取样管型流分相式气液两相流体流量计

提出了用取样管来组成一种分流分相式气液两相流体流量计,通过取样管从被测两相流中成比例地分流出一部分气液混合物,然后应用-小型分离器将其分离成单相气体和液体,并用单相流量计分别测量它们的流量,最后根据测量值计算被测两相流体的各相总流量.文中给出了这种两相流体流量计的组成原理,分流系数特性及实验结果.研究结果表明,取样管的端口形状对分流系数的特性影响较大,其中S型端口的效果较理想,能够在较宽的测量范围内保持分流系数的稳定.     

CO2激光成像雷达距离分辨率测距精度的分析与实验研究

分析了脉冲外差体制CO₂激光成像雷达系统的目标距离分辨率、测距精度和误差的主要来源.对于单个光脉冲测距来讲,信噪比(SNR)起伏引起的探测误差、脉冲前沿触发等概率分布以及脉冲建立时间的随机性等是激光脉冲外差测距的主要随机误差,其它随机误差在数量级上可忽略不计.同时利用现有的CO₂激光脉冲外差探测系统,进行了远目标测距对比实验,观测到了2355 m目标脉冲回波信号,并精确测量出CO₂光脉冲飞行的往返时间,该实验数据可用做系统误差的校正和补偿.     

Exploring interaction effects in two-component gas mixtures using orthogonal signal correction of ultrasound pulses

Within Sweden and the EU, an increased use of biogas gas and natural gas is encouraged to decrease emission of carbon dioxide. To support more effective manufacturing, distribution, and consumption of energy gases, new methods for the measurement of the calorimetric value or the gas composition are needed. This paper presents a method to extract and visualize variations in ultrasound pulse shape, caused by interaction effects between the constituents of a two-component gas mixture. The method is based on a combination of principal component analysis and orthogonal signal correction. Pulse-echo ultrasound experiments on mixtures of oxygen and ethane in the concentration range from 20% to 80% ethane show that the extracted information could be correlated with the molar fraction of ethane in the mixture.     

Incompressible smoothed particle hydrodynamics for free-surface flows: A generalised diffusion-based algorithm for stability and validations for impulsive flows and propagating waves

The incompressible smoothed particle hydrodynamics (ISPH) method with projection-based pressure correction has been shown to be highly accurate and stable for internal flows and, importantly for many problems, the pressure field is virtually noise-free in contrast to the weakly compressible SPH approach (Xu et al., 2009 [31]). However for almost inviscid fluids instabilities at the free surface occur due to errors associated with the truncated kernels. A new algorithm is presented which remedies this issue, giving stable and accurate solutions to both internal and free-surface flows. Generalising the particle shifting approach of Xu et al. (2009) [31], the algorithm is based upon Fick’s law of diffusion and shifts particles in a manner that prevents highly anisotropic distributions and the onset of numerical instability. The algorithm is validated against analytical solutions for an internal flow at higher Reynolds numbers than previously, the flow due to an impulsively started plate and highly accurate solutions for wet bed dam break problems at zero and small times. The method is then validated for progressive regular waves with paddle motion defined by linear theory. The accurate predictions demonstrate the effectiveness of the algorithm in stabilising solutions and minimising the surface instabilities generated by the inevitable errors associated with truncated kernels. The test cases are thought to provide a more thorough quantitative validation than previously undertaken.     

Computer Vision Based Automatic Recognition of Pointer Instruments: Data Set Optimization and Reading

With the promotion of intelligent substations, more and more robots have been used in industrial sites. However, most of the meter reading methods are interfered with by the complex background environment, which makes it difficult to extract the meter area and pointer centerline, which is difficult to meet the actual needs of the substation. To solve the current problems of pointer meter reading for industrial use, this paper studies the automatic reading method of pointer instruments by putting forward the Faster Region-based Convolutional Network (Faster-RCNN) based object detection integrating with traditional computer vision. Firstly, the Faster-RCNN is used to detect the target instrument panel region. At the same time, the Poisson fusion method is proposed to expand the data set. The K-fold verification algorithm is used to optimize the quality of the data set, which solves the lack of quantity and low quality of the data set, and the accuracy of target detection is improved. Then, through some image processing methods, the image is preprocessed. Finally, the position of the centerline of the pointer is detected by the Hough transform, and the reading can be obtained. The evaluation of the algorithm performance shows that the method proposed in this paper is suitable for automatic reading of pointer meters in the substation environment, and provides a feasible idea for the target detection and reading of pointer meters.     

