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71.
Guenter Ahlers 《Journal of Low Temperature Physics》1969,1(6):609-631
In this paper available measurements of the attenuation and dispersion of first sound near the superfluid transition in He4 are re-examined. Particular attention is given to the effect of the gravitational inhomogeneity upon the measurements, and the thermodynamic velocity is used to obtain the dispersion contribution from measured velocities at nonzero frequencies. The re-interpreted results are discussed in terms of current theories. Although there is partial agreement between experiment and theory, a number of aspects of the problem requires further theoretical and experimental investigation. 相似文献
72.
Wilhelm Heitland 《Forschung im Ingenieurwesen》1981,47(5):165-167
Ohne Zusammenfassung
ProfessorWilhelm Heitland, Fachhochschule Bielefeld FBR 3 (Maschinenbau). Lehrgebiet Mathematik. 相似文献
73.
Untersuchung von Eigenspannungen an zwei Stählen mit rd. 1,6% C und einem Gefüge aus Perlit und übereutektoidischem, teilweise netzförmig vorliegendem Zementit nach einachsiger bleibender Dehnung bis zu 2,3% mit röntgenographischen Messungen. Ausbildung von Druckeigenspannungen im Ferrit und Zugeigenspannungen im Zementit. Erklärung der Ergebnisse unter besonderer Berücksichtigung des scheinbaren Ungleichgewichtes zwischen Mikrozug- und -druckeigenspannungen. 相似文献
74.
Sol-gel precipitates of titania were prepared from organometallic precursors, followed by hydrothermal crystallization and spray drying into spherical, micron-size nanostructured granules that were characterized by X-ray diffraction, nitrogen adsorption, and microscopy. A systematic investigation of the effect of hydrothermal processing conditions on the physical properties of the granules was carried out. When the hydrothermal processing time was increased, product granules exhibited larger anatase crystallite size and improved thermal stability in pore structure and phase composition. Increasing the hydrothermal processing temperature retarded crystallite growth and increased the anatase-to-rutile transformation temperature. 相似文献
75.
Ralf?Buscherm?hleEmail author Mark?Br?rkens Ingo?Brückner Werner?Damm Wilhelm?Hasselbring Bernhard?Josko Christoph?Schulte Thomas?Wolf 《Informatik-Spektrum》2004,27(2):146-158
Die Gewährleistung der korrekten
Funktionsweise von Hard- und Software ist ein entscheidender
Faktor bei der heutigen Systementwicklung. Dies trifft ganz
besonders auf das Gebiet der sog. sicherheitskritischen
Systeme zu, bei dem ein Systemversagen Menschenleben gefährden
kann. 相似文献
76.
Zereini F Alt F Messerschmidt J von Bohlen A Liebl K Püttmann W 《Environmental science & technology》2004,38(6):1686-1692
The concentrations and distribution of platinum group elements (Pt, Pd, Rh) in airborne particulate matter were studied in a period of one year from August 2001 to July 2002 in urban and in nonurban areas. Airborne dust samples were collected as a total amount (particles with an aerodynamic diameter <22 microm) and classified using an eight-stage Andersen impactor (<10 microm) at three locations with different traffic density roads in the Frankfurt am Main and nonurban areas. Sampling at the three locations was performed simultaneously for total airborne dust and fractionated airborne dust. Pd was determined by total reflection X-ray fluorescence after Hg coprecipitation. Pt and Rh were analyzed by adsorptive striping voltammetry after HPA digestion. The results show that the PGE concentrations in airborne samples depend on the traffic density. The highest PGE concentrations in air were found in the vicinity of major roads with heavy traffic, and the lowest ones were found in the nonurban area. The presence of PGE at the sampling station relatively free of traffic in a nonurban area hints to a transport of some of the emitted PGE from the city to this station by wind. At all three sampling locations, a heterogeneous distribution of the Pd, Pt, and Rh concentrations during the sampling year can be observed. The sum of PGE concentrations in total airborne dust is comparable with the sum of impactor samples. However, the concentration of Pt and Rh in total airborne dust (<22 microm) is on average higher than in impactor samples (<10 microm). On the contrary, Pd concentration is higher in impactor samples in most cases. The airborne PGE distribution is dominated by Pt, followed by Pd and Rh. The impactor samples are dominated by Pd, followed by Pt and Rh. This fact indicates that palladium occurs mainly in relatively fine airborne particles. The main fraction of PGE is found on average in particle sizes between 1.1 and 4.7 microm. Knowledge of the size distribution of particles containing PGE is important with respect to risk assessment of human inhalation. 相似文献
77.
Entwicklung verschiedener Kalorimeteranordnungen zur Bestimmung des Wärmeinhalts zwischen 0 und 25, 25 und 65, 25 und 1400 und zwischen 25 und 1720 °C. Die mittlere und wahre spezifische Wärme von Schmelzkalk (Kristallkalk). Vergleich der Ergebnisse mit Angaben des Schrifttums über gebrannten Kalk. 相似文献
78.
79.
Bestimmung des Parameters pe′ (tion = 0,5) zur Kennzeichnung der Elektronenteilleitfähigkeit in festen Elektrolyten. Anwendung einer abgewandelten Polarisationsmethode mit EMK-Messung. Angabe der Parameter pe′ für Festelektrolyte aus ZrO2 mit einem Molenbruch xCaO = 0,14 und aus ThO2 mit einem Molenbruch bei Temperaturen zwischen 1200 und 1650 °C. Berechnung korrigierter Eichkurven für die elektrochemische Messung der Sauerstoffaktivitäten in Stahlschmelzen. Empfehlung einer bevorzugten Anwendung von ThO2(Y2O3)-Elektrolyten zur Messung kleinster Sauerstoffaktivitäten. 相似文献
80.
Pauluhn A Rüedi I Solanki SK Schühle U Wilhelm K Lang J Thompson WT Hollandt J 《Applied optics》2001,40(34):6292-6300
Results of an intercalibration between the extreme-ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) are reported. The results of the joint observing program Intercal_01 are described, and intercalibration results up to July 2000 of both SUMER detectors A and B and of the CDS Normal Incidence Spectrometer (NIS) are presented. The instruments simultaneously observed radiance of emission lines at the center of the Sun, and three lines have been chosen for intercomparison: He i 584 A, Mg x 609 A, and Mg x 624 A. Initially the same area was observed by both instruments, but, after restrictions were imposed by the scanning mechanism of SUMER in November 1996, the instruments viewed areas of different sizes. Nevertheless, the temporal correlation between the two instruments remained good through June 1998, when contact with the SOHO spacecraft was lost. Until then the CDS instrument measured (33 ? 5)% and (38 ? 7)% (?1varsigma) higher intensity than SUMER in the He i 584-A line on average for detectors A and B, respectively. Data from SUMER detector B agreed well for Mg x 609 A and Mg x 624 A with the CDS intensities, showing offsets of (2 ? 10)% and (9 ? 15)%, much less than the data of detector A with offsets of (7 ? 8)% and (16 ? 7)% for the two lines, respectively, relative to CDS. Finally, the intercalibration measurements after the loss and recovery of the SOHO spacecraft are analyzed. The data for observations from November 1998 to July 2000 are compared, and it is shown that, although the responses of the instruments have changed, the CDS and the SUMER still perform well, and their temporal correlation is good. 相似文献