共查询到20条相似文献，搜索用时 62 毫秒
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马小宁 《新乡教育学院学报》2005,18(4):76-76
构造了一个二维热传导方程的两层显式格式,截断误差为O(△t △x2),稳定性条件为r=t/x2=t/y2<1/2,优于同类的其它显式格式。 相似文献
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对四阶抛物型方程构造一族新的含参数三层显式差分格式，它包含了DuFort-Frankel型格式，适当选取参数时，可得到一个新的高精度显格式，其截断误差达到O[（△t)^2 (△x)^6],其稳定条件为γ=△t/(△x)^4≤31/360，优于文[1]的稳定条件，当选取γ=1/252时，其截断误差高达O[（△t)^2 (△x)^8]，数值例子表明该格式是有效的。 相似文献
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陶万利 《数理天地(高中版)》2005,(9)
1.物理量x与x对时间的变化率△x/△t(1)物理量x描述物理过程或物理状态的量称为物理量.如:位移s、速度v、加速度a、力F、动量p、电量Q、电流强度I、磁通量Φ、感应电动势E等. 相似文献
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我们知道,数学函数图像中曲线切线的斜率k=△y/△x(在y-x坐标系里).而在物理函数图像中曲线切线的斜率有其物理意义,例如:在s-t图中,tanα=△s/△t=v,表示物体在该时刻速度的大小.在v-t图中k=tanα=△v/△t=a表示物体在该时刻加速度的大小. 相似文献
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讨论了形如x^n P(t)x′ q(t)x=0的二阶齐线性方程，推广了文[1]中该方程两个不变量I(t)△↑-q(t)-1/4q^2(t)-1/2p′（t）和J（t）△↑-q′（t） 2p(t)q(t)/1|q(t)|3/2的证明，并由此推出几类齐线性方程可化为常系数方程或易求解的方程的情形及它的通解，推广了文[2]的4种情形。 相似文献
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方蓉 《广东广播电视大学学报》2010,19(2):92-93,101
本文研究二阶非线性超前型差分方程△τ（α（t）（△τx（t））＋p（t＋τ）f（x（t＋τ））=0一切解为振动的充分条件,推广了已有文献中相关结果。 相似文献
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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. 相似文献
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周子君 《数理天地(高中版)》2009,(9):3-4
1．圆锥曲线的切线求法可导函数y=f（x）上任一点P（x0,y0）处的切线方程为y-y0=f^1（x0）（x-x0）,其中f^1（x0）=lim△r→^△y/△x=lim△x→0f（x0＋△x）-f（x0）/△x, 相似文献
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毛立武 《数学大世界(高中辅导)》2013,(4):20-21
在反比例函数y=k/x(k≠0)中比例系数k有它的特殊几何意义,即过双曲线y=k/x(k≠0)上任意一点P作x轴、t轴的垂线,垂线段与两坐标轴围成的矩形面积为|k",如图1所示,矩形OAPB的面积为|k|,△POA、△POB的面积为1/2|k|,这个结论是不变的,可命题的形 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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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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《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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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
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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