Study of effects of injector geometry on fuel-air mixing and combustion

An implicit finite-difference method has been developed for computing the flow in the near field of a fuel injector as part of a broader study of the effects of fuel injector geometry on fuel-air mixing and combustion. Detailed numerical results have been obtained for cases of laminar and turbulent flow without base injection, corresponding to the supersonic base flow problem. These numerical results indicated that the method is stable and convergent, and that significant savings in computer time can be achieved, compared with explicit methods

Dynamic interactions between hypersonic vehicle aerodynamics and propulsion system performance

Described here is the development of a flexible simulation model for scramjet hypersonic propulsion systems. The primary goal is determination of sensitivity of the thrust vector and other system parameters to angle of attack changes of the vehicle. Such information is crucial in design and analysis of control system performance for hypersonic vehicles. The code is also intended to be a key element in carrying out dynamic interaction studies involving the influence of vehicle vibrations on propulsion system/control system coupling and flight stability. Simple models are employed to represent the various processes comprising the propulsion system. A method of characteristics (MOC) approach is used to solve the forebody and external nozzle flow fields. This results in a very fast computational algorithm capable of carrying out the vast number of simulation computations needed in guidance, stability, and control studies. The three-dimensional fore- and aft body (nozzle) geometry is characterized by the centerline profiles as represented by a series of coordinate points and body cross-section curvature. The engine module geometry is represented by an adjustable vertical grid to accommodate variations of the field parameters throughout the inlet and combustor. The scramjet inlet is modeled as a two-dimensional supersonic flow containing adjustable sidewall wedges and multiple fuel injection struts. The inlet geometry including the sidewall wedge angles, the number of injection struts, their sweepback relative to the vehicle reference line, and strut cross-section are user selectable. Combustion is currently represented by a Rayleigh line calculation including corrections for variable gas properties; improved models are being developed for this important element of the propulsion flow field. The program generates (1) variation of thrust magnitude and direction with angle of attack, (2) pitching moment and line of action of the thrust vector, (3) pressure and temperature distributions throughout the system, and (4) performance parameters such as thrust coefficient, specific impulse, mass flow rates, and equivalence ratio. Preliminary results are in good agreement with available performance data for systems resembling the NASP vehicle configuration

Native title and Indigenous Australian utilisation of wildlife: Policy perspectives

The Native Title Act 1993 specifically recognises Indigenous property rights in Indigenous species; if there is one legislative event that could alter Indigenous utilisation of wildlife in the future it is provisions in this statute. This legal framework means that Indigenous people may in the future hold property or resource rights not just over currently vacant Crown land, but also in national parks or pastoral leasehold land. Some threshold legal issues, currently before the Federal Court, will clarify the significance of native title for Indigenous utilisation of wildlife. In this paper the use of wildlife by Indigenous Australians is assessed from an economic perspective using a standard production function framework in which output is determined by the variable combination of three input factors - land, labour and capital. The assessment shows that wildlife use for subsistence purposes is clearly of economic importance. Although inequalities exist in relation to the allocation of land between States, under the Native Title Act 1993 and the operations of the Indigenous Land Corporation it is possible there will be a significant increase in the amount of land owned or available for use by Indigenous people. This may not only increase access to wildlife resources and provide opportunities for Indigenous people to add to their incomes, but also add to the growing recognition of their ability and right to participate in environmental management. However, Indigenous people will need continuing access to cash to underwrite a subsistence lifestyle. Informed debate is needed to decide whether Indigenous use of wildlife is an economic option worth supporting and what benefits and costs might accrue from such facilitation both for Indigenous people and the wider Australian community

Development of a theory of the spectral reflectance of minerals, part 2

Theory of diffuse reflectance of particulate media including garnet, glass, corundum powders, and mixture

Charge dependence of neoclassical and turbulent transport of light impurities on MAST

Carbon and nitrogen impurity transport coefficients are determined from gas puff experiments carried out during repeat L-mode discharges on the Mega-Amp Spherical Tokamak (MAST) and compared against a previous analysis of helium impurity transport on MAST. The impurity density profiles are measured on the low-field side of the plasma, therefore this paper focuses on light impurities where the impact of poloidal asymmetries on impurity transport is predicted to be negligible. A weak screening of carbon and nitrogen is found in the plasma core, whereas the helium density profile is peaked over the entire plasma radius.Comment: 17 pages, 7 figure

Rhythm in the speech of a person with right hemisphere damage: Applying the pairwise variability index

Although several aspects of prosody have been studied in speakers with right hemisphere damage (RHD), rhythm remains largely uninvestigated. This study compares the rhythm of an Australian English speaker with right hemisphere damage (due to a stroke, but with no concomitant dysarthria) to that of a neurologically unimpaired individual. The speakers' rhythm is compared using the pairwise variability index (PVI) which allows for an acoustic characterization of rhythm by comparing the duration of successive vocalic and intervocalic intervals. A sample of speech from a structured interview between a speech and language therapist and each participant was analysed. Previous research has shown that speakers with RHD may have difficulties with intonation production, and therefore it was hypothesized that there may also be rhythmic disturbance. Results show that the neurologically normal control uses a similar rhythm to that reported for British English (there are no previous studies available for Australian English), whilst the speaker with RHD produces speech with a less strongly stress-timed rhythm. This finding was statistically significant for the intervocalic intervals measured (t(8) = 4.7, p < .01), and suggests that some aspects of prosody may be right lateralized for this speaker. The findings are discussed in relation to previous findings of dysprosody in RHD populations, and in relation to syllable-timed speech of people with other neurological conditions

