8,316 research outputs found

    Proceedings of the MEVTV Workshop on The Evolution of Magma Bodies on Mars

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    The workshop focused on many of the diverse approaches related to the evolution of magma bodies on Mars that have been pursued during the course of the Mars Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Approximately 35 scientists from the Mars volcanology, petrology, geochemistry, and modeling communities attended. Segments of the meeting concentrated of laboratory analyses and investigations of SNC meteorites, the interpretation of Viking Orbiter and Lander datasets, and the interpretation of computer codes that model volcanic and tectonic processes on Mars. Abstracts of these reports are presented

    Comparative analyses of space-to-space central power stations

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    The technological and economical impact of a large central power station in Earth orbit on the performance and cost of future spacecraft and their orbital transfer systems are examined. It is shown that beaming power to remote users cannot be cost effective if the central power station uses the same power generation system that is readily available for provision of onboard power and microwave transmission and reception of power through space for use in space is not cost competitive with onboard power or propulsion systems. Laser and receivers are required to make central power stations feasible. Remote power transmission for propulsion of orbital transfer vehicles promises major cost benefits. Direct nuclear pumped or solar pumped laser power station concepts are attractive with laser thermal and laser electric propulsion systems. These power stations are also competitive, on a mass and cost basis, with a photovoltaic power station

    The origin of the strings in the outer regions of Eta Carinae

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    The narrow optical filaments (`strings' or `spikes') emerging from the Homunculus of Eta Carinae are modelled as resulting from the passage of ballistic `bullets' of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. An archive HST image and new forbidden line profiles of the most distinct of the strings are presented and discussed in terms of this simple model.Comment: 5 pages, 4 figure

    The orbital recovery problem. Part II - Application of analysis technique to selection of recovery sites for return from low circular orbits

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    Lateral range requirements used in selecting spacecraft landing recovery sites for return from low circular orbit

    Spatial Econometric Issues for Bio-Economic and Land-Use Modeling

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    We survey the literature on spatial bio-economic and land-use modelling and review thematic developments. Unobserved site-specific heterogeneity is common in almost all of the surveyed works. Heterogeneity appears also to be a significant catalyst engendering significant methodological innovation. To better equip prototypes to adequately incorporate heterogeneity, we consider a smorgasbord of extensions. We highlight some problems arising with their application; provide Bayesian solutions to some; and conjecture solutions for others.spatial econometrics, bio-economic and land-use modelling, Bayesian solution, Land Economics/Use,

    The Affect of Diversity and Ethical Principles in Primary and Secondary Educational Leadership: A Hermeneutical Phenomenology Study

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    The purpose of this hermeneutical phenomenological study was to understand the experiences of diversity and ethical principles in educational leadership for teachers, administrators, and classified licensed professionals within minority school districts. Downton’s (2016) theory on transformational leadership guided this study\u27s theoretical framework for the research and ensuing findings. This research was created to answer the following central question: What are the perceived effects of diversity and ethical principles on teachers, administrators, and classified licensed professionals within minority school districts? Three sub-questions were used to understand the experiences of diversity and ethical principles in educational leadership within minority school districts. The qualitative methodology was used to capture and comprehend participants\u27 lived experiences in underserved school districts. An underserved school district in a southeast county served as the site from which participants were selected. The study included 11 participants from underserved school districts. Data was collected from interviews, focus groups, and protocol writings. Data analysis transpired through transcribing and coding of salient keywords, with the codes becoming themes. Three themes were identified from data analysis: (a) The need for transformational leadership, (b) the impact of diversity, and (c) the lack of workforce development. Results indicated that transformational leadership contributed to minority student success. All participants agreed that the lack of diversity and the lack of workforce development and training significantly affected their ability to meet the need for minority educational success in underserved school districts

    Ohmic contacts, irradiation effects, and thin film growth of GaAs and Al sub 1-x Ga sub x As

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    The effects of interfacial chemistry on the electrical properties of metal contacts to gallium arsenides and aluminum gallium arsenides are determined

    Charge separation instability in an unmagnetized disk plasma around a Kerr black hole

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    In almost all of plasma theories for astrophysical objects, we have assumed the charge quasi-neutrality of unmagnetized plasmas in global scales. This assumption has been justified because if there is a charged plasma, it induces electric field which attracts the opposite charge, and this opposite charge reduces the charge separation. Here, we report a newly discovered instability which causes a charge separation in a rotating plasma inside of an innermost stable circular orbit (ISCO) around a black hole. The growth rate of the instability is smaller than that of the disk instability even in the unstable disk region and is forbidden in the stable disk region outside of the ISCO. However, this growth rate becomes comparable to that of the disk instability when the plasma density is much lower than a critical density inside of the ISCO. In such case, the charge separation instability would become apparent and cause the charged accretion into the black hole, thus charge the hole up.Comment: 15pages, 1 figur

    The Lore of Low Methane Livestock:Co-Producing Technology and Animals for Reduced Climate Change Impact

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    Methane emissions from sheep and cattle production have gained increasing profile in the context of climate change. Policy and scientific research communities have suggested a number of technological approaches to mitigate these emissions. This paper uses the concept of co-production as an analytical framework to understand farmers’ evaluation of a 'good animal’. It examines how technology and sheep and beef cattle are co-produced in the context of concerns about the climate change impact of methane. Drawing on 42 semi-structured interviews, this paper demonstrates that methane emissions are viewed as a natural and integral part of sheep and beef cattle by farmers, rather than as a pollutant. Sheep and beef cattle farmers in the UK are found to be an extremely heterogeneous group that need to be understood in their specific social, environmental and consumer contexts. Some are more amenable to appropriating methane reducing measures than others, but largely because animals are already co-constructed from the natural and the technical for reasons of increased production efficiency
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