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Non-Abelian gauge structure in nuclear quadrupole resonance 总被引:1,自引:0,他引:1
A Zee 《Canadian Metallurgical Quarterly》1988,38(1):1-6
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氧化锌富集物的进口能弥补我国锌矿资源的不足,但要求其游离态ZnO不小于50%。目前常采用YS/T 1171.10—2017(Na2EDTA滴定法)测定氧化锌富集物中ZnO含量,该方法测定过程冗长繁琐,测定1个样品需要2 d时间,已不能满足大批量氧化锌富集物进口快速通关的需要。故实验建立了采用X射线衍射(XRD)标准曲线法测定氧化锌富集物中游离态ZnO的方法。采用YS/T 1171.10—2017对进口氧化锌富集物样品进行定值,然后选取15个ZnO含量具有梯度的样品作为校准样品,选用ZnO最强衍射线(101)作为测量谱线,建立起积分强度对ZnO含量的标准曲线,曲线呈现较好的线性。采用标准曲线法、全谱图拟合法、化学方法分别测定了3个进口氧化锌富集物中ZnO含量,标准曲线法测定值与化学方法测定值一致,全谱图拟合法测定值与化学方法测定值偏差较大。实验方法测定1个样品仅需26 min,能够满足大批量氧化锌富集物进口快速通关的检测需求。 相似文献
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J Seliger 《Canadian Metallurgical Quarterly》1997,8(4):207-217
A new NQR method of measuring the spectral density of slow motions in solids is proposed. It is shown that also in NQR a 90 degrees phase shift of a resonant rf magnetic field following a 90 degrees pulse locks the nuclear magnetization in a 'rotating frame' similarly as in NMR. The spin-lattice relaxation time T1 rho of the locked magnetization is calculated in general for an arbitrary spin. It is assumed that the fluctuations of the EFG tensor dominate the spin-lattice relaxation. The calculations show that T1 rho depends on the spectral density J(omega) of the electric quadrupole fluctuations at the NQR frequencies, and also at a low frequency omega. Here omega approximately gamma B1 kHz depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor. The term containing J(omega) in the expression for T1 rho-1 depends on the orientation of the rf magnetic field in the principal-axis system of the EFG tensor, only through the orientation dependence of omega. This term vanishes when the electric quadrupole fluctuations do not modulate the frequency of the NQR transition excited by the rf magnetic field. Two particular examples: I = 1 and I = 3/2 are worked out in details. 相似文献
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用燃烧合成法制备纳米氧化锌 总被引:4,自引:0,他引:4
以尿素或三(羟甲基)氨基甲烷(THAM)为燃料,以硝酸锌为锌源和氧化剂,采用燃烧合成的方法制备了纳米氧化锌。由于反应物吸水,直接将它们混合就可以得到均匀的浆状先驱物;这种先驱物可以在电炉上加热点燃,得到蓬松的泡沫状纳米氧化锌。探讨了燃料和氧化剂配比对反应的影响,发现燃料过剩是自蔓延高温合成的必备条件。采用X-射线衍射、透射电镜以及比表面分析等方法对所制得的粉末进行表征。结果表明:燃烧法可以制备纳米氧化锌,具有简单,快速,便宜的优点。 相似文献