1,720,955 research outputs found
A screen-printed amperometric dissolved oxygen sensor utilising an immobilised electrolyte gel and membrane
No full textAn amperometric dissolved oxygen sensor based on potentiostatic operation has been designed and fabricated using thick film technology. Calibration of the sensor has shown a strong linear relationship with dissolved oxygen concentration. The devices have been bulk tested for long-term stability and good device to device repeatability has been observed within the batch. Results indicate that a repeatable response to dissolved oxygen levels can be obtained over a period of several months when intermittently powered. The device has been found to operate efficiently for at least 2 weeks when it is continuously powered in deionised water. Silver and copper deposits have been identified on the working electrode of such devices. It is shown that sensor failure occurs after 3 days when powered in tap water and that it is attributed to deposition on the membrane surface
An investigation of the characteristics of thick film amperometric dissolved oxygen sensors
No full textThe measurement of dissolved oxygen in natural waters is vital as an indicator of pollution incidents, water quality and for the general maintenance of water courses and reservoirs. Commercially available instruments used in such applications tend to be bulky items which require frequent calibration and are prone to fouling problems. Consequently, they are incapable of providing continuous accurate in situ measurements. One of the most predominant problems though is the extreme cost of these instruments, resulting from the employment of expensive fabrication techniques.Thick film technology is a bulk batch automatic fabrication process which affords reproducible, uniform and miniature surfaces at low cost, making it an ideal technique for sensor production. This thesis describes the application of thick film technology to the production of miniature amperometric dissolved oxygen sensors based on a three electrode potentiostatic mode of operation, for initial use hi the water industry. The devices have been designed and fabricated with gold electrodes covered by a gel electrolyte held intact by an oxygen permeable cellulose acetate membrane. Novel screen-printable membrane and gel thick film pastes have been realised in the process. An external silver/silver chloride reference electrode completes the electrochemical cell. When powered, the working electrode of a device is held at an applied potential of-0.6V versus the reference electrode.A full investigation of device performance has been carried out including sensitivity, linearity and response times. The oxygen permeable membrane has been shown to act as a protective layer as well as providing a diffusion barrier to the electrodes. Methods of reducing instability effects and characteristics caused by variations hi physical parameters have been studied. As a consequence an in depth knowledge of the behaviour of membrane covered dissolved oxygen sensors has been acquired. Results show that the use of a more negative applied potential, alternative membranes (such as PVC and PTFE) and a microelectrode configuration reduce instability and fouling problems, maintaining oxygen sensitivity and minimising secondary operating characteristics caused by the effects of parameters such as flow and temperature. This in turn improves the lifetime of thick film dissolved oxygen devices as they are continuously powered
An investigation of the performance characteristics and operational lifetimes of multi-element thick film sensor arrays used in the determination of water quality parameters
Get PDFAbstract An investigation of the useful lifetimes of thick film sensors suitable for the measurement of various aqueous parameters is reported. Batches of sensor arrays designed to simultaneously measure temperature, conductivity, pH, dissolved oxygen and redox potential were investigated. In particular the device to device repeatabilitys of the pH and dissolved oxygen sensor elements were studied as it was found to be the characteristics of these elements that limit the device lifetimes. Errors of less than 5% for pH sensors and 10% for dissolved oxygen sensors were observed over periods of several months continuous immersion in water. An assessment of useful continuous immersion lifetimes was made for the sensors and possible sensor failure mechanisms are postulated
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
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
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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