Prediction of the aerodynamic performance of re-usable single stage to orbit vehicles

Re-usable single stage to orbit launch vehicles promise to reduce the cost of access to space, but their success will be particularly reliant on accurate modelling of their aero-thermodynamic characteristics. Non-equilibrium effects due to the rarefaction of the gas in the atmosphere are important at the very high altitudes at which lifting R-SSTO configurations will experience their greatest thermal load during re-entry. Current limitations in modelling the behaviour of the gas and hence in capturing these effects have a strong impact on the accuracy with which the thermal and aerodynamic loading on the surface of the vehicle can be predicted during this design-critical flight regime. The problem is most apparent in the presence of strong shock interactions, and this is likely to exacerbate the problem of aerodynamic characterisation of re-usable single stage to orbit vehicles, especially given design pressures towards increased geometric complexity compared to historical spacecraft designs, and hence the complexity of the shock structures that the vehicle will produce in high-speed flight. The development of this class of vehicles will thus very likely be paced by the development of the specialised modelling tools that will be required to account fully for the properties of the gas at the high speeds and altitudes that are characteristic of their re-entry into the atmosphere of the earth

The socialization of central office administrators responsible for curriculum and instruction

The purpose of this study was to investigate whether new central office administrators responsible for curriculum and instruction (ARCI) experience the encounter stage as described in stage model socialization theory. It sought to identify, categorize, and describe on-the-job experiences ARCIs encounter during the first year of service to a school district

Ascent trajectory optimisation for a single-stage-to-orbit vehicle with hybrid propulsion

This paper addresses the design of ascent trajectories for a hybrid-engine, high performance, unmanned, single-stage-to-orbit vehicle for payload deployment into low Earth orbit. A hybrid optimisation technique that couples a population-based, stochastic algorithm with a deterministic, gradient-based technique is used to maximize the nal vehicle mass in low Earth orbit after accounting for operational constraints on the dynamic pressure, Mach number and maximum axial and normal accelerations. The control search space is first explored by the population-based algorithm, which uses a single shooting method to evaluate the performance of candidate solutions. The resultant optimal control law and corresponding trajectory are then further refined by a direct collocation method based on finite elements in time. Two distinct operational phases, one using an air-breathing propulsion mode and the second using rocket propulsion, are considered. The presence of uncertainties in the atmospheric and vehicle aerodynamic models are considered in order to quantify their effect on the performance of the vehicle. Firstly, the deterministic optimal control law is re-integrated after introducing uncertainties into the models. The proximity of the final solutions to the target states are analysed statistically. A second analysis is then performed, aimed at determining the best performance of the vehicle when these uncertainties are included directly in the optimisation. The statistical analysis of the results obtained are summarized by an expectancy curve which represents the probable vehicle performance as a function of the uncertain system parameters. This analysis can be used during the preliminary phase of design to yield valuable insights into the robustness of the performance of the vehicle to uncertainties in the specification of its parameters

Poetry Forum: Approaching the Inaccessible Poem

Most of the daily language we use values efficiency and utility: I\u27d like a pastrami on rye with mustard. We rely on our words to be sturdy and clear. We, not surprisingly then, are inclined to praise the poem that displays a reasoned and coherent meaning, well-developed, connected and intact. These types of poems, also, were the reliable models used to initiate us into poetry in grammar school, the ones that, because familiar, make up our inner definition of what a poem is and does as it stops by woods on a snowy evening. And so, many of us coming upon the inaccessible poem, discard its associative leaps, its disruptions, the pressured silences of the poem\u27s white-spaces as so much chaos and mumbo-jumbo. Why is this poem published in this journal, we say, a prestigious journal, no less! I can make absolutely no sense from it. More like the symphony or the Rothko painting, these poems present us with tones, atmospherics, possibilities, but unlike a painting or symphony, we may begrudge them this haziness because we are so accustomed to expect language that\u27s stable, that focuses for us its sense, makes clear its meanings. We thought we\u27d offer—in this installment of the poetry forum—a few thoughts meant to defuse the angst of diving into the wreck of the difficult poem. A few thoughts meant to situate such poems and then a humble attempt at enjoying and mining one inaccessible poem

