共查询到20条相似文献,搜索用时 78 毫秒
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The measurement and analysis of broad nuclear magnetic resonance (NMR) spectra of quasicrystals require experimental methods and theoretical interpretations different from NMR investigations of regular periodic crystals. Frequency- and field-sweep methods for recording quasicrystalline NMR spectra are described and compared with the measurement of27Al NMR spectra of icosahedral AlPdMn and decagonal AlNiCo quasicrystals. The nuclear spin interactions that determine the NMR line shape are the same for both types of the above Al-based quasicrystals, where the electric quadrupolar interaction with the broad distribution of its electric field gradient parameters predominantly determines the shape of the broad satellite “background” intensity. The essential observations are an almost isotropic27Al NMR spectrum of the icosahedral quasicrystals and a strong angular dependence of the spectrum of decagonal quasicrystals. 相似文献
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测定并分析了化合物(Et4_N)_2[Ni_2(SC_6H_4O)_2(μ-SC_6H_4OH)_2]和(Ph_4P)_2[Ni_3(SCH(CH_3)CH_2S)_4]·2CH_3CN的_1H NMR数据,计算了模拟谱,确认它们在DMSO溶液中仍保持原有固体状态的分子结构,它们的抗磁性质得到~(13)C NMR的证实。 相似文献
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基于作者先前提出的过抽样实值离散Gabor变换,本文提出了一有效的算法用于核磁共振自由感应衰减(NMR FID)信号的减噪. 由于NMR FID信号在时域中是一短暂的振荡衰减信号,使得变换后的NMR FID信号能量在时频域中集中在少数变换系数上,而噪声则遍布在整个变换系数上,因此通过对变换系数幅度进行阈值限制方法可达到明显地增强NMR FID信号的目的. 文中在理论和模拟实验上分析表明,过抽样Gabor变换比临界抽样Gabor变换更适宜于NMR FID信号的减噪,因为在过抽样条件下比在临界抽样条件下的综合窗及其对应的分析窗,无论是在时域中还是在频域中都可具有更好的局域分布集中性,同时,Gabor变换在过抽样条件下也比在临界抽样条件下具有更高的时频精度. 相似文献
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固体核磁共振技术是研究固态高分子材料中结构和分子动力学的一种非常重要和有效的手段. 该技术的一个重要特点是可以通过合理的实验方法,实现对研究体系中从低频(Hz)到中频(kHz)乃至高频(MHz)范围内分子运动的观测. 因此,固体核磁共振技术非常适合研究高分子体系中各类不同尺度分子运动. 该文首先简要介绍核磁共振研究分子运动的基本原理和方法,以及固态高分子体系的结构和分子动力学特点,然后结合固态高分子体系中的一些例子对核磁共振在固态高分子多尺度分子运动方面的一些研究成果展开讨论. 相似文献
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Weekley AJ Bruins P Sisto M Augustine MP 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,161(1):91-98
A nuclear magnetic resonance (NMR) probe and spectrometer capable of investigating full intact wine bottles is described and used to study a series of Cabernet Sauvignons with high resolution 1H NMR spectroscopy. Selected examples of full bottle 13C NMR spectra are also provided. The application of this full bottle NMR method to the measurement of acetic acid content, the detection of complex sugars, phenols, and trace elements in wine is discussed. 相似文献
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Study of NMR porosity for terrestrial formation in China 总被引:3,自引:0,他引:3
NMR logging is an effective method for porosity measurement. NMR-derived porosity only comes from the pore fluid and is, in
principle, not affected by rock matrix. However, it is found that the difference between NMR-derived and conventional log-derived
porosities is often between 2 to 6 pu, which is unacceptable, in terrestrial formation in China. In the paper, the theory
of NMR porosity was reviewed. The influence factors on NMR porosity error were analyzed based on NMR core measurements. More
than 30 core samples with a wide range of porosities including sandstone, limestone and artificial ceramic were chosen for
the conventional and NMR porosity measurements. The current NMR data acquisition method was studied based on laboratory NMR
core measurements and found to be not good for terrestrial formation. A new NMR data acquisition method suiting for terrestrial
formation in China was proposed and much improved the accuracy of NMR porosity measurement. It is suggested that the analysis
of core samples from different regions should be carried out before logging in order to obtain accurate NMR porosity. 相似文献
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N. J. Stone 《Hyperfine Interactions》1976,2(1):45-71
Recent developments in nuclear orientation (NO) and radiative detection of NMR (NMR/ON) are reviewed. Details of the hyperfine interaction hamiltonian in cubic ferromagnets and the principles of measurement by these techniques of both magnetic dipole and electric quadrupole terms are outlined. In the experimental survey a full account is given of measurements of the electric quadrupole interaction by frequency modulated and fast passage NMR/ON, with briefer coverage of applications of both techniques to implanted systems, of linewidths, concentration dependent line structure, and Knight shifts in NMR/ON and of NO measurements of electric quadrupole interactions in non-cubic non-magnetic metals. The review incorporates a tabulation of NMR/ON measurements to date. 相似文献
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用脉冲梯度切核磁共振测量固态样品中的扩散遇到很多困难,对于一个不用内锁的电磁体系统,观测到脉冲场梯度过后涡流造成样品处的磁场强度的强烈振荡.提出了一个用该系统测量凝胶聚合物中锂离子扩散可获得较好结果的脉冲序列. 相似文献
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Cappellaro P Emerson J Boulant N Ramanathan C Lloyd S Cory DG 《Physical review letters》2005,94(2):020502
