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排序方式: 共有714条查询结果,搜索用时 15 毫秒
1.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
2.
L. V. Kuzmin V. A. Morozov S. O. Starkov B. A. Khadzhi 《Journal of Communications Technology and Electronics》2006,51(11):1283-1289
The models of indoor multipath propagation of wideband and ultrawideband (UWB) signals are considered. Application of these models is recommended by an IEEE working group. In the framework of one of the models corresponding to the line-of-sight conditions, the algorithms for reception of UWB chaotic signals in the presence of reflection from multiple surfaces (echo signals) are proposed and analyzed. The efficiency of reception techniques is estimated from the viewpoint of the error probabilities. Limitations caused by the specific properties of echo signals are revealed, and the methods for improvement of reception quality are discussed. 相似文献
3.
Dmitri A. Parshin 《Journal of Low Temperature Physics》2004,137(3-4):233-250
Using a simple diagram technique we derive the electric-dipole echo amplitude from two-level systems with a quadrupole nuclear moment in glasses in an external magnetic field. We show, that due to the quadrupole moment interaction of a tunneling particle with a gradient of an internal electric field, the echo amplitude experiences oscillations in rather weak magnetic fields. With an increase of the magnetic field, when the Zeeman energy becomes larger than the quadrupole energy splitting, the average echo amplitude increases and saturates (for high magnetic fields) at some level which is above the average level of echo oscillations for small magnetic fields. PACS numbers: 77.22.Ch, 61.43.Fs, 76.60.Gv, 76.60.Lz 相似文献
4.
Dmitri E. Nikonov George I. Bourianoff Paolo A. Gargini 《Journal of Superconductivity and Novel Magnetism》2006,19(6):497-513
Quantum limits of power dissipation in spintronic computing are estimated. A computing element composed of a single electron
in a quantum dot is considered. Dynamics of its spin due to external magnetic field and interaction with adjacent dots are
described via the Bloch equations. Spin relaxation due to magnetic noise from various sources is described as coupling to
a reservoir. Resulting dissipation of energy is calculated and is shown to be much less than the thermal limit, ∼kT per bit,
if the rate of spin relaxation is much slower than the switching rate. Clues on how to engineer an energy efficient spintronic
device are provided. 相似文献
5.
Yu. I. Kuzmin 《Technical Physics Letters》2002,28(7):568-571
The influence of fractal clusters of a normal phase on the dynamics of a magnetic flux trapped in a percolation superconductor is considered. The critical depinning current distribution and the current-voltage characteristics of fractal superconducting structures in the resistive state are determined for an arbitrary fractal dimension of the cluster boundaries. The interval of fractal dimensions is found in which the dispersion of critical currents exhibits unlimited growth. It is established that the fractality of clusters favors a decrease of the electric field arising during the magnetic flux motion, thus increasing the critical current value. The region featuring the giant dispersion of critical currents can be expected to provide for the maximum current-carrying capacity of a superconductor. 相似文献
6.
Y. Ohshima H.S. Ahn M. Aoki S. Awa M. Fukushima H. Hayashii X.Q. Hu T.W. Hur S. Igarashi H. Ikeda H.C. Jeong K. Kaneyuki D.Y. Kim S.K. Kim A. Kuzmin M.H. Lee S. Noguchi A. Ochi H. Sagawa N. Sato N. Sugiyama K. Tamai T. Tanimori N. Toomi T.J. Wang K. Watanabe Y. Watanabe X.C. Zhong Y.C. Zhu 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):517-523
We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25–3.5 GeV. The prototype consisted of an array of 6 × 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm × 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/π separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector. 相似文献
7.
A method of taking into account the real feed radiation pattern for a Luneberg lens is proposed. According to this, the field
of a feed with the given radiation pattern is expanded into series in spherical harmonics. Using this approach, it is possible
to introduce the radiation patterns of real feeds into strict electrodynamic solution for a Luneberg lens, thus significantly
refining a mathematical model of the antenna. 相似文献
8.
9.
Dmitri V. Besedin Leila Yu. Ustynyuk Yuri A. Ustynyuk Valerij V. Lunin 《Topics in Catalysis》2005,32(1-2):47-60
The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes (propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (Si–O)3ZrIVH, (Si–O)2ZrIVH2, and (Si–O)2ZrIIIH were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (Si–O)3ZrH, and dihydrides, (Si–O)2ZrH2. Cleavage of linear alkanes on the monohydrides (Si–O)3ZrH is thermodynamically unfavorable; however, the dihydrides (Si–O)2ZrH2 can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (Si–O)2ZrIIIH, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes. 相似文献
10.