Performance of a centrifugal pump running in inverse mode

This paper presents the functional characterization of a centrifugal pump used as a turbine. It shows the characteristics of the machine involved at several rotational speeds, comparing the respective flows and heads. In this way, it is possible to observe the influence of the rotational speed on efficiency, as well as obtaining the characteristics at constant head and runaway speed. Also, the forces actuating on the impeller were studied. An uncertainty analysis was made to assess the accuracy of the results. The research results indicate that the turbine characteristics can be predicted to some extent from the pump characteristics, that water flows out of the runner free of swirl flow at the best efficiency point, and that radial stresses are lower than in pump mode

Numerical Study on Catalytic Reaction and Catalytic Mechanism of Ceramic Catalytic Turbine Technology under Variable Operating Conditions during Vehicle Warm-up

In this paper, numerical simulation methods are adopted to explore the influencing factors of a Ceramic Catalytic Turbine (CCT) for reduced exhaust pollution from vehicles during the warm-up stage. Also, an analysis is conducted regarding the potential effects of turbulence on the catalytic reaction mechanism and the sensitivity of relevant parameters to the Arrhenius equation. It is found out that the air-fuel ratio inside the engine has a considerable effect on the reactions of CCT, with the conversion efficiency of each emission species sharply reduced under fuel-rich conditions. At 600K, the conversion efficiency declines by 11.3% for C3H6, 12.26% for CO, and 3.64% for NO. At 700K, the conversion efficiency is reduced by 6.7% for C3H6, 11.56% for CO, and 6.44% for NO. Despite increasing the concentration of reaction gas components, a high flow rate makes little difference to the reaction itself. At the same rotational speed of the turbine, the conversion rate of harmful components drops with an increase in flow rate due to the increase in space velocity. When the flow rate is constant and the temperature is kept in the control zone of chemical kinetics, the conversion efficiency of the catalytic reaction is enhanced at a higher rotational speed. Differently, when the temperature is in the control zone of mass transport and the flow rate is constant, the conversion efficiency decreases as the turbine accelerates. In practical terms, reducing activation energy within a controllable range is equivalent to further reducing the light-off temperature of the catalyst. Meanwhile, this may disrupt the convergence of numerical calculations because the catalytic reactions could occur at around the light-off temperature

Mortality rate among HIV-positive children on ART in Northwest Ethiopia: a historical cohort study.

BackgroundThough highly active antiretroviral therapy (HAART) has been available for more than a decade in Ethiopia, information regarding mortality rates of human immunodeficiency virus (HIV)-positive children after antiretroviral therapy antiretroviral therapy (ART) initiation is very scarce. Thus, this study intends to determine the predictors of mortality among HIV-positive children receiving ART in Amhara Region.MethodsA multicenter facility-based historical cohort study was conducted in 538 HIV-positive children on ART from January 2012 to February 2017. We employed a standardized data extraction tool, adapted from ART entry and follow-up forms. Descriptive analyses were summarized using the Kaplan-Meier survival curve and log rank test. Then, the Cox-proportional hazard regression model was employed to estimate the hazard of death up to five-years after ART initiation. Variables with p-values ≤0.25 in bivariable analysis were candidates to the multivariable analysis. Finally, variables with p-values ResultsThe cohort contributed a total follow-up time of 14,600 child-months, with an overall mortality rate of 3.2 (95% CI: 2.3, 4.3) per 100 child-years. This study also indicated that HIV-infected children presenting with opportunistic infections (OIs) (AHR: 2.5, 95% CI: 1.04, 5.9), anemia (AHR: 3.1, 95% CI: 1.4, 6.7), severe immunodeficiency (AHR: 4.4, 95% CI: 1.7, 11.7), severe stunting (AHR: 3.3, 95% CI: 1.4, 8.0), severe wasting (AHR: 3.1, 95% CI: 1.3, 7.3), and advanced disease staging (III and IV) (AHR: 3.0, 95% CI: 1.2, 7.1) were at higher risk of mortality.ConclusionA higher rate of mortality was observed in our study as compared to previous Ethiopian studies. HIV-positive children presenting with anemia, OIs, severe immunodeficiency, advanced disease staging (III and IV), severe stunting, and severe wasting were at higher risk of mortality

