Experimental Classical Flutter Reesults of a Composite Advanced Turboprop Model

Experimental results are presented that show the effects of blade pitch angle and number of blades on classical flutter of a composite advanced turboprop (propfan) model. An increase in the number of blades on the rotor or the blade pitch angle is destablizing which shows an aerodynamic coupling or cascade effect between blades. The flutter came in suddenly and all blades vibrated at the same frequency but at different amplitudes and with a common predominant phase angle between consecutive blades. This further indicates aerodynamic coupling between blades. The flutter frequency was between the first two blade normal modes, signifying an aerodynamic coupling between the normal modes. Flutter was observed at all blade pitch angles from small to large angles-of-attack of the blades. A strong blade response occurred, for four blades at the two-per-revolution (2P) frequency, when the rotor speed was near the crossing of the flutter mode frequency and the 2P order line. This is because the damping is low near the flutter condition and the interblade phase angle of the flutter mode and the 2P response are the same

Improved design of a high response slotted plate overboard bypass valve for supersonic inlets

The electrohydraulically actuated slotted-plate bypass valve used to control the position of the normal shock during wind-tunnel investigations of supersonic inlets also has proven to be a valuable device for determining inlet dynamics and creating airflow disturbances. Operation of previous valves at high frequencies (to 100 Hz) for extended testing has resulted in numerous failures. An improved bypass-valve design is presented which increases the cyclic tolerance of the device considerably over past designs. The use of dynamic limit criteria to obtain an optimum actuator-piston size results in a frequency response which is flat within + or - 3 decibels to 120 Hz for a peak-to-peak variation of 20 percent of full area

Optical measurement of propeller blade deflections in a spin facility

A nonintrusive optical system for measuring propeller blade deflections has been used in the NASA Lewis dynamic spin facility. Deflection of points at the leading and trailing edges of a blade section can be obtained with a narrow light beam from a low power helium-neon laser. A system used to measure these deflections at three spanwise locations is described. Modifications required to operate the lasers in a near-vacuum environment are also discussed

Bending-torsion flutter of a highly swept advanced turboprop

Experimental and analytical results are presented for a bending-torsion flutter phenomena encountered during wind-tunnel testing of a ten-bladed, advanced, high-speed propeller (turboprop) model with thin airfoil sections, high blade sweep, low aspect ratio, high solidity and transonic tip speeds. Flutter occurred at free-stream Mach numbers of 0.6 and greater and when the relative tip Mach number (based on vector sum of axial and tangential velocities) reached a value of about one. The experiment also included two- and five-blade configurations. The data indicate that aerodynamic cascade effects have a strong destabilizing influence on the flutter boundary. The data was correlated with analytical results which include aerodynamic cascade effects and good agreement was found

Analytical flutter investigation of a composite propfan model

A theoretical model and an associated computer program for predicting subsonic bending-torsion flutter in propfans are presented. The model is based on two-dimensional unsteady cascade strip theory and three-dimensional steady and unsteady lifting surface aerodynamic theory in conjunction with a finite element structural model for the blade. The analytical results compare well with published experimental data. Additional parametric studies are also presented illustrating the effects on flutter speed of steady aeroelastic deformations, blade setting angle, rotational speed, number of blades, structural damping, and number of modes

Fluid Inclusions Usage for Assessing Oil Migration in Duhok, North of Iraq

Studies of primary and secondary fluid inclusions were done on epigenetic barite samples which collected from carbonates in Lower part of Sarmord Formation (Lower Cretaceous and Aqra-Bekhme Formations (Upper Cretaceous) in Duhok localities of North of Iraq. Lead isotopes composition in galena which associated barite that contained fluid inclusions helped the identification two events of fluid inclusions. These fluid inclusions contain brine water and hydrocarbons. Primary and secondary fluid inclusions in barite as well as lead isotopes composition in galena helped the interpretation of oil migration history and the pathway of oil migration. Ages of galena are syngronous with the events of oil and water trapping as inclusions within barite, and hence the interpreted galena generation could be assigned to the fluid inclusions age. Accordingly, the events are two phases of early and late generations that correspond to 120 m.y. and 30 m.y. respectively. Correlation with 10 PetroMod basin modeling of the generated oil from the Jurassic and Lower Cretaceous Formations fitted with the event of early galena generation, whereas the oil migration started before 70 m.y and continued to 30 m.y ago. Palynomorphs study confirms that the oil in source rocks is similar with the migrated oil

Data mining for prediction of length of stay of cardiovascular accident inpatients

The healthcare sector generates large amounts of data on a daily basis. This data holds valuable knowledge that, beyond supporting a wide range of medical and healthcare functions such as clinical decision support, can be used for improving profits and cutting down on wasted overhead. The evaluation and analysis of stored clinical data may lead to the discovery of trends and patterns that can significantly enhance overall understanding of disease progression and clinical management. Data mining techniques aim precisely at the extraction of useful knowledge from raw data. This work describes an implementation of a data mining project approach to predict the hospitalization period of cardiovascular accident patients. This provides an effective tool for the hospital cost containment and management efficiency. The data used for this project contains information about patients hospitalized in Cardiovascular Accident’s unit in 2016 for having suffered a stroke. The Weka software was used as the machine learning toolkit.Fundação para a Ciência e a Tecnologia (UID/CEC/00319/2013

Does transition from an unstable labour market position to permanent employment protect mental health? Results from a 14-year follow-up of school-leavers

<p>Abstract</p> <p>Background</p> <p>Having secure employment, in contrast to being unemployed, is regarded as an important determinant of health. Research and theories about the negative health consequences of unemployment indicated that transition from unemployment to a paid job could lead to improved health. The objective of this study was to test the hypothesis that obtaining permanent employment after being in an unstable labour market position protects mental health.</p> <p>Methods</p> <p>A 14-year follow-up of all graduates from compulsory school in an industrial town in northern Sweden was performed at ages 16, 18, 21 and 30 years. Complete data on the cohort were collected for 1044 individuals with the aid of a comprehensive questionnaire. The response rate was 96.4%. The health measurement used in this study was the psychological symptoms analysed by multivariate logistic regression. Those who obtained permanent employment were the focus of the analysis. This group consisted of people who were in an unstable labour market position for a year or more between the ages of 25 and 29, and who had acquired a permanent job one year before and at the time of the investigation.</p> <p>Results</p> <p>After controlling for gender as well as for an indicator of health-related selection, possible confounders and mediators, an association was found between the lower probability of psychological symptoms and obtaining permanent employment (OR = 0.35, 95% CI 0.19–0.63) as well as having permanent employment (OR = 0.22, 95% CI 0.10–0.51).</p> <p>Conclusion</p> <p>Our findings suggest that transition from an unstable labour market position to permanent employment could be health-promoting, even after controlling for possible confounders and mediators, as well as for an indicator of health-related selection. However, as there are few studies in the field, there is a need for more longitudinal studies in order to further analyse the relationship and to examine possible explanations. The policy implication of our study is that the transformation of unstable labour market positions into permanent employment could contribute to better public health.</p