Investigation into different types of single-phase AC/DC convertors

The work detailed in the thesis compares the performance of single-phase thyristor bridge converters under different control strategies; considering in particular the efficiency, ac side power factor and harmonic content of the current and voltage waveforms. Extensive practical investigations were performed, in which, analogue and digital control circuits were developed to provide the drive signals necessary for a converter to operate in the different control modes for: a) A series -connected fully-controlled double thyristor bridge (used mainly in traction applications) operating under sequence control and; b) A fully controlled single-bridge operating under sequence and conventional control. A novel pulse-width modulation control strategy was developed for the single-bridge converter, using gate turn-off thyristors as the switching elements, whereby output voltage control is obtained by variation of the modulation index. Turn-on and turn-off signals for the power devices were obtained using an analogue control circuit. The advantages and disadvantages of this switching strategy compared with conventional and sequence control were studied, and results clearly showed that an improved input power factor and lower supply current and load voltage harmonics were all obtained. Mathematical models for single and double bridge converters operating under sequence and conventional control were developed using tensor techniques. Using these models, computer programmes were written in Fortran 77 on the University mainframe computer, to assemble automatically and solve the network equations as the converter topology changes. In addition, analytical models were also developed on the assumption that the load current is completely smooth. However, such an assumption is not justifiable with ac-to-dc converters and consequently a novel technique was developed to include the load current ripple in calculating the supply current harmonics. The results obtained are compared with both the computed and experimental ones

Pengaruh Ukuran Kantor Akuntan Publik, Audit Tenure dan Spesialisasi Kantor Akuntan Publik Terhadap Kualitas Audit

This study aims to examine the effect of the size of the Public Accounting Firm, audit tenure, and Specialist Public Accounting Firm on audit quality. The sample used in this research is banking companies listed on the Indonesia Stock Exchange (IDX) for the period 2018 to 2020 which can be accessed via the Indonesian Stock Exchange website (www.idx.co.id). This research uses descriptive research with a quantitative approach. The sample selection method in this study used a purposive sampling technique, with a total sample of 119 data obtained from banking companies. This study uses the hypothesis of multiple regression analysis. The results of the study show that (1) KAP size has an effect on audit quality in banking companies listed on the IDX for the 2018-2020 period, whereas (2) Audit tenure has no effect on audit quality in banking companies listed on the IDX for the 2018-2020 period, and (3) KAP specialization affects audit quality in banking companies listed on the IDX for the 2018-2020 period

Validation of Kiswahili Version of HOQOLHIVBREF Questionnaire Among People Living with HIV/AIDS in Tanzania: A Cross-Sectional Study

Background: Quality of life is an important element of surveillance in people living with HIV/AIDS. WHO has developed an HIV specific quality of life tool (WHOQOLHIV-Bref) for assessing Quality of life of HIV individuals. This tool takes into account the different cultural variations that exist worldwide and hence enable assessment of the quality of life across different cultures. Despite its preliminary sound validity and reliability from several studies, the developers recommend it to be validated in different cultures to fully assess its psychometric properties before its adaptation. Objectives: To evaluate the validity and reliability of WHOQOLHIV-Bref questionnaire in Tanzanian culture among people living with HIV/AIDS. Methods: This was a cross-sectional study of 103 participants interviewed using a Kiswahili WHOQOLHIV-BREF questionnaire. Of, these participants 47 participants were enrolled to repeat an interview two weeks later. Internal consistency and test-retest reliability were analyzed. Validity was assessed through analysis of translational, concurrent, convergent and discriminant validity while the model performance was assessed by Exploratory and confirmatory factor analysis. Results: The mean age of the participants was 40.5 ± 9.702 years. Translation validity was assessed through the WHO translational protocol and was found to be good. The internal consistency and test-retest reliability of the Kiswahili version of WHOQOL- HIV BREF were excellent: Cronbach\u27s alpha values of 0.89-0.90, and ICC of 0.92 p \u3c 0.01 respectively. Concurrent valid was excellent, significant correlations were noted across all domains (correlation coefficient r \u3e 0.3) except for physical and spiritual domains. Confirmatory factor analysis found that the six domain produced an acceptable fit to the data. The convergent and divergent validities were satisfactory. Conclusion: Kiswahili WHOQOLHIV-Bref was found to be reliable and valid questionnaire among Tanzanian people living with HIV/AIDS. These findings provide support for the use of this tool in assessing the quality of life in Tanzania

Supporting African science journalists to cover COP27 from African perspectives

Science journalists, who often write on climate change, are usually deprived of an opportunity to cover major conferences such as the Conference of Parties 27. This means that members of the public miss out on major updates and news which emanate from such big international meetings. To address this issue, MESHA sought financial support from IDRC to grant a few journalists to cover the COP27 in person and virtually. This way, many audiences would benefit from the reporting by the journalists

Smart Watch Detection of Supraventricular Tachycardia (SVT): First Case from Tanzania

Smartwatches like the Apple Watch have been on the rise worldwide and their use is gaining popularity in developing countries. Their ability to detect dysrhythmias is well documented. Present practice discourages the use of these devices as a diagnostic tool. Nevertheless, atypical findings from these devices should be clinically investigated. This case demonstrates an eventual diagnosis of supraventricular tachycardia (SVT) based on an Apple watch alert which was subsequently confirmed by electrophysiological evaluation

Factors Associated with Mortality Among Hospitalized Adults with COVID-19 Pneumonia at a Private Tertiary Hospital in Tanzania: A Retrospective Cohort Study

