叶轮机械叶片流体激振安全性的全功能分析

本文提出了对叶轮机械叶片流体激振安全性实行全功能数值分析的新概念和方法。实现气动力学和弹性力学的弱耦合计算,由弹性力学方法确定三维振型,用振荡流体力学方法确定三维条件下的三维振荡流场,确定在各种振幅条件下的非定常气动力作功与阻尼功,引入气动功等于阻尼功条件下的平衡振幅概念。根据平衡振幅确定叶片流体激振的动应力,并进行寿命评估。这种全功能分析将使叶轮机械流体激振的安全性分析更加符合工程实际的需要,也能够解释大量的流体激振破坏不属于瞬时突然破坏,而是一种疲劳破坏。     

几种扭振复合超声变幅杆的研究

对左、右段为圆柱型、中间段为变截面杆的三段式复合扭振超声变幅杆给出了频率方程和参数计算通式据此得出中间段l2分别为指数型、类国雄型、类悬镇线型和类余弦型，而l1=l3≠0，或l1≠0；或l3≠0的各种组合复合杆的参数计算式，并算出了其参数值，给出了主要参数曲线．测试了十组典型试件的谐振频率和放大系数，实验结果与理论值基本一致，本法可组合成许多适应各种用途的扭振复合杆     

船舶双推进轴系振动分析软件开发研究

为了预防船舶行进过程中轴系振动过大带来的危害,设计实现了船舶双轴系振动分析软件系统,实现了船舶运行过程中轴系振动的分析显示;对扭振和回旋双通道实时测试采集的数据进行了处理,剔除误差过大的野值,提高振动分析的精确度,并对扭振振幅数据进行定点DFT变换,找出扭振在高谐次上的异常振幅尖峰,以预防船舶在此转速下因扭振振幅过大带来的危害;实船测试表明,该系统测试精确度高,振动分析结果显示直观,满足了船舶双推进轴系振动分析的设计要求。     

船舶轴系双通道轴功率与扭振应力测量分析软件研发

为了实现船舶双推进轴系轴功率及扭振应力的动态测量,开发设计了轴功率与扭振应力测量分析软件,描述了轴功率及扭振应力测量的基本原理及所需设备,测量软件通过对船舶推进轴系的扭矩和转速的实时采集和计算转换,实时计算出轴功率及扭振应力,并且能够实时显示和存储扭矩,转速,轴功率即扭振应力。同时根据测量圈数对扭振应力进行频域分析,通过数据回放功能能够选择指定测量文件进行回放观察。最后,实船测试表明,该系统测试精确度高,轴功率与扭振应力分析结果显示直观,满足了船舶双推进轴系轴功率与扭振应力分析的设计要求。     

基于激光多普勒技术扭振测量的研究

提出一种基于激光多普勒技术和光学外差原理对高速回转机械进行扭振测量的新方法,分析了工作原理,推导出光路部分的数学模型,并通过实验分别验证了测量方法的可行性和准确性。高相干激光投射到转轴同一个截面上2点,反射光的多普勒频移正比于转轴转速,通过光学配置,使前后两个时刻的多普勒频移光信号在光探测器上发生光学混频,光电流拍差正比于转轴在两个时刻的速度差,控制两个时刻时间差很小,直接得到角加速度。与其他激光多普勒扭振测量方法相比,该方法直接测量转动角加速度,在保证测量精度的前提下,提高了扭转振动测量的实时性,极大地扩展了扭振测量的动态范围,对大型回转机械运行状态监测和故障诊断具有重要意义。     

超声扭振系统的四端网络设计法

本文将组成超声扭振系统的每一部件都等效为一机械四端网络，将所得的各网络矩阵相乘。得到系统的等效网络矩阵．由此求出该系统的谐振频率或指定频率的某一设计尺寸以及角位移放大系数，方便了设计和计算．文中给出了计算实例，其结果与实际情况吻合得较好．     

扭振阶梯形变幅杆频率方程的一般表示

利用变截面杆扭报方程和边界条件，导出的扭振阶梯形变幅杆的频率方程，在S1=S2，或l1=l2时，并不适于实际情况．本文首先导出了扭振声传输线方程，并用之对阶梯形变幅杆的频率方程作了一般表示．     

几种扭振复合超声变幅杆的研究

对左、右段为圆柱型、中间段为变截面杆的三段式复合扭振超声变幅杆给出了频率方程和参数计算通式据此得出中间段l2分别为指数型、类国雄型、类悬镇线型和类余弦型，而l1=l3≠0，或l1≠0；或l3≠0的各种组合复合杆的参数计算式，并算出了其参数值，给出了主要参数曲线．测试了十组典型试件的谐振频率和放大系数，实验结果与理论值基本一致，本法可组合成许多适应各种用途的扭振复合杆     

