共查询到19条相似文献,搜索用时 46 毫秒
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WANG Yan LIU Zhi-min YAN Jing-yang LIANG Li-zhen WEI Jiang-long HU Chun-dong 《光谱学与光谱分析》2018,38(6):1987-1992
中性束注入是等离子体加热和电流驱动的最有效方法之一。中性束注入的三个基本过程为:离子束的产生,离子束的中性化和中性束的传输,其中,离子束的中性化是关键环节之一。对于EAST-NBI气体中性化室而言,中性化室内气体靶厚度会直接影响离子束的中性化效率,而且还会进一步影响到中性束的传输效率。基于多普勒频移效应,提出了一种新的诊断气体靶厚度的方法,并且已经被应用于EASTNBI测试平台上。该方法主要是基于中性束的束成分随气体靶厚度的演化过程,利用中性束发射Dα光谱线强度完成计算。因此,它被应用于中国科学院等离子体物理研究所EASTNBI装置上。在中性化室出口处的观测窗口上进行测量,在束能量为40~65 keV时,气体靶厚度值为(0.16~0.22)×1016 cm-2,随着引出束流的变化,气体靶厚度随之改变。根据质量守恒定律,对中性化室内的气体靶厚度进行一个粗略的估算,估算的结果与测量的结果基本保持一致,从而证明了该诊断方法的合理性。综上,实验结果表明,该种基于多普勒频移效应的光谱诊断法可以被用于测量中性化室内的气体靶厚度。 相似文献
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考虑了时空变换与速度合成的相对论效应;一个普遍的纵向多普勒频移公式被导出;它对声波和光波均适用;讨论了几种典型情况;结果表明介质中光波多普勒频移;不仅同光源与接收器两者的相对速度有关;也与光源、光波自相对介质速度有关。 相似文献
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在中性原子光晶格钟的系统不确定度评估中,通常黑体辐射引起的频移是最大的一项.黑体辐射频移主要受周围环境温度的影响.针对国家授时中心的锶原子光晶格钟实验系统,通过理论分析、腔体表面温度的测量和软件模拟相结合的方法,评估了锶原子光晶格钟黑体辐射频移的修正量和不确定度.其中主要分析了锶原子炉、蓝宝石加热窗口、透过窗口片进入到真空腔体内的室温以及Zeeman减速装置对原子团处的热辐射引起的黑体辐射频移.在真空腔体外表面设置了5个测温点,利用校准过的铂电阻温度传感器监测真空腔体外表面的温度变化,用SolidWorks绘图软件建立腔体模型,通过有限元分析软件模拟出在真空腔体温度变化0.72 K时,原子团所处位置温度的波动为0.34 K.最终得到黑体辐射频移总的修正量为-2.13(1) Hz,不确定度为2.4×10~(-17). 相似文献
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用移相法测非磁性涂层的厚度贾亚民,姜芸(西安交通大学710049)随着装演技术的不断提高与发展,涂层厚度测量技术在工业生产中的应用愈来愈广,特别是铁磁性材料(如钢、铁等)表面油漆、塑料、搪瓷等喷涂厚度的测量与控制技术应用日益广泛,所以国内在这一领域的... 相似文献
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首次报道孤子光纤中拉曼自频移效庆的研究结果。对满足孤子光纤色散关系条件时含损耗,拉曼延迟效应的广义非线性薛定谔方程进行了微扰分析。求得了拉曼自频移关系表达式。发现改变光纤几何参数可以有效地控制孤子拉曼自频移。 相似文献
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JIAN Guangde MOU Zongze LONG Yongxing ZHOU Caipin WANG Aike HOU Binglin ZOU Hui 《核工业西南物理研究院年报(英文版)》2006,(1):188-189
The three-dimensional finite element method model with 20 degree sector of the ITER overall gravity support system was built by the ANSYS software. The modal analysis of the gravity support system was made and first ten natural frequencies and vibration modes of the gravity support system were calculated by using Block Lanczos method. The results of modal analysis on ITER represent that the stiffness of flexible plates has influenced greatly for the natural frequency of the system. 相似文献
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为了评估柱壳和锥壳结构自由振动特征数值计算的精度,分析不同边界条件、环肋、纵肋以及流体载荷对自由振动特征的影响,计算并校验了典型壳体结构在空气中、浸没以及浸没并充满水情况下的自由振动特征。结果表明,空气中干模态分析在2 kHz内、单面及双面接触水情况下的流固耦合湿模态分析在500 Hz内的计算精度能够控制在10%以内。壳体流固耦合自由振动分析时可以采用实体单元离散也可以采用壳单元离散的方法,前者精度略高,能够有效保证求解收敛的频带范围更宽,但工作量更大。径长比大于0.2时,浸没于水中的自由振动分析可以转换为内部填充水时的自由振动分析,转换时应保证两者流固耦合湿表面积相等,如半浸水和半充满水,能够有效减小计算量;环肋和流体载荷对壳体自由振动特征的影响明显,环肋使柱壳同阶自振频率增加,流体载荷使柱壳同阶自振频率减小且影响幅度更大,两者均会使得柱壳模态振型呈现错序排列;流固耦合效应对无肋柱壳和环肋柱壳自振频率的影响效果相当;柱壳内外有水相对于单面接触水而言,同阶自振频率进一步减小,模态振型基本不变;流体载荷对环肋锥壳的自振频率和模态振型的影响幅度较对环肋柱壳小。 相似文献
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This paper describes theoretical and experimental methods for characterising the performance of a 25 kHz sonochemical reactor (RV-25), which is being developed as a reference facility for studying acoustic cavitation at the National Physical Laboratory (NPL). Field measurements, acquired in different locations inside the sonoreactor, are compared with finite element models at different temperatures, showing that relatively small temperature variations can result in significant changes in the acoustic pressure distribution (and consequent cavitation activity). To improve stability, a deeper insight into the way energy is transferred from the power supply to the acoustic field is presented, leading to criteria - based on modal analysis - to dimension and verify an effective temperature control loop. The simultaneous use of measurements and modelling in this work produced guidelines for the design of multi-frequency cylindrical sonoreactors, also described. 相似文献
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偶极声波换能器振动特性计算 总被引:3,自引:1,他引:2
利用ANSYS有限元软件计算了声波测井中使用的偶极子换能器在不同机械边界条件下的振动模态和频率响应。计算结果显示,偶极子换能器在一定的频率范围内有多个振动模态,不同的机械边界条件不仅影响振动模态的个数而且还影响同一振动模态的谐振频率;从频率响应曲线上还可以看出此结构的偶极子换能器在做弯曲振动时的频带较窄,这对在不同地层井眼中进行的偶极子声波测井非常不利。通过多个不同主频的偶极子换能器组合工作可以从根本上拓宽偶极声波换能器的频带宽度。 相似文献
