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一类带Beddington-DeAngelis反应项的捕食模型平衡态的分歧解 总被引:1,自引:0,他引:1
本文利用极值原理,L-S度理论,特征值扰动理论及分歧理论,主要研究了一类带Beddington-DeAngelis反应项的捕食模型在Dirichlet边界条件下的平衡态局部分歧解与全局分歧解,给出了局部分歧解存在的充分条件和稳定性,并且得到其平衡态全局分歧解及其走向。 相似文献
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《IEEE transactions on instrumentation and measurement》1977,26(3):231-237
A study of a resonant frequency tracking system, to be used in measurement systems where the sensing element is a resonant structure is presented. The tracking system was used to lock an oscillator to the resonant frequency of a cavity operating in the X-band. The resonant frequency of the sensor was assumed to be a function of the quantity being measured. A theoretical analysis of the resonant frequency tracking system was done for both linear and nonlinear operations resulting from the properties of the sensor. A model of the tracking system was designed and an analysis of the system response was performed using computer techniques. 相似文献
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In this article, the micropolar mixture theory for porous media is generalized in the context of generalized L-S theory and classical C-T theory of thermoelasticity. The thermoelastic problem for a micropolar mixture of porous media is investigated in the context of the generalized micropolar mixture theory for porous media. The surface of a semi-infinite porous media is subjected to a zonal time-dependent thermal shock. The problem is solved by using the finite element method. The results, including the temperature, stresses, displacements, and microrotation are presented graphically. Comparisons are made between the results obtained by using two theories. The fluid constituting the mixture has a significant influence on the microrotation but a very slight influence on other responses. 相似文献
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《IEEE transactions on magnetics》2006,42(8):2029-2037
In this paper, we calculate the transient eddy-current response of a driver pickup probe due to a conducting plate by means of series expansions. We consider an excitation current in the driver coil that rises exponentially with time toward a constant value, the step function current being a special case with zero time constant. We find the transient response from the frequency domain expressions for the induced electromotive force in the pickup coil by using the inverse Laplace transform. Usually, the field of the excitation coil is expressed in the form of a Bessel integral with respect to the radial spatial frequency. Here, however, to improve computational efficiency, we approximate the integral as a series expansion by truncating the solution domain at a large but finite radius and setting the field on the truncation boundary to zero. The series is a sum of terms containing discrete spatial frequencies defined by the zeros of the first-order Bessel function of the first kind. We then form an inner summation from the temporal frequency-dependent terms in order to facilitate an analytical inverse Laplace transformation to the time domain. We present two alternative expansions for the inner sum. One is constructed with reference to the short time regime and the other with respect to the long time limit. Numerical results show good agreement between the alternative series approximations at a wide range of intermediate times. 相似文献
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Measurement Techniques - This paper presents the results of identifying the transient response of a relative air humidity sensor. It is shown that the capacitive relative humidity sensor is an... 相似文献
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为了提高灵敏度和消除交叉轴串扰,提出了一种包括有效的微型杠杆结构的谐振式差分微加速度传感器,分析了该结构差分检测和消除交叉轴干扰的原理.推导了该设计的理论模型,包括结构建模和轴向力作用下谐振微梁的固有频率偏移的推导,得到了待测加速度与输出固有频率偏移的关系.使用有限元模拟来证实理论模型.模拟结果说明,该设计的灵敏度每重力加速度g高于4kHz.探讨了具体结构参数的选取与输出频差的关系,说明通过调整微型杠杆的尺寸可以进一步提高本设计的灵敏度. 相似文献
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In this study, one-dimensional transient wave propagation in multilayered functionally graded media is investigated. The multilayered medium consists of N different layers of functionally graded materials (FGMs), i.e., it is assumed that the stiffness and the density of each layer are varying continuously in the direction perpendicular to the layering, but isotropic and homogeneous in the other two directions. The top surface of the layered medium is subjected to a uniform dynamic in-plane time-dependent normal stress; whereas, the lower surface of the layered medium is assumed free of surface tractions or fixed. Moreover, the multilayered medium is assumed to be initially at rest and its layers are assumed to be perfectly bonded to each other. The method of characteristics is employed to obtain the solutions of this initial-boundary-value problem. The numerical results are obtained and displayed in curves showing the variation of the normal stress component with time. These curves reveal clearly the scattering effects caused by the reflections and refractions of waves at the boundaries and at the interfaces of the layers. The curves also display the effects of non-homogeneity in the wave profiles. The curves further show that the numerical technique applied in this study is capable of predicting the sharp variations in the field variables in the neighborhood of the wave fronts. By suitably adjusting the material constants, solutions for the case of isotropic, homogeneous and linearly elastic multilayered media and for some special cases including two different functionally graded layers are also obtained. Furthermore, solutions for some special cases are compared with the existing solutions in the literature; very good agreement is found. 相似文献
