A Modification of an Algorithm by Golub and Plemmons for Large Linear Least Squares in the Context of Doppler Positioning

This paper considers the solution of the geodetic Doppler multi-stationadjustment, i.e. the problem of computing the positions of severalstations observing the Doppler shift on radio frequencies emittedby several artificial satellites passing over the horizon. Amodification of an algorithm due to Golub and Plemmons, forsolving large linear least-squares problems where the observationmatrix has a block dual angular form, is proposed in this framework.This modification is shown to reduce substantially both datatransfer between the tracking stations and the main computingcentre, and the total computational effort required to obtainthe solution of the problem. Preliminary numerical results arediscussed and some further comments presented.     

Two‐dimensional anisotropic Cartesian mesh adaptation for the compressible Euler equations

Simulating transient compressible flows involving shock waves presents challenges to the CFD practitioner in terms of the mesh quality required to resolve discontinuities and prevent smearing. This paper discusses a novel two‐dimensional Cartesian anisotropic mesh adaptation technique implemented for transient compressible flow. This technique, originally developed for laminar incompressible flow, is efficient because it refines and coarsens cells using criteria that consider the solution in each of the cardinal directions separately. In this paper, the method will be applied to compressible flow. The procedure shows promise in its ability to deliver good quality solutions while achieving computational savings. Transient shock wave diffraction over a backward step and shock reflection over a forward step are considered as test cases because they demonstrate that the quality of the solution can be maintained as the mesh is refined and coarsened in time. The data structure is explained in relation to the computational mesh, and the object‐oriented design and implementation of the code is presented. Refinement and coarsening algorithms are outlined. Computational savings over uniform and isotropic mesh approaches are shown to be significant. Copyright © 2004 John Wiley & Sons, Ltd.     

Risk aversion and optimal forest replanting: A stochastic efficiency study

A new stochastic efficiency analysis approach, called stochastic efficiency with respect to a function (SERF), is applied to analyse optimal tree replanting on an area of recently harvested forest land. SERF partitions a set of risky alternative tree replanting strategies in terms of certainty equivalents (CEs) for a specified range of attitudes to risk. Both the entailed risk and the forest owner’s risk aversion are taken into account. The forest owner’s degree of risk aversion affects both the optimal tree replacement strategy and the reinvestment decision. The degree of risk aversion also needs to be taken into account when designing policy measures to affect forest investment.     

一个机器服务模型的可靠性分析

本文讨论了由Ｎ个同型部件和一个服务设备组成的机器服务模型，在服务设备绝对可靠，或服务设备具有指数寿命，修理工对其修理的时间为ＰＨ分布，这两种情况下求得了系统的平稳概率分布，从而求得机器系统和服务设备的稳态可靠性指标，并证明了它们的首次失效时间均服从ＰＨ分布，服务设备和修理工的忙期亦服从ＰＨ分布．     

Fission yields at different fission-product kinetic energies for thermal-neutron-induced fission of 239Pu

At the recoil spectrometer “Lohengrin” of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of ²³⁹Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct kinetic energies between 93 and 112 MeV. The proton odd-even effect which was measured to be (11.6 ± 0.6)% causes considerable fine structure in the yields. The average kinetic energy of even-Z elements in the light fission-product group is 0.3 ± 0.1 MeV larger than for odd-Z elements. The neutron odd-even effect is (6.5 ± 0.7)%. The comparison with previously published data ¹) for thermal-neutron-induced fission of ²³⁵U reveals a correlation between the proton odd-even effect in the yield and in the kinetic energy of the elements. The dependence of the proton odd-even effect on the fragmentation is very similar for ²³⁵U and ²³⁹Pu when it is considered as a function of the nuclear charge of the heavy fission products. The isobaric variances σ_z². for thermal-neutron fission of ²³⁵U and ²³⁹Pu coincide at all kinetic energies if the influence of the proton odd-even effect is averaged out. This supports the hypothesis that the magnitude of σ_z² is determined only by quantum-mechanical zero-point fluctuations. The influence of the spherical shells Z = 50 and N = 82 on the fragmentation is discussed.     

