Response of rainfed bread and durum wheat to source,level and timing of nitrogen fertilizer on two Ethiopian Vertisols: II. N uptake,recovery and efficiency

In trials conducted at 2 highland Vertisol sites in Ethiopia in 1990 and 1991, 2 locally popular wheat cultivars, 1 spring bread wheat (Triticum aestivum L.) and 1 durum wheat (T. durum Desf.), were supplied with nitrogen (N) fertilizer at 0, 60 and 120 kg N ha^–1 in the form of large granular urea (LGU), standard urea prills or ammonium sulfate. N was applied all at sowing, all at mid-tillering or split-applied between these two stages (1/3:2/3). While durum wheat exhibited the highest N concentration in grain and straw, bread wheat, because of its higher productivity, resulted in a greater grain and total N uptake. In general, split application of N and use of LGU as N source enhanced grain and total N uptake, apparent N recovery and agronomic efficiency of N, particularly under severe water-logging stress. Where significant, the interactions among the experimental factors substantiated the superior responsiveness of the bread wheat cultivar to fertilizer N, and the beneficial effects of split N application and LGU as an N source. Split application of N tended to nullify the positive effects of LGU, presumably by approximating the delayed release of N achieved with LGU. Considering the potential benefits to Ethiopian peasant farmers and consumers, split application of N should be advocated, particularly on water-logged Vertisols; LGU could be an advantageous N source assuming a cost comparable to the conventional N source urea.     

Preparation and characterization of poly(lactic acid)/recycled polypropylene blends with and without the coupling agent,n-(6-aminohexyl)aminomethyltriethoxysilane

Blends of polylactide (PLA) and recycled polypropylene (rPP) were prepared by melt-processing using a corotating twin-screw extruder and subsequent pelletizing of the extrudates for injection molding. The PLA/rPP blends were characterized by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), rheometer (MCR-102), scanning electron microscopy(SEM), tensile tests, and impact measurements. The results indicate that the PLA/rPP blend is immiscible and has a two-phase structure. TGA revealed enhancement of the thermal stability of the blends upon addition of rPP. The storage modulus, loss modulus, and complex viscosity of the blends increased with rPP concentration. Mechanical studies showed that introduction of rPP results in a decrease in tensile strength and modulus and enhancement of the impact strength of PLA in the blends. The effects of a silane coupling agent on the morphology and on the tensile and impact properties of the rPP blends of silane-modified PLA were also examined. SEM studies suggest that silane is an effective interfacial modifier. Thus, better interfacial adhesion was observed with silane-modified blends as compared with unmodified blends. Silane also improved the mechanical properties of the modified blends. The blends reached maximum tensile strength at 1.5 wt.% silane (relative to modified PLA content), and impact strength increased with increasing silane concentration. These results confirm the enhancing effect of silane on modified PLA/rPP blends.     

Asymptotic results for Fourier‐PARMA time series

Periodically stationary times series are useful to model physical systems whose mean behavior and covariance structure varies with the season. The Periodic Auto‐Regressive Moving Average (PARMA) process provides a powerful tool for modelling periodically stationary series. Since the process is non‐stationary, the innovations algorithm is useful to obtain parameter estimates. Fitting a PARMA model to high‐resolution data, such as weekly or daily time series, is problematic because of the large number of parameters. To obtain a more parsimonious model, the discrete Fourier transform (DFT) can be used to represent the model parameters. This article proves asymptotic results for the DFT coefficients, which allow identification of the statistically significant frequencies to be included in the PARMA model.     

Cesium tungsten bronze nanostructures and their highly enhanced hydrogen gas sensing properties at room temperature

In this study, cesium tungsten bronze (Cs_xWO₃) a well-known metal oxide semiconductor and excellent photocatalyst and active photothermal material was used as a sensing material toward hydrogen for the first time. The Cs_xWO₃ nanorods were synthesized using a new hydrothermal method and examined through systematic material investigations. The synthesized Cs_xWO₃ nanorods were coated on SiO₂/Si substrates and subsequently fabricated laterally with multi-finger platinum (Pt)-based electrodes to test their gas detecting properties. The gas detecting property of the prepared material was studied toward very toxic hydrogen gas (10–500 ppm concentration). The gas sensing results demonstrate that the synthesized Cs_xWO₃ material has excellent gas sensing properties toward hydrogen (31.3%), which is overwhelmingly superior to as-prepared WO₃ (4.7%) due to its suitable electrical and optical properties at room temperature (RT). The selectivity results also indicate that the material has outstanding selectivity toward hydrogen compared with different gases such as ammonia and carbon dioxide. The critical features of this material are its high reliability, simple synthesis method, low humidity susceptibility, and high selectivity, making it viable for use in hydrogen sensors. Compared with the as-prepared WO₃, the adsorption capability and conductance of the Cs_xWO₃ surface induces active O₂ functional groups, significantly enhancing the gas sensing properties.     

