扶手椅型石墨烯纳米带(AGNRs)电子结构的应力调控

当单轴拉伸应变沿扶手椅型石墨烯纳米带的扶手椅边沿时,利用静力学方法建立石墨烯纳米带的键角、键长与应力的解析关系;利用紧束缚方法对扶手椅边石墨烯纳米带的能带与能隙及应力的关系进行解析计算.研究结果表明:微小应变会导致纳米条带的能带宽度发生变化,并打开金属型扶手椅石墨烯纳米带能隙,费米能级附近的半导体型扶手椅石墨烯纳米带的能隙宽度也相应地发生改变;能隙随应变呈线性的周期变化,并且表现出明显的震荡现象;可达到的最大能隙随应力增大有所增大,随条带横向原子数m增大而减小.     

半导体CdS1-xSex纳米材料的制备、表征及吸收光谱研究

使用二氯化镉(CdCl2.2.5H2O)、硫粉(S)、硒粉(Se)为原料,用乙二胺作溶剂,在180℃的温和条件下,通过改变原料中硫、硒的组分,合成了固溶体半导体CdS1-xSex(0≤x≤1)纳米材料,用XRD、TEM、SAED进行分析表征,产物为六方相、直径约20nm左右、长度约500nm左右的短棒状结构.依据XRD图,对产物的晶格常数随组分x的变化关系进行了研究,其变化关系遵从Vegard定律;测量了产物的紫外吸收光谱,对其能带隙随组分x的变化关系进行了研究,说明可通过对组分x的控制来调制材料的带隙.     

Pb2+掺杂对Cd1-xZnxS光催化产氢性能的影响规律

采用共沉淀法制备了Pb2 掺杂的Cd0.2Zn0.8S及Cd0.8Zn0.2S固溶体光催化剂.实验结果表明,Pb2 掺杂的宽带隙固溶体Cd0.2Zn0.8S在6s轨道与固溶体的价带杂化后提升了价带位置,降低了半导体的带隙,因而提高了产氢活性.当Pb2 掺杂窄带隙固溶体Cd0.8Zn0.2 S后,形成固溶体价带附近的杂质能级,并成为光生电子空穴复合中心,因而不能提高产氢性能.因此,Pb2 对半导体的可见光改性仅适用于较宽带隙的半导体.     

密度对声子晶体带隙的影响

从弹性波动方程出发,利用平面波展开法计算二维（三维）声子晶体的带结构,研究散射体与基体的密度比对最低带隙的影响,得出了最低带隙宽度和带隙边界随密度比的变化规律.数值计算结果显示随着密度比的增加,带隙下边界的频率降低,而上边界的频率升高,从而增加带隙宽度,且带隙能级不变.     

Zr掺杂对Heusler合金Co_2TiGe的电子结构与磁性的影响

利用基于密度泛函理论(DFT)采用第一性原理赝势方法,结合广义梯度近似(GGA),对Co_2Ti_(1-x)Zr_xGe(x=0,0.25,0.5,0.75,1.0)系列四元Heusler合金的电子结构、磁性及半金属特性进行了研究。计算结果表明,Zr掺入Co_2TiGe以后并没有破坏其半金属性,所有成分样品的自旋磁矩都接近于整数磁矩2μB。随Zr含量的增加,晶格常数单调增大,向下能隙宽度逐渐变大,同时费米能级的位置向带隙中部发生移动,这可以在一定程度上调控费米能级附近的能带结构。     

CdS_xSe_(1-x)合金结构、电子结构和光学性质的第一性原理研究

用密度泛函理论究了闪锌矿型三元合金体系Cd SxSe1-x的晶体结构、电子结构和光学性质.计算了组分参数在0≤x≤1范围内Cd SxSe1-x的电子结构、态密度和带隙,计算结果表明Cd SxSe1-x为直接带隙半导体材料,其带隙随Se含量的增加而减小.分析了Cd SxSe1-x的复介电函数和吸收系数等光学性质随光子能量变化的关系,随Se元素含量增加,各光学特性曲线向低能方向移动.     

Cd_(1-x)Zn_xS热学性质的理论研究与设计

CuInSe2太阳能薄膜电池的窗口层材料CdS常掺Zn以降低剧毒元素Cd的使用量.本文应用晶格动力学方法,采用玻恩核-壳经典势参数模型,全面系统地研究了闪锌矿结构Cd1-xZnxS(x=0,0.25,0.5,0.75,1)在不同温度和压力下的晶体结构、力学和热学性质.计算了不同Zn掺杂浓度时的弹性模量、声子态密度、热容、热膨胀系数、格林艾森常数和德拜温度.结果表明:Cd1-xZnxS的晶格常数随掺杂浓度x的递增单调递减.随温度升高,无论是定容热容还是热膨胀系数都逐渐增大并趋于饱和;在某一温度时,二者都随Zn掺杂浓度的增加而略有增加.随掺杂浓度x从0增大到1,0K温度时,Cd1-xZnxS的格林艾森常数从0.78增加到0.94,而德拜温度最小值从约197K增大到约203K.一些实验或模拟结果与作者课题组的数据相符.期望系统的原子模拟研究结果将有助于理解该材料的成分-性能相关性,同时也有助于设计CuInSe2太阳能薄膜电池具有合适热匹配的窗口层材料.     

自洽法计算非晶硅的带隙态密度

本文叙述了一个场效应电导测量氢化非晶硅(a—Si:H)带隙态密度的数据处理方法。该法放弃了对空间电荷区电荷、电场和电势分布的任何假设,采用电子占据局域态的费米统计分布和占据扩展态的玻耳兹曼分布,应用自洽的原理,能够在较大的能量范围内计算出a-Si:H的带隙态密度分布,运算过程中以电势V为自变量,减少了对电势、电场和电荷密度等量空间分布的计算,简化了分析,提高了精度,减少了运算量。应用该法计算出了a—Si:H样品的带隙态密度在费米能级以上0.1eV到0.45 eV能量范围内的分布,它的最小值在费米能级附近,约为10~(16)cm~(-3)·eV~(-1)。     

含有碳链通道的石墨烯纳米带电子特性的第一性原理研究

采用第一性原理的密度泛函理论结合非平衡格林函数的计算方法,研究了含有多碳链通道的石墨烯纳米带的原子结构、电子能带结构与电子输运特性.结果表明,移除大量原子后含有双碳原子链的纳米带的能隙显著增大,这说明电子从占据态到未占据态的跃迁将更加困难;并且最高占据子能带与最低未占据子能带几乎与费米能级平行,说明边缘态几乎完全消失.电子输运特性的计算结果与电子能带结果是自洽的,碳链的引入导致纳米带电导隙的增大和费米能级位置电导的湮没.这说明通过电子束轰击的方式裁剪纳米带的原子结构来制备集成度更高、尺度更小的一维半导体纳米器件是可行的.     

Schottky势垒中的电中性能级、平均键能和费米能级

基于第一原理赝势能带计算。采用电中性能级和平均键能方法计算了7种不同半导体的Schottky接触势垒高度，结果表明2种方法都可用于计算金属-本征半导体的接触势垒高度。文中用于确定接触势垒高度的“本征半导体基态费米能级EF^S,i”不同于半导体物理中所指的“本征费米能级Ei”．n型半导体接触势垒、p型半导体接触势垒和本征半导体势垒，三者在接触界面附近的费米能级都是“钉扎”于本征半导体基态费米能级EF^S,i，是此三者的接触势垒高度大致相同的原因。     

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.     

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-