• Journal of the Korean Society of Safety
• /
• v.38 no.4
• /
• pp.1-7
• /
• 2023

The steel wheels of urban railway vehicles gather a lot of data through regular measurements during maintenance. However, limited research has been carried out utilizing this data, resulting in difficulties predicting the maintenance period. This paper studied a machine learning model suitable for mileage prediction by studying the characteristics of mileage change according to diameter and flange thickness changes. The results of this study indicate that the larger the diameter, the longer the travel distance, and the longest flange thickness is at 30 mm, which gradually shortened at other times. As a result of research on the machine learning prediction model, it was confirmed that the random forest model is the optimal model with a high coefficient of determination and a low root mean square error.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.438-442
• /
• 2003

For an efficient sliding mode control system stability and chattering avoidance should be guaranteed. A continuation method using boundary layer is well known as one solution for this. However since not only model uncertainties and disturbances but also control task itself is variable. it is practically impossible to set controller parameters - control discontinuity, control bandwidth, boundary layer thickness - in advance. In this paper first an adaptation law of control discontinuity is introduced to assure system stability and then fuzzy logic based tuning algorithm of design parameters is applied based on monitored performance indices of tracking error, control chattering, and model precision. In the end maximum control bandwidth not exciting unmodeled dynamics and minimum control discontinuity, boundary layer thickness making system stable and free of chattering are found respectively. This eliminates control chattering and enhances control accuracy as much as possible under given control situation. In order to demonstrate the validity of the proposed algorithm safe headway maintenance control for autonomous transportation system is simulated. The control results show that the proposed algorithm guarantees system stability all the time and tunes control parameters consistently and in consequence implements an efficient control in terms of both accuracy and actuator chattering.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.798-803
• /
• 2009

In this study, dimensionless correlations of frost properties (i.e. the thickness and surface temperature of frost) on heat exchanger fin with nonuniform temperature distribution are proposed from frosting experiments. We analyzed the local fin temperature distribution, frost thickness and frost surface temperature on a 2D fin; in the airflow direction and the direction perpendicular to airflow. As a result, the frost growth on the fin had a close relation with fin heat conduction. The dimensionless correlations for the average frost properties were expressed as a function of dimensionless temperature, humidity ratio, Reynolds number, and Fourier number. These correlations agreed well with experimental data with the error less than 14%.

• Journal of Periodontal and Implant Science
• /
• v.30 no.2
• /
• pp.483-490
• /
• 2000

The aim of this study was to analyze the reliability of an ultrasonic device(SDM) measuring soft tissue thickness in relation to tooth position, and to find factors which can influence the reliability. The results showed that 1. measurement error was the largest in the maxillary second molar position and the smallest in the mandibular central incisor position. 2. in a box whisker plot, the difference between two measurements was most widely distributed in molar positions. 3. in Pearson correlation analysis, the relationship between two measurements was the highest in the maxillary lateral incisor position and, the lowest in the maxillary second molar, mandibular first and second premolar position. 4. a stepwise multiple regression analysis could explain the difference of two measurements with various independent variables in 29.7% (P<0.0001). Gingival thickness was the only variable influencing the measurement difference in a statistically significant level(P<0.0001). It can be concluded that its high reliability, ease to use and patient comfort justified the application of the SDM in measurement of soft tissue thickness.

• Journal of the Korean Vacuum Society
• /
• v.16 no.4
• /
• pp.273-278
• /
• 2007

For the simulation of active region in the quantum cascade lasers (QCL), we solved Schrodinger equation utilizing Runge-Kutta method and Shotting method. Wavelength, phonon resonant energy, and dipole matrix element were simulated with the variation of active region thickness. As a result of such simulation, it was suggested the tolerance range of epi-layer thickness error when 3-quantum well QCL structures are grown.

