New Results on the π+π−\pi^{+}\pi^{-} Electroproduction Cross Sections off Protons

In these proceedings we present preliminary $\pi^{+}\pi^{-}$ electroproduction cross sections off protons in the kinematical area of 1.4 GeV $< W <$ 1.8 GeV and 0.4 GeV$^{2}$ $< Q^{2} < 1.1$ GeV$^{2}$. Our results extend the kinematical coverage for this exclusive channel with respect to previous measurements. Furthermore, the $\pi^{+}\pi^{-}$ electroproduction cross sections were obtained for $Q^2$-bins of much smaller size. The future analysis of this data within the framework of the JLAB-MSU reaction model (JM) will considerably improve our knowledge on the $Q^2$ evolution of the transition $\gamma_{v}NN^*$ electrocouplings, in particular for the resonances with masses above 1.6 GeV.Comment: Will be published in proceedings of NSTAR 2011 conference. 4 pages, 4 figure

On the kinetic equation approach to pair production by time-dependent electric field

We investigate the quantum kinetic approach to pair production from vacuum by time-dependent electric field. Equivalence between this approach and the more familiar S-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.Comment: 8 pages, 4 figure

Energy-efficient adjustable speed double inverter-fed woundrotor induction motor drive

The mathematical and analytical models of adjustable speed electric drive based on double inverter-fed induction motor are considered and analyzed in the article, the main equations which describe energy performances of such type of AC electric drive system are determined. The influence of excitation frequency on energy performances of double inverter-fed induction motor in steady-state at orthogonal flux vector control is considered in the article. The condition ensures minimum of stator steel losses at a predetermined rotor speed and can operate at speeds up to double rated without the magnetic flux reducing is presented. This possibility is one of the most important advantages of this type of electric drive over others types of AC drives for many technological processes.Keywords: power, double-fed wound-rotor induction motor drive, steel and total losses, efficiency, energy-efficient control algorith

Electroproduction of pπ+π− off protons at 0.2

This paper reports on the most comprehensive data set obtained on differential and fully integrated cross sections for the process ep→e′pπ+π−. The data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the as yet unexplored kinematic region of photon virtuality 0.