Jo Nov 12, 2024
Wind power generation system mainly consists of a wind power generator, a battery group to store generated electricity, a controller unit to transmit maximum power to load and an inverter system to supply power to AC load.
Generally, small wind power system is controlled by maximum power point tracking method, whereby the output current is controlled so that the wind power generation system can be operated at the maximum power point of the wind turbine regardless of the changing wind speed when the wind power generation system is operated independently. This method is suitable for systems where the rotational speed of the wind turbine varies sensitively with the change of wind speed due to the small inertia moment.
Hence, present papers introduce a method for maximum power output without a control circuit in a small wind power generation system. It is a driving method that approximates the active power curve of load to the maximum power curve of the wind turbine for maximum power operation by changing the generator’s electromotive force coefficient and the inductance of the two-winding generator. In wind power generation systems with two-winding generators of great inductance, however, the load power characteristics have saturation characteristics with respect to the number of turns. Therefore, the inductance alone is not enough to approximate the load power characteristics to the maximum power curve of wind turbines.
Kim Yong San, a researcher at the Faculty of Electrical Engineering, has solved scientific and technological problems arising in providing maximum power point operation of wind turbines using the two-winding generator and electromotive force coefficients in permanent magnet generators connected with wind turbines.
He theoretically analyzed how the power output of load depends on the generator’s electromotive force coefficient and the inductance of a two-winding generator, and proposed a method for determining the reasonable inductance and electromotive force coefficient that brings the generator’s effective power characteristics depending on the rotational speed closest to approach the maximum power curve of wind turbines.
Through the simulation analysis using MATLAB, he confirmed that the power characteristics of load could be operated near the maximum power curve of wind turbines.
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Jo Nov 11, 2024
Among the national cultural heritages of our people with a 5 000-year-long history is the stone lamp of the Kaeguk Temple known as the stone lamp of the Koryo dynasty.
There was a stone lamp at the Kaeguk Temple in Kaesong City.
The Kaeguk Temple was built in 935. It was famous as one of the top ten temples of the Koryo dynasty, but it became dilapidated during the feudal Joson dynasty.
At the temple there was a seven-storeyed stone tower together with the stone lamp.
The structure of the stone lamp lets us believe that it was made at the same time as the seven-storey tower. According to the records of “Koryo History”, the seven-storey tower was built before 1018.
The stone lamp at the Kaeguk Temple, one of the biggest stone lamps existing in our country, is 3.72 meters tall. It is a square plane lamp made of smoothly faced granite which consists of a base stone, pillars, light space and a lamp head.
Every side of the square plane base stone is 1.92 meters long and the top is engraved with an up-side-down lotus flower.
The stone lamp is one of the precious cultural legacies that demonstrate the stone architecture of the early years of the Koryo dynasty characterized by simplicity and majesty.
At present, it is preserved as a national treasure in the Koryo Museum in Kaesong.
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Jo Nov 8, 2024
Nowadays, according to constant changes in the manufacturing style of products, there arises a requirement for rearrangement of facilities. The way how facilities are laid out might cause bottleneck or not in production processes, and decides production efficiency. Therefore, reasonable layout of facilities is a very important problem in factories to be newly built or already built.
Generally, layout of facilities is based on mathematical modeling and optimized planning. However, its complexity fails to meet the requirements of developing modern production modes.
Paek Chol Yong, a researcher at the Faculty of Automation Engineering, has proposed a reasonable layout of facilities. Deciding that the layout of facilities in the machining workshop is a typical discrete event system, he conducted a simulation of the layout of existing facilities by using FlexSim to find its disadvantages and eliminate bottleneck phenomena.
Then, he applied the proposed layout method to a workshop. As a result, the productivity increased by 1.15 times and the production time decreased by 1.21 times as much as the original layout of facilities.
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Jo Nov 6, 2024
The astronomical chart is another name of the picture of constellation.
“Honchonjondo” shows the level of our country’s astronomical development in the eighteenth century.
“Honchonjondo” literally means “a picture of the whole sky”. Showing the stars in the night sky on a sheet of paper, it gives a description of astronomical phenomena and explanation about them, and keeps a record of astronomical constants.
“Honchonjondo” chiefly shows our own astronomical development dating from the ages of the first Korean state founded by King Tangun, with a brief account of the western astronomical development until the first half of the eighteenth century.
All the astronomical contents found in “Honchonjondo” are a precious astronomical heritage of our country, which shows the astronomical development of that time. The national treasure that enriches the treasure house of Eastern astronomy is now preserved in the Grand People’s Study House.
“Honchonjondo”, which is permeated with the wisdom and intelligence of the Korean nation, was registered as a world heritage of UNESCO in May, 2023. This is a brilliant fruition of the Workers' Party of Korea's policy of national cultural protection, and a significant occasion for inspiring the Korean people with national pride and self-esteem.
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Jo Nov 5, 2024
In order to realize automated and unmanned production processes, it is necessary to supervise and control the production process in real time, and check and evaluate the quality of products. Image processing units such as digital cameras are usually used to implement it. Recently, high-resolution cameras are used to improve the accuracy of data. The higher the resolution is, the bigger the amount of data is. Therefore, data transmission rate between computers and peripherals should be increased.
USB3.0 is a computer interface protocol that makes possible up to 5Gbps of data transmission by means of advanced techniques such as full-duplex transmission mode by multi channels, burst function using integrated packets and high-speed encoding technique by 8b/10b encoding, and its application technology has been widely studied for its good hardware connectivity and ease of use.
Ri Pyong Chol, a researcher at the Faculty of Information Science and Technology, has proposed a configuration and design of a USB high-speed transmission system that can achieve a USB3.0 data transmission rate of up to 3.2Gbps.
First, he combined a USB3.0 chip and Cyclone II FPGA to configure a high-speed data transmission system. Then, he programmed a firmware to set the data packet size and buffer size for maximum data transmission rate of the USB port. He also designed FPGA internal logic to increase the data transmission efficiency through the synchronous SlaveFIFO controller, the internal buffer, and the external I/O controller.
Finally, he measured the data transmission performance from the development system to the computer with a test program, and evaluated the efficiency of the proposed system design method.
He confirmed that the proposed method could ensure the data transmission rate of up to 3.2Gbps.
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Jo Nov 2, 2024
Pine Island on Sea Chilbo is an island off Pochon-ri, Myongchon County.
It is one of the scenic spots in Sea Chilbo of Mt. Chilbo, which has been widely known as “Kumgang in North Hamgyong Province” from olden times.
The island is not too far from the land. It was originally a single one but a crack widened gradually to split the island into two.
On the mid-slope of the island is a cave called “Dragon Cave”.
The island is covered mostly in pine, oak and maple.
The pine island has been known as a noted place of Sea Chilbo from olden times for its wonderful scenic beauty.
The pine island is of academic significance and scenic worth.
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