Uncertainty analysis of flow rate measurement for multiphase flow using CFD

The venturi meter has an advantage in its use,because it can measure flow without being much affected by the type of the measured fluid or flow conditions.Hence,it has excellent versatility and is being widely applied in many industries.The flow of a liquid containing air is a representative example of a multiphase flow and exhibits complex flow characteristics.In particular,the greater the gas volume fraction（GVF）,the more inhomogeneous the flow becomes.As a result,using a venturi meter to measure the rate of a flow that has a high GVF generates an error.In this study,the cause of the error occurred in measuring the flow rate for the multiphase flow when using the venturi meter for analysis by CFD.To ensure the reliability of this study,the accuracy of the multiphase flow models for numerical analysis was verified through comparison between the calculated results of numerical analysis and the experimental data.As a result,the Grace model,which is a multiphase flow model established by an experiment with water and air,was confirmed to have the highest reliability.Finally,the characteristics of the internal flow Held about the multiphase flow analysis result generated by applying the Grace model were analyzed to find the cause of the uncertainty occurring when measuring the flow rate of the multiphase flow using the venturi meter.A phase separation phenomenon occurred due to a density difference of water and air inside the venturi,and flow inhomogeneity happened according to the flow velocity difference of each phase.It was confirmed that this flow inhomogeneity increased as the GVF increased due to the uncertainty of the flow measurement.

Measurement uncertainty in pharmaceutical analysis and its application

The measurement uncertainty provides complete information about an analytical result. This is very important because several decisions of compliance or non-compliance are based on analytical results in pharmaceutical industries. The aim of this work was to evaluate and discuss the estimation of uncertainty in pharmaceutical analysis. The uncertainty is a useful tool in the assessment of compliance or non-compliance of in-process and final pharmaceutical products as well as in the assessment of pharmaceutical equivalence and stability study of drug products.

Identifying uncertainty sources in measurements-A methodology

The overall purpose of performing measurements in science is to increase knowledge and document about some physical quantity. The measurand has a true value but, except for straightforward counting situations, the true value can never be fully determined. When a quantity is measured, the outcome depends on the measuring system, the measurement procedure, the skill of the operator, the environment and other effects. In practice the uncertainty on the result may arise from many possible sources, including examples such as incomplete definition, sampling, matrix effects and interferences, environmental couditions, uncertainties of weights and volumetric equipment, reference wtlues, approximations and assump- tions incorporated in the measurement method and procedure, and random wlriation. The objective of the paper is how to identify the sources of uncertainty in measurement and their importance on the result.

Borehole trajectory uncertainty and its characterization

To solve the problem of borehole trajectory uncertainty, some methods such as error ellipsoid posture characterization, sectional error ellipse solution and error elliptic cylinder construction were proposed and an application example was given. According to the definition of inclination, azimuth and tool-face angle, a characterization method of error ellipsoid posture of borehole trajectory was presented. By intercepting the error ellipsoid with an arbitrary plane in space, the general concept and algorithm of sectional error ellipse were established to analyze the borehole trajectory errors in horizontal plane, plumb plane, normal plane, etc. Based on the theory of surface tangency and curve projection, a construction method of error elliptic cylinder of borehole trajectory was put forward to evaluate the axial enveloping error of borehole trajectory and its variation along well depth. The research shows that the deeper the well, the greater the borehole trajectory error will be. In deep and ultra-deep wells measured using conventional measurement while drilling(MWD),the borehole trajectory position error reaches tens of meters. The research results provide a complete set of analysis methods for borehole trajectory error, which can evaluate the accuracy and reliability of borehole trajectory monitoring.

