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991.
Analysis of dynamics in a general intraguild predation model with intraspecific competition 下载免费PDF全文
This paper is devoted to studying the dynamical properties of a general intraguild predation model with intraspecific competition. We first investigate the stability of all possible equilibria in relation to the ecological parameters, and then study the long time behavior of the solution. Moreover, we provide a detailed analysis of dynamics of a IGP model with linear functional response and intraspecific competition. Our results show that the impact of the intraspecific competition essentially increases the dynamical complexity of the system. 相似文献
992.
We propose randomized inference(RI), a new statistical inference approach. RI may be realized through a randomized estimate(RE) of a parameter vector, which is a random vector that takes values in the parameter space with a probability density function(PDF) that depends on the sample or sufficient statistics,such as the posterior distributions in Bayesian inference. Based on the PDF of an RE of an unknown parameter,we propose a framework for both the vertical density representation(VDR) test and the construction of a confidence region. This approach is explained with the aid of examples. For the equality hypothesis of multiple normal means without the condition of variance homogeneity, we present an exact VDR test, which is shown as an extension of one-way analysis of variance(ANOVA). In the case of two populations, the PDF of the Welch statistics is given by using the RE. Furthermore, through simulations, we show that the empirical distribution function, the approximated t, and the RE distribution function of Welch statistics are almost equal. The VDR test of the homogeneity of variance is shown to be more efficient than both the Bartlett test and the revised Bartlett test. Finally, we discuss the prospects of RI. 相似文献
993.
On <Emphasis Type="Italic">c</Emphasis><Superscript>#</Superscript>-normal subgroups infinite groups
Huaquan Wei Qiao Dai Hualian Zhang Yubo Lv Liying Yang 《Frontiers of Mathematics in China》2018,13(5):1169-1178
A subgroup H of a finite group G is called a c#-normal subgroup of G if there exists a normal subgroup K of G such that G = HK and H ∩ K is a CAP-subgroup of G: In this paper, we investigate the influence of fewer c#-normal subgroups of Sylow p-subgroups on the p-supersolvability, p-nilpotency, and supersolvability of finite groups. We obtain some new sufficient and necessary conditions for a group to be p-supersolvable, p-nilpotent, and supersolvable. Our results improve and extend many known results. 相似文献
994.
Weizhong Dai 《Numerical Methods for Partial Differential Equations》2010,26(5):1079-1098
We consider a mathematical model for thermal analysis in a 3D N‐carrier system with Neumann boundary conditions, which extends the concept of the well‐known parabolic two‐step model for micro heat transfer. To solve numerically the complex system, we first reduce 3D equations in the model to a succession of 1D equations by using the local one‐dimensional (LOD) method. The obtained 1D equations are then solved using a fourth‐order compact finite difference scheme for the interior points and a second‐order combined compact finite difference scheme for the points next to the boundary, so that the Neumann boundary condition can be applied directly without discretizing. By using matrix analysis, the compact LOD scheme is shown to be unconditionally stable. The accuracy of the solution is tested using two numerical examples. Results show that the solutions obtained by the compact LOD finite difference scheme are more accurate than those obtained by a Crank‐Nicholson LOD scheme, and the convergence rate with respect to spatial variables is about 2.6. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
995.
THE EXISTENCE OF POSITIVE SOLUTIONS TO BOUNDARY VALUE PROBLEM OF SECOND ORDER DIFFERENTIAL EQUATIONS
Juan Dai Zongfu Zhou School of Mathematical Science Anhui University Hefei 《Annals of Differential Equations》2010,(1):10-15
In this paper, a fixed point theorem in C1[0,1] space is established using the properties of the fixed point index. This theorem is applied to prove the existence of positive solution to the boundary value problems of second order differential equations. 相似文献
996.
