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For any Sturm-Liouville problem with a separable boundary condition and whose leading coefficient function changes sign (exactly once), we first give a geometric characterization of its eigenvalues λn using the eigenvalues of some corresponding problems with a definite leading coefficient function. Consequences of this characterization include simple proofs of the existence of the λn's, their Prüfer angle characterization, and a way for determining their indices from the zeros of their eigenfunctions. Then, interlacing relations among the λn's and the eigenvalues of the corresponding problems are obtained. Using these relations, a simple proof of asymptotic formulas for the λn's is given. 相似文献
3.
On the leading term and the degree of the polynomial trace mapping associated with a substitution 总被引:1,自引:0,他引:1
Using the trace mapping and the reduced trace mapping associated with a substitution, one obtaines the spectral properties of one-dimensional Schrödinger operators of the formH=–+V onl
2, where is the discrete Laplacian andV is a diagonal operator with elements derived from a substitution rule. In particular, the reduced trace mapping is closely related to the leading term of the original trace mapping. In this paper, the explicit expression of the leading term is given and its properties are discussed. 相似文献
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6.
《TOP》1986,1(1):127-138
Summary Many estimating procedures are carried out with incomplete data by means of different types of EM algorithms. They allow us
to obtain maximum likelihood parameter estimates in classical inference and also estimates based on the posterior mode in
Bayesian inference. This paper analyzes in detail the spectral radii of the Jacobian matrices algorithm as a possible way
to evaluate convergence rates. The eigenvalues of such matrices are explicitly obtained in some cases and, in all of them,
a geometric convergence rate is, at least, guaranteed near the optimum. Finally, a comparison between the leading eigenvalues
of EM and direct and approximate EM-Bayes algorithms may suggest the efficiency of each case. 相似文献
7.
基于多项式组主项解耦消元法 ,将几何定理的假设条件 (多项式组 PS)化为主项只含主变元的三角型多项式组 DTS,可得到定理命题成立的不含变元的非退化条件 ,即充分必要或更接近充分必要的非退化条件 .由于多项式主系数不含变元 ,已不存在 DTS多项式之间的约化问题 ,故方法有普遍意义 .文中例为西姆松定理的机器证明 . 相似文献
8.
A computational and experimental study was conducted to assess the potential of testing waverider configurations in a high-performance,
short-duration expansion tube facility. The tests were performed in the newly commissioned X3 superorbital expansion tube
and provide the first experimental data of a waverider tested at a stagnation enthalpy and equivalent flight speed exceeding
40 MJ/kg and 9 km/s, respectively. Two simple caret configurations were chosen as benchmark test cases to test the use of
the facility, instrumentation and numerical models to investigate these flows. The general performance of the sharp and blunt
leading edge waveriders at angles of attack ranging from 0° to 5° were analyzed and compared to CFD and theoretical predictions.
For the conditions tested, the presence of a strong viscous interaction caused the shock wave to be detached from the leading
edge of the models resulting in a significant loss in performance. An analytical model was developed to account for the strong
coupling between the shock wave and boundary layer. Results were shown to be in very good agreement with CFD estimates for
both configurations at all angles of attack considered. Finite-rate chemistry CFD simulations indicated that real gas effects
other than the residual levels of nonequilibrium freestream dissociation present in the expansion tube flow were negligible
for the conditions tested. The study also revealed that a past flow visualization technique gave a false indication of the
leading edge shock location. An improved experimental visualization technique was successfully tested with results from these
tests correlating well with computational estimates. This study successfully demonstrated the use of the facility to study
waverider performance at speeds representative of orbital flight.
相似文献
9.
Dr. Yuanchen Dong Prof. Dr. Dongsheng Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18018-18023
Frame‐guided assembly, a recently discovered strategy for amphiphilic assembly, is discussed as a strategy for constructing vesicle assemblies with programmed geometries and dimensions under identical surrounding conditions. The strategy is inspired by the cytoskeletal‐membrane protein–lipid bilayer structure and shows great potential in the understanding and controlling of the amphiphilic assembly process. Both the principles and basic requirements are discussed, along with recently reported examples. The prospects and potential investigations of frame‐guided assembly are also proposed. 相似文献
10.
This paper reports results of experiments in which a steadystate nonuniform supercritical openchannel flow was suddenly blocked by a rapidly falling gate at a downstream distance of about one hundred critical depths. This results in a hydraulic jump propagating upstream. Experimental data on the shape, height, and propagation speed of its leading front are given. It is shown that the parameters of the jump differ significantly from the values found using a quasistationary approach. 相似文献