Dynamic Characteristics and Stability Analysis of Space Shuttle Main Engine Oxygen Pump

The dynamic characteristics of the Space Shuttle high pressure oxygen pump are presented. Experimental data is presented to show the vibration spectrum and response under actual engine operation and also in spin pit testing for balancing. The oxygen pump appears to be operating near a second critical speed and is sensitive to self excited aerodynamic cross coupling forces in the turbine and pump. An analysis is presented to show the improvement in pump stability by the application of turbulent flow seals, preburner seals, and pump shaft cross sectional modifications

Aerodynamic stiffness of an unbound eccentric whirling centrifugal impeller with an infinite number of blades

An unbounded eccentric centrifugal impeller with an infinite number of log spiral blades undergoing synchronous whirling in an incompressible fluid is considered. The forces acting on it due to coriolis forces, centripetal forces, changes in linear momentum, changes in pressure due to rotating and changes in pressure due to changes in linear momentum are evaluated

Hydraulic forces on a centrifugal impeller undergoing synchronous whirl

High speed centrifugal rotating machinery with large vibrations caused by aerodynamic forces on impellers was examined. A method to calculate forces in a two dimensional orbiting impeller in an unbounded fluid with nonuniform entering flow was developed. A finite element model of the full impeller is employed to solve the inviscid flow equations. Five forces acting on the impeller are: Coriolis forces, centripetal forces, changes in linear momentum, changes in pressure due to rotation and pressure changes due to linear momentum. Both principal and cross coupled stiffness coefficients are calculated for the impeller

Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making

A method of making a permanent magnet wherein 1) a melt is formed having a base alloy composition comprising RE, Fe and/or Co, and B (where RE is one or more rare earth elements) and 2) TR (where TR is a transition metal selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Al) and at least one of C and N are provided in the base alloy composition melt in substantially stoichiometric amounts to form a thermodynamically stable compound (e.g. TR carbide, nitride or carbonitride). The melt is rapidly solidified in a manner to form particulates having a substantially amorphous (metallic glass) structure and a dispersion of primary TRC, TRN and/or TRC/N precipitates. The amorphous particulates are heated above the crystallization temperature of the base alloy composition to nucleate and grow a hard magnetic phase to an optimum grain size and to form secondary TRC, TRN and/or TRC/N precipitates dispersed at grain boundaries. The crystallized particulates are consolidated at an elevated temperature to form a shape. During elevated temperature consolidation, the primary and secondary precipitates act to pin the grain boundaries and minimize deleterious grain growth that is harmful to magnetic properties

Carbide/nitride grain refined rare earth-iron-boron permanent magnet and method of making

A method of making a permanent magnet wherein 1) a melt is formed having a base alloy composition comprising RE, Fe and/or Co, and B (where RE is one or more rare earth elements) and 2) TR (where TR is a transition metal selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Al) and at least one of C and N are provided in the base alloy composition melt in substantially stoichiometric amounts to form a thermodynamically stable compound (e.g. TR carbide, nitride or carbonitride). The melt is rapidly solidified in a manner to form particulates having a substantially amorphous (metallic glass) structure and a dispersion of primary TRC, TRN and/or TRC/N precipitates. The amorphous particulates are heated above the crystallization temperature of the base alloy composition to nucleate and grow a hard magnetic phase to an optimum grain size and to form secondary TRC, TRN and/or TRC/N precipitates dispersed at grain boundaries. The crystallized particulates are consolidated at an elevated temperature to form a shape. During elevated temperature consolidation, the primary and secondary precipitates act to pin the grain boundaries and minimize deleterious grain growth that is harmful to magnetic properties

Are there prehistoric shell middens on Rottwest Island?

In August 1973 a number of different types of shell bed were observed at Rottnest Island. The most massive of these were seen around the lakes at the eastern end of the island and there is no doubt that these are natural marine shell beds. However elsewhere shelly deposits were seen whose origin we could not determine with certainty. A number of midden like lenses of shell were exposed in road sections, particularly along the north side of the island. All of these deposits displayed some of the characteristics of Aboriginal shell middens

