光功能化 YVO4：Eu3＋／M CM －41介孔材料的制备和发光性质

采用水热方法制备了光功能化的YVO4：Eu3＋／MCM－41介孔结构。采用X射线衍射仪（XRD）、透射电子显微镜（TEM）、傅里叶红外光谱仪（FTIR）和紫外—可见吸收光谱仪（Uv‐vis）等测试分析技术对样品的结构和形貌进行表征。样品的光致发光性质包括激发光谱、发射光谱及荧光动力学等性质被系统地研究,并与水热法制备的YVO4：Eu3＋纳米晶的发光性质进行了对比研究。研究结果表明,光功能化的YVO4：Eu3＋／MCM－41介孔材料保持了MCM－41高度有序的介孔孔道结构,形成的YVO4：Eu3＋晶体形成于MCM－41的孔壁中,其粒径约为0．9nm。在复合材料中,激发带变窄,Eu3＋的本征激发带消失,Eu3＋寿命变短。YVO4：Eu3＋／MCM－41的发光效率比YVO4：Eu3＋纳米晶的发光效率高。     

水热法合成YVO4:Eu3+荧光粉及其发光性能研究

以氧化钇和氧化铕为原料,采用简单的水热法合成YVO4:Eu3+荧光粉,利用XRD、SEM、FTIR和荧光光谱仪对其结构、形貌及其性能进行表征.XRD结果表明:产物为四方晶系YVO4:Eu3+.SEM显示样品为不规则棉花团状.探讨了水热反应温度、反应时间、p H、表面活性剂等因素对产物荧光性能的影响。用波长为283 nm的近紫外光激发,荧光粉的特征发射峰分别对应于Eu3+的5D1→7F1(539nm),5D0→7F1(596nm),5D0→7F2(619nm)电子跃迁.最强发射峰位于619nm处,属于Eu3+的特征红光发射.     

水热反应时间对Ca5（PO4）3（OH）：Eu荧光粉发光性能的影响

在水热反应过程中,水热反应时间是影响纳米晶颗粒尺寸和结晶性的主要因素之一。利用水热合成法,调控水热反应时间,制备了Ca5（PO4）3（OH）：Eu纳米荧光粉。通过X射线衍射、扫描电子显微镜和荧光光谱对合成样品的结构和性能进行了表征。结果表明所合成的样品都为纯的六方相Ca5（PO4）3（OH）纳米颗粒,延长反应时间有利于Ca5（PO4）3（OH）：Eu纳米晶颗粒的长大以及结晶性提高,但对纳米颗粒的形貌影响很小。当采用345nm作为激发波长时,观察到强的蓝光宽带发射峰,可能来自于基质本征发射,而位于长波区域弱的窄线红光发射,应该属于稀土Eu3＋离子的特征发射峰,同时,对荧光发射强度随着纳米颗粒尺寸变化的原因进行了初步探讨。     

YVO_4:Eu~(3+),Bi~(3+)纳米荧光粉沉淀合成及发光性质

采用沉淀法合成YVO4:Eu3+,Bi3+纳米晶.研究掺杂不同Bi3+浓度的YVO4:Eu3+纳米荧光粉在不同温度下的性质.分别采用X射线衍射仪、扫描电子显微镜及荧光光谱仪对荧光粉的结构、形貌和发光性能进行测试.结果表明:合成的荧光粉均为四方相YVO4,形貌呈规则的形状.Bi3+掺杂没有改变荧光粉的形貌.特征发射峰来自于Eu3+的5D0→7FJ跃迁,Bi3+掺杂改变了激发谱峰位,而且使得激发带有一定程度的展宽,同时Bi3+对Eu3+有敏化作用,在适量的浓度范围内纳米荧光粉的发光强度增强.     

NaGdF4：Eu^3＋的水热合成、相变与发光性质

用水热法制备了NaGdF4：Eu3＋（0.5 mol%）发光材料,并研究了退火温度对NaGdF4：Eu3＋的结构和发光性质的影响。X-射线粉末衍射（XRD）结果表明：水热合成得到六方相的NaGdF4,在空气氛的条件下,NaGdF4从六方相到立方相的相转变温度为～650℃.扫描电镜（SEM）的结果显示：具有六方相结构的NaGdF4：Eu3＋发光材料的粒径为200～300nm.荧光光谱（PL）的结果表明：具有六方相结构的NaGdF4：Eu3＋粉末样品的特征发射为Eu3＋5 D0→7F2（615nm）跃迁发射。     

