Dynamic analysis of spur gear with backlash using ADAMS

Gear tooth profile can deviate from its initial design shape and size as a result of increasing service time under time-varying load, introducing external agents like debris, overheating due to friction, wear, and in generally due to other nonlinear factors such as backlash. As a result, the dynamics of the gear will also vary depending on the resulting gear tooth profile. In this study, the worn-out gear tooth is modelled as a backlash by assuming a uniformly distributed worn out surface and the effect on the dynamic performance is investigated. By changing the amount of backlash of the gear tooth from 0 mm to 1 mm by 0.2 mm increment, the gear is modelled and analysed for three loading cases using MSC ADAMS software. This paper discusses the effect of backlash or uniformly worn out spur gear tooth faces on the dynamics specifically the contact and angular accelerations of the gear.publishedVersio

Contact temperature analysis of the classical Geneva mechanism through numerical methods

In this study, the flash temperature of the classical Geneva mechanism has been studied using the numer- ical method. An excessive sliding motion between the wheel and pin leads to the generation of heat at the contact surfaces, which raises the surface temperature of the two contacting bodies. The flash tempera- ture has been anticipated for different loading cases and coefficients of friction. The analytical Blok equa- tion results are compared with the finite element results, and the results are satisfactory for maximum temperature. Based on the simulation results, the maximum contact temperature occurred in the driving crankpin within 10-15° and 70–75° of the angular position, and as the load increased the contact temper- ature also increases. In addition, the angular velocity increment produced higher temperatures than the torque load increments.publishedVersio

Mechanical property characterization of water hyacinth and glass fiber reinforced hybrid composite

While composites of natural fibers have got more attraction because of their advantages, there are some limitations. Therefore, hybridization is a way to minimize some of the limitations of natural fibers composite. This article reports on the study conducted to investigate the mechanical properties of a hybrid glass/water hyacinth reinforced polymer composite using five different forms of volume fractions. The hybrid composite was prepared by hand lay-up method according to ASTM D3410 and ASTM D3039 standards for compression and tensile tests, respectively. The material properties of the composite were analyzed to explore the influence of fiber volume fraction. The results indicate that the mechanical properties change as a function of the volume fraction. Thus, the addition of glass fibers influenced the results of both tensile and compressive properties.publishedVersio

Internal Corrosion Damage Mechanisms of the Underground Water Pipelines

Internal water pipe corrosion is a complicated problem due to the interaction of water quality parameters with pipe wall. This study presents investigations of internal pipe surface corrosion mechanisms related to water physicochemical. Samples of water and corrosion-damaged ductile cast iron (30+ years) and galvanized steel pipe (15-20 years) were collected at in-situ condition from Addis Ababa city water distribution system. Scanning electron microscopy and optical microscopy were used to examine the pipes' corrosion morphology and microstructures, respectively. Additionally, Mountains 9 surface analysis software was used for further pitting corrosion characterization.To identify the causes of internal pipe corrosion, water physicochemical analyses were conducted by using inoLab pH 7310P, DR 900, Palintest Photometer 7100, and Miero 800. Water physicochemical test indicates: CaCO3 is 77 - 215 ppm, pH is 7.05 – 7.86, total dissolved solids (TDS) is 84.10 -262.8 ppm, ClO2 is 0 – 0.5 ppm, and dissolved oxygen (80-81 ppb). From water test results, major causes of internal pipe corrosion damage mechanisms were identified as dissolved oxygen, CaCO3, TDS, ClO2,and resistivity of water which initiates a differential cell that accelerates pipe corrosion. Using Mountain 9 surface analysis software, corrosion morphology and pitting features were characterized. The outputs of this paper will be helpful for water distribution and buried infrastructure owners to investigate corrosion damage mechanisms at early stage. To manage corrosion mechanisms, water supply owners need to conduct frequent inspections, recording of pipe data, testing of water quality, periodic pipelines washing, and apply preventative maintenance.publishedVersio

Major subpopulations of Plasmodium falciparum in sub-Saharan Africa.

Understanding genomic variation and population structure of Plasmodium falciparum across Africa is necessary to sustain progress toward malaria elimination. Genome clustering of 2263 P. falciparum isolates from 24 malaria-endemic settings in 15 African countries identified major western, central, and eastern ancestries, plus a highly divergent Ethiopian population. Ancestry aligned to these regional blocs, overlapping with both the parasite's origin and with historical human migration. The parasite populations are interbred and shared genomic haplotypes, especially across drug resistance loci, which showed the strongest recent identity-by-descent between populations. A recent signature of selection on chromosome 12 with candidate resistance loci against artemisinin derivatives was evident in Ghana and Malawi. Such selection and the emerging substructure may affect treatment-based intervention strategies against P. falciparum malaria

Climatic variables and malaria transmission dynamics in Jimma town, South West Ethiopia

