基于改进相差法的超声波微流量检测

针对传统超声波流量测量方法在微小流速工况下难以实现高精度测量的问题,提出一种基于计数器法与取样积分法相结合的改进相差法测量方法.首先采用高稳定性电子计数器实现整周期延迟相位粗测量,再基于取样积分原理实现剩余子相位的精细测量,通过增大取样积分次数抑制由抖动引起的相位差测量误差;同时通过移相控制,消除传统鉴相器具有的不稳定工作区的影响.仿真与实验结果表明:在DN20管道、常温纯水条件下,微小流量下测量最大相对误差小于1%,中、大流量的测量最大相对误差小于0.5%;在0.02 m3/h微流量点的测量标准差为86 cm3/h.改进相差法可实现比传统时差法更高的测量准确度和测量下限,有助于提高超声波在微流量条件下的检测性能.

LFM信号参数联合估计新方法——域频率相差法

采用分数阶傅里叶变换域频率分析方法,针对线性调频连续波信号分数阶傅里叶变换的特性,提出了分数阶域相差法,可以在低信噪比条件下对线性调频连续波信号进行检测,获得多普勒频移与实验的精确参数估计。同时时频参数联合估计中不必进行二维搜索,具有快速、高效的特点。计算机仿真结果表明了该方法的有效性。

基于相差积分法的超声波热量表设计

针对供热系统分户式热量计量要求,设计了一种基于相差积分法的超声波热量表。主要介绍了相差积分法的超声波流量测量原理和实现方法,以及方案中所涉及到的热量计算、温度测量原理等;根据测量要求,设计了以MSP430F437为控制核心的硬件测试电路。由于热量表需用电池供电,为了保证热量表的长期运行,在硬件和软件上都进行了低功耗设计。最后,对整个系统进行了联机调试和测试实验,并对流量测量结果作了简单的误差分析。

150例血尿相差显微镜法与UF-100法尿红细胞形态检查结果比较分析

目的探讨相差显微镜法和UF-100法检测尿红细胞(RBC)形态的符合率以及这两种方法和临床诊断的符合率。方法用相差显微镜和UF-100同时检测150例已经明确临床诊断的血尿标本的尿RBC形态。结果两种方法检测各型RBC的符合率分别是90.7%、92.0%、75.0%;两种方法检测结果和临床诊断的符合率分别是93.5%、94.7%和89.2%、87.7%。结论相差显微镜法和UF-100法检测尿RBC形态的符合率以及这两种方法和临床诊断的符合率较高,相关性较好(P<0.01)。

UF-1000i尿有形成分分析仪和相差显微镜法对血尿来源定位的方法学评价

目的:以肾脏病理活检结果作为金标准,评价UF-1000i尿有形成分分析仪和相差显微镜法诊断血尿来源的敏感性和特异性。方法:287例肾病理活检确诊为肾小球病变患者,肾活检前用UF-1000i分析法和尿相差显微镜检查结果,分别进行CUTOFF值的确定和检测性能的计算。结果:UF-1000i分析法检查结果:红细胞计数最小值为25个/μL,最大值为3 554个/μL,中位数为63个/μL;P70红细胞中位数为52个/μL;非均一型尿报警提示占80%。相差显微镜结果:红细胞计数最小值为8个/μL,最大值为825个/μL,中位数为55个/μL,非均一红细胞中位数为44个/μL。显微镜法的敏感性为97%,特异性为89.2%。AUC的面积为0.943,判断肾小球血尿诊断界值为:非均一型红细胞所占的比值>69%。UF-1000i分析法的敏感性为92.3%,特异性为86.8%,AUC的面积为0.928。判断肾小球血尿的诊断界值为:RBC-P70FSC 75.0ch。这两种方法的检测结果差异有统计学意义(χ2=24.397,P<0.01)。结论:血尿来源定位肾活检是金标准,相差显微镜法和UF-1000i分析法对血尿来源的定位都是比较理想的诊断实验。相差显微镜法的敏感性和特异性优于UF-1000i分析法;相差显微镜法繁琐费时,UF-1000i操作简便快速,结果准确,自动化程度高,值得广泛应用于临床。

一种基于软件无线电技术的变频系统群时延精确测量方法

对变频系统群时延的精确测量,一直是测量领域的难题,尤其是外本振无法接入的变频系统,测量精度较低的调制法几乎成了测量其群时延的唯一选择。本文从群时延定义出发,提出了一种全新的群时延测量方法——基于软件无线电技术的双频相差法,该方法特别适用于外本振无法接入的变频系统群时延的精确测量。本文详细说明了双频相差法的基本原理,给出了实验测试系统的设计和测试方法。仿真测试结果表明双频相差法的测量精度比传统的调制法提高约一个数量级。

一种基于机器视觉的颜色识别算法的研究

介绍了一种颜色识别转换算法。在机器视觉系统中,对RGB和YUV两种不同颜色空间进行研究,应用相差法进行颜色识别,并对向量表中的结果进行优化。实验结果表明,该算法在保证精确度基本不变的前提下,进一步减少了运算量,对系统处理信号的实时性有很大改善。

