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脉冲相位的不稳定性是导致二维谱中的t1噪声的原因之一.本文从理论上和实验上对脉冲相位不稳定性所引起的t1噪声进行了研究.从角动量算符Ix,Iy和Iz推导中发现,由于磁化矢量在P型和N型DQF-COSY实验的脉冲梯度场中进动方向的内在差异,一部分脉冲相位误差在P型DQF-COSY实验会被重聚掉,在N型DQF-COSY实验中却会被加重.因此P型DQF-COSY实验的t1噪声比N型小.理论推导还得到t1噪声在P型和N型中的理论比值为√3:√11.以上理论结果得到我们实验结果的支持. 相似文献
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995.
Gong Hengfeng Xiao Hong Wu Hailong Meng Fanliang Ren Qisen Liao Yehong Zhang Guoliang 《The European Physical Journal B - Condensed Matter and Complex Systems》2022,95(8):1-7
The European Physical Journal B - Molecular dynamics and Monte Carlo methods are common measurements to study the diffusion coefficients of the fluid particles under restricted conditions. Here,... 相似文献
996.
This study examines the use of stationary Cartesian mesh for steady and unsteady flow computations. The surface boundary conditions are imposed by reflected points. A cloud of nodes in the vicinity of the surface is used to get a weighted average of the flow properties via a gridless least-squares technique. If the displacement of the moving surface from the original position is typically small, a small-perturbation boundary condition method can be used. To ensure computational efficiency, multigrid solution is made via a framework of embedded grids for local grid refinement. Computations of airfoil wing and wing-body test cases show the practical usefulness of the embedded Cartesian grids with the small-perturbation boundary conditions approach. 相似文献
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Wu Wenwei Fan Yanjin Wu Xuehang Liao Sen Li Shushu 《Journal of Physics and Chemistry of Solids》2009,70(3-4):584-587
The layered nanocrystalline NH4MnPO4·H2O was obtained by grinding MnSO4·H2O and (NH4)3PO4·3H2O in the presence of surfactant PEG-400 via a solid-state reaction at room temperature, maintaining the mixture at room temperature for 12 h, washing the mixture with water, and drying at 60 °C. The resulting NH4MnPO4·H2O and its products of thermal decomposition were characterized using thermogravimetry and differential thermal analyses (TG/DTA), IR, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV–vis, and magnetic susceptibility. The data showed that when dried at 60 °C for 5 h, highly crystallized orthorhombic NH4MnPO4·H2O (space group Pmnm(59)) was obtained with an average particle size of 45 nm and an average interlayer distance of 0.8701 nm. On the other hand, monoclinic nanocrystalline Mn2P2O7 with space group C2/m(12) was obtained when the product was calcined at 600 °C for 3 h. Magnetic susceptibility measurements from room temperature to 2.5 K point to ferrimagnetic ordering at TN~17 K. 相似文献
999.
The entropy squeezing of an atom with a k-photon in the Jaynes-Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entropy squeezing is preferable to variance squeezing for zero atomic inversion. Moreover, for initial conditions of the system the relation between squeezing and photon transition number is also discussed. This provides a theoretical approach to finding out the optimal entropy squeezing. 相似文献
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System calibration, which usually involves complicated and time-consuming procedures, is crucial for any three-dimensional (3D) shape measurement system based on vision. A novel improved method is proposed for accurate calibration of such a measurement system. The system accuracy is improved with considering the nonlinear measurement error created by the difference between the system model and real measurement environment. We use Levenberg-Marquardt optimization algorithm to compensate the error and get a good result. The improved method has a 50% improvement of re-projection accuracy compared with our previous method. The measurement accuracy is maintained well within 1.5% of the overall measurement depth range. 相似文献