On a Structural Distortion Effect in the NMR Spectra of Alkali Fullerides

Abstract

An investigation is reported on a possible effect in the NMR-spectrum of the fee-alkali fullerides, caused by the off-centre displacements of the alkali cations. The effect consists in a slight, asymmetrical distortion of the NMR-lines of the tetrahedrally-coordinated alkali cations, in the direction of lower shift values. A typical example is K₃C₆₀.     

On a Structural Distortion Effect in the NMR Spectra of Alkali Fullerides

An investigation is reported on a possible effect in the NMR-spectrum of the fee-alkali fullerides, caused by the off-centre displacements of the alkali cations. The effect consists in a slight, asymmetrical distortion of the NMR-lines of the tetrahedrally-coordinated alkali cations, in the direction of lower shift values. A typical example is K₃C₆₀.     

Simulation of Giant Magnetic Impedance (GMI) Effect in Co-based Amorphous Ribbons with Demagnetizing Field

Considering the role of demagnetizing field, based on linear Maxwell’s equations and the Landau-Lifshitz equation, the expressions of permeability and impedance were obtained using the improved theoretical model in this article. A numerical simulation was conducted using Matlab, and the results of calculations were well matched with the experimental results, indicating the importance of the demagnetizing field and that it should not be ignored. Utilizing the equivalence relation between the shape of the samples and the demagnetization factor which determined the value of the demagnetizing field, the influence of the aspect ratio of the samples on giant magnetic impedance (GMI) effect was researched. The calculations showed that the most significant GMI effect was obtained when the aspect ratio of samples was about 44. In addition, the optimal frequency to obtain the most significant GMI effect of the given sample was calculated. These researches may provide theoretical guidance for the development and use of a GMI sensor.     

Numerical Simulation of Heat Conduction to Liquids from a Thin Vertical Cylinder

The paper presents numerical simulations of heat conduction around a circular vertical cylinder immersed in liquids. A finite volume formulation is used, and the numerical analysis is performed in unsteady state with an explicit scheme. The numerical predictions are compared with experiments performed on liquids to find the temperature inside the cylinder, where a thermocouple is located, and at the wall of the insulated coaxial container, where the liquid is poured. The cylinder is immersed vertically. The numerical results are in good agreement with the temperature at the wall of the container. The experimental temperature measurement of the thermocouple located inside the probe is intermediate between the numerical temperatures on the axis and on the surface of the probe. The natural convection phenomenon is evidenced in the experiments, after a certain time from the beginning of heating, in some of the liquids used, except glycerol. Natural convection is not considered in the present numerical simulations, which solve only the heat conduction equation.     

三维闭空间主动噪声控制的实验研究

本文在一封闭的房间内通过实验研究主动噪声控制技术的特性。采用一个多阶谐频信号在实验房间产生模拟的原始声场，并应用一多通道自适应控制系统进行降噪实验，获得了一些对工程实际有意义的实验结果。     

The Effect of pH and Magnetic Field on the Fluorescence Spectra of Fluorescein Isothiocyanate Conjugated SPION- Dendrimer Nanocomposites

In this study, fluorescent dendro-nized magnetic nanoparticles (FDMNPs) with their unique pH sensitive nature were synthesized for biomedical applications. First, superparamagnetic iron oxide nanoparticles (SPIONs) were prepared by coprecipitation of F e ⁺² and F e ⁺³ with N H ₄ O H, and then modified by amino silane. Polyamidoamine (PAMAM) dendrimer were coated on the SPION-APTS surface using Michel addition method and grew from generation 0.5 to 3. In the final step of synthesis, the reaction between isoslulfosyanic groups of fluorescein isothiocyanate (FITC) and amine terminal groups of DMNPs was lead to the formation of magnetic fluorescent nanocomposites. The FDMNPs were studied using Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible spectroscopy, fluorescence spectroscopy, vibrating-sample magnetometery (VSM) ), zeta potential ,and Dynamic Light Scattering (DLS). The size of SPIONs and FDMNPs were about 10 nm and 14 nm, respectively. The possibility of conjugating a large number of fluorescein isothiocyanate (FITC) molecules on the SPIONs together with high amount of magnetization saturation ,Ms (52 emu/g in our case) and other unique characteristics have nominated FDMNPs as a suitable candidate for biomedical applications.     

