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41.
The main goals of this paper are to: i) relate two iteration-complexity bounds derived for the Mizuno-Todd-Ye predictor-corrector
(MTY P-C) algorithm for linear programming (LP), and; ii) study the geometrical structure of the LP central path. The first
iteration-complexity bound for the MTY P-C algorithm considered in this paper is expressed in terms of the integral of a certain
curvature function over the traversed portion of the central path. The second iteration-complexity bound, derived recently
by the authors using the notion of crossover events introduced by Vavasis and Ye, is expressed in terms of a scale-invariant
condition number associated with m × n constraint matrix of the LP. In this paper, we establish a relationship between these bounds by showing that the first one
can be majorized by the second one. We also establish a geometric result about the central path which gives a rigorous justification
based on the curvature of the central path of a claim made by Vavasis and Ye, in view of the behavior of their layered least
squares path following LP method, that the central path consists of long but straight continuous parts while the remaining curved part is relatively “short”.
R. D. C. Monteiro was supported in part by NSF Grants CCR-0203113 and CCF-0430644 and ONR grant N00014-05-1-0183. T. Tsuchiya
was supported in part by Japan-US Joint Research Projects of Japan Society for the Promotion of Science “Algorithms for linear
programs over symmetric cones” and the Grants-in-Aid for Scientific Research (C) 15510144 of Japan Society for the Promotion
of Science. 相似文献
42.
The free solution mobilities of 26-base pair (bp) DNA oligomers containing A-tracts with and without internal ApT steps have been measured by capillary electrophoresis, using the mobility of a 26-bp random-sequence oligomer as a reference. The background electrolytes (BGEs) contained mixtures of Li+ and tetrapropylammonium (TPA+) ions, keeping the total cation concentration constant at 0.3 M. The mobility ratios equaled 1.00 in 0.3 M TPA+, indicating that the A-tract and reference oligomers had the same B-form conformation in this BGE. With increasing [Li+], the mobility ratio decreased as Li+ ions became localized in the A-tract minor groove, suggesting that the A-tract was now in the B* conformation. If the A-tract contained an internal ApT step and the oligomer contained less than ∼50% A + T, the mobility ratio reached a reduced plateau value that remained constant as the [Li+] increased to 0.3 M. However, for A-tracts without an internal ApT step and for A-tracts embedded in oligomers containing more than 50% A + T, the mobility ratios increased again at high [Li+], eventually reaching a plateau value of 1.00. Hence, DNA A-tracts in solution appear to exist as mixtures of the B and B* conformations, with the fractional concentration of each conformer depending on the [Li+], the A-tract sequence, and the total A + T content of the oligomer. 相似文献
43.
A.?I.?DanilovEmail author R.?R.?Nazmutdinov T.?T.?Zinkicheva E.?B.?Molodkina A.?V.?Rudnev Yu.?M.?Polukarov J.?M.?Feliu 《Russian Journal of Electrochemistry》2008,44(6):697-708
Mechanism of copper underpotential deposition at stepped faces of platinum single crystals Pt(hkl) is studied using cyclic voltammetry, scanning probe microscopy, and quantum-chemical modelling. It is shown that the first stage of UPD is one-dimensional decoration of the (100)- or (110)-orientated steps, then copper monolayer forms at (111)-terraces. The final stage is the secondary step decoration. Quantum-chemical modelling, with the using of long-distance potentials of the Cu-Pt and Cu-Cu pair interactions, allows estimating the energy of copper adsorption at different structure elements of the substrate (steps, kinks, terraces) and revealing the succession of the adatom monolayer formation; it also provides additional information for the identifying of the nature of voltametric peaks for different stages of the copper adsorption-desorption. 相似文献
44.
Zinc underpotential deposition (Zn UPD) was studied by cyclic voltammetry in solutions of various pH and composition, where
the effects of the presence of boric acid or chloride in the solution were observed. We have found that the cyclic voltammograms
of Zn UPD at Pt(111) were dependent on boric acid concentrations, zinc ion concentrations, and pH in acidic solutions. These
suggest that the induced adsorption of borate by releasing of H+ is accompanied with Zn UPD. The preadsorbed chloride species on Pt(110) accelerate the UPD process by their removal just
before the UPD, making the surface sites available for the process, and the UPD remains at identical electrode potentials,
while the chloride ions do not take part in the induced adsorption on UPD Zn at Pt, as clearly found by the radiotracer method.
These show that the anions play versatile roles in the process of adlayer formation by their different but essential chemical
characteristics.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 6, pp. 745–751
The text was submitted by the authors in English. 相似文献
45.
Yao Fan Li Liu Donglei Sun Hanyue Lan Haiyan Fu Tianming Yang Yuanbin She Chuang Ni 《Analytica chimica acta》2016
As a popular detection model, the fluorescence “turn-off” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence “turn-off” model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10−8 mol L−1 and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs. 相似文献
46.
47.
光谱混合机制研究对混合像元解算具有一定指导意义。利用全波段光谱仪累积期和消融期对规则和非规则分布模式下积雪-荒漠植被混合像元及纯净积雪和荒漠植被像元控制式采集反射光谱。K-均值法计算采集影像积雪和荒漠植被面积比并分析其对应混合像元光谱变化特征以获取更加精细的光谱特征信息,准同步Tetracam ADC3(Agricultural Digital Camera 3)采集图像并计算典型指数,从微观尺度上证实了混合像元主要出现在地类边界处。结果发现,1 456~1 697 nm粗粒径冻结雪反射光谱高于新雪反射光谱,新雪反射光谱明显高于陈雪;因冻结覆冰,荒漠植被光谱为积雪、冰晶和植被枝干混合光谱信息,新降积雪覆盖植被光谱特征为积雪和植被枝干的混合光谱信息,不存在常规绿色植被“红边”效应;采集角度为5°和10°时光谱低于垂直角度采集光谱,角度大于10°随角度增加荒漠植被光谱逐渐增大。像元内各个组成物质的面积比及所处像元的位置、采集角度和方向都会影响混合像元的光谱组合信息。 相似文献
48.
49.
揭示了二阶变系数线性微分方程和Riccati方程之间的内在联系,证明了在对这两类方程求解时可以相互转化,从而对二阶变系数线性微分方程和Riccati方程的求解提供更多的思路和途径.. 相似文献
50.
S.A. Teys 《Surface science》2006,600(21):4878-4882
The vicinal Si(1 1 1) surface, inclined towards the direction, was investigated by scanning tunnelling microscopy and spot profile analysing low energy electron diffraction. It has been established that the surface, consisting of regularly spaced triple steps and (1 1 1) terraces with a width equal to that of a single unit cell of the Si(1 1 1)-7 × 7 surface structure, has the (7 7 10) orientation. An atomic model of the triple step is proposed. 相似文献