Jo Oct 19, 2025
LED is widely used in greenhouses as it is a non-pollution light source with high efficiency, long lifetime and small size and thermal radiation. Red light and blue light are efficiently absorbed by chlorophyll a and b, and spectra power distribution (SPD) of light source used in greenhouses has a great effect on the photosynthesis process and growth of plants.
Therefore, the effect of SPD and radiation of LED on the growth of plants is an important research focus.
The research group led by Yang Ki Won, a section head at the Faculty of Electronics, has manufactured a gravity injection vegetable-growing device (GI GROW) LED lamp by compounding red, green and blue using improved Gauss distribution to control the spectra power distribution (SPD) of LED.
This LED lamp consists of red, green and blue LEDs of 1W and its total output power is 1 152W, with 72 green LEDs, 864 red LEDs and 216 blue LEDs.
They have compared it with several other plans to evaluate its effectiveness. The results show that GI GROW (using this LED) could increase the fresh weight of lettuce by 1.5 times while reducing the cultivation period by 2.5 times, compared to the lettuce grown in a conventional vegetable greenhouse under the same conditions.
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Jo Oct 17, 2025
Commonly-used ore of Mn is pyrolusite whose main composition is MnO2. With rapidly growing demand for Mn products, low grade Mn ores and secondary Mn sources impossible to be processed by conventional metallurgical methods have become important Mn sources.
In recent years, various hydrometallurgical methods based on various reductants have been developed for the recovery of Mn from these sources. In other words, the reductive acid leaching of low-grade Mn ores in sulfuric or hydrochloric acid solutions with reductants such as hydrogen peroxide, oxalic acid, glucose, corncob, aqueous methanol, ferrous sulfate, pyrite and sulphur was the main focus. However, these leaching techniques have some drawbacks. For example, oxidants and reductants are expensive and sulfur dioxide may be harmful to the environment, and organic reductants are effective but expensive, and their consumption is too much.
Pak Yong Song, a section head at the Faculty of Metal Engineering, has conducted an experiment to enhance the leaching rate of Mn in the preparation of Mn sulfate by the direct reductive leaching method using sawdust as a reductant and spent electrolyte as leaching solution, and confirmed its effectiveness.
He has examined the effects of experimental parameters such as the amount of concentrated sulfuric acid (95%), the amount of reductant, leaching temperature and leaching time.
The results show the following.
First, in order to enhance the leaching rate of Mn, the amount of concentrated sulfuric acid (95%) has to be 2.5mL, the amount of reductant 0.75g, the leaching temperature 85℃ and the leaching time 6h for 10g of pyrolusite powder. In this case, the leaching rate of Mn reaches 98.25%. Second, suitable solid/liquid ratio by spent electrolyte is needed to reduce the viscosity of the solution and provide suitable conditions for filtration.
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Jo Oct 16, 2025
Chaotic mapping has been widely used in cryptography for its dynamic nature, but it has some unsuitable security characteristics due to its limited precision. Therefore, improving the characteristics of chaotic mapping is essential for improving chaos-based encryption algorithms.
Choe Song Bom, a researcher at the Faculty of Information Science and Technology, has presented a plan to improve one-dimensional logistic mapping by parameter variation with delay coupling method and feedback control, proposed a new two-dimensional chaotic mapping, and further enhanced its randomness by selectively shifting the position of generated chaotic sequences. In addition, he has proposed a new image encryption algorithm based on the improved chaotic mapping.
The results of various simulation experiments showed that the proposed image encryption algorithm provides high-level security and is superior to the previous chaos-based encryption algorithms.
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Jo Oct 14, 2025
Concentration of some heavy metals such as As, Hg, Pb, Cd and Sn in food is a very important hygienic index. Because several of these elements are highly toxic, determining them at low concentration levels is of great importance for food factories.
