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Arusha, Tanzania

Netterberg F.,79 Charles Jackson Street | De Beer M.,PO Box 395
Journal of the South African Institution of Civil Engineering | Year: 2012

Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers, it is shown that from experience with heavy vehicle simulator (HVS) and dynamic cone penetrometer (DCP) testing, the presence of such layers and/or conditions at any depth in the structural layers of a flexible or semi-flexible pavement is far more deleterious than is commonly appreciated. In Part 2 the effects of these weak layers are further modelled and discussed using various examples based an HVS testing and mechanistic pavement analyses. In particular, a weak upper base course of a cemented pavement under a thin bituminous surfacing may lead to severe surfacing (and upper base) failure within a matter of weeks to months after opening to traffic, not excluding failure even during construction. In this paper (Part 1), the causes of weak layers, interlayers, laminations and/or interfaces, together with simple methods for their detection during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented) road pavements, are briefly discussed. Source


The new subspecies Eucalyptus melanophloia subsp. nana is described. The subspecies is of widespread but very scattered distribution in arid regions on rocky sites from the Yaripilangu Range in the Northern Territory in the west (about 250 km WNW of Alice Springs), eastwards to the Mount Isa area in north western Queensland. It is distinguished from subsp. melanophloia by its consistently multi-stemmed, bushy mallee habit and this is unique among the ironbark eucalypts (Eucalyptus series Siderophloiae and E. series Rhodoxylon). Illustrations of the new subspecies (including the holotype), a key to the subspecies of Eucalyptus melanophloia and a distribution map are provided. Source


Candy L.P.,PO Box 395 | Lasenby J.,University of Cambridge
IEEE Transactions on Aerospace and Electronic Systems | Year: 2010

The orientation vector differential equation was first derived by John Bortz to improve the accuracy of strapdown inertial navigation attitude algorithms. These algorithms previously relied on the direct integration of the direction cosine matrix differential equation. A compact derivation of the Bortz equation using geometric algebra is presented. Aside from being as simple and direct as any derivation in the literature, this derivation is also entirely general in that it yields a form of the Bortz equation that is applicable in any dimension, not just the conventional 3D case. The derivation presented has the further advantage that it does not rely on multiple methods of representing rotations and is expressed in a single algebraic framework. In addition to the new derivation, the validity of the notion that it is the effect of the noncommutativity of finite rotations that necessitates the use of such an equation in strapdown inertial navigation systems (SDINS) is questioned, and alternative justification for using the Bortz equation is argued. © 2010 IEEE. Source


Duncker L.C.,PO Box 395
36th WEDC International Conference: Delivering Water, Sanitation and Hygiene Services in an Uncertain Environment | Year: 2013

Limited understanding of the characteristics of different sanitation technology options may affect acceptance of certain technologies in certain circumstances, as well as lead to little appreciation by the users of the long-term financial, environmental and institutional implications of operating and maintaining the various sanitation systems. In South Africa, this has resulted in disturbing increases in the numbers of poorly operated and maintained sanitation technologies across South Africa. The need to establish a facility where people could acquaint themselves with the various sanitation systems was recognised by the CSIR and WRC who made funding available for the establishment of the Sanitation Technology Demonstration Centre at the CSIR. This Centre is aimed at informing local, provincial and national authority officials, NGO's, CBO's, consultants, schools, universities, and importantly, communities themselves in order for them to make informed and educated decisions and choices regarding sanitation technologies. Source


De Beer M.,PO Box 395 | Maina J.W.,PO Box 395 | Netterberg F.,79 Charles Jackson Street
Journal of the South African Institution of Civil Engineering | Year: 2012

This paper (Part 2 of a two-part set of papers) discusses models and illustrates the adverse effects of weak layers, interlayers, laminations and/or weak interfaces in flexible and semi-flexible pavements, also incorporating lightly cemented layers. The modelling is based on mechanistic analyses for pavement design and evaluation. In Part 1, the effects of these relatively weak layers, interlayers, laminations and/or weak interfaces were discussed. It was shown that methodologies are available to detect and investigate the existence of these weak layers in cemented pavement layers. In Part 2, several cases of the above conditions for different road pavement types are discussed, with field examples. Mechanistic analyses were done on a typical hot mix asphalt (HMA), several cases of a cemented base pavement and a granular base pavement, with and without these weak layers and interface conditions to demonstrate their adverse effects. The analyses focus on the strain energy of distortion (SED) as a pavement response parameter to indicate the potential for structural damage expected within the pavement structure or layer. Generally, the higher the SED, the higher the potential damage in the pavement layer. SED shows some potential for quantifying the relative effects of these weak layers, interlayers, laminations and/or weak interfaces within flexible and semi-flexible pavements. Source

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