转子密封系统流体激振问题的流固耦合数值研究

随着叶轮机械的工作转速越来越高,工程中发生了大量的密封流体激振问题。实验证明,高转速下的流体激振属于自激振动,但采用传统的刚度阻尼线形假设无法模拟出这一物理现象。本文发展了一种高精度的流固耦合计算方法,用这种算法成功地模拟出转子密封系统在高转速下的自激振动,且捕捉到频率锁定的现象,而且发现随着转速的提高,固有频率也增大。另外,本文还得到了压比、预旋度对密封转子自激振动的影响规律。     

简明设计复合扭振变幅杆

传统设计复合扭振变幅杆的方法是利用各形状函数杆之间的角位移连续和力矩连续的边界条件,来确定方程中的待定系数,导出频率方程。本文利用各形状函数分界之间机械阻抗相等的方法来设计复合扭振变幅杆。可简化设计,物理意义明显。这种方法也适用于纵振复合变幅杆的设计。     

Effect of power frequency excitation character on ferroresonance in neutral-grounded system

In most earlier ferroresonance studies the traditional excitation characteristic of iron core,in which the traditional excitation characteristic contains harmonic voltages or currents,has been used as if it were made up of pure fundamental voltage or current.However,this is not always true.In comparison with traditional excitation characteristics,this paper introduces the power frequency excitation characteristic of the iron core,which contains no harmonics.The power frequency excitation characteristic of iron core has been obtained by Elector Magnetic Transient Program,resulting in discrete voltage and current pairs.Extensive simulations are carried out to analyse the effect of power frequency excitation characteristic on potential transformer ferroresonance.A detailed analysis of simulation results demonstrates that with power frequency excitation characteristic of iron core inclusion at certain excitation voltage the ferroresonance may happen,conversely it may not happen with traditional excitation characteristic inclusion.     

原子核同核异能态诱发辐射研究进展

介绍了同核异能态的特点和诱发同核异能态的几种机制,如直接光激发、电子跃迁诱导核激发(NEET)和电子俘获诱导核激发(NEEC)。同核异能态的诱发辐射研究目前在国际上竞争激烈,尤其是对最近提出的NEEC的研究。同时探讨了在我国开展这些研究的可能性。     

Extending the excitation sculpting concept for selective excitation

Nowadays, excitation sculpting is probably the most efficient way to achieve selectivity in an NMR experiment, since it associates very clean frequency selection with "user-friendliness." In the present report, it is shown that the excitation sculpting concept, originally based on a double pulse field gradient echo acting on a selected transverse magnetization, can be extended through new experiments designed to act on longitudinal magnetization. This leads to outstanding performances, especially when the transverse relaxation rate is a limiting factor as, for example, in the case of biological macromolecules. Several new sequences are proposed, aiming at the selection of magnetization aligned either/both on a transverse axis or/and on the z-axis. Their potentialities are illustrated in light of different applications including multiplet-selective excitation, band-selective excitation, and water suppression.     

Saturation effects on Ba 6phi （l=0, 2） and 6pnk （｜M｜= 0, 1） autoionization spectra

Using a three-step laser saturation excitation technique, the saturation effects on the Ba 6pns （J = 1） and 6pad （J = 1, 3） autoionization spectra are observed systemically in zero field. These saturation spectra are introduced to determine the high n members of 6pnl （l = 0, 2） autoionizing series and are used to analyse the channel interactions among the autoionizing series in zero field. Furthermore, the saturation excitation technique is applied to the electric field case, in which the saturation spectra of Ba 6pnk （｜M｜= 0, 1） autoionizing Stark states are measured. Most of these saturation spectra are observed for the first time so far as we know, which indicate the mixing of the autoionizing states in the electric fields.     

饱和激发情况下的荧光关联谱测量

研究了激发光增强时其对荧光关联谱(FCS)测量的影响. 强激发光产生的饱和激发会改 变激光诱导荧光的空间分布函数,从而影响FCS的测量结果. 首先根据饱和吸收的物理模型,推导出强激发光情况下有效探测区域变化的定量公式,获得了FCS测量所得到的粒子数和扩散时间与饱和激发光强和激光光强的函数关系,并用于消除饱和吸收造成的系统误差.采用Monte-Carlo模拟方法和实验,对理论分析结果进行了验证. 这将有助于完善FCS分析方法的理论模型,为高激发光强度下的FCS探测提供依据. 关键词： 荧光关联谱 饱和激发 Monte-Carlo模拟     

内/外部励磁方式下高温超导环的俘获场特性

高温超导磁体在闭环运行时,可以提供稳定磁场,但是由于高温超导带材无法实现无阻焊接,成为高温超导磁体闭环运行的技术瓶颈.本文利用第二代高温超导带材制备闭环超导环,采用内部励磁和外部励磁对超导环进行励磁,在液氮温度中(77 K)测量超导环的中心俘获磁场.结果表明超导环在内部励磁俘获的磁场值比外部励磁俘获的磁场值高;外部励磁中,超导环中插入铁芯柱能提高俘获场;内部励磁中,超导环在螺线管闭环运行俘获的磁场值比开环运行俘获的磁场值高.结果对于高温超导闭环磁体励磁和高温超导带材磁通动力学研究具有很重要参考价值.     

