• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1201-1206
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• 2003

A measurement device for gas flow rate using hot-wire module is developed for the utilization in low-accuracy industrial applications. The module has three wires of measuring and heating, and a bridge circuit is installed to detect electric current through the wire in the module. An amplification of the signal and conversion to digital output are conducted for the online measurement with a personal computer. In addition, temperature distribution in the module is numerically analyzed to examine the measured outcome from the module experiment. The flow rate of air and carbon dioxide gas is separately measured for the performance examination of the device. The experimental relation of measurement and flow agrees with the prediction from the numerical analysis. The outcome of the performance test indicates that the accuracy and reproducibility of the module is satisfactory for the purpose of industrial applications.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.427-427
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• 2021

During the rainy season, heavy downpours are always a source of concern for the world. Flooding and heavy rains can devastate communities, disrupt agriculture, and contribute to traffic accidents.. Weir and flow hall effect sensors are the conventional analytical methods for measuring flow rate; in this paper, we analyzed manhole flowrate statistics. The measurement of the flow rate of a notch/weir is a time-consuming task that necessitates continuous mathematical analysis. . We created three types of IoT sensors in this study: (HC-SR04 ultrasonic, YF-S201 magnetic, and HB100 radar), which take the sensor's real-time input signal and estimate the flow using a notch equation and a previously calibrated optimized coefficient of discharge. The proposed systems are cost-effective, but in terms of accuracy, we found that the HC-SR04 ultrasonic sensor is the best of the three systems

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.222-227
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• 1998

The paper proposes a new method for measuring the flow ripple generated by an axial piston pump and motor in a hydrostatic transmission. The method is based on dynamic characteristics between pressure and flow ripple in the pipeline. Also, the self-checking functions develop for the evaluation of accuracy and dynamic response of estimated results by the method proposed here. The experiment carry out open circuit type hydrostatic transmission. By using the self-checking functions, the validity of the method is investigated by comparison with the measured and estimated flow and pressure ripples, and good agreement is achieved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.218-225
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• 2008

When the heat release and acoustic pressure fluctuations are generated in the combustor by irregular combustion, these fluctuations affect the mass flow rate of the propellants injected through the injectors. Also, the variations of the mass flow rate by these fluctuations again bring about irregular combustion and furthermore that is related with combustion instability. Therefore, it is very important to identify the mass variation for the pressure fluctuation on the injector and to investigate its transfer function. So, we first have studied quantifying the variation of mass flow rate generated in simplex swirl injector by injection pressure fluctuation. To acquire the transient mass flow rate in orifice with time, we have tried to measure of the flow axial velocity and liquid film thickness in orifice. The axial velocity is acquired through theoretical approach after measuring the pressure in orifice and the flow area in the orifice is measured by electric conductance method. As results, mass flow rate calculated by axial velocity and liquid film thickness measuring in orifice accorded with mass flow rate acquired by direct measuring method in the small error range within 1 percents in steady state and within 6 percents as average mass flow rate in pulsated state. Hence this method can be used to measure the mass flow rate not only in steady state but also in unsteady state because the mass flow rate in the orifice can acquire with time and this method shows very high accuracy based on the experimental results.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.97-105
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• 1999

Orifice flow meters are frequently used for measuring gas flow in gas industry. However, to insure the accuracy of the measurement, a certain length of the meter run at the upstream of the flow meter is required. The objective of this study is to analyze flow measurement errors of the orifice flow meter quantitatively for shorter lengths of the meter runs than those suggested in the standard manuals with variation of diameter ratio( $\beta$ ratio) and flow rate. The test results showed that the flow measurement errors of the orifice meter were inversely proportional to the diameter ratio. In other words, when the diameter ratio is 0.3 and 0.7, the measurement error is $-7.3\%$ and $-3.5\%$, respectively. the main reason of the measurement error is due to the swirl effect from the configuration of the meter run at the upstream of the flow meter. In case the length of the meter run is shorter than that suggested in the standard manuals, the swirl effect is not removed completely and it affects the flow meter's performance. As mentioned above, the less the pipe diameter ratio, the more the flow measurement error. It means that the swirl effect on the orifice meter increases as the $\beta$ ratio decreases.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.16-23
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• 2003

Keeping the layer thickness constant is very essential for improving the shape accuracy in the stereolithography process. The layer thickness is created by recoating process, and also affected by recoating parameters such as blade speed and thickness. The created layer in this process can determine the whole accuracy of the entire parts. The aim of this paper is to improve the accuracy of the layer thickness by adjusting the recoating process parameters. Several experiments with different recoating conditions are Performed to find the optimal recoating parameters that produce the most accurate layer thickness. The effective recoating method is suggested by measuring and analyzing the cured layer thickness.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.212-212
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• 2000

This study was performed to construct a hot strip speed measuring system and check over whether the measured speed can be used for improving the mass flow of the head-end part of a hot strip in the 7-stand finishing mill. Because the mass flow in hot rolling mill affects the looper operation and the thickness and width control of a strip, accurate measurement of strip speed ie important. The measured speed was compared with the roll speeds of No. 6 and No.7 stand to check the performance of the system and analyzed to find how to apply the speed. As a result, it is shown that the accuracy of the system is enough, strip thickness error can be reduced by -275∼+200$\mu\textrm{m}$ using the measured speed and the existing FSU model has low accuracy for predicting forward slip rate. A neural network was developed to calculate forward slip rate instead of FSU model. The test result of the neural network shows that the neural network is more accurate than the FSU model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.305-306
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• 2007

• Journal of the Korean Society of Visualization
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• v.12 no.1
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• pp.35-42
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• 2014

Magnetic resonance velocimetry (MRV) is a versatile flow visualization technique using magnetic resonance imaging machine developed for the medical purpose. Recently, MRV is often utilized to analyze engineering flows due to its superior features of MRV such as capabilities of measuring flows with complicated, opaque flow geometry unlike optical techniques, 3-dimensional volumetric velocity vectors within a few hours, and etc. The purpose of this study was to validate the MRV data and evaluate the accuracy of the mean velocity profiles that we acquired for a turbulent flow in a circular pipe using a MR machine installed in Korea Basic Science Institute, Ochang, Korea. In addition, we briefly describe a procedure of parameter optimization for the operation of MRV. The results indicate that the MRV measurements provided well resolved mean velocity fields with a quite reasonable accuracy according to the inner and outer layer scaling laws of the turbulent pipe flows.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.6
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• pp.1649-1667
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• 2012

In order to improve the accuracy and universality of the flow metric correlation analysis, this paper firstly analyzes the characteristics of Internet flow metrics as random variables, points out the disadvantages of Pearson Correlation Coefficient which is used to measure the correlation between two flow metrics by current researches. Then a method based on Symmetrical Uncertainty is proposed to measure the correlation between two flow metrics, and is extended to measure the correlation among multi-variables. Meanwhile, the simulation and polynomial fitting method are used to reveal the threshold value between different correlation degrees for SU method. The statistical analysis results on the common flow metrics using several traces show that Symmetrical Uncertainty can not only represent the correct aspects of Pearson Correlation Coefficient, but also make up for its shortcomings, thus achieve the purpose of measuring flow metric correlation quantitatively and accurately. On the other hand, reveal the actual relationship among fourteen common flow metrics.