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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Electrical engineering 74 (1990), S. 69-77 
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Übersicht Dieser Artikel beschreibt ein vollständiges digitales Steuerungssystem für Standard-Induktionsmotoren. Ein neues Wechselrichter-Spannungsvektor-Steuerungssystem für Hochfrequenzschaltung und ein prädiktives Frequenz-Spannungs-Steuerungssystem, das den Bedarf von Tacho-Rückmeldung eliminiert, ist entwickelt worden. Außerdem wurde ein selbsteinstellendes Parameteranpassungsverfahren entwickelt. Dieses Verfahren nimmt Rücksicht auf die große Variation der elektrischen Parameter verschiedener Fabrikate von Standard-Induktionsmotoren. Für Überwachungszwecke sind Schaltschutz, Minimierung des Schaltverlustes und anwendungsspezifische integrierte Schaltungen vielfach benutzt worden. Die stationären und dynamischen Verhältnisse der Antriebe werden dokumentiert und durch Simulationen verglichen.
    Notes: Contents This paper describes a completely digital control system for standard induction motors. A new inverter voltage vector control system for high frequency switching has been designed, and a predictive frequency-voltage control system that eliminates the need of tacho feedback has been developed. In addition, an adaptive parameter tuning method has been developed. This method takes the large variation in electrical parameters of standard induction motors of different manufactures into account. For control purposes, switch protection and switch loss minimizing, custom designed application specific integrated circuits have been used extensively. Steady-state and dynamic performances of the drive are documented and compared to simulations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Time versus concentration data of selected volatile organic compounds (VOCs) emitted from four pre-conditioned building materials were measured in the Field and Laboratory Emission Cell (FLEC) at three air exchange rates, 171, 342, 684 h−1, respectively, during a period of 240 hours. The materials were a carpet, a linoleum, a water-borne paint, and a sealant. Modeling of the time versus concentration data for two air exchange rates showed that the emission of VOCs from the carpet were best described with a diffusion model in which the diffusion coefficient depends on the concentration gradient for all data (exponential diffusion model), while a reduced data set eliminating initial events also could be described with a first order decay incorporating a sink effect. The paint emission data of the polar semi-VOC, Texanol, could be described with a first order decay model incorporating a sink effect for all three air exchange rates. The emission rate constant doubled by doubling the air exchange rate. The emission data for VOCs from the sealant were best described for all three air exchange rates by the exponential diffusion model. The best model correlation fit was obtained for hexane, but satisfactory results were also obtained for 2-ethylhexanol and dimethyloctanols. The decay results of linoleum did not allow for modeling leading to the conclusion that an internal concentration gradient had not yet been established under the experimental conditions
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 38 (1990), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3338-3339 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The dc operation of some laser diodes produces high-frequency amplitude modulation of the laser output in the GHz frequency range. This phenomenon provides a simple and inexpensive method for checking the sweep linearity of a fast-gated streak camera.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2843-2845 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A LIDAR–Thomson scattering system with better than 5 cm spatial resolution to resolve edge electron temperature and density gradients in H-mode operation in JET is needed. A dynamic range in measurable electron temperature of 0.1–1.5 keV and a minimum detectable electron density of 1019/m3 are required. To achieve these levels of performance, it is planned to use a modified section of the existing JET LIDAR–Thomson scattering system. A new detection system, consisting of a streak camera and an intensifier unit, will be used. Spectral dispersion is to be performed by a three-channel edge filter spectrometer. Recording and digitization of the scattered signal will be performed by a CCD camera read out by a personal computer. The system is described and results of experiments to determine the minimum visible light levels using a commercial streak camera, intensifier unit, and CCD camera and a pulsed laser diode light source are briefly presented. In addition, simulations of expected signal-to-noise ratio performance are discussed.
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  • 6
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method has been developed to identify and estimate systematic error in the calibration of Thomson scattering systems. The basis of the technique is an iterative recalculation of electron temperature using successively more self-consistent calibrations. A computational method was developed to calculate from a large dataset a calibration correction factor for each channel. The correction factor was then applied and the fitting routine rerun on the whole dataset with the new calibration factors. The resulting frequency distribution of chi-squared values was close to the theoretical distribution while the calculated electron temperatures were changed by only 1 to 2%. The technique succeeded in identifying and quantifying errors in a dataset known to be of poor quality.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2460-2463 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using the stimulated Brillouin scattering phase conjugation and pulse compression technique, a conventional long pulse ruby laser was successfully converted to give 300 ps pulses at 1 J energy level. The technique allows the use of smaller amplifiers than required in a conventional short pulse laser which in turn leads to operation at increased repetition rate. The completed laser when operated at 1.5 Hz produces stable output parameters. Each laser pulse is characterized by a sharp rise and a measured pre-pulse level of less than 10−6 of the main pulse, making it suitable for LIDAR Thomson scattering measurements.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2926-2928 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The existing single point Thomson scattering apparatus on JET has been modified to allow measurements of local magnetic fields. Multiviewing access will be provided by axicone optics, giving a scattering angle of about 4°, and should provide an accuracy of better than 10% in measuring Bpol over most of the plasma radius. A Fabry–Perot spectrometer will detect the scattered spectra, modulated at the electron gyrofrequency, using a gated image intensifier and a cooled CCD camera. The location of an interference partial fringe will give the magnetic field vector at a particular position in the plasma. From the locus of such partial fringes, the q profile may be determined.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 41 (1994), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: South of the Caledonian Brabant-Wales Massif a more than 200 m thick Tournaisian to Lower Visean replacive dolomite unit can be followed for several hundred kilometres from the Boulonnais (France) to Aachen (Germany). Field observations, of features such as karst cavities occurring at the top of the Lower Visean dolomite which are filled by Lower Visean crinoidal limestone, indicate that dolomitization and karstification took place during the Early Visean. This early development of the dolomite is in agreement with the presence of stylolites cutting the dolomite fabric. The minor element composition of the majority of the dolomites remains almost uniform throughout the entire studied area. Values for Fe, Mn, Na and Sr are normally in the range 700–4700 ppm, 15–400 ppm, 80–300 ppm and 50–200 ppm, respectively. The δ13C values (range-0.72 to +5.31%o) mainly reflect the carbon isotopic composition of the precursor limestones. The δ18O values, in contrast, are highly variable: ranging from-19.15 to +0.85%o. This rather large range of δ18O values is explained by multiple-step re-equilibration/recrystallization during progressive burial and subsequent uplift of the dolomites. These processes are also responsible for the high 87Sr/86Sr values of the dolomites which range from about 0.7088 to 0.7098. They are distinctly more radiogenic than Lower Visean marine carbonates (0.7076–0.7078). Correlation, however, of δ18O values or 87Sr/86Sr ratios with dolomite and/or cathodoluminescenec (CL) textures has not been very successful. This suggests that recrystallization may remain unrecognized if only petrographic techniques are used. Nevertheless, certain CL textures can be related to specific interactions with the ambient recrystallizing fluids.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 932-934 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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