152 research outputs found

    Theory of differential inclusions and its application in mechanics

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    The following chapter deals with systems of differential equations with discontinuous right-hand sides. The key question is how to define the solutions of such systems. The most adequate approach is to treat discontinuous systems as systems with multivalued right-hand sides (differential inclusions). In this work three well-known definitions of solution of discontinuous system are considered. We will demonstrate the difference between these definitions and their application to different mechanical problems. Mathematical models of drilling systems with discontinuous friction torque characteristics are considered. Here, opposite to classical Coulomb symmetric friction law, the friction torque characteristic is asymmetrical. Problem of sudden load change is studied. Analytical methods of investigation of systems with such asymmetrical friction based on the use of Lyapunov functions are demonstrated. The Watt governor and Chua system are considered to show different aspects of computer modeling of discontinuous systems

    Effects of Health Insurance Interruption on Loss of Hypertension Control in Women with and Women Without HIV

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    Background: Among low-income women with and without HIV, it is a priority to reduce age-related comorbidities, including hypertension and its sequelae. Because consistent health insurance access has been identified as an important factor in controlling many chronic diseases, we estimated the effects of coverage interruption on loss of hypertension control in a cohort of women in the United States. Methods: We analyzed prospective, longitudinal data from the Women's Interagency HIV Study. HIV-infected and HIV-uninfected women were included between 2005 and 2014 when they reported health insurance at consecutive biannual visits and had controlled hypertension, and were followed for any insurance break and loss of hypertension control. We estimated hazard ratios (HRs) by Cox proportional hazards regression with inverse-probability-of-treatment-and censoring weights (marginal structural models), and plotted the cumulative incidence of hypertension control loss. Results: Among 890 HIV-infected women, the weighted HR for hypertension control loss comparing health insurance interruption to uninterrupted coverage was 1.37 (95% confidence interval [CI], 0.99-1.91). Inclusion of AIDS Drug Assistance Program (ADAP) participation with health insurance modestly increased the HR (1.47; 95% CI, 1.04-2.07). Analysis of 272 HIV-uninfected women yielded a similar HR (1.39; 95% CI, 0.88-2.21). Additionally, there were indications of uninterrupted coverage having a protective effect on hypertension when compared with the natural course in HIV-infected (HR, 0.82; 95% CI, 0.61-1.11) and HIV-uninfected (HR, 0.78; 95% CI, 0.52-1.19) women. Conclusions: This study provides evidence that health insurance continuity promotes hypertension control in key populations. Interventions that ensure coverage stability and ADAP access should be a policy priority

    Tribological performance of novel Nickel-based composite coatings with lubricant particles

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    Abstract The present study is focused on the evaluation of the tribological performance of novel Ni/hBN and Ni/WS2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubricated and non-lubricated scratch tests were performed on both novel composite coatings and on standard Ni deposits used as a benchmark coating to have an initial idea of the effect of the presence of particles within the Ni matrix. Under lubricated conditions, the performance of the Ni/hBN composite coating was very similar to the benchmark Ni coating, whereas the Ni/WS2 behaved quite differently, as the latter did not only show a lower coefficient of friction, but also prevented the occurrence of stick-slip motion that was clearly observed in the other coatings. Under non-lubricated conditions, whereas the tribological performance of the Ni/hBN composite coating was again very similar to that of the benchmark Ni coating, the Ni/WS2 composite coatings again showed a remarkable enhancement, as the incorporation of the WS2 particles into the Ni coating not only resulted in a lower coefficient of friction, but also in the prevention of coating failure

    Neighborhood Poverty and Control of HIV, Hypertension, and Diabetes in the Women’s Interagency HIV Study

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    Neighborhoods with high poverty rates have limited resources to support residents’ health. Using census data, we calculated the proportion of each Women’s Interagency HIV Study participant’s census tract (neighborhood) living below the poverty line. We assessed associations between neighborhood poverty and (1) unsuppressed viral load [VL] in HIV-seropositive women, (2) uncontrolled blood pressure among HIV-seropositive and HIV-seronegative hypertensive women, and (3) uncontrolled diabetes among HIV-seropositive and HIV-seronegative diabetic women using modified Poisson regression models. Neighborhood poverty was associated with unsuppressed VL in HIV-seropositive women (> 40% versus ≤ 20% poverty adjusted prevalence ratio (PR), 1.42; 95% confidence interval (CI) 1.04–1.92). In HIV-seronegative diabetic women, moderate neighborhood poverty was associated with uncontrolled diabetes (20–40% versus ≤ 20% poverty adjusted PR, 1.75; 95% CI 1.02–2.98). Neighborhood poverty was associated with neither uncontrolled diabetes among HIV-seropositive diabetic women, nor uncontrolled hypertension in hypertensive women, regardless of HIV status. Women living in areas with concentrated poverty may need additional resources to control health conditions effectively

    From Preparedness to Coordination: Operational Excellence in Post-disaster Supply Chain Management in Africa

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    Preparation and coordination have come to dominate discourse on operational excellence in post disaster supply chain management. In this paper we explore the critical success factors (CSF) of operations excellence in post-disaster operations management in Africa, using in-depth interviews with disaster management practitioners. Available studies have often focused on the commercial supply chains, but rarely on the critical success factors in service excellence in post disaster management operations in Africa. Using in-depth semi-structured interviews and desk-top data collection techniques from disaster management experts in Ghana a number of factors were identified. Employing thematic data analysis technique, these factors were categorised into eight (8) themes: management and administration, resources, political, governance structure, socio-cultural, education and training, infrastructure, and stakeholder involvement and co-operation
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