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排序方式: 共有10000条查询结果,搜索用时 22 毫秒
991.
992.
ALEPH Collaboration D. Buskulic D. Casper I. De Bonis D. Decamp P. Ghez C. Goy J. -P. Lees A. Lucotte M. -N. Minard et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):379-392
A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of
B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B**
u,d
mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB**
u,d
denotes the eightL=1(bū) and (bd) states and their charge conjugate.
For the well establishedB* meson the following quantities are obtained:ΔM=M
B*−MB=(45.30±0.35±0.87) MeV/c2 andN
B*/(N
B+N
B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσ
L/(σ
L+σ
T)=(33±6±5)%. 相似文献
993.
V. O. Kur'yanov T. F. Zhelobetskaya A. E. Zemlyakov V. Ya. Chirva 《Chemistry of Natural Compounds》1993,29(1):103-106
The synthesis has been effected of derivatives of MDP having a spacer with an amino or carboxy group. The final stage of the synthesis was the condensation of Boc-L-Ala-D-iGln with 6-aminohexanol (followed by the two-stage replacement of the hydroxy by an azido group) or with benzyl 6-aminohexanoate.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 122–125, January–February, 1993. 相似文献
994.
Subspace-based signal analysis using singular value decomposition 总被引:10,自引:0,他引:10
Van Der Veen A.-J. Deprettere E.F. Swindlehurst A.L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1993,81(9):1277-1308
A unified approach is presented to the related problems of recovering signal parameters from noisy observations and identifying linear system model parameters from observed input/output signals, both using singular value decomposition (SVD) techniques. Both known and new SVD-based identification methods are classified in a subspace-oriented scheme. The SVD of a matrix constructed from the observed signal data provides the key step in a robust discrimination between desired signals and disturbing signals in terms of signal and noise subspaces. The methods that are presented are distinguished by the way in which the subspaces are determined and how the signal or system model parameters are extracted from these subspaces. Typical examples, such as the direction-of-arrival problem and system identification from input/output measurements, are elaborated upon, and some extensions to time-varying systems are given 相似文献
995.
Published in Teoreticheskaya i Matematicheskaya Fizika, Vol. 95, No. 2, pp. 183–186, May, 1993. 相似文献
996.
Wideband chirp measurement technique for high bit rate sources 总被引:1,自引:0,他引:1
A Mach Zehnder (MZ) interferometer has been used as an optical discriminator to measure the time-resolved frequency chirp of an optical source 相似文献
997.
We present a systematic comparison of the correlation contribution at the level of the second-order polarization propagator approximation (SOPPA ) and MP 2 to the static dipole polarizability of (1) Be, BeH?, BH, CH+, MgH?, AIH, SiH+, and GeH+; (2) BH3, CH4, NH3, H2O, HF, BF, and F2; and (3) N2, CO, CN?, HCN, C2H2, and HCHO . Fairly extended basis sets were used in the calculations. We find that the agreement with experimental values is improved in SOPPA and MP .2 over the results at the SCF level. The signs and magnitudes of the correlation contribution in SOPPA are similar to those obtained in analytical derivative MP 2 calculations. However, it is not possible to say, in general, which method gives the largest correlation contribution or the best agreement with experiment, nor is it possible to make a priori prediction of the sign of the correlation contribution. For the first group of molecules, which have a quasi-degenerate ground state, additional CCDPPA and CCSDPPA calculations were performed and compared with polarizabilities obtained as analytical/numerical derivatives of the CCD and CCSD energies. The CCSDPPA results were found to be in better agreement with other calculations than were the SOPPA results, demonstrating the necessity of using methods based on infinite-order perturbation theory for these systems. © 1994 John Wiley & Sons, Inc. 相似文献
998.
Modeling and numerical simulations of the convective flows induced by the vibration of the monocrystal during crystal growth have been performed for two configurations simulating the Cz and FZ methods. This permitted to emphasize the role of different vibrational mechanisms in the formation of the average flows. It is shown that an appropriate combination of these mechanisms can be used to counteract the usual convective flows (buoyancy- and/or thermocapillary-driven) inherent to crystal growth processes from the liquid phase. While vibrational convection is rather complex due to these identified mechanisms, the new modeling used in the present paper opens up very promising perspectives to efficiently control heat and mass transfer during real industrial applications of crystal growth from the liquid phase. 相似文献
999.
1000.
K. Venkatakrishnan B.K.A. Ngoi P. Stanley L.E.N. Lim B. Tan N.R. Sivakumar 《Applied Physics A: Materials Science & Processing》2002,75(4):493-496
Photomasks are the backbone of microfabrication industries. Currently they are fabricated by a lithographic process, which
is very expensive and time consuming since it is a multi-step process. These issues can be addressed by fabricating photomasks
by direct femtosecond laser writing, which is a single-step process and comparatively cheaper and faster than lithography.
In this paper we discuss our investigations on the effect of two types of laser writing techniques, namely front- and rear-side
laser writing, with regard to the feature size and the edge quality of a feature. It is proved conclusively that for the patterning
of masks, front-side laser writing is a better technique than rear-side laser writing with regard to smaller feature size
and better edge quality. Moreover the energy required for front-side laser writing is considerably lower than that for rear-side
laser writing.
Received: 22 May 2001 / Accepted: 14 September 2001 / Published online: 17 October 2001 相似文献