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21.
一类有理交错样条曲线的逼近性及形状修改 总被引:7,自引:3,他引:4
本文提出一类C^2连续的四阶有理交错样条曲线,它能整体或局部逼近于控制多边形。 相似文献
22.
Li Ping Huang 《数学学报(英文版)》2009,25(9):1517-1528
Let F be a field with |F| ≥ 3, Km be the set of all m × m (m ≥ 4) alternate matrices over F. The arithmetic distance of A, B ∈ Km is d(A, B) := rank(A - B). If d(A, B) = 2, then A and B are said to be adjacent. The diameter of Km is max{d(A, B) : A, B ∈ km}. Assume that φ : Km→Km is a map. We prove the following are equivalent: (a) φ is a diameter preserving surjection in both directions, (b) φ is both an adjacency preserving surjection and a diameter preserving map, (c) φ is a bijective map which preserves the arithmetic distance. 相似文献
23.
Noah Karl S. Fox Sandra L. Bruhn Debby F. Thompson David N. Bala Gregory A. 《Applied biochemistry and biotechnology》2002,98(1-9):803-813
The biosurfactant surfactin has the potential to aid in the recovery of subsurface organic contaminants (environmental remediation)
or crude oils (oil recovery). However, high medium and purification costs limit its use in these high-volume applications.
In previous work, we showed that surfactin can be produced from an inexpensive low-solids (LS) potato process effluent with
minimal amendments or pretreatments. Previous research has also shown that 95% or more of the surfactin in Bacillus subtilis cultures can be recovered by foam fractionation. In this work, we present the results of research to integrate surfactin
production with foam fractionation. Experiments were performed in an airlift reactor, with continuous collection of the foam
through a tube at the top of the column. Preliminary results using both purified potato starch and unamended low-solids potato
process effluent as substrates for surfactin production indicate that the process is oxygen limited and that recalcitrant
indigenous bacteria in the potato process effluent may hamper continuous surfactin production. 相似文献
24.
Jayant V Narlikar 《Pramana》1999,53(6):1093-1104
This is a review of an alternative cosmology, recently proposed by Fred Hoyle, Geoffrey Burbidge and this author. It begins
with a brief discussion of why one needs an alternative cosmology, when the standard hot big bang cosmology is claimed to
be doing well. It is argued that the observational and theoretical constraints on the standard big bang cosmology, from various
directions, leave a very narrow window, if any, in the parameter space of plausible models. There is thus a strong case for
alternative cosmologies. The rest of the review concentrates on one alternative, the quasi steady state cosmology (QSSC) and
summarises the recent work on this model. This includes, the theoretical formulation and simple exact solutions of the basic
equations, their relationship to various observations, the stability of solutions and the toy model for understanding the
growth of structures in the Universe. 相似文献
25.
以乙烯和乙炔为探针分子, 采用原位红外光谱技术研究了Pd-Ag/Al2O3和Pd/Al2O3催化剂上乙炔加氢反应, 通过乙炔吸附, 乙炔和氢的共吸附和交替吸附表征了催化剂表面吸附物种的变化. 结果表明, 在Pd-Ag/Al2O3催化体系中, 乙炔在Pd-Ag/Al2O3和Pd/Al2O3催化剂有着不同的吸附性能, 另外, 加氢反应会导致在催化剂表面形成由长分子链的烷烃组成的碳氢化合物层, 该吸附层与绿油有着相似的红外光谱特征, 最关键的是乙炔和氢的吸附顺序和碳氢化合物层的生成量之间存在着一定的关系, 这将直接影响催化剂的加氢性能. 相似文献
26.
使用激发光为785 nm的便携式拉曼光谱仪分别对赤星病菌、谷镰刀病菌和香蕉炭疽悬浮液进行了普通拉曼光谱和表面增强拉曼散射(SERS)光谱检测。实验结果显示,微波法制备的纳米银胶对三种植物病菌均具有较好的增强效果,同时获得了三种病菌信噪比较好的SERS光谱。从整体上看,三种菌谱峰峰强分布具有一定的相似性,如在481 cm-1处均为最强谱峰,500~1 000 cm-1谱峰较弱和1 000~1 600 cm-1谱峰较强。但三者在谱峰的分布和峰形上仍有明显不同,因此通过比较三种病菌的不同SERS谱峰可对其进行快速区分和鉴别。 相似文献
27.
28.
Thompson David N. Fox Sandra L. Bala Gregory A. 《Applied biochemistry and biotechnology》2001,91(1-9):487-501
Pretreatments of low-solids potato process effluent were tested for their potential to increase surfactin yield. Pretreatments
included heat, removal of starch particulates, and acid hydrolysis. Elimination of contaminating vegetative cells was necessary
for surfactin production. After autoclaving, 0.40 g/L of surfactin was produced from the effluent in 72 h, vs 0.24 g/L in
the purified potato starch control. However, surfactin yields per carbon consumed were 76% lower from process effluent. Removal
of starch particulates had little effect on the culture. Acid hydrolysis decreased growth and surfactant production, except
0.5 wt% acid, which increased the yield by 25% over untreated effluent. 相似文献
29.
关于交错级数的一个新的审敛准则 总被引:5,自引:3,他引:2
讨论了交错级数的敛散性,给出了判定交错级数敛散性的一个新的准则. 相似文献
30.
在特征不是2的正交空间中,相关文献给出了Witt定理.华罗庚把它推广到体上的一些内积空间.把域上内积空间中的Witt定理推广到奇异内积空间,并给出相应的证明. 相似文献