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Analysis of Particle Rearrangement during Sintering by Micro Focus Computed Tomography (μCT)
Nothe M.,Schulze M.,Grupp R.,Kieback B.,Haibel A.,Banhart J. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The decrease of the distance between particle centers due to the growth of the sinter necks can be explained by the well known two-particle model. Unfortunately this model fails to provide a comprehensive description of the processes for 3D specimens. Furthermore, there is a significant discrepancy between the calculated and the measured shrinkage because particle rearrangements are not considered. Only the recently developed analysis of the particle movements inside of 3D specimens using micro focus computed tomography (μCT), combined with photogrammetric image analysis, can deliver the necessary experimental data to improve existing sintering theories. In this work, μCT analysis was applied to spherical copper powders. Based on photogrammetric image analysis, it is possible to determine the positions of all particle centers for tracking the particles over the entire sintering process and to follow the formation and breaking of the particle bonds. In this paper, we present an in-depth analysis of the obtaine data. In the future, high resolution synchrotron radiation tomography will be utilized to obtain in-situ data and images of higher resolution.
Vaporization and Diffusion Studies on the Stability of Doped Lanthanum Gallates
Stanislowski, M.,Peck, D.-H.,Woo, S.-K.,Singheiser, L.,Hilpert, K.,Schulz, O.,Martin, M. WILEY-VCH 2006 FUEL CELLS -WEINHEIM- Vol.6 No.3
<P>Vaporization and diffusion determine the stability of doped lanthanum gallates under SOFC operating conditions. Systematic vaporization studies of Ga and other elements were carried out using the vapor transpiration method. It was shown that the Ga vaporization is controlled by diffusion from the bulk to the surface. Diffusion coefficients D<SUB>Ga</SUB> and vaporization coefficients &agr;<SUB>Ga</SUB> were determined by fitting the measured vaporization data to a vaporization model. Secondary phases formed as a result of the vaporization were detected. The influence of different doping levels of Sr, Mg and Fe on the Ga vaporization was elucidated. Moreover, cation self-diffusion of <SUP>139</SUP>La, <SUP>84</SUP>Sr and <SUP>25</SUP>Mg as well as cation impurity diffusion of <SUP>144</SUP>Nd, <SUP>89</SUP>Y and <SUP>56</SUP>Fe in polycrystalline samples of doped lanthanum gallate were directly determined for the composition La<SUB>0.9</SUB>Sr<SUB>0.1</SUB>Ga<SUB>0.9</SUB>Mg<SUB>0.1</SUB>O<SUB>2.9</SUB> as an example, from diffusion profiles determined by SIMS. It was found that diffusion occurs by means of bulk and grain boundaries. The bulk diffusion coefficients are similar for all cations with activation energies which are strongly dependent on temperature. The results are explained by a frozen-in defect structure at low temperatures in the ABO<SUB>3</SUB> perovskite lattice and by proposing a defect cluster containing cation vacancies in the A and B sublattices, as well as oxygen vacancies.</P>
Reiff, William M.,Schulz, Charles E.,Whangbo, Myung-Hwan,Seo, Jung In,Lee, Yoon Sup,Potratz, Gregory R.,Spicer, Charles W.,Girolami, Gregory S. American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.2
<P>Mossbauer, EPR, magnetic susceptibility, and DFT studies of the unusual two-coordinate iron(II) amide Fe[N(t-Bu)(2)](2) show that it retains a linear N-Fe-N framework due to the nonbonding delta nature of the (xy, x(2)-y(2)) orbitals. The resulting near-degenerate ground state gives rise to a large magnetic moment and a remarkably large internal hyperfine field. The results confirm that extraordinary orbital magnetic effects can arise in linear transition metal complexes in which orbital degeneracies are not broken by Jahn-Teller or Renner-Teller distortions.</P>
Neu, V,Schulze, C,Faustini, M,Lee, J,Makarov, D,Suess, D,Kim, S-K,Grosso, D,Schultz, L,Albrecht, M IOP Pub 2013 Nanotechnology Vol.24 No.14
<P>Magnetization reversal processes in Co/Pt multilayers prepared on nanoperforated templates are probed by magnetization relaxation measurements. The signature of pinning controlled domain wall movement as expected for percolated media is identified. This contrasts with the nucleation-type reversal mechanism of a Co/Pt reference film prepared on a smooth substrate. A zero field energy barrier of 93<I>k</I><SUB>B</SUB><I>T</I> is determined by fluctuation field measurements and is elucidated by micromagnetic calculations using the nudged elastic band method. This value is sufficiently large to qualify the material as a promising percolated medium.</P>
Fault Tolerant Operation of the Modular High Frequency Converter
A. Mayer,M. Schulz,C. Rolff,R. Marquardt 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Fault tolerance of converters and drive systems is becoming a key issue for many future applications. The Modular High Frequency Converter (MHF) is a new inverter topology, especially designed for applications, where high reliability and ultra-light weight are important. Besides superior dynamic behavior, continuous operation after defects is one of the main advantages of the Modular High Frequency Converter. Considering fault tolerant operation, different failure scenarios and possible countermeasures are analyzed in this paper. A new control concept, supporting the capability of fault tolerant operation is introduced. Simulation and operating results of the first laboratory prototype prove the fault ride through capability of the presented topology.
Progressive Multifocal Leukoencephalopathy after Ibrutinib Therapy for Chronic Lymphocytic Leukemia
Mathias Lutz,Arik B. Schulze,Elisabeth Rebber,Stefanie Wiebe,Tarek Zoubi,Oliver M. Grauer,Torsten Keßler,Andrea Kerkhoff,Georg Lenz,Wolfgang E. Berdel 대한암학회 2017 Cancer Research and Treatment Vol.49 No.2
Progressive multifocal leukoencephalopathy (PML) is a devastating neurological disease observed nearly exclusively in immunocompromised patients. Recently, the introduction of monoclonal antibodies significantly inhibiting the immune system such as rituximab has led to an increase in PML cases. Although rituximab-based immunochemotherapy remains the standard of treatment for chronic lymphocytic leukemia (CLL), the importance of Bruton’s tyrosine kinase inhibitors such as ibrutinib is steadily increasing. However, long-term experiences regarding possible side effects of these new substances are rare. Here, we report the development of eventually fatal PML possibly associated with ibrutinib therapy for CLL after multiple prior treatment lines, including rituximab. To the best of our knowledge, this is the first study to report such findings. Since the last course of rituximab was applied over 3 years ago, it is conceivable that the strong B cell inhibition by ibrutinib led to PML. With increased awareness of this potential side effect, further clinical studies are certainly warranted to evaluate this possible association.
A. Eckert,R. Neugebauer,M. Rossinger,M. Wahl,F. Schulz 한국소성가공학회 2011 기타자료 Vol.2011 No.8
This paper deals with the determination of application limits of an already presented method [1] to predict distortion of joined car body assemblies caused by mechanical joining technologies. The investigated method is particularly developed concerning the demands coming from the application in the automotive body production. Parameter studies in simulation and experiment are presented which show the influence of pre-straining and clamping on the joints properties and dimensional accuracy of the assembly. The gained cognitions allow conclusions about the quality of prediction of dimensional accuracy using the proposed simplified model in different joining situations. Finally, the investigated method is applied to a car body assembly.