University of Johannesburg

About: University of Johannesburg is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Tourism. The organization has 8070 authors who have published 22749 publications receiving 329408 citations. The organization is also known as: UJ.

A highly responsive NH3 sensor based on Pd-loaded ZnO nanoparticles prepared via a chemical precipitation approach.

Abstract: The gas-detecting ability of nanostructured ZnO has led to significant attention being paid to the development of a unique and effective approach to its synthesis. However, its poor sensitivity, cross-sensitivity to humidity, long response/recovery times and poor selectivity hinder its practical use in environmental and health monitoring. In this context, the addition of noble metals, as dopants or catalysts to modify the ZnO surface has been examined to enhance its sensing performance. Herein, we report preparation of Pd-loaded ZnO nanoparticles via a chemical precipitation approach. Various Pd loadings were employed to produce surface-modified ZnO nanostructure sensors, and their resulting NH3 sensing capabilities both in dry and humid environments were investigated. Through a comparative gas sensing study between the pure and Pd-loaded ZnO sensors upon exposure to NH3 at an optimal operating temperature of 350 °C, the Pd-loaded ZnO sensors were found to exhibit enhanced sensor responses and fast response/recovery times. The influence of Pd loading and its successful incorporation into ZnO nanostructure was examined by X-ray diffraction, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy. XPS studies demonstrated that in all samples, Pd existed in two chemical states, namely Pd° and Pd2+. The possible sensing mechanism related to NH3 gas is also discussed in detail.

Reduction of Vehicle Exhaust Emissions from Diesel Engines Using the Whale Concept Filter

Abstract: In this work, the effect of using a Whale filter on the overall vehicle exhaust emissions was evaluated. A Whale filter is a South African patented diesel particulate filter designed to operate as a secondary diesel filter for the removal of particulate contaminants up to 0.5 microns in size in the fuel prior to injection. It is believed that removal of contaminants prior to injection may improve the fuel injection efficiency, thereby promoting efficient combustion, and thus resulting in reduced emissions and fuel consumption. Emissions tests were conducted on four different vehicle categories to validate this. All vehicles underwent pre-emissions testing prior to installation of the Whale filter. Each test was conducted for a period of approximately 20 minutes by varying the engine speed. The Applus + Autologic Vehicle Emissions Analyser was used to measure the emissions at each stage, and a similar procedure was followed to measure the emissions after installation of the Whale filter. The results showed a significant average reduction in carbon monoxide CO (35.3%), nitrogen oxides NO(subscript x) (26.1%) and hydrocarbons HC (34.3%) emissions after the Whale filter was installed in the four vehicles.

Governing bodies and learner discipline: managing rural schools in South Africa through a code of conduct

Abstract: The South African Schools Act of 1996 provides that school governing bodies (SGBs) should adopt and assist in the enforcement of a learner code of conduct to maintain discipline effectively. This study focuses on the perceptions and experiences of SGBs in managing discipline in rural secondary schools through the design and enforcement of learner codes of conduct. A generic qualitative research paradigm was used to gain insight into the effectiveness of and factors impeding the enforcement of learner codes of conduct in rural secondary schools. For this purpose, data were collected from six secondary schools in the North West Province by means of focus group interviews and analysed according to Tesch’s method of open coding. One of the major findings of the study revealed that many rural school governors still lack the relevant knowledge and skills to design and enforce a learner code of conduct effectively. The literacy levels of the majority of SGB members (parents) make it difficult for them to design and enforce the learner code of conduct, even though the department may have provided training. Furthermore, parent-governors are far removed from the day-to-day operations of the school, and consequently fail to contextualise the seriousness of discipline problems as well as to enforce the learner code of conduct effectively.

Significance of periodogram peaks and a pulsation mode analysis of the Beta Cephei star V403 Car

Abstract: We discuss some commonly used methods for determining the significance of peaks in the periodograms of time series. We review methods for constructing the classical significance tests, their corresponding false alarm probability functions and the role played in these by independent random variables and by empirical and theoretical cumulative distribution functions. We discuss the concepts of independent frequencies and oversampling in periodogram analysis. We then compare the results of new Monte Carlo simulations for evenly spaced time series with results obtained previously by other authors, and present the results of Monte Carlo simulations for a specific unevenly spaced time series obtained for V403 Car.

An easily accessible switch-on optical chemosensor for the detection of noxious metal ions Ni(II), Zn(II), Fe(III) and UO2(II)

Abstract: Two new highly selective colorimetric and fluoregenic aminopyridine Schiff bases (L1 and L2) were synthesized by simple refluxing method and characterised via standard NMR and HRMS techniques. Its excellent metal sensing abilities explored on absorbance and fluorescence spectroscopy. The recognition colorimertric sensing behavior of probes L1 and L2 towards Ni(II), Zn(II), Fe(III) and UO2(II) ions were carefully investigated with different aspects of sensing behavior such as sensitivity, binding constant, stoichiometry, pH range and interference effect. Moreover, L1 and L2 also displayed excellent “off-on” fluoregenic selectivity with Zn(II). The results revealed that the sensors provided colorimetric and fluoregenic sensing excellent response with low limit of detection, under neutral conditions.