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我们研究了托卡马克等离子体进制电子引起的电子回旋激射不稳定性发生的条件,发现由反常多普勒效应及切伦科夫效应确定的准稳态速度分布又会激发电子回旋激射不稳定性,且其对本底电子回旋辐射的放大频段低于回旋频率,这与HL-1实验观察一致。 相似文献
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我们研究了托马克等离子体逃逸电子引起的电子回旋激射不稳定性发生的条件,发现由反常多普勒效应及切伦科夫效应确定的准稳态速度分布又会激发电子回旋激射不稳定性,且其对本底电子回旋辐射的大频段于回旋频率,这与HL-1实验观察一致。 相似文献
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用奈奎斯特图方法得出等离子体川流激发回旋不稳定性的严格判据。分析了川流等离子体温度与静止等离子体温度不等的体系,以及电子温度与离子温度不等的体系。 相似文献
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采用高阻抗探针,测量了热电子等离子体的高频扰动,扰动频率与外磁场的关系及爆发区域匠实验观察表明,高频扰动为离子漂移回旋不稳定性。 相似文献
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详细推导了具有分布损耗波导结构的回旋行波放大器的色散特性。通过绝对不稳定性振荡出现的条件,给出求解具有损耗波导结构回旋行波管放大器的绝对不稳定性起振电流的数值计算方法。研究结果表明:绝对不稳定性起振电流与损耗波导的集肤深度有关,选择有较大的集肤深度的损耗波导可以提高绝对不稳定性起振电流;绝对不稳定性起振电流同时也与工作磁场偏离饱和磁场的程度以及电子束的纵横速度比有关;通过设计具有分布损耗波导结构的注-波互作用电路,以及工作磁场、电子束的纵横速度比,可以在兼顾带宽、效率的条件下,保证回旋行波管放大器稳定工作。 相似文献
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介绍了回旋质谱探测器的原理和设计及其在HT-7 装置欧姆放电下对边缘等离子体中离子的诊断实验。探测器安装在限制器附近, 通过一小孔引进等离子体; 设置的前置偏压使电子和离子分离, 并使离子减速; 进入腔体内部的离子在射频电场和平行磁场的作用下发生回旋共振; 通过考察收集的离子电流信号中的共振峰可得到离子的荷质比、回旋频率等参数。实验中观察到荷质比为1、0. 5、0. 3333、0 . 1819 的离子共振峰。 相似文献
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详细地讨论了托卡马克等离子体对离子回旋波非全吸收,离子回旋共振加热天线为三维模型的条件下,离子回旋波与等离子体的耦合问题。与全吸收等离子体模型所计算得到的结果相比,本文得到的波的驻波场的解及耦合阻抗谐振特性的理论计算结果与中小型托卡马克实验所观察到的现象更为接近。 相似文献
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Charged species structurally related to several isomers of Cl(2)O(2), of considerable importance in atmospheric chemistry, were obtained by chemical ionization (CI) and characterized by collisionally activated dissociation (CAD) mass spectrometry. The ClOClO(+) and [Cl(2)-O(2)](+) species were prepared by positive ion Cl(2)/CI of ClO(2) and O(2), respectively, whereas the ClClO(2)(+) isomer proved an elusive species of considerably lower stability. The ClClO(2)(-) anion was obtained from the negative ion Cl(2)/CI of ClO(2). The formation process, structure and stability of the ions are discussed in connection with available theoretical results and related to the recent preparation of (Cl(2)O(2))(+)SbF(6)(-) and (Cl(2)O(2))(+)Sb(2)F(11)(-) salts in the solid phase. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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A. A. Ponyatov 《Radiophysics and Quantum Electronics》1993,36(10):707-712
A linear theory of the convergent instability (CI) of ionospheric plasma associated with the nonuniform nature of its regular motion is examined. The conditions under which CI appears in the E- and F-layers for vertical ion motion caused by various physical factors are analyzed. The possibility of small-scale strongly geomagnetic-field-aligned nonuniformities of electron concentration (lmin 10–30 m) is demonstrated. The altitude dependence of collision frequency is shown to play a large role in CI.Scientific-Research Radio-Physics Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 10, pp. 921–928, October, 1993. 相似文献
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应用密度范函理论(DTF)的B3LYP方法,在6-31G*基组水平上对CI对称C20富勒烯分子及 C20(1-)、C20(2-)离子进行了几何结构的全局优化、频率以及自然键轨道分析计算(NBO),然后对三者的几何构型、稳定性、振动光谱等做了分析和比较。研究表明:离子的键长普遍比分子的键长长, C20(1-)离子的稳定性最高。 C20(2-)离子的红外峰值较大,C20(1-)离子的拉曼光谱峰值较大,振动光谱可以用来作为区分三者的手段。 相似文献
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The CoCl2- 4 ion has been studied using ab initio methods at various levels of approximation (RHF, UHF, CI and MC SCF). The calculations have been performed both with and without the Madelung field from crystalline surroundings. One of the main purposes has been to investigate the spin density, and determine its dependence on both correlation and external fields. The spin density is found to be fairly dependent on correlation but rather independent of the surrounding crystal. The lower excited quartet states have been calculated using CI expansions based upon ground state RHF and MC SCF wavefunctions. The experimental spectrum is very well reproduced on the MC SCF/CI level, both with and without the Madelung field. 相似文献
