279 research outputs found
Modeling Disk Cracks in Rotors by Utilizing Speed Dependent Eccentricity
This paper discusses the feasibility of vibration-based structural health monitoring for detecting disk cracks in rotor systems. The approach of interest assumes that a crack located on a rotating disk causes a minute change in the system’s center of mass due to the centrifugal force induced opening of the crack. The center of mass shift is expected to reveal itself in the vibration vector (i.e., whirl response; plotted as amplitude and phase versus speed) gathered during a spin-up and/or spin-down test. Here, analysis is accomplished by modeling a Jeffcott rotor that is characterized by analytical, numerical, and experimental data. The model, which has speed dependent eccentricity, is employed in order to better understand the sensitivity of the approach. For the experimental set-up emulated here (i.e., a single disk located mid-span on a flexible shaft), it appears that a rather sizable flaw in the form of a through-thickness notch could be detected by monitoring the damage-induced shift in center of mass. Although, identifying actual disk cracks in complex “real world” environments, where noncritical crack lengths are small and excessive mechanical and/or electrical noise are present, would prove to be rather challenging. Further research is needed in this regard
Child developmental delay and socio-economic disadvantage in Australia: A longitudinal study
Socio-economic inequalities in adult and child health in Australia have been an issue of national concern. While a large body of data has discussed adult health, there have been relatively few Australian reports of socioeconomic inequalities in child health. This occurs in a context where there have been increases in the proportion of Australian children living in poverty and where there has been an increased interest in child developmental delay as an indicator of child health status. This paper reports the result of a longitudinal study of pregnancy outcomes and one indicator of child health, namely child developmental delay. Three indicators of socio-economic status (chronic socio-economic disadvantage, mother's education, family income) were used to predict child developmental delays observed some 5: years after the study commenced. Mothers who had the lowest socio-economic status (using any of the indicators) had substantially higher rates of children manifesting developmental delays
Reclamation status of a degraded pasture based on soil health indicators
Pasture degradation is a concern, especially in susceptible sandy soils for which strategies to recover them must be developed. Microbiological and biochemical soil health indicators are useful in the guindace of soil management practices and sustainable soil use. We assessed the success of threePanicum maximum Jacq. cultivars in the reclamation of a pasture in a sandy Typic Acrudox in the northwest of the state of Paraná, Brazil, based on soil health indicators. On a formerly degraded pasture withUrochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, a trial with threeP. maximum (cv. Massai, Tanzânia, or Mombaça) was conducted. Lime and phosphate were applied at set-up, and mineral N and K as topdressing. A remnant of degraded pasture adjacent to the trial was used as control. Twenty-three chemical, physical, microbiological and biochemical attributes were assessed for the 0-10 cm topsoil. The procedures for reclamation improved most of the indicators of soil health in relation to the degraded pasture, such as soil P, mineral N, microbial biomass C, ammonification rate, dehydrogenase activity and acid phosphatase. CO2 evolution decreased, whereas microbial biomass C increased in the pasture under reclamation, resulting in a lower metabolic quotient (qCO2) that points to a decrease in metabolic stress of the microbial community. The reclamation of the pasture withP. maximum, especially cv. Mombaça, were evidenced by improvements in the microbiological and biochemical soil health indicators, showing a recovery of processes related to C, N and P cycling in the soil
Percepção ambiental dos produtores e qualidade do solo em propriedades orgânicas e convencionais.
