Jo Mar 28, 2025
Nitrite is one of the toxic substances existing in foods such as fish, meat products and vegetables, which has a great impact on human life and health. When nitrite ions enter the body, they bind with blood hemoglobin to form metahemoglobin, causing it to lose its oxygen-carrying capacity. It also combines with amines and amides of the digestive organ to produce carcinogenic nitrosamine compound. Therefore, an accurate measurement of nitrite concentration is very important for protecting human life and health.
So far, various methods of detecting nitrite, such as chromatography, spectrophotometry, and electrochemical analysis, have been developed. Among these methods, the detection of nitrite ions by electrochemical sensing electrodes is a major candidate for nitrite detection due to its high sensitivity, selectivity and fast response. In particular, modified electrodes based on conducting polymers including polyaniline, polypyrrole and polyphenylene have received great attention in the development of sensing electrodes using them because of their ability to prevent surface contamination and improve the electrochemical properties of the electrodes.
Pak Jong Sung, a section head at the Faculty of Chemical Engineering, has developed a novel electrochemically modified carbon paste electrode based on PANI-TiO2/Pt nanocomposites.
The experimental results demonstrate that the PANI-TiO2/Pt electrode has pretty excellent electrocatalytic ability for oxidation of nitrite.
For more information, please refer to his paper “Electrochemical Detection of Nitrite on PANI-TiO2/Pt Nanocomposite−Modified Carbon Paste Electrodes Using TOPSIS and Taguchi Methods” in “ACS Omega” (SCI).
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Jo Mar 27, 2025
Commonly, arsenic-bearing gold ore is very refractory. Therefore, it is necessary to break these ores up to the gold particle size or decompose them to make gold exposed before leaching. The process such as decomposition and crushing prior to leaching is called pretreatment of refractory gold ore. Recently, many researchers have studied the pretreatment of gold bearing arsenopyrite to expose gold and remove arsenic by changing the mineral composition, electrochemical and physicochemical properties of gold ore.
There are many pretreatment methods of refractory gold ores including roasting oxidation, bacterial oxidation, pressure oxidation and chemical pretreatment. Particularly, the chemical treatment methods are widely used due to its low cost. Among them, alkaline pretreatment is considered to be the most economical and eco-friendly. However, this method is not widely used due to the dependence of alkaline concentration, temperature and pressure.
Recently, ultrasound has been widely used to accelerate the speed of chemical reaction. Many researchers have already studied the effects of ultrasound on gold and zinc extraction, on copper extraction from copper ore, on leaching of phosphate using hydrochloric acid, and on sulfuric acid leaching of colemanite. However, the effects of ultrasonic power and intensity of mechanical agitation on leaching of minerals are rarely involved.
Hong Won Chol, a researcher at the Faculty of Mining Engineering, has investigated the effect of the ultrasonic power and mechanical agitation intensity of pulp on alkaline pretreatment of gold-bearing arsenopyrite.
He studied the effect of the pulp temperature on the leaching efficiency in alkaline pretreatment of arsenopyrite under both ultrasonic and non-ultrasonic conditions. Compared with the non-ultrasound condition at the temperature of 60℃, arsenic extraction and gold extraction increased by 20 % and 14.4 %, respectively, in the presence of ultrasound at ambient temperature.
You can find more information in his paper “Effects of Ultrasonic Power and Intensity of Mechanical Agitation on Pretreatment of a Gold-Bearing Arsenopyrite” in “Archives of Acoustics” (SCI).
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Jo Mar 26, 2025
Rapid development of computer network increases the applications of e-learning, which provides teachers and students with convenience and flexibility.
In the environment of distance education, interaction is a very important factor for raising the efficiency of teaching and self-study. Especially, in distance education of design project which deals with the designing of circuits or machinery, ensuring the interaction becomes more important since explicit and implicit knowledge hold large portion at the same time.
To raise the interaction in the distance learning, Jong Kum Sil, a lecturer at the Faculty of Distance Education, has proposed an e-learning system where a virtual board is introduced.
