运用概念密度泛函理论和信息论方法定量描述胺类分子的分子碱度

分子酸碱性是一对在化学、生物和其他学科中广泛运用的化学概念。如何从理论和计算的角度定量描述分子酸碱度仍然是一个尚未完全解决的难题。为此,我们早前从概念密度泛函的角度提出运用分子静电势和自然原子价轨道。随后,我们又提出运用信息理论中的香农熵、费舍尔信息、信息增益等量来定量测定亲电性、亲核性、区域和立体选择性,并成功运用于预测包括单和双取代苯甲酸、苯磺酸、苯亚硒酸、酚和烷基羧酸在内的五类分子酸性,系统地验证了信息论方法的适用性和有效性。作为该工作的延续,本文将概念密度泛函理论和信息论方法结合起来并推广运用至更多更广的体系。为此我们以伯胺、仲胺和叔胺三类胺类体系共179个分子为例,验证其普适性和有效性。运用分子静电势或者等价的自然价原子轨道能量,以及信息理论中香农熵、费舍尔信息、Ghosh-Berkowitz-Parr熵、信息增益、Onicescu信息能量、相对Rényi熵等信息量,发现均能有较地预测三类胺分子的碱性,与实验p Ka值呈较好的相关性。而且,将这些量组合在一起能够得到更准确的预测模型。其原因在于这些描述符均为电子密度泛函。根据密度泛函理论的基本原理,它们包含有足够的信息来描述包括分子酸碱性在内的所有基态性质。我们的结果显示,该方法同样适用于其他体系。本文为有效预测分子酸碱性提供了一个有效途径。

Smart Substation Integration Technology and Its Application in Distribution Power Grid

At present,smart substations use the IEC61850 standard based on the architectural framework of three layers and two networks to realize information digitization and advanced applications.Although the smart substation offers many improvements in design,equipment manufacturing,and construction,the intelligent devices used in smart substations are costly,and are also difficult to maintain since they are dispersed within a single unit.Functionality optimization and device integration,thus,have become important issues in smart substation development.This paper presents an integrated solution and implementation process for a smart substation system.In the process layer,an integrated intelligence component is developed that functions both as an intelligent terminal and a merging unit.In the bay layer,an integrated station-area protection measurement and control master device is designed to achieve such functions as protection,monitoring,control,fault recorder,and power quality monitoring.Finally,in the station control layer,an integrated information platform is established to bring together various system functions and to promote interactive sharing.Integration technology improves the economy and practicality of the smart substation,especially in a distribution power grid.

Partitioning of rare earth elements and yttrium(REY)in five coal-fired power plants in Guizhou,Southwest China

As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products(CCPs).In this study,five coal-fired power plants(CFPPs)in Guizhou of southwest China were selected for investigating REY concentrations of solid samples,atmospheric emissions,and recovery potentials.REY concentrations of feed fuels are higher in this study(147.2-468.6 mg/kg)than what have been reported previously for coals in China and the world.REY atmospheric emissions are extremely low(38.70-180.11 mg REY/t coal).REY are enriched in bottom ash and fly ash,with average of 658±296 mg/kg and maximum of 1257 mg/kg from the five CFPPs.Relative enrichment factors(REF)of REY in bottom ash and fly ash compared with the feed fuel are 0.86-1.02 and 0.91-1.04,respectively.REY concentrations in desulfurized gypsum are very low(6-17 mg/kg),and that is mostly inherited from limestone.Critical REY(Nd,Eu,Tb,Dy,Y,and Er)in bottom/fly ash account for 34%-39%of the total REY and the outlook coefficients(Cout1)are in the range of 0.89-1.11.This study indicates a promising prospect to reclaim REY from REYrich CCPs(bottom and fly ash)in CFPPs in Guizhou,especially in the central-north Guizhou,although such practices require further technology advancement.