Uncertainty analysis of measured geometric variations in turbine blades and impact on aerodynamic performance

Inevitable geometric variations significantly affect the performance of turbines or even that of entire engines;thus,it is necessary to determine their actual characteristics and accurately estimate their impact on performance.In this study,based on 1781 measured profiles of a typical turbine blade,the statistical characteristics of the geometric variations and the uncertainty impact are analyzed,and some commonly used uncertainty modelling methods based on Principal-Component Analysis(PCA)are verified.The geometric variations are found to be evident,asymmetric,and non-uniform,and the non-normality of the random distributions is non-negligible.The performance is notably affected,which is manifested as an overall offset,a notable scattering,and significant deterioration in several extreme cases.Additionally,it is demonstrated that the PCA reconstruction model is effective in characterizing major uncertainty characteristics of the geometric variations and their impact on the performance with almost the first 10 PCA modes.Based on a reasonable profile error and mean geometric deviation,the Gaussian assumption and stochasticprocess-based model are also found to be effective in predicting the mean values and standard deviations of the performance variations.However,they fail to predict the probability of some extreme cases with high loss.Finally,a Chi-square-based correction model is proposed to compensate for this deficiency.The present work can provide a useful reference for uncertainty analysis of the impact of geometric variations,and the corresponding uncertainty design of turbine blades.

Analysis of the Intrinsic Uncertainties in the Laser-Driven Iron Hugoniot Experiment Based on the Measurement of Velocities

One of the most challenging tasks in the laser-driven Hugoniot experiment is how to increase the reproducibility and precision of the experimental data to meet the stringent requirement in validating equation of state models. In such cases, the contribution of intrinsic uncertainty becomes important and cannot be ignored. A detailed analysis of the intrinsic uncertainty of the aluminum-iron impedance-match experiment based on the measurement of velocities is presented. The influence of mirror-reflection approximation on the shocked pressure of Fe and intrinsic uncertainties from the equation of state uncertainty of standard material are quantified, Furthermore, the comparison of intrinsic uncertainties of four different experimental approaches is presented. It is shown that, compared with other approaches including the most widely used approach which relies on the measurements of the shock velocities of AI and Fe, the approach which relies on the measurement of the particle velocity of Al and the shock velocity of Fe has the smallest intrinsic uncertainty, which would promote such work to significantly improve the diagnostics precision in such an approach.

Erratum:Measurement of(n,α)and(n,2n)reaction cross sections at a neutron energy of 14.92±0.02 MeV for potassium and copper with uncertainty propagation,[A.Gandhi,Aman Sharma,Rebecca Pachuau et al.,Chin.Phys.C 46,014002(2022)]

Experimentally measured neutron activation cross sections are presented for the^(65)Cu(n,α)^(62m)Cu,^(41)K(n,α)^(38)Cl,and^(65)Cu(n,2n)^(64)Cu reactions with detailed uncertainty propagation.The neutron cross sections were measured at an incident energy of 14.92±0.02 MeV,and the neutrons were based on the t(d,n)αfusion reaction.The^(27)Al(n,α)^(24)Na reaction was used as a reference reaction for the normalization of the neutron flux.The pre-calibrated lead-shielded HPGe detector was used to detect the residues'γ-ray spectra.The data from the measured cross sections are compared to the previously measured cross sections from the EXFOR database,theoretically calculated cross sections using the TALYS and EMPIRE codes,and evaluated nuclear data.

Uncertainty analysis of forest carbon sink forecast with varying measurement errors:a data assimilation approach

