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971.
Li-xingZhu Wei-xingSong Heng-jianCui 《应用数学学报(英文版)》2003,19(3):353-362
When a regression model is applied as an approximation of underlying model of data, the model checking is important and relevant. In this paper, we investigate the lack-of-fit test for a polynomial error-in-variables model. As the ordinary residuals are biased when there exist measurement errors in covariables,we correct them and then construct a residual-based test of score type. The constructed test is asymptotically chi-squared under null hypotheses. Simulation study shows that the test can maintain the significance level well.The choice of weight functions involved in the test statistic and the related power study are also investigated.The application to two examples is illustrated. The approach can be readily extended to handle more general models. 相似文献
972.
Yun S. Song 《Annals of Combinatorics》2003,7(3):365-379
We study subtree-prune-and-regraft (SPR) operations on
leaf-labelled rooted binary trees, also known as rooted binary phylogenetic trees.
This study is motivated by the problem of
graphically representing evolutionary histories of biological sequences subject to recombination.
We investigate some basic properties of the induced SPR-metric on the space
of leaf-labelled
rooted binary trees with n leaves. In contrast to the case of
unrooted trees, the number |U(T)| of trees in
which are one SPR operation away from a given tree
depends on the
topology of T. In this paper, we construct recursion relations which allow one to determine the
unit-neighbourhood size |U(T)| efficiently for any tree topology. In fact, using the recursion
relations we are able to derive a simple closed-form formula for the unit-neighbourhood size.
As a corollary, we construct sharp upper and lower bounds on the size of unit-neighbourhoods
and investigate the diameter of
.
Lastly, we consider an enumeration problem relevant to population genetics.AMS Subject Classification: 05C05, 92D15. 相似文献
973.
C S?SungEmail author S H?Song 《The Journal of the Operational Research Society》2003,54(12):1283-1295
This paper considers an integrated service network design problem for a given set of freight demands that is concerned with integration of locating cross-docking (CD) centers and allocating vehicles for the associated direct (transportation) services from origin node to a CD center or from a CD center to the destination node. For the vehicle allocation, direct services (sub-routes) should be determined for the given freight demands, and then the vehicle allocation has to be made in consideration of routing for the associated direct service fulfillment subject to vehicle capacity and service time restriction. The problem is modeled as a path-based formulation for which a tabu-search-based solution algorithm is proposed. To guarantee the performance of the proposed solution algorithm, strong valid inequalities are derived based on the polyhedral characteristics of the problem domain and an efficient separation heuristic is derived for identifying any violated valid inequalities. Computational experiments are performed to test the performance of the proposed solution algorithm and also that of a valid-inequality separation algorithm, which finds that the solution algorithm works quite well and the separation algorithm provides strengthened lower bounds. Its immediate application may be made to strategic (integrated) service network designs and to tactical service network planning for the CD network. 相似文献
974.
Multivariate Refinement Equations and Convergence of Cascade Algorithms in Lp(0〈p〈1)Spaces 总被引:1,自引:0,他引:1
SongLI 《数学学报(英文版)》2003,19(1):97-106
We consider the solutions of refinement equations written in the form
where the vector of functions ϕ = (ϕ
1, ..., ϕ
r
)
T
is unknown, g is a given vector of compactly supported functions on ℝ
s
, a is a finitely supported sequence of r × r matrices called the refinement mask, and M is an s × s dilation matrix with m = |detM|. Inhomogeneous refinement equations appear in the construction of multiwavelets and the constructions of wavelets on a finite
interval. The cascade algorithm with mask a, g, and dilation M generates a sequence ϕ
n
, n = 1, 2, ..., by the iterative process
from a starting vector of function ϕ
0. We characterize the L
p
-convergence (0 < p < 1) of the cascade algorithm in terms of the p-norm joint spectral radius of a collection of linear operators associated with the refinement mask. We also obtain a smoothness
property of the solutions of the refinement equations associated with the homogeneous refinement equation.
This project is supported by the NSF of China under Grant No. 10071071 相似文献
975.
