Jo Apr 24, 2025
Birds damage not only farms, orchards, fish farms, airports but also industrial and urban environments. Common methods for preventing bird damage include the use of scarecrows, the use of chemicals, and the use of nets. The method of scarecrows is not effective because of the fast adaptation of birds, the method of chemicals is effective only in small areas, and the method of nets is expensive.
In recent years, there have been many studies using sound waves, ultrasound and laser for bird repelling. The sonic method is difficult to prevent the adaption of birds, and the ultrasonic method has a small prevention area. Since the automatic laser bird repeller repeats illuminating the laser beam along a certain trajectory at regular intervals regardless of the presence or absence of birds, it is difficult to repel birds as soon as they appear in a certain position.
Pyon Su Bong, a section head at the Faculty of Metal Engineering, has developed a laser bird repellent system for scaring birds away as soon as they settle in the area under observation by a camera.
The object classification technique using the Caffe framework detects the bird in real-time captured images of a PTZ camera over a large area, and when a bird settles on an object in the area, the PTZ camera equipped with the laser beam generator is steered to the target bird, thereby scaring the bird away by attacking it by the laser beam.
For more information, please refer to his paper “Development and Efficacy of Laser Bird Repeller with PTZ Camera and Caffe Framework” in “Earth Sciences and Human Constructions” (SCI).
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Jo Apr 23, 2025
Water is one of the most important natural resources for all living organisms such as humans, animals, plants and other organisms. Providing high-quality water is a fundamental factor for human health, environmental protection and sustainable development. Water quality (WQ) is closely linked with human life and health, preservation of ecosystems, economic growth and social development.
The rapid growth and development of industry seriously affect the quality of surface and ground waters in the world. Most river systems are seriously suffering from metal pollution caused by industrial activities. In the iron and steel industry, a large amount of water is used for cooling, gas cleaning, washing operations and scale breaking, and it results in a huge quantity of wastewater. Common pollutants from wastewater include trace metals, dissolved metals, oils, suspended solids, organic compounds and inorganic pollutants. The water pollution caused by industrial activities such as iron and steel industry is one of the most critical problems that seriously threaten the ecosystem. A huge amount of industrial wastewater makes water pollution extremely serious.
Therefore, water quality evaluation (WQE) is very important in decision making for environmental protection and management. As there are different multiple WQ quality parameters, it is difficult to identify the WQ level.
Many WQE techniques have been developed and applied to WQ evaluation. Water quality index (WQI) is one of the most widely used methods for WQE.
Many works have tried to develop different WQIs by modifying the previous WQIs. By considering the previous WQE methods, the WQE problem can be considered as a multi-criteria decision making (MCDM) problem. Namely, it is a MCDM problem for evaluating and ranking the WQ levels of one or multiple monitoring sites in consideration of multiple WQ parameters.
The existing WQE methods have non-negligible disadvantages―lack of visualization and intuitivity of WQE results.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has developed a new effective approach to evaluate the WQ level not only quantitatively but also intuitively without requiring additional complicated graphical technique.
To this end, he proposed a new quadrant constellation graph-based water quality index (QCG-WQI) and map (QCG-WQM). The QCG-WQI evaluates the WQ level quantitatively, and QCG-WQM evaluates the WQ level intuitively.
The results of comparisons with the results obtained from the conventional multiattribute decision-making methods showed that the new method is a very effective, intuitive and quantitative water quality assessment tool.
You can find the details in his paper “A new quadrant constellation graph-based water quality index and map” in “Desalination and Water Treatment” (SCI).
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Jo Apr 22, 2025
The high-pressure die casting process (HPDCP), which has been widely used to manufacture various products with high dimensional accuracy and output, has much higher productivity than other manufacturing methods. Almost all major Al alloy automotive components can be manufactured by the HPDCP technology.
Die castings have usual gas porosity caused by gas in molten metal and air entrainment because molten metal fills up the die cavity at high speed. In addition, they include shrinkage porosity due to unreasonable gating conditions in the HPDCP. As a result, the internal porosity has a significant influence on the quality of castings.
There are several parameters in the HPDCP technology, and the quality of die castings can be improved when the parameters are controlled properly. The controlling parameters in the HPDCP are pouring temperature, mold temperature, filling rate in shot sleeve, piston velocity, injection pressure and holding pressure. In order to determine the reasonable HPDCP parameters, numerical simulations have been widely introduced.
Carburetor housing, one of the parts of internal combustion engine, is manufactured by HPDCP. Therefore, the numerical HPDCP simulation of the carburetor housing has to be performed to determine the optimal parameters such as pouring temperature, filling rate in shot sleeve, piston velocity and die temperature.
Kim Ryong Chol, a researcher at the Faculty of Materials Science and Technology, has proposed an HPDCP optimization method for improving the shrinkage porosity and air entrainment using Taguchi-based ProCAST simulations and MADM-based overall quality index (OQI), and determined the optimal HPDCP parameters such as pouring temperature (PT), filling rate (FR), piston velocity (PV) and preheating mold temperature (PMT) for simultaneously improving the shrinkage porosity and air entrainment in the carburetor housing made of Al alloy AlSi9Cu1Mg.
