An Invariant Dual-beam Snowflake Antenna for Future 5G Communications

A broadband snowflake antenna for future 5G and millimeter-wave communications is presented. The proposed antenna has a size of 8 × 5 mm 2 . The antenna consists of a central hexagon surrounded by a series of symmetrically placed smaller hexagons around it, resulting in broadband characteristics. The impedance bandwidth of the proposed antenna ranges from 25.284-29.252 GHz. The antenna has a gain of 3.12 dBi at 28 GHz and is more than 98% efficient. A distinct feature of the proposed antenna is its dual-beam radiation pattern. The two beams remain fixed at ±50° even if the frequency is varied with in its operating band. The proposed antenna is modelled on thin Rogers substrate which makes it very useful for future 5G smart phones

Using EBSD and TEM-Kikuchi patterns to study local crystallography at the domain boundaries of lead zirconate titanate

Reliable EBSD mapping of 90° domains in a tetragonal ferroelectric perovskite has been achieved for the first time, together with reliable automated orientation determination from TEM-Kikuchi patterns. This has been used to determine misorientation angles at 90° domain boundaries and thus local <i>c</i>/<i>a</i> ratios. The sources of orientation noise/error and their effects on the misorientation angle data have been thoroughly analyzed and it is found that this gives a cosine distribution of misorientation angles about the mean with a characteristic width related to the width of the orientation noise distribution. In most cases, a good agreement is found between local <i>c</i>/<i>a</i> ratios and global measurements by X-ray diffraction, but some clear discrepancies have also been found suggesting that real local variations are present, perhaps as a consequence of compositional inhomogeneities

The Norwegian overnight interbank market during the Covid pandemic

We analyse the behaviour of the Norwegian unsecured overnight interbank market in response to heightened uncertainty and the central bank's liquidity support measures following the Covid-19 pandemic. The liquidity measures enabled banks to fulfil their liquidity needs primarily through participation in extraordinary liquidity auctions. The distribution of central bank reserves across banks did not change due to these measures, but interbank trading fell sharply. Ample liquidity support through the auctions and low interbank trading contributed to low and overly stable overnight rates. Actually, throughout our sample period from 2017 to 2021, the overnight rates remained largely unaffected by fluctuations in uncertainty and overall liquidity conditions.publishedVersio

Properties of blended mortars produced with recycled by-products from different waste streams

The construction industry encounters significant challenges in effectively managing solid waste produced during the extraction and production of building materials. In different countries, slurry waste generated from granite and marble processing industries, such as glass industry waste, constitutes a considerable portion of the total solid waste. Its undesirable disposal is causing unprecedented environmental damage. Using these non-biodegradable wastes to produce building materials would reduce the environmental burden and contribute to sustainable construction. This study, in detail, investigates the feasibility of utilizing Granite Powder (GP), Ground Granite Powder (GGP), and Ground Glass Waste (GGW) as partial replacements of components in blended mortar mixes. The mix modifications consist of partial replacement of cement with GGW, GP, and GGP in the range of 5–15% and fine aggregate replacement with Marble powder (MP) in 10–30% by mass. The mechanical, physical, and microstructure properties of blended and control mortar mixes were studied on the 3rd, 7th, 28th, and 91st curing days. The results demonstrate that the partial substitution of 10% GGW and 5% GP with cement and 10% MP with fine aggregates in blended mortars enhance the compressive strength at the later curing age (28 and 91 days) compared to that of a control mortar, which is associated to the development of higher pozzolanic reactivity. The XRD results showed the formation of the lowest content of calcium hydroxide (CH) and the highest content of calcium silicate gel in the blended mortars compared to the control mortar. The results enrich the data available in the literature not always univocal, as in the case of using marble and glass waste, providing also interesting information about the influence of granite powder on the hydration process in a mortar mix actually missing

Synthesis, structural and photo-physical studies of transition metal complexes with Mannich bases derived from 2-mercaptobenzimidazole

