共查询到20条相似文献，搜索用时 62 毫秒
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在ＧＭＡＮＯＶＡ－ＭＡＮＯＶＡ模型中，对于指定的非负定矩阵Ｃ，本文给出了ｔｒ（Ｃ∑）是ｔｒ（Ｃ∑）的一致最小方差非负二次无偏估计的充要条件，这里∑是∑的（一定意义下的）最小二乘估计。 相似文献
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丁平仁 《喀什师范学院学报》1999,19(1):23-26
讨论了增长曲线模型，Ｙ＝ＡＢＣ＋ｅ，Ｅ（ｅ）＝０，ＣＯＶ（ｅ）＝Ｉ，∑（∑〉０）的最二乘估计相对于Ｇａｕｅｓｓ－Ｍａｒｋｏｖ估计的几种相对效率，并给出了上界。 相似文献
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考察一般Gauss-Markov模型中未知参数向量β的岭估计的优良性质,在文献[1]提出的估计(~β)相对于估计(^β)的(相对)效率e((~β)|(^β))下,进一步讨论了最小二乘估计(LSE)相对于岭估计的效率下界,得到更好的结果.证明了:当X呈病态时,采用些估计以损失无偏性来换取更小的均方误差是可取的. 相似文献
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刘焕彬 《黄冈师范学院学报》1988,(3)
称为多元线性模型,以下简记为H。定义2 (?)元素的线性函数trA′(?)称为可估的,如果存在y元素的线性函数tr B′y使 Etr B′y=trA′(?)即tr B′y是trA′(?)的无偏估计。定义3 设tr B′y是trA′(?)的一个估计,则 L(B,A,(?))=E(tr B′y-trA′(?))~2叫做损失函数,而 R(B,A,(?),σ~2)=EL(B,A,(?)) =E(tr B′y-trA′(?))~2叫做风险函数。 相似文献
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以金融时间序列中同积向量的充分改进为对象,分析充分改进的最小二乘估计。在统计量的极限分布非标准时,构造充分改进的最小二乘估计。研究表明,改进的最小二乘估计方法是一种非参数方法,有助于充分的最小二乘估计。 相似文献
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讨论一类含参数λ的n(≥2)元实二次型∑ni=1∑nj=1(λij+i+j)xixj,证明其秩等于2,正、负惯性指标都等于1,符号差等于0,均与参数λ无关,从而证明这类二次型是不定的. 相似文献
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线性混合模型是一类有着广泛应用的统计模型,对其中的方差分量,常使用方差分析法来估计。本文研究了在一种特殊情况下,含三个方差分量的线性混合随机效应模型的ANOVA估计,讨论了在何种条件下此估计在均方损失下一致优于ANOVA估计。由于此方差分析估计取负值的概率大于零,用在某非负点截尾的方法给出了方差分量的非负估计,并给出了得到的估计在均方损失意义下优于截尾之前的估计的充分条件。 相似文献
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讨论强度为指数分布,应力为强度函数毫（l）∑（i=0）λit^i的复合非时齐Poisson过程模型结构可靠度的估计问题．获得强度函数（l）∑（i=0）λit^i的复合非时齐Poisson过程的最大值分布与当量正态变量,指数分布一强度函数（l）∑（i=0）λit^i的复合非时齐Poisson过程模型结构可靠度的最小方差无偏估计． 相似文献
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对于一般增长曲线模型 ,在二次损失函数下分别找到了参数阵的线性可估函数在给定的齐次线性估计类和非齐次线性估计类中的容许Miniarx估计 ,并证明了这两种估计分别是唯一的 相似文献
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朱雪芳 《赤峰学院学报(自然科学版)》2010,26(6):1-2
研究非负矩阵最大特征值的界值,给出了非负矩阵最大特征值界的一个新估计.提高了已有估计的精确度,并通过实例与以往的结论作比较,验证了该界值估计的有效性. 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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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 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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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 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