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Logarithmic CMOS image sensors are appealing for their high-contrast and high-speed response but they require postprocessing to achieve high-quality images. Previously published work has explained the fixed pattern noise (FPN) in these image sensors using a steady-state analysis. This paper explains how the transient response of the readout circuit may also contribute to FPN. Thus, the performance of these CMOS cameras may be optimized with a proper understanding of the transient response, which is explained here through modeling and simulation with some experimental validation. In particular, the gain variation of a logarithmic camera is shown to be caused primarily by premature digitization. As logarithmic and linear active pixel sensors use similar circuits, some results in this paper, e.g., an analysis of readout capacitance, apply equally to the latter. 相似文献
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M. A. Hader M. A. Al-Nimr V. A. Hammoudeh 《International Journal of Thermophysics》2006,27(2):665-680
The transient thermal behavior of a homogeneous composite domain described by three macroscopic heat-conduction models, under the effect of a fluctuating heating source, was investigated analytically. The composite domain consists of a matrix (domain 1) and inserts (domain 2), each made of different material. The matrix has a high concentration or volume fraction (>0.5) while the insert has a low concentration or volume fraction (< 0.5). The range of parameters within which the use of the hyperbolic or the dual-phase-lag heat-conduction models is a necessity was traced. The role that the frequency and amplitude of the fluctuating thermal disturbance plays in using the appropriate macroscopic heat-conduction model was studied. 相似文献
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A Dual Reciprocity Boundary Element Method is formulated to solve non-linear heat conduction problems. The approach is based on using the Kirchhoff transform along with lagging of the effective non-linear thermal diffusivity. A posteriori error estimate is used to provide effective estimates of the temporal and spatial error. A numerical example is used to demonstrate the approach. 相似文献
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D. I. Bradley S. N. Fisher A. M. Guénault R. P. Haley G. R. Pickett J. E. Roberts S. O’Sullivan V. Tsepelin 《Journal of Low Temperature Physics》2007,148(5-6):603-607
We present measurements of the response of the A-like phase of superfluid 3He in aerogel to an applied flow. The measurements are made using a cylindrical piece of 98% silica aerogel attached to a
vibrating wire resonator. The resonator is immersed in superfluid 3He at low temperatures and relatively high magnetic fields such that the aerogel confined superfluid is in the A-like phase,
while the surrounding fluid is in the bulk B-phase. We observe a variety of interesting non-linear and hysteretic effects
when the resonator is driven to higher velocities. We present some of our preliminary findings and speculate on their implications. 相似文献
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A. V. Gusev 《Measurement Techniques》2005,48(9):843-847
The class of generalized Poisson distributions is proposed for the probabilistic distribution of coincidences in a gravitational
wave experiment with a complicated data processing system. Formulas are given for the parameters of these distributions in
terms of sample (empirical) estimators for the origin moments of the background coincidences. Optimal and quasioptimal algorithms
are considered for observing gravitational pulses from coincidences in the class of such distributions.
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Translated from Izmeritel'naya Tekhnika, No. 9, pp. 8–11, September, 2005. 相似文献
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对于具有多点约束的大型旋转火箭-发射装置系统,提出了计算瞬态响应的混合方法,为柔性火箭发射系统的建模与姿态控制提供了有效的途径。数值算例表明该方法的准确度与可靠性。 相似文献
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Summary The theory of relatively undistorted waves is used to study the finite-amplitude waves in a hot-electron model of plasma. A simple asymptotic expansion accounting for the non-linear effects has been used in the small amplitude limit to calculate the first and the second order solutions. The speed of propagation and the location of weak shocks has been determined through solutions of high-frequency waves. 相似文献
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An analytic solution has been obtained for the steady-state temperature field of two coaxial finite cylinders, the inner of which is a rotor. Two cases corresponding to different conditions of cooling of the outer cylinder, or housing, are considered. 相似文献