171,566 research outputs found

    Advanced Manned Launch System

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    Several alternatives exist for the development of the next manned launch system. The Advanced Manned Launch System (AMLS), which represents a clean-sheet replacement for the Space Shuttle, faces competition from concepts such as (1) the Personnel Launch System, which would serve as a personnel transport to complement the Space Shuttle, and (2) an advanced version of the existing Space Shuttle. An AMLS system could begin operations sometime between 2005 and 2020, depending upon the level of national interest and support. It would probably demonstrate a payload capacity less than that of the Space Shuttle, although performance specifications are far from certain. Even the form of the AMLS is still under discussion. Design studies have considered a wide variety of options including all levels of hardware reusability; single-, dual- and multiple-staging; and airbreathing vs. rocket propulsion. An evaluation of the relative cost-effectiveness of these options is impossible without guidance regarding basic mission requirements such as total number of launches over the system's life cycle and the date required. The availability of more advanced technologies will enable single-stage-to-orbit (SSTO) designs that are in general not feasible using current technology

    Avida: a software platform for research in computational evolutionary biology

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    Avida is a software platform for experiments with self-replicating and evolving computer programs. It provides detailed control over experimental settings and protocols, a large array of measurement tools, and sophisticated methods to analyze and post-process experimental data. We explain the general principles on which Avida is built, as well as its main components and their interactions. We also explain how experiments are set up, carried out, and analyzed

    Awarding Innovation: An Assessment of the Digital Media and Learning Competition

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    Increasing availability and accessibility of digital media have changed the ways in which young people learn, socialize, play, and engage in civic life. Seeking to understand how learning environments and institutions should transform to respond to these changes, the John D. and Catherine T. MacArthur Foundation (the Foundation) launched the Digital Media and Learning (DML) Initiative in 2005. This report highlights the successes and challenges of one component of the DML Initiative: the DML Competition (the Competition)

    ART Neural Networks: Distributed Coding and ARTMAP Applications

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    ART (Adaptive Resonance Theory) neural networks for fast, stable learning and prediction have been applied in a variety of areas. Applications include airplane design and manufacturing, automatic target recognition, financial forecasting, machine tool monitoring, digital circuit design, chemical analysis, and robot vision. Supervised ART architectures, called ARTMAP systems, feature internal control mechanisms that create stable recognition categories of optimal size by maximizing code compression while minimizing predictive error in an on-line setting. Special-purpose requirements of various application domains have led to a number of ARTMAP variants, including fuzzy ARTMAP, ART-EMAP, Gaussian ARTMAP, and distributed ARTMAP. ARTMAP has been used for a variety of applications, including computer-assisted medical diagnosis. Medical databases present many of the challenges found in general information management settings where speed, efficiency, ease of use, and accuracy are at a premium. A direct goal of improved computer-assisted medicine is to help deliver quality emergency care in situations that may be less than ideal. Working with these problems has stimulated a number of ART architecture developments, including ARTMAP-IC [1]. This paper describes a recent collaborative effort, using a new cardiac care database for system development, has brought together medical statisticians and clinicians at the New England Medical Center with researchers developing expert systems and neural networks, in order to create a hybrid method for medical diagnosis. The paper also considers new neural network architectures, including distributed ART {dART), a real-time model of parallel distributed pattern learning that permits fast as well as slow adaptation, without catastrophic forgetting. Local synaptic computations in the dART model quantitatively match the paradoxical phenomenon of Markram-Tsodyks [2] redistribution of synaptic efficacy, as a consequence of global system hypotheses.Office of Naval Research (N00014-95-1-0409, N00014-95-1-0657

    Organized for parliament? Explaining the electoral success of radical right parties in post-communist Europe

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    Over the last three decades a great deal of research has been carried out in an attempt to explain the electoral performance of radical right parties in Europe. Most approaches concentrate on demand-side determinants and have some limitations. We compensate for these shortcomings and focus on the context of party competition and supply-side determinants (consistency of ideological discourse, functioning party propaganda, the continuity of the leader in office and strong party organization) to explain the electoral success of radical right parties in post-communist Europe. We conducted our analysis at party level in nine radical right parties in four countries from Central and Eastern Europe (Bulgaria, the Czech Republic, Hungary and Romania) between 1990 and 2014. The bivariate and multivariate (ordinal logistic regression) analyses draw on unique data collected from primary and secondary sources

    The utility of a digital simulation language for ecological modeling

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    Dynamic modeling of ecological phenomena has been greatly facilitated by the recent development of continuous system simulator programs. This paper illustrates the application of one of these programs, S/360 Continuous System Modeling Program (S/360 CSMP), to four systems of graduated complexity. The first is a two species system, with one feeding on the other, using differential equations with constant coefficients. The second and third systems involve two competing plant species in which the coefficients of the differential equations are varying with time. The final example considers the management of a postulated buffalo herd in which the dynamics of the herd population and composition by sex and age is combined with various strategies to control its size and to optimize buffalo production
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