共查询到20条相似文献，搜索用时 31 毫秒
1.
Lu Guofu 《福建师大福清分校学报》1994,(3)
In this paper we consider the following problem
where the summation convention is used. We call the equation as porous medium equation with convection.
Let u = u(x,t) be a continuous weak solution of the equation in Rn × (0 ,T] for some T> 0. Then we can establish BCP estimates and the intrinsic Harnack inequality for the solution of the equation just as the standard equation discussed by other authors previously. This work lay a main foundation of studying other properties of this problem further. 相似文献
2.
Last summer I went to Dalian with my parents for our summer holiday, and we had a very good time there.Dalian is a city by the sea. It is in North China, and lots of people go there to spend their holiday. 相似文献
3.
We derive some results on the dividend payments prior to ruin in the classical surplus process with interest. An integro-differential equation with a boundary conditions satisfied by the expected present value of dividend payments is derived and solved. Furthermore, we derive an integro-differential equation for the moment generating function, through which we analyze the higher moment of the present value of dividend payments. Finally, closed-form expressions for exponential claims are given. 相似文献
4.
《湘南学院学报》1995,(2)
<正> In this paper, we consider the oscillation of first order differential equation with several delays of the formWhere Pi,ri,(i= 1,2,...,n) are positive constants. Our aim is to give a necessary and sufficient condition for all sollution of (0. 1) to be oscillation. Which answers an open problem by B.G Zhang in [1]. 相似文献
5.
The life of shipboard cables will decrease due to the complex aging processes. In terms of the safety perspective, remaining life prediction of the cable is essential to maintain a reliable operation. In this paper, firstly, based on Arrhenius equation, residual life of new styrene-butadiene cable is calculated; result indicates that the degradation rate which changes with time is proportional to thermal temperature. Then second order dynamic model is adopted into the residual life prediction, combined with the time-temperature superposition method （TTSP）, and a new residual life model is proposed. According to the accelerated thermal aging experiment data and Arrhenius equation, TTSP method demonstrates to be an efficient way for life prediction, and life at normal temperature can be estimated by this model. In order to monitor the state of styrene-butadiene cable more accurately, an improved residual life model based on equivalent environment temperature of cable is proposed, and life of cable under real operation is analyzed. Result indicates that this model is credible and reliable, and it provides an important theoretical base for residual life of cables. 相似文献
6.
We used computational fluid dynamics （CFD） and mode superposition method instead of the energy balance method to compute transmission line aeolian vibrations induced by the Karman vortex. Firstly, we obtained the wind power inputs using CFD theory. The result is effective for aeolian vibration analyses compared with the power which were measured in wind tunnel tests. Then a new aeolian excitation was derived using the wind power equivalent principle, and the aeolian vibration distribution along transmission lines and the wind power input obtained by CFD can be account. Secondly, we formulated the motion equation of a conductor-damper system and derived a semi-analytial solution using the mode superposition method. The Stockbridge-type dampers attached were simplified to the forces transmitted by the clamps. Finally, the semi-analytical solution can be solved by iterative methods. Taking a 1 000 kV Ultra High Voltage transmission line as an example, we analyzed the line with and without dampers by the semi-analytical solution. Compared with the results which were computed by the energy balance method, the semi-analytical solution is precise enogh for aeolian vibration analyses. Besides, we also analyzed the influence of damper position and quantity. 相似文献
7.
THYLEN L. HE Sailing WOSINSKI L. DAI Daoxin 《浙江大学学报(A卷英文版)》2006,7(12):1961-1967
We formulate a ＂Moore＇s law＂ for photonic integrated circuits （PICs） and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent basic elements, which makes a comparison with the generic elements of electronic integrated circuits more meaningful. The other is making a complex component equivalent to a series of basic elements of the same functionality, which is used to calculate the integration density for functional components realized with different structures. The results serve as a benchmark of the evolution of PICs and we can conclude that the density of integration measured in this way roughly increases by a factor of 2 per year. The prospects for a continued increase of spatial integration density are discussed. 相似文献
8.
Metacogonitive strategies are in connection with the reading process. It is essential for language learners to master a se?ries of metacogonitive strategies. Teachers should conduct metacognitive train... 相似文献
9.
In this paper, a new branch-and-bound algorithm based on the Lagrangian dual relaxation and continuous relaxation is proposed for discrete multi-factor portfolio selection model with roundlot restriction in financial optimization. This discrete portfolio model is of integer quadratic programming problems. The separable structure of the model is investigated by using Lagrangian relaxation and dual search. Computational results show that the algorithm is capable of solving real-world portfolio problems with data from US stock market and randomly generated test problems with up to 120 securities. 相似文献
10.
Metacogonitive strategies are in connection with the reading process. It is essential for language learners to master a series of metacogonitive strategies. Teachers should conduct metacognitive training among students. Thus, students are sure to improve their reading proficiency with some metacognitive knowledge during the reading process. 相似文献
11.
A rectangular thin plate vibration model subjected to inplane stochastic excitation is simplified to a quasinonintegrable Hamiltonian system with two degrees of freedom. Subsequently a one-dimensional Ito? stochastic differential equation for the system is obtained by applying the stochastic averaging method for quasi-nonintegrable Hamiltonian systems. The conditional reliability function and conditional probability density are both gained by solving the backward Kolmogorov equation numerically. Finally, a stochastic optimal control model is proposed and solved. The numerical results show the effectiveness of this method. 相似文献
12.
