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61.
62.
C.G. Cassapakis H.C. Bryant B.D. Dieterle C.P. Leavitt D.M. Wolfe B.E. Bonner J.E. Simmons C.W. Bjork P.J. Riley M.L. Evans G. Glass J.C. Hiebert M. Jain R.A. Kenefick L.C. Northcliffe D.W. Werren 《Physics letters. [Part B]》1976,63(1):35-38
The measured cross sections show a narrow high-energy peak (20–30 MeV/cFWHM) and a broad bump at lower momenta associated with pion production. Comparison is made to an intranuclear cascade calculation. 相似文献
63.
Among other things we prove the following. (A) A number theory is convex if and only if it is inductive. (B) No r.e. number theory has JEP. (C) No number theory has AP. We also give some information about the hard cores of number theories. 相似文献
64.
An analysis of seismic attenuation in random porous media 总被引:1,自引:0,他引:1
LIU Jiong BA Jing MA JianWei & YANG HuiZhu Institute of Seismic Exploration School of Aerospace Tsinghua University Beijing China Research Institute of Petroleum Exploration & Development PetroChina Beijing 《中国科学:物理学 力学 天文学(英文版)》2010,(4)
The attenuation of seismic wave in rocks has been one of the interesting research topics, but till now no poroelasticity models can thoroughly explain the strong attenuation of wave in rocks. In this paper, a random porous medium model is designed to study the law of wave propagation in complex rocks based on the theory of Biot poroelasticity and the general theory of stochastic process. This model sets the density of grain, porosity, permeability and modulus of frame as random parameters in space, and only one fluid infiltrates in rocks for the sake of better simulation effect in line with real rocks in earth strata. Numerical simulations are implemented. Two different inverse quality factors of fast P-wave are obtained by different methods to assess attenuation through records of virtual detectors in wave field (One is amplitude decay method in time domain and the other is spectral ratio method in frequency domain). Comparing the attenuation results of random porous medium with those of homogeneous porous medium, we conclude that the attenuation of seismic wave of homogeneous porous medium is far weaker than that of random porous medium. In random porous media, the higher heterogeneous level is, the stronger the attenuation becomes, and when heterogeneity σ = 0.15 in simulation, the attenuation result is consistent with that by actual observation. Since the central frequency (50 Hz) of source in numerical simulation is in earthquake band, the numerical results prove that heterogeneous porous structure is one of the important factors causing strong attenuation in real stratum at intermediate and low frequency. 相似文献
65.
Haiping Lin Janosch M. C. Rauba Kristian S. Thygesen Karsten W. Jacobsen Michelle Y. Simmons Werner A. Hofer 《Frontiers of Physics in China》2010,5(4):369-379
The investigation of electron transport processes in nano-scale architectures plays a crucial role in the development of surface
chemistry and nano-technology. Experimentally, an important driving force within this research area has been the concurrent
refinements of scanning tunneling microscopy (STM) techniques. The theoretical treatment of the STM operation has traditionally
been based on the Bardeen and Tersoff-Hamann methods which take as input the single-particle wave functions and eigenvalues
obtained from finite cluster or slabs models of the surface-tip interface. Here, we present a novel STM simulation scheme
based on non-equilibrium Green’s functions (NEGF) and Wannier functions which is both accurate and very efficient. The main
novelty of the scheme compared to the Bardeen and Tersoff-Hamann approaches is that the coupling to the infinite (macroscopic)
electrodes is taken into account. As an illustrating example we apply the NEGF-STM method to the Si(001)-(2×1):H surface with
sub-surface P doping and discuss the results in comparison to the Bardeen and Tersoff-Hamann methods. 相似文献
66.
V.Z. Goldberg B.T. Roeder G.V. Rogachev G.G. Chubarian E.D. Johnson C. Fu A.A. Alharbi M.L. Avila A. Banu M. McCleskey J.P. Mitchell E. Simmons G. Tabacaru L. Trache R.E. Tribble 《Physics letters. [Part B]》2010
We measured the excitation function for 13O + p elastic scattering to obtain data on the unknown 14F nucleus. The ground state and several low-lying excited states in 14F were observed and spin/parity assignments were made. 14F appears to be much less unstable than was predicted. We compare theoretical predictions for the 14F level scheme with the experimental results. 相似文献
67.
一些企业以轨道交通产业为纽带形成了交通产业链,轨道交通产业链上的企业要注重对相关工程项目实施全过程中的成本控制.从产业链的视角出发,围绕财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个方面,构建了评价指标体系和成本控制指标体系.运用层次分析法和模糊综合评价法进行评价和分析,找出了影响轨道交通产业链上企业工程项目成本控制的主要因素.研究表明,有55%的人认为财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个因素对轨道交通工程项目成本控制的影响较大. 相似文献
68.
[reaction: see text] A general approach to the tricyclic core of the icetexane natural products via the cycloisomerization of alkynyl indenes using GaCl(3) is presented. This strategy provides an efficient synthesis of the natural product salviasperanol and sets the stage for access to other members of this family of diterpenoids. 相似文献
69.
[reaction: see text] An expedient, atom-economical, asymmetric synthesis of 1-aryl-3-azabicyclo[3.1.0]hexanes, including (+)-Bicifadine and DOV21947, in a single-stage through process without isolation of any intermediates has been developed. The key of this synthesis is the in-depth mechanistic understanding of the complicated epoxy nitrile coupling at each reaction stage. Therefore, the desired trisubstituted cyclopropane can be prepared in high ee and yield by controlling the reaction pathway through manipulating the nitrile anion aggregation state. 相似文献
70.
D E Simmons 《The Journal of the Operational Research Society》2013,64(11):1622-1629
This paper formulates a simple model to examine the appropriate mix of dedicated and flexible maintenance technicians (servers) required when total delay cost is a non-linear function of mean delay time. The primary decision variable is the number of flexible servers needed to minimize system-related costs. Non-linear delay costs appear to significantly increase the level of cross-training required compared with previous research using a linear cost function, which showed that a small proportion of flexible servers was sufficient. This has important implications for service system designers in regard to the amount of cross-training that might be appropriate. 相似文献