The Approach to Vortex Reconnection

We present numerical solutions of the Gross–Pitaevskii equation corresponding to reconnecting vortex lines. We determine the separation of vortices as a function of time during the approach to reconnection, and study the formation of pyramidal vortex structures. Results are compared with analytical work and numerical studies based on the vortex filament method.     

Vortex Reconnection and Acoustic Emission by the Numerical Analysis of the Gross-Pitaevskii Equation

Reconnection of quantized vortices and concurrent acoustic emission are studied numerically by analyzing the Gross-Pitaevskii equation. Although vortex reconnection was studied earlier by Koplik and Levine, the present work first investigates in more detail how the singular vortex cores reconnect. Second, acoustic emission, i.e., the emission of the density waves of the condensate, is studied when two vortices annihilate or reconnect. The local drastic change of the condensate density is found to work as an acoustic source to emit the density waves. This phenomenon may be related to the vortex tangle decay observed at mK temperatures and the eddy viscosity which is thought to be an intrinsic dissipative mechanism in a vortex tangle.     

Quantum Statistics of Three-Dimensional Vortex Filament in Superfluid 4He

The quantum statistics of three-dimensional vortex filament in superfluid ⁴ He is investigated by the use of path integral techniques. The free energy evaluated in the saddle point approximation decreases abruptly at a certain critical value of the applied superflow velocity. This critical behavior is in quantitative agreement with the experimental result of vortex nucleation by a moving ion. The dissipation effects are also discussed within the damped harmonic oscillator approximation.     

The Effect of the Air-Delivery Method on Parameters of the Precessing Vortex Core in a Hydrodynamic Vortex Chamber

The effect of the method of gas-phase injection into a swirled fluid flow on parameters of a precessing vortex core is studied experimentally. Conditions of the appearance of the vortex-core precession effect were modeled in a hydrodynamic sudden expansion vortex chamber. The dependences of the vortexcore precession frequency, flow-pulsation level, and full pressure differential in the vortex chamber on the consumption gas content in the flow have been obtained. The results of measurements permit one to determine optimum conditions for the most effective control of vortex-core precession.     

模型修正的逆特征灵敏度方法

本文将文献[1]提出的无阻尼系统逆特征灵敏度理论推广到线性粘性阻尼系统中,推导了线性粘性阻尼系统的一阶逆特征灵敏度公式。本文还探讨了将逆特征灵敏度理论用于修正结构动力模型的方法,并对简单的例子进行了计算机数值模拟。算例表明,利用该法无需分段线性迭加就能在修正量较大的情况下达到较高的精度。此法与其他模型修正方法比较,具有公式简单、物理意义明确,修正精度高等优点。     

机械分析天平灵敏度的调修方法

天平灵敏度的调修分为两大块,一是天平平线时灵敏度的调修,二是天平非平线(即吃线或离线)时灵敏度的调修。调修方法是:平线时调整天平横梁上的重心铊;非平线时首先通过调整刀子高低来解决天平平线问题,然后再通过调整重心铊来调整灵敏度。调修原则是天平吃线时降刀子,天平离线时升刀子,始终保持天平三刀处于平线状态。     

一种提高薄膜厚度测量灵敏度的方法

针对薄膜材料厚度无损测试技术,提出一种三电极平行板电容传感器薄膜测厚方法。具体采用了三电极平行板电容器结构,该电容传感器含有三个相同的几何尺寸是毫米级的平板电极探头,电极之间的间距可变。依据电容原理和保角变换方法建立理论模型。通过Fortran语言编写算法,将得出的计算结果与传统方法进行比较。结果表明用此方法检测薄膜厚度变化,不仅继承了传统电容测厚技术具有的结构简单,操作快捷,便于控制,低功耗,低成本等优点,还大大提高了薄膜厚度检测的灵敏度。     

Sensitivity of Cost Functions in Inventory Models

This article is concerned with the effects of alternative forms of surplus and shortage cost functions and also with the effects of alternative forms of probability density function of demand in an inventory control situation.     

涡街流量计在蒸汽和空气介质下的比对试验

通过涡街流量计分别在以空气为介质的音速喷嘴法气体流量标准装置和以蒸汽为介质的蒸汽流量标准装置的比对试验,检验了涡街流量计从最小流量到最大流量的20%、40%、60%、80%、100%的各个流量点时,仪表系数与介质的关系.试验结果表明:以空气作为检定介质的蒸汽涡街流量计不一定完全适用于蒸汽介质,在实际使用时会存在一定的误差.     