基于相差统计的小电流单相接地选线新判据

小电流接地系统发生单相接地故障时,故障线路与健全线路在特征频段内零序电流的相位差别是接地选线判据的重要依据之一。文中在详细分析小电流单相接地故障暂态过程的基础上,提出了一种新的基于相差统计的小电流接地系统单相接地选线新判据。这种方法直接利用复小波提取各条线路零序电流各子频段信号的相位,借鉴统计学的方法计算出特征频段内线路间整体的相位差,通过对相位的直接比较选择出故障线路,充分利用了特征频段内的所有信息,计算方法简单可靠,抗干扰能力强,且判据不受系统接地方式、过渡电阻、合闸角的影响。仿真结果表明,这种方法能够可靠地选择出故障线路。

三种尿红细胞检测方法在肾性血尿诊断中的临床应用评价

目的:对肾性血尿(G.N)与非肾性血尿(N.G)进行临床鉴别诊断。方法:尿沉渣镜检为血尿的51例肾性血尿标本和65例非肾性血尿标本分别采用相差显微镜观察尿中红细胞形态。Sysmex UF-1000i全自动尿沉渣分析仪检测尿红细胞均一性和非均性分布;尿红细胞微柱凝胶直接抗人球蛋白法检测被免疫球蛋白致敏的尿红细胞。结果:相差显微镜法特异性为83.0%,敏感性为84.3%;Sysmex UF-1000i全自动尿沉渣分析仪的特异性为66.2%,敏感性为90.2%;尿红细胞微柱凝胶直接抗人球蛋白法的特异性为70.8%,敏感性为86.3%;三种方法联合检测的特异性为70.9%,敏感性为96.1%。Sysmex UF-1000i全自动尿沉渣分析仪检测法与尿红细胞微柱凝胶直接抗人球蛋白法组合,其特异性为73.8%,敏感性为88.2%。结论:三种方法对判断肾性血尿准确性存在差异,以相差显微镜法的特异性最高,两两组合中,相差显微镜法联合尿红细胞微柱凝胶直接抗人球蛋白检测的敏感性最高。

调频连续波雷达测距算法综述

为了解连续波雷达测距精度的影响因素,开展了两个主流算法与补偿算法的研究,提到了泰勒级数建模和人工神经网络算法的相关改进,展望了雷达与人工智能和交通领域等更集成化的发展趋势。

三种方法对鉴别血尿来源的比较

血尿是一种常见的临床症状，但要正确判断血尿的来源常常遇到困难。随着实验诊断技术的发展，已有多种鉴别血尿来源的方法为临床采用，但其方法间的比较，尚未见报道。本文目前公认较好的尿中红细胞染色法，相差显微镜法和血细胞分析仪测定尿中红细胞体积极（MCV）及分布曲线法，

围隔实验中海洋浮游植物对石油烃污染物中正构烷烃的生物富集

本文应用海洋围隔生态实验研究了浮游植物对石油烃污染物生物富集动力学过程 ,提出了“水相差法”测定海洋浮游植物体内石油烃浓度 ,以及包括石油烃挥发和生物生长等影响因素的石油烃生物富集动力学模型 ,并利用非线性拟合技术得到了海洋浮游植物对 0 #柴油 WAF中正构烷烃的生物富集动力学参数 kup,kel和 BCFPOC,结果与 Kováts色谱保留指数具有很好的相关性 ,与利用生物分析平衡法测定的文献数据基本一致。本模型及实验方法简便可靠 ,可在现场实验中广泛应用 ,得到的动力学参数应用于多介质环境模型和生态动力学模型 。

GNSS接收机抗干扰电路的硬件实现

针对全相位FFT/FFT(apFFT/FFT)综合相差法硬件资源和功耗大的问题,基于FFT算法求解最大峰值谱线位置仅与各谱线峰值相对大小有关的特点,提出一种用于减少FFT电路面积的阈值判断移位方法.首先对apFFT/FFT综合相差法与修正Rife算法进行性能比较;然后利用阈值判断移位方法对apFFT/FFT综合相差法硬件实现中的FFT运算结构进行改进,称为改进apFFT/FFT算法,使FFT计算位宽减少1/2;最后将改进的apFFT/FFT综合相差法硬件结构应用到GNSS抗干扰模块的电路实现中,并利用FPGA进行抗干扰功能验证.结果表明,在基本不降低频率估计精度下,改进apFFT/FFT算法可以减少约50%的面积资源和功耗;在接近相同面积资源和功耗下,改进apFFT/FFT算法的频率估计精度约为修正Rife算法的2倍;GNSS抗干扰硬件模块具备良好的滤除干扰能力.