Evidence of heterogeneity in statin-associated type 2 diabetes mellitus risk: A meta-analysis of randomized controlled trials and observational studies

Aims: To conduct a meta-analysis of statin-associated type 2 diabetes mellitus (T2D) risk among randomized controlled trials (RCTs) and observational studies (OBSs), excluding studies conducted among secondary prevention populations. Methods: Studies were identified by searching PubMed (1994-present) and EMBASE (1994-present). Articles had to meet the following criteria: (1) follow-up >one year; (2) >50% of participants free of clinically diagnosed ASCVD; (3) adult participants ≥30 years old; (4) reported statin-associated T2D effect estimates; and (5) quantified precision using 95% confidence interval. Data were pooled using random-effects model. Results: We identified 23 studies (35% RCTs) of n = 4,012,555 participants. OBS participants were on average younger (mean difference = 6.2 years) and had lower mean low-density lipoprotein cholesterol (LDL-C, mean difference = 20.6 mg/dL) and mean fasting plasma glucose (mean difference = 5.2 mg/dL) compared to RCT participants. There was little evidence for publication bias (P > 0.1). However, evidence of heterogeneity was observed overall and among OBSs and RCTs (P Cochran = <0.05). OBS designs, younger baseline mean ages, lower LDL-C concentrations, and high proportions of never or former smokers were significantly associated with increased statin-associated T2D risk. Conclusions: Potentially elevated statin-associated T2D risk in younger populations with lower LDL-C merits further investigation in light of evolving statin guidelines targeting primary prevention populations

Erratum: Author Correction: Transitions from Ideal to Intermediate Cholesterol Levels may vary by Cholesterol Metric (Scientific reports (2018) 8 1 (2782))

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper

Transitions from Ideal to Intermediate Cholesterol Levels may vary by Cholesterol Metric

To examine the ability of total cholesterol (TC), a low-density lipoprotein cholesterol (LDL-C) proxy widely used in public health initiatives, to capture important population-level shifts away from ideal and intermediate LDL-C throughout adulthood. We estimated age (≥20 years)-, race/ethnic (Caucasian, African American, and Hispanic/Latino)-, and sex- specific net transition probabilities between ideal, intermediate, and poor TC and LDL-C using National Health and Nutrition Examination Survey (2007–2014; N = 13,584) and Hispanic Community Health Study/Study of Latinos (2008–2011; N = 15,612) data in 2016 and validated and calibrated novel Markov-type models designed for cross-sectional data. At age 20, >80% of participants had ideal TC, whereas the race/ethnic- and sex-specific prevalence of ideal LDL-C ranged from 39.2%-59.6%. Net transition estimates suggested that the largest one-year net shifts away from ideal and intermediate LDL-C occurred approximately two decades earlier than peak net population shifts away from ideal and intermediate TC. Public health and clinical initiatives focused on monitoring TC in middle-adulthood may miss important shifts away from ideal and intermediate LDL-C, potentially increasing the duration, perhaps by decades, that large segments of the population are exposed to suboptimal LDL-C

Rapport I.17 The effect of front shroud on the partial flow and cavitation performance of centrifugal impellers

The significance of the absence or presence of a front shroud which classifies a centrifugal impeller as fully shrouded (closed) or half shrouded (open) is examined, in particular the part load and cavitation performances. It is shown that the absence or presence of the front-shroud has some hydraulic effects but not critical enough to be consided as a main design criteria.Engeda A., Rautenberg M. Rapport I.17 The effect of front shroud on the partial flow and cavitation performance of centrifugal impellers. In: Machines hydrauliques. Conception et exploitation. Développements récents et Applications aux différents secteurs industriels. Vingtièmes journées de l'hydraulique. Lyon, 4-6 avril 1989. Tome 1, 1989

Steam as turbine blade coolant: Experimental data generation

Steam as a coolant is a possible option to cool blades in high temperature gas turbines; however there is practically no experimental data. This work deals with an attempt to generate such data and with the design of an experimental setup used for the purpose. Initially, in order to guide the direction of experiments, a preliminary theoretical and empirical prediction of the expected experimental data is performed and is presented here. This initial analysis also compares the coolant properties of steam and air