Aims Accurate forecast of ecosystem states is critical for improving natural resourcemanagement and climate change mitigation.Assimilating observed data into models is an effective way to reduce uncertainties in ecological forecasting.However,influences ofmeasurement errors on parameter estimation and forecasted state changes have not been carefully examined.This study analyzed the parameter identifiability of a process-based ecosystem carbon cycle model,the sensitivity of parameter estimates and model forecasts to the magnitudes of measurement errors and the information contributions of the assimilated data to model forecasts with a data assimilation approach.Methods We applied a Markov Chain Monte Carlo method to assimilate eight biometric data sets into the Terrestrial ECOsystemmodel.The data were the observations of foliage biomass,wood biomass,fine root biomass,microbial biomass,litter fall,litter,soil carbon and soil respiration,collected at the Duke Forest free-air CO_(2)enrichment facilities from 1996 to 2005.Three levels ofmeasurement errorswere assigned to these data sets by halving and doubling their original standard deviations.Important Findings Results showed that only less than half of the 30 parameters could be constrained,though the observations were extensive and themodelwas relatively simple.Highermeasurement errors led to higher uncertainties in parameters estimates and forecasted carbon(C)pool sizes.The longterm predictions of the slow turnover pools were affected less by the measurement errors than those of fast turnover pools.Assimilated data contributed less information for the pools with long residence times in long-term forecasts.These results indicate the residence times of C pools played a key role in regulating propagation of errors from measurements to model forecasts in a data assimilation system.Improving the estimation of parameters of slowturnover C pools is the key to better forecast long-term ecosystem C dynamics.

Measurement of(n,α)and(n,2n)reaction cross sections at a neutron energy of 14.92±0.02 MeV for potassium and copper with uncertainty propagation

Experimentally measured neutron activation cross sections are presented for the ^(65)Cu(n,0)^(62m)Cu,^(41) K(n,a)^(38C)l,and ^(65)Cu(n.2n)^(64)Cu reactions with detailed uncertainty propagation.The neutron cross secions were measured at an incident energy of 14.92±0.02 MeV,and the neutrons were based on the(d,n)a fusion reaction.The ^(27) Al(n,a)^(24)Na reaction was used as a reference reaction for the normalization of the neutron flux.The pre-calib-rated lead-shielded HPGe detector was used to detect the residues'γ-ray spetra.The data from the measured cross sections are compared to the previously measured cross sections from the EXFOR database,theoretically calculated cross sections using the TALYS and EMPIRE codes,and evaluated nuclear data.

Uncertainty analysis of a pavement reflectance measurement system based on a gonio-photometer

A pavement reflectance measurement system is established based on a gonio-photometerexisting by chang- ing a bracket to carry the road sample and luminance meter, adding a collimated light source to provide incident light. This automated system could finish the reflection measurement of a road sample in 4 h. An uncertainty budget of this measurement system is made and the combined standard uncertainty of Q0 is 5.26%.

计及源荷不确定性的电力系统静态电压稳定极限预警方法研究

针对源荷双侧不确定性问题,对电力系统静态电压稳定极限进行预警研究。首先通过数学推导与理论分析证明快慢系统在分叉及噪声双重诱导发生临界转变的过程中,系统变量的方差系数趋势变化显著。由于存在噪声诱导失稳,电压变化趋势观测难度增大,固定阈值趋势检测方法会失效。其次,对新能源电力系统节点电压的临界转变特点和扰动情况进行分析,提出基于临界转变电压崩溃预警方法。针对噪声导致的趋势预测困难问题,基于量测数据,利用贝叶斯变点检测,对节点电压的方差进行实时监测,并根据贝叶斯变点检测得到的概率在趋势发生显著变化之初预警节点电压崩溃,并通过仿真计算验证该方法的有效性。

阿勒泰市移动源排放清单及时空分布特征

通过“自上而下”调查方式获取移动源活动水平,采用排放因子法建立了阿勒泰市移动源排放清单,并进行移动源排放的时空特征分析和清单不确定性分析。结果表明,2021年阿勒泰市移动源9种大气污染物排放总量,CO为669.12 t,NO_(x)为617.92 t,SO_(2)为29.85 t,NH_(3)为32.61 t,VOCs为136.35 t,PM_(2.5)为35.74 t,PM_(10)为38.06 t,BC为20.33 t,OC为6.41 t。其中,CO、SO_(2)、NH_(3)、VOCs主要来源于载客汽车,贡献率均超过40%;NO_(x)主要来源于农业机械和载货汽车,贡献率均超过30%;PM_(2.5)、PM_(10)、BC、OC主要来源于农业机械,贡献率均超过75%。时空分布特征表现为6—8月排放量最高,人口密集的市区排放量高于其他区域。移动源9种污染物排放清单不确定性均在−39.23%~56.27%以内,本清单计算结果相对可靠。

