Jo Jun 11, 2024
A distributed air microbubble generator can produce microbubble solutions of uniform bubble diameter and high concentration. Two-phase fluid mixers of rotor-stator structure are usually used for generating microbubbles by distributed air. The structure design of its stator and rotor depends on the composition of two-phase medium to disperse. Both the stator and the rotor have independent effects on the characteristics of the two-phase fluid mixing device.
Rotor-stator mixers are of several types including the Silverson mixer, which is often used for homogenization and dissolution in liquid-liquid two-phase fluids. However, it reveals some defects in gas-liquid two-phase fluid mixtures. It is because the viscosity of gas-liquid two-phase fluid is relatively low compared to liquid-liquid two-phase fluid and the difference in gas and liquid density is very large. It is also because gas dispersion in the liquid is very difficult, and the conventional rotor-stator mixer configuration cannot provide sufficient pressure gradients in the shear gap, an important indicator of microbubble generation, due to the self-characteristics of gas-liquid two-phase fluid flow.
In order to increase the pressure gradient in the shear gap, Cha Su Song, a researcher at the Nano Physics Engineering Institute, has proposed a stator structure with a shear blade and rotor-stator engagement relationship. Then, he has evaluated the bubble diameter distribution formed in gas-liquid two-phase fluid flowing through the generator by the CFD-PBM method and compared it with experimental results.
Both the rotor and stator are of a shear blade structure. He analyzed the bubble diameter distribution in the fluid analysis program ANSYS Fluent 18.1. Then, he built a microbubble generator with the same structure as in the analysis and did some experiments. After that, he measured bubble diameter distribution by zeta potential analyzer (Malvern Zetasizer Nano ZS) and compared it with the analytical results.
The average bubble diameters obtained by CFD analysis and experiments were about 107nm and 113nm, respectively, which were in good agreement. In conclusion, the improvement of stator structure in the distributed air microbubble generator has a significant effect on generator characteristics.
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Jo Jun 10, 2024
In recent years, motion analysis technology based on inertial measurement units (IMU) has been widely used in the field of sports science due to its advantages such as its low cost and good adaptability in both indoor and outdoor environments. Xsens MVN BIOMECH, one of the motion analysis technologies that are being widely used all over the world, generally uses several IMUs and processes the rotary motion or position changes of body segments quantitatively.
This technology has been applied to motion analysis in several sporting events including horse riding, ski, basketball, tennis, etc.
Choe Nam Chol, a researcher at the Faculty of Electronics, has applied it to the motion analysis of a table tennis player. As the upper limb plays an important role in the table tennis player’s motion using a racket, he set it as a target.
Every player has their own modality in 3D-changes of wrist, elbow and shoulder joints during the stroke of each type. Those unique modalities would be very important for managers to assess and improve each player’s performance. Therefore, he analyzed the modalities of individual players by using the motion analysis system.
First, he mounted four IMUs on the thoracic spine, the upper limb, the forearm and the back of the hand of a player to measure in real time the 3D-angles of rotation of three joints during the forehand, backhand and topspin forehand strokes. Next, he analyzed the motion pattern and the range of motion (ROM) of wrist, elbow and shoulder joints on the basis of the measured data.
The results showed that the proposed analysis method is effective for improvement of technical skills of players.
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Jo Jun 7, 2024
With the development of large CFB boilers, a cyclone separator with a downward gas exit that provides convenience for the construction and compact layout of boilers appeared. Later, a square cyclone separator was suggested for Π-arrangement in CFB boilers and for convenient installation of heat transfer surfaces on the inner separator walls.
Previous studies of the flow field in cyclone separators with a downward gas exit that focused only on the space between the vertex and the gas exit failed to get flow characteristics in each section of the separator.
Ryom Jun Ho, a researcher at the Faculty of Heat Engineering, has conducted a detailed simulation of the flow characteristics in a square cyclone separator with a downward gas exit.
He used the computational fluid dynamic (CFD) method to predict and evaluate the flow field and collection performance inside the square cyclone separator. In addition, he employed the Reynolds stress model (RSM) for flow field analysis in two cyclone separators with different dust exits.
The results demonstrate that the flow characteristics and collection performance of the square cyclone separator with a vertical dust exit are better than that with an inclined exit.
