共查询到20条相似文献，搜索用时 156 毫秒
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陈目 《广东教育学院学报》2006,26(5):34-39
通过利用平均积分法和黎卡提变换,对一类二阶非线性带阻尼项中立型微分方程[r(t)(x(t) a(t)x(t-τ))′]′ p(t)x′(t) q(t)f(x(t-δ))=0,其中τ,δ是正常数,r,p,q,a∈C([t0,∞),R),f∈C(R,R)作进一步的讨论,所得的结果推广了已知的结论,应用更加广泛. 相似文献
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一阶具连续变量中立型差分方程解的振动性 总被引：1，自引：0，他引：1
熊万民 《陕西理工学院学报(社会科学版)》2001,19(6):9-12
借助研究时滞微分方程振动性的一般方法 ,建立了一阶具连续变量中立型差分方程Δ[x(t) -p(t)x(t-τ) ]+q(t)x(t-σ) =0解的的振动性的充分条件 ,其中τ,σ为正常数 ,p ,q∈C(R+,R+) ,Δ指步长为τ的向前差分算子 . 相似文献
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考虑二阶不稳定型中立型时滞微分方程[x（t）-p（t）x（t-τ）]″=q（t）｜x（t-σ）｜^α-1x（t-σ），t≥t0，其中α〉1，τ〉0，σ〉0，且p，q∈C（[t0，＋∞），R^＋）获得了该方程的一个无界正解，推广了文献中的结论。 相似文献
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给出了不稳定型阶超线性时滞微分方程[x（t）-px（t-τ）]^（n）=q（t）｜x（t-σ）｜^βsign[x（t-σ）]．t≥t0所有有界解振动的充要条件．这里n≥1为偶整数,β〉1,τ〉0,σ〉0,和0〈p〈1,q∈C（[t0,∞）,[0,∞））． 相似文献
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张晓声 《忻州师范学院学报》2002,18(2):48-50
对于P∈C(犤to,∞),R),Q∈C(犤t0,∞),R ),给出了中立型方程犤x(t)-P(t)x(t-τ)犦(n) Q(t)x(t-σ)=0,的充分条件,改进了已知的结果。 相似文献
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研究具有正负系数的中立型时滞微分方程d2/dt2y[y(t)-p(t)y(t-τ)] q(t)f(y(t-σ))=0其中p(t)∈C([t0, ∞),R),q(t)∈C([0, ∞,[0, ∞)),τ,σ∈(0, ∞),对于上面方程非振动解的存在性,得到一个用∫∞sq(s)ds＜∞来表示的充分条件,推广了[2]的结果. 相似文献
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封屹 《湖南师范大学教育科学学报》2000,(5)
研究具有正负系数线性中立型微分方程 (x(t) -p(t)x(t-τ) )′+Q(t)x(t -σ) -R(t)x(t-δ) =0 ,t≥t0 ,其中P(t) ,Q(t) ,R(t) ∈C([T0 ,+∞ ) ,(0 ,+∞ ) ,τ>0 ,σ>δ≥ 0 ,Q(t) =Q(t) -R(t-σ+δ) >0 ( 0 ) ,获得了保证方程每一解振动的新的充分条件 相似文献
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讨论了具有正负系数的一阶中立型微分方程 [x(t) - p(t)x (t -τ) ]′ q(t) f(x(t -σ) ) -r(t) f(x(t-δ) ) =0解的渐近性 ,获得了方程解振动充分条件的振动性 相似文献
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在临界状态下建立了一阶非线性中立型时滞微分方程(x(t)-cx(t-τ))’ ∑pix(t-τi) f(t，x(t-σ1(t))，…，x(t-σn(t))=0与一个相关的二阶常微分方程振动性等价定理，进而给出了一阶非线性中立型微分方程(x(t)-cx(t-τ))’ ∑pif(x(t-τi))=0与相应的线性方程振动性等价的充分条件，从而推广了[1]的相应结果。 相似文献
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利用Bellman-Bihari积分不等式,讨论了二阶非线性中立型微分方程,(x(t)+px(t-τ))″=f(t,x(t),x′(t)),t≥1,τ＞0(f∈C[[1,∞]×R×R,R])解的渐近质,得到了方程解渐近于直线的一个充分条件. 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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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
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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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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