Über die Verzerrung der Spannung bei Hochspannungsprüfsätzen

Zusammenfassung Das neue Me\verfahren benutzt unmittelbar die Verzerrung der Spannung eines Generators für die Bestimmung der Ursachen dieser Verzerrung; es ergibt also das klarste, mögliche Bild. Das Verfahren ergibt, da\ die für die Verzerrung ma\gebende Generatorinduktivität genügend genau mit der Streuinduktivität Übereinstimmt, die mit den bekannten Verfahren bestimmt wird. Ferner zeigt sich, da\ das inverse Feld bei vielen Generatoren einen unerwartet gro\en Einflu\ ausübt. Durch einen Kunstgriff gelingt es allerdings, das inverse Feld nach Belieben teilweise oder völlig auszuschalten. Da die 3. Harmonische in der Spannung, die vom inversen Feld herrührt, in vielen Fällen der durch die Streuung hineingebrachten Oberschwingung entgegen wirkt, gelingt es sogar, die Gesamtverzerrung der Spannung auf Null zu bringen. Ob das unter allen Umständen möglich ist, mu\ durch weitere Untersuchungen geklärt werden.Herrn Prof. Dr. Schering danke ich für die Anregung zu der vorliegenden Arbeit sowie für die stete Förderung, die er ihr zuteil werden lie\.     

Comparative emission analysis of low-energy and zero-emission buildings

Different designs and concepts of low-energy and zero-emission buildings (ZEBs) are being introduced into the Norwegian market. This study analyses and compares the life cycle emissions of CO₂ equivalents (CO₂e) from eight different single-family houses in the Oslo climate. Included are four ZEBs: one active house, two passive houses, and a reference house (Norwegian building code of 2010). Monthly differences in CO₂e emissions are calculated for the seasonally sensitive Norwegian context for electricity generation and consumption. This is used to supplant the previous applied symmetric weighting approach for CO₂e/kWh factors for import and export of electricity for the ZEB cases. All the ZEBs have lower use-stage emissions compared with the other buildings or the reference case. Embodied impacts are found to be 60–75% for the analysed ZEB cases, confirming the importance of embodied impacts in Norwegian ZEBs. The lowest total emissions were from the smallest ZEB, emphasizing area efficiency. The highest emissions were from the reference case. By abandoning the symmetric approach, a new perspective was developed for assessing the performance of ZEBs within the Norwegian context. One of four ZEB cases managed to balance out its annual energy-related emissions.     

Space-multiplexed multifocal nonlinear microscopy

Standard forms of nonlinear microscopy rely on single beam scanning, but the usually weaker signal and the need to image in real-time call for parallelization of the image formation. Since the nonlinear susceptibilities necessitate a comparatively large illumination power, with current laser systems the brightness or field of view of any parallelized nonlinear microscope is limited by the brightness of the laser. For example, by producing an array of high aperture foci, multifocal multiphoton microscopy (MMM) provides real-time, light-efficient three-dimensional fluorescence imaging at high-resolution. The available power limits the degree of parallelization and hence codetermines the field of view. As the utilization of all the laser power is imperative, the focal intensity can be adjusted only through altering the number of foci. This compromises to some extent the flexibility to adjust the focal intensity to benign and effective levels. Here we introduce space-multiplexing (SMX) as a novel option in parallelized nonlinear microscopy, which enables an improved exploitation of the total laser power and facilitates changing the intensity levels in selected regions, without attenuating the total laser power. The basic idea of SMX is to overlap arrays of slightly offset coherent focal fields whose interference modulates the intensity across the sample. For a given degree of parallelization and power, SMX increases the two- and three-photon excited signal of parallelized nonlinear microscopy by a factor of up to 1.5 and 2.5, respectively. To some extent, sensitive regions may be spared out, whereas in regions with weaker nonlinear susceptibilities the intensity is increased. SMX is relevant to all modes of nonlinear microscopy, including parallelized second- and third-harmonic imaging, coherent anti-Stokes Raman scattering, and widefield multiphoton excitation.     