The optimal HPDCP parameters obtained through the simulations were PT of 640℃, FR of 40%, PV of 6.5m/s, and PMT of 150℃.
The proposed method could be actively applied to not only HPDCP but also to other casting processes and manufacturing processes.
For further details, please refer to his paper “High-pressure die casting process optimization for improving shrinkage porosity and air entrainment in carburetor housing with aluminum alloy using Taguchi-based ProCAST simulation and MADM-based overall quality index” in “The International Journal of Advanced Manufacturing Technology” (SCI).
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Jo Apr 21, 2025
Detecting and characterizing lineaments using satellite images or digital elevation model data is a field of satellite image processing, providing a lot of useful information for geological structure analysis and mineral exploration. In recent years, many studies have been devoted to the identification of lineaments and their relationship with their distribution characteristics, geological structure and mineral deposit distribution.
Song Man Hyok, a section head at the Faculty of Earth Science and Technology, has proposed a new method for extracting the image features and lineaments related to the local extrema of an image or a digital elevation model (DEM) such as ridges and valleys, based on the continuous wavelet transform (CWT) of a set of variously illuminated hillshades.
The method is based on the principle that a hillshade can exactly reflect the lineaments nearly perpendicular to the illumination direction of the hillshade, but not other ones.
The method consists of four steps: (1) preparation of a set of differently illuminated hillshades of the input data, (2) detection of directional edges nearly perpendicular to the illumination direction from each hillshade based on the CWT, (3) a combination of multidirectional edges into an omnidirectional feature image, and (4) identification of lineaments through linkage and linearization of image feature lines.
He applied this method to the geological structure analysis of the study areas to provide a prerequisite for resource exploration and land development.
For detailed information, please refer to his paper “A Method to Extract Image Features and Lineaments Based on a Multi-hillshade Continuous Wavelet Transform” in “Mathematical Geosciences” (SCI).
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Jo Apr 20, 2025
In general, there are different types of uncertain systems with small samples and poor information in the real world. The grey system is a system with partially known (white) and partially unknown (black) information. Grey models play an important role in modeling, prediction, evaluation, decision making, control and system analysis in many fields because of their simple expression and computation, and excellent prediction performance with insufficient data.
GM(1, 1) model is an important part of the grey model, where ‘GM’ stands for ‘grey model’ while the first number ‘1’ in brackets indicates the first order differential equation and the second number ‘1’ indicates the differential equation of one variable. It is mathematically based on the first order linear ordinary differential equation and least square method. It requires a relatively small amount of data (four or more samples) to develop a mathematical model, and a simple calculation process to analyze the behavior of an unknown system. It has been widely used because it does not require a large number of samples and has low computational complexity and there is no limitation of statistical assumptions.
Up to now, many research works to improve the accuracy of the GM(1, 1) have been carried out on the following aspects. Most of them have used mean absolute error (MAE), mean absolute percentage error (MAPE), mean squared error (MSE) and root mean squared error (RMSE). The accuracy measures are calculated using the arithmetic average operation of errors at the fitting points, and they include no sufficient information about prediction accuracy. Consequently, most of the previous works may be regarded as the works for improving the fitting accuracy of the GM(1, 1). It may be a common drawback of the previous works for improving the performance of the GM(1, 1).
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has proposed an improved GM(1, 1) model based on weighted mean squared error (MSE) and optimal weighted background value: OB-WMSE-GM(1, 1). He applied it to one simulation example and two application examples to verify its effectiveness.
In the simulations and applications, the errors for GM(1, 1) were much smaller than conventional GM(1, 1).
You can find the details in his paper “An improved GM(1, 1) model based on weighted MSE and optimal weighted background value and its application” in “Scientific Reports” (SCI).
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Jo Apr 18, 2025
Water is one of the most important natural resources for humans, and water quality is closely related to human health and life. Therefore, water quality evaluation (WQE) is very important for human health, life and environment and for water management. Since there are many water quality parameters that characterize the quality of water, it is very difficult to evaluate water quality levels.
Water quality index (WQI) is the most widely used WQE method that measures the comprehensive effect of the water quality parameters and ensures integration. It transforms multiple water quality parameters into a single value that quantifies the water quality level based on different mathematical approaches. It evaluates the water quality based on the relative weighted summation of multiple water quality parameters. The aim of WQI is to quantitatively evaluate water quality levels, and rank and classify water bodies according to their chemical, physical and biological water quality parameters.
Many international and local organizations have developed about twenty WQIs by making great efforts for water quality evaluation in different environments.
However, the WQE methods have non-negligible disadvantages. Their common drawback is the lack of visualization of WQE results.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has proposed a new visualized pointer meter-type virtual water qualimeter (VWQ-meter) based on a quadrant circular constellation graph (QCCG), by introducing the pointer meter and CG for WQE.
The proposed water qualimeter has a changeable broken linear pointer with variable lengths and shapes. It can evaluate water quality quantitatively as well as intuitively like traditional water qualimeters.
For more information, please refer to his paper “A new virtual water qualimeter with a changeable broken linear pointer based on a quadrant circular constellation graph” in “Water Science & Technology” (SCI).
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