白光LED用新型高效红色荧光粉的制备及其发光性能研究

用Na＋做电荷补偿剂,Sm3＋做敏化剂,采用高温固相法制备了Ca0.5MoO4：Eu3＋0.25-x,Sm3＋x,Na＋0.25（x=0,0.001,0.003,0.005,0.008,0.01,0.02,0.03,0.05,0.07,0.09）系列红色荧光粉,实验结果表明：Sm3＋的加入没有改变CaMoO4：Eu3＋,Na＋的晶体结构,也没有改变粉体发射光谱的形状和发射峰的位置,而是加宽了荧光粉CaMoO4：Eu3＋,Na＋激发光谱在400 nm左右的吸收峰,有利于样品的激发峰和近紫外LED芯片相匹配,并且提高了荧光粉在615 nm处发射光谱的发光强度.本文主要对Sm3＋提高荧光粉的发光强度的原理进行探讨,研究结果证明在CaMoO4基质中存在Sm3＋-Eu3＋之间能量传递,此外得出Sm3＋的最佳掺杂浓度是0.5 at.%.     

Sr2SiO4∶Eu2+发光材料的燃烧法制备及其光谱特性

采用燃烧法制备Sr2SiO4∶Eu2+发光材料.采用X线衍射仪、扫描电镜和荧光光度计对样品的晶体结构、微观形貌和光谱特性进行表征.研究结果表明:退火后样品的晶体结构属于正交晶系的α'-Sr2SiO4,掺杂Eu+对晶体结构没有影响.荧光光谱测试表明:Sr2SiO4∶Eu2+材料的激发和发射光谱均为宽带谱,激发和发射主峰分别为335 nm和493 nm,分别对应于Eu2+的4f7→4f65d1和4f65d1→4f7跃迁.随着点火温度的增加,激发和发射光谱强度均呈先增后降的变化.点火温度750℃时材料的激发和发射峰强度最大.随着Eu2+掺杂量的增加,Sr2SiO4∶Eu2+材料的激发和发射强度均先增大,在掺杂0.01 mol Eu2+时达到最高值,而后随着Eu2+掺杂量的增大,激发和发射峰强度减小.制备的Sr2SiO4∶Eu2发光材料有望用于白光LED领域.     

KSrGd(PO_4)_2︰Eu~(2+),Mn~(2+)红色荧光粉的合成和发光性能

采用改进的高温固相法合成了Eu2+/Mn2+掺杂的KSrGd(PO4)2荧光粉.用X射线粉晶衍射仪和荧光光谱仪对样品进行了表征.结果表明:Eu2+离子和Mn2+离子成功掺入了KSrGd(PO4)2晶格中,基质晶体结构未见明显变化.Eu2+的发射峰位于522 nm,Mn2+的发射峰位于618 nm.通过Eu2+和Mn2+之间的能量传递,KSrGd(PO4)2荧光粉在紫外光激发下发出明亮的红光.     

Ca3 La7(Si O4)5(PO4)O2:Eu2+,Eu3+荧光粉的制备及发光性能研究

采用高温固相反应法制备了系列Ca3 La7(SiO4)5(PO4)O2:Eu2+,Eu3+荧光粉,并对其光致发光性能进行了系统研究.X射线衍射测试结果表明,制备样品具有单相磷灰石结构.在332 nm紫外光激发下,荧光粉的发射光谱包含源于Eu2+的发射带,并出现Eu3+特征发射峰.随着激活剂浓度的增加,荧光粉的发光强度先...     

Sr_2SiO_4:Eu~(2+)发光材料的燃烧法制备及其光谱特性

采用燃烧法制备Sr2SiO4:Eu2+发光材料。采用X线衍射仪、扫描电镜和荧光光度计对样品的晶体结构、微观形貌和光谱特性进行表征。研究结果表明:退火后样品的晶体结构属于正交晶系的α′-Sr2SiO4,掺杂Eu2+对晶体结构没有影响。荧光光谱测试表明:Sr2SiO4:Eu2+材料的激发和发射光谱均为宽带谱,激发和发射主峰分别为335 nm和493 nm,分别对应于Eu2+的4f7→4f65d1和4f65d1→4f7跃迁。随着点火温度的增加,激发和发射光谱强度均呈先增后降的变化。点火温度750℃时材料的激发和发射峰强度最大。随着Eu2+掺杂量的增加,Sr2SiO4:Eu2+材料的激发和发射强度均先增大,在掺杂0.01 mol Eu2+时达到最高值,而后随着Eu2+掺杂量的增大,激发和发射峰强度减小。制备的Sr2SiO4:Eu2发光材料有望用于白光LED领域。     

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