Background: The emergence of the novel coronavirus disease 2019 (COVID-19) has caused millions of deaths worldwide. There has been paucity of data for hospitalized African patients suffering from COVID-19. This study aimed to identify factors associated with in-hospital mortality in patients suffering from COVID-19 in Tanzania. Methods: This was a single center, retrospective, observational cohort study in adult patients hospitalized with confirmed COVID-19 infection. Demographics, clinical pattern, laboratory and radiological investigations associated with increased odds of mortality were analyzed. Results: Of the 157 patients, 107 (68.1%) patients survived and 50 (31.8%) died. Mortality was highest in patients suffering with severe (26%) and critical (68%) forms of the disease. The median age of the cohort was 52 years (IQR 42– 61), majority of patients were male (86%) and of African origin (46%), who presented with fever (69%), cough (62%) and difficulty in breathing (43%). Factors that were associated with mortality among our cohort were advanced age (OR 1.07, 95% CI 1.03– 1.11), being overweight and obese (OR 9.44, 95% CI 2.71– 41.0), suffering with severe form of the disease (OR 4.77, 95% CI 1.18– 25.0) and being admitted to the HDU and ICU (OR 6.68, 95% CI 2.06– 24.6). Conclusion: The overall in-hospital mortality was 31.8%. Older age, obesity, the severe form of the disease and admission to the ICU and HDU were major risk factors associated with in-hospital mortality

The pattern of admission, clinical characteristics, and outcomes among patients admitted to the Intensive Care Unit of a tertiary hospital in Tanzania: a 5-year retrospective review

Introduction: Despite the implementation of complex interventions, ICU mortality remains high and more so in developing countries. The demand for critical care in Sub-Saharan Africa is more than ever before as the region experiences a double burden of rising rates of non-communicable diseases (NCD) in the background battle of combating infectious diseases. Limited studies in Tanzania have reported varying factors associated with markedly high rates of ICU mortality. Investigating the burden of ICU care remains crucial in providing insights into the effectiveness and challenges of critical care delivery. Material and Methods: A single-center retrospective study that reviewed records of all medically admitted patients admitted to the ICU of the Aga Khan Hospital, Dar-es-Salaam, from 1st October 2018 to 30th April 2023. To define the population in the study, we used descriptive statistics. Patients’ outcomes were categorized based on ICU survival. Binary logistic regression was run (at 95% CI and p-value \u3c 0.05) to identify the determinants for ICU mortality. Results: Medical records of 717 patients were reviewed. The cohort was male (n=472,65.8%) and African predominant (n=471,65.7%) with a median age of 58 years (IQR 45.0–71.0). 17.9% of patients did not survive. The highest mortality was noted amongst patients with septic shock (29.3%). The lowest survival was noted amongst patients requiring three organ support (n=12,2.1%). Advanced age (OR 1.02,CI 1.00–1.04), having more than three underlying comorbidities (OR 2.50,CI 1.96–6.60), use of inotropic support (OR 3.58,CI 1.89–6.80) and mechanical ventilation (OR 9.11,CI 4.72–18.11) showed association with increased risk for mortality in ICU. Conclusion: The study indicated a much lower ICU mortality rate compared to similar studies conducted in other parts of SubSaharan Africa. Advanced age, underlying multiple comorbidities and organ support were associated with ICU mortality. Large multicenter studies are needed to highlight the true burden of critical care illness in Tanzania

Исследовательская деятельность эколого-биологической направленности в НОУ "Эврика" - эффективное средство профессиональной ориентации учащихся

В статье научно-исследовательская деятельность эколого-биологической направленности старшеклассников НОУ "Эврика" г. Нижнего Новгорода рассматривается как одна из значимых инновационных форм профессионального самоопределения. Материалом исследования послужил анализ программ конференции городского научного общества учащихся "Эврика" и судьбы выпускников данного общества. Отмечена тенденция роста популярности эколого-биологических исследований среди старшеклассников г. Нижнего Новгорода и успешное вхождение в профессию выпускников научного общества учащихся.In the article, the research activity of the ecology and biology of senior pupils of the scientific society of the pupils "Eureka" in Nizhny Novgorod is considered as one of the significant innovative forms of professional self-determination. The material of the study was the analysis of the programs of the conference of the city scientific society of the students "Eureka" and the fate of the graduates of this society. The tendency of growth of popularity of ecological and biological researches among senior pupils of Nizhny Novgorod and successful entry into the profession of graduates of the scientific society of students is noted

High strain deformation of steels

The changes in mechanical properties and structure which occur when metals are deformed to high strains by cold working are summarised from the published literature, with particular emphasis on the behaviour of iron. In addition to this, the effects of second phase particles, the deformation behaviour during machining and the influence of strain history on ductile fracture are also outlined. The results of mechanical tests, carried out at various stages of deformation, are compounded to show the overall changes in mechanical properties occurring during the process, which are then interpreted in terms of the results of structural investigations and fractography. Investigations have included a number of different steels, which were selected and heat treated in order to investigate the fundamental changes which occur, the affect on deformation and subsequent fracture of free machining additions and the affect of a dispersion of hard particles. It is concluded that deformation is microscopically heterogeneous, that changes in mechanical properties are associated with the formation and subsequent behaviour of an increasing number of microbands in the substructure, that ductile fracture is nucleated at pre-existing fracture centres which are formed early in the deformation process and that these play an important part in the mechanism of machine chip formation. An important, previously unreported strengthening mechanism is seen to be operating in one of the steels

Computerized well testing models

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