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  • 1
    Electronic Resource
    Electronic Resource
    Zylinder mit Leitfähigkeitsstruktur im Hochfrequenzfeld (1970)
    Springer
    Electrical engineering 53 (1970), S. 207-214 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents In this paper Maxwell's Equations are integrated, taking into consideration special boundery conditions. An infinite cylinder is placed into a given electromagnetic field. The surface conductivity of the cylinder is not assumed to be infinite but finite, anisotropic and a coordinate function. By a suitable specialization it is possible to obtain results for the typical case, that a surface conductivity only occurs in one direction.
    Notes: Übersicht In dieser Arbeit werden die Maxwellschen Gleichungen für spezielle Randbedingungen integriert. Ein unendlich langer Zylinder wird in ein gegebenes elektromagnetisches Feld gebracht. Die Oberflächenleitfähigkeit ist aber nicht unendlich groß, sondern endlich, anisotrop und eine Funktion des Ortes. Durch eine entsprechende Sopezialisierung werden auch Ergebnisse für den Fall abgeleitet, daß auf dem Zylinder nur eine einzige Leitfähigkeitsrichtung existiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01407136
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Theorie der Schirmung von zweidimensionalen Magnetfeldern (1981)
    Springer
    Electrical engineering 63 (1981), S. 29-33 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents The present method permits investigating the shielding effect of cylindric or prismatic shielding covers of arbitrary cross sections. Ferromagnetic materials and electrically thick walls can be taken into consideration, too. The vector potential and herewith the current density in the shielding cover are determined by an integral equation. An integral represetation of the vector potential for the whole space is given by the current density in the shielding cover, from which also integral representations for the components of the magnetic field can be obtained.
    Notes: Übersicht Die vorliegende Methode gestattet es, beliebige Querschnitte von zylindrischen oder prismatischen Schirmhüllen auf ihre Schirmwirkung zu untersuchen. Auch ferromagnetisches Material und elektrisch dicke Wandstärken können berücksichtigt werden. Das Vektorpotential und damit die Stromdichte in der Schirmhülle wird durch eine Integralgleichung bestimmt. Durch die Stromdichte in der Schirmhülle ist ferner eine Integraldarstellung des Vektorpotentials für den ganzen Raum gegeben, aus der auch Integraldarstellungen für die Komponenten des magnetischen Feldes gewonnen werden können.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01574584
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Algorithmic methods of induction machines parameters estimation from measured slip-curves (1989)
    Springer
    Electrical engineering 72 (1989), S. 239-249 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht Der Beitrag stellt Methoden zur Bestimmung der Parameter von mathematischen Modellen der Induktionsmaschinen dar. Es wird auf eine objektive algorithmische Weise die Schrittregressionmethode angewendet. Die experimentelle Grundlage der Parameterschätzung sind gemessene Schlupfkennlinien. Zuerst wird die einfache Schätzmethode beschrieben, die nur eine ausgewählte Charakteristik als Grundlage zur Parameterbestimmung ausnutzt. Danach werden die mehrdimensionalen Schätzverfahren dargestellt, die zur Parameterbestimmung gleichzeitig eine Zahl von Schlupfkennlinien ausnutzen. Als Ergebnis bekommt man einen universellen Parametersatz. Die vorgestellten Methoden sind allgemein, aber die Beziehungen im Beitrag betreffen nur Doppelkäfigmaschinen. Am Schluß des Beitrags werden die Anwendungsbeispiele für die Doppelkäfigmaschine und den Stromverdrängungsmotor angegeben. Die erhaltenen Parameter werden für Berechnungen der typischen dynamischen Vorgänge benutzt. Die rechnerischen Ergebnisse werden mit auf experimentellem Weg ermittelten Verläufen verglichen.
    Notes: Contents The paper presents methods of determining the parameters of induction machine models in objective, algorithmic way employing the stepwise-regression method. The experimental base for parameter-estimation are measured slip-curves of the machine. At first a singular estimation method is presented, which uses one slip-curve as the source for determining the parameters. Then multidimensional estimation methods are introduced, which take several slip-curves into account and result in one versatile set of parameters. The methods are quite general, but in this paper specific formulae are given for double-cage machines. The paper is concluded with examples of application to double-cage and deep-bar motors, and the obtained parameters are used in computations of typical transients which are compared with recorded curves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01573847
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  • 4
    Electronic Resource
    Electronic Resource
    On reducing the vibration and noise level of induction motors with integral and fractional slot windings (1990)
    Springer
    Electrical engineering 73 (1990), S. 163-171 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht Im Beitrag werden Methoden zur Berechnung von magnetischen Radialkräften und Oberschwingungsanteilen des elektromagnetischen Moments von Induktionsmotoren mit Ganzloch- und Bruchloch-Wicklungen des Ständers und Käfigläufern vorgestellt. Ziel der Berechnung ist die Reduzierung von Schwingungen und Geräuschen elektromagnetischer Herkunft. Diese Methoden helfen bei der Auswahl der Nutzahl von Ständer und Läufer sowie anderer Konstruktionsdaten. Damit können Oberschwingungsanteile von auftretenden inneren Kräften derart beeinflußt werden, daß Komponenten, die im Bereich der mechanischen Eigenfrequenz des Motors liegen, nicht auftreten. Besondere Aufmerksamkeit wird den frequenzabhängigen Oberschwingungsanteilen des Momentes gewidmet. Es werden experimentelle und theoretische Ergebnisse, die anhand eines Motors großer Leistung gewonnen wurden, gegenübergestellt.
    Notes: Contents The paper presents a method of calculating the radial magnetic forces and pulsating torques in induction motors with integral and fractional stator slot winding and squirrel-cage rotors, which aims on reducing the forces of vibration and the noise level of electromagnetic origin. The method leads to a proper choice of stator and rotor slot numbers and other design data, which allow to avoid cases where force components of considerable value and frequencies in the resonant band of the motor are generated. Special attention is paid to the generation of time dependent (synchronous) parasitic torques and their frequencies. Finally the paper includes the experimental verification and presents a case of successful application in a high power motor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01574023
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  • 5
    Electronic Resource
    Electronic Resource
    A simulation of common-bus drives in power plants (1992)
    Springer
    Electrical engineering 75 (1992), S. 293-302 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht Im Beitrag werden die mathematischen Modelle sowie die Simulationsmethoden von Gruppenantrieben dargestellt.N Asynchromotoren werden aus einer Sammelschiene gespeist, wobei die speisende Quelle eine bestimmte Impedanz besitzt. Induktionsmotoren werden durch ihre Doppelkäfigmodelle vertreten, was praktisch alle typischen Motorkonstruktionen einschließlich der Stromverdrängungsmotoren umfaßt. Das Modell simuliert auch Auslaufprobleme der Motorgruppe, die an der Sammelschiene angeschlossen ist. Das tritt in bestimmten Praxisfällen auf. Die Berechnungsmethode wird auf die Umschaltung von Kraftwerkelektroantrieben an die Reservesammelscheine angewendet. Die Berechnungsergebnisse werden mit Meßresultaten verglichen.