• Journal of Sensor Science and Technology
• /
• v.24 no.3
• /
• pp.208-213
• /
• 2015

The purpose of this study is to optimize the design of a capacitive pressure sensor element using the simulation of electrical characteristics. The simulation of the ceramic sensor diaphragm ($Al_2O_3$) was performed by permitting pressure to change the curvature of the diaphragm. The pressure capacitance ($C_P$) was increased from 19.63 pF to 15.26 pF by applying pressure because the distance between the electrodes has been changed from $30{\mu}m$ to $15{\mu}m$. When the thickness of the diaphragm was changed to 0.46~0.52 mm, a larger capacitance change showed in accordance with the reduced thickness, which means an increase of sensitivity. However, considering the viewpoint of the signal linearity, it was selected for the optimum thickness of the diaphragm to 0.50 mm. The designed sensor element based on simulated results was tested to measure the output characteristics. Comparing of simulated and measured results, there was a margin of error of approximately 2%.

• Journal of Welding and Joining
• /
• v.15 no.5
• /
• pp.74-83
• /
• 1997

Effect of welding parameters such as current, speed and electrode pressure on the weld quality of tin coated steels for small containers was discussed in this paper. Welding was performed with low frequency wire seam welding system which was loaded with 1.5mm in diameter copper wire electrode. The welding parameters were monitored at the position close to the welding spot so as to minimize the instrumentation error, and the signals were stored into a digital data acquisition system before analysis. Results showed that critical current for sufficient nugget size increased as the base material thickness increased, while the width of the optimum welding range was reduced. The acceptable welding condition derived from this study was found to be effective within the thickness range of $\pm$10% of the nominal (0.25mm) thickness. Tin coating layer was proved not to affect seriously on the weld quality, i.e. strength and formability, since consumable wire electrode was used in this process. Test results also demonstrated that the welding current was thought to be the most effective parameter to form an acceptable weld, while welding speed or electrode pressure exerted less effect on the nugget formation. However, these two parameters played an important role because the former was related to the nugget overlap interval, and the latter, to the formation of expulsion during welding.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.6
• /
• pp.1401-1406
• /
• 2014

Knowledge of the manufacturing process of semiconductor devices in order to obtain a copper pattern using chemical mechanical polishing (CMP) planarization using a Wafer polishing process is applied with a thickness of the copper measured in real time, which need to be precisely controlled by, where the acquisition the actual thickness of the sensor value with the calculated value in terms of error can occur in the process. Approximated the actual measurement values so as to obtain a method using a simple average, moving average, compared to the results using filters onggo Strom real-time measurements of the thickness of the units of the control system to reduce the variation in the implementation of the method described for the.

• The Journal of Korean Physical Therapy
• /
• v.33 no.4
• /
• pp.187-192
• /
• 2021

Purpose: The purpose of the current study was to determine the intra- and inter-rater reliability of muscle thickness measurement of the TA using ultrasonography (US) conducted at different inward pressures of approximately 0.5 kg, 1.0 kg, and no pressure control. Methods: Twenty healthy subjects were recruited for this study. Two different examiners measured the thicknesses of the dominant TA of each subject randomly to assess the intra- and inter-rater reliability. The measurement values were analyzed using the intra-class correlation coefficient (ICC) with a 95% confidence interval, standard error of measurement, minimal detectable change, and coefficient of variance. Results: All intra-rater reliability ICC values showed high reliability above 0.9. Inter-rater reliability ICC values showed high reliability above 0.9 with 0.5 and 1.0 kg of inward pressure. In contrast, Inter-rater reliability ICC values showed poor reliability (0.23) with no pressure control of inward pressure. Conclusion: The findings showed that maintaining consistent inward pressure is essential for reliable results when the muscle thickness of the TA is measured by different examiners in a clinical setting.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.19 no.1
• /
• pp.211-218
• /
• 2019

All display devices require more wider, higher resolution and precision owing to advanced display technology. As the display pannels become wider, BLU also become wider and brighter. The upper glass of the BLU must achieve the constant of its shape and thickness and have uniform brightness. These deformity cause the display quality to make less. Thus high performance of the BLU shape's height and thickness measurement is inevitable. The high speed and precision measurement system will be proposed. To minimize the measurement error we can achieve the desirous results by 2 dividing intervals with different moving velocity on measuring.