Another type of log-periodic oscillations on Polish stock market?

Log-periodic oscillations have been used to predict price trends and crashes on financial markets. So far two types of log-periodic oscillations have been associated with the real markets. The first type are oscillations which accompany a rising market and which ends in a crash. The second type oscillations, called "anti-bubbles" appear after a crash, when the prices decreases. Here, we propose the third type of log-periodic oscillations, where a exogenous crash initializes a log-periodic behavior of market, and the market is growing up. Such behavior has been identified on Polish stock market index between the "Russian crisis" (August 1998) and the "New Economy crash" in April 2000.Comment: 10 pages (6 figures): conference APFA4 (Warsaw, November 2003

A note on bound entanglement and local realism

We show using a numerical approach that gives necessary and sufficient conditions for the existence of local realism, that the bound entangled state presented in Bennett et. al. Phys. Rev. Lett. 82, 5385 (1999) admits a local and realistic description. We also find the lowest possible amount of some appropriate entangled state that must be ad-mixed to the bound entangled state so that the resulting density operator has no local and realistic description and as such can be useful in quantum communication and quantum computation.Comment: 5 page

Violations of local realism by two entangled quNits are stronger than for two qubits

Tests of local realism vs quantum mechanics based on Bell's inequality employ two entangled qubits. We investigate the general case of two entangled quNits, i.e. quantum systems defined in an N-dimensional Hilbert space. Via a numerical linear optimization method we show that violations of local realism are stronger for two maximally entangled quNits (N=3,4,...,9), than for two qubits and that they increase with N. The two quNit measurements can be experimentally realized using entangled photons and unbiased multiport beamsplitters.Comment: 5 pages, 2 pictures, LaTex, two columns; No changes in the result

High-Power Induction Motors Supplied with Voltage Containing Subharmonics

In some power networks, components of frequency less than the frequency of the fundamental voltage harmonic called subharmonics or subsynchronous interharmonics occur. In this paper, the effect of voltage subharmonics on currents, power losses, speed fluctuations and electromagnetic torque is examined. The results of numerical computations using the finite element method for an induction cage motor of rated power of 5.6 MW and four motors of rated power of 200 kW with different numbers of poles are presented. An extraordinary harmful effect on high-power induction motors is demonstrated. Among other effects, voltage subharmonics cause significant torque pulsations whose frequencies may correspond to the elastic-mode natural frequency. Possible resonance can result in excessive torsional vibration and the destruction of a power train

Preliminary investigations of 5600 kW induction motor under voltage containing subharmonics

This work deals with investigations of 5600 kW induction cage motor designed for driving a fan of high value moment of inertia, under supply voltage containing subharmonics injection. The results of field calculations in Ansys Electronics (Ansys Electromagnetics) environment are presented for subharmonics of various frequencies. The article presents the influence of subharmonic voltage on the stator windings current waveforms, electromagnetic torque fluctuations and power losses of the motor. It was found that subharmonics occurring in real power systems can cause significant fluctuations of the electromagnetic torque and increase in power losses of high power machines. The increase of power losses is particularly important in the case of low frequency subharmonics and it can cause excessive windings heating. The operation of high power machines with a higher stator windings temperature can lead to a faster thermal degradation of insulation system and motor destruction.Artykuł poświęcony jest badaniom silnika o mocy 5600 kW przeznaczonym do napędu wentylatora o dużym masowym momencie bezwładności, zasilanym napięciem zawierającym subharmoniczne. Wyniki obliczeń polowych wykonane w środowisku Ansys Electronics (Ansys Electromagnetics) zostały przedstawione dla subharmonicznych napięcia o różnych częstotliwościach. W artykule przedstawiono wpływ subharmonicznych napięcia na przebiegi prądu w uzwojeniu stojana, wahania momentu elektromagnetycznegooraz straty mocy. Stwierdzono, że subharmoniczne występujące w rzeczywistych systemach elektroenergetycznych mogą powodować znaczące wahania momentu elektromagnetycznego oraz wzrost strat w uzwojeniach silników dużej mocy. Wzrost strat jest szczególnie istotny w przypadku subharmonicznych o niskiej częstotliwości i może spowodować nadmierny wzrost temperatury uzwojeń. Praca maszyny z wyższą temperaturą uzwojenia może doprowadzić do szybszej degradacji termicznej układu izolacyjnego i do uszkodzenia silnika

Power losses and windings temperature of an induction machine under voltage subharmonics

This paper deals with the effect of voltage subharmonics on power losses and heating of an induction motor. An increase in power losses in stator and rotor windings and their impact on windings temperature is presented for subharmonics of various frequencies. The results of this study’s investigations are provided for subharmonics occurring as a single power quality disturbance and combined with voltage deviation. The appropriate electromagnetic computations were performed with the finite element method, and thermal ones – with an analytical method

Induction Motor Supplied with Voltage Containing Symmetrical Subharmonics and Interharmonics

Sinusoidal voltage fluctuations can be considered a specific result of the occurrence of voltage subharmonics and interharmonics, which are components of low frequency or not being an integer multiple of the frequency of the fundamental voltage harmonic. These components—symmetrical subharmonics and interharmonics—are of the same magnitude, while their frequencies are symmetrical with respect to the fundamental frequency. Depending on their phase angles, various kinds of voltage fluctuations can be distinguished: amplitude modulation, phase modulation and intermediate modulation. In this study, the effect of phase angles on noxious phenomena in induction motors was analyzed. Additionally, torque pulsations and vibrations of an induction motor under sinusoidal voltage fluctuation and a single voltage subharmonic or interharmonic were compared. The investigations were performed with the finite element method and an experimental method. Among other findings, it was found that for some phase angles torque pulsations could be about ten times higher than for other angles, roughly corresponding to the amplitude modulation