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The increasing presence of low frequency sources and the lack of acoustic standard measurement procedures make the extension of reverberation time measurements to frequencies below 100 Hz necessary. In typical ordinary rooms with volumes between 30 m3 and 200 m3 the sound field is non-diffuse at such low frequencies, entailing inhomogeneities in space and frequency domains. Presence of standing waves is also the main cause of bad quality of listening in terms of clarity and rumble effects. Since standard measurements according to ISO 3382 fail to achieve accurate and precise values in third octave bands due to non-linear decays caused by room modes, a new approach based on reverberation time measurements of single resonant frequencies (the modal reverberation time) has been introduced. From background theory, due to the intrinsic relation between modal decays and half bandwidth of resonant frequencies, two measurement methods have been proposed together with proper measurement procedures: a direct method based on interrupted source signal method, and an indirect method based on half bandwidth measurements. With microphones placed at corners of rectangular rooms in order to detect all modes and maximize SNRs, different source signals were tested. Anti-resonant sine waves and sweep signal turned out to be the most suitable for direct and indirect measurement methods respectively. From spatial measurements in an empty rectangular test room, comparison between direct and indirect methods showed good and significant agreements. This is the first experimental validation of the relation between resonant half bandwidth and modal reverberation time. Furthermore, comparisons between means and standard deviations of modal reverberation times and standard reverberation times in third octave bands confirm the inadequacy of standard procedure to get accurate and precise values at low frequencies with respect to the modal approach. Modal reverberation time measurements applied to furnished ordinary rooms confirm previous results in the limit of modal sound field: for highly damped modes due to furniture or acoustic treatment, the indirect method is not applicable due to strong suppression of modes and the consequent deviation of the acoustic field from a non-diffuse condition to a damped modal condition, while standard reverberation times align with direct method values. In the future, further investigations will be necessary in different rooms to improve uncertainty evaluation. 相似文献
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Fluctuations of optical phase of diffracted light for Raman–Nath diffraction in acousto–optic effect
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The Raman–Nath diffraction in acousto–optic effect was studied theoretically and experimentally in the paper.Up to now,each order of diffracted light in Raman–Nath diffraction was still considered simply to be just frequency-shifted and to be a plane wave.However,we find that the phase and frequency shifts occur simultaneously and individually in Raman–Nath diffraction.The findings demonstrate that,in addition to the frequency shift,the optical phase of each order of diffracted light is also shifted by the sound wave and fluctuates with the sound wave and is related to the location in the acoustic field from which the diffracted light originates.As a result,the wavefront of each order of diffracted light is modulated to fluctuate spatially and temporally with the sound wave.Obviously,these findings are significant for applications of Raman–Nath diffraction in acousto–optic effect because the optical phase plays an important role in optical coherence technology. 相似文献
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An analysis of the linear and nonlinear vibration responses of composites with delaminations is presented. The effect of delamination size on the linear and nonlinear vibration response is studied. The composite material used in this paper is a glass fibre reinforced plastic (GFRP) having delaminations at the plies interfaces. The experimental procedure consists in inducing the specimen on its resonance flexural modes with different excitation levels (amplitudes) for six bending modes and for each delamination length. The presence of the nonlinearity introduced by the delamination was clearly identified by the variation of natural frequencies for increasing excitation levels. Then, nonlinear elastic parameters for progressive delamination length were determined and discussed for the first six bending modes. The linear and the nonlinear elastic parameters were compared in their sensitive modes. 相似文献