Given a right-angled Artin group A, the associated BestvinaBrady group is defined to be the kernel of the homomorphism A → Z that maps each generator in the standard presentation of A to a fixed generator of Z. We prove that the Dehn function of an arbitrary finitely presented BestvinaBrady group is bounded above by n. This is the best possible universal upper bound.

The class of multivariate Archimedean copulas is defined by using a realvalued function called the generator of the copula. This generator satisfies some properties, including d-monotonicity. We propose here a new basic transformation of this generator, preserving these properties, thus ensuring the validity of the transformed generator and inducing a proper valid copula. This transformation ac...

It is noted that as a generalized characteristic of the functional gas generator, which sensitive to variations in its parameters, it advisable use transfer function, or analogue - amplitude-phase frequency generator. The generator includes two components amplitude-frequency and phase-frequency characteristics. During operation there will be parameters transmission coefficient time constants, d...

HMAC DRBG is a deterministic random bit generator using HMAC specified in NIST SP 800-90. The document claims that HMAC DRBG is a pseudorandom bit generator if HMAC is a pseudorandom function. However, no proof is given in the document. This article provides a security analysis of HMAC DRBG and confirms the claim.

in this article our objective is to obtain steady state characteristics of shunt, series, and separately excited dc motors coupled with a centrifugal water pump supplied through a step-up, step-down, and cuk converter from photovoltaic generator. we assume that there are no storage batteries and, of course, the system must operate on maximum utilization i.e. maximum water must be pumped. it is ...

We prove that the generator of any uniformly bounded set-valued Nemytskij operator acting between generalized Hölder function metric spaces, with nonempty compact and convex values is an affine function with respect to the function variable.

In 2011 ISO standardized [2] a family of deterministic pseudorandom bit generators MQ—DRBG, based on multivariate quadratic functions satisfying certain properties. The security of the generator could be described in terms of complexity of solving the corresponding system of multivariate quadratic equations. In our previous article [1] we proposed two different techniques for constructing syste...

The paper examines permutation generators which are designed using four rounds of the Data Encryption Standard and a single pseudorandom function. We have proved that such generators are pseudorandom only if the pseudorandom function is used internally at least five times. The proof is given using two different approaches: deterministic and probabilistic. Some cryptographic implications are als...

Let H1, H2 be two hash functions. We wish to construct a new hash function H that is collision resistant if at least one of H1 or H2 is collision resistant. Concatenating the output of H1 and H2 clearly works, but at the cost of doubling the hash output size. We ask whether a better construction exists, namely, can we hedge our bets without doubling the size of the output? We take a step toward...