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1.
Periodic solutions of reaction-diffusion systems with time delays are investigated. It is constructed that the - per and lower control function of nonmonotone reaction term, and it is showed that the function satisfies a global Lipschitz condition and quasimonotone. A sort of effective method of studying differential equation with nonmonotone reaction term is gained. By using the method of upper and lower solutions and fixed point theorem, it is shown that periodic solutions of this system exist when reaction-term is not monotone and the boundary value system has a pair of coupled-upper and lower solutions. Some methods for proving the stability of the periodic solution are also given. And some known resuits are extended. 相似文献
2.
This paper gives a brief presentation of the influence of different information structures on portfolio selection and some simple examples to demonstrate their basic algorithms. The first is the familiar mean_variance model. The model does not need more hypotheses on the motion of the asset price along the full continuous time axis,but sometimes many unanticipated computation problems may be involved because of the difficulty in computing the inverse of some matrices with high dimension. The second is the stochastic optimal control model. It is to solve a stochastic optimal control problem,which is often related to Hamilton_Jacobi_Bellman eqution.It results in solving partial differential equations of Riccati matrix differential equations. Their closed_form solutions are usually very hard to obtain. The last is the differential game model. The existence,uniqueness,and the computation for its equilibrium solution are all very difficult mathematical problems. 相似文献
3.
In this paper,we make an attempt to study forced vibrations of the nth-order linear neutral delay differential equations with real constant coefficients. Sufficient and necessary conditions of the existence and uniqueness of periodic solutions for the equations are obtained by use of theory of Pourier series. Furthmore ,some brief and practical critiria are given. 相似文献
4.
Partial functional differential equations come from many mathematical models in physics,biology,engineering and other fields,which have strongly practical background.The oscillation theory is the one of the important branches of qualitative theory of partial functional differential equations. Therefore,it is of great theoretical and practical value to research the oscillation of partial functional differential equations.The anthors study the oscillation of the systems of a class of high order nonlinear delay partial functional differential equations.By using Green's theorem and Riccati transformation,they obtain some sufficient criteria for oscillation of all solutions of the systems under two kinds of different boundary value conditions,which are illustrated by some examples.These results offer the foundation of mathematical theory for solving the practical problems of the above fields. 相似文献
5.
YAO Qing-liu 《保鲜与加工》2007,(9):93
The purpose of this paper is to consider a kind of special nonlinear Neumann boundary value problems. The kind of boundary value problems has not Green function. Using suitable transformation,we can change these problems to general Neumann boundary value problems. By applying integral equation and degree theory on cone,the existence of n positive solutions is proved for the kind of problems,where n is an arbitrary natural number. 相似文献
6.
The singular perturbation problem of 2-order quasilinear elliptic is discussed, the outer solution and N-order successive equation of boundary layer term is given,and the remaind term is estimated. Hence,the asymptotic expantion of solution and the existence and uniqueness of the solution of the perturbation problem are derived. 相似文献
7.
The basic principle of infinite-dimensional dynamic system is to try to reduce the original infinite-dimensional system to an infinite-dimensional system. However,due to the unknown structure of the reduced system, it is difficult to describe its dynamical behaviour. To overcome this difficulty, the idea of approximate inertial manifolds is introduced, for NSE, the existence of AIM was studied, it is shown that the global attractor lies within a neighborhood of the graph of an Lipschitz function by the squeezing property. In this paper, by constructing a finite dimensional solution sequence, we will prove that it tends to the global attractor, theoretically, this provides a metod of constructing the asymptotic attractors, theoretically, this provides a method of constructing the asymptotic attractors for the evolution equations. 相似文献
8.
Periodic solutions of reaction-diffusion systems with time delays are investigated. The upper and lower control function of nonmonotone reaction term is constructed. It is showed that the function satisfies a global Lipschitz condition and quasimonotone. A sort of effective method of studying differential equation with nonmonotone reaction term is gained. It is shown that periodic solutions of this system exist when reaction-term is not monotone and the boundary value system has a pair of coupled to-upper and lower solutions. 相似文献
9.
GONG Xian sheng 《保鲜与加工》1999,(5):6-12
A method,stroboscopic harmonicbalance method which is used to solve strong nonlinear system, is proposed. The method is used to find the solution of strong nonlinear system. In investigation,the existence conditions of primary resonance solution and subharmonic resonance solutions are obtained. The results which are obtained by the stroboscopic harmonicbalance method are compared with those by computer numerical simulation. The results show that the stroboscopic harmonicbalance method is correct in qualitative analysis and it can meet the demands in engineering. 相似文献
10.
