非线性项变号的奇异边值问题的正解

讨论带有延滞项的奇异三点边值问题:u″(t)+f(t,u(t-τ))=0,t∈(0,1)\τu(t)=η(t),t∈u(1)=βu(α)(1)正解的存在性,其中f变号且可能在t=0,t=1,u=0处奇异,文章的最后给出了这个定理的具体应用.     

带阻尼项不可压Euler方程爆破解的存在性

研究了带阻尼项α||u||L∞u(α0)的不可压Euler方程。首先,我们利用Galerkin方法、Poincare不等式、Sobolev嵌入定理、能量不等式,我们得到了带有阻尼项不可压Euler方程有类似于古典不可压Euler方程的不变性(爆破解的存在性)。其次,我们证明了古典不可压Euler方程的解v(x,t)和带有非线性项不可压Euler方程解u(x,t)之间存在下面关系:u(x,t)=φ(t,x)v(x,t)φ(t)=λ∫t0exp[∫τ0||u||L∞ds]dτ)。     

测度链上一类时滞微分方程组的振动准则

考虑如下时滞微分方程组y^△i（t）=fi（t,y1（τ1（t））,y2（τ1（t））,y1（τ2（t））,t≥t0,i=1,2其中（i）fi（t,u1,u2,v1,v2）对参数都是连续的;（ii）τi（t）∈Crd[t0,R^＋],τi（t）≤t,且τi（t）≤t,且τi（t）单调不减,lim t→∞τi（t）=∞,获得了该方程组所有解振动的充分条件．     

LTI因果系统零状态响应与卷积

对于线性时不变(LTI)因果系统,其系统单位冲激响应h(t)应满足h(t)=h(t)u(t),尽管卷积公式有∫∞-∞x(τ)h(t-τ)dτ=∫∞-∞h(τ)x(t-τ)dτ,但是,上式中h(t-τ)是非因果,所以,公式∫∞-∞x(τ)h(t-τ)dτ不满足实际物理系统。通过实际信号作用于系统的讨论和分析,揭示了在任意时刻的系统零状态响应和满足实际物理系统的卷积∫∞-∞x(τ)h(t-τ)dτ的物理意义。     

一类含时滞反应扩散方程波前解的存在性

研究一类含时滞反应扩散方程δu/δt（x，t）=δ^2u/δx^2（x，t）＋u（x，t）（a＋bu（x，t—τ）-c^2u^2（x，t—τ））的波前解，其中x∈R，t≥0，a〉0，c≠0，b∈R，通过构造合适的上下解，证明了当时滞充分小时，方程存在波前解，用线性化方法，给出了存在波前解的τ值的一个估计。     

具非线性扩散系数和阻尼项的双曲型偏微分方程系统解的振动性

研究了一类具非线性扩散系数和阻尼项的双曲型偏微分方程系统(a)2u1(x,t)/(a)t2+m(t)(a)u1(x,t)/(a)t=ai(t)hi(ui)△ui+n∑j=1aij(t)hij(u1(x,t-τj(t)))△ui(x,t-τj(t))-m∑k=1bik(x,t)uk(x,t-σ(t)) (x,t)∈Ω×R+≡G,i=1,2,…m,获得了该方程组在Robin边值条件下解振动的充分条件.     

变系数多维线性结构关系EV模型参数的加权M估计

考虑变系数多维线性结构关系EV模型y=xτβ(t),Y=y+ε,X=x+u中的参数β(t)=(β1(t),β2(t),….,βP(t))τ的估计,利用线性模型中的M方法和权函数方法,构造出t=t0处的参数β(t0)的加权M估计量βn(t0),并证明了它具有相合性.     

分数阶Volterra型积分微分方程解的存在唯一性

考虑分数阶Volterra型积分微分方程 D^Su=f（t，u） -cu∫0^tu（τ）dτ，t≥ 0 ，0〈s〈1，c〉0，D^su取Riemann-Liouville导数，获得了解的存在唯一性定理.     

非线性奇异微分方程周期解的存在性和多重性

利用变分法研究非线性奇异微分方程(g(t)|u′(t)|p-2u′(t))′-|u(t)|p-2u(t)=λF(t,u(t)),a.e.t∈[0,T]u(0)-u(T)=gq-1(0)u′(0)-gq-1(T)u′(T)=0(P)周期解的存在性和多重性问题,其中T>0,λ>0,g∈L∞(0,T;R+),ess.infg>0,p2,1p+1q=1,F:[0,T]×RN→R满足下面的假设:(A)对任意的u∈RN,F(t,u)关于t可测;对几乎所有的t∈[0,T],F(t,u)关于u连续可微.并且存在a∈C(R+,R+),b∈L1(0,T;R+),使得对一切的u∈RN,几乎所有的t∈[0,T],有|F(t,u)|a(|u|)b(t),|F(t,u)|a(|u|)b(t).     

非线性多变延迟奇异摄动问题的稳定性分析

讨论了形如x′(t) =f(x(t) ,x(t -τ1(t) ) ,… ,x(t -τm(t) ) ,y(t) ,y(t -τ1(t) ) ,… ,y(t-τm(t) ) )和εy′(t) =g(x(t) ,x(t -τ1(t) ) ,… ,x(t -τm(t) ) ,y(t) ,y(t -τ1(t) ) ,… ,y(t -τm(t) ) ) (0 <ε 1)的非线性多变延迟奇异摄动系统的理论解的稳定性 ,得到了系统稳定的一个充分条件 .在此条件下还证明了隐式Euler方法的数值解是稳定的 .     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.