电站进水口快速闸门振动特性研究

电站进水口快速闸门是机组和引水系统一旦发生事故后进行快速应对、控制事态扩大的控流设施.论文研究溪洛渡电站快速闸门水力学及流激振动问题.着重对机组甩负荷时的闸门动水压力作用、门体结构的振动状态及待命高度之间的关系、闸门启闭力等进行了深入研究,取得了快速闸门净动水作用力、水流脉动压力、振动加速度等水力结构参数,论证了设计方案的合理性,提出了安全运行建议.     

Universal Norms on Abelian Varieties over Global Function Fields

We examine the Mazur-Tate canonical height pairing defined between an abelian variety over a global field and its dual. We show in the case of global function fields that certain of these pairings are annihilated by universal norms coming from Carlitz cyclotomic extensions. Furthermore, for elliptic curves we find conditions for the triviality of these universal norms.     

石墨烯过渡层对金属/SiC接触肖特基势垒调控的第一性原理研究

由于SiC禁带宽度大,在金属/SiC接触界面难以形成较低的势垒,制备良好的欧姆接触是目前SiC器件研制中的关键技术难题,因此,研究如何降低金属/SiC接触界面的肖特基势垒高度(SBH)非常重要.本文基于密度泛函理论的第一性原理赝势平面波方法,结合平均静电势和局域态密度计算方法,研究了石墨烯作为过渡层对不同金属(Ag,Ti,Cu,Pd,Ni,Pt)/SiC接触的SBH的影响.计算结果表明,单层石墨烯可使金属/SiC接触的SBH降低;当石墨烯为2层时,SBH进一步降低且Ni,Ti接触体系的SBH呈现负值,说明接触界面形成了良好的欧姆接触;当石墨烯层数继续增加,SBH不再有明显变化.通过分析接触界面的差分电荷密度以及局域态密度,SBH降低的机理可能主要是石墨烯C原子饱和了SiC表面的悬挂键并降低了金属诱生能隙态对界面的影响,并且接触界面的石墨烯及其与金属相互作用形成的混合相具有较低的功函数.此外,SiC/石墨烯界面形成的电偶极层也可能有助于势垒降低.     

The system evaluation strategy in practice,allowing direct estimation of peak heights and limits of detection in HPLC

Summary The novel system evaluation strategy recently developed describes an HPLC system in terms of two parameters, that ideally are independent of the test conditions. These describe the peak height response, or dilution, occurring in the column and the system. Limits of detection (LOD’s) can thus also be calculated. System parameters, (e.g. cell length, external dispersion), chromatographic parameters (e.g. retention, column length, flow-rate), and sample parameters (e.g. sample volume & absorptivity), are all included. Consequently this approach is applicable to the chromatographer and LC system designer alike. The system evaluation strategy was previously demonstrated under typical chromatographic conditions, on two HPLC systems, and systematic changes were studied. In principle this is applicable to any compound under any chromatographic conditions, on any column. This is now to be investigated further, under a wide range of conditions, and applied to the calculation of an LOD in a real LC analysis.     

Asymptotic Properties of Ranked Heights in Brownian Excursions

Pitman and Yor^{(20, 21)} recently studied the distributions related to the ranked excursion heights of a Brownian bridge. In this paper, we study the asymptotic properties of the ranked heights of Brownian excursions. The heights of both high and low excursions are characterized by several integral tests and laws of the iterated logarithm. Our analysis relies on the distributions of the ranked excursion heights considered up to some random times.     

On calculation of moments of ladder heights

Let X,X ₁,X ₂, … be independent identically distributed random variables, F(x) = P{X < x}, S ₀ = 0, and S _n =Σ _i=1 ⁿ X _i . We consider the random variables, ladder heights Z ₊ and Z ₋ that are respectively the first positive sum and the first negative sum in the random walk {S _n }, n = 0, 1, 2, …. We calculate the first three (four in the case EX = 0) moments of random variables Z ₊ and Z ₋ in the qualitatively different cases EX > 0, EX < 0, and EX = 0. __________ Translated from Lietuvos Matematikos Rinkinys, Vol. 46, No. 2, pp. 159–179, April–June, 2006.     

Bias of estimator of change point detected by a CUSUM procedure

For independent observations from a standard one-parameter exponential family, the estimator of change point after being detected by a CUSUM procedure is defined as the last zero point of the CUSUM process before the alarm time. By assuming that the change occurs far away from beginning and the control limit is large, an explicit form for the bias of estimator is derived conditioning on the change being detected. By further assuming that the change magnitude and its reference value approach zero at the same order, the local second order expansion of the bias is obtained for numerical evaluation. It is found that, surprisingly, even in the normal distribution case, the bias is non-zero when the change magnitude equals to its reference value, in contrast to the continuous time analog and the fixed sample size case. Numerical results show that the approximations are quite satisfactory.     

Coupled‐cluster reaction barriers of : An application of the coupled‐cluster//Kohn–Sham density functional theory model chemistry

In this work, we report a theoretical investigation concerning the use of the popular coupled‐cluster//Kohn‐Sham density functional theory (CC//KS‐DFT) model chemistry, here applied to study the entrance channel of the reaction, namely by comparing CC//KS‐DFT calculations with KS‐DFT, MRPT2//CASSCF, and CC//CASSCF results from our previous investigations. This was done by performing single point energy calculations employing several coupled cluster methods and using KS‐DFT geometries optimized with six different functionals, while conducting a detailed analysis of the barrier heights and topological features of the curves and surfaces here obtained. The quality of this model chemistry is critically discussed in the context of the title reaction and also in a wider context. © 2013 Wiley Periodicals, Inc.