We propose a new approach to the measurement of a single spin state, based on nuclear magnetic resonance (NMR) techniques and inspired by the coherent control over many-body systems envisaged by quantum information processing. A single target spin is coupled via the magnetic dipolar interaction to a large ensemble of spins. Applying radio frequency pulses, we can control the evolution so that the spin ensemble reaches one of two orthogonal states whose collective properties differ depending on the state of the target spin and are easily measured. We first describe this measurement process using quantum gates; then we show how equivalent schemes can be defined in terms of the Hamiltonian and thus implemented under conditions of real control, using well established NMR techniques. We demonstrate this method with a proof of principle experiment in ensemble liquid state NMR and simulations for small spin systems. 相似文献
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Hashi K Shimizu T Goto A Kiyoshi T Matsumoto S Wada H Fujito T Hasegawa K Yoshikawa M Miki T Ito S Hamada M Hayashi S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):318-321
We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR. 相似文献
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核磁共振测井中,受激回波导致CPMG序列中前2个回波与期望值存在较大差异,严重影响仪器信噪比和储层评价效果. 为进一步改善核磁共振测井仪性能,通过探究受激回波产生机理,揭示其对CPMG回波串作用规律,提出了受激回波的校正方法. 同时针对仪器负载不同,相同发射功率产生射频场强度各异的特性,建立受激回波校正系数与射频场强的数学关系,在不同应用环境中实现对CPMG测量结果的校正. 实验表明,在信噪比较低的应用环境中,采用传统的舍去前2个回波的方法误差达24.58%,而该文设计的校正算法误差仅为4.9%. 相似文献
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A compact nuclear magnetic resonance (NMR) relaxometer–spectrometer with the continuous generation of the high-frequency energy and double magnetic field modulation has been designed for studying biological objects. Spin–lattice relaxation times and second-derivative spectra of the NMR signals have been measured. The relationship between the shape of the spectrum and the spin–lattice relaxation time has been established. This device is supposed to be used for the noninvasive measurement of the glucose concentration in the human blood from the measurement of the spin–lattice relaxation time and the NMR spectrum in a finger of a human hand. 相似文献
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The NMR probe and the matching network has been designed for the1H NMR study in CeNiInH0.53 down to liquid helium temperature using Bruker MSL 100 spectrometer. NMR line-shape measurement shows the absence of any
signature of proton pairing in CeNiInH0.53 down to 3.86 K, as it was observed for high hydrogen concentration. The measurement of the spin-lattice relaxation time in
the temperature range 300–20K reveals that the relaxation rate is mainly governed by the Korringa-type relaxation mechanism. 相似文献
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Feng Deng Lizhi Xiao Guangzhi Liao Fangrong Zong Weiliang Chen 《Applied magnetic resonance》2014,45(2):179-192
Driven-equilibrium fast saturation recovery (DEFSR), as a new method for two-dimensional (2-D) nuclear magnetic resonance (NMR) relaxation measurement based on pulse sequence in flowing fluid, is proposed. The two-dimensional functional relationship between the ratio of transverse relaxation time to longitudinal relaxation time of fluid (T 1/T 2) and T 1 distribution is obtained by means of DEFSR with only two one-dimensional measurements. The rapid measurement of relaxation characteristics for flowing fluid is achieved. A set of the down-hole NMR fluid analysis system is independently designed and developed for the fluid measurement. The accuracy and practicability of DEFSR are demonstrated. 相似文献
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Jan Schlenke Lars Hildebrand Susanne Felsinger Bernd Reusch Lothar Brecker 《Applied magnetic resonance》2013,44(6):745-758
Off line analysis of proton nuclear magnetic resonance (NMR) spectra by computerized peak detection is used to determine the shim quality from Fourier transformed spectra. The method is designed to analyze spectra independently from any further information about the measurement. For this purpose, the number of maxima in a spectral region is determined and compared to the number of peaks identified by an automatic routine utilizing a curvature-based method. The resulting “shim quality quotient” represents a good indicator for the magnetic field homogeneity present during the measurement. This method can be applied to separated single signals as well as to entire spectral regions. Hence, its brought use as tool in automatic interpretation of NMR spectra is possible. An example is shown for an in situ proton NMR measurement of glucose mutarotation. 相似文献
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Feng Deng Lizhi Xiao Huabing Liu Tianlin An Mengying Wang Zongfu Zhang Wei Xu Jiajie Cheng Qingming Xie Vladimir Anferov 《Applied magnetic resonance》2013,44(9):1053-1065
Nuclear magnetic resonance (NMR) under motion has drawn significant attention in recent years. Motion of the NMR probe has serious effects on NMR measurement. For example, NMR logging normally runs at downhole condition with tool motion at a speed of 30 ft/min. We propose here methods for motion corrections of NMR data based on the quantitative analysis of motion effects on polarization and echo acquisition. We also produced a multi-functional NMR scanning system to verify the theoretical analysis. Presented experiments demonstrate that the theoretical and experimental results match very well. 相似文献