一种新的气液两相流体流量计-三通管型分流分相式两相流体流量计

利用三通管的相分离特性,从被测气液两相流体中分流分离出一部分单相气体,通过测量这部分单相气体的流量计算被测气液两相流体的流量或干度.文中给出了这种分流分相式气液两相流体流量计的组成原理,分流系数特性及实验结果.     

非线性电阻特性实验的探讨

采用两种方法和两种电表研究非线性电阻特性的实验,使学生了解磁电式仪表和数字式仪表的结构和性能,了解电表内阻、电路本身的电阻及接点电阻产生的误差及其消除方法,了解采用各种方法和电表的优缺点.     

0.1 Hz 800 kA驱动源模块研制北大核心CSCD

介绍了面向Z箍缩驱动聚变裂变混合堆(Z-FFR)能源的重复频率800kA快上升沿的线性变压器驱动源(LTD)模块的设计和测试。LTD模块由34组RLC电路组成,每组包含2台100kV/40nF脉冲电容器、1个多间隙气体开关和非晶磁芯。研制的模块可以在匹配水电阻负载上以0.1 Hz的重复频率输出上升沿约100ns的800kA的电流脉冲。采用了一个高压触发信号来触发整个模块的新触发方式,将外触发信号通过模块内布置的角向传输线等网络同时到达并触发所有的高压开关,实验结果表明采用一路140kV、25ns前沿的触发脉冲可以可靠地触发整个模块。为了保证LTD模块每10s输出一个80kV/800kA的电流脉冲,非晶磁芯的去磁复位采用了一个5.2kA、脉宽30!s的电流脉冲,其运行频率为0.1 Hz。模块采用的多间隙气体开关运行寿命超过10 000次,其抖动小于3ns。     

高频共振预探测多脉冲激光测距方法

在无合作目标激光测距中,提出了一种高频共振预探测和多脉冲相关处理对远目标距离进行高精度测量的技术方案.脉冲回波光电流信号经高频共振预探测电路进行放大滤波处理并转换为包含高精度定时特征点的高信噪比的双极性衰减振荡脉冲信号;之后利用多脉冲相关处理构造出的新脉冲函数进一步改善其信噪比.理论计算结果表明:最小可探测光脉冲电流仅为17 nA,与直接探测脉冲方法相比信噪比可提高60倍;在回波光电流脉冲峰值1:10000的动态范围内,走离误差小于0.1 ps.根据此原理研制出了脉冲激光测距仪,仪器在激光发射平均功率约为1 mW时,无合作目标测程大于2000 m,在1.5—300 m范围内测距精度达到±(3 mm+2 ppm),远目标测距精度为±(10 mm+10 ppm).该测距仪系统已用于全站仪产品中.     

超声动态向量血流成像的产品化实现

传统超声彩色多普勒成像测量的是血流沿超声传播方向上的速度分量,故无法得到垂直于超声传播方向的血流。向量血流成像是一种更加先进的超声血流成像技术。它不受角度限制,可以直接计算出血流速度的大小和方向。本文总结了现有多种超声向量血流成像技术的特点和发展情况,并从产品化实现的角度分析了各项技术的优缺点。从超声系统发射接收、血流成像、向量速度方向合成、显示等几个方面详述了迈瑞超声向量血流成像技术产品化实现过程中遇到的主要问题及解决方案。实验采用了中科院声学所研制的超声多普勒仿血流体模,通过向量血流成像和脉冲多普勒成像分别测量体模的仿血流速度。将向量血流成像直接计算出来的速度值与脉冲多普勒经过角度校正得到的速度进行对比。在不同条件下,经过多次测量,二者的平均相对误差均在10%以内。     

