Improvement of Identification of Spoofing

Jo Feb 14, 2025

Rapid development of information technology has greatly changed the pattern of teaching and learning in education, and e-learning is the most widely used mode of learning nowadays. In e-learning systems, some cheating phenomena can occur because the teacher cannot see the students' learning process. User authentication by user names and passwords only when logging on in most e-learning systems might cause cheating. In other words, someone else may substitute for learners, and the learner may leave before the lecture is over.

If a student enrolled in e-learning system is able to complete a course without actually learning, the reliability of the course and e-learning system is diminished, and since lectures or learning materials are intellectual assets, such deception should be prevented. Therefore, in e-learning systems, it is necessary to identify the learner during the learning activities as well. To detect spoofing in e-learning is of great significance in enhancing the reliability of e-learning systems and protecting the copyright of learning content.

Therefore, biometric authentication techniques such as face recognition, fingerprint recognition and speech recognition have been introduced into user identification in e-learning systems, and prevention of spoofing of learning by face recognition in e-learning process is in active use. However, face recognition is usually conducted at the beginning of user engagement, lectures and tests, and there has been no intense research to prevent spoofing of learning in the learning process.

Ryu Chang Sik, a section head at the Faculty of Distance Education, has proposed a new method to prevent spoofing, based on implicit face matching at randomly selected time intervals during online learning.

In the proposed method, face-matching identification is performed at the time of system login and the beginning of learning, and in each learning process (e.g., learning a section). In addition, implicit face-matching is performed several times without interaction with students at random time intervals to calculate the similarity value and detect the impostor. If not detected in the random check, explicit user identification would be required.

The proposed method has been applied to an e-learning system that provides a graduate qualification. The result shows that the system can effectively distribute the server load and prevent the spoofing of learning, while significantly reducing the number of stoppage of learning due to face contrasts.

You can find more information in his paper “Identification of Spoofing in e-Learning system with the implicit face recognition” in “INFORMATICA”.

Efficient Post-HCl Treatment for Promoting DTO Perf...

Jo Feb 13, 2025

At present, since energy depletion and environmental pollution are global issues, many attempts have been made to produce light olefins by low energy consumption, low carbon dioxide emission and environment-friendly methods from coal and natural gas which is more abundant than petroleum or from sustainable biomass resources. One of these methods is the methanol to olefins (MTO) process using a microporous catalyst.

Dimethyl ether (DME) is an intermediate of MTO, and it is easily converted to olefins by catalysis, a surface phenomenon. The key of DTO technology is to synthesize catalysts with high light olefins selectivity and long lifetime. SAPO-18 structure that is extensively used in MTO, DTO, CO₂/CH₄ separation and SCR of NO_x processes, and is structurally similar to SAPO-34 (with CHA framework).

Many attempts have been made to enhance the catalytic performance and lifetime of SAPO-18 catalysts, such as synthesis of catalysts with different organic structure directing agent (OSDA), incorporation of nonmetallic and metallic elements into the framework, and the mechanism of coke formation, but the role of post-acid treatment on DTO performance of SAPO-18 has been barely addressed.

Jong Song Chol, a researcher at the Faculty of Chemical Engineering, has proposed post-HCl treatment as a method to promote DTO performance of SAPO-18, and compared with S-0 and NiS-0 the catalytic performance of acid-treated catalysts such as crystalline structure, morphology, specific surface area, textural properties, acidity and DTO performance.

He has found that the optimum HCl concentration and treating time of SAPO-18 catalyst for the catalytic performance enhancement in DTO are 0.1M and 3h, respectively.

You can find the details in his paper “Efficient post-HCl treatment for promoting DTO performance of SAPO-18 and Ni-substituted SAPO-18” in “Journal of Saudi Chemical Society” (SCI).

Effect of Hot-Carrier-Induced Degradation of NPT-IG...

Jo Feb 12, 2025

IGBT, a high-voltage high-power integrated circuit device, has a wide range of high-power switching applications such as mobile driving, power supply, railway transportation, industry control, etc. NPT-IGBT is a composite device of MOSFET and BJT.

Since NPT-IGBT usually operates at high voltage and high current, hot-carrier-induced degradation will be generated inside the device. Hot carriers with high energy will damage the oxide region of the device and the interface between silicon and silicon-dioxide, and increase the trap charge of the interface and the oxide region.

Although many researchers have described the issues on hot carriers of IGBT device, little literature is on the reliability of hot carrier of NPT-IGBT.

Kim Hak Bong, a section head at the Semiconductor Institute, has analyzed the degradation mechanisms due to the hot carrier effect in NPT-IGBT through the voltage stress measurement, TCAD simulation and charge pumping measurement.

He has concluded the following from the results. First, the device might have different degradation mechanisms under different gate voltage conditions. Second, when the gate voltage is relatively high, degradation is caused in three regions. The boundary state is generated in the body region, while the oxide layer trap charge is caused in the accumulation region, the field-oxide region and the drift region. Third, when the gate voltage is relatively low, the boundary state and the oxide layer trap charge are formed in the drift region and the degradation in the body region is relatively small.

If more information is needed, please refer to his paper “Analysis on Effect of Hot-Carrier-Induced Degradation of NPT-IGBT” in “Solid-State Electronics” (SCI).