Füllstandsmessung mit Streustrahlungssonden

Es wird die Abhängigkeit der Impulsdichte vom Füllstand bei Meßanordnungen mit γ-Streustrahlungssonden verschiedener Länge untersucht. Verwendet werden die Nuklide ⁶⁰Co und ¹³⁷Cs. Ein nahezu linearer Anstieg der Impulsdichte mit dem Füllstand wird bei Füllgütern kleiner Ordnungszahl nur bei Sondenlängen L ≥ μ₀ ^?1.erzielt. Der Einfluß des Schüttwinkels und der Dichte des Füllgutes wird diskutiert.     

Probenchemische Methode zur Bestimmung von 15N an in Gesteinen fixiertem Stickstoff

Zur Klärung geologischer Prozesse werden in zunchmendem Maße die Isotopenvariationen des Stickstoffs herangezogen. Da der größte Teil des Stickstoffs der Gesteine in gebundener Form als Ammoniumstickstoff [1–6] vorliegt, kommt der Untersuchung der Isotopenvariationen desselben eine große Bedeutung zu.     

Über den Einfluß von Isotopieeffekten auf die Verbreitung der Isotope in der Natur

Die Isotopenzusammensetzung der chemischen Elemente in ihren natürlichen Vorkommen wird von kernphysikalischen Vorgängen, vom Einfall extraterrestrischer Materie und, namentlich bei den leichten Elementen (etwa bis zum Chlor), von kinetischen und thermodynamischen Isotopieeffekten beeinfluβt. Deshalb ist die Kenntnis der in der Natur wirkenden Isotopieeffekte eine entscheidende Voraussetzung für das Verständnis der Gesetzmäβigkeiten der Verbreitung der Isotope in der Natur und für die Anwendung dieser Gesetzmäβigkeiten als Mittel der geo- und kosmoswissenschaftlichen Forschung und der Umweltforschung [1].     

透射强度比X射线荧光光谱法测定金属镀层组分

本文介绍了X射线荧光光谱透射强度比测定中等可变厚度金属镀层的组分方法。采用镀层元素强度和基片透射强度之比对镀层元素镀布分量制作工作曲线。     

Synthesis methods of multiple phase-cycled SSFP images to reduce the band artifact and noise more reliably

The band artifact in steady-state free precession can be reduced by synthesizing the multiple images obtained through different phase increments of successive radiofrequency pulses. Even though the complex summation method was reported to be effective in reducing the band artifact, it has the pitfalls of intensity abnormality and sensitivity to the phase abnormality. Two new methods have been developed for more reliable reduction of the band artifact than the complex summation method. One method is to sum the complex images partially and to take the maximum intensity of the partially summed images. The other method is to sum the free induction decay (FID) and primary echo components of the Fourier series that are obtained through Fourier analysis of the complex base images. Both proposed methods were compared with other magnitude (maximum intensity projection, spectrally decomposed synthesis, sum-of-squares, nonlinear averaging) and complex-based (complex summation, magnitude-weighted complex summation) methods experimentally at 3 T for the phantom and volunteer's head imaging. Both proposed methods were confirmed to maintain the advantage of the complex summation in reducing both the dark and bright band artifacts while reducing the intensity abnormality and sensitivity to the phase abnormality from that of the complex summation method over a wide range of flip angles and relaxation times.     

循环倍率对动力和液体燃料多联产系统的电与蒸汽自平衡影响分析

本文以煤气化(240万吨/年)动力,液体燃料(甲醇,醋酸,醋酐)多联产系统(串联式)为研究对象,分析了循环倍率对系统动力输出、蒸汽、液体燃料产量的影响;确定了可满足具有不同优先级的目标、达到系统动力和蒸汽自平衡的循环倍率、燃气轮机选型等关键单元和系统参数。     

Spectral indices to assess the carotenoid/chlorophyll ratio from adaxial and abaxial leaf reflectance

The ratio between the carotenoid and chlorophyll concentrations can indicate the physiology and phenology of plants. Most of the vegetation indices related to the ratio between the carotenoid and chlorophyll contents only consider the reflectance from the adaxial leaf surface. In this study, it was found that the leaf reflectance from the abaxial surface is lower than that of the adaxial surface in the visible wavelength region. On the contrary, the reflectance is higher on the adaxial surface in the near-infrared wavelength region. The difference ratio index resulted in the best correlation with the carotenoid/chlorophyll ratio and was the most robust among all the spectral indices studied when the spectral information on the adaxial and abaxial surfaces was pooled. The result indicated that this index can accurately estimate the carotenoid/chlorophyll ratio because of the insensitivity to the differences between adaxial and abaxial leaf surfaces.     

Synthesis and characterization of nanostructured strontium hexaferrite thin films by the sol–gel method

Nanostructured single phase strontium hexaferrite, SrFe₁₂O₁₉, thin films have been synthesized on the (100) silicon substrate using a spin coating sol–gel process. The thin films with various Fe/Sr molar ratios of 8–12 were calcined at different temperatures from 500 to 900 °C. The composition, microstructure and magnetic properties of the SrFe₁₂O₁₉ thin films were characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetry, X-ray diffraction, electron microscopy and vibrating sample magnetometer. The results showed that the optimum molar ratio for Fe/Sr was 10 at which the lowest calcination temperature to obtain the single phase strontium hexaferrite thin film was 800 °C. The magnetic measurements revealed that the sample with Fe/Sr molar ratio of 10, exhibited higher saturation magnetization (267.5 emu/cm³) and coercivity (4290 Oe) in comparison with those synthesized under other Fe/Sr molar ratios.     

Study of scalar meson a0(980) from B→a0(980)π decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0, a0+(980)π-, a0-(980)π and B- →a00(980)π-, a0-(980)π0 by employing the perturbative QCD (pQCD) factorization approach at the leading order. We found that (a) the pQCD predictions for the branching ratios are around (0.4 - 2.8) × 10-6, consistent with currently available experimental upper limits; (b) the CP asymmetries of B0→ao(980)π0 and B-→a0-(980)π0 decays can be large, about (70-80)% for α = 100°.     

Schnell-Methode zur Umsetzung von Kohlenwasserstoffen zu Wasserstoff für die Isotopenanalyse

Es wird eine weiterentwickeltes, isotopenanalytisches Verfahren zur probenchemischen Umsetzung von Kohlenwasserstoffen mit Chromium zu Wasserstoff bei 1300 K vorgestellt. Die erzielten Testergebnisse zeigen anhand der gemessenen δD-Werte, daβ Quarzöfen bei diesen Temperaturen noch keine die Isotopenmeβwerte beeinflussende Diffusion von Wasserstoff durch die Wandung zulassen. Auβerdem erfolgte die Reaktion nahezu spontan und vollständig, was die Methode zeitlich sehr effektiv macht.

A modified isotope analytical method is presented for the chemical reaction of hydrocarbons with chromium at 1300 K to form hydrogen. The test results obtained (i.e. the measured δD-values) show that at this temperature quartz heating tubes do not allow hydrogen to diffuse through the wail, which fact would influence the isotopic composition. Furthermore the reaction proceeds nearly spontaneously and quantitatively, which yields an effective method, especially with respect to time.