Bestimmung niedriger Borgehalte in feuerfesten Stoffen und Stahlwerksschlacken

Anpassen des für die Stahlanalyse entwickelten photometrischen Curcuminverfahrens an die Belange der Oxidanalyse. Vergleich mit dem für die Untersuchung von Magnesitprodukten vorgeschlagenen Carminsäureverfahren sowie mit drei weiteren photometrischen Verfahren.     

A knowledge-based system for information management in an automated and integrated manufacturing system

In recent years there has been considerable interest in flexible automation of manufacturing processes in an effort to improve the productivity of manufacturing industry. Central to an integrated, flexible and intelligent manufacturing system is the information management function. The sharing of data is the basis of flexible and intelligent decision-making, the means of integrating the system components, the mode of synchronizing their processes and the method of maintaining the consistency of their states.

It appears that the data management and manipulation function in manufacturing systems is increasingly becoming a bottleneck for further performance improvement of manufacturing systems. New information management systems need to be developed that meet the needs of modern manufacturing systems in terms of efficiency, flexibility, reliability and intelligence. A new model for an integrated manufacturing information system is presented. A double structure of two parallel but independent system is proposed for manufacturing control and manufacturing information management. The objective is to improve service efficiency. representational adequacy, consistency of information and reliability in the information system.     

Some observations on current transfer at iron/calcium fluoride electrodes – Model experiments for current transfer in the ESR process

Measurement of current density-potential curves with direct and alternating current at iron electrodes immersed into CaF₂ or CaF₂/10wt.% CaO slag. Theoretical interpretation of overpotentials in low current range. Dependence of overpotential on FeO content of slag.     

Information content of multiwavelength lidar data with respect to microphysical particle properties derived from eigenvalue analysis

The multiwavelength Raman lidar technique in combination with sophisticated inversion algorithms has been recognized as a new tool for deriving information about the microphysical properties of atmospheric aerosols. The input optical parameter sets, provided by respective aerosol Raman lidars, are at the theoretical lower limit at which these inversion algorithms work properly. For that reason there is ongoing intense discussion of the accuracy of these inversion methods and the possibility of simultaneous retrieval of the particle size distribution and the complex refractive index. We present results of the eigenvalue analysis, used to study the information content of multiwavelength lidar data with respect to microphysical particle properties. Such an analysis provides, on a rather mathematical basis, more insight into the limitations of these inversion algorithms regarding the accuracy of the retrieved parameters. We show that the effective radius may be retrieved to 50% accuracy and the real and imaginary part of the complex refractive index to +/- 0.05 and +/- 0.005i, if the imaginary part is < 0.02i. These results are in accordance with the classic approach of simulation studies with synthetic particle size distributions. Major difficulties are found with a particle effective radius of < 0.15 microm. In that case the complex refractive index may not be derived with sufficient accuracy. The eigenvalue analysis also shows that the accuracy of the derived parameters degrades if the imaginary part is > 0.02i. Furthermore it shows the importance of the simultaneous use of backscatter and extinction coefficients for the retrieval of microphysical parameters.     

Daytime operation of a pure rotational Raman lidar by use of a Fabry-Perot interferometer

We propose to use a Fabry-Perot interferometer (FPI) in a pure rotational Raman lidar to isolate return signals that are due to pure rotational Raman scattering from atmospheric nitrogen against the sky background. The main idea of this instrumental approach is that a FPI is applied as a frequency comb filter with the transmission peaks accurately matched to a comb of practically equidistant lines of a pure rotational Raman spectrum (PRRS) of nitrogen molecules. Thus a matched FPI transmission comb cuts out the spectrally continuous sky background light from the spectral gaps between the PRRS lines of nitrogen molecules while it is transparent to light within narrow spectral intervals about these lines. As the width of the spectral gaps between the lines of the PRRS of nitrogen molecules is -114 times the width of an individual spectral line, cutting out of the sky background from these gaps drastically improves the signal-to-background ratio of the pure rotational Raman lidar returns. This application of the FPI enables one to achieve daytime temperature profiling in the atmosphere with a pure rotational Raman lidar in the visible and near-UV spectral regions. We present an analysis of application of the FPI to filtering out the pure rotational Raman lidar returns against the solar background. To demonstrate the feasibility of the approach proposed, we present temperature profiles acquired during a whole-day measurement session in which a Raman lidar equipped with a FPI was used. For comparison, temperature profiles acquired with Vaisala radiosondes launched from the measurement site are also presented.     

Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 1. system setup and characterization

We describe an instrument for measuring the particle extinction coefficient at ambient conditions in the spectral range from 270 to 1000 nm. It is based on a differential optical absorption spectroscopy (DOAS) system, which was originally used for measuring trace-gas concentrations of atmospheric absorbers in the ultraviolet-visible wavelength range. One obtains the particle extinction spectrum by measuring the total atmospheric extinction and subtracting trace-gas absorption and Rayleigh scattering. The instrument consists of two nested Newton-type telescopes, which are simultaneously used for emitting and detecting light, and two arrays of retroreflectors at the ends of the two light paths. The design of this new instrument solves crucial problems usually encountered in the design of such instruments. The telescope is actively repositioned during the measurement cycle. Particle extinction is simultaneously measured at several wavelengths by the use of two grating spectrometers. Optical turbulence causes lateral movement of the spot of light in the receiver telescope. Monitoring of the return signals with a diode permits correction for this effect. Phase-sensitive detection efficiently suppresses background signals from the atmosphere as well as from the instrument itself. The performance of the instrument was tested during a measurement period of 3 months from January to March 2000. The instrument ran without significant interruption during that period. A mean accuracy of 0.032 km(-1) was found for the extinction coefficient for an 11-day period in March.     

Chemical vapor synthesis of size-selected zinc oxide nanoparticles

ZnO can be regarded as one of the most important metal oxide semiconductors for future applications. Similar to silicon in microelectronics, it is not only important to obtain nanoscale building blocks of ZnO, but also extraordinary purity has to be ensured. A new gas-phase approach to obtain size-selected, nanocrystalline ZnO particles is presented. The tetrameric alkyl-alkoxy zinc compound [CH(3)ZnOCH(CH(3))(2)](4) is chemically transformed into ZnO, and the mechanism of gas-phase transformation is studied in detail. Furthermore, the morphological genesis of particles via gas-phase sintering is investigated, and for the first time a detailed model of the gas-phase sintering processes of ZnO is presented. Various analytical techniques (powder XRD, TEM/energy-dispersive X-ray spectroscopy, magic-angle spinning NMR spectroscopy, FTIR spectroscopy, etc.) are used to investigate the structure and purity of the samples. In particular, the defect structure of the ZnO was studied by photoluminescence spectroscopy.