The main system consists of a teacher’s computer equipped with various exam and plagiarism-prevention tools, and client computers connected with the teacher’s by network. It also includes various tools for assessing the students’ design projects and the virtual board which is connected with teacher’s computer, so the students can ask questions online through the virtual board for teacher’s guidance. By inserting authentication to the students’ multi-media, she raised the fairness and objectiveness in assessing the students’ tasks.
For further details, please refer to her paper “An interactive e-learning system equipped with plagiarism detection tool for the distance education of the design course” in “INFORMATICA” (SCI).
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Jo Mar 25, 2025
Hydrogen sulfide is a polluting gas that is produced in various industrial fields including oil processing and fertilizer production. It is also generated in the course of people’s living. Hydrogen sulfide is very toxic to human health. Hydrogen sulfide can cause blood poisoning and its high concentrations (higher than 250ppm) may lead to death.
Therefore, detection of toxic gases has been a major focus of sensor research in recent years. Accurate measurement of hydrogen sulfide gas concentration is very important for protecting human life and health. So far, various sensors for detecting hydrogen sulfide gas have been developed.
Chemoresistive sensors based on conductive polymer are cheap and operable and responsive at room temperature. In particular, nanocomposites based on conductive polymer and metal oxide nanoparticles have excellent nanostructural properties and high sensitivity and their responses to gases are fast.
Cha Ho San, a student at the Faculty of Chemical Engineering, has prepared a chemoresistive H2S gas sensor based on PANI/TiO2/CuCl2 nanocomposite (PTCN) impregnated fabric by in situ synthesis method (ISM).
For more information, please refer to his paper “Chemoresistive H2S sensor based on PANI/TiO2/CuCl2 nanocomposite impregnated conductive fabric using TOPSIS and Taguchi method” in “Engineering Research Express” (SCI).
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Jo Mar 23, 2025
Elimination of parasitic vibration presents itself as a nuisance for the industrial application of self-mixing sensors. The parasitic vibration is the vibration of the self-mixing sensor itself, which has an evil effect on the measurement accuracy. Although the elimination of the parasitic vibration is very important, there have not been enough studies on it.
A solid-state accelerometer (SSA) is often used for the removal of parasitic vibration. The SSA coupled with the SM sensor measures the acceleration of the parasitic vibration and it is double integrated to obtain the displacement, which is subtracted from the displacement reconstructed from the SM sensor to extract true target motion. The fatal shortcoming of the elimination of parasitic vibration based on SSAs is that the error of the SSA has a direct effect on the measurement. The error of the SSA keeps on being accumulated with time in a real-time displacement measurement in particular.
Kim Chol Hyon, a section head at the Faculty of Physical Engineering, has proposed a method of eliminating the hand-induced parasitic vibration based on FFT.
His method can provide the displacement reconstruction error less than 30nm by taking a proper cutoff frequency and data length and it can be applied to the measurement of mechanic vibration of 10 to 1 000Hz. Besides, this method can be applied to all cases where there is some difference between the main frequency of parasitic vibration and the frequency of the measured object.
For more information, please refer to his paper “Elimination of hand-induced parasitic vibration in self-mixing displacement measurement based on FFT” in “Applied Optics” (SCI).
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Jo Mar 21, 2025
Self-mixing interferometry (SMI) is well known as a very effective technology for the measurement of displacement, vibration, velocity, etc. due to its unique advantages. Hence, many achievements have been made in the research of the SMI theory and its application.
Unfortunately, however, few studies on the stability of self-mixing signals (SMSs) can be found. In fact, stable SMSs are not readily obtained because many factors have an effect on their stability. The injection current of the semiconductor laser (SL) in particular has a vital effect on the stability.
Kim Chol Hyon, a section head at the Faculty of Physical Engineering, has investigated the effect of the injection current on the stability of SMSs in SMI theoretically and experimentally while varying the injection current, and consequently found the law of stable injection current.
This law demonstrates that there exist stable injection current points suppressing bifurcations, and their positions depend only on the external cavity length. The law advises driving the SL at an injection current corresponding to a non-bifurcation range in order to acquire clear SMSs favorable for displacement reconstruction.
For further details, please refer to his paper “Regularity of bifurcation in a self-mixing laser diode” in “Applied Optics” (SCI).
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