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11.
I.A. Moghrabi 《Computational Optimization and Applications》2001,19(3):337-345
We consider multi-step quasi-Newton methods for unconstrained optimization. These methods were introduced by Ford and Moghrabi (Appl. Math., vol. 50, pp. 305–323, 1994; Optimization Methods and Software, vol. 2, pp. 357–370, 1993), who showed how interpolating curves could be used to derive a generalization of the Secant Equation (the relation normally employed in the construction of quasi-Newton methods). One of the most successful of these multi-step methods makes use of the current approximation to the Hessian to determine the parameterization of the interpolating curve in the variable-space and, hence, the generalized updating formula. In this paper, we investigate new parameterization techniques to the approximate Hessian, in an attempt to determine a better Hessian approximation at each iteration and, thus, improve the numerical performance of such algorithms. 相似文献
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The overlap of magnetization of the giound state in a RKKY spin glass system with the Dzyaloshinsky-Moriya interaction is studied based on the theory of infinite number of order parameter. It is shown that the nonmagnetic impurities are coupled with the host lattice.The results are in good agreement with experiments. 相似文献
15.
ÜMMÜHAN OCAK HALIT KANTEKIN YAŞAR GÖK H. BASIR ŞENTÜRK 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):87-91
The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N2O2S2-macrobicycle. Metal picrates such as Pb2+, Co2+, Zn2+, Ni2+,Cu2+ and Cd2+ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb2+ only among the other metals. The extraction constant (log K
ex) was determined to be 13.8 for Pb2+ complex. 相似文献
16.
GRIGORII YA. FRAIKIN MARINA G. STRAKHOVSKAYA EMMA V. IVANOVA REW B. RUBIN 《Photochemistry and photobiology》1989,49(4):475-477
Near-UV (337 nm) photoactivation of the 5-hydroxytryptophan decarboxylation reaction producing serotonin has been observed. The photoactivation effect was investigated as a function of fluence rate and fluence, and pH. Photoactivation of decarboxylase activity was found to occur at nearly neutral pH values (low activity of the enzyme in the dark). The findings indicate that the effect of light is similar to a pH shift toward the acid region, which causes the enzyme conversion from the inactive to active form. Pyridoxal phosphate, the decarboxylase cofactor, in the form of an adduct absorbing at 330-340 nm, is suggested as a candidate for the role of the photoactive chromophore of decarboxylase. 相似文献
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为建立大批量谷类产品中重金属元素的快速检测方法,采用快速消解法,样品于聚丙烯刻度离心管中经硝酸消解,用电感耦合等离子体质谱仪同时检测Pb、Cd、Cr、Cu、Zn、Ni、As、Hg等8种重金属元素含量。研究了消解酸用量及消解时间对结果的影响,并优化了仪器工作参数。研究结果表明,样品在120℃消解1 h后直接定容测定,各元素在实验浓度范围内线性良好,相对标准偏差RSD值1.1%~7.2%,Pb、Cd、Cr、Cu、Zn、Ni、As、Hg各元素的方法检出限分别为0.02、0.000 3、0.03、0.02、0.08、0.01、0.002和0.000 4 mg/kg。试剂用量少、简便、快捷、准确性好,适用于电感耦合等离子体质谱法定量检测稻米、小麦、玉米等谷类产品中重金属元素的含量。 相似文献
19.
E. A. PAZYUK A. V. STOLYAROV V. I. PUPYSHEV N. F. STEPANOV S. YA. UMANSKII A. A. BUCHACHENKO 《Molecular physics》2013,111(2):91-101
The valence electronic states of the iodine molecule are analysed by means of a simple atoms-in-molecule model which accounts for the lowest 2P states of iodine atoms and approximates the spin-orbit interaction by its atomic part. For this model, an inverse problem is solved, i.e. non-relativistic potential energy curves and diabatic couplings are determined by a least-squares fit to known relativistic potential energy curves. The resulting adiabatic wave functions are used to calculate the electronic matrix elements responsible for natural, hyperfine and magnetic predissociation of the iodine molecule in the B0+ u: state. The results are in reasonable agreement with experimental data, being stable enough with respect to the variation of input relativistic potentials. They also indicate the importance of diabatic couplings between the non-relativistic states of the same symmetry. 相似文献
20.
M.I. Yanovskaya N.M. Kotova N.V. Golubko N.YA. Turova 《Journal of Sol-Gel Science and Technology》1998,11(1):23-29
The interaction between magnesium and titanium alkoxides is studied in order to chose the best precursors for synthesis of MgTiO3. No reaction between magnesium and titanium methoxides and isopropoxides occurs. The solubility diagrams for Mg(OR)2-Ti(OR)4-ROH, R = Et,-Bu at 20°C are studied. Magnesium ethoxotitanates of variable composition MgnTi4-n (OEt)16-2n2nEtOH (n=2.0-0) which are structural analogs of Ti4(OR)16 (R = Me, Et) are isolated. This is a quite unusual example of statistical distribution of heteroatoms in molecular structures of metal alkoxides. Among the systems of metal alkoxides with simple aliphatic radicals only Mg(OBu)2-Ti(OBu)4-BuOH gives a convenient precursor for the synthesis of MgTiO3. A simple scheme of preparation of magnesium titanate from the alkoxide solutions is suggested. The phase purity of MgTiO3 is to a considerable extent dependent on the hydrolysis conditions. The alkoxy-derived magnesium titanate is obtained in the form of a uniform fine powder, it can be sintered into dense ceramics in the temperature range of 1140–1220°C which is 150–200°C lower in comparison with the conventional powders. 相似文献