Jo Nov 11, 2025
It is very important to correct the synchronization errors that occur if the receiver is not completely synchronized with the transmitter. However, it is impossible to achieve perfect synchronization in many communication systems.
Synchronization errors due to the insertion and deletion of symbols can cause serious performance degradation if the coding scheme does not possess the capability to recover from such errors.
Pak Jang Son, a researcher at the Faculty of Communications, has proposed a method for correcting synchronization errors that occur in Turbo code sequence using the algebraic operation principle of Scarce-State-Transition (SST) Viterbi decoder.
The encoding/decoding procedures of Turbo code in this method are similar to the common case, except making corrupted bit positions caused by bit insertion/deletion in received Turbo code sequence take their original positions.
The simulation result shows that the proposed method is capable of correcting synchronization errors occurring in the received Turbo code sequences.
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Jo Nov 10, 2025
Unlike the Optical Character Recognition (OCR) in traditional document images, video subtitle text recognition is still a challenging task in the fields of computer vision and artificial intelligence because of complex background, different size and color of fonts, low contrast between texts and background regions and different location of subtitle texts in video frames. Due to these factors, the traditional OCR developed for document images has proved to be inappropriate for video subtitle texts.
In order to solve this problem, unified models for both detecting and recognizing texts have been proposed. However, these methods have the disadvantage of low accuracy in the recognition of unknown words or sequences of arbitrary characters.
Yun Chol Song, a researcher at the Faculty of Information Science and Technology, has designed and implemented two types of models―one is a video subtitle text detection model, a combination of a convolutional neural network model and an adaptive scale fusion model, and the other is a subtitle text recognition model, a combination of a convolutional neural network model and a BLSTM model.
The results of the experiments have demonstrated that the subtitle text detection accuracy in the video is 93.4% and the subtitle text recognition accuracy is 94.6%, which proves to be superior to the previous methods.
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Jo Nov 9, 2025
Since the rotary angular sensor is a main sensor for measuring accurate positions and directions, it plays an important role in various applications such as robot control, cameras and industrial machines.
Generally, the rotary angular sensor can be divided into sensors based on the changes in electric field and magnetic field, and optical sensors according to the underlying physical principle. Electric field-based and magnetic field-based sensors have their own drawbacks respectively.
However, optical sensors operating in visible or infrared light have the advantage of contactless measurements and insensitivity to electromagnetic fields. The sensitivity of an optical sensor might be reduced by external light, but this problem can be solved using a housing and pulsed light. Today, optical angular sensors are indispensable displacement/position sensors for their high resolution, light weight and insensitivity to electromagnetic fields.
Jo Myong Jin, a researcher at the Semiconductor Institute, has proposed a new absolute rotary angular sensor using 1D PSD (position sensitive detector).
Sinusoidal signals with rotation angles are output from the 1D PSD by the sinusoidal path of the optical disc, which allows easy reduction of 1-bit measurement errors present in the binary code disc.
The proposed method is simple in design and the output signal is a combination of an absolute binary code and an analog signal, which can achieve high resolution. In addition, it has the advantage of high linearity and accuracy.
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Jo Nov 7, 2025
The shell and tube heat exchanger among a variety of heat exchangers is widely used in many industrial applications for its advantages of long lifetime, simplicity of manufacture and wide operation range. In multi-channel systems including the shell and tube heat exchanger, flow distribution significantly affects their performance and lifetime. When a heat exchanger is designed, flow distribution is usually assumed to be uniform, but flow maldistribution may be an inevitable occurrence in practice. In particular, flow distribution in the tube-side of a single-pass shell-and-tube heat exchanger (SSTHX) with axial connections of bonnet nozzles is extremely non-uniform.
Generally, flow uniformity in multi-channel systems like heat exchangers has been realized in a limited flow regime (e.g. laminar flow or turbulent flow).
Pak Sin Myong, a section head at the Faculty of Heat Engineering, has proposed an innovative header baffle to effectively uniformalize flow distribution in the tube-side of a single-pass shell-and-tube heat exchanger (SSTHX) with axial connections of bonnet nozzles, even within the extensive range of Reynolds number.
He simulated the flow in the SSTHX using the commercial CFD code-ANSYS Fluent, and modeled the tube bundles as a porous medium. In the new structure of SSTHX, flow distribution was uniformalized ideally from extreme laminar regime to strong turbulent regime (Reynolds number of 40-80 000) although pressure loss was significantly increased (about 35%).
The effects of structural and thermo-hydraulic factors on flow uniformity were very small.
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Jo Nov 6, 2025
The high-pressure common-rail fuel injection system starts and finishes fuel injection by the high-speed solenoid valve of the pilot injector, and eliminates anomalous injection caused by pressure fluctuations and the breakdown of pumps caused by high injection pressure during high-speed flow in large quantity. In addition, it achieves stable injection at relatively high injection pressure in different situations. It can also improve diesel combustion and performance, reduce NOx in the exhaust gas emissions and diesel engine noise, and improve cold start performance and exhaust gas emission.
The fuel injection of a common-rail system is performed by the electrical signal of the high-speed solenoid valve. In other words, the high-speed solenoid valve determines the start, finish and quantity of fuel injection.
Therefore, researchers involved in the development of high-pressure common-rail systems in many countries have paid great attention to high-speed solenoid valves.
Ri Tong Hyon, a researcher at the Faculty of Electrical Engineering, has built a mathematical model of the high-speed response solenoid valve for a common-rail injector, investigated the influence of various parameters on the dynamic response of the high-speed response solenoid valve, and determined the optimum parameters.
In other words, he has investigated the effects of the inner and outer diameters of the stator outer core, the number of windings turns, the suction current, the outer diameter, thickness and inclination angle of the armature, the drive voltage, the spring preload, the elastic coefficient and the eddy current on the response characteristics of solenoid valves, and determined the optimum structural parameters and structural design.
As a result, he has managed to accurately calculate the dynamic response characteristics of a high-speed solenoid valve in the mixture of various fields.
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Jo Nov 5, 2025
Oungum is a musical instrument which was initiated, led to completion and named by Chairman
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