This paper briefly describes elasticity theory with different moduli and research progress in recent twenty years,analyzes computational results respectively from these two theories to all kinds of engineering structures and concludes that applying different moduli theory to solve some engineering components conforms to the real mechanics performance.This paper also deals with the differences between analytical solution and numerical one.Though finite element method is an effective measure to solve these nonlinear problems,seeking analytical solutions is still a difficulty and goal for some problems. 相似文献
11.
Taking into the feature of computer computing method, using Stress solution of elasticity theory and according to different method of solving of system of second order ordinary differential equations , this article provides two numerical value computing method as for the stress and deformation of the turbine impeller which is within the scope of elasticity . One combines the initial value computing method of system of ordinary differential equations (Runge-Kutta Method) with optimization method, another combines the boundary value computing method of system of ordinary differential equations difference method-with optimization method and three points interpolation method . The proposed method can eliminate the deficiencies of Secondary Calculation method and is particularly suited for programmable computer-based solution . The sample show that results gotten by two methods is nearly equal to the precise results,so they are practicable. They completes the quick and precise calculating of stress and deformation . They have some general meaning , large commonality and the project employing value. 相似文献
12.
PAA-AM/SH/MMT多功能保水剂的溶胀和保水性能研究 总被引：2，自引：0，他引：2
以丙烯酸（AA）、丙烯酰胺（AM）、腐殖酸钠（SH）和膨润土（MMT）为原料,采用水溶液聚合法合成了聚（丙烯酸－丙烯酰胺）/腐殖酸钠/膨润土复合多功能保水剂（PAA-AM/SH/MMT）。开展了复合多功能保水剂吸水速率、不同pH溶液和重复使用的溶胀行为以及在实际土壤中保水效果的研究。结果表明：与单独引进SH或MMT相比,在PAA-AM体系中同时引入SH和MMT所制备的多功能保水剂,不仅具有较快的吸水速率,而且具有良好的反复使用性能和较好的保水性能。 相似文献
13.
Branch -like pipeline is a common structure in gas transmission pipeline. In the light of the constituent properties of natural gas branch - like pipeline system, the system can be divided into fundamental constituent units. This paper presents a realistic unsteady flow model consisting of simple models of pipeline units and connecting conditions, boundary conditions and initial condition associated with units by using system analysis method. The solutions in wide sense are obtained by theory of functional analysis and operator series method, Such a method has the properties of both analytical solution and numerical solution methods. When the divided pipeline unit is larger, an intuitive approximate analytical solution may be obtained; while the one is smaller, a more accurate numerical solution may be acquired. Based on this, a general computer program has been developed for this model and solutions have been used successfully in a local natural gas transmission network in Sichuan. It is proved that the model and algorithm proposed in this paper are of the advantages of convenient calculation, high precision, time saving and wide application range by way of analysis and application. 相似文献
14.
Rainfall is the main input for probabilistic analysis and prediction of rainfall-triggered landslide. The joint probabilistic structure of daily rainfall (DR) and cumulative rainfall (CR), which are dominant parameters of rainfall related on landslide in Chongqing region, was analyzed. Following the traditional technology, daily rainfall was translated into discrete variable by rainfall grade and cumulative rainfall became continuous variable if records with very small cumulative rainfall were ignored. Then joint probabilistic model of discrete variable and continuous one was derived, and transiting solution of conditional density function was put forward, together with its approximation via a family of Dirac δ sequences. Naturally, the proposed method was used to analyze conditional density function of cumulative rainfall in Chongqing region, and the numerical results were verified by comparison. However, most of the conditional density functions were irregular and not modeled by simple probability density function, thus the finite mixture distribution was introduced, which is of uncomplicated format and relatively high precision. At last, the joint probabilistic model of daily rainfall and cumulative rainfall was built up by combining frequency function of grade of daily rainfall with conditional density model of cumulative rainfall. 相似文献
15.
A higher-order shear deformation theory is used to analyse nonlinear bending of symmetrically laminated angle-ply rectangular plates. The nonlinear governing differential equations are solved here by using perturbation method. Numerical rerults are presented graphically for vairous parameters of laminated plate. The present solutions are compared with those obtained using the classical plate theory. A lot of significient conclusions are obtained. 相似文献
16.
