• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.767-770
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• 2017

Quadruple tank liquid level systems are popular in testing multivariable control systems for multivariable processes with positive or negative zeros. The liquid level system is nonlinear and it will help to illustrate the robustness of control systems. However, due to nonlinearity, it can be cumbersome to obtain process parameters for testing linear control systems. Perturbation sizes are limited for valid linearized process models, requiring level sensors with high precision. A simple method where the outlet orifice is replaced to a long tube is proposed here. The effluent flow rate becomes proportional to the liquid level due to the friction loss of long tube and the liquid level system shows near linear dynamics. It is applied to the quadruple tank system for easier experiments.

• Journal of Environmental Science International
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• v.32 no.5
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• pp.303-313
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• 2023

In this study, the hydraulic gradient was calculated using the groundwater level and rainfall observed in the Hyogyo-ri area for a year, and the change in the hydraulic gradient according to the rainfall was analyzed. It was found that the groundwater level increased as the rainfall increased in all groundwater wells in the research site, and the groundwater level rise decreased as the altitude of the groundwater well increased. The hydraulic gradient in the research site ranged from 0.016 to 0.048, decreasing during rainfall and increasing after the end of the rainfall. As the rainfall increased, the groundwater level rise in the low-altitude area was more than the high-altitude area, and the hydraulic gradient decreased due to the difference in groundwater level rise according to the altitude. Through this study, it was found that the influence of rainfall is dominant for the fluctuation of the hydraulic gradient in the unconfined aquifer.

• Journal of Korean Society of Rural Planning
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• v.21 no.4
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• pp.177-186
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• 2015

The main objective of this study was to assess the applicability of IoT (Internet of Things)-based flood management under climate change by developing intelligent water level monitoring platform based on IoT. In this study, Arduino Uno was selected as the development board, which is an open-source electronic platform. Arduino Uno was designed to connect the ultrasonic sensor, temperature sensor, and data logger shield for implementing IoT. Arduino IDE (Integrated Development Environment) was selected as the Arduino software and used to develop the intelligent algorithm to measure and calibrate the real-time water level automatically. The intelligent water level monitoring platform consists of water level measurement, temperature calibration, data calibration, stage-discharge relationship, and data logger algorithms. Water level measurement and temperature calibration algorithm corrected the bias inherent in the ultrasonic sensor. Data calibration algorithm analyzed and corrected the outliers during the measurement process. The verification of the intelligent water level measurement algorithm was performed by comparing water levels using the tape and ultrasonic sensor, which was generated by measuring water levels at regular intervals up to the maximum level. The statistics of the slope of the regression line and $R^2$ were 1.00 and 0.99, respectively which were considered acceptable. The error was 0.0575 cm. The verification of data calibration algorithm was performed by analyzing water levels containing all error codes in a time series graph. The intelligent platform developed in this study may contribute to the public IoT service, which is applicable to intelligent flood management under climate change.

• The Korean Journal of Ecology
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• v.10 no.2
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• pp.81-89
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• 1987

This study was carried out to inverstigate the oribatid fauna at Mt. Moak near Chonju, Korea. Samples were taken from 4 sites at the north sides, 200, 300, 500 and 600 above sea levels and south sides, 200, 400, 600, and 700m above sea levels. The results were as follows: Oribatid mites of 37 families, 62 genera, 118 species were collected in this study. Numbers of species were less at high level than at low level sites. Species diversity index was less at high level than at low level sites, and less at the south than at the north side. Species similarity index indicated that there are two types, i.e. "high sea level type", and "low sea level type" at Mt. Moak. According to the MGP analysis-I, most of the sites belonged to "Type G". "Group M" and "Group P" appeared more in the lower level sites.up P" appeared more in the lower level sites.ites.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.300-303
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• 2001

