QUANTITATIVE SCHLIEREN MEASUREMENT OF 3 DIMENSIONAL TEMPERATURE, CONCENTRATION AND VELOCITY FIELDS IN A GAS FLOW

Background Oriented Schlieren (BOS) estimates the flow behaviour that exists between the camera and background from the shift in the background image features due to the change in the transfer channel function. The current optical flow techniques used to find the deflection vectors of the change in background images rely on two main assumptions: global constant value of intensity and continuity of local motion. The global intensity invariance assumption hardly works for BOS technique when imaging a self luminous flow. In this thesis, an optical flow equation which takes the change in intensity into account and an estimation motion model that considers both translational and rotational deflections were developed. The results showed that for a transparent gas jet all the tested optical flow algorithms worked well. However the proposed model gave better results for BOS images taken through natural gas flames and smoke from a fog generator. The developed deflection vector estimation algorithm and optical tomography served as a tool to extract the index of refraction of the gaseous fields. The Gladstone-Dale relationship was used to show the direct correlation between the index of refraction and density of the flow. Three different types of axi-symmetric flows were used as gas sample media. These were a CNG injected fuel jet, an open methane flame and a hot air jet. Based on the measured index of refraction the species mole fractions of CNG injected jet and methane flame were measured. In addition, the three dimensional temperature fields of the methane flame and the hot air were also measured and displayed. The other main contribution of this research was the use of Background Oriented Schlieren (BOS) technique for the measurement of the velocity field of a variable density round jet. The density field was further exploited to extract the axial and radial velocity vectors for six different jet-exit temperature values with the aid of the continuity and energy equations. Results of the measured temperature and velocity vector fields were compared with thermocouples and hot wire anemometry readings respectively and showed good agreements

Application of Rain Intensity Dependent Rain Admittance Factor (RAF) in Hygrothermal Performance Assessment of Wall Systems

Wind-driven rain (WDR) is one of the main moisture loading sources on the exterior enclosures. The direct impact of wind-driven rain on the hygrothermal performance of building envelope has been well documented. Rain admittance factor (RAF) and rain penetration values characterize the amount of water reaching the exterior surface and the exterior surface of the water-resistive barrier respectively based on measured horizontal rain intensity. In common RAF factor calculation from horizontal rainfall data procedures, such as ASHRAE 160, RAF values are not affected by the intensity of the rainfall. However, a previous study shows RAF coefficients are sensitive to the rainfall intensity. Thus it is important to investigate how the sensitivity of using horizontal rainfall intensity dependent RAF factors and the subsequent rain penetration relates to hygrothermal performance assessment of building envelope components. This study is based on five years of WDR and horizontal rainfall data collected at different orientations of façades at a two-story test building in a mild coastal climate. The data is categorized into two sets based on rain intensity. The correlation between the measured moisture content on the sheathing board of a building envelope at different points utilizing RAF values based on the proposed approach and the overall measured RAF values is studied using WUFI simulation. Results show that an average percentage difference between the moisture content values of a sheathing board using RAF values of the rain intensity dependent approach and the overall RAF measured value can be as large as 9 %

Evolution of the Broadly Rifted Zone in Southern Ethiopia Through Gravitational Collapse of Dynamic Topograpy

The Broadly Rifted Zone (BRZ) is a 300 km wide diffused zone of extension in southern Ethiopia that connects the narrow (50-65 km wide) South Main Ethiopian Rift and the Eastern Branch of the East African Rift System (EARS) represented by the Kenya and Turkana rifts. The topographic features of the BRZ resemble those of the Basin-and-Range in the western United States in that they are characterized by the presence of NE-trending ridges and valleys superimposed on regionally uplifted (~2 km average elevation) terrain. This rift morphology, which is unique to the BRZ within the EARS, resulted from the presence of tilted blocks of Eocene-Pliocene volcanic rocks bounded by steep normal faults that exhibit half-grabens geometry. The tilted blocks rest unconformably on Precambrian crystalline basement and the half-grabens are filled with Miocene-Pliocene sedimentary rocks. The geodynamic mechanism through which the BRZ was developed is not well understood. Previous studies proposed that the BRZ hosts both tectonically active and inactive rift basins resulting from northward propagation of the Kenyan Rift and southward propagation of the Southern Main Ethiopian Rift. In order to understand the relationship between crustal and upper mantle structures beneath the BRZ and its unique morphological expression and extensional style, we first estimated the Moho depths using two-dimensional (2D) radially-averaged power spectral analysis of the World Gravity Map (WGM 2012) satellite gravity data. Subsequently, to verify results from the 2D radially averaged power spectral analysis, we developed lithospheric-scale 2D forward models along E-W profiles across the BRZ and extensional structures to north and south of it. We found that the Moho topography depicts a dome shape beneath the BRZ and it shallows to a minimum depth of 27 km in the central part of this dome. We suggest that the Moho doming, topographic uplift and arching of the crust underlying the BRZ is the result of mantle upwelling beneath the BRZ from a deeper asthenospheric source that changed to northeast lateral flow at shallower depth. This is supported by seismic tomography results which show the presence of low velocity anomaly of shear wave at lithospheric depth of 0-100 km and 100-175 km stretching in a NE-direction from beneath the BRZ to the Afar Depression. At depths between 175-250 km and 250-325 km the low shear wave velocity anomaly became only a broad elliptical feature centered beneath the BRZ. This created gravitationally unstable dynamic topography that triggered extensional collapse leading to the formation of the BRZ as a wide rift within the narrow rift system of the EARS.Geolog

