Numerical modelling of wave-structure interaction by a three-dimensional nonlinear boundary element method: A step towards the numerical wave tank

A three-dimensional numerical model for determination of the interaction between non-linear water waves and a structure is developed. The model is based on a boundary integral equation method for the spatial solution of a potential theory problem, combined with a time-stepping method based on the fully non-linear free surface conditions for temporal updating of moments on a structure in the fluid domain. Comparison with experimental results shows good agreement. The present model is considered to be one of the steps towards a three-dimensional numerical model in which the wave-structure interaction in a wave tank can be simulated.     

Comparison of the performance of net radiation calculation models

Daily values of net radiation are used in many applications of crop-growth modeling and agricultural water management. Measurements of net radiation are not part of the routine measurement program at many weather stations and are commonly estimated based on other meteorological parameters. Daily values of net radiation were calculated using three net outgoing long-wave radiation models and compared to measured values. Four meteorological datasets representing two climate regimes, a sub-humid, high-latitude environment and a semi-arid mid-latitude environment, were used to test the models. The long-wave radiation models included a physically based model, an empirical model from the literature, and a new empirical model. Both empirical models used only solar radiation as required for meteorological input. The long-wave radiation models were used with model calibration coefficients from the literature and with locally calibrated ones. A measured, average albedo value of 0.25 was used at the high-latitude sites. A fixed albedo value of 0.25 resulted in less bias and scatter at the mid-latitude sites compared to other albedo values. When used with model coefficients calibrated locally or developed for specific climate regimes, the predictions of the physically based model had slightly lower bias and scatter than the empirical models. When used with their original model coefficients, the physically based model had a higher bias than the measurement error of the net radiation instruments used. The performance of the empirical models was nearly identical at all sites. Since the empirical models were easier to use and simpler to calibrate than the physically based models, the results indicate that the empirical models can be used as a good substitute for the physically based ones when available meteorological input data is limited. Model predictions were found to have a higher bias and scatter when using summed calculated hourly time steps compared to using daily input data.     

南天山川乌鲁碱性杂岩体的岩石学和地球化学特征及其岩石成因

位于中国南天山西侧阔克萨彦岭一带的川乌鲁碱性杂岩体,与该区川乌鲁铜金多金属矿床有着直接的成因联系,该杂岩体由早期的辉长岩—闪长岩岩、主期的二长岩—正长岩和晚期的正长花岗斑岩脉组成,各期岩石在矿物组成和化学成分上有明显的变化。从早到晚,SiO2含量增加,变化范围是50.52%～70.64%;全碱含量先增后减,在SiO2含量小于61.69%时,随SiO2含量增加而增加,而当SiO2含量大于61.69%时,与SiO2含量负相关。在AR-SiO2图解上,大多样品落入碱性区间,在A/CNK-A/NK图解上表现出由准铝质向过碱性演化的趋势。微量元素表现为大离子亲石元素相对高场强元素富集,Rb、Ba、Th、Sr等元素的相对富集和Nb、Ta、P、Ti等元素的负异常。稀土元素表现为轻稀土相对富集的特征,其(La/Yb)N为14.13～25.09,具有Eu的正异常或极微弱的Eu负异常。一些元素比值的线性关系暗示了该杂岩体为岩浆混合成因,基性岩浆的源区为富水的岩石圈地幔,而酸性岩浆是中下地壳中性火成岩在含饱和水条件下部分熔融的产物。这些性质指示川乌鲁杂岩体是在后碰撞拉张环境中由岩石圈地幔熔融的基性岩浆的底侵作用导致地壳的熔融以及后期的岩浆混合作用有关。     

Free energy of formation for green rust sodium sulphate (NaFe6Fe3(OH)18(SO4)2(s))

In a recent study, sulphate-bearing green rust (GR_SO4) was shown to incorporate Na⁺ in its structure (NaFe^II₆Fe^III₃(OH)₁₈(SO₄)_2(s); GR_Na,SO4). The compound was synthesised by aerial oxidation of Fe(OH)_2(s) in the presence of NaOH. This paper reports on its free energy of formation .Freshly synthesised GR_Na,SO4 was titrated with 0.5 M H₂SO₄ in an inert atmosphere at 25 °C, producing dissolved Fe²⁺ and magnetite or goethite. Solution concentrations, PHREEQC and the MINTEQ database were used to calculate reaction constants for the reactions: