基于群论的晶格扰动介质纳米孔阵列多重Fano共振机理及演变

基于全介质超构材料独特的电磁属性,提出了一种晶格扰动介质纳米孔阵列超构表面来激发近红外区域的多重Fano共振.结合群论深入探究了该超构表面在其原胞为方形晶格构型与方形晶格对称性被破坏两情况下多重Fano共振的形成机理及演变规律.研究表明,在方形晶格超构表面中,外部辐射连续体分别与由正入射平面波直接激发的双重简并模式共振干涉形成双重Fano共振,且该共振与原胞中是否含孔及孔的形状无关,在晶格扰动超构表面中,原本不耦合的非简并模式由正入射平面波激发出来并与外部辐射连续体干涉形成Q值更高的三重Fano共振.进一步探讨了正入射平面波的xy极化方向对上述五重Fano共振的影响,结果表明,双重简并模式Fano共振偏振无关,三重非简并模式Fano共振偏振依赖.本文将为利用方形晶格构型的超构表面实现多重Fano共振的激发及演变提供有效的理论参考.     

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt.Waliguan Observatory(China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon（WIRC） component of total suspended particulates（TSP）,collected weekly during 2003,as well as from October 2005 to May 2006 at the WMO-GAW Mt.Waliguan（WLG） site.The overall average WIRC mass concentration was（1183±120）ng/m³（n = 79）,while seasonal averages were 2081 ±1707（spring）,454±205（summer）,650±411（autumn）,and 1019±703（winter） ng/m3.Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer,although WIRC concentrations were typically higher,especially in winter and spring.The δ¹³C PDB value（-25.3 ± 0.8）%.determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion.No seasonal change in δ¹³C PDB was evident.The average percent Modern Carbon（pMC） for ¹⁴C in WIRC for winter and spring was（67.2 ± 7.7）%（n = 29）.Lower pMC values were associated with air masses transported from the area east of WLG,while higher pMC values were associated with air masses from the Tibetan Plateau,southwest of WLG.Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.     

可发生多种故障的可修复系统稳定性分析

研究了可发生多种故障的可修复系统.运用C_0半群理论,通过服务率均值的观念,对系统主算子的谱界进行了估值,并得到该谱上界即为各服务率均值的最小者的相反数.然后运用了共尾的概念及相关的理论,得到了系统算子的谱界与系统算子产生的半群的增长界相等.最后由分析了系统算子的谱分布,得到了系统的指数稳定性.     

含硫氨基酸与本征及缺陷石墨烯表面的相互作用

半胱氨酸及蛋氨酸是人体的两种含硫氨基酸,在生物活性中发挥着巨大的作用.本研究采用密度泛函理论方法对以上两种氨基酸在本征及缺陷石墨烯表面的吸附机理进行了详细研究.主要考虑了两种吸附体系:半胱氨酸及蛋氨酸平躺在两种石墨烯表面;两种氨基酸垂直地放置于两种石墨烯表面,且含硫的基团靠近表面.研究结果表明,半胱氨酸及蛋氨酸初始构型对它们之间的相互作用有一定的影响.两种氨基酸平躺时有较大的吸附能.此外,吸附能的结果显示两种氨基酸可以更好的与缺陷石墨烯表面紧密结合.同时,蛋氨酸与本征及缺陷石墨烯相互作用均大于半胱氨酸与本征及缺陷石墨烯相互作用.模拟结果有望为含硫氨基酸的石墨烯传感器提供有用的指导.     

考虑空化效应的螺旋槽机械密封液膜动力学特性研究

考虑液膜空化效应的影响，研究螺旋槽液体润滑机械密封的动力学特性. 基于液体润滑理论和小扰动法，建立了考虑液膜空化的密封微扰膜压控制方程，采用有限单元法对端面液膜三自由度微扰下的液膜刚度和阻尼系数进行了数值求解，分析了不同参数对液膜密封动力系数的影响. 螺旋槽深度在10 μm左右、槽坝比在0.75左右、槽宽比在0.4左右，螺旋角在9°左右时液膜具有最大的轴向和角向刚度系数. 螺旋槽深度在5 μm左右、槽宽比在0.6左右、螺旋角在20°左右时，两角向交叉阻尼绝对值最大. 初始偏角的存在使密封压力呈现非对称性，从而使两角向动力系数绝对值不再相等. 液膜轴向刚度k_zz在数量级上远大于其余液膜刚度值，液膜轴向阻尼d_zz、角向阻尼d_αα和d_ββ远大于液膜其余阻尼值且随着转速和间隙的增大而减小.      

