Analysis of the Effects of Severe Voltage Unbalance on the DC Bus of a Variable Frequency Drive and DC Bus Passive Filtering Harmonic Mitigation

The power quality of a distribution system can greatly effect the way devices connected to that power source operate. Sometimes one poor power quality characteristic can lead to another poor power quality characteristic. In the case presented in this paper, severe voltage unbalance at the input of a variable frequency drive leads to increased harmonic content in the power distribution system and the device under operation. This paper addresses, in particular, the effects of severe voltage unbalance on the DC bus of a 6-pulse variable frequency drive. The steady-state balanced voltage harmonic behavior of the DC bus is analyzed along with standard filtering techniques used to mitigate the characteristic harmonics on the DC bus. The steady-state severe unbalanced voltage harmonic behavior of the DC bus is then analyzed and additional filtering techniques are then introduced to mitigate the non-characteristic harmonics on the DC bus that were produced by the severe voltage unbalance. Simulations of the balanced and unbalanced conditions mentioned above are presented in MATLAB$^\circledR$. Bode plots of the 6-pulse converter are then analyzed to measure the frequency response of the system under these conditions and the Fast Fourier Transform of different signals in the system are generated to graphically represent the harmonics in the system. Finally, experimental results will show the successful application of the filtering techniques, presented in this paper, on a 6-pulse variable

Doctor of Philosophy

dissertationThe terahertz frequency band extends from deep infrared (100 THz) down to millimeter waves (0.4 THz), and this band was mostly inaccessible due to the lack of appropriate sources and detectors. Those with access to this band had to endure the small-intensity pulsed signals (nanowatts to microwatts) that the terahertz sources of those times could provide. In recent years, however, sufficient development has led to the availability of terahertz sources with sufficient power (1-100 μW) and the ease of use these sources has in turn enabled researchers to develop newer sources, detectors, and application areas. The terahertz regime is interesting because a) many molecules have vibrational, rotation and transition absorption bands in this regime, b) the terahertz electromagnetic wavelength is sufficiently small to resolve centimeter to millimeter scale objects, and c) scattering and absorption in metals in the terahertz regime make it very challenging to devise terahertz signal processing circuits. Thus, performing terahertz reflection/transmission measurements may enable precise identification of chemicals in a sample. Furthermore, small wavelengths and strong scattering by metallic objects make imaging with terahertz waves quite attractive. Finally, the ability to devise terahertz communication circuits and links will provide access to a frequency domain that is restricted and not available to others. One of the main objectives of this work is to develop 0.75 - 1.1 terahertz (free space wavelength 272 μm â€" 400 μm) amplifiers. Another objective of this work is to explore the suitability of terahertz waves in biological imaging and sensing. The terahertz amplifiers developed in this work consisted of distributed components such as rectangular waveguides and cylindrical dielectric resonators. In contrast to discrete amplifiers, which are based on solid-state devices, distributed traveling wave amplifiers can potentially handle and produce larger powers. Three different distributed terahertz amplifier circuits were considered in this work. These were based on a) coupled dielectric resonators, b) dielectric waveguides with periodic slots, and c) metallic meandering waveguides. The result of the hot test of the last circuit on interaction with an electron beam energy source yielded an amplification of 12 dB of a -55 dBm, 0.9 terahertz signal over ~1 gigahertz bandwidth. The electron beam acceleration voltage was 4.8 kV and its current was approximately 20 microamps. The terahertz biosensing system developed in this work was used to study the unique interaction of terahertz waves with the chemical and physical components of biological tissues, and the products of biochemical reactions. A terahertz near-field imaging system was also developed to image mouse brain slices, plants, and bug wings. In addition, this work also demonstrated the capabilities and limitations of terahertz waves for the real-time noninvasive monitoring of bioethanol production by yeast cells

Preparing medical students to recognize and respond to gender based violence: a mixed method study in SouthWest Nigeria.