QUANTITATIVE SCHLIEREN MEASUREMENT OF 3 DIMENSIONAL TEMPERATURE, CONCENTRATION AND VELOCITY FIELDS IN A GAS FLOW

Background Oriented Schlieren (BOS) estimates the flow behaviour that exists between the camera and background from the shift in the background image features due to the change in the transfer channel function. The current optical flow techniques used to find the deflection vectors of the change in background images rely on two main assumptions: global constant value of intensity and continuity of local motion. The global intensity invariance assumption hardly works for BOS technique when imaging a self luminous flow. In this thesis, an optical flow equation which takes the change in intensity into account and an estimation motion model that considers both translational and rotational deflections were developed. The results showed that for a transparent gas jet all the tested optical flow algorithms worked well. However the proposed model gave better results for BOS images taken through natural gas flames and smoke from a fog generator. The developed deflection vector estimation algorithm and optical tomography served as a tool to extract the index of refraction of the gaseous fields. The Gladstone-Dale relationship was used to show the direct correlation between the index of refraction and density of the flow. Three different types of axi-symmetric flows were used as gas sample media. These were a CNG injected fuel jet, an open methane flame and a hot air jet. Based on the measured index of refraction the species mole fractions of CNG injected jet and methane flame were measured. In addition, the three dimensional temperature fields of the methane flame and the hot air were also measured and displayed. The other main contribution of this research was the use of Background Oriented Schlieren (BOS) technique for the measurement of the velocity field of a variable density round jet. The density field was further exploited to extract the axial and radial velocity vectors for six different jet-exit temperature values with the aid of the continuity and energy equations. Results of the measured temperature and velocity vector fields were compared with thermocouples and hot wire anemometry readings respectively and showed good agreements

On crustal and lithospheric structures of rift basins formed within the Turkana Depression in the east Africa and the Trans-Southern African Orogen in the southwest Africa

This doctoral dissertation examines the crustal and lithospheric structures of rift basins formed within the Turkana Depression (TD) in east Africa and the Trans-Southern African Orogen (TSAO) in southwest Africa. Both regions have undergone complex structural and petrological evolution since the Archean eon and exhibit belts of deformations that resulted from the assembly and fragmentation of both Rodina and Pangaea. Since the Cenozoic, the crust and the sub-continental lithospheric mantle beneath the TD and the TSAO have been significantly weakened and stretched by plume related dynamics triggering the southward and the southwestward propagation of the East African Rift System. The Precambrian suture zones and the Mesozoic rift basins have also influenced these zones of extensional deformations. This doctoral dissertation is designed to explore the spatial extent of these structurally complex tectonic entities and investigate the role of these structures in the nucleation and development of various zones of extensional deformations, particularly rift basins related to the East African Rift System. To this end, geophysical, remote sensing, and numerical methods have been implemented to model the upper crustal-, crustal-, and lithospheric-scale structures beneath the TD and TSAO. For the first time, this doctoral work also introduces improved methods to estimate depth to the Moho and the Precambrian crystalline basement using potential field data. The details are presented in the following chapters summarized as three independent projects

Missed antenatal care follow-up and associated factors in Eastern Zone of Tigray, Northern Ethiopia

Introduction: Focused antenatal care improves the survival and health of the mother as well as the babies. However, there are real challenges in keeping the subsequent antenatal care follow up in Ethiopia. Hence, the aim of this study was to assess missed antenatal care follow up and associated factors in the Eastern zone of Tigray Methods: Hospital based cross-sectional study was conducted among systematically selected 548 women who came for delivery services from March to April 2016. The data were collected using pre-tested and structured questionnaire through face to face exit interview. Data entry and analysis were made using EPI info version 7 software and SPSS version 20 respectively. Both binary and multiple logistic regression was performed. Results: This study revealed that 33.4% of participants were missing their Antenatal care follow-up. Having no formal education [AOR=1.778 (1.102, 2.869)], attending primary education [AOR= 1.756 (1.040, 2.964)], self-employee [AOR=1.589 (1.030, 2.452)], government employee [AOR=0.503 (0.503, 0.953)], being unmarried [AOR=2.36 (1.11, 5.04)], didn\u2019t informed about institutional delivery [AOR=3.34 (1.44, 7.78)], and travel distance more than two hours to hospital [AOR=1.93 (1.08, 3.44)] were factors significantly associated with missed Antenatal care follow-up. Conclusion: The proportion of missed antenatal care follow-up was lessened as compared to local and national evidences. Nevertheless, still a coordinated effort on tracking of pregnant women who missed their antenatal care appointment is required by health policy implementers so as to increase the uptake of four complete visits

