IUS solid rocket motor contamination prediction methods

A series of computer codes were developed to predict solid rocket motor produced contamination to spacecraft sensitive surfaces. Subscale and flight test data have confirmed some of the analytical results. Application of the analysis tools to a typical spacecraft has provided early identification of potential spacecraft contamination problems and provided insight into their solution; e.g., flight plan modifications, plume or outgassing shields and/or contamination covers

Soil Properties and their Influence on Grassland Production under Low Input and Organic Farming Conditions

End of project reportThis project set out to identify soil properties that most influence grassland production under low mineral nitrogen input conditions. Sixteen farms were selected in Counties Limerick and Clare and the soil sampled. Soil physical and chemical characteristics and soil biological aspects involved in the carbon and nitrogen cycles were studied in the laboratory. Nutrient additions to farms as well as the nature of grazing by livestock (numbers, types of grazing animals, grazing practices), grassland management, and production from the farms were recorded

Experimental study of bubble cavities attached to a rotating shaft in a reservoir

Bubble cavities formed by air entrainment and attached to a rotating shaft in an oil reservoir were studied. The cavities appear to the unaided eye as toroidal. High speed photography, however, reveals the individuality of the bubble cavities and their near solid body rotational characteristics. The cavities are distorted by the rotation effects but remain attached and tend to merge because of edge effects in the axial direction. The flow field within the reservoir is influenced by the unusual character of the two phase fluid found there; the vorticity is readily visualized. Other examples of vapor entrapment at the inlet of an eccentric rotor are also discussed. A simplified analytical method is provided, and a numerical analysis is being investigated. Vapor (void) entrainment and generation can significantly alter leakage rates and stability of seals, bearings, and dampers. Recognition of these effects in the component design systems will result only after detailed studies of the above phenomena

Nested subcritical flows within supercritical systems

In supercritical systems the design inlet and outlet pressures are maintained above the thermaodynamic critical pressure P sub C. Designers rely on this simple rule of thumb to circumvent problems associated with a subcritical pressure regime nested within the supercritical pressure system along with the uncertainties in heat transfer, fluid mechanics, and thermophysical property variations. The simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines and linear systems, where nested two-phase regions can exist. Examples for a free-jet expansion with backpressure greater than P sub C and a rotor (bearing) with ambient pressure greater than P sub C illustrate the existence of subcritical pressure regimes nested within supercritical systems

Facing Up to Unpalatable Evidence for the Sake of Our Patients

Paul Mullen discusses Seena Fazel and colleagues' paper on the association between violent behavior and having been diagnosed with a schizophrenic disorder, and its implications for care of these individuals

Racial Disparities in Intravenous Recombinant Tissue Plasminogen Activator Use Persist at Primary Stroke Centers.

BACKGROUND: Primary stroke centers (PSCs) utilize more recombinant tissue plasminogen activator (rt-PA) than non-PSCs. The impact of PSCs on racial disparities in rt-PA use is unknown. METHODS AND RESULTS: We used data from the Nationwide Inpatient Sample from 2004 to 2010, limited to states that publicly reported hospital identity and race. Hospitals certified as PSCs by The Joint Commission were identified. Adults with a diagnosis of ischemic stroke were analyzed. Rt-PA use was defined by the International Classification of Diseases, 9th Revision procedure code 99.10. Discharges (304 152 patients) from 26 states met eligibility criteria, and of these 71.5% were white, 15.0% black, 7.9% Hispanic, and 5.6% other. Overall, 24.7% of white, 27.4% of black, 16.2% of Hispanic, and 29.8% of other patients presented to PSCs. A higher proportion received rt-PA at PSCs than non-PSCs in all race/ethnic groups (white 7.6% versus 2.6%, black 4.8% versus 2.0%, Hispanic 7.1% versus 2.4%, other 7.2% versus 2.5%, all P CONCLUSIONS: Racial disparities in intravenous rt-PA use were not reduced by presentation to PSCs. Black patients were less likely to receive thrombolytic treatment than white patients at both non-PSCs and PSCs. Hispanic patients were less likely to be seen at PSCs relative to white patients and were less likely to receive intravenous rt-PA in the fully adjusted model

Numerical modeling of multidimensional flow in seals and bearings used in rotating machinery

The rotordynamic behavior of turbomachinery is critically dependent on fluid dynamic rotor forces developed by various types of seals and bearings. The occurrence of self-excited vibrations often depends on the rotor speed and load. Misalignment and rotor wobbling motion associated with differential clearance were often attributed to stability problems. In general, the rotative character of the flowfield is a complex three dimensional system with secondary flow patterns that significantly alter the average fluid circumferential velocity. A multidimensional, nonorthogonal, body-fitted-grid fluid flow model is presented that describes the fluid dynamic forces and the secondary flow pattern development in seals and bearings. Several numerical experiments were carried out to demonstrate the characteristics of this complex flowfield. Analyses were performed by solving a conservation form of the three dimensional Navier-Stokes equations transformed to those for a rotating observer and using the general-purpose computer code PHOENICS with the assumptions that the rotor orbit is circular and that static eccentricity is zero. These assumptions have enabled a precise steady-state analysis to be used. Fluid injection from ports near the seal or bearing center increased fluid-film direct dynamic stiffness and, in some cases, significantly increased quadrature dynamic stiffness. Injection angle and velocity could be used for active rotordynamic control; for example, injection, when compared with no injection, increased direct dynamic stiffness, which is an important factor for hydrostatic bearings

First Principles Analysis of Electron-Phonon Interaction in Graphene

The electron-phonon interaction in monolayer graphene is investigated by using density functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic phonon contribution that is much weaker than previously thought, revealing the role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the high values reported in suspended samples.Comment: 12 pages, 4 figure