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1.
采用正电子寿命谱和双探头Doppler展宽测量在原子尺度上研究了α-Fe/Nd2Fe14B复合纳米晶的界面结构.正电子寿命研究表明, α-Fe/Nd2Fe14B复合纳米晶存在两类界面.一类为非晶界面层, 正电子湮没寿命为155 ps; 另一类为具有原子空位的松懈界面, 含有空位尺寸大于1~2个铁原子空位的结构自由体积, 正电子湮没寿命为246 ps.电子-正电子湮没光子的共谐Doppler展宽测量表明这类松懈界面富集非磁性原子Nd和B, 这将削弱α-Fe/Nd2Fe14B复合纳米晶晶粒间的磁交换耦合. 相似文献
2.
Resch Laura Karner Anna Sprengel Wolfgang Wrschum Roland Schennach Robert 《Cellulose (London, England)》2022,29(3):1357-1363
Cellulose - In this study, for the first time, the experimental technique of positron annihilation lifetime spectroscopy (PALS) has been applied to monitor in situ the microstructural changes of... 相似文献
3.
Winfried Sickel Frauke Sprengel 《Journal of Computational Analysis and Applications》1999,1(3):263-288
We investigate the order of convergence of periodic interpolation on sparse grids (blending interpolation) in the framework of tensor products of Nikol'skij–Besov spaces. To this end, we make use of the uniformity of the considered tensor norms and provide a unified approach to error estimates for the interpolation of univariate periodic functions from Nikol'skij–Besov spaces. 相似文献
4.
Hermann Sprengel 《Fresenius' Journal of Analytical Chemistry》1864,3(1):115-117
Ohne ZusammenfassungVon dem Verfasser in englischer Sprache mitgetheilt 相似文献
5.
Nested spaces of multivariate periodic functions forming a non-stationary multiresolution analysis are investigated. The scaling
functions of these spaces are fundamental polynomials of Lagrange interpolation on a sparse grid. The approach based on Boolean
sums leads to sample and wavelet spaces of significantly lower dimension and good approximation order. The algorithms for
complete decomposition and reconstruction are of simple structure and low complexity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
N. Marquardt D. Sprengel H. v. Buttlar W. Hoppe 《Zeitschrift für Physik A Hadrons and Nuclei》1978,285(1):89-92
Excitation functions of the10B+10B elastic scattering at 80° (c.m.) and of the10B(10B,α)16O reaction at 5° (cm.) and 175° (c.m.) have been measured simultaneously for c.m. energies between 3 and 10 MeV. Whereas the elastic scattering is varying smoothly with energy, large resonant structures of intermediate width of about 600 keV have been found for the first time near 40 MeV excitation of20Ne in most reaction channels to16O. 相似文献
7.
A. A. Valeeva A. A. Rempel’ W. Sprengel H. -E. Schaefer 《Physics of the Solid State》2009,51(5):924-929
Local atomic environment of vacancies in nonstoichiometric titanium monoxide ranging in composition from TiO0.74 to TiO1.26 was studied by electron-positron annihilation. Analysis of the Doppler broadening spectra of the annihilation gamma line for titanium and liquid oxygen showed that positrons in titanium monoxide are trapped by titanium vacancies. Experiments revealed that the lifetime of positrons in ordered and disordered titanium monoxide TiO y increases with increasing oxygen content y and varies from 184 to 210 ps. Data on the valence electron density permitted the prediction that the lifetime of free positrons in stoichiometric titanium monoxide is about 140 ps and the lifetime of positrons localized in an oxygen vacancy is about 170 ps. The method used to analyze the gamma-line Doppler broadening spectra makes it possible to determine the type and number of atoms around a vacancy and to investigate order-disorder phase transformations in nonstoichiometric compounds. 相似文献
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9.
In the present paper we succeeded in studying structural phase transitions from an atomistic point of view by positron annihilation Doppler broadening. This differs and is complementary to conventionally used diffraction experiments with large coherence lengths. In the exemplary case of the 1140 K order-disorder transition in decagonal Al71.5Ni14Co14.5 quasicrystals the importance of this atomistic approach and its wide scope of application is demonstrated. 相似文献
10.
Rempel AA Sprengel W Blaurock K Reichle KJ Major J Schaefer HE 《Physical review letters》2002,89(18):185501
The identification of atomic defects in solids is of pivotal interest for understanding atomistic processes and solid state properties. Here we report on the exemplary identification of vacancies on each of the two sublattices of SiC by making use of (i) electron irradiation, (ii) measurements of the positron lifetimes, (iii) coincident Doppler broadening studies of the positron-electron annihilation radiation, and (iv) a comparison of the experimental data with theoretical studies. After 0.3 MeV electron irradiation, carbon vacancies V(C) are identified, where, after 0.5 MeV electron irradiation, predomi-nantly silicon vacancies V(Si) are observed. After 2.5 MeV irradiation, divacancies V(Si)-V(Si) are detected. The present results are expected to be of general importance for reliable identification of defects and atomic processes in complex solids. 相似文献