NATURAL RESOURCE ACCOUNTS FOR THE STATE AND ECONOMIC CONTRIBUTION OF FORESTS AND WOODLAND RESOURCES IN SWAZILAND

Resource /Energy Economics and Policy,

Evaluation of the impact of distributed synchronous generation on the stochastic estimation of financial costs of voltage sags

Abstract: Power system faults can cause voltage sags that, if they are less than voltage sensitivity threshold of equipment, can lead to interruption of supply and lead to incurring of financial losses. The impact of distributed generation (DG) on these financial losses is investigated in this work. Using the method of fault positions, a stochastic approach to determine voltage sag performance, profiles of magnitudes of remaining voltages at a monitoring point for faults occurring along lines in the network is developed. It follows that an expected number of critical voltage sags at a monitoring point is calculated and the expected cost of these sags is derived for various voltage sensitivity threshold limits. An illustrative study is carried out comparing the expected costs of voltage sags for a network without DG with a DG case, for various mixes of customers. It is shown that in the presence of DG, the expected costs of voltage sags are lesser for all voltage sensitivity criteria assumed and for all customer mixes. The study demonstrates that the impact of incorporating DG sources results in a reduction in the expected cost of voltage sags

Evaluation of chitosan/sisal fiber/polyethylene membranes

Composites of ternary blend of chitosan/sisal fiber/high density polyethylene, were prepared by using the Rheomixer, followed by hot press, in order to form dense microfiltration membranes. The effective operation of the membranes was tested via the utilization of distilled water. The structural arrangement of the membranes was examined with the aid of using scanning electron microscopy (SEM). The chemical structure and phase identification of the membranes were examined using attenuation total reflectioninfrared spectroscopy (ATR-IR) and X-ray diffraction (XRD), respectively. The water permeability of the composite membranes is dependent on how rough the surface is, the sizes of pores and the membrane porosity. The membranes with highest amount of sisal fiber, gave highest flux of 1.4 m3/m2/h

Lead absorption and renal dysfunction in a South African battery factory

OBJECTIVES: To test the association between inorganic lead (Pb) exposure, blood pressure, and renal function in South African battery factory workers, with both conventional and newer measures of renal function and integrity. METHODS: Renal function measures included serum creatinine, urea, and urate (n = 382). Urinary markers (n = 199) included urinary N-acetyl-beta-D-glucosaminidase (NAG), retinol binding protein, intestinal alkaline phosphatase, tissue non-specific alkaline phosphatase, Tamm-Horsfall glycoprotein, epidermal growth factor, and microalbuminuria. RESULTS: Mean current blood Pb was 53.5 micrograms/dl (range 23 to 110), median zinc protoporphyrin 10.9 micrograms/g haemoglobin (range 1.9 to 104), and mean exposure duration 11.6 years (range 0.5 to 44.5). Mean historical blood Pb, available on 246 workers, was 57.3 micrograms/dl (range 14 to 96.3). After adjustment for age, weight and height, positive exposure response relations were found between current blood Pb, historical blood Pb, zinc protoporphyrin (ZPP), and serum creatinine and urate. Blood pressure was not associated with Pb exposure. Among the urinary markers, only NAG showed a positive association with current and historical blood Pb. CONCLUSION: An exposure-response relation between Pb and renal dysfunction across the range from < 40 to > 70 micrograms/dl blood Pb was found in this workforce, with conventional measures of short and long term Pb exposure and of renal function. This could not be explained by an effect on blood pressure, which was not associated with Pb exposure. The findings probably reflect a higher cumulative renal burden of Pb absorption in this workforce in comparison with those in recent negative studies. The results also confirm the need for strategies to reduce Pb exposure among industrial workers in South Africa.

Paraffin and other fuels as sources of indoor air pollution in a poor urban settlement in Cape Town, South Africa

R S Bailie, L S Pilotto, R I Ehrlich, S Mbuli, R Truter, P Terblanch