Definition und Berechnung der Induktivitäten bei Gleich- und periodischem Strom

Übersicht Die im einschlägigen Schrifttum benutzten Induktivitätsdefinitionen beiperiodischem Strom im nichtlinearen Teil der magnetischen Kennlinie bilden nich eine Erweiterung der bei Gleichstrom eingeführten Grundinduktivitäten. Die im Gebrauch befindlichen Schwingungsinduktivitäten sind nur für eine bestimmte Harmonische gültig. Erst mit den eingeführten periodischen Induktivitäten gelingt es, die bei Grundinduktivitäten vorkommenden Größen über die ganze Periode vollständig und exakt zu erfassen. Zur Veranschaulichung der Erläuterungen dieses und des vorhergehenden Aufsatzes werden die verschiedenen Induktivitäten an Hand einer Ersatzgleichung für die magnetische Kennlinie berechnet. Schließlich behandelt man mit der periodischen reziproken Differentialinduktivität den Einfluß der Vormagnetisierung durch netzfrequente Ströme auf die Selbsterregung bei Reihenschlußmaschinen.

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Summary The definitions of inductance used in the literature for periodic current in the nonlinear part of the saturation characteristic do not constitute an extension of basic inductances which are introduced at d. c. The inductances used for harmonics apply inherently to a couple of harmonics of the same order. This paper extends the basic inductances to include also the case of the periodic current. Thus it becomes possible with the periodic inductances introduced here to include over the whole period completely and exactly the quantities which are present in the basic inductances. To illustrate the discussions of this and the preceding paper the different inductances are calculated with an approximate equation for the saturation characteristic. Finally the influence of the saturation by currents with network frequency upon the self-excitation of series machines is studied by means of the periodic reciprocal of the incremental inductance.

     

Computationally efficient wavelet affine invariant functions for shape recognition

An affine invariant function for object recognition is constructed from wavelet coefficients of the object boundary. In previous works, undecimated dyadic wavelet transform was used to construct affine invariant functions. In this paper, an algorithm based on decimated wavelet transform is developed to compute an affine invariant function. As a result computational complexity is reduced without decreasing recognition performance. Experimental results are presented.     

In vitro and ex vivo permeation studies of chlorpheniramine maleate gels prepared by carbomer derivatives

The antihistaminic chlorpheniramine maleate (CPM) is used for symptomatic relief of hypersensitivity reactions and in pruritic skin disorders. At present, the drug is marketed in tablet, capsule, syrup, cream, and injectable dosage forms. Chlorpheniramine maleate has some side effects when taken orally. Due to its first pass effect, only 25%-45% of the orally administered dose reaches the blood circulation. To bypass these disadvantages, we aimed to investigate percutaneous absorption of CPM from gel formulations prepared with different carbomer derivatives (Carbopol 934, 940, 941, 2984, 980, and 981; main differences are related to presence of a comonomer and cross-link density). Cellulose membrane was used as the diffusion barrier for all the formulations' drug-release studies. The release of active substance from carbopol derivatives, which have the least cross-linking density (Carbopol 941 and 981) was found to be numerically higher than the others. The formulation (F8; 1% Carbopol 941) that exhibited the maximum drug release through the cellulose membrane was further studied for drug release by using polyurethane membrane, excised rat skin, and human skin. The penetration of the active substance through different diffusion barriers was found to be statistically different (p<0.05) when compared. Of all the different diffusion barriers, rat skin gave the closest results to human skin. Thus topical application of CPM in the carbomer gel may be of potential use for local activity. The type and concentration of carbomers can affect drug release. The synthetic membranes are useful in assessments of formulations in quality assurance but they do not give definite indication of how a formulation will behave when it is used on skin.     

Characterization of sleep spindles using higher order statistics and spectra

This work characterizes the dynamics of sleep spindles, observed in electroencephalogram (EEG) recorded from humans during sleep, using both time and frequency domain methods which depend on higher order statistics and spectra. The time domain method combines the use of second- and third-order correlations to reveal information on the stationarity of periodic spindle rhythms to detect transitions between multiple activities. The frequency domain method, based on normalized spectrum and bispectrum, describes frequency interactions associated with nonlinearities occurring in the observed EEG.     

Preconditioned methods for simulations of low speed compressible flows

A time-derivative preconditioned system of equations suitable for the numerical simulation of inviscid compressible flow at low speeds is formulated. The preconditioned system of equations are hyperbolic in time and remain well-conditioned in the incompressible limit. The preconditioning formulation is easily generalized to multicomponent/multiphase mixtures. When applying conservative methods to multicomponent flows with sharp fluid interfaces, nonphysical solution behavior is observed. This stimulated the authors to develop an alternative solution method based on the nonconservative form of the equations which does not generate the aforementioned nonphysical behavior. Before the results of the application of the nonconservative method to multicomponent flow problems is reported, the accuracy of the method on single component flows will be demonstrated. In this report a series of steady and unsteady inviscid flow problems are simulated using the nonconservative method and a well-known conservative scheme. It is demonstrated that the nonconservative method is both accurate and robust for smooth low speed flows, in comparison to its conservative counterpart.     

Vision-based single-stroke character recognition for wearable computing

Particularly when compared to traditional tools such as a keyboard or mouse, wearable computing data entry tools offer increased mobility and flexibility. Such tools include touch screens, hand gesture and facial expression recognition, speech recognition, and key systems. We describe a new approach for recognizing characters drawn by hand gestures or by a pointer on a user's forearm captured by a digital camera. We draw each character as a single, isolated stroke using a Graffiti-like alphabet. Our algorithm enables effective and quick character recognition. The resulting character recognition system has potential for application in mobile communication and computing devices such as phones, laptop computers, handheld computers and personal data assistants.     

VyrdMC: Driving Runtime Refinement Checking with Model Checkers

This paper presents VyrdMC, a runtime verification tool we are building for concurrent software components. The correctness criterion checked by VyrdMC is refinement: Each execution of the implementation must be consistent with an atomic execution of the specification. VyrdMC combines testing, model checking, and Vyrd, the runtime refinement checker we developed earlier. A test harness first drives the component to a non-trivial state which serves as the starting state for a number of simple, very small multi-threaded test cases. An execution-based model checker explores for each test case all distinct thread interleavings while Vyrd monitors executions for refinement violations. This combined approach has the advantage of improving the coverage of runtime refinement checking at modest additional computational cost, since model checkers are only used to explore thread interleavings of a small, fixed test program. The visibility and detailed checking offered by using refinement as the correctness criterion differentiate our approach from simply being a restricted application of model checking. An important side benefit is the reduction in program instrumentation made possible if VyrdMC is built using a model checker with its own virtual machine, such as Java PathFinder [Guillaume Brat, Klaus Havelund, Seung-Joon Park, and Willem Visser. Model Checking Programs. In IEEE International Conference on Automated Software Engineering (ASE), September 2000]. We are investigating the use of two different model checkers for building VyrdMC: Java PathFinder, an explicit-state model checker and Verisoft, a “stateless” model checker [P. Godefroid. Model Checking for Programming Languages using VeriSoft. In Proceedings of the 24th ACM Symposium on Principles of Programming Languages, pages 174–186, Paris, January 1997].     

Modeling traffic signal control using Petri nets

This paper focuses on the use of Petri nets (PN) to model the control of signalized intersections. The application of PN to an eight-phase traffic signal controller is illustrated. Structural analysis of the control PN model is performed to demonstrate how the model enforces the traffic operation safety rules. This is followed by a discussion of why this modeling tool has future value as the use of more advanced control strategies continue to expand.     

Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.