The stereodynamic properties of the F+HO(v,j) → HF+O reaction on~1 A' and ~3A' potential energy surfaces by quasi-classical trajectory calculations:Initial excitation effect(v=1-3, j=0 and v= 0, j=1-3)

The stereodynamic properties of the F ＋ HO （v, j） reaction are explored by quasi-classical trajectory （QCT） calculations performed on the 1At and 3At potential energy surfaces （PESs）. Based on the polarization-dependent differential cross sections （PDDCSs） and the angular distributions of the product angular momentum with the reactant at different values of initial v or j, the results show that the product scattering and product polarization have strong links with initial vibrationalrotational numbers of v and j. The significant manifestation of the normal DCSs is that the forward scattering gradually becomes predominant with the initial vibrational excitation increasing, and the scattering angle of the HF product taking place on the 3At potential energy surface is found to be more sensitive to the initial value of v. The product orientation and alignment are strongly dependent on the initial rovibrational excitation effect. With enhancement in the initial rovibrational excitation effect, there is an overall decrease in the product orientation as well as in the product alignment either perpendicular to the reagent relative velocity vector k or along the direction of the y axis, for which the initial rotational excitation effect is much more noticeable than the vibrational excitation effect. Moreover, the initial rovibrational excitation effect on the product polarization is more pronounced for the 3At potential energy surface than for the 1At potential energy surface.     

Surface excitation probabilities in surface electron spectroscopies

The phenomenon of surface excitation is competitive in nature for elastic and other inelastic scattering processes in surface electron spectroscopies; the knowledge of influence of surface excitations in electron energy loss spectra is then essential for quantitative surface analysis with these spectroscopies. The inelastic scattering of an electron moving in the vicinity of a surface is considered in a self-energy formalism to estimate the contribution of surface excitation in electron-solid interactions via the total surface excitation probability. The formulation uses the optical bulk dielectric function and provides the spatial and angular dependence of the differential and total inelastic cross-sections. The kinetic energy range of probing electrons considered is 100-5000 eV and the numerical evaluation of total surface excitation probabilities are performed for several metals, Au, Ag, Cu, Ni, Fe and Ti; empirical formulae for the surface excitation probability are given for each of these materials and compared with experimental results for the surface excitation parameter. The total surface excitation probability is higher in Ag as compared to other metals under consideration, for identical conditions of electron-solid interactions.     

Dissociative excitation cross sections of the lead atom in collisions between electrons and PbI2 molecules

Dissociative excitation of the lead atom in e-PbI₂ collisions has been studied experimentally. 27 excitation cross sections were measured for an energy of the exciting electrons equal to 100 eV. Nine optical excitation functions were recorded with variation of the electron energy in the range 0–100 eV. The most probable reaction channels for low electron energies are discussed, as well as the ratio of the dissociative excitation cross sections for the lead atom in e-PbI₂ and e-PbCl₂ collisions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 701–706, November–December, 2006.     

New Insights in the Interpretation of Tryptophan Fluorescence

Origin of tryptophan fluorescence is still up to these days a quiz which is not completely solved. Fluorescence emission properties of tryptophan within proteins are in general considered as the result of fluorophore interaction within its environment. For example, a low fluorescence quantum yield is supposed to be the consequence of an important fluorophore–environment interaction. However, are we sure that the fluorophore has been excited upon light absorption? What if fluorophore excitation did not occur as the result of internal conformation specific to the fluorophore environment? Are we sure that all absorbed energy is used for the excitation process? Fluorescence lifetimes of Trp residues are considered to originate from rotamers or conformers resulting from the rotation of the indole ring within the peptide bonds. However, how can we explain the fact that in most of the proteins, the two lifetimes 0.5 and 3 ns, attributed to the conformers, are also observed for free tryptophan in solution? The present work, performed on free tryptophan and tyrosine in solution and on different proteins, shows that absorption and excitation spectra overlap but their intensities at the different excitation wavelengths are not necessarily equal. Also, we found that fluorescence emission intensities recorded at different excitation wavelengths depend on the intensities at these excitation wavelengths and not on the optical densities. Thus, excitation is not equal to absorption. In our interpretation of the data, we consider that absorbed photons are not necessary used only for the excitation, part of them are used to reorganize fluorophore molecules in a new state (excited structure) and another part is used for the excitation process. A new parameter that characterizes the ratio of the number of emitted photons over the real number of photons used to excite the fluorophore can be defined. We call this parameter, the emission to excitation ratio. Since our results were observed for fluorophores free in solution and present within proteins, structural reorganization does not depend on the protein backbone. Thus, fluorescence lifetimes (0.5 and 3 ns) observed for tryptophan molecules result from the new structures obtained in the excited state. Our theory allows opening a new way in the understanding of the origin of protein fluorescence and fluorescence of aromatic amino acids.