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用吸收光谱法对锌(Ⅱ)-酸性铬蓝K(ACBK)配合物与牛血清白蛋白的相互作用进行了研究。实验结果表明,在pH10.0的NH3-NH4Cl缓冲溶液中,阳离子表面活性剂溴化十六烷基三甲基铵(CTAB)存在下,锌(Ⅱ)-酸性铬蓝K(ACBK)光谱探针能与蛋白质形成稳定的复合物,导致最大吸收波长红移,表观摩尔吸光系数为2.45×105L·mol-1·cm-1。由摩尔比法求得该光谱探针与蛋白质相互作用的结合比n(ACBK)∶n[Zn(Ⅱ)]∶n(BSA)为1∶1∶1,结合常数是1.63×106L·mol-1。不同温度下(298,308K)实验所得到的热力学参数(ΔH°=-9.43kJ/mol,ΔS°=86.90J·mol-1·K-1)表明光谱探针与蛋白质的相互作用力主要是疏水作用和静电作用。 相似文献
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NJ Oldham 《Rapid communications in mass spectrometry : RCM》1999,13(16):1694-1698
Ion/molecule reactions leading to formation of the diagnostically useful [C(3)H(4)N](+) ion (m/z 54), from acetonitrile CI plasma, have been studied using a tandem quadrupole mass spectrometer. Evidence is presented to demonstrate that [C(3)H(4)N](+) is produced from an ion/molecule reaction between [C(2)H(2)N](+) (m/z 40) and neutral acetonitrile, via a [C(4)H(5)N(2)](+) (m/z 81) intermediate. Loss of HCN, where the H atom arises from neutral acetonitrile and the CN group from [C(2)H(2)N](+) (m/z 40), leads to the production of [C(3)H(4)N](+) (m/z 54). These results are consistent with a proposed concerted elimination of HCN, generating m/z 54 as a methylene vinylidene ammonium ion. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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I. H. Suzuki E. Weigold C. E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1980,20(3):289-303
The binding energy spectra and momentum distributions for the valence orbital transitions of molecular oxygen have been obtained using the (e,2e) reaction at total electron energies of 400 and 1200 eV. The outer πg orbital is found to have a wave-function which is significantly more extended in momentum space than that of the more-tightly bound πu orbitals. This is interpreted as a consequence of the single occupancy of the anti-bonding πg orbitals. Peaks at 39 and 47 eV are assigned to 4,2Σg− ion states on the basis of the observed momentum distributions. The momentum distribution and observed intensity for the 32.5 eV transition supports the assignment of 2 Πu for this ion state. The measured relative strengths for the various Πu and Σu transitions are in qualitative agreement with CI and Green's function calculations. 相似文献
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Mauger SJ Dawson PW Hersbach AA 《The Journal of the Acoustical Society of America》2012,131(1):327-336
Noise reduction in cochlear implants has achieved significant speech perception improvements through spectral subtraction and signal-to-noise ratio based noise reduction techniques. Current methods use gain functions derived through mathematical optimization or motivated by normal listening psychoacoustic experiments. Although these gain functions have been able to improve speech perception, recent studies have indicated that they are not optimal for cochlear implant noise reduction. This study systematically investigates cochlear implant recipients' speech perception and listening preference of noise reduction with a range of gain functions. Results suggest an advantageous gain function and show that gain functions currently used for noise reduction are not optimal for cochlear implant recipients. Using the cochlear implant optimised gain function, a 27% improvement over the current advanced combination encoder (ACE) stimulation strategy in speech weighted noise and a 7% improvement over current noise reduction strategies were observed in babble noise conditions. The optimized gain function was also most preferred by cochlear implant recipients. The CI specific gain function derived from this study can be easily incorporated into existing noise reduction strategies, to further improve listening performance for CI recipients in challenging environments. 相似文献