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A statistical exploration of interval-deficient wind speed data for application to wind power assessments

Gathering quality wind speed data can be time-consuming and expensive. The present study established whether interval-deficient wind speed data could be rendered useful for wind power assessments. The effect of interval deficiency on the quality of the wind speed data was investigated by studying the behaviour of the Weibull scale and shape factors as the interval size between wind speed measurements increased. Five wind speed data sets obtained from the Southern African Universities Radiometric Network (Sauran) were analysed, based on a proposed procedure to find the true Weibull parameters from an interval-deficient wind speed data set. It was found that the relative errors in the Weibull parameters were, on average, less than 1%, compared with the Weibull parameters computed from a wind speed data set that complies with the IEC 61400-12-1:2005(E) standard. This finding may contribute to time and cost reduction in wind power assessments. It may also promote the application of statistical methods in the renewable energy sector

Communication about HIV and death: Maternal reports of primary school-aged children's questions after maternal HIV disclosure in rural South Africa

Introduction: Children's understanding of HIV and death in epidemic regions is under-researched. We investigated children's death-related questions post maternal HIV-disclosure. Secondary aims examined characteristics associated with death-related questions and consequences for children's mental health. Methods: HIV-infected mothers (N = 281) were supported to disclose their HIV status to their children (6–10 years) in an uncontrolled pre-post intervention evaluation. Children's questions post-disclosure were collected by maternal report, 1–2 weeks post-disclosure. 61/281 children asked 88 death-related questions, which were analysed qualitatively. Logistic regression analyses examined characteristics associated with death-related questions. Using the parent-report Child Behaviour Checklist (CBCL), linear regression analysis examined differences in total CBCL problems by group, controlling for baseline. Results: Children's questions were grouped into three themes: ‘threats’; ‘implications’ and ‘clarifications’. Children were most concerned about the threat of death, mother's survival, and prior family deaths. In multivariate analysis variables significantly associated with asking death-related questions included an absence of regular remittance to the mother (AOR 0.25 [CI 0.10, 0.59] p = 0.002), mother reporting the child's initial reaction to disclosure being “frightened” (AOR 6.57 [CI 2.75, 15.70] p=<0.001) and level of disclosure (full/partial) to the child (AOR 2.55 [CI 1.28, 5.06] p = 0.008). Controlling for significant variables and baseline, all children showed improvements on the CBCL post-intervention; with no significant differences on total problems scores post-intervention (β -0.096 SE1.366 t = -0.07 p = 0.944). Discussion: The content of questions children asked following disclosure indicate some understanding of HIV and, for almost a third of children, its potential consequence for parental death. Level of maternal disclosure and stability of financial support to the family may facilitate or inhibit discussions about death post-disclosure. Communication about death did not have immediate negative consequences on child behaviour according to maternal report. Conclusion: In sub-Saharan Africa, given exposure to death at young ages, meeting children's informational needs could increase their resilience

Autotransplantation of the lung: experimental studies on the cape baboon

Autotransplantation of the left lung was performed on 15 adult baboons with an 8-day survival rate of 80% and a long-term survival rate of 60%. On 5 of the survivors a subsequent contralateral pneumonectomy was performed without mortality. Most deaths occurred early in the series due to technical problems. A surgical technique has been standardized and with further experience in this field the mortality associated with autotransplantation of the lung in baboons should be less than 10%. Xenon-l33 ventilation-perfusion studies of the transplanted lung demonstrated a significant reduction in perfusion, and to a lesser extent of ventilation. Ventilation rapidly recovered towards normal but perfusion only approached normal values several months after transplantation. These physiological alterations may be due to the denervation attendant upon complete removal of tlu lung with reimplantation. The jilt! imbalance does not appear to be of major consequence when a contralateral pneumonectomy is performed. The autotransplanted lung appears to be a valuable model for studying the effects of lung transplantation alone, without the problems of rejection. These studies seem to be particularly valuable in the primate who closely resembles the human anatomically and physiologically. Further studies are currently in progress

Offside goals and induced breaches of contract

An analysis of Global Resources Group Ltd v Mackay which explores the possibility of building links between the offside goals rule and nominate delict of inducing breach of contract

Examining the link between the antecedents of relationship commitment and loyalty within the road transport industry of South Africa

Abstract: The study investigates the extent to which the relationship commitment by customers of road transport service providers is influenced by trust, communication, shared values and the attractiveness of alternatives. In turn, the influence of the extent of their commitment towards future loyalty is determined. Design/methodology/approach – An explanatory research design was followed and data was collected from road transport service provider customers using self-administered questionnaires. A total of 120 responses were suitable for analysis. Multiple regression analysis as well as the one-way analysis of variance (ANOVA) technique was used to analyse the results and to uncover the interrelationships between constructs..

State Control over Private Military and Security Companies in Armed Conflict by H Tonkin

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Mathematical basis for three dimensional circular interpolation on CNC machines

The control units of numerically controlled manufacturing machines allow the programmer only a limited number of mathematical functions with which programmes can be written. Despite these limitations it is now possible to write programmes with which three dimensional (3D) circular interpolation can be performed directly on the .machines. The necessary mathematical techniques to perform 3D circular interpolation directly on the machines are deduced, although somewhat roundabout to overcome the programming limitations. The main programming limitations as well as cutter speed limitations are indicated.Die beheereenhede van numeriesbeheerde vervaardigingsmasjiene beskik:oor 'n beperkte aantal wiskundige funksies wat tot die beskikking van die programmeerder gestel word om programme mee te skryf. Selfs met .hierdie beperkings is dit nou moontlik om programme te skryf waarmee driedimensionele (3D) sirkelinterpolasie direk op die masjiene uitgevoer kan word. Die nodige wiskundige tegnieke waarmee 3D sirkelinterpolasie gedoen kan word, al is dit 'n effens omslagtige manier om die beperkings te oorkom, word afgelei. Die belangrikste programmeringsbeperkings asook snyspoedbeperkings word aangetoon.http://sajie.journals.ac.z

Praktiese driedimensionele sirkel-interpolasie vir numeriesbeheerde masjiene

Numerically controlled manufacturing machines provide for machining circles only in two dimensions. As a result of this limitation a wide variety of shapes can only be machined by making use of computer-aided design. In this article the theory is derived and a subroutine developed with which three dimensional circular interpolation with radius correction is made available for application in practice.Numeriesbeheerde vervaardigingsmasjiene maak voorsiening vir die sny van sirkels in slegs twee dimensies. Hierdie beperking veroorsaak dat 'n wye reeks vorme slegs m.b.v. rekenaargesteunde ontwerpprogrammatuur gesny kan word. In hierdie artikel word die teorie, afgelei en ' n subroetine ontwikkel waarmee driedimensionele sirkel-interpolasie met radiuskorreksie vir praktykgebruik beskikbaar gestel word.http://sajie.journals.ac.z