scholarly journals Efficient semiparametric inference for two‐phase studies with outcome and covariate measurement errors

2020 ◽  
Vol 40 (3) ◽  
pp. 725-738
Author(s):  
Ran Tao ◽  
Sarah C. Lotspeich ◽  
Gustavo Amorim ◽  
Pamela A. Shaw ◽  
Bryan E. Shepherd
Keyword(s):  
Measurement Errors ◽  
Two Phase ◽  
Semiparametric Inference ◽  
Covariate Measurement Errors

scholarly journals Study on Weight Function Distribution of Hybrid Gas-Liquid Two-Phase Flow Electromagnetic Flowmeter

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1431 ◽  
Author(s):  
Yulin Jiang
Keyword(s):  
Weight Function ◽  
Green’S Function ◽  
Green's Function ◽  
General Model ◽  
Measurement Errors ◽  
Two Phase Flow ◽  
Electromagnetic Flowmeter ◽  
Phase Flow ◽  
Two Phase ◽  
Function Distribution

The electromagnetic flowmeter is usually used for single-phase fluid parameter measurement. When the measured fluid is gas-liquid two-phase flow, the geometry of the sensor measurement space will change with the movement of the gas, which will cause measurement errors. The weight function distribution is an important parameter to analyze such measurement errors. The traditional method for calculating the weight function of gas-liquid two-phase flow involves complex dimensional space transformation, which is difficult to understand and apply. This paper presents a new method for calculating the weight function of the gas-liquid two-phase flow electromagnetic flowmeter. Firstly, based on the measurement principle of the electromagnetic flowmeter, a general model of weight function of the gas-liquid two-phase flow electromagnetic flowmeter is built. Secondly, the bubbles in the fluid are regarded as the “isolated” points in the flow field. According to the physical connection between the “field” of the measured fluid and the “source” of the sensor electrode, the Green’s function expression based on gas-liquid two-phase flow is established. Then, combined with the boundary conditions of the measurement space of the electromagnetic flowmeter, the Green’s function is analyzed. Finally, the general model of weight function is solved by using the expression of Green’s function, then the expression of the weight function of the electromagnetic flowmeter is obtained when the measured fluid is hybrid gas-liquid two-phase flow. The simulation results show that the proposed method can reasonably describe the influence of the gas in the measured fluid on the output signal of the sensor, and the experimental results also indirectly prove the rationality of this method.

scholarly journals Accuracy of single-jet and multi-jet water meters under the influence of the filling process in intermittently operated pipe networks

2017 ◽  
Vol 18 (2) ◽  
pp. 679-687 ◽  
Author(s):  
David Walter ◽  
Miran Mastaller ◽  
Philipp Klingel
Keyword(s):  
Measurement Error ◽  
Measurement Errors ◽  
Distribution Systems ◽  
Air Flow ◽  
Pipe Network ◽  
Filling Process ◽  
Two Phase ◽  
Single Jet ◽  
Water Meters ◽  
The Impact

Abstract In many areas of the world water distribution systems are operated intermittently. The alternate filling and emptying of the pipe network leads to effects, which have negative impacts on water meter accuracy. For example, air that is present in the pipe network due to the emptying process must exit the network during the subsequent filling process. A part of this air is discharged through service connections and, thus, through water meters. In this paper, a study is presented in which the measurement error of single-jet and multi-jet water meters due to the filling process of an empty pipe is investigated experimentally. From the start of air flow to the steady-state flow of water, several causes of measurement errors can be distinguished, such as pure air flow, the impact of the water front on the impeller, the existence of two-phase flow or unsteady flow conditions. For both meter types, it has been discovered that the measurement error is mainly caused by the air flow. The experimental results show that up to 93% of the air volume in the pipe is registered by the water meters. Based on these results, an approach for estimating the measurement error for both meter types is presented.

scholarly journals Radioisotope measurement of selected parameters of liquid-gas flow using single detector system

2018 ◽  
Vol 180 ◽  
pp. 02124
Author(s):  
Marcin Zych ◽  
Robert Hanus ◽  
Marek Jaszczur ◽  
Volodymyr Mosorov ◽  
Dariusz Świsulski
Keyword(s):  
Void Fraction ◽  
Signal Analysis ◽  
Measurement Errors ◽  
Gas Flow ◽  
Gamma Ray ◽  
Time Delay Estimation ◽  
Dispersed Phase ◽  
Two Phase ◽  
Single Detector

To determine the parameters of two-phase flows using radioisotopes, usually two detectors are used. Knowing the distance between them, the velocity of the dispersed phase is calculated based on time delay estimation. Such a measurement system requires the use of two gamma-ray sealed sources. But in some situations it is also possible to determine velocity of dispersed phase using only one scintillation probe and one gamma-ray source. However, this requires proper signal analysis and prior calibration. This may also cause larger measurement errors. On the other hand, it allows measurements in hard to reach areas where there is often no place for the second detector. Additionally, by performing a previous calibration, it is possible to determine the void fraction or concentration of the selected phase. In this work an autocorrelation function was used to analyze the signal from the scintillation detector, which allowed for the determination of air velocities in slug and plug flows with an accuracy of 8.5%. Based on the analysis of the same signal, a void fraction with error of 15% was determined.

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