Thermodynamic modeling and phase diagram prediction of salt lake brine systemsⅡ.Aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems

It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component,multitemperature and high concentration.The essential subsystem of sulfate type brine,aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model.Liquid parameters(Δg_(IJ),Δh_(IJ),and ΔC_(p,IJ))associated with the contributions of Gibbs energy,enthalpy,and heat capacity to the binary interaction parameters,i.e.the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression,are determined via multi-objective optimization method.The solid constantsΔ_(f)G_(k)°^((298.15))andΔ_(f)H_(k)°^((298.15))of11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities.The modeling results show the accurate representation of(1)solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K;(2)isothermal phase diagrams for Li_(2)SO_(4)-Na_(2)SO_(4)-H_(2)O,Li_(2)SO_(4)-K_(2)SO_(4)-H_(2)O and Na_(2)SO_(4)-K_(2)SO_(4)-H_(2)O ternary systems.The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.

风险因子调整的三阶段剩余收益模型的应用研究——基于中国资本市场1999～2010年截面数据分析

在总结梳理奥尔森模型及后来学者所提出的系列三阶段剩余收益模型基础上,选择有代表性的三阶段剩余收益模型(TSSV-θ),结合作者提出的新的三阶段剩余收益模型,即风险因子调整的三阶段剩余收益模型(RIM-σ2),利用中国市场的数据进行实用性比较研究,同时选择单一上市公司数据就RIM-σ2模型进行实际的运用分析。结果表明,RIM-σ2模型在理论和实证上均具有较好的优越性和实用性,可以作为一种有效的企业价值评估方法。

Formation of Li Salts from Natural Brines during Isothermal Evaporation at 25℃

Li brines are the primary resources for Li salt industries.Evaporation is necessary to concentrate Li due to its low level of concentration in raw brines.The salt sequences during the evaporation of Li brines,especially the behavior of Li salts,represent key data for solar technologies.However,chemists cannot use any phase diagram to estimate Li salt sequences during evaporation at 25℃.The thermodynamic model proposed by us in 2003 represents the only tool for the prediction of equilibrium conditions during the evaporation of solutions containing Li^+,Na^+,K^+,Mg^2+/Cl^-,SO4^2-,and-H2O components at 25℃.In this paper,the predicted salt sequences of 20 brines are reported.The results indicate that (1) the first crystallized Li salt during evaporation of Li brine varies in brine composition;(2) lithium sulfate is crystallized in many cases initially for brines of magnesium sulfate subtype,while Db4 (Li2SO4 ·K2SO4 ) or Db3 (2Li2SO4 ·Na2SO4 ·K2SO4 ) appears first for sodium sulfate and magnesium sulfate subtypes with lower Mg/Li composition,and the final eutectic point is H+LiC+Lc+Ls+Car;(3) the final eutectic point is H+LiC+Lc+Car for brines of chloride type;and (4) Li content corresponding to the first crystallized Li salt is in the range of 0.43%-1%.These findings enhance our knowledge of Li chemistry and provide insights into solar pond technology of the Li-brine process.

RIM-σ^2模型：理论与实证

针对奥尔森系列剩余收益模型的不足,基于一般的三阶段剩余收益模型提出一个新模型,即线性风险因子调整的三阶段剩余收益模型(RIM-σ2模型)。同时,利用沪深1999—2011年非金融类上市公司的截面数据对该模型的适用性进行实证分析。结果证实,总体上体现出RIM-σ2模型相对以往的剩余收益模型有较大的改进,RIM-σ2模型具有适用性与优越性,在一定程度上可以作为预测公司价值的一种有效的补充工具。

Investigation of radionuclide ^(60)Co(Ⅱ) binding to TiO_2 by batch technique,surface complexation model and DFT calculations

The interaction between radionuclides and solid/water interfaces is important to understand the physicochemical processes of radionuclides in the natural environment.Herein,the interaction of 60Co(Ⅱ) with TiO 2 in aqueous solution as a function of pH and ionic strength was studied by using batch technique combined with surface complexation model and density functional theory(DFT) calculations.The batch experimental results showed that the adsorption of 60Co(Ⅱ) was dependent on pH and independent of ionic strength,indicating the formation of inner-sphere surface complexes on TiO 2 surfaces.The results of surface complexation models and DFT calculations indicated that the surface species of 60Co(Ⅱ) adsorbed on TiO 2 followed the trend:B structure(i.e.,60Co(Ⅱ) was linked to one bridge oxygen site) was the dominant surface species at low pH,and TT structure(i.e.,60Co(Ⅱ) was linked to two terminal oxygen sites) became the important surface complex at neutral and alkaline pH values.These results demonstrated that a multi-technique approach could lead to definitive information on the structures of adsorbed 60Co(Ⅱ) at the molecular level at the TiO 2 /water interfaces,as well as realistic models to rationalize and accurately evaluate the macroscopic manifestations of radionuclide adsorption phenomena.

Precursory specialties of apparent stresses in Yunnan earthquake series

On the basis of the assumption that ω^2 model accords with source displacement spectra, we have obtained the mathematical expressions for calculating apparent stresses of moderate-small shocks from low-frequency flat level and comer frequency. By using digital seismic records, apparent stress values are calculated for 823 moderate-small shocks of 4 earthquake series in Yunnan area following corrections for instrument response, propagation influence and site effect. The results show that for the 4 earthquake series in Yunnan area, apparent stress hints precursory information, which means that if a moderate-small shock occurs with apparent stress larger than 1 MPa in an earthquake series, a moderate-strong earthquake will occur afterwards; and if there is not moderate-small shock with apparent stress larger than 1 MPa after a moderate-strong event in an earthquake series, strong aftershock will not occur. The research also indicates that the average apparent stress value is 0.8 MPa in Yunnan area, therefore, apparent stress is not obviously related to seismic magnitude.

Application of apparent stress in earthquake prediction

On the basis of the assumption that ω^2 model accords with source displacement spectra of moderate-small shocks, we calculate the apparent stress values of 1 020 moderate-small shocks recorded by the Digital Seismic Network of Yunnan Province by using the low-frequency fiat level and corner frequencies. The results show that the apparent stress is of good significance in earthquake prediction. The moderate-small shock with apparent stress larger than 0.9 MPa can be used as a referential index to predict moderate-strong earthquakes in Yunnan area. And its relevant predictability evaluation （R value） has a high confidence level.

Neutron-rich ^(104,106,108)Mo Isotopes in the Generalized Collective Model

The Generalized Collective Model (GCM) is applied to the even even neutron rich 104,106,108 Mo isotopes. With GCM the energy spectra, absolute B(E2) values, some B(E2) branching ratios and Potential Energy Surfaces (PES) for the 104,106,108 Mo isotopes are calculated. The PES of all these isotopes show a prolate minimum which becomes more pronounced in 106 Mo. The results are in agreement with the recent experimental report but are different from the viewpoint of the triaxial rotors, or γ soft deformation. Through a systematic study of PES, it is suggested that the even even neutron rich 104,106,108 Mo isotopes have prolate deformation.

Sources of nitrous and nitric oxides in paddy soils: Nitrification and denitrification

Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH^-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification （N2On） among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one （from 1.26 to 6.47）. We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity.