On the theory of 3-phase squirrel-cage induction motors includingspace harmonics and mutual slotting

General equations for squirrel-cage induction motors are derived based on the real geometry of the motor. The squirrel cage is described by its meshes; no equivalent windings are used. By means of complex time-dependent transformations free angles are introduced which simplify the set of equations when the specific geometrical properties of both types in which the asynchronous machines fundamentally can be divided are taken into account. The equations are general in the sense that all space harmonics are taken into account, due to the MMF and double slotting. This provides a better calculation of the synchronous, pulsating, and asynchronous torques. The final equations enable the formulation of some specific properties of both types in connection to their electromechanical behavior. Further, they are valid for star and delta connections and for any arbitrary source voltage     

Symmetrical components in the time domain and their application topower network calculations

Although the symmetrical component transformation has existed for 80 years, its application in the time-dependent form is practically restricted to the electric-machine theory. In the power systems field one uses the transformation applied to steady-state sinusoidal phasors in a nonunitary form for fault calculations. For time-domain calculations the real equivalent, 0, α, β, is preferred, usually extended to 0, d, q-components. In network calculations, however, the application of time-dependent symmetrical components makes sense, since many net-component parameters are already available in this form. In this paper a short historical overview of the symmetrical-component transformation and the application of unitary and orthogonal transformations are presented. From these general transformations logic choices for base quantities necessary in per unit calculations are derived. The relations between real and complex transformations, steady-state phasors and well-known sequence networks are given and illustrated through the use of some examples with asymmetrical faults     

An introduction to learning

At a symbolic level cognition can be modelled as a production system where meaning units are represented as condition-action rules. Anderson (1982, 1987) provides a good example of how learning can occur with this type of knowledge representation. At a subsymbolic level cognition can be modelled with a connectionist network where meaning units are represented as patterns of parallel distributed activity. The work of the McClelland and Rumelhart (1986) group is a prototype of this approach. We elaborate on these two approaches to learning and contrast the symbolic search space paradigm with the connectionist paradigm.     

On the steady-state determination of networks containing magnetic nonlinearities

Contents In this paper the Newton-Raphson algorithm is applied to obtain the steady-state solution of networks with a weak damping, containing nonlinear reactive elements. The fast obtaining of the steady-state solution is demonstrated in an example, in which the phenomenon of ferroresonance is treated because of its very nonlinear character.

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Über die Bestimmung des stationären Zustandes von Netzwerken mit magnetischen Nichtlinearitäten

Übersicht In diesem Aufsatz wird das Newton-Verfahren verwendet für die beschleunigte Berechnung des stationären Zustands von Netzwerken mit nichtlinearen magnetischen Elementen und einer geringen Dämpfung. Diese Methode wird anhand eines Beispieles erläutert.Dieses Beispiel ist Ferro-Resonanz-Erscheinungen gewidmet, da diese einen stark nichtlinearen Charakter aufweisen.

     

The Promises of Natural Killer Cell Therapy in Endometriosis

Endometriosis is a gynaecological disease defined by the growth of endometrium-like tissue outside the uterus. The disease is present in approximately 5–10% of women of reproductive age and causes pelvic pain and infertility. The pathophysiology is not completely understood, but retrograde menstruation and deficiency in natural killer (NK) cells that clear endometriotic cells in the peritoneal cavity play an important role. Nowadays, hormonal therapy and surgery to remove endometriosis lesions are used as treatment. However, these therapies do not work for all patients, and hormonal therapy prevents patients from getting pregnant. Therefore, new treatment strategies should be developed. Since the cytotoxicity of NK cells is decreased in endometriosis, we performed a literature search into the possibility of NK cell therapy. Available treatment options include the inhibition of receptor–ligand interaction for KIR2DL1, NKG2A, LILRB1/2, and PD-1/PD-L1; inhibition of TGF-β; stimulation of NK cells with IL-2; and mycobacterial treatment with BCG. In preclinical work, these therapies show promising results but unfortunately have side effects, which have not specifically been studied in endometriosis patients. Before NK cell treatment can be used in the clinic, more research is needed.     

Discrete threshold versus continuous strength models of perceptual recognition.

