Renee Koen - Academia.edu (original) (raw)

Papers by Renee Koen

CHRIS RUST holds a PhD in Civil Engineering from the University of the Witwatersrand and is curre... more CHRIS RUST holds a PhD in Civil Engineering from the University of the Witwatersrand and is currently the Strategic Innovation Manager at the CSIR Built Environment Unit. He is a registered professional civil engineer and has 25 years' experience in research in infrastructurerelated topics. His fi elds of expertise include pavement engineering, pavement materials, strategic planning and strategic research management.

Journal of Energy in Southern Africa, Dec 19, 2014

In a developing country such as South Africa, understanding the expected future demand for electr... more In a developing country such as South Africa, understanding the expected future demand for electricity is very important in various planning contexts. It is specifically important to understand how expected scenarios regarding population or economic growth can be translated into corresponding future electricity usage patterns. This paper discusses a methodology for forecasting long-term electricity demand that was specifically developed for applying to such scenarios. The methodology uses a series of multiple regression models to quantify historical patterns of electricity usage per sector in relation to patterns observed in certain economic and demographic variables, and uses these relationships to derive expected future electricity usage patterns. The methodology has been used successfully to derive forecasts used for strategic planning within a private company as well as to provide forecasts to aid planning in the public sector. This paper discusses the development of the modelling methodology, provides details regarding the extensive data collection and validation processes followed during the model development, and reports on the relevant model fit statistics. The paper also shows that the forecasting methodology has to some extent been able to match the actual patterns, and therefore concludes that the methodology can be used to support planning by translating changes relating to economic and demographic growth, for a range of scenarios, into a corresponding electricity demand. The methodology therefore fills a particular gap within the South African long-term electricity forecasting domain.

Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese, 2011

Many decisions regarding capital investment in electricity generation technologies need to be mad... more Many decisions regarding capital investment in electricity generation technologies need to be made well in advance, usually when there is still a large amount of uncertainty regarding the favourability of future conditions. There may be uncertainty about the amount of electricity required in future as well as the the variability in the demand, and both of these uncertainties can affect decisions pertaining to such capital investment decisions. This paper presents an approach that uses multilevel models to develop scenario forecasts for South African load profiles (hour-to-hour changes in the electricity demand), which can then be used to support decisions regarding the electricity generation capacity required. Although historical load profile patterns are known, there is uncertainty about how future patterns will deviate from historical ones. By developing scenarios that represent different views about future load profile patterns, forecasts can be obtained for each scenario and, in turn, these scenario forecasts can be used to investigate the effect of changes in demand patterns on future electricity generation requirements. The approach of using multilevel modelling to obtain long-term hourly forecasts for a particular scenario has not been seen elsewhere in the literature, but shows promise for providing appropriate support electricity generation expansion decisions.

Changing the face of waste management in South Africa, includes waste diversion from landfill to ... more Changing the face of waste management in South Africa, includes waste diversion from landfill to alternative management options. There are a number of interventions to consider which may vary from very low tech, labour intensive solutions to extremely high tech, capital intensive technology options. Making an informed decision about the preferred technology choice will require a certain level of knowledge of the composition of the waste stream at hand. The level of detail that is required from the waste characterisation study will be determined by site specific conditions, and the level of change you want to achieve. In some instances, a mere screening exercise will do the trick, but if the envisaged change include high tech, capital intensive solutions, you may want to have a high level of confidence in the characteristics and volumes of waste that will be diverted to the particular solution in question. This paper will unpack the considerations to take into account when conducting or evaluating a waste characterisation study in support of changed waste management in South Africa.

South African prosecution resources: Challenges and approach

Aggregate shape properties are used to characterize aggregate product from quarry operations. How... more Aggregate shape properties are used to characterize aggregate product from quarry operations. However, aggregate shape depends on rock type and crushing process. A meta-quartzite, a relatively low grade thermal metamorphic rock was crushed through four crushers. In this paper, a description is provided on the quantification of particle shapes using data from a 3-D laser scanning device. The images from the laser were fully utilized in quantifying the shape descriptors in order to identify the differences between individual aggregates. It was possible to quantify differences in particle shape characteristics at the small particle scale and aggregate shape distributions between the different types of crushers and possible influence of particle sizes as well as interaction effects. Aggregate products vary significantly according to the nature of their processing. For all the shape parameters, a statistically significant difference was found between the four different crusher types. For...