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Jo Jun 5, 2024
A research team led by Kim Mun Hui, a researcher at the Faculty of Electrical Engineering, has developed a small wind power generation system (SWPGS) for producing maximum power using a permanent magnet generator with two coils.
The generator with two coils ensures not only higher efficiency but also lower expense of the SWPGS than that with one coil, because it can automatically make the load curve more closely approach to the maximum power characteristic curve of a wind turbine without any control circuits.
The system consists of a three-blade horizontal axis wind turbine, a permanent magnet generator (PMG) with two coils, a rectifier, a battery, a load, etc.
PMG with two coils ensures higher accuracy of power control than that with one coil.
In the PMG, only the first coil works at low wind speed, and if the wind speed becomes higher, the second coil works, too.
As a result, the power generation system is driven at its maximum power because it is able to steadily approximate the load curve to the maximum power curve of the wind turbine.
Thus, this system can produce more electric power from the same wind resources in low wind speed areas.
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Jo Jun 3, 2024
From ancient times, Korean people have made active use of hot spring water, a natural resource especially good for medical treatment and longevity.
The old books like “Chronicles of the Feudal Joson Dynasty” give a good deal of records that the ancestors learnt about the medicinal effects of hot spring water and used it for treatment. The visual evidence of the records is the Kalsan Hot Spring Relic discovered near the Kalsan Hot Spring Sanatorium in Kudang-ri, Phangyo County, Kangwon Province.
Kalsan Hot Spring is a simple radon spring. It has been widely known as an excellent remedy for several illnesses such as dermatosis, neuralgia, chronic gastritis, arthritis, etc. from long ago.
The Kalsan Hot Spring Relic, the indoor bath house relic, consists of the building site and four water tanks in it.
On the building site are still found some properly-faced granite cornerstones and platforms and there are two water tanks in the east and west each symmetrically.
The tanks are connected to the long granite water channel with a semicircular hollow for a supply of hot spring water.
The whole floor except the parts with the tanks is covered with granite slabs.
The hot spring, which is some distance from the bath house site, is located higher than the relic, so spring water is allowed to flow down to the tanks on its own.
According to “Chronicles of the Feudal Joson Dynasty”, it is estimated that the bath house was built by the order of King Sejong, the fourth king of the feudal Joson dynasty.
Some historical records say that King Sejong saw to it that a hot spring bath house and a temporary palace were built and he personally visited it to have a hot spring cure.
Tens of meters north-east away from this relic is still found the site of the temporary palace.
All those historical records may be regarded as the evidence to prove that the Kalsan Hot Spring Relic has a long history of over 570 years.
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Jo Jun 2, 2024
Under the great love and benevolence of the Workers’ Party of Korea (WPK), a general experimental education hall composed of tens of modern laboratories equipped with advanced experimental arrangements was built at Kim Chaek University of Technology (KUT).
With the total floor space of thousands of square meters, it has 46 kinds of up-to-date equipment including those for experiments on flexible production and Internet of Things, and 35 kinds of self-made ones including a comprehensive experimental device for sea-bottom minerals.
Open experiment and practice is introduced in this hall in line with the global trend of educational development. Here, the lecturers, researchers and students are allowed to do any experiments and practice needed at any time. It will provide a solid foundation on which the university can further speed up the project to build itself into a university of research and the most prestigious university while realizing the integration of education, scientific research and production together with the bases for experiment and practice at the faculties and the Mirae Sci-tech Center.
The opening ceremony was held on April 14.
Present there were Kim Sung Du, minister of Education, and the officials, teaching staff and students of the university.
KUT President Pak Ji Min delivered an opening address.
He said:
The opening ceremony of KUT General Experimental Education Hall is being held at a time when all the people of the country are dynamically stepping up the general advance for accelerating the overall development period of Korean-style socialism, by turning out for implementing the decision of the 9th Plenary Meeting of the 8th Central Committee of the WPK.
The university, by making the most of the experimental arrangements, should wage dynamic campaigns of brains and research to solve scientific and technological problems arising in the major fields for the development of the national economy and the improvement of the people’s living standard.
All the officials, teaching staff and students should, bearing in mind the great trust and expectation of the Party that put forward KUT as a revolutionary university and the eldest son university of the country, exert all their wisdom and passion on the sacred struggle for the comprehensive development and prosperity of the country.
After the ceremony the participants looked around the general experimental education hall.
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