Tested discrete-threshold models of letter and word recognition against models that assume that decision criteria are applied to measures of continuous strength. Some of the predictions for discrete-threshold were generated from J. Grainger and A. M. Jacobs' (see record 1995-16120-001) dual-readout model (DROM) and some predictions for continuous strength were generated from a revised version of the activation-verification model (K. R. Paap et al; see record 1982-31874-001). Exp 1 used a 2-alternative forced-choice task, followed by an assessment of confidence and then a whole report if a word was recognized. Factors were manipulated to assess the presence or magnitude of a neighbourhood-frequency effect, a lexical-bias effect, a word-superiority effect, and a pseudoword advantage. Discrepancies between DROM's predictions and the obtained data are noted. Both types of models were also used to predict the distribution of responses across the levels of confidence for each. The predictions based on continuous strength were superior. Exp 2 used a same-different task and confidence ratings to enable the generation of receiver operating characteristics (ROCs). The shapes of the ROCs are more consistent with the continuous strength assumption than with a discrete threshold. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

PES Digital Library

This paper introduces a traveling wave-based relaying approach dedicated to sophisticated protection of six-phase transmission lines. In this ultra-high-speed (UHS) approach fault detection, classification, and faulted phase selection can be achieved within a quarter of a cycle. Two discriminants are used to differentiate between transients due to faults in the protected zone from other transients or faults occurring outside the protected zone.     

The general equations of 3-phase transformers with a symmetrical and linear magnetic circuit for use in network calculations

Contents In this paper general differential equations are derived for the 3-phase transformer with the help of the symmetrical component transformation. With respect to their phase shifting properties the 3-phase transformers can be divided into two basic groups, depending on whether or not the phase displacement is an even multiple of /6. This holds for both the steady state and for the transients. Only the appearance of a zero sequence component system may introduced differences. The derivation of the equations gives a clear insight into the internal behaviour of the transformer. The applicability of the general equations is demonstrated in an example.

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Die allgemeinen Gleichungen für dreiphasige Transformatoren mit symmetrischem und linearem magnetischen Kreis für Netzberechnungen

Übersicht In diesem Aufsatz wird mit Hilfe der Transformation symmetrischer Komponenten ein allgemeines Gleichungssystem für dreiphasige Transformatoren entwickelt. Bezüglich der Phasendrehung lassen sich alle dreiphasigen Transformatoren in nur zwei Gruppen einteilen, wobei innerhalb einer Gruppe die Transformatoren ein-und dasselbe stationäre und dynamische Verhalten haben. Lediglich ein Nullsystem kann innerhalb einer Gruppe Unterschiede einbringen. Bei Entwicklung der Gleichungen erhält man eine gute Einsicht in das innere Verhalten der unterschiedlichen Transformatoren. Anhand eines Beispiels wird die Anwendungsfähigkeit des allgemeinen Gleichungssystems erläutert.

     

Insights into the radial water jet drilling technology – Application in a quarry

In this context, we applied the radial water jet drilling (RJD) technology to drill five horizontal holes into a quarry wall of the Gildehaus quarry close to Bad Bentheim, Germany. For testing the state-of-the-art jetting technology, a jetting experiment was performed to investigate the influence of geological heterogeneity on the jetting performance and the hole geometry, the influence of nozzle geometry and jetting pressure on the rate of penetration, and the possibility of localising the jetting nozzle utilizing acoustic activity. It is observed that the jetted holes can intersect fractures under varying angles, and the jetted holes do not follow a straight path when jetting at ambient surface condition. Cuttings from the jetting process retrieved from the holes can be used to estimate the reservoir rock permeability. Within the quarry, we did not observe a change in the rate of penetration due to jetting pressure variations. Acoustic monitoring was partially successful in estimating the nozzle location. Although the experiments were performed at ambient surface conditions, the results can give recommendations for a downhole application in deep wells.     

On a hysteresis model for transient analysis

The letter describes an approach to a representation of transient behavior due to switching off complex nonlinear circuits. For this purpose the widely known Jiles model (JM) was implemented into the Alternative-Transient-Program (ATP). Calculations have been made on simplified transformer single-phase and three-phase circuits