Browsing by Subject "reliability"

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    Reducing uncertainty – responses for electricity utilities to severe solar storms
    (2014) Gaunt, Charles Trevor
    Until recently, electricity utilities in mid- and low-latitude regions believed that solar storms had no (or only insignificant) effect on their power systems. Then it was noticed that the onset of damage in several large transformers, leading to their failure, correlated very closely with the Halloween storm of 2003. Since then engineers have started to appreciate that a very severe storm could have serious consequences outside the high-latitude regions. There are many uncertainties in predicting the effects of solar storms on electrical systems. The severity and time of arrival of a storm are difficult to model; so are the geomagnetically induced currents (GICs) expected to flow in the power networks. Published information about the responses of different types of transformers to GICs is contradictory. Measurements of the abnormal power flows in networks during solar storms generally do not take into account the effects of the current distortion and unbalance, potentially giving misleading signals to the operators. The normal requirement for optimum system management, while allowing for the possibility of faults caused by lightning, birds and other causes, limits the capacity of system operators to respond to the threats of GICs, which are not assessed easily by the N − 1 reliability criterion. A utility’s response to the threat of damage by GICs depends on the expected frequency and magnitude of solar storms. Approaches to formulating a response are located in a system model incorporating space physics, network analysis, transformer engineering, network reliability and decision support and the benefits are identified. Approaches adopted in high-latitude regions might not be appropriate where fewer storms are expected to reach damaging levels. The risks of an extreme storm cannot be ignored, and understanding the response mechanisms suitable for low-latitude regions has the capacity to inform and reduce the uncertainty for power systems planners and operators worldwide.
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    The validation of a screening tool for the identification of feeding and swallowing difficulties in the paediatric population aged 0-2 years admitted to general medical wards
    (2019) Sibanda, Cynthia; Norman, Vivienne; Morrow, Brenda
    Background: Feeding and swallowing difficulties (FSD) have been found in typically developing children as well as in children with complex medical conditions and developmental disabilities. These difficulties cause negative health consequences such as aspiration pneumonia, chronic lung disease, failure to thrive, prolonged hospital stay and even death. The early identification and management of feeding and swallowing difficulties is important as it prevents the negative effects on health and quality of life. Hence, there is a need for a validated screening tool to use in the general hospitalized paediatric population. Research Aims: The aim of this study was to validate the Feeding and Swallowing Questionnaire as a screening tool, in the paediatric population aged 0 – 2 years admitted to general medical wards. The secondary aim was to describe the FSD presenting in the paediatric population aged 0 - 2 years who are hospitalized in the general medical wards. Methodology: A prospective, descriptive, clinimetric design was utilized. A sample of 107 participants admitted to the general medical wards at Steve Biko Academic Hospital were included in the study. Participants’ feeding and swallowing was screened by a research assistant using the Feeding and Swallowing Questionnaire. After the screening, a clinical feeding and swallowing assessment was conducted for comparison, the assessment was conducted by the student researcher using the Clinical Feeding and Swallowing Assessment Tool. Results: There was a 27% FSD prevalence, with the majority of cases (92%) occurring in children under one year of age. One hundred and three children (63% male; median (IQR) age 5.2 (2.1 – 12.8) months) underwent screening and clinical assessment for feeding and swallowing disorders. The criterion validity of the Feeding and swallowing Questionnaire was established with a sensitivity of 88% and a specificity of 32%. Internal consistency was achieved with an acceptable Cronbach’s alpha of 0.79, and good inter-rater reliability (80%). Participants presented with feeding difficulties in all the phases of swallowing, while some participants had behavioural feeding difficulties. Those who had FSD had the following medical conditions: cardiorespiratory, neurological and gastrointestinal disorders namely acute gastroenteritis and liver disease. Feeding and swallowing difficulties were associated with increased mealtime duration (p=0.005) and supplementary oxygen support (p=0.03). Conclusion: The results confirm that the Feeding and Swallowing Questionnaire shows promising findings as a reliable and valid tool for the identification of FSD in the general hospitalized paediatric population. However, further research in other setting with general paediatric medical wards is required to increase the robustness of the screening tool.
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    Towards the development and validation of an isiXhosa tool for the assessment of apraxia speech in adults: A descriptive study
    (2024) Allie, Nasreen; Singh, Shajila; Pascoe, Michelle
    South Africa is a culturally and linguistically diverse country. Serving isiXhosa speakers is a challenge for many Speech-Language Pathologists as there is a lack of appropriate assessment tools for this population. Current methods of adapting existing English tools are not appropriate as this does not allow the isiXhosa linguistic features to be assessed. Changing the method of scoring renders the tool invalid and unreliable. This project consisted of 3 sequential studies based in an exploratory quantitative framework. Each study has its own methodology and sub-aims with the overall aim to develop and determine the validity and reliability of isiXhosa speech stimuli for the assessment of Apraxia of Speech (AOS) in adults. Study 1 aimed to describe and generate criteria and corresponding speech stimuli for an assessment of AOS in isiXhosa. IsiXhosa has distinguishing linguistic features – such as additional phonemes, alternate places and manners of articulation (e.g. ejectives), as well as phonetic features unique to the language (e.g. prenasalised consonants and tonal contrasts). Inclusion of these features were considered to be important in the creation of the tool. Study 2 aimed to determine the face, content and construct validity of the generated criteria and speech stimuli. The speech stimuli which consisted of words, phrases and sentences were found to be culturally appropriate and to have face, content and construct validity as judged by a group of isiXhosa speakers and a Delphi panel. The speech stimuli met the criteria for an assessment of AOS as set out in Study 1. Study 3 assessed the theoretical constructs outlined in Study 1 and Study 2 determined whether the revised criteria, which generated the newly devised speech stimuli, was valid and reliable in diagnosing AOS. The speech stimuli were based on criteria for the assessment of AOS and considered the isiXhosa linguistic features. There was high inter-rater reliability (79.2 – 98.4%) for determining the presence of features of AOS. Many of the error patterns displayed were similar to that documented in the literature for AOS, such as a higher number of errors were present on less frequently used speech stimuli and stimuli with an increasing number of syllables. It was it was hypothesized that the differences in the language such as clicks and tonal contrasts may add to complexity. Clicks presented with a higher number of errors whereas tonal contrasts had fewer errors suggesting tone was less affected by AOS. Results further suggested that the first consonant of the stimulus rather than the initial phoneme in words add to complexity in isiXhosa. Further research in this area and refinement of the speech stimuli are required to create a comprehensive tool for assessment of AOS in adults.