排序方式: 共有48条查询结果,搜索用时 15 毫秒
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"任务驱动"的教学方法旨在实现以"学生为中心",调动学生的学习积极性,从而培养学生独立解决问题的能力,非常适用于计算机课程的教学。 相似文献
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We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su-Schrieffer-Heeger (SSH) model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value. This means that the Schottky barrier is pinned for a small work-function electrode. For polymer/electrode structures, we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontaneous electron transfer from electrodes to polymers. 相似文献
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为了能很好地鉴别碎片质量,建立一个好的飞行时间测量方法是十分必要的。阐述了建立用于裂变碎片质量测量的微通道板(MCP)和金硅面垒探测器(SBD)飞行时间探测系统。对于80 μg/cm2厚的碳膜,241Am的α粒子的探测效率约为39%,252Cf(sf)裂变碎片的探测效率约为98%。在动能为78 MeV条件下,对252Cf(sf)重裂变碎片(138~148 u)得到的时间分辨为(224:1±6:1)ps;在动能为102 MeV条件下,对252Cf(sf)轻裂变碎片(101~111 u),得到的时间分辨为(154:5±5:8)ps。In order to separate the mass number of fragments in the fission reactions, it is essential to develop a good time-of-flight (TOF) method. The purpose of this article is to set up a TOF detector system including a microchannel plate (MCP) and a Au-Si surface-barrier detector (SBD). The TOF system shows a detection efficiency of 39% for α-particles released from 241Am and 98% for fragments in the spontaneous fission of 252Cf. The experimental results show that the time resolutions of (224:1±6:1) ps for the heavy fragments (Ek=78 MeV, AH=138~148 u) and (154:5±5:8) ps for the light fragments (Ek=102 MeV, AL=101~111 u) can be obtained. 相似文献
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用一个包含了半导体探测器, 液体闪烁计数器和60%效率的HPGe探测器的四参数关联实验测量了252Cf(sf)反应的中子多重性和γ多重性与裂变碎片特征参数(质量, 总动能TKE)间的关联. 由于在测量裂变中子多重性绝对值的同时, 本工作首次从实验数据确定了特定碎片的γ多重性的绝对值, 故测量数据为进一步深入研究碎片角动激发提供了新的信息. 结果表明, 角动激发并不与裂变核在断点的形变成正关联, 但两者间却存在着复杂的关联特性. 实验数据不能从现有核理论的弯曲(bending)和扭动(wriggling)碎片角动量激发模式得到理解; 但可用碎片角动激发与裂变核的断点核激发能存在正关联而得到部分解释. 相似文献
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Cu2O-ZnO异质结具有成本低廉、环境友好及制备方法多样等优点,在太阳能电池领域有很好的应用前景。Cu2O薄膜的高电阻率和低载流子浓度是制约其效率提高的主要原因。本文采用磁控溅射法,在qV(Ar)∶qV(O2)=90∶0.3时得到单相p型Cu2O薄膜,电阻率为88.5Ω·cm,霍尔迁移率为16.9 cm2·V-1·s-1,载流子浓度为4.19×1015cm-3。并结合Cu2O-ZnO异质结能带结构的研究,对Cu2O-ZnO异质结太阳能电池今后的研究提出了一些建议。 相似文献
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利用直流反应磁控溅射技术分别在玻璃、n-〈111〉Si、氧化硅(SiO2/Si)、石英衬底上制得Ga-N共掺杂ZnMgO薄膜。利用X射线衍射(XRD)、Hall实验、场发射扫描电镜(FE-SEM)和X射线光电子能谱(XPS)对不同衬底上生长的ZnMgO薄膜的性能进行表征。结果表明,Ga-N共掺杂p型ZnMgO薄膜具有高度c轴择优取向的结构特征。生长在玻璃、(111)Si和氧化硅衬底上的ZnMgO薄膜显示p型导电性,而生长在石英衬底上的ZnMgO薄膜显示n型导电性。生长在氧化硅片衬底上的共掺杂ZnMgO薄膜的晶体质量和电学性能最优,载流子浓度为2.28×1017cm-3,电阻率为27.7Ω·cm。而且其表面形貌明显不同于生长在其他衬底上的薄膜。Ga2p和N1s的XPS谱表明Ga-N共掺杂ZnMgO薄膜中存在Ga—N键,有利于N的掺入,从而易于实现p型生长。 相似文献
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