421 research outputs found
Automation - Development of the Material-Technological Basis - Changed Conditions of Efficiency
This paper was presented at a joint seminar on flexible automation held in Berlin (East) from June 8-11, 1982. The seminar was a collaborative project between IIASA and the Academy of Sciences of the German Democratic Republic.
The report and the working material presented to the conference deal, among other things, with the influence of the flexible automation on the further development of the material-technological basis and on the whole system of the productive forces. Hence the following questions arise: Does the qualitatively new level of automation mean in connection with the development and application of micro-electronics and what is flexible automation? What are the constituent elements of the new level of automation and which are the consequences for the development of the material-technological basis? and Which changes within the conditions of efficiency take place due to the new level of automation on the basis of micro-electronics? The presented paper offers some aspects regarding these questions
Volume estimates for equiangular hyperbolic Coxeter polyhedra
An equiangular hyperbolic Coxeter polyhedron is a hyperbolic polyhedron where
all dihedral angles are equal to \pi/n for some fixed integer n at least 2. It
is a consequence of Andreev's theorem that either n=3 and the polyhedron has
all ideal vertices or that n=2. Volume estimates are given for all equiangular
hyperbolic Coxeter polyhedra.Comment: 27 pages, 11 figures; corrected typo in Theorem 2.
Six topics on inscribable polytopes
Inscribability of polytopes is a classic subject but also a lively research
area nowadays. We illustrate this with a selection of well-known results and
recent developments on six particular topics related to inscribable polytopes.
Along the way we collect a list of (new and old) open questions.Comment: 11 page
Two-sided combinatorial volume bounds for non-obtuse hyperbolic polyhedra
We give a method for computing upper and lower bounds for the volume of a
non-obtuse hyperbolic polyhedron in terms of the combinatorics of the
1-skeleton. We introduce an algorithm that detects the geometric decomposition
of good 3-orbifolds with planar singular locus and underlying manifold the
3-sphere. The volume bounds follow from techniques related to the proof of
Thurston's Orbifold Theorem, Schl\"afli's formula, and previous results of the
author giving volume bounds for right-angled hyperbolic polyhedra.Comment: 36 pages, 19 figure
Theory of commensurable magnetic structures in holmium
The tendency for the period of the helically ordered moments in holmium to
lock into values which are commensurable with the lattice is studied
theoretically as a function of temperature and magnetic field. The
commensurable effects are derived in the mean-field approximation from
numerical calculations of the free energy of various commensurable structures,
and the results are compared with the extensive experimental evidence collected
during the last ten years on the magnetic structures in holmium. In general the
stability of the different commensurable structures is found to be in accord
with the experiments, except for the tau=5/18 structure observed a few degrees
below T_N in a b-axis field. The trigonal coupling recently detected in holmium
is found to be the interaction required to explain the increased stability of
the tau=1/5 structure around 42 K, and of the tau=1/4 structure around 96 K,
when a field is applied along the c-axis.Comment: REVTEX, 31 pages, 7 postscript figure
Irreducible triangulations of surfaces with boundary
A triangulation of a surface is irreducible if no edge can be contracted to
produce a triangulation of the same surface. In this paper, we investigate
irreducible triangulations of surfaces with boundary. We prove that the number
of vertices of an irreducible triangulation of a (possibly non-orientable)
surface of genus g>=0 with b>=0 boundaries is O(g+b). So far, the result was
known only for surfaces without boundary (b=0). While our technique yields a
worse constant in the O(.) notation, the present proof is elementary, and
simpler than the previous ones in the case of surfaces without boundary
Small grid embeddings of 3-polytopes
We introduce an algorithm that embeds a given 3-connected planar graph as a
convex 3-polytope with integer coordinates. The size of the coordinates is
bounded by . If the graph contains a triangle we can
bound the integer coordinates by . If the graph contains a
quadrilateral we can bound the integer coordinates by . The
crucial part of the algorithm is to find a convex plane embedding whose edges
can be weighted such that the sum of the weighted edges, seen as vectors,
cancel at every point. It is well known that this can be guaranteed for the
interior vertices by applying a technique of Tutte. We show how to extend
Tutte's ideas to construct a plane embedding where the weighted vector sums
cancel also on the vertices of the boundary face
Contracting on litigation
Two risk‐averse litigants with different subjective beliefs negotiate in the shadow of a pending trial. Through contingent contracts, the litigants can mitigate risk and/or speculate on the trial outcome. Contingent contracting decreases the settlement rate and increases the volume and costs of litigation. These contingent contracts mimic the services provided by third‐party investors, including litigation funders and insurance companies. The litigants (weakly) prefer to contract with risk‐neutral third parties when the capital market is transaction‐cost free. However, contracting with third parties further decreases the settlement rate, increases the costs of litigation, and may increase the aggregate cost of risk bearing.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/1/rand12274.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/2/rand12274_am.pd
Persistent Spin Currents in Helimagnets
We demonstrate that weak external magnetic fields generate dissipationless
spin currents in the ground state of systems with spiral magnetic order. Our
conclusions are based on phenomenological considerations and on microscopic
mean-field theory calculations for an illustrative toy model. We speculate on
possible applications of this effect in spintronic devices.Comment: 9 pages, 6 figures, updated version as published, Journal referenc
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