In recent years, hydride generation atomic fluorescence spectrometers useful for determining the elements that form hydrides such as Pb, Hg, Cd, Zn, As, Sb, Bi, Ge, Sn and Se have been developed. Hydride generation technique provided a method for concentrating analytes and led to enhancing the detection limits for these elements by a factor of 10 to 100. This single-channel hydride generation atomic fluorescence spectrometer (HG-AFS) has some shortages like impossible simultaneous determination of several elements and long analysis time.
The advent of atomic fluorescence spectrometers equipped with a non-dispersive system led to the development of a multichannel atomic fluorescence spectrometer for simultaneous determination of several elements. The non-dispersive atomic fluorescence spectrometry (NDAFS) has several advantages of simple and low-cost instrumentation, adaptability to multi-element analysis, and highly-sensitive and simultaneous collection of energy from multiple lines.
There have been many reports on simultaneous determination by this spectrometer, but most of them are for two elements, and the only three-element simultaneous determination is As-Sb-Se simultaneous determination.
Ri Un Hui, a researcher at the Faculty of Metal Engineering, has studied the optimal conditions and method for simultaneous determination of As, Sn and Cd, and successfully introduced them into the analysis of several kinds of food.
This method can be widely used for analyzing not only food but also soil, water, biological samples, the environment, etc.
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Jo Oct 13, 2025
Welding has been widely used in many fields of industry. Its advantages include high efficiency of joining, simple operation, good flexibility and low cost. However, uneven temperature distribution inevitably exists during welding. Such uneven temperature distribution causes rapid thermal expansion, which leads to heterogeneous plastic deformation by thermal constriction in and near the welding joint. Thus, residual stress appears in welding structure after cooling.
In order to accurately predict welding residual stress and deformation, welding temperature distribution should be simulated properly. What is important in welding simulation is to apply suitable heat source models according to the welding methods. The models include spot heat source model, line heat source model (HSM), surface heat source model and volume heat source model. As heat is transferred to workpieces in the form of volume in most welding methods, volume HSM is most widely used. Volume HSM is classified into semi-sphere HSM, elliptical heat source model and double-elliptical heat source model. At present, double-elliptical model is accepted as the most appropriate heat source model for gas metal arc welding (GMAW) with steep temperature slope at the front section of the welding pool and smooth slope at the rear section.
Cha Kwang Jin, a researcher at the Faculty of Materials Science and Technology, has performed a welding temperature simulation by FEM and predicted temperature distribution while varying welding parameters such as welding current.
For the simulation, he employed ANSYS software widely used for welding simulations across the world that offers the most approximate parameters to the desired result by varying several parameters of its own optimization module.
The FEM analysis results and experiment results of welding show that the analysis result is accurate when Gauss-distributed double-elliptical heat source for GMAW process simulation is used.
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Jo Oct 9, 2025
Recently, attempts have been made to use fiber-reinforced plastic composites as aircraft structural materials, but aluminum alloys still have 70% utilization as airborne fuselage materials. In particular, high-alloy duralumin Du16 has been used as the main material for manufacturing aircraft fuselage surfaces and blades.
The body material of an airplane varies in its nature with the speed of flight, so it is very important to determine whether a given alloy can be used as a body material for subsonic and supersonic aircrafts.
Previous studies show that the grain growth of duralumin alloy at annealing temperatures above 300 °C leads to poor mechanical properties, but they failed to deal with annealing at temperatures below that. What is more, they did not cover the changes in the texture and property with temperature when the body of an airplane is heated during the flight.
Therefore, Ri Hyon Song, a researcher at the Faculty of Materials Science and Technology, has measured the fuselage heating temperature range by means of simulation analysis and investigated the changes in the texture and property with annealing temperature.
First, he designed a model of a supersonic aircraft and conducted a simulation analysis of the temperature distribution of the body surface according to flight speed. Then, he performed hardness and microstructure observation experiments.
The results showed that Du16 alloy does not degrade its hardness at 100℃ for 8 hours of annealing, and above 300℃, the hardness is gradually degraded with time.
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