不同流体条件下涡街流量计的测量特性研究

本文详细阐述了涡街流量计的工作原理,先通过实验对在不同流体条件下的相对示值误差进行分析,再利用SOLIDWORKS FLOWSIMULATION流体计算软件对涡街流量计进行相应的流场分析等。     

静电纺丝细流踪迹图像采集方法研究

介绍了对高场强中的纺丝细流以"爆炸"方式喷射所形成的踪迹图像进行高速采集的方法。选用逐行扫描方式的全帧转移型高分辨力面阵CCD摄像机与能够在极短时间内(1/100000 s)完成单场图像采集的采集卡,可以获得十分清晰的高速踪迹图像。     

Shadowgraph Visualization of Turbulent Exchange between a Vortex Ring and the Environment at Different Densities of the Fluid in the Vortex Interior and Exterior

Technical Physics Letters - The turbulent exchange between a vortex ring and the environment was observed using shadowgraph imaging of the process when the density of the fluid inside and outside...     

一种提高CCD探测灵敏度的方法

阐述了影响ＣＣＤ探测灵敏度的暗电流及暗电流噪声的产生机理,分析了其对ＣＣＤ性能的影响。在此基础上,提出了一种新型的利用半导体致冷器件ＴＥＣ对ＣＣＤ进行致冷的方案,并对设计过程中要注意的问题进行了具体分析。最后运用实例说明了通过此方法,大大地降低了ＣＣＤ暗电流,提高了其探测灵敏度。文章还对这种新颖的热电致冷方法和传统的液氮致冷方法进行了分析、比较,指出了ＣＣＤ热电致冷的优势及发展前景。     

不同材质管道的连接方法

(1)出户管新型新型材质塑料管与室外镀锌钢管碰头连接. 首先将新型塑料管材接头处打毛,使凹凸不光滑,再用一大规格钢套管将两不同材质的管道连接在一起,缝灌水泥砂浆用水泥捻口或用石棉水泥捻口,捻口必须饱满光滑.     

气体涡街流量计不同密度下流量特性的试验研究

利用正压法音速喷嘴气体流量标准装置,通过调节试验管道中介质的工作压力(0.23～0.5 MPa)来改变介质密度,分别在空气密度为2.774 kg/m3、3.619 kg/m3、4.782 kg/m3、5.987 kg/m3四种情况下对50mm口径涡街流量计的流量特性(仪表系数、线性度、不确定度、流量下限)进行了大量试验研究.试验结果表明,不同密度下涡街流量计仪表系数的最大相对误差为0.405%,验证了涡街流量计仪表系数几乎不受流体密度变化的影响;并发现涡街流量计的流量下限随着介质密度的增大而向下延伸,对此现象进行了分析.     

The Temperature Coefficient of Tungsten Filament Lamps

The results of an investigation of the effect of temperature drift of the lamp base on the brightness temperature produced by a tungsten filament lamp are presented. The dependence of the temperature coefficient of gas-filled and vacuum lamps on the brightness temperature is determined. The error in the calibration characteristic of the lamp, connected with the temperature instability of the lamp base with time, is estimated.     

不同材料外推模型的精冲有限元模拟对比

将35铜的应力应变曲线用VOSS模型、Ludwik模型外推并插入到DEFROM2D中,对精冲过程进行有限元模拟,对比了VOSS模型、Ludwik模型及DEFORM自带材料模型的计算结果,表明DEFORM自带材料模型与VOSS模型计算结果相近,DEFORM自带材料模型在大塑性应变下仍具有可靠性。     

回转水纺线法制取锡金属细线的成线性研究

本文采用自制的“回转水纺线法”装置研制出圆截面金属锡连续细微线(线径 d=1.2×10~(-4)m)。通过 SEM 观察了各种参数下所形成的连续细微线的表面形态,文中在实验观察的基础上,进一步阐明了回转水纺线法的成线机理。     

基于噪声模板与互相关计算的涡街流量计抗强振动方法

根据涡街流量计在工作现场受强振动噪声干扰的情况,搭建振动实验平台,进行振动实验。对采集的数据进行功率谱分析和带宽特征分析,建立噪声模板,并量化描述噪声的带宽特性。进行噪声模板与传感器输出信号功率谱的互相关计算,提出利用噪声和涡街信号归一化互相关系数曲线进行噪声判别的抗强振动干扰的方法。对振动实验中采集的传感器数据进行处理,验证了该方法的有效性。     

The Research of Jet Vortex Mills

ABSTRACT

The construction of two types of vortex mills was considered. In the first type, a gas is reduced tangentialiy through orifices in a cylindrical chamber wall. The coarse particles are loaded in the cylindrical rarefaction zone on the axis of the center orifice; in ihe second type, a gas-particle mixture is reduced by the pressure head device tangenlially through orifices in an internal cylindrical wall. The accelerated particles are ground by collisions with the external chamber wall in both cases. The mathematical modeling of gas-particle flow in these vortex chambers was executed. The numerical results showed that the first type of mill is suited for superfine grinding in the wide range of initial particle sizes (10 μm-lmm). While the second type of mill proved to he considerably more economical than the first type, the particles had to have initial sizes between 10-200 μm.