7,702 research outputs found
Flexibly Instructable Agents
This paper presents an approach to learning from situated, interactive
tutorial instruction within an ongoing agent. Tutorial instruction is a
flexible (and thus powerful) paradigm for teaching tasks because it allows an
instructor to communicate whatever types of knowledge an agent might need in
whatever situations might arise. To support this flexibility, however, the
agent must be able to learn multiple kinds of knowledge from a broad range of
instructional interactions. Our approach, called situated explanation, achieves
such learning through a combination of analytic and inductive techniques. It
combines a form of explanation-based learning that is situated for each
instruction with a full suite of contextually guided responses to incomplete
explanations. The approach is implemented in an agent called Instructo-Soar
that learns hierarchies of new tasks and other domain knowledge from
interactive natural language instructions. Instructo-Soar meets three key
requirements of flexible instructability that distinguish it from previous
systems: (1) it can take known or unknown commands at any instruction point;
(2) it can handle instructions that apply to either its current situation or to
a hypothetical situation specified in language (as in, for instance,
conditional instructions); and (3) it can learn, from instructions, each class
of knowledge it uses to perform tasks.Comment: See http://www.jair.org/ for any accompanying file
Long-Run Structural and Productivity Change in U.S. Agriculture: Effects of Prices and Policies
Long-Run Structural and Productivity Change in U.S. Agriculture: Effects of Prices and Policies by Wallace E. Huffman and Robert E. Evenson The paper presents (1) a conceptual framework for structural change when farms may be multiproduct or specialized and (2) an econometrics examination of causes of structural and total factor productivity (TFP) change for U.S. agriculture. Farm size, farm specialization, and part-time farming are the structural dimension emphasized, and they become potential channels to TFP change. Using state aggregate data starting in 1950, we conclude that input prices, public and private research, public extension, and government commodity programs have directly and indirectly caused change in U.S. farm structure and TFP. Our results suggest that changes in farm size, however, have been dominated by input price changes rather than by technology or government programs.farm structure, productivity, farm size, farm specialization, part-time farming, research, technical change, agriculture
Effect of canard position and wing leading-edge flap deflection on wing buffet at transonic speeds
A generalized wind-tunnel model, with canard and wing planform typical of highly maneuverable aircraft, was tested. The addition of a canard above the wing chord plane, for the configuration with leading-edge flaps undeflected, produced substantially higher total configuration lift coefficients before buffet onset than the configuration with the canard off and leading-edge flaps undeflected. The wing buffet intensity was substantially lower for the canard-wing configuration than the wing-alone configuration. The low-canard configuration generally displayed the poorest buffet characteristics. Deflecting the wing leading-edge flaps substantially improved the wing buffet characteristics for canard-off configurations. The addition of the high canard did not appear to substantially improve the wing buffet characteristics of the wing with leading-edge flaps deflected
Dynamic concept categorization : a systematic approach to improving classroom performance.
A study technique requiring participants to form unique combination of categories was implemented to explore its impact on test scores. Findings suggest that study aids in general seem to be more beneficial for college senior level courses than freshmen. The paradigm incorporated flash cards as a study aid prior to a psychology exam. The shallow condition allowed participants to use flash cards in an unstructured form while the elaborative condition was instructed to organize the flash cards into a small number of meaningful categories. Test performance declined for the freshman level classes regardless of condition. It was found that the dynamic concept categorization task (elaborative) was ineffective when compared to a self-driven control group (shallow). The trend of the data found from this experiment suggests that attending a review session and participating in a study aid task is more beneficial than not participating in one at all.--Abstract
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PERSIANN-MSA: A precipitation estimation method from satellite-based multispectral analysis
Visible and infrared data obtained from instruments onboard geostationary satellites have been extensively used for monitoring clouds and their evolution. The Advanced Baseline Imager (ABI) that will be launched onboard the Geostationary Operational Environmental Satellite-R (GOES-R) series in the near future will offer a larger range of spectral bands; hence, it will provide observations of cloud and rain systems at even finer spatial, temporal, and spectral resolutions than are possible with the current GOES. In this paper, a new method called Precipitation Estimation from Remotely Sensed information using Artificial Neural Networks-Multispectral Analysis (PERSIANN-MSA) is proposed to evaluate the effect of using multispectral imagery on precipitation estimation. The proposed approach uses a self-organizing feature map (SOFM) to classify multidimensional input information, extracted from each grid box and corresponding textural features of multispectral bands. In addition, principal component analysis (PCA) is used to reduce the dimensionality to a few independent input features while preserving most of the variations of all input information. The above method is applied to estimate rainfall using multiple channels of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) satellite. In comparison to the use of a single thermal infrared channel, the analysis shows that using multispectral data has the potential to improve rain detection and estimation skills with an average of more than 50% gain in equitable threat score for rain/no-rain detection, and more than 20% gain in correlation coefficient associated with rain-rate estimation. © 2009 American Meteorological Society
Block synchronization for quantum information
Locating the boundaries of consecutive blocks of quantum information is a
fundamental building block for advanced quantum computation and quantum
communication systems. We develop a coding theoretic method for properly
locating boundaries of quantum information without relying on external
synchronization when block synchronization is lost. The method also protects
qubits from decoherence in a manner similar to conventional quantum
error-correcting codes, seamlessly achieving synchronization recovery and error
correction. A family of quantum codes that are simultaneously synchronizable
and error-correcting is given through this approach.Comment: 7 pages, no figures, final accepted version for publication in
Physical Review
In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells
We present a method to simultaneously constrain both far-field horizontal stress magnitudes (S hmin and S Hmax) and in situ rock unconfined compressive strength (UCS), using geophysical logging data from two boreholes located 70Â m apart that access the uppermost accretionary prism of the Nankai subduction zone . The boreholes sample the same sediments and are affected by the same tectonic stress field, but were drilled with different annular pressures, thus providing a unique opportunity to refine estimates of both in situ stress magnitudes and rock strength. We develop a forward model to predict the angular width of compressional wellbore failures (borehole breakouts), and identify combinations of S Hmax and UCS that best match breakout widths observed in resistivity images from the two boreholes. The method requires knowledge of S hmin, which is defined by leak-off tests conducted during drilling. Our results define a normal to strike-slip stress regime from 900 to 1386Â m below seafloor, consistent with observations from seismic and core data. Our analysis also suggests that in situ values of UCS are generally slightly lower that commonly assumed on the basis of published empirical relations between UCS and P-wave velocity
Long-Run Structural and Productivity Change in U.S. Agriculture: Effects of Prices and Policies
Ordered Measurements of Permutationally-Symmetric Qubit Strings
We show that any sequence of measurements on a permutationally-symmetric
(pure or mixed) multi-qubit string leaves the unmeasured qubit substring also
permutationally-symmetric. In addition, we show that the measurement
probabilities for an arbitrary sequence of single-qubit measurements are
independent of how many unmeasured qubits have been lost prior to the
measurement. Our results are valuable for quantum information processing of
indistinguishable particles by post-selection, e.g. in cases where the results
of an experiment are discarded conditioned upon the occurrence of a given event
such as particle loss. Furthermore, our results are important for the design of
adaptive-measurement strategies, e.g. a series of measurements where for each
measurement instance, the measurement basis is chosen depending on prior
measurement results.Comment: 13 page
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