Stanford B.K.,NASA |
Jutte C.V.,CAPE Technologies
Computers and Structures | Year: 2017
A series of aeroelastic optimization problems are solved on a high aspect ratio wingbox of the Common Research Model, in an effort to minimize structural mass under coupled stress, buckling, and flutter constraints. Two technologies are of particular interest: tow steered composite laminate skins and curvilinear stiffeners. Both methods are found to afford feasible reductions in mass over their non-curvilinear structural counterparts, through both distinct and shared mechanisms for passively controlling aeroelastic performance. Some degree of diminishing returns are seen when curvilinear stiffeners and curvilinear fiber tow paths are used simultaneously. © 2017
Faasen M.,CAPE Technologies |
Fourie-Malherbe M.,Stellenbosch University
IMSCI 2016 - 10th International Multi-Conference on Society, Cybernetics and Informatics, Proceedings | Year: 2016
This paper reports on the implementation of audience response activities in five academic contexts at a higher education institution, and highlights some pitfalls in the introduction of this kind of technology for teaching and learning purposes. The paper firstly gives an overview of audience response technology, before contextualising the study. The study followed a mixed methods approach, and data collection included both quantitative and qualitative data in the form of observations of lessons, interviews with lecturers, student surveys and artefact analysis. This is followed by an analysis of the five cases. Pitfalls in integrating audience response technology in teaching and learning included the inefficient use of the aggregated feedback produced by the audience response system; technical difficulties encountered with the audience response system itself; drawbacks related to the size of the mobile device, and lack of motivation by students to participate in the activity. The paper concludes that the strength of audience response technology is the aggregated feedback given by the system, but for lecturers and students to benefit from this, lecturers need to redesign their current pedagogical practices. However, in order to do this they need sufficient technological and pedagogical support from the institution.
Njombolwana N.S.,Stellenbosch University |
Njombolwana N.S.,Citrus Research International |
Erasmus A.,Citrus Research International |
van Zyl J.G.,Stellenbosch University |
And 5 more authors.
Postharvest Biology and Technology | Year: 2013
Wax application plays an important role in prolonging fruit quality, and the addition of imazalil (IMZ) furthermore protects fruit against green mould caused by Penicillium digitatum. The objectives of this study were to evaluate green mould control and quality preservation effects of carnauba or polyethylene citrus coatings supplemented with IMZ, as well as the effect of synthetic or horsehair brush types used on sweet orange fruit. Single applications of IMZ at 3000μgmL-1 at rates of 0.6, 1.2 and 1.8Lt-1 resulted in residues that increased with increasing coating loads on navel oranges (1.31 to 3.32μgg-1) and Valencia oranges (3.22 to 6.00μgg-1). Coating with IMZ generally provided poorer curative control (≈14%) than protective control (≈58%), with less sporulation in treatments using horsehair (≈59%) than synthetic brushes (≈64%). More fruit weight and firmness losses were found in fruit treated with the polyethylene coating (≈1.18 and ≈0.93 ratios of treated vs. untreated, respectively) and lower in carnauba treated fruit (≈0.76 and ≈0.74 ratios, respectively). However, polyethylene coatings resulted in shinier fruit before (≈10.85 shine ratio) and after storage (11.60), whereas carnauba coatings resulted in lower shine ratios (≈7.45 and 10.15, respectively). Gas (CO2) exchange ratios remained similar for both waxes (≈0.67). Higher polyethylene coating loads (1.8Lt-1) resulted in off-tastes similar to uncoated control fruit (≈2.21 rating on a 5-point scale) and higher than the rating for carnauba coated fruit (≈1.82) at this rate. Scanning electron micrographs showed an amorphous crystallised natural wax layer with uncovered stomatal pores on the surface of uncoated fruit. The thickness of the applied wax layer increased with increasing coating load. A single application of IMZ in wax provided good protective green mould control and sporulation inhibition, with differing effects on some fruit quality parameters due to coating and brush types. © 2013 Elsevier B.V.
Gamerota W.R.,University of Florida |
Gamerota W.R.,IBM |
Uman M.A.,University of Florida |
Hill J.D.,CAPE Technologies |
Jordan D.M.,University of Florida
Geophysical Research Letters | Year: 2015
Corona streamers are a critical component of lightning leader step formation and are postulated to produce the very high electric fields at their tips that produce runaway electrons resulting in the observed X-ray bursts associated with leader stepping. Corona emanating from the vicinity of the leader tip between leader steps was analyzed using three sequential high-speed video sequences of dart-stepped leaders in three different triggered lightning flashes during the summers of 2013 and 2014 in northeast Florida. Images were recorded at 648 kiloframes per second (1.16μs exposure time, 380ns dead time) at an altitude of 65m or less. In each image sequence, the leader propagates downward in consecutive frames, with corona streamers observed to fan outward from the bright leader tip in less than the image frame time of about 1.5μs. In 21 exposures, corona streamers propagate, on average, 9m below the bright leader tip. Key Points Corona streamers imaged in three dart-stepped leaders near ground Average streamer length about 9m Side corona duration less than 1.54μs ©2015. American Geophysical Union. All Rights Reserved.
Bezuidenhout D.,University of Cape Town |
Bezuidenhout D.,CAPE Technologies |
Williams D.F.,CAPE Technologies |
Williams D.F.,Wake Forest Institute of Regenerative MedicineNC |
And 2 more authors.
