自蔓延高温合成钒基固溶体贮氢合金的理论研究

提出采用自蔓延高温合成法制备钒基固溶体贮氢合金的新工艺.计算知NH4VO3-TiO2-Cr2O3-Ni-Al反应体系的绝热温度(Tad)为1 889.27 K,单位质量反应热为-2.67 kJ/g;对NH4VO3-TiO2-Cr2O3-Ni-Al反应体系的相关反应进行了热力学分析,表明体系生成V+Ti+Cr+Al2O3的趋势最大,生成物最稳定.确定了采用自蔓延模式的可行性.     

Li-Fe-Si-H_2O体系的热力学分析

根据已有热力学数据,绘制25℃时Li-Fe-Si-H2O体系各溶解组分的lgc-pH图、Li-Fe-Si-H2O体系主要物种的优势区图和强碱性区域Li-Fe-Si-H2O体系各沉淀的优势区图。利用这些平衡图对液相制备硅酸铁锂的工艺条件进行热力学分析。研究结果表明:控制溶液的碱度是制备磷酸铁锂前驱体Li2H2SiO4·Fe(OH)2的关键因素,若要利用Li+,Fe2+和H2SiO24-在液相形成Li2H2SiO4·Fe(OH)2,则要维持溶液较高的碱度,使得Li+能与H2SiO42-生成Li2H2SiO4沉淀,并且抑制FeH2SiO4的生成,使Fe2+以Fe(OH)2的形式沉淀;溶液体系的碱性越强,Li2H2SiO4·Fe(OH)2的优势区域越宽,更有利于Li2H2SiO4·Fe(OH)2的合成;采用液相法制备硅酸铁锂时,由于pH值大于15,体系的碱度较高,溶液中Fe2+极容易被氧化,故制备过程难以实现;而利用固相法制备硅酸铁锂,其保护性气氛容易控制,工艺简单,流程短,便于实现。     

关于退火温度对VO_2薄膜制备及其电学性质影响的研究

采用真空蒸发-真空退火工艺由V2O5粉末制备VO2薄膜,研究了退火温度对薄膜的影响.经XRD,XPS及电阻-温度测试发现,随退火温度的升高,VO2薄膜先后经历了单斜晶系VO2(B)型→单斜晶系VO2(A)型→四方晶系VO2的变化,在3种类型的薄膜中V均以V4+为主,且在VO2(A)型薄膜中V4+含量最高.薄膜电阻以退火温度460℃时为分界线,低于460℃时,VO2(B)型薄膜电阻和电阻温度系数随退火温度的升高而增大;高于460℃时,四方晶系VO2薄膜的电阻及其电阻温度系数随退火温度的升高呈现相反的趋势.     

气相中VO_2~++CH_4反应的理论研究

运用密度泛函B3LYP/6-311++G(3df,3pd)//6-311G(2d,p)法研究了VO2+(1A1/3A')+CH4生成P1[V(OCH2)++H2O]和P2[(OCH2)++H2]的气相反应,揭示了VO2+活化甲烷的微观机理,研究结果表明生成P2的反应是主反应通道,并对影响反应机理和反应速率的势能面交叉现象进行了讨论。     

非磁性/磁性掺杂剂对SnO2体系的性能调控

本文通过第一性原理计算在GGA + U 框架下系统地研究了非磁性掺杂剂(Li)和磁性掺杂剂(V)以及相应的点缺陷(VO/VSn)掺杂SnO2基稀磁半导体(DMS)的稳定性、电子结构、键合性质、磁性以及光学性质. 计算得到的形成能结果表明, V元素单掺杂体系比Li元素单掺杂体系更稳定. 其中, VO存在的掺杂体系稳定性更高, 而VSn对掺杂体系的稳定性不利. 磁性分析表明, Li掺杂体系的磁矩大于V掺杂体系的磁矩. 当有点缺陷存在时, VSn的加入显著提高了掺杂体系的磁性, 而VO对非磁性金属元素/磁性金属元素掺杂体系的磁性影响不同：当VO存在于Li掺杂体系时, Li原子周围的O原子自旋极化减少, 因此导致磁矩降低;当V掺杂体系中有VO存在, 磁性不仅来源于V原子的自旋极化, 同时来源于VO周围的O原子的自旋极化,因此磁矩增大. 结合电子结构分析可知, Li掺杂体系的磁性是由O-p和Li-p轨道之间的双交换作用产生的, V掺杂体系的磁性是由O-p和V-d轨道之间的双交换作用产生的. 键合分析发现VO的存在可以提高两种金属掺杂体系键(Li-O和V-O)的共价性. 在可见光区域内, Sn15LiO32和Sn15VO32具有较高的光学透明度. 以上这些结果为非磁性金属元素(Li)和磁性金属元素(V)及相应的点缺陷(VO/VSn)掺杂SnO2在自旋电子器件中的应用提供了新的思路.     

