We provide a uniform framework for proving the collapse of the hierarchy NC(C) for an exact arithmetic class C of polynomial degree. These hierarchies collapse all the way down to the third level of the AC-hierarchy, AC3(C). Our main collapsing exhibits are the classes C ∈ {C=NC,C=L,C=SAC,C=P}. NC(C=L) and NC(C=P) are already known to collapse [1,18,19]. We reiterate that our contribution is a ...

The article discusses application of AC/DC/AC converter cooperating with an induction generator in small hydroelectric power plants. The induction generator works with power grid or a separated group of receivers, enabling to generate power even at low speeds of the turbine. The article provides also results of the investigation concerning the functioning of the generator coupled with AC/DC/AC ...

Bacterial exopolysacchrides (EPSs) are produced by many bacteria. Nowadays there is an increasing interest in the isolation and exploitation of these polymers for industrial purposes. In general, biosynthesis of EPS varies from one strain to other strain and it depends on genes and enzymes involved in EPS production and secretion. In this study, EPS producing strains were isolated from municipa...

A seven-port wave-correlator based vector network analyzer is proposed. The seven-port wave-correlator is a combination of two six-port wave-correlators which share common components. Furthermore, the complex wave ratio measurement accuracy is improved since the input signals can be directly detected by the side-arm ports. A seven-port wave-correlator is fabricated using microstrip branch line ...

• The circuit used for the phase angle control in triac-based single-phase ac regulators (ac to ac voltage converters) • The operation of the various blocks used in the circuit, along with the waveforms • The harmonic analysis of the output voltage of a single-phase ac regulator with resistive load

This paper deals with the problem of controlling doubly-fed induction machines (DFIM). A nonlinear model of the whole controlled system, including the DFIM and the associated AC/DC rectifier and DC/AC inverter, is developed within the Park coordinates. A multi-loop nonlinear controller is developed, using the backstepping design technique. The controller is formally shown to meet its objectives...

In this paper some photovoltaic, PV, conversion chains architectures for on-grid applications have been proposed and the advantage of the direct use of a Low Voltage Direct Current (LVDC) bus for the DC loads has been shown. The evaluation of the efficiency of the proposed chains compared to the classical one was performed. It is shown that LVDC use instead of standard AC plugs, in numerous app...

Following partial discharge activity within a gaseous void, charges will accumulate on the wall of the void. In the present paper, the decay of such charges due to surface currents at the void wall is studied analytically, and the factors affecting this decay are indicated.

Several metastable Ac alleles at the maize p locus were identified that produced novel pericarp variegation patterns. From the transmission analysis of pericarp sectors, we show that Ac inactivation is a somatic process. Ac excision from P and transactivation of an unlinked Ds was delayed or absent in plants with metastable Ac alleles. These decreases in Ac activity were correlated to increases...