电池热释放烟气分析系统的校准

提出电池热释放烟气分析系统的校准方法。采用氧气、二氧化碳、一氧化碳、氢气、甲烷标准物质进行试验,选取示值误差、重复性、响应时间、零点漂移和量程漂移作为校准项目,建议计量技术指标:每种气体在量程内,示值误差为±3.0%,重复性不大于1.5%,响应时间不大于30 s,零点漂移和量程漂移均为±2.0%。通过校准实例对校准方法进行验证,验证结果表明该校准方法切实可行,可为该类设备计量技术规范的制订提供参考。

本科量子物理实验课程探索

近20年,国际量子科技取得重大进展,在未来科技发展中占据重要地位.因此,在物理专业本科实验教学中设置量子物理实验,让学生深入理解微观量子物理基本原理,掌握一定的量子前沿技术非常必要.华东师范大学物理学专业自主开发量子物理本科实验教学仪器和虚拟仿真实验,在物理学专业拔尖班开设量子物理实验,取得了优异的成果.本文详细介绍了华东师范大学量子物理实验课程设置以及实施过程,分析开展相关本科量子物理实验的可能性及其普及性,为全国高校开设量子物理实验课程提供参考.

气体减压器用压力表示值误差测量不确定度评定及自动计算

针对气体减压器校准规范给出压力表示值误差测量不确定度评定实例,结合气体减压器校准的实际情况,重点分析了评定实例的评定方法,指出评定方法的不足,并提出优化方法。根据优化后的评定实例计算过程,通过Excel设计了自动计算公式,校准人员只需输入测量值和被检表相关信息即可实现测量不确定度的自动计算,极大地提高了校准效率。

碳排放清单在天然气场站应用的不确定性研究

温室气体清单编制指南为有效推进节能减排措施提供了重要参考和政策支撑,但目前各清单标准不一、推荐缺省值的偏差是碳排放计算误差的主要来源。从计算方法的角度建立研究排放清单不确定性的模型,通过对比采用蒙特卡洛模拟法和拉丁超立方抽样法对不确定性因素进行模拟的结果;提出采用消减技术找到具有代表性典型数据的方法,改善仅采用平均值计算碳排放量带来的误差。将模型应用于阿克苏管理站2022年碳排放计算中,依据不同清单计算造成的碳排放不确定度在1%~4%,采用不确定性模型计算的碳排放结果比确定性模型计算的碳排放量少,更具代表性,有助于企业更早实现“双碳”目标。

Inverse uncertainty characteristics of pollution source identification for river chemical spill incidents by stochastic analysis

Identifying source information after river chemical spill occurrences is critical for emergency responses.However,the inverse uncertainty characteristics of this kind of pollution source inversion problem have not yet been clearly elucidated.To fill this gap,stochastic analysis approaches,including a regional sensitivity analysis method,identifiability plot and perturbation methods,were employed to conduct an empirical investigation on generic inverse uncertainty characteristics under a well-accepted uncertainty analysis framework.Case studies based on field tracer experiments and synthetic numerical tracer experiments revealed several new rules.For example,the release load can be most easily inverted,and the source location is responsible for the largest uncertainty among the source parameters.The diffusion and convection processes are more sensitive than the dilution and pollutant attenuation processes to the optimization of objective functions in terms of structural uncertainty.The differences among the different objective functions are smaller for instantaneous release than for continuous release cases.Small monitoring errors affect the inversion results only slightly,which can be ignored in practice.Interestingly,the estimated values of the release location and time negatively deviate from the real values,and the extent is positively correlated with the relative size of the mixing zone to the objective river reach.These new findings improve decision making in emergency responses to sudden water pollution and guide the monitoring network design.