Proceedings of the 23rd WasteCon Conference, 17-21 October 2016, Emperors Palace, Johannesburg, S... more Proceedings of the 23rd WasteCon Conference, 17-21 October 2016, Emperors Palace, Johannesburg, South Africa

Prior to 1987, the emphasis of the CSIR was on promoting science with most of the statistical wor... more Prior to 1987, the emphasis of the CSIR was on promoting science with most of the statistical work involving either statistical theory development or consulting to CSIR researchers. In 1987, the CSIR went through a period of transition, with the focus changing to contract research and statistical consulting to external clients. In 2005, the CSIR again went through a major reorganisation to coincide with the organisation’s 60 year anniversary, designed to bring more balance between contract research and contributing to the scientific community. Operating environment of statisticians Although there are analysts and statisticians scattered as individual researchers, usually focused on very specific application domains, throughout the organisation, the Statistical Modelling and Analysis Research Group (SMARG), consisting of nine researchers, are focussed on inter-disciplinary statistical modelling and analysis. This is a relatively small group within an organisation employing almost 2 5...

Proceedings of the ICA, May 16, 2018

In South Africa, a team of analysts has for some years been using statistical techniques to predi... more In South Africa, a team of analysts has for some years been using statistical techniques to predict election outcomes during election nights in South Africa. The prediction method involves using statistical clusters based on past voting patterns to predict final election outcomes, using a small number of released vote counts. With the US presidential elections in November 2016 hitting the global media headlines during the time period directly after successful predictions were done for the South African elections, the team decided to investigate adapting their method to forecast the final outcome in the US elections. In particular, it was felt that the time zone differences between states would affect the time at which results are released and thereby provide a window of opportunity for doing election night prediction using only the early results from the eastern side of the US. Testing the method on the US presidential elections would have two advantages: it would determine whether the core methodology could be generalised, and whether it would work to include a stronger spatial element in the modelling, since the early results released would be spatially biased due to time zone differences. This paper presents a high-level view of the overall methodology and how it was adapted to predict the results of the US presidential elections. A discussion on the clustering of spatial units within the US is also provided and the spatial distribution of results together with the Electoral College prediction results from both a 'test-run' and the final 2016 presidential elections are given and analysed.

South African Journal of Economic and Management Sciences, 2018

Background: This study involves forecasting electricity demand for long-term planning purposes. L... more Background: This study involves forecasting electricity demand for long-term planning purposes. Long-term forecasts for hourly electricity demands from 2006 to 2023 are done with in-sample forecasts from 2006 to 2012 and out-of-sample forecasts from 2013 to 2023. Quantile regression (QR) is used to forecast hourly electricity demand at various percentiles. Three contributions of this study are (1) that QR is used to generate long-term forecasts of the full distribution per hour of electricity demand in South Africa; (2) variabilities in the forecasts are evaluated and uncertainties around the forecasts can be assessed as the full demand distribution is forecasted and (3) probabilities of exceedance can be calculated, such as the probability of future peak demand exceeding certain levels of demand. A case study, in which forecasted electricity demands over the long-term horizon were developed using South African electricity demand data, is discussed. Aim: The aim of the study was: (1...

Inflammation, 1995

Relationships between plasma levels of beta-carotene (BC) and the numbers and oxidant-generating ... more Relationships between plasma levels of beta-carotene (BC) and the numbers and oxidant-generating activities of circulating neutrophils have been investigated in a group of asymptomatic young male cigarette smokers (N = 40) and in a group of nonsmoking control subjects. Plasma BC levels were measured using HPLC, while oxidant generation was measured using a phorbol myristate acetate (PMA) activated whole blood luminol-enhanced chemiluminescence (LECL) method. Relative to nonsmokers, the numbers of circulating neutrophils, as well as the LECL responses of these cells, were increased by 41% (p = 0.0001) and 47% (p = 0.004), respectively, while plasma BC levels were decreased by 24% (p = 0.01). In cigarette smokers, but not in nonsmokers, the numbers of circulating neutrophils, as well as the LECL responses of these cells, were significantly and inversely correlated with plasma BC levels (r =-0.36, p = 0.02; and r =-0.33, P = 0.04 respectively). Diminished plasma levels of BC in cigarette smokers probably reflect the increased numbers and prooxidative activities of circulating neutrophils. Intake of this antioxidant nutrient may be a determinant of susceptibility to smoking-related pulmonary dysfunction mediated by oxidants derived from smoke-activated phagocytes.

Free Radical Biology and Medicine, 1995

Relationships among the plasma levels of vitamin E (VE), the numbers and prooxidative activities ... more Relationships among the plasma levels of vitamin E (VE), the numbers and prooxidative activities of circulating phagocytes, serum alpha-1-protease inhibitor (API), and pulmonary functions were investigated in 83 asymptomatic male cigarette smokers and 65 nonsmoking controls. Plasma levels of VE, of cholesterol, and of API were measured using high performance liquid chromatography, spectrophotometry, and nephelometry, respectively, whereas reactive oxidant (ROS) generation by activated blood phagocytes was measured using a whole blood luciginen-enhanced chemiluminescence method. Smoking was associated with significantly increased circulating neutrophil counts (p 0.0001), serum API (p 0.0001) and phagocyte-derived ROS-generation (p 0.0001), and decreased spirometric values (FEV1: p 0.0138 and FEF25-75: p 0.0654). Plasma VE and cholesterol levels were not significantly different between smokers and nonsmokers. However, in smokers both plasma VE and cholesterol correlated significantly and positively with serum API (r 0.24, p 0.03 and r 0.30, p 0.005, respectively), neutrophil counts (r 0.24, p 0.03 and r 0.25, p 0.03, respectively), and phagocyte-derived ROS-generation (r 0.32, p 0.003 and r 0.32, p 0.003, respectively), and significantly and inversely with FEV1 (r -0.23, p 0.03 and r -0.22, p 0.04, respectively) and FEF25-75 (r -0.32, p 0.003 and r -0.26, p 0.02, respectively). In nonsmokers plasma VE, but not cholesterol, was positively correlated with FEV1 (r 0.34, p 0.007) and FEF25-75 (r 0.40, p 0.001). The results suggest that VE protects the lungs of both smokers and nonsmokers and may act as a mobilizable antioxidant in response to smoking-induced oxidative stress.

Journal of the South African Institution of Civil …, 2011

Atherosclerosis, 1996

In this study we have measured circulating levels of autoantibodies to cardiolipin and oxidised l... more In this study we have measured circulating levels of autoantibodies to cardiolipin and oxidised low-density lipoprotein (ox-LDL) and correlated these with plasma concentrations of the anti-oxidant nutrients vitamin C, vitamin E and beta-carotene, in a group (79) of asymptomatic, male cigarette smokers and in non-smoking control subjects. Cigarette smoking, a well-known risk factor for development of atherosclerosis, was found to be associated with moderately elevated levels of autoantibodies to both cardiolipin and ox-LDL. Increased levels of these autoantibodies were most evident in the older smokers (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30 years) and were significantly and inversely correlated with plasma vitamin C, but not with vitamin E or beta-carotene. Absorption studies designed to investigate the specificity of these autoantibodies demonstrated a high degree of cross-reactivity of cardiolipin antibodies with ox-LDL, while antibodies to the oxidatively modified lipoprotein tended to be specific for this antigen. These findings suggest that cigarette smoking promotes formation of autoantibodies to both cardiolipin and ox-LDL and that these may be involved in the initiation and/or perpetuation of atherosclerosis. Dietary intake of vitamin C may be a determinant of susceptibility to development of this cardiovascular disorder.

This study looked at a specific application of cluster analysis using the recently released popul... more This study looked at a specific application of cluster analysis using the recently released population census 2011 data for the Ekurhuleni Metro in the Gauteng Province of South Africa. The main focus of the clustering was to distinguish housing and household patterns in order to create homogenous groups with similar demands for infrastructure, facilities and services. The k-means algorithm was specifically applied to groups of variables (factors) such as the dwelling types, conditions and location characteristics, socioeconomic profiles, as well as demographic factors. These groups of clusters were later combined in a sequential manner to obtain a final set of meaningful clusters that could be used as inputs into an urban growth simulation tool.

Journal of Energy in Southern Africa