GARCH模型的贝叶斯局部影响分析及其应用

广义自回归条件异方差(GARCH)模型能够很好地刻画金融资产收益二阶矩的相依关系,因此在金融时间序列中受到了广泛的应用。在GARCH模型的框架下,本文利用贝叶斯局部影响分析来评价先验、个体观测和样本分布的微小扰动的影响,利用扰动模型来刻画不同类型的扰动形式。我们构建了扰动模型的贝叶斯扰动形式,计算其几何量来表征扰动模型的内部结构。基于几个目标函数,本文利用几个不同的局部影响测量来量化不同扰动的程度。数值模拟研究验证了所提方法的有限样本表现。对纽约证券交易所综合指数(NYSE)和标准普尔500指数的GARCH建模说明了所提方法在实例研究中的有效性。     

敬告读者——《光谱学与光谱分析》已全文上网

从2008年第7期开始在《光谱学与光谱分析》网站(www.gpxygpfx.com)“在线期刊”栏内发布《光谱学与光谱分析》期刊全文,读者可方便地免费下载摘要和PDF全文,欢迎浏览、检索本刊当期的全部内容;并陆续刊出自2004年以后出版的各期摘要和PDF全文内容。2009年起《光谱学与光谱分析》每期出版日期改为每月1日。     

Tail behavior of supremum of a random walk when Cramér’s condition fails

We investigate tail behavior of the supremum of a random walk in the case that Cramer＇s condition fails, namely, the intermediate case and the heavy-tailed ease. When the integrated distribution of the increment of the random walk belongs to the intersection of exponential distribution class and O-subexponential distribution class, under some other suitable conditions, we obtain some asymptotic estimates for the tail probability of the supremum and prove that the distribution of the supremum also belongs to the same distribution class. The obtained results generalize some corresponding results of N. Veraverbeke. Finally, these results are applied to renewal risk model, and asymptotic estimates for the ruin probability are presented.     

二阶哈密尔顿系统的对称扰动(英文)

我们研究二阶Hamiltonian系统-ü=▽F1(t,u)+ε▽F2(t,u)a.e.t∈[0,T]的多重周期解,其中ε是一个参数,T0.F1(F2)∶R×RN→R关于t是T周期的,▽F1(t,x)关于x是奇的;并且Fi(t,x)(i=1,2)对所有x∈RN关于t是可测的,对几乎所有t∈[0,T]关于x是连续可微的,而且存在a∈C(R+,R+),b∈L+(0,T;R+)使得|Fi(t,x)|≤a(|x|)b(t),|▽Fi(t,x)|≤a(|x|)b(t)对所有x∈RN及几乎所有t∈[0,T]成立.我们对F1施加适当的条件,能够证明对任意的j∈N存在εj0使得|ε|≤εj,则上述问题至少有j个不同的周期解.     

Stereoselective interactions of chiral dipeptides on amylose based chiral stationary phases

Dipeptides are stereo-specifically involved in several biological functions that are challenging to separate enantiomerically. Elution order of enantiomers is an important issue in chiral chromatography. Amylose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase(CSP) is the best and most-widely-used CSP in chiral separations, but experimental data of enantiomeric separation of dipeptides on this CSP is lacking. Simulation studies were conducted to determine the order of elution and the chiral recognition mechanism of didpetides on this CSP. Results indicated that the docking energy of SR-enantiomers were higher than SS-antipodes. The range of docking energies for SR-enantiomers was -7.44 to -5.92 kcal/mol with CSP, but -7.15 to -5.87 kcal/mol for SS-stereoisomers. Therefore it is predicted that SS-enantiomer will elute first, followed by SR-antipode. Furthermore, hydrogen bondings, van der Waal’s interactions and electrostatic interactions were observed among SR- and SSenantiomers and chiral grooves of CSP. The number of hydrogen bonds was one in each enantiomer binding except S-Ala-R-Tyr, which contained two hydrogen bonds. No hydrogen bond was found in S-Ala-R-Trp, S-Leu-S-Trp, and S-Leu-S-Tyr dipeptides bindings. The chiral recognition mechanisms dictate different strengths of stereoselective bindings of the enantiomers on CSP.