\u3ci\u3eCTENOSAURA SIMILIS\u3c/i\u3e (Black Spiny-tailed Iguana) PREDATION

The Exotic Amphibians and Reptiles of Florida. Krieger Publishing Co., Malabar, Florida. 155 pp.). In particular, they were released on Gasparilla Island (Charlotte and Lee Counties) 3&35 years ago, where they are now abundant (Krysko et al. 2003. Florida Sci. 66:141-146). This species may pose a threat to a number of endemic threatened and endangered species on Gasparilla Island such as eggs of nesting shore birds, beach mice, hatchling sea turtles and gopher tortoises (Gopherus polyphemus) (Krysko et al., op. cit.), but to date, local predators on C. similis are unreported (Meshaka et al., op. cit.). Indigenous predators might exert one controlling influence on exotic Florida herpetofauna (Butterfield et al. 1997. In Simberloff et al. [eds.], Strangers in Paradise, pp. 123-138. Island Press, Washington, DC). Hence, we report evidence of Bobcat (Felis rufus) predation on C. similis on Gasparilla Island

How Artificial Intelligence and Virtual Reality Benefit the Elderly and Individuals with Disabilities

The growing and evolving use  of emerging technology including Artificial Intelligence (AI)  and Virtual Reality (VR),  has significantly impacted the lives of two specific groups—the elderly and the disabled.  This paper investigates potential reasons for this phenomenon.  Clearly, AI and VR Technology alters the everyday lives of people with disabilities and how they navigate the world.  Technological developments increasingly work to address the isolation that people with disabilities as well as the elderly experience for  they are often unable or limited in how they  engage with their communities.  This research paper outlines the way technology has improved  social communication, information distribution, and day-to-day living for those with disabilities and the elderly.Undoubtedly,  the internet has transformed social communication and interaction for most people.   socially isolated individuals with disabilities have gained exposure to social environments through social media.  Moreover, the broad range of information available on the internet  has increased access to resources such as government services, health services, and social services support. On a related point, assistive devices have enabled disabled people including many seniors to overcome motor, sensory, or cognitive difficulties that may have previously hindered them from performing daily tasks.  However, although AI and VR technology has been effectively integrated in the lives of those with disabilities, many such individuals lack access to commonplace technologies, like a personal computer.  This paper examines how  AI and VR technology has enhanced communication, information access, and everyday activities for the disabled and aging communities despite such socio-economic limitations

\u3ci\u3eCtenosaura similis\u3c/i\u3e (Black Spiny-Tailed Iguana), ,i\u3eGopherus Polyphemus\u3c/i\u3e (Gopher Tortoise) Concurrent Burrow Use

Ctenosaura similis is exotic to Florida (Meshaka et al. 2004. The Exotic Amphibians and Reptiles of Florida, Krieger Publ. Co., Malabar, Florida. 155 pp.), whereas Gopherus polyphemus is listed as a species of special concern by the state of Florida (Florida Wildlife Code Chap. 39 F.A.C.), and as a threatened species by the Florida Committee on Rare and Endangered Plants and Animals (FCREPA) (Moler 1992. Rare and Endangered Biota of Florida: Volume III, Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 291 pp.)

Upper Precambrian (Eocambrian) Mineral Fork Tillite of Utah: A Continental Glacial and Glaciomarine Sequence: Discussion and Reply

Christie-Blick discussion abstract: The observations and interpretation of the Mineral Fork Tillite by Ojakangas and Matsch (1980) are most welcome. I concur with them and others that the formation is glaciogenic. However, I suggest that polish and striations on the underlying unconformity for the most part are not due to Proterozoic glacial activity, and I propose modifications to their over-all interpretation of the sequence in the Mineral Fork area. Ojakangas and Matsch reply abstract: We welcome Christie-Blick's comments, for they may serve to generate further interest in the excellent exposures of diamictite in the Big Cottonwood Canyon area of the Wasatch Range, exposures which may be among the best preserved late Proterozoic (Eocambrian) diamictites anywhere. Basically, he concurs with our major interpretation that the Mineral Fork Tillite is indeed of glacial origin, but his interpretation differs from ours in some important aspects

Modelling Adaptation and Mitigation Strategies for Southern Livestock Industries of Australia

Climate change will impact on the Australian grazing industries both through mitigation policies and the impact of warmer temperatures, increased atmospheric CO2 and changed rainfall patterns (Cullen et al. 2009; Eckard et al. 2010). Mechanistic models are useful tools to inform our understanding of the complex interactions between future climates and the soil, plant, animal and management in livestock production systems. This paper summarises the results of a number of whole farm systems modelling studies investigating likely impacts of climate change, adaptation options and emissions implications for livestock production in southern Australia