Wrocław University of Science and Technology
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Constitution of Bi2(Sr1-xCax)2Cu2Oy and of Bi8(Sr1-xCax)8Ca4Cu100y type solid solution
Get PDFAnalytical explanation of an unexpected behaviour of sample densities is given. Three different types of construction of the investigated solid solutions have been recognised: normal for Z = constant versus increasing contribution of Sr substituent {X} ; atom-deficient for Z decreasing with X; atom-overcrowded for Z increasing with X. The mechanism of mutual transformation of the 2201-type matrix to that of the 2212-type is proposed
The Effect of Low Temperature on the Role Played by Electrodes in Vacuum Breakdown
Get PDFElectrical breakdown requires the creation of plasma in inter electrode space. The electrodes are the source of plasma, but the more important dense plasma is created on the anode. In a system with an insulating spacer, the insulator material is the source of plasma. The cooling of the anode needs more energy for plasma creation. Similarly, cooling of the insulator part where the plasma is created increases the electrical strength
Effect of short HV pulses on bacteria and fungi
Get PDFThe survival of three kinds of microorganisms under strongpulse electric field conditions was investigated with a possible application of the electric pulse method for sterilization of consumable liquids. The results of the investigations of survival ratio of Gram-negative (Escherichia coli, Yersinia enterocolitica) and Gram-positive (Staphylococcus aureus, Listeria monocytogenes) bacteria and yeastlike fungi (Candida albicans) are presented. The HV pulses with peak voltage U = 0 to 100 kV and rise time t, = 0.5 to 1.2 ps were applied. The microorganisms were suspended in an NaCl solution with 7 = 6 to 13 mS/cm conductivity and pH = 7.2. The experimental setup and the dependency of the microorganism survival ratio on the rise time, peak voltage and on the number of pulses applied, are presented. It has been found that the lethal effect on microorganisms caused by HV pulses depends on the pulse parameters as well as on the kind of microorganism being treated
Development of a bipolar space charge-limited current problem for metal-insulator-metal system. Some numerical results
Get PDFA solid in which the trapped negative charge can become mobile or immobile is considered. The different contact processes for a bipolar space charge transport are taken into account. A problem of the current flow through a solid is solved by a numerical method. The integral problem basing on the theory of characteristics for numerical calculations is defined
Some further description for a current flow trough an amorphous solid. A case of an imperfect contact
Get PDFIncluding a secondary electron emission for the cathode in a double injection problem, a new mathematical model is presented. In a planar capacitor system the carrier mobilities are discontinuous. The metal-solid-metal system can act as an n-n or p-n blocking diode. A new boundary condition for the "V" type current-voltage characteristic is determined
Nonrelativistic change of magnetic flux within a closed conductor: translatory and rotary motion
Get PDFThe equality is proved in the case when contour L is rigid and performs a translatory and rotary motion around an axis in the plane of contour L
Analysis of three-phase chopper circuits controlled by asymmetrical firing of thyristors
Get PDFUsing thyristor and thyristor-diode ac choppers causes distortion of currents and voltages in electrical power networks. In this paper the currents in three-phase, three wire circuits with thyristor and thyristor-diode a.c. choppers are analysed, making allowances for asymmetrical phase-angle triggering. The computation results of the extinction angles versus firing angles, phase shift angles of the load and degree of asymmetry are shown. The dc and harmonic components of the current waveforms were calculated by applying Fourier analysis. The computation results of the magnitudes, which are characteristic of deformed waveforms are also presented.------Analyse von gesteuerten Drehstromnetzen durch asymmetrisch gezundete Thyristoren. Der Einsatz von Thyristoren und Thyristordioden verursacht Verzerrungen von Stromen und Spannungen in elektrischen Versorgungsnetzen. In diesem Beitrag werden Stromverlaufe in Drehstromnetzen unter Berucksichtigung unsgmmetrischer Ansteuerung durch Thyristoren analrsiert. Die errechneten Abhangigkeiten des Loschwinkels 0 von der Phasenlage der Last und der Unsymmetrie der Ansteuerung werden dargestellt. Mit Hilfe der Fourieranalyse werden Gleichstromanteil und Oberschwingungen der Strome ermittelt. Berechnet und dargestellt werden auch andere Groessen, die fuer nichtlinear verzerrte Vorgange charakteristisch sind
Rezystancja, rezystywność - zadania
No full textZadania z teorii pola dot. rezystancji. Podstawy Elektrotechniki
Measurement of IEC Groups and Subgroups Using Advanced Spectrum Estimation Methods
Get PDFThe International Electrotechnical Commission (IEC) standards characterize the waveform distortions in power systems with the amplitudes of harmonic and interharmonic groups and subgroups. These groups/subgroups utilize the waveform spectral components obtained from a fixed frequency resolution discrete Fourier transform (DFT). Using the IEC standards allows for a compromise among the different goals, such as the needs for accuracy, simplification, and unification. In some cases, however, the power-system waveforms are characterized by spectral components that the DFT cannot capture with enough accuracy due to the fixed frequency resolution and/or the spectral leakage phenomenon. This paper investigates the possibility of a group/subgroup evaluation using the following advanced spectrum estimation methods: adaptive Prony, estimation of signal parameters via rotational invariance techniques, and root MUltiple-SIgnal Classification (MUSIC). These adaptive methods use variable lengths of time windows of analysis to ensure the best fit of the waveforms; they are not characterized by the fixed frequency resolution and do not suffer from the spectral leakage phenomenon. This paper also presents the results of the applications of these methods to three test waveforms, to current and voltage waveforms obtained from simulations of a real dc arc-furnace plant, and to waveforms measured at the point of common coupling of the low-voltage network supplying a high-performance laser printer
Echtzeitberechnung der modalen Drehstromkomponenten nach plötzlichen Zustandsänderungen
Get PDFZur schnellen digitalen Ermittlung der Modalkomponenten in Drehstromsystemen werden in des Regel nichtrekursive Filterverfahren verwendet. Durch die Anwendung dieser Verfahren auf die aß-Komponenten läßt sich im Vergleich mit den RST-Originalgrößen der Rechenaufwand etwa um ein Drittel reduzieren. Bei uebergangsvorgängen kann die Berechnung durch Schrittweise aufbauende Filter bis auf eine Viertelperiode verkuerzt werden, wenn sich der Zeitptinkt der plötzlichcn Zustandsänderung feststellan laesst