Iron loss of paddy soil in China and its environmental implications

Iron(Fe)is an important element for the terrestrial and marine ecosystems through its biogeochemical cycling on the Earth’s surface.China has a long rice cultivation history,with extensive rice distribution across many types of paddy soils.Paddy soils are the largest anthropogenic wetlands on earth with critical roles in ecosystem functions.The periodic artificial submergence and drainage during paddy soil evolution result in significant changes in soil moisture regime and redox conditions from the natural soils,which facilitate the increase of Fe solubility and mobilization.However,there is a lack of systematic assessment on the magnitude of the migration and loss amount of Fe from paddy soils.In order to quantify the Fe loss and assess the dynamic evolution of Fe in the soils after rice cultivation,seven paddy soil chronosequences derived from different landscapes(bog,plain,terrace)and parent materials(acidic,neutral,calcareous)with cultivation history from 0 to 2,000 yr were studied.Results showed that the rates and trajectories of Fe evolution showed distinct patterns among the studied seven paddy soil chronosequences.However,net losses of Fe from 1 m soil depth occurred at all studied paddy soil chronosequences regardless of the original landscapes and parent materials.Fe in the paddy soils derived from the calcareous lacustrine sediments in the bog area showed a slight accumulation during the initial stage(50 yr)of paddy cultivation,with a loss rate of0.026 kg m^(-2)yr^(-1) during the 50-to 500-yr time period.For the paddy soils developed on the calcareous marine sediments in the plain area,Fe evolution was dominated by the internal movement in soil profiles through coupled reducing-eluviation reactions in the surface horizons and oxidation-illuviation in the subsurface horizons within 1,000 yr of paddy cultivation,with an averaged net loss rate of 0.029 kg m^(-2)yr^(-1) during the 1,000-to 2,000-yr time period of rice cultivation.In contrast,Fe in the paddy soils derived from the acidic and neutral parent materials in the plain and terraced upland areas was rapidly lost during the initial stage of paddy cultivation,with a maximum loss rate of 1.106 kg m^(-2)yr^(-1),while the Fe loss rate decreased gradually with increasing paddy cultivation age.Soil pH,CaCO_(3),and organic matter contents of the original soils,the length of time of paddy cultivation,landscape types and positions,and changes in soil moisture regime and redox condition induced by artificial submergence and drainage were the main factors controlling the rates and trajectories of Fe loss during paddy soils evolution.The amount of Fe loss caused by rice cultivation at the national scale was estimated based on the data collected from this study and the literature.The Fe loss fluxes of paddy soils in China were about 46.4–195.7 Tg yr^(-1),and the amounts of Fe losses from paddy fields nationwide were about 5,121.5–9,412.2 Tg.Quantifying Fe loss from paddy fields is important to scientifically assess the impact of paddy cultivation on the Fe biogeochemical cycle.

大分子和凝聚相体系的快速量子化学计算:普适的基于能量的分块方法的发展和应用

大分子和凝聚相体系的量子化学计算是理论化学的挑战之一,为了处理实验研究中越来越复杂的体系,线性标度的量子化学方法发展一直是理论研究的热点.由于简单有效且易于推广,基于能量的分块方法近十几年来得到较快的发展.本文主要介绍本课题组的普适的基于能量的分块量子化学方法的发展和应用,包括大体系的基态能量、结构和性质、局域激发态的计算方法及周期性体系的算法.该方法有望应用于多种类型的大体系(包括团簇、超分子、生物体系、分子晶体和溶液等)的能量、结构、振动光谱、核磁化学位移及电子吸收光谱等性质的计算.

Passivity-based Active Stabilization for DC Microgrid Applications

In this paper,an improved active stabilization strategy of the interface converters in microgrid applications is proposed on the basis of the passivity-based stability criterion(PBSC).As a critical part of AC and DC hybrid microgrids,the DC microgrid is taken as an example.In particular,a stabilization method with a proportional-integral(PI)controller and firstorder high-pass filter(HPF)is proposed to meet the passivity requirements of the overall control diagram with respect to the output voltage.Meanwhile,an output current feedback control loop is introduced to ensure the output impedance passivity.Moreover,a small-signal model of the parallel interface converter system is established to comprehensively study the influence of control parameters on the passivity of the converters.Based on the active stabilization method proposed in this study,by manipulating the control diagram of each interface converter,the passivity and stability of the DC microgrids with variable configuration can be guaranteed.Therefore,a generic and simplified design approach is realized.A simulation model with three interface converters is implemented in MATLAB/Simulink,and the effectiveness of the proposed passivity-based active stabilization algorithm is verified by using this simulation model.