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光磁共振实验中扫场和水平场关系的探究 总被引:1,自引:0,他引:1
光泵磁共振实验中,在磁共振信号观察时,常常会有光抽运信号同时出现的现象,这严重影响了实验的有效观察和准确测量。本文阐述了取合适的扫场和水平场的大小的关系,从而避免实验过程中磁共振信号和光抽运信号的同时出现,以确保实验的精准。 相似文献
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用于铁磁共振的扫场电源 总被引:1,自引:0,他引:1
叙述了一种新型的适于用记录仪记录输出信号的铁共振扫场电源,其结构简单,调试容易,复用性好,在电压0-150V,最大电流0.5A,周期5. 5 s,负载阻抗33Ω时,线性优于95%。同时还可用作其它实验中要求的长周期、大功率扫描电源。 相似文献
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SUO Yu-ting LUO Hua-ping LIU Jin-xiu LI Wei CHEN Chong XU Jia-yi WANG Chang-xu 《光谱学与光谱分析》2021,41(6):1737-1744
不同光照下,如何消除或减小反演数据差异,提高检测精度,是目前南疆冬枣户外检测中遇到的一大难题,因此通过用高光谱相机获得的南疆冬枣二向反射分布函数(BRDF)测量值,采用最小二乘法拟合Roujean模型和Ross-Li模型的参数,最后对比Roujean模型和Ross-Li模型反演的结果,提出何种天气何段波长用何种模型反演效果最好的建议,实验结果表明:(1)多云天气,反演南疆冬枣线偏振度(Dolp)时,Ross-Li模型的R2是0.974 8,Roujean模型的R2是0.969 9;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.972 3,Roujean模型的R2是0.974 9。阴天反演南疆冬枣Dolp时,Ross-Li模型的R2是0.965 1,Roujean模型的R2是0.977 8;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.942 0,Roujean模型的R2是0.968 8。晴天反演南疆冬枣Dolp时,Ross-Li模型的R2是0.965 5,Roujean模型的R2是0.926 2;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.928 5,Roujean模型的R2是0.833 1。整体反演的最佳方案是多云天气下的南疆冬枣Dolp用Ross-Li模型反演,强度分量用Roujean模型反演;晴天南疆冬枣Dolp和强度分量均用Ross-Li模型反演;阴天南疆冬枣Dolp和强度分量均用Roujean模型反演。(2)多波段反演的最佳方案是:多云天气下,反演南疆冬枣强度分量时,波长为1 000~1 100 nm范围,需用Ross-Li模型,波长为1 450~1 600 nm范围,需用Roujean模型,其余波段处两种模型均可;反演南疆冬枣Dolp时,在波长为1 300 nm附近,需用Ross-Li模型,其余波段处两种模型均可。阴天反演南疆冬枣强度分量时,在1 000~1 350 nm范围,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型,其余波段处两种模型均可;反演南疆冬枣Dolp时,在1 000~1 350 nm范围,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型。晴天反演南疆冬枣强度分量时,波长为1 000~1 350和1 600 nm附近,需用Ross-Li模型,其余波段处则无特殊要求;反演南疆冬枣Dolp时,在1 000 nm附近,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型。探索出消除或减小反演数据差异的方法,为南疆冬枣户外检测提高精度奠定基础。 相似文献
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A classical result in Lorentzian geometry states that a strongly causal spacetime is globally hyperbolic if and only if the Lorentzian distance is finite valued for every metric choice in the conformal class. It is proved here that a non-total imprisoning spacetime is globally hyperbolic if and only if for every metric choice in the conformal class the Lorentzian distance is continuous. Moreover, it is proved that a non-total imprisoning spacetime is causally simple if and only if for every metric choice in the conformal class the Lorentzian distance is continuous wherever it vanishes. Finally, a strongly causal spacetime is causally continuous if and only if there is at least one metric in the conformal class such that the Lorentzian distance is continuous wherever it vanishes. 相似文献
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The differences of the pitch and duration of Chinese syllables between Putonghua (PTH) and Taiwan Mandarin (TM) were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that: For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM. 相似文献
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介绍了一种新型的、针对污染源中特定污染气体在紫外波段的成像方法,该方法基于朗伯比尔吸收定律,结合紫外带通滤光片分光,能以较高的时间分辨率和空间分辨率直观再现污染气体浓度在空间的二维分布。以SO2气体作为研究对象,在实验室内搭建了测量系统;阐述了该成像技术的测量方法,分析了该方法的线性响应,实验结果表明该方法的线性响应良好,响应系数R2高达0.985;探讨了该成像方法在不同成像区域内的灵敏度变化,其差异在1%~3%;讨论了成像方法获取柱浓度的准确性,实验室分析结果显示误差约为1%, 准确性较高;最后分析了该成像方法的检测限并且根据线性最小二乘拟合方法解析出目标气体SO2在样品池横截面上的二维空间分布。 相似文献
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Mahendra K. Verma 《Pramana》2005,64(3):333-341
It is well-known that incompressible turbulence is non-local in real space because sound speed is infinite in incompressible
fluids. The equation in Fourier space indicates that it is non-local in Fourier space as well. However, the shell-to-shell
energy transfer is local. Contrast this with Burgers equation which is local in real space. Note that the sound speed in Burgers
equation is zero. In our presentation we will contrast these two equations using non-local field theory. Energy spectrum and
renormalized parameters will be discussed. 相似文献
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Solid-state dye doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper, the laser characteristics of Coumarin 503 (C503) doped polymethyl methacrylate (PMMA) rods modified with ethyl alcohol (EtOH) are studied under nitrogen laser excitation in a transverse pumping configuration and the variation of gain of the dye in solid medium for different pumping powers is studied. The gain of Coumarin 503 in solid medium is compared with the gain of Coumarin 503 in liquid medium and it is found that the gain of the dyes in the solid environment is less than that in the liquid environment. The photobleaching of dye in polymer medium under nitrogen laser excitation is also studied by keeping the rod in a fixed position and by rotating the rod about its cylindrical axis. It is found that the photobleaching rate is faster when the rod is in a fixed position. 相似文献
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R. Sekar G. Vaidyanathan R. Hemalatha S. Sendhilnathan 《Journal of magnetism and magnetic materials》2006
Thermoconvective instability in a multicomponent fluid has very wide applications in industrial, ionospheric and geothermal systems. More often, it is found that the thermal diffusivity and mass diffusivity interact with each other in fluid systems. But in a liquid system, the effect of heat transport on mass transport is pronounced. In a ferrofluid system which is a synthesized liquid, it is often found that more than one component co-exists in the fluid system contributing to interactive diffusion. In the present analysis, it is intended to study the Soret effect on multicomponent ferrofluid saturating a porous medium with large variation in permeabilities. Linear stability analysis is used. Normal mode technique is applied. The numerical results are presented for both stationary and oscillatory instabilities. It is found that stationary instability is preferred irrespective of values of permeability of pores. 相似文献
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