Preparation of value added composite boards using finished leather waste and plant fibers—a waste utilization effort in Ethiopia

Preparation of composite materials with better mechanical properties and agreeable use is a need of the time for the reason that it is eco-friendly. Having this objective in mind, the work of preparing value-added leather composites using finished leather waste and various plant fibers as raw materials is done in the laboratory of Council of Scientific and Industrial Research–Central Leather Research Institute, India. In the leather goods and footwear manufacturing industries, about 20–30% of leather is discarded as waste, and presently it is imperative to make effort to utilize this waste in Ethiopia because it is huge and untapped resource. The recycled leather (RCL) as control and its composite boards (CBs) which are the mixtures of leather fibers with plant fibers like jute (Corchorus trilocularis L.), hibiscus (Hibiscus cannabinus), sisal (Agave sisalana), palm (Phoenix dactylifera) and enset (Ensete ventricosum) in the proportion of 10, 20, 30, and 40% are characterized for their physicochemical properties (tensile strength, elongation at break, stitch tear strength, water absorption, water desorption, and flexing strength), scanning electron microscope (SEM), Fourier transform infrared, thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). Composites exhibited better mechanical properties compared to those of control boards. SEM pictures showed the composite nature of the boards. TGA studies revealed better thermal stability for composites. In the DSC study, the CBs of RCL-S and RCL-P exhibited higher melting point values than those of RCL-J, RCL-H, and RCL-E samples. Based on these results, all the composite boards may be used as raw material for the preparation of consumer products such as insoles, chapel-uppers, wallets, light hand bags, mouse pads, roofing, wall partitioning, and components of furniture and interior decorations.     

Effects of a liquid metal co-filler on the properties of epoxy/binary filler composites

Liquid metals (LMs) with high fluidity and high thermal conductivity (TC) are receiving considerable attention in the research on thermal management polymer composites as alternatives to conventional rigid solid fillers or as co-fillers to overcome the trade-off between TC and composite processability at high filler loads. While most previous studies have investigated the effects of LM fillers in soft elastomeric matrices, their effects on the composite properties with rigid matrices, such as epoxy-based polymers, have not been discussed extensively. Herein, we investigated the effects of LM eutectic Ga-In (EGaIn) as a co-filler on the properties of rigid epoxy-based composites with a binary filler (Al₂O₃/EGaIn) system. The increase in the volume fraction of LM fillers significantly improves the processability of uncured precursor composites but markedly decreases the mechanical strength of the cured composites at their high loads—the latter effects have rarely been examined in previous studies. However, with adequate LM loads, the composites exhibited superior mechanical properties compared with the all-solid-filler system, withstanding a surprisingly high compressive load (~100 kN) under which the all-solid-filler system fractured. Furthermore, the epoxy/binary filler composites exhibited reasonably high TC values (~1 W/mK) comparable to that of commercial epoxy molding compounds, suggesting their potential applicability for electronic packaging.     

NIR Light Stimulated Self-Healing Reduced Tungsten Oxide/Polyurethane Nanocomposite Based on the Diels−Alder Reaction

Cracks formed in materials can influence the performances and shorten their lifetime. Self-healing materials can repair cracks caused by mechanical damage using external stimuli, which increases their safety, extend their service life, and can save renovation costs. In this work, a novel thermo-responsive linear Diels-Alder polyurethane (DAPU) and reduced tungsten oxide (WO_3−x) (W-DAPU) is developed for the first time. Its near-infrared (NIR) light-induced self-healing properties are evaluated using qualitative optical observation and quantitative tensile measurements. The NIR light-induced self-healing and photothermal conversion property of W-DAPU is also systematically investigated. The results show that linear DAPU has an excellent thermo-reversible self-healing efficiency of 94.8% and heals within 6 s due to the presence of a DA bond. In addition, the W-DAPU has a self-healing efficiency of 83.2% with outstanding photothermal conversion. This study paves the way to design and fabricate stimuli-responsive nanocomposite materials for various applications.     

Comparison of photovoltaic devices containing various blends of polymer and fullerene derivatives

Large area photovoltaic devices based on an interpenetrating network of donor and acceptor molecules have been fabricated showing power conversion efficiencies up to 1.5% under monochromatic illumination at 500 nm. Devices containing blends of solubilized poly (paraphenylene vinylene), (PPV) or poly thiophene derivatives as donors with various fullerene derivatives as acceptors are compared. It is shown that among the various combinations of materials both the open-circuit voltage and the short-circuit current are maximal for a blend of PPV and a highly soluble methano fullerene. For a further increase of the efficiency of these devices, a reduction of the thickness of the active layer is suggested.     

Augmenting machine learning for Amharic speech recognition: a paradigm of patient’s lips motion detection

Multimedia Tools and Applications - The method of automatic lip motion recognition is an essential input for visual speech detection. It is a technological approach to demystify people who are hard...