Theoretical study of N-doped TiO2 rutile crystals 总被引:1,自引:0,他引:1
The N-doping effects on the electronic and optical properties of TiO2 rutile crystal have been studied using density functional theory (DFT). The calculations of several possible N-doped structures show that band gaps have little reduction but some N 2p states lie within the band gap in the substitutional N to O structure and interstitial N-doped rutile supercell, which results in the reduction of the photon-transition energy and absorption of visible light. In contrast, substitutional N to Ti doped model has a significant band-gap narrowing. The results maybe clarify confusions in nitrogen-doped TiO2 rutile crystal. 相似文献
997.
We report first-principles calculations on the electrical transport properties of two kinds of one-dimensional nanowires: (a) a carbon nanowire (CNW) with alternating single and triple bonds and (b) a boron-nitrogen nanowire (BNNW) with equidistant bonds. We demonstrate the similarity and difference between the carbon nanowire and its boron-nitrogen analogue in the molecular orbital and transport properties, and then explore the potential innovations. The effects of molecular orbitals and nanowire-electrode coupling on the transport properties are analyzed. The cases of the nanowires sandwiched between both nanoscale and bulk electrodes are considered. It suggests that the characteristics of the transmission spectra and the current-voltage characteristics (I-V curves) are determined both by the electrodes and by the molecule as well as their coupling. In particular, the negative differential resistance (NDR) phenomenon is more apparent when the nanowires are positioned between two nanoscale electrodes. The tuning of the transport properties is also probed through the changes of nanowire-electrode separation and the inclusion of a gate voltage. These lead to dramatic variations in the equilibrium conductance, which can be understood from the shift and alignment of the molecular orbital relative to the Fermi level of the electrodes. In the analysis of the effects of nanowire-electrode separation, it shows that the equilibrium conductance has the same variation behavior as that of the projected density of states (PDOS) for CNW, while the localized molecular orbitals of BNNW result in its conductance varies differently from its PDOS. The different molecular orbital characteristics near the Fermi level of these two kinds of nanowires underlie their different transport properties. 相似文献
998.
Ablikim M Bai JZ Ban Y Bian JG Cai X Chang JF Chen HF Chen HS Chen HX Chen JC Chen J Chen J Chen ML Chen YB Chi SP Chu YP Cui XZ Dai HL Dai YS Deng ZY Dong LY Du SX Du ZZ Fang J Fang SS Fu CD Fu HY Gao CS Gao YN Gong MY Gong WX Gu SD Guo YN Guo YQ Guo ZJ Harris FA He KL He M He X Heng YK Hu HM Hu T Huang GS Huang L Huang XP Ji XB Jia QY Jiang CH Jiang XS Jin DP Jin S Jin Y Lai YF Li F Li G Li HB Li HH Li J Li JC Li QJ Li RB Li RY Li SM Li WG Li XL Li XQ Li XS Liang YF Liao HB Liu CX Liu F Liu F 《Physical review letters》2006,97(6):062001
The decay J/psi-->NNpi provides an effective isospin 1/2 filter for the piN system due to isospin conservation. Using 58x10(6) J/psi decays collected with the Beijing Electromagnetic Spectrometer at the Beijing Electron Positron Collider, more than 100 thousand J/psi-->ppi-n+c.c. events are obtained. Besides the two well-known N* peaks at around 1500 MeV/c2 and 1670 MeV/c2, there are two new, clear N* peaks in the ppi invariant mass spectrum around 1360 MeV/c2 and 2030 MeV/c2 with statistical significance of 11sigma and 13sigma, respectively. We identify these as the first direct observation of the N*(1440) peak and a long-sought missing N* peak above 2 GeV/c2 in the piN invariant mass spectrum. 相似文献
999.
1000.
We study three types of practical optimization problems faced by a firm that can control its liquid reserves by paying dividends
and by issuing new equity. In the first problem, we consider the classical dividend problem without equity issuance. The second
problem aims at maximizing the expected discounted dividend payments minus the expected discounted costs of issuing new equity
over strategies associated with positive reserves at all times. The third problem has the same objective as the second one,
but with no constraints on the reserves. Under the assumption of proportional transaction costs, we identify the value functions
and the optimal strategies. We also present the relationship between three problems. 相似文献