Two Mannich base ligands, [1-(di-n-butylamine-N-methyl)mercapto-1H-benz-imidazole] (L1) and [1-(diphenylamine-N-methyl)mercapto-1H-benzimidazole] (L2)have been synthesized and further reacted with Co(II), Ni(II), Cu(II) and Zn(II) ionsto afford their respective complexes. The progress of the reaction was monitored by thin layer chromatography. The structural elucidation of Mannich base ligands and their metal complexes was done by Fourier Transform Infrared (FTIR), UV-Visible, Nuclear Magnetic Resonance spectroscopy (1H NMR & 13C NMR) and Atomic absorption spectroscopy (AAS) / Inductively coupled plasma emission spectroscopy (ICPES). FTIR and NMR studies supported the monoanionic bidentate coordination mode of L1 and L2 while tetrahedral geometries of metal complexes were proposed on the basis of AAS/ICP, magnetic moment and electronic spectroscopic data. The synthesized compounds were also investigated for their luminescent behavior which exhibited broad emission bands indicating charge transfer nature of the involved transitions.               KEY WORDS: Metal complexes, Mannich bases, 2-Mercaptobenzimidazole, Luminescence Bull. Chem. Soc. Ethiop. 2018, 32(3), 481-490.DOI: https://dx.doi.org/10.4314/bcse.v32i3.

Laboratory and field investigations in granular soils to correlate relative density, relative compaction and grain size

An attempt has been made to correlate relative density and relative compaction based on laboratory and field test data. In this investigation, 185 sandy soil samples were tested in the laboratory. The experimental investigations include classification tests, maximum and minimum density tests, and standard and modified Proctor and in-situ density tests. The values of the dry unit weight of these samples obtained by performing different tests fall between 14.7 kN/m(3) and 20.8 kN/m(3). Based on these results, linear and multivariate regression analyses were carried out to (a) relate relative compaction and relative density, (b) relate maximum (e(max)) and minimum void ratios (e(min)), and (c) express e(max) and e(min) in terms of median grain size (D-50) and uniformity coefficient (C-u). Experimental and predicted values varied +/- 5%, with a 95% confidence interval for the relation between relative compaction and relative density, and for other relations the variation was +/- 10%. The proposed equations were validated using a new data set which had not been used for the development of the correlations. Proposed equations were also compared with equations presented by various other researchers. Validation of the proposed equations suggests that these equations may be used for future prediction of the respective variables

Defect engineering for improved photocatalytic performance of reduced lead titanate (PbTiO3) under solar light irradiation

Lead titanate (PbTiO3) nanoparticles were prepared successfully by template free hydrothermal  method. Size, crystallinity, morphology and phase determination of the nanoparticles were made by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FESEM). FESEM results had shown that all nanoparticles were in the range between 20 to 40 nm size and found in the form of agglomerates. The average crystallite size of PbTiO3 nanoparticles was calculated to be nearly 35 nm. PbTiO3 nanoparticles were reduced by hydrogenation at high temperature to make the material active for visible light. Furthermore, optical absorbance of PbTiO3 nanoparticles was determined by applying ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. By using Davis-Mott model, the direct optical band gap of 2.65 eV was acquired. Methyl orange (MO) was used as pollutant to check the photocatalytic activity of reduced PbTiO3 nanoparticles under solar light irradiation. Photocatalytic activity of reduced PbTiO3 nanoparticles increased 2.6 times more than that of pure PbTiO3 nanoparticles for methyl orange (MO) under solar light irradiation.               KEY WORDS: Lead titanate (PbTiO3), Photocatalytic performance, Hydrothermal growth, Solar light, Irradiation Bull. Chem. Soc. Ethiop. 2019, 33(2), 373-380.DOI: https://dx.doi.org/10.4314/bcse.v33i2.1

Insights into the composition of recalcitrant organic matter from estuarine sediments using NMR spectroscopy

peer-reviewedThe full text of this article will not be available on ULIR until the embargo expires on the 24/05/2018Sediment cores (ca. 6 m) from an estuarine environment gave insights into the composition and preservation of recalcitrant organic carbon (OC) in the environment. The coring locations provided organic matter (OM) of terrestrial origin and of marine origin. Our study specifically focused on the humin (HU), the OM fraction that is most difficult to isolate and to characterize. HU fractions were compared with the total OM recovered after removal of the associated mineral colloids. Solid state and multiphase (nuclear magnetic resonance) NMR experiments were carried out on dried and swollen samples to obtain comparative information about the whole samples and the fractionated samples. The total OM associated with the clay-size fraction provided a standard that allowed differences between the fractions to be observed. The NMR data provided new insights into the molecular structures that become part of the long term C sink in sediments. The recalcitrant OC in the sediments is composed mainly of aliphatic hydrocarbon material that may be protected from, or otherwise unavailable for, degradation. Microbial peptides and carbohydrates were also shown to be important contributors to the C sink and these biomolecules may be from living biomass or preserved necromass. Lignin residues formed only a small part of the OM in the surface sediments but made a greater contribution at depth. Highly ordered components in HU (that resists swelling by dimethylsulfoxide, DMSO) play a major role in C sequestration