar industry. However, biomass fuels contain alkali metals (Na and K) which may be released during the gasification processes and cause deleterious effects on the downstream hardware (e.g. the blades of gas turbines). Much research has therefore been focused on different kinds of gas cleaning. Most of these projects are using a fluidised bed gasifier and includes extensive gas cleaning which leads to a high capital investment.

Increasing alkali retention/separation during the gasification may lead to improved producer gas quality and reduced costs for gas cleaning. However, very little quantitative information is available about the actual potential of this effect. In the present work, comparative bench-scale tests of bagasse gasification were therefore run in an isothermal fluidised bed gasifier and in a cyclone gasifier to evaluate which gasification process is most attractive as regards alkali retention/separation, and to try to elucidate the mechanisms responsible for the retention.

The alkali retention in the fluidised bed gasifier was found to be in the range of 12–4% whereas in the cyclone gasifier the alkali separation was found to be about 70%. No significant coating of the fluidised bed's bed material particles could be observed. The SEM/EDS and the elemental maps of the bed material show that a non-sticky ash matrix consisting of mainly Si, Al and K were distributed in a solid form separated from the particles of bed material. This indicates the formation of a high temperature melting potassium containing silicate phase, which is continuously scavenged and lost from the bed through elutriation.     

Pressure–time characteristics in diesel engine fueled with natural gas

Combustion pressure data are measured and presented for a dual fuel engine running on dual fuel of diesel and compressed natural gas, and compared to the diesel engine case. The maximum pressure rise rate during combustion is presented as a measure of combustion noise. Experimental investigation on diesel and dual fuel engines revealed the noise generated from combustion in both cases. A Ricardo E6 diesel version engine is converted to run on dual fuel of diesel and compressed natural gas and is used throughout the work. The engine is fully computerized and the cylinder pressure data, crank angle data are stored in a PC for off-line analysis. The effect of engine speeds, loads, pilot injection angle, and pilot fuel quantity on combustion noise is examined for both diesel and dual engine. Maximum pressure rise rate and some samples of ensemble averaged pressure–crank angle data are presented in the present work. The combustion noise, generally, is found to increase for the dual fuel engine case as compared to the diesel engine case.     

Co-Doped ZnO Nanoparticles:Structural,Morphological,Optical,Magnetic and Antibacterial Studies

Un-doped and Co-doped ZnO nanoparticles （NPs） with different weight ratios （0.5, 1.0, 1.5, and 2.0 wt% of Co） were synthesized by a facile and rapid microwave-assisted combustion method using urea as a fuel. The prepared NPs were characterized by X-ray diffraction （XRD）, high resolution scanning electron microscopy （HR-SEM）, energy dispersive X-ray analysis （EDX）, diffuse reflectance spectroscopy （DRS）, photoluminescence （PL） spectroscopy and vibrating sample magnetometry （VSM）. XRD patterns refined by the Rietveld method indicated that Co-doped ZnO had a single pure phase with wurtzite structure suggesting that Co^2＋ ions would occupy Zn^2＋ ionic sites within the ZnO crystal lattice. Interestingly, the morphology was found to convert substantially from grains to nanoparticles with close-packed periodic array of hexagonal-like shape and then into randomly distributed spherical NPs with the variation of Co-content. The optical band gap estimated using DRS was found to be red-shifted from 3.22 eV for the un-doped ZnO NPs then decrease up to 2.88 eV with increasing Co-content. PL spectra showed a strong green emission band thus confirming the formation of pure single ZnO phase. Magnetic studies showed that Co-doped ZnO NPs exhibited room temperature ferromagnetism （RTFM） and that the saturation magnetization attained a maximum value of 2.203 × 10^-3 emu/g for the highest Co-content. The antibacterial studies performed against a set of bacterial strains showed that the 2.0 wt% Co-doped ZnO NPs possessed a greater antibacterial effect.     

Stabilising and Trimming 3D Woven Fabrics for Composite Preforming Applications

The work presented here focusses on the developments in the stabilising and trimming of 3D woven preforms. Dry fibre preforms are notoriously difficult to trim; once a fabric is cut, it loses its edge stability and consequently the fabric frays. The result is an unstable fabric which can easily be displaced/ distorted prior to composite manufacturing. In this work, three stabilisation and three trimming techniques were investigated. Of the stabilisation techniques these included powder binder, thermoplastic binder yarn (activated to give fabric stabilization); and polyester stitching. The stabilised fabrics were trimmed to near-net-shape using different trimming techniques. The trimming techniques investigated were laser, clicker press and ultrasonic knife. Each stabilisation method was trialled with each trimming method to assess the most suitable combination. The assessment of quality and suitability was made by observing the level of stabilisation, amount of fraying fibres, quality of the cut, ease of application and repeatability of the process. This paper details the assessments made for each combination alongside practical application conclusions. The key findings were; cutting by means of a laser is capable of sealing the fabric edges, producing high edge quality. Stitching as a method of stabilising is not sufficient in preventing fibres from moving during the cutting process, hence producing an unclean cut.     