<p>Abstract</p> <p>Background:-</p> <p>In Ethiopia, malaria is seasonal and unstable, causing frequent epidemics. It usually occurs at altitudes < 2,000 m above sea level. Occasionally, transmission of malaria occurs in areas previously free of malaria, including areas > 2,000 m above sea level. For transmission of malaria parasite, climatic factors are important determinants as well as non-climatic factors that can negate climatic influences. Indeed, there is a scarcity of information on the correlation between climatic variability and malaria transmission risk in Ethiopia in general and in the study area in particular. Therefore, the aim of this study was to determine the level of correlation between meteorological variables and malaria cases.</p> <p>Methods: -</p> <p>Time-series analysis was conducted using data on monthly meteorological variables and monthly total malaria in Jimma town, south west Ethiopia, for the period 2000-2009. All the data were entered and analyzed using SPSS-15 database program. Spearman correlation and linear regression analysis were used to asses association between the variables.</p> <p>Results: -</p> <p>During last ten years (2000-2009), a fluctuating trend of malaria transmission was observed with <it>P.vivax </it>becoming predominant species. Spearman correlation analysis showed that monthly minimum temperature, total rainfall and two measures of relative humidity were positively related with malaria but monthly maximum temperature negatively related. Also regression analysis suggested that monthly minimum (p = 0.008), monthly maximum temperature (p = 0.013) and monthly total rainfall (p = 0.040), at one month lagged effect, were significant meteorological factors for transmission of malaria in the study area.</p> <p>Conclusion: -</p> <p>Malaria incidences in the last decade seem to have a significant association with meteorological variables. In future, prospective and multidisciplinary cooperative research involving researchers from the fields of parasitology, epidemiology, botany, agriculture and climatology is necessary to identify the real effect of meteorological factors on vector- borne diseases like malaria.</p

Urban malaria and associated risk factors in Jimma town, south-west Ethiopia

<p>Abstract</p> <p>Background</p> <p>Malaria kills millions around the world. Until recently it was believed to be a disease of rural areas, since the <it>Anopheles </it>mosquito, which transmits <it>Plasmodium </it>species breeds in rural areas. Urban malaria is emerging as a potential, but "avertable" crisis, in Africa. In view of the rapidly growing number of small and medium-sized towns in Ethiopia there is a pressing need to improve the understanding of the epidemiology of malaria. Therefore, the aim of this study was to determine malaria prevalence and associated risk factors in Jimma town.</p> <p>Methods</p> <p>A cross-sectional study was carried out in Jimma town from April 1 to May 28, 2010. 804 study participants were included from 291 households for microscopic examination of malaria parasites. Socio-demography data and risk factors were collected using structured questionnaires. Logistic regression analysis was done using SPSS 15.0 statistical software.</p> <p>Results</p> <p>From a total of 804 study participants in current survey only 42 (5.2%) were positive for malaria parasites. <it>Plasmodium vivax, Plasmodium falciparum </it>and mixed infection accounted 71.4%, 26.2% and 2.4%, respectively. Higher malaria prevalence rate was observed among under-five children (11%). Those who do not use insecticide-treated bed nets (ITN) were more likely to be infected with malaria (OR = 13.6; 95% CI 4.9-37.2, p < 0.001) compared with those who use the ITN. Living in areas where stagnant water existed (OR = 2.1; 95% CI 1.00-4.2, p = 0.047) and its distance of existence <1 km from the house(OR = 2.1; 95% CI 2.0-15.8, p = 0.001) were more likely to be infected with malaria parasite compared with those who live away from stagnant at a distance greater than 1 km.</p> <p>Conclusion</p> <p>Malaria is a major health problem with <it>P. vivax </it>becoming a predominant species in the town. The prevalence was strongly associated with proximity of residence to potential mosquito breeding sites. Malaria is affecting significant proportions of the urban settlers and human activities nevertheless play an important role in bringing the mosquito breeding sites closer to residences.</p

An open dataset of Plasmodium falciparum genome variation in 7,000 worldwide samples.

MalariaGEN is a data-sharing network that enables groups around the world to work together on the genomic epidemiology of malaria. Here we describe a new release of curated genome variation data on 7,000 Plasmodium falciparum samples from MalariaGEN partner studies in 28 malaria-endemic countries. High-quality genotype calls on 3 million single nucleotide polymorphisms (SNPs) and short indels were produced using a standardised analysis pipeline. Copy number variants associated with drug resistance and structural variants that cause failure of rapid diagnostic tests were also analysed.  Almost all samples showed genetic evidence of resistance to at least one antimalarial drug, and some samples from Southeast Asia carried markers of resistance to six commonly-used drugs. Genes expressed during the mosquito stage of the parasite life-cycle are prominent among loci that show strong geographic differentiation. By continuing to enlarge this open data resource we aim to facilitate research into the evolutionary processes affecting malaria control and to accelerate development of the surveillance toolkit required for malaria elimination