Determinants of Nursing Process Implementation in North East Ethiopia: Cross-Sectional Study

Nursing process is a framework used to provide an effective, coordinated, and organized quality care for patients. Effective implementation of this framework leads to improved quality of care and decreases potential complication, hospital length of stay, and the cost of care. To assess implementation of nursing process and its hindering factors, a quantitative cross-sectional study was conducted among nurses in Afar region hospitals from October 2016 to December 2016. The data were collected from 102 nurses using primary Brooking’s ward nurses’ self-report questionnaire and with some newly prepared questions. The collected data were entered using Epi-Data version 3.1 and analyzed by SPSS version 20 and then presented by tables, graphs, and figures. Forty-three (42.1%) nurses were implementing nursing process at the time of data collection. Assessment and diagnosis were carried out by 57 (56.9%) nurses, planning by 46% of nurses, implementation by 38.2% of nurses, and evaluation by 36.2% of nurses in Afar region. Among the hindering factors towards nursing process implementation, lack of preparedness or knowledge about the nursing process or some part of it (83.3%) and absence of in-service training pertinent to nursing process (75.5%) were the most mentioned ones. Generally, nursing process was poorly implemented in Afar region mainly due to lack of knowledge and absence of in service training. Therefore, giving emphasis for cognitive parts of students about nursing process during their school time and refreshing nurse staffs with continuous training will definitively improve level of nursing process implementation

Knowledge and attitude of healthcare workers toward advanced cardiac life support in Felege Hiwot Referral Hospital, Bahir Dar, Ethiopia, 2022

Objective: The aim of this study was to investigate the knowledge and attitude regarding advanced cardiac life support among healthcare workers, 2022. Methods: A cross-sectional study was conducted from March to May 2022 among healthcare workers who were working in Felege Hiwot Comprehensive Specialized Hospital Bahir Dar, Ethiopia. All physicians and nurses who were willing to participate this study were involved. A structured self-administered questionnaire was used for data collection. The data were entered into the statistical software Epi Data version 4.6.0.4 and analyzed with statistical package for social science version 26. Logistic regression analysis was used to differentiate the effects of each independent variable on the dependent variable. Results: Among the total study participants (400) with a response rate of 96%, most (238) (59.5%) healthcare workers (nurses and physicians) had poor knowledge toward advanced cardiac life support. Two hundred twenty-five (56.25%) healthcare workers had positive attitude. Being a physician, having more than 6 years of work experience, working in an emergency department for more than 10 years, and having advanced cardiac life support training all contribute to superior knowledge of advanced cardiac life support. Conclusion: Most healthcare workers, especially, nurses, have under estimated knowledge and a negative attitude toward advanced cardiac life support. This implies they require knowledge building and attitude empowerment regarding advanced cardiac life support. Being a physician, having training in advanced cardiac life support, having work experience of more than 6 years, and working in an emergency unit for more than 10 years were positively associated with better knowledge of advanced cardiac life support among healthcare workers

sj-docx-1-smo-10.1177_20503121221150101 – Supplemental material for Knowledge and attitude of healthcare workers toward advanced cardiac life support in Felege Hiwot Referral Hospital, Bahir Dar, Ethiopia, 2022

Supplemental material, sj-docx-1-smo-10.1177_20503121221150101 for Knowledge and attitude of healthcare workers toward advanced cardiac life support in Felege Hiwot Referral Hospital, Bahir Dar, Ethiopia, 2022 by Ousman Adal and Solomon Emishaw in SAGE Open Medicine</p

Highly Insulated Wall Systems with Exterior Insulation of Polyisocyanurate under Different Facer Materials: Material Characterization and Long-Term Hygrothermal Performance Assessment

The application of exterior insulation in both new construction and retrofits is a common practice to enhance the energy efficiency of buildings. In addition to increased thermal performance, the rigid insulation can serve to keep the sheathing board warm and serve as a water-resistive barrier to keep moisture-related problems due to condensation and wind-driven rain. Polyisocyanurate (PIR) rigid boards have a higher thermal resistance in comparison to other commonly used exterior insulation boards. However, because of its perceived lower permeance, its use as exterior insulation is not very common. In this study, the hygrothermal property of PIR boards with different facer types and thicknesses is characterized. The material data obtained through experimental test and extrapolation is used in a long term hygrothermal performance assessment of a wood frame wall with PIR boards as exterior insulation. Results show that PIR with no facer has the smallest accumulated moisture on the sheathing board in comparison to other insulation boards. Walls with a bigger thickness of exterior insulation perform better when no vapor barrier is used. The PIR exterior insulation supports the moisture control strategy well in colder climates in perfect wall scenarios, where there is no air leakage and moisture intrusion. In cases where there is trapped moisture, the sheathing board has a higher moisture content with PIR boards with both aluminum or fiberglass type facers. An innovative facer material development for PIR boards can help efforts targeting improved energy-efficient and durable wall systems