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991.
992.
Hong‐Qing Wang Zhao‐Jie Liu Li‐Min Yang Ming‐Wu Ding 《Journal of heterocyclic chemistry》2004,41(3):393-397
A series of new 1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one Derivatives 5 has been designed and regio‐selectively synthesized via a tandem aza‐Wittig reaction. The structures of all compounds prepared have been confirmed by 1H NMR, IR, EI‐MS spectroscopy and elemental analyses. The results of preliminary bioassay indicate that most compounds 5 possess an inhibition effect against Botrytis cinereapers and Pyricularia oryzae at the concentration of 50 mg/L. 相似文献
993.
Piaoping Yang Jianfeng Yu Zhenlü Wang Qingsheng Liu Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2004,83(2):275-282
Mg-Al, Zn-Al and Ni-Al hydrotalcite-like compounds with high crystallinity were synthesized by using the decomposing property
of urea at high temperature. The crystallinity and the regularly of the samples were much preferable to those synthesized
by other methods.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
994.
提出一种单光子探测器量子效率的绝对自身标定方案,利用光参量下转换过程中产生的光子对在时间上的相关性,先将参量光束分为两路,然后引入相对延时,使同时产生的孪生光子先后进入单光子探测器,然后将探测器之后的电路分为三路,其中一路直接进入计数器得到探测器所探测到的光子的总计数率,另两路用电路方法引入和光路相当的相对延时,经符合电路后进入计数器,得到前后到达探测器的光子对之间的符合计数率.这样,从符合计数率与总光子计数率之比即可在不需要任何其他探测器或者参照标准的情况下获得探测器的量子效率.文中给出两种方案,分别适 相似文献
995.
A new method based on anion exchange resin separation and graphite furnace atomic absorption spectrometry (GFAAS) detection
is proposed for the determination of inorganic tin species. The result showed that Sn(IV) was quantitatively retained on the
resin when [HCl] = 9.0 mol · L−1, but Sn(II) could not be adsorbed on the resin under the same condition. Thus, a separation of Sn(II) and Sn(IV) has been
realized. When the concentration of NaOH solution was between 2.0–7.0 mol · L−1, Sn(IV) that adsorbed on the resin could be eluated from the resin completely. Meanwhile, under the atmosphere and the nitrogen
states, the translation between Sn(II) and Sn(IV) was investigated. Under the optimal conditions, the detection limit of Sn(IV)
is 0.40 μg · L−1 with RSD of 2.3% (n = 5, c = 2.0 μg · L−1). The proposed method was applied to the speciation analysis of tin in different water samples and the recovery of total
Sn was in the range of 98.7–101.7%. In order to verify the accuracy of the method, a certified reference water sample was
analyzed and the results obtained were in good agreement with the certified value. 相似文献
996.
The influence of hydrogen bonds on the physical and chemical properties of hydrogen bonding fluid system of A a D d type is investigated from two viewpoints by the principle of statistical mechanics. In detail, we proposed two new ways that can be used to obtain the equilibrium size distribution of the hydrogen bonding clusters, and derived the analytical expression of a relationship between the hydrogen bonding free energy and hydrogen bonding degree. For the nonlinear hydrogen bonding systems, it is shown that the sol-gel phase transition can take place under proper conditions, which is further proven to be a kind of geometrical phase transition rather than a thermodynamic one. Moreover, several problems associated with the geometrical phase transition and liquid-solid phase transition in nonlinear hydrogen bonding systems are discussed. 相似文献
997.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
998.
The properties of pulsed laser vapor doping on p-Si(1 0 0) with a KrF (248 nm) excimer pulsed laser (248 nm) and BCl3 gas are reported in this paper. The doped samples are characterized by the resistance measured using a four-probe method, since the sheet resistance changes with the carrier concentration of the sample. The doping effects with the variation of laser energy density, pulse number, and the pressure of BCl3 were investigated in terms of the sheet resistance. In this way, the optimized parameters were obtained and used for the positive heavy doping on p-Si(1 0 0) and p-Si(1 1 1). Then, using a square mesh under the above conditions, an image doping was completed. Finally, the metal–semiconductor Ohmic contacts were realized by plating Ag and Cu films on the doped surface. 相似文献
999.
基于增广Lagrange函数的RQP方法 总被引:3,自引:0,他引:3
Recursive quadratic programming is a family of techniques developd by Bartholomew-Biggs and other authors for solving nonlinear programming problems.This paperdescribes a new method for constrained optimization which obtains its search di-rections from a quadratic programming subproblem based on the well-known aug-mented Lagrangian function.It avoids the penalty parameter to tend to infinity.We employ the Fletcher‘s exact penalty function as a merit function and the use of an approximate directional derivative of the function that avoids the need toevaluate the second order derivatives of the problem functions.We prove that thealgorithm possesses global and superlinear convergence properties.At the sametime, numerical results are reported. 相似文献
1000.