Discretization of the solutions to Poisson’s equation

Sharp estimates (in the power scale) are obtained for the discretization error in the solutions to Poisson’s equation whose right-hand side belongs to a Korobov class. Compared to the well-known Korobov estimate, the order is almost doubled and has an ultimate value in the power scale.     

机翼大攻角下失速颤振的气动弹性研究

本文采用流固耦合的数值方法研究了机翼在0°～50°攻角下的颤振。计算结果表明,随着来流攻角α0的增大,机翼的固有频率对颤振的影响越来越大,颤振由线性的强迫振动逐渐发展成为非线性的自激振动,而当α0增加到一定程度以后,大尺度分离流交替地从机翼头部和尾部产生,机翼和流场会发生共振,引起机翼的失速颤振。     

High-temperature expansions to fifteenth order

High-temperature series expansions of the susceptibility and second moment to 15th order are calculated for zero external field on the linear chain (LC), plane square (PSQ), simple cubic (SC), and body-centered cubic (BCC) lattices. Checks for specific models against pertinent work in the literature are detailed.     

基于同步辐射加速器的康普顿背散射γ射线源(Ⅰ)产生MeV量级γ光子的数值计算

提出在筹建的上海同步辐射装置上建造一条MeV量级γ射线束及应用站,采用μm波长的红外(或远红外)激光与储存环中3.5GeV电子束进行康普顿背散射,从而获得能区为1—25MeV的康普顿背散射γ光子束,该光子束具有高强度、高极化度(线和圆极化)、准单色、方向性好的优点,可以广泛地应用于核物理和核天体物理基础研究及相关的应用研究领域.介绍了康普顿背散射的基本原理,并结合储存环参数给出了光子束性能的数值计算结果.     

贝克曼AllegraTM21R型超高速离心机故障排除一例

贝克曼Allegra^TM 21R型超高速离心机开机后，操作面板上出现错误代码“28”，离心机不旋转。离心机的电机采用无刷感应驱动，由电机驱动电源模块BSMl0GD60DN2驱动离心机的电机。故障是由于电源模块BSMl0GD60DN2损坏引起的。采用东芝三相桥式IGBT电源模块MG25Q6ES42代替BSMl0GD60DN2，并更换已烧毁的栅极电阻后。开机试验，仪器恢复正常。     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes

A systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of ?14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and ?5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation, structure and properties of novel 1,3-dithiol-2-ylidene derivatives containing bis(ethynylpyridine) units

1,3-Dithiol-2-ylidene derivatives containing bis(ethynylpyridine) units were synthesized using a Pd-catalyzed reaction of the corresponding dibromide. X-Ray crystal analysis revealed unique crystal structures depending on the aromatic groups. The absorption spectra and redox properties indicated intramolecular charge-transfer interactions between the 1,3-dithiole unit and the pyridyl parts.     

Estimation of integrated volatility in stochastic volatility models

In the framework of stochastic volatility models we examine estimators for the integrated volatility based on the pth power variation (i.e. the sum of pth absolute powers of the log‐returns). We derive consistency and distributional results for the estimators given high‐frequency data, especially taking into account what kind of process we may add to our model without affecting the estimate of the integrated volatility. This may on the one hand be interpreted as a possible flexibility in modelling, for example adding jumps or even leaving the framework of semimartingales by adding a fractional Brownian motion, or on the other hand as robustness against model misspecification. We will discuss possible choices of p under different model assumptions and irregularly spaced data. Copyright © 2005 John Wiley & Sons, Ltd.     

The semi‐iterative method applied to the hyper‐power iteration

The semi‐iterative method (SIM) is applied to the hyper‐power (HP) iteration, and necessary and sufficient conditions are given for the convergence of the semi‐iterative–hyper‐power (SIM–HP) iteration. The root convergence rate is computed for both the HP and SIM–HP methods, and the quotient convergence rate is given for the HP iteration. Copyright © 2005 John Wiley & Sons, Ltd.     

A rigid subspace of the real line whose square is a homogeneous subspace of the plane

Working in ZFC, we give an example as indicated in the title.