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1.
一类捕食-被食系统的全局渐近稳定性 总被引:1,自引:0,他引:1
本文对如下形式的具分布时滞的捕食-被食系统:通过构造Liapunov泛函,得到了该系统正平衡解全局渐近稳定的充分条件,所得结果包括了一些相关的已有结果为其特例。 相似文献
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The aim of this paper is to study the invariant and attracting set of fuzzy cellular neural networks with variable delays. Based on a delayed differential inequality and the properties fuzzy logic operation and M-matrix, the invariant and attracting set is obtained. Moreover, two examples are given to illustrate the effectiveness of our theoretical result. 相似文献
4.
The boundary layer structure of oscillatory shallow open channel flows has been studied in a wide flume. Fluorescence solution
was released at a porous rough bed through a diffuser covered by gravel of 0.5 cm grain size. A planar laser-induced fluorescence
(PLIF) system was used to visualise the dye plumes in both vertical and horizontal planes for a qualitative understanding
of the roles of large-scale flow structures in mass transport. A variety of tests were conducted for a range of oscillatory
periods (30–240 s), water depths (3–16 cm) and velocity amplitudes (0.027–0.325 m/s), which cover a wide range of oscillatory
flows with Reynolds numbers Re
a
varied from 0.3 × 104 (laminar) to 2.1 × 106 (fully turbulent). For quantitative investigation, a novel technique, namely combined laser-induced fluorescence (LIF) and
2D laser Doppler velocimetry (LDV) (LIF/LDV), was developed and used to measure the velocity and solute concentration simultaneously
in a vertical plane over 50 cycles. From the dye plumes revealed by the PLIF in transitional flows, there are different patterns
of flow structure and solute transport with three representative stages of acceleration, deceleration and flow reversal. In
the acceleration stage, turbulence was suppressed with dye layers adhering to the surface with little vertical mass transport.
In the deceleration stage, flame-like turbulent structures occurred when turbulence generation was prominent. This was investigated
quantitatively by recording the percentage occurrence of the adhered smooth layers per cycle. For those smooth bed cases with
Re
a
< 1.8 × 105, the adhered smooth dye layers type of boundary layer occupied 100% of the oscillation period. Over a sufficiently high Re
a
, a rough bed can generate fully turbulent oscillatory flows without the appearance of adhering dye layers. Between these
two extremes, a transitional flow regime occurs in a wide range of flow conditions: Re
a
> 2.7 × 104 over the rough bed and Re
a
> 8.3 × 106 over a smooth bed. 相似文献
5.
稳定性理论中几个基本定理的推广 总被引:5,自引:0,他引:5
本文推广了经典的稳定性,有界性定理及关于渐近稳定的充分条件。去掉了原始定理中,函数的导数在其定义域内常负或定负的要求,并应用于集合稳定性判定. 相似文献
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<正>Diffraction efficiency of volume Bragg grating,whose period is in the same order as the incident wavelength, is related to the polarization direction of the incident linear polarized beam.When two linearly polarized recording beams with the same polarization direction are used for recording volume Bragg gratings in a photopolymer with diffusion amplification,the azimuth of polarization of the reconstruction beam influences the diffraction efficiency of the grating.When the probe beam is linearly polarized and oriented orthogonally to the grating vectors,the±1-order diffraction beams are also linearly polarized with polarization direction parallel to that of the probe beam.According to the results,a two-dimensional nonspatial optical filter consisting of the volume Bragg gratings would achieve significantly higher efficiency. 相似文献
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In this paper, a nonlinear impulsive neutral integro-differential equation with time-varying delays is considered. By establishing a singular impulsive delay integro-differential inequality and transforming the n-dimensional impulsive neutral integro-differential equation to a 2n-dimensional singular impulsive delay integro-differential equation, some sufficient conditions ensuring the global exponential stability in PC1 of the zero solution of an impulsive neutral integro-differential equation are obtained. The results extend and improve the earlier publications. An example is also discussed to illustrate the efficiency of the obtained results. 相似文献
9.
Feifei Sun Meiqin Lin Zhaoxia Dong Daoyi Zhu Shuang Long Wang Jie Yang 《Journal of Dispersion Science and Technology》2016,37(6):753-759
A delayed crosslinking system employed with hydrolyzed polyacrylamide (HPAM) and chromium acetate was developed for high profile control in low-temperature reservoirs. The crosslinking system formed strong gel at polymer concentration range of 3000–5000 mg/L, and the gelation time was delayed to 8–30 days, which offered the crosslinking system enough time to flow into deep water-producing zones and plug large pore paths, forcing follow-up fluids to enter low-permeability layer and reduce disproportionate permeability. The effect of polymer hydrolysis degree, polymer concentration, pH, and crosslinker concentration on delaying gelation time was evaluated using bottle testing. Meanwhile, sand-packed tube displacement experiments revealed the plugging performance of delayed crosslinking system. According to Fourier transform infrared spectroscopy (FTIR) analysis, as well as crosslinking mechanism between polymer and chromium acetate, the delayed mechanism of crosslinked system demonstrated that due to stronger affinity of acetate complexes as a ligand, its substitution in situ by carboxylate group of polyacrylamide slowed down the initial rate-determining step of crosslinking reaction. 相似文献
10.
In this paper, the global exponential stability of impulsive fuzzy cellular neural networks with mixed delays and reaction-diffusion terms is considered. By establishing an integro-differential inequality with impulsive initial condition and using the properties of M-cone and eigenspace of the spectral radius of nonnegative matrices, several new sufficient conditions are obtained to ensure the global exponential stability of the equilibrium point for fuzzy cellular neural networks with delays and reaction-diffusion terms. These results extend and improve the earlier publications. Two examples are given to illustrate the efficiency of the obtained results. 相似文献