The self-consistent gravitational self-force

I review the problem of motion for small bodies in General Relativity, with an emphasis on developing a self-consistent treatment of the gravitational self-force. An analysis of the various derivations extant in the literature leads me to formulate an asymptotic expansion in which the metric is expanded while a representative worldline is held fixed; I discuss the utility of this expansion for both exact point particles and asymptotically small bodies, contrasting it with a regular expansion in which both the metric and the worldline are expanded. Based on these preliminary analyses, I present a general method of deriving self-consistent equations of motion for arbitrarily structured (sufficiently compact) small bodies. My method utilizes two expansions: an inner expansion that keeps the size of the body fixed, and an outer expansion that lets the body shrink while holding its worldline fixed. By imposing the Lorenz gauge, I express the global solution to the Einstein equation in the outer expansion in terms of an integral over a worldtube of small radius surrounding the body. Appropriate boundary data on the tube are determined from a local-in-space expansion in a buffer region where both the inner and outer expansions are valid. This buffer-region expansion also results in an expression for the self-force in terms of irreducible pieces of the metric perturbation on the worldline. Based on the global solution, these pieces of the perturbation can be written in terms of a tail integral over the body's past history. This approach can be applied at any order to obtain a self-consistent approximation that is valid on long timescales, both near and far from the small body. I conclude by discussing possible extensions of my method and comparing it to alternative approaches.Comment: 44 pages, 4 figure

Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis basin

Definitive exposures of pristine, ancient crust on Mars are rare, and the finding that much of the ancient Noachian terrain on Mars exhibits evidence of phyllosilicate alteration adds further complexity. We have analyzed high-resolution data from the Mars Reconnaissance Orbiter in the well-exposed Noachian crust surrounding the Isidis basin. We focus on data from the Compact Reconnaissance Imaging Spectrometer for Mars as well as imaging data sets from High Resolution Imagine Science Experiment and Context Imager. These data show the lowermost unit of Noachian crust in this region is a complex, brecciated unit of diverse compositions. Breccia blocks consisting of unaltered mafic rocks together with rocks showing signatures of Fe/Mg-phyllosilicates are commonly observed. In regions of good exposure, layered or banded phyllosilicate-bearing breccia rocks are observed suggestive of pre-Isidis sedimentary deposits. In places, the phyllosilicate-bearing material appears as a matrix surrounding mafic blocks, and the mafic rocks show evidence of complex folded relationships possibly formed in the turbulent flow during emplacement of basin-scale ejecta. These materials likely include both pre-Isidis basement rocks as well as the brecciated products of the Isidis basin–forming event at 3.9 Ga. A banded olivine unit capped by a mafic unit covers a large topographic and geographic range from northwest of Nili Fossae to the southern edge of the Isidis basin. This olivine-mafic cap combination superimposes the phyllosilicate-bearing basement rocks and distinctly conforms to the underlying basement topography. This may be due to draping of the topography by a fluid or tectonic deformation of a previously flatter lying morphology. We interpret the draping, superposed olivine-mafic cap combination to be impact melt from the Isidis basin–forming event. While some distinct post-Isidis alteration is evident (carbonate, kaolinite, and serpentine), the persistence of olivine from the time of Isidis basin suggests that large-scale aqueous alteration processes had ceased by the time this unit was emplaced

Deciphering the mechanisms of phonological therapy in jargon aphasia

Background: Severe word production difficulties remain one of the most challenging clinical symptoms to treat in individuals with jargon aphasia. Clinically, it is important to determine why some individuals with jargon aphasia improve following therapy when others do not. We report a therapy study with AM, an individual with severe neologistic jargon aphasia, and provide a subsequent comparison to previous cases, with the purpose of informing both our theoretical and clinical understanding of jargon aphasia. Aims: This research aimed to investigate AM’s locus of word production deficit and determine the effectiveness of Phonological Component Analysis (PCA) therapy, a phonological cueing therapy, in the re-learning and generalization of naming responses for words. In addition, AM’s performance in therapy, linguistic profile, and ability to engage with therapy/cues were compared in a retrospective analysis with the background linguistic and therapy data of two other individuals with jargon aphasia (P9, Leonard et al., 2008; FF, Bose, 2013), who responded differentially to PCA. This was undertake to explore possible prognostic indicators of phonological therapy for jargon aphasia. Methods and Procedures: A battery of linguistic and neuropsychological tests was used to identify AM’s word production deficit. A single-subject multiple probe design across behaviours was employed to evaluate the effects of PCA therapy on the re-learning and generalization of naming responses. In the retrospective analysis of AM, P9 and FF, we compared differences and similarities in performance on various linguistic tasks, the ability to engage in therapy (i.e., ability to generate and utilize the cues), as well as to retain and maintain cues. Outcomes and Results: AM’s locus of deficit was identified in the mapping between semantics and phonology. PCA was found to be effective in improving naming in two of the three treated word lists during the treatment phase; however, these gains were not maintained. Generalization to untreated picture names was not observed. Findings from the retrospective analysis illustrated that oral reading skills, ability to segment phonological information from words and active engagement with provided cues are likely prerequisites for obtaining robust and long-term gains. Conclusions and Implications: We demonstrated that phonological therapy could be beneficial for the remediation of naming abilities at least in the re-learning phase; however, maintenance and generalization of these gains were limited. This research helps to elucidate the considerations and evaluations necessary for the appropriateness of phonological therapy and candidacy of individuals with jargon aphasia for this treatment approach