金属硫化物在电催化二氧化碳还原反应中的应用

金属硫化物作为催化剂材料具有高稳定性、金属边缘活性和硫空位的协同效应等特点，特别是对二氧化碳(CO₂)电还原反应表现出良好的活性和选择性，有望成为高效的CO₂电还原催化剂.鉴于此，综述了金属硫化物在电催化CO₂还原反应中的研究进展，分别归纳了第四周期、第五周期及第六周期中主要的金属硫化物电催化CO₂还原反应的性能、还原产物特点及影响因素等；特别分析了金属硫化物中S组分调控对催化性能的影响规律，以期实现更高效的电催化CO₂还原转化过程.此外，总结分析了目前金属硫化物催化剂存在的主要问题和瓶颈，并展望未来的研究重点和发展方向.     

生物质油提质加氢脱氧催化剂研究进展

随着化石能源的日益减少,来源于木质纤维素基可再生生物质油越来越受到人们的关注.但是,与石油相比,生物质油含氧量高,导致其能量密度低、黏度高、热和化学稳定性差,因而必须进行脱氧提质才能用作发动机燃料.在生物质油提质方法中,加氢脱氧(HDO)最具应用前景.综述了木质纤维素基生物质油HDO催化剂的研究进展,包括过渡金属硫化物、磷化物、氮化物和碳化物,贵金属,金属-酸双功能催化剂,过渡金属以及非晶态合金等.过渡金属硫化物催化剂用于HDO时,会因S被氧化物或水中O逐步取代而失活;贵金属催化剂虽具有高HDO活性和选择性,但因价格高、资源受限而无法大规模应用;过渡金属氮化物、碳化物和过渡金属催化剂活性较高,但会在HDO中因结焦或氧的嵌入导致催化剂失活;非晶态合金催化剂具有较高HDO活性,但热稳定性较差;过渡金属磷化物的HDO活性高,稳定性好,是一类优良的HDO催化活性相.载体的表面性质和孔结构对其负载的HDO催化剂性能影响较大.碳沉积和结构破坏是HDO催化剂失活的主要原因.     

类钙钛矿型La1．6Ba0．4MO4（M=Co、Ni、Cu）复合氧化物催化分解NO性能的研究

采用柠檬酸络合爆炸法合成了La1．6Ba0．4MO4（M=Co、Ni、Cu）系列类钙钛矿复合氧化物催化剂,通过 XRD、H2-TPR等分析方法表征了其物相组成及氧化还原能力的变化,并考察了该系列催化剂催化分解 NO的活性．结果表明:Ba的掺杂对于不同过渡金属的氧化性的影响是不同的,但都提高了过渡金属的氧化还原能力,从而提高了样品的催化活性,其中Ni基类钙钛矿的直接分解NO的催化活性是最理想的．     

元素电负性的力标、能标和距标

为了研究键型过渡问题,本文以双原子键的三中心模型及其物理参量表达式为基础,定义了键电荷迁移指数,键能偏离指数和键长偏离指数三个键型参数。为了便于在化学化工中应用,又从这三个参数引出了电负性力标、能标和距标,并用物性实验值对这些参数进行了验证,结果表明它们能有效地概括物性规律。     

基于3d过渡金属的氧电极材料研究进展

氧还原催化剂及缓慢的阴极氧还原动力学是制约低温燃料电池商业化的关键瓶颈因素之一.非贵金属氧还原催化剂是近年来低温燃料电池最受关注的研究热点之一.在简要介绍燃料电池及氧还原反应机理的基础上,详细地综述了近年来低温燃料电池用3d过渡金属基氧还原催化剂的主要研究进展,包括过渡金属大环化合物、过渡金属-氮/碳类化合物、过渡金属硫族化合物和过渡金属氧化物,总结了提高催化活性和稳定性、降低催化剂制备成本以及催化剂制备工艺等方面所取得的研究结果,并指出了各类催化剂目前尚待解决的问题和发展方向.     

电催化析氧反应过渡金属硫化物催化剂研究进展

析氧反应（oxygen evolution reaction, OER）、析氢反应（hydrogen evolution reaction, HER）和氧还原反应（oxygen reduction reaction, ORR）为电解水、金属-空气电池等能源器件的半反应。其中,OER由于涉及4e^-转移和O-O键的形成而导致反应动力学迟缓和过电势高,因此,开发优异的OER电催化剂能够有效提高能量转换效率。到目前为止,过渡金属硫化物催化剂（transition metal sulfide catalysts, TMSs）被研究人员大量研究和报道,并且取得飞跃发展。介绍在不同电解质中的OER机制,并通过对近几年相关文献的综合归纳,探究TMSs催化剂的组成、导电性、质子传输、缺陷程度、界面化学等多种因素对OER的影响。综述目前过渡金属硫化物电催化剂在OER领域所面临的挑战和研究进展,希望为TMSs的研究者提供借鉴。     

过渡金属掺杂硫化钼基催化剂加氢脱硫研究进展

加氢脱硫技术广泛应用于国内外清洁油品生产，目前硫化钼基催化剂是工业中最主要的加氢脱硫催化剂。Co和Ni等金属掺杂可以精细调变MoS₂活性相微观结构和反应机理，极大地提升了其催化性能，使其成为加氢脱硫领域的研究热点。本文综述了过渡金属掺杂MoS₂基催化剂的研究进展：首先概述了过渡金属掺杂MoS₂基催化剂制备方法；其次在原子水平上讨论了过渡金属的引入对MoS₂活性相微观结构的影响；并对3种噻吩类含硫化合物在MoS₂基催化剂上的加氢脱硫反应机理进行了总结；最后汇总了近期过渡金属掺杂MoS₂基加氢脱硫催化剂的研究成果。     

应用ABEEMσπ模型确定大分子体系的电荷分布

以密度泛函理论(DFT)和电负性均衡原理为基础，明确处理了双键的结构，发展建立原子一键电负性均衡方法中的σπ模型(ABEFMσπ).本模型将双键划分为一个σ键区域和四个π键区域(每个双键原子各有2个π键区域)，其中，σ电荷中心位于两成键原子之间共价半径之比处；π电荷中心垂直于双键所在平面，置于双键原子上下两侧.本文给出分子中各部分有效电负性的精密公式，以及参数确定方法.并应用该方法简捷快速地计算了C     

类钙钛矿型La1.6Ba0.4MO4-δ(M=Co,Ni,Cu)复合氧化物催化分解NO性能的研究

采用柠檬酸络合爆炸法合成了La1.6Ba0.4MO4-δ(M=Co,N,iCu)系列类钙钛矿型复合氧化物催化剂,通过XRD、H2-TPR等分析方法表征了其物相及氧化还原能力,并考察了该系列催化剂催化分解NO的活性.结果表明:Ba的掺杂对于不同过渡金属的氧化还原能力的影响程度各不相同,但都提高了过渡金属的氧化还原能力,从而提高了样品的催化活性,其中1123K时以Ni基类钙钛矿型的复合氧化物直接分解NO的催化活性相对最高,NO分解率达88%.     

单核和双核过渡金属羰基化合物及双核过渡金属羰基夹心化合物的理论研究

用量子化学理论方法研究了一系列过渡金属羰基化合物及第一长周期双核过渡金属羰基夹心化合物.根据理论研究结果,对一些早期有关过渡金属羰基化合物的实验结论提出了质疑,对一些同族过渡金属元素原子形成的羰基化合物的结构和成键规律进行了探讨;对第一长周期过渡金属双核羰基夹心化合物进行的理论研究表明,不饱和程度较高的V2 (CO)n...     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the