带有惩罚和软容量约束的下界设施选址问题的双标准近似算法研究

研究带惩罚和软容量约束的下界设施选址问题. 扩展Guha等(Guha S, Meyerson A, Munagala K. Hierarchical placement and network design problems [C]//Proceedings of Foundations of Computer Science, 2000: 892328, DOI: 10.1109/SFCS.2000.892328)和Karger等(Karger D R,Minkoff M. Building steiner trees with incomplete global knowledge [C]//Proceedings of Foundations of Computer Science, 2000: 892329, DOI: 10.1109/SFCS.2000.892329)的工作到带有惩罚的下界约束设施选址问题,提出了一个新的双标准近似算法,得到了同样的近似比ρ(1+α)/(1-α). 进一步考虑带惩罚和软容量约束的下界设施选址问题,得到了近似比为2ρ(1+α)/(1-α)的双标准近似算法.     

软容量约束的动态设施选址问题的近似算法

考虑软容量约束的动态设施选址问题.假设设施的开放费用及连接费用都与时间有关,而且每一个设施均有容量约束.对此问题给出了第一个近似比为6的原始对偶(组合)算法.运行贪婪增加程序后,近似比进一步改进到3.7052.     

Structural and optical properties study of nanocrystalline Si (nc-Si) thin films deposited on porous aluminum by plasma enhanced chemical vapor deposition

In this paper we report detail investigation and correlation between micro-structural and optical properties of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. The influence of the microstructure of the nc-Si thin films on their optical properties was investigated through an extensive characterization. The effect of anodisation currents on the microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). The optical constants (n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The silicon layer (SL) was modeled as a mixture of void, crystalline silicon and aluminum using the Bruggeman approximation. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. A very bright photoluminescence (PL) was obtained and find to depend on anodisation current.     

最大割问题和最大平分割问题基于半定规划松弛的近似算法

考虑每条边具有非负权重的无向图, 最大割问题要求将顶点集划分为两个集合使得它们之间的边的权重之和最大. 当最大割问题半定规划松弛的最优解落到二维空间时, Goemans将近似比从0.87856...改进为0.88456. 依赖于半定规划松弛的目标值与总权和的比值的曲线, 此曲线的最低点为0.88456, 当半定规划松弛的目标值与总权和的比值在0.5到0.9044之间时, 利用Gegenbauer多项式舍入技巧, 改进了Zwick的近似比曲线. 进一步, 考虑最大割问题的重要变形------最大平分割问题, 在此问题中增加了划分的两部分的点数相等的要求. 同样考虑了最大平分割问题半定规划松弛的最优解落到二维空间的情形, 并利用前述的Gegenbauer多项式舍入技巧得到0.7091-近似算法.     

A cross-monotonic cost-sharing scheme for the concave facility location game

In this paper, we present a cost-sharing scheme for the concave facility location game by exploring the concavity structure. We show that it is cross-monotonic and competitive, and recovers 1/3 fraction of the total cost.     

Effect of Cr incorporation on the structural and optoelectronic properties of TiO2:Cr deposited by means of a magnetron co-sputtering process

In this work, we report on the effect of Cr incorporation on the microstructural and optical properties of TiO₂:Cr thin films deposited by the RF-magnetron sputtering method. The structural, morphological, chemical bonding and optoelectronic properties of the sputter-deposited TiO₂:Cr films were systematically investigated, as a function the incorporated Cr content, by means of various techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-Transform Infra-Red (FTIR) absorption, X-ray Photoelectron Spectroscopy (XPS) and ellipsometry. The Cr incorporation into the TiO₂ films was controlled by adjusting the RF power (P_Cr) on the Cr target during the co-sputtering process of TiO₂ and Cr. We were thus able to demonstrate that by varying P_Cr from 8 W to 150 W, the Cr content of the TiO₂:Cr films can be fairly controlled from ∼2 at.% to ∼18 at.% and their associated bandgap engineered from 3.3 eV to 1.5 eV. The room-temperature deposited TiO₂:Cr are mainly amorphous with the presence of some TiO₂ nanocrystallites, and their density increases as their Cr content is increased. The Cr inclusions were found to coexist under both metallic and oxidized forms in the films. By subjecting the TiO₂:Cr films to post-annealing treatment (at 550 °C), their crystalline structure was found to be sensitive to their Cr content. Indeed, an anatase-to-rutile phase transformation has been pointed out to occur at a Cr content of ∼7 at.%. Likewise, the Cr-content dependence of the bandgap of annealed TiO₂:Cr films undergoes a transition around the 7 at.% of Cr. Our results demonstrate the ability to control the Cr-content of TiO₂:Cr films, which leads to tune their optoelectronic properties, such as bandgap or optical absorption edge.     