BEPCⅡ直线加速器速调管的反射保护

为了使速调管陶瓷窗免受大功率微波反射信号的损伤,延长速调管使用寿命,要求当前反射信号功率超过阈值后,系统能够在下一个脉冲到达之前发出报警信号,进而切断触发信号,实现对速调管的保护。提出了3种较高性价比、易实施的方案,即PicoScope虚拟示波器的遮罩报警方案、基于自带检波和报警输出功能的芯片制作反射保护插件以及原功率计的升级改进。创新性地提出“3+1”反射保护响应时间测试法,并对上述3种方案进行详细测试。最终后两种方案取得较好的结果,综合考虑后,将改进型功率计作为最终实施方案。目前该改进型功率计已稳定可靠地上线运行超过1年。     

相位测量轮廓术中随机相移误差的校正算法

在相位测量轮廓术(PMP)中．随机相移误差足导致测量误差的重要因素,提出一种新的随机相移误差的校正算法,在五步相移的基础上不需要求解相位分布．通过近似处理可以直接求解相移过程中存在的随机相移误差,在保证精度的情况下,能大大减少迭代次数和计算量。推导了新算法的计算公式,详细说明了随机相移误差的求解过程。计算机模拟和实验证实了新的算法的有效性。与In-bok Kong的算法相比较,新算法能大大减少迭代次数和计算量。该新算法也同样适用于相移干涉计量。     

斩波法在激光微能量计标定中的应用

针对激光微能量测量的问题,提出一种激光微能量计标定新方法与装置。研究内容包括使用稳功率连续激光作为光源,通过基于斩波的脉冲发生器组件产生微能量的脉冲激光,分别使用脉冲宽度测量组件与功率测量组件进行采集、软件分析,计算微能量值及通过比对给出待标定能量计的修正系数,计算机自动控制。结果表明,该方法获得的脉冲激光波形稳定,脉冲宽度测量不确定度为0.08%,激光功率测量不确定度为0.25%,实现了对0.1 pJ～1 mJ的激光能量进行准确复现和传递。     

智能型多相流量计现场试验研究

本文首先简要介绍了我们自主开发的智能型多相流量计的基本原理,包括气相流量和液相流量计量,以及液相含水率的计量。继而,对工业样机的现场试验条件以及试验结果进行了详细的论述。数据表明:该多相流量计工业样机的液相流量计量相对误差在±8%以内,其中95%以上位于±5%范围内;气相流量计量相对误差在±20%以内,其中67%在±5%以内,88%在±10%以内,98%在±15%范围内;液相含水率绝对误差在±2%以内。该工业样机计量精度可以满足油田生产的需要。     

Development of the liquid level meters for the PandaX dark matter detector

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors that are custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and are recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.     

一种基于Radon逆变换的半覆盖螺旋锥束CT重建算法

半覆盖螺旋锥束计算机断层成像能够扩展传统螺旋锥束计算机断层成像的成像视野, 实现小面板探测器成像超视野物体. 但是, 各角度下的投影都存在数据截断, 会使重建结果中产生截断伪影, 降低图像质量. 本文提出了一种基于Radon逆变换的半覆盖螺旋锥束重建算法, 该算法在滤波时先使用局部算子, 再使用全局算子. 局部算子不受数据截断的影响, 并且降低了运算后的值由于数据截断所造成的不连续性, 因此, 减少了随后全局运算产生的截断误差. 仿真和实际实验结果均验证了本文算法的有效性. 和现有算法的对比也表明, 本文算法针对半覆盖螺旋锥束投影具有更强的截断伪影抑制能力, 能够有效提高重建图像的质量.     

