Simulating three-dimensional vortex motion by a vortex blob method

A three-dimensional vortex blob method was applied to calculate several vortex motions: the deformation of pseudo-elliptic vortex rings, the jet issuing from the pseudo-elliptic nozzle into flow of uniform velocity, the unsteady separated flow around a circular disk with an angle of attack, and the interaction of several vortex rings which approximately reproduced the Kolmogorov spectrum. In the first three cases, the viscous diffusion of vorticity was included. The pseudo-elliptic vortex rings experienced axis switching and split into a few deformed vortex rings. Rolling-up vortices in the pseudo-elliptic jet had a symmetric arrangement in the minor-axis plane and an antisymmetric arrangement in the major-axis plane in the developing region; further downstream, the vortices were arranged antisymmetrically in both planes. The wake behind the disk normal to the main flow reproduced the spiral and columnar modes of instability. A problem in the three-dimensional vortex method is that vorticity tends to diverge at a stage of evolution of the vortex motions. An approximate method of avoiding the divergence of vorticity is proposed.     

有限环计算的数字式神经网络方法

本文提出一种用于有限环算术的数字式神比网络方法。它采用非对称的数字式神经网络结构，在整个矢量空间上具有唯一的平衡点，因而不存在计算误差。这种方法保持了神经网络的高度并行结构，能够实时完成有限环上的模运算。它还被应用于中国余数定理的实现。     

A theorem on neutral delay systems

It is known that the stabilization of neutral delay differential tems requires first the stabilization of the difference operator or D-operator. In case all delays in the system are commensurable, necessary and sufficient conditions for the existence of suitable derivative feedback for the stabilization of the D-operator have been known for some time [14]. In this note we derive a result in the case of noncommensurable delays analogous to the known results for the commensurable delay case.     

活塞环结构设计研究

应用弯曲理论，将活塞环处理为平面曲杆，考虑轴向力和初始曲率对活塞环变形的影响，分析计算了活塞环装配后的变形和内力，从而设计出活塞环在自由状态下的理论廓形，该设计精度较高，对活塞环的结构设计具有一定的实用性。     

同轴环形磁铁磁作用力计算的等效磁荷法

以电磁学中的假想磁荷理论为基础，建立了内外同轴的两环形永久磁铁相互作用力的力学模型，并在此基础上，推证出了两环形磁铁磁作用力的数学模型，从而在不做任何假设及简化的条件下，建立了内外同轴的两环形磁体承载力的计算公式．应用该计算公式能够使两环形磁体相互作用的各机械量具有很高的计算精度．该公式的推证建立方法对分析和建立其它形式的磁体相互作用力的计算公式具有普遍意义．因此，计算磁体磁作用力的等效磁行法是研究永久磁体承载力的一个新的有效途径．     

高能气体压裂试验效果分析

本阐述了高能气体压裂的原理，通过5口井的试验对比，分析了试验井的效果和用高能气体发生器压裂对套管及水泥环的影响，试验结果表明，用高能气体发生器压裂对解除近井地带污染，改善油层渗流条件有明显效果。     

钢球磨煤机减速机轴封漏油治理

对乌海热电厂二期2×200 MW燃煤机组钢球磨煤机减速机轴封漏油问题进行了分析,原因为减速机油位过高、密封轴套有刮痕、轴封没有装设挡油密封以及骨架密封油唇磨损.结合实际情况采用降低减速机油位、加装迷宫式密封及挡油密封环等措施对其进行技术改造,改造后钢球磨煤机减速机轴封未再发生漏油现象,改造效果良好.     

弹性分组环MAC公平性评价指标研究

鉴于目前大多数公平算法只有评价准则,而无评价指标,论文在RIAS公平性评价准则的基础上提出关于流传送速率和BE类流的公平效果的公平性评价指标。通过仿真验证,该公平性评价指标能很好地检验算法的公平性,能为各具体的MAC协议公平性算法提供很好的依据。     

Effects of the number of benzene rings on the properties of single-source ZrC-based liquid precursors and nano zirconium carbide powders thereof

Effects of carbon source in single-source ZrC-based liquid precursors on the properties of the precursors and precursor-derived nano ZrC powders were investigated. The liquid precursors were prepared by directly blending and heating zirconium n-butoxide with either 2,4-pentanedione, benzoyl acetone or 1,3-diphenyl-1,3-propanedione additives which have the same chemical composition and structure except for the number of benzene rings (0, 1 and 2, respectively) in order to control the carbon content in the precursors. The ceramic yield of the precursor decreased as the number of benzene rings in the precursors increased. The stability of the precursors in air and the carbon content of the ceramic powder increased when using 1,3-diphenyl-1,3-propanedione additive. X-ray pure nano zirconium carbide powders with ultra-fine size (30 nm), isotropic shape and homogeneous particle size distribution were synthesized from the liquid precursors containing two benzene rings in the structure. Compared with ZrC powders derived from the precursors containing zero or one benzene ring, the powder from the precursor containing two benzene rings was finer and more homogeneous in size distribution.     

Analysis of color volume of multi‐chromatic displays using gamut rings

There are claims that multi‐chromatic displays can achieve a wider color gamut by the use of additional highly saturated secondary color channels. However, there are other claims that these displays lose lightness and/or color saturation at brighter levels. These apparently divergent views have led to some controversy in the display industry and at standard setting organizations. This study examines the color gamut volume for a variety of simulated and measured multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays using combinations of white and/or secondary color channels, such as cyan, magenta, and yellow. Furthermore, a two‐dimensional gamut representation, referred to as “gamut rings,” is introduced to illustrate that the addition of nonprimary optical color channels to a trichromatic (RGB) display can result in a significant decrease in the chroma at higher lightness levels. The additional saturated color channels can increase the gamut volume only around their hues at darker levels. The results also confirm the validity of comparing the color light output and white light output for revealing the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays.