High impedance fault detection device tester

High impedance or down conductor power system fault detection devices are now commercially available for evaluation. However, security and dependability of these devices can not be tested using conventional relay test apparatus and procedures. This paper presents a test apparatus and procedures for testing high impedance fault detection devices. The apparatus is capable of playing back, in real-time, waveforms selected from a data library, which includes seventy seven field recordings of high-impedance faults and feeder loads. Each recording is approximately five minutes long and stored in the form of digitized data sampled at 20 kHz     

Immobilisierte Enzyme – Kinetik,Wirkungsgrad und Anwendung

Immobilized enzymes – kinetics, efficiency, and applications. Immobilized enzymes represent an important class of catalysts. They are used in many industrial processes, some of which are economically significant. The introduction of other new processes is to be expected, and some examples are briefly described. Certain conditions have to be satisfied for their practical application. They can be summarized in a set of characteristic parameters or properties. The principal properties of a biocatalyst include its kinetics and its efficiency. Both of these are discussed at length. Possible catalyst designs permitting improvement of efficiency with mass transfer limitation are described.     

Workshop Report: Modeling the Molecular Mechanism of Bacterial Spore Germination and Elucidating Reasons for Germination Heterogeneity

ABSTRACT:  Over the course of 2 days, top researchers in the fields of bacterial spore biology and computational biology discussed approaches to determine the cause of spore germination heterogeneity. Biological and mathematical data gaps were identified, and experimental approaches and computational strategies for modeling spore germination were presented and evaluated. As a result of these interactions, future research directions were defined, the outcome of which should result in a robust model to help define the molecular mechanism(s) of spore germination. Mechanistic understanding of germination will be instrumental for developing novel sterilization, treatment, and decontamination strategies to mitigate threats posed by spores.     

Die zweidimensionale Stromverdrängung in einer wechselstromdurchflossenen,trapezförmigen Nut

Übersicht Es wird in dieser Arbeit die Stromverteilung in einem hinreichend langen, metallischen Stab von trapezförmigem Querschnitt berechnet, der von einem Wechselstrom durchflossen wird und bis auf einen schmalen, von einem magnetischen Wechselfeld erfüllten Luftschlitz von allen Seiten ohne merklichen Luftzwischenraum und isoliert in eine unendlich permeable, metallische Hülle eingebettet liegt. Der Umriß des Leiters mit dem trapezförmigen Querschnitt besteht aus zwei gegenüberliegenden, gleich langen, auseinander-strebenden Geradenstücken, deren Endpunkt oben und unten durch konzentrische Kreisbogen verbunden sind. Die maßgebende partielle Differentialgleichung für die FeldkomponenteE _z (, ) in Richtungz der Längsstreckung eines solchen Nutenleiters entspricht dann der ebenen Wellengleichugn in Zylinderkoordinaten.Nicht streng erfaßbar ist bei Anwendung dieser Methode geradeso wie in den beiden anderen bereits durchgerechneten Fällen, wo es sich um einen rechteckigen oder kreisförmigen Nutenquerschnitt handelt, der Einfluß der Öffnungsweite des Nutenschlitzes in der Oberfläche des Nutenleiters. Ist er hinreichend schmal, so kann die Verteilung der maßgebenden magnetischen Feldkomponente als gleichmäßig angesehen werden. Bei genaueren Rechnungen müßte man über die Fourierkomponenten des Feldes der magnetischen Induktion im Nutenschlitz Bescheid wissen. Diese Annahme wird in der Arbeit gemacht.

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Summary In this paper is reported on the distribution of an alternating current over the trapezoid crosssection of a metallic and sufficiently long conductor, who ist embedded in an infinitely permeable envelop up to a narrow air slit containing an alternating magnetic field, the feeler of the airgapfield between stator and rotor. The contour of the conductor with the trapezoid cross-section is composed here of two equally long opposite but divergent straight lines. The endpoints of which on the two ends are connected by two concentric circular arcs. The decisive partial differential equation for the field componentE _z (, ) in the direction of the conductor corresponds to the two dimensional wave equation in cylinder coordinates.As in the two other cases which are already counted over conformal with this method, namely in the cases of the rectangular and circular cross-section, the influence of the width of the slit is not exactly to realise. In cases which call for more excit calculations, it would be necessary to have knowledge of the Fourier-components of the magnetic induction in the slits of the grooves.

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Übersicht der Abkürzungen und der mathematischen Zeichen E die elektrische Feldstärke in V/m als Betrag des Vektors , - H die magnetische Feldstärke in A/m als Betrag des Vektors , - B die magnetische Induktion oder die Flußdichte in Vs/m² als Betrag von , - ₀ die magnetische Feldkonstante von der Größe 4·10^–9 H/m, die elektrische Leitfähigkeit des Nutenleiters in S/m - =2f die Kreisfrequenz in 1/s - d=(2/₀)^1/2 das Eindringmaß in m - die imaginäre Einheit - eine besondere komplexe Konstante mit der Dimension 1/m - 2 die totale Winkelbreite des keilförmigen Nutenleiters - , ,z die drei Zylinderkoordinaten mit [, ,z] in m - _i , _a die Radien der oberen und unteren Begrenzungskreisbögen des Nutenquerschnitts von Bild 1 in m - 2 der doppelte öffnungswinkel zwischen den Zahnflanken - I (h )K _r (h ) die beiden modifizierten Zylinderfunktionen mit dem Parameter - die beiden, in ihren Richtungen von abhängenden Einheitsvektoren im Zylinderkoordinatensystem - der dritte, stets parallel zurz-Achse gerichtete Einheitsvektor - D _n die Koeffizienten in der maßgebenden Fourier-Entwicklung vonB (, ) in Gl. 2(9) mit der Dimension Vs/m (n=0, 1, 2 ...), - e ^jt das Gesetz der zeitlichen Strom- und Feldänderungen Mit 4 Textabbildungen     

Meßmethoden in Fermentern unter sterilen Bedingungen

Measuring methods for fermentations under sterile conditions . In process development as well as in industrial production it is necessary to obtain information about the state of the process by the measurement of characteristic variables. This is true for bioengineering in the same way as for chemical processes in general. Characteristic variables to be taken into consideration include temperature, pressure, masses and mass-flow rates, operating parameters such as liquid level and impeller speed, and especially the concentrations of reactants, intermediates, and products. In contrast to other processes, a particular problem exists in fermentation because introduction of microorganisms, into the system by the measurement has to be prevented. Since taking samples from the reactor is hardly suitable for controlling the process for various reasons (amount of work, loss of time), this review considers only those methods which can be used for measurements directly in the fermentor. Essentially these are physical and physico-chemical methods, e. g. for concentrations (O₂ and CO₂ in gas and liquid phase, pH, biomass). Of special interest for future development are spectroscopic and enzymatic methods for fast determination of substrates and of important intermediates and products. Here the sterility required entails special problems in the case of enzyme electrodes. Important information on the state of the process can, of course, also be obtained from physical variables, such as gas hold-up, bubble size, viscosity, and turbulence properties of the medium. These variables are less critical with regard to sterility.