首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 502 毫秒
1.
Cu元素、O元素在铜氧化物高Tc超导体中对超导电性的产生,超导转变温度的变化,掺杂元素的特征效应具有决定性作用。对Cu元素、O元素的性质特征认识,成键特点,以及在铜氧化物高Tc超导体中的同位素效应清楚的理解,对全面揭示高Tc铜氧化物超导体超导电性机理具有关键作用。通过分析Cu元素、O元素在铜氧化物超导体中的同位素效应,得出了高Tc铜氧化物超导电性的机理仍是电声机制,CuO2平面上的Cu元素,O元素的声子直接参于电声子配对,CuO2平面上的Cu、O元素的键态的声子模对电声配对具有决定性作用。  相似文献   

2.
通过F,O两元素性质参数的不同特征,分析F元素替代Bi系高温氧化物超导体中O元素作用特征.依据F元素的性质参数,对F替代O后引起Bi系氧化物超导体性能改善的机制,给出解释.  相似文献   

3.
研究了氧化物的超导电性与元素电负性之间的关系。笔者用电负性均衡值Xcq作为氧化物超导电性的新的经验判据,并用一个式子确定氧化物中元素电负性的均衡值Xcq。笔者用该式计算了230种氧化物超导体的电负性均衡值Xcq,结果表明,所有氧化物超导体的电负性均衡值Xcq集中在5.00到5.63这样窄的范围内,而电负性均衡值在此范围之外的氧化物都不具有超导性。该判据几乎适用于一切氧化物超导体。显然,笔者的工作对进一步探讨氧化物的超导机制是有益的。  相似文献   

4.
从新的角度由Cu,O元素的电子构型,及电子构型决定的元素性质参数,分析了Cu,O在高Tc氧化物超导体中的成键特点,首次揭示了Cu,O在铜氧系列氧化物高温超导体中的作用本质起因,得出了:Cu,O元素的电子构型所决定的成键特点是铜氧系列氧化物高温超导体超导电性的根本内禀因素。取得了诠释含Cu高温氧化物超导体有别于其他含氧超导体Tc差异大的本质因素。  相似文献   

5.
氧化物超导电性与硬度的密度泛函理论计算值   总被引:1,自引:0,他引:1  
通过对氧化物超导体元素硬度的平均值进行研究,发现其具有较好的规律性.本文提出用硬度均衡值ηcq作为氧化物超导电性新的经验判据.笔者依据Slater过渡态法计算元素的硬度作为标度,用均方根的方法得出氧化物中元素硬度的均衡值ηcq;计算了200余种氧化物中元素硬度的均方根值η.,结果表明,氧化物超导体的硬度均方根均衡值总是介于4.790~5.429之间;而硬度均衡值在此范围之外的氧化物不具有超导电性,这无疑为氧化物超导电性的判定提供了一种全新的判据.  相似文献   

6.
自Villars等人首先尝试用黄金坐标对高Tc(氧化物超导体的临界温度)超导电性进行分析以来,此法一直为研究人员所重视,本文亦用此法对近百种高Tc氧化物超导体进行分析,得出高Tc氧化物超导电性的又一新的经验判据:一切高Tc氧化物超导体其平均价电子数都在3.9至6.6之间,其值不在此范围内的氧化物都不具有高Tc超导电性.  相似文献   

7.
提出确定稀土氧化物中元素电负性均衡值Xcq的计算公式,并用该式计算了200多种稀土氧化物超导体的电负性均衡值Xcq,得出了稀土氧化物的超导性与稀土氧化物电负性均衡值之间的关系.结果表明,稀土氧化物超导体的电负性均衡值Xcq多数集中在1.654-2.650之间,而电负性均衡值在此范围之外的稀土氧化物一般不具有超导性.因此,电负性均衡值Xcq可作为稀土氧化物超导性的新的经验判据,这对进一步探讨稀土氧化物的超导机制有一定意义.  相似文献   

8.
提出了确定稀土氧化物中元素硬度均衡值町ηcq的计算公式,用该式计算了252种稀土氧化物超导体的硬度均衡值ηcq。研究了稀土氧化物的超导性与稀土氧化物硬度均衡值之间的关系.结果表明,稀土氧化物超导体的硬度均衡值ηcq多数集中在4.511-5.343之间,而硬度均衡值在此范围之外的稀土氧化物一般不具有超导性.显然硬度均衡值ηcq。可作为稀土氧化物超导性的新的经验判据,这对进一步探讨稀土氧化物的超导机制有一定意义.  相似文献   

9.
自Villars等人首先尝试用黄金坐标对高Tc(氧化物超导体的临界温度)超导电性进行分析以来,此法一直为研究人员所重视,本文亦用此法对近百种高Tc氧化物超导体进行分析,得出高Tc氧化物超导电性的又一新的经验判据:一切高Tc氧化物超导体其平均价电子数都在3.9至6.6这间,其值不在此范围内的氧化物都不具有高Tc超导电性。  相似文献   

10.
提出确定稀土氧化物中元素电负性均衡值X_(cq)的计算公式,并用该式计算了200多种稀土氧化物超导体的电负性均衡值X_(cq),得出了稀土氧化物的超导性与稀土氧化物电负性均衡值之间的关系.结果表明,稀土氧化物超导体的电负性均衡值X_(cq)多数集中在1.654~2.650之间,而电负性均衡值在此范围之外的稀土氧化物一般不具有超导性.因此,电负性均衡值X_(cq)可作为稀土氧化物超导性的新的经验判据,这对进一步探讨稀土氧化物的超导机制有一定意义.  相似文献   

11.
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.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
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.  相似文献   

13.
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.  相似文献   

14.
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。  相似文献   

15.
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.  相似文献   

16.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

17.
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.  相似文献   

18.
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.  相似文献   

19.
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-  相似文献   

20.
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-  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号