DC反应磁控溅射制备VO2薄膜及XPS分析

文章通过改变玻璃基温度和靶基间距,采用m(O2)/m(A r)为1∶12.5,溅射功率为190 W,工作真空度为2.2 Pa,用DC磁控溅射法在玻璃基上沉积VO2薄膜,并经真空退火处理,制备的试样通过XPS测试分析薄膜表面的元素组成及成分。测试分析结果表明,基片温度在室温或超过350℃,易于生成VO2薄膜,真空退火可以显著改善制备薄膜的氧缺陷,提高V与O的化学计量比。     

丙烷选择氧化制丙烯醛VTeO/SiO2催化剂的反应性能与结构表征

运用浸渍法制备了一系列不同组成的VTeO／SiO2催化剂，并采用XRD、TPR、Raman等技术，研究了VTeO／SiO2催化剂的结构及其对丙烷选择氧化制丙烯醛反应的催化性能．结果表明，在VO；／SiO2催化剂中添加适量Te，丙烯醛选择性和收率显著提高．VTeO／SiO2催化剂与单组分催化剂结构明显不同．由于V、Te之间的相互作用，在VTeO／SiO2催化剂表面由[TeO4]、[Te2O5]和多钒酸盐类物种形成一种高分散的无定形结构．这种结构可能由于催化活性中心的高度分散而有利于丙烷选择氧化生成丙烯醛．     

退火条件对氧化钒薄膜微观结构的影响

采用直流对向靶磁控溅射的方法在SiO2／Si衬底上制备了具有（001）择优取向的V2O5薄膜，利用X射线衍射、场发射扫描电子显微镜和四探针测试方法对退火前后薄膜的表面形貌、物相组分和电阻温度系数进行了测量．结果表明：200℃衬底温度下溅射得到的薄膜为多晶V2O5，膜表面颗粒呈细长针状，经700℃、1h退火后，薄膜中VO2相成分增多，颗粒变为长方形柱状；退火后薄膜的电阻温度系数达到-3.2％／K，与薄膜的微结构和物相组分有很大关系：3h退火后．得到高纯度的V2O5薄膜．     

Eu~(3+)与V共掺杂SiO_2材料的制备及其发光性质

利用溶胶-凝胶技术制备Eu3+、V共掺杂的SiO2材料,通过差热-热重分析、傅立叶红外光谱、X射线衍射、激发光谱与发射光谱等测试手段对粉末的晶型、结构、发光性质进行研究.结果表明:材料属于非晶态,800℃退火后Eu3+、V共掺杂的SiO2样品的结构基本稳定,只存在SiO2的网状结构; 激发光谱显示,Eu-O电荷迁移带随着V掺杂量的增加而消失,产生强度较大的320nm处的7F0→5H3跃迁; 发射光谱显示,随着V的掺入,最佳激发波长由393nm向320nm转移,同时出现了467nm,577nm,588nm,612nm处的发射峰,它们分别归属于Eu3+的5D2→7F0跃迁与VO3-4的蓝色发射的叠加跃迁、Eu3+的5D0→7F0跃迁、5D0→7F1磁偶极跃迁和5D0→7F2的电偶极跃迁,实现了同一物质同时产生蓝色荧光和红色荧光.同时发现,VO3-4对Eu3+的发光有较好的敏化作用,并通过所得的能级图对样品的跃迁机理进行了分析.     

Li~+/TiO_2/ITO工作电极的制备及其异相反应动力学特性

采用溶胶-凝胶法在ITO导电玻璃基片表面制备一层TiO2薄膜,将其作为工作电极,与作为参比电极的饱和甘汞电极、作为辅助电极的铂黑电极、作为电解质溶液的碳酸丙烯酯+高氯酸锂一起构成三电极测试体系.采用原子力显微镜和X射线衍射仪对薄膜进行了表征,测试了在电极电势分别在±0.5 V,±1.0 V和±2.0 V时的循环伏安曲线.结果表明,扫描电位在±2 V时,循环伏安曲线出现明显的Li+注入峰和抽出峰,Li+在电解质溶液和TiO2层中的扩散速度是电极过程动力学的决速步骤;而扫描电位在±1 V和±0.5 V时,循环伏安曲线没出现Li+注入峰和抽出峰,工作电极电位是电极过程动力学的决速步骤;研究工作电极的...     

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