The effect of pressure on the Raman spectrum of NH4Cl

The Raman spectra of NH₄C1 are reported over a very wide pressure range at room temperature and some features of the well-known disorder-order transition as well as the spectra of the ordered phase at high pressures are discussed. The mode Grüneisen parameter has been determined to be equal to 2.1 ± 0.03 for ν₅(TO) in this phase showing that the volume-dependent anharmonicity is relatively large. Above 110kbar, significant spectral changes take place, a large number of lattice modes appear and some internal modes also reflect changes. Since these features closely resemble the ones observed in the newly discovered V of NH₄I, it is concluded that phase V also exists in NH₄Cl. The structure of phase V as well as the mechanism of the IV–V transition are still largely unknown but it is shown that the IV–V transition pressures in the ammonium halides vary linearly with the anionic radii.     

A method for real-time condition monitoring of haul roads based on Bayesian parameter estimation

Current haul road management techniques, such as routine, periodic and urgent maintenance have shortcomings in many complex haul road environments. Real-time road condition monitoring may significantly reduce maintenance costs, both to the road and to the vehicles. A recent idea is that vehicle on-board data collection systems could be used to monitor haul roads on a real-time basis by means of vibration signature analysis. This paper proposes a methodology based on Bayesian regression to isolate the effect of varying vehicle speed on the measured vehicle response metric. A key feature of the proposed methodology is that it avoids the costly need to generate analytical or empirical vehicle models.     

A computationally efficient 3D finite‐volume scheme for violent liquid–gas sloshing

We describe a semi‐implicit volume‐of‐fluid free‐surface‐modelling methodology for flow problems involving violent free‐surface motion. For efficient computation, a hybrid‐unstructured edge‐based vertex‐centred finite volume discretisation is employed, while the solution methodology is entirely matrix free. Pressures are solved using a matrix‐free preconditioned generalised minimum residual algorithm and explicit time‐stepping is employed for the momentum and interface‐tracking equations. The high resolution artificial compressive (HiRAC) volume‐of‐fluid method is used for accurate capturing of the free surface in violent flow regimes while allowing natural applicability to hybrid‐unstructured meshes. The code is parallelised for solution on distributed‐memory architectures and evaluated against 2D and 3D benchmark problems. Good parallel scaling is demonstrated, with almost linear speed‐up down to 6000 cells per core. Finally, the code is applied to an industrial‐type problem involving resonant excitation of a fuel tank, and a comparison with experimental results is made in this violent sloshing regime. Copyright © 2015 John Wiley & Sons, Ltd.     

库仑加线性位基态解析解

应用新发展的单一轨迹积分方法求解库仑加线性位的基态量子波函数,得到基态能量和波函数的一般解析表达式,并讨论了解的收敛性.应用此方法讨论了重夸克偶素系统.     

The infrared and Raman spectra of water in sodium hexafluorophosphate monohydrate, NaPF6·H2O

The O---H and O---D stretching modes in partially deuterated NaPF₆·H₂O occur at what seem to be the highest frequencies so far recorded for HDO groups in crystalline hydrates, showing that the hydrogen bonds in this compound are very weak.     

The vibrational spectra and crystallographic properties of CsPF6

Indications are that CsPF₆(I) at ambient conditions is cubic with a possible space group of Fm3m-O⁵_h. A slight distortion of the unit cell cannot, however, be ruled out. Assuming Fm3m symmetry the Raman spectra of CsPF₆(I) are consistent with a disordered model in which the PF^?₆ ions are tilted away from the crystallographic axes. The phase transition which occurs below 90 K in CsPF₆ is reflected in the vibrational spectra and further significant changes occur below 60 K particularly in the Raman bands. It is not yet clear whether these changes represent the establishment of long-range order or whether a further phase of CsPF₆ exists below 60 K. A possible structure for CsPF₆ at very low temperatures is discussed.