Thresholds for surfactant use in preterm neonates: a network meta-analysis

Objective: To perform a network meta-analysis of randomised controlled trials of different surfactant treatment strategies for respiratory distress syndrome (RDS) to assess if a certain fraction of inspired oxygen (FiO2) is optimal for selective surfactant therapy. Design: Systematic review and network meta-analysis using Bayesian analysis of randomised trials of prophylactic versus selective surfactant for RDS. Setting: Cochrane Central Register of Controlled Trials, MEDLINE, Embase and Science Citation Index Expanded. Patients: Randomised trials including infants under 32 weeks of gestational age. Interventions: Intratracheal surfactant, irrespective of type or dose. Main outcome measures: Our primary outcome was neonatal mortality, compared between groups treated with selective surfactant therapy at different thresholds of FiO2. Secondary outcomes included respiratory morbidity and major complications of prematurity. Results: Of 4643 identified references, 14 studies involving 5298 participants were included. We found no statistically significant differences between 30%, 40% and 50% FiO2 thresholds. A sensitivity analysis of infants treated in the era of high antenatal steroid use and nasal continuous positive airway pressure as initial mode of respiratory support showed no difference in mortality, RDS or intraventricular haemorrhage alone but suggested an increase in the combined outcome of major morbidities in the 60% threshold. Conclusion: Our results do not show a clear benefit of surfactant treatment at any threshold of FiO2. The 60% threshold was suggestive of increased morbidity. There was no advantage seen with prophylactic treatment. Randomised trials of different thresholds for surfactant delivery are urgently needed to guide clinicians and provide robust evidence. PROSPERO registration number: CRD42020166620

Production method for making rare earth compounds

A method of making a rare earth compound, such as a earth-transition metal permanent magnet compound, without the need for producing rare earth metal as a process step, comprises carbothermically reacting a rare earth oxide to form a rare earth carbide and heating the rare earth carbide, a compound-forming reactant (e.g. a transition metal and optional boron), and a carbide-forming element (e.g. a refractory metal) that forms a carbide that is more thermodynamically favorable than the rare earth carbide whereby the rare earth compound (e.g. Nd.sub.2 Fe.sub.14 B or LaNi.sub.5) and a carbide of the carbide-forming element are formed

Effects of peatland management on aquatic carbon concentrations and fluxes

Direct land-to-atmosphere carbon exchange has been the primary focus in previous studies of peatland disturbance and subsequent restoration. However, loss of carbon via the fluvial pathway is a significant term in peatland carbon budgets and requires consideration to assess the overall impact of restoration measures. This study aimed to determine the effect of peatland land management regime on aquatic carbon concentrations and fluxes in an area within the UK's largest tract of blanket bog, the Flow Country of northern Scotland. Three sub-catchments were selected to represent peatland land management types: non-drained, drained, and restoration (achieved through drain blocking and tree removal). Water samples were collected on a fortnightly basis from September 2008 to August 2010 at six sampling sites, one located upstream and one downstream within each sub-catchment. Concentrations of dissolved organic carbon (DOC) were significantly lower for the upstream non-drained sub-catchment compared to the drained sub-catchments, and there was considerable variation in the speciation of aquatic carbon (DOC, particulate organic carbon (POC), CO2, and CH4) across the monitoring sites, with dissolved gas concentrations inversely correlated with catchment area and thereby contributing considerably more to total aquatic carbon in the smaller headwater catchments. Significantly higher POC concentrations were observed in the restored sub-catchment most affected by tree removal. Aquatic carbon fluxes were highest from the drained catchments and lowest from the non-drained catchments at 23.5 and 7.9 g C m−2 yr−1, respectively, with variability between the upstream and downstream sites within each catchment being very low. It is clear from both the aquatic carbon concentration and flux data that drainage has had a profound impact on the hydrological and biogeochemical functioning of the peatland. In the restoration catchment, carbon export varied considerably, from 21.1 g C m−2 yr−1 at the upper site to 10.0 g C m−2 yr−1 at the lower site, largely due to differences in runoff generation. As a result of this hydrological variability, it is difficult to make definitive conclusions about the impact of restoration on carbon fluxes, and further monitoring is needed to corroborate the longer-term effects

Application of microseismic technology to hydraulic fracture diagnostics: GRI/DOE Field Fracturing Multi-Sites Project

The objective of the Field Fracturing Multi-Sites Project (M-Site) is to conduct field experiments and analyze data that will result in definitive determinations of hydraulic fracture dimensions using remote well and treatment well diagnostic techniques. In addition, experiments will be conducted to provide data that will resolve significant unknowns with regard to hydraulic fracture modeling, fracture fluid rheology and fracture treatment design. These experiments will be supported by a well-characterized subsurface environment as well as surface facilities and equipment conducive to acquiring high-quality data. It is anticipated that the project`s research advancements will provide a foundation for a fracture diagnostic service industry and hydraulic fracture optimization based on measured fracture response. The M-Site Project is jointly sponsored by the Gas Research Institute (GRI) and the US Department of Energy (DOE). The site developed for M-Site hydraulic fracture experimentation is the former DOE Multiwell Experiment (MWX) site located near Rifle, Colorado. The MWX project drilled three closely-spaced wells (MWX-1, MWX-2 and MWX-3) which were the basis for extensive reservoir analyses and tight gas sand characterizations in the blanket and lenticular sandstone bodies of the Mesaverde Group. The research results and background knowledge gained from the MWX project are directly applicable to research in the current M-Site Project