Biomaterials | Year: 2015
Efficient function and long-term durability without the need for anticoagulation, coupled with the ability to be accommodated in many different types of patient, are the principal requirements of replacement heart valves. Although the clinical use of valves appeared to have remained steady for several decades, the evolving demands for the elderly and frail patients typically encountered in the developed world, and the needs of much younger and poorer rheumatic heart disease patients in the developing world have now necessitated new paradigms for heart valve technologies and associated materials. This includes further consideration of durable elastomeric materials. The use of polymers to produce flexible leaflet valves that have the benefits of current commercial bioprosthetic and mechanical valves without any of their deficiencies has been held desirable since the mid 1950s. Much attention has been focused on thermoplastic polyurethanes in view of their generally good physico-chemical properties and versatility in processing, coupled with the improving biocompatibility and stability of recent formulations. Accelerated invitro durability of between 600 and 1000 million cycles has been achieved using polycarbonate urethanes, and good resistance to degradation, calcification and thrombosis invivo has been shown with some polysiloxane-based polyurethanes. Nevertheless, polymeric valves have remained relegated to use in temporary ventricular assist devices for bridging heart failure patients to transplantation. Some recent studies suggest that there is a greater degree of instability in thermoplastic materials than hitherto believed so that significant challenges remain in the search for the combination of durability and biocompatibility that would allow polymeric valves to become a clinical reality for surgical implantation. Perhaps more importantly, they could become candidates for use in situations where minimally invasive transcatheter procedures are used to replace diseased valves. Being amenable to relatively inexpensive mass production techniques, the attainment of this goal could benefit very large numbers of patients in developing and emerging countries who currently have no access to treatment for rheumatic heart disease that is so prevalent in these areas. This review discusses the evolution and current status of polymeric valves in wide-ranging circumstances. © 2014 Elsevier Ltd.
Suttorp M.J.,St Antonius Hospital |
Stella P.R.,University Utrecht |
Dens J.,Hospital Oost Limburg |
McKenzie J.M.,DISAVascular |
And 2 more authors.
Netherlands Heart Journal | Year: 2015
Aim To report clinical follow-up at 6 months after implantation of the ultra-thin strut cobalt chromiumSolarFlex stent in a real-world setting. Methods and results Patients (n=240) with single or multiple vessel coronary artery disease undergoing percutaneous coronary intervention (PCI) at four sites in Europe were enrolled in the SOLSTICE (SolarFlex Stent in Routine Clinical Practice) registry. Follow-up at 6 months was 100%. Diabetes was present in 29% of the patients, 30% presented with acute myocardial infarction and 17% had unstable angina. Of the patients, 27% had previously undergone PCI or coronary artery bypass surgery. Lesion complexity was high (50% B2+C type lesions). Device success was achieved in 99.7% of cases and themajor adverse cardiac event (MACE) ratewas 5.8% at 6 months of follow-up. Target lesion revascularisation (TLR) was 5.0% at 6 months. Conclusions The SOLSTICE registry showed that in a complex real-world setting the SolarFlex bare metal stent, with ultra-thin struts and customised scaffolding, provided low clinical MACE and TLR rates. These results provide support for the use of the latest generation bare metal stent in contemporary European practice. © The Author(s) 2014.
Stanford B.K.,NASA |
Jutte C.V.,CAPE Technologies |
Chauncey Wu K.,NASA
Composite Structures | Year: 2014
The use of tow steered composites, where fibers follow prescribed curvilinear paths within a laminate, can improve upon existing capabilities related to aeroelastic tailoring of wing structures, though this tailoring method has received relatively little attention in the literature. This paper demonstrates the technique for a cantilevered flat plate in low-speed flow. A genetic algorithm is used to locate the Pareto front between static aeroelastic stresses and dynamic flutter boundaries. The impact of various tailoring choices upon the aeroelastic performance is quantified: curvilinear fiber steering versus straight fiber steering and certifiable versus non-certifiable stacking sequences. © Published by Elsevier Ltd.
Nesbitt A.B.,CAPE Technologies
Minerals Engineering | Year: 2010
Two case studies are presented in which a continuous loss of capacity in two samples of acid resin, are observed over 900 cycles of loading and regeneration. By completing the batch kinetic testing of the resin at different turbulences and calculating the intra-particle diffusion rates of the counter and co-ion, the effect of turbulence on the independence/dependence of the intra-particle diffusion could be established. A systematic loss in capacity and change in kinetics is reported in both case studies and it is postulated that the reason for this is the loss of active sites within the resin matrix. The significance of this observation is that standard tests done for a new resin application could significantly overestimate the commercial performance of the resin concerned. This paper proposes a method in which resin might be studied prior to inclusion in a particular process, with the objective of determining its effective life span. © 2009.
Stanford B.K.,NASA |
Jutte C.V.,CAPE Technologies |
AIAA Journal | Year: 2016
Several minimum-mass aeroelastic optimization problems are solved to evaluate the effectiveness of a variety of novel tailoring schemes for subsonic transport wings. Aeroelastic strength and panel buckling constraints are imposed across several trimmed maneuver loads, in addition to flutter constraints. Tailoring with metallic thickness variations, functionally graded materials, composite laminates, tow steering within composite laminates, and distributed trailing-edge control effectors are all found to provide reductions in structural wing mass with varying degrees of success. The question as to whether this wing mass reduction will offset the increased manufacturing cost is left unresolved for each case. Copyright © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.