Investigation on laser beam machining of miniature gears

Abstract: Micro‐machining has become a fast growing field in the global manufacturing sector due to increasing demand of miniature machines and devices. The trend involves the fabrication of precision miniature parts that have widespread applications in many areas such as, electronics, biomedical, aerospace, robotics, automobiles and consumer products. Miniature gears are essential components of miniaturised devices such as miniature motors and pumps, scientific instruments, medical equipment, timing devices, and robots etc. These gears are generally fine‐pitched gears running at very high speed, mainly used for transmission of motion and/or torque. Therefore, minimum running noise, accurate motion transfer and long service life are the required qualities of these gears. Considering that a laser beam is capable of cutting complex shapes with great precision and little waste, motivates its use to machine small sized parts including miniature gears. This article reports on the fabrication of stainless steel miniature gears by laser beam machining (LBM) process. A total of twenty experiments have been conducted following one factor at a time design of experiment strategy on CO2 laser machine. The fabricated gears have 9 mm pitch diameter, 10 teeth, and 4.5 mm thickness. The effects of laser machining parameters on surface roughness (mainly average roughness ‘Ra’ and mean roughness depth ‘Rz’) of gears have been analysed. The best quality miniature gear fabricated by LBM possesses 1.04 μm average roughness and 5.797 μm mean roughness depth at par with that obtained by conventional and other advanced processes of miniature gear manufacturing. Investigation reveals that LBM is capable to produce miniature gears of good surface finish and integrity ensuring their high functional performance and long service life. The outputs of this preliminary work encourage further exploration of LBM to establish it as an alternative process for fabrication of precision miniature gears

3D printing of carbon nanofiber‐PLA composite

Abstract: The aim of this research study was to study the mechanical properties of carbon nanofiber (CNF) and Polylactide (PLA) composite. The composite material was developed by mixing Polylactide with carbon nano fiber using a three dimensional printer. The research study presents the following; the mixing ratios which were used, time intervals, mixing equipment and mixing method. After the composite material was developed, the mechanical properties of the material were studied. These mechanical properties include the ultimate tensile strength and yield strength between the two materials that is PLA and PCM composites. The effect of processing methods and conditions on the properties of CNF/PLA composites were also taken to consideration due to the impact they might have in the results obtained. An excel Anova software was also used to compare the UTS of the two materials and conclude if there is a significant difference between the parent material and the developed composite material. The Ultimate tensile strength improved by 4.16% from the initial ultimate tensile strength obtained from PLA samples, while the yield strength increased by 38.05% from the PLA. These results obtained conclude that the mechanical properties of the PCM have improved. At the end of the paper, recommendations of possible future challenges for CNF/PLA composites will be presented

Biogas use as fuel in spark ignition engines

Abstract: This paper reviews the utilization of biogas in spark ignition engines with a view to making a case for it as an efficient substitute fuel for petrol. However, its gaseous nature which accounts for its low volumetric density implies that apart from the basic modification needed to accommodate the fuel, the engine might need further alterations to get the best from this relatively low cost and readily available fuel. Various modes of enhancing performance particularly methane enrichment, prechamber combustion, alteration of ignition parameters, increasing compression ratio and addition of hydrogen to improve performance and emissions were drawn from previous works to validate its efficiency as a viable substitute fuel in SI engines

The use of needs assessment methodologies to focus technical interventions in root and tuber crop post-harvest systems: a case study to improve the marketing and post-harvest handling of cassava entering Dar es Salaam, Tanzania

The accurate targeting of research and technology transfer strategies within root and tuber crops post-harvest systems is essential to ensure that developmental funds within national programmes are used to maximum advantage. Needs assessment studies have important roles to play in initially defining problem areas. Such procedures must be cost effective and generate genuine information quickly and efficiently. This paper describes the use of an urban demand/needs assessment strategy to define the problems evident in the marketing of fresh cassava roots in Oar es Salaam, Tanzania. By examining secondary data and collecting primary information from key participants in the marketing chain, the principal constraints and sources of cassava wastage within the system were identified as were opportunities for possible technical interventions. As a result of these assessments, a more detailed case study was undertaken to quantify the losses of cassava within the system and, thereafter, an adaptive technology transfer programme was initiated to test, adapt and later disseminate elements of the low cost ambient storage technology derived from protocols developed by the Centro Internacional de Agricultura Tropical (CIAT) and the Natural Resources Institute (NRI). Observations made suggest that the adoption of the ambient storage techniques will help reduce financial losses (both physical and financial) to the benefit of producers, marketing agents and consumers

Importance of common bean genetic zinc biofortification in alleviating human zinc deficiency in sub-Saharan Africa

