Extremes of deterministic sub‐sampled moving averages with heavy‐tailed innovations

Let {X<sub>ksub>}<sub>k?1sub> be a strictly stationary time series. For a strictly increasing sampling function g:?→? define Y<sub>ksub>=X<sub>g(k)sub> as the deterministic sub‐sampled time series. In this paper, the extreme value theory of {Y<sub>ksub>} is studied when X<sub>ksub> has representation as a moving average driven by heavy‐tailed innovations. Under mild conditions, convergence results for a sequence of point processes based on {Y<sub>ksub>} are proved and extremal properties of the deterministic sub‐sampled time series are derived. In particular, we obtain the limiting distribution of the maximum and the corresponding extremal index. Copyright © 2003 John Wiley & Sons, Ltd.     

Lattice Boltzmann method for the fractional sub‐diffusion equation

A lattice Boltzmann model for the fractional sub‐diffusion equation is presented. By using the Chapman–Enskog expansion and the multiscale time expansion, several higher‐order moments of equilibrium distribution functions and a series of partial differential equations in different time scales are obtained. Furthermore, the modified partial differential equation of the fractional sub‐diffusion equation with the second‐order truncation error is obtained. In the numerical simulations, comparisons between numerical results of the lattice Boltzmann models and exact solutions are given. The numerical results agree well with the classical ones. Copyright © 2015 John Wiley & Sons, Ltd.     

Green ultra‐fast high‐performance liquid chromatographic method using a short narrow‐bore column packed with fully porous sub‐2 μm particles for the simultaneous determination of selected pharmaceuticals as surface water and wastewater pollutants

Fast separations are very desirable in laboratories that analyze large numbers of samples per day or those needing short turn‐around times. Traditional HPLC methods using conventional stationary phases and standard column dimensions require significant amounts of organic solvents and generate large volumes of waste. With growing awareness about the environment, the development of green technologies has been receiving increasing attention. In this work, a very fast green analytical method based on LC‐UV using a short narrow bore column packed with fully porous sub‐2 μm particles has been developed for simultaneous determination of nine pharmaceuticals in wastewater and surface water. The chromatographic separation was optimized in order to achieve short analysis time and good resolution for all analytes in a single run. All analytes could be separated in 1 min with good resolution. Sample preparation was executed by solid phase extraction using Oasis HLB cartridges. The method developed was validated based on parameters such as linearity, precision, accuracy, detection, and quantification limits. The recovery ranged from 70.9 to 92.5% with SDs not higher than 5.4%, except for acetaminophen and sulphanilamide. LODs ranged from 0.6–2.5 μg/L, while the LOQs were in the range 2–8 μg/L.     

铁酸镍用于热化学循环反应CO2分解制CO的研究

采用共沉淀法制备了NiFe<sub>2sub>O<sub>4sub>和NiFe<sub>2sub>O<sub>4sub>/ZrO<sub>2sub>催化剂,用TGA考察了其热化学法,CO<sub>2sub>高温分解反应性能。通过对反应前后催化剂的表征发现,反应高温使两种催化剂都发生了明显的烧结,导致在热还原反应中形成的还原态氧化物不能完全被CO<sub>2sub>氧化从而降低了催化剂的反应性能;ZrO<sub>2sub>的加入对于提高催化剂的热稳定性以及循环反应稳定性具有重要的作用。在高温反应炉中考察了NiFe<sub>2sub>O<sub>4sub>/ZrO<sub>2sub>的CO<sub>2sub>分解实验,结果表明,提高热还原温度可以提高CO产量,然而,随着循环次数的增加CO的产量降低得更明显。     

Generation of sub‐terahertz repetition rates from a monolithic self‐mode‐locked laser coupled with an external Fabry‐Perot cavity