The first 7 years of altimeter data from the TOPEX/POSEIDON (T/P) were analyzed to study the surface circulation and its variability in the East Asian Marginal Seas. Long term averaged T/P sea level time series data where compared with in situ sea level measurements from a float-operated type tide gauge around of south Korea and Japan. T/P data are a large contaminated by 60-day tidal aliasing effect, very near the alias periods of M2 and S2. When this 60-day effect is removed, the data agree well with the tide gauge data with 4.6 cm averaged RMS difference. The T/P derived sea level variability reveals clearly the well-known, strong current-topography such as Kuroshio. The T/P mean sea level of North Pacific (NP) was higher than Yellow Sea (YS) and East Sea (ES). The T/P sea level valibility, with strong eddy and meandaring, was the largest in eastern part of Japan and this variability was mainly due to the influence of bottom topography in Kuroshio Extention area.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.3
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• pp.386-393
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• 2004

This study was conducted to investigate the effects of feeding dried leftover food (DLF) on growth, body composition and feed conversion of broiler chicks. One hundred ninety-six of one-day old Ross broiler chicks were assigned to 7 treatments in a completely randomized design. Each treatment had four replications with seven chicks per replication. The treatments groups included control without DLF, dietary 10% level of DLF, dietary 20% level of DLF and dietary 30% level of DLF, 5% higher protein level of diet containing 10% DLF, 10% higher protein level of diet containing 20% DLF and 15% higher protein level of diet containing 30% DLF than control diet. Body weight gain was slightly higher in control group than that of DLF-fed groups. However, there were no significant differences in body weight gain among those groups fed diets containing different levels of DLF. In general, increasing dietary level of DLF resulted in decreasing feed conversion. Content of crude protein in whole broiler body was slightly higher in control group although any significant difference was not found among treatments (p>0.05). Content of crude fat in whole broiler body was lowest in groups fed diets containing 30% DLF with 15% higher protein level than control diet, showing significant difference from groups fed diets containing 20% DLF (p<0.05). Contents of total cholesterol, free cholesterol, cholesterol ester and LDL- cholesterol in blood of broilers fed DLF-containing diets generally appeared to be higher compared with control group without significant difference (p>0.05). Fatty acid contents in broiler meat were higher in the order of oleic acid, palmitic acid and linoleic acid without significant differences among treatments. Content of DHA in broiler meat was higher in groups fed diets containing DLF than that of control group although there were no significant differences among treatments (p>0.05).

• The Journal of the Acoustical Society of Korea
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• v.28 no.3E
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• pp.118-135
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• 2009

The level set based approach is one of active methods for contour extraction in image segmentation. Since Osher and Sethian introduced the level set framework in 1988, the method has made the great impact on image segmentation. However, there are some problems to be solved; such as multi-objects segmentation, noise filtering and much calculation amount. In this paper we address the drawbacks of the previous level set methods and propose an extension of the traditional fast level set to cope with the limitations. We introduce a relationship matrix, a new split-and-merge criterion, a modified Chan-Vese criterion and a novel filtering criterion into the traditional fast level set approach. With the segmentation experiments we evaluate the proposed method and show the promising results of the proposed method.

• Communications of Mathematical Education
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• v.22 no.3
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• pp.369-382
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• 2008

We discuss the effect of ability grouping calculus courses based upon student's proficiency of the subject and their collective examination of midterms and finals among mid-level and low-level classes. We assess incoming freshmen at Seoul National University of Technology(SNUT) of their proficiency in calculus and assign them to the appropriate levels within the course(i.e., high-level, mid-level, low-level). We found that this was beneficial to both students and instructors. Instructors can easily determine the pace in which each class should be kept, and students can quickly adapt to the learning environment.

• Korean Educational Research Journal
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• v.37 no.1
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• pp.103-116
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• 2016

In this study, we examined scientific concept of middle school students about the concept of 'separation of mixtures' Understanding level of students was different by the educational achievement level, and the higher the educational achievement level, the more exactly they understood scientific concept. Misconception was observed at all the achievement level. The higher the achievement level, the common misconception was associated with concept definition. And the lower the achievement level, the common misconception was associated with phenomenon.

• Nuclear Engineering and Technology
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• v.32 no.2
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• pp.157-168
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• 2000

The nuclear steam generator level control system is designed by robust control methods. The feedwater controller is designed by three methods of the H$\infty$, the mixed weight sensitivity and the structured singular value. Then the controller located on the feedback loop of the level control system is designed. For the system performance, the controller of simple PID whose coefficients vary with the power is selected. The simulations show that the system has a good performance with proper stability margins.