    Notes: Contents The paper presents mathematical models and the simulation of a group ofN induction motors supplied by a common bus from a source with defined impedance. The induction motors are represented by the double cage model, which in practice, covers all induction motors of typical construction, including the deepbar rotor. The simulation model includes the problem of common-bus coasting of a group of induction motors, which happens in some practical situations. The theory is applied to auxiliary drives in a power plant during the transfer of bus-bar systems, and the computed results are compared with measurements for a high power unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01579757
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    An iterative linearized optimization technique for non-linear ill-posed problems applied to cardiac activation time imaging (2001)
    Bradford : Emerald
    Compel 20 (2001), S. 676-688 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A promising approach for the solution of the electrocardiographic inverse problem is the calculation of the cardiac activation sequence from body surface potential (BSP) mapping data. Here, a two-fold regularization scheme is applied in order to stabilize the inverse solution of this intrinsically ill-posed problem. The solution of the inverse problem is defined by the minimum of a non-linear cost function. The L-curve method can be applied for regularization parameter determination. Solving the optimization problem by a Newton-like method, the L-curve may be of pronged shape. Then a numerically unique determination of the optimal regularization parameter will become difficult. This problem can be avoided applying an iterative linearized algorithm. It is shown that activation time imaging due to temporal and spatial regularization is stable with respect to large model errors. Even neglecting cardiac anisotropy in activation time imaging results in an acceptable inverse solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321640110393644
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Design, construction and experimental investigation of ultrasonic pulse transducers with different bandwidths
    Amsterdam : Elsevier
    Ultrasonics 25 (1987), S. 229-236 
    Details
    ISSN: 0041-624X
    Keywords: fabrication techniques ; pulse-echo techniques ; transducers
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0041-624X(87)90038-2
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of interface properties by spatial echo distribution processing
    Amsterdam : Elsevier
    Ultrasonics 15 (1977), S. 216-220 
    Details
    ISSN: 0041-624X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0041-624X(77)90084-1
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Three-dimensional computer model of the entire human heart for simulation of reentry and tachycardia: Gap phenomenon and Wolff-Parkinson-White syndrome (1991)
    Springer
    Basic research in cardiology 86 (1991), S. 485-501 
    Details
    ISSN: 1435-1803
    Keywords: computermodel ; tachycardia ; reentryrhythms ; WPW-syndrome ; gapphenomenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A computer model of the entire human heart has been developed for simulation of the excitation and repolarization process. Spatial distribution of refractory periods and conduction velocities in the different cardiac tissues, the anisotropy of conduction in the ventricles, and the cycle length dependence of refractory periods and conduction velocities are taken into account. The algorithm calculating the activation process is based on a modified version of Huygen's principle for constructing wavefronts. This study presents simulations concerning the gap phenomenon of the conduction system and the initiation of tachycardias in a heart with Wolff-Parkinson-White syndrome. Results are compared for different basic cycle lengths and for normal and prolonged refractory periods in the His-Purkinje system. The gap phenomenon was found to be present only when using the prolonged refractory periods in the His-Purkinje-system at a cycle length of 700 ms. Induction of tachycardia by a single extrastimulus in the high right atrium in a heart with a bidirectionally conducting accessory pathway is possible by properly timed extrastimuli. The coupling interval of the stimulus for initiating a reentrant tachycardia depends on the cycle length, the conduction velocities and the set of refractory periods used. The same parameters determine whether or not a gap phenomenon in atrioventricular conduction occurs. The model may be useful for investigating similar questions concerning the reentry phenomena of tachycardia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190716
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    A Bidomain Model Based BEM-FEM Coupling Formulation for Anisotropic Cardiac Tissue (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 1229-1243 
    Details
    ISSN: 1573-9686
    Keywords: Electrocardiography ; Forward problem ; Magnetocardiography ; Vortex sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A hybrid boundary element method (BEM)/finite element method (FEM) approach is proposed in order to properly consider the anisotropic properties of the cardiac muscle in the magneto- and electrocardiographic forward problem. Within the anisotropic myocardium a bidomain model based FEM formulation is applied. In the surrounding isotropic volume conductor the BEM is adopted. Coupling is enabled by requesting continuity of the electric potential and the normal of the current density across the boundary of the heart. Here, the BEM part is coupled as an equivalent finite element to the finite element stiffness matrix, thus preserving in part its sparse property. First, continuous convergence of the coupling scheme is shown for a spherical model comparing the computed results to an analytic reference solution. Then, the method is extended to the depolarization phase in a fibrous model of a dog ventricle. A precomputed activation sequence obtained using a fine mesh of the heart was downsampled and used to calculate body surface potentials and extracorporal magnetic fields considering the anisotropic bidomain conductivities. Results are compared to those obtained by neglecting in part or totally (oblique or uniform dipole layer model) anisotropic properties. The relatively large errors computed indicate that the cardiac muscle is one of the major torso inhomogeneities. © 2000 Biomedical Engineering Society. PAC00: 8719Nn, 8719Hh, 8719Ff, 8710+e, 8717Nn
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.1318927
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    Paper (German National Licenses)
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