Deposition of aerosol particles on rough surfaces inside a test chamber

We investigated the deposition rate of aerosol particles (diameter between 0.03 and 5 μm) on rough surfaces of wallpapers, wall-plasters, and two types of carpets inside a test chamber. Compared to a smooth aluminum surface, the deposition rate of aerosol particles on the tested surfaces was up to 20 times depending on the surface roughness, mixing intensity, and particle size. A rough surface with a dimensionless surface roughness height k⁺ < 0.06 can be treated as a hydraulically smooth. The estimated deposition rates in this study and those predicted by a deposition model, which incorporates surface roughness, were in good agreement for coarse mode particles (diameter > 1 μm) when k⁺ < 1.04 and for ultrafine particles (diameter < 0.1 μm) when k⁺ < 0.48. The agreement between the model prediction and our estimation was better for coarse mode particles than for ultrafine particles. Deposition of aerosol particles, especially fine particles, needs more empirical investigations aiming at improving the existing models.     

Grafting vinyl monomers onto nylon 6. VI. Graft copolymerization of methyl methacrylate onto nylon 6 using acetylacetonate complex of Mn(III), Co(III), and Fe(III)

The graft copolymerization of methyl methacrylate onto nylon 6 using metal complexes of Mn³⁺, Co³⁺, and Fe³⁺ as initiators was studied. The rate of polymerization, R_p, increased with increasing complex concentrations in the initial stages; but it decreased upon further increase of complex concentrations. With increasing monomer concentrations, the rate of polymerization increased progressively. The graft yield increased with increaing temperature within the range 60–75°C. A suitable kinetic scheme is presented and rate equations are derived.     

Effect of metal-fingers/doped-ZnO transparent electrode on performance of GaN/InGaN solar cell

The effect of doped-ZnO transparent conductive oxide (TCO) with metal (Ag)-fingers contact on GaN/InGaN solar cell is investigated through numerical simulations. An optical and electrical analysis of different dopant elements (such as B, Al, Ga, In and Sn) with ZnO as a top TCO layer is studied. A comparative analysis of metal square pad electrode, metal grid pattern electrode and metal-finger/ZnO type electrodes are taken into consideration to ensure the effect of anti-reflectivity by ZnO. The effect of thickness of ZnO and i-InGaN layer on performance of solar cell is also studied in detail. The proposed solar cell structure with Ag-fingers/ZnO:Al as top contact electrode shows interesting device characteristics compared to other dopants and metal top electrodes. The device achieves open circuit voltage~2.525 V, short circuit current~4.256 mA/cm², fill factor~87.86% and efficiency~9.22% under 1 Sun, air mass 1.5 global illumination.     

Reinforcing Housing Assets in the Wrong Location? The Case of Botshabelo,South Africa

Apartheid policies were instrumental in displacing black urbanisation away from key urban areas. Botshabelo, 55 km east of Bloemfontein, is an example of this. This paper uses asset-building theory to argue that post-apartheid policy for Botshabelo has largely reinforced apartheid spatial planning patterns and locked in a significant percentage of the Botshabelo population. Population growth is slow, with evidence of the working age population leaving Botshabelo. At the same time, substantial investment in infrastructure services has increased investment in housing in the past 20 years.     

Informal settlement upgrading in South Africa: beneficiaries’ perceptions over nearly twenty-five years

Research on informal settlement upgrading tends to focus on one-off case studies. This article investigates the changing experiences, over nearly 25 years, of people living in an upgraded informal settlement. We sought to determine how the perceptions of the residents of Freedom Square changed. Our latest survey (2014) included responses from 199 household representatives and followed earlier surveys. Firstly, we find that the upgrading of Freedom Square represents a first step towards ensuring the housing rights of black people in urban South Africa. Secondly, spatial infilling and locational advantage continue to play valuable roles. Thirdly, dweller control, in terms of which residents themselves are able to design extensions to their houses, remains important. Fourthly, social cohesion among community members is proving to be more important than access to a stand. Fifthly, urban management remains an important long-term requirement. Lastly, elements of informality persist in the area.     

Revitalizing the Bloemfontein CBD: Prospects,Obstacles and Lost Opportunities

Urban change has systematically been researched for more than a century. One of the key foci has been the Central Business Districts (CBDs) of cities. The past decades has seen an extensive literature develop on CBD decline focusing on why such decay sets in and which strategies, as well as policies, that might be deployed to stimulate the revitalisation of these areas. The debates are, however, in the main developed within the context of large cities, whilst the geographical focus tends to be on countries of the post-industrial north. In the South African context, a small, but nevertheless significant literature has developed chronicling both CBD decline and subsequent revitalisation strategies deployed to reverse such decline. Similar to the international experience, the focal point has been South Africa’s main metropolitan regions, whilst secondary cities have remained beyond the investigatory focus. The aim of this paper was to provide an outline of the prospects and obstacles that face CBD revitalisation in the secondary city of Bloemfontein. It is argued that whilst generic revitalisation programmes in cities such as Cape Town and Johannesburg have seemingly stemmed further CBD decline, other strategies might be required in secondary cities such as Bloemfontein.

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NMR study of temperature-induced phase separation and polymer-solvent interactions in poly(vinyl methyl ether)/D2O/ethanol solutions

The changes in the dynamic structure during temperature-induced phase transition in D₂O/ethanol solutions of poly(vinyl methyl ether) (PVME) were studied using NMR methods. The effect of polymer concentration and ethanol (EtOH) content in D₂O/EtOH mixtures on the appearance and extent of the phase separation was determined. Measurements of ¹H and ¹³C spin-spin and spin-lattice relaxations showed the presence of two kinds of EtOH molecules: besides the free EtOH expelled from the PVME mesoglobules there are also EtOH molecules bound in PVME mesoglobules. The existence of two different types of EtOH molecules at temperatures above the phase transition was in solutions with polymer concentration 20 wt% manifested by two well-resolved NMR signals (corresponding to free and bound EtOH) in ¹³C and ¹H NMR spectra. With time the originally bound EtOH is slowly released from globular-like structures. From the point of view of polymer-solvent interactions in the phase-separated PVME solutions both EtOH and water (HDO) molecules show a similar behaviour so indicating that the decisive factor in this behaviour is a polar character of these molecules and hydrogen bonding.     

Evaluation of environmental impact assessment effectiveness in Slovakia

Environmental impact assessment (EIA) practice in Slovakia is about 20 years old. EIA was first introduced in Slovakia based on the Environment Law of 1992. The practice in EIA started developing shortly after the Law No. 127/1994 Coll. came into force. The first group of experts was certified as being EIA/strategic environmental assessment (SEA) professionally qualified persons. During 20 years, the numbers of EIA procedures were performed and number of EIA practitioners has considerably increased. Many discussions arise about EIA procedure effectiveness and quality in Slovakia. The task of this study has been to investigate EIA system applications in Slovakia and evaluate its effectiveness. In this paper, the views of professionally qualified persons are examined closely, using a questionnaire survey. Data from the questionnaires are analysed to find information relating to current EIA/SEA and EIA/SEA practice and the future for EIA. The objective of this study was to assess the potential for improving the effectiveness of EIA in Slovakia, and finally the recommendations for improvement are presented. The results of this research suggest that the use of new legislation should be extended in Slovakia in order to improve EIA effectiveness.