圆柱绕流噪声预报的流场与声场模拟方法对比研究

以三维圆柱为研究对象,使用Lighthill声类比法研究其绕流发声问题。第一步进行流场计算,分别用大涡模拟(LES)、脱体涡模拟(DES)和瞬态雷诺平均法(URANS)模拟声源区流场,通过对比流场压力和涡量等参数,据此选取合适的流场仿真方法;第二步用基于Lighthill方程FW-H积分法和边界元法预报远场直发声,通过和Revell试验结果比较,分析各种计算方法差别。研究表明:进行流场仿真时LES计算结果最好,IDDES法在保证计算精度条件下能有效减少流场网格数量,URANS法误差很大;进行辐射噪声预报时,FW-H积分法和边界元法基本相同。     

发动机室内试车台流场品质研究

流场品质对航空发动机室内试车台上性能试验结果有重要影响,高品质流场是室内试车台进行气动附加阻力准确修正的基础。本文对比介绍了国内外室内试车台气动流场参数要求差异,分析了室内试车台进排气结构等因素对流场品质的影响,提出了以试车间气流速度均匀性、引射比、进气道总压均匀性为核心参数的流场品质评价参数体系,并针对未来国内室内试车台在提高流场品质方面需开展的工作提出了建议。     

Intensification of the Electric Convection of Weakly Conducting Liquids by a Pulsed Electric Field

Results of an investigation of the kinematic characteristics of the electric convection of weakly conducting liquids intensified by a pulsed electric field are reported.     

The Effect of External Magnetic Field on a Vacuum Arc

The effect of an external longitudinal magnetic field on the time required for anode spot formation in a high-current (5 to 12 kA) vacuum arc is experimentally studied, and the minimal value of a magnetic field inhibiting the anode spot formation is determined. The experimental results are compared with theory. The phenomenon of break of current in a low-current (100 to 300 A) vacuum discharge upon superposition of a magnetic field with transverse component on the discharge is investigated. The probability of break of current increases with the magnetic field. The possible mechanism of break of current is discussed.     

The Effect of Magnetic Field on a Quantum Rod Qubit

The Hamiltonian of a quantum rod (QR) with an ellipsoidal boundary is given after a coordinate transformation, which changes the ellipsoidal boundary into a spherical one. We then study the eigenenergies and eigenfunctions of the ground and the first excited states of an electron strongly coupled to the LO-phonon in the QR under a magnetic field. The present system may be used as a two-level qubit. When the electron is in the superposition state of the ground and the first excited states, we obtained the time evolution of the electron probability density oscillating in the QR. It is found that the magnitude of the probability density is increased by the magnetic field, whereas it decreases the oscillation period of the probability density. The oscillation period is a increasing function of the ellipsoid aspect ratio, the transverse and longitudinal effective confinement lengths of the QR, but a decreasing one of the electron-phonon coupling strength and the cyclotron frequency of the magnetic field.     

The Effect of a Longitudinal Magnetic Field on the Radiation of Glow Discharge in Helium

The effect of a longitudinal magnetic field on the radiation of a glow discharge in helium is investigated experimentally. It is demonstrated that, with pressures in the discharge chamber below approximately 140 Pa, the intensity of radiation of spectral lines of helium and of continuous spectrum increases by a factor of 200–300 under the effect of a magnetic field. So strong an increase in the radiation of glow discharge in helium is observed in the region where no electric field of discharge is present. An attempt is made at attributing the obtained result to the decrease in the ambipolar diffusion of electrons to the wall; this brings about an increase in the density and temperature of electrons which start exciting metastable states of helium.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 4, 2005, pp. 516–525.Original Russian Text Copyright © 2005 by I. M. Ulanov and A. Yu. Litvintsev.     

