一种新型机械式延时自闭水嘴的设计与操作性能分析

针对目前市场上延时自闭水嘴在操作性能上的不足, 设计了一种新型机械式延时自闭水嘴. 对该水嘴启闭过程中的操作性能和延时性能进行分析, 得到了水嘴操作力矩、延时时间与卷簧结构参数之间的函数关系, 并提出了水嘴操作力矩的大小与变动率优化模型. 以操作力轻便、稳定为指标, 得到了水嘴延时组件结构参数的最优组合解. 结果表明: 参数优化后的水嘴最大操作力矩为374N?mm, 且趋于稳定, 性能明显提高.     

基于点球弹簧修匀法的混合网格变形并行算法A parallel algorithm for hybrid mesh deformation based on Vertex-Ball Spring Smoothing

针对二维/三维混合网格,提出基于点球弹簧修匀法的并行网格变形算法。按特定模板将混合网格中的非三角形/四面体单元分解成三角形/四面体单元。针对每个内部节点及其相邻节点建立相应的子弹簧系统,并通过增加Ball-Vertex弹簧避免弹簧系统的塌陷问题。由于点球弹簧法在计算中逐点对网格内部节点进行计算,在计算过程中具有良好的弱耦合性质,因此有利于算法并行化。在并行化时仅需对网格进行虚拟分区操作,不必进行复杂的几何分区操作,同时避免了混合网格不同单元之间的兼容性问题。该方法适用于具有复杂外形的大规模混合网格的变形问题,能够显著提高网格变形的效率,同时具有良好的适应性。     

Some basic solutions for nonlinear creep

The aim of the paper is to derive the exact analytical expressions for torsion and bending creep of rods that obey the Norton–Bailey, Prandtl–Garofalo and Naumenko–Altenbach–Gorash constitutive models. The common secondary creep constitutive model is the Norton–Bailey law which gives a power law relationship between creep rate and stress. The closed form solutions for fractional Norton–Bailey creep law are derived. The analytical formulas express the torque and bending moment as functions of the time for the period of relaxation. Other formulas express the twist rate and curvature as functions of the time for the duration of engineering creep experiment. The derived formulas are suitable for the practically important problems of machinery. Namely, the formulas are relevant for calculation of hereditary effects for helical, leaf and disk springs and twisted shafts.     

Synthesis and magnetic properties of hard/soft SrFe12O19/Ni0.7Zn0.3Fe2O4 nanocomposite magnets

Magnetic nanocomposite SrFe₁₂O₁₉/Ni_0.7Zn_0.3Fe₂O₄ powders with different weight fractions of the Ni_0.7Zn_0.3Fe₂O₄ soft ferrite were synthesized by a combination of the sol–gel self-propagation and glyoxilate precursor methods. The results of magnetic measurements revealed the higher Mr/Ms ratio for the nanocomposites than that for the single phase SrFe₁₂O₁₉ which proves the existence of the intergrain exchange coupling between hard and soft magnetic phases with the exchange spring behavior. The highest Mr/Ms ratio of 0.63 was obtained in the composite consisting of 80 wt% of SrFe₁₂O₁₉ and 20 wt% Ni_0.7Zn_0.3Fe₂O₄. The microstructural studies of this sample exhibited the average dimensions of hard and soft phases about 20 nm and 15 nm, respectively which are small enough for strong exchange coupling according to the theoretical studies. The variations of the reduced remanence (Mr/Ms) with increasing the weight fraction of the soft phase could be also explained by the role of the exchange and dipolar interactions in tuning the magnetic properties of the nanocomposites.     

Using spring repulsions to model entanglement interactions in Brownian dynamics simulations of bead–spring chains

We develop a bead–spring Brownian dynamics model for simulating the topological interactions between polymers and thin obstacles and apply this method to electrophoretically translating DNA strands interacting with an immovable post. The use of a bead–spring method allows for the simulation of entanglement interactions of polymer chains too long to be simulated using bead–rod or pearl necklace models. Using stiff “FENE-Fraenkel” springs, we are able to model short chains as well. Our new method determines the shortest distance between a spring and the post, calculates a repulsive force inversely related to this distance using an exponential potential, and corrects for the rare situation when a spring passes beyond the post despite the repulsive interaction. As an example problem, we consider single-chain collisions with a single post in weak electric fields. We explore a wide range of chain lengths (25–1,515 Kuhn steps), and we find that the average delay produced by the collision is a function of both the chain length and the Peclet number. Chains of all lengths reach the same upper limit at high Peclet number, but they follow separate curves with similar slopes at lower Peclet number. Our results are consistent with published results for a 25-Kuhn-step chain at Peclet number Pe = 10. Our new method is a general one that allows us to compute the effects of entanglements in systems with rare entanglements and long chains that cannot be simulated by other more microscopic methods.     

Enhancement of Axial Trapping Force in a Single-beam Gradient Optical Trap by a Pair of Axicons

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弹簧振子实验方法的运用和改进

对弹簧振子振动周期经验公式的实验拟合中所用的实验方法进行了总结,对部分实验方法和实验装置进行了改进。     

A novel finite element model for helical springs

A general and accurate finite element model for helical springs subject to axial loads (extension or/and torsion) is developed in this paper. Due to the establishment of precise boundary conditions, only a slice of the wire cross-section needs to be modelled; hence, more accurate results can be achieved. An example application to a circular cross-sectional spring is analysed in detail.     

引力波探测中的被动隔振系统

介绍了引力波探测实验中的被动隔振系统的基本原理和研究现状,讨论其性能及特点.低频被动隔振系统,如七级气体弹簧隔振系统,多级隔振堆,四级悬臂弹簧隔振系统以及三级弯曲弹簧隔振系统在10Hz以上,都具有好的隔振性能;倒摆、折叠摆、 X摆和锥摆等超低频水平隔振系统实现了几十秒的共振周期;建立在对称扭杆弹簧系统基础上,构思新颖的被动垂直隔振系统克服了传统被动垂直隔振系统无法解决的困难,实现了超低频被动垂直隔振.      

对称扭杆弹簧系统隔振性能研究2000-04-03收稿.

对扭杆弹簧隔振系统的研究表明,扭臂的质量对系统的性能有比较大的影响。虽然系统可获得长的共振周期,但由于扭臂的质量不为零,地基振动的加速度被直接耦合进系统,从而严重地降低了系统的隔振性能。