BaIr0,67Be0,33O3: Eine stabilisierte kubische Form von BaIrO3

Inhaltsübersicht. Es ist gelungen, ein durch BeO stabilisiertes Bariumoxoiridat der Zusammensetzung BaIr_0,67Be_0,33O₃ in der Kristallform eines kubischen Perowskits mit kleiner Elementarzelle erstmals darzustellen. Raumgruppe O¹_h–Pm3m, a = 4,1009 Å, Z = 1. Ir⁵⁺ und Be² + besetzen die Oktaederposition des Perowskits statistisch. BaIr_0,67Be_0,33O₃: A Stabilized Cubic Form of BaIrO₃ For the first time it was possible to prepare a new barium-oxoiridate of the formula BaIr_0,67Be_0,33O₃, stabilized by BeO. It crystallizes in a small cubic unit cell of the perovskite type. Space group O¹_h–Pm3m; a = 4.1009 Å; Z = 1. Ir⁵⁺ and Be²⁺ occupy the octahedra positions of the perovskite structure statistically.     

Density functional study of XH4 (XSi and Ge) reactivity upon dissociative adsorption onto the Si(100) surface

Total energy calculations based on density functional theory (DFT) with generalized gradient approximation (GGA) and ultrasoft pseudopotential approximation and an analysis tool of atom‐resolved density of states (ADOS) have been used to investigate (1) the energetic profiles for the possible initial dissociative adsorption of XH₄ (X?Si and Ge) onto the Si(100)? (2 × 2) surface to evaluate their reactivity and (2) the effect of surface electronic states of Si(100)? (2 × 2) on gaseous molecular precursors XH₄ (X?Si and Ge) during initial dissociative adsorption to understand the factors governing their reactivity. Our calculated lower‐energy barrier for initial dissociative adsorption of GeH₄ is due to the forming of stronger bond of Si? H between H within GeH₄ and buckled‐down Si atom on the Si(100)? (2 × 2) surface accompanying the larger extent of unbuckling of the buckled Si?Si dimer on the Si(100)? (2 × 2) surface at the transition state. Our evaluated better reactivity for GeH₄ than SiH₄ (a factor of around 14.6) is slightly larger than observed higher reactivity for GeH₄ than SiH₄ (a factor of between 2 and 5 depending on the incident kinetic energy) employed supersonic molecular bean techniques. Finally, our calculated ADOS indicate that the surface electronic states of buckled Si?Si dimer on the Si(100)? (2 × 2) surface energetically favorably participate in the transition state during GeH₄ initial dissociative adsorption to reduce the energy barrier, i.e., enhance its reactivity, in comparison with SiH₄ initial dissociative adsorption onto the Si(100)? (2 × 2) surface under the same reaction conditions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Identification and quantification of tamoxifen and four metabolites in serum by liquid chromatography-tandem mass spectrometry

We have developed a method for the determination of tamoxifen (tam) and its metabolites 4-hydroxytamoxifen (4OHtam), N-demethyltamoxifen (NDtam), N-dedimethyltamoxifen (NDDtam), tamoxifen-N-oxide (tamNox), and 4-hydroxy-N-demethyltamoxifen (4OHNDtam) in 50 microl human serum. Serum proteins were precipitated with acetonitrile. Deuterated-tamoxifen (D5 tam) was added as internal standard. Sample supernatant was injected into an on-line reversed-phase extraction column coupled with a C18 analytical column and analytes were detected by tandem mass spectrometry. The lower limits of quantification were 0.25 ng/mL for 4OHtam, NDtam and tam, 1.0 ng/mL for NDDtam and tamNox. Ranges of within- and between-day variation were 2.9-15.4% and 4.4-12.9%, respectively.