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 62 毫秒
1.
本文导出了类氢杂质第二激发态的一维化方程,该方程适于计算层状介质中浅杂质第二激发态束缚能及状态随层厚、势垒高度和杂质中心位置的变化规律。在极限情形下方程具有与所有已知三维及二维精确解一致的解析解。  相似文献   

2.
本文利用类氢有效质量理论,讨论了nipi-si有限深非方量子阱模型下掺杂超晶格材料中的浅杂质问题。并进一步计算了受主束缚能与库仑力中心位置的关系。这些结论在定性上与前人对GaAs/Ga_xAl_(1-x)As中浅杂质态的研究是完全符合的。  相似文献   

3.
在利用MOCVD方法制备的调制掺杂GaAs/AlGaAs多量子阱超晶格材料中,由于深能级杂质形成的非辐射复杂合中心的存在,使样品具有较大的暗电流并削弱了该材料的光致发光强度,样品经过氢等离子体处理后,其光电性质明显改善。  相似文献   

4.
二维碳基材料,因导电性强、比表面积大、成本低廉等诸多优势,被广泛应用于光/电催化等新兴领域,尤其是光催化裂解水产氢技术,普遍被认为是解决当前能源短缺和环境污染问题的有效途径之一。虽然,近年来关于二维碳基材料在光催化产氢领域的研究层出不穷,但其固有的光生电子/空穴分离效率低、还原/氧化能力弱、界面传输速率慢等问题仍亟待解决。因此,如何显著增加二维碳基材料表面催化活性位点密度,提高其在光催化产氢过程中的电子传输速率和稳定性,具有重要的现实意义。以石墨炔(GDY)、氮化碳(C3N4)、共价有机框架化合物(COF)、过渡金属碳/氮化合物(MXenes)四种典型的二维碳基材料为研究对象,系统总结了掺杂/空位缺陷和异质结构建两种改性策略对二维碳基材料物理化学性质的影响关系,并深入剖析了其光催化产氢活性增强机制。最后,还对新型二维改性碳基材料的发展和挑战提出了展望,为高性能光催化产氢材料的设计、制备和应用提供理论指导。  相似文献   

5.
本文通过测量掺杂a-Si:H和a-Sic:H薄膜的电导率随退火温度和退火时间变化研究了温度对掺杂效率的影响以及杂质激活的微观过程。结果表明,(1)杂质激活过程是伸展指数形式,(2)在低温区掺杂效率正比于,(3)在高温区掺杂效率达到一饱和值。通过一个与氢运动有关的杂质激活模型,我们解释了上述实验结果。  相似文献   

6.
本文通过测量掺杂a-Si:H和a-SiC"h薄膜的电导率随退火温度和退火时间变化研究了温度对掺杂效率的影响以及杂质激活的微观过程。结果表明(1)杂质激活过程中伸展指数形式,(2)在低温区掺杂效率正比于e^-Rk/KT,(3)在高温区掺杂效率达到-饱和值。通过一个与氢运动有关的杂质激活模型,我们解释了上述实验结果。  相似文献   

7.
运用量子统计的格林函数方法和费曼图技术,在自洽T矩阵近似下研究二维d密度波的非磁性杂质散射效应,并计算出直流电导率和热导率,推导出在低温和弱掺杂的情况下Wiedemann-Franz(WF)定律成立.  相似文献   

8.
为了改善MOSFET的短沟道效应和驱动电流,首次提出了非对称Halo掺杂的异质栅SOIMOSFET结构,这种结构在沟道源端一侧注入浓度较高的杂质,再由具有不同功函数的两种材料拼接形成栅极.通过求解二维电势Poisson方程,建立了全耗尽器件表面势和阈值电压的解析模型.研究表明,该结构能有效抑制漏致势垒降低和热载流子效应,且在沟道长度小于100nm条件下,阈值电压表现出明显的反短沟道特征,在Halo和栅材料界面附近的电场峰值使通过沟道的载流子的传输速度显著提高,解析模型与二维数值模拟软件MEDICI所得结果吻合度较高.  相似文献   

9.
采用基于密度泛函理论的第一性原理赝势平面波方法对H,F,Al, K,Zn掺杂二维MgCl2单层材料的几何结构和电子性质进行研究.结果表明:几种掺杂体系的晶体结构均有不同程度变化;由于H,Al, Zn的s态电子影响,这3种元素掺杂的MgCl2在禁带中明显出现杂质能级,F和K掺杂体系的杂质能级出现在价带顶,与本征MgCl2材料的5.996 eV带隙相比,H,F,Al, K,Zn掺杂体系的禁带宽度分别减小至5.665,5.903,4.409,5.802,5.199 eV; 5种掺杂体系杂质原子周围的电荷均重新分布;电荷转移情况与差分电荷密度结果一致;与本征MgCl2的功函数8.250 eV相比,H,F,Al, K,Zn掺杂体系的功函数分别减小至7.629,7.990,3.597,7.685,7.784 eV.  相似文献   

10.
点缺陷不可避免存在于新型二维材料中,并往往对其物理性质有重要的影响. 该文运用第一性原理计算方法,研究了第五主族原子(N、P、Sb和Bi)替位掺杂对砷烯几何结构和电子性质的影响. 首先,研究发现第五主族原子替代掺杂原子在砷烯晶体中会引起明显的局部晶格形变. 其次,第五主族原子掺杂会导致二维砷烯晶体能带带隙的不同程度的减小,随后根据电子态密度和差分电荷密度的计算结果对其进行了分析和解释. 最后,给出了第五主族原子掺杂砷烯的STM图像,为实验科研者识别和分析砷烯缺陷提供有益的参考. 研究结果将对二维砷烯纳米材料在光电器件等领域的应用提供有价值的参考和依据.  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.
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.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
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.  相似文献   

14.
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   

15.
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   

16.
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.  相似文献   

17.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

18.
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   

19.
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   

20.
Quality traits in wheat (Triticum aestirum L.) were studied by quantitative trait locus (QTL) analysis in a recombinant inbred line (RIL) population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross (ChSh). Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.  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