王冬梅 《读与写:教育教学刊》2007,4(11):1-2
The Awakening is a remarkable work of feminism written by Kate Chopin. The novel mainly depicts how Edna comes to her awakening and develops into a new woman with a heartfelt concern for freedom, equality and independence. The novel had significant influence on the formation of women's literature and contributed a lot to the achievements of feminist movement. 相似文献
13.
张兴友 《重庆大学学报(英文版)》2003,2(1)
1. Introduction Consider the problem (P) below 2 i(), for (,),txxxuuuuufxxtT++++=未a where the initial condition is 0(0,)()uxux=. Herein 0u and 2()fLT are square integrable complex functions on T; T is the 1-dimensional torus, +Ris the set of positive numbers, and a a real positive number. This type of equation was first introduced in the study of optical fibers [1]. Y. Martel [2] proved the well-posedness for the case of whole space R(the set of all real numbers) with a = … 相似文献
14.
A rectangular thin plate vibration model subjected to inplane stochastic excitation is simplified to a quasinonintegrable Hamiltonian system with two degrees of freedom. Subsequently a one-dimensional Ito stochastic differential equation for the system is obtained by applying the stochastic averaging method for quasi-nonintegrable Hamiltonian systems. The conditional reliability function and conditional probability density are both gained by solving the backward Kolmogorov equation numerically. Finally, a ... 相似文献
15.
My eyes are filled with tears that threaten to 1)spill over as I look at grandpa's blank,2)pale blue eyes.My sister is just finished reading a book written by Richard Paul Evans注1,and my mom turns to face her father who doesn't even remember reading the same book the day before."You were that dad for me," she 3)whispers."Really?" he replies,smiling with his 4)childlike 5)oblivion.My mom nods,crying,and I 6)clench my hands until my fingers turn white from loss of blood flow. 相似文献
16.
The current method to solve the problem of active suspension control for a vehicle is often dealt with a quarter-car or half-car model.But it is not enough to use this kind of model for practical applications.In this paper,based on considering the influence of factors such as,seat and passengers a MDOF(multi-degree-of-freedom)model describing the vehicle motion is set up.The MODF model,which is 8DOF of four independent suspensions and four wheel tracks,is more applicable by comparison of its analysis result with some conventional vehicle models.Therefore,it is more suitable to use the 8DOF full-car model than a conventional 4DOF half-car model in the active control design for car vibration.Based on the derived 8DOF odel,a controller is designed by using LQ(linear quadratic)control theory,and the appropriate control scheme is selected by testing various performance indexes.Computer simulation 8is carried out for a passenger car running on a road with step disturbance and random road disturbance expressed by Power Spectral Density(PSD).Vibrations corresponding to ride comfort are derived under the foregoing road disturbances.The response results for uncontrolled and controlled system are compared.The response of vehicle vibration is greatly suppressed and quickly damped.which testifies the effect of the active suspenson.The results achieved for various controllers are compared to invesigate the influence of different control schemes on the control effect. 相似文献
17.
The Great Gatsby is a 1925 novel written by American author F.Scott Fitzgerald.Besides great popularity for its vivid depiction of the Ameri-can Dream,the novel also impresses the world with its skillfully used American English which is interwoven with the plots,the characters and the theme.The article is to explore how Fitzgerald analyzes the class system of the American society and what enables him to express this analysis through different types of A-merican English. 相似文献
18.
张芸 《初中生世界(初三物理版)》2004,(26)
This is Teachers’Day and a time to be grateful to all teachers.Our beloved teacher,the love and care you have given us will encourage us to go through a long and arduous journey.On the voyage of life,you have kindled the light of hope for me. What you have done enriches my mind and broadens my view. On this day I honour you sincerely.Thank you for making learning not a dull thing but a great joy.You have been a qualified teacher and even a better friend.We wish to show our gratitude and th… 相似文献
19.
LU Li-gang YAN Li-tan XIANG Li-chi 《浙江大学学报(A卷英文版)》2007,8(1):158-163
INTRODUCTION Throughout this paper, we shall work with a filtered complete probability space (?,F,(Ft),P) sat-isfying the usual conditions. Let B=(Bt)t≥0 be a stan-dard Brownian motion with B0=0. Denote by ú the set of all non-negative real numbers. Recall that a diffusion process X starting at x≥0 is called the square of a Bessel process of dimension δ>0 if d X t = δd t 2 | X t |d Bt , X 0= x, (1) Clearly, this equation has a unique non-negative strong solution X, i.e., … 相似文献
20.
图的符号全划分数 总被引：1，自引：0，他引：1
Let G = （V, E） be a graph, and let f ： V →{-1, 1} be a two-valued function. If ∑x∈N（v） f（x） ≥ 1 for each v ∈ V, where N（v） is the open neighborhood of v, then f is a signed total dominating function on G. A set {fl, f2,… fd} of signed d total dominating functions on G with the property that ∑i=1^d fi（x） ≤ 1 for each x ∈ V, is called a signed total dominating family （of functions） on G. The maximum number of functions in a signed total dominating family on G is the signed total domatic number on G, denoted by dt^s（G）. The properties of the signed total domatic number dt^s（G） are studied in this paper. In particular, we give the sharp bounds of the signed total domatic number of regular graphs, complete bipartite graphs and complete graphs. 相似文献