Jo Nov 13, 2025
Sorting of data elements is a technical problem arising in many fields including statistics. Sorting is the process of rearranging disordered data elements according to the values.
The most important problem in sorting is to decrease the complexity of sorting. Previous papers described several methods to improve selective sorting, one of which is to select and store small data elements during a single scan to shorten the sorting time using a queue.
In order to further update the time of selective sorting, Jong Yong Bok, a researcher at the Faculty of Information Science and technology, has proposed a method of shortening the run time for sorting by half over the existing methods by selecting and storing both the minimum and maximum elements at the same time during one pass using a queue and a stack.
The proposed method proves to be effective for sorting data elements in the fields where they appear iteratively with fortuity including statistics of population according to age and grade management.
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Jo Nov 12, 2025
Brittle material cutting by laser, which is performed below the glass transition temperature, exerts no external force on blanks and leaves no need for grinding as it ensures smooth edges and clean cutting.
The controlled cutting technique generates tensile stress along the cutting path and maintains the temperature below the glass transition temperature. With this technique, it is difficult to control fissure propagation inside the glass because of its cutting characteristics and stress distribution. What is important for it is to generate precise temperature and thermal stress fields and to decrease the cut deviation at the leading and trailing edges of glass.
Kim Yong Il, a researcher at the Institute of Nano Science and Technology, has built a finite element model for temperature and stress fields of glass, established boundary conditions, and studied the effect of laser cutting speed on minimizing the cutting path deviations at the leading and trailing edges while decreasing the thermal stresses.
Through the simulation, he has proved that the cutting deviations at the trailing and leading edges seem to be decreased remarkably at the optimized power and cutting speed during continuous laser cutting. In addition, he has predicted that continuous laser is not suitable for soda-lime glass of 5mm in thickness above 900W of mean power and 22.5mm/s of scanning speed.
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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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