This research article published by Taylor & Francis Online, 2021Zinc deficiency is among the leading risks to human health in sub-Saharan Africa, its adverse exposure leads to diarrhea, pneumonia, and malaria. Furthermore, it is the leading cause of stunting in children and negatively influences the human immune system, body iron, and vitamin A and D. High zinc deficiency in sub-Saharan Africa is due to the consumption of staple foods with low zinc contents. Genetic zinc biofortification of common bean among staple food crops is the best approach for alleviating zinc deficiency, as it is cost-effective and can easily reach low-income households. Genetic zinc biofortification by conventional breeding coupled with marker-assisted selection is the best strategy for sub-Saharan Africa, as the selection of crosses is precise and takes short time to develop high zinc-containing varieties. Zinc content increase in common bean seeds has a high impact on alleviating zinc deficiency as it is consumed whole compared to cereal grains which undergo milling, the process that removes zinc-rich parts before being consumed. This review explains the current status of zinc deficiency in sub-Saharan Africa, conventional methods for alleviating the problem, current and potential of modern genetic approaches for zinc biofortification of common bean in alleviating zinc deficiency in the region

Environmental and genotypes influence on seed iron and zinc levels of landraces and improved varieties of common bean (Phaseolus vulgaris L.) in Tanzania

This research article published by Elsevier, 2020Phaseolus vulgaris L. (common bean) is a grain legume rich in proteins and micronutrients particularly iron and zinc. This study determined the concentration of iron and zinc in 99 common bean genotypes (landraces and cultivars) grown in Tanzania. The bean genotypes were planted in three different agro-ecologies in Tanzania following alpha lattice design with 3 replications each with five blocks of 20 plots. Adaptability and stability of common bean genotypes on seed iron and zinc contents were assessed using the additive main effect and multiplicative interaction (AMMI) analysis, genotype stability index (GSI) and genotype main effect plus genotype-by-environment interaction (GGE). Highly significant effects of bean genotypes, environments, and genotype by environment interaction were observed for both seed iron and zinc contents. The AMMI analysis of variance showed that genotype contributed 69.5% of the total sum of squares for seed iron and 28.6% of seed zinc contents. Environmental effects contributed 1.7% and 39.7% of the total sum of squares for seed iron and zinc contents respectively. Genotype by environment interaction effects contributed 26.3% and 28.6% of the total sum of squares for seed iron and zinc contents respectively. Among individual weather and soil parameters of the experimental sites, total rainfall, soil available phosphorus, iron, silt %, and exchangeable potassium positively significantly influenced the contents of seed iron, while temperature, total soil nitrogen, and manganese influenced negatively and significantly seed iron contents. Twelve most high and stable seed iron-containing bean genotypes identified by both GSI and GGE, includes SMC 18, Selian 94, Urafiki, Kyakaragwe, CODMLB 033, Kikobe, Malirahinda, ACC 714, Jabeyila, Mwamikola, Kasukari and Wifi nygela. These bean genotypes can be used for iron biofortification and or further tested for seed iron contents and other agronomic traits in more bean growing environments involving farmers and seed certifying institutes for release as varieties

Impact of antiretroviral therapy on pregnancy outcomes

Background.The majority of HIV-positive women in South Africa are of reproductive age, and pregnancies among women using antiretroviral therapy (ART) are common. However, there are mixed data regarding the impact of ART on pregnancy outcomes. Objective. To examine the impact of ART on pregnancy outcome according to the timing of initiation of treatment. Methods. A retrospective cohort study was conducted among women delivering at a tertiary hospital from 1 October 2008 to 31 March 2009. Results. A total of 245 mothers were receiving ART: 76 mothers (31%) started ART pre-conception and 169 mothers (69%) started ART after the first trimester. No significant differences were observed in the rates of preterm delivery and low birth weight (LBW) between the pre- and post-conception groups (21% v. 24% and 21% v. 25%, respectively). Conclusion. In this cohort of women receiving ART in pregnancy, timing of ART initiation did not have any adverse effect on the measured pregnancy outcomes such as preterm delivery and LBW

Health trends, inequalities and opportunities in South Africa's provinces, 1990-2019: findings from the Global Burden of Disease 2019 Study

