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Collisions of Si(14.5A GeV+Au are investigated in the relativistic-quantum-molecular-dynamics approach. The calculated pseudorapidity distributions for central collisions compare well with recent experimental data, indicating a large degree of nuclear stopping and thermalization. Nevertheless, nonequilibrium effects play an important role in such complex multihadron reactions: They lead to a strong enhancement of the total kaon production cross sections, in good agreement with the experimental data, without requiring the formation of a deconfined quark-gluon plasma.
The quantum molecular dynamic method is used to study multifragmentation and fragment flow and their dependence on in-medium cross sections, momentum dependent interactions, and the nuclear equation of state, for collisions of 197Au+197Au and 93Nb+93Nb in the bombarding energy regime from 100 to 800A MeV. Time and impact parameter dependence of the fragment formation and their implications for the conjectured liquid-vapor phase transition are investigated. We find that the inclusive fragment mass distribution is independent of the equation of state and exhibits a power-law behavior Y(A)∼A-τ with an exponent τ≊-2.3. True multifragmentation events are found in central collisions for energies Elab∼30–200 MeV/nucleon. The associated light fragment (d,t,α) to proton ratios increase with the multiplicity of charged particles and decrease with energy, in agreement with recent experiments. The calculated absolute charged particle multiplicities, the multiplicities of intermediate mass (A>4) fragments, and their respective rapidity distributions do compare well with recent 4π data, but are quite insensitive to the equation of state. On the other hand, these quantities depend sensitively on the nucleon-nucleon scattering cross section, and can be used to determine σ experimentally. The transverse momentum flow of the complex fragments increases with the stiffness of the equation of state. Reduced (in-medium) n-n scattering cross sections reduce the fragment flow. Momentum dependent interactions increase the fragment flow. It is shown that the measured fragment flow at 200A MeV can be reproduced in the model. We find that also the increase of the px/A values with the fragment mass is in agreement with experiments. The calculated fragment flow is too small as compared to the plastic ball data, if a soft equation of state with in-medium corrections (momentum dependent interactions plus reduced cross sections) is employed. An alternative, most intriguing resolution of the puzzle about the stiffness of the equation of state could be an increase of the scattering cross sections due to precritical scattering in the vicinity of a phase transition.
Performance and storage requirements of topology-conserving maps for robot manipulator control
(1989)
A new programming paradigm for the control of a robot manipulator by learning the mapping between the Cartesian space and the joint space (inverse Kinematic) is discussed. It is based on a Neural Network model of optimal mapping between two high-dimensional spaces by Kohonen. This paper describes the approach and presents the optimal mapping, based on the principle of maximal information gain. It is shown that Kohonens mapping in the 2-dimensional case is optimal in this sense. Furthermore, the principal control error made by the learned mapping is evaluated for the example of the commonly used PUMA robot, the trade-off between storage resources and positional error is discussed and an optimal position encoding resolution is proposed.
The semantics of gradation
(1989)
The term 'gradation' is meant to cover a range of phenomena which for the time being I shall call quantitative evaluations regarding dimensions or features. I shall actually be looking into the principles governing the way gradation is expressed in language. The quantitative aspect of the adjectives of dimension occupies a key position which can be systematically explained and this aspect will be the crucial point of the discussion. I shall focus on the various grammatical forms of comparison: comparative, equative, superlative and some related constructions, and indications of measurement and adverbial indications of degree.
This list of microscopic features for hardwood identification is the successor to the "Standard List of Characters Suitable For Computerized Hardwood Identification" published in 1981 (IAWA Bulletin n.s. 2: 99-145) with an explanation of the coding procedure by R.B. Miller. The 1981 publication greatly stimulated international exchange of information and experience on characters suitable for hardwood identification, and inspired considerable debate on the most desirable coding procedures and identification programs. Therefore, at the IA W A meeting during the XIV International Botanical Congress in Berlin, July 1987, it was decided to revise the 1981 standard list. Because of the continuing developments in computer technology and programming, it was agreed to limit the scope of the new list to definitions, explanatory commentary, and illustrations of wood anatomical descriptors, rather than concentrate on coding procedures. A new Committee was appointed by the IA W A Council to work towards the new list, and thanks to a substantial grant from the USDA Competitive Research Grants - Wood Utilization Program (Grant No. 88-33541-4081), a workshop was held by the Committee from October 2-7, 1988, in the Department of Wood & Paper Science, North Carolina State University, Raleigh, NC, USA, under the joint auspices of IA WA and IUFRO Division S. A preliminary list was prepared during the workshop. IA W A members were invited to comment on this list, and these comments helped with the final preparation of the new list. The list presented here was agreed to after review of subsequent drafts and extensive internal consultation between committee members. Although this list has 163 anatomical and 58 miscellaneous features, it is not a complete list encompassing all the structural patterns that one can encounter in hardwoods. Instead it is intended to be a concise list of features useful for identification purposes. Also, the numbers assigned to each feature in the present list are not meant to be codes for a computer program, but are intended to serve for easy reference, and to help translate data from one program/database to another. Wood and wood cells are biological elements, formed in trees, shrubs, and climbers to fulfill a physiological or mechanical function. Although there is more discrete diversity in wood structure than in many other plant parts, there is also much continuous variation, and any attempt to classify this diversity into well-defined features has an artificial element. Yet we are confident that in the feature list presented here ambiguity of descriptors has been limited to a minimum, and we hope that all present and future colleagues engaged in wood identification and descriptive wood anatomy will find this list a valuable guide and reference.