Song XF Sorin V Sosebee M Sotnikova N Souza M Stanton NR Steinbruck G Stephens RW Stevenson ML Stichelbaut F Stoker D Stolin V Stoyanova DA Strauss M Streets K Strovink M Stutte L Sznajder A Tarazi J Taylor W Tentindo-Repond S Thomas TL Thompson J Toback D Trippe TG Turcot AS 《Physical review letters》2000,85(2):256-261
The D0 collaboration has performed a study of spin correlation in t&tmacr; production for the process t&tmacr;-->bW(+)&bmacr;W-, where the W bosons decay to enu or &mgr;nu. A sample of six events was collected during an exposure of the D0 detector to an integrated luminosity of approximately 125 pb(-1) of sqrt[s] = 1.8 TeV p&pmacr; collisions. The standard model (SM) predicts that the short lifetime of the top quark ensures the transmission of any spin information at production to the t&tmacr; decay products. The degree of spin correlation is characterized by a correlation coefficient kappa. We find that kappa>-0.25 at the 68% confidence level, in agreement with the SM prediction of kappa = 0.88. 相似文献
976.
In this work an interleaved multiple-gradient-echo chemical shift imaging (IMGE-CSI) technique was designed, implemented and evaluated at 1.5 and 4T for high-resolution lipid quantification and R(2)* measurement in-vivo. The method is analogous to echo planar CSI but utilizes conventional gradient echoes, exploiting the principle of spectroscopic bandwidth extension by interleaving temporally offset gradient-echo trains. It is shown that IMGE-CSI is able to measure true fat volume fraction in oil/water mixtures with high accuracy, not possible with Dixon-type methods which approximate the spectrum as consisting of only two spectral components. Correlation of the CSI- derived volume fractions with volumetry afforded r(2) > 0.99 with a slope of 0.98. The method is shown to be able to quantify regional variations in bone marrow composition in vivo with a spatial resolution of 2.5 x 2.5 x 5 mm(3.) R(2)* was obtained by multi-line spectral curve fitting. For the measurement of R(2)* in cancellous bone marrow the method is shown to agree well with time-domain fitting techniques but is superior in instances where the marrow has both hematopoietic and fatty constituents. Finally, excellent inter-scan reproducibility (1% coefficient of variation for global means and medians) was achieved, yielding r(2) = 0.98 of the test-retest correlation for three scans in four test subjects. In conclusion, IMGE-CSI is found to enable highly accurate lipid quantification and measurement of cancellous bone marrow R(2)* at spatial resolutions and scan times typical of standard clinical protocols. 相似文献
977.
With unusually slow and high-resolution sweeps of magnetic field, strong ultranarrow (width down to 100 &mgr;T) resistance peaks are observed when high currents are applied through quantum Hall samples. The peaks are dependent on the directions and even the history of magnetic field sweeps, indicating the involvement of a very slow physical process. Such a process and the sharp peaks are, however, not predicted by existing theories. We also find that the sharp resistance peaks are influenced by the nuclear spin flips. 相似文献
978.
Terry A. Egerton Lorna M. Kessell Ian R. Tooley Liwei Wang 《Journal of nanoparticle research》2007,9(2):251-260
Photogreying, the change in brightness on UV irradiation in the absence of oxygen, of TiO2 nanoparticulate dispersions is shown to depend on the nature of the liquid, consistent with a surface reaction. Measurements
on a series of TiO2 particles (mainly 75×10 nm) dispersed in, e.g., alkyl benzoate correlate well with those on the same TiO2’s dispersed in a second liquid (e.g. propan-2-ol). Photogreying in propan-2-ol is paralleled by photocatalytic-oxidation
activity, indicating a common origin – UV-generation of charge carriers. Further, photogreying parallels Ti3+ formation. Hence, although appearance and the visible spectra of photogreyed particles both differ from those of Ti3+ in ≤10 nm colloidal TiO2, we suggest that photogreying is caused by capture of UV excited electrons to form Ti3+. Surface treatment reduces photogreying, and we speculate that differences between uncoated samples reflect differences in
the number of potentially reducible Ti’s. 相似文献
979.
980.
Bulk mechanical alloying (BMA) followed by hot pressing (HP) was used to prepare Mg2Si0.6Ge0.4 thermoelectric material with high densification. Starting from the elemental power mixture, the Mg2Si0.6Ge0.4 solid solution was solid‐state synthesized via BMA. In fact, the peaks for the cubic‐structured Mg2Si0.6Ge0.4 solid solution phase were detected after 300 cycles in BMA. The single phase of Mg2Si0.6Ge0.4 was synthesized at 600 cycles in BMA. Mg2Si0.6Ge0.4 showed p‐type semiconduction without doping. Effects of hot pressing conditions on thermoelectric properties were investigated. With increasing hot pressing temperature from 673 to 773 K and pressure from 500 MPa to 1 GPa, the electrical conductivity increased and the Seebeck coefficient decreased. The maximum figure of merit was obtained with the processing parameter of 600 cycles BMA and hot pressing at 773 K, 1 GPa for 1 h. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献