Fundamental modeling of environmental cracking for improved design and lifetime evaluation in BWRs

An approach for improved design and lifetime evaluation of environmental cracking is presented based on fundamental modeling of the underlying processes operative in crack advance. In outlining this approach and its application in energy industries, the requirements for a life prediction methodology will be highlighted and the shortcomings of the existing design and lifetime evaluation codes will be discussed. Examples will be given of its use in a variety of cracking systems, such as stainless steels and nickel alloys in hot water, and irradiation assisted stress corrosion cracking.     

Synthetic aperture focusing for a single-element transducer undergoing helical motion

This paper describes the application of 3-D synthetic aperture focusing (SAF) to a single-element trans-rectal ultrasound transducer. The transducer samples a 3-D volume by simultaneous rotation and translation, giving a helical motion. Two different 3-D SAF methods are investigated, a direct and a two-step approach. Both methods perform almost identically for simulated scatterers and give a significant improvement in azimuth resolution and a constant resolution in elevation. Side lobes below -60 dB are achievable for both methods. Validation of the method is achieved by scanning a simple wire phantom and a complex phantom containing wires in azimuth and elevation. The simple wire phantom shows the same results as that found through simulation. The complex phantom shows simultaneous focusing in azimuth and elevation for the wire scatterers. Consideration of the processing requirements for both 3-D SAF methods shows that the two-step approach can give equivalent performance using an order of magnitude fewer calculations. This reduction requires a temporary storage of 9.1 GB of data for the investigated setup.     

The stress-corrosion-cracking model for high-level radioactive-waste packages

A stress-corrosion cracking (SCC) model has been adapted for performance prediction of high-level radioactive-waste packages to be placed in the proposed Yucca Mountain repository. For these waste packages, the outer barrier material is the highly corrosion-resistant alloy UNS-N06022 (alloy 22). The tensile stress is principally from weld-induced residual stress. To account for crack propagation, the slip dissolution/film rupture (SDFR) model is adopted to provide mathematical formulae for prediction of the crack growth rate. Once the crack growth rate at an initiated SCC is determined, it can be used to determine the time to through-wall penetration for the waste package. This paper presents the development of the SDFR crack growth rate model. A seismic-damage-related SCC crack opening area density model is also briefly described. For more information, contact P.L. Andresen, GE Global Research, One Research Circle Schenectady, NY 12309; e-mail: andresen@crd.ge.com.     

Die numerische Behandlung eines Schrankenverfahrens mit Anwendung auf axialsymmetrisches Stauchen

Zusammenfassung Das Stauchen einfacher axialsymmetrischer Proben wird mit Hilfe des Verfahrens von der oberen Schranke untersucht. Die angegebene numerische Methode, ein iteratives Ritz-Verfahren für mehrparametrige Ansatzfunktionen, liefert bessere Schranken für die Stauchkraft als vergleichbare Verfahren in der Literatur. Zudem erhält man eine gute Approximation des momentanen Geschwindigkeitsfeldes und kann damit den Verlauf der Umformung schrittweise verfolgen. Das angegebene Verfahren läßt sich durch Wahl geeigneter Ansatzfunktionen sinnvoll auf andere Umformprozesse anwenden.

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Numerical Evaluation of an Upper Bound Theorem with Application to Axisymmetric Compression

Summary The compression of simple axisymmetric specimen is treated by means of the upper bound theorem. An iterative Ritz-method, proposed in this paper, yields better upper bound loads than comparable methods known in literature. Moreover, a good approximation of the instantaneous velocity field is derived. Using this field the non-stationary deformation is examined step by step. By choosing a proper system of functions for the velocity field the given method well applies to other forming processes.

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Mit 7 Abbildungen     

Berechnung des Kegeldruckversuches mit einer Finite-Element-Methode

Anwendung eines verallgemeinerten Schrankenverfahrens für starrplastische Umformung mit der Methode der finiten Elemente auf das Kegelstauchen. Bestimmung des Stauchdruckes in Abhängigkeit von der Geometrie und von der Werkstoffeigenschaft und Vergleich mit Versuchsergebnissen.