一类带Beddington-DeAngelis反应项的捕食模型平衡态的分歧解

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。     

非线性体积收缩模型应用于多孔材料非稳态收缩的可行性分析

将半径收缩与平均干基含水率呈线性关系模型和Possion公式模型应用于香蕉各离散单元,对香蕉组织收缩进行了计算。结果表明,前者虽能够定性反映香蕉干燥过程中内部组织收缩的物理特性,但是其预测的香蕉半径收缩情况与实测结果相差较大;而后者不能反映香蕉内部组织失水滞后收缩现象。     

The Dynamic Response of a Resonant Frequency Tracking System

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.     

适用瞬态响应计算的火箭结构动力学模型修正方法

大型火箭结构十分复杂,其连接型式多,存在多分支结构。分析火箭结构中存在弱刚度的内-外翻边连接、螺栓点连接等典型连接型式,基于元素型法,以这些部位刚度为修正参数,开展动力学模型修正方法研究。结果表明,采用的方法能保证修正后模型的物理意义和真实性,能够适用于瞬态外激励作用下的结构响应计算,特别是内力响应计算。修正后模型的各阶模态结果和试验吻合较好,且与实际试验中瞬态响应的实测结果相比,计算具有较高精度,能够满足工程需求。     

Transient Response in a Micropolar Mixture of Porous Media During Thermal Shock

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.     

Transient Eddy-Current Driver Pickup Probe Response Due to a Conductive Plate

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.     

Identification of the Transient Response of a Capacitive Relative Humidity Sensor

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...     

非线性高维自治微分系统 SEIQR 流行病模型全局稳定性

研究具有隔离仓室及饱和接触率的非线性高维自治微分系统SEIQR流行病传播数学模型,得到疾病绝灭与否的阈值一基本再生数R_0,证明了无病平衡点和地方病平衡点的存在性及全局渐近稳定性,揭示了隔离对疾病控制的积极作用,推广了已有的研究结果。     

基于微型杠杆结构谐振式差分微加速度传感器的理论建模

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．     

One-Dimensional Transient Dynamic Response in Functionally Graded Layered Media

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.     

Transient Response and Fixed Pattern Noise in Logarithmic CMOS Image Sensors

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.     

具有Holling-Tanner项反应扩散模型正平衡解的存在性

本文首先运用极值原理以及Hopf边界引理讨论了一类具有Holling-Tanner项的反应扩散模型的平衡态系统在第三边值条件下的正解的先验估计。然后运用拓扑不动点理论,将Banach空间的Leray-Schauder度推广到正锥上,分析了系统正解的存在性。随后利用锥上紧算子的不动点指数计算方法,结合线性算子的谱性质,极值原理和上下解方法,得到了平衡态系统的正解存在的充要条件。     

Transient Thermal Response of a Homogeneous Composite Thin Layer Exposed to a Fluctuating Heating Source under the Effect of the Dual-Phase-Lag Heat-Conduction Model

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.     

Transient Non-linear Heat Conduction Solution by a Dual Reciprocity Boundary Element Method with an Effective Posteriori Error Estimator

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.     

Non-linear Mechanical Response of the A-like Phase of Superfluid 3He in Aerogel

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.     

A Parametric Model for a Priori Uncertainty in Coincidence Processing for Resonant Gravitational Antenna Output

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. __________ Translated from Izmeritel'naya Tekhnika, No. 9, pp. 8–11, September, 2005.     

大型旋转火箭发射系统瞬态响应的混合解法

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。     

Non-linear wave propagation in a hot-electron plasma

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.     

Steady-state temperature field of a finite cylinder in a housing

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.     

常利率古典风险模型的按比例分红问题

分红问题是目前保险精算研究的一个重要课题,本文利用HJB方程的方法证明了常利率古典风险模型的最优分红策略为边界策略;推导出了最优分红策略下常利率古典风险模型的期望红利总量现值所满足的积分方程;通过拉Laplace变换技巧给出了当保险公司的初始资金u大于或等于红利界线b时的期望红利总量现值的精确结果。为保险公司更合理的分配红利和掌控资金运营提供了理论依据。