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

The Australian Movement against Uranium Mining: Its Rationale and Evolution

This paper begins with a brief historical overview of the Australian movement against uranium mining, before focussing on two major campaigns: Roxby and Jabiluka. It describes the reasons the activists gave at the time for their blockades of the Roxby Downs uranium mine in South Australia in 1983 and 1984. These reasons – such as perceptions that the industry is unsafe - have changed little over time and were the basis for the campaign against the proposed Jabiluka mine in the Northern Territory in 1998. They continue to be cited by environmental groups and Aboriginal Traditional Owners to this day as new situations arise, such as the 2011 Fukushima Daiichi nuclear accident.The paper then describes how the movement evolved between the Roxby and Jabiluka blockades, with changes to the movement’s philosophy, strategy, tactics and internal dynamics. This analysis includes a comparison between two anti-nuclear bike rides, one a year after the 1984 Roxby blockade and involving some of the same activists, and another at the time of the Jabiluka blockade. This author was present at all these events, and provides an emic (insider) perspective within a longitudinal participant-observation methodology. Although this perspective obviously has a subjective element, the paper fills a gap in that there is little written history of these blockades (particularly Roxby) and more generally of Australian resistance to uranium mining, let alone the aspects of nonviolence and movement evolution. It is an introductory history of these campaigns, examining the direct action components, the practicalities of nonviolent campaigning, and the evolution of Australian anti-uranium activism

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

The Formation of Metal Nanoparticle-Carbon Nanotube Composite Materials for the Non-enzymatic Detection of Glucose

Nano composite materials consisting of gold nanoparticles (AuNPs) and functionalised multiwalled carbon nanotubes (fMWCNTs) were initially prepared using simple synthetic reduction methods, involving the chemical agents sodium borohydride and trisodium citrate. These composites were named fMWCNT-Aunano(NaBH4) and fMWCNT-Aunano(TriSodCit). AuNPs of a face-centred cubic structure were successfully formed on the sidewalls of the fMWCNTs. The fMWCNT-Aunano(NaBH4) composite had an Au loading of 2.0% wt. and contained AuNPs with a mode diameter of 7.5 nm. The fMWCNT-Aunano(TriSodCit) composite had an Au loading of 5.0% wt. and contained AuNPs with a mode diameter of 23 nm. These composites were used to form films on glassy carbon and screen printed electrodes for the non-enzymatic electrochemical detection of glucose in PBS buffer at physiological pH. Electrochemical pre-treatments in sodium hydroxide and sulfuric acid provided films with improved sensitivity. These films were combined with a Nafion® membrane to improve selectivity towards glucose in the presence of commonly occurring interferants. The fMWCNT-Aunano(NaBH4) composite was also combined with palladium nanoparticles (PdNPs) to form a composite named fMWCNT-Aunano/Pdnano. This bi-metallic composite was formed using a potentiostatic electrodeposition of Pd onto the surface of pre-existing fMWCNT-Aunano(NaBH4) films. These PdNPs had a mode diameter of 95 nm and the Pd loading was close to 3.0%. This composite film was used for the electrochemical detection of glucose, whereby it facilitated its oxidation at more negative potentials in comparison to the fMWCNT-Aunano composites. Interference studies were carried out using chemical species commonly present in the blood; ascorbic acid, uric acid, fructose, galactose, serum albumins, chloride and acetaminophen. The severity of interference varied at each electrode and it was shown that Nafion® reduced the level of interference. Sensor reusability and shelf-life studies were also carried out using the composite modified films. These films provided accurate glucose detection over twelve successive uses, although they were not deemed to be suitable for storage. The materials were characterised using TEM, SEM, EDX, AAS, XRD, EIS, UV-Vis and Raman spectroscopy. An electrochemical characterisation also showed that a significant electroactive area of Au was present in the fMWCNT-Aunano(NaBH4) and fMWCNT-Aunano(TriSodCit) composite when cast onto an electrode surface. Overall these composite materials show good initial promise for use as non-enzymatic glucose sensors based on these preliminary studies

A metallurgical approach toward alloying in rare-earth permanent magnet systems

A metallurgical approach was developed toward alloying in rare earth permanent magnet systems to allow for microstructural enhancement and control during solidification and subsequent processing. Compound additions of Group IVA, VA, or VIA transition metals (TM) along with carbon were added to the Nd[subscript]2Fe[subscript]14B system (2-14-1). Transition metal carbides will form in the quintary Nd-Fe-B-TM-C system if the phase stability of the precipitates in the specific multicomponent system is higher than the phase stability of all other phases involving the additive elements and the constituent elements. Transition metal carbide formation was found in the Group IVA (TiC, ZrC, and HfC) and Group VA systems (VC, NbC and TaC). Transition metal carbide precipitates can form at high temperatures in the liquid, during cooling after solidification, or during an appropriate heat treatment. Carbide formation did not occur in the Group VIA system;The alloying ability of each transition metal carbide system was graded using criteria which dealt with phase stability, liquid and equilibrium solid solubility, and high temperature carbide stability. Titanium with carbon additions satisfied all of the proposed alloying criteria and were chosen as the best system for further study. Titanium and carbon have a significant liquid solubility and an equilibrium solid solubility which was extremely low and below detectable limits. No equilibrium solid solubility means that the titanium and carbon additions will ultimately form TiC after an appropriate heat treatment which allows the development of a composite microstructure consisting of the 2-14-1 phase and TiC. Thus, the excellent intrinsic magnetic properties of the 2-14-1 phase remain unaltered and the extrinsic properties relating to the microstructure are enhanced due to the TiC stabilized microstructure which was found to be much more resistant to grain growth;When titanium with carbon are dissolved in the liquid melt or solid phases, such as the glass or the 2-14-1 phase, the intrinsic properties of the phases are changed. Favorable intrinsic changes include; large increases in glass forming ability, a significant reduction in the optimum cooling rate, an increase in the optimum energy product, and an enhancement in the nucleation kinetics of crystallization

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