共查询到20条相似文献，搜索用时 250 毫秒
1.
张海丽 《宜宾师范高等专科学校学报》2013,(6):25-28
利用强单调映象原理和临界点理论讨论2m阶微分方程边值问题{（-1）^m·u^（2m）（t）=f（t,u（t））,t∈[0.1] u^（2i）（0）=u^（2i）（1）=0 （i=0,1…,m-1）,其中f：[0,1]xR^1→R^1连续,得到其解的存在性和多重性． 相似文献
2.
何红军 《赤峰学院学报(自然科学版)》2012,(19):3-6
本文研究了一类时标上高阶动力方程m点边值问题（-1）^n u^（△V）^n （t）=λa（t）f（u） t∈[0,T]T
u^（△V）^i （0）=0 u^（△V）^i （T）=m-2∑i=1 aju^（△V）^i（ξj）（0≤i≤n-1）其中T是时标,aj∈[0,＋∞],ξj∈[0,ρ（T））T是满足适当条件的常数-并Ij用泛函型锥上压缩拉伸不动点定理,得到该问题的正解存在性,并且推广了一些原有的结果． 相似文献
3.
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
4.
王彩华 《赤峰学院学报(自然科学版)》2010,26(3):14-16
本文利用锥上的不动点定理研究了下列奇异非线性二阶三点边值方程组{-u″=f（t,v）, t∈（0,1） -v″=g（t,u）,t∈（0,1） u′（0）=v′（0）=0,u（1）=αu′（η）,v（1）=αv′（η）其中η∈（0,1）,α〈0在某些较弱条件下正解的存在性． 相似文献
5.
研究四阶奇异两参数常微分方程周期边值问题{u^（4）（t）-βu″（t）＋au（t）=f（t,u）（T（t）））,t∈[0,1]u^（i）（0）=u^（i）（1）,i=0,1,2,3}正解的存在性和多重性．当允许f（t,u）在u=0在u=c（c〉0）处同时奇异时,可用锥上的不动点指数理论证明该问题多个正解的存在性． 相似文献
6.
令ai≥0,i=1,…,m-3且am-2>0.再令ξi满足0<ξ1<ξ2<…<ξm-2<1且∑m-2i=1aiξi<1.我们研究下面边值问题正解的存在性u?(t)+a(t)f(t)=0,t∈(0,1),u(0)=u′(0)=0,u′(1)=∑m-2i=1aiu′(ξi)其中a(t)∈C([0,1],[0,∞]),f(t)∈C([0,1],[0,∞]).通过锥上的不动点定理证明了在f满足超线性或次线性条件下,上述问题至少存在一个正解. 相似文献
7.
何利平 《晋城职业技术学院学报》2011,4(5):73-75
考虑一类具有正负系数的时滞微分方程x（＇t）＋1tlntni=1Σpix（tα）i-1tlntni=1Σqix（tβ）i=0,其中0〈αi〈1,0〈βi〈1,pi〉0,qi≥0是常数,证明了方程所有解振动的一个充分条件为αi〈βi,ni=1Σpi〉ni=1Σqi,ni=1Σqilnβiα≤1,ni=1Σ（pi-qi）ln1α〉1e其中α=max{α1,α2,…,αn≤≤}. 相似文献
8.
研究均匀分布区间[a,b]上U=ηn^＊-η1^＊——（1-q）a＋qb-η1^＊的统计规律,其中,0〈q〈1,η1,η2…,ηn为取自总体η的容量为n的简单随机子样,η1^＊=min_l≤i≤n{ηi},ηn^＊=max_l≤i≤n{ηi},求出它的密度函数,分布函数。 相似文献
9.
利用Leggett-williams不动点定理研究了一类n阶m点边值问题{u(n)(t)+f(t,u(t))=0,00(i=1,2,…,m-2),0<ξ1<ξ2<…<ξm-2<1,0< kiξi<1. 相似文献
10.
于丽君 《忻州师范学院学报》2009,25(2)
文章主要研究了如下一类四阶含参微分方程周期边值问题解的存在性和多解性结果.u(4)(t)-ηu"(t)+ξu(t)=λf(t,u(t)),t∈[0,1],u(i)(0)=u(i)(1),i=0,1,2,3,其中f:[0,1]×R1→R1连续,η,ξ∈R1,λ∈R1+为参数.通过利用临界点理论和Morse理论,并满足条件:(H0)ξ＞0,η≥-4π2,则当λ落入某具体区间时,上述边值问题有多个解. 相似文献
11.
12.
13.
《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
14.
邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
15.
《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
16.
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
17.
Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
18.
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
19.
20.
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