Search

No abstract.

No abstract.

A simple multiplexing technique is shown to lead to a starvation-free process-dispatching strategy without making any assumptions about the behaviour of a process. A strong implementation of semaphores is presented using associative hardware.

No abstract.

Several concepts in discrete mathematics such as block designs, Latin squares, Hadamard matrices, tactical configurations, errorcorrecting codes, geometric configurations, finite groups, and graphs are by no means independent. Combinations of these notions may serve the development of any one of them, and sometimes reveal hidden interrelations. In the present paper a central role in this respect is played by the notion of strongly regular graph, the definition of which is recalled below.In § 2, a fibre-type construction for graphs is given which, applied to block designs withλ= 1 and Hadamard matrices, yields strongly regular graphs. The method, although still limited in its applications, may serve further developments. In § 3 we deal with block designs, first considered by Shrikhande[22],in which the number of points in the intersection of any pair of blocks attains only two values.

No abstract.

No abstract.

C-matrices appear in the literature at various places; for a survey, see [11]. Important for the construction of Hadamard matrices are the symmetric C-matrices, of order v ≡ 2 (mod 4), and the skew C-matrices, of order v ≡ 0 (mod 4). In § 2 of the present paper it is shown that there are essentially no other C-matrices. A more general class of matrices with zero diagonal is investigated, which contains the C-matrices and the matrices of (v, k, λ)-systems on k and k + 1 in the sense of Bridges and Ryser [6]. Skew C-matrices are interpreted in § 3 as the adjacency matrices of a special class of tournaments, which we call strong tournaments. They generalize the tournaments introduced by Szekeres [24] and by Reid and Brown [21].

No abstract.

No abstract.

Synopsis The thermodynamic theory for viscosity and plasticity phenomena, given by the author in some previous papers, is further developed. A rather general Theological equation is derived from which the rheological equations for Poynting-Thomson, Jeffreys, Maxwell, Kelvin, Hooke, Newton, Prandtl-Reuss, and Bingham media may be considered as degeneracies. The physical meaning of these degeneracies is discussed. In particular it is seen that a Bingham medium may be considered as a special case of a Jeffreys medium. Explicit expressions are given for the free energy, the internal energy, and the entropy of the substances just mentioned. Temperature phenomena are taken into account. Some higher order effects (Poynting effect, structural viscosity, and thixotropy) are discussed from the point of view of the developed theory. A generalization of the Von Mises yield criterion is proposed. With the help of this criterion the Bauschinger effect may be explained as a consequence of memory phenomena. For media without memory this new criterion and the Von Mises criterion coalesce. It will be seen that for plastic media with memory a rheological equation holds, which may be considered as a generalization of the Poynting-Thomson equation. Both distortional and volumetric phenomena are considered. It is assumed that the deformations and rotations are small.

No abstract.

This paper is concerned with the diffraction of an electromagnetic wave by a unidirectionally conducting circular disk. First, the behavior of a time-harmonic electromagnetic field near the edge of an arbitrary plane unidirectionally conducting screen is determined from the condition that the energy density must be integrable over any finite domain. Secondly, the problem of the diffraction of an arbitrary time-harmonic electromagnetic wave by a plane unidirectionally conducting circular disk is treated for the low-frequency case, i.e., the product $ka$ of the wave number $k$ and the disk radius $a$ is small. Expansions in powers of $ka$ are derived for the far field, the scattered energy and the field on the disk. Some special results for the case of plane-wave excitation are presented.

No abstract.

No abstract.

In this paper we discuss in Section 1 the finest group topology on Z zuch that {2n}nN is a sequence converging to zero. We prove that Z is a complete topological group with respect to that topology. The proof is almost entirely self-contained. In section 2 we give an example of a monothetic group (that is a topological group which contains a dense copy of Z) which is complete metrizable, totally disconnected and which has no continuous characters except 0. The example is constructed by starting with a complete meterizable totally disconnected monothetic group and factoring out a discrete subgroup which is dense in the Bohr compactification. The main difficulty here is in proving discreteness. Section 2 relies heaviliy on a trick developed in Section 1, namely the use of a kind of "coordinates" for 2-adic numbers. Section 0 contains a survey of related results already existing in the literature.

No abstract.

Closed-form results are presented for some $n$-fold integrals where the integrand contains the exponential of a specific quadratic form in $n$ variables. These integrals arise in the ray-optical analysis of reflection and diffraction problems for an open-ended parallel-plane waveguide. The results are obtained by three methods: the first method is elementary, the second method uses an,integral equation which is solved by the Wiener–Hopf technique, and the third method is based on a probabilistic interpretation of the integrals.