Literature Review on Thermomechanical Modelling and Analysis of Residual Stress Effects in Wire Arc Additive Manufacturing

The wire arc additive manufacturing (WAAM) process is a 3D metal-printing technique that builds components by depositing beads of molten metal wire pool in a layer-by-layer style. Even though manufactured parts commonly suffer from defects, the search to minimize defects in the product is a continuing process, for instance, using modeling techniques. In areas where thermal energy is involved, thermomechanical modeling is one of the methods used to determine the input thermal load and its effect on the products. In the WAAM fabrication process, the thermal load is the most significant cause of residual stress due to the extension and shrinkage of the molten pool. This review article explores the thermomechanical effect and stress existing in WAAM-fabricated parts due to the thermal cycles and other parameters in the process. It focuses on thermomechanical modeling and analysis of residual stress, which has interdependence with the thermal cycle, mechanical response, and residual stress in the process during printing. This review also explores some methods for measuring and minimizing the residual stress during and after the printing process. Residual stress and distortion associated with many input and process parameters that are in complement to thermal cycles in the process are discussed. This review study concludes that the thermal dependency of material characterization and process integration for WAAM to produce structurally sound and defect-free parts remain central issues for future research.publishedVersio

Adverse Drug Reaction Monitoring in Ethiopia: Analysis of case reports, 2002-2007

Background: Ensuring the health and safety of the public from adverse reaction of drugs is paramount. Adverse Drug Reactions Monitoring (ADRM) is a system that is put in place to ensure the health and safety of the public from adverse reactions of drugs. It heavily relies on health professionals (HPs) reporting of adverse events of drugs to drug regulators, in Ethiopia to the Drug Administration and Control Authority (DACA). The processed information, based on reported cases, is used to improve evidence based practice and underpins decisions to mitigate drug safety issues by drug regulators. However, the effectiveness of the ongoing ADRM system in Ethiopia in terms of its detection has never been evaluated.Objective: To explore the magnitude of ADRM and suggest some practical improvement in Ethiopia.Methods: The study analyzed the number of adverse drug reaction case reports received by DACA in a period of six years (2002 – 2007GC). All cases reported over the study period were included for analysis. Descriptive analysis was carried out to estimate the prevalence of adverse drug reactions and to assess their trend over the study period. To assess the strengths and weakness of the ongoing national ADRM, cases were analyzed by their location, time of occurrence, type of the health professional who made the case reports, drugs implicated, clinical manifestations and age of subjects affected.Results: A total of 249 ADR cases were reported between 2002 and 2007. An average of 0.5 ADR cases per million populations were reported annually. The majority (36%) of all the cases were for 31 to 40 years of age. Cases were reported mainly (63%) from health facilities in the capital city. Physicians made 76% of all cases reported. Antiretroviral drugs were implicated in 70% of the cases reported. The most widely adverse events reported were dermatological disorders.Conclusions: The level of ADR case reporting is very low showing the need to address major constraints of ongoing ADR monitoring. Thus, comprehensive measures aimed at improving under-reporting and effectiveness of ADRM should be instituted. [Ethiop. J. Health Dev. 2011;25(2):168-173

Exploring barriers to the use of formal maternal health services and priority areas for action in Sidama zone, southern Ethiopia.

In 2015 the maternal mortality ratio for Ethiopia was 353 per 100,000 live births. Large numbers of women do not use maternal health services. This study aimed to identify factors influencing the use of maternal health services at the primary health care unit (PHCU) level in rural communities in Sidama zone, south Ethiopia in order to design quality improvement interventions. We conducted a qualitative study in six woredas in 2013: 14 focus group discussions (FGDs) and 44 in-depth interviews with purposefully selected community members (women, male, traditional birth attendants, local kebele administrators), health professionals and health extension workers (HEWs) at PHCUs. We digitally recorded, transcribed and thematically analysed the interviews and FGDs using Nvivo. The 'three delay model' informed the analytical process and discussion of barriers to the use of maternal health services. Lack of knowledge on danger signs and benefits of maternal health services; cultural and traditional beliefs; trust in TBAs; lack of decision making power of women, previous negative experiences with health facilities; fear of going to an unfamiliar setting; lack of privacy and perceived costs of maternal health services were the main factors causing the first delay in deciding to seek care. Transport problems in inaccessible areas were the main contributing factor for the second delay on reaching care facilities. Lack of logistic supplies and equipment, insufficient knowledge and skills and unprofessional behaviour of health workers were key factors for the third delay in accessing quality care. Use of maternal health services at the PHCU level in Sidama zone is influenced by complex factors within the community and health system. PHCUs should continue to implement awareness creation activities to improve knowledge of the community on complications of pregnancy and benefits of maternal health services. The health system has to be responsive to community's cultural norms and practices. The mangers of the woreda health office and health centres should take into account the available budgets; work on ensuring the necessary logistics and supplies to be in place at PHCU

Retention of deposited ammonium and nitrate and its impact on the global forest carbon sink

The impacts of enhanced nitrogen (N) deposition on the global forest carbon (C) sink and other ecosystem services may depend on whether N is deposited in reduced (mainly as ammonium) or oxidized forms (mainly as nitrate) and the subsequent fate of each. However, the fates of the two key reactive N forms and their contributions to forest C sinks are unclear. Here, we analyze results from 13 ecosystem-scale paired 15N-labelling experiments in temperate, subtropical, and tropical forests. Results show that total ecosystem N retention is similar for ammonium and nitrate, but plants take up more labelled nitrate (202515%) (meanmaximumminimum) than ammonium (12168%) while soils retain more ammonium (576549%) than nitrate (465932%). We estimate that the N deposition-induced C sink in forests in the 2010s is 0.720.960.49 Pg C yr−1, higher than previous estimates because of a larger role for oxidized N and greater rates of global N deposition

Safe Delivery Service Utilization in Metekel Zone, NorthWest Ethiopia

No abstract - Available on PD

Optimisation of Graphene Nanofiller Addition on the Mechanical and Adsorption Properties of Woven Banana/Polyester Hybrid Nanocomposites by Grey-Taguchi Method

Throughout history, techniques have shifted from mainstream metals and minerals to nanocomposites to generate smaller, more practical elements for particular purposes. Natural fibres have greater advantages than glass fibres, such as being cheaper, recyclable, and nonflammable. The main objective of the current experiment is to determine how the accumulation of graphene to hybrid polyester composites reinforced with woven banana fibre affects their mechanical properties. Composites were constructed utilising the hand lay-up process with the following limitations: (i) graphene filler weightiness, (ii) woven banana fibre thickness in gsm, and (iii) number of woven banana layers, all at three different levels. Using the L9 (33) orthogonal design, nine composite samples are generated and tested according to the ASTM standard. According to the grey research, hybrid composites having 5% graphene powder and 350 grammes per square metre of woven banana fibre in three layers have high mechanical strength. Adding fibre content to immaculate polyester increased its mechanical properties in general. As the fibre and filler concentrations grew, more energy was required to break the fibre bundles between the matrix and its resin. The confirmation test by the optimal process value utilising the grey relation analysis is considerably better than the actual test data. Tension strength has improved by 17.14%, bending strength has improved by 96.75%, and impact energy has increased by 16.17%