Photo-sensing properties of Cd-doped In2S3 thin films fabricated via low-cost nebulizer spray pyrolysis technique

In this study, we report the fabrication of cadmium-doped indium sulfide thin films (In₂S₃:Cd) using a low-cost nebulizer-aided spray pyrolysis process at 350 °C on glass substrates for photo-sensing applications. The impact of 0, 2, 4, and 8 wt% cadmium concentrations on the structure, morphology, optical properties, and photo-sensing capabilities of In₂S₃ thin films were examined systematically. From X-ray diffraction (XRD) analysis, the major peak is located in the (103) plane for all Cd-doped In₂S₃ thin film samples, and the maximum crystallite size for the 4 wt% sample is 59 nm. The field emission scanning electron microscope (FESEM) image revealed a homogenous large-grained surface of Cd-doped In₂S₃ film that completely covered the substrate. UV–Vis absorption analysis demonstrated good absorption for all thin film samples in the visible and ultraviolet regions of the electromagnetic spectrum, particularly, the 4% Cd-doped concentration showed excellent absorption as is observed from Tauc relation. The highest PL intensity at 680 nm was observed for the sample coated with 4 wt% of Cd. Under UV light, the I–V behavior depicts a light current of 1.06?×?10^–6 A for a 5 V bias voltage. The In₂S₃: Cd (4%) sample had the highest responsivity of 2.12?×?10^?1A/W and a detectivity of 1.84?×?10¹¹ Jones, with a high EQE of 50%. The study manifests that the developed Cd (4%)-doped In₂S₃ thin film sample might be better suited for the application of photodetectors.

     

Antimicrobial and antioxidant activities of different propolis samples from north‐western Algeria

The aim of this study was the investigation of antimicrobial and antioxidant activities of different ethanolic extracts of propolis (EEP) collected from north‐western Algeria. Total polyphenols and flavonoids contents of extracts were measured. The UV absorption spectrum showed and confirmed their polyphenols constituents. All EEPs exerted antibacterial activity against Gram‐positive bacteria, but no effect on Gram‐negative bacteria. The minimum inhibitory concentration (MIC) of EEPs ranged from 0.01% to 2.6% v/v. The antioxidant activity was measured using ferric‐reducing power (FRAP), 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical‐scavenging and ESR methods. Propolis TIA‐2 and MOH‐MAS samples showed the highest antioxidative capacity, after 35 min, while TIA‐1, NED‐TL and SFS‐SBA samples showed the highest antioxidative potential of measured EEPs, after 3 min. TIA‐2 sample showed the highest antibacterial, antioxidant activity and highest DPPH free radical‐scavenging activity as well as the highest polyphenols and flavonoids content, compared with other propolis samples.     

Inhibition of enterotoxicogenic strains Bacillus cereus GT1 and Staphylococcus aureus S1 isolated from double white cream cheese

In this study three different food preservatives (sodium nitrate, sodium benzoate and sodium sorbate) were used to evaluate their effect on two enterotoxicogenic strains (Bacillus cereus GT1 and Staphylococcus aureus S1). A significant decrease in the viability and production of virulence factors was observed. Yet, obvious tolerance to increasing concentrations (from 1 to 6?g/l) of the three preservatives was recorded reflecting possible resistance mechanisms within the tested strains. The two strains were subjected to increasing doses of gamma radiation (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10?kGy). Obvious correlation was observed between the initial counts of bacterial spores contaminating the products and the required dose for their complete elimination. Whereas the eliminating dose of B. cereus GT1 strain was 10?kGy only 4?kGy was sufficient to suppress the growth and virulence of S. aureus S1, reflecting its sensitivity to low doses of gamma irradiation. Also, inhibition of the two strains by probiotic strain Bacillus pumilus G4 was studied both in situ (in cheese) and in vitro (in culture media). The viable cell population of B. cereus GT1 increased from 10⁶ to 2.9?×?10⁸?CFU/g within 60?h in controls but decreased from 2.1?×?10⁶ to 2.3?×?10³?CFU/g after treatment with the probiotic strain. No viable count was observed after 60?h of incubation. Whereas, the viable cell population of S. aureus S1 increased from 10⁶ to 2.5?×?10⁸?CFU/g within 60?h in controls but decreased from 1.5?×?10⁶ to 4.3?×?10²?CFU/g after treatment with the probiotic strain. No viable count was observed after 54?h of incubation.