1,721,433 research outputs found
The effect of fibre reinforcements on the mechanical behaviour of railway ballast
No full textBallast is a primary component of the railway track and it has several functions including the ability to resist vertical, lateral and longitudinal forces applied to the sleepers from the train wheels. In response to the stresses induced during a train passage, ballast typically experiences plastic settlement which can reach unacceptable magnitudes. Thus, ballast is the focus of the majority of maintenance and renewal activities. In response to the growing need for resilient track materials (including ballast) to cope with increasing train speed, load and frequency, means of optimizing its performance and minimizing maintenance requirements are required.Ballast improvement techniques, such as the use of geogrids, have attracted a great deal of attention in terms of research, but huge potential for reducing costs through ballast improvement still exist. It has been shown from previous research that the use of randomly oriented fibres in sands can significantly improve their strength. This technique might be used to improve ballast strength and reduce track geometry deterioration. In addition, fibre reinforcements in ballast can potentially provide a new method of reinforcing ballast whilst maintaining the capability of withstanding typical tamping operations which are incompatible with geogrids. However, there is a lack of rigorous scientific understanding of the effects of fibre reinforcements on relatively large aggregates such as railway ballast.This research examines the effect of random fibre inclusions on the packing structure of granular materials (coarse sand and scaled ballast) and describes the physical implications associated with the observed changes. The mechanical properties of fibre reinforced granular materials across different particle sizes and a hypothesis of fibre/particle reinforcement suitable for relatively large particles are presented. An image-based deformation measurement technique has also been used to investigate the effects of fibre reinforcements on the local deformation of triaxial specimens to corroborate the observed mechanical behaviour of the reinforced specimens. Finally, the mechanical behaviour of a fibre reinforced ballast layer below a cyclically loaded railway sleeper was investigated using a full scale laboratory tests
An Economic Feasibility Model for Sustainable 5G Networks in Rural Dwellings of South Africa
Full text linkNumerous factors have shown Internet-based technology to be a key enabler in achieving the sustainable development goals (SDG), as well as narrowing the divide between the global north and south. For instance, smart farming, remote/online learning, and smart grids can be used to, respectively, address SDGs 1 and 2 (ending poverty and hunger), 3 (quality education), and 7 and 9 (energy and infrastructure development). Though such Internet-based solutions are commonplace in the global north, they are missing or sparsely available in global south countries. This is due to several factors including underdevelopment, which dissuades service providers from investing heavily in infrastructure for providing capable Internet solutions such as 5G networks in these regions. This paper presents a study conducted to evaluate the feasibility of deploying 5G networks in the rural dwellings of South Africa at affordable rates, which would then serve as a pre-cursor for deploying solutions to improve lives and achieve the SDGs. The study evaluates the economic viability of a hybrid network model which combines terrestrial and aerial networks to provide 5G coverage in rural areas. The feasibility study reveals that such a network can be engineered at low monthly subscription fees to the end users and yield good returns to the service providers in rural areas; however, for large but sparsely populated suburban locations, the traditional terrestrial network with base stations is more suitable
Systematic review and meta-analysis to determine the efficacy of a single stage laparoscopic management versus two-stage combined laparoscopic and endoscopic management of symptomatic gallstones with common bile duct stones
No full textFeasibility study of random fibre reinforced railway ballast using image-based deformation measurements
No full textErrata: Histopathological analysis of salivary gland tumors over A 10-year period, Lagos University Teaching Hospital
No full textErrata: Histopathological Analysis of Salivary Gland Tumors OverA 10-year Period, Lagos University Teaching Hospital *Akinde OR1, Awolola NA1, Odukoya LA,1 Bamigboye B,2 Adebayo LA,1 Olawuyi AB3 and AJAYI O
Effects of random fibre reinforcement on the density of granular materials
Full text linkThe growing need for the development of resilient track materials (including ballast) to cope with increasing train speed, load and frequency has led to a focus on optimizing performance and minimizing maintenance requirements. The use of fibres of random orientation has been shown to improve significantly the mechanical properties of sand. It is reasonable to expect that such random reinforcement will have similar effects on ballast, provided that a thorough understanding of the reinforcement mechanisms at both the micro and macro-scale is reached. This paper presents data based on macro-observations of fibre reinforced scaled ballast that suggest that fibres influence the micro-mechanical interactions governing the volume change of the mixture rather than influencing shear strength mobilization which is enhanced by the tensile capacity of the fibres in the mixture. In addition, the potential benefits of the proposed reinforcement technique in railway ballast are illustrated and discusse
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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