Solution Spectra and Stability of Current Biased Josephson Junctions in a Magnetic Field

We examine the solutions of the non-linear equations governing the behavior of a current biased Josephson junction. Both inline and overlap current bias geometries are considered. The solution space is investigated analytically and using numerical techniques. We characterize the types of solutions expected analytically and find good approximations for large magnetic fields. For small magnetic fields the solution space is large and its stability is entangled. We study this space and its stability as a function of magnetic field and applied bias current. Selective results are presented that characterize the general behavior of the solution space.     

滚筒跳动对柔性版印刷质量的影响

目的 研究压印滚筒径向跳动对印刷压强与网点变形的影响,为降低柔性版印刷中网点扩大率、提高印品质量提供参考依据。方法 论文以柔性版印刷为例,运用接触力学基础理论分析压印滚筒与印版滚筒间接触状态,构建柔性版最大印刷压强分析模型。运用有限元分析方法,得出印刷压强与柔性版网点压缩变形关系,从而构建出压印滚筒跳动引起柔性版网点扩大率分析模型。通过实测得到柔性版印刷机压印滚筒径向跳动波形。结果 最大印刷压强的增加会增大网点顶端接触面积,使网点扩大率增大;压印滚筒的径向跳动改变了印刷过程中的实际合压量,造成印刷过程中最大印刷压强的波动,因而在柔性版印刷过程中需要严格控制合压量;在合压量为0.1 mm时,径向跳动量为-0.053 99～0.054 48 mm。对于加网线数为69线/厘米、50%网点的印版,网点扩大率在3.639%～9.526%波动。结论 压印滚筒径向跳动改变了滚筒间的实际合压量,引起印刷压强的变化,使网点产生不同的变形,从而严重影响印刷质量。     

The Effect of Magnetic Field on 2-D Problem for a Mode-I Crack of a Fiber-Reinforced in Generalized Thermoelasticity

In the present paper, the coupled theory, Lord–?hulman theory, and Green–Lindsay theory are introduced to study the influence of a magnetic field on the 2-D problem of a fiber-reinforced thermoelastic. These theories are also applied to study the influence of reinforcement on the total deformation of an infinite space weakened by a finite linear opening Mode-I crack. The material is homogeneous and an isotropic elastic half-space. The crack is subjected to a prescribed temperature and stress distribution. Normal mode analysis is used to solve the problem of a Mode-I crack. Numerical results for the temperature, the displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field. A comparison between the three theories is also made for different depths.     

立式锌锅高频磁场悬浮力和封流特性研究

本文采用专门设计的悬浮力和电磁封流实验装置，在铜、铝、锌高频磁场电磁悬浮力研究的基础上，讨论了电磁封流影响因素，得出了铜、铝、锌三种金属在固态和液态的不同工艺参数的影响规律，讨论了立式锌锅高频磁场电磁封流的可行性。     

E150柴油机缸内压缩温度场的全息干涉测量

介绍了采用激光双曝光全息干涉技术测取柴油机压缩温芳场的基本原理及实验过程。提出了利用绝热压缩缩区的温度作为计算干涉条纹的初始条件,从而为计算全息干涉条纹所对应温度提供了可行的方法。由柴油机压缩过程中缸内的温度场的测量结果可以看出,在柴油机压缩过程中,缸内温度变化幅度在４０Ｋ左右,最大温度梯度是在靠近燃烧室壁面大约０．５ｍｍ的区域内。本文的实验结果,为分析柴油机压缩过程缸内传热过程提供了依据;所使用     

Effect of Electron Correlation on Phonon Spectra in Cuprates

We examine theoretically the phonon dynamics in the electron-phonon-coupled systems. The model Hamiltonian is a one-dimensional Hubbard model where the hopping of electrons induces the electron-phonon coupling. The numerically exact diagonalization of the Hamiltonian with truncation of the total number of phonons is performed. We calculate the phonon excitation spectra and find that the softening of phonons occurs in insulating case, and a diffusive character appears in the metallic case. We also calculate the charge and spin excitation spectra and find that the dynamics of the phonon coupled with the hopping of electrons is affected by the low energy charge and spin excitations.