Precipitation kinetics of 2519A aluminum alloy based on aging curves and DSC analysis

The precipitation kinetics of 2519 A aluminum alloy after different cold rolling reductions before aging was investigated by hardness test and differential scanning calorimetry（DSC）. The activation energy was calculated according to DSC curves using single heating rate method. The microstructures of as-rolled and peak-aged alloys were observed by transmission electron microscopy（TEM）. The result shows that the age hardenability reduces and the activation energy rises with increasing the reduction from 7% to 40%. Nonuniform dislocations are found in as-rolled alloy and inhomogeneous distribution of θ′ phase is revealed in peak-aged alloy when the reduction is 15%. The inhomogeneous distribution of θ′ phase may be related to the age hardenability reducing and activation energy rising.

LARGE-EDDY SIMULATION OF TWO-PHASE REACTING FLOW IN MODEL COMBUSTOR

The gas-droplet two-phase reacting flow in a model combustor with the V-gutter flame holder is studied by an Eulerian-Lagrangian large-eddy simulation (LES) approach. The k-equation subgrid-scale model is used to simulate the subgrid eddy viscosity, and the eddy-break-up (EBU) combustion subgrid-scale model is used to determine the chemical reaction rate. A two-step turbulent combustion subgrid-scale model is employed for calculating carbon monoxide CO concentration, and the NO subgrid-scale pollutant formation model for the evaluation of the rate of NO formation. The heat flux model is applied to the prediction of radiant heat transfer. The gas phase is solved with the SIMPLE algorithm and a hybrid scheme in the staggered grid system. The liquid phase equations are solved in a Lagrangian frame in reference of the particle-source-in-cell (PSIC) algorithm. From simulation results, the exchange of mass, moment and energy between gas and particle fields for the reacting flow in the afterburner with a V-gutter flame holder can be obtained. By the comparison of experimental and simulation results, profile temperature and pollutant of the outlet are quite in agreement with experimental data. Results show that the LES approach for predicting the two-phase instantaneous reacting flow and pollutant emissions in the afterburner is feasible.

Analysis of Test Methods for Parts to Follow Relative Requirements

Testing the parts of mechanical products and ensuring their accuracy to the design requirements are essential to products’ quality, market competitiveness and manufacturers’ maximum economical benefits from these products. One of the latest subjects of study in the area of precision measurement is the testing of parts to follow the relative requirements, viz. design requirements for the size tolerance of size features and related geometrical tolerances of the central feature, including the envelope requirement, maximum material requirement and least material requirement. The article analyzes test methods for parts to follow the envelope requirement or maximum material requirement, as well as further requirements of geometrical tolerances for its central feature. The method is effective in improving product quality and rejecting unqualified parts.

Phase aberration correction in ultrasonic phased array non-destructive testing systems

Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in various fields, the problem of phase aberrations in the process of NDT testing is considered. The technique of cross-covariance for phase aberration correction is presented. The performance of the technique for phase aberration correction is tested by means of echo signals obtained in practical non-destructive testing experiment. The results show that the technique has the better accuracy of phase correction.

Determination of Trace Elements in Potatoes by Flame Atomic Absorption Spectrometry

[Objective] This study aimed to analyze the contents of trace elements in potatoes from different production areas in Qinghai Province. [Method] By flame atomic absorption spectrometry （FAAS）, the contents of various trace elements in potatoes were determined. [Result] Potatoes contain abundant trace elements such as Cu, Zn, Fe, Mn, Ca, K and Mg. To be specific, the contents of Ca, K and Mg were relatively high. [Conclusion] By using FAAS, the relative standard deviation was 1.17%-2.75% and the recovery rate was 97%-99.5%, indicating accurate and reli-able results with high precision.

Phase Difference Method for DOA Estimation

The phase difference method (PDM) is presented for the direction of arrival (DOA) estimation of the narrowband source. It estimates the DOA by measuring the reciprocal of the phase range of the sensor output spectra at the interest frequency bin. The peak width and variance of the PDM are presented. The PDM can distinguish closely spaced sources with different and unknown center frequencies as long as they are separated with at least one frequency bin. The simulation results show that the PDM has a better resolution than that of the conventional beamforming.

Effects of liquefaction-induced large lateral ground deformation on pile foundations

The pile-soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method.Considering an elastic-plastic subgrade reaction method,numerical methods involving finite difference approach of pile in liquefaction-induced lateral spreading ground were derived and implemented into a finite difference program.Based on the monotonic loading tests on saturated sand after liquefaction,the liquefaction lateral deformation of the site where group piles are located was predicted.The effects of lateral ground deformation after liquefaction on a group of pile foundations were studied using the fmite difference program mentioned above,and the failure mechanism of group piles in liquefaction-induced lateral spreading ground was obtained.The applicability of the program was preliminarily verified.The results show that the bending moments at the interfaces between liquefied and non-liquefied soil layers are larger than those at the pile＇s top when the pile＇s top is embedded.The value of the additional static bending moment is larger than the peak dynamic bending moment during the earthquake,so in the pile foundation design,more than the superstructure＇s dynamics should be considered and the effect of lateral ground deformation on pile foundations cannot be neglected.