On KKT points of Celis-Dennis-Tapia subproblem

The Celis-Dennis-Tapia(CDT) problem is a subproblem of the trust region algorithms for the constrained optimization. CDT subproblem is studied in this paper. It is shown that there exists the KKT point such that the Hessian matrix of the Lagrangian is positive semidefinite, if the multipliers at the global solution are not unique. Next the second order optimality conditions are also given, when the Hessian matrix of Lagrange at the solution has one negative eigenvalue. And furthermore, it is proved that all feasible KKT points satisfying that the corresponding Hessian matrices of Lagrange have one negative eigenvalue are the local optimal solutions of the CDT subproblem.     

Foetidissimosides C–F,Novel Glycosides from the Roots of Cucurbita foetidissima

Two novel echinocystic acid (=(3β,16α)‐3,16‐dihydroxyolean‐12‐en‐28‐oic acid) glycosides, foetidissimosides C ( 1 ), and D ( 2 ), along with new cucurbitane glycosides, i.e., foetidissimosides E/F ( 3 / 4 ) as an 1 : 1 mixture of the (24R)/(24S) epimers, were obtained from the roots of Cucurbita foetidissima. Their structures were elucidated by means of a combination of homo‐ and heteronuclear 2D‐NMR techniques (COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC), and by FAB‐MS. The new compounds were characterized as (3β,16α)‐28‐{[O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl]oxy}‐16‐hydroxy‐28‐oxoolean ‐12‐en‐3‐yl β‐D ‐glucopyranosiduronic acid ( 1 ), (3β,16α)‐16‐hydroxy‐28‐oxo‐28‐{{O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐[β‐D ‐xylopyranosyl‐(1→4)]‐O‐6‐deoxy‐α‐L ‐mannopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl}oxy}olean‐12‐en‐3‐yl β‐D ‐glucopyranosiduronic acid ( 2 ), and (3β,9β,10α,11α,24R)‐ and (3β,9β,10α,11α,24S)‐25‐(β‐D ‐glucopyranosyloxy)‐9‐methyl‐19‐norlanost‐5‐en‐3‐yl 2‐O‐β‐D ‐glucopyranosyl‐β‐D ‐glucopyranoside ( 3 and 4 , resp.).     

ZnO and carbon nanocomposites for enhanced photoelectrochemical sensing activity: influence of the carbon content

Journal of Solid State Electrochemistry - In this work, carbon and zinc oxide (ZnO:C) nanocomposites were obtained by a hydrothermal reaction process. ZnO nanoparticles were first prepared by a...     

柱前衍生反相高效液相色谱法测定山黧豆中的毒素β-ODAP

建立了柱前衍生反相高效液相色谱法测定山黧豆中β-ODAP含量的方法。采用luna-C18色谱柱(4.6 mm×250 mm,5 μm),以乙腈和HAc-NaAc为混合流动相(17 : 83),λ=360 nm,柱温40 ℃,取20 μL进样分析。β-ODAP标准品在0.007~1.000 mg/mL范围内线性关系良好,y=5 164x+167.74,R=0.993 9,相对标准偏差(RSD)为1.6%,山黧豆不同部位(种子、根、茎、叶)中β-ODAP含量最高的为种子。方法操作简便、快速、准确,可用于植物样品中β-ODAP含量的测定。