O sistema orgânico de produção deve resultar na utilização mais racional dos recursos naturais, sobretudo do solo. Os produtores orgânicos devem adotar práticas conservacionistas, alĂ©m de atender a outros princĂpios deste sistema de produção. Neste trabalho foram avaliadas as práticas de manejo e conservação do solo adotadas por produtores orgânicos e convencionais nas regiões dos municĂpios de Socorro (Serra da Mantiqueira e Mogiana) e IbiĂşna, situados no Estado de SĂŁo Paulo. O objetivo dessa pesquisa foi verificar o grau de adoção de práticas conservacionistas pelos produtores e avaliar a qualidade do solo na agricultura orgânica e convencional. Foi elaborado e aplicado um questionário, com visitas locais para verificação das práticas conservacionistas e ocorrĂŞncia de erosĂŁo, em 30 propriedades. Os resultados foram expressos em Ăndices indicadores de diversidade de uso do solo, atitude conservacionista, percepção de erosĂŁo e do impacto sobre os recursos hĂdricos. Foram tambĂ©m realizadas análises de atributos quĂmicos, fĂsicos e biolĂłgicos indicadores da qualidade do solo. Concluiu-se que os produtores orgânicos tĂŞm maior percepção quanto Ă atitude conservacionista e nas propriedades orgânicas há maior diversidade de cultivos, embora nĂŁo haja maior diversidade geral de uso do solo. A produção orgânica de alface, em IbiĂşna proporcionou maior atividade biolĂłgica no solo e maior colonização por fungos micorrĂzicos arbusculares. O sistema orgânico possui maiores teores de matĂ©ria orgânica e menores de potássio e nĂŁo houve diferença entre os atributos fĂsicos do solo dos sistemas orgânico e convencional
Solving an Avionics Real-Time Scheduling Problem by Advanced IP-Methods
We report on the solution of a real-time scheduling problem that arises in the design of software-based operation control of aircraft. A set of tasks has to be distributed on a minimum number of machines and offsets of the tasks have to be computed. The tasks emit jobs periodically starting at their offset and then need to be executed on the machines without any delay. Also, further constraints in terms of memory usage and redundancy requirements have to be met. Approaches based on standard integer programming formulations fail to solve our real-world instances. By exploiting structural insights of the problem we obtain an IP-formulation and primal heuristics that together solve the real-world instances to optimality and outperform text-book approaches by several orders of magnitude. Our methods lead, for the first time, to an industry strength tool to optimally schedule aircraft sized problems
Socioeconomic, Psychosocial, and Clinical Factors Associated with Employment in Women with HIV in the United States: A Correlational Study
Employment is a social determinant of health, and women living with HIV (WLWH) are often underemployed. This correlational study examined the socioeconomic, psychosocial, and clinical factors associated with employment among WLWH (n = 1,357) and women at risk for HIV (n = 560). Descriptive and inferential statistics were used to evaluate factors associated with employment status. Employment was associated (p ≤.05) with better socioeconomic status and quality of life (QOL), less tobacco and substance use, and better physical, psychological, and cognitive health. Among WLWH, employment was associated (p ≤.05) with improved adherence to HIV care visits and HIV RNA viral suppression. Using multivariable regression modeling, differences were found between WLWH and women at risk for HIV. Among WLWH, household income, QOL, education, and time providing childcare remained associated with employment in adjusted multivariable analyses (R2=.272, p <.001). A better understanding of the psychosocial and structural factors affecting employment is needed to reduce occupational disparities among WLWH
Codes of Fair Competition: The National Recovery Act, 1933-1935, and the Women’s Dress Manufacturing Industry
Controversial issues prevalent in today’s ready-to-wear apparel industry include the right of workers to join unions, the proliferation of sweatshops and sweatshop conditions, and design piracy. The idea of forming codes of conduct to establish criteria of ethical business practices is not new to the apparel industry. Indeed, the women’s dress manufacturing industry discussed and debated codes of fair competition under the New Deal Policies of the National Recovery Act (NRA) of 1933 to 1935. Primary sources for this study included governmental hearings in the establishment of the NRA Dress Code, The New York Times, Women’s Wear Daily, and the Journal of the Patent Office Society. The history of the NRA codes implemented in the U.S. women’s ready-to-wear apparel industry provides an important case study highlighting the difficulties and complexities of creating and achieving industry-wide standard practices through self-regulation. The failure of the NRA demonstrates that even with the joint cooperation of industry, labor, and consumer groups and the backing of the force of law, codes of fair competition proved impossible to enforce
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