Min Huang Yingbin Zou Yuehua Feng Zhaowei Cheng Yali Mo Md. Ibrahim Bing Xia Peng Jiang 《European Journal of Agronomy》2011,34(4):278-286
No-tillage and direct seeding (NTDS) is an effective crop production method for reducing production costs and soil conservation. In order to understand performance of super hybrid rice under NTDS in rice–oilseed rape cropping system, a researcher-managed trail (2004–2010) and an on-farm research (2002–2005) were conducted to compare different tillage (conventional tillage or no-tillage) and rice establishment methods (transplanting or direct seeding) in super hybrid rice–oilseed rape cropping system. Under researcher-managed condition, grain yields of super hybrid rice under NTDS and conventional tillage and transplanting (CTTP) were equal. Compared with under CTTP, super hybrid rice under NTDS was characterized by more panicle number per m2 but less spikelet number per panicle, and lower aboveground biomass production before heading but higher aboveground biomass accumulated during heading to maturity. Higher maximum tiller number per m2 and lower spikelet production efficiency were responsible for the more panicle number per m2 and less spikelet number per panicle under NTDS, respectively. Under farmer-managed condition, super hybrid rice under NTDS had more panicle number m2 than under CTTP, which resulted in higher grain yield. Labor input under NTDS was lower than that under CTTP. Moreover, adoption of NTDS for super hybrid rice production had no significant impacts on seed yield and yield components of oilseed rape in rice–oilseed rape cropping system. Our study showed that CTTP could be replaced with NTDS to maintain yield and save labor for super hybrid rice production in rice–oilseed rape cropping system. 相似文献
17.
In 1995, Padmanabhan and Vrat presented inventory models for deteriorating items with a constant selling price and stock dependent selling rate . Based on the result, in 2000, Kun-Jen Chung, Peter Chu and Shaw-Ping Lan devoloped the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging. Actually, the selling price need not be constant, it may be variable . This paper puts forward an EOQ model when the selling price is variable without backlogging, discusses the existence and uniqueness of optimum solution. The example is provided to illustrate the model. The theoretical evidence is provided for the inventory system to make management decision. 相似文献
18.
Based on theory of cylinders subjected to uniform internal pressure, the mechanical performance of a steel tubular column filled with equidistant fiber reinforced polymer (FRP) ring stiffening concrete is investigated. The solutions for the stress and displacement are regarded as the superposition of elementary and improved solutions. The elementary solutions are found by using two dimensional elastic theory. The improved solutions are found by using the Love displacement function method. Considering the conditions of the displacement continuum of the FRP ring and the steel tube exterior, a more accurate solution for an equidistantly FRP ring stiffened cylinder subjected to a uniform internal pressure is obtained. Several numerical calculations are also carried out. The results indicate the solutions possess good convergence. 相似文献
19.
The governing partial differential equations (PDEs) are deduced from the asymptotically correct, geometrically nonlinear theory to research the bucking and mode jumping behavior of biaxially antisymmetric angle-ply composite laminates. The PDEs are transformed into a system of nonlinear ordinary differential equations (ODEs) by using the generalized Galerkin method. Then, the post-buckling behavior is analyzed by using the solution extension software. At last, the paths of buckling mode jumping and critical loads for the composite laminates under the in-plane boundary condition of straight edge are determined. An example of 4-layer composite laminates shows that the numerical results in the primary post-buckling region from the present method agree with the finite element analysis (FEA); while the FEA may lose its convergence when solution comes close to the secondary bifurcation point, the analytic method has the capability to explore deeply into the post-secondary bucking realm and capture the mode jumping phenomenon. 相似文献
20.
As the self weight of cable affects mechanical behavior obviously with the inerease of span length.FRP (fiber reinforced polymer) cable that has the lighter weight than the conventional cables has advantage for long span structures.The analysis of single cable is the fundamental theory for the design of cable structures.Based on different considerations of gravity loads.the solutions of the single cable on gravity loads have three sets of solutions: parabola solution.catenary solution and elastic catenary solution.And the equations for the three sets of solutions are derived by taking the end tension force of cable as the control parameter.The comparison between FRP cables and steel cables is conducted by elastic catenary solution.and the results show that the lager span structure can be realized by FRP cables.The precision for the parabola solution and catenary solution is compared for stay cables and horizontal cables.and the proper ranges of both approximate methods are proposed.Based on the above methods.the ultimate span length of FRP cable and steel cable are analyzed.It is concluded that the ultimate span of FRP cable is 4.4 times larger than that of steel cable. 相似文献