喷射等离子体触发气体开关导通特性

利用内嵌微孔火花放电产生喷射等离子体、作用于两电极开关,研究了间隙距离、气压、气体种类、开关工作系数和电压极性配合等因素对等离子体喷射控制开关导通特性的影响。实验结果表明,等离子体喷射触发开关可在工作系数为10%的条件下可靠快速导通,当开关采用0.5 MPa_N₂作为绝缘介质、间隙距离5 mm时,触发导通时延为11.7 μs,抖动为1.42 μs;当间隙距离增大到18 mm时,触发导通时延增大至19.7 μs,触发可靠性降低;当工作系数由10%增大到60%时,触发导通时延由11.7 μs降低至1.1 μs。在确保开关自击穿电压一致的前提下,短间隙、高气压、负触发脉冲电压、正工作电压更有利于减小开关触发导通时延。     

Relativistic field formulation of simultaneous quantum measurement

The simultaneous measurement of Dirac field operators is formulated in analogy to the work of von Neumann and Arthurs-Kelly. Meter fields are coupled to the system field with a relativistically invariant bilinear interaction. Measurement of vacuum meter field expectation values provides for the simultaneous measurement of noncommuting system components. It is shown that two meter coupling allows for a simultaneous minimum in the variance of the subsequent meter measurements. A pseudoscalar self-interaction of the Dirac field is shown to allow simultaneous measurement of positive energy field operators with negative energy meters. The simultaneous measurement ofn noncommuting field operators is obtained by coupling the system ton fermionic fields. Also, in this paper the related concept of mutual simultaneous measurement is developed. This requires that any operators in the enlarged Hilbert space are measurable by the remaining fields as meters. System embedding into a larger Hilbert space results in added noise due to the zero point motion of the meter fields. By the negentropy principle of Brillouin, the added noise is equivalent to entropy. A criterion determining the interaction among fields is that the averaged added noise in the components of each quantum field is minimized. This criterion defines an optimum fermionic mass matrix through the determination of the entangling interaction.1. This work was sponsored by the Department of the Air Force under contract F19628-90-C-0002.     

几项新技术在“闪光二号”加速器上的应用

 为追踪国际上脉冲功率技术的发展方向,在“闪光二号”加速器上开展了水介质形成线并联技术、多级多通道气体开关技术和同步触发技术等研究。经过3维结构下电场分布的模拟计算和绝缘设计,采用3根6 Ω小水线并联组成了2 Ω水介质形成线,研制成功了作为主开关的3 MV多级多通道气体触发开关,并实现了3个多级多通道气体开关的并联运行;采用工作时延446 ns的同步触发系统实现了Marx发生器与主开关的延时同步运行。真空负压下的涡流循环冲刷消除水中气泡技术应用于水介质形成线上,有效消除了并联形成线汇聚结构处的气泡,提高了加速器运行的安全性。经过调试后,加速器重新获得了稳定的运行状态,几项新技术的应用获得成功。     

An improved particle correction procedure for the particle level set method

The particle level set method [D. Enright, R. Fedkiw, J. Ferziger, I. Mitchell, A hybrid particle level set method for improved interface capturing, J. Comput. Phys. 183 (2002) 83–116.] can substantially improve the mass conservation property of the level set method by using Lagrangian marker particles to correct the level set function in the under-resolved regions. In this study, the limitations of the particle level set method due to the errors introduced in the particle correction process are analyzed, and an improved particle correction procedure is developed based on a new interface reconstruction scheme. Moreover, the zero level set is “anchored” as the level set functions are reinitialized; hence the additional particle correction after the level set reinitialization is avoided. With this new scheme, a well-defined zero level set can be obtained and the disturbances to the interface are significantly reduced. Consequently, the particle reseeding operation will barely result in the loss of interface characteristics and can be applied as frequently as necessary. To demonstrate the accuracy and robustness of the proposed method, two extreme particle reseeding strategies, one without reseeding and the other with reseeding every time step, are applied in several benchmark advection tests and the results are compared with each other. Three interfacial flow cases, a 2D surface tension driven oscillating droplet, a 2D gas bubble rising in a quiescent liquid, and a 3D drop impact onto a liquid pool are simulated to illustrate the advantages of the current method over the level set and the original particle level set methods with regard to the smoothness of geometric properties and mass conservation in real physical applications.