5,714 research outputs found
Human transfer characteristics in flight and ground simulation for a roll tracking task
Human transfer characteristics in flight and ground simulation for roll tracking tas
A pattern-recognition theory of search in expert problem solving
Understanding how look-ahead search and pattern recognition interact is one of the important research questions in the study of expert problem-solving. This paper examines the implications of the template theory (Gobet & Simon, 1996a), a recent theory of expert memory, on the theory of problem solving in chess. Templates are "chunks" (Chase & Simon, 1973) that have evolved into more complex data structures and that possess slots allowing values to be encoded rapidly. Templates may facilitate search in three ways: (a) by allowing information to be stored into LTM rapidly; (b) by allowing a search in the template space in addition to a search in the move space; and (c) by compensating loss in the "mind's eye" due to interference and decay. A computer model implementing the main ideas of the theory is presented, and simulations of its search behaviour are discussed. The template theory accounts for the slight skill difference in average depth of search found in chess players, as well as for other empirical data
Navigation for Spin Stabilized Deep Space Planetary Spacecraft
Navigation for planetary missions is well understood as shown by the successful flights to Venus and Mars by the JPL Mariner spacecraft. However, when we consider the farther planets, such as Jupiter and ultimately Pluto, the trip time requirements are so .long (on the order of 2 years to Jupiter and 8 to 1 0 years to Pluto) that spacecraft reliability becomes the paramount consideration.
A basic approach to achieving reliability is to simplify the spacecraft system as much as possible within the limits of mission objectives, which usually arise from the scientific payload. System simplicity and reliability can be greatly enhanced if the spacecraft system is spin stabilized, since this reduces control system requirements substantially and in general minimizes onbeard navigation tasks.
However, spin stabilization itself imposes a number of problems which must be solved before such a simplifying technique can be adapted. As an illustration, the present Pioneer VI spacecraft is spin stabilized and has no onboard control requirements after the first few days of the mission; hence its lifetime appears to be limited only by the lifetime of the electronic components. Pioneer VI, shown in Figure 1, is injected in a heliocentric orbit while spinning and is then torqued by a nitrogen system to place its spin axis perpendicular to the plane of the ecliptic. A phased array antenna mounted along the spin axis then provides a fan beam pattern lying in the plane of the ecliptic, thus always illuminating the earth and assuring the constant communication with the DSIF for ranges up to 2 AU. All perturbing factors, such as solar pressure, have been accounted for and this spacecraft will apparently retain its attitude indefinitely. (There is a small change in body attitude during the course of 1/2 of the orbit around the sun but this change is cancelled out in the next 1/2 of the orbit)
Advanced study of coastal zone oceanographic requirements for ERTS E and F
Earth Resources Technology Satellites E and F orbits and remote sensor instruments for coastal oceanographic data collectio
Bostonia. Volume 6
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Persistence of Manifolds in Nonequilibrium Critical Dynamics
We study the persistence P(t) of the magnetization of a d' dimensional
manifold (i.e., the probability that the manifold magnetization does not flip
up to time t, starting from a random initial condition) in a d-dimensional spin
system at its critical point. We show analytically that there are three
distinct late time decay forms for P(t) : exponential, stretched exponential
and power law, depending on a single parameter \zeta=(D-2+\eta)/z where D=d-d'
and \eta, z are standard critical exponents. In particular, our theory predicts
that the persistence of a line magnetization decays as a power law in the d=2
Ising model at its critical point. For the d=3 critical Ising model, the
persistence of the plane magnetization decays as a power law, while that of a
line magnetization decays as a stretched exponential. Numerical results are
consistent with these analytical predictions.Comment: 4 pages revtex, 1 eps figure include
Deep Eyes: Binocular Depth-from-Focus on Focal Stack Pairs
Human visual system relies on both binocular stereo cues and monocular
focusness cues to gain effective 3D perception. In computer vision, the two
problems are traditionally solved in separate tracks. In this paper, we present
a unified learning-based technique that simultaneously uses both types of cues
for depth inference. Specifically, we use a pair of focal stacks as input to
emulate human perception. We first construct a comprehensive focal stack
training dataset synthesized by depth-guided light field rendering. We then
construct three individual networks: a Focus-Net to extract depth from a single
focal stack, a EDoF-Net to obtain the extended depth of field (EDoF) image from
the focal stack, and a Stereo-Net to conduct stereo matching. We show how to
integrate them into a unified BDfF-Net to obtain high-quality depth maps.
Comprehensive experiments show that our approach outperforms the
state-of-the-art in both accuracy and speed and effectively emulates human
vision systems
Green consumer markets in the fight against climate change
Climate change has become one of the greatest threats to environmental security, as attested by the growing frequency of severe flooding and storms, extreme temperatures and droughts. Accordingly, the European Union’s (EU) 6th Environment Action Programme (2010) lists tackling climate change as its first priority. A key aim of the EU has been to cut CO2 emissions, a major factor in climate change, by 8% until 2012 and 20% until 2020. The European Commission has proposed the encouragement of private consumer market for green products and services as one of several solutions to this problem. However, existing research suggests that the market share of these products has been only 3%, although 30% of individuals favour environmental and ethical goods. This article uses Public Goods Theory to explain why the contribution of the green consumer market to fighting climate change has been and possibly may remain limited without further public intervention
Statistical Description of Acoustic Turbulence
We develop expressions for the nonlinear wave damping and frequency
correction of a field of random, spatially homogeneous, acoustic waves. The
implications for the nature of the equilibrium spectral energy distribution are
discussedComment: PRE, Submitted. REVTeX, 16 pages, 3 figures (not included) PS Source
of the paper with figures avalable at
http://lvov.weizmann.ac.il/onlinelist.htm
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