Algorithmen zur Pulsweitenmodulation für Wechselrichter mit in Echtzeit berechnetem Pulsmuster

Übersicht Mit Hinblick auf die zunehmend Verbreitung findende Pulsmusterberechnung in Echtzeit werden in dem Aufsatz Gesichtspunkte diskutiert, die sich aus den Eigenschaften des leistungselektronischen Stellgliedes, des Pulswechselrichters, ergeben. Die bei Abtastregelungen für die Dauer einer Abtastperiode konstante Stellgröße muß bei ihm durch Pulsweitenmodulation in ein Pulsmuster mit konstanter Amplitude und Pulsen variabler Breite umgesetzt werden. Durch ein neues Verfahren mit versetzter Abtastung haben dabei Rechentotzeiten bis zur Dauer einer halben Abtastperiode keinen Einfluß mehr auf das Pulsmuster.

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Algorithms for pulswidth modulation of inverters with online calculated pulse patterns

Contents Online calculation of pulse patterns will be employed more intensively in the future. Aspects concerning the powereleotronic circuit, the pulsewidth-modulated inverter, are to be discussed. The set value being constant for the duration of a sampling interval, has to be converted by a modulation algorithm into a pulse pattern with constant amplitude and pulses of variable width. Calculation dead-times up to half of sampling interval have no influence on the pulse pattern when using a new algorthm with shifted sampling instants.

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Herrn Prof. Dr.-Ing. Klemens Heumann zum 60. Geburtstag gewidmet     

Finite difference time-domain analysis of planar microwave circuits

Contents The application of finite difference time domain analysis techniques to planar microwave integrated circuit design is discussed. It is shown that using this technique, three-dimensional discontinuity problems in planar microstrip and coplanar circuits can be analyzed in a full-wave approach.

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Finite-Differenzen-Analyse von planaren Mikrowellen-schaltungen im Zeitbereich

Übersicht Es wird die Anwendung der Finiten-Differenzen-Analyse elektromagnetischer Felder im Zeitbereich auf den Entwurf integrierter Mikrowellenschaltungen diskutiert. Es wird gezeigt, daß durch Anwendung dieser Technik eine Lösung der Beschreibungsprobleme für dreidimensionale Schaltkreis-Diskontinuitäten in planarer Mikrostreifenleitungstechnik und in koplanarer Leitungstechnik unter Berücksichtigung der vollen Welleneigenschaften gefunden werden kann. Verschiedene Beispiele von Analysen planarer Mikrowellenbauelemente werden diskutiert und die Ergebnisse mit Messungen verglichen.

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Dedicated to Prof. Dr.-Ing. Herbert Döring on the occasion of his 80th birthday     

Shape optimization of inclined ribs as heat transfer augmentation device

This work presents numerical optimization techniques for the design of a rectangular channel with inclined ribs toenhance turbulent heat transfer.The response surface method with Reynolds-averaged Navier-Stokes analysis isused for optimization.Shear stress transport turbulence model is used as a turbulence closure.Computational re-sults for local heat transfer rate show a reasonable agreement with the experimental data.Width-to-rib height ratioand attack angle of the rib are chosen as design variables.The objective function is defined as a linear combina-tion of heat-transfer and friction-loss related terms with the weighting factor.Full-factorial experimental designmethod is used to determine the data points.Optimum shapes of the channel have been obtained in a range of theweighting factor.     

Einflüsse von Triazolapplikationen auf Kornertrag und -qualität von Winterraps

Effects of Growth Substance Applications (Triazole) on Yield Formation and Grain Quality of Winter Rape Field trials have been conducted for two years (1986/87 and 1987/88) with cv. Lirabon (low erucic acid and low glucosinolate content). At several growth stages uptil beginning of flowering and at different rates the triazole RSW 0411 (Bayer) was applied. The problem was to investigate growth regulator effects on agronomically important traits, the utilization of yield potential and on seed quality. Applications during stem elongation reduced plant height phoma lingam infestation and lodging. Branching and numbers of pods/plant increased, partly on costs of pod filling. In 1986/87 grain yields/ha indicated (not significant) increases without any effects on grain quality. In 1987/88 grain yield/ha decreased significantly combined with increasing protein- and glucosinolate contents.     

Adsorption of soy oil free fatty acids by rice hull ash

Studies demonstrated that free fatty acids can be adsorbed from a soybean oil/hexane miscella by inorganic rice hull ash. A 1% dose was effective in diminishing free fatty acid concentrations but acid activation reduced the adsorption. Binding of free fatty acids followed a Freundlich isotherm with smaller doses of ash adsorbing more efficiently. Addition of isopropanol to the miscella promoted the adsorption, while water deactivation of the ash had no effect, possibly because water occupied sites not accessible to free fatty acids. Impaired adsorption behavior of ash heated above 700°C could have been due to disruption of the crystal form. The adsorption behavior of rice hull ash may be more fully understood with a better knowledge of adsorbent structure.     

Expert system applications in software engineering

This paper presents an overview of research in expert systems and artificial intelligence as they relate to software engineering. The paper begins with a review of current thinking regarding the software process. This is followed by a discussion of artificial intelligence (AI) and the paradigms it uses. Six current projects are described: three are concerned with programming in the large and three with programming in the small. These six projects provide a representative sample of the AI research now underway in the software engineering domain. The paper concludes with some observations regarding when and how the concepts represented by these projects will be available for application to operational projects.     

Heterodyne performance of a quasioptical Schottky diode detector: Theoretical and experimental results

A detailed theoretical and experimental study of the heterodyne performance of a quasioptical Schottky diode detector is presented. The experimental results have been obtained by mixing the radiation from a FIR laser with the output of a 67–73 GHz Klystron. The heterodyne signal variation versus various parameters and its relation to the special case of two lasers mixing are described. The mixer characteristics are a NEP value of 2×10^?19W/Hz and a detector bandwidth of at least 9 GHz. Experimental evidence of harmonics generation of submillimetric frequencies at the diode junction is also presented.     

Algorithm 45. Automatic computation of improper integrals over a bounded or unbounded planar region

An automatic quadrature algorithm especially designed for double integration of functions with some form of singular behaviour on the boundary of the integration region is described, and its FORTRAN code is presented. The algorithm is based on the use of the product trapezoidal rule, after a non-linear transformation of the integrand in both variables renders a new integrand function whose derivatives vanish on the (transformed) boundary. Numerical results demonstrate the ability of the algorithm to obtain high accuracies in dealing automatically with pathological singularities of non-specific types.     

Computing turning points of curves implicitly defined by nonlinear equations depending on a parameter

Let the space curveL be defined implicitly by the (n, n+1) nonlinear systemH(u)=0. A new direct Newton-like method for computing turning points ofL is described that requires per step only the evaluation of one Jacobian and 5 function values ofH. Moreover, a linear system of dimensionn+1 with 4 different right hand sides has to be solved per step. Under suitable conditions the method is shown to converge locally withQ-order two if a certain discretization stepsize is appropriately chosen. Two numerical examples confirm the theoretical results.     

Schrankentreue Berechnung der Exponentialfunktion wesentlich-nichtnegativer Matrizen

An algorithm is proposed for computation of the exponential of a matrixX which uses the well known continued fraction expansion of tanhX. ForX essentially-nonnegative the following is proved: In interval arithmetic the algorithm is feasible, numerically convergent and bound conserving; after possibly a few initial steps it gives alternatively lower and upper bounds to the exact result.