Doctoral Degree. University of KwaZulu-Natal, Durban.Background: Medical practitioners are ideally positioned to mitigate the impact of violence on the health of women. Not only are they well placed to educate students but also to screen and treat victims of violence. However, there is a lack of information on the knowledge and skills required of medical students to identify and manage victims of GBV. Aim: This study determined the factors that impact on student’s knowledge and skills in managing victims of GBV. It gathered the perceptions of victims on screening for violence by physicians and health professionals. Lastly, it established consensus amongst inter professional faculty on the content and strategies of a GBV training curriculum. Methodology: The study adopted a mixed method design. The qualitative methods included the review of curriculum documents, interview of departmental heads, three rounds (RDs) of the Delphi technique and interview of victims. The quantitative method analysed the questionnaire survey of final year medical students from three Schools in South West, Nigeria. The study was in 4 phases: - preliminary phase involving medical students (109) and departmental heads (6). Phase 1 involved medical students (388); Phase II the stakeholders of training (51) and Phase III the victims (33). Results: Younger respondents, females and married students were found to be less skilled to manage victims. Respondents with prior training in GBV were four times more likely to be skilled than their peers [AOR = 4.33, 95% CI: 2.37 – 7.90 and AOR 3.53; 95% CI 2.16- 5.78 respectively]. Consensus was reached on the content, methods and faculty for training medical students about GBV. There was agreement on the disciplines best suited and the need to assess the training. Further discussions are needed per institution on the contact hours and, duration of training. Most (n=24/33) victim participants advocated for medical practitioners to enquire of all women about their experience of GBV. Physically, medically and socially vulnerable women were identified as vulnerable women. The majority (n=24/33) indicated a need for medical students to be trained about GBV by a trans-disciplinary team. Conclusion: Formalised skills training on GBV is a necessity, especially for young, female students. The results will inform the design of a GBV curriculum for medical students in the African context

Fall Prevention: Increasing Awareness and Preventive Care in Older Adults

Falls in community-dwelling older adults are significant health concerns and continues to be on the rise. Those with a history of falls have a higher risk of subsequent falls. However, many are not open to discussing falls and fall-related topics, especially with their healthcare providers (Center for Disease Control and Prevention [CDC], 2017). A review of the literature revealed a lack of being cognizance of the major risk factors which are mostly related to age, medication, and the environment. It was noted that barriers to the available evidence-based fall prevention interventions could be overcome by adequate education and a patient-centered and collaborative approach. This project developed and piloted the use of post-discharge calls and a fall-risk education tool to increase the awareness of fall-risk factors and as a step towards empowering older adults to be proactive in fall prevention strategies. The goal was to provide an educational opportunity to reach older adults after discharge to increase their awareness to fall risk factors and to further seek helpful resources in the community, especially from their primary care provider. This would foster patient-centered, preventive, collaborative care for this population. A prospective benefit is the extension of this awareness and education to the family members, caregivers, and other support systems. The expected outcome was a reduction in falls, which would translate to a reduction of healthcare cost and improve safety and quality of life in older adults. Promotion of education and preventive care is an important aspect of healthcare and best practice for Nurse Practitioners as well as a priority in healthcare. This pilot study yielded positive feedback from the participants and revealed the education tool as a relevant and informative reminder about falls

Women’s status within the household as a determinant of maternal health care use in Nigeria

Background: Although gender inequality is often cited as a barrier to improving maternal health in sub-saharan Africa, there is lack of empirical data on how women’s socio-cultural characteristics may influence use of health services in Nigeria.Objective: To describe how women’s position in the household affects receipt of maternity care services.Methods: Secondary data analysis of 10,052 and 4,590 currently married women aged 15 to 49 years from the 2008 Nigerian DHS who receive skilled antenatal and delivery care at least till pregnancy was done.Results: Receipt of skilled delivery care was by 37.9% while, natal care was by 98.4%. Education, residence and wealth index all significantly influenced receipt of maternal health care. Women who were involved in decision making on their own health (aOR=1.97; 95%CI=1.88-2.06) and were employed throughout the year (aOR=1.11; 95%CI=1.01-1.23) were more likely to receive skilled antenatal care, while those who justified physical intimate partner violence were less likely to receive both skilled antenatal care (aOR=0.92; 95%CI=0.85-0.98) and delivery services (aOR 0.54; 95% CI 0.33-0.87).Conclusion: Interventions aimed at improving maternal care should promote women empowerment (decision making, self worth, educational and economic) and should involve partners.Key words: women’s position, women’s status, skilled antenatal care, skilled delivery care, gender inequality in Africa, physical intimate partner violenc

Prevalence and correlates of violence against female sex workers in Abuja, Nigeria

