共查询到20条相似文献，搜索用时 46 毫秒
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本文主要处理非局部波动方程组解的全局存在与爆破问题,考虑如下非局部波动方程组的初值问题：{δ^2u1/δt^2=δ^2u1/δx^2＋‖u2（·,t）‖p1,δ^2u2/δt^2＋‖u3（·,t）‖p2,δ^2u3/δt^2=δ^2u3/δx^2＋‖u1（·,t）‖p3,-∞〈x〈∞,t〉0 ui（x,0）=fi（x）,δui/δt（x,0）=gi（x）,i=1,2,3,-∞〈x〈∞ 这里0〈p1,p2,p3〈＋∞,‖ui（·,t）‖=∫-∞^＋∞ φi（x）｜u（x,t）｜dx,i=1,2,3,其中φi（x）≥∫-∞^＋∞ φi（x）dx=1,i=1,2,3。所有这些初值函数都为连续的且｜fi（x）｜＋｜gi（x）｜恒不等于0,i=1,2,3.根据对称性,本文假定p1≤p2≤p3. 相似文献
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用上、下解方法研究了n阶非线性微分方程k点边值问题y(n)=f(t,y(n-2),y(n-1))y(i)(di)=ai(i=0,1,…,n-3),g(y(n-2)(t1),y(n-1)(t1))=0,h(y(n-2)(tk),y(n-1)(tk))=0(1) 解的存在性、唯一性。其中tj∈R,j=1,2,…,k;t1相似文献
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利用锥理论和Leggett-Williams不动点定理对偶数阶常微分方程组三点边值问题多个正解的存在性{u^（2m）（t）=（-1）^mf（t,v（t））,0≤t≤1,v^（2m）（t）=（-1）^mg（t,v（t））,0≤t≤1,u^（2i）（0）=u^（2i）（1）-αu^（2i）（ξ）=0,i=0,1…,m-1,v^（2i）（0）=v^（2i）（1）-βv^（2i）（η）=0,i=0,1…,m-1进行了讨论和证明,其中0〈ξ,η〈1,0〈α〈1/ξ,0〈β〈1／η且f,g∈C（[0,1]×[0,＋∞],[0,＋∞]）． 相似文献
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王权 《雁北师范学院学报》2011,27(5)
主要讨论时标上二阶中立型动力方程（x（t）-sum pi（t）x（t-τ））from i=1 to n△△＋=sum fi（t,x（t-δi））from i=1 to n=0的振动性,其中pi∈Crd（T,R＋）,τ,δi∈（0,∞）,使得对所有t∈T,有t-τ,t-δi∈T,fi∈C（T×R,R）,i=1,2,…,n。利用导数的符号来判断解的性质,通过不等式的放缩,得到结论,并得到所有解振动的充分条件。 相似文献
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《小雪花(小学生成长指南)》2006,(12)
快过圣诞节了,怪猫妈给大家准备了四样礼物,不过,其中只有一样是怪怪猫的哟!怪怪猫急得抓耳挠腮,不知选哪一样好,还是大家来帮他选一选吧。记住,是四选一哟!上期答案:teacher doctor postman policemanw a t c h r u f k jb k v n d y i t u fi e g h k v m n v oc x g u y t y u t oy r h o l k c x o tc p g k v u x i y bl k m l k m l h i ae y i r i s i r f lv g s k y n b i t lo p u p p y s g v u“怪眼小飞侠”:何绮泳广东省佛山市孙岩伟黑龙江省宝清县第七小学五(2)班肖舒阳黑龙江省佳木斯市十七小学五(2)班圣诞节礼物… 相似文献
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一、求函数的最值及值域 例 1.求函数 y=的最大值与最小值 . 解：令 u=， v=则有 u2＋ v2=20,y=2u＋ v,在同一坐标系内画出四分之一个圆： u2＋ v2=20和直线系： v=－ 2u＋ y的图象 .如图 1，直线与圆相切时，有 ymax=OA.直线过点 B(0， 2 )时，有， ymin=OB.∴ ymax=10.ymin=2 . 例 2.求函数 y=2x－ 2 的值域 . 解：把给定函数变形为－ 2x＋ y=－ 2 ,令 y=t，得－ 2x＋ t=－ 2. .在同一坐标系中分别作出直线系 y=－ 2x＋ t及半双曲线 y=－ 2的图象 .如图 2直线系 y=－ 2x＋ t与下半双曲线 y=－ 有交点时， t≤－ 4或 0 二、比较大小 例 3… 相似文献
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本文用上下解单调迭代方法讨论了四阶常微分方程周期边值问题
｛u^（4）-βu^n（t）＋αu（t）=f（t,u（t））,0≤t≤1,
u^（i）（0）=u^（i）（1）,i=0,1,2,3
解的存在性,所得的结果推广了Cabada的相关工作． 相似文献
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《钦州师专钦州教院学报》1995,9(1):27-32
设G是连通偶图，（X1，X2）是其顶点的二分类，|X1|=|X2|=n,δ（G）≥t≥3，且对于X中的任意两点u和v，均有|N(u)∪N（v)|≥n-(t-2),i=1,2，文中对t≤6的情况，证明G是点圈偶图。 相似文献
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命题 设直线l：f（x,y）=0与二次曲线g（x,y）=0交于不同的两点A（x1,y1）,B（x2,y2）,由{f（x,y）=0 g（x,y）=0，分别消去y,x，得u（x）=0,v（y）=0（使u（x）,v（y）的二次项系数相等），则以线段AB为直径的圆的方程为：u（x）＋v（y）=0.[第一段] 相似文献
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研究具有连续变量的非线性偏差分方程 [A(x+r,y) +A(x ,y+r) -aA(x ,y) ] k-(bA(x ,y) ) k+ ∑ui=1pi(x ,y)Ak(x-τi,y-σi) =0 ,其中pi(x ,y) ∈C(R+×R+,R+/ { 0 } ) ,u是正整数 ,k=c/d>1 ,c,d为奇数 ,a为非负实数 ,b为正实数 ,θ =b-a ,满足 0 <θ≤ 1 ,r,σi,τi∈R+,i=1 ,2 ,… ,u ,得到了保证方程的所有解都具有振动性的若干充分条件 . 相似文献
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《海外英语》2007,(5):10-11
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? 相似文献
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《海外英语》2007,(4):36
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. 相似文献
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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. 相似文献
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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. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献