A novel scheme to multiply the repetition rate of a monolithic self‐mode‐locked laser for generating sub‐terahertz pulse sources is successfully demonstrated. A coated Yb:KGW crystal is designed to achieve a self‐mode‐locked operation at a repetition rate of 24 GHz with an average output power exceeding 1.0 W at a pump power of 4.8 W. A partially reflective mirror is utilized to combine with the output surface of the gain medium to constitute an external Fabry‐Perot cavity. It is theoretically and experimentally verified that adjusting the external cavity length to satisfy the commensurate condition can lead to the frequency spacing to be various order harmonics of the mode spacing of the monolithic cavity. The maximum pulse repetition rate of the laser output can be up to 216 GHz and the pulse duration is as short as 330 fs. More importantly, the overall characteristics of the first‐order temporal autocorrelation traces obtained by sequentially scanning the external cavity.length display an intriguing phenomenon of temporally fractional revivals, similar to the feature of spatial Talbot revivals.

     

贵金属负载TiO2对光催化还原CO2选择性的影响

利用光沉积方法在TiO<sub>2sub>表面分别负载1%(质量分数) Pt、Pd、Au和Ag助催化剂.用TEM、XRD、UV-vis等技术对催化剂进行了表征,并利用连续瞬态电流时间响应和线性扫描伏安法等电化学方法,对贵金属负载的TiO<sub>2sub>光催化剂在光照条件下的电流响应强度及电催化析氢电位等特性加以测试.分析了贵金属助催化剂对光催化还原CO<sub>2sub>性能的差异.结果表明,负载贵金属助催化剂能显著加速光生电子空穴的分离,降低复合率;另外,助催化剂对还原CO<sub>2sub>选择性的顺序为Ag>Au>Pd>Pt.贵金属助催化剂还原CO<sub>2sub>的加氢选择性和析氢过电位存在相关性,即越不利于析氢过程的助催化剂,其催化CO<sub>2sub>加氢还原产物的选择性越高.     

不同碱处理制备多级孔HZSM-5催化剂及噻吩烷基化性能研究

用Na<sub>2sub>CO<sub>3sub>、TPAOH和TPA⁺/CO<sub>3sub>^2-混合碱分别处理HZSM-5分子筛,采用FT-IR、XRD、XRF、N<sub>2sub>吸附脱附、SEM、NH<sub>3sub>-TPD及Py-FTIR表征手段对各类碱处理前后的HZSM-5分子筛进行表征。结果表明,3种类型的碱处理HZSM-5分子筛后,均能形成微孔-介孔多级孔道的HZSM-5(A)催化剂,并能调变催化剂的酸性,其中,TPA⁺/CO<sub>3sub>^2-混合碱处理得到的HZSM-5(TPA⁺/CO<sub>3sub>^2-)催化剂,比表面积最大,介孔数量最多。在小型固定床反应器上,考察了HZSM-5和HZSM-5(A)催化剂的噻吩烷基化性能,结果表明,HZSM-5(TPA⁺/CO<sub>3sub>^2-)催化剂因为具有适当的多级孔孔道和较多的B酸中心而表现出较高的噻吩转化率和1-己烯对噻吩的选择性。     

Homology of Nilpotent Subalgebras of the Lie Superalgebra K(1,1).3

We calculate the dimensions of the second homology groups with trivial coefficients of nilpotent subalgebras of the Lie superalgebra , which is the natural superanalog of the Witt algebra. The proof is based on direct calculations of the rank of the differential. As an application, we find deformations of the maximal nilpotent subalgebra in .     

Uniqueness and asymptotic behaviour for solutions of semilinear problems with boundary blow-up

In this paper we prove uniqueness of positive solutions to logistic singular problems , , 1$">, 0$"> in , where the main feature is the fact that . More importantly, we provide exact asymptotic estimates describing, in the form of a two-term expansion, the blow-up rate for the solutions near . This expansion involves both the distance function and the mean curvature of .

     

非紧超凸度量空间中的一个新的极大元定理及其对抽象经济的应用

在非紧超凸度量空间中建立了一个新的极大元定理.作为应用，获得了连续选择及其不动点定理和一个Browder-Fan不动点定理.最后，新建了非紧超凸度量空间中的定性对策和抽象经济的平衡点存在定理.