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991.
992.
Stephen P. Humphries 《Israel Journal of Mathematics》2004,143(1):189-222
We prove that (with two possible exceptions) the Hurwitz braid group action on the sequence of standard generators of an irreducible
Artin group has a finite orbit if and only if the Artin group is of finite type (i.e., the corresponding Coxeter group is
finite). 相似文献
993.
基于cDNA宏阵列的系统聚类分析猪发育阶段的基因表达谱 总被引:3,自引:0,他引:3
取杜洛克猪胚胎第33,45,55,65.75天的背最长肌样本.用cDNA Macroarray分析方法和聚类分析技术分析了327个EST在骨骼肌内不同发育阶段的基因表达谱.结果表明有98条EST在不同发育时期显著差异表达.第33天和第45天两阶段基因表达状态相似.第55天和第65天基因表达状态相似.而第75天的基因表达与第55天和第65天两个阶段的基因表达具有相近的聚类关系.表达状态相近,基因功能相似的基因大都被聚类在一起. 相似文献
994.
Oleg Safronov 《Arkiv f?r Matematik》2004,42(2):363-377
We study the spectral properties of Jacobi matrices. By combining Killip's technique [12] with the technique of Killip and
Simon [13] we obtain a result relating the properties of the elements of Jacobi matrices and the corresponding spectral measures.
This theorem is a natural extension of a recent result of Laptev-Naboko-Safronov [17].
The author thanks Sergei Naboko for useful discussions and Barry Simon for pointing out the conjecture. 相似文献
995.
Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors 下载免费PDF全文
The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors. 相似文献
996.
Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3 下载免费PDF全文
We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485-1553nm signal wave and 3383-3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal. 相似文献
997.
On the characterisation of paired monotone metrics 总被引:1,自引:1,他引:0
Paolo Gibilisco Tommaso Isola 《Annals of the Institute of Statistical Mathematics》2004,56(2):369-381
Hasegawa and Petz introduced the notion of paired monotone metrics. They also gave a characterisation theorem showing that
Wigner-Yanase-Dyson metrics are the only members of the paired family. In this paper we show that the characterisation theorem
holds true under hypotheses that are more general than those used in the above quoted references. 相似文献
998.
999.
Let A be a Weil algebra. The bijection between all natural operators lifting vector fields from m-manifolds to the bundle functor K
A
of Weil contact elements and the subalgebra of fixed elements SA of the Weil algebra A is determined and the bijection between all natural affinors on K
A
and SA is deduced. Furthermore, the rigidity of the functor K
A
is proved. Requisite results about the structure of SA are obtained by a purely algebraic approach, namely the existence of nontrivial SA is discussed. 相似文献
1000.