Background:. Few studies in Africa provide detailed descriptions of the vulnerabilities of female sex workers (FSWs) to violence.Objective: To document the prevalence and types of violence experienced by FSWs, identify the risk factors of experiencing violence to women (VAW) and the perpetrators of these acts.Methods: An analytical cross sectional survey of 305 brothel-based FSWs and in-depth interview of 20 chairpersons residing in brothels in Abuja, Nigeria was done.Results: The prevalence of VAW six months preceding the survey was 52.5%. Sexual violence was the commonest type (41.9%) of violence experienced, followed by economic (37.7%), physical violence (35.7%) and psychological (31.9%). The main perpetrators of sexual violence were clients (63.8%) and brothel management (18.7%). Sexual violence was significantly more experienced (aOR 2.23; 95%CI 1.15-4.36) by older FSWs than their younger counterparts, by permanent brothel residents (aOR 2.08; 95%CI 1.22-3.55) and among those who had been in the sex industry for more than five years (aOR 2.01; 95%CI 0.98-4.10).  Respondents with good knowledge levels of types of violence were less vulnerable to physical violence (aOR 0.45; 95%CI 0.26-0.77).  Psychological violence was more likely among FSWs who smoked (aOR 2.16; 95%CI 1.26-3.81). Risk of economic violence decreased with educational levels (aOR 0.54; 95%CI 0.30-0.99 and aOR 0.42; 95%CI 0.22-0.83 for secondary and post secondary respectively). Consequences of the violence included sexually transmitted infections (20%) and HIV (8.0%).Conclusion: Interventions that educate FSWs on their rights and enable them avoid violence are urgently required. Young women need economic and educational empowerments to enable them avoid sex work.Key words: female sex workers, violence against women, brothel based sex workers, prostitution in Afric

Toxic effects of endosulfan on haematological and biochemical indices of Clarias gariepinus

The effects of endosulfan pesticide were investigated on juvenile of Clarias gariepinus. Acute test was carried out using 0.04, 0.05, 0.06, 0.07 and 0.08 ppm of endosulfan pesticide with the 96 h LC50 value determined by probit analysis. Chronic bioassays were evaluated on haematological and biochemical indices of the fish for a period of 60 days using four sub lethal concentrations (0.0005, 0.0010, 0.0025 and 0.0050 ppm). Blood sample was collected on days 15, 30, 45 and 60 for haematological and at day 60 only for biochemical analysis. The 96 h LC50 value of endosulfan for C. gareipinus was 0.052 ppm. There was significant reduction (P<0.05) in red blood cell (RBC) at days 15, 30 and 45, haemoglobin (Hb) at days 15 and 45, and packed cell volume (PCV) at all days of the evaluation. White blood cell (WBC) values however showed significant increase (P<0.05) at days 45 and 60. There were variations in mean values of mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC) with significant increase observed only at day 15 of MCHC. Significant reduction in values was obtained for total protein and globulin while significant increase was observed in cholesterol. Results obtained in this study suggest that exposure to low concentrations of endosulfan induced stress and altered the haematological and biochemical indices of treated fish.Key words: Chronic, acute, biochemical, haematological, endosulfan, cholesterol and glucose, Clarias

Effects of mutant cytoplasmic factors on the expression of agronomic traits in cowpea, Vigna unguiculata (L.) Walp.

Nuclear genes have to a large extent been exploited in genetic cowpea improvement, but little is known about the effects of cytoplasmic mutations on agronomic traits. This study investigated the effect of cytoplasmic factors agronomic traits in crosses between two cytoplasmic mutants and some nuclear cowpea lines. The experiment was conducted at Department of Crop Protection Environmental Biology, University of Ibadan. A yellow variant derived from the sorting-out of mutant plastids of mixed cells lineage (IB-Y-Cyt.) was crossed to four normal green lines and a variegated mutant in all possible combinations. F1 and reciprocal-F1 progenies from the crosses and six generations comprising parents, F1, F2 and their reciprocals from four selected crosses were evaluated in pots using Randomized Complete Block Design with four replicates. Data were collected on the following quantitative traits; days to flowering and ripe pod, pod length and seed traits. Data were analyzed using t-test and correlation coefficient analysis. Crosses involving the cytoplasmic mutants as female parents had negative effects on most of the traits studied. The mutant cytoplasms had negative effects on traits affecting the productive capacity of the plants as well as related traits in the F1 generation, these effects in turn transcend to most of the quantitative traits leading to poor seed formation especially in the yellow cytoplasmic mutant.Keywords: Cytoplasmic mutation, Agronomic traits, Cowpea, Uniparental, Reciprocal difference

Gynaecological Emergencies in the Tropics: Recent Advances in Management

No AbstractKeywords: Gynaecological emergencies, ectopic pregnancy, unsafe abortion, pelvic infection, adnexal mas