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71.
Wolfgang Muessel Helmut Strobel Maxime Joos Eike Nicklas Ion Stroescu Jiří Tomkovič David B. Hume Markus K. Oberthaler 《Applied physics. B, Lasers and optics》2013,113(1):69-73
We report on the optimization of high-intensity absorption imaging for small Bose–Einstein condensates. The imaging calibration exploits the linear scaling of the quantum projection noise with the mean number of atoms for a coherent spin state. After optimization for atomic clouds containing up to 300 atoms, we find an atom number resolution of $\varDelta_{\rm det}= 3.7$ atoms, mainly limited by photon shot noise and radiation pressure. 相似文献
72.
Hong-wei Zhang Shao-ying Zhang Bao-gen Shen Helmut Kronmüller 《Journal of magnetism and magnetic materials》2003,260(3):352-360
The magnetization behavior in nanocrystalline permanent magnets has been investigated using mean field Stoner–Wohlfarth model. The model is comparatively simple but allows the numerical treatment of extended nanostructures. The predominant intergrain exchange coupling is expressed by a mean field constant Nm in spite of no explicit relationship between Nm and the microstructure. By this model, the experimental phenomena, such as the remanence enhancement, the shape of demagnetization curve, the irreversible magnetization, the exchange bias field and their respective temperature dependence, can be well explained. The Nm dependence of magnetic properties has been extensively discussed in the present paper. 相似文献
73.
74.
A. Hoffmann P. Betz H. Röpke B. H. Wildenthal 《Zeitschrift für Physik A Hadrons and Nuclei》1989,332(3):289-304
Theγ-decay of levels in21Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the18O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus21Na. The resulting values of Ex[keV]?J π are as follows: 4525-5+, 4686-3+, 5431-7+, 5549-3+, 5819-7?, 6175-7+, 6268-9+, 6550-9, 6639-9, 7006-7+, 7041-9, 7356-7 or 9, 7422-11(?), 7648-7+, 7981-11 or (7+), 8154-9, 8240-11, 8664-9? or 11 or 13?, 9401-13?, 9867-13? or 15+, 9941-13? or 15 or 17+. The assignment of mirror levels in21Ne —21Na has been extended to the 6175 keV level of21Ne. Excitation energies, electromagnetic properties, Gamow?Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of shell-model calculations which employ a unifieds—d shell Hamiltonian and the unrestricted configuration space of the 0d 5/2 —1s 1/2—0d3/2 shell. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in21Ne is observed to begin with a 5628 keV,J π=7/2+ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands. 相似文献
75.
Helmut R. Brand Charles R. Doering Robert E. Ecke 《Journal of statistical physics》1989,54(5-6):1111-1119
A brief introduction to the field is given together with an overview of the lectures given at the workshop on External Noise and its Interaction with Spatial Degrees of Freedom in Nonlinear Dissipative Systems organized by the Center for Nonlinear Studies at Los Alamos, March 28–31, 1988. It is hoped that the publication of papers presented at the workshop in a single issue of theJournal of Statistical Physics will help draw attention to the recent developments in this rapidly area of nonequilibrium phenomena. 相似文献
76.
The boundary of a fractal object, represented in a two-dimensional space, is theoretically a line with an infinitely small width. In digital images this boundary or contour is limited to the pixel resolution of the image and the width of the line commonly depends on the edge detection algorithm used. The Minkowski dimension was evaluated by using three different edge detection algorithms (Sobel, Roberts, and Laplace operator). These three operators were investigated because they are very widely used and because their edge detection result is very distinct concerning the line width. Very common fractals (Sierpinski carpet and Koch islands) were investigated as well as the binary images from a cancer invasion assay taken with a confocal laser scanning microscope. The fractal dimension is directly proportional to the width of the contour line and the fact, that in practice very often the investigated objects are fractals only within a limited resolution range is considered too. 相似文献
77.
78.
The sputtering of clusters consisting of 13, 27, and 75 copper atoms from the (0001) graphite surface under bombardment by
Cu2 dimers with energies of 100, 200, and 400 eV has been simulated using the molecular dynamics method. A comparative analysis
of the distributions of backscattered particles and their energies over polar angles and the energy distributions of sputtered
atoms has been performed. The factors responsible for the large sputtering yield from surface clusters under their bombardment
with dimers as compared to copper and xenon monomers have been discussed. It has been demonstrated that, in the case of bombardment
with dimers, the substantial role in the sputtering of surface clusters is played by the overlap of collision cascades initiated
by each atom of the incident dimer. The differences in the sputtering under cluster and atom bombardments are especially pronounced
in the case of large surface clusters. 相似文献
79.
Helmut Eberl Elena Ginina Keisho Hidaka 《The European Physical Journal C - Particles and Fields》2017,77(3):189
We study the two-body decays of the gluino at full one-loop level in the Minimal Supersymmetric Standard Model with quark-flavour violation (QFV) in the squark sector. The renormalisation is done in the \(\overline{\mathrm{DR}}\) scheme. The gluon and photon radiations are included by adding the corresponding three-body decay widths. We discuss the dependence of the gluino decay widths on the QFV parameters. The main dependence stems from the \(\tilde{c}_R \)–\( \tilde{t}_R\) mixing in the decays to up-type squarks, and from the \(\tilde{s}_R \)–\( \tilde{b}_R\) mixing in the decays to down-type squarks due to the strong constraints from B-physics on the other quark-flavour-mixing parameters. The full one-loop corrections to the gluino decay widths are mostly negative and of the order of about ?10%. The QFV part stays small in the total width but can vary up to ?8% for the decay width into the lightest \(\tilde{u}\) squark. For the corresponding branching ratio the effect is somehow washed out by at least a factor of two. The electroweak corrections can be as large as 35% of the SUSY QCD corrections. 相似文献
80.