Generalized Sperner lemma and subdivisions into simplices of equal volume

A generalization of the well-known Sperner lemma is suggested, which covers the case of arbitrary subdivisions of (convex) polyhedra into (convex) polyhedra. It is used for giving a new proof of the Thomas-Monsky-Mead theorem saying that the n-cube can be subdivided into N simplices of equal volume if and only if N is divisible by n!. Some new related results are announced. Bibliography: 6 titles. Published inZapiski Nauchnykh Seminarov POMI, Vol. 231, 1995, pp. 245–254.     

Queues with waiting time dependent service

Motivated by service levels in terms of the waiting-time distribution seen, for instance, in call centers, we consider two models for systems with a service discipline that depends on the waiting time. The first model deals with a single server that continuously adapts its service rate based on the waiting time of the first customer in line. In the second model, one queue is served by a primary server which is supplemented by a secondary server when the waiting of the first customer in line exceeds a threshold. Using level crossings for the waiting-time process of the first customer in line, we derive steady-state waiting-time distributions for both models. The results are illustrated with numerical examples.     

Series representations for densities functions of a family of distributions—Application to sums of independent random variables

Series representations for several density functions are obtained as mixtures of generalized gamma distributions with discrete mass probability weights, by using the exponential expansion and the binomial theorem. Based on these results, approximations based on mixtures of generalized gamma distributions are proposed to approximate the distribution of the sum of independent random variables, which may not be identically distributed. The applicability of the proposed approximations are illustrated for the sum of independent Rayleigh random variables, the sum of independent gamma random variables, and the sum of independent Weibull random variables. Numerical studies are presented to assess the precision of these approximations.     

Preparation of a macrocrystalline pressure calibrant SrB4O7:Sm 2+ suitable for the HP-HT powder diffraction

A new simplified synthesis of monocrystalline chips of SrB₄O₇: Sm²⁺ pressure calibrant, well-suited for the diamond anvil cell (DAC) powder diffraction experiments, is proposed. It consists of ordinary solid-state synthesis of fine-grained SrB₄O₇: Sm²⁺ and subsequent annealing near melting temperature. The obtained material was characterized and tested in HP-HT DAC experiment.     

Force and virial of torsional-angle-dependent potentials

Simple expressions for the forces due to dihedral-angle interactions are derived using first principles of mechanics. The expressions require significantly fewer numerical operations than those generally used in the literature and provide insight into the physics of dihedral-angle interactions. It is also shown that the scalar virial due to angle-dependent interactions is zero. © 1995 by John Wiley & Sons, Inc.     

Reciprocity laws for algebras over function fields

A study is made of simple central algebras over an algebraic function field of one variable with a number field of constants. It is proved that there exists an algebra with a given collection of local invariants satisfying the reciprocity law under the assumption that the orders of the invariants are odd or the field of constants is purely imaginary.     

Synthesis of 1,2-O-isopropylidene-α-d-glucofuranose 3,6-cyclophosphates

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2191–2192, September, 1988.