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排序方式: 共有240条查询结果,搜索用时 31 毫秒
231.
<正> 概率论是中专学校唯一的一门研究随机现象统计规律的数学课程。由于随机现象的不确定性,使得学生在学习概率论的过程中,往往感到对某些概念、公式理解不透,从而解题时就不那么得心应手。本文是自己在概率论教学中的一点体会。 相似文献
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In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape in calorimeter. Using 100 GeV proton beam incident on the center of the ECAL, detailed plots of lateral and longitudinal hadronic shower behavior were given and we found the formulae can describe the development of the hadronic shower with the test beam data. The possible application of the parametrized formulae including e±-π± discrimination and tau jet reconstruction was discussed. 相似文献
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We propose a three-party scheme for quantum information splitting(QIS) of an arbitrary single-photon polarization state based on weak cross-Kerr nonlinearity combined with linear optics elements such as polarization beam splitters(PBSs) and half wave plates(HWPs). The scheme is generalized to the arbitrary-party case. With the help of quantum nondemolition(QND) measurements, our schemes can be accomplished in an almost deterministic way. The two schemes are feasible with the current technology. 相似文献
235.
The electric field enhancement properties of an active gold nanoshell with gain material inside have been investigated by using Mie theory. As the gain coefficient of the inner core increases to a critical value, a super-resonance appears in the active gold nanoshell, and enormous enhancements of the electric fields can be found near the surface of the particle. With increasing shell thickness, the critical value of the gain coefficient for the super-resonance of the active gold nanoshell first decreases and then increases, and the corresponding surface enhanced Raman scattering (SERS) enhancement factor (G factor) also first increases and then decreases. The optimized active gold nanoshell can be obtained with an extremely high SERS G factor of the order of 1019-1020. Such an optimized active gold nanoshell possesses a high-efficiency SERS effect and may be useful for single-molecule detection. 相似文献
236.
为了满足超远程和高速空间激光通信的需求,设计了一种以1.06 m光纤激光4支路相控阵作为发射源的通信系统结构。采用53 Mb/s、120 Mb/s、155 Mb/s速率调制的伪随机序列,实验了相控阵种子源和一条支路处调制的2种方案。结果表明:相同速率下,种子源调制的接收眼图质量较好,通过相位控制,可以进一步提高接收质量。实验中,研究了2条支路光分别调制的相控阵多载波特性,调制信号采用5/5.08 MHz及20/40 MHz两组正弦波,经光束合成和相位控制,在接收端观测到相应的频域信号。实验初步验证了光纤激光相控阵空间通信系统的可行性。 相似文献
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一种研究生物大分子与其小分子配基相互作用的毛细管电泳新方法 总被引:3,自引:0,他引:3
建立了一种定量研究大分子与小分子间相互作用的毛细管电泳新方法,即在线微透 析三电极系统亲和毛细管电泳法。本法可测定小分子的自由浓度而不受蛋白质大分子的干 扰。详细介绍了实验装置的制作,探讨了进样机制。作为实例,研究了生理条件下pH7.4, 50mmol/L磷酸介质中,牛血清白蛋白与磺胺甲基异噁唑、L-色氨酸、D-色氨酸的亲和常数的 测定,其值分别为5.8×10~ 4L/mol, 2.3 ×10~4L/mol, 1.77×10~3L/mol。本法较简便,能在生理环 境下测定,样品用量亦少。 相似文献
240.
CONTRIBUTION FROM MOLDCULAR FIELD TO THE TEMPERATURE DEPENDENCE OF TUNNELING MAGNETORESISTANCE 下载免费PDF全文
Based on the nearly free-electron approximation, we have investigaed the temperature (T) dependence of spin-polarized tunneling in the magnetic tunnel junction with an asymmetrical barrier, with emphasis on the variation of molecular field with T in the same way as that of surface magnetization. It is found that the Slonczewski model can describe well the T depen-dence of spin-polarized tunneling, while the Julliere model only describes the T dependence of JMR qualitatively, but does accurately that of the difference of tunneling conductance between the parallel and antiparallal alignments for the magnetizations of FMs; Differing from the pre-vious finding, we find the electron spin polarization is not strictly proportional to the surface magnetization, for the former decreases with the increasing T more rapidly than the latter does. 相似文献