1,721,003 research outputs found
Modeling and Simulation of Low Current Atmospheric and High-Pressure Helium Plasma Discharges
Get PDFA plasma discharge in a Helium gas reactor at different pressures and at low currents (0.25-0.45 A) has been investigated by Computational Fluid Dynamic modeling coupled with the Maxwell's equations. The results show different discharge dynamics across the pressure range (0.1-8 MPa), with an arc discharge obtained at high pressure and a low current arc discharge observed at atmospheric pressure. A large density gradient at higher pressure causes a strong natural convection effect in the reactor. This density gradient affects drastically the discharge shape and the velocity field at high pressures while at atmospheric pressure, a lower density gradient was observed resulting in a low velocity magnitude. It has been observed that the velocity magnitude is not affected by the electric current. The discharge electric potential has been calculated by considering the electrical characterization of the electrodes and numerical results have been compared with experimental results. The comparison shows a good agreement between the measured and calculated discharge electric potential at lower pressures. These devices can be used as plasma sources for wastewater treatment
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Degradation studies of carbamazepine and escherichia coli in wastewater using a non-thermal electrical discharge reactor.
Get PDFMasters Degree. University of KwaZulu-Natal, Durban.Over the last 30 years, there has been increasing detection of emerging chemical pollutants and biological contaminants in the aquatic environment. As Wastewater Treatment Plants (WWTP) are considered the primary gateway for chemical and biological contaminants into water bodies, it can be inferred that WWTP in their current configuration are ineffective against the emerging contaminants. Therefore, it is imperative to investigate new technologies capable of removing emerging chemical and biological contaminants. With this background, Advanced Oxidation Processes (AOP) are a candidate technology that can be utilised for wastewater remediation.
This study explores the potential application of an AOP electrohydraulic discharge as a non-conventional tertiary stage technology for the inactivation of Escherichia coli (ATCC 25922) (E. coli) and degradation of carbamazepine (CBZ) as representative contaminants in wastewater. A reactor geometry with vertical copper electrodes with a 2 mm electrode gap in a point-to-plane configuration, connected in negative polarity to a high voltage direct current power supply, was utilised. Separate semi-batch studies were conducted for E. coli and CBZ. All the experiments were conducted using synthetic wastewater.
For the E. coli studies, the effects of the electrode gap on the electric discharge, the influence of initial bacterial density, copper electrode material on bacterial inactivation were investigated. The target treatment criterion in the study was the total bacterial inactivation of E. coli. For an electrode gap of 2 mm, total inactivation for E. coli cell density ranging from 3.96 × 104 to 2.5 × 107 CFU/mL was achieved in 180 seconds. Short inactivation times can probably be attributed to the synergy of shockwaves, radicals, and Ultraviolet radiation within the reactor. Control reactor experiments confirmed the anti-bacterial properties of the copper ions in solution. However, bacteria inactivation can be attributed primarily to plasma discharges in water due to the observed higher inactivation in plasma-treated cells. For example, at 3.96 × 104 CFU/mL initial E. coli density, 4.5 log reduction by plasma treatment was observed at 180 seconds compared to 1.7 log reduction in 300 seconds for copper control. The bacterial cell walls were damaged by plasma treatment as observed for plasma-treated cells through the Scanning Electron Microscope imaging. Thus, the destruction of the cell wall can be proposed as one of the possibly numerous contributing mechanisms resulting in E. coli inactivation by plasma. In preliminary benchmarking against chlorination and ozonation, the electrohydraulic discharge reactor used in this study had considerably higher treatment costs per cubic metre of wastewater.
For CBZ degradation, discharge current, air flow rate, and initial concentration were investigated, with removal efficiency and energy consumption being the response variables. CBZ degradation experiments utilised Liquid-liquid chromatography for extraction followed by GC-FID and GC-MS for quantitative and qualitative analysis, respectively. Discharge current, air flow rate, and initial concentration all influenced the removal efficiency to different degrees. However, for energy consumption, only current and air flow rate were significant variables. The highest removal efficiency obtained was 93% ± 4% for 10 and 40 mg/L initial CBZ concentration after 10 minutes of plasma treatment at a current of 0.45 A and no air flow rate. The high removal efficiency could be attributed to higher currents (0.45 A), resulting in an improved generation of highly reactive and high energy species and UV generation. Additionally, no air could also improve discharge stability resulting in an uninterrupted discharge. The experimental setup and plasma reactor used in this study show a prospect for sectors where the concentration level of the contaminants in the effluent is above 10 mg/L based on the investigations carried out within the context of this research. Treatment cost per cubic metre benchmarking of the reactor against established technologies revealed that the reactor still requires significant optimisation.
The research on the reactor demonstrated its capability to treat high chemical and biological contaminants in wastewater with possible applications being in pre-concentrated wastewater remediation. However, there is still room for optimisation. One key area of focus being reducing treatment cost, which may be achieved theoretically, pending further experimental investigation, by the introduction of an AC power supply.List of Conferences on page iv
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Kinetic mechanism study and waste tyre characterisation for valuable chemicals production.
Get PDFMasters Degree. University of KwaZulu-Natal,Durban.Researchers have extensively investigated waste tyre pyrolysis kinetics and mechanisms. However, available literature shows limitations as the studies were primarily aimed at tracking the devolatilisation of the main components of the feedstock than the formation of chemicals. In the present study, truck tyre crumbs of less than 1 mm were pyrolysed in a multi-shot pyrolyser connected to a mass spectrometer. The aim is to investigate the kinetics and reaction pathways that favour the formation of specific valuable chemicals (such as limonene and indene) in tyre-derived oil to maximise their production and content.
The multi-shot pyrolyser (EGA/PY-3030D) equipment and accessories have been used to track the temperature and heating rate influence on the formation of chemicals. For temperature influence, experiments were conducted in single-shot mode and at different temperatures (400, 500, 600, and 700 °C), based on thermogravimetric analysis data. Chromatograms analysed regarding the area % of the considered chemicals proved that the selectivity to limonene decreases as temperature increases, reaching a minimum of 28.5% around 700 °C. In contrast, there was no discernible effect of temperature on indene in the considered range of temperature. The selectivity ratios of limonene to isoprene and indene to styrene presented a plateau between 400 and 600 °C. This trend evidenced that several equilibrated reactions steps could have taken place between limonene and isoprene as well as indene and styrene. Above 600 °C, the selectivity ratio of limonene to isoprene decreases, characteristic of cyclisation, hydrogenation and aromatisation reactions.
The influence of heating rate on the production of the chemicals was conducted through Direct Evolved Gas Analysis (EGA) experiments at heating rates of 20, 30, 40, 50 and 100 °C /min and optimum temperature of 500 °C, obtained from temperature influence on the production of the chemical. The selectivity to limonene presented a continuous increase with the increase of heating rate from 30.8 % at 20 °C /min to 37.8 % at 50 °C /min and 42.7% at 100 °C /min. Hence, limonene formation is maximised at higher heating rates.
The kinetic study conducted through combined model fitting and model-free approaches presented values in the range of 122 and 145 kJ.mol-1. The highest value has been obtained using the differential method (144.4 kJ.mol-1) with a difference of about five units with the two model-free methods of Kissinger (138.5 kJ.mol-1) and Starink's (139.7 kJ.mol-1). The Friedman's (122.0 kJ.mol-1) and Coats-Redfern (130.6 kJ.mol-1) methods present lower activation energy values with a difference of about 22 and 16 with the differential method. Therefore, a simplified reaction map has been presented and includes equilibrated reactions that contribute to the production of limonene-isoprene and styrene-indene
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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