12,924 research outputs found

    Practopoiesis: Or how life fosters a mind

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    The mind is a biological phenomenon. Thus, biological principles of organization should also be the principles underlying mental operations. Practopoiesis states that the key for achieving intelligence through adaptation is an arrangement in which mechanisms laying a lower level of organization, by their operations and interaction with the environment, enable creation of mechanisms lying at a higher level of organization. When such an organizational advance of a system occurs, it is called a traverse. A case of traverse is when plasticity mechanisms (at a lower level of organization), by their operations, create a neural network anatomy (at a higher level of organization). Another case is the actual production of behavior by that network, whereby the mechanisms of neuronal activity operate to create motor actions. Practopoietic theory explains why the adaptability of a system increases with each increase in the number of traverses. With a larger number of traverses, a system can be relatively small and yet, produce a higher degree of adaptive/intelligent behavior than a system with a lower number of traverses. The present analyses indicate that the two well-known traverses-neural plasticity and neural activity-are not sufficient to explain human mental capabilities. At least one additional traverse is needed, which is named anapoiesis for its contribution in reconstructing knowledge e.g., from long-term memory into working memory. The conclusions bear implications for brain theory, the mind-body explanatory gap, and developments of artificial intelligence technologies.Comment: Revised version in response to reviewer comment

    Particle simulation of plasmas on the massively parallel processor

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    Particle simulations, in which collective phenomena in plasmas are studied by following the self consistent motions of many discrete particles, involve several highly repetitive sets of calculations that are readily adaptable to SIMD parallel processing. A fully electromagnetic, relativistic plasma simulation for the massively parallel processor is described. The particle motions are followed in 2 1/2 dimensions on a 128 x 128 grid, with periodic boundary conditions. The two dimensional simulation space is mapped directly onto the processor network; a Fast Fourier Transform is used to solve the field equations. Particle data are stored according to an Eulerian scheme, i.e., the information associated with each particle is moved from one local memory to another as the particle moves across the spatial grid. The method is applied to the study of the nonlinear development of the whistler instability in a magnetospheric plasma model, with an anisotropic electron temperature. The wave distribution function is included as a new diagnostic to allow simulation results to be compared with satellite observations

    Magnetic nanocomposites at microwave frequencies

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    Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

    Federated Simulation and Gaming Framework for a Decentralized Space-Based Resource Economy

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    Future human space exploration will require large amounts of resources for shielding and building materials, propellants, and consumables. A space-based resource economy could produce, transport, and store resource at distributed locations such as the lunar surface, stable orbits, or Lagrange points to avoid Earth's deep gravity well. Design challenges include decentralized operation and management and socio-technical complexities not commonly addressed by modeling and simulation methods. This paper seeks to tackle these challenges by applying aspects of military wargaming to promote effective communication between decision-makers. A software architecture for federated simulation based on IEEE-1516 (HLA-Evolved) is presented in the context of multiple lunar in-situ resource production processes, resource depots, and intermediate transportation. The federation-level framework identifies interfaces between simulation models (federates), focusing on persistent assets (elements) and resources exchanged. Future work will develop the federated resource economy model and evaluate with decision-makers playing the roles of competing and collaborating players.United States. Dept. of DefenseUnited States. Air Force Office of Scientific ResearchAmerican Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship (32 CFR 168a

    NASA SBIR abstracts of 1991 phase 1 projects

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    The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

    BICEP2 II: Experiment and Three-Year Data Set

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    We report on the design and performance of the BICEP2 instrument and on its three-year data set. BICEP2 was designed to measure the polarization of the cosmic microwave background (CMB) on angular scales of 1 to 5 degrees (ℓ\ell=40-200), near the expected peak of the B-mode polarization signature of primordial gravitational waves from cosmic inflation. Measuring B-modes requires dramatic improvements in sensitivity combined with exquisite control of systematics. The BICEP2 telescope observed from the South Pole with a 26~cm aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new detector design in which beam-defining slot antenna arrays couple to transition-edge sensor (TES) bolometers, all fabricated on a common substrate. The antenna-coupled TES detectors supported scalable fabrication and multiplexed readout that allowed BICEP2 to achieve a high detector count of 500 bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree angular scales. After optimization of detector and readout parameters, BICEP2 achieved an instrument noise-equivalent temperature of 15.8 μ\muK sqrt(s). The full data set reached Stokes Q and U map depths of 87.2 nK in square-degree pixels (5.2 μ\muK arcmin) over an effective area of 384 square degrees within a 1000 square degree field. These are the deepest CMB polarization maps at degree angular scales to date. The power spectrum analysis presented in a companion paper has resulted in a significant detection of B-mode polarization at degree scales.Comment: 30 pages, 24 figure
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