Vladimir Vand

Bio: Vladimir Vand is an academic researcher. The author has contributed to research in topics: Decay theory & Decay energy. The author has an hindex of 1, co-authored 1 publications receiving 243 citations.

A theory of the irreversible electrical resistance changes of metallic films evaporated in vacuum

Abstract: Metallic films prepared by evaporation show characteristic irreversible changes, especially if prepared at low temperatures. The changes can be explained by a decay of lattice distortions. To allow of a mathematical treatment, a set of simplifying assumptions is formulated. To initiate a decomposition of a distortion, a certain energy must be reached, but the observed changes cannot be explained if all distortions have the same decay energy. A characteristic function F0 expressing the law of distribution of the decay energies is formulated, calculated from measurements available and found to be of the expected order. The shape of this function and the position of its maxima depend on the structure of the support and on the thickness of the film. The resistance measurement at a constant temperature has the disadvantage that it reveals only a small part of F0. This is overcome if uniformly rising temperature is used. A possibility that the changes are caused by a recombination of interstitial atoms and lattice vacancies is investigated, but as this requires essentially only a single value of the transition energy, the results are inconsistent with the observed changes, so that the decay theory should be preferred, as it gives more consistent results.

Thermally Stimulated Discharge of Polymer Electrets

Abstract: A special form of depolarization of polymer electrets is described: the thermally stimulated discharge (TSD). After reviewing its principles and exposing its mathematical analysis, results are presented which show that TSD is a powerful method to gain insight into the molecular mechanisms of the electret effect. In fact, TSD reveals all low-frequency molecular motions. It enables one to determine, e.g., the glass-rubber transition of polymers. Its merits are compared with those of isothermal dielectric, and mechanical methods of investigation.

A Simple Method for Estimating f(E) and k0(E) in the Distributed Activation Energy Model

Abstract: A new method that is simpler and more accurate than the author's previous method is presented for estimating f(E) and k0(E) in the distributed activation energy model. It utilizes at least three se...

An overview of distributed activation energy model and its application in the pyrolysis of lignocellulosic biomass

Abstract: Research interest in the conversion of lignocellulosic biomass into energy and fuels through the pyrolysis process has increased significantly in the last decade as the necessity for a renewable source of carbon has become more evident. For optimal design of pyrolysis reactors, an understanding of the pyrolysis kinetics of lignocellulosic biomass is of fundamental importance. The distributed activation energy model (DAEM) has been usually used to describe the pyrolysis kinetics of lignocellulosic biomass. In this review, we start with the derivation of the DAEM. After an overview of the activation energy distribution and frequency factor in the DAEM, we focus on the numerical calculation and parameter estimation methods of the DAEM. Finally, this review summarizes recent results published in the literature for the application of the DAEM to the pyrolysis kinetics of lignocellulosic biomass.