G. de Saussure

Autonomous mobile robot navigation and learning

Research focused on the development and experimental validation of intelligent control techniques for autonomous mobile robots able to plan and perform a variety of assigned tasks in unstructured environments is presented. In particular, an autonomous mobile robot, HERMIES-IIB intelligence experiment series, is described. It is a self-powered, wheel-driven platform containing an onboard 16-node Ncube hypercube parallel processor interfaced to effectors and sensors through a VME-based system containing a Motorola 68020 processor, a phased sonar array, dual manipulator arms, and multiple cameras. Research on navigation and learning is examined.<<ETX>>

Measurement of the uranium-238 capture cross section for incident neutron energies up to 100 keV

AbstractThe neutron capture cross section of 238U was measured for incident neutron energies between 5 eV and 100 keV using a pulsed electron Linac neutron source and the time-of-flight technique. Capture gamma rays were detected by a large liquid scintillator located on a 40-m flight path. The incident neutron flux was monitored by a 10BF3 ionization chamber. The cross section was normalized by the saturated resonance technique.The data have uncertainties which increase from ∼5% at 1 keV to 10% at 100 keV. These data are compared with results from other measurements and with various evaluations.

Measurement and Resonance Analysis of Neutron Transmission Through Uranium-238

Neutron transmissions through 0.076-, 0.254-, 1.080-, and 3.620-cm-thick samples of isotopically enriched /sup 238/U were measured from 0.88 to 100.0 keV by means of a time-of-flight technique over a path length of 150 m, the ORELA pulsed neutron source, and a 13-mm-thick lithium-glass detector. To obtain resonance parameters, these transmissions from 0.88 to 4.00 keV were simultaneously least-squares shape-fitted with a multilevel Breil--Wigner cross-section formalism. In general, large neutron widths were obtained, resulting in an s-wave strength function of (1.208 +- 0.045) x 10/sup -4/ over the interval from 0.0 to 4.0 keV. An absolute energy scale accurate to 2 parts in 10,000 was established. 11 figures, 16 tables.

Learning by an autonomous robot at a process control panel

The authors describe initial work in autonomous learning, using HERMIES-IIB, their current robotic experimental testbed. The integrated system in HERMIES-IIB (the hostile environment robotic machine intelligence experiment, series IIB) is the latest in a series of autonomous, intelligent machines designed to perform in environments that humans cannot readily enter. They describe a system that learns the control panels system dynamics and remembers the most efficient series of responses to shut down a control process in case of future encounters with similar (but not necessarily identical) situations. Ultimately, this system could infer a classification scheme for panel categories, enabling it to hypothesize about correct response sequences for panels not yet encountered. They discuss preliminary work on the systems inferencing section.<<ETX>>

An R matrix analysis of the sup 235 U neutron-induced cross sections up to 500 eV

In this paper a detailed evaluation of the R matrix resonance parameters describing the interaction of neutrons with {sup 235}U has been performed up to 500 eV using the most recent high-resolution measurements of the {sup 235}U neutron cross sections. The availability of {sup 235}U spin-separated neutron cross-section data, in conjunction with the use of the {Delta}{sub 3} statistics of Metha and Dyson, has made possible a detailed study of the statistical distribution of the resonance parameters and their average values. The present R matrix resonance parameters have been converted into equivalent sets of Adler- Adler parameters and multipole momentum space expansion parameters. Extensive validation of this evaluation has been performed by comparing self-shielded fission rates computed with these R matrix parameters with the measurements of Czirr; a test of the ENDF/B unresolved resonance formalism for the calculation of {sup 235}U of self-shielding factors is also presented.

Ratio of Capture to Fission in U235 at keV Neutron Energies

AbstractThe ratio of the neutron-capture cross section to the fission cross section (α) for U235 has been measured for incident neutron energies from 12 to 690 keV by a large gadolinium-loaded liquid-scintillator technique. Additional measurements at 30 and 64 keV were made by a method employing a liquid scintillator and a fission chamber. The experimental values of α can be approximately described by a linear decrease from 0.374 at 10 keV to 0.177 at 210 keV followed by a less rapid linear decrease to 0.095 at 700 keV. The results of these experiments are consistent and in reasonable agreement with other reported values of α in this energy range.

R matrix analysis of sup 239 Pu neutron cross sections in the energy range up to 1000 eV

This paper reports on the results of an R matrix analysis of the {sup 239}Pu neutron cross sections up to 1000-eV neutron energy. The analysis was performed with the multilevel multichannel Reich-Moore code SAMMY. The method of analysis is describe, and the selection of experimental data is discussed. Some tabular and graphical comparisons between calculated and measured cross sections and transmissions are presented. The statistical properties of the resonance parameters are examined. The resonance parameters are proposed for the new evaluated data files ENDF/B-VI and JEF2.

Autocorrelation technique for determining the average level spacing of the intermediate subthreshold structure in the fission cross section of 235U and 239Pu

Abstract The interpretation given to the correlogram of the 235U and 239Pu fission cross sections is questioned as to its validity to estimate the average level displacement in the Strutinsky well, appearing in the fission barrier for highly deformed nuclei.

Representation of the neutron cross sections of several fertile and fissile nuclei in the resonance regions

Abstract In this paper we review several problems related to the measurement, analysis and evaluation of the neutron cross sections of the main fertile and fissile nuclides in the resonance region. In particular we discuss the ENDF/B-V representation of these cross sections. In recent years little progress has been made in improving our knowledge of the resolved resonance parameters of the fertile nuclei. We suggest that this absence of progress is due to a lack of adequate methodologies to deal with the systematic errors arising from uncertainties in the analysis of the measurements. We comment on the ENDF/B treatment of the unresolved resonance region and recommend the validation of the unresolved resonance range evaluations with appropriate transmission and self-indication measurements.

Parallelism In Rule-Based Systems

Rule-based systems, which have proven to be extremely useful for several Artificial Intelligence and Expert Systems applications, currently face severe limitations due to the slow speed of their execution. To achieve the desired speed-up, this paper addresses the problem of parallelization of production systems and explores the various architectural and algorithmic possibilities. The inherent sources of parallelism in the production system structure are analyzed and the trade-offs, limitations and feasibility of exploitation of these sources of parallelism are presented. Based on this analysis, we propose a dedicated, coarse-grained, n-ary tree multiprocessor architecture for the parallel implementation of rule-based systems and then present algorithms for partitioning of rules in this architecture.