氧化锆超细粉末二次团聚状态的控制

研究了共沉淀法制备氧化锆超细粉末过程中团聚体的形成机理及其团聚状态的控制。结果表明,氧化锆超细粉末以二次团聚体形式存在,粉末的二次团聚结构在凝胶制备过程中就已形成。其中,一次团聚体在氢氧化锆沉淀过程中形成,二次团聚体在凝胶干燥过程中形成。在凝胶制备过程中加入高分子表面活性剂可有效地控制粉末的一次团聚状态和二次团聚状态。而采用乙醇脱水工艺只能控制粉末的二次团聚状态,对一次团聚状态影响不大。文中还讨论了粉末团聚状态与粉末物理性能参数的关系。     

液相沉淀法制备纳米晶ZrO2微粉新工艺研究

本文研究液相沉淀法制备ZrO2纳米晶微粉过程中团聚状态的控制,研究结果表明沉淀过程中引入适宜的表面活性剂,可增强静电和位阻效应,获得均匀分散的胶粒悬浮液;经水洗后的湿凝胶采用非均相共沸蒸馏可有效地进行脱水,克服后处理过程中形成硬团聚体.     

溶胶-凝胶法制备超细Ce-Ti复合粉体的研究

采用溶胶-凝胶法制备了Ce-Ti复合超细粉体,主要研究了溶胶-凝胶法制备过程中溶胶-凝胶形成的条件及不同焙烧温度对超细粉体粒径的影响.结果表明,C2H5OH与H2O摩尔比在0.5~2.0时能形成稳定的凝胶;采用真空干燥能形成松散的结构,不易团聚,真空干燥温度60℃,真空干燥压力5 kPa左右,真空干燥时间大于24 h;超细Ce-Ti复合粉体的平均粒径随干凝胶焙烧温度的升高而增加,在600℃下焙烧1 h,能得到较好的效果,粒径可达5.9 nm.     

La2O3-Y2O3-ZrO2低团聚纳米复合陶瓷粉末的制备

以ZrOCl2·8H2O、Y(NO3)3·6H2O和La2O3为原料,聚乙二醇(PEG)为分散剂,无水乙醇/水(醇水体积比为5:1)和水为溶剂,在溶胶和溶液体系中采用反向共沉淀方法,制备0.6%La2O3-4.473%Y2O3-ZrO2(LaYSZ,摩尔分数)纳米复合陶瓷粉末.通过透射电镜、扫描电镜、X线衍射等表征.结合胶体稳定性的DLVO理论分析以醇水为溶剂制备的LaYSZ粉末团聚程度低、粒径细小的原因.研究结果表明;以醇水为溶剂时,随着加热反应时间增加LaYSZ粉末的比表面积增加,加热反应7 h,采用反向滴淀方式制备的LaYSZ粉末的粒径约为15 nm,粉末团聚少;以水为溶剂时,采用反向滴淀方式制备的LaYSZ粉末粒径约为100nm,粉末团聚严重.     

化学沉淀法制备 ZrO_2 超细微粉的研究

文章采用化学沉淀法制备ＺｒＯ２超细微粉，研究了各工艺参数对凝胶及粉末性能的影响，着重测试和研究沉淀过程中ｐＨ值与Ｚｅｔａ电位（ζ－电位）之间的关系以及添加不同表面活性剂对Ｚｅｔａ电位的影响。得到均匀分布的胶体溶液，凝胶采用表面活性剂处理，改变胶粒的界面结构。从而使得粉体中的团聚现象得到控制。     

表面活性剂在胶体制备中的作用

本文通过测定胶体的Zeta电位和观察胶粒结构等方法,研究了沉淀过程中加入非离子表面活性剂或阴离子表面活剂对胶体溶液所起到的静电效应和空间位阻效应.结果表明,加入PMG(20000 200)或PAA1460可使胶体分散,防止胶粒的团聚,可制得均匀分散的Zr(OH)_4等胶体溶液.     

黄淮地区不同土地利用方式下土壤团聚体特征

选取三种土地利用方式(耕地、林地和草地)0-100 cm土层土壤为研究对象,采用湿筛法和干筛法通过计算0.25 mm大团聚体的比例、平均重量直径和几何平均直径分析土壤团聚体粒级分布和稳定性.不同土地利用方式下,土壤机械稳定性团聚体以0.25-0.5 mm粒级团聚体比例最低,在0-40 cm土层以5 mm粒级团聚体比例最高;土壤水稳性团聚体以0.25 mm粒级团聚体比例最高,各土层0.25-0.5 mm粒级团聚体比例最低.三种土地利用方式下,土壤团聚体机械稳定性水稳定性总体表现为林地和草地高于耕地.综合分析表明,林地土壤团聚体稳定性较高,耕地土壤团聚体稳定性表现最差.     

粒径均匀的纳米BaTiO3粉体制备

本文分析了纳米超细粉体制备的化学沉淀法中溶液滴加法混合的缺点:胶粒生成、团聚与陈化等在时间顺序上逐渐发生而严重不同一,成为粉体颗粒分散性好、粒径均匀的障碍.本文将溶液滴加混合改为快速混合,发挥各因素同一性和优势,通过草酸共沉淀法制备成颗粒分散性好、粒径均匀、只有软团聚的纳米BaTiO3粉体,平均粒径达到28 nm.     

粒径均匀的纳米BaTiO3粉体制备

本文分析了纳米超细粉体制备的化学沉淀法中溶液滴加法混合的缺点：胶粒生成、团聚与陈化等在时间顺序上逐渐发生而严重不同一,成为粉体颗粒分散性好、粒径均匀的障碍．本文将溶液滴加混合改为快速混合。发挥各因素同一性和优势,通过草酸共沉淀法制备成颗粒分散性好、粒径均匀、只有软团聚的纳米BaTiO3粉体,平均粒径达到28nm。     

纳米磁性液体的分散稳定性分析

从纳米磁性液体中磁性颗粒的沉淀和团聚的角度分析了磁性液体稳定分散的条件,讨论了在外场下磁性颗粒的尺寸对其沉淀的影响,并引入势能的概念定量研究了决定磁性颗粒团聚体形成的3种主要作用力。利用数值计算的方法,讨论了3种相互作用势能以及净势能与磁性颗粒间表面间距和表面活性剂层厚度的关系。结果表明,增大表面活性剂层的厚度是避免磁性颗粒团聚体形成的关键措施。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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