严重事故工况下反应堆热工水力参数对源项释放行为影响研究

为了进一步研究反应堆严重事故进程中热工参数对源项释放的影响,识别对其影响较大的物理过程,从而进一步改进和发展数值模型以提高计算精度降低不确定性,以第三代压水堆为对象,利用一体化严重事故分析程序ISAA对大破口失水事故导致的严重事故开展了数值分析研究,并基于Wilks公式利用自主开发的不确定性程序代码SAUP对17个热工参数进行了拉丁超立方抽样(LHS)执行批量计算,对目标输出(FoM)即氢气与裂变产物的释放进行了不确定性与敏感性分析。结果表明:在热工参数的不确定性范围内,氧化产氢以及裂变产物的释放呈现正态分布且存在较大的不确定带,包壳氧化层的失效温度、堆芯碎片尺寸以及碎片孔隙率对高挥发性裂变产物的释放有较为显著的相关性。该研究有助于理解反应堆严重事故中热工参数与源项之间的复杂联系,同时对核电厂安全系统的设计以及严重事故的预防与缓解具有参考意义。

基于物理水平基准的组合式高程测量方法

针对空间坐标点相对于测量基准的高程测量准确性问题,提出一种基于物理水平基准的组合式高程测量方法。利用激光三角测量原理及其测量光路的几何特性,搭建了物理水平基准的高程测量系统,在朗伯散射光场中,分析了倾角变化对激光光能质心偏移量的影响,建立了相应的误差修正模型,利用倾角传感器实现了高程测量的倾角误差补偿,自主研制了标定平台对本文提出的高程测量系统进行标定验证试验。结果表明:本文提出的组合式高程测量方法能够在500 mm测量量程下将重复性测量误差控制在±20μm的波动范围内,相较于单一激光位移传感器测量方式,其组合式高程测量误差波动量大幅度降低,能够适应空间坐标点在任意姿态下的精准测量,有效改善激光位移传感器在高程测量领域的性能,使其测量结果更为真实有效。

地面目标的中波红外高光谱成像特性测量

利用Telops公司设计的Hyper-Cam中波高光谱成像仪对水泥地上某坦克模型进行3~5μm波段的红外高光谱成像测量。对实验数据进行了逐像素点的大气校正。基于矫正后的实验数据,分析了仪器误差、随机误差、大气校正传递误差等对测试不确定度的影响。分析了该坦克模型在不同谱段上的亮度分布和模型上不同部位的光谱分布特性。结果表明:在波数为2000~3000 cm-1波段,其相对不确定度一直稳定在10%以内,但是在大于3000 cm-1的波段,其误差迅速上升,主要因为常温物体的中波辐射低,在该波段目标辐射与大气路程辐射接近,而引起的噪声增大,造成的测试信噪比降低。该坦克模型光谱辐射亮度测试数据的平均相对不确定度在20%以内,整体误差较低。光谱分布上,坦克各部分特征点和水泥地表的光谱辐射亮度在波长为4.2~5μm波段时的差异性比波长为3.0~4.2μm波段时的差异性更大,且探测器接收到的4.2~5μm波段的光谱辐射亮度要大于3.0~4.2μm的光谱辐射亮度。由于4.3μm波段处于大气吸收带,大气透射率几乎为0,以至于无法获得目标的光谱辐射亮度的真实测量值。空间分布上,模型的辐射亮度主要集中在侧边涂层上,炮口处和履带处的辐射亮度较小。目标各部位辐射亮度分布与周边水泥地表的辐射亮度有着明显差异性。在3~5μm的辐射亮度中,4.4~4.8μm波段的辐射亮度占比较高,该波段成像效果最好。3.2~3.8μm波段的辐射亮度占比较低,该波段成像效果较差。处于大气吸收带的4.2~4.4μm波段,由于大气透射率几乎为0,无法获得其准确的空间辐射亮度分布。研究表明该拓展中波高光谱成像仪在地面目标的中波红外高光谱成像特性研究上具有目标区分精确、误差小、“图像光谱合一”的特点,测试数据可以应用于目标的红外高光谱隐身设计、目标的分类与识别等领域。