Background Over the last 30 years, South Africa has experienced four ‘colliding epidemics’ of HIV and tuberculosis, chronic illness and mental health, injury and violence, and maternal, neonatal, and child mortality, which have had substantial effects on health and well-being. Using data from the 2019 Global Burden of Diseases, Injuries and Risk Factors Study (GBD 2019), we evaluated national and provincial health trends and progress towards important Sustainable Development Goal targets from 1990 to 2019. Methods We analysed GBD 2019 estimates of mortality, non-fatal health loss, summary health measures and risk factor burden, comparing trends over 1990–2007 and 2007–2019. Additionally, we decomposed changes in life expectancy by cause of death and assessed healthcare system performance. Results Across the nine provinces, inequalities in mortality and life expectancy increased over 1990–2007, largely due to differences in HIV/AIDS, then decreased over 2007–2019. Demographic change and increases in non-communicable diseases nearly doubled the number of years lived with disability between 1990 and 2019. From 1990 to 2019, risk factor burdens generally shifted from communicable and nutritional disease risks to non-communicable disease and injury risks; unsafe sex remained the top risk factor. Despite widespread improvements in healthcare system performance, the greatest gains were generally in economically advantaged provinces. Conclusions Reductions in HIV/AIDS and related conditions have led to improved health since 2007, though most provinces still lag in key areas. To achieve health targets, provincial governments should enhance health investments and exchange of knowledge, resources and best practices alongside populations that have been left behind, especially following the COVID-19 pandemic

Global, regional, and national incidence, prevalence, and years lived with disability for 354 diseases and injuries for 195 countries and territories, 1990-2017 : a systematic analysis for the Global Burden of Disease Study 2017

Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017) includes a comprehensive assessment of incidence, prevalence, and years lived with disability (YLDs) for 354 causes in 195 countries and territories from 1990 to 2017. Previous GBD studies have shown how the decline of mortality rates from 1990 to 2016 has led to an increase in life expectancy, an ageing global population, and an expansion of the non-fatal burden of disease and injury. These studies have also shown how a substantial portion of the world's population experiences non-fatal health loss with considerable heterogeneity among different causes, locations, ages, and sexes. Ongoing objectives of the GBD study include increasing the level of estimation detail, improving analytical strategies, and increasing the amount of high-quality data. Methods: We estimated incidence and prevalence for 354 diseases and injuries and 3484 sequelae. We used an updated and extensive body of literature studies, survey data, surveillance data, inpatient admission records, outpatient visit records, and health insurance claims, and additionally used results from cause of death models to inform estimates using a total of 68 781 data sources. Newly available clinical data from India, Iran, Japan, Jordan, Nepal, China, Brazil, Norway, and Italy were incorporated, as well as updated claims data from the USA and new claims data from Taiwan (province of China) and Singapore. We used DisMod-MR 2.1, a Bayesian meta-regression tool, as the main method of estimation, ensuring consistency between rates of incidence, prevalence, remission, and cause of death for each condition. YLDs were estimated as the product of a prevalence estimate and a disability weight for health states of each mutually exclusive sequela, adjusted for comorbidity. We updated the Socio-demographic Index (SDI), a summary development indicator of income per capita, years of schooling, and total fertility rate. Additionally, we calculated differences between male and female YLDs to identify divergent trends across sexes. GBD 2017 complies with the Guidelines for Accurate and Transparent Health Estimates Reporting. Findings: Globally, for females, the causes with the greatest age-standardised prevalence were oral disorders, headache disorders, and haemoglobinopathies and haemolytic anaemias in both 1990 and 2017. For males, the causes with the greatest age-standardised prevalence were oral disorders, headache disorders, and tuberculosis including latent tuberculosis infection in both 1990 and 2017. In terms of YLDs, low back pain, headache disorders, and dietary iron deficiency were the leading Level 3 causes of YLD counts in 1990, whereas low back pain, headache disorders, and depressive disorders were the leading causes in 2017 for both sexes combined. All-cause age-standardised YLD rates decreased by 3·9% (95% uncertainty interval [UI] 3·1–4·6) from 1990 to 2017; however, the all-age YLD rate increased by 7·2% (6·0–8·4) while the total sum of global YLDs increased from 562 million (421–723) to 853 million (642–1100). The increases for males and females were similar, with increases in all-age YLD rates of 7·9% (6·6–9·2) for males and 6·5% (5·4–7·7) for females. We found significant differences between males and females in terms of age-standardised prevalence estimates for multiple causes. The causes with the greatest relative differences between sexes in 2017 included substance use disorders (3018 cases [95% UI 2782–3252] per 100 000 in males vs s1400 [1279–1524] per 100 000 in females), transport injuries (3322 [3082–3583] vs 2336 [2154–2535]), and self-harm and interpersonal violence (3265 [2943–3630] vs 5643 [5057–6302]). Interpretation: Global all-cause age-standardised YLD rates have improved only slightly over a period spanning nearly three decades. However, the magnitude of the non-fatal disease burden has expanded globally, with increasing numbers of people who have a wide spectrum of conditions. A subset of conditions has remained globally pervasive since 1990, whereas other conditions have displayed more dynamic trends, with different ages, sexes, and geographies across the globe experiencing varying burdens and trends of health loss. This study emphasises how global improvements in premature mortality for select conditions have led to older populations with complex and potentially expensive diseases, yet also highlights global achievements in certain domains of disease and injury. Funding: Bill & Melinda Gates Foundation